WO2017179179A1

WO2017179179A1 - Power conversion device

Info

Publication number: WO2017179179A1
Application number: PCT/JP2016/062051
Authority: WO
Inventors: 充弘門田; 泰明乗松; 尊衛嶋田
Original assignee: 株式会社日立製作所
Priority date: 2016-04-15
Filing date: 2016-04-15
Publication date: 2017-10-19

Abstract

A power conversion device of the present invention is characterized in that: the power conversion device is provided with a plurality of power converter cells, and a control device for controlling the power converter cells; output terminals of the power converter cells are connected in series; one or more reactors are inserted in series into a path, in which an output current of each of the power converter cells flows; a first bypass section is connected in parallel to at least one reactor; and the control device controls the first bypass section.

Description

Power converter

The present invention relates to a power conversion device.

In high-voltage or large-capacity power conversion, a power conversion device in which a plurality of power converter cells (hereinafter abbreviated as cells) are connected in series or in parallel is used.

Also, the introduction of natural energy power generation such as solar power generation and wind power generation is expanding worldwide. There is a PCS (Power Conditioning System) as a power conversion device for converting electric power obtained from natural energy and outputting it to an electric power system. In this PCS as well, a configuration using a plurality of cells as described above is considered effective when dealing with higher voltages and larger capacities.

As such a power conversion device, Patent Document 1 discloses that “power converters 3a to 3d are provided for each of the solar battery panels 2a to 2d. These power converters 3a to 3d are connected to the solar battery panels 2a to 2d. The output power of 2d is subjected to voltage-current conversion by tracking the maximum power point, and the reactors 6 and 7 and the capacitor C between the output terminals O1 and O2 can be reduced in size.

JP 2013-192382 A

A power conversion device including a switching circuit such as an inverter is often used together with a reactor (also called a coil or an inductor) in order to reduce harmonic current flowing through a load. Large-capacity power converters require large reactors to cope with high voltages and currents, and their weight and cost are also issues. Moreover, the reactor is often installed separately from the power converter, and wiring between the power converter and the reactor is also necessary. Therefore, the number of installation steps as a whole apparatus and the installation cost have increased.

By the way, when a current flows through the reactor, a power loss called copper loss occurs in the reactor. Moreover, the higher the inductance of the reactor, the higher the harmonic current reduction effect, but the copper loss tends to increase, and the conversion efficiency of the power converter decreases. Therefore, the inductance of the reactor should be set to a minimum value for reducing the harmonic current to a desired value. In particular, when the voltage or current generated in the power converter varies during operation, the minimum inductance required to reduce the harmonic current also varies. At this time, if the inductance necessary for reducing the harmonic current is set in consideration of all the operating conditions, the inductance becomes excessive under certain operating conditions, the copper loss increases, and the efficiency decreases.

Patent Document 1 describes that a reactor is provided for each of a plurality of power conversion units. However, Patent Document 1 only describes that the inductance value is constant regardless of the operating conditions.

Therefore, an object of the present invention is to provide a highly efficient power converter that can set an appropriate inductance value according to operating conditions.

The above-described problem includes, for example, a plurality of power converter cells and a control device that controls the plurality of power converter cells, and output terminals of the plurality of power converter cells are connected in series, respectively, One or more reactors are inserted in series in the path through which the output current of the reactor cell flows, and the first bypass unit is connected in parallel to at least one reactor, and the control device controls the first bypass unit. It solves by the power converter device characterized by this.

According to the present invention, it is possible to provide a high-efficiency power converter that can set an appropriate inductance value according to operating conditions.

It is a structure of the power converter device in Example 1. FIG. It is a modification regarding the structure of the power converter device in Example 1. FIG. This is a configuration example of a reactor, in which two

reactors

302 and 305 are connected in series to the output terminal of the cell 102. This is a configuration example of a reactor, in which a reactor 302 is connected to one of output terminals of the cell 102 and a reactor 306 is connected to the other. This is a configuration example of a reactor, in which a fuse 307 is connected in series with a reactor 302. This is a configuration example of a reactor, in which a capacitor 308 is connected between

reactors

302 and 306. It is a structural example of a power converter cell. It is an example of the synthetic | combination output voltage waveform of a power converter device. It is an example of the synthetic | combination output voltage waveform in the case of utilizing PWM. It is a structural example of a 1st bypass part. It is the relationship between the DC link voltage and the combined inductance in the control of the first embodiment. 2 is a block diagram of a control device in Embodiment 1. FIG. It is a flowchart by which the control apparatus 200 controls a 1st bypass part based on DC link voltage. It is an example of the mounting form of the cell with which a power converter device is provided, a reactor, and the 1st bypass part, and is a top view at the time of seeing this from the upper part. It is an example of the mounting form of a reactor and a 1st bypass part, and is a top view at the time of seeing this from upper direction. It is another example of the mounting form of a reactor and a 1st bypass part. It is another example of the mounting form of a reactor and a 1st bypass part. It is a structure of the power converter device in Example 2. FIG. It is a structural example of a 2nd bypass part. FIG. 5A shows a waveform of the combined output voltage Vos when one cell is stopped. FIG. 5A described in the first embodiment is a Vos waveform during normal operation, and the comparison is shown. FIG. 5B is a waveform of the combined output voltage Vos when one cell is stopped, and FIG. 5B described in the first embodiment is a Vos waveform during normal operation, and a comparison with this is shown. The processing and calculation contents of the control device 202 in Embodiment 2 are represented as a block diagram. 7 is a part of a configuration of a power conversion device according to a third embodiment. 10 is another example of the configuration in the third embodiment. It is an example of the mounting form of a cell, a reactor, an auxiliary | assistant winding, a 2nd bypass part, and a control apparatus, and is a top view at the time of seeing this from upper direction. It is a structure of the power converter device 4000 in Example 4. FIG. In Example 5, it is a timing chart which carries out on / off control of the some 1st bypass part in order.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of the power conversion apparatus according to Embodiment 1 of the present invention.

The power conversion device 1000 converts the power input from the external power source 400 and outputs it to the external load 500. The power conversion apparatus 1000 includes a plurality of cells 101 to 104 and a control apparatus 200 that controls these cells, and the output terminals of each cell are connected in series. The power conversion apparatus 1000 includes reactors 301 to 304, and the reactors are inserted in series at the connection points between the cells as shown in FIG. Although FIG. 1 shows an example in which four cells are used, the number of cells is arbitrary.

The cells 101 to 104 convert the input voltage from the outside to generate output voltages Vo1 to Vo4, respectively. Since the output terminals of the cells are connected in series, Vo1 to Vo4 are synthesized, and the power converter 1000 can output a high voltage. Hereinafter, a voltage obtained by combining the output voltages of the cells 101 to 104 is defined as a combined output voltage Vos (= Vo1 + Vo2 + Vo3 + Vo4). If the voltage drop at the reactor is ignored as being sufficiently small, Vos can be considered as the output voltage of the power converter 1000.

The control device 200 controls the output voltage or output current of the power conversion device 1000 to a predetermined value by controlling Vo1 to Vo4 and thus Vos. The control device 200 outputs a control signal to each cell in order to control Vo1 to Vo4. Each cell outputs a detection signal indicating a physical quantity such as voltage, current, and temperature of each cell and a state such as presence or absence of abnormality to the control device 200. In FIG. 1, only signals that are input and output between the control device 200 and the cell 101 are shown in order to prevent the drawing from becoming complicated. In practice, signals are input and output in the same manner between the control device 200 and the cells 102 to 104. Further, the signal expressed as one arrow in FIG. 1 may include a plurality of pieces of information. All elements of the control device 200 need not be mounted on a single substrate. Although details will be described in a later embodiment, some elements of the control device 200 may be mounted on a substrate on which the components of each cell are mounted.

Although details will be described later, the cell output voltages Vo1 to Vo4 and the combined output voltage Vos include harmonic components. Reactors 301 to 304 reduce harmonic components included in the output current of power conversion device 1000. In addition, when the impedance of the load 500 changes abruptly, it plays a role of preventing the occurrence of overcurrent.

The effect of reducing harmonic current depends on the inductance of the reactor. As shown in FIG. 1, when a plurality of reactors are inserted in series with respect to a current path that feeds power from the power converter to the load 500, that is, an output current path of the power converter, the total value of inductance increases as the number of reactors increases. (Hereinafter, defined as the combined inductance Ls) increases, and the harmonic current reduction effect increases. On the other hand, the more reactors, the greater the loss generated in the reactor, especially the copper loss. By adjusting the number of reactors inserted in series with respect to the output current path of the power converter, and thus Ls, it is possible to reduce the loss of the reactor while minimizing the harmonic current to a predetermined magnitude. desirable.

Bypass units 311 to 314 are connected in parallel to the reactors 301 to 304, respectively. Below, the bypass part connected in parallel with a reactor in this way is called a 1st bypass part. Although the first bypass units 311 to 314 are illustrated as switches in FIG. 1, relays, switching elements (semiconductors), and the like can be applied as these switches. In addition, the 1st bypass part does not need to be connected with respect to all the reactors, and may be connected only with respect to some reactors.

1 outputs a bypass signal for ON / OFF control of each first bypass unit. In FIG. 1, only the bypass signal for the first bypass unit 311 is shown to prevent the drawing from becoming complicated. Actually, a bypass signal is similarly output to the first bypass units 312 to 314. In the control device 200, the element that outputs the control signal to the cells 101 to 104 and the element that outputs the bypass signal to the first bypass units 311 to 314 are different from each other even if they are mounted on the same substrate. It may be mounted on a substrate.

When all of the first bypass units 311 to 314 are off, there are four reactors inserted in series with respect to the current path that feeds power from the power converter 1000 to the load 500, that is, the output current path of the power converter 1000. is there. Here, when the first bypass unit 311 is turned on, no current flows through the reactor 301, and the number of reactors inserted in series with respect to the output current path is reduced to three. As a result, the combined inductance Ls is also reduced and the effect of reducing the harmonic component of the output current is reduced, but the conversion efficiency of the power converter 1000 is improved by the amount that the reactor 301 is not lost.

It is considered that the inductance necessary for reducing the harmonic component to a predetermined value, and hence the number of reactors for realizing this, vary depending on the operating conditions of the cells 101 to 104 or the load 500 conditions. Specifically, the required inductance varies depending on the DC link voltage of each cell, which will be described later, and the current output to the load 500. By adjusting the number of reactors in the output current path, and thus the combined inductance, according to the operating conditions, the loss of the reactor can be minimized while the harmonic current is reduced to a predetermined value. Further, as shown in FIG. 1, since a plurality of reactors are inserted in series with respect to the output current path of the power converter, the combined inductance Ls can be finely adjusted.

The power source 400 may be either a DC power source or an AC power source. As an example, when the power conversion apparatus 1000 is applied to a PCS for photovoltaic power generation, the power source 400 is a solar battery. FIG. 1 shows a configuration in which each cell is connected in parallel to the power source 400. However, similar to the output unit of the power conversion apparatus 1000, the input terminal of each cell may be connected in series to the power supply 400. As an example, when the power conversion apparatus 1000 is applied to drive a high voltage motor, the power supply 400 is generally a high voltage AC power supply, and the high voltage can be handled by connecting the input terminals of each cell in series. Let In this case, in order to balance the voltage input to each cell, a resistor or a capacitor may be connected between the input terminals of each cell.

Examples of the load 500 include a high voltage motor and other electric power equipment. Moreover, the load 500 may be a power system as in the case where the power conversion apparatus 1000 is applied to a PCS for photovoltaic power generation. The power conversion apparatus 1000 may include elements such as a protective component (relay, fuse, etc.) and a noise filter in addition to the configuration described above. Further, as will be described in a later embodiment, a three-phase output power converter can be configured by using three power converters 1000.

FIG. 2 is a modification of the configuration of the power conversion device.

The power conversion device 2000 in FIG. 2 has a configuration in which the

reactors

301 and 303 are deleted (short-circuited) from the power conversion device 1000 in FIG. 1 and the

first bypass units

311 and 313 connected in parallel with these are deleted. . Thus, the structure by which a reactor is inserted in series in at least 1 place among the connection places of cells may be sufficient. In addition, about the installation position of the cell in which a reactor is provided, it is arbitrary.

FIG. 3 is a diagram showing the configuration of the reactor in the power conversion device.

In FIG. 3, the cell 102 and the reactor 302 connected thereto are extracted from the power conversion apparatus 1000 of FIG. 1, and an additional configuration is shown. Similar other examples may be applied to reactors connected to other cells (101, 103, 104). Although illustration of the 1st bypass part connected in parallel with a reactor is abbreviate | omitted in FIG. 3, in fact, a 1st bypass part is connected in parallel with all or one part reactor in FIG.

FIG. 3A shows an example in which two

reactors

302 and 305 are connected in series to the output terminal of the cell 102. As described above, a plurality of reactors may be inserted at one place where the cells are connected to each other. Although illustration is abbreviate | omitted, the structure which inserts the reactor group which connected the several reactor in parallel in the connection location of cells may be sufficient.

3B, the reactor 302 is connected to one of the output terminals of the cell 102, and the reactor 306 is connected to the other.

Reactors

302 and 306 may share a core (iron core). In the configuration of FIGS. 3A and 3B, the combined inductance Ls is adjusted by changing the number of reactors inserted in series with respect to the output current path of the power converter. Since a plurality of reactors are used as shown in FIG. 1, a small-sized and low-cost general-purpose product can be used for each reactor, and the number of reactors can be easily changed.

FIG. 3C is a configuration diagram in which a fuse 307 is connected in series with the reactor 302. Other protective parts such as resistors and thermistors are not limited to fuses. With this configuration, the cell 102 and the load can be protected from overcurrent.

3D is a configuration diagram in which a capacitor 308 is connected between the

reactors

302 and 306 in addition to connecting the

reactors

302 and 306 as in FIG. 3B. By providing the capacitor 308, the effect of reducing the harmonic current can be enhanced.

FIG. 4 is a configuration example of the power converter cell. In the configuration of FIG. 4, it is assumed that the power source 400 is a DC power source and the power converter outputs AC power to the load 500. The other cells 102 to 104 have the same configuration.

4 is composed of a converter 11 and an inverter 21. Converter 11 converts the voltage input to cell 101 to generate DC link voltage Vdc1. Similarly, the cells 102 to 104 include converters, and generate DC link voltages Vdc2 to Vdc4, respectively. Here, the DC link voltages Vdc1 to Vdc4 of the respective cells may all be equal values or may be different values. However, in the following, for convenience of explanation, it is assumed that the DC link voltages Vdc1 to Vdc4 are all controlled to the same value, and the value is “Vdc” unless otherwise specified.

FIG. 4 shows a resonant converter, which is a kind of isolated DC-DC converter, as a specific circuit system of the converter 11. Resonant converters are isolated DC-DC converters suitable for miniaturization and high efficiency, and are used in a wide range of fields from industry to consumer. Since the resonant converter itself is a publicly known technique, although details are omitted, the DC link voltage Vdc1 can be controlled to a predetermined value by the on / off operation of four switching elements (MOSFETs in FIG. 4). Note that the specific circuit system of the converter is not limited as long as the DC link voltage can be generated.

The inverter 21 converts the DC link voltage Vdc1 to generate the output voltage Vo1 of the cell 101. Similarly, the cells 102 to 104 include inverters, and convert DC link voltages Vdc2 to Vdc4 to generate output voltages Vo2 to Vo4 of the respective cells. In FIG. 4, an H-bridge single-phase inverter is shown as a specific circuit system of the inverter 21. Since the H-bridge type single-phase inverter itself is a well-known technique, the details thereof will be omitted, but the inverter 21 has an Vo1 (instantaneous value) by ON / OFF operation of four switching elements (MOSFETs in FIG. 4). Can be controlled to any of + Vdc, 0, and −Vdc. In other words, the inverter 21 outputs the DC link voltage as it is, or makes the output voltage substantially zero, or outputs it by inverting the polarity of the DC link voltage. In addition, the specific circuit system of an inverter is not ask | required.

PWM (pulse width modulation) can be applied to control the inverter 21. In this case, the inverter 21 can output any voltage satisfying −Vdc ≦ Vo1 ≦ + Vdc as the average voltage in the PWM cycle. That is, within the above range, Vo1 can be controlled according to the target value. Details of the PWM will be described with reference to FIG.

A voltage detector 10 for detecting the DC link voltage Vdc1 is shown in the converter 11 of FIG. The value of the DC link voltage Vdc1 detected by the voltage detector 10 is output to the control device 200. The detection value of the DC link voltage Vdc1 corresponds to the detection signal described in the description of FIG. Control device 200 uses the detected value of DC link voltage Vdc1 for feedback control of DC link voltage Vdc1. As an example of the voltage detector 10, a voltage dividing circuit using a resistor can be considered. The converter 11 may include a current and temperature detector in addition to the voltage detector 10. Similarly, the inverter 21 may include a voltage, current, and temperature detector.

As the configuration of the converter 11 when the power source 400 is an AC power source, a configuration in which a rectifier circuit (AC-DC converter) is added to the previous stage of the resonant converter in FIG. The configuration of FIG. 4 can also be applied to later embodiments.

FIG. 5A is an example of a combined output voltage (Vos) waveform of the power converter. FIG. 5B is a waveform of Vos when PWM is used. A sine wave indicated by a broken line in FIGS. 5A and 5B is a fundamental wave component included in Vos. This fundamental wave component may be considered as the target value of Vos, that is, the target value of the output voltage of the power converter. The inverter of each cell can output either + Vdc, 0, or −Vdc as an instantaneous value. Therefore, the instantaneous value of Vos is any of -4Vdc, -3Vdc, ..., 0, ..., + 3Vdc, + 4Vdc. Then, as shown in FIGS. 5A and 5B, a stepped Vos is generated using these voltage values. The voltage of one step of the staircase becomes the DC link voltage Vdc.

The Vos waveform in FIG. 5A is generated by changing the number of cells that output + Vdc in accordance with the phase of the AC voltage if the AC voltage is a positive half cycle. That is, as the AC voltage phase advances and the instantaneous value of the fundamental wave component increases, the number of cells that output + Vdc is increased. The same applies to the negative half cycle, and the number of cells that output −Vdc may be changed according to the phase of the AC voltage.

FIG. 5B shows a Vos waveform when PWM is used. FIG. 5B also shows a waveform in which the time axis is expanded for a period in which the instantaneous value of Vos alternately repeats +3 Vdc and +4 Vdc. The time Ts shown in this enlarged waveform is a PWM cycle, and is set as a sufficiently short time compared to the Vos cycle. The average value of Vos in the PWM period is controlled to an arbitrary value within the range of −4 Vdc ≦ Vos ≦ + 4 Vdc. By changing Vos (average value thereof) into a sine wave with the PWM cycle Ts as the control cycle, the pseudo sine wave voltage shown in FIG. 5B can be generated.

5A and 5B, the combined output voltage Vos is a stepped pseudo sine wave voltage, and therefore includes a harmonic component in addition to the fundamental wave component indicated by the broken line. Therefore, the reactors 301 to 304 are used to reduce the harmonic component of the output current.

FIG. 6 is a configuration example of the first bypass unit 311. FIG. 6 also shows the cell 101, the control device 200, and the reactor 301. In FIG. 6, the 1st bypass part 311 is comprised by a switching element. Specifically, a bidirectional switch is configured by two IGBTs and a diode, and is used as the first bypass unit 311. The control device 201 outputs two IGBT drive signals as bypass signals. The other first bypass units 312 to 314 can be similarly configured.

6 can be mounted on a substrate by using discrete component IGBTs. The first bypass unit 311 may be mounted on a substrate on which the cell 101 is mounted. The same applies to other cells.

An example of the specific control method of the first bypass unit, including the cell control method, will be described. In this example, as shown in FIG. 4, it is assumed that the cell 101 includes a converter 11 and an inverter 21, and the other cells have the same configuration.

The control device 200 controls the DC link voltage Vdc to a target value by outputting a control signal to the converter of each cell. Here, when the power conversion apparatus 1000 is applied to a PCS for photovoltaic power generation, the voltage of the power supply 400, that is, the voltage of the solar battery may fluctuate every moment. When a resonant converter is used as shown in FIG. 4, it is known that the conversion efficiency of the resonant converter can be improved by controlling Vdc higher as the voltage of the power supply 400 is higher, and suppressing fluctuations in the boost ratio of the resonant converter. It has been.

Further, when the power conversion apparatus 1000 is applied to driving a high voltage motor, the amplitude of the combined output voltage Vos to be output varies depending on the rotational speed of the motor. It is conceivable that the DC link voltage Vdc is also controlled to be high under the condition of increasing the amplitude of Vos. As described above, a method of varying the voltage Vdc according to the operating conditions of the power conversion apparatus 1000 can be considered.

As shown in FIG. 5, the waveform of the composite output voltage Vos has a stepped shape in which the voltage of one step is the DC link voltage Vdc. Since the voltage for one step of the Vos waveform increases as Vdc increases, the harmonic component included in Vos also increases. Therefore, the inductance necessary for reducing the harmonic current to a predetermined value is also increased.

Therefore, the control device 200 outputs a bypass signal to the first bypass units 311 to 314 so that the combined inductance (Ls) increases as the DC link voltage Vdc increases. That is, the higher the DC link voltage Vdc, the smaller the number (N) of first bypass sections to be turned on among the first bypass sections 311 to 314.

FIG. 7 shows the relationship between the DC link voltage Vdc and the combined inductance Ls realized by this control. 7 is stored in a storage unit (not shown) in the control device 200. In FIG. 7, the horizontal axis is the DC link voltage Vdc, and Vdc is controlled in the range of the minimum value V1 to the maximum value V5. In FIG. 7, the vertical axis represents the combined inductance Ls, and all the inductances of the reactors 301 to 304 are L1, and Ls is controlled in the range of the minimum value L1 to the maximum value 4L1. In FIG. 7, N is the number of first bypass units to be turned on. For example, when Vdc is greater than V1 and less than or equal to V2, the required inductance is L1, and the number N of first bypass parts to be turned on is 3. That is, the number of reactors to be bypassed is determined for each range of Vdc, and the number of reactors to be bypassed is determined according to the detected value of DC link voltage Vdc.

Of the reactors 301 to 304, which reactor is bypassed is arbitrary. Even if the inductance values of reactors 301 to 304 are different from each other, the number N of first bypass sections to be turned on may be determined so as to satisfy Ls suitable for DC link voltage Vdc. Note that since the output voltage (Vo1 to Vo4) of each cell includes information on the DC link voltage Vdc, the number N of first bypass units to be turned on by indirectly detecting Vdc from the output voltage of each cell is determined. You may decide.

As a modification of the specific control method of the first bypass unit, the harmonic current component becomes relatively larger as the load current of the power converter is smaller. Control may be performed to decrease the number N.

FIG. 8 shows a configuration example of the control device 200 that realizes the above-described control, and shows processing / calculation contents as a block diagram. In FIG. 8, the cell 101, the reactor 301, and the first bypass unit 311 are also shown. Actually, the control device 200 outputs signals to other cells, reactors, and first bypass units.

The control device 200 includes a target value setting unit 210, a converter control unit 211, an inverter control unit 212, and a first bypass control unit 213.

The target value setting unit 210 determines the target values of the DC link voltages (Vdc1 to Vdc4) of each cell and the output voltages (Vo1 to Vo4) of each cell based on the target value related to the output voltage or output current of the power converter 1000. The target values of Vdc1 to Vdc4 are output to the converter control unit 211, and the target values of Vo1 to Vo4 are output to the inverter control unit 212, respectively. Here, the target value related to the output voltage or output current of the power conversion apparatus 1000 is input from the outside or is generated inside the control apparatus 200.

Further, the target value setting unit 210 sets the number of first bypass units to be turned on based on the calculated target values of the DC link voltages Vdc1 to Vdc4 and the relationship between the DC link voltage Vdc and Ls shown in FIG. N) is determined and output to the first bypass control unit 213. If all of Vdc1 to Vdc4 are controlled to be equal, these can be considered as Vdc in FIG. 7 and the relationship in FIG. 7 can be used as it is. In the case of controlling Vdc1 to Vdc4 to different values, a method in which the average value or the median value thereof is set to Vdc in FIG. 8 can be considered. Note that the detection values of Vdc1 to Vdc4 may be used instead of the target values of Vdc1 to Vdc4.

Based on the target values of DC link voltages Vdc1 to Vdc4 input from target value setting unit 210 and the detected values of Vdc1 to Vdc4 input from the converters of each cell, converter control unit 211 sets Vdc1 to Vdc4 as target values. A control signal is output to the converter of each cell so as to be a value. Specific calculation contents of the converter control unit 211 are feedback control calculation and PWM control in the resonance type converter. Since these are publicly known techniques, details are omitted.

Based on the target value of the output voltage (Vo1 to Vo4) of each cell input from the target value setting unit 210, the inverter control unit 212 sends a control signal to the inverter of each cell so that Vo1 to Vo4 become the target value. Output. Since the specific calculation contents of the inverter control unit 212 are described when FIG. 5 is described, they are omitted here.

The first bypass control unit 213 outputs a bypass signal to the first bypass units 311 to 314 in accordance with the input from the target value setting unit 210. For example, when one of the reactors 301 to 304 is bypassed, that is, when N = 1, a specific algorithm for determining which reactor is bypassed is arbitrary.

FIG. 9 is a flowchart in which the control device 200 controls the first bypass unit based on the DC link voltage Vdc. First, the control device 200 refers to the detected value of the DC link voltage Vdc or the target value of Vdc (step 901). Thereafter, the number (N) of reactors to be bypassed is obtained using the relationship between Vdc and the combined inductance Ls (step 902). Further, a first bypass unit to be turned on among the first bypass units 311 to 314 is obtained, and a bypass signal is output from the first bypass control unit 213 to the target first bypass unit (step 903), and the control ends. To do.

FIG. 10 is an example of a mounting form of all the cells, reactors, and first bypass units included in the power conversion device, and is a plan view when viewed from above. A reactor and a first bypass unit are mounted on the substrates 701 to 704 in the same manner as the substrate 701 in FIG. As shown in FIG. 10, the cells 101 to 104 and the substrates 701 to 704 are arranged, and these are wired by a conductor bar (bus bar) or the like, thereby connecting the outputs of the cells 101 to 104 and the reactor in series. A lead wire may be used instead of the conductor rod. In FIG. 10, the symbol 710 is added to one of the plurality of conductor rods, and the symbols are omitted for the other conductor rods. Also, the wiring connecting the cells 101 to 104 and the power supply 400 is not shown.

The cells 101 to 104 and the substrates 701 to 704, that is, all the components of the power conversion device can be housed in the same housing, and there is no need to provide a separate housing for the reactor or the bypass unit. As a result, the power conversion device as a whole can be reduced in size and cost.

FIG. 11 is an example of a mounting form of the reactor 301 and the first bypass unit 311 and is a plan view when viewed from above.

The reactor 301 and the first bypass unit 311 are mounted on the substrate 701. Note that the wiring pattern of the substrate 701 is not shown. Examples of the reactor that can be easily mounted on the substrate 701 include a reactor using a toroidal core often used in a switching power supply device, or a reactor using an E-type core. Since a plurality of reactors are used, that is, the reactor is divided into a plurality of reactors, a small and lightweight reactor that can be mounted on a substrate can be applied to each reactor.

FIG. 11 shows an example in which the first bypass unit 311 is configured by two switching elements (71 and 72). Each switching element incorporates one IGBT and one diode shown in FIG.

The substrate 701 is connected to the cell 101 using a conductor rod 711 for wiring. Two

conductor rods

711 and 712 are connected to the cell 101, and these are connected to two output terminals provided in the cell 101, respectively. In addition, illustration was abbreviate | omitted about the internal structure of the cell 101, ie, the detail of the member with which the cell 101 is provided.

With such a mounting form, the substrate 701, that is, the reactor 301 and the first bypass unit 311 can be arranged near the cell 101, and all of them can be housed in the same casing.

In addition to the reactor 301 and the first bypass unit 311, the first bypass control unit 213 of the control device 200 can be mounted on the substrate 701 as shown in FIG. Components included in the first bypass control unit 213 include a drive device for the first bypass unit 311, a control device such as a microcomputer and an IC, and peripheral components of the control device, all of which can be mounted on the substrate 701. . In addition, illustration was abbreviate | omitted about the detail of the 1st bypass control part 213, and connection (wiring) with the other element with which the control apparatus 200 is provided.

The first bypass control unit 213 is mounted near the first bypass unit 311 according to such a mounting form. Further, the first bypass control unit 213 can control the first bypass unit 311 using the wiring pattern of the substrate 701. In this configuration, the first bypass control unit 213 is disposed away from the first bypass unit 311, and electromagnetic noise is generated in the bypass signal compared to the case where the first bypass unit 311 is controlled using a long-distance wiring. This is advantageous in preventing mixing.

FIG. 12 is another example of the mounting form of the reactor and the first bypass unit. In FIG. 12, as illustrated in FIGS. 3B and 3D, it is assumed that the reactor is connected to the two output terminals included in the cell 101. Moreover, the case where the 1st bypass part was connected to each reactor was assumed.

On the substrate 705, two

reactors

301 and 305 and two

first bypass parts

311 and 315 are mounted. The first bypass unit 315 includes two switching elements (73 and 74).

The substrate 705 is connected to the cell 101 by

conductor bars

714 and 715. The two

conductor rods

714 and 715 are connected to two output terminals provided in the cell 101, respectively. Three more substrates having the same configuration as the substrate 705 can be prepared and connected to the cells 102 to 104, respectively.

FIG. 13 is another example of the mounting form of the reactor and the first bypass unit. In addition to the reactor and the first bypass unit, the components of the cell 101 are mounted on the substrate 706. As the components of the cell 101, only the inverter 21 shown in FIG. 4 (the four switching elements included in the inverter 21 are 75 to 78) and the inverter control unit 212 of the control device 200 are shown. 706 may be mounted.

13 can be said to be a form in which the cell, the reactor, and the first bypass unit are integrated. With such a mounting form, it is possible to further reduce the size and cost of the power conversion apparatus as a whole.

In this embodiment, even if the operating conditions of the power conversion device fluctuate during operation, by switching the composite inductance by bypassing the reactor, the harmonic current is reduced to a predetermined value while the reactor current is reduced. Loss can be minimized.

In the power conversion device of the present invention, since the reactor is divided into a plurality of reactors, a small-sized and low-cost general-purpose product can be used for each reactor. In addition, the combined inductance can be finely adjusted. Since the reactor, the first bypass unit, and the control device can be arranged close to each other, the wiring connecting them can be shortened, and the switching of the combined inductance can be realized at low cost and in a small space. If the cell, reactor, first bypass unit, and control device can be mounted on the same board, or if they can be placed close together in the same housing, the number of components and the number of installation processes as a whole device will be reduced, and compact, low-cost power conversion The device can be realized and the conversion efficiency of the power conversion device can be improved. At least one reactor is sufficient, and even in one case, power conversion efficiency can be expected to be improved by turning on and off the first bypass unit according to the DC link voltage.

FIG. 14 shows the configuration of the power conversion device according to the second embodiment of the present invention.

In the power conversion device 3000, the second bypass units 321 to 324 are connected between the output terminals of the cells 101 to 104, respectively. Although the second bypass units 321 to 324 are illustrated as switches in FIG. 14, relays, switching elements (semiconductors), and the like can be applied as these switches.

14 outputs a bypass signal for ON / OFF control of the second bypass units 321 to 324. In FIG. 14, only the bypass signal for the second bypass unit 321 is shown in order to prevent the drawing from becoming complicated. Actually, a bypass signal is also output to the second bypass units 322 to 324.

The configuration shown in FIG. 4 of the first embodiment is applied as the configuration of the cell 101 in the second embodiment. That is, the cell 101 includes the converter 11 and the inverter 21. The other cells have the same configuration. The configuration described in the first embodiment can be applied to the reactors 301 to 304 and the first bypass units 311 to 314.

FIG. 15 is a configuration example of the second bypass unit 321. FIG. 15 also shows the cell 101, the control device 201, the reactor 301, and the first bypass unit 311. The second bypass unit 321 is configured by a switching element. Specifically, a bidirectional switch is configured by two IGBTs and a diode, and is used as the second bypass unit 321. The control device 201 outputs two IGBT drive signals as bypass signals.

The control device 201 turns off all the second bypass units 321 to 324 during normal operation (when operating by operating all the cells). On the other hand, when stopping some cells due to a failure or maintenance, the second bypass unit connected to the same cell is turned on, and the DC link voltage is applied to at least one of the other cells. Increase. For example, when the cell 101 is stopped, the second bypass unit 321 is turned on and the DC link voltage of the cells 102 to 104 is increased. As a result, the power conversion device 3000 can continue operation without damaging the output voltage range by the cells 102 to 104 even after the cell 101 is stopped.

FIGS. 16A and 16B are waveforms of the combined output voltage Vos when one cell is stopped. FIGS. 5A and 5B described in the first embodiment are shown in FIGS. Comparison with these is shown as a Vos waveform during normal operation. FIG. 16 shows a case where the DC link voltage is increased from Vdc in FIG. 5 to Vdc ′ = (4/3) × Vdc for three cells that continue to operate. In the Vos waveform of FIG. 16, the number of steps of the Vos waveform decreases by (3/4) times compared to FIG. 5, but the voltage value per step increases by (4/3) times. Amplitude can be maintained.

As described in the first embodiment, when the voltage for one step of the Vos waveform increases, the harmonic voltage included in Vos also increases. Therefore, the reactor inductance required to reduce the harmonic current to a predetermined value also increases. Therefore, the control device 201 outputs a bypass signal to the first bypass units 311 to 314 so that the combined inductance Ls becomes large. That is, as the number of cells to be stopped increases and the DC link voltage is increased, the number (N) of first bypass sections to be turned on among the first bypass sections 311 to 314 is decreased. As the relationship between the DC link voltage and Ls at this time, the relationship shown in FIG.

FIG. 17 is a configuration example of the control device 201 that realizes the above control, and shows processing and calculation contents as a block diagram. FIG. 17 also shows the cell 101, the reactor 301, the first bypass unit 311, and the second bypass unit 321. Actually, the control device 201 also outputs signals to other cells, the first bypass unit, and the second bypass unit.

The control device 201 includes a second bypass control unit 214 in addition to the target value setting unit 210, the converter control unit 211, the inverter control unit 212, and the first bypass control unit 213 described in the first embodiment.

Each cell outputs a physical quantity such as voltage, current, temperature, or a state such as abnormality to the target value setting unit 210 as a detection signal. FIG. 17 shows a case where the converter 11 and the inverter 21 of the cell 101 output detection signals to the target value setting unit 210, respectively. Although illustration is omitted, when the user intentionally stops the cell for reasons such as maintenance, a signal may be input to the target value setting unit 210 from the outside.

The target value setting unit 210 determines whether or not to stop each cell in addition to the operation described in the first embodiment, and outputs a signal indicating this to the second bypass control unit 214.

The second bypass control unit 214 outputs a bypass signal to the second bypass units 321 to 324 in accordance with the input from the target value setting unit 210. The converter control unit 211, the inverter control unit 212, and the first bypass control unit 213 operate in the same manner as in the first embodiment.

In Example 2 described above, even when some of the cells are stopped, the operation can be continued without damaging the output voltage range with the remaining cells. As a result, there is an advantage that the reliability as the power conversion device is improved and the maintenance of the cell can be realized even during operation. Further, even if the DC link voltage is increased in the process of realizing this, the loss of the reactor can be minimized while reducing the harmonic current to a predetermined value.

In the third embodiment of the present invention, an auxiliary winding is provided in the reactor, and a voltage generated in the auxiliary winding is converted to obtain a power supply voltage of the control device. This configuration can be applied to all the power conversion devices described in the first and second embodiments.

FIG. 18 is a part of the configuration of the power conversion device according to the third embodiment, and illustrates additions and changes in the third embodiment based on the configuration illustrated in FIG. 17 of the second embodiment. . In FIG. 18, the reactor 301 includes an auxiliary winding 331. The control power generation unit 220 converts the AC voltage generated in the auxiliary winding 331 and outputs the power supply voltage of the control device 202. The power supply voltage of the control device 202 corresponds to an operating voltage of a microcomputer or IC, an operating voltage of a driving device for a switching element, or the like. The control device 202 includes a target value setting unit 210, a converter control unit 211, an inverter control unit 212, a first bypass control unit 213, and a second bypass control unit 214 as components other than the control power generation unit 220.

In FIG. 18, plus (+) and minus (−) symbols are given to the two output terminals provided in the control power generation unit 220. These mean the voltage output from the control power supply generation unit 220, that is, the positive electrode and the negative electrode of the power supply voltage of the control device 202, respectively. Similarly, plus (+) and minus (−) symbols are assigned to the components of the control device 202. The positive terminal of the power supply voltage output from the control power generation unit 220 is input to the input terminal described as plus (+). Similarly, the negative side of the power supply voltage output from the control power supply generation unit 220 is input to the input terminal described as minus (−).

The output terminal of the control power generation unit 220 is connected to each component of the control device 202 and supplies power for operating them. However, the control power generation unit 220 may be configured to supply power to some components included in the control device 202. The control power generation unit 220 is a type of DC power supply device, and can be configured using a rectifier circuit, a DC-DC converter, a smoothing capacitor, and the like. As long as the DC voltage can be generated, the specific circuit system of the control power generation unit 220 is not limited. In FIG. 18, the control power generation unit 220 is illustrated as a component of the control device 202, but it is not necessary to be mounted on the same board as the control device 202.

As described in the first embodiment, the control device 202 may be provided for each cell. Similarly, the reactors 302 to 304 can be provided with auxiliary windings to supply power to the control devices of the cells 102 to 104, respectively. Not all of the reactors 301 to 304 need to have auxiliary windings.

Consider the case where the cell 101 is stopped for reasons such as failure or maintenance and the operation is continued only with the cells 102 to 104 as described in the second embodiment. Even if the cell 101 is stopped, if the second bypass unit 321 is on and the remaining cells 102 to 104 operate, a current flows through the reactor 301, so that a voltage is generated in the auxiliary winding 331. Using this voltage, the second bypass control unit 214 can be operated, and the second bypass unit 321 can be kept on.

The configuration in which the auxiliary winding is provided in the reactor and the power supply voltage of the control device is obtained by converting the voltage generated in the auxiliary winding can be applied even when the first bypass unit and the first bypass control unit are not provided. FIG. 19 is another example of the configuration in the third embodiment, and is a configuration obtained by removing the first bypass unit 311 and the first bypass control unit 213 from FIG.

Also in the configuration of FIG. 19, when the cell 101 is stopped due to a failure or maintenance, the second bypass control unit 214 is operated using the voltage generated in the auxiliary winding 331 and the second bypass unit 321 is operated. Can be kept on.

FIG. 20 is an example of a mounting form of the cell, the reactor and the auxiliary winding, the second bypass unit, and the control device, and is a plan view when viewed from above.

In FIG. 20, as shown in FIGS. 3B and 3D, it is assumed that a reactor is connected to each of the two output terminals included in the cell 101. Of the two

reactors

301 and 306, the reactor 301 is provided with an auxiliary winding 331. FIG. 20 illustrates a configuration in which the auxiliary winding 331 is wound around the reactor 301 using the toroidal core.

In addition to the reactor and the auxiliary winding, the second bypass unit 321, the second bypass control unit 214 included in the control device 202, and the control power generation unit 220 are mounted on the substrate 707. The second bypass unit 321 includes two switching elements (79 and 80). The substrate 707 is connected to the cell 101 by

conductor bars

720 and 721. The two

conductor rods

720 and 721 are connected to the two output terminals provided in the cell 101, respectively. Three more substrates having the same configuration as the substrate 707 can be prepared and used by being connected to the cells 102 to 104, respectively.

According to such a mounting form, the substrate 707, that is, the reactor, the auxiliary winding, the second bypass unit, and the control device can be arranged near the cell 101, and all of them can be stored in the same casing. The second bypass control unit 214 is mounted near the second bypass unit 321. In addition, the second bypass control unit 214 can control the second bypass unit 321 using the wiring pattern of the substrate 707. In this configuration, the second bypass control unit 214 is disposed at a location away from the second bypass unit 321, and electromagnetic noise is generated in the bypass signal as compared with the case where the second bypass unit 321 is controlled using a long-distance wiring. This is advantageous in preventing mixing.

In the fourth embodiment of the present invention, a three-phase AC output power converter is configured using three power converters described above.

FIG. 21 shows the configuration of the power conversion device 4000 in the fourth embodiment. The power conversion device 4000 includes three power conversion devices 1000 described in the first embodiment. As shown in FIG. 21, one of the output terminals included in the three power conversion apparatuses 1000 constitutes a three-phase output terminal and is connected to the three-phase load 501. The other of the output terminals included in the three power converters 1000 is connected to each other to form a neutral point in a Y-connected three-phase AC circuit.

As described in the first embodiment, the power conversion device 1000 includes the control device 200. Therefore, the power conversion device 4000 of FIG. 21 includes three control devices 200, but the three control devices may be combined into one. In FIG. 21, three sets of power converters 1000 are used, but power converters 2000 to 3000 described above can also be used.

With the above configuration, the effect of the present invention can be obtained even in a power converter that outputs three-phase alternating current, and can be applied to an inverter that drives a three-phase high-voltage motor and a PCS for a three-phase alternating current power system.

FIG. 22 is a timing chart for sequentially turning on / off the plurality of first bypass units 311 to 314 in the fifth embodiment. In FIG. 22, it is assumed that only one of the first bypass units 311 to 314 is turned on. As shown in FIG. 22, the first bypass unit to be turned on is replaced with time, and the time during which each first bypass unit is in the on state is equalized. As a result, the life of the first bypass portion can be extended. This control can be applied to all the power conversion devices described in the first to fourth embodiments.

101 to 104 Power converter cells 200 to 203 Control device 210 Target value setting unit 211 Converter control unit 212 Inverter control unit 213 First bypass control unit 214 Second bypass control unit 220 Control power generation unit 301 to 306 Reactor 307 Fuse 308 Capacitor 311 to 314 First bypass part 321 to 324 Second bypass part 331 Auxiliary winding 400 Power source 500 Load 501 Three-phase load 701 to 707 Substrate 710 to 723 Conductor bar (bus bar)
DESCRIPTION OF SYMBOLS 10 Voltage detector 11 Converter 12 Inverter 71-80

Switching element

1000, 2000, 3000, 4000 Power converter

Claims

A plurality of power converter cells;
A control device for controlling the plurality of power converter cells,
The output terminals of the plurality of power converter cells are respectively connected in series,
One or more reactors are inserted in series in a path through which the output current of the power converter cell flows, and a first bypass unit is connected in parallel to at least one of the reactors, The power converter is configured to control the first bypass unit.
The power conversion device according to claim 1,
The said reactor is inserted in series in at least 1 place among the connection places of said each power converter cell, The power converter device characterized by the above-mentioned.
In the power converter device according to claim 1 or 2,
Each of the power converter cells includes a converter that converts an input voltage from the power source to generate a DC link voltage, and an inverter that converts the DC link voltage to an AC voltage and outputs the AC link voltage. The power converter is characterized in that, as the DC link voltage is higher, the number of first bypass units to be turned on among the first bypass units is reduced.
In the power converter device in any one of Claims 1 thru | or 3,
The power converter cell includes a second bypass unit between output terminals, and the control device outputs a bypass signal for ON / OFF control of the second bypass unit, and one of the power converter cells. When stopping the unit, the second bypass unit included in the power converter cell to be stopped is turned on, and the DC link voltage is increased in at least one power converter cell among the power converter cells not to be stopped. A power conversion device.
In the power converter device in any one of Claims 1 thru | or 4,
The number of the 1st bypass parts to turn on among the 1st bypass parts is decreased, so that the load current of the power converters is small.
In the power converter device in any one of Claims 1 thru | or 5,
At least one of the reactors includes an auxiliary winding, and generates a power supply voltage of the control device from a voltage generated in the auxiliary winding.
In the power converter device in any one of Claims 2 thru | or 5,
The power converter according to claim 1, wherein the converter is a resonant converter, and the inverter is an H-bridge type single-phase inverter circuit including four switching elements.
In the power converter device in any one of Claims 1 thru | or 7,
All of the input terminals of the plurality of power converter cells are connected in parallel to the power supply.
In the power converter device in any one of Claims 1 thru | or 8,
Each power converter cell and the first bypass unit provided on the output side of each power converter cell are housed in a single casing.