DE102016122655A1 - CURRENT AND CONTROL METHOD - Google Patents

Abstract

A power converter 100 includes isolated DC-DC converters 70a and 70b for converting a direct current through alternating current into another direct current. The isolated DC-DC converters 70a and 70b include a first capacitor 1 connected to a first conductive path 21 of a direct current, a second capacitor 2 connected to a second conductive path 22 of another direct current, and a first current limiting circuit 3 connected by a third Conduction path 23 for AC flowing current controls.

Description

BACKGROUND OF THE INVENTION

1. Subject of the invention

The present invention relates to a power converter and a control method.

2. Description of the Related Art

As a drive system of a railway vehicle that receives power from an AC power source, a widely used indirect conversion system includes a main transformer that steps down a voltage, a pulse width modulation (PWM) converter that performs high power factor AC to DC conversion (hereafter referred to as "PWM"). AC-DC conversion "), and a VVVF inverter that generates three-phase variable-voltage variable-frequency AC power for driving a DC-voltage based motor. That is, in the indirect conversion system, the power conversion is performed in the order of single-phase AC through DC to three-phase AC.

AC power lines with voltage frequencies from 16.7 Hz to 60 Hz are widely used, and main transformers are designed in accordance with the frequencies. For a main transformer, the lower the voltage frequency, the higher the magnetic flux through a core at the same terminal voltage. Therefore, when the voltage frequency is low, a core must have a large cross-sectional area to avoid saturation magnetization in the core. This will make the transformer big. Consequently, main transformers make up a large proportion of the weights and dimensions of electrical components installed on railway vehicles.

On the other hand, a drive system which does not require a main transformer has been described. For example disclosed JP 2005-73362 A the arrangement of a power converter, which uses a plurality of power converter cells in modules, can be obtained by the power from an AC power source without a main transformer. The power converter cells convert once an AC voltage into a DC voltage. Then, using a DC-DC converter comprising a high-frequency insulator and converting direct current into direct current, the power converter cells generate direct current of the same or different voltage according to the direct current voltage converted from the alternating voltage. AC-side input ends of the power converter cells are connected in series, so that the power converter cells are directly connected to a high-voltage AC power line, which meets withstand voltage requirements of their components. Such a system is called a "semiconductor transformer".

In a semiconductor transformer, the number of independent DC bus bars is larger than in a conventional main transformer system. Each busbar is connected to a smoothing capacitor which compensates for residual ripple on the DC voltage. When starting the device, care must be taken to avoid excessive charging current in the capacitors. For example disclosed WO 2012/098107 A a method of precharging an AC line side smoothing capacitor in a power converter of a railway vehicle receiving power from an AC line having a main transformerless arrangement.

JP 62-104586 U in that as a circuit arrangement similar to a semiconductor transformer forming converter cells, a switching current source is composed of a set of a diode rectifier and an isolated Eintaktflusswandler discloses a method for precharging a smoothing capacitor at an input portion of the isolated Eintaktflusswandlers and a smoothing capacitor to a Output section of the isolated single-ended flux converter.

When there is a voltage difference between two smoothing capacitors electrically isolated by a high frequency insulator during start-up of a semiconductor transformer, an overcurrent may be introduced into components such. B. semiconductor devices, which form a DC-DC converter, are generated at the beginning of the switching of the DC-DC converter. An overcurrent caused by components such. B. semiconductor devices flows, such a disturbance can result in that a replacement of components such. As semiconductor devices, is required. This tendency becomes more pronounced as the voltage difference between the two smoothing capacitors increases, since the capacitance of the smoothing capacitors is greater, or as the impedance of the high-frequency isolator decreases.

This invention has been made in view of the foregoing, and has an object to provide a power converter and a control method capable of starting up without generating excessive current into components constituting a DC-DC converter even when there is a voltage difference between two capacitors.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to at least partially solve the problems of the conventional art.

To solve the problem and to achieve the object, a power converter according to the present invention comprises: at least one DC-DC converter for converting DC power to AC power to another DC power, the at least one DC-DC converter connecting a first capacitor connected to a first DC power conduction path , a second capacitor connected to a second conduction path of another direct current, and a first current limiting circuit controlling current passing through a third conduction path.

A control method according to the invention is a control method in a power converter comprising at least one isolated DC-DC converter for converting a direct current through alternating current into another direct current, the at least one isolated direct current converter having a first capacitor connected to a first conducting path of a direct current a second capacitor connected to a second conductive path of a second direct current, a first current limiting circuit controlling current flowing through a third alternating current path, a first ac-to-dc conversion circuit and a second ac-dc conversion circuit, the direct current and Convert alternating current, and comprises a transformer, wherein DC terminals of the first AC-DC conversion circuit are connected to the first conduction path, AC terminals of the first W AC-DC conversion circuit connected to the third conductive path, DC terminals of the second AC-DC conversion circuit are connected to the second conductive path, AC terminals of the second AC-DC conversion circuit are connected to the third conductive path, the AC terminals of the first AC-DC Conversion circuit with the AC terminals of the second AC-DC conversion circuit via the transformer and the first current limiting circuit are connected and the first current limiting circuit, a first current limiter, which controls current, and a first switch, which is connected in parallel with the first current limiter, wherein the method of the transformer, a primary-side winding, which is connected to the AC terminals of the first AC-DC conversion circuit, and a secondary-side winding, the is connected to the AC terminals of the second AC-DC conversion circuit, and, if a voltage ratio, a value of a voltage of the second capacitor divided by a gear ratio, a value of a number of turns of the secondary-side winding divided by a number of turns the primary-side winding, and a voltage of the first capacitor is less than a predetermined value, a control unit performs a Vorladeschritt by opening the first switch and then transmitting current from the first capacitor to the second capacitor in the at least one isolated DC-DC converter.

The above and other objects, features and advantages, as well as the technical and industrial significance of this invention, will be better understood by reading the following detailed description of presently preferred embodiments of the invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

1 Fig. 12 is a circuit diagram of a power conversion system including a power converter according to a first embodiment of this invention;

2 Fig. 10 is a circuit diagram of a DC-DC converter in the power converter according to the first embodiment of this invention;

3 Fig. 10 is a circuit diagram of the DC-DC converter in the power converter according to the first embodiment of this invention;

4 Fig. 10 is a circuit diagram of the DC-DC converter in the power converter according to the first embodiment of this invention;

5 Fig. 10 is a circuit diagram of the DC-DC converter in the power converter according to the first embodiment of this invention;

6 Fig. 10 is a circuit diagram illustrating a modification of the circuit diagram of the power converter according to the first embodiment of this invention;

7 is a diagram showing a capacitor charging in a power converter according to a second embodiment of this invention illustrated;

8th Fig. 10 is a flowchart illustrating the capacitor charging operation in the power converter according to the second embodiment of this invention;

9 Fig. 12 is a diagram illustrating an operation of a DC-DC converter in the power converter according to the second embodiment of this invention;

10 Fig. 12 is a diagram illustrating another operation of the DC-DC converter in the power converter according to the second embodiment of this invention;

11 Fig. 12 is a circuit diagram of a power converter according to a third embodiment of this invention;

12 Fig. 12 is a circuit diagram of an AC-DC converter in the power converter according to the third embodiment of this invention;

13 FIG. 12 is a vector diagram illustrating an operation of the AC-DC converter in the power converter according to the third embodiment of this invention; FIG.

14 is a circuit diagram in a conventional power converter;

15 Fig. 15 is a modification of the circuit diagram of the power converter according to the third embodiment of this invention;

16 Fig. 12 is a diagram illustrating an operation of a power converter according to a fourth embodiment of this invention;

17 Fig. 12 is a diagram illustrating an operation of the power converter according to the fourth embodiment of this invention; and

18 FIG. 12 is a circuit diagram of a power converter according to a fifth embodiment of this invention. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a power converter and its control method according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, a power converter used in a railway vehicle will be described as an example. However, the power converter and its control method according to this invention are not limited to use in railway vehicles and can be used for other applications in which power is obtained from a DC power source or an AC power source.

First embodiment.

1 Fig. 12 is a circuit diagram of a power conversion system including a power converter according to a first embodiment for practicing this invention. The components of the DC-DC converter 70a and 70b in 1 are the same, so that reference numerals in the components of the DC-DC converter 70b be omitted.

A power conversion system 200 in 1 includes a power converter 100 , two DC sources 110 and a consumer 120 , The power conversion system 200 leads to the consumer 120 Electricity from the DC sources 110 over the power converter 100 to.

The power converter 100 includes a power conversion circuit 95 and a control unit 90 , The power conversion circuit 95 includes the two DC-DC converters 70a and 70b and a discharge circuit 80 , The consumer 120 corresponds to z. As an inverter for driving a motor.

The DC-DC converter 70a and 70b each comprise a first capacitor 1 , a second capacitor 2 , a first current limiting circuit 3 , a first AC-DC conversion circuit 4 , a second AC-DC conversion circuit 5 , a transformer 6 , a pair of clamps 70-1 and 70-2 at input-side terminals and a pair of terminals 70-3 and 70-4 at output-side connections. For each of the DC-DC converters 70a and 70b It is an isolated DC-DC converter for converting a direct current via alternating current into another direct current.

Here, a conduction path of a direct current is a first conduction path 21 , a conduction path for AC is a third conduction path 23 and a conduction path of another direct current is a second conduction path 22 , The first route 21 is a conduction path from the DC power source 110 to a pair of clamps 4-1 and 4-2 at DC side terminals of the first AC-DC conversion circuit 4 , The second conduction path 22 is a conduit path from a pair of terminals 5-1 and 5-2 at DC side terminals of the second AC-DC conversion circuit 5 to the consumer 120 , The third route 23 is a conduit path from a pair of terminals 4-3 and 4-4 to AC-side terminals of the first AC-DC conversion circuit 4 to a pair of clamps 5-3 and 5-4 at AC-side terminals of the second AC-DC conversion circuit 5 ,

The pair from the clamps 70-1 and 70-2 at the input side terminals in each of the DC-DC converters 70a and 70b is single with one of the DC sources 110 connected to receive the DC power supply. The pair from the clamps 70-3 and 70-4 at the output side terminals in the DC-DC converter 70a is with the pair out of the clamps 70-3 respectively. 70-4 at the output side terminals of the DC-DC converter 70b connected.

Furthermore, the pair is out of the clamps 70-3 and 70-4 at the output side terminals in each of the DC-DC converters 70a and 70b with the discharge circuit 80 connected. The pair from the clamps 70-3 and 70-4 at the output side terminals in each of the DC-DC converters 70a and 70b is also with the consumer 120 connected. That means, the output side connections, those with the second line path 22 in each of the DC-DC converters 70a and 70b are connected to the discharge circuit 80 and the consumer 120 connected in parallel.

The first AC-DC conversion circuit 4 dismisses the pair from the clamps 4-1 and 4-2 at the DC-side terminals and the pair from the terminals 4-3 and 4-4 at the AC-side terminals. That is, the DC side terminals of the first AC-DC conversion circuit 4 are with the first conduction path 21 connected and the AC-side terminals of the first AC-DC conversion circuit 4 are with the third conduction path 23 connected.

The second AC-DC conversion circuit 5 dismisses the pair from the clamps 5-1 and 5-2 at the DC-side terminals and the pair from the terminals 5-3 and 5-4 at the AC-side terminals. That is, the DC side terminals of the second AC-DC conversion circuit 5 are with the second conduction path 22 and the AC side terminals of the second AC-DC conversion circuit 5 are with the third conduction path 23 connected.

The DC side terminals of the second AC-DC conversion circuits 5 in the DC-DC converters 70a and 70b they are all connected in parallel.

For each of the DC-DC converters 70a and 70b is the first capacitor 1 with the pair out of the clamps 70-1 and 70-2 on the input-side terminals and the pair of terminals 4-1 and 4-2 at the DC side terminals of the first AC-DC conversion circuit 4 connected. The second capacitor 2 is with the pair out of the clamps 70-3 and 70-4 on the output side terminals and the pair of terminals 5-1 and 5-2 at the DC side terminals of the second AC-DC conversion circuit 5 connected. That means the DC-DC converter 70a and 70b each comprise the first capacitor 1 that with the first conduction path 21 connected to a direct current, and the second capacitor 2 that with the second conduction path 22 connected to another direct current.

For each of the DC-DC converters 70a and 70b is the first capacitor 1 for the purpose of smoothing a DC input to the pair of terminals 70-1 and 70-2 installed on the input side connections. For each of the DC-DC converters 70a and 70b is the second capacitor 2 for the purpose of smoothing a DC output from the pair of terminals 70-3 and 70-4 installed on the output side connections.

For each of the DC-DC converters 70a and 70b is the clamp 4-3 at one of the AC side terminals of the first AC-DC conversion circuit 4 with a primary-side winding 61 of the transformer 6 connected. the clamp 4-4 at the other AC side terminal of the first AC-DC conversion circuit 4 is with the primary-side winding 61 of the transformer 6 via the first current limiting circuit 3 connected.

For each of the DC-DC converters 70a and 70b are the clamp 5-3 and the clamp 5-4 at the AC side terminals of the second AC-DC conversion circuit 5 with a secondary-side winding 62 of the transformer 6 connected.

The first current limiting circuit 3 is not on the in 1 shown arrangement limited and can between the terminal 4-3 at one of the AC side terminals of the first AC-DC conversion circuit 4 and the primary-side winding 61 of the transformer 6 or between one of the pair of clamps 5-3 and 5-4 at the AC side terminals of the second AC-DC conversion circuit 5 and the secondary-side winding 62 of the transformer 6 be connected. That means the pair out of the clamps 4-3 and 4-4 at the AC side terminals of the first AC-DC conversion circuit 4 is with the pair out of the clamps 5-3 and 5-4 at the AC-side terminals of the second AC DC conversion circuit 5 over the transformer 6 and the first current limiting circuit 3 connected. The first current limiting circuit 3 is further connected to the third conduction path 23 connected.

Each of the first AC-DC conversion circuits 4 converts a DC input to each of the DC-DC converters 70a and 70b in an alternating voltage with a frequency of z. B. several hundred Hz or more and performs this primary-side winding 61 of the transformer 6 to. At the transformer 6 is the gear ratio (also called "Umspannungsverhältnis"), a value of the number of turns n2 of the secondary-side winding 62 divided by the number of turns n1 of the primary-side winding 61 , indicated by n = n2 / n1. In this case, the relationship between AC voltage vn1 is the primary-side winding 61 and AC voltage vn2 of the secondary-side winding 62 equal to vn1 = vn2 / n. The second AC-DC conversion circuit 5 converts one from the secondary side winding 62 of the transformer 6 supplied AC voltage to a DC voltage and leads them to the consumer 120 to.

The first current limiting circuit 3 has a first current limiter 31 passing through the third conduction path 23 , the conduction path for alternating current, current flowing controls, and a first switch 32 on. The first current limiter 31 and the first switch 32 are connected in parallel.

The control unit 90 includes a processor 91 and a memory 92 , The control unit 90 controls the DC input to the pair from the terminals 70-1 and 70-2 at the input side terminals and the DC output from the pair of terminals 70-3 and 70-4 at the output side terminals, input and output of each of the DC-DC converters 70a and 70b in the power conversion circuit 95 ,

The memory 92 includes volatile memory, such as B. Random Access Memory, and nonvolatile secondary storage such. B. Flash memory, which are not shown. The memory 92 can a secondary storage, such. As a hard disk, instead of the nonvolatile secondary storage include.

The processor 91 executes a program input from the memory 92 out. Because of the memory 92 includes the secondary memory and the volatile memory, the program from the secondary memory via the volatile memory in the processor 91 entered. The processor 91 can data such. As operating results, to the volatile memory of the memory 92 output or can store the data in the secondary memory via the volatile memory.

The control unit 90 in 1 is through the processor 91 who is in the store 92 stored program executes, or a processing circuit, not shown, such. As an LSI system implemented. Alternatively, a plurality of processors 91 and a plurality of memories 92 cooperate to perform the above-mentioned function, or a plurality of processing circuits may cooperate to perform the above-mentioned function. Alternatively, a combination of a plurality of processors 91 and a plurality of memories 92 and a plurality of processing circuits cooperate to perform the above-mentioned function.

Next, the arrangement and operation of the DC-DC converter 70a and 70b described. 2 FIG. 12 is a circuit diagram of the DC-DC converter in the power converter according to the present embodiment. FIG. 2 is an example in which a half-bridge circuit in each of the DC-DC converters 70a and 70b is used. In 2 is the first AC-DC conversion circuit 4 around a bridge circuit, the two semiconductor devices 4a and 4b used. The second AC-DC conversion circuit 5 is a bridge circuit, the two semiconductor devices 5a and 5b used. On the side of the first AC-DC conversion circuit 4 are the semiconductor devices 4a and 4b connected in series and are the capacitors 1a and 1b are connected in series and are also the set of semiconductor devices 4a and 4b and the set of the capacitors 1a and 1b connected in parallel. On the side of the second AC-DC conversion circuit 5 are the semiconductor devices 5a and 5b connected in series and are the capacitors 2a and 2 B are connected in series and are also the set of semiconductor devices 5a and 5b and the set of the capacitors 2a and 2 B connected in parallel. The sentence from the capacitors 1a and 1b forms the first capacitor 1 and the set of the capacitors 2a and 2 B forms the second capacitor 2 ,

DC, that of input terminals 70-1 and 70-2 in each of the DC-DC converters 70a and 70b the first capacitor 1 is supplied as alternating current from one terminal of the semiconductor devices 4a and 4b and a connection of the capacitors 1a and 1b the primary-side winding 61 of the transformer 6 fed. Alternating current, that of the primary-side winding 61 on the secondary side winding 62 of the transformer 6 is transmitted as DC from one Connection of the semiconductor devices 5a and 5b and a connection of the capacitors 2a and 2 B the second capacitor 2 fed. In the second capacitor 2 stored electricity is the consumer 120 fed.

Each of the DC-DC converters 70a and 70b is controlled so that z. B. the voltage of the second capacitor 2 is set to a desired value. When different from each of the DC-DC converters 70a and 70b on the second capacitor 2 transmitted current proportional to current, that of the second capacitor 2 to the consumer 120 is transmitted, the voltage of the second capacitor 2 always firm. Therefore, the control unit calculates 90 the amount of through each of the DC-DC converters 70a and 70b to the consumer 120 transmitted current based on the difference between the value of the voltage of the second capacitor 2 which is obtained from a voltage sensor (not shown) and a voltage target value of the second capacitor 2 , Then, based on the calculated amount of current, the control unit determines 90 the on and off states of the semiconductor devices in the first AC-DC conversion circuit 4 and the second AC-DC conversion circuit 5 ,

As another process, which is reversed to the process described above, it is also possible to control the electricity consumed by the consumer 120 recovered and in the second condenser 2 is stored, to the first capacitor 1 through each of the DC-DC converters 70a and 70b transferred to. Thus, each of the DC-DC converters 70a and 70b Power transmitted bidirectionally. The primary-side winding 61 and the secondary side winding 62 of the transformer 6 are isolated. That means each of the DC-DC converters 70a and 70b is a bidirectionally isolated DC-DC converter for converting a direct current via alternating current into another direct current.

3 FIG. 12 is a circuit diagram of the DC-DC converter in the power converter according to the present embodiment. FIG. 3 FIG. 14 is an illustration of a case where the second AC-DC conversion circuit. FIG 5 and the second capacitor 2 in 2 are each double. In 3 form the second AC-DC conversion circuits 51 and 52 a bridge circuit using four semiconductor devices 5a . 5b . 5c and 5d , On the side of the second AC-DC conversion circuit 52 are the semiconductor devices 5c and 5d connected in series and are the capacitors 2c and 2d are connected in series and are also the set of semiconductor devices 5c and 5d and set of the capacitors 2c and 2d connected in parallel. A set of the capacitors 2a and 2 B forms a second capacitor 25 and the set of the capacitors 2c and 2d forms a second capacitor 26 , There is also a pair of clamps 70-3 and 70-4 on output side terminals with a pair of terminals 70-5 respectively. 70-6 connected to output side terminals and are the set of capacitors 2a and 2 B and the set of the capacitors 2c and 2d connected in parallel.

Alternating current coming from the input terminals 70-1 and 70-2 from each of the DC-DC converters 70a and 70b the first capacitor 1 supplied and from the primary-side winding 61 on a secondary side winding 63 of the transformer 6 via the first AC-DC conversion circuit 4 is transmitted as DC from a terminal of the semiconductor devices 5c and 5d and a connection of the capacitors 2c and 2d the capacitors 2c and 2d fed. Subsequently, in the capacitors 2a . 2 B . 2c and 2d , the second capacitor 2 , stored electricity to the consumer 120 fed.

As described above, the DC-DC converters 70a and 70b in each case the second capacitors 25 and 26 and the second AC-DC conversion circuits 51 and 52 have the power from the common transformer 6 convert. In this case, the second AC-DC conversion circuits are 51 and 52 and the second capacitors 25 and 26 connected in parallel.

4 FIG. 12 is a circuit diagram of the DC-DC converter in the power converter according to the present embodiment. FIG. 4 is an example in which a full-bridge circuit in each of the DC-DC converters 70a and 70b is used. As in 4 illustrates, the DC-DC converters 70a and 70b be formed by a full bridge circuit. In 4 is a first AC-DC conversion circuit 41 a bridge circuit, the four semiconductor devices 4a . 4b . 4c and 4d used. A second AC-DC conversion circuit 53 is a bridge circuit, the four semiconductor devices 5a . 5b . 5c and 5d used. On the side of the first AC-DC conversion circuit 41 are the semiconductor devices 4a and 4b connected in series and are the semiconductor devices 4c and 4d are connected in series and are also the two sets of semiconductor devices 4a and 4b and the semiconductor devices 4c and 4d and the first capacitor 1 connected in parallel. On the side of the second AC-DC conversion circuit 53 are the semiconductor devices 5a and 5b connected in series and are the semiconductor devices 5c and 5d in row switched and there are also the two sets of the semiconductor devices 5a and 5b and the semiconductor devices 5c and 5d and the second capacitor 2 connected in parallel.

For each of the DC-DC converters 70a and 70b is DC, which comes from the input terminals 70-1 and 70-2 the first capacitor 1 is supplied as alternating current from a terminal of the semiconductor devices 4a and 4b and a terminal of the semiconductor devices 4c and 4d the primary-side winding 61 of the transformer 6 fed. Alternating current, that of the primary-side winding 61 the secondary-side winding 62 of the transformer 6 is supplied as direct current from a terminal of the semiconductor devices 5a and 5b and a terminal of the semiconductor devices 5c and 5d the second capacitor 2 fed. Subsequently, in the second capacitor 2 stored electricity to the consumer 120 fed.

When switching in 4 will be just like the circuit in 2 each of the DC-DC converters 70a and 70b through the control unit 90 controlled such that the voltage of the second capacitor 2 is set to a desired value.

As with the circuit in 2 It is also possible, as another process, which is reversed to the process described above, electricity, that of the consumer 120 recovered and in the second condenser 2 is stored, to the first capacitor 1 through each of the DC-DC converters 70a and 70b transferred to. The primary-side winding 61 and the secondary side winding 62 of the transformer 6 are isolated. That means each of the DC-DC converters 70a and 70b is a bidirectionally isolated DC-DC converter for converting a direct current via alternating current into another direct current.

5 FIG. 12 is a circuit diagram of the DC-DC converter in the power converter according to the present embodiment. FIG. 5 FIG. 14 is an illustration of a case where the second AC-DC conversion circuit. FIG 53 and the second capacitor 2 in 4 are each double. In 5 is a second AC-DC conversion circuit 54 a bridge circuit, the four semiconductor devices 5a . 5b . 5c and 5d is used, and is a second AC-DC conversion circuit 55 a bridge circuit, the four semiconductor devices 5e . 5f . 5g and 5h used. On the side of the second AC-DC conversion circuit 55 are the semiconductor devices 5e and 5f connected in series and are the semiconductor devices 5g and 5h are connected in series and are also the two sets of semiconductor devices and a capacitor 2 B connected in parallel. A set of the capacitors 2a and 2 B forms the second capacitor 2 , A clamp 70-3 on an output side terminal is with a terminal 70-5 connected to an output side terminal and a terminal 70-4 on an output side connection is separate with a clamp 70-6 connected to an output side terminal so that the capacitors 2a and 2 B are connected in parallel.

Further, in each of the DC-DC converters 70a and 70b Alternating current coming from the input terminals 70-1 and 70-2 the first capacitor 1 supplied and from the primary-side winding 61 on a secondary side winding 63 of the transformer 6 via the first AC-DC conversion circuit 41 is transmitted as a direct current from a terminal of the semiconductor devices 5e and 5f and a terminal of the semiconductor devices 5g and 5h the capacitor 2 B fed. Subsequently, in the capacitors 2a and 2 B , the second capacitor 2 , stored electricity to the consumer 120 fed.

As described above, the DC-DC converters 70a and 70b in each case the second capacitors 2a and 2 B and the second AC-DC conversion circuits 54 and 55 have the power from the common transformer 6 convert. In this case, the second AC-DC conversion circuit 54 and the second capacitor 2a connected in parallel and the second AC-DC conversion circuit 55 and the second capacitor 2 B connected in parallel.

Each of the DC-DC converters 70a and 70b is not on the circuit arrangements 2 to 5 limited and only has to be able to transmit direct current bi-directionally, and the primary-side winding 61 and the secondary side winding 62 have, by the transformer 6 are electrically isolated.

As described above, the arrangement in which electricity to the consumer 120 over the DC-DC converter 70a and 70b is supplied, an electrical insulation between the DC power sources 110 and the consumer 120 provide. Furthermore, if the power converter 100 according to the present embodiment, by at least two DC-DC converters 70a and 70b is formed, in the event of an anomaly in one of the DC-DC converter, a remaining normal DC-DC converter continue the power supply to the load, so that the redundancy of the power converter increases.

The number of DC-DC converters 70a and 70b is determined according to the amount of electricity that the consumer 120 needed. DC, the DC-DC converters 70a and 70b each is supplied, can from the same DC power source 110 can be supplied or can from different DC sources 110 be supplied. The number of DC-DC converters 70a and 70b is not limited to two and only needs to be at least one.

6 FIG. 12 is a diagram illustrating a modification of the circuit diagram of the power converter according to the present embodiment. FIG. At an in 6 illustrated power conversion system 201 includes a power conversion circuit 96 a power converter 101 a DC-DC converter 70a ,

At the power converters 100 and 101 According to the present embodiment, the discharge circuit 80 with the second capacitor 2 connected in parallel. The discharge circuit 80 is through a discharge switch 81 and a discharge resistor 82 formed, which are connected in series. If an overvoltage in the second capacitor 2 is generated, the discharge switch 81 shorted. When the discharge switch 81 is shorted, the charge in the second capacitor 2 quickly derived to the overvoltage in the second capacitor 2 to control. If a short circuit or a ground fault in a section in the power converters 100 and 101 occurs or if z. B. a failure of a semiconductor device occurs, the discharge switch 81 also to protect the power converters 100 and 101 be shorted.

Here is a procedure for starting the power converter 100 described. So that the power converter 100 according to the present embodiment, the power supply to the consumer 120 starts, the first capacitors must 1 and the second capacitors 2 previously charged to a predetermined voltage. A process to charge the first capacitors 1 and the second capacitors 2 , which are smoothing capacitors, before starting the converter 100 is called "pre-loading".

First, a start of the power converter 100 from a state where there is no charge in both the first capacitors 1 as well as the second capacitors 2 is left over. When the first capacitors 1 be summoned, the power converter 100 with the DC power sources 110 connected via a resistor. Alternatively, the DC sources 110 and the power converter 100 connected to the condition that from the DC sources 110 supplied voltage is zero, and that of the DC sources 110 supplied voltage is gradually increased to a specified voltage.

For each of the DC-DC converters 70a and 70b are the first capacitor 1 and the second capacitor 2 through the transformer 6 electrically isolated. Therefore, the second capacitor 2 can not be charged unless both or one of the first AC-DC conversion circuit 4 and the second AC-DC conversion circuit 5 is operated.

Furthermore, a current path that the transformer 6 includes, typically a low impedance. Consequently, when the switching of the semiconductor devices 4a . 4b . 4c and 4d and switching the semiconductor devices 5a . 5b . 5c and 5d the first AC-DC conversion circuit 4 and the second AC-DC conversion circuit 5 be started in a state in which the voltage difference between the first capacitor 1 and the second capacitor 2 is high, the inrush current is excessive.

Therefore, while the first capacitor 1 through the DC power source 110 is charged, the DC-DC converter 70a and 70b each operated so that electricity from the first capacitor 1 on the second capacitor 2 is transmitted. That means the first capacitor 1 and the second capacitor 2 must be pre-charged at the same time to prevent the voltage difference between the first capacitor 1 and the second capacitor 2 gets too big.

Next is a reboot after the discharge switch 81 shorted and the second capacitors 2 were discharged quickly described. Thus the DC-DC converter 70a and 70b the power supply to the consumer 120 restart after the second capacitors 2 have been discharged, the second capacitors 2 be summoned.

However, when the discharge switch 81 is shorted to perform a protection operation, only the second capacitors 2 discharge while the first capacitors 1 be kept in the charged state. Consequently, when the switching of the first AC-DC conversion circuits 4 for charging the second capacitors 2 is started, the voltage difference between the first capacitors 1 and the second capacitors 2 applied to the impedance of current paths which the transformers 6 and may cause excessive inrush current.

The higher the current capacity of the converter 100 is, the higher is usually the capacity of the first capacitors 1 and the second capacitors 2 , The higher the capacity of the first capacitors 1 and the second capacitors 2 or the smaller the impedance of charge current paths, the greater the inrush current.

In order to solve the problem, the first AC-DC conversion circuits must 4 when precharging the second capacitors 2 be switched with a sufficiently high operating frequency. However, the semiconductor devices used in high capacity power converters are 4a . 4b . 4c and 4d and semiconductor devices 5a . 5b . 5c and 5d limited in operating switching speed due to limitations of device characteristics.

Alternatively, there is a conceivable method in which the DC-DC converter 70a and 70b be disconnected from the power sources and then the first capacitors 1 discharged by a discharge circuit (not shown) and then the first capacitors 1 and the second capacitors 2 be reloaded at the same time. However, this procedure increases the time it takes to supply the power to the load 120 is restarted. It also increases due to the disconnection and reconnection of the converter 100 and the DC sources 110 the number of operations in a main switch between each of the DC-DC converters 70a and 70b and the DC power source 110 is provided for switching between the power supply and interruption. Furthermore, it is shortened by the increased number of charges and discharges of the first capacitors 1 the life of the first capacitors 1 ,

To solve the above problem, the power converter includes 100 According to the present embodiment, the first current limiting circuit 3 connected to a terminal of the primary-side winding 61 of at least one of the respective transformers 6 the DC-DC converter 70a and 70b connected is. The first current limiting circuit 3 is with the third conduction path 23 connected. The first current limiting circuit 3 indicates the first current limiter 31 passing through the third conduction path 23 , the conduction path for alternating current, current flowing controls, and the first switch 32 on. The first current limiter 31 and the first switch 32 are connected in parallel.

If only the second capacitors 2 be recharged after the second capacitors 2 by shorting the discharge switch 81 are discharged, the DC-DC converter 70a or 70b that's the first switch 32 includes, with the first switch open 32 operated, so that electricity from the first capacitors 1 on the second capacitors 2 is transmitted.

This being the first current limiter 31 is included in the charge current path, the impedance of the charging current path increases temporarily. Therefore, even if a voltage difference between the first capacitors 1 and the second capacitors 2 present, an inrush current that comes with the charging of the second capacitors 2 is accompanied, controlled. That means the first current limiting circuit 3 controls the current flowing through the third conduction path 23 , the conduction path for alternating current, flows.

The first switch 32 is shorted after the voltage of the second capacitors 2 has reached a predetermined value or after the voltage difference between the first capacitors 1 and the second capacitors 2 has become smaller than a predetermined value. This creates a current path that is the first current limiter 31 bypasses so that it is possible to prevent operation when restarting the power supply to the consumer 120 is impaired.

Furthermore, it is possible to use a variable resistor which is the resistance value as the first current limiter 31 in the first current limiting circuit 3 can change to switch at first 32 to renounce. This arrangement can also control current through the third conduction path 23 , the conduction path for alternating current, flows.

The first current limiter 31 is z. B. designed as a resistor or choke. To the first current limiting circuit 3 cost-effective to implement, it is the first current limiter 31 preferably a resistor.

On the other hand, as the DC-DC converter 70a and 70b operate at a high frequency of a few hundred Hz or more, even if the first current limiter 31 is a choke, the inrush current is controlled by increasing the impedance. A choke, due to its low resistance loss during precharge, is suitable for use that is frequently started and stopped. It goes without saying that the first current limiter 31 can be implemented as a combination of a resistor and a throttle.

A spot where the first current limiting circuit 3 installed, instead of the terminal of the primary-side winding 61 of the transformer 6 between the first capacitor 1 and the first AC-DC conversion circuit 4 or between the second AC-DC conversion circuit 5 and the second capacitor 2 be what the same effects are to be expected. Thus, the first current limiting circuit 3 between the first capacitor 1 and the first AC-DC conversion circuit 4 or between the second AC-DC conversion circuit 5 and the second capacitor 2 be installed.

The wiring between the first capacitor 1 and the first AC-DC conversion circuit 4 and the wiring between the second AC-DC conversion circuit 5 and the second capacitor 2 However, it is typically designed such that the parasitic inductance is low. The purpose here is to reduce a surge in the switching of the semiconductor devices 4a . 4b . 4c and 4d and the semiconductor devices 5a . 5b . 5c and 5d occurs.

This increases by installing the first current limiting circuit 3 between the first capacitor 1 and the first AC-DC conversion circuit 4 or between the second AC-DC conversion circuit 5 and the second capacitor 2 typically the wiring length, which is very likely to affect the operation of the DC-DC converter 70a and 70b effect.

On the other hand, the windings of the transformer include 6 some inductance components. The inductance components are for the operation of the DC-DC converter 70a and 70b required.

Therefore, it is more desirable to use the first current limiting circuit 3 to a terminal of the transformer 6 to join. This arrangement can prevent an increase in parasitic inductance, which affects the switching of a main device, so that the effects on the operation of a main circuit can be minimized and the arrangement and wiring of components are facilitated.

Further, a location at which the first current limiting circuit 3 is installed, a terminal of the secondary-side winding 62 of the transformer 6 be what the same effects are to be expected. When the first current limiting circuit 3 on the secondary-side winding 62 of the transformer 6 However, there is the possibility that magnetizing inrush current in the transformer 6 increases.

The excitation impedance of the transformer 6 is usually higher than the short circuit impedance. Thus, magnetizing current is in the transformer 6 lower than the pre-charge current in the second capacitor 2 , When switching the DC-DC converter 70a and 70b started and a square wave voltage to the primary-side winding 61 is applied, the internal magnetic flux in the transformer 6 but temporarily biased depending on the phase of the voltage. This lowers the excitation impedance when the transformer 6 causes saturation magnetization due to the bias, resulting in a magnetizing inrush current. In addition to the pre-charge current in the second capacitor 2 this current flows through the semiconductor devices 4a . 4b . 4c and 4d and the semiconductor devices 5a . 5b . 5c and 5d the DC-DC converter 70a and 70b ,

Therefore, the first current limiting circuit 3 Control power more efficiently at start-up, if it is on the primary-side winding 61 instead of the secondary-side winding 62 of the transformer 6 is installed. However, with regard to the design of the transformer 6 if it can be determined that the effects of a magnetizing inrush current are low, the first current limiting circuit 3 on the secondary-side winding 62 of the transformer 6 for easier installation and wiring of components.

When the power converter 100 According to the present embodiment, at least two DC-DC converters 70a and 70b includes, the first current limiting circuit 3 in at least one of the DC-DC converters 70a and 70b be installed. The pairs from the clamps 70-3 and 70-4 at the output terminals of the DC-DC converter 70a and 70b are connected in parallel. That means that all second capacitors 2 are connected in parallel. Therefore, when the second capacitor 2 by operating one of the DC-DC converters 70a and 70b in which the first current limiting circuit 3 is installed, charging, the other second capacitor 2 also loaded.

As above, the power converter according to the present embodiment includes the first current limiting circuit 3 passing through the third conduction path 23 , the conduction path for alternating current, current flowing controls, so even if the voltage difference between the first capacitors 1 and the second capacitors 2 is high, the inrush current by precharging the second capacitors 2 over the first current limiter 31 can be controlled.

Furthermore, the power converter according to the present embodiment includes the first current limiting circuit 3 that with the third conduction path 23 , the conduction path for alternating current, which achieves the same effects while preventing the parasitic inductance from increasing so much that it interferes with the operation of the main circuit.

Furthermore, the power converter includes 100 , as in 1 , at least two DC-DC converters 70a and 70b so even if one of the DC-DC converters 70a and 70b is disturbed and fails, the other the DC-DC converter 70a and 70b can be driven without interference. Thus, the reliability of the converter increases 100 ,

Even if the first current limiting circuit 3 in the single DC-DC converter 70a is installed, as with the power converter 101 in 6 shown, the inrush current can also by precharging the second capacitor 2 over the first current limiter 31 to be controlled.

Second embodiment.

7 FIG. 15 is a diagram illustrating a charging process of capacitors in a power converter according to a second embodiment for practicing this invention. FIG. 7 schematically represents a voltage ratio (hereinafter referred to as "voltage ratio") vC2 / (n * vC1) in performing the charging operation described above. The voltage ratio becomes the value of the voltage vC2 of the second capacitor 2 obtained by the gear ratio n and the voltage vC1 of the first capacitor 1 divided. The gear ratio n becomes the value of the number of turns n2 of the secondary-side winding 62 in the transformer 6 divided by the number of turns n1 of the primary-side winding 61 , receive.

In 7 The horizontal axes in the top, middle and bottom lines represent the time. The vertical axis in the upper line represents the voltage ratio vC2 / (n · vC1). The vertical axis in the middle row gives the voltage vC2 of the second capacitor 2 again. The vertical axis in the bottom row gives the peak value of the second capacitor 2 flowing charging current again. Waveforms with continuous lines are in 7 for waveforms where the first switch 32 is shorted at a time t1. Waveforms with dashed lines are in 7 for waveforms where the first switch 32 is not short-circuited at time t1 (open). The voltage vC1 of the first capacitor 1 and the voltage vC2 of the second capacitor 2 after completion of loading, the relation vC1 = vC2 / n. Thus, the voltage ratio vC2 / (n · vC1) for the vertical axis becomes 7 used.

As described in the first embodiment, when the first switch 32 is open and the second capacitor 2 is charged while the inrush current is controlled, the time required for charging, as in the waveforms with the broken lines in 7 elevated. A problem in a case where inrush current (ie charging current) during charging of the second capacitor 2 is suppressed, is the peak value of the charging current, which is generated during the charging process.

In 7 takes when the second capacitor 2 over the first current limiter 31 is charged, the peak value of the charging current while the voltage of the second capacitor 2 increases. Therefore, at time t1, before charging the second capacitor 2 is complete, the first switch 32 be shorted. At the same time the voltage of the second capacitor 2 and the peak value of the charging current in the waveforms with the solid lines in FIG 7 in front. The control unit 90 determines, however, the time t1 such that the peak value of the charging current immediately after the shorting of the first switch 32 does not exceed a permissible value.

Thus, as in 7 shown, after charging start, the voltage ratio vC2 / (n · vC1) gradually and the peak value of the charging current gradually decreases. After the voltage ratio vC2 / (n · vC1) has increased to a certain value, the control unit closes 90 the first switch 32 short. When the voltage vC2 of the second capacitor 2 is higher than a predetermined value a, represents the control unit 90 states that precharging the second capacitor 2 is completed, and starts a normal operating mode. These controls further reduce the time required for charging than when the first switch 32 is not shorted (the waveforms with the dashed lines in 7 ), so far that the peak value of the charging current does not exceed a peak value c immediately after charging.

To reduce the charging time required while avoiding the peak of the second capacitor 2 flowing charging current is too high, the state of the first switch must 32 depending on the voltage difference between the first capacitor 1 and the second capacitor 2 to be selected.

In 7 opens the control unit 90 the first switch 32 and the preloading starts. The voltage ratio vC2 / (n * vC1) gradually increases from zero. The control unit 90 performs a control to short-circuit the first one switch 32 when the voltage ratio vC2 / (n * vC1) is greater than a predetermined value b, and to open the first switch 32 when the voltage ratio vC2 / (n · vC1) is less than or equal to the predetermined value b by.

The value b is set at a value at which the peak value of the charging current does not exceed the peak value c immediately after the charging start. After that puts the control unit 90 fixed when the voltage vC2 of the second capacitor 2 greater than the value a is that the precharging of the second capacitor 2 is completed and starts the normal operating mode. These controls further reduce the time required for charging than when the first switch 32 is not shorted (the waveforms with the dashed lines in 7 ), so far that the peak value of the charging current does not exceed the peak value c immediately after charging.

8th FIG. 10 is a flowchart illustrating the charging operation of the capacitors in the power converter according to the present embodiment. In 8th the boot process described above is illustrated. In 8th vC1, vC2 and n represent the voltage of the first capacitor 1 , the voltage of the second capacitor 2 or the gear ratio, which is the value of the number of turns n2 of the secondary-side winding 62 in the transformer 6 divided by the number of turns n1 of the primary-side winding 61 , acts.

In step S1, the control unit detects 90 if a parent control to the control unit 90 a start command to start the power converter 100 initially outputs the voltage vC2 of the second capacitor 2 ,

In step S2, when the voltage vC2 of the second capacitor 2 greater than the predetermined value a, the control unit 90 notice that the charging of the second capacitor 2 is completed.

Subsequently, in step S7, the normal operating mode is started and the starting of the power converter 100 completed (step S8). As a predetermined value a in this case z. B. a threshold value at which the DC-DC converter 70a and 70b in a state in which they are stable, depending on the consumer 120 required power set.

Further, the control unit detects 90 when the voltage vC2 of the second capacitor 2 is less than the threshold a in step S2 and the precharging of the second capacitor 2 is required, in step S3, the voltage vC1 of the first capacitor 1 for comparison with vC2.

When the voltage ratio vC2 / (n · vC1) is less than or equal to the predetermined value b in step S3, the control unit turns on 90 in step S4, ie it opens the first switch 32 ,

When the voltage ratio vC2 / (n · vC1) is larger than the predetermined value b in step S3, the control unit turns on 90 in step S5, ie it closes the first switch 32 short. The predetermined value b is set in this case to a value at which the charging current in the second capacitor 2 a maximum current in components which the DC-DC converter 70a and 70b do not exceed.

Then the control unit starts 90 in step S6, a precharge mode and starts switching the semiconductor devices 4a . 4b . 4c and 4d and the semiconductor devices 5a . 5b . 5c and 5d in the DC-DC converters 70a and 70b , The DC-DC converter 70a and 70b control switching patterns of the semiconductor devices 4a . 4b . 4c and 4d and the semiconductor devices 5a . 5b . 5c and 5d whereby they are capable of, that of the first capacitor 1 on the second capacitor 2 adjusted amount of electricity. When switching in the precharge mode, a switching pattern is applied in which the amount of current transmitted is limited, so that the charging current in the second capacitor 2 does not exceed the permissible value.

Subsequently, the process returns from step S6 to step S2 and the control unit 90 performs again a first Vorladeschritt by the steps S2, S3, S4 and S6 or a second Vorladeschritt by the steps S2, S3, S5 and S6 until the voltage vC2 of the second capacitor 2 becomes larger than the predetermined value a, that is, until the precharging of the second capacitor 2 is no longer necessary to continue the preload mode.

In the above-described determination process in step S2, when the voltage vC2 of the second capacitor becomes 2 is equal to the threshold a, a determination of "No" is made and proceeded to step S3. Alternatively, when the voltage vC2 of the second capacitor becomes 2 is equal to the threshold a, a determination of "Yes" is made and proceeded to step S7. This means when the voltage vC2 of the second capacitor 2 is equal to the threshold a, a determination made may be either "yes" or "no".

In the above-described determination process in step S3, if the voltage ratio vC2 / (n · vC1) is equal to the value b, a determination of "no" is made and the operation proceeds to step S4. Alternatively, when the voltage ratio vC2 / (n · vC1) is equal to the value b, a determination of "Yes" is made, and the operation proceeds to step S5. The that is, when the voltage ratio vC2 / (n * vC1) is equal to the value b, a determination made may be either "yes" or "no".

9 FIG. 10 is a diagram illustrating an operation of the DC-DC converter in the power converter according to the present embodiment. FIG. 10 FIG. 12 is a diagram illustrating another operation of the DC-DC converter in the power converter according to the present embodiment. The 9 and 10 are examples of switching patterns in precharge mode when dealing with DC-DC converters 70a and 70b is a half bridge, as in 2 shown. In the 9 and 10 the horizontal axes represent the time. The vertical axes indicate the operating states of the semiconductor devices 4a . 4b . 5a and 5b again.

In 9 only the two semiconductor devices 4a and 4b the first AC-DC conversion circuit 4 switched at a given frequency so that the line ratio is 50%. In this case, the second AC-DC conversion circuit operates 5 as a diode rectifier. In 10 become the semiconductor devices 5a and 5b the second AC-DC conversion circuit 5 switched at a line ratio of 50% and at a given frequency. The switching pattern of the semiconductor devices 5a and 5b the second AC-DC conversion circuit 5 is equal to the switching pattern of the semiconductor devices 4a and 4b the first AC-DC conversion circuit 4 ,

At the in 8th shown start sequence first exceeds the voltage ratio vC2 / (n · vC1) the threshold b and the first switch 32 will be shorted. Further, upon further charging of the second capacitor 2 when the voltage vC2 of the second capacitor 2 is greater than the threshold a, it is determined that the precharge is complete and the startup is complete, and the DC / DC converters 70a and 70b go into the normal operating mode.

With the above-described method, the same effects as those of the first embodiment can be obtained and, in addition, the time required for precharging the second capacitor can be reduced 2 is required.

When the voltage ratio vC2 / (n * vC1) is larger than the predetermined value b in step S3 in FIG 8th , in step S5, closes the control unit 90 the first switch 32 short (turns it on). If it is not necessary to reduce the time required for precharge, the control unit may 90 in step S5, the first switch 32 leave open (off) as in step S4. That means the control unit 90 performs a control in which step S5 of the second precharge step of steps S2, S3, S5 and S6 is replaced by step S4.

As with the power converter 101 in 6 can be shown, even if the first current limiting circuit 3 in the single DC-DC converter 70a is installed, the same control as above are performed.

Third embodiment.

11 Fig. 12 is a diagram illustrating an operation for charging capacitors in a power converter according to a third embodiment for practicing this invention. The components of the DC-DC converter 70a and 70b in 11 are the same, so that the reference numerals for the components of the DC-DC converter 70b be omitted.

In 11 differs a power conversion system 202 according to the present embodiment of the first embodiment in that it is a power converter 102 instead of the power converter 100 in 1 and an AC power source 111 instead of the two DC sources 110 in 1 includes.

The power converter 102 includes a power conversion circuit 97 instead of the power conversion circuit 95 in 1 and a control unit 90 , The power conversion circuit 97 includes the two DC-DC converters 70a and 70b , a discharge circuit 80 and an AC-DC power converter 71 , The power conversion circuit 97 differs from the power conversion circuit 95 in 1 in that it further comprises the AC-DC power converter 71 includes.

The AC-DC converter 71 includes two third AC-DC conversion circuits 7 , a second current limiting circuit 8th passing through a line path for alternating current from the AC source 111 flowing electricity controls, a main switch 9 switching between power supply and interruption, a throttle 10 , two pairs from the clamps 71-1 and 71-2 such as 71-3 and 71-4 on DC side connections and a pair off the terminals 71-5 and 71-6 at AC-side terminals, which are for the third AC-DC conversion circuits 7 are provided. The AC-DC converter 71 Converts AC and DC into each other.

In this case forms a path for AC power from the AC source 111 a fourth conduction path 24 , The fourth route 24 is a conduction path from the AC power source 111 to a pair out of the clamps 7-3 and 7-4 at AC side terminals of each third AC-DC conversion circuit 7 in 11 ,

In 11 is the pair out of the clamps 71-5 and 71-6 at the AC side terminals in the AC-DC converter 71 with the AC power source 111 connected. The two pairs from the clamps 71-1 and 71-2 such as 71-3 and 71-4 at the DC side terminals in the AC-DC converter 71 are with the corresponding pairs of clamps 70-1 and 70-2 at input side terminals of the DC-DC converter 70a and 70b connected.

The third AC-DC conversion circuits 7 each have a pair of the terminals 7-1 and 7-2 on DC side terminals that form a DC conduction path, and the pair on the terminals 7-3 and 7-4 at the AC side terminals, which forms a conduction path for AC. DC terminals of the third AC-DC conversion circuits 7 are with a first conduction path 21 connected and AC terminals of the third AC-DC conversion circuits 7 are with the fourth conduction path 24 connected.

The respective pairs from the clamps 7-1 and 7-2 at the DC side terminals of the two third AC-DC conversion circuits 7 are with the corresponding two pairs of the terminals 71-1 and 71-2 such as 71-3 and 71-4 at the DC side terminals in the AC-DC converter 71 connected. That means the pairs out of the clamps 7-1 and 7-2 at the DC side terminals of the two third AC-DC conversion circuits 7 are with the corresponding pairs of clamps 4-1 respectively. 4-2 at DC side terminals of the two first AC-DC conversion circuits 4 connected.

The respective pairs from the clamps 7-3 and 7-4 at the AC side terminals of the two third AC-DC conversion circuits 7 they are all connected in series. the clamp 7-3 at one of the AC side terminals of one of the two third AC-DC conversion circuits 7 is with the clamp 71-5 at one of the AC side terminals in the AC-DC converter 71 over the throttle 10 , the second current limiting circuit 8th and the main switch 9 connected. the clamp 7-4 at the other AC side terminal of the other of the two third AC-DC conversion circuits 7 is with the clamp 71-6 at the other AC-side terminal in the AC-DC converter 71 connected. That means the main switch 9 is with the AC side terminal in the AC-DC converter 71 connected.

The second current limiting circuit 8th has a second current limiter 83 passing through the fourth conduction path 24 , the conduction path for AC power from the AC power source 111 , flowing current controls, and a second switch 84 on. The second current limiter 83 and the second switch 84 are connected in parallel.

The third AC-DC conversion circuits 7 Convert alternating current and direct current into each other. The third AC-DC conversion circuits 7 convert an AC input from the AC source 111 to the AC-DC converter 71 in DC voltage and lead them to the respective pairs of the terminals 70-1 and 70-2 at the input side terminals of the DC-DC converter 70a and 70b to.

Next to the input and output of each of the DC-DC converters 70a and 70b controls the control unit 90 an AC input to the pair from the terminals 71-5 and 71-6 at the AC side terminals and a DC output from the two pairs of terminals 71-1 and 71-2 such as 71-3 and 71-4 at the DC side terminals, these currents being the input and output of the AC to DC converter 71 are.

12 FIG. 12 is a circuit diagram of the AC-DC converter in the power converter according to the present embodiment. FIG. The third AC-DC conversion circuits 7 each form a bridge circuit, such. In 12 shown. In 12 are the semiconductor devices 7a and 7b Connected in series are the semiconductor devices 7c and 7d connected in series and further, the two sets of semiconductor devices are connected in parallel. A connection of the semiconductor devices 7a and 7b forms the clamp 7-3 at one of the AC side terminals in the third AC-DC conversion circuit 7 and a terminal of the semiconductor devices 7c and 7d forms the clamp 7-4 at the other AC side terminal in the third AC-DC conversion circuit 7 , Furthermore, the terminal forms the semiconductor devices 7a and 7c the clamp 7-1 at one of the DC side terminals in the third AC-DC conversion circuit 7 and forms the terminal of the semiconductor devices 7b and 7d the clamp 7-2 at the other DC side terminal in the third AC-DC conversion circuit 7 ,

Next, an operation of the third AC-DC conversion circuits 7 with reference to a vector diagram in 13 described.

13 FIG. 15 is a vector diagram illustrating an operation of the AC-DC converter in the power converter according to the present embodiment. FIG. Here, the voltage of the AC power source Vs, one through the throttle 10 flowing AC is Is, an AC output from the nth third AC-DC conversion circuit 7 to the pair from the clamps 7-3 and 7-4 at the AC side terminals in the third AC-DC conversion circuit 7 is Vn, the total of V1 to Vn is equal to Vg and the impedance of the choke 10 is X.

A voltage corresponding to the difference between Vs and Vg goes to the choke 10 applied and a current with a phase delay of 90 ° with respect to the applied voltage flows through the throttle 10 , The resistance of the throttle 10 is not considered. Therefore, by making the third AC-DC conversion circuits 7 adjust the size and phase of Vg, the size and phase of the current is t controlled. 13 FIG. 12 is a vector diagram in which Vg is output such that the power factor on the AC power source side is equal to one.

The larger the current Is, the greater the current that is in the pairs of terminals 7-1 and 7-2 at the DC side terminals of the third AC-DC conversion circuits 7 flows. The pairs from the clamps 7-1 and 7-2 at the DC side terminals of the third AC-DC conversion circuits 7 are with the corresponding pairs of clamps 4-1 respectively. 4-2 at the DC side terminals of the two first AC-DC conversion circuits 4 connected and are connected to the first capacitors 1 connected. Therefore, the third AC-DC conversion circuits 7 by adjusting the magnitude and phase of Vg, the voltage of the first capacitors 1 Taxes.

The control unit 90 receives the voltage of the first capacitors 1 from a voltage sensor (not shown) and calculates a setpoint for the current Is of the reactor 10 based on the difference between the detected voltage value of the first capacitors 1 and a target voltage value of the first capacitors 1 , Furthermore, the control unit receives 90 an actual value of the current Is from a current sensor (not shown), compares the detected current value of the current Is and the set value of the current Is, and calculates a target value for the output voltage Vg of the third AC-DC conversion circuits 7 , Subsequently, the on and off states of the semiconductor devices become 7a to 7d determined based on the target value of the output voltage Vg.

As described above, converts the power converter 102 according to the present embodiment, from the AC power source 111 AC power obtained in direct current through the third AC-DC conversion circuits 7 and converts the converted direct current to the respective pairs from the terminals 70-1 and 70-2 at the input side terminals of the DC-DC converter 70a and 70b to. Thereupon, DC, which is in a desired voltage through the DC-DC converter 70a and 70b was converted to a consumer 120 fed. These are the AC power source 111 and the consumer 120 through a transformer 6 in each of the DC-DC converters 70a and 70b electrically isolated.

On the other hand, as an arrangement of a device, the power from the AC source 111 receives and electricity to the consumer 120 after electrical insulation has been provided, an arrangement as in 14 conceivable.

14 is a circuit diagram in a conventional power converter. In a power conversion system 900 in 14 becomes AC from an AC source 111 through a transformer 806 in a power converter 800 isolated and an AC-DC conversion circuit 807 fed. AC becomes DC through the AC-DC conversion circuit 807 converted and the DC becomes a consumer 120 fed. In this arrangement, the transformer 806 designed to be at the same frequency as the AC source 111 to work. As the frequency of the AC power source 111 is in this case typically z. B. a frequency of 50 Hz or 60 Hz applied.

When the terminal voltage in the transformer 806 is set constant, so the higher the operating frequency of the transformer 806 is that through a core inside the transformer 806 flowing magnetic flux all the smaller. The smaller the through the core inside the transformer 806 flowing magnetic flux, the smaller the cross-sectional area of the core inside the transformer 806 be executed.

On the other hand, the DC converters lead 70a and 70b in the present embodiment 1 or 11 the switching operation at a frequency of a few hundred Hz or more. Therefore, the transformer 6 in each of the DC-DC converters 70a and 70b designed for a frequency of a few hundred Hz or more. Consequently, the size of the transformer 6 in 1 or 11 opposite the transformer 806 in 14 be reduced.

In the converter 102 According to the present embodiment, semiconductor devices used 4a . 4b . 4c . 4d . 5a . 5b . 5c . 5d . 7a . 7b . 7c and 7d is it z. B. insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs) or the like. In IGBTs, the withstand voltage limit of currently widely used devices is about 6.5 kV. In the bridge circuit, as in the 2 . 3 . 4 . 5 or 12 As shown, the withstand voltage per semiconductor device must be about twice as high as the DC voltage, including a tolerance range. Therefore, in the bridge circuit, as in the 2 . 3 . 4 . 5 or 12 shown, the nominal voltage limit of the first capacitors 1 and the second capacitors 2 in the range of 3 kV to 4 kV.

Further, with reference to the vector diagram in FIG 13 determine that the voltage amplitude of Vg must be greater than that of Vs, so that the controller can control the power factor of the AC power source 111 can adjust to one. The fundamental wave amplitude of the voltage which the third AC-DC conversion circuits 7 to the couples from the clamps 7-3 and 7-4 at the AC side terminals in the third AC-DC conversion circuits 7 can output the same value as the voltage of the first capacitors 1 at a maximum. By applying the so-called overmodulation method to PWM, the fundamental wave amplitude of the voltage applied to the pairs from the terminals 7-3 and 7-4 at the AC side terminals in the third AC-DC conversion circuits 7 can be increased, but this is not desirable, as this leads to a distortion of the current in the AC power source 111 leads. Therefore, in the power factor control, the AC power source is 111 to one, the control of the third AC-DC conversion circuits 7 a stress-increasing process.

As above, when a third AC-DC conversion circuit 7 is present, the connectable voltage of the AC power source 111 limited. When two third AC-DC conversion circuits 7 In the present embodiment, the pairs are out of the clamps 7-3 and 7-4 at the AC side terminals of the third AC-DC conversion circuits 7 connected in series to each current from the AC source 111 so that the power converter 102 with the AC power source 111 a higher voltage than in the presence of a third AC-DC conversion circuit 7 can be connected.

Further, in an application where the AC power source 111 and the consumer 120 must be electrically isolated by insulation by means of the isolated DC-DC converter 70a and 70b that are provided at a high frequency, the size of the transformers is provided 6 in the power converter 102 be reduced according to the present embodiment. Furthermore, even if the voltage difference between the first capacitors 1 and the second capacitors 2 is high, by precharging the second capacitors 2 via the first current limiting circuits 3 as in the first embodiment, the inrush current can be controlled.

The power conversion circuit 97 of the power converter 102 Can a DC-DC converter 70a include and the AC-DC power converter 71 may be a third AC-DC conversion circuit 7 include.

15 FIG. 12 is a modification of the circuit diagram of the power converter according to the present embodiment. FIG. At an in 15 illustrated power conversion system 203 includes a power conversion circuit 98 a power converter 103 a DC-DC converter 70a and includes an AC to DC power converter 71 a third AC-DC conversion circuit 7 , Even if a first current limiting circuit 3 in the single DC-DC converter 70a can be installed by pre-charging a second capacitor 2 via a first current limiter 31 an inrush current are also controlled.

Fourth embodiment.

In a fourth embodiment, a method for starting the power converter described in the third embodiment 102 described.

16 Fig. 12 is a diagram illustrating an operation of a power converter according to the fourth embodiment for practicing this invention. In 16 The horizontal axes give time in both the top and bottom lines again. The vertical axis in the upper line gives the voltages of the first capacitors 1 and the second capacitors 2 again. The vertical axis in the lower row indicates the operating states of the switching of the first switches 32 , the second switch 84 , the main switch 9 and the DC-DC converter 70a and 70b again, when the first capacitors 1 and the second capacitors 2 getting charged. 16 illustrates the voltages of the first capacitors 1 and the second capacitors 2 as well as the operating conditions of the first switch 32 , the second switch 84 , the main switch 9 and the DC-DC converter 70a and 70b when the power converter 102 is started.

The power converter 102 According to the present embodiment requires that the first capacitors 1 and the second capacitors 2 be charged to a predetermined voltage value before the power supply to the load 120 is started. Therefore, when starting the power converter 102 a pre-charge of the first capacitors 1 and the second capacitors 2 necessary.

To start from a state where neither in the first capacitors 1 still the second capacitors 2 Charge is left, the control unit stops 90 before starting, first the first switch 32 and the second switch 84 shorted, holds the main switch 9 open and has the operation of the DC-DC converter 70a and 70b stopped.

Subsequently, the control unit opens 90 the second switch 84 and closes the main switch 9 short. Thereafter, the third AC-DC conversion circuits operate 7 as a diode rectifier and it will be charging the first capacitors 1 started. At this time, the inrush current becomes due to the effects of the second current limiter 83 controlled. The control unit stops 90 the first switches 32 shorted. 16 illustrates a state in which the main switch 9 from open (off) to shorted (on) when the second switch is on 84 from shorted (on) to open (off). In view of the operating time required for switching the state of the second switch 84 is required, the main switch 9 desirably some time after opening the second switch 84 shorted.

While the first capacitors 1 to be charged, the control unit stops 90 the operation of the DC-DC converter 70a and 70b upright, allowing current from the first capacitors 1 on the second capacitors 2 is transmitted. The reason for this process is that when switching the semiconductor devices 4a . 4b . 4c . 4d . 5a . 5b . 5c and 5d the DC-DC converter 70a and 70b is performed in a state where the voltage difference between the first capacitors 1 and the second capacitors 2 is high, an inrush current may be excessive.

Further, when the voltage of the first capacitors results 1 is less than a predetermined value d, the control unit 90 a controller for opening the second switch 84 by. And if the voltage of the first capacitors 1 becomes larger than the predetermined value d, the control unit performs 90 a controller for short-circuiting the second switch 84 by. If the second switch 84 becomes shorted, becomes the second current limiter 83 bypassed. This can reduce the time required for the voltages of the first capacitors 1 and the second capacitors 2 reach a precharge target.

If neither in the first capacitors 1 still the second capacitors 2 Charge is left, they can be pre-charged at the same time, as described above. The control unit stops 90 the first switches 32 desirably shorted. Because if the first capacitors 1 and the second capacitors 2 simultaneously precharged by a charge equal to zero, the voltage ratio vC2 / (n * vC1) does not become smaller than an estimate in a normal operation. In this case, when you open the first switch 32 the charging current is excessively controlled, resulting in an increase in the time required for precharging.

In 16 leads when the voltage of the first capacitors 1 greater than a predetermined value d, the control unit 90 a controller for short-circuiting the second switch 84 by. However, if it is not necessary to reduce the time required for precharge, the second switch may 84 be kept open.

If only in the second capacitors 2 Charge left over, the charging circuit of the DC-DC converter 70a and 70b for charging the first capacitors 1 be left off. The control unit performs this 90 the same control except for the charging circuit of the DC-DC converter 70a and 70b in 16 by.

Next, with respect to restarting, after shorting the discharge switch 81 described as the second capacitors 2 be quickly discharged and the charge in the second capacitors 2 becomes zero.

17 FIG. 15 is a diagram illustrating an operation of the power converter according to the present embodiment. FIG. In 17 The horizontal axes in the top, middle and bottom lines represent the time. The vertical axis in the upper line gives the voltage ratio vC2 / (n · vC1) again. The vertical axis in the middle row gives the voltage vC2 of the second capacitors 2 again. The vertical axis in the lower row indicates the operating states of the switching of the first switches 32 , the second switch 84 , the main switch 9 and the DC-DC converter 70a and 70b again, when the first capacitors 1 and the second capacitors 2 getting charged. 17 illustrates the voltage ratio vC2 / (n · vC1) and the operating states of the first switch 32 , the second switch 84 , the main switch 9 and the DC-DC converter 70a and 70b when the power converter 102 is started.

Thus the DC-DC converter 70a and 70b the power supply to the consumer 120 restart, the second capacitors need 2 be summoned. Therefore, the control unit performs 90 First, a controller for opening the first switch 32 of at least one of the DC-DC converters 70a and 70b and performs a control to transfer power from the first capacitor 1 on the second capacitor 2 in the DC-DC converter 70a or 70b , this first switch 32 through, so that the second capacitors 2 getting charged. The control unit stops 90 the second switch 84 and the main switch 9 shorted. When restarting after shorting the discharge switch 81 the voltage ratio vC2 / (n * vC1) is less than or equal to the predetermined value b. However, due to the effects of the first current limiter 31 with the charging of the second capacitors 2 accompanying inrush current controlled.

17 FIG. 10 illustrates a state in which a charging circuit of the DC-DC converter. FIG 70a and 70b is performed when the first switch 32 from shorted (on) to open (off). Considering the operating time required to switch the state of the first switch 32 is required, the control is carried out for power transmission from the first capacitors 1 on the second capacitors 2 through the DC-DC converter 70a and 70b desirably some time after opening the first switch 32 ,

The control unit 90 just needs one of the DC-DC converters 70a and 70b who opened the first switch 32 includes, operate. Because all second capacitors 2 operating in parallel with each other, operating only one of the DC-DC converters automatically causes all second capacitors 2 getting charged. If the voltage ratio vC2 / (n * vC1) is greater than the predetermined value b, the control unit may 90 the DC-DC converter 70a or 70b , the first switch not open, ie short-circuited 32 includes, operate.

In 17 opens the control unit 90 the first switch 32 and the preloading starts. The voltage ratio vC2 / (n * vC1) gradually increases from zero. When the voltage ratio vC2 / (n · vC1) is larger than the predetermined value b, the control unit performs 90 a controller for short-circuiting the first switch 32 by. When the voltage ratio vC2 / (n · vC1) is less than or equal to the predetermined value b, the control unit performs 90 a controller for opening the first switch 32 by. The value b is set at a value at which the peak value of the charging current does not exceed a peak value c immediately after charging start, as in the first embodiment. After that puts the control unit 90 when the voltage vC2 is greater than a value a, that the precharging of the second capacitors 2 is completed, and starts a normal operating mode. By these controls, the time required for charging can be reduced so much that the peak value of the charging current does not exceed the peak value c immediately after charging.

Even if the discharge circuit 80 in 11 is not provided, the process is in 17 possible in a case where the second capacitors 2 by the consumer 120 or the like, and the charge in the second capacitors 2 becomes zero.

As described above, the control unit opens 90 of the power converter 102 according to the present embodiment, when neither in the first capacitors 1 still the second capacitors 2 Charge is left, the second switch 84 for simultaneous precharging of the first capacitors 1 and the second capacitors 2 , When the voltage ratio vC2 / (n · vC1) is less than or equal to the predetermined value b, the control unit opens 90 the first switch 32 for pre-charging only the second capacitors 2 , That means the power converter 102 can be started regardless of the charge states of the first and second capacitors while suppressing the inrush current, and the same effects as in the first embodiment can be obtained.

In 17 leads the control unit 90 a controller for short-circuiting the first switch 32 when the voltage ratio vC2 / (n * vC1) is greater than the predetermined value b. However, if it is not necessary to reduce the time required for precharge, the first switch 32 be kept open. Further, in 17 the second switch 84 be in an open state until the voltage vC2 of the second capacitors 2 becomes larger than the predetermined value a.

In the second current limiting circuit 8th can the second switch 84 by using a Variable resistance eliminates the resistance value as the second current limiter 83 can change. By this arrangement can also by the fourth conduction path 24 The conduction path for AC, flowing current can be controlled.

Even if the first current limiting circuit 3 in a DC-DC converter 70a as in the converter 103 in 15 shown, the same control can be performed as above.

Fifth embodiment.

18 Fig. 12 is a circuit diagram of a power converter according to a fifth embodiment for practicing this invention. In 18 differs a power conversion system 204 according to the present embodiment, that of the third embodiment in that it is a power converter 104 instead of the power converter 102 in 11 includes, the power converter 104 a power conversion circuit 99 instead of the power conversion circuit 97 in 11 includes and the power conversion circuit 99 the DC-DC converter 70c and 70d instead of the DC-DC converter 70a and 70b in 11 includes and also balancing resistors 11 includes.

At the power converter 104 in 18 include the DC-DC converter 70c and 70d Furthermore, the compensation resistors formed from resistors 11 , The balancing resistors 11 are with the first capacitors 1 connected in parallel. The voltage of the first capacitors 1 becomes constant at the balancing resistors 11 created. Therefore, the resistance of the trimming resistors becomes 11 set to a sufficiently high value to prevent one in the balancing resistors 11 becomes a problem.

A function of balancing resistors 11 This is a voltage imbalance between the first capacitors 1 to reduce. A voltage imbalance between the first capacitors 1 occurs when a through the DC-DC converter 70c and 70d transmitted power varies individually. A control unit 90 controls the DC-DC converter 70c and 70d and the third AC-DC conversion circuits 7 such that the respective current of the DC-DC converter 70c and 70d not varied. However, since the line pads of the DC-DC converter 70c and 70d and the third AC-DC conversion circuits 7 vary, a certain current imbalance can not be avoided.

Because the balancing resistors 11 with the first capacitors 1 are connected in parallel, the higher the voltage of the first capacitors 1 is the current in the balancing resistors 11 the bigger. By the current in the balancing resistors 11 gets the charge in the first capacitors 1 derived, so the voltage of the first capacitors 1 is lowered. Thus, the balancing resistors 11 a voltage deviation between the first capacitors 1 suppressive function.

Another function of balancing resistors 11 is to prevent charge in the first capacitors 1 lags behind after the power converter 104 was turned off for maintenance, inspection or the like. In a state in which a current path has been interrupted, it takes a very long time for the charge in the first capacitors 1 discharged in a natural way. Thus, it is not desirable that the first capacitors 1 remain electrically charged, even after the power converter 104 was turned off.

For this purpose, a case is assumed in which a discharge switch 81 shorted and the power converter 104 is temporarily switched off for protection. This is while the second capacitors 2 quickly discharge the charge in the first capacitors 1 maintained. The second capacitors 2 do not need to be re-summoned to the power converter 104 to restart. However, when switching the semiconductor devices 4a . 4b . 4c and 4d and when switching the semiconductor devices 5a . 5b . 5c and 5d the first AC-DC conversion circuits 4 and the second AC-DC conversion circuits 5 In this state, an excessive inrush current arise.

One way to prevent the occurrence of inrush current is to use a main switch 9 to open and the first capacitors 1 and the second capacitors 2 pre-charge after the first capacitors 1 through the balancing resistors 11 were unloaded. However, if the power converter 104 is temporarily turned off for protection, the main switch 9 opened each time and on a discharge of the first capacitors 1 maintained. This is an increase in the number of operations at the main switch in consideration of an increase in the time required for the restart 9 and an increase in the number of charges and discharges of the first capacitors 1 undesirable.

Therefore, the control unit 90 of the power converter 104 in the present embodiment, when shorting the discharge switch 81 and switching off the power converter 104 the switching of all semiconductor devices 4a . 4b . 4c . 4d . 5a . 5b . 5c . 5d . 7a . 7b . 7c and 7d on to put them in an off state, and holds the main switch 9 shorted. That means the control unit 90 performs a control of a discharge step in which the discharge switch 81 is shorted and the main switch 9 shorted. By the main switch 9 shorted, can the voltage of the first capacitors 1 be maintained after the power converter 104 was turned off. Further, by opening the first switch 32 for precharging the second capacitors 2 the inrush current are controlled. Consequently, the opening and closing operations on the main switch 9 and the number of charges and discharges of the first capacitors 1 be reduced to the power converter 104 to restart quickly.

If the balancing resistors 11 missing, may be due to the fact that the control unit 90 a controller for shorting the discharge switch 81 and shorting the main switch 9 performs the voltage of the first capacitors 1 be maintained.

Thus, it is for restarting the power converter 104 only required the first switch 32 to open and only the second capacitors 2 so that the opening and closing operations of the main switch 9 and the number of charges and discharges of the first capacitors 1 can be reduced. As a result, wear of the main switch 9 and the first capacitors 1 suppressed.

As in 15 shown, the power conversion circuit 99 a DC-DC converter 70c include and the AC-DC power converter 71 may be a third AC-DC conversion circuit 7 include. Even if the balance resistance 11 in the single DC-DC converter 70c can be installed by maintaining the voltage of the first capacitor 1 as described above, the opening and closing operations of the main switch 9 and the number of charges and discharges of the first capacitor 1 decreases and wear of the main switch 9 and the first capacitor 1 be limited.

In the controller for performing a restart after shorting the discharge switch 81 become the second capacitor 2 quickly discharge and charge in the second capacitors 2 becomes zero; the DC-DC converter 70c and 70d need the balancing resistors 11 do not include. In this state, even after turning off the power converter 104 the control unit 90 also the voltage of the first capacitors 1 maintained by performing a control to the discharge switch 81 short circuit and the main switch 9 to be short-circuited.

This invention provides the current limiter at the terminal of the high-frequency insulator, thereby achieving an effect in which it is possible to start the operation without generating excessive current in the DC-DC converter forming components, even if there is a voltage difference between the two capacitors.

The arrangements illustrated in the above embodiments show examples of the details of the present invention and may be combined with another prior art. The arrangements may be partially omitted or changed without departing from the scope of the present invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2005-73362 A [0004]
• WO 2012/098107 A [0005]
• JP 62-104586 U [0006]

Claims (16)

Power converter ( 100 . 101 . 102 . 103 . 104 ), comprising: at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ) for converting a direct current via alternating current into another direct current, wherein the at least one isolated direct current converter ( 70a . 70b . 70c . 70d ) Comprising: a first capacitor ( 1 . 1a . 1b ) connected to a first conduction path ( 21 ) of a direct current, a second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ), which is connected to a second conduction path ( 22 ) of another direct current, and a first current limiting circuit ( 3 ) through a third conduction path ( 23 ) for AC current flowing controls. Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 1, wherein said first current limiting circuit ( 3 ) with the third conduction path ( 23 ) connected is. Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 1 or 2, wherein the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d Further, a first AC-DC conversion circuit ( 4 ) and a second AC-DC conversion circuit ( 5 . 51 . 52 ), which convert DC and AC into each other, and a transformer ( 6 ), DC terminals of the first AC-DC conversion circuit ( 4 ) with the first conduction path ( 21 ), AC terminals of the first AC-DC conversion circuit ( 4 ) with the third conduction path ( 23 ), DC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ) with the second conduction path ( 22 ), AC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ) with the third conduction path ( 23 ) and the AC terminals of the first AC-DC conversion circuit ( 4 ) with the AC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ) over the transformer ( 6 ) and the first current limiting circuit ( 3 ) are connected. Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 3, wherein said at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ) a plurality of isolated DC-DC converters ( 70a . 70b . 70c . 70d ) and the DC terminals of the second AC-DC conversion circuits ( 5 . 51 . 52 ) in the plurality of isolated DC-DC converters ( 70a . 70b . 70c . 70d ) are all connected in parallel. Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 3, further comprising: an AC-DC converter ( 71 ), which converts alternating current and direct current into one another, whereby the alternating current direct current converter ( 71 ) at least a third AC-DC conversion circuit ( 7 ), which converts AC and DC into each other, and a second current limiting circuit ( 8th ) passing through a fourth conduction path ( 24 ), wherein DC connections of the at least one third AC-to-DC conversion circuit ( 7 ) with the first conduction path ( 21 ) and AC terminals of the at least one third AC-DC conversion circuit ( 7 ) with the fourth conduction path ( 24 ) are connected. Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 5, wherein the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ) a plurality of isolated DC-DC converters ( 70a . 70b . 70c . 70d ), the AC-DC converter ( 71 ) the at least one third AC-DC conversion circuit ( 7 ) comprising a plurality of third AC-DC conversion circuits ( 7 ), the DC terminals of the plurality of third AC-DC conversion circuits ( 7 ) to the respective DC terminals of the first AC-DC conversion circuits ( 4 ) in the plurality of isolated DC-DC converters ( 70a . 70b . 70c . 70d ), the AC terminals of the plurality of third AC-DC conversion circuits ( 7 ) are all connected in series with each other and the DC terminals of the second AC-DC conversion circuits ( 5 . 51 . 52 ) are all connected in parallel. Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 3 or 4, further comprising: a control unit ( 90 ), the input and output of the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ) controls, wherein the first current limiting circuit ( 3 ) a first current limiter ( 31 ), which controls power, and a first switch ( 32 ), which is connected to the first current limiter ( 31 ) is connected in parallel, the transformer ( 6 ) a primary-side winding ( 61 ) connected to the AC terminals of the first AC-to-DC conversion circuit ( 4 ), and a secondary-side winding ( 62 . 63 ) connected to the AC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ), and when a voltage ratio (vC2 / (n * vC1)) is less than or equal to a predetermined value, wherein the voltage ratio (vC2 / (n * vC1)) is a value of a voltage (vC2) of the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) divided by a gear ratio (n), a value of a number of turns (n2) of the secondary-side winding ( 62 . 63 ) divided by a number of turns (n1) of the primary-side winding ( 61 ), and a voltage (vC1) of the first capacitor ( 1 . 1a . 1b ), the control unit ( 90 ) a controller for opening the first switch ( 32 ) and then transmitting power from the first capacitor ( 1 . 1a . 1b ) to the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) in the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ). Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 5 or 6, further comprising: a control unit ( 90 ), the input and output of the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ) and the input and output of the AC-DC converter ( 71 ), wherein the AC-DC converter ( 71 ) further comprises a main switch ( 9 ), which switches between power supply and interruption, the main switch ( 9 ) with the fourth conduction path ( 24 ), the first current limiting circuit ( 3 ) a first current limiter ( 31 ), which controls power, and a first switch ( 32 ), which is connected to the first current limiter ( 31 ) is connected in parallel, the transformer ( 6 ) a primary-side winding ( 61 ) connected to the AC terminals of the first AC-to-DC conversion circuit ( 4 ), and a secondary-side winding ( 62 . 63 ) connected to the AC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ) and the control unit ( 90 ) the main switch ( 9 ) and, when a voltage ratio (vC2 / (n * vC1)) is less than or equal to a predetermined value, wherein the voltage ratio (vC2 / (n * vC1)) is a value of a voltage (vC2) of the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) divided by a gear ratio (n), a value of a number of turns (n2) of the secondary-side winding ( 62 . 63 ) divided by a number of turns (n1) of the primary-side winding ( 61 ), and a voltage (vC1) of the first capacitor ( 1 . 1a . 1b ), a controller for opening the first switch ( 32 ) and then transmitting power from the first capacitor ( 1 . 1a . 1b ) to the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) in the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ). Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 7 or 8, wherein, if the voltage ratio is greater than the predetermined value, the control unit ( 90 ) a controller for short-circuiting the first switch ( 32 ) and transmitting power from the first capacitor ( 1 . 1a . 1b ) to the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) in the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ). Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 5 or 6, further comprising: a control unit ( 90 ), the input and output of the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ) and the input and output of the AC-DC converter ( 71 ), wherein the AC-DC converter ( 71 ) further comprises a main switch ( 9 ), which switches between power supply and interruption, the main switch ( 9 ) with the fourth conduction path ( 24 ), the second current limiting circuit ( 8th ) a second current limiter ( 83 ), which controls power, and a second switch ( 84 ) connected to the second current limiter ( 83 ) is connected in parallel, and when a voltage of the first capacitor ( 1 . 1a . 1b ) is less than or equal to a predetermined value, the control unit ( 90 ) a controller for opening the second switch ( 84 ) and then short circuit the main switch ( 9 ) and transmitting power from the first capacitor ( 1 . 1a . 1b ) to the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) in the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ). Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 10, wherein when the voltage of the first capacitor ( 1 . 1a . 1b ) is greater than the predetermined value, the control unit ( 90 ) a controller for short-circuiting the second switch ( 84 ), Short-circuit the main switch ( 9 ) and transmitting power from the first capacitor ( 1 . 1a . 1b ) to the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) in the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ). Power converter ( 100 . 101 . 102 . 103 . 104 ) according to one of claims 7 to 9, wherein the first current limiter ( 31 ) is a resistor or a choke. Power converter ( 100 . 101 . 102 . 103 . 104 ) according to claim 8, further comprising: a discharge circuit in which a discharge switch and a discharge resistor are connected in series, wherein the discharge circuit with the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) is connected in parallel, and the control unit ( 90 ) short-circuits the discharge switch and the main switch ( 9 ) short circuits. Control method in a power converter ( 100 . 101 . 102 . 103 . 104 ), comprising: at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ) for converting a direct current via alternating current into another direct current, wherein the at least one isolated direct current converter ( 70a . 70b . 70c . 70d ) Comprising: a first capacitor ( 1 . 1a . 1b ) connected to a first conduction path ( 21 ) of a direct current, a second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ), which is connected to a second conduction path ( 22 ) of a different direct current, a first current limiting circuit ( 3 ) through a third conduction path ( 23 ) for AC flowing current, a second current limiting circuit ( 8th ) passing through a fourth conduction path ( 24 ) for alternating current flowing from an AC power source, a first AC-DC conversion circuit ( 4 ) and a second AC-DC conversion circuit ( 5 . 51 . 52 ), which convert DC and AC into each other, and a transformer ( 6 ), wherein DC terminals of the first AC-DC conversion circuit ( 4 ) with the first conduction path ( 21 ), AC terminals of the first AC-DC conversion circuit ( 4 ) with the third conduction path ( 23 ), DC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ) with the second conduction path ( 22 ), AC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ) with the third conduction path ( 23 ), the AC terminals of the first AC-DC conversion circuit ( 4 ) with the AC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ) over the transformer ( 6 ) and the first current limiting circuit ( 3 ) and the first current limiting circuit ( 3 ) a first current limiter ( 31 ), which controls power, and a first switch ( 32 ), which is connected to the first current limiter ( 31 ) is connected in parallel, wherein in the method the transformer ( 6 ) a primary-side winding ( 61 ) connected to the AC terminals of the first AC-to-DC conversion circuit ( 4 ), and a secondary-side winding ( 62 . 63 ) connected to the AC terminals of the second AC-DC conversion circuit ( 5 . 51 . 52 ), when a voltage ratio (vC2 / (n · vC1)) is less than or equal to a predetermined value, wherein the voltage ratio (vC2 / (n · vC1)) is a value of a voltage (vC2) of the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) divided by a gear ratio (n), a value of a number of turns (n2) of the secondary-side winding ( 62 . 63 ) divided by a number of turns (n1) of the primary-side winding ( 61 ), and a voltage (vC1) of the first capacitor ( 1 . 1a . 1b ), is a control unit ( 90 ) a precharge step by opening the first switch ( 32 ) and then transmitting power from the first capacitor ( 1 . 1a . 1b ) to the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) in the at least one isolated DC-DC converter ( 70a . 70b . 70c . 70d ). A control method according to claim 14 in the power converter, further comprising: an AC-DC power converter ( 71 ), which converts alternating current and direct current into one another, whereby the alternating current direct current converter ( 71 ) a third AC-DC conversion circuit ( 7 ), which converts AC and DC into each other, and a main switch ( 9 ), which switches between power supply and interruption, wherein DC connections of the third AC-DC conversion circuit ( 7 ) with the first conduction path ( 21 ), AC terminals of the third AC-DC conversion circuit ( 7 ) with the fourth conduction path ( 24 ) and the main switch ( 9 ) with the fourth conduction path ( 24 ), wherein in the method the main switch ( 9 ) is shorted in the precharge step. Control method according to claim 15 in the power converter ( 100 . 101 . 102 . 103 . 104 ), further comprising: a discharge circuit ( 80 ), in which a discharge switch ( 81 ) and a discharge resistor ( 82 ) are connected in series, the discharge circuit ( 80 ) with the second capacitor ( 2 . 2a . 2 B . 2d . 2c . 25 . 26 ) is connected in parallel, wherein the control unit ( 90 ) a discharging step by short-circuiting the discharge switch ( 81 ) before the precharging step.

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