WO2017090118A1

WO2017090118A1 - Power conversion device and rail vehicle

Info

Publication number: WO2017090118A1
Application number: PCT/JP2015/083052
Authority: WO
Inventors: 隆誠藤田; 秋山　悟; 将太三次
Original assignee: 株式会社日立製作所
Priority date: 2015-11-25
Filing date: 2015-11-25
Publication date: 2017-06-01
Also published as: JP6467524B2; JPWO2017090118A1

Abstract

Provided are a power conversion device and a rail vehicle in which the reduction of power loss can be achieved. In the power conversion device, switching elements S1-S4 apply an AC voltage to the primary coil L1 of a transformer TR. A diode circuit DDU includes: rectifier diodes for rectifying the output voltage of the secondary coil L2 of the transformer TR; and free-wheeling diodes for allowing free-wheeling current to flow. A filter circuit FLU smooths the output voltage of the diode circuit DDU. A resonant circuit RSU is provided between the diode circuit DDU and the filter circuit FLU and includes a resonant inductor Lr, a resonant capacitor Cr, and a resonant switch Sr which are connected in series. A control circuit CTLU turns on the resonant switch Sr during a period when the switching elements S1-S4 are off.

Description

Power converter and railway vehicle

The present invention relates to a power conversion device and a railway vehicle, and, for example, to a technology of an insulation type DC-DC converter.

For example, Patent Document 1 shows a configuration in which a resonance circuit is provided between a switching element and a smoothing filter in a chopper type DC-DC converter. The resonance circuit includes a reactor, a capacitor, a resonance switch, and a diode, and the resonance switch is controlled to be turned on in an on period when the switching element is turned off. Thereby, the switching element can be turned off in a state of zero current.

Patent Documents

2 and 3 show a configuration in which an isolated DC-DC converter includes a resonance circuit on the output side of the rectifier circuit on the secondary side of the transformer.

The resonance circuit of Patent Document 2 includes a reactor, a capacitor, and a resonance switch, and the resonance switch is controlled to be turned on in an on period when the switching element on the primary side of the transformer is turned off. Thereby, the switching element on the primary side can be turned off in a substantially zero current state. Furthermore, by providing a reactor in the resonant circuit and reducing the leakage inductance of the transformer, it is possible to suppress overvoltage that may occur during recovery of the rectifier circuit or when the transformer is turned on on the primary side. On the other hand, the resonant circuit of Patent Document 3 has a configuration in which a reactor is connected in series with a capacitor and a resonant switch. The reactor is used as an element for resonance operation and also as an element for suppressing an inrush surge current when the resonance switch is turned on.

JP-A-4-275060 JP 2012-75210 A JP 2014-195373 A

For example, in a power supply device that supplies power to lighting, air conditioning, or the like of a railway vehicle or the like, an overhead wire DC voltage (for example, several kV) is converted into a commercial frequency (for example, 60 Hz) AC voltage, and the voltage level is converted by a transformer. Thus, a method of generating a commercial power supply (for example, AC440V of 60 Hz) is used. However, if a commercial frequency AC voltage is converted using a transformer in this way, a large transformer is required, which may increase the size of the power supply device.

Therefore, it is beneficial to use a system in which the DC voltage of the overhead wire is once converted into a predetermined DC voltage via an insulated DC-DC converter and then converted into a commercial power source via an inverter. In this case, since the high-frequency transformer can be used in the insulated DC-DC converter, it is possible to reduce the size of the transformer and hence the power supply device. However, when such a method is used, since a relatively large number of switching elements are required, there is a concern about power loss associated therewith. For example, when the method of Patent Document 2 or the like is used, it is possible to reduce power loss, but further reduction of power loss is required particularly in high power applications typified by railway vehicles.

The present invention has been made in view of such circumstances, and one of its purposes is to provide a power conversion device and a railway vehicle capable of realizing a reduction in power loss.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

Among the inventions disclosed in the present application, the outline of a typical embodiment will be briefly described as follows.

The power conversion device according to the present embodiment includes a transformer, a switching element, a diode circuit, a filter circuit, a resonance circuit, and a control circuit. The switching element applies an AC voltage to the primary coil of the transformer. The diode circuit includes a rectifier diode that rectifies the output voltage of the secondary coil of the transformer, and a freewheeling diode that flows a freewheeling current. The filter circuit smoothes the output voltage of the diode circuit. The resonant circuit is provided between the diode circuit and the filter circuit and includes a resonant inductor, a resonant capacitor, and a resonant switch connected in series. The control circuit turns on the resonance switch in a period in which the switching element is off.

Of the inventions disclosed in the present application, the effects obtained by the representative embodiments will be briefly described, and a reduction in power loss can be realized.

1 is a circuit diagram illustrating an example configuration of a power conversion device according to a first embodiment of the present invention. It is the schematic explaining the main operation examples in the power converter device of FIG. It is the schematic explaining the main operation examples in the power converter device of FIG. It is a wave form diagram which shows the detailed operation example in the power converter device of FIG. FIG. 2 is a schematic diagram illustrating a configuration example of a main part of a control circuit CTLU in the power conversion device of FIG. 1. FIG. 4B is a flowchart showing an example of main processing contents in the state (ST2) in the state machine circuit of FIG. 4A. In the power converter device by Embodiment 1 of this invention, it is a wave form diagram which shows an example of the main effects. In the power converter device by Embodiment 2 of this invention, it is a circuit diagram which shows the structural example. In the power converter device by Embodiment 3 of this invention, it is a circuit diagram which shows the structural example. It is the schematic explaining the example of main operations in the power converter device of FIG. It is the schematic explaining the example of main operations in the power converter device of FIG. FIG. 8 is a waveform diagram showing a detailed operation example in a powering mode operation in the power conversion device of FIG. 7. FIG. 8 is a waveform diagram showing a detailed operation example during a regeneration mode operation in the power conversion device of FIG. 7. It is the schematic which shows the example of a structure in the rail vehicle by Embodiment 4 of this invention. It is the schematic which shows the structural example of the inverter apparatus in the main converter of FIG. It is the schematic which shows the structural example of the PWM converter apparatus in the main converter of FIG. It is the schematic which shows the other structural example in the power converter device by one embodiment of this invention.

In the following embodiment, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant, and one is the other. Some or all of the modifications, details, supplementary explanations, and the like are related. Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

(Embodiment 1)
<Configuration of power converter>
FIG. 1 is a circuit diagram showing a configuration example of the power conversion device according to the first embodiment of the present invention. The power converter shown in FIG. 1 is an insulated DC-DC converter. The power converter includes a transformer TR including a primary coil L1 and a secondary coil L2, a primary side drive circuit L1DU and a capacitor C1 provided on the primary side of the transformer TR, and a diode circuit DDU provided on the secondary side of the transformer TR. And a resonance circuit RSU and a filter circuit FLU, and a control circuit CTLU. A power source E that generates a DC voltage is connected in parallel to the capacitor C1. A load circuit LD is connected to the tip of the filter circuit FLU. In practice, a leakage inductor Lleak due to leakage power, wiring impedance, etc. of the transformer TR is equivalently connected in series to the secondary coil L2.

The primary side drive circuit L1DU is a full bridge circuit in this example, and is supplied with a DC voltage from the power source E and applies an AC voltage to the primary coil L1. The primary drive circuit L1DU includes switching elements S1 and S4 that apply a positive AC voltage to the primary coil L1, and switching elements S2 and S3 that apply a negative AC voltage to the primary coil L1. Each of the switching elements S1 to S4 is composed of an IGBT (Insulated Gate Gate Bipolar Transistor) in this example. In addition, free-wheeling diodes D1 to D4 are connected in parallel to the switching elements S1 to S4, respectively.

The diode circuit DDU is a full bridge diode circuit including diodes D5 to D8 in this example. The diodes D5 and D8 flow a return current when the output voltage of the secondary coil L2 is rectified according to the positive AC voltage of the primary coil L1 and when the switching elements S1 to S4 of the primary side drive circuit L1DU are turned off. Perform reflux operation. The diodes D6 and D7 pass a reflux current when the output voltage of the secondary coil L2 is rectified according to the negative AC voltage of the primary coil L1 and when the switching elements S1 to S4 of the primary side drive circuit L1DU are turned off. Perform reflux operation.

Filter circuit FLU includes an inductor L connected in series to the output of diode circuit DDU and a capacitor C2 connected in parallel to the output of diode circuit DDU, and smoothes the output voltage (and output current) of diode circuit DDU. . The resonant circuit RSU is provided between the diode circuit DDU and the filter circuit FLU, and is connected in series with a capacitor (referred to as a resonant capacitor) Cr, an inductor (referred to as a resonant inductor) Lr, and a switching element (referred to as a resonant switch) Sr. including. The resonance capacitor Cr, the resonance inductor Lr, and the resonance switch Sr are connected in series between two nodes that are output nodes of the diode circuit DDU, and are also connected in series between two nodes that are input nodes of the filter circuit FLU. Connected.

In this example, the resonance switch Sr is constituted by a MOSFET (Metal Oxide Semiconductor Semiconductor Field Field Effect Transistor). A diode (referred to as a resonance diode) Dr is connected in parallel to the resonance switch Sr. The resonant diode Dr is, for example, a MOSFET built-in diode. The control circuit CTLU controls on / off of the switching elements S1 to S4 and the resonance switch Sr of the primary side drive circuit L1DU.

Although not particularly limited, the power source E generates a DC voltage such as several kV, for example, and a DC voltage such as several hundred V is generated from the filter circuit FLU. Further, each element (Cr, Lr, Sr) in the resonance circuit RSU may be connected in series, and the connection order is not particularly limited.

<< Schematic operation of power converter >>
2A and 2B are schematic diagrams for explaining a main operation example in the power conversion apparatus of FIG. First, as shown in FIG. 2A, the control circuit CTLU in FIG. 1 controls the switching elements S1 and S4 to be on, thereby transmitting power from the primary coil L1 to the secondary coil L2 (referred to as power transmission operation). ) Is executed (step SP100). In this case, the AC voltage output from the secondary coil L2 is rectified by the diodes D5 and D8 operating as rectifier diodes, smoothed by the filter circuit FLU, and then supplied to the load circuit LD (step SP100).

Next, the control circuit CTLU shifts to the reflux operation as described in FIG. 2B by turning off the switching elements S1 and S4, and turns on the resonance switch Sr as a pre-processing at the time of the transition. As a result, the resonance current ir flows through the resonance circuit RSU (step SP101), and after the time determined by the resonance frequency of the resonance circuit RSU (and the leakage inductor Lleak) has elapsed, the resonance current (−ir) in the reverse direction flows. (Step SP102).

When the reverse resonance current (−ir) becomes equal to the load current iLD, the current flowing through the secondary coil L2 becomes zero, and accordingly, the current flowing through the primary coil L1 (that is, the current flowing through the switching elements S1 and S4). Will also be zero. At this time, strictly speaking, a current corresponding to the exciting current of the transformer TR flows through the switching elements S1 and S4. However, since the current is very small, it is ignored in this specification. The control circuit CTLU turns off the switching elements S1 and S4 in a state where the current flowing through the switching elements S1 and S4 becomes zero in this way (step SP103). As a result, switching loss can be reduced.

When the switching elements S1, S4 are turned off, the flow returns to the reflux operation as shown in FIG. 2B. That is, in FIG. 2B, the control circuit CTLU controls the switching elements S1 to S4 to turn off, thereby causing the current flowing through the filter circuit FLU to flow back through the diodes D5 to D8 that operate as freewheeling diodes (step SP104). . Next, the control circuit CTLU turns on the switching elements S2 and S3 to shift to the same power transmission operation as in FIG. 2A (however, the polarity is reversed). The resonant switch Sr is turned on while the switching elements S1 to S4 are off.

Thereby, the resonance current ir flows through the resonance circuit RSU (step SP105), and after the time determined by the resonance frequency of the resonance circuit RSU has elapsed, the resonance current (-ir) in the reverse direction flows (step SP106). When the reverse resonance current (−ir) becomes equal to the load current iLD, the currents of the diodes D5 to D8 become zero. The control circuit CTLU turns off the switching elements S2 and S3 in such a state that the current flowing through the diodes D5 and D8 becomes zero (step SP107).

As a result, the recovery loss of the diodes D5 and D8 can be reduced. That is, when the switching elements S2 and S3 are turned on in a state in which a return current (in other words, forward current) flows through the diodes D5 to D8 as shown in FIG. 2B, the diodes are similar to the diodes D6 and D7 in FIG. 2A. A reverse bias is applied to D5 and D8. It is known that when a diode is switched from a forward bias (a state in which a forward current flows) to a reverse bias, a large current called a recovery current flows and a power loss called a recovery loss occurs. When the method of FIG. 2B is used, since the diode can be switched from the zero current state to the reverse bias, no recovery current flows.

<Detailed operation of power converter>
FIG. 3 is a waveform diagram showing a detailed operation example in the power conversion device of FIG. 1. In FIG. 3, vT is the voltage of the primary coil L1, and iT is the current of the primary coil L1. i1 to i4 are currents flowing through the switching elements S1 to S4 and / or diodes D1 to D4, respectively, and i5 to i8 are currents flowing through the diodes D5 to D8, respectively. ir is a current (resonant current) flowing through the resonance circuit RSU, vCr is a voltage of the resonance capacitor Cr, and vLr is a voltage of the resonance inductor Lr. vLleak is the voltage of the leakage inductor Lleak. Here, for convenience of explanation, it is assumed that the turns ratio of the transformer TR is 1: 1.

First, in a period before time t1, the control circuit CTLU controls the switching elements S1 and S4 to be on and the switching elements S2 and S3 to be off. Thereby, the voltage vT becomes equal to the DC voltage of the power source E. Also, each of the currents iT, i1, i4, i5, i8 is equal to the load current iLD.

Next, in the period from time t1 to time t2, as shown in FIG. 2A, the control circuit CTLU turns on the resonance switch Sr. As a result, the currents iT, i1, i4, i5, and i8 have values obtained by adding the resonance current ir to the load current iLD. After that, when the resonance current ir becomes smaller than zero (that is, when the polarity of the resonance current ir is reversed), the control circuit CTLU turns off the resonance switch Sr because the current path moves to the resonance diode Dr.

Subsequently, during the period from time t2 to t3, the resonance current (−ir) becomes equal to the load current iLD. Accordingly, as described in FIG. 2A, the currents iT, i1, i4, i5, and i8 become zero. In this state, the control circuit CTLU turns off the switching elements S1 and S4. As a result, since the switching elements S1 and S4 can be turned off in a state where the current is zero, switching loss can be reduced. Thereafter, during the period from time t3 to time t4, current continues to flow through the resonant diode Dr until the discharge of the resonant capacitor Cr is completed.

Next, at time t4, the discharge of the resonance capacitor Cr ends (the resonance current becomes zero), and a reflux path is formed in the diodes D5 to D8 instead of the resonance diode Dr. As a result, during the period from time t4 to time t5, each of the currents (return currents) i5 to i8 is “iLD / 2”.

In the period from time t5 to t6, the control circuit CTLU turns on the resonance switch Sr as shown in FIG. 2B in a state in which the return current flows (in other words, the period in which the switching elements S1 to S4 are off). To do. As a result, each of the currents i5 to i8 is “(iLD + ir) / 2”. Thereafter, when the resonance current ir becomes smaller than zero (that is, when the polarity of the resonance current ir is inverted), the control circuit CTLU turns off the resonance switch Sr.

Subsequently, during the period from time t6 to time t7, as described with reference to FIG. 2B, the resonance current (−ir) becomes equal to the load current iLD, and accordingly, the currents i5 to i8 become zero. Further, the resonance current ir continues to flow through the resonance diode Dr until the discharge of the resonance capacitor Cr is completed. In this state, at time t7, the control circuit CTLU turns on the switching elements S2 and S3. As a result, the voltage vT becomes a voltage (negative voltage) having a polarity opposite to that of the DC voltage of the power supply E, and the diodes D5 and D8 are turned off with the reverse bias. However, at this time, since the current is zero, no recovery loss occurs.

Thereafter, at times t7 to t8, the currents i2, i3, i6, i7 and the current (−iT) are equal to the load current iLD, and the primary side drive circuit L1DU and A similar operation is performed in a state where the current paths in the diode circuit DDU are switched. In the period from time t8 to t14, the same operation as in the period from time t1 to t7 is performed.

<< Schematic configuration and operation of control circuit >>
FIG. 4A is a schematic diagram illustrating a configuration example of a main part of the control circuit CTLU in the power conversion device of FIG. 1. The control circuit CTLU in FIG. 4A includes, for example, a detection circuit such as an analog-digital converter ADC, a state machine (sequencer) circuit SMU, and a driver circuit DVU. The analog-digital converter ADC detects, for example, the source-drain voltage Vds of the resonance switch (MOSFET) in FIG. 1 and currents i5 to i8 flowing through the diodes D5 to D8.

The currents i5 to i8 do not need to be detected individually. For example, by connecting a general current sensor using the Hall effect, current transformer, or the like to the output node of the diode circuit DDU of FIG. You may detect as an output current of DDU. The state machine circuit SMU includes three states ST1A, ST1B, and ST2, and shifts between the states ST1A and ST2, and also shifts between the states ST1B and ST2.

As shown in FIG. 2A, the state ST1A is a state in which the above-described power transmission operation is executed mainly by controlling the switching elements S1 and S4 to be on (switching elements S2 and S3 are off). Similarly, the state ST1B is a state in which the power transmission operation described above is executed mainly by controlling the switching elements S2 and S3 to be on (switching elements S1 and S4 are off). On the other hand, as shown in FIG. 2B, the state ST2 is a state in which the above-described reflux operation is performed mainly by turning off the switching elements S1 to S4. The driver circuit DVU controls on / off of the switching elements S1 to S3 and the resonance switch Sr based on a control signal output from the state machine circuit SMU.

FIG. 4B is a flowchart showing an example of main processing contents in the state (ST2) in the state machine circuit of FIG. 4A. 4B, first, the state machine circuit SMU turns off the switching elements S1 and S4 when the transition source is the state ST1A, and turns off the switching elements S2 and S3 when the transition source is the state ST1B (step SP301). ). Thereafter, the state machine circuit SMU turns on the resonance switch Sr at a predetermined timing, for example (step SP302).

Next, the state machine circuit SMU waits for the polarity of the resonance current ir of the resonance circuit RSU to be reversed as shown at time t6 in FIG. 3 (step SP303). Specifically, the state machine circuit SMU may monitor the polarity of the voltage Vds of the resonance switch Sr detected by the analog-digital converter ADC of FIG. 4A, for example. When the polarity of the resonance current ir is reversed, the state machine circuit SMU turns off the resonance switch Sr (step SP304).

Subsequently, the state machine circuit SMU waits for the currents (circulation currents) i5 to i8 of the diodes D5 to D8 to fall below a predetermined threshold current Ith (for example, a current close to zero) (step SP305). Specifically, the state machine circuit SMU may monitor the output current of the diode circuit DDU detected by the analog-digital converter ADC of FIG. 4A, for example. When the currents i5 to i8 decrease below the predetermined threshold current Ith, the state machine circuit SMU transitions to the state ST1A or the state ST1B (step SP306).

Although not shown, the state machine circuit SMU monitors the output current of the diode circuit DDU even when the state ST1A transitions to the state ST2 in, for example, step SP103 in FIG. 2A (time t3 in FIG. 3). By doing so, it can be determined whether or not the currents i1 and i4 have become zero. Further, the state machine circuit SMU and the analog-digital converter ADC in the control circuit CTLU of FIG. 4A are configured by hardware such as an ASIC (Application Specific Integrated Circuit), a microcontroller (MCU: Micro Control Unit), or the like. It is also possible to implement by program processing of a processor using.

Further, the detection circuit for detecting each current is of course not limited to the analog-digital converter ADC as shown in FIG. 4A, but may be hardware such as a comparator. The present invention is not limited to the example, and a current sensor or the like may be appropriately provided at a place necessary for executing the operation of FIG. In the example of FIG. 4B, the control timing of each of the switching elements S1 to S4 and the resonance switch Sr is determined based on the detection result of the current or the like. It is also possible to determine the timing by design values.

That is, for example, in step SP107 in FIG. 2B (time t7 in FIG. 3), the switching elements S2 and S3 are preferably turned on with the currents i5 and i8 being zero. However, the currents i5 and i8 do not necessarily have to be zero. If the currents i5 and i8 are reduced as compared with the case where the resonance switch Sr is not used, the recovery loss can be reduced accordingly. Here, for example, the length of each period from time t5 to time t7 in FIG. 3 can be predicted to some extent at the design stage according to the characteristics of the resonance circuit RSU. Therefore, even if a slight variation according to manufacturing variation or environment occurs in the length of the period, the effect of reducing the recovery loss can be sufficiently obtained.

<< Main effects of the first embodiment >>
FIG. 5 is a waveform diagram showing an example of main effects in the power conversion device according to Embodiment 1 of the present invention. FIG. 5 also shows a waveform diagram when the method of the first embodiment is not applied as a comparative example. First, in the comparative example, the resonance switch Sr is not turned on as a pre-processing when shifting from the return operation to the power transmission operation (here, the switching elements S2 and S3 are turned on). In this case, for example, in the diode D5, in addition to the forward conduction loss occurring in the period of the reflux operation, a large recovery loss can be caused by the recovery current and the reverse bias generated when the switching elements S2 and S3 are turned on. .

On the other hand, when the method of the first embodiment is applied, in the diode D5, forward conduction loss occurs in the period of the return operation, but no recovery current is generated when the switching elements S2 and S3 are turned on. Can be reduced. As a result, for example, the power loss can be reduced together with the effect of reducing the switching loss when the switching element is turned off as shown in step SP103 in FIG. 2A and time t3 in FIG.

(Embodiment 2)
<< Configuration of Power Converter (Modification) >>
FIG. 6 is a circuit diagram illustrating a configuration example of the power conversion device according to the second embodiment of the present invention. The power converter shown in FIG. 6 differs from the configuration example of FIG. 1 in the configuration of the resonance circuit RSU1. As in the case of FIG. 1, the resonance circuit RSU1 of FIG. 6 is provided between the diode circuit DDU and the filter circuit FLU, and includes a resonance inductor Lr, a resonance capacitor Cr, and a resonance switch Sr connected in series.

The resonant inductor Lr, the resonant capacitor Cr, and the resonant switch Sr are connected in series between two nodes that are output nodes of the diode circuit DDU. However, unlike the case of FIG. 1, a resonant capacitor Cr and a resonant switch Sr are connected in series between two nodes that are input nodes of the filter circuit FLU, and the resonant inductor Lr is connected to one of the output nodes of the diode circuit. Are provided between one of the input nodes of the filter circuit FLU.

Even if such a configuration is used, the same effect can be obtained by performing the same operation as in the first embodiment.

(Embodiment 3)
<< Configuration of power converter (application example) >>
FIG. 7 is a circuit diagram showing a configuration example of the power conversion device according to the third embodiment of the present invention. The power conversion device shown in FIG. 7 differs from the configuration example of FIG. 1 in the configurations of the diode circuit DDU1 and the control circuit CTLU1. The diode circuit DDU1 of FIG. 7 includes switching elements (referred to as synchronous switches) S5 to S8 connected in parallel to the diodes D5 to D8, respectively. Each of the synchronous switches S5 to S8 is configured by, for example, a MOSFET. In addition to performing the same operation with the same configuration as in FIG. 1, the control circuit CTLU1 further controls on / off of the synchronous switches S5 to S8.

Schematically, the control circuit CTLU1 controls the synchronous switches S5 and S8 to be on during the period in which the diodes D5 and D8 perform the rectification operation and the return operation as described in the first embodiment. Similarly, the control circuit CTLU1 controls the synchronous switches S6 and S7 to be on during the period in which the diodes D6 and D7 perform the rectification operation and the return operation. Thereby, it is possible to reduce the conduction loss during the reflux operation as shown in FIG. Further, it is possible to reduce conduction loss when the diodes D5 to D8 perform the rectification operation.

<< Schematic operation of power converter (application example) >>
8A and 8B are schematic diagrams for explaining a main operation example in the power conversion device of FIG. The power conversion device shown in FIG. 7 includes the synchronous switches S5 to S8, so that the power transmission operation (including the return operation) from the primary side to the secondary side of the transformer TR as described in the first embodiment is performed. In addition to the operation in the mode, it is also possible to perform a power transmission operation (referred to as an operation in the regeneration mode) from the secondary side of the transformer TR to the primary side. 8A and 8B show schematic operation contents of the operation in the regeneration mode. In this case, the load circuit LD is a motor or the like that can generate regenerative power.

First, as shown in FIG. 8A, the control circuit CTLU1 in FIG. 7 controls the synchronous switches S5 to S8 to be turned on so that the regenerative power from the load circuit LD is accumulated in the inductor L of the filter circuit FLU. (Referred to as regenerative power storage operation) is executed (step SP400). Thereafter, the control circuit CTLU1 turns off the synchronous switches S6 and S7 to shift to the regenerative power transmission operation as described in FIG. 8B, but turns on the resonance switch Sr as preprocessing at the time of the shift.

Thereby, the resonance current ir flows through the resonance circuit RSU (step SP401). When the resonance current ir becomes equal to the load current (−iLD) accompanying the regenerative power, the current flowing through the synchronous switches S5 to S8 becomes zero. The control circuit CTLU1 turns off the synchronous switches S6 and S7 in a state where the current flowing through the synchronous switches S6 and S7 becomes zero in this way (step SP402). As a result, switching loss in the synchronous switches S6 and S7 can be reduced.

Thereafter, in the resonance circuit RSU, after a time determined by the resonance frequency of the resonance circuit RSU has elapsed, a resonance current (-ir) in the reverse direction flows (step SP403). This resonance current (−ir) flows to the secondary coil L2 through the synchronous switches S5 and S8 which are turned on in step SP402 during the regenerative power transmission operation as shown in FIG. 8B.

In FIG. 8B, as described in FIG. 8A, the control circuit CTLU1 controls the synchronous switches S5 and S8 to be turned on and the synchronous switches S6 and S7 to be turned off, so that the regenerative power and resonance accumulated in the inductor L are controlled. An operation (referred to as regenerative power transmission operation) of transmitting electric power accompanying the current (−ir) from the secondary coil L2 to the primary coil L1 is executed (step SP403). The regenerative power transmitted to the primary coil L1 is transmitted to the power source E via the return diodes D1 and D4 of the switching elements S1 and S4 (step SP403).

After that, the control circuit CTLU1 turns on the synchronous switches S6 and S7 to shift to the regenerative power storage operation as described in FIG. 8A, but turns on the resonance switch Sr as pre-processing at the time of the shift. Thereby, the resonance current ir flows through the resonance circuit RSU (step SP404). When the resonance current ir becomes equal to the load current (−iLD) associated with the regenerative power, the current flowing through the secondary coil L2 becomes zero, and the current flowing through the primary coil L1 (in other words, the current flowing through the diodes D1 and D4). ) Is also zero.

The control circuit CTLU1 turns on the switching elements S6 and S7 in a state where the current flowing through the diodes D1 and D4 becomes zero in this way (step SP405). As a result, recovery loss in the diodes D1 and D4 can be reduced. That is, if the diode D1 and D4 shift from the forward current flow to the regenerative power storage operation as shown in FIG. 8A, the diodes D1 and D4 are switched from the forward bias to the reverse bias, and recovery at that time is performed. Recovery loss can occur due to the current. On the other hand, when the diodes D1 and D4 are switched to the reverse bias in the state where the currents flowing through the diodes D1 and D4 are zero as shown in FIG. 8B, no recovery current is generated.

Thereafter, after a time determined by the characteristics of the resonance circuit RSU and the like has elapsed, a resonance current (-ir) in the reverse direction flows through the resonance circuit RSU (step SP406). The resonance current (−ir) is accumulated in the inductor L of the filter circuit FLU during the regenerative power accumulation operation as shown in FIG. 8A.

Thereafter, the control circuit CTLU1 controls the synchronous switches S6 and S7 to be turned on and the synchronous switches S5 and S8 to be turned off after the regenerative power storage operation (that is, the synchronous switches S5 and S8 are turned off). A regenerative power transmission operation similar to that in the case of FIG. As described above, the control circuit CTLU1 reduces the recovery loss by turning on the resonance switch Sr in a period in which the switching elements S1 to S4 are off (in other words, a period in which forward current can flow in the diodes D1 to D4). To do.

<< Detailed operation of power converter (application example) >>
FIG. 9 is a waveform diagram showing a detailed operation example in the power running mode operation in the power conversion device of FIG. In FIG. 9, on / off signals of the synchronous switches S5 to S8 are added to FIG. 3 described above. Each of the currents i5 to i8 is a current that flows through the corresponding diode and / or synchronous switch. Here, the description will be made focusing on differences from the case of FIG.

First, in a period before time t2, the diodes D5 and D8 perform rectifying operation as the switching elements S1 and S4 are turned on, so the control circuit CTLU1 controls the synchronous switches S5 and S8 to be turned on. Thereby, since the currents i5 and i8 mainly flow through the synchronous switches S5 and S8, the conduction loss during the rectifying operation of the diodes D5 and D8 can be reduced.

Next, as in the case of FIG. 3, the resonance current (−ir) in the reverse direction flows through the resonance diode Dr from time t2 to t3, and the resonance current (−−) in the reverse direction from time t3 to t4. ir) becomes zero, and the reflux current starts to flow through the diodes D5 to D8. During this period, since the diodes D5 and D8 perform the recirculation operation, the control circuit CTLU1 continues to keep the synchronous switches S5 and S8 on.

Further, the control circuit CTLU1 turns on the synchronous switches S6 and S7 at time t4 in response to the start of the return operation of the diodes D6 and D7 from time t3 to t4. Subsequently, at times t4 to t6, the diodes D5 to D8 continue to perform the reflux operation, so the control circuit CTLU1 continues to keep the synchronous switches S5 to S8 on. As a result, the currents i5 to i8 mainly flow through the synchronous switches S5 to S8, so that the conduction loss during the return operation of the diodes D5 to D8 can be reduced.

Here, from time t6 to t7, the control circuit CTLU1 turns off the synchronous switches S5 and S8 before the currents i5 and i8 become zero in response to the turn-on of the resonance switch Sr at time t5, and the path of the currents i5 and i8. Is transferred to diodes D5 and D8. At time t7, the control circuit CTLU1 turns on the switching elements S2 and S3 when the currents i5 and i8 become zero. At this time, since the synchronous switches S5 and S8 are already in the off state, a reverse bias is applied to the diodes D5 and D8. However, since the currents i5 and i8 are zero, no recovery current is generated.

After that, from time t7 to t9, the diodes D6 and D7 perform rectifying operation as the switching elements S2 and S3 are turned on, so that the control circuit CTLU1 continues to keep the synchronous switches S6 and S7 on. In the period from time t9 to t14, the same operation is performed in the state where the current paths in the primary side drive circuit L1DU and the diode circuit DDU1 are exchanged in the period from time t2 to t7.

FIG. 10 is a waveform diagram showing a detailed operation example during the regeneration mode operation in the power conversion device of FIG. Here, for convenience of explanation, it is assumed that the turns ratio of the transformer TR is 1: 1. First, in a period before time t1, the control circuit CTLU1 performs a regenerative power transmission operation as shown in FIG. 8B. That is, the control circuit CTLU1 controls the synchronous switches S5 and S8 to be on and the synchronous switches S6 and S7 to be off. As a result, each of the currents i5, i8, iT, i1, i4 is equal to the load current iLD. At this time, since the load current iLD has a negative polarity, the currents i5, i8, iT, i1, i4 also have a negative polarity. Further, during this period, the voltage vT of the transformer TR becomes a positive voltage, and negative currents i1 and i4 flow through the diodes D1 and D4.

Next, in the period from time t1 to time t2, the control circuit CTLU1 turns on the resonance switch Sr as shown in step SP404 in FIG. 8B. Thereby, the resonance current ir flows, and each of the currents i5, i8, iT, i1, i4 becomes “iLD + ir”. Since “iLD” has a negative polarity and “ir” has a positive polarity, each of the currents i5, i8, iT, i1, and i4 approaches zero as the resonance current ir increases.

Subsequently, during the period from time t2 to time t3, the resonance current ir becomes equal to “−iLD”, and the currents i5, i8, iT, i1, i4 become zero. In this state, the control circuit CTLU1 turns on the synchronous switches S6 and S7, and shifts to a regenerative power storage operation as shown in FIG. 8A. When the synchronous switches S6 and S7 are turned on, the diodes D1 and D4 are automatically turned off because a reverse bias of “V / 2” is applied when the DC voltage of the power source E is “V”. At this time, since the currents of the diodes D1 and D4 are zero, the recovery loss can be reduced. Further, since the resonance current ir has positive polarity (> 0), the control circuit CTLU1 keeps the resonance switch Sr on.

Next, from time t3 to t4, the resonance current ir becomes negative (≦ 0), and the current flows through the resonance diode Dr. When the polarity of the resonance current ir is thus inverted, the control circuit CTLU1 turns off the resonance switch Sr. The resonance current ir continues to flow until the discharge of the resonance capacitor Cr is completed, and accordingly, each of the currents i5 to i8 becomes “(iLD + ir) / 2”. Further, power is not transmitted to the transformer TR, and regenerative power is accumulated in the inductor L of the filter circuit FLU.

After that, at time t4, the discharge of the resonance capacitor Cr ends, and from time t4 to t5, each of the currents i5 to i8 settles to “iLD / 2”. Subsequently, at time t5 to t6, the control circuit CTLU1 turns on the resonance switch Sr as in step SP401 of FIG. 8A. As a result, the resonance current ir flows and each of the currents i5 to i8 becomes “(iLD + ir) / 2”. Since “iLD” has a negative polarity and “ir” has a positive polarity, each of the currents i5 to i8 approaches zero as the resonance current ir increases.

Next, at time t6, the resonance current ir becomes equal to “−iLD”, and each of the currents i5 to i8 becomes zero. In this state, the control circuit CTLU1 turns off the synchronous switches S5 and S8. Thereby, the switching loss in synchronous switch S5, S8 can be reduced similarly to the case of FIG. 8A.

From time t6 to t7, the control circuit CTLU1 shifts to the regenerative power transmission operation by turning off the synchronous switches S5 and S8. Each of the currents i6 and i7 is “(iLD + ir) / 2”. Further, since a negative voltage is applied to the transformer TR, each of the currents i2 and i3 is also “(iLD + ir) / 2”. Furthermore, since the resonance current ir is positive (> 0), the control circuit CTLU1 keeps the resonance switch Sr on.

Next, at times t7 to t8, the resonance current ir becomes negative (≦ 0), and the current flows through the resonance diode Dr. When the polarity of the resonance current ir is thus inverted, the control circuit CTLU1 turns off the resonance switch Sr. The resonance current ir continues to flow until the discharge of the resonance capacitor Cr ends, and the electric power accompanying the resonance current ir is transmitted to the primary side via the transformer TR. When the discharge of the resonance capacitor Cr ends at time t8, each of the currents i6 and i7 settles to “iLD / 2”.

From time t8 to t9, the same operation is performed with the current paths in the primary side drive circuit L1DU and the diode circuit DDU1 switched for the period before time t1 described above. In the period from time t9 to t16, the same operation as that in the period from time t1 to t8 is performed.

<< Main effects of the third embodiment >>
As described above, when the power conversion device of the third embodiment is used, in addition to the various effects described in the first embodiment, the conduction loss of each diode in the diode circuit DDU1 can be reduced during the powering mode operation. . Further, it is possible to perform a regenerative mode operation, and also at this time, it is possible to reduce switching loss when each switching element is turned off and recovery loss of each diode. As a result, a reduction in power loss can be realized.

Here, the switching elements S1 to S4 are formed of IGBTs, but the present invention is not particularly limited to this, and any suitable power transistor can be used as long as it can satisfy the required element breakdown voltage. For example, the switching elements S1 to S4 can be configured by a MOSFET using a wide band gap material typified by SiC or the like. In this case, if the same synchronous rectification as in the case of the diode circuit DDU1 during the power running mode operation is performed in step SP403 in FIG. 8B, the conduction loss of the diodes D1 and D4 can be reduced. Further, the control circuit CTLU1 in the third embodiment is configured in the same manner as in FIG. 4A, for example, by appropriately adding a state during the regeneration mode operation to the state machine circuit SMU in FIG. 4A. be able to.

(Embodiment 4)
<< Schematic configuration of railcar >>
FIG. 11 is a schematic diagram showing a configuration example of a railway vehicle according to the fourth embodiment of the present invention. The railway vehicle shown in FIG. 11 includes a pantograph PT, a wheel WH, a main conversion device CI, a battery device BAT, an auxiliary power supply device APU, and load devices LODm and LODs. The pantograph PT collects power from the overhead line OW. For example, a DC voltage of about several kV may be transmitted to the overhead line OW, or an AC voltage of about several tens of kV may be transmitted. Here, the case where an alternating voltage is transmitted is taken as an example.

The main converter CI includes a PWM converter PWMC, an insulation type DC-DC converter DCCm, an inverter INVm, and DC link capacitors C10 and C11. The main converter CI operates, for example, using the wheel WH as the ground power supply voltage. The PWM converter device PWMC converts the AC voltage from the overhead wire OW into a DC voltage v1 and holds it in the DC link capacitor C10.

The insulated DC-DC converter device DCCm converts the DC voltage v1 stored in the DC link capacitor C10 into a DC voltage v2 having a predetermined voltage level, and holds it in the DC link capacitor C11. The inverter device INVm converts the DC voltage v2 held in the DC link capacitor C11 into an AC voltage.

The load device LODm is, for example, a motor that serves as a power source for the vehicle, and operates using an AC voltage from the inverter device INVm as a power source. The battery device BAT is charged with the direct current voltage v2 from the insulated DC-DC converter device DCCm. For example, even when the power supply from the overhead wire OW is stopped, the battery device BAT is direct current to the inverter device INVm and the auxiliary power supply device APU. The voltage v2 can be supplied.

The auxiliary power unit APU includes an insulation type DC-DC converter unit DCCs, a DC link capacitor C12, and an inverter unit INVs. The isolated DC-DC converter device DCCs converts the DC voltage v2 from the DC link capacitor C11 or the battery device BAT into a DC voltage v3 having a predetermined voltage level, and holds the DC voltage v2 in the DC link capacitor C12. The inverter device INVs converts the DC voltage v3 held in the DC link capacitor C12 into an AC voltage (for example, an AC voltage of a commercial power supply). The load devices LODs are lighting equipment, air conditioning equipment, and the like in the vehicle, and operate using AC voltage from the inverter device INVs as a power source.

In such a configuration, the power conversion device as described in the first to third embodiments is applied to one or both of the isolated DC-DC converter devices DCCm and DCCs. In particular, in the isolated DC-DC converter device DCCm, it is possible to obtain regenerative power from the load device LODm (for example, a motor or the like), so it is beneficial to apply the configuration of the third embodiment.

In addition, in the isolated DC-DC converter devices (power conversion devices) DCCm and DCCs, a transformer TR having a relatively high frequency (for example, about several kHz) can be used. Compared to a general configuration that performs conversion, it is possible to reduce the size and weight of the transformer TR. In addition, the effect of reducing power loss as described in the first to third embodiments can be obtained more remarkably particularly in a system for high power use such as a railway vehicle.

FIG. 12 is a schematic diagram showing a configuration example of an inverter device in the main converter shown in FIG. The inverter device INVm in FIG. 12 includes three-phase (u-phase, v-phase, w-phase) upper arms HAu, HAv, HAw and lower arms LAu, LAv, LAw. Each arm (HAu, HAv, HAw, LAu, LAv, LAw) is composed of, for example, a MOSFET and its built-in diode.

The inverter device INVm drives the load device LODm such as a motor by converting the DC voltage v2 from the isolated DC-DC converter device DCCm into a three-phase AC voltage by switching of each arm. Further, the inverter device INVm converts the regenerative power from the load device LODm into a DC voltage by switching of each arm (ie, synchronous rectification), and transmits the DC voltage to the isolated DC-DC converter device DCCm. Is possible.

On the other hand, the insulation type DC-DC converter device DCCm transmits the regenerative power from the load device LODm to the PWM converter device PWMC by performing the regenerative mode operation shown in FIG. 10 with the configuration shown in FIG. Is possible. In order to perform such a regeneration mode operation, for example, as shown in FIG. 7, when the synchronous switches S5 to S8 are constituted by MOSFETs, normally, PN junction diodes that become MOSFET built-in diodes are used for the diodes D5 to D8. It is done. In high power applications such as railway vehicles, it may be desirable to use a PN junction diode from the viewpoint of withstand voltage and conduction loss. However, in the PN junction diode, there is a possibility that the recovery loss is increased as compared with a Schottky barrier diode or the like. Therefore, it is beneficial to reduce recovery loss by the method of this embodiment.

FIG. 13 is a schematic diagram showing a configuration example of a PWM converter device in the main converter of FIG. The PWM converter device PWMC shown in FIG. 13 includes an inductor Lp, switching elements Sh1, Sh2, Sl1, Sl2, and diodes Dh1, Dh2, Dl1, Dl2 connected in parallel to the switching elements Sh1, Sh2, Sl1, Sl2, respectively. Prepare. Each of the switching elements Sh1, Sh2, Sl1, and Sl2 is configured by, for example, an IGBT or the like.

The diodes Dh1 and Dl2 convert the positive voltage of the AC power transmitted from the pantograph PT through the inductor Lp into a DC voltage v1. Similarly, the diodes Dh2 and Dl1 convert the negative voltage of the AC power transmitted from the pantograph PT through the inductor Lp into a DC voltage v1 by rectification. On the other hand, the switching elements Sh1 and Sl2 convert the DC voltage from the insulation type DC-DC converter device DCCm accompanying the regeneration mode operation into a positive voltage by modulating with a PWM (Pulse Width Modulation) signal, and the inductor Lp Is transmitted to the overhead wire OW. Similarly, the switching elements Sh2 and S11 convert the DC voltage from the isolated DC-DC converter device DCCm accompanying the regenerative mode operation into a negative voltage by modulating it with a PWM signal, and via the inductor Lp Transmit to OW.

As described above, by using the railway vehicle according to the fourth embodiment, it is possible to reduce the power loss as in the first to third embodiments. Furthermore, as shown in FIG. 11, by using a method of converting the electric power from the overhead wire OW into an alternating voltage after being converted into a direct current voltage that is low to some extent by the insulated DC-DC converter devices DCCm and DCCs. A transformer TR having a relatively high frequency can be used, and downsizing of the railway vehicle can be realized.

As described above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. . Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

For example, in each of the above-described embodiments, a full bridge type isolated DC-DC converter is used as an example of the power converter. However, the power conversion device according to the present embodiment is not necessarily limited to such a configuration, and in some cases, a one-stone forward converter (insulated DC-DC converter) as shown in FIG. It may be. FIG. 14 is a schematic diagram illustrating another configuration example of the power conversion device according to the embodiment of the present invention.

In the configuration example of FIG. 14, an AC voltage is applied to the primary coil L1 of the transformer TR by the switching element S10. When the switching element S10 is on, the output voltage from the secondary coil L2 is transmitted to the filter circuit FLU via the rectifier diode D10 in the diode circuit DDU2. On the other hand, when the switching element S10 is off, the current flowing through the inductor L of the filter circuit FLU is returned via the free-wheeling diode D11 in the diode circuit DDU2.

For example, in such a configuration, the same effect as in the first embodiment can be obtained by providing the resonance circuit RSU between the stages of the diode circuit DDU2 and the filter circuit FLU. That is, by turning on the resonance switch in the resonance circuit RSU while the switching element S10 is on, the switching element S10 can be turned off while the current is zero. Further, the switching element S10 is turned on in a state in which the current of the freewheeling diode D11 is zero by turning on the resonance switch in the period in which the switching element S10 is off (that is, the period in which the freewheeling diode D11 performs the freewheeling operation). , A reverse bias can be applied to the free-wheeling diode D11), and recovery loss can be reduced.

ADC Analog to digital converter APU Auxiliary power supply BAT Battery device C1, C2 Capacitor C10 to C12 DC link capacitor CI Main converter CTLU, CTLU1 Control circuit Cr Resonant capacitor D1 to D8 Diode D10, D11 Diode Dh1, Dh2, Dl1, Dl2 Diode DCCm, DCCs Isolated DC-DC converter device DDU, DDU1, DDU2 Diode circuit DVU driver circuit E Power supply FLU filter circuit HAu, HAv, Haw Upper arm INVm, INVs Inverter device L Inductor L1 Primary coil L1DU Primary side drive circuit L2 Secondary Coil LAu, LAv, LAw Lower arm LD Load circuit Lleak Leakage inductor LODm, LODs Load device Lr Resonant inductor O Overhead line PT pantograph PWMC PWM converter device RSU, RSU1 resonant circuits S1 ~ S4 switching elements S5 ~ S8 switching element (synchronous switch)
S10 switching element Sh1, Sh2, Sl1, Sl2 switching element SMU state machine circuit Sr switching element (resonance switch)
TR transformer WH wheel

Claims

A transformer including a primary coil and a secondary coil;
A switching element for applying an alternating voltage to the primary coil;
A diode circuit including a rectifier diode that rectifies the output voltage of the secondary coil, and a freewheeling diode that supplies a freewheeling current;
A filter circuit including an inductor and a capacitor, and smoothing an output voltage of the diode circuit;
A resonant circuit including a resonant inductor, a resonant capacitor, and a resonant switch provided between the diode circuit and the filter circuit and connected in series;
A control circuit for controlling on / off of the switching element and the resonance switch, and for turning on the resonance switch in a period in which the switching element is off;
A power conversion device.
The power conversion device according to claim 1,
The control circuit includes:
A first operation of transmitting power from the primary coil to the secondary coil by controlling the switching element to be on;
A second operation for circulating the current flowing through the filter circuit through the free-wheeling diode by controlling the switching element to be off;
Run
As a pretreatment when shifting from the second operation to the first operation, the resonant switch is turned on.
Power conversion device.
The power conversion device according to claim 2,
The control circuit further turns on the resonance switch as a pre-processing when shifting from the first operation to the second operation.
Power conversion device.
The power conversion device according to claim 1,
The switching element is
A first switching element that is supplied with a DC voltage from a power source and applies an AC voltage of a first polarity to the primary coil;
A second switching element that is supplied with a DC voltage from the power source and applies an AC voltage having a second polarity opposite to the first polarity to the primary coil;
With
The diode circuit is:
A first diode that performs a rectification operation for rectifying the output voltage of the secondary coil according to the alternating voltage of the first polarity and a return operation for flowing the return current;
A second diode that performs a rectification operation for rectifying the output voltage of the secondary coil in accordance with the alternating voltage of the second polarity and a return operation for flowing the return current;
With
The control circuit turns on the resonance switch in a period in which both the first switching element and the second switching element are off.
Power conversion device.
The power conversion device according to claim 4, wherein
The control circuit includes:
A third power is transmitted from the primary coil through the secondary coil and the first diode by controlling the first switching element on and the second switching element off. Operation and
By controlling the second switching element to be turned on and the first switching element to be turned off, power is transmitted from the primary coil via the secondary coil and the second diode. Operation and
A fifth operation in which both the first switching element and the second switching element are controlled to be turned off, whereby the current flowing through the filter circuit is circulated through the first diode and the second diode; ,
Run
As a pre-processing when shifting from the fifth operation to the third operation, the resonance switch is turned on, and as a pre-processing when shifting from the fifth operation to the fourth operation, the resonance switch Turn on the
Power conversion device.
The power conversion device according to claim 5, wherein
The diode circuit further includes:
A first synchronous switch connected in parallel to the first diode;
A second synchronous switch connected in parallel to the second diode;
With
The control circuit further controls to turn on the first synchronous switch during a period in which the first diode performs the rectification operation and the return operation, and the second diode performs the rectification operation and the return operation. Controlling the second synchronous switch to be ON in a period to be performed;
Power conversion device.
The power conversion device according to claim 6, wherein
The control circuit further controls the first synchronous switch and the second synchronous switch to be turned on, thereby storing a regenerative power in the inductor of the filter circuit;
By controlling the first synchronous switch to be turned on and the second synchronous switch to be turned off, the regenerative power is transferred from the secondary coil to the primary coil and the freewheeling diode of the first switching element. A seventh operation to transmit to the power supply;
By controlling the second synchronous switch to be turned on and the first synchronous switch to be turned off, the regenerative power is transferred from the secondary coil to the primary coil and the freewheeling diode of the second switching element. An eighth operation of transmitting to the power supply;
Run
As a pre-processing when shifting from the seventh operation to the sixth operation, the resonance switch is turned on, and as a pre-processing when shifting from the eighth operation to the sixth operation, the resonance switch Turn on the
Power conversion device.
The power conversion device according to claim 7, wherein
The control circuit further turns on the resonance switch as pre-processing when shifting from the sixth operation to the seventh operation, and switches from the sixth operation to the eighth operation. As a pretreatment, the resonant switch is turned on.
Power conversion device.
A transformer including a primary coil and a secondary coil;
A switching element for applying an alternating voltage to the primary coil;
A diode circuit including a rectifier diode that rectifies the output voltage of the secondary coil, and a freewheeling diode that supplies a freewheeling current;
A filter circuit including an inductor and a capacitor, and smoothing an output voltage of the diode circuit;
A resonant circuit including a resonant inductor, a resonant capacitor, and a resonant switch provided between the diode circuit and the filter circuit and connected in series;
A control circuit that controls on / off of the switching element and the resonance switch, and turns on the resonance switch as a pretreatment when switching the return diode from a forward bias to a reverse bias by turning on the switching element;
A power conversion device.
The power conversion device according to claim 9, wherein
Furthermore, a current sensor for detecting a current flowing through the reflux diode is provided,
The control circuit turns on the resonance switch and then turns off the resonance switch when the polarity of the current flowing in the resonance circuit is reversed, so that the current detected by the current sensor falls below a predetermined threshold value. When the switching element is turned on,
Power conversion device.
A power conversion device that converts a first DC voltage generated using power from an overhead line into a second DC voltage having a predetermined voltage level;
An inverter device for converting the second DC voltage into an AC voltage;
A load device that operates using the AC voltage from the inverter device as a power source;
A railway vehicle having
The power converter is
A transformer including a primary coil and a secondary coil;
A first switching element that applies a first polarity AC voltage to the primary coil using the first DC voltage as a power source;
A second switching element that applies an AC voltage of a second polarity opposite to the first polarity to the primary coil using the first DC voltage as a power source;
A first diode that performs a rectification operation for rectifying the output voltage of the secondary coil in accordance with the AC voltage of the first polarity and a return operation for flowing a return current; and the response in response to the AC voltage of the second polarity. A diode circuit comprising: a rectifying operation for rectifying the output voltage of the secondary coil; and a second diode for performing the recirculation operation for flowing the recirculation current;
A filter circuit including an inductor and a capacitor, and smoothing an output voltage of the diode circuit;
A resonant circuit including a resonant inductor, a resonant capacitor, and a resonant switch provided between the diode circuit and the filter circuit and connected in series;
The first switching element, the second switching element, and the resonance switch are controlled to be turned on / off, and the resonance switch is turned on while both the first switching element and the second switching element are off. A control circuit;
Comprising
Railway vehicle.
The railway vehicle according to claim 11, wherein
The control circuit includes:
A third power is transmitted from the primary coil through the secondary coil and the first diode by controlling the first switching element on and the second switching element off. Operation and
By controlling the second switching element to be turned on and the first switching element to be turned off, power is transmitted from the primary coil via the secondary coil and the second diode. Operation and
A fifth operation in which both the first switching element and the second switching element are controlled to be turned off, whereby the current flowing through the filter circuit is circulated through the first diode and the second diode; ,
Run
As a pre-processing when shifting from the fifth operation to the third operation, the resonance switch is turned on, and as a pre-processing when shifting from the fifth operation to the fourth operation, the resonance switch Turn on the
Railway vehicle.
The railway vehicle according to claim 12,
The diode circuit further includes:
A first synchronous switch connected in parallel to the first diode;
A second synchronous switch connected in parallel to the second diode;
With
The control circuit further controls to turn on the first synchronous switch during a period in which the first diode performs the rectification operation and the return operation, and the second diode performs the rectification operation and the return operation. Controlling the second synchronous switch to be ON in a period to be performed;
Railway vehicle.
The railway vehicle according to claim 13,
The control circuit further controls the first synchronous switch and the second synchronous switch to be turned on, thereby storing a regenerative power in the inductor of the filter circuit;
By controlling the first synchronous switch to be turned on and the second synchronous switch to be turned off, the regenerative power is transferred from the secondary coil to the primary coil and the freewheeling diode of the first switching element. A seventh operation to transmit to the power supply;
By controlling the second synchronous switch to be turned on and the first synchronous switch to be turned off, the regenerative power is transferred from the secondary coil to the primary coil and the freewheeling diode of the second switching element. An eighth operation of transmitting to the power supply;
Run
As a pre-processing when shifting from the seventh operation to the sixth operation, the resonance switch is turned on, and as a pre-processing when shifting from the eighth operation to the sixth operation, the resonance switch Turn on the
Railway vehicle.
The railway vehicle according to claim 14, wherein
The control circuit further turns on the resonance switch as pre-processing when shifting from the sixth operation to the seventh operation, and switches from the sixth operation to the eighth operation. As a pretreatment, the resonant switch is turned on.
Railway vehicle.