Power converter

Abstract

The present invention addresses the problem of improving power conversion efficiency. In a power converter (100), a controller (50) performs a first control operation for enabling a high-level period of a control signal of a corresponding switch (8) of a plurality of switches (8) corresponding to each of a plurality of switching circuits (10) to overlap with a dead time, and the start of the high-level period is set at a point in time earlier than the start of the dead time by an additional time. The controller (50) selectively performs a second control operation or a third control operation according to a potential detected at a fourth terminal (154) of the regenerative capacitor (15) and polarities of a plurality of output currents (iU, iV, iW) supplied from a plurality of AC terminals (41). And a second control operation for enabling the respective high-level segments of the control signals of two switches (8) belonging to the plurality of switches (8) to overlap each other, and a third control operation for prohibiting the high-level segments of the control signals of the plurality of switches (8) from overlapping each other.

Description

Technical Field

[0001] The present disclosure generally relates to a power converter. More particularly, the present disclosure relates to a power converter having the capability of converting DC power into AC power. Background Art

[0002] Patent Document 1 discloses a power converter for converting DC power into multi-phase AC power.

[0003] The power converter of patent document 1 includes a main switching component (power conversion circuit), two capacitors, a coil (resonant inductor), a plurality of auxiliary switching elements and a control component. The main switching component includes a plurality of main switching circuits provided for each phase of the multi-phase AC power. Each of the plurality of main switching circuits is implemented as a pair of main switching elements connected in series between two terminals of a DC power supply, and the interconnection node of the pair of main switching elements is used as the output node of its associated phase. The two capacitors divide the voltage of the DC power supply. One terminal of the coil is connected to the voltage dividing node of the two capacitors. The plurality of auxiliary switching elements connect the other terminals of the coil to the output nodes of each phase. When it is determined that multiple phase currents flow through the coil, the control component controls the plurality of auxiliary switching elements so that the amount of current flowing through at least one phase is less than a preset amount.

[0004] Due to changes in load conditions, the power converter may sometimes experience a decrease in power conversion efficiency.

[0005] Citation List

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-233306 Summary of the Invention

[0007] An object of the present disclosure is to provide a power converter having the capability of improving power conversion efficiency.

[0008] According to one aspect of the present disclosure, a power converter includes first and second DC terminals, a power conversion circuit, multiple AC terminals, multiple switches, multiple resonant capacitors, a resonant inductor, a regenerative capacitor, and a controller. The power conversion circuit includes multiple first switching elements and multiple second switching elements. In the power conversion circuit, the multiple switching circuits are connected in parallel with each other, and in each of the multiple switching circuits, one of the multiple first switching elements and a corresponding second switching element of the multiple second switching elements are connected in series one-to-one. In the power conversion circuit, the multiple first switching elements are connected to the first DC terminal, and the multiple second switching elements are connected to the second DC terminal. The multiple AC terminals are provided one-to-one for each of the multiple switching circuits. Each of the multiple AC terminals is connected to a connection node between the first switching element and the second switching element of a corresponding switching circuit in the multiple switching circuits. The multiple switches are provided one-to-one for each of the multiple switching circuits. The first terminal of each of the multiple switches is connected to a connection node between the first switching element and the second switching element of the corresponding switching circuit in the multiple switching circuits. The second terminals of each of the multiple switches are connected to a common connection node. The multiple resonant capacitors are provided one-to-one for each of the multiple switches. Each of the plurality of resonant capacitors is connected between a first terminal and a second DC terminal of a corresponding switch in the plurality of switches. A resonant inductor has a first terminal and a second terminal. In the resonant inductor, the first terminal of the resonant inductor is connected to a common connection node. A regenerative capacitor has a third terminal and a fourth terminal. In the regenerative capacitor, the third terminal is connected to the first DC terminal or the second DC terminal. A controller applies a PWM signal having a potential alternating between a high level and a low level to each of the plurality of first switching elements and the plurality of second switching elements. The controller performs a first control operation. The controller performs the first control operation by setting a dead time between a high level period of the PWM signal of the first switching element and a high level period of the PWM signal of the second switching element for each of the plurality of switching circuits. The controller performs the first control operation by enabling a high level period of the control signal of the corresponding switch in the plurality of switches corresponding to each of the plurality of switching circuits to overlap with the dead time and setting the start of the high level period to a time point that is an additional time earlier than the start of the dead time. The controller selectively performs a second control operation or a third control operation according to the potential detected at the fourth terminal of the regenerative capacitor and the polarities of the plurality of output currents supplied from the plurality of AC terminals, wherein the second control operation includes enabling high-level periods of control signals belonging to two switches of the plurality of switches to overlap with each other, and the third control operation includes prohibiting high-level periods of control signals of the plurality of switches from overlapping with each other.

[0009] According to another aspect of the present disclosure, a power converter includes first and second DC terminals, a power conversion circuit, multiple AC terminals, multiple switches, multiple resonant circuits, a regenerative capacitor, and a controller. The power conversion circuit includes multiple first switching elements and multiple second switching elements. In the power conversion circuit, the multiple switching circuits are connected in parallel with each other, and in each of the multiple switching circuits, one of the multiple first switching elements and a corresponding second switching element of the multiple second switching elements are connected in series one-to-one. In the power conversion circuit, the multiple first switching elements are connected to the first DC terminal, and the multiple second switching elements are connected to the second DC terminal. The multiple AC terminals are provided one-to-one for each of the multiple switching circuits. Each of the multiple AC terminals is connected to a connection node between the first switching element and the second switching element of a corresponding switching circuit in the multiple switching circuits. The multiple switches are provided one-to-one for each of the multiple switching circuits. The first terminal of each of the multiple switches is connected to a connection node between the first switching element and the second switching element of the corresponding switching circuit in the multiple switching circuits. The multiple resonant circuits are provided one-to-one for each of the multiple switches. Each of the multiple resonant circuits has a variable resonant frequency. The regenerative capacitor has a third terminal and a fourth terminal. In a regenerative capacitor, a third terminal is connected to a first DC terminal or a second DC terminal, and a fourth terminal is connected to a plurality of resonant circuits. A controller applies a PWM signal having a potential alternating between a high level and a low level to each of the plurality of first switching elements and the plurality of second switching elements. Each of the plurality of resonant circuits includes a resonant capacitor connected between a first terminal and a second DC terminal of a corresponding switch among the plurality of switches; and a resonant inductor connected between a second terminal of the corresponding switch among the plurality of switches and a fourth terminal of the resonant capacitor. The controller sets a dead time between a high-level period of the PWM signal of the first switching element and a high-level period of the PWM signal of the second switching element for each of the plurality of switching circuits. The controller performs a first control operation. The first control operation includes enabling a high-level period of the control signal of a corresponding switch among the plurality of switches corresponding to each of the plurality of switching circuits to overlap with the dead time, and setting the start of the high-level period to a time point that is an additional time earlier than the start of the dead time. The controller changes the resonant frequency of at least one resonant circuit belonging to the plurality of resonant circuits based on the potential at the fourth terminal of the regenerative capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a circuit diagram of a system including a power converter according to a first embodiment;

[0011] Figure 2shows how the power converter operates when its controller has performed a first control operation;

[0012] Figure 3 It also shows how the power converter operates when its controller has performed a first control operation;

[0013] Figure 4 Shows how the controller operates in a power converter;

[0014] Figure 5 shows how duty ratios corresponding to three-phase voltage commands in AC loads connected to a plurality of AC terminals of a power converter, respectively, vary over time;

[0015] Figure 6 is a timing diagram showing a case where a controller has independently controlled two-phase switches in a power converter;

[0016] Figure 7 is a timing diagram showing a situation where a controller has simultaneously controlled two-phase switches in a power converter;

[0017] Figure 8 is a timing diagram showing a situation where a controller has simultaneously controlled two-phase switches in a power converter;

[0018] Figure 9 is a timing diagram showing a case where a controller has independently controlled two-phase switches in a power converter;

[0019] Figure 10 is a timing diagram showing a situation where a controller has simultaneously controlled two-phase switches in a power converter;

[0020] Figure 11 is a timing diagram showing a case where a controller has independently controlled two-phase switches in a power converter;

[0021] Figure 12 1 is a timing diagram showing a case where a controller in a power converter controls two-phase switches simultaneously;

[0022] Figure 13 is a circuit diagram of a system including a power converter according to a first modification of the first embodiment;

[0023] Figure 14 is a circuit diagram of a system including a power converter according to a second modification of the first embodiment;

[0024] Figure 15 is a circuit diagram of a system including a power converter according to a third modification of the first embodiment;

[0025] Figure 16is a circuit diagram of a system including a power converter according to a fourth modification of the first embodiment;

[0026] Figure 17 is a circuit diagram of a system including a power converter according to a fifth modification of the first embodiment;

[0027] Figure 18 is a circuit diagram of a system including a power converter according to a second embodiment;

[0028] Figure 19 is a circuit diagram of a system including a power converter according to a third embodiment;

[0029] Figure 20 is a circuit diagram of a power converter according to a fourth embodiment;

[0030] Figure 21 is a timing diagram illustrating how a power converter may operate;

[0031] Figure 22 is a timing diagram showing how the power converter may also operate; and

[0032] Figure 23 is a circuit diagram of a system including a power converter according to a fifth embodiment. DETAILED DESCRIPTION

[0033] (First embodiment)

[0034] Will refer to Figures 1 to 12 A power converter 100 according to a first embodiment will be described.

[0035] (1) Overall configuration of power converter

[0036] For example, Figure 1 As shown, the power converter 100 includes a first DC terminal 31 and a second DC terminal 32 and a plurality of (e.g., three) AC terminals 41. A DC power source E1 is connected between the first DC terminal 31 and the second DC terminal 32. An AC load RA1 is connected to the plurality of AC terminals 41. The AC load RA1 may be, for example, a three-phase motor. The power converter 100 converts the DC output of the DC power source E1 into AC power and outputs the AC power to the AC load RA1. The DC power source E1 may include, for example, a solar cell or a fuel cell. The DC power source E1 may include a DC-DC converter. In the power converter 100, if the plurality of AC terminals 41 are three AC terminals 41, the AC power may be, for example, three-phase AC power having a U phase, a V phase, and a W phase.

[0037] Power converter 100 includes power conversion circuit 11, multiple (e.g., three) switches 8, multiple (e.g., three) resonant capacitors 9, regenerative capacitor 15, resonant inductor L0, and controller 50. Power converter 100 also includes protection circuit 17 and capacitor C10. Each of the multiple switches 8 can be, for example, a bidirectional switch.

[0038] The power conversion circuit 11 includes a plurality (e.g., three) of first switching elements 1 and a plurality (e.g., three) of second switching elements 2. In the power conversion circuit 11, a plurality (e.g., three) of switching circuits 10 are connected in parallel. In each switching circuit 10, one of the plurality of first switching elements 1 and a corresponding second switching element of the plurality of second switching elements 2 are connected in series on a one-to-one basis. In the power conversion circuit 11, the plurality of first switching elements 1 are connected to a first DC terminal 31, and the plurality of second switching elements 2 are connected to a second DC terminal 32. A plurality of AC terminals 41 are provided for each of the plurality of switching circuits 10. Each of the plurality of AC terminals 41 is connected to a connection node 3 between the first switching element 1 and the second switching element 2 of a corresponding switching circuit 10. A plurality of switches 8 are provided for each of the plurality of switching circuits 10. A first terminal 81 of each of the plurality of switches 8 is connected to a connection node 3 between the first switching element 1 and the second switching element 2 of a corresponding switching circuit 10. A plurality of resonant capacitors 9 are provided for each of the plurality of switches 8. Each of the plurality of resonant capacitors 9 is connected between the first terminal 81 and the second DC terminal 32 of a corresponding switch 8 among the plurality of switches 8. The resonant inductor L0 has a first terminal and a second terminal. The first terminal of the resonant inductor L0 is connected to the common connection node 25. The regenerative capacitor 15 has a third terminal 153 and a fourth terminal 154. In the regenerative capacitor 15, its third terminal 153 is connected to the second DC terminal 32, and its fourth terminal 154 is connected to the common connection node 25. The controller 50 controls the plurality of first switching elements 1, the plurality of second switching elements 2, and the plurality of switches 8.

[0039] (2) Details of power converter

[0040] In the following description, for the sake of convenience, with respect to a plurality of switching circuits 10, the switching circuits 10 for the U-phase, V-phase, and W-phase will be referred to as “switching circuit 10U,” “switching circuit 10V,” and “switching circuit 10W,” respectively, hereinafter. In addition, in the following description, the first switching element 1 and the second switching element 2 of the switching circuit 10U will be referred to as “first switching element 1U” and “second switching element 2U,” respectively, hereinafter. Similarly, in the following description, the first switching element 1 and the second switching element 2 of the switching circuit 10V will be referred to as “first switching element 1V” and “second switching element 2V,” respectively, hereinafter. Similarly, in the following description, the first switching element 1 and the second switching element 2 of the switching circuit 10W will be referred to as “first switching element 1W” and “second switching element 2W,” respectively, hereinafter. Furthermore, in the following description, the connection node 3 between the first switching element 1U and the second switching element 2U will be referred to as "connection node 3U," the connection node 3 between the first switching element 1V and the second switching element 2V will be referred to as "connection node 3V," and the connection node 3 between the first switching element 1W and the second switching element 2W will be referred to as "connection node 3W." Furthermore, in the following description, the AC terminal 41 connected to the connection node 3U will be referred to as "AC terminal 41U," the AC terminal 41 connected to the connection node 3V will be referred to as "AC terminal 41V," and the AC terminal 41 connected to the connection node 3W will be referred to as "AC terminal 41W." Furthermore, in the following description, the resonant capacitor 9 connected in parallel to the second switching element 2U will be referred to as "resonant capacitor 9U," the resonant capacitor 9 connected in parallel to the second switching element 2V will be referred to as "resonant capacitor 9V," and the resonant capacitor 9 connected in parallel to the second switching element 2W will be referred to as "resonant capacitor 9W." In addition, in the following description, the switch 8 connected to the connection node 3U will be referred to as "switch 8U" below, the switch 8 connected to the connection node 3V will be referred to as "switch 8V" below, and the switch 8 connected to the connection node 3W will be referred to as "switch 8W" below.

[0041] In the power converter 100, the high potential output terminal (positive electrode) of the DC power source E1 is connected to the first DC terminal 31, and the low potential output terminal (negative electrode) of the DC power source E1 is connected to the second DC terminal 32. In addition, in the power converter 100, the U-phase, V-phase, and W-phase of the AC load RA1 are connected to the three AC terminals 41U, 41V, and 41W, respectively.

[0042] In the power conversion circuit 11, each of the plurality of (e.g., three) first switching elements 1 and the plurality of (e.g., three) second switching elements 2 has a control terminal, a first main terminal, and a second main terminal. The control terminals of the plurality of first switching elements 1 and the plurality of second switching elements 2 are connected to the controller 50. In each of the plurality of switching circuits 10 of the power converter 100, the first main terminal of the first switching element 1 is connected to the first DC terminal 31, the second main terminal of the first switching element 1 is connected to the first main terminal of the second switching element 2, and the second main terminal of the second switching element 2 is connected to the second DC terminal 32. In each of the plurality of switching circuits 10, the first switching element 1 is a high-side switching element (P-side switching element), and the second switching element 2 is a low-side switching element (N-side switching element). Each of the plurality of first switching elements 1 and the plurality of second switching elements 2 can be, for example, an insulated gate bipolar transistor (IGBT). Thus, in each of the plurality of first switching elements 1 and the plurality of second switching elements 2 , the control terminal, the first main terminal, and the second main terminal thereof are the gate terminal, the collector terminal, and the emitter terminal, respectively.

[0043] The power conversion circuit 11 also includes: a plurality of (e.g., three) first diodes 4, which are connected in anti-parallel to the plurality of (e.g., three) first switching elements 1 on a one-to-one basis; and a plurality of (e.g., three) second diodes 5, which are connected in anti-parallel to the plurality of (e.g., three) second switching elements 2 on a one-to-one basis. In each of the plurality of first diodes 4, the anode of the first diode 4 is connected to the second main terminal (emitter terminal) of the first switching element 1 corresponding to the first diode 4, and the cathode of the first diode 4 is connected to the first main terminal (collector terminal) of the first switching element 1 corresponding to the first diode 4. In each of the plurality of second diodes 5, the anode of the second diode 5 is connected to the second main terminal (emitter terminal) of the second switching element 2 corresponding to the second diode 5, and the cathode of the second diode 5 is connected to the first main terminal (collector terminal) of the second switching element 2 corresponding to the second diode 5.

[0044] The U-phase of the AC load RA1 can be connected to the connection node 3U between the first switching element 1U and the second switching element 2U via, for example, an AC terminal 41U. The V-phase of the AC load RA1 can be connected to the connection node 3V between the first switching element 1V and the second switching element 2V via, for example, an AC terminal 41V. The W-phase of the AC load RA1 can be connected to the connection node 3W between the first switching element 1W and the second switching element 2W via, for example, an AC terminal 41W.

[0045] Multiple resonant capacitors 9 are provided one-to-one with each of the multiple switches 8. Each of the multiple resonant capacitors 9 is connected between the first terminal 81 and the second DC terminal 32 of its corresponding switch 8. The power converter 100 includes multiple resonant circuits. The multiple resonant circuits include a resonant circuit including a resonant capacitor 9U and a resonant inductor L0, a resonant circuit including a resonant capacitor 9V and a resonant inductor L0, and a resonant circuit including a resonant capacitor 9W and a resonant inductor L0. The multiple resonant circuits share the resonant inductor L0.

[0046] Each of the plurality of switches 8 may, for example, include two IGBTs (i.e., a first IGBT 6 and a second IGBT 7) connected in anti-parallel. In each of the plurality of switches 8, the collector terminal of the first IGBT 6 and the emitter terminal of the second IGBT 7 are connected to each other, and the emitter terminal of the first IGBT 6 and the collector terminal of the second IGBT 7 are connected to each other. In each of the plurality of switches 8, the emitter terminal of the first IGBT 6 is connected to the connection node 3 of the switching circuit 10 corresponding to the switch 8 including the first IGBT 6. In each of the plurality of switches 8, the collector terminal of the second IGBT 7 is connected to the connection node 3 of the switching circuit 10 corresponding to the switch 8 including the second IGBT 7. Switch 8U is connected to the connection node 3U between the first switching element 1U and the second switching element 2U. Switch 8V is connected to the connection node 3V between the first switching element 1V and the second switching element 2V. Switch 8W is connected to the connection node 3W between the first switching element 1W and the second switching element 2W. In the following description, for convenience of explanation, the first IGBT 6 and the second IGBT 7 of the switch 8U will be referred to as the "first IGBT 6U" and the "second IGBT 7U", respectively, the first IGBT 6 and the second IGBT 7 of the switch 8V will be referred to as the "first IGBT 6V" and the "second IGBT 7V", respectively, and the first IGBT 6 and the second IGBT 7 of the switch 8W will be referred to as the "first IGBT 6W" and the "second IGBT 7W", respectively.

[0047] The plurality of switches 8 are controlled by the controller 50. In other words, the first IGBT 6U, the second IGBT 7U, the first IGBT 6V, the second IGBT 7V, the first IGBT 6W, and the second IGBT 7W are controlled by the controller 50.

[0048] The resonant inductor L0 has a first terminal and a second terminal. In the resonant inductor L0 , the first terminal of the resonant inductor L0 is connected to the common connection node 25 , and the second terminal of the resonant inductor L0 is connected to the fourth terminal 154 of the regenerative capacitor 15 .

[0049] The regenerative capacitor 15 is connected between the second terminal of the resonant inductor L0 and the second DC terminal 32. The regenerative capacitor 15 may be, for example, a film capacitor.

[0050] Protection circuit 17 includes a third diode 13 and a fourth diode 14. Third diode 13 is connected between common connection node 25 and first DC terminal 31. The anode of third diode 13 is connected to common connection node 25, and the cathode of third diode 13 is connected to first DC terminal 31. Fourth diode 14 is connected between common connection node 25 and second DC terminal 32. The anode of fourth diode 14 is connected to second DC terminal 32, and the cathode of fourth diode 14 is connected to common connection node 25. Thus, fourth diode 14 is connected in series to third diode 13.

[0051] The capacitor C10 is connected between the first DC terminal 31 and the second DC terminal 32, and is connected in parallel to the power conversion circuit 11. The capacitor C10 may be, for example, an electrolytic capacitor.

[0052] The controller 50 controls a plurality of first switching elements 1, a plurality of second switching elements 2 and a plurality of switches 8. An agent for performing the functions of the controller 50 includes a computer system. The computer system includes a single or multiple computers. The computer system may include a processor and a memory as its main hardware components. The computer system is used as an agent for performing the functions of the controller 50 according to the present disclosure by causing the processor to execute a program stored in the memory of the computer system. The program may be pre-stored in the memory of the computer system. Alternatively, the program may also be downloaded via a telecommunications line, or distributed after being recorded in a non-transitory storage medium such as a memory card, an optical disc or a hard disk drive (disk) (any of which storage media is readable for the computer system). The processor of the computer system may be composed of a single or multiple electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). These electronic circuits may be integrated together on a single chip or distributed on multiple chips, whichever is appropriate. These multiple chips may be aggregated together in a single device or distributed in multiple devices without limitation.

[0053] The controller 50 outputs pulse-width modulation (PWM) signals SU1, SV1, and SW1 for controlling the on / off states of the plurality of first switching elements 1U, 1V, and 1W, respectively. Each of the PWM signals SU1, SV1, and SW1 has a potential level that alternates between a first potential level (hereinafter referred to as a "low level") and a second potential level (hereinafter referred to as a "high level") that is higher than the first potential level. The first switching elements 1U, 1V, and 1W are turned on when the PWM signals SU1, SV1, and SW1 are at a high level, respectively, and are turned off when the PWM signals SU1, SV1, and SW1 are at a low level, respectively. Furthermore, the controller 50 outputs PWM signals SU2, SV2, and SW2 for controlling the on / off states of the plurality of second switching elements 2U, 2V, and 2W, respectively. Each of the PWM signals SU2, SV2, and SW2 is a signal having a potential level that alternates between a first potential level (hereinafter referred to as a "low level") and a second potential level (hereinafter referred to as a "high level") higher than the first potential level. The second switching elements 2U, 2V, and 2W are turned on when the PWM signals SU2, SV2, and SW2 are at a high level, respectively, and are turned off when the PWM signals SU2, SV2, and SW2 are at a low level, respectively.

[0054] The controller 50 uses a carrier signal having a sawtooth waveform (reference Figure 2 ) to generate PWM signals SU1, SV1, SW1 for the plurality of first switching elements 1U, 1V, 1W, and PWM signals SU2, SV2, SW2 for the plurality of second switching elements 2U, 2V, 2W, respectively. More specifically, the controller 50 generates the PWM signals SU1, SU2 to be applied to the first switching element 1U and the second switching element 2U, respectively, based at least on the carrier signal and the U-phase voltage command. In addition, the controller 50 generates the PWM signals SV1, SV2 to be applied to the first switching element 1V and the second switching element 2V, respectively, based at least on the carrier signal and the V-phase voltage command. In addition, the controller 50 generates the PWM signals SW1, SW2 to be applied to the first switching element 1W and the second switching element 2W, respectively, based at least on the carrier signal and the W-phase voltage command. The U-phase voltage command, the V-phase voltage command, and the W-phase voltage command can, for example, be sinusoidal wave signals whose phases differ by 120 degrees from each other and whose amplitudes (voltage command values) vary with time. In addition, the U-phase voltage command, the V-phase voltage command, and the W-phase voltage command each have a cycle of the same length. In addition, one cycle of the U-phase voltage command, the V-phase voltage command, and the W-phase voltage command is longer than one cycle of the carrier signal.

[0055] The duty ratios of the PWM signals SU1 and SU2 to be applied from the controller 50 to the first switching element 1U and the second switching element 2U, respectively, vary according to the U-phase voltage command. The controller 50 generates the PWM signal SU1 to be applied to the first switching element 1U by comparing the U-phase voltage command with the carrier signal. The controller 50 generates the PWM signal SU2 to be applied to the second switching element 2U by inverting the PWM signal SU1 to be applied to the first switching element 1U. In addition, in order to prevent the respective on-periods of the first switching element 1U and the second switching element 2U from overlapping each other, the controller 50 sets a dead time Td (reference time Td) between the high-level period of the PWM signal SU1 and the high-level period of the PWM signal SU2. Figure 2 ).

[0056] The duty ratios of the PWM signals SV1 and SV2 to be applied from the controller 50 to the first switching element 1V and the second switching element 2V, respectively, vary according to the V-phase voltage command. The controller 50 generates the PWM signal SV1 to be applied to the first switching element 1V by comparing the V-phase voltage command with the carrier signal. The controller 50 generates the PWM signal SV2 to be applied to the second switching element 2V by inverting the PWM signal SV1 to be applied to the first switching element 1V. In addition, in order to prevent the respective on-periods of the first switching element 1V and the second switching element 2V from overlapping each other, the controller 50 sets a dead time Td (reference time Td) between the high-level period of the PWM signal SV1 and the high-level period of the PWM signal SV2. Figure 2 ).

[0057] The duty ratios of the PWM signals SW1 and SW2 to be applied from the controller 50 to the first switching element 1W and the second switching element 2W, respectively, vary according to the W-phase voltage command. The controller 50 generates the PWM signal SW1 to be applied to the first switching element 1W by comparing the W-phase voltage command with the carrier signal. The controller 50 generates the PWM signal SW2 to be applied to the second switching element 2W by inverting the PWM signal SW1 to be applied to the first switching element 1W. In addition, in order to prevent the respective on-periods of the first switching element 1W and the second switching element 2W from overlapping each other, the controller 50 sets a dead time Td (reference time Td) between the high-level period of the PWM signal SW1 and the high-level period of the PWM signal SW2. Figure 3 ).

[0058] The U-phase voltage command, the V-phase voltage command, and the W-phase voltage command may be, for example, sinusoidal signals whose phases differ by 120 degrees from each other and whose amplitudes vary with time. Figure 5As shown, the duty ratios of the PWM signals SU1, SV1, and SW1 vary in the form of sinusoidal waves with a phase difference of 120 degrees. Similarly, the duty ratios of the PWM signals SU2, SV2, and SW2 vary in the form of sinusoidal waves with a phase difference of 120 degrees.

[0059] Controller 50 generates PWM signals SU1, SU2, SV1, SV2, SW1, and SW2 based on the carrier signal, the voltage commands, and information about the state of AC load RA1. For example, if AC load RA1 is a three-phase motor, the information about the state of AC load RA1 may include detection values ​​provided by a plurality of current sensors for detecting output currents iU, iV, and iW flowing through the U-phase, V-phase, and W-phase of AC load RA1, respectively.

[0060] A plurality of switches 8 , a resonant inductor L0 , a plurality of resonant capacitors 9 , and a regenerative capacitor 15 are provided to perform zero-voltage soft switching of the plurality of first switching elements 1 and the plurality of second switching elements 2 .

[0061] In this power converter 100 , the controller 50 controls not only the plurality of first switching elements 1 and the plurality of second switching elements 2 of the power conversion circuit 11 , but also the plurality of switches 8 .

[0062] The controller 50 generates control signals SU6, SU7, SV6, SV7, SW6, SW7 for respectively controlling the on / off states of the first IGBT 6U, the second IGBT 7U, the first IGBT 6V, the second IGBT 7V, the first IGBT 6W, and the second IGBT 7W, and outputs the control signals SU6, SU7, SV6, SV7, SW6, SW7 to the gate terminals of the first IGBT 6U, the second IGBT 7U, the first IGBT 6V, the second IGBT 7V, the first IGBT 6W, and the second IGBT 7W.

[0063] If the first IGBT 6U is turned on and the second IGBT 7U is turned off, the switch 8U allows a charging current to flow through the regenerative capacitor 15, the resonant inductor L0, the switch 8U, and the resonant capacitor 9U in this order to charge the resonant capacitor 9U. On the other hand, if the first IGBT 6U is turned off and the second IGBT 7U is turned on, the switch 8U allows a discharging current to flow through the resonant capacitor 9U, the switch 8U, the resonant inductor L0, and the regenerative capacitor 15 in this order to remove the charge from the resonant capacitor 9U.

[0064] If the first IGBT 6V is turned on and the second IGBT 7V is turned off, the switch 8V allows a charging current to flow through the regenerative capacitor 15, the resonant inductor L0, the switch 8V, and the resonant capacitor 9V in this order to charge the resonant capacitor 9V. On the other hand, if the first IGBT 6V is turned off and the second IGBT 7V is turned on, the switch 8V allows a discharging current to flow through the resonant capacitor 9V, the switch 8V, the resonant inductor L0, and the regenerative capacitor 15 in this order to remove the charge from the resonant capacitor 9V.

[0065] If the first IGBT 6W is turned on and the second IGBT 7W is turned off, the switch 8W allows a charging current to flow through the regenerative capacitor 15, the resonant inductor L0, the switch 8W, and the resonant capacitor 9W in this order to charge the resonant capacitor 9W. On the other hand, if the first IGBT 6W is turned off and the second IGBT 7W is turned on, the switch 8W allows a discharging current to flow through the resonant capacitor 9W, the switch 8W, the resonant inductor L0, and the regenerative capacitor 15 in this order to remove charge from the resonant capacitor 9W.

[0066] (3) Operation of power converter

[0067] In the following description, for the current iL0 flowing through the resonant inductor L0, if the current is Figure 1 If the current iL0 flows in the direction indicated by the arrow shown in FIG, the polarity of the current iL0 is assumed to be positive. On the other hand, if the current iL0 flows in the direction indicated by the arrow shown in FIG, the polarity of the current iL0 is assumed to be positive. Figure 1 If the current iL0 flows in the direction opposite to the direction indicated by the arrow shown in FIG1 , the polarity of the current iL0 is assumed to be negative. In the following description, for each of the output currents iU, iV, iW flowing through the U-phase, V-phase, and W-phase of the AC load RA1, if the currents iU, iV, iW are Figure 1 If the currents iU, iV, iW flow in the direction indicated by the corresponding arrows in the arrows shown, the polarity of the currents iU, iV, iW is assumed to be positive. On the other hand, if the currents iU, iV, iW flow in the direction indicated by the corresponding arrows in the arrows shown, the polarity of the currents iU, iV, iW is assumed to be positive. Figure 1 If the load currents iU, iV, and iW flow in the direction opposite to the direction indicated by the arrow shown in FIG. 1 , the polarity of the load currents iU, iV, and iW is assumed to be negative. In addition, for each of the currents i9U, i9V, and i9W flowing through the resonant capacitors 9U, 9V, and 9W, respectively, if the currents i9U, i9V, and i9W are Figure 1 If the currents i9U, i9V, i9W flow in the direction indicated by the corresponding arrows in the arrows shown, the polarity of the currents i9U, i9V, i9W is assumed to be positive. On the other hand, if the currents i9U, i9V, i9W flow in the direction indicated by the corresponding arrows in the arrows shown, the polarity of the currents i9U, i9V, i9W is assumed to be positive. Figure 1 If the currents i9U, i9V, and i9W flow in a direction opposite to the direction indicated by the arrows shown, the polarity of the currents i9U, i9V, and i9W is assumed to be negative.

[0068] In this power converter 100, for example, when the first IGBT 6U of the switch 8U is on and a positive current iL0 is flowing through the resonant inductor L0, the first IGBT 6U of the switch 8U can be turned off. In this case, the current iL0 flowing through the resonant inductor L0 is regenerated to the power conversion circuit 11 via the third diode 13 until the current iL0 flowing through the resonant inductor L0 reaches zero due to energy dissipation in the resonant inductor L0. Furthermore, in this power converter 100, for example, when the second IGBT 7U of the switch 8U is on and a negative current iL0 is flowing through the resonant inductor L0, the second IGBT 7U of the switch 8U can be turned off. In this case, the current iL0 flows through the resonant inductor L0 along a path that passes through the fourth diode 14, the resonant inductor L0, and the regeneration capacitor 15 in this order until the current iL0 reaches zero due to energy dissipation in the resonant inductor L0.

[0069] Furthermore, in this power converter 100, for example, when the first IGBT 6V of the switch 8V is on and a positive current iL0 is flowing through the resonant inductor L0, the first IGBT 6V of the switch 8V can be turned off. In this case, the current iL0 flowing through the resonant inductor L0 is regenerated to the power conversion circuit 11 via the third diode 13 until the current iL0 flowing through the resonant inductor L0 reaches zero due to energy dissipation in the resonant inductor L0. Furthermore, in this power converter 100, for example, when the second IGBT 7V of the switch 8V is on and a negative current iL0 is flowing through the resonant inductor L0, the second IGBT 7V of the switch 8V can be turned off. In this case, the current iL0 flows through the resonant inductor L0 along a path that passes through the fourth diode 14, the resonant inductor L0, and the regeneration capacitor 15 in this order until the current iL0 reaches zero due to energy dissipation in the resonant inductor L0.

[0070] Furthermore, in this power converter 100, for example, when the first IGBT 6W of the switch 8W is on and a positive current iL0 is flowing through the resonant inductor L0, the first IGBT 6W of the switch 8W can be turned off. In this case, the current iL0 flowing through the resonant inductor L0 is regenerated to the power conversion circuit 11 via the third diode 13 until the current iL0 flowing through the resonant inductor L0 reaches zero due to energy dissipation in the resonant inductor L0. Furthermore, in this power converter 100, for example, when the second IGBT 7W of the switch 8W is on and a negative current iL0 is flowing through the resonant inductor L0, the second IGBT 7W of the switch 8W can be turned off. In this case, the current iL0 flows through the resonant inductor L0 along a path that passes through the fourth diode 14, the resonant inductor L0, and the regeneration capacitor 15 in this order until the current iL0 reaches zero due to energy dissipation in the resonant inductor L0.

[0071] Next, we will refer to Figures 1 to 3 How the controller 50 operates when performing zero-voltage soft switching control of each of the plurality of first switching elements 1 and each of the plurality of second switching elements 2 will be described.

[0072] The controller 50 performs the first control operation by setting a dead time Td between the high-level period of the PWM signal SU1, SV1, SW1 of the first switching element 1U, 1V, 1W and the high-level period of the PWM signal SU2, SV2, SW2 of the second switching element 2U, 2V, 2W for each of the plurality of switching circuits 10. Furthermore, the controller 50 performs the first control operation by causing the high-level period of the control signal of the corresponding switch 8 among the plurality of switches 8 corresponding to each of the plurality of switching circuits 10 to overlap with the dead time Td, and setting the start of the high-level period to a time point earlier than the start of the dead time Td by an additional time.

[0073] The first control operation will now be described in more detail.

[0074] When performing zero-voltage soft switching control on the first switching element 1, the voltage across the first switching element 1 must be reduced to zero immediately before the first switching element 1, which is the subject of zero-voltage soft switching, turns on. Therefore, the controller 50 turns on the first IGBT 6 corresponding to the first switching element 1, which is the subject of zero-voltage soft switching control. In this way, the controller 50 causes the resonant inductor L0 and the resonant capacitor 9 connected to the first switching element 1 to resonate, and charges the resonant capacitor 9 with the charge removed from the regenerative capacitor 15, thereby reducing the voltage across the first switching element 1 to zero.

[0075] On the other hand, when performing zero-voltage soft-switching control on the second switching element 2, the voltage across the second switching element 2 must be reduced to zero immediately before the second switching element 2, which is the subject of zero-voltage soft-switching control, becomes conductive. Therefore, the controller 50 turns on the second IGBT 7 corresponding to the second switching element 2, which is the subject of zero-voltage soft-switching control. In this way, the controller 50 causes the resonant inductor L0 and the resonant capacitor 9 connected to the second switching element 2 to resonate, and discharges the resonant capacitor 9 into the regenerative capacitor 15, thereby reducing the voltage across the second switching element 2 to zero. The controller 50 charges and discharges the resonant capacitor 9 via the switch 8 so that the dead time Td coincides with the half-cycle (π×√LC) of the LC resonance. This enables the power converter 100 to perform zero-voltage soft switching. In (π×√LC), which represents the half-cycle of the LC resonance, "L" is the inductance of the resonant inductor L0, and "C" is the capacitance of the resonant capacitor 9.

[0076] Figure 2 PWM signals SU1 and SU2 to be applied from the controller 50 to the first switching element 1U and the second switching element 2U of the switching circuit 10U are shown in FIG. Figure 2 Also shown are the control signal SU6 to be applied from the controller 50 to the first IGBT 6U of the switch 8U, the output current iU of the U phase flowing through the AC load RA1, the current iL0 flowing through the resonant inductor L0, and the voltage V across the first switching element 1U. 1U .also, Figure 2 PWM signals SV1 and SV2 to be applied from the controller 50 to the first switching element 1V and the second switching element 2V of the switching circuit 10V are shown in FIG. Figure 2 Also shown are the control signal SV6 to be applied from the controller 50 to the first IGBT 6V of the switch 8V, the V-phase output current iV flowing through the AC load RA1, the current iL0 flowing through the resonant inductor L0, and the voltage V across the first switching element 1V. 1V .

[0077] also, Figure 2 The figure also shows the dead time Td set by the controller 50 to prevent the first switching element 1 and the second switching element 2 of the same phase from being turned on at the same time. Figure 2 8U and 8V. Also shown are additional time Tau and Tav set by the controller 50 for the control signal SU6 of the first IGBT 6U of the switch 8U and the control signal SV6 of the first IGBT 6V of the switch 8V. The additional time Tau and the additional time Tav will be described later.

[0078] Figure 3The PWM signals SW1 and SW2 to be respectively applied from the controller 50 to the first switching element 1W and the second switching element 2W of the switching circuit 10W are shown. Additionally, Figure 3 The control signal SW6 to be applied from the controller 50 to the first IGBT 6W of the switch 8W and the output current iW flowing through the W-phase of the AC load RA1 are also shown. Figure 3 The current iL0 flowing through the resonant inductor L0 is also shown. Figure 3 The voltage V across the first switching element 1W is also shown. 1W .

[0079] Furthermore, Figure 3 The dead time Td set by the controller 50 to prevent the first switching element 1W and the second switching element 2W from becoming conductive simultaneously is also shown. Furthermore, Figure 3 The additional time Taw set by the controller 50 for the control signal SW6 of the first IGBT 6W of the switch 8W is also shown. The additional time Taw will be described later.

[0080] As Figure 2 shown, the additional time Tau is the amount of time that the controller 50 sets such that the start t1 of the high-level period of the control signal SU6 is set earlier than the start t2 of the dead time Td, making the high-level period of the control signal SU6 longer than the dead time Td. The length of the additional time Tau is determined by the value of the output current iU. To generate LC resonance starting from the start t2 of the dead time Td, it is preferable that the value of the current iL0 coincides with the value of the output current iU at the start t2 of the dead time Td. This is because as long as iL0 < iU, all the current flows through the AC load RA1, and thus the resonant capacitor 9U cannot be charged. The end of the high-level period of the control signal SU6 can be simultaneous with or later than the end t3 of the dead time Td. In the Figure 2 example shown, the end of the high-level period of the control signal SU6 is set to be simultaneous with the end t3 of the dead time Td. The controller 50 sets the high-level period of the control signal SU6 to Tau + Td. The voltage V across the first switching element 1U 1U becomes zero at the end t3 of the dead time Td. In the Figure 2 example shown, the current iL0 starts flowing through the resonant inductor L0 at the start t1 of the high-level period of the control signal SU6 and becomes zero at the time t4 after the additional time Tau has elapsed from the end t3 of the dead time Td. At this time, starting from the start t2 of the dead time Td, the current iL0 satisfies iL0 ≥ iU, so from Figure 2The current iL0 in the shaded portion of the current waveform shown as the fifth waveform from the top flows into the resonant capacitor 9U to generate LC resonance. From the end t3 of the dead time Td, the current iL0 is regenerated to the power conversion circuit 11 via the third diode 13 directly connected to the resonant inductor L0.

[0081] As described above, to initiate LC resonance at the start t2 of dead time Td, controller 50 determines additional time Tau based on output current iU, such that iL0 = iU at the start t2 of dead time Td. More specifically, for example, controller 50 uses the current sensor's detection result of output current iU or its signal-processed value, or an estimated value of current iU, a pre-stored inductance L of resonant inductor L0, and the potential V15 of regenerative capacitor 15 to determine additional time Tau using the equation Tau = iU × (L / V15). In this case, the output current iU detection result or its signal-processed value can be a detection value at the carrier cycle to which additional time Tau is added, or a detection value at a timing closest to the carrier cycle. Furthermore, in this case, the estimated output current iU value can be, for example, an estimated output current iU value at the carrier cycle to which additional time Tau is added.

[0082] Note that Figure 4 As shown, if the polarity of the output current iU is negative, the power converter 100 can charge the resonant capacitor 9U and perform zero-voltage soft switching of the first switching element 1U without turning on the first IGBT 6U of the switch 8U. Figure 4 The voltage V across the first switching element 1U is also shown. 1U and the voltage V across the second switching element 2U 2U Note that in the case of a discharge operation to discharge the resonant capacitors 9U, 9V, 9W, the polarity of the currents i9U, i9V, i9W is positive. On the other hand, in the case of a charge operation to charge the resonant capacitors 9U, 9V, 9W, the polarity of the currents i9U, i9V, i9W is negative. Figure 4 In FIG, the current i9U is also shown.

[0083] like Figure 2As shown, the additional time Tav is the amount of time that the controller 50 sets to make the start t5 of the high-level period of the control signal SV6 earlier than the start t6 of the dead time Td so that the high-level period of the control signal SV6 is longer than the dead time Td. The length of the additional time Tav is determined by the value of the output current iV. In order to generate the LC resonance starting from the start t6 of the dead time Td, it is preferable that the value of the current iL0 coincides with the value of the output current iV at the start t6 of the dead time Td. This is because as long as iL0 < iV, all the current flows through the AC load RA1, and thus the resonance capacitor 9V cannot be charged. The end of the high-level period of the control signal SV6 can be simultaneous with or later than the end t7 of the dead time Td. In Figure 2 the example shown, the end of the high-level period of the control signal SV6 is set to be simultaneous with the end t7 of the dead time Td. The controller 50 sets the high-level period of the control signal SV6 to Tav + Td. The voltage V 1V across the first switching element 1V becomes zero at the end t7 of the dead time Td. In Figure 2 the example shown, the current iL0 starts flowing through the resonance inductor L0 at the start t5 of the high-level period of the control signal SV6 and becomes zero at the time t8 after the additional time Tav has elapsed from the end t7 of the dead time Td. At this time, starting from the start t6 of the dead time Td, the current iL0 satisfies iL0 ≥ iV, and thus the current iL0 in the shaded portion of the current waveform shown by the tenth waveform from the top of Figure 2 flows into the resonance capacitor 9V to generate the LC resonance. Starting from the end t7 of the dead time Td, the current iL0 will be regenerated to the power conversion circuit 11 via the third diode 13 directly connected to the resonance inductor L0.

[0084] As described above, in order to start generating the LC resonance at the start t6 of the dead time Td, the controller 50 determines the additional time Tav based on the output current iV such that iL0 = iV is satisfied at the start t6 of the dead time Td. More specifically, for example, the controller 50 uses the detection result of the output current iV by the current sensor or its signal processing value, or the estimated value of the current iV, and the detection result of the potential V15 at the regeneration capacitor 15, and determines the additional time Tav by the formula Tav = iV × (L / V15). In this case, as the detection result of the output current iV or its signal processing value, the detection value according to the carrier period plus the additional time Tav or the detection value at the timing closest to the carrier period can be used. In addition, in this case, as the estimated value of the output current iV, for example, the value of the output current iV estimated according to the carrier period plus the additional time Tav can be used.

[0085] Note that if the polarity of the output current iV is negative, the power converter 100 can charge the resonance capacitor 9V and perform zero-voltage soft switching of the first switching element 1 without turning on the first IGBT 6V of the switch 8V.

[0086] As Figure 3 shown, the additional time Taw is the amount of time that the controller 50 sets to make the start t9 of the high-level period of the control signal SW6 earlier than the start t10 of the dead time Td so that the high-level period of the control signal SW6 is longer than the dead time Td. The length of the additional time Taw is determined by the value of the output current iW. In order to generate LC resonance starting from the start t10 of the dead time Td, it is preferable that the value of the current iL0 coincides with the value of the output current iW at the start t10 of the dead time Td. This is because as long as iL0 < iW, all the current flows through the AC load RA1, and thus the resonance capacitor 9W cannot be charged. The end of the high-level period of the control signal SW6 can be simultaneous with or later than the end t11 of the dead time Td. In Figure 3 the example shown, the end of the high-level period of the control signal SW6 is set to be simultaneous with the end t11 of the dead time Td. The controller 50 sets the high-level period of the control signal SW6 to Taw + Td. The voltage V across the first switching element 1W 1W becomes zero at the end t11 of the dead time Td. In Figure 3 ]>the example shown, the current iL0 starts flowing through the resonance inductor L0 at the start t9 of the high-level period of the control signal SW6 and becomes zero at the time t12 after the additional time Taw has elapsed from the end t11 of the dead time Td. At this time, starting from the start t10 of the dead time Td, the current iL0 satisfies iL0 ≥ iW, and thus the current iL0 in the shaded portion of the current waveform shown by the fourth waveform starting from the top of Figure 3 flows into the resonance capacitor 9W to generate LC resonance. Starting from the end t11 of the dead time Td, the current iL0 will be regenerated to the power conversion circuit 11 via the third diode 13 directly connected to the resonance inductor L0.

[0087] The controller 50 determines the additional time Taw based on the output current iW. More specifically, for example, the controller 50 uses the current sensor's detection results of the output current iW, the pre-stored inductance L of the resonant inductor L0, and the potential V15 at the regenerative capacitor 15 to determine the additional time Taw using the equation Taw = iW × (L / V15). In this case, the output current iW detection result or its signal-processed value can be a detection value based on the carrier cycle to which the additional time Taw is added, or a detection value based on a timing closest to the carrier cycle. Furthermore, in this case, an estimated value of the output current iW can be used, for example, a value estimated based on the carrier cycle to which the additional time Taw is added.

[0088] Note that if the polarity of the output current iW is negative, the power converter 100 can charge the resonant capacitor 9W and perform zero-voltage soft switching of the first switching element 1 without turning the first IGBT 6W of the switch 8W conductive.

[0089] The power converter 100 causes the resonant capacitor 9 and the resonant inductor L0 associated with the switching elements that are the target of zero-voltage soft switching, which are among the plurality of first switching elements 1 and the plurality of second switching elements 2, to resonate. In this case, the voltage across the resonant capacitor 9 associated with the switching elements that are the target of zero-voltage soft switching varies according to the amplitude of the resonant voltage centered at the potential V15 at the fourth terminal 154 of the regenerative capacitor 15. At this time, by reducing the voltage across the switching elements from the voltage value Vd (reference voltage) of the DC power source E1 to be applied between the first DC terminal 31 and the second DC terminal 32, the voltage across the resonant capacitor 9 varies. Figure 2 and Figure 3) becomes zero, completing zero-voltage soft switching. Furthermore, the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 also varies according to the amount of charge stored in or removed from the regenerative capacitor 15 whenever the resonant capacitor 9 and the resonant inductor L0 resonate. Furthermore, the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 also varies according to the amount of charge stored in or removed from the regenerative capacitor 15 in each carrier cycle. In each carrier cycle, the amount of charge stored in or removed from the regenerative capacitor 15 is determined in association with the output currents iU, iV, iW of the U-phase, V-phase, and W-phase. In this case, the amount of charge stored or removed becomes the largest in association with the output current iU, iV, iW of the U-phase, V-phase, and W-phase having the largest absolute value. Thus, in the power converter 100, the amount of charge stored in or removed from the regenerative capacitor 15 varies in accordance with each carrier cycle. However, in the power converter 100, if the motor as the AC load RA1 is operating normally, the output currents iU, iV, iW in each phase have a sine wave, and their phases are 120 degrees different from each other, thereby achieving charge / discharge balance at the regeneration capacitor 15 and reducing the change in the potential V15 at the fourth terminal 154 of the regeneration capacitor 15.

[0090] The controller 50 performs the first control operation by setting a dead time Td between the high-level period of the PWM signals SU1, SV1, SW1 of the first switching elements 1U, 1V, 1W and the high-level period of the PWM signals SU2, SV2, SW2 of the second switching elements 2U, 2V, 2W for each of the plurality of switching circuits 10. Furthermore, the controller 50 performs the first control operation by causing the high-level period of the control signal of the corresponding switch 8 among the plurality of switches 8 corresponding to each of the plurality of switching circuits 10 to overlap with the dead time Td, and setting the start of the high-level period to a time point earlier than the start of the dead time Td by an additional time.

[0091] In power converter 100, if its controller 50 performs only the first control operation, any change in the load state (such as the locking of the motor serving as AC load RA1) will cause the output currents iU, iV, and iW in each phase to have different constant values. Then, in power converter 100, the difference between the potential V15 at the fourth terminal 154 of regenerative capacitor 15 relative to the ground potential and half the voltage value Vd of DC power supply E1 (Vd / 2) will widen. In this case, in power converter 100, when resonant capacitors 9U, 9V, 9W and resonant inductor L0 are caused to resonate to perform zero-voltage soft switching, the amplitude of the resonant voltage will decrease too much to achieve zero-voltage soft switching.

[0092] On the other hand, the controller 50 is configured to selectively perform independent control or simultaneous control when it is determined that two-phase resonant currents corresponding to two switching circuits 10 belonging to the plurality of switching circuits 10 flow simultaneously through the resonant inductor L0 during the first control operation.

[0093] As used herein, “independent control” includes control that, when it is determined that a two-phase resonant current flows through the resonant inductor L0, shifts the high-level period of at least one of the two control signals of two switches through which the resonant current flows among the plurality of switches to prevent the high-level periods of the two control signals from overlapping each other.

[0094] For the case where the high level periods of the two control signals SV7 and SW7 of two switches 8V and 8W among the three switches 8U, 8V and 8W are shifted within one cycle of the carrier signal so as not to overlap each other, Figure 6 In this example, for a situation where the output currents iU, iV, iW have different constant values ​​due to the locking of the motor as an exemplary AC load RA1, Figure 6 , the control signals SU6, SV7, SW7, the plurality of output currents iU, iV, iW, the current iL0 flowing through the resonant inductor L0, and the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 are shown. Figure 6 , the absolute value of output current iU > the absolute value of output current iW > the absolute value of output current iV, and the high-level period of control signal SU7 > the high-level period of control signal SW6 > the high-level period of control signal SV6. During the high-level period of control signal SU6 of switch 8U, corresponding to output current iU, which has the largest absolute value among the multiple output currents iU, iV, and iW, the amplitude of current iL0 reaches its maximum. Therefore, during the high-level period of control signal SU6 among the high-level periods of control signals SU6, SV7, and SW7, the change in potential V15 at regenerative capacitor 15 reaches its maximum.

[0095] As used herein, "simultaneous control" includes the following control: when it is determined that the two-phase resonant current flows through the resonant inductor L0, the high-level periods of the two control signals of the two switches through which the resonant current flows are enabled to overlap with each other. In addition, as used herein, the phrase "enabling the high-level periods of the two control signals to overlap with each other" is not limited to enabling the entire high-level period of the first control signal as one of the two control signals and the entire high-level period of the second control signal as the other control signal to overlap with each other. On the contrary, the phrase "enabling the high-level periods of the two control signals to overlap with each other" may also at least refer to enabling only the portion of the high-level period of the first control signal corresponding to the entire dead time Td between the two PWM signals used to determine the high-level period of the first control signal and only the portion of the high-level period of the second control signal corresponding to the entire dead time Td between the two PWM signals used to determine the high-level period of the second control signal to overlap with each other.

[0096] For the case where the high level periods of the two control signals SV7, SW7 of two switches 8V, 8W among the three switches 8U, 8V, 8W are shifted to overlap with each other within one cycle of the carrier signal, Figure 7 and Figure 8 In this example, for the case where the output currents iU, iV, iW have different constant values ​​due to the locking of the motor as an exemplary AC load RA1, the two control signals SV7 and SW7 are shown in FIG. Figure 7 and Figure 8 The control signals SU6, SV7, SW7, a plurality of output currents iU, iV, iW and the current iL0 flowing through the resonant inductor L0 are shown in FIG. Figure 7 Also shown in FIG. 1 is the potential V15 at the fourth terminal 154 of the regenerative capacitor 15. Figure 7 and Figure 8 In , the absolute value of the output current iU>the absolute value of the output current iW>the absolute value of the output current iV. Figure 7 , the high-level period of control signal SV7 = the high-level period of control signal SW7. During the period in which the high-level periods of the two control signals SV7 and SW7, which are enabled to overlap, overlap, the amplitude of current iL0 reaches its maximum. Therefore, during the period in which the high-level periods of two of the three control signals SU6, SV7, and SW7 overlap, the magnitude of the change in potential V15 at regenerative capacitor 15 reaches its maximum.

[0097] Thus, the controller 50 of the power converter 100 acquires the potential V15 detected at the fourth terminal 154 of the regenerative capacitor 15. For example, the controller 50 may acquire the detected potential at each cycle of the carrier signal. The controller 50 may pre-store, for example, the DC voltage value Vd applied between the first DC terminal 31 and the second DC terminal 32, or may acquire the detection result of the voltage value Vd. The controller 50 determines the details of the control operation based on the potential detected at the fourth terminal 154 of the regenerative capacitor 15, the value of Vd / 2, and the detection results of the output currents iU, iV, and iW.

[0098] The controller 50 selectively performs the second control operation or the third control operation based on the potential detected at the fourth terminal 154 of the regenerative capacitor 15 and the polarity of each of the plurality of output currents iU, iV, and iW supplied from the plurality of AC terminals 41. As used herein, "the potential detected at the fourth terminal 154 of the regenerative capacitor 15" refers to the potential V15 detected at the fourth terminal 154 of the regenerative capacitor 15 relative to the ground potential. The second control operation is an operation for simultaneously controlling two switches 8 belonging to the plurality of switches 8. The third control operation is an operation for independently controlling two switches 8 belonging to the plurality of switches 8.

[0099] The controller 50 performs a second control operation including shifting the high-level periods of each of the two control signals belonging to two switches 8 of the plurality of switches 8 so that the high-level periods can overlap with each other.

[0100] The controller 50 performs a third control operation including shifting the high level periods of the two control signals belonging to two switches 8 of the plurality of switches 8 to prohibit the high level periods from overlapping each other. In the third control operation, for example, Figure 6 As shown, the end of the high-level period of the first control signal, one of the two control signals, and the start of the high-level period of the second control signal, the other control signal, can be simultaneous. However, this is merely an example and should not be construed as limiting. Alternatively, after the high-level period of the first control signal has ended, the high-level period of the other control signal, the second control signal, can begin. The controller 50 performs the third control operation by preventing the high-level periods of the control signals of the plurality of switches 8 from overlapping.

[0101] The controller 50 performs the second control operation when the first condition or the second condition is satisfied, and performs the third control operation when the third condition or the fourth condition is satisfied.

[0102] The first condition is that the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is less than the first threshold Vth1 and the product of the multiple output currents iU, iV, and iW (i.e., iU×iV×iW) is positive. When calculating iU×iV×iW, iU, iV, and iW are instantaneous values ​​and can each be positive, zero, or negative. The second condition is that the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is greater than the second threshold Vth2 and the product of the multiple output currents iU, iV, and iW is negative. The third condition is that the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is less than the first threshold Vth1 and the product of the multiple output currents iU, iV, and iW is negative. The fourth condition is that the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is greater than the second threshold Vth2 and the product of the multiple output currents iU, iV, and iW is positive. The first threshold Vth1 is less than half the voltage Vd applied between the first DC terminal 31 and the second DC terminal 32 (i.e., Vd / 2). The second threshold value Vth2 is greater than Vd / 2. The first threshold value Vth1 may be, for example, 90% of Vd / 2. The second threshold value Vth2 may be, for example, 110% of Vd / 2. When the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is equal to or greater than the first threshold value Vth1 and equal to or less than the second threshold value Vth2, the controller 50 performs the above-described first control operation.

[0103] Table 1 below summarizes the relationship among the first condition, the second condition, the third condition, and the fourth condition, the second control operation (ie, two-phase simultaneous control), and the third control operation (ie, two-phase independent control).

[0104] [Table 1]

[0105]

[0106] Note that "iU×iV×iW" is the output current. Figure 1 The polarity of each of the plurality of output currents iU, iV, iW is defined as positive when the output currents iU, iV, iW flow in the direction indicated by the arrow. Figure 1 The product calculated when the polarity of each of the multiple output currents iU, iV, and iW is defined as negative when the output currents flow in the opposite direction of the direction indicated by the arrow. Alternatively, "iU×iV×iW" can be replaced by sgn(iU)×sgn(iV)×sgn(iW). In this case, if the value of sgn(iU)×sgn(iV)×sgn(iW) is positive "1", the product of the multiple output currents iU, iV, and iW can be judged to be positive. If the value of sgn(iU)×sgn(iV)×sgn(iW) is "-1", the product of the multiple output currents iU, iV, and iW can be judged to be negative.

[0107] As described above, the first control operation includes allowing the high-level periods of the control signals of the respective switches 8 among the plurality of switches 8 corresponding to the respective switching circuits 10 among the plurality of switching circuits 10 to overlap with the dead time Td, and setting the start of the high-level periods to be an additional time earlier than the start of the dead time Td. The high-level period of the control signal of the switch 8U is the period during which the potential level of the control signal SU6 of the first IGBT 6U is high, or the period during which the potential level of the control signal SU7 of the second IGBT 7U is high. The high-level period of the control signal of the switch 8V is the period during which the potential level of the control signal SV6 of the first IGBT 6V is high, or the period during which the potential level of the control signal SV7 of the second IGBT 7V is high. The high-level period of the control signal of the switch 8W is the period during which the potential level of the control signal SW6 of the first IGBT 6W is high, or the period during which the potential level of the control signal SW7 of the second IGBT 7W is high. The additional time for causing the start of the high-level period of the control signal of the switch 8U to be earlier than the start of the dead time Td is the aforementioned additional time Tau. The additional time for making the high level period of the control signal of the switch 8V start earlier than the start of the dead time Td is the additional time Tav. The additional time for making the high level period of the control signal of the switch 8W start earlier than the start of the dead time Td is the additional time Taw.

[0108] As described above, the controller 50 performs the second control operation when it is determined that the first condition or the second condition is satisfied, and performs the third control operation when it is determined that the third condition or the fourth condition is satisfied. Figures 9 to 12 An example of the second control operation and an example of the third control operation are described.

[0109] Figure 9 1 is a timing chart showing an exemplary case in which the controller 50 performs the second control operation (ie, two-phase simultaneous control) by determining that the first condition is satisfied. Figure 10 1 is a timing chart showing an exemplary case in which the controller 50 performs the second control operation (ie, two-phase simultaneous control) by determining that the second condition is satisfied. Figure 11 1 is a timing chart showing an exemplary case in which the controller 50 performs the third control operation (ie, two-phase independent control) when it is determined that the third condition is satisfied. Figure 12 1 is a timing chart showing an exemplary case in which the controller 50 performs the third control operation (ie, two-phase independent control) by determining that the fourth condition is satisfied.

[0110] exist Figures 9 to 12In FIG, six PWM signals SU1, SU2, SV1, SV2, SW1, SW2 and three control signals among the six control signals SU6, SU7, SV6, SV7, SW6, SW7 are shown. Figures 9 to 12 Also shown are the current iL0, the three output currents iU, iV, iW, and the voltages V across the three second switching elements 2U, 2V, and 2W. 2U 、V 2V 、V 2W And the potential V15 at the fourth terminal 154 of the regenerative capacitor 15. Figures 9 to 12 , for each of the PWM signals SU1, SU2, SV1, SV2, SW1, SW2 and the three control signals SU6, SV7, SV7, if their high-level periods have been changed, their states before the change are indicated by double-dashed lines. If the controller 50 has shifted the high-level periods of the control signals (SU6, SU7, SV6, SV7, SW6, SW7), the controller 50 also shifts the high-level periods of the PWM signals (SU1, SU2, SV1, SV2, SW1, SW2) associated with the control signals. Specifically, the PWM signal associated with control signal SU6 is the PWM signals SU1 and SU2. The PWM signal associated with control signal SU7 is the PWM signals SU1 and SU2. The PWM signal associated with control signal SV6 is the PWM signals SV1 and SV2. The PWM signal associated with control signal SV7 is the PWM signals SV1 and SV2. The PWM signal associated with control signal SW6 is the PWM signals SW1 and SW2. The PWM signal associated with control signal SW7 is the PWM signals SW1 and SW2. In addition, Figures 9 to 12 In FIG, if the high level period of any of the three control signals SU6, SV7, and SW7 has changed, the current iL0 flowing through the resonant inductor L0 before the high level period is changed is indicated by a two-dot chain line. Figures 9 to 12 , the timing of detecting the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 is indicated by an arrow. The potential V15 at the fourth terminal 154 of the regenerative capacitor 15 is detected for each carrier cycle. This enables the controller 50 to acquire the potential detected at the fourth terminal 154 of the regenerative capacitor 15 in each carrier cycle. For example, the timing at which the controller 50 acquires the potential detected at the fourth terminal 154 of the regenerative capacitor 15 may be simultaneous with the timing at which the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 is detected, but does not necessarily have to be simultaneous with this timing.

[0111] exist Figure 9In the example shown, if the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is less than the first threshold value Vth1, the product of the three output currents iU, iV, and iW is positive. Therefore, in this case, the controller 50 performs a second control operation to allow the high-level periods of the control signals SV7 and SW7 to overlap. As a result, in the power converter 100, the amplitude of the current iL0 flowing through the resonant inductor L0 increases, and the amount of charge stored in the regenerative capacitor 15 increases, thereby enabling the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 to be equal to or greater than the first threshold value Vth1. This enables the power converter 100 to perform soft switching of the three first switching elements 1 and the three second switching elements 2.

[0112] exist Figure 10 In the example shown, if the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is greater than the second threshold value Vth2, the product of the three output currents iU, iV, and iW becomes negative. Therefore, in this case, the controller 50 performs a second control operation to allow the high-level periods of the control signals SV6 and SW6 to overlap. As a result, in the power converter 100, the amplitude of the current iL0 flowing through the resonant inductor L0 increases, and the amount of charge extracted into the regenerative capacitor 15 increases, thereby enabling the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 to be equal to or less than the second threshold value Vth2. This enables the power converter 100 to perform soft switching of the three first switching elements 1 and the three second switching elements 2.

[0113] exist Figure 11 In the example shown, if the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is less than the first threshold value Vth1, the product of the three output currents iU, iV, and iW becomes negative. Therefore, in this case, the controller 50 performs a third control operation to prevent the high-level periods of the control signals SV7 and SW7 from overlapping. As a result, in the power converter 100, the amount of charge stored in the regenerative capacitor 15 increases, thereby enabling the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 to be equal to or greater than the first threshold value Vth1. This enables the power converter 100 to perform soft switching of the three first switching elements 1 and the three second switching elements 2.

[0114] exist Figure 12In the example shown, if the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is greater than the second threshold value Vth2, the product of the three output currents iU, iV, and iW is positive. Therefore, in this case, the controller 50 performs a third control operation to prevent the high-level periods of the control signals SV7 and SW7 from overlapping. As a result, in the power converter 100, if the polarity of the current iL0 flowing through the resonant inductor L0 is negative, the amplitude of the current iL0 decreases, thereby enabling the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 to be equal to or less than the second threshold value Vth2. This enables the power converter 100 to perform soft switching of the three first switching elements 1 and the three second switching elements 2.

[0115] Note that the second control operation and the third control operation performed by the controller 50 may include control for not shifting the high-level periods of the two control signals belonging to two switches 8 of the plurality of switches 8 .

[0116] (4) Summary

[0117] In the power converter 100 according to the first embodiment, the controller 50 performs a first control operation that includes enabling the high-level period of the control signal for each of the plurality of switches 8 corresponding to each of the plurality of switching circuits 10 to overlap with the dead time Td, and setting the start of the high-level period to a time point that is an additional time earlier than the start of the dead time Td. This enables the power converter 100 to perform zero-voltage soft switching for each of the plurality of first switching elements 1 and the plurality of second switching elements 2. Furthermore, the controller 50 of the power converter 100 selectively performs either a second control operation (simultaneously controlling two switches 8 belonging to the plurality of switches 8) or a third control operation (independently controlling two switches 8 belonging to the plurality of switches 8) based on the potential detected at the fourth terminal 154 of the regenerative capacitor 15 and the polarity of the plurality of output currents iU, iV, iW supplied from the plurality of AC terminals 41. This enables the power converter 100 to reduce variations in the potential V15 at the regenerative capacitor 15. In addition, compared to the case where no operation is performed in response to the change in the potential V15 at the regenerative capacitor 15 , this increases the ratio of soft switching, thereby ultimately contributing to improved power conversion efficiency and reduced noise.

[0118] Furthermore, in the power converter 100 according to the first embodiment, the controller 50 performs the second control operation when the first condition or the second condition is satisfied, and performs the third control operation when the third condition or the fourth condition is satisfied. This enables the power converter 100 according to the first embodiment to reduce variations in the potential V15 at the regenerative capacitor 15 regardless of the polarities of the plurality of output currents iU, iV, iW supplied from the plurality of AC terminals 41.

[0119] Furthermore, in the power converter 100 according to the first embodiment, the controller 50 performs the second control operation by shifting the high-level periods of the two control signals belonging to two switches 8 of the plurality of switches 8 so that the high-level periods of the two control signals can overlap with each other. This enables the power converter 100 to increase the absolute value of the current iL0 flowing through the resonant inductor L0, thereby increasing the adjustment magnitude (i.e., change magnitude) of the potential V15 at the regenerative capacitor 15.

[0120] Furthermore, in the power converter 100 according to the first embodiment, the controller 50 performs a third control operation by shifting the high-level periods of the two control signals belonging to two switches 8 of the plurality of switches 8 to prevent the high-level periods of the two control signals from overlapping with each other. This enables the power converter 100 to reduce the absolute value of the current iL0 flowing through the resonant inductor L0.

[0121] (First Modification)

[0122] Will refer to Figure 13 A power converter 100A according to a first modification of the first embodiment will be described. In the following description, the power converter 100A according to the first modification of the first embodiment has the same features as the power converter 100 according to the first embodiment described above (see FIG. 1 ). Figure 1 ) will be designated by the same reference numerals as those of the corresponding parts, and description thereof will be omitted herein.

[0123] In power converter 100A according to the first modification, in each of the plurality of switches 8, first IGBT 6 and second IGBT 7 are connected in anti-series. In power converter 100A according to the first modification, in each of the plurality of switches 8, the collector terminal of first IGBT 6 and the collector terminal of second IGBT 7 are connected to each other, the emitter terminal of first IGBT 6 is connected to connection node 3 of corresponding switching circuit 10 in the plurality of switching circuits 10, and the emitter terminal of second IGBT 7 is connected to common connection node 25. Furthermore, each of the plurality of switches 8 further includes a diode 61 connected in anti-parallel to first IGBT 6 and a diode 71 connected in anti-parallel to second IGBT 7.

[0124] In the power converter 100A according to the first modification, each of the first IGBT 6 and the second IGBT 7 may be replaced by a MOSFET or a bipolar transistor. In this case, Figure 13 The diode 61 and the diode 71 shown can be replaced by, for example, a parasitic diode of a replacement element or an element built into a single chip of the replacement element. Furthermore, in the power converter 100A according to the first modification, the diode 61 and the diode 71 do not necessarily need to be provided as external elements to the first IGBT 6 and the second IGBT 7, respectively, but can also be elements built into a single chip.

[0125] (Second Modification)

[0126] Will refer to Figure 14 A power converter 100A according to a second modified example of the first embodiment will be described. In the following description, the power converter 100A according to the second modified example of the first embodiment has the same features as the power converter 100 according to the first embodiment described above (see FIG. 1 ). Figure 1 ) will be designated by the same reference numerals as those of the corresponding parts, and description thereof will be omitted herein.

[0127] In the power converter 100A according to the second modification, in each switch 8, the first MOSFET 6A and the second MOSFET 7A are connected in anti-series. In the power converter 100A according to the second modification, in each of the plurality of switches 8, the drain terminal of the first MOSFET 6A and the drain terminal of the second MOSFET 7A are connected to each other. Furthermore, each of the plurality of switches 8 includes a diode 61 connected in anti-parallel to the first MOSFET 6A and a diode 71 connected in anti-parallel to the second MOSFET 7A. In each of the plurality of switches 8, the source terminal of the second MOSFET 7A is connected to the common connection node 25. In each of the plurality of switches 8, the source terminal of the first MOSFET 6A is connected to the connection node 3 of the switching circuit 10 corresponding to the switch 8 including the first MOSFET 6A. Control signals SU6 and SU7 are applied from the controller 50 to the first MOSFET 6A and the second MOSFET 7A of the switch 8U, respectively. Control signals SV6 and SV7 are applied from the controller 50 to the first MOSFET 6A and the second MOSFET 7A of the switch 8V, respectively. Control signals SW6, SW7 are applied from the controller 50 to the first MOSFET 6A and the second MOSFET 7A of the switch 8W, respectively.

[0128] (Third Modification)

[0129] Will refer to Figure 15 A power converter 100A according to a third modified example of the first embodiment will be described. In the following description, the power converter 100A according to the third modified example of the first embodiment has the same features as the power converter 100 according to the first embodiment described above (see FIG. 1 ). Figure 1 ) will be designated by the same reference numerals as those of the corresponding parts, and description thereof will be omitted herein.

[0130] In the power converter 100A according to the third modification, in each of the plurality of switches 8, a diode 63 is connected in series to the first MOSFET 6A, and a diode 73 is connected in series to the second MOSFET 7A. In the power converter 100A according to the third modification, the series circuit of the first MOSFET 6A and the diode 63 and the series circuit of the second MOSFET 7A and the diode 73 are connected in antiparallel to each other.

[0131] (Fourth Modification)

[0132] Will refer to Figure 16 A power converter 100A according to a fourth modified example of the first embodiment will be described. In the following description, the power converter 100A according to the fourth modified example of the first embodiment has the same features as the power converter 100 according to the first embodiment described above (see FIG. 1 ). Figure 1 ) will be designated by the same reference numerals as those of the corresponding parts, and description thereof will be omitted herein.

[0133] In a power converter 100A according to the fourth modification, each of the plurality of switches 8 includes: a MOSFET 80; a diode 83 connected in antiparallel to the MOSFET 80; a series circuit of two diodes 84 and 85 connected in antiparallel to the MOSFET 80; and a series circuit of two diodes 86 and 87 connected in antiparallel to the MOSFET 80. In each of the plurality of switches 8, the connection node between the diodes 84 and 85 (i.e., the first terminal 81 of the switch 8) is connected to the connection node 3 of the corresponding switching circuit 10 in the plurality of switching circuits 10, and the connection node between the diodes 86 and 87 (i.e., the second terminal 82 of the switch 8) is connected to the common connection node 25. In each of the plurality of switches 8, when the MOSFET 80 is on, the switch 8 is on. On the other hand, when the MOSFET 80 is off, the switch 8 is off.

[0134] The MOSFETs 80 of the plurality of switches 8 are controlled by the controller 50. The controller 50 outputs a control signal SU8 for controlling the on / off state of the MOSFET 80 of the switch 8U, a control signal SV8 for controlling the on / off state of the MOSFET 80 of the switch 8V, and a control signal SW8 for controlling the on / off state of the MOSFET 80 of the switch 8W.

[0135] In switch 8, when MOSFET 80 is turned on, a resonant current generated by the resonant circuit including resonant inductor L0 and resonant capacitor 9 flows. In power converter 100A, when one switch 8 among the plurality of switches 8 is turned on, a charging current including the resonant current flows along a path that passes through regenerative capacitor 15, resonant inductor L0, diode 86, MOSFET 80, diode 85, and resonant capacitor 9 in this order. Furthermore, in power converter 100A, when one switch 8 among the plurality of switches 8 is turned on, a discharging current including the resonant current flows along a path that passes through resonant capacitor 9, diode 84, MOSFET 80, diode 87, resonant inductor L0, and regenerative capacitor 15 in this order.

[0136] In the power converter 100A according to the fourth modification, each of the plurality of MOSFETs 80 can be replaced by an IGBT. Furthermore, in the power converter 100A according to the fourth modification, each of the plurality of switches 8 can include, for example, a bipolar transistor or a GaN-based gate injection transistor (GIT) instead of the MOSFET 80.

[0137] (Fifth Modification)

[0138] Will refer to Figure 17 A power converter 100A according to a fifth modification of the first embodiment will be described. In the following description, the power converter 100A according to the fifth modification of the first embodiment has the same features as the power converter 100 according to the first embodiment described above (see FIG. 1 ). Figure 1 ) will be designated by the same reference numerals as those of the corresponding parts, and description thereof will be omitted herein.

[0139] In the power converter 100A according to the fifth modification, each of the multiple switches 8 is a dual-gate GaN-based GIT including a first source terminal, a first gate terminal, a second gate terminal, and a second source terminal. In the power converter 100A according to the fifth modification, a control signal SU6 is applied between the first gate terminal and the first source terminal of the dual-gate GaN-based GIT serving as switch 8U, and a control signal SU7 is applied between the second gate terminal and the second source terminal of the dual-gate GaN-based GIT. Furthermore, a control signal SV6 is applied between the first gate terminal and the first source terminal of the dual-gate GaN-based GIT serving as switch 8V, and a control signal SV7 is applied between the second gate terminal and the second source terminal of the dual-gate GaN-based GIT. Furthermore, a control signal SW6 is applied between the first gate terminal and the first source terminal of the dual-gate GaN-based GIT serving as switch 8W, and a control signal SW7 is applied between the second gate terminal and the second source terminal of the dual-gate GaN-based GIT.

[0140] (Second embodiment)

[0141] Will refer to Figure 18 The power converter 100B according to the second embodiment is described. The power converter 100B according to the second embodiment further includes a capacitor 16 connected between the second terminal of the resonant inductor L0 and the first DC terminal 31, which is different from the power converter 100 according to the first embodiment (refer to FIG. Figure 1 In the following description, any constituent elements in the power converter 100B according to the second embodiment that have the same functions as those of the corresponding portions of the power converter 100 according to the first embodiment described above will be designated by the same reference numerals as those of the corresponding portions, and description thereof will be omitted herein.

[0142] Power converter 100B does not include capacitor C10 as in power converter 100 according to the first embodiment. Capacitor 16 is connected in series to regenerative capacitor 15. Thus, in this power converter 100B, the series circuit of capacitor 16 and regenerative capacitor 15 is connected between first DC terminal 31 and second DC terminal 32. The capacitance of capacitor 16 is the same as that of regenerative capacitor 15. As used herein, the expression "the capacitance of capacitor 16 is the same as that of regenerative capacitor 15" refers not only to a case where the capacitance of capacitor 16 is completely equal to that of regenerative capacitor 15, but also to a case where the capacitance of capacitor 16 is equal to or greater than 95% and equal to or less than 105% of the capacitance of regenerative capacitor 15.

[0143] In the power converter 100B according to the second embodiment, the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 has a value calculated by dividing the voltage value Vd of the DC power supply E1 by 2, which is the number of capacitors (i.e., the capacitor 16 and the regenerative capacitor 15). Therefore, the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 is Vd / 2. In the power converter 100B according to the second embodiment, the controller 50 can pre-store the value of the potential V15 at the fourth terminal 154 of the regenerative capacitor 15.

[0144] Like the controller 50 of the power converter 100 according to the first embodiment, the controller 50 of the power converter 100B according to the second embodiment performs the first control operation, the second control operation, and the third control operation. Thus, like the power converter 100A according to the second embodiment, the power converter 100B according to the second embodiment can contribute to improving power conversion efficiency.

[0145] (Third embodiment)

[0146] Will refer to Figure 19 The power converter 100C according to the third embodiment is described. In the power converter 100C according to the third embodiment, the regenerative capacitor 15 is connected between the second terminal of the resonant inductor L0 and the first DC terminal 31, which is different from the power converter 100 according to the first embodiment (refer to FIG. Figure 1 In the following description, any constituent elements in the power converter 100C according to this third embodiment that have the same functions as those of the corresponding portions of the power converter 100 according to the first embodiment described above will be designated by the same reference numerals as those of the corresponding portions, and description thereof will be omitted herein.

[0147] Like the controller 50 of the power converter 100 according to the first embodiment, the controller 50 of the power converter 100C according to the third embodiment performs the first control operation, the second control operation, and the third control operation. Thus, like the power converter 100 according to the first embodiment, the power converter 100C according to the third embodiment can contribute to improving power conversion efficiency.

[0148] (Fourth embodiment)

[0149] Will refer to Figure 20 A power converter 100D according to a fourth embodiment will be described. In the following description, the power converter 100D according to the fourth embodiment has the same features as the power converter 100 according to the first embodiment (see FIG. 1 ). Figure 1 ) will be designated by the same reference numerals as those of the corresponding parts, and description thereof will be omitted herein.

[0150] In power converter 100D, fourth terminal 154 of regenerative capacitor 15 is connected to a plurality of resonant circuits 20. Each of the plurality of resonant circuits 20 includes a resonant capacitor 9 and a resonant inductor L4. Resonant capacitor 9 is connected between first terminal 81 and second DC terminal 32 of a corresponding switch 8 among the plurality of switches 8. Resonant inductor L4 is connected between second terminal 82 of a corresponding switch 8 among the plurality of switches 8 and fourth terminal 154 of regenerative capacitor 15. In the following description, resonant inductor L4 connected to switch 8U will be referred to as "resonant inductor L11," resonant inductor L4 connected to switch 8V will be referred to as "resonant inductor L21," and resonant inductor L4 connected to switch 8W will be referred to as "resonant inductor L31." The inductances of resonant inductors L11, L21, and L31 are the same.

[0151] Each of the multiple resonant circuits 20 includes a second resonant inductor L5 provided separately from the first resonant inductor L4, which serves as the resonant inductor L4, and a selection switch 18 connected to the second resonant inductor L5. In each of the multiple resonant circuits 20, a series circuit of the second resonant inductor L5 and the selection switch 18 is connected in parallel to the first resonant inductor L4. Each of the multiple resonant circuits 20 has a resonant frequency that changes as the selection switch 18 turns on and off. In the following description, the second resonant inductor L5 and the selection switch 18, which form a series circuit connected in parallel with the first resonant inductor L11, will be referred to as "second resonant inductor L12" and "selection switch 18U," respectively. Furthermore, the second resonant inductor L5 and the selection switch 18, which form a series circuit connected in parallel with the first resonant inductor L21, will be referred to as "second resonant inductor L22" and "selection switch 18V," respectively. Furthermore, the second resonant inductor L5 and the selection switch 18 forming a series circuit connected in parallel with the first resonant inductor L31 will hereinafter be referred to as “second resonant inductor L32 ” and “selection switch 18W”, respectively.

[0152] The inductances of the second resonant inductors L12 , L22 , and L32 are the same as each other.

[0153] Each of the selection switches 18U, 18V, and 18W may be, for example, an IGBT. The selection switches 18U, 18V, and 18W are controlled by control signals SU3, SV3, and SW3, respectively, supplied from the controller 50. Note that each of the selection switches 18U, 18V, and 18W need not necessarily be an IGBT, but may also be, for example, a MOSFET, a GIT, or a bipolar transistor.

[0154] For each of the plurality of switching circuits 10 , the controller 50 sets a dead time Td between the high level period of the PWM signal SU1 , SV1 , SW1 of the first switching element 1 and the high level period of the PWM signal SU2 , SV2 , SW2 of the second switching element 2 .

[0155] The controller 50 performs a first control operation. The first control operation includes: enabling a high-level period of a control signal for a corresponding switch 8 among the plurality of switches 8 corresponding to each of the plurality of switching circuits 10 to overlap with the dead time Td; and setting the start of the high-level period to a time point that is an additional time earlier than the start of the dead time Td. The controller 50 changes the resonant frequency of at least one resonant circuit 20 among the plurality of resonant circuits 20 based on the potential V15 at the fourth terminal 154 of the regenerative capacitor 15.

[0156] Figure 21 and Figure 22 The figure shows the carrier signal, three control signals SU6, SU7, SV6, SV7, SW6, SW7, currents iL1, iL2, iL3, and voltages V across the three second switching elements 2U, 2V, and 2W. 2U 、V 2V 、V 2W And the potential V15 at the fourth terminal 154 of the regenerative capacitor 15. Figure 21 and Figure 22 , the timing of detecting the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 is indicated by an arrow. The potential V15 at the fourth terminal 154 of the regenerative capacitor 15 is detected for each carrier cycle. This enables the controller 50 to acquire the potential detected at the fourth terminal 154 of the regenerative capacitor 15 in each carrier cycle. For example, the timing at which the controller 50 acquires the potential detected at the fourth terminal 154 of the regenerative capacitor 15 may be simultaneous with the timing at which the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 is detected, but does not necessarily have to be simultaneous with this timing.

[0157] If the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is less than the first threshold value Vth1, the controller 50 may turn on, for example, one selection switch 18U among the three selection switches 18U, 18V, and 18W, thereby shortening the high-level period of the control signal SU6 of the first IGBT 6U of the switch 8U (at Figure 21, the control signal SU6 that has not been shortened is indicated by a two-dot chain line. In this way, the power converter 100D can shorten the resonance period of the resonance circuit 20 including the first resonance inductor L11 and the resonance capacitor 9U among the three resonance circuits 20, thereby enabling the amount of charge removed from the regenerative capacitor 15 to be reduced and the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 to be greater than the first threshold value Vth1.

[0158] On the other hand, if the potential detected at the fourth terminal 154 of the regenerative capacitor 15 is greater than the second threshold value Vth2, the controller 50 may turn on, for example, one selection switch 18U among the three selection switches 18U, 18V, 18W, thereby shortening the high-level period of the control signal SU7 of the second IGBT 7U of the switch 8U (at Figure 22 , the control signal SU7 that has not been shortened is indicated by a two-dot chain line. In this way, the power converter 100 can shorten the resonance period of the resonance circuit 20 including the first resonance inductor L11 and the resonance capacitor 9U among the three resonance circuits 20, thereby enabling the amount of charge stored in the regenerative capacitor 15 to be reduced and the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 to be greater than the first threshold value Vth1.

[0159] In the power converter 100D according to the fourth embodiment, the controller 50 changes the resonance period of at least one resonant circuit 20 belonging to the plurality of resonant circuits 20 according to the potential V15 at the fourth terminal 154 of the regenerative capacitor 15. This enables the power converter 100D according to the fourth embodiment to reduce the variation in the potential V15 at the fourth terminal 154 of the regenerative capacitor 15 even in the case of a variation in the load state caused by, for example, locking of the motor serving as the AC load RA1, thereby contributing to improvement in power conversion efficiency.

[0160] (Fifth embodiment)

[0161] Will refer to Figure 23 A power converter 100E according to a fifth embodiment will be described. In the following description, any constituent elements in the power converter 100E according to this fifth embodiment that have the same functions as their counterparts in the power converter 100D according to the fourth embodiment described above will be designated by the same reference numerals as those of the corresponding portions, and description thereof will be omitted herein.

[0162] In power converter 100E, each of the multiple (e.g., three) resonant circuits 20 includes a resonant inductor L4. In the following description, resonant inductor L4 connected to switch 8U will be referred to as "resonant inductor L1," resonant inductor L4 connected to switch 8V will be referred to as "resonant inductor L2," and resonant inductor L4 connected to switch 8W will be referred to as "resonant inductor L3." Resonant inductors L1, L2, and L3 each have the same inductance.

[0163] In addition, in the power converter 100E, each of the plurality of resonant circuits 20 includes a second resonant capacitor 91 provided separately from the first resonant capacitor 9 serving as the resonant capacitor 9, and a selection switch 92 connected to the second resonant capacitor 91. In each of the plurality of resonant circuits 20, a series circuit of the second resonant capacitor 91 and the selection switch 92 is connected in parallel to the first resonant capacitor 9. Each of the plurality of resonant circuits 20 has a resonant frequency that changes as the selection switch 92 turns on and off.

[0164] In the following description, the first resonant capacitor 9 connected to the switch 8U will be referred to as "first resonant capacitor 9U," the first resonant capacitor 9 connected to the switch 8V will be referred to as "first resonant capacitor 9V," and the first resonant capacitor 9 connected to the switch 8W will be referred to as "first resonant capacitor 9W." Furthermore, in the following description, the second resonant capacitor 91 connected to the switch 8U will be referred to as "second resonant capacitor 91U," the second resonant capacitor 91 connected to the switch 8V will be referred to as "second resonant capacitor 91V," and the second resonant capacitor 91 connected to the switch 8W will be referred to as "second resonant capacitor 91W." Furthermore, the selection switch 92 connected in series to the second resonant capacitor 91U will be referred to as "selection switch 92U," the selection switch 92 connected in series to the second resonant capacitor 91V will be referred to as "selection switch 92V," and the selection switch 92 connected in series to the second resonant capacitor 91W will be referred to as "selection switch 92W."

[0165] The second resonant capacitors 91U, 91V, and 91W have the same capacitance as each other.

[0166] Each of the selection switches 92U, 92V, and 92W may be, for example, an IGBT. The selection switches 92U, 92V, and 92W are controlled based on control signals SU9, SV9, and SW9 supplied from the controller 50. Note that each of the selection switches 92U, 92V, and 92W does not necessarily have to be, for example, an IGBT, but may also be, for example, a MOSFET, a GIT, or a bipolar transistor.

[0167] For each of the plurality of switching circuits 10 , the controller 50 sets a dead time Td between the high level period of the PWM signal SU1 , SV1 , SW1 of the first switching element 1 and the high level period of the PWM signal SU2 , SV2 , SW2 of the second switching element 2 .

[0168] The controller 50 performs a first control operation. The first control operation includes: enabling the high-level period of the control signal of each of the plurality of switches 8 corresponding to each of the plurality of switching circuits 10 to overlap with the dead time Td; and setting the start of the high-level period to a time point that is an additional time earlier than the start of the dead time Td. The controller 50 changes the resonance period by turning on and off the selection switch 92 of at least one of the plurality of resonant circuits 20, based on the potential V15 at the fourth terminal 154 of the regenerative capacitor 15. This allows the power converter 100E according to the fifth embodiment to reduce changes in the potential V15 at the fourth terminal 154 of the regenerative capacitor 15, even when the load state changes, such as when the motor serving as the AC load RA1 is locked, thereby contributing to improved power conversion efficiency.

[0169] (Other Modifications)

[0170] Note that the first to fifth embodiments and their modifications described above are merely exemplary embodiments and their modifications among the various embodiments of the present disclosure and should not be construed as limiting. Rather, the first to fifth exemplary embodiments and their modifications can be easily modified in various ways according to design choices or any other factors without departing from the scope of the present disclosure.

[0171] For example, each of the plurality of first switching elements 1 and the plurality of second switching elements 2 does not necessarily have to be an IGBT, but may also be a MOSFET. In this case, each of the plurality of first diodes 4 may also be replaced by, for example, a parasitic diode of the MOSFET used as its corresponding first switching element 1. In addition, each of the plurality of second diodes 5 may also be replaced by, for example, a parasitic diode of the MOSFET used as its corresponding second switching element 2. The MOSFET may be, for example, a Si-based MOSFET or a SiC-based MOSFET. Each of the plurality of first switching elements 1 and the plurality of second switching elements 2 may also be, for example, a bipolar transistor or a GaN-based GIT.

[0172] Optionally, in the power converters 100, 100A, 100B, 100C, 100D, 100E, if each of the multiple resonant capacitors 9 has a relatively small capacitance, the parasitic capacitors across the multiple second switching elements 2 can also be used as multiple resonant capacitors 9, instead of setting the multiple resonant capacitors 9 as separate elements.

[0173] For example, each of the plurality of switches 8 according to the second to fifth embodiments other than the first embodiment may have Figures 13 to 17 Any of the exemplary alternative configurations shown.

[0174] Furthermore, power converters 100 , 100A, 100B, 100C, 100D, and 100E are not necessarily configured to output three-phase AC power, and may be configured to output multi-phase AC power having more than three phases.

[0175] (all aspects)

[0176] The foregoing description provides specific implementations of the following aspects of the present disclosure.

[0177] According to the first aspect, a power converter (100; 100A; 100B; 100C) includes a first DC terminal (31) and a second DC terminal (32), a power conversion circuit (11), a plurality of AC terminals (41), a plurality of switches (8), a plurality of resonant capacitors (9), a resonant inductor (L0), a regenerative capacitor (15), and a controller (50). The power conversion circuit (11) includes a plurality of first switching elements (1) and a plurality of second switching elements (2). In the power conversion circuit (11), a plurality of switching circuits (10) are connected in parallel to each other, and in each switching circuit of the plurality of switching circuits (10), one first switching element (1) of the plurality of first switching elements (1) and a corresponding second switching element (2) of the plurality of second switching elements (2) are connected in series one to one. In the power conversion circuit (11), the plurality of first switching elements (1) are connected to the first DC terminal (31), and the plurality of second switching elements (2) are connected to the second DC terminal (32). The plurality of AC terminals (41) are provided one to one for the plurality of switching circuits (10). Each of the plurality of AC terminals (41) is connected to a connection node (3) between a first switching element (1) and a second switching element (2) of a corresponding switching circuit (10) in a plurality of switching circuits (10). A plurality of switches (8) are provided one-to-one for each of the plurality of switching circuits (10). A first terminal (81) of each of the plurality of switches (8) is connected to a connection node (3) between a first switching element (1) and a second switching element (2) of a corresponding switching circuit (10) in a plurality of switching circuits (10). A second terminal (82) of each of the plurality of switches (8) is commonly connected to a common connection node (25). A plurality of resonant capacitors (9) are provided one-to-one for each of the plurality of switches (8). Each of the plurality of resonant capacitors (9) is connected between a first terminal (81) and a second DC terminal (32) of a corresponding switch in the plurality of switches (8). A resonant inductor (L0) has a first terminal and a second terminal. In the resonant inductor (L0), the first terminal of the resonant inductor (L0) is connected to the common connection node (25). The regenerative capacitor (15) has a third terminal (153) and a fourth terminal (154). In the regenerative capacitor (15), the third terminal (153) of the regenerative capacitor (15) is connected to the first DC terminal (31) or the second DC terminal (32). The controller (50) applies a PWM signal (SU1, SV1, SW1, SU2, SV2, SW2) having a potential alternating between a high level and a low level to each of the plurality of first switching elements (1) and each of the plurality of second switching elements (2). The controller (50) performs a first control operation.The first control operation includes setting a dead time (Td) between a high level period of a PWM signal (SU1, SV1, SW1) of a first switching element (1) and a high level period of a PWM signal (SU2, SV2, SW2) of a second switching element (2) for each of the plurality of switching circuits (10). The controller (50) performs the first control operation, which includes enabling a high level period of a control signal of a corresponding switch (8) among the plurality of switches (8) corresponding to each of the plurality of switching circuits (10) to overlap with the dead time (Td), and setting the start of the high level period at a time point earlier than the start of the dead time (Td) by an additional time. The controller (50) selectively performs the second control operation or the third control operation according to a potential detected at a fourth terminal (154) of the regenerative capacitor (15) and the polarity of a plurality of output currents (iU, iV, iW) supplied from the plurality of AC terminals (41). The second control operation includes: enabling high level periods of control signals of two switches (8) belonging to the plurality of switches (8) to overlap with each other. The third control operation includes: prohibiting high level periods of control signals of the plurality of switches (8) from overlapping with each other.

[0178] This aspect helps to improve power conversion efficiency.

[0179] In a power converter (100; 100A; 100B; 100C) according to the second aspect that can be implemented in combination with the first aspect, the controller (50) performs a second control operation when a first condition or a second condition is satisfied, and performs a third control operation when a third condition or a fourth condition is satisfied. The first condition is that the potential detected at the fourth terminal (154) of the regenerative capacitor (15) is less than a first threshold value (Vth1) and the product of a plurality of output currents (iU, iV, iW) is positive, the first threshold value (Vth1) being less than half the voltage value (Vd) applied between the first DC terminal (31) and the second DC terminal (32). The second condition is that the potential detected at the fourth terminal (154) of the regenerative capacitor (15) is greater than a second threshold value (Vth2) and the product of a plurality of output currents (iU, iV, iW) is negative, the second threshold value (Vth2) being greater than half the voltage value (Vd) applied between the first DC terminal (31) and the second DC terminal (32). The third condition is that the potential detected at the fourth terminal (154) of the regenerative capacitor (15) is less than a first threshold value (Vth1) and the product of the plurality of output currents (iU, iV, iW) is negative, the first threshold value (Vth1) being less than half the voltage value (Vd) applied between the first DC terminal (31) and the second DC terminal (32). The fourth condition is that the potential detected at the fourth terminal (154) of the regenerative capacitor (15) is greater than a second threshold value (Vth2) and the product of the plurality of output currents (iU, iV, iW) is positive, the second threshold value (Vth2) being greater than half the voltage value (Vd) applied between the first DC terminal (31) and the second DC terminal (32).

[0180] This aspect can reduce the variation in the potential (V15) at the regenerative capacitor (15) regardless of the polarities of the plurality of output currents (iU, iV, iW) supplied from the plurality of AC terminals (41).

[0181] In a power converter (100; 100A; 100B; 100C) according to a third aspect that can be implemented in combination with the first aspect or the second aspect, a controller (50) performs a second control operation by shifting the high-level periods of two control signals belonging to two switches (8) of a plurality of switches (8) so that the high-level periods can overlap with each other.

[0182] This aspect enables the absolute value of the current (iL0) flowing through the resonant inductor (L0) to be increased, thereby enabling the adjustment size (ie, the size of the change) of the potential (V15) at the regenerative capacitor (15) to be increased.

[0183] In a power converter (100; 100A; 100B; 100C) according to a fourth aspect that can be implemented in combination with the first aspect or the second aspect, a controller (50) performs a second control operation by shifting high-level periods of two control signals belonging to two switches (8) of a plurality of switches (8) so that the high-level periods can partially overlap with each other.

[0184] This aspect enables the absolute value of the current (iL0) flowing through the resonant inductor (L0) to be increased, thereby enabling the adjustment size (ie, the size of the change) of the potential (V15) at the regenerative capacitor (15) to be increased.

[0185] In a power converter (100; 100A; 100B; 100C) according to a fifth aspect that can be implemented in combination with any one of the first to fourth aspects, a controller (50) performs a third control operation by offsetting the high-level periods of two control signals belonging to two switches (8) of a plurality of switches (8) to prohibit the high-level periods from overlapping each other.

[0186] This aspect enables the absolute value of the current (iL0) flowing through the resonant inductor (L0) to be reduced.

[0187] In the power converter (100; 100A; 100B; 100C) according to the sixth aspect, which can be implemented in combination with any one of the first to fifth aspects, the controller (50) performs the second control operation and the third control operation without shifting the high level periods of two control signals belonging to two switches (8) of the plurality of switches (8).

[0188] According to the seventh aspect, a power converter (100D; 100E) includes a first DC terminal (31) and a second DC terminal (32), a power conversion circuit (11), a plurality of AC terminals (41), a plurality of switches (8), a plurality of resonant circuits (20), a regenerative capacitor (15), and a controller (50). The power conversion circuit (11) includes a plurality of first switching elements (1) and a plurality of second switching elements (2). In the power conversion circuit (11), a plurality of switching circuits (10) are connected in parallel to each other, and in each switching circuit (10) of the plurality of switching circuits (10), one first switching element (1) of the plurality of first switching elements (1) and a corresponding second switching element (2) of the plurality of second switching elements (2) are connected in series one-to-one. In the power conversion circuit (11), the plurality of first switching elements (1) are connected to the first DC terminal (31), and the plurality of second switching elements (2) are connected to the second DC terminal (32). The plurality of AC terminals (41) are provided one-to-one for the plurality of switching circuits (10). Each AC terminal (41) among the plurality of AC terminals (41) is connected to a connection node (3) between a first switching element (1) and a second switching element (2) of a corresponding switching circuit (10) among the plurality of switching circuits (10). A plurality of switches (8) are provided one-to-one for the plurality of switching circuits (10). A first terminal (81) of each switch (8) among the plurality of switches (8) is connected to a connection node (3) between a first switching element (1) and a second switching element (2) of a corresponding switching circuit (10) among the plurality of switching circuits (10). A plurality of resonant circuits (20) are provided one-to-one for the plurality of switches (8). Each resonant circuit (20) among the plurality of resonant circuits (20) has a variable resonant frequency. The regenerative capacitor (15) has a third terminal (153) and a fourth terminal (154). In the regenerative capacitor (15), the third terminal (153) is connected to the first DC terminal (31) or the second DC terminal (32), and the fourth terminal (154) is connected to the plurality of resonant circuits (20). A controller (50) applies a PWM signal having a potential alternating between a high level and a low level to each of the plurality of first switching elements (1) and each of the plurality of second switching elements (2). Each of the plurality of resonant circuits (20) includes: a resonant capacitor (9) connected between a first terminal (81) and a second DC terminal (32) of a corresponding switch (8) among the plurality of switches (8); and a resonant inductor (L4) connected between a second terminal (82) of a corresponding switch (8) among the plurality of switches (8) and a fourth terminal (154) of the regenerative capacitor (15).The controller (50) sets a dead time (Td) between a high level period of a PWM signal of a first switching element (1) and a high level period of a PWM signal of a second switching element (2) for each switching circuit (10) among the plurality of switching circuits (10). The controller (50) performs a first control operation. The controller (50) performs the first control operation, which includes: enabling a high level period of a control signal of a corresponding switch (8) among the plurality of switches (8) corresponding to each switching circuit (10) among the plurality of switching circuits (10) to overlap with the dead time (Td), and setting the start of the high level period at a time point earlier than the start of the dead time (Td) by an additional time. The controller (50) changes a resonance period of at least one resonant circuit (20) belonging to the plurality of resonant circuits (20) according to a potential (V15) at a fourth terminal (154) of the regenerative capacitor (15).

[0189] This aspect helps to improve power conversion efficiency.

[0190] In the power converter (100D) according to the eighth aspect, which can be implemented in combination with the seventh aspect, each of the plurality of resonant circuits (20) includes: a second resonant inductor (L5) provided separately from a first resonant inductor (L4) serving as a resonant inductor (L4); and a selection switch (18) connected to the second resonant inductor (L5). In each of the plurality of resonant circuits (20), a series circuit of the second resonant inductor (L5) and the selection switch (18) is connected in parallel to the first resonant inductor (L4). Each of the plurality of resonant circuits (20) has a resonant frequency that changes as the selection switch (18) turns on and off.

[0191] In the power converter (100E) according to the ninth aspect, which can be implemented in combination with the seventh aspect, each of the plurality of resonant circuits (20) includes: a second resonant capacitor (91) provided separately from a first resonant capacitor (9) serving as a resonant capacitor (9); and a selection switch (92) connected to the second resonant capacitor (91). In each of the plurality of resonant circuits (20), a series circuit of the second resonant capacitor (91) and the selection switch (92) is connected in parallel to the first resonant capacitor (9). Each of the plurality of resonant circuits (20) has a resonant frequency that changes as the selection switch (92) turns on and off.

[0192] Description of Reference Numerals

[0193] 1 First switching element

[0194] 2 Second switching element

[0195] 3 Connecting Nodes

[0196] 8 switches

[0197] 81 First terminal

[0198] 82 Second terminal

[0199] 9 Resonance capacitor (first resonant capacitor)

[0200] 10 Switching Circuit

[0201] 11 Power conversion circuit

[0202] 15 Regeneration capacitor

[0203] 153 Third terminal

[0204] 154 Fourth terminal

[0205] 18 Selector switch

[0206] 20 Resonant Circuit

[0207] 31 First DC terminal

[0208] 32 Second DC terminal

[0209] 41 AC terminal

[0210] 50 Controller

[0211] 91 Second resonant capacitor

[0212] 92 Selector switch

[0213] 100, 100A, 100B, 100C, 100D, 100E power converters

[0214] iU, iV, iW output current

[0215] L0 resonant inductor

[0216] L1 first resonant inductor

[0217] L2 Second resonant inductor

[0218] L3 third resonant inductor

[0219] L4 First resonant inductor

[0220] L5 Second resonant inductor

[0221] Td Dead time

[0222] Vd voltage value

[0223] Vth1 first threshold

[0224] Vth2 Second threshold

Claims

1. A power converter, comprising: a first DC terminal and a second DC terminal; a power conversion circuit comprising a plurality of first switching elements and a plurality of second switching elements, the power conversion circuit being implemented as a parallel connection of a plurality of switching circuits, in each of the plurality of switching circuits, a first switching element of the plurality of first switching elements and a corresponding second switching element of the plurality of second switching elements being connected in series one-to-one, the plurality of first switching elements being connected to the first DC terminal, and the plurality of second switching elements being connected to the second DC terminal; a plurality of AC terminals provided one-to-one for the plurality of switching circuits, each of the plurality of AC terminals being connected to a connection node between the first switching element and the second switching element of a corresponding switching circuit of the plurality of switching circuits; a plurality of switches, which are arranged one-to-one for the plurality of switching circuits, wherein a first terminal of each of the plurality of switches is connected to a connection node between the first switching element and the second switching element of a corresponding switching circuit in the plurality of switching circuits, and a second terminal of each of the plurality of switches is commonly connected to a common connection node; a plurality of resonant capacitors, which are arranged one-to-one for the plurality of switches, each of the plurality of resonant capacitors being connected between the first terminal and the second DC terminal of a corresponding switch among the plurality of switches; a resonant inductor having a first terminal and a second terminal, the first terminal of the resonant inductor being connected to the common connection node; a regeneration capacitor having a third terminal and a fourth terminal, the third terminal of the regeneration capacitor being connected to the first DC terminal or the second DC terminal; as well as a controller configured to apply a PWM signal having a potential alternating between a high level and a low level to each of the plurality of first switching elements and the plurality of second switching elements, wherein the controller is configured to perform a first control operation, the first control operation being used to: for each of the plurality of switching circuits, set a dead time between a high level period of the PWM signal of the first switching element and a high level period of the PWM signal of the second switching element; enable a high level period of a control signal of a corresponding switch among the plurality of switches corresponding to each of the plurality of switching circuits to overlap with the dead time; and set the start of the high level period at a time point earlier than the start of the dead time by an additional time, and The controller is configured to selectively perform a second control operation or a third control operation according to the potential detected at the fourth terminal of the regenerative capacitor and the polarities of the multiple output currents supplied from the multiple AC terminals, wherein the second control operation is used to enable the high level periods of the control signals of two switches belonging to the multiple switches to overlap with each other, and the third control operation is used to prohibit the high level periods of the control signals of the multiple switches from overlapping with each other.

2. The power converter according to claim 1, wherein: The controller is configured to: When the first condition or the second condition is met, performing the second control operation; and When the third condition or the fourth condition is met, the third control operation is performed. the first condition being that the potential detected at the fourth terminal of the regenerative capacitor is less than a first threshold value and the product of the plurality of output currents is positive, the first threshold value being less than half the value of the voltage applied between the first DC terminal and the second DC terminal, the second condition being that the potential detected at the fourth terminal of the regenerative capacitor is greater than a second threshold value greater than half of a voltage value applied between the first DC terminal and the second DC terminal and the product of the plurality of output currents is negative, The third condition is that the potential detected at the fourth terminal of the regenerative capacitor is less than the first threshold value, which is less than half the value of the voltage applied between the first DC terminal and the second DC terminal, and the product of the plurality of output currents is negative, and The fourth condition is that the potential detected at the fourth terminal of the regenerative capacitor is greater than the second threshold value greater than half of a voltage value applied between the first DC terminal and the second DC terminal and the product of the plurality of output currents is positive.

3. The power converter according to claim 1 or 2, wherein: The controller is configured to perform the second control operation by shifting high level periods of respective two control signals belonging to two switches of the plurality of switches so that the high level periods can overlap each other.

4. The power converter according to claim 1 or 2, wherein: The controller is configured to perform the second control operation by shifting high level periods of respective two control signals belonging to two switches of the plurality of switches so that the high level periods can partially overlap each other.

5. The power converter according to any one of claims 1 to 4, wherein: The controller is configured to perform the third control operation by shifting high level periods of respective two control signals belonging to two switches of the plurality of switches to prohibit the high level periods from overlapping each other.

6. The power converter according to any one of claims 1 to 5, wherein: The controller is configured to perform the second control operation and the third control operation without shifting high level periods of two control signals belonging to two switches of the plurality of switches.

7. A power converter comprising: a first DC terminal and a second DC terminal; a power conversion circuit comprising a plurality of first switching elements and a plurality of second switching elements, the power conversion circuit being implemented as a parallel connection of a plurality of switching circuits, in each of the plurality of switching circuits, a first switching element of the plurality of first switching elements and a corresponding second switching element of the plurality of second switching elements being connected in series one-to-one, the plurality of first switching elements being connected to the first DC terminal, and the plurality of second switching elements being connected to the second DC terminal; a plurality of AC terminals provided one-to-one for the plurality of switching circuits, each of the plurality of AC terminals being connected to a connection node between the first switching element and the second switching element of a corresponding switching circuit of the plurality of switching circuits; a plurality of switches provided one-to-one for the plurality of switching circuits, a first terminal of each of the plurality of switches being connected to a connection node between the first switching element and the second switching element of a corresponding switching circuit of the plurality of switching circuits; a plurality of resonant circuits, which are arranged one by one for the plurality of switches, each of the plurality of resonant circuits having a variable resonant frequency; a regenerative capacitor having a third terminal and a fourth terminal, the third terminal of the regenerative capacitor being connected to the first DC terminal or the second DC terminal, and the fourth terminal of the regenerative capacitor being connected to the plurality of resonant circuits; as well as a controller configured to apply a PWM signal having a potential alternating between a high level and a low level to each of the plurality of first switching elements and the plurality of second switching elements, Wherein, each resonant circuit in the plurality of resonant circuits comprises: a resonant capacitor connected between the first terminal and the second DC terminal of a corresponding switch among the plurality of switches; and a resonant inductor connected between a second terminal of a corresponding switch of the plurality of switches and a fourth terminal of the regenerative capacitor, The controller is configured to perform a first control operation, the first control operation being used to: set a dead time between a high level period of the PWM signal of the first switching element and a high level period of the PWM signal of the second switching element for each of the plurality of switching circuits; enable a high level period of a control signal of a corresponding switch among the plurality of switches corresponding to each of the plurality of switching circuits to overlap with the dead time; and set a start of the high level period at a time point earlier than a start of the dead time by an additional time, and The controller is configured to change a resonance period of at least one resonance circuit belonging to the plurality of resonance circuits according to a potential at a fourth terminal of the regenerative capacitor.

8. The power converter according to claim 7, wherein: Each of the plurality of resonant circuits includes: a second resonant inductor provided separately from a first resonant inductor serving as the resonant inductor; and a selection switch connected to the second resonant inductor, In each of the plurality of resonant circuits, a series circuit of the second resonant inductor and the selection switch is connected in parallel to the first resonant inductor, and Each of the plurality of resonant circuits has a resonant frequency that changes as the selection switch becomes on and off.

9. The power converter according to claim 7, wherein: Each of the plurality of resonant circuits includes: a second resonant capacitor provided separately from a first resonant capacitor serving as the resonant capacitor; and a selection switch connected to the second resonant capacitor, In each of the plurality of resonant circuits, a series circuit of the second resonant capacitor and the selection switch is connected in parallel to the first resonant capacitor, and Each of the plurality of resonant circuits has a resonant frequency that changes as the selection switch becomes on and off.

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