JP7001558B2 - Current control method in power converters and power converters - Google Patents

Description

The present invention relates to a power conversion device and a current control method in the power conversion device, and is suitable for application to, for example, a power conversion device for driving a power semiconductor element having a body diode.

There is a power conversion device that uses a power semiconductor element. For example, the mainstream of a railroad vehicle drive device is a configuration in which a motor is rotated by a three-phase AC power obtained by converting electric power taken from an overhead wire into a desired frequency and voltage by a power conversion device such as an inverter to obtain a drive force. There is.

In recent years, in such a power converter, for further energy saving, for example, a SiC- MOSFET (Metal Oxide Semiconductor Field Effect Transistor) has been used as a power semiconductor element instead of an IGBT (Insulated Gate Bipolar Transistor). SiC has a larger bandgap than silicon and has a dielectric strength of about 10 times that of silicon. Therefore, in the SiC- MOSFET, the thickness of the element can be reduced to about 1/10 as compared with the IGBT, the resistance at the time of conduction can be suppressed to about 1/10, and the conduction loss can be reduced.

Further, since the SiC- MOSFET can reduce the resistance at the time of conduction, even when it is used as a high withstand voltage element of a railway vehicle having a rated voltage of, for example, 3.3 kV, it is a bipolar device that accumulates electric charge and lowers the conduction resistance like an IGBT. It does not have to be structured. That is, the SiC-PWM can be a unipolar device structure such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or a JFET (Junction FET). The unipolar device has a smaller switching loss due to the absence of charge accumulation as compared with the bipolar device, and can contribute to further energy saving of the power conversion device.

Further, unlike the IGBT, the SiC- MOSFET can conduct a current in the opposite direction by applying a predetermined voltage to the gate (see, for example, Patent Document 1). Therefore, the SiC- MOSFET does not require a freewheel diode and has a feature that the element can be miniaturized.

Japanese Unexamined Patent Publication No. 2013-207821

Generally, in a power conversion device, when some abnormality (mismatch between the on / off gate command and the actual on / off state, etc.) is detected in the power semiconductor element, it is determined that the power semiconductor element has failed, and the power semiconductor element is determined to have failed. Is being turned off to stop the power conversion device. In this way, in the power conversion device, it is possible to prevent the failure from spreading to other power semiconductor elements and spreading the element destruction.

However, for example, in a railroad vehicle, when some abnormality is detected in the SiC-PLC and the SiC-PLC is turned off completely to stop the power conversion device, the current generated by the permanent magnet type synchronous motor that continues to rotate is converted to power. It flows into the device. This current flows through the body diode, which is a parasitic diode of the SiC- MOSFET, because the SiC- MOSFET cannot flow the current in the opposite direction because the gate is turned off. The body diode has a problem that the voltage drop in the forward direction is large, a large loss occurs when energized, and the SiC- MOSFET is thermally destroyed.

As a countermeasure to this problem, when some abnormality is detected in the SiC- MOSFET, the SiC- MOSFET is turned on completely and the current is passed to the switching element side (between the source and drain) of the SiC- MOSFET instead of the body diode, so-called. There is a method of performing synchronous rectification drive. However, in the power conversion device that has stopped due to some abnormality, there is a possibility that one of the SiC- MOSFETs has failed. A so-called arm short circuit may occur in which the SiC- MOSFET and the SiC- MOSFET forming the opposite arm are turned on at the same time to short-circuit the positive and negative power supply lines, which may cause a large failure.

The present invention has been made in consideration of the above points, and prevents damage to the power semiconductor element by allowing a part or most of the return current flowing through the body diode of the power semiconductor element forming the pair of arms to flow to the switching element side. This is an attempt to propose a power conversion device and a current control method in a power conversion device that can achieve energy saving and high reliability.

In order to solve such a problem, in the present invention, the power conversion device responds to a plurality of power semiconductor elements forming a pair of arms, a control unit for outputting a control command of a gate of the plurality of power semiconductor elements, and the control command. It has a gate drive device for driving the power semiconductor element by applying a voltage to the gate. When an abnormality is detected by the power conversion device, the control unit outputs a recirculation operation command for applying a predetermined voltage for conducting a current in the reverse direction of the power semiconductor element to the gate drive device, and the control unit outputs the gate drive device. The gate drive device applies the predetermined voltage to all the power semiconductor elements of the pair arm in response to the recirculation operation command.

Further, in the present invention, a plurality of power semiconductor elements forming a pair of arms, a control unit for outputting a control command for the gates of the plurality of power semiconductor elements, and a voltage applied to the gate in response to the control command are applied. In a current control method executed in a power conversion device having a gate drive device for driving a power semiconductor device, the control unit recirculates to apply a predetermined voltage for conducting a current in the opposite direction of the power semiconductor device. An operation command is output to the gate drive device, and the gate drive device applies the predetermined voltage to all the power semiconductor elements of the pair arm in response to the recirculation operation command.

According to the current control method in the power conversion device and the power conversion device, a part or most of the return current flowing through the body diode of the power semiconductor element forming the pair arm can flow to the switching element side.

According to the present invention, it is possible to realize a power conversion device and a current control method in a power conversion device that can prevent damage to a power semiconductor element, save energy, and achieve high reliability.

It is a figure which shows the structure of the power conversion apparatus of 1st Embodiment. It is a figure which shows the structure of the gate drive device of 1st Embodiment. It is a figure which shows the structure of the gate voltage output circuit of 1st Embodiment. It is a time chart which shows the change of the current flowing through the switching element and the parasitic diode of 1st Embodiment. It is a figure which shows the structure of the power conversion apparatus of the modification of 1st Embodiment. It is a figure which shows the structure of the power conversion apparatus of the modification of 1st Embodiment. It is a figure which shows the structure of the power conversion apparatus of the modification of 1st Embodiment. It is a figure which shows the structure of the power conversion apparatus of the modification of 1st Embodiment. It is a figure which shows the structure of the gate drive device of the 2nd Embodiment. It is a figure which shows the structure of the gate voltage output circuit of the 2nd Embodiment. It is a figure which shows the structure of the gate voltage output circuit of 3rd Embodiment. It is a figure which shows the structure of the gate voltage output circuit of the modification of the 3rd Embodiment. It is a figure which shows the structure of the power conversion apparatus of 4th Embodiment.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In the following description of each embodiment and each modification, the same elements are designated by the same reference numerals, and the description below will be omitted. In addition, each of the following embodiments and each modification may be combined in part or in whole within a consistent range.

(1) Configuration of the power conversion device according to the first embodiment (1-1) First embodiment FIG. 1 is a diagram showing the configuration of the power conversion device according to the first embodiment. The railroad vehicle 100 including the power conversion device 4 of the first embodiment uses, for example, a two-level inverter as the power conversion device 4 included in the drive device of the electric motor.

As shown in FIG. 1, the railroad vehicle 100 includes a current collector (pantograph) 1, a filter reactor 2, a filter condenser 3, a power conversion device 4, an electric motor (motor) 5, wheels 6, and a current collector (pantograph) 1 for collecting electric power from an overhead wire. It has a circuit breaker 7.

The power conversion device 4 is connected to a positive power supply line and a negative power supply line. The positive power line is connected to the overhead line via the current collector 1. The negative power line is connected to the rail via the wheel 6. The filter reactor 2 and the filter capacitor 3 constitute a filter circuit that operates at, for example, several tens of Hz.

The circuit breaker 7 protects the power conversion device 4 by cutting off the electric power from the overhead wire when an overcurrent and an overvoltage occur. The power conversion device 4 converts the power taken in from the overhead wire into three-phase AC power of U, V, and W and outputs the power. The electric motor 5 is connected to the output terminals of each of the U, V, and W phases of the power conversion device 4, and is driven by the three-phase AC power output from the power conversion device 4. The electric motor 5 is, for example, a Permanent Magnet Synchronous Motor (PMSM).

The power conversion device 4 includes a control unit 11, gate drive devices 21 to 26, and power semiconductor elements 41 to 46. The control unit 11 and the gate drive devices 21 to 26 are connected via a signal line 12.

The control unit 11 issues a gate command 111 (on gate command and off gate command, see FIG. 2) for turning on / off each gate of the power semiconductor elements 41 to 46 via the signal line 12 to the gate drive devices 21 to 26. Output to each. Further, the control unit 11 outputs a recirculation operation command 117 (see FIG. 2) for recirculating the power semiconductor elements 41 to 46 to each of the gate drive devices 21 to 26 via the signal line 12. Further, the control unit 11 receives feedback signals (see FIG. 2) indicating an on / off state of each gate of the power semiconductor elements 41 to 46 from each of the gate drive devices 21 to 26 via the signal line 12.

The power semiconductor elements 41 to 46 are SiC- MOSFETs (SiC-Metal Oxide Semiconductor Field Effect Transistor). Each of the power semiconductor elements 41 to 42, 43 to 44, and 45 to 46 constitutes the upper and lower arms of each phase of the two-level inverter.

The power semiconductor element 41 includes a switching element 41a and a body diode 41b connected in parallel to the switching element 41a. In the present embodiment, the source-drain of the power semiconductor element 41 that conducts the current when the gate is turned on and cuts off the current when the gate is turned off is referred to as a switching element 41a. The body diode 41b is a parasitic diode of the power semiconductor element 41. A gate drive device 21 is connected to the gate of the switching element 41a. Similarly, the power semiconductor devices 42 to 46 have switching elements 42a to 46a and body diodes 42b to 46b, respectively, as shown in FIG. Gate driving devices 22 to 26 are connected to the gates of the switching elements 42a to 46a, respectively.

(1-2) Configuration of Gate Drive Device According to First Embodiment FIG. 2 is a diagram showing a configuration of a gate drive device according to the first embodiment. FIG. 2 shows the gate drive device 21 for driving the power semiconductor element 41 constituting the upper arm of the U phase among the three phases U, V, and W of the gate drive devices 21 to 26 of the first embodiment. The same applies to the gate drive device 22 for driving the power semiconductor element 42 constituting the lower arm of the U phase, and the other two-phase power semiconductor elements 43 to 46 and the gate drive devices 23 to 26.

The gate drive device 21 includes an insulation circuit 101, a gate voltage output circuit 102, and an on / off state determination circuit 103.

The insulation circuit 101 insulates the gate command 111, the return operation command 117, and the feedback signal 116. Further, the insulation circuit 101 converts the gate command 111 received from the control unit 11 into the gate command 112 and outputs it to the gate voltage output circuit 102 and the on / off state determination circuit 103. Further, the insulation circuit 101 converts the recirculation operation command 117 received from the control unit 11 into the recirculation operation command 118 and outputs the recirculation operation command 117 to the gate voltage output circuit 102. Further, the insulation circuit 101 converts the feedback signal 115 received from the on / off state determination circuit 103 into the feedback signal 116 and outputs it to the control unit 11.

The gate voltage output circuit 102 receives the gate command 112 from the insulation circuit 101, and applies the gate voltage 113 in response to the gate command 112 to the gate of the power semiconductor element 41. Further, the gate voltage output circuit 102 receives the recirculation operation command 118 from the insulation circuit 101, and applies the gate voltage 113 in response to the recirculation operation command 118 to the gate of the power semiconductor element 41. Further, the gate voltage output circuit 102 monitors the gate voltage of the power semiconductor element 41, and outputs the gate voltage monitoring signal 114 indicating the gate voltage to the on / off state determination circuit 103 at the same time as the output of the gate voltage 113.

In the case of the on gate command 112, the gate voltage 113 is a first voltage (VDD1) having a threshold voltage Vth or more for turning on the gate of the power semiconductor element 41 and conducting a current in the forward direction. Further, in the case of the off gate command 112, the gate voltage 113 is a second voltage (0 or a predetermined negative voltage) less than the threshold voltage Vth for turning off the gate of the power semiconductor element 41 to cut off the current. VSS). Further, in the case of the return operation command 118, the gate voltage 113 is less than the threshold voltage Vth and from the second voltage (VSS) for conducting the current in the opposite direction (source-drain) of the power semiconductor element 41. It is a large third voltage (SiO2). For example, when the threshold voltage Vth of the power semiconductor element 41 is 4V, the third voltage (00572) is controlled to be less than 4V.

Here, when a third voltage (00572) is applied to the power semiconductor devices 41 to 46, the current flows in the opposite direction of the power semiconductor devices 41 to 46 because of the substrate bias effect. The board bias effect means that the threshold voltage Vth fluctuates depending on the voltage of the back gate (board). When a current flows in the reverse direction due to the substrate bias effect, that is, when a reverse voltage is applied to the power semiconductor elements 41 to 46, the drain voltage becomes negative, so that the threshold voltage Vth drops equivalently and the gate Even if a voltage lower than the threshold voltage Vth is applied, a channel is formed and a current flows through the power semiconductor elements 41 to 46. On the other hand, when the current flows in the forward direction, that is, when the forward voltage is applied to the power semiconductor devices 41 to 46, the substrate bias effect becomes small or does not occur, and the threshold voltage Vth returns to the normal value. When the voltage applied to the gate is less than the threshold voltage Vth, no current flows through the power semiconductor devices 41 to 46.

The on / off state determination circuit 103 receives the gate voltage monitoring signal 114 from the gate voltage output circuit 102, and determines the gate state of the power semiconductor element 41 based on the gate voltage monitoring signal 114. For example, the on / off state determination circuit 103 compares the gate voltage monitoring signal 114 with the reference voltage, and if the gate voltage monitoring signal 114 is equal to or higher than the reference voltage, the gate of the power semiconductor element 41 is turned on, and if it is lower than the reference voltage, the gate is turned off. A feedback signal 115 indicating that the state is in state is generated and output to the insulation circuit 101.

The control unit 11 monitors the state of the power semiconductor element 41 based on the feedback signal 116 converted from the feedback signal 115 by the insulation circuit 101, and the gate command 111 and the feedback signal 116 do not match (hereinafter referred to as “FB mismatch”). When it is detected), it is determined that the power semiconductor element 41 has failed. When the control unit 11 detects the FB mismatch, it outputs an off gate command 111 to the gate drive devices 21 to 26, turns off all the power semiconductor elements 41 to 46, and stops the power conversion device 4. The control unit 11 monitors, for example, a drop in the overhead wire voltage, an overvoltage, or the like, and when any abnormality is detected in these, the control unit 11 outputs an off gate command 111 to the gate drive devices 21 to 26, and power semiconductor elements 41 to 41. The power conversion device 4 may be stopped by turning off all 46.

Here, since the electric motor 5 has a magnet in the rotor, the electric motor 5 generates electric power when the control unit 11 detects some abnormality during the rotation of the electric motor 5 and stops the power conversion device 4. It operates as a machine, and the current generated by the rotation of the electric motor 5 flows into the power conversion device 4. This current flows into the filter capacitor 3 through the body diodes 41b to 46b of the power semiconductor elements 41 to 46 stopped by the abnormality detection, and charges the filter capacitor 3.

Therefore, the control unit 11 determines that a failure has occurred due to some abnormality while the motor 5 is operating, turns off all the power semiconductor elements 41 to 46, and then outputs the return operation command 117 to the gate drive devices 21 to 26. do. Upon receiving the return operation command 117, the gate drive devices 21 to 26 apply a third gate voltage to the power semiconductor elements 41 to 46. The power semiconductor devices 41 to 46 flow a current in the opposite direction in response to the application of the third gate voltage, so that part or most of the return current from the motor 5 is used in the switching elements 41a to the power semiconductor devices 41 to 46. Performs a reflux operation to flow to the 46a side. As a result, the reflux current flowing through the body diodes 41b to 46b of the power semiconductor elements 41 to 46 can be suppressed, and the body diodes 41b to 46b can be prevented from being destroyed by heat generation.

When the control unit 11 and the gate drive device 21 are connected by an electric wire, the control unit 11 driven at a low voltage, the power semiconductor element 41 driven at a high voltage, the gate voltage output circuit 102, and the on / off state determination circuit 103 are insulated. Therefore, the insulation circuit 101 is provided with an insulation function. On the other hand, when the control unit 11 and the gate drive device 21 are connected by an optical line, the insulation circuit 101 only converts the gate command 111, the return operation command 117, and the feedback signal 116 from an optical signal to an electric signal. Therefore, this insulation function is not necessary.

(1-3) Configuration of Gate Voltage Output Circuit According to First Embodiment FIG. 3 is a diagram showing a configuration of a gate voltage output circuit according to the first embodiment. The gate voltage output circuit 102 of the first embodiment includes transistors 121, 122, and 123, switches 125, resistors 131, 132, and 133, level converters 141, 142, and 143, and voltage generators 151, 152. And 161. The resistor 131 controls the switching characteristics of the power semiconductor devices 41 to 46. The voltage generation units 151 and 152 output the voltage VDD1. The voltage generation unit 161 outputs the voltage VDD2. The intermediate potentials between the level converters 141 and 142, 143, and the voltage generators 151 and 152 are grounded by the source ground line 110.

The gate voltage output circuit 102 turns on the transistor 121 when the gate command 112 is on, and outputs the gate voltage 113 of the first voltage (VDD1). Further, the gate voltage output circuit 102 turns on the transistor 122 when the gate command 112 is off, and outputs the gate voltage 113 of the second voltage (VSS). Further, when the return operation command 117 is on, the gate voltage output circuit 102 turns off the transistor 122 by the switch 125, and outputs the gate voltage 113 of the third voltage (ldap2).

Although FIG. 3 illustrates the case where MOSFETs are used for the transistors 121 to 123, the same effect can be obtained even when a bipolar transistor is applied.

(1-4) Change in current flowing through the switching element and the parasitic diode of the first embodiment FIG. 4 is a time chart showing the change of the current flowing through the switching element and the parasitic diode of the first embodiment. FIG. 4 shows a case where the control unit 11 detects an abnormality at time t1 while the control unit 11 issues an ON command to the gate drive devices 21 and 24, and the U phase of the three phases of the power conversion device 4 is shown. The power semiconductor elements 41 to 42 of the upper and lower arms will be described by way of example, but the same applies to the power semiconductor elements 43 to 44 and 45 to 46 connected in series forming a pair of arms of other phases.

At time t2, the control unit 11 outputs an off gate command 111 to the gate drive devices 21 and 24. The gate voltage 113 of the power semiconductor element 41 begins to decrease due to the off gate command 111, and at a time t3 when the gate voltage 113 falls below the threshold voltage Vth, the current flowing back from the electric motor 5 to the body diode 41b of the power semiconductor element 42. Id2 flows out. At time t4 when the gate voltage 113 of the power semiconductor element 41 is set to the voltage VSS, the control unit 11 outputs a return operation command 117 to all of the gate drive devices 21 to 26.

Since the MOSFET does not have a storage carrier like the IGBT, switching according to the gate command 111 ends when a predetermined time of, for example, 0.5 μs elapses after the control unit 11 outputs the gate command 111. .. Therefore, it is preferable that the control unit 11 outputs the reflux operation command 117 after the time t4, for example, when the first predetermined time of 0.5 μs has elapsed after outputting the all-off gate command 111 at the time t2. As a result, the influence of switching based on the all-off gate command 111 can be eliminated and the reflux operation can be performed.

When the control unit 11 outputs the recirculation operation command 117, the gate voltage 113 of the power semiconductor element 41 and the gate voltage 113-2 of the power semiconductor element 42 start to increase, and at the same time, the recirculation current from the electric motor 5 causes the power semiconductor element 42. The current Id2 flowing from the body diode 42b of the above is commutated to the switching element 42a (between the source and the drain of the power semiconductor element 42), the current Id2 flowing through the body diode 42b decreases, and the current Ids2 flowing through the switching element 42a increases.

Then, after the time t5 when the potential between the power semiconductor elements 41 and 42 exceeds the zero cross, the currents Id2 and Ids2 do not flow, and the currents Id1 and the switching element 41a of the body diode 41b of the power semiconductor element 42 (source of the power semiconductor element 41). -The current Ids1 flowing between the drains flows. In this way, by passing a part or most of the reflux current through the switching element 41a of the power semiconductor element 41, the current Id1 flowing through the body diode 41b is reduced, the heat generation of the body diode 41b is suppressed, and the power semiconductor element 41 is destroyed. Can be prevented.

When the control unit 11 turns on the gates of the power semiconductor devices 41 to 46, the control unit 11 applies a third voltage to the power semiconductor devices 41 to 46, and then, for example, takes a second predetermined time of 0.5 μs. After the lapse of time, the gate command 111 for applying the first voltage (00571) for turning on the gate to the power semiconductor devices 41 to 46 is output. The first and second predetermined times may be the same or different.

(1-5) Effect of First Embodiment According to the first embodiment, when an abnormality of a power semiconductor element is detected, all the power semiconductor elements are turned off and then all the power semiconductor elements are subjected to. A third voltage is applied so that the current flows in the opposite direction due to the substrate bias effect, and a part or most of the recirculation current flowing through the body diode is recirculated to the switching element side. Therefore, it is possible to prevent the power semiconductor element from being thermally destroyed by the reflux current flowing through the body diode. Further, when an abnormality occurs in the power semiconductor element forming the pair arm, it is possible to prevent the failure from spreading to other power semiconductor elements constituting the pair arm.

(1-6) Modification Example of First Embodiment In this embodiment, the power conversion device 4 that outputs three phases is exemplified, but the present invention is not limited to this, and a pair of upper and lower arms constituting one phase are configured. It may be a power conversion device having a power semiconductor element or having two pairs of power semiconductor elements constituting a two-phase upper and lower arm.

Further, in the present embodiment, the control unit 11 outputs the return operation command 117 at a time after a predetermined time elapses after outputting the gate command 111 for all off of the power semiconductor element, but the present invention is not limited to this. The return operation command 117 may be output immediately after the all-off gate command 111 is output.

Further, in the present embodiment, SiC- MOSFETs have been exemplified and described as power semiconductor devices 41 to 46. However, the power semiconductor element is not limited to this, and the body diode can be used as a free wheel diode, and other wide-gap semiconductor elements having a bandgap of a predetermined value or more, that is, power semiconductors such as silicon, gallium nitride, and diamond. It may be an element.

Further, in the present embodiment, the case where the body diodes 41b to 46b of the power semiconductor elements 41 to 46 are used as the freewheel diode is shown. However, the present invention is not limited to this, and freewheel diodes 51 to 52 are connected in parallel with the power semiconductor elements 41 to 42 as in the power conversion device 4A exemplified by the U-phase power semiconductor elements 41 to 42 in FIG. May be good. In this case as well, the current flowing through the body diodes 41b to 42b can be suppressed to prevent the power semiconductor element from being destroyed.

Further, in the present embodiment, it is assumed that one power semiconductor element 41 to 46 is driven by the gate drive devices 21 to 26, respectively. However, the present invention is not limited to this, and two or more power semiconductor elements 41-1 to 41 connected in parallel, such as the power conversion device 4B exemplified by the U-phase power semiconductor elements 41-1 to 44-2 in FIG. -2 may be driven by the gate drive device 21-1, and the two power semiconductor elements 42-1 to 42-2 connected in parallel may be driven by the gate drive device 22-1. In this case, the return current flowing through the body diodes 41b of the power semiconductor elements 41-1 to 41-2 and 42-1 to 42-2 connected in parallel is dispersed, and a part of the current flowing through the body diodes 41b to 42b. Alternatively, by flowing most of the current through each switching element 41a, the effect of suppressing heat generation and preventing the destruction of the power semiconductor element can be enhanced. In the example shown in FIG. 6, power semiconductor devices 41-1 to 41-2 form an upper arm, power semiconductor devices 42-1 to 42-2 form a lower arm, and these upper arms and lower arms form a lower arm. Form an anti-arm. In FIG. 6, one gate driver 21-1 drives the power semiconductor elements 41-1 to 41-2, and one gate driver 22-1 drives the power semiconductor elements 42-1 to 42-2. show. However, the present invention is not limited to this, and as in the power conversion device 4B-1 shown in FIG. 7, the gate driver 21-1 drives the power semiconductor element 41-1 and the gate driver 21-2 drives the power semiconductor element 41-2. It may be driven, the power semiconductor element 42-1 may be driven by the gate driver 22-1, and the power semiconductor element 42-2 may be driven by the gate driver 22-2.

Further, in the present embodiment, the power conversion device 4 is a two-level inverter. However, the present invention is not limited to this, and even if it is a multi-level inverter having three or more levels, such as the power conversion device 4C exemplified by the power semiconductor elements 41-3, 41-4, 42-5, and 42-6 in FIG. good. In FIG. 8, a three-level inverter is illustrated, and the power semiconductor element 41-3 driven by the gate drive device 21-3 and the power semiconductor element 41-4 driven by the gate drive device 21-4 are paired arms. Further, the power semiconductor element 42-5 driven by the gate drive device 22-3 and the power semiconductor element 42-6 driven by the gate drive device 22-4 are paired arms.

Further, in the present embodiment, the control unit 11 monitors the state of the gates of the individual power semiconductor elements 41 to 46 based on the feedback signal 116 converted from the feedback signal 115 output by the on / off state determination circuit 103. It was decided to judge the failure. However, the present invention is not limited to this, and various known methods can be used to monitor the state of the individual power semiconductor devices 41 to 46 and determine the failure based on the monitoring result.

Further, in the present embodiment, when the failure of the power semiconductor elements 41 to 46 is detected, the control unit 11 turns off all the power semiconductor elements 41 to 46 to stop the power conversion device 4, and then all of them. It was decided that the power semiconductor devices 41 to 46 of the above would be made to perform a recirculation operation. However, the present invention is not limited to this, and when the power conversion device 4 is stopped, the control unit 11 applies to all the power semiconductor elements 41 to 46 regardless of whether or not a failure of the power semiconductor elements 41 to 46 is detected. The reflux operation may be performed.

(2) Second Embodiment FIG. 9 is a diagram showing the configuration of the gate drive device of the second embodiment. FIG. 10 is a diagram showing a configuration of a gate voltage output circuit according to a second embodiment. The power conversion device 4D of the second embodiment is different from the first embodiment in that a temperature sensor 105 such as a thermistor for measuring the temperature of the power semiconductor element is added. FIG. 9 illustrates a gate drive device 21D for driving a power semiconductor element 41 constituting the upper arm of the U phase among the three phases U, V, and W, but the power semiconductor element constituting the lower arm of the U phase is illustrated. The same applies to the gate drive device 22D for driving the 42, and the other two-phase power semiconductor elements 43 to 46 and the gate drive device.

The threshold voltage Vth of the SiC- MOSFET has a temperature characteristic that it decreases at a high temperature and increases at a low temperature. Therefore, it is necessary to correct the third voltage (00572) according to the temperature according to the fluctuation of the threshold voltage Vth. As shown in FIG. 10, in the present embodiment, the voltage generation unit 119 of the gate voltage output circuit 102D is smaller than the threshold voltage Vth that changes depending on the temperature indicated by the temperature signal 120 of the power semiconductor element 41 and is second. Generates a third voltage (VDD2) that is greater than the voltage (VSS) of.

The voltage generation unit 119 may be mounted by a programmable circuit such as a PLD (Programmable Logic Device). In this case, for example, the voltage generation unit 119 refers to a table or the like prepared in advance based on the temperature data obtained by AD (Analog to Digital) conversion of the temperature signal 120, and obtains a third voltage corresponding to the temperature data. It is acquired, converted to DA (Digital to Analog), and output. Alternatively, for example, the voltage generator 119 changes the voltage dividing resistance by switching a plurality of parallel resistors having different resistance values based on the temperature data obtained by AD (Analog to Digital) conversion of the temperature signal 120, or by using a regulator. By making it, a third voltage may be output.

The gate voltage output circuit 102D applies the third voltage thus generated to the gate of the power semiconductor element 41 at the time of abnormality detection. In this way, by correcting the temperature of the third voltage, a recirculation current can be passed through the power semiconductor module by the substrate bias effect regardless of the temperature, so that it is stable regardless of the heat generation of the power semiconductor element and the ambient temperature. Therefore, it is possible to suppress the heat generation of the body diode and prevent the power semiconductor element from being destroyed.

(3) Configuration of the Gate Voltage Output Circuit of the Third Embodiment (3-1) Configuration of the Gate Voltage Output Circuit of the Third Embodiment FIG. 11 is a diagram showing the configuration of the gate voltage output circuit of the third embodiment. The gate voltage output circuit 102F included in the power conversion device of the third embodiment is different from the first embodiment in that it generates a third voltage (VDD2) by resistance voltage division. When the gate voltage output circuit 102F receives the recirculation operation command 118, the transistors 121 to 122 are turned off, the transistors 123 to 124 are turned on, and the resistance divided pressure of the resistor 133 and the resistor 134 causes the third voltage (00572) to be turned off. A gate voltage 113 is generated and output. According to the present embodiment, there is an advantage that the voltage generation unit 161 for generating the third voltage (VDD2) in the first embodiment can be reduced.

(3-2) Modification Example of the Third Embodiment Further, FIG. 12 shows a modification of generating a third voltage (VDD2) by resistance voltage division. FIG. 12 is a diagram showing a configuration of a gate voltage output circuit according to a modification of the third embodiment. The condition for outputting the third voltage (00572) in the configuration of the gate voltage output circuit 102G shown in FIG. 12 is that the resistance value of the resistor 132 is about 10 mΩ, which is the resistance value turned on by the transistors 122 to 123. When it is sufficiently large (for example, 10Ω or more). Under this condition, the loss in the transistors 122 to 123 is small, and the allowable loss overrun or deterioration due to the heat generation of the transistors 122 to 123 does not become a problem. In this modification, the transistors 122 to 123 can be turned on, and the third voltage (VDD2) can be generated and output by the resistance voltage division of the resistors 132 and 133. According to this modification, the voltage generation unit 161 can be reduced, and the transistor 124 and the resistance 134 can be reduced from the configuration of the gate voltage output circuit 102F in FIG. 11, so that the gate voltage output circuit and the gate drive device can be further miniaturized. It is possible.

(4) Fourth Embodiment FIG. 13 is a diagram showing the configuration of the power conversion device of the fourth embodiment. As shown in FIG. 13, the railroad vehicle 100H of the fourth embodiment has a current collector 1, a filter reactor 2, a filter capacitor 3, a power conversion device 4, an electric motor 5, and wheels 6 that collect electric power from an overhead wire. It has a breaker 7, a transformer 8, and a converter 9. The converter 9 includes a control unit 61, gate drive devices 27 to 30, and power semiconductor elements 91 to 94. The control unit 61 and the gate drive devices 27 to 30 are connected via a signal line 62.

The AC voltage input from the current collector 1 connected to the overhead wire is rectified by the power semiconductor elements 91 to 94 and converted into a DC voltage smoothed by the filter capacitor 3. The circuit breaker 7 protects the converter 9 by cutting off the electric power from the overhead wire when an overcurrent and an overvoltage occur.

The control unit 61 outputs gate commands (on gate command and off gate command) for turning on and off each gate of the power semiconductor elements 91 to 94 to each of the gate drive devices 27 to 30 via the signal line 62. Further, the control unit 61 outputs a recirculation operation command for recirculating the power semiconductor elements 91 to 94 to each of the gate drive devices 27 to 30 via the signal line 62. Further, the control unit 61 receives feedback signals indicating the on / off states of the gates of the power semiconductor elements 91 to 94 from the gate drive devices 27 to 30 via the signal line 12.

The power semiconductor devices 91 to 94 are SiC- MOSFETs. Each of the power semiconductor elements 91 to 92 and 93 to 94 constitutes the upper and lower arms of each phase of the converter.

The power semiconductor element 91 has a switching element 91a and a body diode 91b connected in parallel to the switching element 91a. In the present embodiment, the source-drain of the power semiconductor element 91 that conducts the current when the gate is turned on and cuts off the current when the gate is turned off is referred to as a switching element 91a. The body diode 91b is a parasitic diode of the power semiconductor element 91. A gate drive device 27 is connected to the gate of the switching element 91a. Similarly, the power semiconductor devices 92 to 94 have switching elements 92a to 94a and body diodes 92b to 94b, respectively, as shown in FIG. Gate driving devices 28 to 30 are connected to each gate of the switching elements 92a to 94a.

The control unit 61 monitors the state of the power semiconductor elements 92 to 94, and determines that the power semiconductor element that has detected a mismatch between the gate command and the feedback signal (FB mismatch) is a failure. When the control unit 61 detects the FB mismatch, it outputs an off gate command 111 to the gate drive devices 27 to 30, turns off all the power semiconductor elements 91 to 94, and stops the converter 9.

At this time, since the AC current from the overhead wire flows into the power semiconductor elements 92 to 94, the current flows through the body diodes 91b to 94b of the power semiconductor elements 92 to 94 if the power semiconductor elements 92 to 94 are left completely off, and the power semiconductor element 91 It leads to the destruction of ~ 94.

Therefore, similarly to the control unit 11 of the first embodiment, the control unit 61 returns to the gate drive devices 27 to 30 when, for example, 0.5 μs or more has elapsed after all the power semiconductor elements 91 to 94 are turned off. Output an operation command. As a result, a part or most of the alternating current from the overhead wire flows through the switching elements 91a to 94a of the power semiconductor elements 92 to 94, so that the current flowing through the body diodes 91b to 94b is reduced and the heat generation is suppressed, so that the power semiconductor It is possible to prevent the elements 91 to 94 from being destroyed.

The converter 9 is not limited to the two-level converter, and may be a multi-level converter having three or more levels.

(5) Fifth Embodiment In the first to fourth embodiments, when some abnormality occurs in the power semiconductor element of the power conversion device, all the power semiconductor elements of the power conversion device are turned off. However, it is not limited to this. In the fifth embodiment, when the control units 11 and 62 detect some abnormality in the power semiconductor element, the power semiconductor element that detects the FB mismatch and the power semiconductor element connected in series to the power semiconductor element are used. Similar to the first to fourth embodiments, a recirculation operation command is output to the power semiconductor element of the pair arm composed of the above. This prevents short-circuit breakage that occurs when the power semiconductor device connected in series with the failed power semiconductor device is turned on, suppresses the current flowing through the body diode, and prevents the power semiconductor device from being broken.

On the other hand, for the power semiconductor element of the pair arm that has not failed, the gate command is turned on at the timing when the return current flows, and the synchronous rectification operation in which the return current flows to the switching element side of the power semiconductor element is continued. As a result, loss and heat generation in the power semiconductor element unrelated to the failure can be suppressed.

The present invention is not limited to the above-described embodiments and modifications, and the present invention also relates to other embodiments that can be considered within the scope of the technical idea of the present invention as long as the gist of the present invention is not deviated. It is included in the range of. Further, it can be carried out in various forms as long as it does not deviate from the gist of the present invention. For example, each configuration and each process exemplified in each of the above-described embodiments and modifications may be integrated or separated as appropriate according to the mounting form and processing efficiency.

4, 4A, 4B, 4B-1, 4C, 4D ... Power converter, 5 ... Electric motor, 9 ... Converter, 11, 61 ... Control unit, 21-26, 21-1-21 -4, 22-2 to 22-4, 21D, 22D, 27 to 30 ... Gate drive device, 41 to 46, 41-1 to 41-2, 42-1 to 42-2, 41-3-41 -6, 91 to 94 ... Power semiconductor devices, 41a to 46a, 91a to 94a ... Switching elements, 41b to 46b, 91b to 94b ... Body diodes, 105 ... Temperature sensors, 111, 112. .. Gate command, 113 ... Gate output voltage, 114 ... Gate voltage monitoring signal, 115, 116 ... Feedback signal, 117, 118 ... Circulation operation command.

Claims (16)

A plurality of power semiconductor elements forming a pair of arms, a control unit that outputs a control command for the gates of the plurality of power semiconductor elements, and a voltage applied to the gate in response to the control command to drive the power semiconductor element. In a power conversion device having a gate drive device and
The control unit outputs a reflux operation command for applying a predetermined voltage for conducting a current in the reverse direction of the power semiconductor element to the gate drive device.
The gate drive device is a power conversion device characterized in that a predetermined voltage is applied to all the power semiconductor elements of the pair arm in response to the return operation command. The power conversion device according to claim 1, wherein the control unit outputs the recirculation operation command to the gate drive device when an abnormality is detected in the power conversion device. When an abnormality is detected in the power conversion device, the control unit outputs a cutoff command for cutting off the current of the power semiconductor element to the gate drive device, and then sends the return operation command to the gate drive device. Output and
The gate drive device is characterized in that, after applying a voltage that cuts off a current in response to the cutoff command to all the power semiconductor elements of the pair arm, the predetermined voltage is applied in response to the return operation command. The power conversion device according to claim 2. The electric power according to claim 3 , wherein the control unit outputs the recirculation operation command to the gate drive device after a first predetermined time has elapsed after outputting the cutoff command to the gate drive device. Converter. The gate drive device outputs the monitoring result of the state of the gate to the control unit, and outputs the monitoring result to the control unit.
The invention according to any one of claims 2 to 4, wherein the control unit outputs the recirculation operation command to the gate drive device when the monitoring result indicates an abnormality that does not match the control command. Power converter. Including a plurality of the anti-arms
The control unit outputs the recirculation operation command for applying the predetermined voltage to all the power semiconductor elements of the pair arm including the power semiconductor element whose monitoring result indicates an abnormality to the gate drive device. ,
The gate drive device is characterized in that a predetermined voltage is applied to all the power semiconductor elements of the pair arm including the power semiconductor element whose monitoring result indicates an abnormality in response to the reflux operation command. Item 5. The power conversion device according to Item 5. 3. The predetermined voltage is a voltage that causes a substrate bias effect in the power semiconductor element, which is less than the threshold voltage of the power semiconductor element and larger than the voltage that cuts off the current of the power semiconductor element. The power conversion device according to any one of 6 to 6 . The power conversion device according to claim 7 , wherein the predetermined voltage is a voltage at which a reflux current flows between a source and a drain together with a parasitic diode in the power semiconductor element. When the control unit conducts a current in the forward direction of the power semiconductor element, the control unit performs a current in the forward direction of the power semiconductor element after a second predetermined time elapses after applying the predetermined voltage to the power semiconductor element. The power conversion device according to claim 4 , wherein a continuity command for conducting the current is output to the gate drive device. Including a plurality of the anti-arms
The control unit outputs the recirculation operation command for applying the predetermined voltage to the power semiconductor element of all the pair arms to the gate drive device.
The gate driving device according to any one of claims 1 to 5, 7 to 9 , wherein the gate driving device applies the predetermined voltage to all the power semiconductor elements of the pair arm in response to the reflux operation command. The power converter described. The power conversion device according to any one of claims 1 to 10, wherein the predetermined voltage is corrected according to the temperature of the power semiconductor element detected by the temperature detection unit. The power conversion device according to any one of claims 1 to 11, wherein the power semiconductor element is a wide-gap semiconductor having a bandgap of a predetermined value or more. The power conversion device according to any one of claims 1 to 12, wherein the power semiconductor elements are connected in parallel in each arm of the pair of arms. The power conversion device according to any one of claims 1 to 13, wherein the power conversion device is an inverter that converts DC power into AC power. The power conversion device according to any one of claims 1 to 14, wherein the power conversion device is a converter that converts AC power into DC power. Multiple power semiconductor devices that form a pair of arms,
A control unit that outputs control commands for the gates of the plurality of power semiconductor elements, and
In a current control method executed in a power conversion device having a gate drive device for driving the power semiconductor element by applying a voltage to the gate in response to the control command.
The control unit outputs a recirculation operation command for applying a predetermined voltage for conducting a current in the opposite direction of the power semiconductor element to the gate drive device.
A current control method in a power conversion device, wherein the gate drive device applies the predetermined voltage to all the power semiconductor elements of the pair arm in response to the return operation command.

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