JP2023052719A - Power conversion circuit, power conversion system, method for controlling power conversion circuit, and program - Google Patents

Abstract

To suppress common-mode noise without providing a capacitor on a DC side.SOLUTION: A power conversion circuit 1 includes a high-side arm 11, a low-side arm 12, and a filter circuit 13. The power conversion circuit 1 performs first control of turning on all of a plurality of first switching elements Q11, Q13, and Q15, or second control of turning on all of a plurality of second switching elements Q12, Q14, and Q16. A third terminal T103 is electrically connected to a specific terminal excluding a plurality of AC terminals T21, T22, and T23.SELECTED DRAWING: Figure 1

Description

The present disclosure generally relates to a power conversion circuit, a power conversion system, a power conversion circuit control method, and a program. More specifically, the present disclosure relates to a power conversion circuit that converts power in at least one direction between DC power and AC power, a power conversion system, a control method for the power conversion circuit, and a program.

Patent Literature 1 describes a grid-connected inverter that converts the output of a DC power supply into an AC power supply and connects it to the power system of an electric utility company. The grid-connected inverter described in Patent Document 1 includes an inverter, a first capacitor pair, a second capacitor pair, and a bypass.

The first capacitor pair is two capacitors connected in series and placed between the input terminals of the inverter. The second capacitor pair has two capacitors connected in series, and is arranged between output terminals of a filter circuit provided on the output side (AC side) of the inverter. A connection point between the two capacitors of the first capacitor pair and a connection point between the two capacitors of the second capacitor pair are connected by a neutral point connection line to form a bypass path.

Japanese Patent No. 5422178

By the way, in the grid-connected inverter (power conversion system) described in Patent Document 1, if the first capacitor pair is not provided between the input terminals of the inverter (power conversion circuit), it is possible to form the bypass path described above. Therefore, it was difficult to suppress common mode noise.

An object of the present disclosure is to provide a power conversion circuit, a power conversion system, a power conversion circuit control method, and a program capable of suppressing common mode noise without providing a capacitor on the DC side.

A power conversion circuit according to an aspect of the present disclosure is a power conversion circuit that converts power in at least one direction between DC power and AC power. The power conversion circuit includes a high-side arm, a low-side arm, and a filter circuit. The high-side arm has a plurality of first switching elements. The plurality of first switching elements are electrically connected between one of the plurality of AC terminals different from each other and the same first terminal. The low-side arm has a plurality of second switching elements. The plurality of second switching elements are electrically connected between one of the plurality of AC terminals and the same second terminal. The filter circuit has a plurality of capacitors and smoothes the AC voltage output via the high-side arm and the low-side arm. An AC power source or an AC load is electrically connected to the plurality of AC terminals. Each of the plurality of capacitors is electrically connected between one of the plurality of AC terminals and the same third terminal. The power conversion circuit performs first control to turn on all of the plurality of first switching elements or second control to turn on all of the plurality of second switching elements. The third terminal is electrically connected to specific terminals other than the plurality of AC terminals.

A power conversion system according to an aspect of the present disclosure includes the power conversion circuit and another power conversion circuit. The other power conversion circuit is provided on the DC side of the power conversion circuit. The other power conversion circuit performs power conversion in at least one direction between first DC power and second DC power as the DC power.

A power conversion circuit control method according to an aspect of the present disclosure converts power in at least one direction between DC power and AC power, and includes a high-side arm, a low-side arm, and a filter circuit. It is a control method of the power inverter circuit provided. The high-side arm has a plurality of first switching elements. The plurality of first switching elements are electrically connected between one of the plurality of AC terminals different from each other and the same first terminal. The low-side arm has a plurality of second switching elements. The plurality of second switching elements are electrically connected between one of the plurality of AC terminals and the same second terminal. The filter circuit has a plurality of capacitors and smoothes the AC voltage output via the high-side arm and the low-side arm. An AC power supply or an AC load is electrically connected to the plurality of AC terminals. Each of the plurality of capacitors is electrically connected between one of the plurality of AC terminals and the same third terminal. The third terminal is electrically connected to specific terminals other than the plurality of AC terminals. In the control method for the power conversion circuit, first control for turning on all of the plurality of first switching elements or second control for turning on all of the plurality of second switching elements is performed.

A program according to one aspect of the present disclosure is a program for causing one or more processors to execute the control method for the power conversion circuit.

According to the present disclosure, there is an effect that common mode noise can be suppressed without providing a capacitor on the DC side.

FIG. 1 is a circuit diagram showing a schematic configuration of a power conversion circuit and a power conversion system according to an embodiment. FIG. 2 is a waveform diagram showing the operation in the inverter mode of the power conversion system according to Comparative Example 1. FIG. FIG. 3 is a partially omitted circuit diagram showing a first state of the same power conversion circuit. FIG. 4 is a partially omitted circuit diagram showing a second state of the same power conversion circuit. FIG. 5 is a partially omitted circuit diagram showing a third state of the same power conversion circuit. FIG. 6 is a partially omitted circuit diagram showing a fourth state of the same power conversion circuit. FIG. 7 is a diagram showing a simulation result of the same power conversion system. FIG. 8 is a partially omitted circuit diagram showing the first state of the power conversion circuit according to Comparative Example 2. As shown in FIG. FIG. 9 is a partially omitted circuit diagram showing a second state of the same power conversion circuit. FIG. 10 is a partially omitted circuit diagram showing a third state of the same power conversion circuit. FIG. 11 is a partially omitted circuit diagram showing a fourth state of the same power conversion circuit. FIG. 12 is a diagram showing a simulation result of the same power conversion system. FIG. 13 is a waveform diagram showing operation in the inverter mode of the power conversion system according to the embodiment. FIG. 14 is a diagram showing a simulation result of the same power conversion system. 15 is a circuit diagram illustrating a schematic configuration of a power conversion circuit and a power conversion system according to Modification 1 of the embodiment; FIG. FIG. 16 is a circuit diagram showing a schematic configuration of a power conversion circuit and a power conversion system according to Modification 2 of the embodiment. FIG. 17 is a circuit diagram showing a schematic configuration of a power conversion circuit and a power conversion system according to Modification 3 of the embodiment. FIG. 18 is a circuit diagram showing a schematic configuration of a power conversion circuit and a power conversion system according to Modification 4 of the embodiment.

(embodiment)
A power conversion circuit and a power conversion system according to embodiments will be described below with reference to the drawings. However, the embodiments and modifications described below are merely examples of the present disclosure, and the present disclosure is not limited to the embodiments and modifications described below. Other than the embodiments and modifications described below, various modifications can be made according to the design and the like within the scope of the technical idea of the present disclosure.

Each drawing described in the following embodiments and the like is a schematic drawing, and the ratio of the size and thickness of each component in each drawing does not necessarily reflect the actual dimensional ratio. Not necessarily.

(1) Overview First, an overview of the power conversion circuit 1 and the power conversion system 10 according to the present embodiment will be described with reference to FIG.

A power conversion system 10 according to the present embodiment, as shown in FIG. It is a system that converts power between AC terminals T21, T22, and T23. That is, the power conversion circuit 1 according to the present embodiment is a circuit that converts power in at least one direction between DC power and AC power. A storage battery 5 is electrically connected to the plurality of DC terminals T11 and T12. A power system 6 is electrically connected to the plurality of AC terminals T21, T22, T23. The “power system” referred to in the present disclosure means the entire system for an electric power company such as an electric power company to supply electric power to power receiving facilities of consumers.

The power conversion system 10 according to the present embodiment converts the DC power input from the storage battery 5 into three-phase AC power having a U phase, a V phase, and a W phase, and outputs (transmits) this AC power to the power system 6 )do. The power conversion system 10 also converts three-phase AC power having U-phase, V-phase, and W-phase input from the power system 6 into DC power, and outputs this DC power to the storage battery 5 . In other words, the power conversion system 10 bi-directionally converts power between the two DC terminals T11, T12 and the three AC terminals T21, T22, T23.

In other words, when the storage battery 5 is discharged, the power conversion system 10 converts the DC power input from the storage battery 5 into AC power, and outputs (discharges) the AC power to the power system 6 . At this time, the storage battery 5 functions as a "DC power supply", and the power system 6 functions as a "three-phase AC load" having U-phase, V-phase and W-phase. When charging the storage battery 5 , the power conversion system 10 converts AC power input from the power system 6 into DC power, and outputs (charges) the storage battery 5 with this DC power. At this time, the storage battery 5 functions as a "DC load", and the power system 6 functions as a "three-phase AC power supply" having U-phase, V-phase and W-phase. That is, the three AC terminals T21, T22, T23 are electrically connected to the electric power system 6 functioning as an AC power source or an AC load.

As described above, in the grid-connected inverter described in Patent Document 1, when the first capacitor pair is not provided between the input terminals of the inverter, the bypass path between the first capacitor pair and the second capacitor pair is It was difficult to suppress common mode noise. The power conversion circuit 1 and the power conversion system 10 according to the present embodiment employ the following configurations in order to solve the above-described problems.

That is, the power conversion circuit 1 according to the present embodiment is a circuit that converts power in at least one direction between DC power and AC power. The power conversion circuit 1 includes a high-side arm 11 , a low-side arm 12 , and a filter circuit 13 . The high-side arm 11 has a plurality of first switching elements Q11, Q13, Q15. The plurality of first switching elements Q11, Q13, Q15 are electrically connected between one of the plurality of AC terminals T21, T22, T23 different from each other and the same first terminal T101. The low-side arm 12 has a plurality of second switching elements Q12, Q14, Q16. The plurality of second switching elements Q12, Q14, Q16 are electrically connected between one of the plurality of AC terminals T21, T22, T23 and the same second terminal T102. The filter circuit 13 has a plurality of capacitors C11, C12, C13, and smoothes the AC voltage output via the high-side arm 11 and the low-side arm 12. FIG.

An AC power supply or an AC load (the electric power system 6 in this embodiment) is electrically connected to the plurality of AC terminals T21, T22, and T23. Each of the plurality of capacitors C11, C12, C13 is electrically connected between one of the plurality of AC terminals T21, T22, T23 and the same third terminal T103. The power conversion circuit 1 performs first control to turn on all of the plurality of first switching elements Q11, Q13, Q15, or second control to turn on all of the plurality of second switching elements Q12, Q14, Q16. . The third terminal T103 is electrically connected to a specific terminal (the second terminal T102 in this embodiment) other than the AC terminals T21, T22, T23.

Further, the power conversion system 10 according to this embodiment includes the power conversion circuit 1 described above and another power conversion circuit 2 . Another power conversion circuit 2 is provided on the DC side of the power conversion circuit 1 (on the side of the DC terminals T11 and T12). The other power conversion circuit 2 converts power in at least one direction between the first DC power and the second DC power.

As described above, in the power conversion circuit 1 and the power conversion system 10 according to the present embodiment, the third terminal T103 as the neutral point of the plurality of capacitors C11, C12, C13 is connected to the first terminal T101 and the second terminal T102. is electrically connected to any one of a plurality of connection terminals including As a result, common mode noise can be returned to the DC side via the connection terminal, and as a result, common mode noise can be suppressed.

In addition, although the conversion efficiency of the system may decrease only by connecting the third terminal T103 to the connection terminal, for example, the third terminal T103 is connected to the second terminal T102 for a predetermined period (an inversion period to be described later). By performing the second control at Td1), it is also possible to suppress a decrease in the conversion efficiency of the system.

In this embodiment, as an example, a case where a power storage system including the power conversion system 10 and the storage battery 5 is installed in non-residential facilities such as office buildings, hospitals, commercial facilities, and schools will be described.

Especially in recent years, there has been an increasing number of corporations or individuals "selling power" in which power obtained from distributed power sources (for example, solar cells, storage batteries, or fuel cells) is reverse-flowed to the commercial power system. Power selling is realized by grid interconnection that connects the distributed power sources with the commercial power grid. In grid interconnection, a power conversion system 10 called a power conditioner is used to convert power from a distributed power supply into power suitable for a commercial power system. The power conversion system 10 according to the present embodiment is used as a power conditioner as an example, and between the storage battery 5 as a distributed power source and the power system 6, DC power and three-phase AC power are mutually converted. do.

(2) Configuration Next, configurations of the power conversion circuit 1 and the power conversion system 10 according to the present embodiment will be described with reference to FIG. 1 .

A power conversion system 10 according to the present embodiment includes a power conversion circuit 1 and another power conversion circuit 2, as shown in FIG. In addition, in the present embodiment, the power conversion circuit 1 includes a connection portion 3, a control circuit 4, a plurality of (two in the illustrated example) DC terminals T11 and T12, and a plurality of (three in the illustrated example) AC terminals. T21, T22, and T23 are further provided. The power conversion system 10 is a system that converts power between two DC terminals T11, T12 and three AC terminals T21, T22, T23.

A storage battery 5 functioning as a DC power source or a DC load is electrically connected to the two DC terminals T11 and T12. The three AC terminals T21, T22, T23 are electrically connected to a power system 6 that functions as a three-phase AC power supply or a three-phase AC load having U-phase, V-phase and W-phase. However, the two DC terminals T11, T12 and the three AC terminals T21, T22, T23 may not be included in the power conversion system 10 components. In addition, the term “terminal” used in the present disclosure does not have to be a component for connecting electric wires or the like, and may be, for example, a lead of an electronic component or a part of a conductor included in a circuit board.

(2.1) Power Conversion Circuit The power conversion circuit 1 is, for example, a three-phase inverter circuit. The power conversion circuit 1 includes a high-side arm 11, a low-side arm 12, and a filter circuit 13, as shown in FIG.

The high-side arm 11 has three switching elements Q11, Q13, Q15 as a plurality of first switching elements. Also, the low-side arm 12 has three switching elements Q12, Q14, Q16 as a plurality of second switching elements.

Each of the switching elements Q11 to Q16 is, for example, a depletion-type or enhancement-type n-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). Each of switching elements Q11-Q16 includes a parasitic diode. The parasitic diode of each switching element Q11-Q16 has an anode electrically connected to the source of the corresponding switching element Q11-Q16, and a cathode electrically connected to the drain of the corresponding switching element Q11-Q16.

The switching element Q11 is electrically connected in series with the switching element Q12 between the first terminal T101 and the second terminal T102. Also, the switching element Q13 is electrically connected in series with the switching element Q14 between the first terminal T101 and the second terminal T102. Also, the switching element Q15 is electrically connected in series with the switching element Q16 between the first terminal T101 and the second terminal T102. That is, a series circuit of switching elements Q11 and Q12, a series circuit of switching elements Q13 and Q14, and a series circuit of switching elements Q15 and Q16 are electrically connected between the first terminal T101 and the second terminal T102. connected in parallel to

Drains of the switching elements Q11, Q13, Q15 are electrically connected to the first terminal T101. The sources of the switching elements Q12, Q14, Q16 are electrically connected to the second terminal T102. The source of switching element Q11 is electrically connected to the drain of switching element Q12, and the source of switching element Q13 is electrically connected to the drain of switching element Q14. Also, the source of the switching element Q15 is electrically connected to the drain of the switching element Q16.

The first terminal T101 is electrically connected to a terminal P3 of the connecting portion 3, which will be described later. The second terminal T102 is electrically connected to a terminal N3 of the connecting portion 3, which will be described later.

The filter circuit 13 smoothes the square-wave AC voltage output via the high-side arm 11 and the low-side arm 12 . As a result, the AC voltage is converted into a sinusoidal AC voltage having an amplitude corresponding to the pulse width.

Specifically, as shown in FIG. 1, the filter circuit 13 includes multiple (three in the illustrated example) inductors L11, L12, and L13 and multiple (three in the illustrated example) capacitors C11, C12, and C13. ,have. A first end of inductor L11 is electrically connected to a connection point between switching elements Q11 and Q12, and a second end of inductor L11 is electrically connected to AC terminal T21. A first end of inductor L12 is electrically connected to a connection point of switching elements Q13 and Q14, and a second end of inductor L12 is electrically connected to AC terminal T22. A first end of inductor L13 is electrically connected to a connection point of switching elements Q15 and Q16, and a second end of inductor L13 is electrically connected to AC terminal T23. Capacitor C11 is electrically connected between the second end of inductor L11 and third terminal T103. Capacitor C12 is electrically connected between the second end of inductor L12 and third terminal T103. Capacitor C13 is electrically connected between the second end of inductor L13 and third terminal T103. A third terminal T103 is the neutral point of the capacitors C11, C12, C13.

In other words, the connection point of switching elements Q11 and Q12 is electrically connected to AC terminal T21 corresponding to the U phase via inductor L11. A connection point between switching elements Q13 and Q14 is electrically connected to an AC terminal T22 corresponding to the V phase via an inductor L12. A connection point of switching elements Q15 and Q16 is electrically connected to AC terminal T23 corresponding to the W phase via inductor L13.

By the way, in this embodiment, as shown in FIG. 1, the second terminal T102 and the third terminal T103 are electrically connected. That is, the third terminal T103 is electrically connected to a specific terminal (here, the second terminal T102) other than the AC terminals T21, T22, T23. Furthermore, in this embodiment, the third terminal T103 is directly and electrically connected to the specific terminal. Therefore, in this embodiment, the specific terminal is the second terminal T102.

(2.2) Other power conversion circuit The other power conversion circuit 2 is, for example, a DC/DC converter. The other power conversion circuit 2 includes a first capacitor C1, a first converter section 21, a second converter section 22, and a transformer 23, as shown in FIG. However, the first capacitor C1 does not have to be included in other components of the power conversion circuit 2 .

A first capacitor C1 is electrically connected between the two DC terminals T11 and T12. In other words, the first capacitor C1 is electrically connected to the storage battery 5 via the two DC terminals T11, T12. The first capacitor C1 is, for example, an electrolytic capacitor. The first capacitor C1 has the function of stabilizing the voltage between the two DC terminals T11 and T12.

The first converter unit 21 is a high-frequency inverter that converts the DC voltage applied to the two DC terminals T11 and T12 into, for example, a 20 kHz rectangular-wave high-frequency AC voltage, and supplies the AC voltage to the primary winding 231 of the transformer 23. be.

As shown in FIG. 1, the first converter section 21 has a plurality (four in the illustrated example) of third switching elements Q21 to Q24. Hereinafter, the third switching elements Q21-Q24 may be referred to as "switching elements Q21-Q24". Each of the plurality of switching elements Q21 to Q24 is, for example, a depletion-type or enhancement-type n-channel MOSFET. Each of switching elements Q21-Q24 includes a parasitic diode. The parasitic diode of each switching element Q21-Q24 has an anode electrically connected to the source of the corresponding switching element Q21-Q24, and a cathode electrically connected to the drain of the corresponding switching element Q21-Q24.

The switching element Q21 is electrically connected in series with the switching element Q22 between the fourth terminal T104 and the fifth terminal T105. Also, the switching element Q23 is electrically connected in series with the switching element Q24 between the fourth terminal T104 and the fifth terminal T105. That is, a series circuit of switching elements Q21 and Q22 and a series circuit of switching elements Q23 and Q24 are electrically connected in parallel between the fourth terminal T104 and the fifth terminal T105.

The fourth terminal T104 is electrically connected to the DC terminal T11 on the high potential (positive) side of the two DC terminals T11 and T12. The fifth terminal T105 is electrically connected to the DC terminal T12 on the low potential (negative) side of the two DC terminals T11 and T12. That is, a DC voltage is applied to the fourth terminal T104 and the fifth terminal T105 so that the fourth terminal T104 has a high potential and the fifth terminal T105 has a low potential.

Drains of the switching elements Q21 and Q23 are electrically connected to the fourth terminal T104. The sources of the switching elements Q22 and Q24 are electrically connected to the fifth terminal T105. The source of switching element Q21 is electrically connected to the drain of switching element Q22, and the source of switching element Q23 is electrically connected to the drain of switching element Q24.

The second converter section 22 converts the square-wave AC voltage having positive and negative polarities alternately supplied to the secondary winding 232 of the transformer 23 into a voltage having a positive polarity, and converts the voltage to the terminal of the connection section 3 . It is supplied between P3 and terminal N3. Here, a voltage is supplied between the terminals P3 and N3 so that the terminal P3 has a relatively high potential (positive electrode) and the terminal N3 has a relatively low potential (negative electrode).

As shown in FIG. 1, the second converter section 22 has a plurality of (four in the illustrated example) third switching elements Q25 to Q28. Hereinafter, the third switching elements Q25-Q28 may be referred to as "switching elements Q25-Q28". Each of the plurality of switching elements Q25 to Q28 is, for example, a depletion-type or enhancement-type n-channel MOSFET. Each of switching elements Q25-Q28 includes a parasitic diode. The parasitic diode of each switching element Q25-Q28 has an anode electrically connected to the source of the corresponding switching element Q25-Q28, and a cathode electrically connected to the drain of the corresponding switching element Q25-Q28.

Switching element Q25 is electrically connected in series with switching element Q26 between terminals P3 and N3. Switching element Q27 is electrically connected in series with switching element Q28 between terminals P3 and N3. That is, a series circuit of switching elements Q25 and Q26 and a series circuit of switching elements Q27 and Q28 are electrically connected in parallel between terminals P3 and N3.

The drains of switching elements Q25 and Q27 are electrically connected to terminal P3. The sources of switching elements Q26 and Q28 are electrically connected to terminal N3. The source of switching element Q25 is electrically connected to the drain of switching element Q26, and the source of switching element Q27 is electrically connected to the drain of switching element Q28.

The transformer 23 has a primary winding 231 and a secondary winding 232 magnetically coupled to each other, as shown in FIG. A first end of the primary winding 231 is electrically connected to a connection point between the switching elements Q21 and Q22, and a second end of the primary winding 231 is electrically connected to a connection point between the switching elements Q23 and Q24. there is A first end of secondary winding 232 is electrically connected to a connection point of switching elements Q25 and Q26, and a second end of secondary winding 232 is electrically connected to a connection point of switching elements Q27 and Q28. It is In this embodiment, the first end of the primary winding 231 and the first end of the secondary winding 232 are the beginning of the windings, and the second end of the primary winding 231 and the second end of the secondary winding 232 are is the winding end of the winding. Also, the turns ratio of the primary winding 231 and the secondary winding 232 is, for example, 1:1. The turns ratio of the primary winding 231 and the secondary winding 232 can be arbitrarily changed according to the specifications of the power conversion system 10 and the like.

In short, the other power conversion circuit 2 has a plurality of third switching elements Q21-Q28 and a transformer 23 electrically connected to the plurality of third switching elements Q21-Q28. Transformer 23 also includes a primary winding 231 and a secondary winding 232 that are magnetically coupled to each other. Another power conversion circuit 2 is provided on the DC side of the power conversion circuit 1 described above, as shown in FIG.

(2.3) Connection Portion The connection portion 3 is electrically connected to the secondary winding 232 of the transformer 23 via the second converter portion 22, as shown in FIG. Furthermore, the power conversion circuit 1 is electrically connected to the connecting portion 3 . In other words, the connection portion 3 electrically connects the second converter portion 22 and the power conversion circuit 1 . The connection portion 3 includes the terminal P3 and the terminal N3, as described above. Then, the second converter section 22 operates so that the voltage of the terminal P3 with respect to the terminal N3 becomes positive, that is, so that the potential of the terminal P3 becomes relatively high with respect to the terminal N3.

The connection unit 3 includes the two terminals P3 and N3 described above, a plurality of (two in the illustrated example) diodes D1 and D2, a plurality of (two in the illustrated example) switching elements Q31 and Q32, an inductor L31, It has a plurality of (two in the illustrated example) second capacitors C31 and C32. Connection portion 3 is a snubber circuit electrically connected to secondary winding 232 of transformer 23 .

Diode D1 is electrically connected in series with second capacitor C31 between terminals P3 and N3. Diode D2 is electrically connected in series with second capacitor C32 between terminals P3 and N3. The anode of diode D1 is electrically connected to terminal P3, and the cathode of diode D1 is electrically connected to terminal N3 via second capacitor C31. The anode of diode D2 is electrically connected to terminal N3 via a second capacitor C32, and the cathode of diode D2 is electrically connected to terminal P3. That is, the diode D1 and the diode D2 are connected in opposite directions between the terminals P3 and N3.

The switching element Q31 is electrically connected via an inductor L31 between the connection point of the diode D1 and the second capacitor C31 and the connection point of the diode D2 and the second capacitor C32. The switching element Q32 is electrically connected between the connection point of the switching element Q31 and the inductor L31 and the terminal N3.

(2.4) Control Circuit The control circuit 4 is mainly composed of a computer system having one or more processors and one or more memories. That is, the functions of the control circuit 4 are realized by one or more processors executing programs recorded in one or more memories of the computer system. The program may be prerecorded in a memory, may be provided through an electric communication line such as the Internet, or may be provided by being recorded in a non-temporary recording medium such as a memory card.

The control circuit 4 is configured to control the power conversion circuit 1 and the other power conversion circuits 2 . The control circuit 4 supplies the power conversion circuit 1 with a drive signal Sig1 for driving the switching elements Q11, Q13, Q15 of the high-side arm 11 and the switching elements Q12, Q14, Q16 of the low-side arm 12, respectively. ˜Sig6 is output. Further, the control circuit 4 outputs drive signals Sig7 to Sig14 for driving the switching elements Q21 to Q28 to the other power conversion circuits 2, respectively. Each of drive signals Sig1 to Sig14 is a PWM signal composed of a binary signal that switches between high level and low level.

Here, drive signal Sig1 corresponds to switching element Q11, drive signal Sig2 corresponds to switching element Q12, and drive signal Sig3 corresponds to switching element Q13. Drive signal Sig4 corresponds to switching element Q14, drive signal Sig5 corresponds to switching element Q15, and drive signal Sig6 corresponds to switching element Q16.

Further, drive signal Sig7 corresponds to switching element Q21, drive signal Sig8 corresponds to switching element Q22, drive signal Sig9 corresponds to switching element Q23, and drive signal Sig10 corresponds to switching element Q24. Drive signal Sig11 corresponds to switching element Q25, drive signal Sig12 corresponds to switching element Q26, drive signal Sig13 corresponds to switching element Q27, and drive signal Sig14 corresponds to switching element Q28.

(3) Operation Next, the operation of the power conversion circuit 1 and the power conversion system 10 according to this embodiment will be described.

The power conversion system 10 according to the present embodiment bidirectionally converts (transmits) power between the DC terminals T11 and T12 and the AC terminals T21, T22 and T23 via the transformer 23 . That is, the power conversion system 10 has two operation modes, an inverter mode and a converter mode. The inverter mode is a mode in which the DC power input to the DC terminals T11 and T12 is converted into three-phase AC power and the AC power is output from the AC terminals T21, T22 and T23. The converter mode is a mode in which three-phase AC power input to AC terminals T21, T22, T23 is converted into DC power, and this DC power is output from DC terminals T11, T12.

In other words, the inverter mode is a mode in which a voltage drop occurs between the AC terminals T21, T22, and T23 in the same direction as the current flowing through the electric power system 6, that is, voltage and current of the same polarity are generated. mode. The converter mode is a mode in which a voltage drop occurs between the AC terminals T21, T22, and T23 in the direction opposite to the direction in which current flows through the power system 6, that is, a mode in which voltages and currents of opposite polarities are generated. is.

In the following, an example will be described in which the operation mode of the power conversion system 10 is the inverter mode, and the power conversion system 10 converts DC power into three-phase AC power with a frequency of 50 Hz or 60 Hz. Further, the case where the driving frequency of the switching elements Q21 to Q28 is 20 kHz will be exemplified below.

(3.1) Comparative Example 1
First, the operation of the power conversion system according to Comparative Example 1 will be described with reference to FIGS. 2 to 7. FIG. The power conversion system according to Comparative Example 1 is the same as the power conversion system 10 according to the present embodiment, except that the second terminal T102 and the third terminal T103 are not electrically connected. . Therefore, hereinafter, description will be made using the reference numerals used in the power conversion system 10 according to the present embodiment. 3 to 6, of the six switching elements Q11 to Q16, only the switching elements Q11 to Q14 are illustrated, and the switching elements Q15 and Q16 are omitted. Also, in FIGS. 3 to 6, the switching elements Q11 to Q14 are illustrated so that ON/OFF of the switching elements Q11 to Q14 can be easily understood.

FIG. 2 is a waveform diagram showing the operation in the inverter mode of the power conversion system according to Comparative Example 1. FIG. The horizontal axis of FIG. 2 is the time axis.

In FIG. 2, from the top, drive signals Sig8, 9, 12, 13, drive signals Sig7, 10, 11, 14, drive signal Sig1, drive signal Sig2, drive signal Sig3, drive signal Sig4, drive signal Sig5, drive signal Sig6 and current I2 are shown. Regarding the drive signals Sig1 to Sig14, the high level is indicated as "H" in the drawing, and the low level is indicated as "L" in the drawing. Each of switching elements Q1-Q14 is turned on when corresponding drive signals Sig1-Sig14 are at high level, and turned off when at low level. A current I2 is a current that flows from the secondary winding 232 of the transformer 23 to the terminal P3.

The control circuit 4 controls the first converter section 21 such that positive and negative voltages are alternately applied to the primary winding 231 of the transformer 23 . Further, the control circuit 4 controls the second converter section 22 so that the voltage of the terminal P3 with respect to the terminal N3 becomes positive.

Specifically, the control circuit 4 turns off the switching elements Q22, Q23, Q26 and Q27 while turning on the switching elements Q21, Q24, Q25 and Q28. Further, the control circuit 4 turns on the switching elements Q22, Q23, Q26 and Q27 while turning off the switching elements Q21, Q24, Q25 and Q28. Here, the control circuit 4 controls the switching elements Q21 to Q28 with the same duty ratio. In this embodiment, the duty ratio of the switching elements Q21 to Q28 is "0.5" (substantially 50%).

That is, the control circuit 4 controls the first converter section 21 so that a high-frequency AC voltage is supplied to the primary winding 231 and the secondary winding 232 of the transformer 23, and a positive voltage is applied between the terminal P3 and the terminal N3. The second converter section 22 is controlled so that a voltage having polarity is supplied.

The control circuit 4 turns on or off each of the switching elements Q11 to Q16 to control the amplitude of at least one of the voltage and current output from the AC terminals T21, T22 and T23.

Here, the control circuit 4 switches the power between the power conversion circuit 1 and the other power conversion circuit 2 during the first period T1 including the inversion period Td1 in which the polarity of the voltage applied to the primary winding 231 is reversed. is controlled so that the power conversion circuit 1 is not transmitted. In other words, in the power conversion circuit 1, power is transmitted between the power conversion circuit 1 and the other power conversion circuit 2 at the reversal timing (reversal period Td1) at which the polarity of the voltage applied to the primary winding 231 is reversed. The high-side arm 11 and the low-side arm 12 are controlled so as not to perform In addition, the control circuit 4 controls the flow of power in a first direction toward the power inverter circuit 1 from the other power inverter circuit 2 or in a second direction opposite to the first direction in a second period T2 different from the first period T1. The power converter circuit 1 is controlled so that the transfer takes place.

Specifically, the control circuit 4 operates to repeat first to fourth modes described below.

In the first mode, the control circuit 4 causes the first converter section 21 and the second converter section 22 to turn on the switching elements Q21, Q24, Q25 and Q28 and turn off the switching elements Q22, Q23, Q26 and Q27. It outputs drive signals Sig7 to Sig14. At this time, in the power conversion circuit 1, for example, as shown in FIG. 3, the switching elements Q11 and Q14 are on, the switching elements Q12 and Q13 are off, and current flows in the direction of arrow A1.

In the second mode, the control circuit 4 causes the power conversion circuit 1 to turn off the switching elements Q12, Q14, Q16 of the low-side arm 12 and turn on the switching elements Q11, Q13, Q15 of the high-side arm 11. It outputs drive signals Sig1 to Sig6. Thereby, for example, as indicated by arrow A2 in FIG. At this time, in the other power conversion circuit 2, the switching elements Q21, Q24, Q25 and Q28 are on, and the switching elements Q22, Q23, Q26 and Q27 are off.

In the third mode, the control circuit 4 causes the first converter section 21 and the second converter section 22 to turn on the switching elements Q22, Q23, Q26 and Q27 and turn off the switching elements Q21, Q24, Q25 and Q28. It outputs drive signals Sig7 to Sig14. At this time, in the power conversion circuit 1, for example, as shown in FIG. 5, the switching elements Q11 and Q14 are on, the switching elements Q12 and Q13 are off, and current flows in the direction of arrow A3.

In the fourth mode, the control circuit 4 causes the power conversion circuit 1 to turn off the switching elements Q11, Q13, Q15 of the high-side arm 11 and turn on the switching elements Q12, Q14, Q16 of the low-side arm 12. It outputs drive signals Sig1 to Sig6. As a result, for example, as indicated by an arrow A4 in FIG. 6, a circulation mode in which current circulates within the power conversion circuit 1 is established. At this time, in the other power conversion circuit 2, the switching elements Q22, Q23, Q26, Q27 are on, and the switching elements Q21, Q24, Q25, Q28 are off.

The control circuit 4 repeats the operations of the first, second, third and fourth modes in this order. That is, the first mode and the third mode are performed in the above-described second period T2, respectively, and the second mode and the fourth mode are performed in the above-described first period T1, respectively.

Here, the inversion period Td1 and the circulation period are assigned to the first period T1, and the supply period is assigned to the second period T2. If the operation mode of the power conversion system is the inverter mode, the supply period is assigned to the second period T2 as described above. period is assigned. The circulation period is a period during which the circulation mode described above is performed. The supply period is a period during which AC power is supplied to the power system 6 . The regeneration period is a period during which electrical energy is regenerated. That is, each of the above-described first mode and third mode is performed during the second period T2, and each of the above-described second mode and fourth mode is performed during the first period T1.

7 is a simulation result of the power conversion system according to Comparative Example 1. FIG. "V12", "V14" and "V16" in FIG. 7 indicate voltages across switching elements Q12, Q14 and Q16, respectively. "V2" in FIG. 7 indicates the voltage across the secondary winding 232 of the transformer 23, and "I2" indicates the current flowing from the secondary winding 232 to the terminal P3. "Iac" in FIG. 7 indicates the ground current generated in the AC path, and "Idc" indicates the ground current generated in the DC path.

As shown in FIG. 7, in the power conversion system according to Comparative Example 1, both ground currents Iac and Idc are large, and common mode noise is a problem.

(3.2) Comparative Example 2
In the power conversion system according to Comparative Example 2, in order to suppress the above-described common mode noise, the second terminal T102 and the third terminal T103 are directly electrically connected as shown in FIG. there is The operation of the power conversion system according to Comparative Example 2 will be described below with reference to FIGS. 8 to 12. FIG. The circuit configuration of the power conversion system according to Comparative Example 2 is the same as the circuit configuration of the power conversion system 10 according to this embodiment. Therefore, hereinafter, description will be made using the reference numerals used in the power conversion system 10 according to the present embodiment. 8 to 11 show only the switching elements Q11 to Q14 among the six switching elements Q11 to Q16, and the switching elements Q15 and Q16 are omitted. 8 to 11, the switching elements Q11 to Q14 are illustrated so that ON/OFF of the switching elements Q11 to Q14 can be easily understood.

In the power conversion system according to Comparative Example 2, the control circuit 4 operates to repeat first to fourth modes described below.

In the first mode, the control circuit 4 causes the first converter section 21 and the second converter section 22 to turn on the switching elements Q21, Q24, Q25 and Q28 and turn off the switching elements Q22, Q23, Q26 and Q27. It outputs drive signals Sig7 to Sig14. At this time, in the power conversion circuit 1, for example, as shown in FIG. 8, the switching elements Q11 and Q14 are on, the switching elements Q12 and Q13 are off, and current flows in the direction of arrow B1.

In the second mode, the control circuit 4 causes the power conversion circuit 1 to turn off the switching elements Q12, Q14, Q16 of the low-side arm 12 and turn on the switching elements Q11, Q13, Q15 of the high-side arm 11. It outputs drive signals Sig1 to Sig4. At this time, in the power conversion circuit 1, for example, current flows through the secondary side of the transformer 23 without circulating in the power conversion circuit 1, as indicated by arrows B2 and B3 in FIG. At this time, in the other power conversion circuit 2, the switching elements Q21, Q24, Q25 and Q28 are on, and the switching elements Q22, Q23, Q26 and Q27 are off.

In the third mode, the control circuit 4 causes the first converter section 21 and the second converter section 22 to turn on the switching elements Q22, Q23, Q26 and Q27 and turn off the switching elements Q21, Q24, Q25 and Q28. It outputs drive signals Sig7 to Sig14. At this time, in the power converter circuit 1, for example, as shown in FIG. 10, the switching elements Q11 and Q14 are on, the switching elements Q12 and Q13 are off, and current flows in the direction of arrow B4.

In the fourth mode, the control circuit 4 causes the power conversion circuit 1 to turn off the switching elements Q11, Q13, Q15 of the high-side arm 11 and turn on the switching elements Q12, Q14, Q16 of the low-side arm 12. It outputs drive signals Sig1 to Sig6. As a result, for example, as indicated by an arrow B5 in FIG. 11, a circulation mode in which current circulates within the power conversion circuit 1 is established. At this time, in the other power conversion circuit 2, the switching elements Q22, Q23, Q26, Q27 are on, and the switching elements Q21, Q24, Q25, Q28 are off.

12 is a simulation result of the power conversion system according to Comparative Example 2. FIG. "V12", "V14", and "V16" in FIG. 12 indicate voltages across switching elements Q12, Q14, and Q16, respectively. "V2" in FIG. 12 indicates the voltage across the secondary winding 232 of the transformer 23, and "I2" indicates the current flowing from the secondary winding 232 to the terminal P3. "Iac" in FIG. 12 indicates the ground current generated in the AC path, and "Idc" indicates the ground current generated in the DC path.

As shown in FIG. 12, according to the power conversion system according to Comparative Example 2, compared to the power conversion system according to Comparative Example 1, ground currents Iac and Idc are smaller, and common mode noise can be suppressed. I understand.

However, in the power conversion system according to Comparative Example 2, as described above, current flows through the secondary side of the transformer 23 in the second mode, so that the conversion efficiency of the power conversion system decreases.

More specifically, in Comparative Example 1 in which the second terminal T102 and the third terminal T103 are not connected, the current I2 in the first period T1 is substantially zero as shown in FIG. , the current I2 flows in the first period T1 by connecting the second terminal T102 and the third terminal T103 (see FIG. 12). of switching loss occurs, and the conversion efficiency decreases.

(3.3) Example In the power conversion system 10 according to the present embodiment, while suppressing the above-described common mode noise, it is possible to suppress a decrease in the conversion efficiency of the power conversion system 10. is employed. The operation of the power conversion system 10 according to this embodiment will be described below with reference to FIGS. 13 and 14. FIG.

First, the circuit configuration of the power conversion system 10 is the same as that of the power conversion system according to Comparative Example 2, and the second terminal T102 and the third terminal T103 are directly electrically connected (Fig. 1).

Then, in the power conversion system 10 according to the present embodiment, during the first period T1 during which the above-described second mode (circulation mode) is executed, the control circuit 4 controls the high-side arm 11 as shown in FIG. Drive signals Sig1 to Sig6 are output to the power conversion circuit 1 so that the switching elements Q11, Q13, Q15 are turned off and the switching elements Q12, Q14, Q16 of the low-side arm 12 are turned on. As a result, in the power conversion circuit 1, the switching elements Q11, Q13, Q15 are turned off, and the switching elements Q12, Q14, Q16 are turned on. That is, in the power conversion circuit 1 according to the present embodiment, in the first period T1 in which the above-described second mode is executed, the second control that turns on all of the plurality of (second) switching elements Q12, Q14, Q16 I do. In other words, in the power conversion circuit 1 according to this embodiment, the second control is performed when the specific terminal is the second terminal T102.

In particular, in the power conversion system 10 according to the present embodiment, as shown in FIG. 13, a period during which the second control is performed and a reversal period Td1 during which the polarity of the voltage applied to the primary winding 231 of the transformer 23 is reversed. are matching. That is, in the power conversion circuit 1 according to this embodiment, the second control is synchronized with the reversal timing at which the polarity of the voltage applied to the primary winding 231 is reversed. In other words, in the power inverter circuit 1 according to the present embodiment, the second control and the control of the other power inverter circuit 2 provided on the DC side of the power inverter circuit 1 are synchronized.

As a result, as shown in FIG. 14, ground currents Iac and Idc are smaller than in the power conversion system according to Comparative Example 1, and common mode noise can be suppressed. Further, in this case, as shown in FIG. 11 described above, the current circulates in the power conversion circuit 1 in the circulation mode, so the current I2 in the first period T1 during which the second mode is executed is shown in FIG. becomes almost zero, as shown in . That is, in the power conversion system 10 according to the present embodiment, unlike the power conversion system according to Comparative Example 2, current does not flow to the secondary side of the transformer 23, so the reduction in conversion efficiency of the power conversion system 10 is suppressed. be able to.

(4) Modifications The above-described embodiment is just one of various embodiments of the present disclosure. The above-described embodiments can be modified in various ways according to design and the like as long as the object of the present disclosure can be achieved. Also, the same functions as the power inverter circuit 1 according to the above-described embodiment may be embodied by a control method of the power inverter circuit 1, a (computer) program, or a non-temporary recording medium recording the program.

A control method of a power conversion circuit 1 according to one aspect converts power in at least one direction between DC power and AC power, a high-side arm 11, a low-side arm 12, a filter circuit 13, It is a control method of the power conversion circuit 1. The high-side arm 11 has a plurality of first switching elements Q11, Q13, Q15. The plurality of first switching elements Q11, Q13, Q15 are electrically connected between one of the plurality of AC terminals T21, T22, T23 different from each other and the same first terminal T101. The low-side arm 12 has a plurality of second switching elements Q12, Q14, Q16. The plurality of second switching elements Q12, Q14, Q16 are electrically connected between one of the plurality of AC terminals T21, T22, T23 and the same second terminal T102. The filter circuit 13 has a plurality of capacitors C11, C12, C13, and smoothes the AC voltage output via the high-side arm 11 and the low-side arm 12. FIG.

An AC power supply or an AC load (the electric power system 6 in this embodiment) is electrically connected to the plurality of AC terminals T21, T22, and T23. Each of the plurality of capacitors C11, C12, C13 is electrically connected between one of the plurality of AC terminals T21, T22, T23 and the same third terminal T103. The third terminal T103 is electrically connected to a specific terminal (the second terminal T102 in this embodiment) other than the AC terminals T21, T22, T23. In the control method of the power conversion circuit 1, a first control that turns on all of the plurality of first switching elements Q11, Q13, and Q15, or a second control that turns on all of the plurality of second switching elements Q12, Q14, and Q16. control.

A program according to one aspect is a program for causing one or more processors to execute the control method of the power conversion circuit 1 described above.

Modifications of the above-described embodiment are listed below. Modifications described below can be applied in combination as appropriate.

(4.1) Modification 1
In the above-described embodiment, the second terminal T102 and the third terminal T103 are directly electrically connected and the polarity of the voltage applied to the primary winding 231 of the transformer 23 is reversed at the reversal timing (reversal period). Td1), the second control is performed to turn off all of the plurality of (second) switching elements Q12, Q14, Q16.

On the other hand, as shown in FIG. 15, the first terminal T101 and the third terminal T103 may be electrically connected directly. In this case, in the fourth mode in which the switching elements Q11, Q13, Q15 are turned off and the switching elements Q12, Q14, Q16 are turned on, the current flows through the secondary side of the transformer 23 without circulating in the power conversion circuit 1. . Therefore, in this case, the control circuit 4 controls the power conversion circuit so that the switching elements Q11, Q13, Q15 of the high-side arm 11 are turned on and the switching elements Q12, Q14, Q16 of the low-side arm 12 are turned off. 1 to output drive signals Sig1 to Sig6. As a result, in the power conversion circuit 1, the switching elements Q11, Q13, Q15 are turned on, and the switching elements Q12, Q14, Q16 are turned off. As a result, in the first period T1 in which the above-described fourth mode is executed, the current circulates in the power conversion circuit 1 in a circulation mode, and similarly, while suppressing common mode noise, the conversion efficiency of the power conversion system 10 can be suppressed.

That is, in the power conversion circuit 1 according to Modification 1, when the third terminal T103 is electrically connected to the first terminal T101, all of the plurality of (first) switching elements Q11, Q13, Q15 are turned on. 1st control is performed. In other words, in the power conversion circuit 1 according to Modification 1, the first control is performed when the specific terminal is the first terminal T101.

(4.2) Modification 2
In the above-described embodiment, the second terminal T102 and the third terminal T103 are directly electrically connected and the polarity of the voltage applied to the primary winding 231 of the transformer 23 is reversed at the reversal timing (reversal period). Td1), the second control is performed to turn off all of the plurality of (second) switching elements Q12, Q14, Q16.

On the other hand, as shown in FIG. 16, the fifth terminal T105 and the third terminal T103 may be directly electrically connected. In this case, in the second mode (see FIG. 9) in which the switching elements Q11, Q13, Q15 are turned on and the switching elements Q12, Q14, Q16 are turned off, the current does not circulate in the power conversion circuit 1, and the transformer 23 flow to the secondary side. Therefore, in this case, the control circuit 4 controls the power conversion circuit so that the switching elements Q11, Q13, Q15 of the high-side arm 11 are turned off and the switching elements Q12, Q14, Q16 of the low-side arm 12 are turned on. 1 to output drive signals Sig1 to Sig6. As a result, in the power conversion circuit 1, the switching elements Q11, Q13, Q15 are turned off, and the switching elements Q12, Q14, Q16 are turned on. As a result, in the first period T1 in which the above-described second mode is executed, the current circulates in the power conversion circuit 1 in a circulation mode, and similarly, while suppressing common mode noise, the conversion efficiency of the power conversion system 10 can be suppressed.

That is, in the power conversion circuit 1 according to the modification 2, the specific terminal is one of the two DC terminals T11 and T12 (here, the DC terminal T12) to which the DC power supply or the DC load (here, the storage battery 5) is electrically connected ) is the fifth terminal T105 electrically connected to the terminal T105. Further, in the power conversion circuit 1 according to Modification 2, when the specific terminal is the fifth terminal T105, second control is performed to turn on all of the plurality of (second) switching elements Q12, Q14, and Q16.

(4.3) Modification 3
In the above-described embodiment, the second terminal T102 and the third terminal T103 are directly electrically connected and the polarity of the voltage applied to the primary winding 231 of the transformer 23 is reversed at the reversal timing (reversal period). Td1), the second control is performed to turn off all of the plurality of (second) switching elements Q12, Q14, Q16.

On the other hand, as shown in FIG. 17, the fourth terminal T104 and the third terminal T103 may be electrically connected directly. In this case, in the fourth mode in which the switching elements Q11, Q13, Q15 are turned off and the switching elements Q12, Q14, Q16 are turned on, the current flows through the secondary side of the transformer 23 without circulating in the power conversion circuit 1. . Therefore, in this case, the control circuit 4 controls the power conversion circuit so that the switching elements Q11, Q13, Q15 of the high-side arm 11 are turned on and the switching elements Q12, Q14, Q16 of the low-side arm 12 are turned off. 1 to output drive signals Sig1 to Sig6. As a result, in the power conversion circuit 1, the switching elements Q11, Q13, Q15 are turned on, and the switching elements Q12, Q14, Q16 are turned off. As a result, in the first period T1 in which the above-described fourth mode is executed, the current circulates in the power conversion circuit 1 in a circulation mode, and similarly, while suppressing common mode noise, the conversion efficiency of the power conversion system 10 can be suppressed.

That is, in the power conversion circuit 1 according to Modification 3, the specific terminal is one of the two DC terminals T11 and T12 (here, T11) to which the DC power supply or the DC load (here, the storage battery 5) is electrically connected. It is the 4th terminal T104 electrically connected. Further, in the power conversion circuit 1 according to Modification 2, when the specific terminal is the fourth terminal T104, first control is performed to turn on all of the plurality of (first) switching elements Q11, Q13, Q15.

(4.4) Modification 4
A power conversion system 10a according to Modification 4 will be described with reference to FIG. Note that the power conversion circuit 1 is the same as that of the power conversion system 10 according to the above-described embodiment, and description thereof is omitted here.

As shown in FIG. 18, a power conversion system 10a according to Modification 4 includes a power conversion circuit 1, another power conversion circuit 2a, a connection section 3a, a control circuit 4, and a converter circuit 7. there is In addition, the power conversion system 10a according to Modification 4 includes a plurality of (two in the illustrated example) DC terminals T11 and T12, a plurality of (three in the illustrated example) AC terminals T21, T22, and T23, and a plurality of (figure It is further provided with DC terminals T31 and T32 (two in the illustrated example).

A storage battery 5 is electrically connected to the two DC terminals T11 and T12. The power system 6 is electrically connected to the three AC terminals T21, T22, T23. A solar cell 9 is electrically connected to the two DC terminals T31 and T32.

(4.4.1) Other power conversion circuit The other power conversion circuit 2a is, for example, a DC/DC converter. Another power conversion circuit 2a includes a first capacitor C1, a first converter section 21, a second converter section 22, and a transformer 23, as shown in FIG. However, the 1st capacitor|condenser C1 does not need to be contained in the component of the other power inverter circuit 2a.

A first capacitor C1 is electrically connected between the two DC terminals T11 and T12. In other words, the first capacitor C1 is connected to the storage battery 5 via the two DC terminals T11, T12. The first capacitor C1 is, for example, an electrolytic capacitor. The first capacitor C1 has a function of stabilizing the voltage between the DC terminals T11 and T12.

The first converter section 21 has a plurality of (two in the illustrated example) switching elements Q21 and Q22. The second converter section 22 has a plurality of (two in the illustrated example) switching elements Q23 and Q24. Each of switching elements Q21-Q24 is, for example, a depletion-type or enhancement-type n-channel MOSFET. Each of switching elements Q21-Q24 includes a parasitic diode. The parasitic diode of each switching element Q21-Q24 has an anode electrically connected to the source of the corresponding switching element Q21-Q24, and a cathode electrically connected to the drain of the corresponding switching element Q21-Q24.

The transformer 23 has a primary winding 231 and a secondary winding 232 magnetically coupled to each other. Primary winding 231 is electrically connected to first capacitor C<b>1 via first converter section 21 . The secondary winding 232 is electrically connected to the connecting portion 3a through the second converter portion 22. As shown in FIG.

The transformer 23 is, for example, a high-frequency isolation transformer with a center tap. The primary winding 231 of the transformer 23 is composed of a series circuit of two windings L211 and L212 with the primary side center tap CT1 as a connection point. Similarly, the secondary winding 232 of the transformer 23 is composed of a series circuit of two windings L221 and L222 with the secondary side center tap CT2 as a connection point. That is, the two windings L211 and L212 are electrically connected in series to form the primary winding 231. FIG. Similarly, two windings L221 and L222 are electrically connected in series to form a secondary winding 232. The primary side center tap CT1 is electrically connected to a terminal on the positive electrode side (direct current terminal T11 side) of the first capacitor C1. The secondary center tap CT2 is electrically connected to the terminal P3. The turns ratio of the windings L211, L212, L221, L222 is, for example, 1:1:1:1. The turns ratio of the windings L211, L212, L221, and L222 can be arbitrarily changed according to the specifications of the power conversion system 10a.

(4.4.2) Connection Portion The connection portion 3a is electrically connected to the secondary winding 232 of the transformer 23 via the second converter portion 22, as shown in FIG. Further, the power conversion circuit 1 is electrically connected to the connecting portion 3a. In other words, the connection portion 3 a electrically connects the second converter portion 22 and the power conversion circuit 1 . The connection portion 3a includes the terminal P3 and the terminal N3, as described above. Then, the second converter section 22 operates so that the voltage of the terminal P3 with respect to the terminal N3 becomes positive, that is, so that the potential of the terminal P3 becomes relatively high with respect to the terminal N3.

The connecting portion 3a includes the above-described two terminals P3 and N3, a plurality of (two in the illustrated example) diodes D1 and D2, a resistor R1, and a plurality of (two in the illustrated example) second capacitors C31 and C32. ,have. Connection portion 3 a is a snubber circuit electrically connected to secondary winding 232 . Diode D1 is electrically connected in series with second capacitor C31 between terminals P3 and N3. Diode D2 is electrically connected in series with second capacitor C32 between terminals P3 and N3. The anode of diode D1 is electrically connected to terminal P3, and the cathode of diode D1 is electrically connected to terminal N3 via second capacitor C31. The anode of diode D2 is electrically connected to terminal N3 via a second capacitor C32, and the cathode of diode D2 is electrically connected to terminal P3. That is, the diode D1 and the diode D2 are connected in opposite directions between the terminals P3 and N3. The resistor R1 is electrically connected between the connection point of the diode D1 and the second capacitor C31 and the connection point of the diode D2 and the second capacitor C32.

(4.4.3) Control Circuit The control circuit 4 is mainly composed of a computer system having one or more processors and one or more memories. That is, the functions of the control circuit 4 are realized by one or more processors executing programs recorded in one or more memories of the computer system. The program may be prerecorded in a memory, may be provided through an electric communication line such as the Internet, or may be provided by being recorded in a non-temporary recording medium such as a memory card.

The control circuit 4 is configured to control the power conversion circuit 1 , another power conversion circuit 2 a and the converter circuit 7 . The control circuit 4 supplies the power conversion circuit 1 with a drive signal Sig1 for driving the switching elements Q11, Q13, Q15 of the high-side arm 11 and the switching elements Q12, Q14, Q16 of the low-side arm 12, respectively. ~Sig6 is output. Further, the control circuit 4 outputs drive signals Sig7 to Sig10 for driving the switching elements Q21 to Q24, respectively, to the other power conversion circuit 2a. Control circuit 4 also outputs drive signals Sig11 and 12 for driving switching elements Q71 and Q72 to converter circuit 7, respectively. Each of drive signals Sig1 to Sig12 is a PWM signal composed of a binary signal that switches between high level and low level.

(4.4.4) Converter Circuit The converter circuit 7 is, for example, a DC/DC converter. More specifically, converter circuit 7 is a boost chopper circuit that boosts the DC voltage input from solar cell 9 . The converter circuit 7, as shown in FIG. 18, includes a third capacitor C2, an inductor L1, and two switching elements Q71 and Q72. However, the third capacitor C2 does not have to be included in the components of the converter circuit 7 .

A third capacitor C2 is electrically connected between the two DC terminals T31 and T32. In other words, the third capacitor C2 is connected to the solar cell 9 via two DC terminals T31, T32. The third capacitor C2 is, for example, an electrolytic capacitor. The third capacitor C2 has the function of stabilizing the voltage between the DC terminals T31 and T32.

Each of the switching elements Q71 and Q72 is, for example, a depletion-type or enhancement-type n-channel MOSFET. The switching element Q71 on the high potential side is electrically connected in series with the switching element Q72 on the low potential side between the terminals P3 and N3. That is, a series circuit of switching elements Q71 and Q72 is electrically connected between terminals P3 and N3.

Each of switching elements Q71 and Q72 includes a parasitic diode. The parasitic diode of each switching element Q71, Q72 has an anode electrically connected to the source of the corresponding switching element Q71, Q72, and a cathode electrically connected to the drain of the corresponding switching element Q71, Q72.

The drain of the switching element Q71 on the high potential side is electrically connected to the terminal P3. The source of the switching element Q72 on the low potential side is electrically connected to the terminal N3. The source of the switching element Q71 on the high potential side is electrically connected to the drain of the switching element Q72 on the low potential side.

Switching elements Q71 and Q72 are turned on/off according to drive signals Sig11 and Sig12 output from control circuit 4, respectively.

A first end of inductor L1 is electrically connected to DC terminal T31, and a second end of inductor L1 is electrically connected to a connection point between switching elements Q71 and Q72.

(4.4.5) Operation In the power conversion system 10a according to Modification 4, the second terminal T102 and the third terminal T103 are directly electrically connected. Therefore, as in the power conversion system 10 according to the above-described embodiment, the polarity of the voltage applied to the primary winding 231 of the transformer 23 is reversed during the first period T1 during which the second mode is executed. During the period Td1, a plurality of (first) switching elements Q11, Q13, Q15 are turned off and a plurality of (second) switching elements Q12, Q14, Q16 are turned on, so that current circulates in the power conversion circuit 1. Circulation mode. As a result, current does not flow to the secondary side of the transformer 23 during the first period T1 in which the second mode is executed, and reduction in conversion efficiency of the power conversion system 10a can be suppressed. Moreover, since the second terminal T102 and the third terminal T103 are directly electrically connected, it is possible to suppress common mode noise.

Also in Modification 4, the first terminal T101, the fourth terminal T104 or the fifth terminal T105 and the third terminal T103 may be electrically connected directly. Furthermore, in Modification 4 as well, any one of the first terminal T101, the second terminal T102, the fourth terminal T104, and the fifth terminal T105 and the third terminal T103 are indirectly connected via an inductor or a resistor, for example. It may be electrically connected.

(4.5) Other Modifications The power conversion system 10 in the present disclosure includes a computer system in the control circuit 4, for example. A computer system is mainly composed of a processor and a memory as hardware. The functions of the power conversion system 10 in the present disclosure are realized by the processor executing a program recorded in the memory of the computer system. The program may be recorded in advance in the memory of the computer system, may be provided through an electric communication line, or may be recorded in a non-temporary recording medium such as a computer system-readable memory card, optical disk, or hard disk drive. may be provided. A processor in a computer system consists of one or more electronic circuits, including semiconductor integrated circuits (ICs) or large scale integrated circuits (LSIs). The integrated circuit such as IC or LSI referred to here is called differently depending on the degree of integration, and includes integrated circuits called system LSI, VLSI (Very Large Scale Integration), or ULSI (Ultra Large Scale Integration). In addition, an FPGA (Field-Programmable Gate Array), which is programmed after the LSI is manufactured, or a logic device capable of reconfiguring the bonding relationship inside the LSI or reconfiguring the circuit partitions inside the LSI, shall also be adopted as the processor. can be done. A plurality of electronic circuits may be integrated into one chip, or may be distributed over a plurality of chips. A plurality of chips may be integrated in one device, or may be distributed in a plurality of devices. A computer system, as used herein, includes a microcontroller having one or more processors and one or more memories. Accordingly, the microcontroller also consists of one or more electronic circuits including semiconductor integrated circuits or large scale integrated circuits.

Moreover, it is not an essential configuration of the power conversion system 10 that the plurality of components of the power conversion system 10 are integrated in one housing. The components of the power conversion system 10 may be distributed over a plurality of housings. Furthermore, at least part of the functions of the power conversion system 10, for example the functions of the control circuit 4, may be realized by the cloud (cloud computing) or the like.

Conversely, in the above-described embodiments, at least some of the functions of the power conversion system 10 distributed among multiple devices may be consolidated within one housing.

Although the power conversion circuit 1 is a three-phase inverter circuit in the above-described embodiment, it is not limited to a three-phase inverter circuit and may be a single-phase inverter circuit.

In the above-described embodiment, the second terminal T102 and the third terminal T103 are directly electrically connected. good. The same applies between the first terminal T101 and the third terminal T103, between the fourth terminal T104 and the third terminal T103, and between the fifth terminal T105 and the third terminal T103.

In the above-described embodiment, the power conversion system 10 converts power in both directions, but it is sufficient to convert power in at least one direction. For example, the power conversion system 10 may have only a function of converting DC power input from the storage battery 5 into AC power, or may have only a function of converting AC power input from the power system 6 into DC power. may have.

In the above-described embodiment, one other power conversion circuit 2 is connected to the power conversion circuit 1. However, for example, a plurality of other power conversion circuits may be connected in parallel to the power conversion circuit 1. may

In the above-described embodiment, the period during which the first control or the second control is performed and the inversion period Td1 match, but the period in which the first control or the second control is performed may be included in the inversion period Td1. The two do not have to match.

(summary)
As described above, the power conversion circuit (1) according to the first aspect is a power conversion circuit (1) that converts power in at least one direction between DC power and AC power. A power conversion circuit (1) comprises a high side arm (11), a low side arm (12) and a filter circuit (13). The high-side arm (11) has a plurality of first switching elements (Q11, Q13, Q15). The plurality of first switching elements (Q11, Q13, Q15) are electrically connected between one of the plurality of mutually different AC terminals (T21, T22, T23) and the same first terminal (T101) . The low-side arm (12) has a plurality of second switching elements (Q12, Q14, Q16). The plurality of second switching elements (Q12, Q14, Q16) are electrically connected between one of the plurality of AC terminals (T21, T22, T23) and the same second terminal (T102). The filter circuit (13) has a plurality of capacitors (C11, C12, C13) and smoothes the AC voltage output via the high side arm (11) and the low side arm (12). An AC power source or an AC load (for example, the power system 6) is electrically connected to the plurality of AC terminals (T21, T22, T23). Each of the plurality of capacitors (C11, C12, C13) is electrically connected between one of the plurality of AC terminals (T21, T22, T23) and the same third terminal (T103). In the power conversion circuit (1), first control for turning on all of the plurality of first switching elements (Q11, Q13, Q15) or turning on all of the plurality of second switching elements (Q12, Q14, Q16) second control is performed. The third terminal (T103) is electrically connected to a specific terminal (for example, the second terminal T102) other than the AC terminals (T21, T22, T23).

According to this aspect, common mode noise can be suppressed without providing a capacitor on the DC side of the power conversion circuit (1).

In the power conversion circuit (1) according to the second aspect, in the first aspect, the third terminal (T103) is directly electrically connected to the specific terminal.

According to this aspect, common mode noise can be suppressed without providing a capacitor on the DC side of the power conversion circuit (1).

In the power conversion circuit (1) according to the third aspect, in the first or second aspect, the specific terminal is the first terminal (T101), the second terminal (T102), the fourth terminal (T104) or the fifth terminal (T105). The fourth terminal (T104) and the fifth terminal (T105) are electrically connected to two DC terminals (T11, T12) to which a DC power source or a DC load (eg, storage battery 5) is electrically connected, respectively. .

According to this aspect, common mode noise can be suppressed without providing a capacitor on the DC side of the power conversion circuit (1).

In the power conversion circuit (1) according to the fourth aspect, in the third aspect, the fourth terminal (T104) has a high potential and the fifth terminal (T105) has a high potential. A DC voltage is applied so that T105) has a low potential. In the power conversion circuit (1), the first control is performed when the specific terminal is the first terminal (T101) or the fourth terminal (T104). In the power conversion circuit (1), the second control is performed when the specific terminal is the second terminal (T102) or the fifth terminal (T105).

According to this aspect, common mode noise can be suppressed without providing a capacitor on the DC side of the power conversion circuit (1).

In the power conversion circuit (1) according to the fifth aspect, in any one of the first to fourth aspects, the high-side arm (11) includes three switching elements ( Q11, Q13, Q15). The low-side arm (12) has three switching elements (Q12, Q14, Q16) as a plurality of second switching elements.

According to this aspect, power can be converted between DC power and three-phase AC power.

In the power inverter circuit (1) according to the sixth aspect, in any one of the first to fifth aspects, the first control or the second control and the control of the other power inverter circuit (2) are synchronizing. Another power conversion circuit (2) is provided on the DC side of the power conversion circuit (1).

According to this aspect, a decrease in conversion efficiency of the power conversion system (10; 10a) can be suppressed.

In the power conversion circuit (1) according to the seventh aspect, in the sixth aspect, the other power conversion circuit (2) has a plurality of third switching elements (Q21 to Q28) and a transformer (23) ing. A transformer (23) is electrically connected to a plurality of third switching elements (Q21 to Q28). The transformer (23) includes a primary winding (231) and a secondary winding (232) magnetically coupled to each other. In the power conversion circuit (1), the first control or the second control is synchronized with the inversion timing. The inversion timing is the timing at which the polarity of the voltage applied to the primary winding (231) is inverted.

According to this aspect, a decrease in conversion efficiency of the power conversion system (10; 10a) can be suppressed.

In the power conversion circuit (1) according to the eighth aspect, in any one of the first to seventh aspects, the other power conversion circuit (2) is provided on the DC side of the power conversion circuit (1) there is Another power conversion circuit (2) has a plurality of third switching elements (Q21 to Q28) and a transformer (23). A transformer (23) is electrically connected to a plurality of third switching elements (Q21 to Q28). The transformer (23) includes a primary winding (231) and a secondary winding (232) magnetically coupled to each other. In the power conversion circuit (1), at the inversion timing, the high side arm (11) and the low side arm (11) are arranged so that power is not transmitted between the power conversion circuit (1) and the other power conversion circuit (2). Control the arm (12). The inversion timing is the timing at which the polarity of the voltage applied to the primary winding (231) is inverted.

According to this aspect, soft switching can be realized.

A power conversion system (10; 10a) according to a ninth aspect includes the power conversion circuit (1) according to any one of the first to eighth aspects and another power conversion circuit (2; 2a). . Another power conversion circuit (2; 2a) is provided on the DC side of the power conversion circuit (1). Another power conversion circuit (2; 2a) converts power in at least one direction between first DC power and second DC power as DC power.

According to this aspect, common mode noise can be suppressed without providing a capacitor on the DC side of the power conversion circuit (1).

A control method for a power conversion circuit (1) according to a tenth aspect converts power in at least one direction between DC power and AC power, and includes a high-side arm (11) and a low-side arm (12). ) and a filter circuit (13). The high-side arm (11) has a plurality of first switching elements (Q11, Q13, Q15). The plurality of first switching elements (Q11, Q13, Q15) are electrically connected between one of the plurality of mutually different AC terminals (T21, T22, T23) and the same first terminal (T101) . The low-side arm (12) has a plurality of second switching elements (Q12, Q14, Q16). The plurality of second switching elements (Q12, Q14, Q16) are electrically connected between one of the plurality of AC terminals (T21, T22, T23) and the same second terminal (T102). The filter circuit (13) has a plurality of capacitors (C11, C12, C13) and smoothes the AC voltage output via the high side arm (11) and the low side arm (12). An AC power source or an AC load (here, the power system 6) is electrically connected to the AC terminals (T21, T22, T23). Each of the plurality of capacitors (C11, C12, C13) is electrically connected between one of the plurality of AC terminals (T21, T22, T23) and the same third terminal (T103). The third terminal (T103) is electrically connected to a specific terminal (for example, the second terminal T102) other than the AC terminals (T21, T22, T23). In the control method of the power conversion circuit (1), a first control that turns on all of the plurality of first switching elements (Q11, Q13, Q15) or all of the plurality of second switching elements (Q12, Q14, Q16) is turned on.

According to this aspect, common mode noise can be suppressed without providing a capacitor on the DC side of the power conversion circuit (1).

A program according to an eleventh aspect is a program for causing one or more processors to execute the control method for the power conversion circuit (1) according to the tenth aspect.

According to this aspect, common mode noise can be suppressed without providing a capacitor on the DC side of the power conversion circuit (1).

The configurations according to the second to eighth aspects are not essential to the power conversion circuit (1), and can be omitted as appropriate.

1 power conversion circuits 2, 2a other power conversion circuits 10, 10a power conversion system 11 high-side arm 12 low-side arm 13 filter circuit 23 transformer 231 primary winding 232 secondary winding C11, C12, C13 capacitors Q11, Q13 , Q15 switching element (first switching element)
Q12, Q14, Q16 switching element (second switching element)
Q21 to Q28 switching element (third switching element)
T11, T12 DC terminals T21, T22, T23 AC terminal T101 First terminal (specific terminal)
T102 second terminal (specific terminal)
T103 Third terminal T104 Fourth terminal (specific terminal)
T105 fifth terminal (specific terminal)

Claims (11)

A power conversion circuit that converts power in at least one direction between DC power and AC power,
a high-side arm having a plurality of first switching elements electrically connected between any one of a plurality of AC terminals different from each other and the same first terminal;
a low-side arm having a plurality of second switching elements electrically connected between any one of the plurality of AC terminals and the same second terminal;
A filter circuit that has a plurality of capacitors and smoothes the AC voltage output via the high-side arm and the low-side arm,
An AC power supply or an AC load is electrically connected to the plurality of AC terminals,
each of the plurality of capacitors is electrically connected between one of the plurality of AC terminals and the same third terminal;
performing a first control to turn on all of the plurality of first switching elements or a second control to turn on all of the plurality of second switching elements;
The third terminal is electrically connected to a specific terminal excluding the plurality of AC terminals,
power conversion circuit. The third terminal is directly electrically connected to the specific terminal,
The power conversion circuit according to claim 1. the specific terminal is the first terminal, the second terminal, the fourth terminal, or the fifth terminal;
The fourth terminal and the fifth terminal are electrically connected to two DC terminals to which a DC power supply or a DC load is electrically connected, respectively.
The power conversion circuit according to claim 1 or 2. DC voltage is applied to the fourth terminal and the fifth terminal such that the fourth terminal has a high potential and the fifth terminal has a low potential,
performing the first control when the specific terminal is the first terminal or the fourth terminal;
performing the second control when the specific terminal is the second terminal or the fifth terminal;
4. A power conversion circuit according to claim 3. the high-side arm has three switching elements as the plurality of first switching elements,
The low-side arm has three switching elements as the plurality of second switching elements,
The power conversion circuit according to any one of claims 1 to 4. Synchronizing the first control or the second control with control of another power conversion circuit provided on the DC side of the power conversion circuit,
The power conversion circuit according to any one of claims 1 to 5. The other power conversion circuit has a plurality of third switching elements and a transformer electrically connected to the plurality of third switching elements,
the transformer includes a primary winding and a secondary winding magnetically coupled to each other;
Synchronizing the first control or the second control with a reversal timing at which the polarity of the voltage applied to the primary winding is reversed,
7. A power conversion circuit according to claim 6. Another power conversion circuit having a plurality of third switching elements and a transformer electrically connected to the plurality of third switching elements is provided on the DC side of the power conversion circuit,
the transformer includes a primary winding and a secondary winding magnetically coupled to each other;
At an inversion timing when the polarity of the voltage applied to the primary winding is reversed, the high-side arm and the low-side arm are arranged so that power is not transmitted between the power conversion circuit and the other power conversion circuit. to control the arm of
The power conversion circuit according to any one of claims 1-7. A power conversion circuit according to any one of claims 1 to 8;
Another power conversion circuit that is provided on the DC side of the power conversion circuit and performs power conversion in at least one direction between the first DC power and the second DC power as the DC power,
power conversion system. converting power in at least one direction between DC power and AC power;
a high-side arm having a plurality of first switching elements electrically connected between any one of a plurality of AC terminals different from each other and the same first terminal;
a low-side arm having a plurality of second switching elements electrically connected between any one of the plurality of AC terminals and the same second terminal;
A control method for a power conversion circuit including a filter circuit that has a plurality of capacitors and smoothes an AC voltage that is output via the high-side arm and the low-side arm,
An AC power supply or an AC load is electrically connected to the plurality of AC terminals,
each of the plurality of capacitors is electrically connected between one of the plurality of AC terminals and the same third terminal;
The third terminal is electrically connected to a specific terminal other than the plurality of AC terminals,
perform a first control that turns on all of the plurality of first switching elements, or a second control that turns on all of the plurality of second switching elements;
A control method for a power conversion circuit. A program for causing one or more processors to execute the power conversion circuit control method according to claim 10 .

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