WO2018061077A1

WO2018061077A1 - Power conversion device

Info

Publication number: WO2018061077A1
Application number: PCT/JP2016/078395
Authority: WO
Inventors: 尊衛嶋田; 瑞紀中原; 祐樹河口; 泰明乗松
Original assignee: 株式会社日立製作所
Priority date: 2016-09-27
Filing date: 2016-09-27
Publication date: 2018-04-05

Abstract

Provided is a low cost power conversion device having little energy loss. A power conversion device (100) is provided with: an inverter (20), etc., that performs power conversion; voltage dividing capacitors (Cdc1, Cdc2) connected to a direct current side of the inverter (20), etc., that perform voltage division of DC voltage applied from the direct current side; and an auxiliary power supply circuit (30) connected to both ends respectively of the voltage dividing capacitors (Cdc1, Cdc2), that inputs to itself a larger current from the voltage dividing capacitor with the higher voltage among the voltage dividing capacitors (Cdc1, Cdc2).

Description

Power converter

The present invention relates to a power conversion device that performs power conversion.

Known are photovoltaic power generation systems that convert DC power generated by solar cells into AC power, inverter devices that drive motors, and uninterruptible power supply systems that continue to supply power to loads even during power outages. . Each of the above systems is usually provided with a capacitor that smoothes the DC voltage. When this DC voltage is higher than the rated voltage of the capacitor or when a voltage obtained by dividing the DC voltage is obtained, a plurality of capacitors connected in series are provided.

However, in a configuration in which a plurality of capacitors are connected in series, when there is a difference in the leakage current of each capacitor, the voltage of each capacitor becomes unbalanced. As a result, the voltage of the capacitor may exceed the rated voltage of the capacitor.

Regarding such a problem, Patent Document 1 describes that a difference in leakage current between a plurality of capacitors connected in series is compensated by a transistor and a resistor to equalize the voltage balance of each capacitor.

Also, Patent Document 2 describes that a plurality of capacitors connected in series are charged by a power supply device, and the voltage between terminals of each capacitor is equalized.

Japanese Patent Laid-Open No. 10-295081 JP 2005-354788 A

However, in the technique described in Patent Document 1, since power is consumed by causing a current accompanying equalization of the capacitor voltage to flow through the transistor and the resistor, energy loss tends to increase.
Further, the technique described in Patent Document 2 requires a power supply device for equalizing the capacitor voltage, which increases costs.

Therefore, an object of the present invention is to provide a low-cost power conversion device with low energy loss.

In order to solve the above problems, a power conversion device according to the present invention includes a power conversion circuit that performs power conversion, and a plurality of DC converters that are connected to a DC side of the power conversion circuit and that divide a DC voltage applied from the DC side. And a power supply circuit that is connected to both ends of each of the plurality of voltage dividing capacitors, and inputs a larger current to itself from a voltage dividing capacitor having a higher voltage among the plurality of voltage dividing capacitors, It is characterized by providing.

According to the present invention, it is possible to provide a low-cost power conversion device with low energy loss.

It is a block diagram containing the power converter device which concerns on 1st Embodiment of this invention. It is a lineblock diagram of an auxiliary power circuit with which a power converter concerning a 1st embodiment of the present invention is provided. It is explanatory drawing regarding operation | movement of the auxiliary power supply circuit with which the power converter device which concerns on 1st Embodiment of this invention is provided. It is a flowchart of the process which the control part of the auxiliary power supply circuit with which the power converter device which concerns on 1st Embodiment of this invention is provided is performed. It is a block diagram of the uninterruptible power supply system to which the power converter device which concerns on 2nd Embodiment of this invention is applied. It is a block diagram of the auxiliary power supply circuit with which the power converter device which concerns on 3rd Embodiment of this invention is provided. It is explanatory drawing in case the voltage V1 is higher than the voltage V2 in the power converter device which concerns on 3rd Embodiment of this invention. It is explanatory drawing in case the voltage V2 is higher than the voltage V1 in the power converter device which concerns on 3rd Embodiment of this invention. In the power converter device which concerns on 3rd Embodiment of this invention, it is explanatory drawing when voltage V1, V2 is substantially equal. It is a block diagram of the auxiliary power circuit with which the power converter device which concerns on 4th Embodiment of this invention is provided. It is a block diagram of the auxiliary power supply circuit with which the power converter device which concerns on the modification of this invention is provided.

<< First Embodiment >>
<Configuration of power converter>
FIG. 1 is a configuration diagram including a power conversion device 100 according to the first embodiment.
The power conversion device 100 is a device that converts the DC power input from the solar cell E into predetermined AC power and outputs the AC power to the power system F.
As shown in FIG. 1, the power conversion apparatus 100 includes a DC-DC converter 10 (power conversion circuit, DC-DC converter), voltage dividing capacitors Cdc1, Cdc2, and an inverter 20 (power conversion circuit). ing. The power conversion device 100 includes an auxiliary power supply circuit 30 (power supply circuit), a control circuit 40 (power supply target), and a fan 50 (power supply target) in addition to the configuration described above. .

The DC-DC converter 10 is a power converter that boosts or lowers a DC voltage. That is, the DC-DC converter 10 has a function of converting the voltage applied from the solar cell E into a predetermined DC voltage Vdc.

The inverter 20 is a power converter that converts a DC voltage into an AC voltage. That is, the inverter 20 has a function of converting a DC voltage smoothed by voltage dividing capacitors Cdc1 and Cdc2 described later into an AC voltage and outputting the AC voltage to the power system F. As shown in FIG. 1, the inverter 20 is connected to the DC-DC converter 10 via a positive-side wiring kp and a negative-side wiring kn.

The voltage dividing capacitors Cdc1 and Cdc2 are capacitors that divide the DC voltage Vdc applied from the DC-DC converter 10, and are connected in series with each other. The voltage dividing capacitors Cdc1 and Cdc2 also have a function of smoothing the DC voltage Vdc.

As shown in FIG. 1, the voltage dividing capacitors Cdc1 and Cdc2 are connected to the output side of the DC-DC converter 10 and to the input side (DC side) of the inverter 20. The positive electrode of one voltage dividing capacitor Cdc1 is connected to the wiring kp, and the negative electrode of the other voltage dividing capacitor Cdc2 is connected to the wiring kn. In the present embodiment, as an example, it is assumed that the rated voltages of the voltage dividing capacitors Cdc1 and Cdc2 are substantially equal.

The auxiliary power supply circuit 30 is a circuit that supplies power to the control circuit 40 using DC power input from the voltage dividing capacitors Cdc1 and Cdc2. The auxiliary power supply circuit 30 also has a function of supplying power to the fan 50 via the control circuit 40.

As shown in FIG. 1, the auxiliary power supply circuit 30 is connected to the positive electrode of the voltage dividing capacitor Cdc1 through the wiring kp1, and is connected to the negative electrode of the voltage dividing capacitor Cdc1 through the wiring kn1.
The auxiliary power supply circuit 30 is connected to the positive electrode of the voltage dividing capacitor Cdc2 through the wiring kp2 and is connected to the negative electrode of the voltage dividing capacitor Cdc2 through the wiring kn2. As described above, the auxiliary power circuit 30 is connected to both ends of the voltage dividing capacitors Cdc1 and Cdc2.

As shown in FIG. 1, the voltage across the voltage dividing capacitor Cdc1 is V1, and the voltage across the voltage dividing capacitor Cdc2 is V2. Further, a current flowing through the voltage dividing capacitor Cdc1, the wiring kp (part), the wiring kp1, the auxiliary power supply circuit 30, and the wiring kn1 in this order is denoted by I1. Further, the current flowing through the voltage dividing capacitor Cdc2, the wiring kp2, the auxiliary power supply circuit 30, and the wiring kn2 in this order is defined as I2.

Note that in FIG. 1, the wirings kn1 and kp2 are illustrated as separate wirings for easy understanding, but these wirings kn1 and kp2 may be a single wiring.

Although not shown, the control circuit 40 includes electronic circuits such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and various interfaces. Then, the program stored in the ROM is read out and expanded in the RAM, and the CPU executes various processes.

The control circuit 40 is driven by the power input from the auxiliary power supply circuit 30 and has a function of controlling the DC-DC converter 10 and the inverter 20. That is, on / off of a switching device (not shown) included in the DC-DC converter 10 and the inverter 20 is switched by the control circuit 40. In addition, the control circuit 40 has a function of controlling the fan 50 described below.

The fan 50 is driven by power supplied via the control circuit 40 and has a function of cooling the DC-DC converter 10 and the inverter 20. That is, a switching device (not shown) included in the DC-DC converter 10 and the inverter 20 is cooled by the fan 50.

<Configuration of auxiliary power circuit>
FIG. 2 is a configuration diagram of the auxiliary power supply circuit 30 included in the power conversion apparatus 100.
As shown in FIG. 2, the auxiliary power circuit 30 includes DC-DC converters 31 and 32 (DC-DC converters),

voltage sensors

33 and 34, and a control unit 35.

The DC-DC converter 31 is a power converter that adjusts the current input from the voltage dividing capacitor Cdc1 according to a command from the control unit 35. The input side of the DC-DC converter 31 is connected to the positive electrode of the voltage dividing capacitor Cdc1 (see FIG. 1) through the wiring kp1, and is connected to the negative electrode of the voltage dividing capacitor Cdc1 through the wiring kn1. In this manner, the DC-DC converter 31 has a one-to-one correspondence with the voltage dividing capacitor Cdc1, and its input side is connected to both ends of the voltage dividing capacitor Cdc1. The output side of the DC-DC converter 31 is connected to the control circuit 40.

The DC-DC converter 32 is a power converter that adjusts the current input from the voltage dividing capacitor Cdc2 according to a command from the control unit 35. The input side of the DC-DC converter 32 is connected to the positive electrode of the voltage dividing capacitor Cdc2 (see FIG. 1) through the wiring kp2, and is connected to the negative electrode of the voltage dividing capacitor Cdc2 through the wiring kn2. As described above, the DC-DC converter 32 has a one-to-one correspondence with the voltage dividing capacitor Cdc2 and its input side is connected to both ends of the voltage dividing capacitor Cdc2. The output side of the DC-DC converter 32 is connected to the control circuit 40.

The DC-

DC converters

31 and 32 may be well-known flyback converters, or may be other types of circuits.

The voltage sensor 33 is a sensor that detects the voltage V1 across the voltage dividing capacitor Cdc1. The voltage sensor 34 is a sensor that detects the voltage V2 across the voltage dividing capacitor Cdc2. The detection values of the

voltage sensors

33 and 34 are output to the control unit 35 described below.

Although not shown, the control unit 35 includes electronic circuits such as a CPU, a ROM, a RAM, and various interfaces. The control unit 35 reads out a program stored in the ROM, expands the program in the RAM, and the CPU executes various processes. It has become. The control unit 35 has a function of controlling the DC-

DC converters

31 and 32. That is, the control unit 35 controls on / off of a switching device (not shown) included in the DC-

DC converters

31 and 32 based on the detection values of the

voltage sensors

33 and 34.

<Operation of auxiliary power circuit>
FIG. 3 is an explanatory diagram relating to the operation of the auxiliary power supply circuit 30.
The horizontal axis in FIG. 3 is the voltage V1 across the voltage dividing capacitor Cdc1. The vertical axis in FIG. 3 is the voltage V2 across the voltage dividing capacitor Cdc2. Moreover, the broken line shown in FIG. 3 is a straight line representing the state of V1 = V2.
The auxiliary power supply circuit 30 performs a predetermined operation according to the magnitude relationship between the voltage V1 of the voltage dividing capacitor Cdc1 and the voltage V2 of the voltage dividing capacitor Cdc2. Hereinafter, the operation of the auxiliary power supply circuit 30 will be described with reference to FIG. 3 and the flowchart of FIG.

FIG. 4 is a flowchart of processing executed by the control unit 35 of the auxiliary power circuit 30.
In step S101, the control unit 35 reads the detection values of the voltages V1 and V2. That is, the control unit 35 reads the detected values of the voltage V1 of the voltage dividing capacitor Cdc1 and the voltage V2 of the voltage dividing capacitor Cdc2.

In step S102, the control unit 35 determines whether or not the voltage V1 of the voltage dividing capacitor Cdc1 is higher than the voltage V2 of the other voltage dividing capacitor Cdc2. When the voltage V1 is higher than the voltage V2 (S102: Yes), the process of the control unit 35 proceeds to step S103.

In step S103, the control unit 35 controls the DC-

DC converters

31 and 32 so that the current I1 is larger than the current I2 (see the region “I1> I2” shown in FIG. 3). For example, the control unit 35 makes the on-duty of the switching device (not shown) of the DC-DC converter 31 larger than the on-duty of the switching device (not shown) of the DC-DC converter 32. As a result, the current I1 flowing from the voltage dividing capacitor Cdc1 becomes larger than the current I2 flowing from the voltage dividing capacitor Cdc2, and the voltages of the voltage dividing capacitors Cdc1 and Cdc2 are equalized (that is, V1 = V2). Approach).

On the other hand, when the voltage V1 is not higher than the voltage V2 in step S102 (S102: No), the process of the control unit 35 proceeds to step S104.
In step S104, the control unit 35 determines whether or not the voltage V2 of the voltage dividing capacitor Cdc2 is higher than the voltage V1 of the other voltage dividing capacitor Cdc1. When the voltage V2 is higher than the voltage V1 (S104: Yes), the process of the control unit 35 proceeds to step S105.

In step S105, the control unit 35 controls the DC-

DC converters

31 and 32 so that the current I2 is larger than the current I1 (refer to the region “I2> I1” shown in FIG. 3). As a result, the voltages of the voltage dividing capacitors Cdc1 and Cdc2 are equalized.

As described above, the control unit 35 adjusts the current I1 flowing from the voltage dividing capacitor Cdc1 to the DC-DC converter 31 based on the detection values of the

voltage sensors

33 and 34, and from the voltage dividing capacitor Cdc2 to the DC-DC converter 32. The current I2 flowing through is adjusted. As described above, the auxiliary power supply circuit 30 operates to input a larger current to itself from the voltage dividing capacitor having a higher voltage among the voltage dividing capacitors Cdc1 and Cdc2.

If the voltage V2 is not higher than the voltage V1 in step S104 (S104: No), the process of the control unit 35 proceeds to step S106. That is, when the voltages V1 and V2 are substantially equal, the process of the control unit 35 proceeds to step S106.
In step S106, the control unit 35 controls the DC-

DC converters

31 and 32 so that the currents I1 and I2 are maintained substantially equal (see the broken line “V1 = V2” shown in FIG. 3).

After performing the process of step S103, S105, or S106, the process of the control unit 35 proceeds to step S107.
In step S107, the control unit 35 determines whether or not a stop command for the power conversion apparatus 100 is input from a host controller or the like (not shown). When the stop instruction | command of the power converter device 100 is input (S107: Yes), the process of the control part 35 progresses to step S108.
In step S108, the control unit 35 stops power supply to the control circuit 40 and the like, and ends a series of processing (END).

On the other hand, when the stop instruction | command of the power converter device 100 is not input in step S107 (S107: No), the process of the control part 35 returns to step S101. Then, as described above, the control unit 35 controls the DC-

DC converters

31 and 32 so as to equalize the voltages of the voltage dividing capacitors Cdc1 and Cdc2.

<Effect>
According to the first embodiment, even if the voltage V1 of the voltage dividing capacitor Cdc1 and the voltage V2 of the voltage dividing capacitor Cdc2 are temporarily imbalanced due to the difference in leakage current, the currents I1, I2 By adjusting the voltage V1, the voltages V1 and V2 can be equalized. Therefore, the voltage of the voltage dividing capacitors Cdc1 and Cdc2 can be suppressed below the rated voltage.

Further, power is supplied to the control circuit 40 and the like using power for equalizing the voltages of the voltage dividing capacitors Cdc1 and Cdc2. Therefore, since there is almost no energy loss accompanying equalization, the power converter 100 can be highly efficient. The auxiliary power supply circuit 30 has both a function of a power supply for supplying power to the control circuit 40 and a function of equalizing the voltages of the voltage dividing capacitors Cdc1 and Cdc2. Therefore, the cost can be reduced compared to a configuration in which a circuit for equalizing the voltages of the voltage dividing capacitors Cdc1 and Cdc2 is provided separately.

If the auxiliary power supply circuit 30 is connected to both ends of the series-connected voltage dividing capacitors Cdc1 and Cdc2, it is necessary to use a high breakdown voltage switching device (not shown) for the auxiliary power supply circuit 30. In contrast, in the present embodiment, both ends of the voltage dividing capacitors Cdc1 and Cdc2 are connected to the auxiliary power circuit 30. Therefore, a device having a relatively low withstand voltage can be used as the switching device of the auxiliary power supply circuit 30, and as a result, the cost of the power conversion device 100 can be reduced.

<< Second Embodiment >>
The second embodiment is different from the first embodiment in that the power conversion device 100A (see FIG. 5) is applied to the uninterruptible power supply system S (see FIG. 5). The configuration and the like (see FIG. 2) are the same as those in the first embodiment. Therefore, a different part from 1st Embodiment is demonstrated and description is abbreviate | omitted about the overlapping part.

FIG. 5 is a configuration diagram of an uninterruptible power supply system S to which the power conversion device 100A according to the second embodiment is applied.
The uninterruptible power supply system S normally converts AC power from the AC power supply G into AC power having a predetermined amplitude and frequency, and also converts DC power from the battery B into predetermined AC power when the AC power supply G fails. System.
As shown in FIG. 5, the uninterruptible power supply system S includes a power conversion device 100A and a battery B.

The power conversion device 100A includes a converter 60 (power conversion circuit, AC / DC converter), an inverter 70, and a DC-DC converter 80 (power conversion circuit, DC-DC converter). In addition to the above-described configuration, the power conversion device 100A includes voltage dividing capacitors Cdc1 and Cdc2, an auxiliary power supply circuit 30, a control circuit 40, and a fan 50.

Converter 60 is a power converter that converts a three-phase AC voltage input from AC power supply G into DC voltage Vdc.
The inverter 70 is a power converter that converts the DC voltage Vdc applied from the converter 60 into an AC voltage and outputs the AC voltage to the AC load H. As shown in FIG. 5, the inverter 70 is connected to the converter 60 via a positive-side wiring kp and a negative-side wiring kn.

The DC-DC converter 80 is a chopper circuit that converts the DC voltage of the battery B into a predetermined DC voltage Vdc when the AC power supply G fails. As shown in FIG. 5, the DC-DC converter 80 has an input side connected to the battery B and an output side connected to the wirings kp and kn.

The voltage dividing capacitors Cdc1 and Cdc2 are capacitors that divide the DC voltage Vdc applied from the converter 60 (the DC-DC converter 80 in the event of a power failure), and are connected in series with each other. As shown in FIG. 5, the voltage dividing capacitors Cdc1 and Cdc2 are connected to the output side (DC side) of the converter 60 and the DC-DC converter 80 and to the input side (DC side) of the inverter 70. .

The auxiliary power circuit 30 has the same configuration as that of the first embodiment, and is connected to both ends of the voltage dividing capacitor Cdc1 and is connected to both ends of the voltage dividing capacitor Cdc2. The operation of the auxiliary power supply circuit 30 is also the same as that of the first embodiment (see FIG. 4), and thus the description thereof is omitted.
Further, since the control circuit 40 and the fan 50 have the same configuration as that of the first embodiment, description thereof is omitted.

The battery B functions as a power source when the AC power source G fails, and is connected to the input side of the DC-DC converter 80.

<Effect>
According to the second embodiment, the auxiliary power supply circuit 30 can supply power to the control circuit 40 while equalizing the voltages of the voltage dividing capacitors Cdc1 and Cdc2. Therefore, energy loss in the auxiliary power supply circuit 30 can be reduced, and the cost of the power conversion device 100A can be reduced. In addition, even if the AC power supply G fails, the power supply to the AC load H can be continued by operating each circuit using the power of the battery B.

«Third embodiment»
The third embodiment differs from the first embodiment in the configuration of the auxiliary power supply circuit 30B (see FIG. 6), but the other (the overall configuration of the power conversion device 100: see FIG. 1) is the same as that in the first embodiment. It is the same. Therefore, a different part from 1st Embodiment is demonstrated and description is abbreviate | omitted about the overlapping part.

<Configuration of auxiliary power circuit>
FIG. 6 is a configuration diagram of an auxiliary power circuit 30B included in the power conversion device.
As shown in FIG. 6, the auxiliary power supply circuit 30B is a flyback type comprising an iron core T that is a magnetic circuit, primary side circuits J11 and J12, secondary side circuits J20 to J24, and a control unit M. It is a power supply circuit.

The primary windings N1 and N2 are wound on the primary side of the iron core T, and the secondary windings N20 to N24 are wound on the secondary side. The iron core T, the primary windings N1 and N2, and the secondary windings N20 to N24 constitute a transformer (transformer).

The primary side circuit J11 is a circuit to which the voltage V1 of the voltage dividing capacitor Cdc1 (see FIG. 1) is applied. As shown in FIG. 6, the primary circuit J11 includes a primary capacitor C1, a primary winding N1, a primary diode Db1, a switching element Q1, a freewheeling diode D1, and a snubber circuit Sn1. ing.

The primary capacitor C1 is a capacitor for suppressing voltage fluctuation when the switching element Q1 is turned off. The primary capacitor C1 is a capacitor different from the smoothing voltage dividing capacitor Cdc1 (see FIG. 1). The positive electrode of the primary capacitor C1 is connected to the positive electrode of the voltage dividing capacitor Cdc1 through the wiring kp1. The negative electrode of the primary capacitor C1 is connected to the negative electrode of the voltage dividing capacitor Cdc1 through the wiring kn1.

Further, a “series connection body” in which the primary winding N1, the primary diode Db1, and the switching element Q1 are sequentially connected in series is connected in parallel to the primary capacitor C1. That is, the above-described “series connection body” has a one-to-one correspondence with the voltage dividing capacitor Cdc1 (see FIG. 1), and both ends thereof are connected to both ends of the voltage dividing capacitor Cdc1.

As shown in FIG. 6, the primary winding N1 has one end connected to the positive electrode of the primary capacitor C1 and the other end connected to the anode of the primary diode Db1. The switching element Q1 has a drain connected to the cathode of the primary diode Db1, and a source connected to the negative electrode of the primary capacitor C1. In addition, a free-wheeling diode D1 is connected in antiparallel to the switching element Q1.
In the example shown in FIG. 6, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is used as the switching element Q1, but another type of switching element may be used.

The primary diode Db1 is connected so as to allow a current from the positive electrode of the voltage dividing capacitor Cdc1 (see FIG. 1) to the self through the wiring kp1 and the like, and prevent a reverse current. The provision of the primary diode Db1 (and the other primary diode Db2) is one of the main features of the third embodiment.

The snubber circuit Sn1 is a circuit that suppresses a surge voltage generated between the drain and source of the switching element Q1. The snubber circuit Sn1 has a one-to-one correspondence with the primary winding N1 and is connected in parallel to the primary winding N1. The snubber circuit Sn1 includes a diode Ds1, a capacitor Cs1, and a resistor Rs1.

As shown in FIG. 6, a diode Ds1 is connected in series to a “parallel connection body” in which a capacitor Cs1 and a resistor Rs1 are connected in parallel. The anode of the diode Ds1 is connected to the anode of the primary diode Db1, and the cathode is connected to the “parallel connection body” described above. When a surge voltage is generated between the drain and source of the switching element Q1, the surge voltage is suppressed by the capacitor Cs1, and energy associated with the surge voltage is consumed by the resistor Rs1.

The primary side circuit J12 is a circuit to which the voltage V2 of the voltage dividing capacitor Cdc2 (see FIG. 1) is applied. The primary side circuit J12 has the same configuration as the primary side circuit J11 described above.
As shown in FIG. 6, a “series connection body” in which a primary winding N2, a primary diode Db2, and a switching element Q2 are sequentially connected in series is connected in parallel to the primary capacitor C2. That is, the above-described “series connection body” has a one-to-one correspondence with the voltage dividing capacitor Cdc2 (see FIG. 1), and both ends thereof are connected to both ends of the voltage dividing capacitor Cdc2.
The primary diode Db2 is connected so as to allow a current from the positive electrode of the voltage dividing capacitor Cdc2 toward itself through the wiring kp2 and the like and to block a reverse current.

The secondary side circuit J21 includes a secondary winding N21, a secondary diode D21, and a secondary capacitor C21. As shown in FIG. 6, the secondary winding N21 and the secondary diode D21 are connected in series. A secondary capacitor C21 is connected in parallel to the secondary winding N21 and the secondary diode D21.

The secondary diode D21 has an anode connected to the secondary winding N21 and a cathode connected to the positive electrode of the secondary capacitor C21. That is, the secondary diode D21 is connected so as to allow a current from the secondary winding N21 toward the positive electrode of the secondary capacitor C21 through itself and prevent a reverse current. Electric power is output from both ends of the secondary capacitor C21.

Since the secondary side circuits J20, J22 to J24 have the same configuration as the secondary side circuit J21 described above, description thereof is omitted.
Note that power is supplied to the control circuit 40 (see FIG. 1) from one or more of the secondary side circuits J21 to J24. Note that power may be supplied from one or more of the secondary side circuits J21 to J24 to other devices such as the fan 50 (see FIG. 1).

The control unit M is configured to include an electronic circuit such as an IC (not shown), reads a program stored in the ROM, develops it in the RAM, and the CPU executes various processes. As shown in FIG. 6, the control unit M is connected to both ends of the secondary capacitor C20. The controller M controls the on / off of the switching elements Q1, Q2 so that the voltage V20 of the secondary capacitor C20 becomes a predetermined value.

<Operation of auxiliary power circuit>
Next, the operation of the auxiliary power supply circuit 30B will be described with reference to FIG. 7 (when V1> V2), FIG. 8 (when V1 <V2), and FIG. 9 (when V1 = V2) sequentially. 7 to 9, illustration of the snubber circuits Sn1 and Sn2 (see FIG. 6) is omitted. In the following description, it is assumed that the number of turns of the primary winding N1 is substantially equal to the number of turns of the primary winding N2.

(1. When V1> V2)
FIG. 7A is an explanatory diagram when the switching elements Q1 and Q2 are turned on when the voltage V1 is higher than the voltage V2.
In addition, the broken-line arrow shown to Fig.7 (a), (b) represents the flow of an electric current. As shown in FIG. 7A, when the control unit M turns on the switching elements Q1 and Q2, a voltage substantially equal to the voltage V1 is applied to the primary winding N1. As a result, the primary diode Db1 becomes forward biased, and the current flowing through the primary winding N1 increases. As a result, predetermined energy is accumulated in the exciting inductance of the transformer constituted by the iron core T, the primary windings N1, N2, the secondary winding N21, and the like.

As described above, the primary windings N1 and N2 have substantially the same number of turns and are wound around a common iron core T. Accordingly, a voltage V1 of the same level as that of the primary winding N1 is generated in the primary winding N2. Since the voltage V1 is higher than the voltage V2 applied to the primary capacitor C2, the primary diode Db2 is reverse-biased. Therefore, as shown in FIG. 7A, no current flows through the primary winding N2.

Although voltages are also generated in the secondary windings N20 to N24, the secondary diodes D20 to D24 are reversely biased, respectively. Accordingly, as shown in FIG. 7A, no current flows through the secondary windings N20 to N24.
Next, as shown in FIG. 7B, the control unit M turns off the switching elements Q1 and Q2 (that is, switches to the off state).

FIG. 7B is an explanatory diagram showing a state immediately after the switching elements Q1 and Q2 are turned off when the voltage V1 is higher than the voltage V2.
When switching elements Q1, Q2 are turned off, a voltage is generated in secondary windings N20-N24, and secondary diodes D20-D24 become forward biased and become conductive. As a result, the energy accumulated in the magnetizing inductance of the transformer is released, and power is supplied to the control circuit 40 (see FIG. 1) via the secondary capacitors C20 to C24.

FIG. 7C is an explanatory diagram showing a state after energy is released from the transformer when the voltage V1 is higher than the voltage V2.
If the OFF state continues for a predetermined time after the switching elements Q1 and Q2 are turned off, all the energy stored in the exciting inductance of the transformer is released. As a result, no current flows through the secondary windings N20 to N24. At this time, no current flows through the primary windings N1 and N2.

Thereafter, when the switching elements Q1 and Q2 are turned on by the control unit M, the state returns to the state of FIG. In this way, the control unit M repeats the process of turning on the switching elements Q1, Q2 at the same timing and then turning off at the same timing. That is, the switching elements Q1 and Q2 included in the auxiliary power supply circuit 30B operate so as to have a period in which the auxiliary power supply circuit 30B is simultaneously in an on state and a period in which the auxiliary power supply circuit 30B is in an off state. In other words, the switching element Q1 is also in the on state when the other switching element Q2 is in the on state, and is also in the off state when the other switching element Q2 is in the off state.

When the voltage V1 is higher than the voltage V2, as shown in FIG. 7A, a current flows through the primary winding N1, but a current flows through the other primary winding N2. Absent. That is, current flows from the voltage dividing capacitor Cdc1 (see FIG. 1), but no current flows from the other voltage dividing capacitor Cdc2 (see FIG. 1). As a result, the voltage V1 of the voltage dividing capacitor Cdc1 decreases and the voltages V1 and V2 are equalized.

(2. When V1 <V2)
FIG. 8A is an explanatory diagram when the switching elements Q1 and Q2 are turned on when the voltage V2 is higher than the voltage V1.
When the control unit M turns on the switching elements Q1 and Q2, a voltage substantially equal to the voltage V2 is applied to the primary winding N2. As a result, the primary diode Db2 becomes forward biased, and the current flowing through the primary winding N2 increases. As a result, predetermined energy is accumulated in the exciting inductance of the transformer constituted by the iron core T, the primary windings N1, N2, the secondary winding N21, and the like.

The primary windings N1 and N2 have substantially the same number of turns and are wound around a common iron core T. Accordingly, a voltage V2 of the same level as that of the primary winding N2 is generated in the primary winding N1. Since this voltage V2 is higher than the voltage V1 applied to the primary capacitor C1, the primary diode Db1 is reverse-biased. Therefore, as shown in FIG. 8A, no current flows through the primary winding N1.

Although voltages are also generated in the secondary windings N20 to N24, the secondary diodes D20 to D24 are reversely biased, respectively. Therefore, as shown in FIG. 8A, no current flows through the secondary windings N20 to N24.
Next, as shown in FIG. 8B, the control unit M turns off the switching elements Q1 and Q2.

FIG. 8B is an explanatory diagram showing a state immediately after the switching elements Q1 and Q2 are turned off when the voltage V2 is higher than the voltage V1.
When switching elements Q1 and Q2 are turned off, secondary diodes D20 to D24 conduct, and current flows through secondary capacitors C20 to C24.

FIG. 8C is an explanatory diagram showing a state after energy is released from the transformer when the voltage V2 is higher than the voltage V1.
If the OFF state continues for a predetermined time after the switching elements Q1 and Q2 are turned off, all the energy stored in the exciting inductance of the transformer is released. As a result, no current flows through the secondary windings N20 to N24.

Thereafter, when the switching elements Q1 and Q2 are turned on by the control unit M, the state returns to the state of FIG. In this way, the control unit M repeats the process of turning on the switching elements Q1, Q2 at the same timing and then turning off at the same timing.

Further, as shown in FIG. 8A, a current flows through the primary winding N2, but no current flows through the primary winding N1. That is, current flows from the voltage dividing capacitor Cdc2 (see FIG. 1), but no current flows from the voltage dividing capacitor Cdc1 (see FIG. 1). As a result, the voltage V2 of the voltage dividing capacitor Cdc2 is reduced and the voltages V1 and V2 are equalized.

(3. When V1 = V2)
FIG. 9A is an explanatory diagram when the switching elements Q1 and Q2 are turned on when the voltages V1 and V2 are substantially equal.
As shown in FIG. 9A, when the control unit M turns on the switching elements Q1 and Q2, the voltages V1 and V2 are substantially equal. Therefore, both the primary diodes Db1 and Db2 become forward biased, and the primary Current flows through both windings N1 and N2.

FIG. 9B is an explanatory diagram showing a state immediately after the switching elements Q1 and Q2 are turned off when the voltages V1 and V2 are substantially equal.
When switching elements Q1, Q2 are turned off, secondary diodes D20-D24 are turned on, and current is supplied to secondary capacitors C20-C24.

FIG. 9C is an explanatory diagram showing a state after energy is released from the transformer when the voltages V1 and V2 are substantially equal.
If the OFF state continues for a predetermined time after the switching elements Q1 and Q2 are turned off, all the energy stored in the exciting inductance of the transformer is released. As a result, no current flows through the secondary windings N20 to N24.

Then, when the switching elements Q1 and Q2 are turned on by the control unit M, the state returns to the state of FIG. In this way, the control unit M repeats the process of turning on the switching elements Q1, Q2 at the same timing and then turning off at the same timing. Thereby, the state where the voltages V1 and V2 are substantially equal is maintained.

If the above-described transformer has a relatively large excitation inductance, the operations of FIGS. 7C, 8C, and 9C may be omitted. In this case, even if the switching elements Q1 and Q2 are maintained in the OFF state, the current continues to flow to the secondary side due to the exciting inductance of the transformer.

<Effect>
According to the third embodiment, when the voltage V1 is higher than the voltage V2 (see FIG. 7), when the voltage V2 is higher than the voltage V1 (see FIG. 8), and when the voltages V1 and V2 are substantially equal (see FIG. 9), the auxiliary power supply circuit 30B performs the same operation. That is, switching the switching elements Q1, Q2 on and off at the same timing results in equalization of the voltages V1, V2 regardless of the magnitude relationship between the voltages V1, V2. That is, a current flows from the higher voltage of the voltage dividing capacitors Cdc1 and Cdc2 to the primary side. This is due to the characteristic that approximately the same voltage is generated in the primary windings N1 and N2, and the characteristic of the primary diodes Db1 and Db2.

Also, the control unit M operates the switching elements Q1 and Q2 with the same gate pattern so that any one of the voltages V20 to V24 output from the secondary side is a predetermined value. Therefore, the voltages of the voltage dividing capacitors Cdc1 and Cdc2 can be equalized by a simple control method similar to that of a conventional flyback converter having no primary diodes Db1 and Db2.

<< Fourth Embodiment >>
The fourth embodiment differs from the first embodiment in the configuration of the auxiliary power supply circuit 30C (see FIG. 10), but the other embodiments (the overall configuration of the power conversion device 100: see FIG. 1) are the first embodiment. It is the same. Therefore, a different part from 1st Embodiment is demonstrated and description is abbreviate | omitted about the overlapping part.

FIG. 10 is a configuration diagram of an auxiliary power circuit 30C included in the power conversion device according to the fourth embodiment. In FIG. 10, illustration of wirings that connect the gates of the switching elements Q1, Q2, Q4, and Q5 and the control unit M is omitted.
As shown in FIG. 10, the auxiliary power supply circuit 30C includes a forward power supply including an iron core T, which is a magnetic circuit, primary circuits P11 and P12, secondary circuits P20 to P24, and a control unit M. Circuit.

A transformer is constituted by the iron core T, the primary windings N1 and N2, and the secondary windings N20 to N24.

The primary side circuit P11 is a circuit to which the voltage V1 of the voltage dividing capacitor Cdc1 (see FIG. 1) is applied. As shown in FIG. 10, the primary circuit P11 includes a primary capacitor C1, a primary winding N1, a primary diode Db1, a switching element Q1, a freewheeling diode D1, and a snubber circuit Sn4. Yes. The elements other than the snubber circuit Sn4 are the same as the primary side circuit J11 (see FIG. 6) described in the third embodiment, and thus the description thereof is omitted.

A snubber circuit Sn4 shown in FIG. 10 is an active clamp type circuit that suppresses a surge voltage generated between the drain and source of the switching element Q1, and corresponds to the primary winding N1 in a one-to-one correspondence. The line N1 is connected in parallel. The snubber circuit Sn4 includes a capacitor Cs4, a switching element Q4, and a free wheeling diode D4.

As shown in FIG. 10, a capacitor Cs4 and a switching element Q4 are connected in series. The switching element Q4 has a drain connected to the negative electrode of the capacitor Cs4 and a source connected to the anode of the primary diode Db1. The switching element Q4 is connected with a freewheeling diode D4 in antiparallel.

The primary side circuit P12 is a circuit to which the voltage V2 of the voltage dividing capacitor Cdc2 (see FIG. 1) is applied. Since the configuration of the primary side circuit P12 is the same as the primary side circuit P11 described above, the description thereof is omitted.

The secondary side circuit P21 includes a secondary winding N21, secondary diodes D21 and D25, a secondary capacitor C21, and an inductor L21. As shown in FIG. 10, a secondary winding N21 and a secondary diode D21 are connected in series, and a secondary diode D25 is connected in parallel to the secondary winding N21 and the secondary diode D21. The secondary diode D21 has an anode connected to the secondary winding N21 and a cathode connected to the cathode of another secondary diode D25.

A secondary capacitor C21 is connected in parallel to the secondary diode D25 via an inductor L21 connected to the cathodes of the secondary diodes D21 and D25. Both ends of the secondary capacitor C21 are secondary output terminals.
Since the secondary side circuits P20, P22 to P24 have the same configuration as the secondary side circuit J21 described above, description thereof is omitted.

Further, the switching elements Q1 and Q4 are alternately switched on and off by the control unit M. That is, when one of the switching elements Q1 and Q4 is on, the control unit M turns off the other. Further, the control unit M provides a predetermined dead time (period in which both the switching elements Q1 and Q4 are in the off state) when the switching elements Q1 and Q4 are switched on and off. The switching elements Q2 and Q5 are similarly switched on and off in the same manner.

Also, the control unit M repeats the process of turning off the switching elements Q1 and Q2 at the same timing and then turning off at the same timing. That is, the switching elements Q1 and Q2 included in the auxiliary power supply circuit 30C operate so as to have a period in which the auxiliary power supply circuit 30C is in the on state and a period in which the auxiliary power supply circuit 30C is in the off state at the same time. In other words, the switching element Q1 is also in the on state when the other switching element Q2 is in the on state, and is also in the off state when the other switching element Q2 is in the off state.

For example, when the voltage V1 is higher than the voltage V2, when the switching elements Q1 and Q2 are on and the switching elements Q4 and Q5 are off, current flows as follows. That is, as in the third embodiment (FIG. 7A), the primary diode Db1 is forward biased and the other primary diode Db2 is reverse biased. Therefore, a current flows from the voltage dividing capacitor Cdc1 (see FIG. 1) to the primary winding N1, but no current flows from the voltage dividing capacitor Cdc2 (see FIG. 1) to the primary winding N2. As a result, the voltage V1 of the voltage dividing capacitor Cdc1 and the voltage V2 of the voltage dividing capacitor Cdc2 are equalized.

In the switching process described above, in the secondary circuit P21, the secondary diode D21 is forward biased and another secondary diode D25 is reverse biased. As a result, a current flows through the inductor L21, and power is supplied to the control circuit 40 and the like (see FIG. 1) via the secondary capacitors C20 to C24.

Thereafter, when the switching elements Q1 and Q2 are turned off and the switching elements Q4 and Q5 are turned on, the energy accumulated in the leakage inductance of the transformer is charged to the capacitor Cs4 via the freewheeling diode D4, and the surge voltage Is absorbed.

Even when the voltage V2 is higher than the voltage V1 or when the voltages V1 and V2 are substantially equal, the voltages V1 and V2 are equalized by performing the same control as described above.

<Effect>
According to the fourth embodiment, switching the switching elements Q1, Q2 on and off at the same timing results in equalization of the voltages V1, V2 regardless of the magnitude relationship between the voltages V1, V2.
Further, since the auxiliary power supply circuit 30C is a forward type, higher efficiency can be achieved and a large output power can be obtained compared to the third embodiment using the flyback type auxiliary power supply circuit 30B (see FIG. 6). be able to.

≪Modification≫
As mentioned above, although each embodiment demonstrated the power converter device 100 grade | etc., Which concerns on this invention, this invention is not limited to these description, A various change can be performed.
For example, in the third embodiment (see FIG. 6), the configuration in which the auxiliary power supply circuit 30B includes the two primary side circuits J11 and J12 has been described, but the configuration is not limited thereto. For example, as described below, a configuration including three primary side circuits J11, J12, and J13 may be adopted.

FIG. 11 is a configuration diagram of an auxiliary power circuit 30D included in a power conversion device according to a modification.
As shown in FIG. 11, the auxiliary power circuit 30D includes primary circuits J11, J12, and J13. Although not shown, the primary side circuits J11, J12, and J13 are connected to three voltage dividing capacitors on a one-to-one basis. As in the third embodiment, the control unit M repeats the process of turning on the switching elements Q1, Q2, and Q3 at the same timing and then turning off at the same timing. As a result, the voltages V1, V2, and V3 of the three voltage dividing capacitors (not shown) are equalized.
The number of voltage dividing capacitors (not shown) and the primary side circuit J11 may be three as described above, or may be four or more. The same can be said for the first, second, and fourth embodiments.

In the third embodiment, the process of switching on / off of the switching elements Q1, Q2 at the same timing has been described. However, the present invention is not limited to this. For example, when a voltage sensor (not shown) for detecting the voltages V1 and V2 is provided, and the voltage V1 is higher than the voltage V2, the control unit M repeatedly turns on and off the switching element Q1, thereby switching the switching element Q2 may be maintained in the off state. Even in this case, as in the third embodiment (see FIG. 7A), current flows from the voltage dividing capacitor Cdc1 to the primary winding N1 when the switching element Q1 is in the ON state. This is because when the voltage V1 is higher than the voltage V2, no current flows from the voltage dividing capacitor Cdc2 to the primary winding N2 regardless of the ON / OFF state of the switching element Q2. (See FIG. 7). Further, when the voltage V2 is higher than the voltage V1, the control unit M repeats on / off of the switching element Q2, and maintains the switching element Q1 in the off state. As a result, the voltage V1 of the voltage dividing capacitor Cdc1 and the voltage V2 of the voltage dividing capacitor Cdc2 are equalized. The same applies to the fourth embodiment.

In the third embodiment (see FIG. 6), the configuration in which the freewheeling diodes D1 and D2 are provided has been described. However, the freewheeling diodes D1 and D2 may be omitted. This is because almost no current flows through the freewheeling diodes D1 and D2 in the normal control (see FIGS. 7 to 9). The same applies to the fourth embodiment.
Moreover, when using the element which has the reverse blocking capability which primary diode Db1 and Db2 were carrying out as switching element Q1 and Q2 (refer FIG. 6), you may abbreviate | omit these primary diodes Db1 and Db2. . That is, the auxiliary power supply circuit may be configured to use “the reverse blocking ability of the switching element as the primary diode”. Thereby, further cost reduction can be achieved.

In the third embodiment, the case where the numbers of turns of the primary windings N1 and N2 are substantially equal has been described. However, according to the target voltage division ratio between the voltage V1 and the voltage V2 (that is, the voltage dividing capacitors Cdc1 and Cdc2 Depending on the characteristics, the primary windings N1, N2 may have different numbers of turns. In this case, the voltage division ratio between the voltages V1 and V2 is substantially equal to the turn ratio of the primary windings N1 and N2. The same applies to the fourth embodiment.

Further, the flyback circuit described in the third embodiment (see FIG. 6) and the forward circuit described in the fourth embodiment (see FIG. 10) are examples, and other known flyback circuits or A forward type circuit may be used.

In the third embodiment (see FIG. 6), the configuration in which the primary winding N1, the primary diode Db1, and the switching element Q1 are sequentially connected in series has been described. However, the present invention is not limited to this. For example, the primary winding N1, the switching element Q1, and the primary diode Db1 may be sequentially connected in series. The same applies to the fourth embodiment.

Further, each embodiment can be applied to a multi-level inverter or the like in addition to a PCS (Power Conditioning System) for photovoltaic power generation and an uninterruptible power system (UPS).

Further, the embodiments can be combined as appropriate. For example, the uninterruptible power supply system S may be configured to include the auxiliary power supply circuit 30B illustrated in FIG. 6 by combining the second embodiment and the third embodiment. Further, for example, the uninterruptible power supply system S may include the auxiliary power supply circuit 30C illustrated in FIG. 10 by combining the second embodiment and the fourth embodiment.

Each embodiment is described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of the embodiment. In addition, the above-described mechanisms and configurations are those that are considered necessary for the description, and do not necessarily indicate all the mechanisms and configurations on the product.

100, 100A, 100B, 100C, 100D Power conversion device 10 DC-DC converter (power conversion circuit)
20 Inverter (Power conversion circuit)
30, 30A, 30B, 30C, 30D Auxiliary power circuit (power circuit)
31, 32 DC-DC converter (Power conversion circuit, DC-DC converter)
33, 34 Voltage sensor 35 Control unit 40 Control circuit (power supply target)
50 fans (subject of power supply)
60 Converter (power conversion circuit, AC / DC converter)
70 Inverter (Power conversion circuit)
80 DC-DC converter (Power conversion circuit, DC-DC converter)
Cdc1, Cdc2 Voltage dividing capacitor C20, C21, C22, C23, C24 Secondary capacitor D20, D21, D22, D23, D24 Secondary diode Db1, Db2, Db3 Primary diode M Control unit N1, N2, N3 Primary winding N20, N21, N22, N23, N24 Secondary winding Q1, Q2, Q3 Switching element Sn1, Sn2, Sn4, Sn5 Snubber circuit T Iron core

Claims

A power conversion circuit for performing power conversion;
A plurality of voltage dividing capacitors connected to the DC side of the power conversion circuit and dividing a DC voltage applied from the DC side;
A power supply circuit that is connected to both ends of each of the plurality of voltage dividing capacitors and inputs a larger current to itself from a voltage dividing capacitor having a higher voltage among the plurality of voltage dividing capacitors. Power converter.
The power supply circuit is
A plurality of DC-DC converters,
A controller that controls the plurality of DC-DC converters,
The DC-DC converter has a one-to-one correspondence with the voltage dividing capacitor, its input side is connected to both ends of the voltage dividing capacitor, and its output side is connected to a power supply target,
The power converter according to claim 1, wherein the control unit adjusts a current input from the voltage dividing capacitor to the DC-DC converter.
The power supply circuit is
A plurality of serially connected bodies in which a primary winding wound around a primary side of an iron core that is a magnetic circuit, a primary diode, and a switching element are connected in series,
A secondary winding wound around the secondary side of the iron core;
A control unit for controlling on / off of the switching element,
The series connection body has a one-to-one correspondence with the voltage dividing capacitor, and both ends thereof are connected to both ends of the voltage dividing capacitor,
2. The power converter according to claim 1, wherein the primary diode is connected so as to allow a current from the positive electrode of the voltage dividing capacitor toward the self and to block a reverse current.
The power conversion device according to claim 3, wherein the plurality of switching elements included in the power supply circuit operate so as to have a period in which the switching elements are simultaneously on and a period in which the switching elements are simultaneously off.
The power converter according to claim 3, wherein the power supply circuit uses a reverse blocking capability of the switching element as the primary diode.
The power supply circuit includes a plurality of snubber circuits that suppress a surge voltage generated in the switching element,
The power converter according to claim 3, wherein the snubber circuit is connected in parallel to the primary winding in a one-to-one correspondence with the primary winding.
The power supply circuit is
With a primary winding wound around the primary side of the iron core, which is a magnetic circuit,
A secondary winding wound around the secondary side of the iron core, a secondary diode connected in series to the secondary winding, and a secondary capacitor connected in parallel to the secondary winding and the secondary diode And comprising
The secondary diode is connected so as to allow a current from the secondary winding to the positive electrode of the secondary capacitor through itself and prevent a reverse current;
The power converter according to claim 1, wherein power is output from both ends of the secondary capacitor.
The power converter according to any one of claims 1 to 7, wherein the power supply circuit supplies power to a control circuit that controls the power converter circuit.
The power converter according to any one of claims 1 to 7, wherein the power supply circuit supplies power to a fan that cools the power converter circuit.
The power conversion circuit includes an inverter that converts a DC voltage into an AC voltage;
The power converter according to any one of claims 1 to 7, wherein the plurality of voltage dividing capacitors are connected to a direct current side of the inverter.
The power conversion circuit includes an AC / DC converter that converts an AC voltage into a DC voltage,
The power converter according to any one of claims 1 to 7, wherein the plurality of voltage dividing capacitors are connected to a DC side of the AC / DC converter.
The power conversion circuit includes a DC-DC converter that boosts or reduces a DC voltage,
The power converter according to any one of claims 1 to 7, wherein the plurality of voltage dividing capacitors are connected to an output side of the DC-DC converter.