JP2019146357A - Voltage converter, method for controlling voltage converter, and computer program - Google Patents

Abstract

To provide a voltage converter, a method for controlling a voltage converter, and a computer program which can suppress a switching loss when a DC voltage is converted to an AC voltage, using a full-bridge circuit and an inductor.SOLUTION: The voltage converter includes: a full-bridge circuit with two legs; an inductor; a transformer in which one winding is connected between the connection points of two arms of each leg; an application circuit for applying a voltage to the other winding; and a controller for controlling a full-bridge circuit to convert a DC voltage applied to both ends of each leg through the inductor. The controller controls one of the legs so that the leg is in the state of short-circuit for a first length of time, and controls the application circuit so that the application circuit applies a predetermined voltage to the other winding of the transformer in a second length of time of the first length of time. The controller also conducts control so that one arm of the other leg is in the state of short circuit in a third length of time, which overlaps with the second length of time of the first length of time, so that a current generated in one winding flows in the other arm of one leg in a reverse direction to flow back.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a voltage converter that converts a DC voltage applied to a full bridge into an AC voltage, a control method for the voltage converter, and a computer program.

  A plug-in hybrid vehicle (PHEV) that is equipped with an AC / DC converter that converts an AC voltage supplied from a commercial power source for household use into a DC voltage, and that charges the battery with the DC voltage converted by the AC / DC converter. : Electric vehicles such as Plug-in Hybrid Electric Vehicle (EV) and Electric Vehicle (EV) are widely used.

  In recent years, it is expected that batteries of electric vehicles such as plug-in hybrid vehicles and electric vehicles will be used as household power supplies (V2H: Vehicle to Home) or buffers (V2G: Vehicle to Grid) in the event of a disaster or emergency. Has been. In this case, the AC / DC converter must be operable as a bidirectional converter.

  For example, Patent Document 1 discloses a power conversion device that bidirectionally converts an AC voltage from an AC power source and a DC voltage from a battery. The disclosed power converter includes an isolated DC / DC converter having two full bridge circuits coupled by a transformer (corresponding to a transformer). The DC / DC converter converts a DC voltage applied to one full-bridge circuit into an AC voltage, and applies the converted AC voltage to the other full-bridge circuit via a transformer to convert it into a DC voltage. It has become.

  In the DC / DC converter described in Patent Document 1, in particular, when a DC voltage applied to one full bridge circuit from an external battery via an inductor is boosted and converted to an AC voltage, 2 of the one full bridge circuit is used. Control is performed in which the two legs are alternately short-circuited to store energy in the inductor. For example, when one leg is short-circuited, the current flowing in the inductor is then controlled when one arm of one leg is controlled to open and one arm of the other leg is controlled to short-circuit. , And commutates to flow through one arm of the other leg, one winding of the transformer, and the other arm of one leg.

  In this case, unless special control is performed, a surge voltage is applied to the other arm of the other leg. Therefore, in Patent Document 1, the other side of the transformer is only applied for a predetermined period before the commutation is started. It has been proposed to apply a voltage from a winding to cause a current to flow through one of the windings of the transformer first. Thereby, said surge voltage is suppressed.

International Publication No. 2016/194790

  However, even in the case of the technique proposed in Patent Document 1, when the above commutation occurs, the arm is controlled to be open while the current is flowing through one arm of the one leg. Therefore, there is a problem that switching loss (off loss) occurs.

  The present invention has been made in view of such circumstances, and an object of the present invention is to suppress a switching loss when converting a DC voltage to an AC voltage using a full bridge circuit and an inductor. The object is to provide a voltage conversion device, a control method for the voltage conversion device, and a computer program.

  In the voltage conversion device according to one aspect of the present invention, one winding is connected between a full-bridge circuit having two legs connected in parallel, an inductor, and connection points of two arms of each leg. A transformer, an application circuit that applies a voltage to the other winding of the transformer, and a control unit that controls switching of the full bridge circuit, and is applied to both ends of each leg via the inductor. A voltage converter for converting a DC voltage into an AC voltage, wherein the control unit controls one leg to be in a short-circuit state only for a first period, and only for a second period of the first period. The first period is controlled so that a predetermined voltage is applied to the other winding from the application circuit, and the current induced in the one winding flows in the reverse direction through one arm of the one leg. Of which overlap with the second period Only three periods, are to control the one of the arms of the other leg is short-circuited.

  A voltage converter control method according to an aspect of the present invention includes a full-bridge circuit having two legs connected in parallel, an inductor, and one winding between connection points of two arms of each leg. A voltage converter that converts a DC voltage applied to both ends of each leg through the inductor into an AC voltage, and a transformer that is connected to the other winding of the transformer. A method for controlling a voltage converter that controls switching of the full bridge circuit in a device, the step of controlling one leg to a short-circuit state for a first period, and a second period of the first period, Controlling to apply a predetermined voltage from the application circuit to the other winding of the transformer, and a current induced in the one winding flows in one arm of the one leg in the reverse direction and circulates. Therefore, the first Only the third period with overlap and the second period of between, and controlling the one of the arms of the other leg is short-circuited.

  In a computer program according to an aspect of the present invention, one winding is connected between a full-bridge circuit having two legs connected in parallel, an inductor, and connection points of two arms of each leg. A transformer, and an application circuit for applying a voltage to the other winding of the transformer, and a voltage converter for converting a DC voltage applied to both ends of each leg through the inductor into an AC voltage. A computer program for causing a computer to control switching of a full bridge circuit, wherein the computer controls one leg to a short-circuited state for a first period, and only for a second period of the first period. A step of applying a predetermined voltage from the application circuit to the other winding of the transformer, and a current induced in the one winding is applied to one arc of the one leg. In order to reflux the flow in the direction opposite to the direction, only the third time period having an overlap with the second period of the first period, and a step of controlling one of the arms of the other leg is short-circuited.

  In addition, this application implement | achieves as a voltage converter provided with such a characteristic process part, implement | achieves as a control method of the voltage converter which makes a characteristic process a step, or makes a computer perform the step concerned In addition, the voltage conversion device can be realized as a semiconductor integrated circuit or as a system including the voltage conversion device.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress the switching loss at the time of converting a DC voltage into an AC voltage using a full bridge circuit and an inductor.

It is a circuit diagram which shows one structural example of a bidirectional | two-way AC / DC converter. It is a block diagram which shows one structural example of a control part. FIG. 4 is an explanatory diagram illustrating an example of a basic operation of the inverter according to the first embodiment. FIG. 3 is an explanatory diagram illustrating an example of an operation state of the inverter according to the first embodiment. 4 is a timing chart illustrating an operation when a surge voltage is generated in the IGBT in the inverter according to the first embodiment. 6 is an explanatory diagram illustrating an example of an operation for suppressing a surge voltage in the inverter according to the first embodiment. FIG. 3 is a timing chart illustrating an operation when a surge voltage is suppressed by the inverter according to the first embodiment. FIG. 6 is an explanatory diagram illustrating an example of an operation for suppressing switching loss of the IGBT in the inverter according to the first embodiment. 5 is a timing chart illustrating an operation when switching loss of the IGBT is suppressed in the inverter according to the first embodiment. 3 is a flowchart illustrating a processing procedure of a CPU that suppresses switching loss of an IGBT in the inverter according to the first embodiment. 3 is a flowchart illustrating a processing procedure of a CPU that suppresses switching loss of an IGBT in the inverter according to the first embodiment. FIG. 10 is an explanatory diagram illustrating an example of a basic operation of the inverter according to the second embodiment. FIG. 6 is an explanatory diagram illustrating an example of an operation state of an inverter according to a second embodiment. 6 is a timing chart showing an operation when a surge voltage is generated in the IGBT in the inverter according to the second embodiment. 6 is an explanatory diagram illustrating an example of an operation for suppressing a surge voltage in an inverter according to Embodiment 2. FIG. 6 is a timing chart showing an operation when a surge voltage is suppressed by the inverter according to the second embodiment. 6 is an explanatory diagram illustrating an example of an operation for suppressing switching loss of an IGBT in an inverter according to Embodiment 2. FIG. 10 is a timing chart illustrating an operation when switching loss of the IGBT is suppressed in the inverter according to the second embodiment.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described. Moreover, you may combine arbitrarily at least one part of embodiment described below.

(1) A voltage conversion device according to an aspect of the present invention includes a full-bridge circuit having two legs connected in parallel, an inductor, and one winding between connection points of two arms of each leg. Is connected to the other winding of the transformer, and a control unit for controlling the switching of the full bridge circuit, and the both ends of each leg via the inductor. A voltage conversion device that converts an applied DC voltage into an AC voltage, wherein the control unit controls one leg to a short-circuited state for a first period, and only for a second period of the first period. Control is performed to apply a predetermined voltage from the application circuit to the other winding of the transformer, and the current induced in the one winding flows in the reverse direction through one arm of the one leg to return to the current. Overlapping the second period of the first period Only the third period with, are to control the one of the arms of the other leg is short-circuited.

(6) A method for controlling a voltage conversion device according to an aspect of the present invention includes a full bridge circuit having two legs connected in parallel, an inductor, and a connection point between two connection points of two arms of each leg. A transformer connected to the other winding and an application circuit for applying a voltage to the other winding of the transformer, and converts a DC voltage applied to both ends of each leg through the inductor into an AC voltage. A method for controlling a voltage converter that controls switching of the full bridge circuit in a voltage converter that performs a step of controlling one leg to a short-circuited state for a first period, and a second of the first periods. A step of applying a predetermined voltage from the application circuit to the other winding of the transformer for a period, and a current induced in the one winding flows in one arm of the one leg in a reverse direction. To recirculate Only the third period with overlap and the second period of the first period, and controlling the one of the arms of the other leg is short-circuited.

(7) A computer program according to an aspect of the present invention includes a full bridge circuit having two legs connected in parallel, an inductor, and one winding between connection points of two arms of each leg. A voltage converter that includes a connected transformer and an application circuit that applies a voltage to the other winding of the transformer, and converts a DC voltage applied to both ends of each leg through the inductor into an AC voltage. A computer program for causing the computer to control switching of the full bridge circuit, wherein the computer controls one leg to a short-circuit state for a first period; and a second period of the first period The step of controlling the other winding of the transformer to apply a predetermined voltage from the application circuit, and the current induced in the one winding is one of the one leg. In order to reflux flows arm in the opposite direction, only the third time period having an overlap with the second period of the first period, and a step of controlling one of the arms of the other leg is short-circuited.

  In this aspect, one winding of the transformer is connected between the connection points of the two arms included in each of the two legs of the full bridge circuit, and the other winding of the transformer is connected to the other winding. Is connected to an application circuit. When converting the DC voltage applied to both ends of the two legs via the inductor into the AC voltage, the control unit controls one leg to a short-circuit state only for the first period and transfers the current from the inductor to the one leg. Conduction is performed, and control is performed so that a predetermined voltage is applied to the other winding of the transformer by the application circuit only during the second period. This induces a voltage in one winding of the transformer. In this case, since one arm of the other leg does not conduct in the forward direction, when each arm conducts in the reverse direction, the current induced in one winding causes the other arm of the other leg to reverse. And flows in the forward direction on the other arm of one leg to return to one winding. The control unit further controls one arm of the other leg to be in a short-circuited state for a third period having an overlap with the second period. Thus, only during the period in which the second and third periods overlap, the current induced in one winding flows in the forward direction on one arm of the other leg and flows in the reverse direction on one arm of the one leg. Return to one winding. For this reason, the current from the inductor flowing in one arm of one leg is reduced by the amount of current induced in one winding.

(2) The two arms of each leg include first and second switching elements having diodes connected in anti-parallel.

  Since the two arms of each leg include the first and second switching elements, the control unit controls the first and second switching elements to be on / off, so that one and the other arm are in a conductive state / non-conductive state. To be controlled. In addition, since a diode is connected to each switching element in antiparallel, a current flows in the opposite direction even if each switching element is controlled to be off.

(3) The control unit controls the one leg to the first state in which the first and second switching elements are on only during the first period, and controls the other leg to the first period only during the third period. The switching element is controlled to the second state in which the switching element is turned on, and the one leg is controlled to the third state in which the second switching element is turned on only during the fourth period following the first period. Is controlled to the second state.

  In a basic state where the first and second switching elements are controlled to be turned off, the control unit controls both switching elements to be turned on for only the first period for one of the legs to enter the first state. In the second leg, the first switching element is controlled to be turned on for the third period to be in the second state. The controller further controls the first switching element to be turned off for one of the legs and the second switching element to be in the third state for the fourth period following the first period, and sets the first state for the other leg. The switching element is turned on and the second switching element is turned off to enter the second state. As a result, the current flowing through the inductor through the leg controlled to be short-circuited in the first period, the second switching element of one leg, one winding of the transformer, and the other in the fourth period Because the commutation is performed so as to flow through the first switching element of the second leg, the energy stored in the inductor in the first period is released to one winding of the transformer in the fourth period.

(4) The controller controls the other leg to the first state only during a fifth period following the fourth period, and controls the other winding of the transformer only during a sixth period of the fifth period. The line is controlled to apply a voltage having a polarity different from that of the predetermined voltage from the application circuit, and the one leg is in the second state only in a seventh period of the fifth period that overlaps with the sixth period. And controlling the one leg to the second state for the eighth period from the end of the fifth period to the start of the first period in the next switching period, and the other leg The third state is controlled.

  The control unit turns on both switching elements for the other leg of the leg for the fifth period following the fourth period to the first state, and applies the other of the transformers by the application circuit only for the sixth period of the fifth period. Control is performed so that a voltage having a polarity opposite to the predetermined voltage is applied to the winding. This induces a voltage opposite to the second period in one winding of the transformer. In this case, since one arm of one leg does not conduct in the forward direction, when each arm conducts in the reverse direction, the current induced in one winding causes the other arm of one leg to reverse. And flow forward in the other arm of the other leg to return to one winding. The control unit also controls to turn on the first switching element that is one arm for one of the legs for the seventh period that overlaps with the sixth period. Thus, only during the period in which the sixth and seventh periods overlap, the current induced in one winding flows in the forward direction on one arm of one leg and flows in the reverse direction on one arm of the other leg. Return to one winding. For this reason, the current from the inductor flowing in one arm of the other leg is reduced by the amount of current induced in one winding. The control unit further turns on the first switching element and turns off the second switching element for one of the legs only during the eighth period from the end of the fifth period to the start of the first period in the next switching cycle. The second state is controlled and the first switching element is turned off and the second switching element is turned on for the other of the legs to the third state. As a result, the energy stored in the inductor in the first period is released in one polarity to one winding of the transformer in the fourth period, and the energy stored in the inductor in the fifth period is in the eighth period. Since the state of being discharged with the other polarity in one winding of the transformer is repeated, an AC voltage is generated in the other winding of the transformer.

  In other words, the control unit 9 controls the one leg and the other leg in the period from the fifth period to the eighth period, and controls the other leg and the one leg in the period from the first period to the fourth period. It is executed in the same way as the control for The controller 9 also sets the voltage applied to the other winding 72 of the transformer 7 in the sixth period corresponding to the second period to a voltage having a polarity opposite to that in the second period. Accordingly, the switching loss of the first switching element included in one arm of each of the one leg and the other leg is alternately suppressed during one switching period.

(5) The application circuit includes a second full-bridge circuit having two legs connected in parallel, and the second full-bridge circuit is provided between connection points of two arms of each leg. The other winding of the transformer is connected.

  Since the application circuit is a second full-bridge circuit and the other winding of the transformer is connected between the connection points of the two arms of each leg, the voltage to be applied to the other winding The polarity is arbitrarily selected. Further, the AC voltage generated in the other winding is rectified by the second full bridge circuit and converted into a DC voltage.

[Details of the embodiment of the present invention]
Specific examples of a voltage conversion device, a voltage conversion device control method, and a computer program according to embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included. In addition, the technical features described in each embodiment can be combined with each other.

(Embodiment 1)
FIG. 1 is a circuit diagram showing a configuration example of a bidirectional AC / DC converter. The bidirectional AC / DC converter 1 is an insulating converter that is mounted on an electric vehicle such as a plug-in hybrid vehicle or an electric vehicle and converts an AC voltage and a DC voltage bidirectionally.

  The AC input / output terminals T1 and T2 of the bidirectional AC / DC converter 1 have an AC power source 2 and a power load 21 via a charging cable (both not shown) that is detachably attached to the inlet of the electric vehicle, for example. Connected. Both ends of the external battery 3 are connected to the DC input / output terminals T3 and T4 of the bidirectional AC / DC converter 1.

  The bidirectional AC / DC converter 1 is a noise filter that has a pair of terminals connected to the AC input / output terminals T1, T2 and removes high-frequency noise contained in the AC voltage input / output to / from the AC input / output terminals T1, T2. 4 and the other terminal pair of the noise filter 4 are connected to AC input / output terminals T51 and T52 via inductors L1 and L2, respectively, and an inverter 5 for bidirectionally converting an AC voltage and a DC voltage, and the inverter 5 DC input / output terminals T53 and T54 are connected to one DC input / output terminals T61 and T62, and a converter 10 for bidirectionally converting a DC voltage and a control unit for controlling voltage conversion by the inverter 5 and the converter 10 are provided. 9. A capacitor C1 that smoothes the AC voltage converted by the inverter 5 is connected in parallel to the other terminal pair of the noise filter 4.

  The converter 10 includes an inverter 6 (corresponding to an application circuit) and an inverter 8 (corresponding to a voltage converter) that convert a DC voltage and an AC voltage bidirectionally, and a transformer 7 that connects the inverters 6 and 8 to each other. Comprising. In the transformer 7, one winding 71 and the other winding 72 are connected to the AC input / output terminals T 81 and T 82 of the inverter 8 and the AC input / output terminals T 63 and T 64 of the inverter 6. The DC input / output terminals T61 and T62 of the inverter 6 also function as one DC input / output terminal of the converter 10, and the DC input / output terminals T83 and T84 of the inverter 8 also function as other DC input / output terminals of the converter 10. Yes.

  The bidirectional AC / DC converter 1 also includes a capacitor C2 connected in parallel to the DC input / output terminals T53 and T54 of the inverter 5 and the DC input / output terminals T61 and T62 of the converter 10, and the other converter 10 And a series circuit of an inductor L3 and a capacitor C3 connected in parallel to the DC input / output terminals T83 and T84. Both ends of the capacitor C3 are connected to DC input / output terminals T3 and T4. One end of the capacitors C2 and C3 on the plus side is connected to the control unit 9. The current flowing through the inductor L3 is detected by the current transformer CT1 and supplied to the control unit 9. One end of the inductor L3 connected to the DC input / output terminal T83 may be connected to the DC input / output terminal T84.

  The inverter 5 includes a switching element such as an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) configured as a full bridge circuit. In the first embodiment, IGBTs 51, 52, 53, and 54 are used as switching elements. The same applies to the inverters 6 and 8.

  The emitter of the IGBT 51 and the collector of the IGBT 52 are connected to the AC input / output terminal T51 of the inverter 5 connected to one end of the inductor L1. The emitter of the IGBT 53 and the collector of the IGBT 54 are connected to the AC input / output terminal T52 of the inverter 5 connected to one end of the inductor L2. The collectors of the IGBTs 51 and 53 are connected to the DC input / output terminal T53 of the inverter 5. The emitters of the IGBTs 52 and 54 are connected to the DC input / output terminal T54 of the inverter 5, respectively. Diodes 55, 56, 57, and 58 are connected in reverse parallel between the collectors and emitters of the IGBTs 51, 52, 53, and 54, respectively.

  When the inverter 5 converts the AC voltage into a DC voltage, the AC voltage applied from one end of each of the inductors L1 and L2 to the AC input / output terminals T51 and T52 is switched by the IGBT 52 (or 54), and the inductors L1 and L2 are switched. The induced DC voltage is output to the DC input / output terminals T53 and T54 via the diodes 55 and 58 (or 57 and 56). Thereby, the power factor of the alternating current power supplied from the alternating current power supply 2 is improved and rectified. When the inverter 5 converts a DC voltage into an AC voltage, the polarity of the DC voltage applied to the DC input / output terminals T53 and T54 is alternately changed by turning on and off the IGBTs 51 and 54 and the IGBTs 53 and 52 alternately. Inverted and output from AC input / output terminals T51 and T52.

  The inverter 6 includes IGBTs 61, 62, 63, and 64 configured as a full bridge circuit 60 (corresponding to a second full bridge circuit). The collectors of the IGBTs 61 and 63 are connected to the DC input / output terminal T61 of the inverter 6. The IGBTs 62 and 64 are connected to the DC input / output terminal T62 of the inverter 6, respectively. The emitter of the IGBT 61 and the collector of the IGBT 62 are connected to the AC input / output terminal T 63 of the inverter 6. The emitter of the IGBT 63 and the collector of the IGBT 64 are connected to the AC input / output terminal T 64 of the inverter 6. Diodes 65, 66, 67, and 68 are connected in antiparallel between the collectors and emitters of the IGBTs 61, 62, 63, and 64, respectively.

  When the inverter 6 converts a DC voltage into an AC voltage, the control unit 9 alternately turns on / off the IGBTs 61 and 64 and the IGBTs 63 and 62 to thereby change the DC voltage applied to the DC input / output terminals T61 and T62. The polarities are alternately inverted and output from the AC input / output terminals T63 and T64. This AC voltage is applied to AC input / output terminals T81 and T82 of the inverter 8 via the transformer 7. When the inverter 6 converts the AC voltage into the DC voltage, the AC voltage applied to the AC input / output terminals T63 and T64 while the control unit 9 turns off the IGBTs 61, 62, 63, and 64 is converted into the diode 65. , 66, 67, 68 are full-wave rectified by a diode bridge and output from DC input / output terminals T61, T62.

  The inverter 8 is formed by configuring IGBTs 81, 82, 83, and 84 in a full bridge circuit 80. The emitter of the IGBT 81 and the collector of the IGBT 82 are connected to the AC input / output terminal T 81 of the inverter 8. The emitter of IGBT 83 and the collector of IGBT 84 are connected to the AC input / output terminal T 82 of the inverter 8. The collectors of the IGBTs 81 and 83 are connected to the DC input / output terminal T83 of the inverter 8. The emitters of the IGBTs 82 and 84 are connected to the DC input / output terminal T84 of the inverter 8. Diodes 85, 86, 87, and 88 are connected in reverse parallel between the collectors and emitters of the IGBTs 81, 82, 83, and 84, respectively.

  When the inverter 8 converts the AC voltage into the DC voltage, the AC voltage applied to the AC input / output terminals T81 and T82 while the control unit 9 turns off the IGBTs 81, 82, 83, and 84 is connected to the diode 85. , 86, 87, 88 are full-wave rectified by a diode bridge and output from DC input / output terminals T83, T84. When the inverter 8 converts a DC voltage into an AC voltage, the control unit 9 alternately turns on / off the IGBTs 81 and 84 and the IGBTs 83 and 82, so that the DC voltage applied to the DC input / output terminals T 83 and T 84 is changed. The polarities are alternately inverted and output from the AC input / output terminals T81 and T82. This AC voltage is applied to the AC input / output terminals T63 and T64 of the inverter 6 via the transformer 7.

  The control unit 9 controls the on / off of the IGBTs 51, 52, 53, 54, the on / off of the IGBTs 61, 62, 63, 64, and the on / off of the IGBTs 81, 82, 83, 84 in association with each other. Then, conversion control and conversion direction control by the inverter 5 and the converter 10 are performed. That is, when the AC voltage is converted into the DC voltage by the bidirectional AC / DC converter 1, the control unit 9 causes the inverter 5 to convert the AC voltage into the DC voltage and changes the direction of conversion by the converter 10 to the DC input / output terminal. The first direction is from T61 and T62 toward the DC input / output terminals T83 and T84. Further, when the DC voltage is converted into the AC voltage by the bidirectional AC / DC converter 1, the control unit 9 changes the conversion direction by the converter 10 from the DC input / output terminals T83 and T84 to the DC input / output terminals T61 and T62. In the second direction, the inverter 5 converts the DC voltage into an AC voltage.

  Next, details of the control unit 9 will be described. FIG. 2 is a block diagram illustrating a configuration example of the control unit 9. The control unit 9 has a CPU (Central Processing Unit) 91 that controls the operation of each unit in the control unit 9, and the CPU 91 is temporarily generated by a storage unit 92 that stores information such as a control program. A RAM (Random Access Memory) 93 that stores information and a communication unit 94 that performs CAN communication via a CAN (Controller Area Network) bus (not shown) are bus-connected to each other. Communication performed by the communication unit 94 is not limited to CAN communication. The CPU 91 also includes a timer 95 for measuring time, an A / D conversion unit 96 for detecting the voltages of the capacitors C2 and C3 and converting the current detected by the current transformer CT1, and inverters 5, 6, A driving unit 97 for supplying a driving signal to the gates of the IGBTs 8 is connected to the bus.

  CPU91 performs the process which implement | achieves the voltage converter which concerns on Embodiment 1 of this invention according to the control program previously stored in the memory | storage part 92, and the computer program 99 mentioned later.

  The storage unit 92 is composed of a nonvolatile memory such as an EEPROM (Electrically Erasable Programmable ROM: registered trademark), for example, and is a computer for causing the CPU 91 to control the switching of the full bridge circuit 80 by the voltage converter according to the first embodiment of the present invention. A program 99 is stored. When the computer program 99 is recorded on a recording medium 98 such as a CD (Compact Disc) -ROM, a DVD (Digital Versatile Disc) -ROM, and a hard disk drive, which are portable media recorded in a readable manner, the CPU 91 The computer program 99 may be read from the recording medium 98 and stored in the storage unit 92 in advance.

  The RAM 93 is a readable / writable memory such as a DRAM (Dynamic RAM) and an SRAM (Static RAM). The RAM 93 may be preloaded with the control program and the computer program 99 stored in the storage unit 92. In this case, the control program and the computer program 99 are executed on the RAM 93.

  The communication unit 94 is a circuit that receives instruction signals such as a charge instruction that instructs conversion from an AC voltage to a DC voltage, a discharge instruction that instructs conversion from a DC voltage to an AC voltage, and an end instruction that instructs the end of conversion. is there. The instruction signal received by the communication unit 94 is notified to the CPU 91.

  In the configuration shown in FIGS. 1 and 2, when the CPU 91 receives a charging instruction through the communication unit 94, the inverter 5 converts the AC voltage into a DC voltage by switching control and the converter 10 converts the DC voltage in the first direction. Let Moreover, when CPU91 receives the discharge instruction | indication by the communication part 94, while making the converter 10 convert a DC voltage to a 2nd direction by switching control, it makes the inverter 5 convert a DC voltage into an AC voltage.

  Next, the operation of the inverter 8 will be described. FIG. 3 is an explanatory diagram illustrating an example of a basic operation of the inverter 8 according to the first embodiment. FIG. 3 schematically shows how the DC voltage from the battery 3 is converted into an AC voltage. Hereinafter, FIGS. 3A to 3D will be described. The time from the start of the state shown in FIG. 3A to the end of the state shown in FIG. 3D, that is, the on / off period T of the IGBTs 81, 82, 83, 84 is, for example, 20 μs, but is not limited thereto. It is not a thing. In the first embodiment, the IGBTs 81 and 83 correspond to first switching elements, and the IGBTs 82 and 84 correspond to second switching elements.

  As shown in FIG. 3A, the control unit 9 first controls the IGBTs 81 and 82 (corresponding to the other leg, two arms) to be in an open state, and IGBTs 83 and 84 (one leg, two arms). To the first state (that is, refer to FIG. 5 to be described later for the first to eighth periods) to be in the first state, that is, the short circuit state. For example, the length of the first period may be calculated by the CPU 91 in a timely manner according to the alternating current to be supplied to the one winding 71 of the transformer 7. In the state shown in FIG. 3A, since the current from the battery 3 flows to the IGBTs 83 and 84 via the inductor L3, energy is stored in the inductor L3.

  At the time when the first period ends, the control unit 9 controls the IGBT 83 to be turned off and the IGBT 84 to be turned on only in the fourth period as shown in FIG. Turn on and turn off IGBT 82 to put the other leg in the second state. The length of the fourth period may be calculated by subtracting the length of the first period from 1/2 of the period T, for example. In the state shown in FIG. 3B, a current flows in one winding 71 of the transformer 7 in the direction indicated by the arrow. In this case, since the energy stored in the inductor L3 is released, the voltage applied to one winding 71 is boosted.

  At the time when the fourth period ends, the control unit 9 controls the IGBTs 83 and 84 to be in an open state as shown in FIG. 3C, and controls the IGBTs 81 and 82 to be on to control the first period only for the fifth period. Set to the state (short circuit state). The length of the fifth period may be the same as or different from the length of the first period. In the state shown in FIG. 3C, since the current from the battery 3 flows to the IGBTs 81 and 82 via the inductor L3, energy is stored in the inductor L3.

  At the time when the fifth period ends, the control unit 9 controls the IGBT 83 to be turned on and the IGBT 84 to be turned off for the eighth period as shown in FIG. Turn off and control IGBT 82 on to put the other leg in the third state. Thereafter, the control unit 9 periodically repeats the control for setting the inverter 8 to the state shown in FIGS. 3A to 3D. The length of the eighth period may be calculated by subtracting the length of the fifth period from ½ of the period T, for example. In the state shown in FIG. 3D, a current flows in one winding 71 of the transformer 7 in the direction opposite to that shown in FIG. In this case, since the energy stored in the inductor L3 is released, the voltage applied to one winding 71 is a boosted AC voltage.

  Next, the surge voltage generated by the operation of the inverter 8 will be described. FIG. 4 is an explanatory diagram illustrating an example of an operation state of the inverter 8 according to the first embodiment. FIG. 5 is a timing chart illustrating an operation when a surge voltage is generated in the IGBT 82 in the inverter 8 according to the first embodiment. is there. 4 indicates the current flowing in the state of FIG. 3A, that is, the first period, and the current indicated by the solid line arrow in FIG. 4 indicates the state of FIG. 3B, that is, the current flowing in the fourth period. Show. In the timing chart shown in FIG. 5 divided into six stages, the horizontal axis is the same time axis (t), and the vertical axis represents voltage or current. The timing chart from the uppermost stage to the fourth stage in FIG. 5 shows the gate voltage Vg applied to the gates of the IGBTs 81, 83, 82, and 84 corresponding to the sign, and Vg is high (H) level. Sometimes the corresponding IGBT is turned on. The timing charts at the fifth and sixth stages from the top in FIG. 5 show the current Ir flowing through one winding 71 and the collector-emitter voltage Vc of the IGBT 82, respectively.

  The first period in FIG. 5 is a period in which the IGBTs 83 and 84 that are one leg are turned on to be in the first state, and the IGBTs 81 and 82 that are the other leg are controlled to be in the open state. In this period, a current indicated by a broken arrow in FIG. 4 flows. In addition, the fourth period in FIG. 5 is a period in which the IGBTs 83 and 84 are controlled to be turned off and on to be in the third state, and the IGBTs 81 and 82 are respectively turned on and off to be in the second state. In FIG. 4, a current indicated by a solid arrow flows.

  As shown in FIG. 5, when the transition from the first period to the fourth period, that is, when the IGBT 83 is turned from on to off and the IGBT 81 is turned on from off, the current from the inductor L3 is changed as shown in FIG. The commutation from the dashed arrow path to the solid arrow path. In this case, when the leakage inductance of the transformer 7 is represented by 7a and 7b, the voltage Vc1 proportional to the temporal change of the current Ir as shown in FIG. • Generated as a surge voltage between emitters. A similar surge voltage is also generated between the collector and emitter of the IGBT 83 that is turned off from on at this timing.

  Although detailed description is omitted, when the transition from the fifth period shown in FIG. 5 to the eighth period, that is, when the IGBT 81 is turned from on to off and the IGBT 83 is turned on from off, the current from the inductor L3 is It commutates from the path indicated by the arrow in FIG. 3C to the path indicated by the arrow in FIG. 3D. In this case, a voltage Vc2 (not shown) proportional to the temporal change of the current Ir is generated as a surge voltage between the collector and the emitter of the IGBT 84 at the fall of the current Ir flowing through the leakage inductance 7a of the transformer 7. A similar surge voltage is also generated between the collector and emitter of the IGBT 81 that is turned off from on at this timing.

  Therefore, in the first embodiment, the surge voltage is first suppressed by the method disclosed in Patent Document 1. FIG. 6 is an explanatory diagram illustrating an example of an operation for suppressing the surge voltage in the inverter 8 according to the first embodiment. FIG. 7 illustrates an operation when the surge voltage is suppressed in the inverter 8 according to the first embodiment. It is a timing chart which shows. 6 indicates the current flowing in the first period, and the current indicated by the solid arrow in FIG. 6 indicates the current flowing in the second period (see FIG. 7) of the first period. . In the timing chart shown in FIG. 7 divided into nine stages, the horizontal axis is the same time axis (t), and the vertical axis represents voltage or current.

  The timing chart from the uppermost stage to the fourth stage in FIG. 7 shows the gate voltage Vg applied to the gates of the IGBTs 81, 83, 82, 84 in correspondence with the reference numerals as in FIG. The timing charts at the fifth and sixth stages from the top of FIG. 7 indicate the gate voltages Vg applied to the gates of the IGBTs 62 and 63 and the IGBTs 61 and 64 of the inverter 6 in correspondence with the reference numerals. The timing charts at the seventh and eighth stages from the top of FIG. 7 show the current Ir flowing through one winding 71 and the collector-emitter voltage Vc of the IGBT 82, respectively. The timing chart of the ninth stage (bottom stage) from the top of FIG. 7 shows the collector-emitter voltage Vc with a thick solid line and the collector current Ic with a thin solid line for the IGBT 83.

  The controller 9 controls the IGBTs 62 and 63 to turn on to apply a predetermined voltage to the other winding 72 of the transformer 7 as shown in FIG. 6 only in the second period of the first period shown in FIG. To do. As a result, as shown in FIG. 7, a current corresponding to the applied voltage of the capacitor C2 and the leakage inductance 7b flows to the other winding 72 of the transformer 7, and a current Ir1 that rises linearly is induced in one winding 71. To do. For this reason, when the IGBTs 81 and 84 are turned on, the amount of change in the current flowing through one winding 71 is reduced, and the surge voltage generated between the collector and emitter of the IGBT 82 is suppressed. Since the IGBT 81 does not conduct in the forward direction during the second period, the current Ir1 flows in the reverse direction through the IGBT 82 and returns to the one winding 71. Below, the electric current which flows through each IGBT in the reverse direction is represented by the arrow which passes along the paper surface right side of the diode respectively connected in antiparallel.

  More specifically, the control unit 9 determines that the current Ir1 that flows in one winding 71 at the end of the first period is the same as the current Ir that should flow in one winding 71 at the start of the fourth period. (See FIG. 7), control is performed to apply a predetermined voltage to the other winding 72. As a result, the current from the inductor L3 shown in FIG. 4 quickly commutates from the dashed arrow path to the solid arrow path at the start of the fourth period, thereby suppressing the voltage generated in the leakage inductance 7a. The surge voltage applied between the collector and the emitter of the IGBT 82 in the off state and the IGBT 83 in the off state can be suppressed.

  The surge voltage applied between the collectors and emitters of the IGBTs 84 and 81 when shifting from the fifth period to the eighth period can be suppressed by the same method as described above. Specifically, as shown in FIG. 7, the IGBTs 61 and 64 are applied only to the sixth period out of the fifth periods in order to apply a voltage having a polarity opposite to the predetermined voltage to the other winding 72 of the transformer 7. Can be controlled to ON. As a result, as shown in FIG. 7, a current Ir2 that falls linearly can flow in one winding 71, and therefore when one of the windings 71 shifts to the eighth period when the IGBTs 82 and 83 are turned on, The amount of change in the flowing current is reduced, and the surge voltage applied between the collector and emitter of the IGBT 84 in the off state and the IGBT 81 in the off state can be suppressed.

  Here, paying attention to the 9th (bottom) stage timing chart from the top of FIG. 7, the collector current rises when the collector voltage of the IGBT 83 rises at the end of the first period (that is, the start of the fourth period). The switching loss occurs. Therefore, in the first embodiment, the switching loss when the IGBT 83 is turned off is suppressed by the following method.

  FIG. 8 is an explanatory diagram illustrating an example of an operation for suppressing the switching loss of the IGBT 83 in the inverter 8 according to the first embodiment. FIG. 9 illustrates the switching loss of the IGBT 83 in the inverter 8 according to the first embodiment. 6 is a timing chart showing an operation in the case of 8 indicates the current flowing in the first period, and the current indicated by the solid arrow in FIG. 8 indicates the current flowing in the third period (see FIG. 9) of the first period. . In the timing chart shown in FIG. 9 divided into 10 stages, the horizontal axis is the same time axis (t), and the vertical axis represents voltage or current.

  The timing chart from the uppermost stage to the fourth stage in FIG. 9 shows the gate voltage Vg applied to the gates of the IGBTs 81, 83, 82, and 84 in correspondence with the symbols as in FIGS. The hatched portion represents a period in which each of these IGBTs (hereinafter simply referred to as each IGBT) is on. The timing chart from the fifth stage to the eighth stage from the top of FIG. 9 shows the collector-emitter voltage Vc with a thick solid line and the collector current Ic with a thin solid line for each of the IGBTs 81, 83, 82, and 84. is there. The timing charts at the 9th stage and the 10th stage (bottom stage) from the top of FIG. 9 show the gate voltage Vg applied to the gates of the IGBTs 62 and 63 and the IGBTs 61 and 64 of the inverter 6 in correspondence with the reference numerals. is there.

  The control unit 9 controls the IGBT 81 of the other leg to be turned on as shown in FIG. 8 and short-circuits one arm during the third period that overlaps the second period in the first period shown in FIG. Put it in a state. As a result, both the IGBTs 81 and 83 are turned on, and the voltage drop is smaller than the path (see FIG. 6) flowing through the IGBTs 82 and 84, so that the current flows in one winding 71 during the period in which the second and third periods overlap. The current Ir1 is refluxed so as to flow through the IGBTs 81 and 83. In this case, since the current Ir1 flows in the IGBT 83 (corresponding to one arm) in one leg in the reverse direction, the current from the inductor L3 flowing in the IGBT 83 is reduced by the amount of the current Ir1.

  More specifically, as shown in FIG. 9, the current Ir1 flowing through the IGBT 81 rises linearly during the period in which the second and third periods overlap, and the current flowing through the IGBT 83 falls linearly by that amount. Therefore, when the period in which the second and third periods overlap is appropriately set, the collector current of the IGBT 83 becomes zero at the end of the first period, that is, the start of the fourth period, so-called zero cross switching is realized. , Switching loss is reduced.

  The control unit 9 performs the same control as that in the first period in the fifth period. That is, the control unit 9 controls the IGBT 83 to be in a short-circuited state only during the seventh period that overlaps the sixth period in the fifth period. As a result, the IGBTs 81 and 83 are both turned on, and the voltage drop is smaller than the path flowing through the IGBTs 82 and 84. Therefore, the current Ir2 that flows in one winding 71 during the period in which the sixth and seventh periods overlap (FIG. 7). ) Is refluxed to flow through the IGBTs 81 and 83. In this case, since the current Ir2 flows in the reverse direction through the IGBT 81 of the other leg, the current from the inductor L3 flowing in the IGBT 81 is reduced by the amount of the current Ir2. Therefore, when the period in which the sixth and seventh periods overlap is appropriately set, the collector current of the IGBT 81 becomes zero at the end of the fifth period, that is, the start of the eighth period, so-called zero cross switching is realized. , Switching loss is reduced.

  Below, operation | movement of the control part 9 mentioned above is demonstrated using the flowchart which shows it. The processing shown below is executed by the CPU 91 according to a computer program 99 stored in advance in the storage unit 92 or the RAM 93. Note that a control program for determining a period during which the CPU 91 turns on / off each IGBT by the drive unit 97 is known per se, and thus description thereof will be omitted.

  10 and 11 are flowcharts showing the processing procedure of the CPU 91 that suppresses the switching loss of the IGBTs 82 and 84 in the inverter 8 according to the first embodiment. The process of FIG. 10 is activated when the CPU 91 is notified of the start of discharge. In FIGS. 10 and 11, the IGBTs 81, 82, 83, and 84 are referred to as first, second, third, and fourth IGBTs, respectively. Timers A and B in the figure are included in the timer 95, time the set time, and notify the CPU 91 of the end of the time measurement.

  In the flowcharts shown in FIGS. 10 and 11, for the sake of simplicity, it is assumed that the third period coincides with the second period and the seventh period coincides with the sixth period. However, the present invention is not limited to this. is not. In addition, in the flowchart here, the second and / or third period may end before the first period, or the sixth and / or seventh period ends before the fifth period. It may be a thing.

  When the process of FIG. 10 is activated, the CPU 91 controls the third and fourth IGBTs to be on in the initial state where the first to fourth IGBTs are off (S10), and starts the first period. Thereafter, the CPU 91 sets the length of the first period in the timer A (S11), sets the time difference between the start points of the first and third periods in the timer B (S12), and measures the time by the timers A and B. Start (S13).

  Next, the CPU 91 determines whether or not the timer B has finished counting time (S14), and if not finished (S14: NO), the CPU 91 waits until the timing is finished. When the timer B finishes timing (S14: YES), the CPU 91 controls the first IGBT to be turned on (S15) to start the third period, and further controls the IGBTs 62 and 63 of the inverter 6 to be turned on (S16). ) Start the second period. The third period preferably includes the second period.

  Next, the CPU 91 determines whether or not the timer A has finished counting (S17), and if not finished (S17: NO), the CPU 91 waits until the timing is finished. When the timer A finishes timing (S17: YES), the CPU 91 controls the IGBTs 62 and 63 to be turned off. Further, the CPU 91 controls the third IGBT to be turned off (S19), ends the first, second, and third periods, and starts the fourth period.

  Thereafter, the CPU 91 sets the length of the fourth period in the timer A (S20), and starts measuring time by the timer A (S21). Next, the CPU 91 determines whether or not the timer A has finished timekeeping (S22), and if not finished (S22: NO), the CPU 91 waits until timekeeping is finished. When the timer A finishes timing (S22: YES), the CPU 91 controls the second IGBT to be turned on (S23), starts the fifth period, and controls the fourth IGBT to be turned off (S24). End.

  Moving to FIG. 11, the CPU 91 sets the length of the fifth period in the timer A (S31), and sets the time difference between the start points of the fifth and seventh periods in the timer B (S32). Time measurement by B is started (S33). Next, the CPU 91 determines whether or not the timer B has finished timing (S34), and if not finished (S34: NO), the CPU 91 waits until the timing is finished. When the timer B finishes timing (S34: YES), the CPU 91 controls the third IGBT to be turned on (S35) to start the seventh period, and further controls the IGBTs 61 and 64 of the inverter 6 to be turned on (S36). ) Start the sixth period. The seventh period preferably includes the sixth period.

  Next, the CPU 91 determines whether or not the timer A has finished counting (S37), and if not finished (S37: NO), the CPU 91 waits until the timing is finished. When the timer A finishes counting time (S37: YES), the CPU 91 controls the IGBTs 61 and 64 to be turned off (S38) and ends the sixth period. Further, the CPU 91 controls the first IGBT to be turned off (S39), ends the fifth, sixth, and seventh periods and starts the eighth period.

  Thereafter, the CPU 91 sets the length of the eighth period in the timer A (S40), and starts measuring time by the timer A (S41). Next, the CPU 91 determines whether or not the timer A has finished timekeeping (S42), and if not finished (S42: NO), the CPU 91 waits until timekeeping is finished. When the timer A finishes timing (S42: YES), the CPU 91 controls the fourth IGBT to be turned on (S43), starts the first period of the next cycle, and controls the second IGBT to be turned off (S44). ) End the eighth period.

  Thereafter, the CPU 91 determines whether or not the conversion end is notified from the communication unit 94 (S45). If not notified (S45: NO), the CPU 91 performs the process in step S11 to repeat the process of controlling the inverter 8. Move. On the other hand, when notified of the end of conversion (S45: YES), the CPU 91 ends the processes of FIGS.

  In the first embodiment described above, the IGBTs 83 and 84 correspond to one leg and the IGBTs 81 and 82 correspond to the other leg. However, the IGBTs 81 and 82 correspond to one leg, The IGBTs 83 and 84 may be read as equivalent to the other leg. In this case, in the drawings of FIGS. 5, 7, 9, 10, and 11 and in the description according to FIGS. 3 to 11, the first, second, third, fourth, fifth, sixth, seventh, Each of the eighth periods may be read as the fifth, sixth, seventh, eighth, first, second, third, and fourth periods. Hereinafter, a case where the correspondence relationship between one leg and the other leg and the IGBTs 83 and 84 and the IGBTs 81 and 82 is rewritten is described in parentheses.

  Considering the above replacement, Step S43 to Step S11 to Step S19 (or Step S23 to Step S39) correspond to “a step of controlling one leg to a short-circuit state only for the first period”. Further, from step S16 to step S18 (or from step S36 to step S38), “To apply a predetermined voltage from the application circuit to the other winding of the transformer during the second period of the first period. This corresponds to “control step”. Further, from step S15 to step S19 (or from step S35 to step S39), “the current induced in one winding flows through one arm of the one leg in the reverse direction to return to the first coil. This corresponds to “a step of controlling one arm of the other leg to a short-circuit state only during a third period that overlaps the second period”.

  As described above, according to the first embodiment, the control unit 9 controls the one leg including the IGBTs 83 and 84 (or the IGBTs 81 and 82) to be in a short-circuited state only for the first period, so that the current from the inductor L3 is The leg is conducted, and the inverter 6 is controlled to apply a predetermined voltage to the other winding 72 of the transformer 7 only during the second period. As a result, a voltage is induced in one winding 71 of the transformer 7. The control unit 9 further controls one arm including the IGBT 81 (or IGBT 83) of the other leg to a short-circuited state for the third period that overlaps with the second period. As a result, only during the period in which the second and third periods overlap, the current Ir1 induced in one winding 71 flows forward in one arm of the other leg, and the IGBT 83 (or IGBT 81) of one leg flows. One arm including the air flows in the opposite direction to return to one winding 71. For this reason, the current from the inductor L3 flowing through the IGBT 83 (or IGBT 81) is reduced by the amount of current induced in one of the windings 71. Therefore, it is possible to suppress the switching loss of the IGBT 83 (or IGBT 81).

  In addition, according to the first embodiment, each leg includes the first switching element that is the IGBT 81 or 83 and the second switching element that is the IGBT 82 or 84, so the control unit 9 is the IGBT 81, 83 and the IGBT 82, 84, respectively. By controlling the on / off state, one and the other arm can be controlled to be in a conductive state / non-conductive state. In addition, since the diodes 85, 86, 87, 88 are connected in reverse parallel to the IGBTs 81, 82, 83, 84, respectively, current flows in the reverse direction even if the IGBTs 81, 82, 83, 84 are controlled to be off. be able to.

  Furthermore, according to the first embodiment, the control unit 9 sets the IGBTs 83 and 84 (or the IGBTs 81 and 82) for one of the legs as the basic state where the IGBTs 81, 82, 83, and 84 are controlled to be off. The IGBT 81 (or IGBT 83) is controlled to ON for the third period and is set to the second state for the other leg during that time. The control unit 9 further controls the IGBT 83 (or IGBT 81) to be turned off and the IGBT 84 (or IGBT 82) to be turned on for one of the legs only in the fourth period following the first period, and sets the other state of the leg. The IGBT 81 (or IGBT 83) is turned on and the IGBT 82 (or IGBT 84) is turned off for the second state. Thereby, the current flowing in the inductor L3 via the leg controlled in the short-circuit state in the first period, the IGBT 84 (or IGBT 82) of one leg and the one winding of the transformer 7 in the fourth period. 71 and the other leg IGBT 81 (or IGBT 83) are commutated so that the energy stored in the inductor L3 in the first period is released to one winding 71 of the transformer 7 in the fourth period. The

(Embodiment 2)
In the first embodiment, the IGBTs 81 and 83 correspond to the first switching elements, and the IGBTs 82 and 84 correspond to the second switching elements, whereas in the second embodiment, the IGBTs 82 and 84 correspond to the first switching elements. And IGBT81,83 is a form corresponded to a 2nd switching element. In this case, the IGBTs 82 and 84 correspond to one arm. The circuit configuration of the bidirectional AC / DC converter 1 and the block configuration of the control unit 9 in the second embodiment are the same as those in the first embodiment shown in FIGS. Are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 12 is an explanatory diagram illustrating an example of a basic operation of the inverter 8 according to the second embodiment. Here, the description is given assuming that the IGBTs 81 and 82 correspond to one leg and the IGBTs 83 and 84 correspond to the other leg. As shown in FIG. 12A, the control unit 9 first controls the IGBTs 83 and 84 to be turned off to open the other leg, and controls the IGBTs 81 and 82 to be turned on to set one leg to the first period (first time). The first state to the eighth period are set to the first state, that is, the short circuit state only (see FIG. 14 described later).

  At the time when the first period ends, the control unit 9 controls the IGBT 82 to be turned off and the IGBT 81 to be turned on only in the fourth period as shown in FIG. The IGBT 83 is turned off and the other leg is set to the second state. Here, when FIGS. 12A and 12B are compared with FIGS. 3C and 3D of the first embodiment, the order in which the two arms of each leg are turned on / off is apparently different. Therefore, in order to clarify the difference from the first embodiment, the description of the second embodiment will be continued below.

  When the fourth period ends, the control unit 9 controls the IGBTs 81 and 82 to be in an open state as shown in FIG. 12C, and controls the IGBTs 83 and 84 to be on to control the first period only for the fifth period. Set to the state (short circuit state). At the time when the fifth period ends, the control unit 9 controls the IGBT 82 to be turned on and the IGBT 81 to be turned off only in the eighth period, as shown in FIG. The IGBT 83 is turned on and the other leg is set to the third state. Thereafter, the control unit 9 periodically repeats the control for setting the inverter 8 to the state shown in FIGS. 12A to 12D.

  Next, the surge voltage generated by the operation of the inverter 8 will be described. FIG. 13 is an explanatory diagram illustrating an example of an operation state of the inverter 8 according to the second embodiment. FIG. 14 is a timing chart illustrating an operation when a surge voltage is generated in the IGBT 84 in the inverter 8 according to the second embodiment. is there. 13 indicates the current flowing in the state of FIG. 12A, that is, the first period, and the current indicated by the solid line arrow in FIG. 13 indicates the current flowing in the state of FIG. 12B, that is, the fourth period. Show. In the timing chart shown in FIG. 14 divided into six stages, the horizontal axis is the same time axis (t), and the vertical axis represents voltage or current. The timing chart from the uppermost stage to the fourth stage in FIG. 14 shows the gate voltage Vg applied to the gates of the IGBTs 81, 83, 82, 84 corresponding to the reference numerals. The timing charts at the fifth and sixth stages from the top of FIG. 14 show the current Ir flowing through one winding 71 and the collector-emitter voltage Vc of the IGBT 83, respectively.

  As shown in FIG. 14, when the transition from the first period to the fourth period is performed, that is, when the IGBT 82 is turned off from on and the IGBT 84 is turned on from off, the current from the inductor L3 is changed as shown in FIG. The commutation from the dashed arrow path to the solid arrow path. In this case, at the rise of the current Ir flowing through the leakage inductance 7a, a voltage Vc1 proportional to the temporal change of the current Ir is generated as a surge voltage between the collector and emitter of the IGBT 83 as shown in FIG. A similar surge voltage is also generated between the collector and emitter of the IGBT 82 that is turned off from on at this timing.

  Similarly to the first embodiment, when the transition from the fifth period to the eighth period shown in FIG. 14 is performed, that is, when the IGBT 84 is turned from on to off and the IGBT 82 is turned on from off, the current from the inductor L3 is changed to FIG. From the path indicated by the arrow to the path indicated by the arrow in FIG. 12D. In this case, a voltage Vc2 (not shown) proportional to the temporal change of the current Ir is generated as a surge voltage between the collector and the emitter of the IGBT 81 at the fall of the current Ir flowing through the leakage inductance 7a. A similar surge voltage is also generated between the collector and emitter of the IGBT 84 that is turned off from on at this timing.

  Therefore, in the second embodiment, the surge voltage is first suppressed by the method disclosed in Patent Document 1. FIG. 15 is an explanatory diagram illustrating an example of an operation for suppressing a surge voltage in the inverter 8 according to the second embodiment. FIG. 16 illustrates an operation when the surge voltage is suppressed in the inverter 8 according to the second embodiment. It is a timing chart which shows. A current indicated by a dashed arrow in FIG. 15 indicates a current flowing in the first period, and a current indicated by a solid arrow in FIG. 15 indicates a current flowing in the second period (see FIG. 16) of the first period. . In the timing charts shown in FIG. 16 divided into nine stages, the horizontal axis is the same time axis (t), and the vertical axis represents voltage or current.

  The timing chart from the uppermost stage to the fourth stage in FIG. 16 shows the gate voltage Vg applied to the gates of the IGBTs 81, 83, 82, 84 in correspondence with the reference numerals as in FIG. 14. The timing charts at the fifth and sixth stages from the top in FIG. 16 show the gate voltages Vg applied to the gates of the IGBTs 62 and 63 and the IGBTs 61 and 64 of the inverter 6 in correspondence with the reference numerals. The timing charts at the seventh and eighth stages from the top of FIG. 16 show the current Ir flowing through one winding 71 and the collector-emitter voltage Vc of the IGBT 83, respectively. The timing chart of the ninth stage (bottom stage) from the top in FIG. 16 shows the collector-emitter voltage Vc with a thick solid line and the collector current Ic with a thin solid line for the IGBT 82.

  The controller 9 controls to turn on the IGBTs 62 and 63 so as to apply a predetermined voltage to the other winding 72 of the transformer 7 as shown in FIG. 15 only during the second period of the first period shown in FIG. To do. As a result, as shown in FIG. 16, a current corresponding to the voltage applied to the capacitor C2 and the leakage inductance 7b flows to the other winding 72 of the transformer 7, and a current Ir1 that rises linearly in one winding 71 is induced. To do. For this reason, when the IGBTs 81 and 84 are turned on, the amount of change in the current flowing through one winding 71 is reduced, and the surge voltage generated between the collectors and emitters of the IGBTs 83 and 82 is suppressed. The Since the IGBT 84 does not conduct in the forward direction during the second period, the current Ir1 flows in the reverse direction through the IGBT 83 and returns to the one winding 71.

  The surge voltage applied between the collectors and emitters of the IGBTs 84 and 81 when shifting from the fifth period to the eighth period can be suppressed by the same method as described above. Specifically, as shown in FIG. 16, the IGBTs 61 and 64 are applied so that a voltage having a polarity opposite to the predetermined voltage is applied to the other winding 72 of the transformer 7 only in the sixth period of the fifth period. Can be controlled to ON. Accordingly, as shown in FIG. 16, a current Ir2 that falls linearly can flow in one winding 71, and therefore when one of the windings 71 shifts to the eighth period when the IGBTs 82 and 83 are turned on, The amount of change in the flowing current is reduced, and the surge voltage applied between the collector and emitter of the IGBT 81 in the off state and the IGBT 84 in the transition to the off state can be suppressed.

  Here, paying attention to the 9th (bottom) stage timing chart from the top of FIG. 16, the collector current rises when the collector voltage of the IGBT 82 rises at the end of the first period (that is, the start of the fourth period). The switching loss occurs. Therefore, in the second embodiment, the switching loss when the IGBT 82 is turned off is suppressed by the following method.

  FIG. 17 is an explanatory diagram illustrating an example of an operation for suppressing the switching loss of the IGBT 82 in the inverter 8 according to the second embodiment. FIG. 18 illustrates the switching loss of the IGBT 82 in the inverter 8 according to the second embodiment. 6 is a timing chart showing an operation in the case of The current indicated by the dashed arrow in FIG. 17 indicates the current flowing in the first period, and the current indicated by the solid arrow in FIG. 17 indicates the current flowing in the third period (see FIG. 18) of the first period. . In the timing charts shown in FIG. 18 divided into 10 stages, the horizontal axis is the same time axis (t), and the vertical axis represents voltage or current.

  The timing chart from the uppermost stage to the fourth stage in FIG. 18 shows the gate voltage Vg applied to the gates of the IGBTs 81, 83, 82, and 84 in correspondence with the reference numerals as in FIGS. The hatched portion represents a period during which each IGBT is on. The timing chart from the fifth stage to the eighth stage from the top in FIG. 18 shows the collector-emitter voltage Vc with a thick solid line and the collector current Ic with a thin solid line for each of the IGBTs 81, 83, 82, and 84. is there. The timing charts at the 9th stage and the 10th stage (bottom stage) from the top of FIG. 18 show the gate voltage Vg applied to the gates of the IGBTs 62 and 63 and the IGBTs 61 and 64 of the inverter 6 in correspondence with the reference numerals. is there.

  The control unit 9 controls to turn on the IGBT 84 (corresponding to one arm) of the other leg as shown in FIG. 17 only in the third period of the first period shown in FIG. 18 that overlaps with the second period. To short circuit. As a result, both the IGBTs 82 and 84 are turned on, and the voltage drop is smaller than the path (see FIG. 15) flowing through the IGBTs 81 and 83, so that the current flows through one winding 71 during the period in which the second and third periods overlap. The current Ir1 is refluxed so as to flow through the IGBTs 82 and 84. In this case, since the current Ir1 flows through the IGBT 82 (corresponding to one arm) of one leg in the reverse direction, the current from the inductor L3 flowing through the IGBT 82 is reduced by the amount of the current Ir1.

  The control unit 9 performs the same control as that in the first period in the fifth period. That is, the control unit 9 controls the IGBT 82 to be turned on so that one arm is short-circuited only during a seventh period that overlaps the sixth period in the fifth period. As a result, the IGBTs 82 and 84 are both turned on, and the voltage drop is smaller than the path flowing through the IGBTs 81 and 83. Therefore, the current Ir2 flowing in one winding 71 during the period in which the sixth and seventh periods overlap (FIG. 16). ) Flows back through the IGBTs 82 and 84. In this case, since the current Ir2 flows in the reverse direction through the IGBT 84 of the other leg, the current from the inductor L3 flowing through the IGBT 84 is reduced by the amount of the current Ir2. Therefore, when the period in which the sixth and seventh periods overlap is appropriately set, the collector current of the IGBT 84 becomes zero at the end of the fifth period, that is, the start of the eighth period, and so-called zero cross switching is realized. , Switching loss is reduced.

  The flowchart showing the operation of the control unit 9 is the flowchart shown in FIGS. 10 and 11 of the first embodiment. The first, second, third, and fourth IGBTs are changed to the fourth, third, second, and first IGBTs, respectively. Therefore, the illustration and description thereof are omitted.

  In the second embodiment described above, the IGBTs 81 and 82 correspond to one leg and the IGBTs 83 and 84 correspond to the other leg, but the IGBTs 83 and 84 correspond to one leg, The IGBTs 81 and 82 may be read as equivalent to the other leg. In this case, each of the first, second, third, fourth, fifth, sixth, seventh, and eighth periods in the drawings of FIGS. 14, 16, and 18 and in the description according to FIGS. May be read as the fifth, sixth, seventh, eighth, first, second, third and fourth periods. Hereinafter, a case where the correspondence relationship between one leg and the other leg and the IGBTs 81 and 82 and the IGBTs 83 and 84 is rewritten is described in parentheses.

  As described above, according to the second embodiment, the control unit 9 controls the one leg including the IGBTs 81 and 82 (or the IGBTs 83 and 84) to be in a short-circuited state only for the first period, so that the current from the inductor L3 is The leg is conducted, and the inverter 6 is controlled to apply a predetermined voltage to the other winding 72 of the transformer 7 only during the second period. As a result, a voltage is induced in one winding 71 of the transformer 7. Further, the control unit 9 controls one arm including the IGBT 84 (or IGBT 82) of the other leg to be in a short-circuited state for the third period that overlaps with the second period. Thereby, only during the period in which the second and third periods overlap, the current Ir1 induced in one winding 71 flows forward in one arm of the other leg, and the IGBT 82 (or IGBT 84) of the one leg flows. One arm including the air flows in the opposite direction to return to one winding 71. For this reason, the current from the inductor L3 flowing through the IGBT 82 (or IGBT 84) is reduced by the amount of current induced in one of the windings 71. Therefore, the switching loss of the IGBT 82 (or IGBT 84) can be suppressed.

  Further, according to the second embodiment, each leg includes the first switching element that is the IGBT 82 or 84 and the second switching element that is the IGBT 81 or 83, so that the control unit 9 has the IGBTs 82 and 84 and the IGBTs 81 and 83, respectively. By controlling the on / off state, one and the other arm can be controlled to be in a conductive state / non-conductive state. In addition, since the diodes 85, 86, 87, 88 are connected in reverse parallel to the IGBTs 81, 82, 83, 84, respectively, current flows in the reverse direction even if the IGBTs 81, 82, 83, 84 are controlled to be off. be able to.

  Furthermore, according to the second embodiment, the control unit 9 sets the IGBTs 81 and 82 (or the IGBTs 83 and 84) as the first state for one of the legs based on the state where the GBTs 81, 83, and 84 are controlled to be off. The IGBT 84 (or IGBT 82) is controlled to be turned on for the third period and is set to the second state for the other leg during this time. The control unit 9 further controls the IGBT 82 (or IGBT 84) to be turned off and the IGBT 81 (or IGBT 83) to be turned on for one of the legs for the fourth period following the first period, and sets the other state of the leg. In the second state, the IGBT 84 (or IGBT 82) is turned on and the IGBT 83 (or IGBT 81) is turned off. As a result, the current flowing through the inductor L3 via the leg controlled in the short-circuit state in the first period, the IGBT 81 (or IGBT 83) of one leg and the one winding of the transformer 7 in the fourth period. 71 and the other leg IGBT 84 (or IGBT 82) are commutated so that the energy stored in the inductor L3 in the first period is discharged to one winding 71 of the transformer 7 in the fourth period. The

  Furthermore, according to the first or second embodiment, the control unit 9 controls the IGBTs 83 and 84 and the IGBTs 81 and 82 in the period from the fifth period to the eighth period in the period from the first period to the fourth period. The control is executed in the same manner as the control for the IGBTs 81 and 82 and the IGBTs 83 and 84. The controller 9 also sets the voltage applied to the other winding 72 of the transformer 7 in the sixth period corresponding to the second period to a voltage having a polarity opposite to that in the second period. Therefore, the switching loss of the IGBTs 83 and 81 in the first embodiment and the switching loss of the IGBTs 82 and 84 in the second embodiment can be suppressed alternately during one switching period. Further, an AC voltage can be generated in the other winding 72 of the transformer 7. Further, the length of the period can be changed between the first and fourth periods and the fifth and eighth periods, and the voltage control of the inverter 8 can be finely performed.

  Furthermore, according to the first and second embodiments, the application circuit is the full bridge circuit 60, and the other winding 71 of the transformer 7 is connected between the connection points of the two arms of each leg. The polarity of the voltage to be applied to the other winding 71 can be arbitrarily selected. Further, the AC voltage generated in the other winding 72 can be rectified by the full bridge circuit 60 and converted into a DC voltage.

DESCRIPTION OF SYMBOLS 1 Bidirectional AC / DC converter 2 AC power source 3 Battery 4 Noise filter 5, 6, 8 Inverter 51, 52, 53, 54, 61, 62, 63, 64, 81, 82, 83, 84 IGBT
55, 56, 57, 58, 65, 66, 67, 68, 85, 86, 87, 88 Diode 7 Transformer 71, 72 Winding 7a, 7b Leakage inductance 9 Control unit 91 CPU
92 storage unit 93 RAM
94 Communication unit 95 Timer 96 A / D conversion unit 97 Drive unit 98 Recording medium 99 Computer program 10 Converter T1, T2 AC input / output terminal T3, T4 DC input / output terminal T51, T52, T63, T64, T81, T82 AC input / output Terminals T53, T54, T61, T62, T83, T84 DC input / output terminals C1, C2, C3 capacitors L1, L2, L3 Inductors CT1 Current transformer

Claims (7)

A full-bridge circuit having two legs connected in parallel, an inductor, a transformer with one winding connected between the connection points of the two arms of each leg, and the other winding of the transformer A voltage converter that includes an application circuit that applies a voltage to a wire and a control unit that controls switching of the full bridge circuit, and that converts a DC voltage applied to both ends of each leg through the inductor into an AC voltage. There,
The controller is
One leg is controlled to be short-circuited only for the first period,
Control to apply a predetermined voltage from the application circuit to the other winding of the transformer only in the second period of the first period,
In order to allow the current induced in the one winding to flow in the reverse direction through one arm of the one leg and return, only the third period of the first period overlaps with the second period. A voltage converter for controlling one arm of a leg to a short circuit state.   The voltage conversion apparatus according to claim 1, wherein the two arms of each leg include first and second switching elements having diodes connected in antiparallel. The controller is
Controlling the one leg to the first state in which the first and second switching elements are on only during the first period;
Controlling the other leg to the second state in which the first switching element is on only during the third period;
Only during a fourth period following the first period, the one leg is controlled to a third state in which the second switching element is on, and the other leg is controlled to the second state. Item 3. The voltage converter according to Item 2. The controller is
Controlling the other leg to the first state for a fifth period following the fourth period;
Control to apply a voltage having a polarity different from that of the predetermined voltage from the application circuit to the other winding of the transformer only in the sixth period of the fifth period,
Of the fifth period, the one leg is controlled to the second state only during the seventh period overlapping with the sixth period,
The one leg is controlled to be in the second state and the other leg is in the third state only during the eighth period from the end of the fifth period to the start of the first period in the next switching cycle. The voltage conversion device according to claim 3, wherein the voltage conversion device is controlled in the manner described above. The application circuit comprises a second full bridge circuit having two legs connected in parallel;
5. The voltage conversion according to claim 1, wherein the second full-bridge circuit has the other winding of the transformer connected between connection points of two arms of each leg. 6. apparatus. A full-bridge circuit having two legs connected in parallel, an inductor, a transformer with one winding connected between the connection points of the two arms of each leg, and the other winding of the transformer A voltage converter that controls switching of the full-bridge circuit in a voltage converter that converts a DC voltage applied to both ends of each leg through the inductor into an AC voltage. Control method,
Controlling one leg to a short circuit state for a first period;
Controlling to apply a predetermined voltage from the application circuit to the other winding of the transformer only in the second period of the first period;
In order to allow the current induced in the one winding to flow in the reverse direction through one arm of the one leg and return, only the third period of the first period overlaps with the second period. Controlling one of the legs to a short-circuited state. A full-bridge circuit having two legs connected in parallel, an inductor, a transformer with one winding connected between the connection points of the two arms of each leg, and the other winding of the transformer An application circuit for applying a voltage to a line, and for causing a computer to control switching of the full bridge circuit in a voltage converter that converts a DC voltage applied to both ends of each leg through the inductor into an AC voltage. Computer program,
On the computer,
Controlling one leg to a short circuit state for a first period;
Controlling to apply a predetermined voltage from the application circuit to the other winding of the transformer only in the second period of the first period;
In order to allow the current induced in the one winding to flow in the reverse direction through one arm of the one leg and return, only the third period of the first period overlaps with the second period. And a step of controlling one arm of the leg to a short-circuit state.

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