JP2007028860A - Power-converting device and rolling stock equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small power conversion device that reduces the number of component parts, constituting a multiple-level power-converting device and that has less power loss. <P>SOLUTION: In this power-converting device, connection units, in which a plurality of switching devices comprising IGBTs and diodes connected inverse parallel are connected in series, are connected to both ends of two DC voltage source connected in series. The connection point of the series connection of the switching devices comprising IGBTs and diodes connected inverse parallel is used as an AC output terminal. Furthermore, two switching elements, having backward breakdown strength voltage are connected in reverse parallel, and its one end is connected to an intermediate terminal of the DC voltage, and the other end connected to the AC output terminal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power conversion device that converts direct current and alternating current to each other, and a railway vehicle including the power converter.

  One of the most important technologies in power conversion technology is an inverter that generates alternating current from direct current. In particular, IGBT inverters using IGBTs as switching elements are used in a wide range of fields from home appliances to railway vehicles.

  There are two-level inverters that generate AC from two DC potentials and multi-level inverters that generate AC from three or more DC potentials. The two-level inverter has a small number of parts, and is small and inexpensive. On the other hand, multi-level inverters are characterized by low distortion and low noise with little distortion in the output AC.

  FIG. 2 shows a three-level inverter circuit disclosed in Patent Document 1 in which only the U phase is extracted. In FIG. 2, reference numerals 201 to 204 are transistors, 211 and 214 are free wheel diodes, 231 and 232 are clamp diodes, 250 is an AC output terminal, 251 and 252 are power supply capacitors, and 253 is a neutral point.

  In the circuit of FIG. 2, when the transistor 201 is turned on and the transistor 204 is turned off, a positive DC potential is output to the AC output terminal 250, the transistors 202 and 203 are turned on, and the transistors 201 and 204 are turned off. , The potential of the neutral point 253 is output, and when the transistor 204 is turned on and the transistor 201 is turned off, a negative potential is output. As a result, alternating current is generated from the direct current power source.

Japanese Patent Application Laid-Open No. 56-121374 (FIGS. 3 and 6, description on page 2, lower left column, line 6 to page 2, lower right column, line 13 and page 3, lower right column, lines 5 to 14)

  However, in the prior art inverter shown in FIG. 2, when a positive voltage is output, the transistor 201 is turned on and current flows from the DC side to the AC side, but in this case, only one transistor passes through the element. Therefore, the loss is the resistance R × current value I of the transistor. On the other hand, when a current is passed from the neutral point to the AC output terminal 250, since the current passes through the two elements of the diode and the transistor, the loss becomes (diode resistance Rd + transistor resistance R) × current value I. The loss in the case of outputting current from becomes large.

  An object of the present invention is to provide a small and lightweight power conversion device with reduced loss and a railway vehicle equipped with the power conversion device.

  The power converter of the present invention includes a first DC voltage source and a second DC voltage source connected in series, a first terminal and a second terminal at both ends of the DC voltage source, a first DC power source, A first terminal and a second IGBT, which are semiconductor switching elements having a self-extinguishing capability, and a third terminal connected to the connection point of the second DC power source, At least two switching devices composed of diodes connected in antiparallel are used, the two switching devices are connected in series, and both ends thereof are connected to the first terminal and the second terminal, A first circuit having an AC output terminal as a connection point of the two switching devices; a third switching device including a third IGBT and a fourth IGBT connected in reverse parallel; and the third switching device. The and a second circuit connected to said AC output terminal and the third terminal, the third IGBT and the fourth IGBT has a reverse breakdown voltage.

  An ON command is input to the fourth IGBT at least 1 μs or more before the third IGBT shifts from the ON state to the OFF state. Similarly, the ON command is input to the third IGBT at least 1 μs or more before the fourth IGBT shifts from the ON state to the OFF state. The third IGBT and the fourth IGBT are non-punch through IGBTs, and the forward breakdown voltage and the reverse breakdown voltage of the third IGBT and the fourth IGBT are the first breakdown voltage of the DC power supply. It is higher than ½ of the voltage between the terminal and the second terminal.

  According to the present invention, the power device can be reduced in size and weight, and loss can be reduced. By reducing the loss, the radiator can be made smaller and lighter, and in the railway vehicle equipped with the power conversion device of the present invention, the capacity of passenger seats and cargo space can be increased and the speed of the vehicle can be increased.

  Hereinafter, details of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of a power conversion apparatus according to this embodiment. 1, reference numerals 101 and 104 are IGBTs, 102 and 103 are reverse blocking IGBTs, 111 and 114 are free wheel diodes, 121 to 124 are gate drivers, 150 is an AC output terminal, 151 and 152 are power supply capacitors, and 153 is neutral. Is a point. Here, the reverse blocking IGBT is an IGBT having a reverse breakdown voltage.

  The operation of the circuit of this embodiment will be described using the waveforms in FIG. FIG. 3 shows a command pattern input to the gate drivers 121 to 124 of the circuit of FIG. 1 and a voltage waveform output to the AC output terminal 150. A case where current flows from the AC output terminal 150 to the load will be described. Prior to time t1, only the reverse blocking IGBT 103 is on. However, since the reverse blocking IGBT 103 is connected in the reverse direction to the current, the current flowing out from the AC output terminal 150 is supplied from the negative power supply side through the freewheel diode 114. For this reason, the potential of the AC output terminal 150 during this period is negative.

  Next, when reverse blocking IGBT 102 is turned on at time t <b> 1, current flows from neutral point 153 through reverse blocking IGBT 102 to AC output terminal 150. At this time, the potential of the AC output terminal 150 becomes the potential of the neutral point 153. Next, the reverse blocking IGBT 103 is turned off at time t2, but since no current flows through the reverse blocking IGBT 103, the current does not change. Subsequently, when the IGBT 101 is turned on at time t3, a current flows from the positive side of the DC power supply to the AC output terminal 150 through the IGBT 101. The reverse blocking IGBT 102 is turned off because a voltage is applied in the reverse direction. Further, although the reverse blocking IGBT 103 is applied with a voltage in the forward direction, no current flows because the input signal to the gate driver 123 is off. During this period, a positive voltage is output to the AC output terminal. When the IGBT 101 is turned off at time t 4, the current again flows from the reverse blocking IGBT 102, and the voltage at the neutral point 153 is output to the AC output terminal 150. Even if the reverse blocking IGBT 103 is turned on at time t5, the current flow does not change because the reverse direction is applied, and the output voltage does not change. At time t6, when the reverse blocking IGBT 102 is turned off, current flows from the negative side of the DC voltage to the AC output terminal 150 through the free wheel diode 114. At this time, a reverse voltage is applied to the reverse blocking IGBT 103. Further, although a forward voltage is applied to the reverse blocking IGBT 102, no current flows because an OFF signal is input to the gate driver 122. During this period, a negative potential is output to the AC output terminal 150. Even if the IGBT 104 is turned on at the time t7, the current flows through the free wheel diode 114, so that no change occurs. Even if the IGBT 104 is turned off at time t8, the current does not change in the same manner, and the output voltage remains at a negative potential. When the reverse blocking IGBT 102 is turned on again at time t9, the current flows from the neutral point 153 through the reverse blocking IGBT 102 to the AC output terminal 150, and the potential of the neutral point 153 is output to the AC output terminal 150. . In this way, an AC waveform composed of a negative voltage, a neutral point, and a positive potential is generated from the DC voltage.

  What should be noted in the control of this circuit is the timing when the reverse blocking IGBT 102 and the reverse blocking IGBT 103 are turned on and off. A reverse blocking IGBT, which is an IGBT having a reverse withstand voltage, must apply a positive voltage to the gate when applying a voltage in the reverse direction. This is because if a reverse voltage is applied to the gate without applying a positive voltage, a leakage current is generated and a loss occurs. In the worst case, the IGBT may be destroyed due to heat generated by the loss. For this reason, it is preferable to apply a positive voltage in advance to the gate of the IGBT to which a reverse voltage is applied. In FIG. 3, the IGBT 101 is turned on at time t <b> 3 and a positive voltage is input to the gate of the reverse blocking IGBT 103 at time t <b> 2 before reverse voltage is applied to the reverse blocking IGBT 103. The interval between t2 and t3 needs to be at least 1 μs in consideration of the operation delay of the IGBT. This is the time required for the gate voltage of the IGBT to actually increase to the ON state after the ON signal is input from the gate driver to the gate of the IGBT.

  The drive sequence as described above is unique in a circuit using a reverse blocking IGBT having a reverse breakdown voltage. When a conventional IGBT and a diode are connected in series, the diode holds a reverse applied voltage. There is no need to consider a positive voltage applied to the gate of the IGBT.

  The case where the current flows from the DC power source side to the AC output side has been described above. However, when the current flows from the AC output side toward the power source side, the operation is complementary to the above operation, and the IGBT 101 and the IGBT 104 and the reverse blocking IGBT 102 are operated. It will be apparent to those skilled in the art that the reverse movement IGBT 103 is replaced and considered to perform the same movement.

  The breakdown voltage of the IGBT 101 and the IGBT 104 must be higher than the voltage across the DC power supply, but the breakdown voltage of the reverse blocking IGBT 102 and the reverse blocking IGBT 103 only needs to be greater than ½ of the voltage across the DC power supply. Alternatively, an element having a lower withstand voltage than that of the IGBT 104 can be used. As the breakdown voltage of the IGBT decreases, the conduction loss decreases. Therefore, when an IGBT having a low breakdown voltage is applied to the reverse blocking IGBT 102 and the reverse blocking IGBT 103, the loss as a power converter system can be reduced.

FIG. 4 shows a cross-sectional structure of an IGBT applied to this embodiment. In FIG. 4, reference numeral 401 denotes a collector electrode, 402 denotes a p collector layer, 403 denotes an n ⁻ drift layer, 404 denotes a gate oxide film, 405 denotes a gate electrode, 406 denotes an interlayer insulating film, 407 denotes an n ⁺ emitter layer, and 408 denotes p. ^{The +} layer, 409 is a p base layer, and 410 is an emitter electrode.

IGBT of FIG. 4, the forward, that is, when the collector side is positive and the application of a rated voltage in the direction in which the emitter side becomes negative, p base layer 409 and the n ^- n from the pn junction formed by the drift layer 403 ^- drift layer 403 The depletion layer extending inward has a so-called non-punch through type (NPT type) IGBT structure that does not reach the p collector layer 402. This is due to the following reason. In the reverse blocking IGBT, a reverse voltage, that is, a negative voltage is applied to the collector side and a positive voltage is applied to the emitter side. When a reverse voltage is applied, a strong electric field is generated at the pn junction formed by the p collector layer 402 and the n ⁻ drift layer 403. For this reason, this junction needs to be a so-called step junction where the concentration of either the p-type or n-type is low, and the p collector layer 402 and the n ⁻ drift layer 403 are in direct contact as shown in FIG. Become. In this structure a depletion layer in the case of applying a rated voltage n ^- spreads throughout the drift layer 403, it must be so-called punch-through phenomenon does not occur, n ^- the thickness of the drift layer 403, generated when the rated voltage is applied It is necessary to make it thicker than the thickness of the depletion layer. This is because when the punch-through phenomenon occurs, the p collector layer 402 and the p base layer 409 are connected by a depletion layer and current flows.

  As described above, in this embodiment, by applying the NPT type IGBT structure having the reverse breakdown voltage to the reverse blocking IGBT 102 and the reverse blocking IGBT 103, the clamp diode necessary for the conventional multilevel inverter can be eliminated.

  FIG. 5 is a circuit diagram showing the power converter of this embodiment. 5, reference numerals 501, 503, 506, and 508 are IGBTs, reference numerals 502, 504, 505, and 507 are reverse blocking IGBTs, 511 to 514 are free wheel diodes, 521, 523 to 528, 530 are gate drivers, and 550 is an AC output. Terminals, 531 to 534 are power supply capacitors, 535 is a neutral point, and 541 and 542 are clamp diodes.

  In this embodiment, an example applied to a 5-level inverter is shown. The five-level inverter has five potentials, namely, a potential at both ends of the power source, a neutral point 535, and an intermediate potential point provided between the neutral point 535 and the positive and negative potentials. The neutral point 535 and the AC output terminal 550 are connected by reverse blocking IGBTs 504 and 505 connected in antiparallel. Further, the intermediate potential point and the AC output terminal 550 are connected by reverse blocking IGBT 502 and IGBT 503 or reverse blocking IGBT 507 and IGBT 506. According to the present embodiment, since the IGBT has a reverse breakdown voltage, it is not necessary to connect diodes in series, and the number of elements to be used can be reduced.

  In the present embodiment, an example of a five-level inverter is shown, but of course it is not limited to this, and a multi-level inverter of 7 levels or more can be similarly applied.

  The example in which the present invention is applied to an inverter that generates alternating current from direct current has been described above, but the same applies to a converter that generates direct current from alternating current. That is, if the AC output terminal of the above-described embodiment is used as an AC input terminal and the DC input terminal is used as a DC output terminal, it can be operated as a converter, and the same effect as the above-described inverter embodiment can be obtained. This will be apparent to those skilled in the art.

  FIG. 6 shows an embodiment in which the present invention is applied to a railway vehicle power converter. In FIG. 6, reference numeral 600 is an AC overhead wire, 601 is a current collector, 602 is a transformer, 603 is a converter, 604 is a filter capacitor, 605 is an inverter, and 606 is a motor.

  The operation of FIG. 6 will be described. The alternating current taken from the AC overhead line 600 through the current collector 601 is stepped down by the transformer 602 and supplied to the converter 603. In the converter 603, the supplied alternating current is converted into a direct current and input to the inverter 605. The filter capacitor 604 is connected to stabilize the DC voltage, and preferably has a capacity that can sufficiently cope with a sudden change in load. The inverter 605 converts the input direct current into a three-phase alternating current and supplies it to the motor 606.

  If the power conversion device according to the first to third embodiments is applied to the converter 603 and the inverter 605, the number of parts can be reduced, and the device can be reduced in size and weight and loss can be reduced. If the loss is reduced, the cooler of the power conversion device can be reduced in size, so that the electric equipment in the vehicle can be mounted on the railway vehicle in a small space. For this reason, the comfort for passengers can be improved by increasing the space for passengers, and the transportation capacity can be increased by increasing the number of seats. In addition, since the electrical equipment becomes lighter, the maximum speed can be increased, the time for passengers and luggage to reach the destination can be shortened, and convenience can be improved.

  As described above, the present embodiment shows an example in which the present invention is applied to an AC vehicle that takes in electric power from an AC overhead line. Needless to say, the present invention is also effective in a DC vehicle that travels by taking in electric power from a DC overhead line. Moreover, although the example which applies the power converter circuit of this invention to both converter inverters was shown in the example of AC vehicle, of course, it is also possible to apply only to a converter or only an inverter. In particular, it is preferable to apply a multi-level converter that hardly generates noise / noise to the converter side having a high operating frequency.

It is explanatory drawing of the circuit of the power converter device of Example 1. FIG. It is explanatory drawing of the 3 level inverter circuit of a prior art. It is explanatory drawing of the operation | movement sequence of the power converter device of Example 1. FIG. 6 is a cross-sectional view of a reverse blocking IGBT of Example 2. FIG. It is explanatory drawing of the circuit of the power converter device of Example 3. FIG. It is explanatory drawing of the railway vehicle carrying the power converter device of Example 4. FIG.

Explanation of symbols

101, 104, 501, 503, 506, 508 ... IGBT, 102, 103, 502, 504, 505, 507 ... Reverse blocking IGBT, 111, 114, 211, 214, 511-514 ... Freewheel diode, 121-124, 521, 523-528, 530 ... Gate driver, 150, 250, 550 ... AC output terminal, 151, 152, 251, 252, 531-534 ... Power supply capacitor, 153, 253, 535 ... Neutral point, 201-204 ... transistors, 231,232,541,542 ... clamping diodes, 401 ... a collector electrode, 402 ... p collector layer, 403 ... n ^- drift layer, 404 ... gate oxide film, 405 ... gate electrode, 406 ... interlayer insulating film, 407 ... n ⁺ emitter layer, 408 ... p ⁺ layer, 409 ... p base layer, 4 0 ... emitter electrode, 600 ... AC overhead wire, 601 ... current collector, 602 ... transformer, 603 ... converter, 604 ... filter capacitor 605 ... inverter, 606 ... motor.

Claims (12)

In the power converter that alternately converts direct current and alternating current,
The power converter is
A first terminal and a second terminal connected to both ends of the first DC voltage source and the second DC voltage source connected in series, and a connection point between the first DC voltage source and the second DC voltage source. A third terminal to be connected;
A self-extinguishing first semiconductor switching element and a second semiconductor switching element connected in series, and a diode connected in antiparallel to the first semiconductor switching element and the second semiconductor switching element; Both ends of the first semiconductor switching element and the second semiconductor switching element connected in series are connected to the first terminal and the second terminal, and the first semiconductor switching element and the second semiconductor switching element are connected to each other. A first circuit having the connection point as an AC output terminal;
One connection point of the third semiconductor switching element and the fourth semiconductor switching element connected in antiparallel is connected to the third terminal, and the third semiconductor switching element and the fourth semiconductor connected in antiparallel are connected. A second circuit for connecting the other connection point of the switching element to the AC output terminal,
The power conversion device, wherein the third semiconductor switching element and the fourth semiconductor switching element are elements having a reverse breakdown voltage. The power conversion device according to claim 1,
An on-command is input to the fourth semiconductor switching element when the third semiconductor switching element shifts from an on state to an off state. The power conversion device according to claim 2,
The power conversion device, wherein an ON command is input to the fourth semiconductor switching element at least 1 μs before the third semiconductor switching element shifts from the ON state to the OFF state. The power conversion device according to claim 1,
An on-command is input to the third semiconductor switching element when the fourth semiconductor switching element shifts from an on state to an off state. The power conversion device according to claim 4,
The power conversion device according to claim 1, wherein an on command is input to the third semiconductor switching element at least 1 μs before the fourth semiconductor switching element shifts from the on state to the off state. The power conversion device according to claim 1,
The power conversion device, wherein the third semiconductor switching element and the fourth semiconductor switching element are non-punch-through IGBTs. The power conversion device according to claim 1,
The forward breakdown voltage and reverse breakdown voltage of the third semiconductor switching element and the fourth semiconductor switching element are higher than ½ of the voltage between the first terminal and the second terminal of the DC power supply. Power conversion device characterized by The power conversion device according to claim 1,
The third semiconductor switching element and the fourth semiconductor switching element are:
A pair of main surfaces, a first conductivity type first layer adjacent to one main surface, a second conductivity type second layer adjacent to the other main surface and the first layer, and the other main surface A third layer of the first conductivity type adjacent to the surface and selectively formed in the second layer, and a second conductivity type adjacent to the other main surface and selectively formed in the third layer A fourth layer, an insulating electrode formed between the second layer and the fourth layer on the surface portion of the third layer exposed on the other main surface via an insulating film, and a third layer And a fourth electrode formed in contact with the fourth layer, and a third electrode formed in contact with the first layer. In the power converter that alternately converts direct current and alternating current,
The power converter is
A first terminal and a second terminal connected to both ends of a plurality of DC voltage sources connected in series; a plurality of intermediate DC terminals connected to a connection point of the plurality of DC voltage sources; and a neutral point terminal;
A plurality of semiconductor switching element connecting bodies each having a diode connected in antiparallel to a self-extinguishing semiconductor switching element are connected in series, and both ends of the plurality of connecting bodies connected in series are connected to the first terminal. A first circuit connected to the second terminal and having one of the connection points of the series-connected connectors as an AC output terminal;
A second connection point where one connection point of two semiconductor switching elements connected in reverse parallel is connected to the neutral terminal, and the other connection point of the two semiconductor switching elements connected in reverse parallel is connected to the AC output terminal. And the circuit
Another semiconductor switching element connection body having a diode connected in reverse parallel to a self-extinguishing type semiconductor switching element connected to a connection point of the connection body of the first circuit and the intermediate DC terminal; and ,
The power conversion device, wherein the two semiconductor switching elements connected in reverse parallel and the semiconductor switching element of the different connection body are elements having a reverse breakdown voltage. In a railway vehicle comprising a current collector that collects power from an overhead line, an inverter that converts the collected power into AC power, and a motor that is driven by AC power output from the inverter,
The inverter is
A first terminal and a second terminal connected to both ends of the first DC voltage source and the second DC voltage source connected in series, and a connection point between the first DC voltage source and the second DC voltage source. A third terminal to be connected;
A self-extinguishing first semiconductor switching element and a second semiconductor switching element connected in series, and a diode connected in antiparallel to the first semiconductor switching element and the second semiconductor switching element; Both ends of the first semiconductor switching element and the second semiconductor switching element connected in series are connected to the first terminal and the second terminal, and the first semiconductor switching element and the second semiconductor switching element are connected to each other. A first circuit having the connection point as an AC output terminal;
One connection point of the third semiconductor switching element and the fourth semiconductor switching element connected in antiparallel is connected to the third terminal, and the third semiconductor switching element and the fourth semiconductor connected in antiparallel are connected. A second circuit for connecting the other connection point of the switching element to the AC output terminal,
The railway vehicle, wherein the third semiconductor switching element and the fourth semiconductor switching element are elements having a reverse breakdown voltage. The railway vehicle according to claim 10,
The railway vehicle, wherein the power collected from the overhead wire is DC power, and the third semiconductor switching element and the fourth semiconductor switching element of the inverter are non-punch-through IGBTs. The railway vehicle according to claim 10,
The power collected from the overhead wire is AC power, and includes a converter that converts the AC power to DC power,
A first terminal and a second terminal connected to both ends of the first DC voltage source and the second DC voltage source connected in series, and a connection point between the first DC voltage source and the second DC voltage source. A third terminal to be connected;
A self-extinguishing first semiconductor switching element and a second semiconductor switching element connected in series, and a diode connected in antiparallel to the first semiconductor switching element and the second semiconductor switching element; Both ends of the first semiconductor switching element and the second semiconductor switching element connected in series are connected to the first terminal and the second terminal, and the first semiconductor switching element and the second semiconductor switching element are connected to each other. A first circuit having the connection point as an AC output terminal;
One connection point of the third semiconductor switching element and the fourth semiconductor switching element connected in antiparallel is connected to the third terminal, and the third semiconductor switching element and the fourth semiconductor connected in antiparallel are connected. A second circuit for connecting the other connection point of the switching element to the AC output terminal,
The railway vehicle, wherein the third semiconductor switching element and the fourth semiconductor switching element are elements having a reverse breakdown voltage.

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