GB2533212A

GB2533212A - Power conversion device and railway vehicle including the same

Info

Publication number: GB2533212A
Application number: GB1519871.6A
Authority: GB
Inventors: Ando Masato; Ogawa Kazutoshi; Ishikawa Katsumi; Tanaka Takeshi; Konno Akitoyo
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2014-11-28
Filing date: 2015-11-11
Publication date: 2016-06-15
Anticipated expiration: 2035-11-11
Also published as: CN105656323A; JP2016103897A; JP6457800B2; GB2533212B; DE102015223002A1; GB201519871D0; CN105656323B

Abstract

A power conversion device in which a plurality of semiconductor modules is connected in parallel unifies and reduces surge voltages resulting from parasitic inductances at the time of switching. The device includes first and second capacitors 102,103, and first and second semiconductor modules 108, 109. The positive terminals of the first and second capacitors and positive terminals of the first and second semiconductor modules are connected by positive wiring 201. Negative terminals of the first and second capacitors and negative terminals of the first and second semiconductor modules are connected by negative wiring 202. The first capacitor is connected to first ends of the positive wiring and the negative wiring via the positive terminal and the negative terminal and the second capacitor is connected to second ends of the positive wiring and the negative wiring via the positive terminal and the negative terminal. The first and second semiconductor modules are connected by the positive wiring via the positive terminals and connected by the negative wiring via the negative terminals in areas between the first ends and the second ends of the positive wiring and the negative wiring. The arrangement is particularly suitable for a railway vehicle.

Description

DESCRIPTION

Title of Invention: POWER CONVERSION DEVICE AND RAILWAY VEHICLE INCLUDING THE SAME

Technical Field

[0001] The present invention relates to a power conversion device.

Background Art

[0002] In recent years, semiconductor modules with a plurality of insulated gate bipolar transistors (IGETs) and metal oxcide semiconductor field effect transistors (MOSFETs) have been applied to power conversion devices typified by inverters and converters.

[0003] The material for the semiconductor modules has been developed basically based on Si (silicon). For further reduction of loss, however, the application of wide-band gap semiconductors based on SiC (silicon carbide) or GaN (gallium nitride) has been contemplated. The use of Sic would achieve a higher switching speed as compared to using Si to reduce a switching loss.

[0004] Meanwhile, a surge voltage is generated as an instantaneous high voltage at the time of switching resulting from a parasitic inductance of the wiring between a capacitor and a semiconductor module constituting a power conversion device. In general, the surge voltage increases at a higher switching speed. When the surge voltage differs among semiconductor modules or exceeds the maximum rating for the semiconductor modules, this may cause a deterioration or breakdown.

[0005] JP 2009-153246 A (PTI, 1) discloses the background technique in the relevant technical field. The publication describes that "DC-AC conversion circuitry is formed by semiconductor modules of respective phases connected to an output stage in parallel to each other, a plurality of electrolytic capacitors is supported with alternate arrangement of connection electrodes via a capacitor support tool on the semiconductor modules of respective phases, the electrolytic capacitors are connected in parallel to one another to connection portions of DC conductors attached for parallel connection of the semiconductor modules of respective phases, and AC conductors of respective phases are connected to the output sides of the semiconductor modules of respective phases.

Citation List Patent Literature [0006] PTL 1: JP 2009-153246 A

Summary of Invention Technical Problem [0007]

As a method for suppressing a surge voltage generated in a semiconductor element described above, the wiring may be shortened to reduce the parasitic inductance of the wiring as described in PTL 1. However, even if the parasitic inductance of the wiring can be reduced, when there are differences in wiring length between the capacitors and the semiconductor modules, variations occur in parasitic inductances between the semiconductor modules and the capacitor. This produces imbalances in surge voltages generated in the semiconductor modules, and certain ones of the semiconductor modules become likely to suffer a deterioration or breakdown. As a result, the power conversion device is decreased in reliability.

Accordingly, an object of the invention is to unify the parasitic inductances of the wiring between the capacitors and the semiconductor modules to unify the surge voltages generated in the semiconductor modules.

Solution to Problem [0008] To solve the foregoing problem, the present invention employs the configurations described in the claims, for example. The subject application includes a plurality of means for solving the foregoing problem. As an example, one of them is a power conversion device including first and second capacitors, and first and second semiconductor modules, wherein positive terminals of the first and second capacitors and positive terminals of the first and second semiconductor modules are connected by positive wiring, negative terminals of the first and second capacitors and negative terminals of the first and second semiconductor modules are connected by negative wiring, the first capacitor is connected to first ends of the positive wiring and the negative wiring via the positive terminal and the negative terminal, the second capacitor is connected to second ends of the positive wiring and the negative wiring via the positive terminal and the negative terminal, and the first and second semiconductor modules are connected by the positive wiring via the positive terminals and connected by the negative wiring via the negative terminals in areas between the first ends and the second ends of the positive wiring and the negative wiring.

Advantageous Effects of Invention [0009] According to the invention, it is possible to unify surge voltages generated in the semiconductor modules of the power conversion device.

Brief Description of Drawings

[0010] [FIG. 1] FIG. 1 is a schematic view of a drive system for railway vehicle to which a power conversion device according to a first example of the present invention is applied.

[FIG. 2] FIG. 2 is a circuit diagram of a single-phase power conversion device according to the first example of the present invention.

[FIG. 3] FIG. 3 illustrates operation waveforms of the single-phase power conversion device according to the first example of the present invention.

[FIG. 4] FIG. 4 is an exploded bird's-eye view of the single-phase power conversion device according to the first example of the present invention.

[FIG. 5] FIG. 5 is a bird's-eye view of the single-phase power conversion device according to the first example of the present invention.

[FIG. 6] FIG. 6 illustrates capacitors according to the first example of the present invention.

[FIG. 7] FIG. 7 illustrates a capacitor module according to the first example of the present invention.

[FIG. 6] FIG. 8 is an exploded bird's-eye view of a single-phase power conversion device according to a second example of the present invention.

[FIG. 9] FIG. 9 is a circuitdiagramofathree-phasepower conversion device according to a third embodiment of the present invention.

[FIG. 10] FIG. 10 is a bird's-eye view of the three-phase power conversion device according to the third example of the present invention.

[FIG. 11] FIG. 11 is an exploded bird's-eye view of a single-phase power conversion device according to a fourth example of the present invention.

[FIG. 12] FIG. 12 is an exploded bird's-eye view of a single-phase power conversion device according to a comparison example.

Description of Embodiments

[0011] Hereinafter, examples will be described with reference to the accompanying drawings. In the drawings and the descriptions of the examples, MOSFETs are taken as semiconductor modules. However, the present invention is also applicable to IGBTs.

[First Example]

[0012] FIG. 1 is a schematic view of a drive system for railway vehicle to which a power conversion device according 7.o a first example of the present invention is applied. The drive system for railway vehicle is powered from an overhead line 2 via a current collector, and AC power at a variable voltage and variable frequency is supplied to a motor 111 through a power conversion device 1 to drive the motor 111. The motor 111 is coupled to the axle shaft of the railway vehicle to control the running of the railway vehicle. The electric ground is connected via a rail 3. In this example, the voltage of the overhead line 2 maybe DC or AC. In the following description, the DC voltage is assumed to be 1500 V. In the case where the voltage of the overhead line 2 is AC, the drive system includes an AC-DC convertor between the power conversion device 1 and the overhead line.

[0013] FIG. 2 is a circuit diagram of a single-phase power conversion device 4 according to the first example of the present invention. The single-phase power conversion device 4 is composed of capacitors 102 and 103 that smooth out a DC power source 101 and switching elements Q1 to Q4. In the case of using a two-in-one package in which the switching elements Q1 and Q2, Q3 and Q4 are identical, the single-phase power conversion device 4 is composed of a semiconductor module 108 having the switching elements Q1 and Q2 and a semiconductor module 109 having the switching elements Q3 and Q4. The capacitors 102 and 103 may be electrolytic capacitors or film capacitors. To increase the capacitances of the capacitors 102 and 103, a large number of small-capacitance capacitor cells maybe connected in parallel in the capacitors 102 and 103. In the case where the switching elements Q1 to Q4 are IGBTs, diodes D1 to D4 need to be connected in parallel in the direction opposite to the IGBTs. In the case where the switching elements Ql to Q4 are MOSFETs, the diodes D1 to D4 may be parasitic diodes of the MOSFETs. The drain electrode, the gate electrode, and the source electrode of the switching elements Q1 are indicated with reference signs D, G, and S, respectively.

[0014] In the semiconductor module 108, the switching elements Q1 and Q2 are connected in series, and the point of connection between the switching elements Q1 and Q2 constitutes the point of AC output to the motor 111. Similarly, in the semiconductor module 109, the switching elements Q3 and Q4 are connected in series, and the point of connection between the switching elements Q3 and Q4 constitutes the point of AC output to the motor 111.

[0015] Wiring is used to electrically connect the capacitors 102 and 103 and the semiconductor modules 108 and 109. The wiring includes parasitic inductances 104, 105, and 106, and their values depend on the material, length, and shape of the wiring. FIG. 3 illustrates operation waveforms of the first example of the present invention. The single-phase power conversion device 4 operates such that the DC power source 101 supplies DC power and the switching elements Ql to Q4 perform switching actions to convert the DC power to AC power to drive the motor 111. In the following description, the switching element Q1 is taken as an example.

[0016] At t = to, a gate-source voltage VGS of the switching element Q1 is 0 V. Since the switching element Q1 is then in the off state, 1500 V is applied by the DC power source 101 as a drain-source voltage VDS, and drain current ID is not flown. [0017] At t = tl, a voltage equal to or higher than a threshold turn-on voltage of the switching element Q1, for example, 15 V is applied as the gate-source voltage VGS, the switching element Ql is turned on to flow the drain current ID. The on-time of the switching element Ql is controlled by the current flowing into the motor 111. For example, the on-time of the switching element Ql is PWM (pulse width modulation)-controlled.

[0018] At t = t2, the gate-source voltage VGS of the switching element Q1 becomes 0 V and the switching element Q1 shifts to the off state. Then, the drain current ID decreases to 0 A according to the current change rate di/dt, and induced electromotive force is generated in the parasitic inductances 104, 105, and 106 in the wiring between the capacitors 102 and 103 and the semiconductor modules 108 and 109. That is, an instantaneous surge voltage 11 is generated in the drain-source voltage VDS in the switching element Q1. When the surge voltage 11 exceeds the maximum rating voltage of the switching element Ql, the single-phase power conversion device 4 suffers a breakdown.

[0019] At gate-off timings oft = t4, t6, and t8, as at the timing of t = t2, thesurgevoltageIIis generated when the gate voltage VGS of the switching element Q1 becomes 0 V and the switching element Q1 shifts to the off state. The surge voltage can be calculated by multiplying the current change rate di/dt by the value of the wiring parasitic inductance. In general, the current change rate di/dt differs among the switching-elements Q1 to Q4, but the difference in wiring parasitic inductance between the capacitors 102 and 103 and the semiconductor modules 108 and 109 has larger influence on the surge voltage 11. That is, the surge voltage 11 generated in the switching elements Q1 to Q4 varies depending on the difference among the wiring parasitic inductances. Accordingly, when the difference in wiring parasitic inductance between the semiconductor modules is large, the degree of progress of deterioration and breakdown varies among the switching elements Q1 to Q4. It is thus an important issue to unify the wiring parasitic inductances between the semiconductor modules and desirably reduce the wiring parasitic inductances.

[0020] When the switching speed is increased, that is, when the current change rate di/dt is increased to reduce a switching loss, induced electromotive force generated in the parasitic inductances between the capacitors 102 and 103 and the semiconductor modules 108 and 109 becomes large, which may cause a breakdown of the single-phase power conversion device 4. That is, it is further required to solve the foregoing issue in the case of using switching elements of Sic and GaN that allow-a higher switching speed as compared to the conventional Si switching elements.

[0021] FIG. 4 is an exploded perspective view of the single-phase power conversion device 4 according to the first example of the present invention. FIG. 5 is a perspective view of the single-phase power conversion device 4 according to the first example of the present invention. Positive electrodes of the capacitors 102 and 103 and positive electrodes of the semiconductor modules 108 and 109 are electrically connected by the use of a positive bus bar 201. Negative electrodes of the capacitors 102 and 103 and negative electrodes of the semiconductor module 108 and 109 are electrically connected by the use of a negative bus bar 202. The positive bus bar 201 and the negative bus bar 202 include parasitic inductances. The magnitudes of the parasitic inductances depend on the material, length, and shape of a current pathway.

[0022] It is not practical to change the material and shape of the wiring for each of the semiconductor module because the design and manufacturing process would become complicated. Accordingly, as described above, to unify the parasitic inductances in the wiring from the semiconductor module 108 and 109 to the capacitors 102 and 103, it is necessary to make the total length of wiring from the positive electrode of the semiconductor module 108 through the capacitor 102 to the negative electrode of the semiconductor module 108 and the wiring from the positive electrode of the semiconductor module 108 through the capacitor 103 to the negative electrode of the semiconductor module 108 almost equal to the total length of the wiring from the positive electrode of the semiconductor module 109 through the capacitor 102 to the negative electrode of the semiconductor module 109 and the wiring from the positive electrode of the semiconductor module 109 through the capacitor 103 to the negative electrode of the semiconductor module 109. [0023] Accordingly, in the present invention, as illustrated in FIG. 4, the positive electrodes of the semiconductor modules are connected by positive wiring to the positive electrodes of the two capacitors 102 and 103, and the negative electrodes of the semiconductor modules are connected by negative wiring to the negative electrodes of the two capacitors 102 and 103, and the points of connection with the electrodes of the semiconductor modules are positioned between the points of connection with the electrodes of the two capacitors 102 and 103 on the positive wiring and the negative wiring. That is, the electrodes of the capacitors 102 are connected to first ends of the positive wiring and the negative wiring, the electrodes of the capacitor 103 are connected to second ends of the positive wiring and the negative wiring, and the electrodes of the semiconductor modules 108 and 109 are connected to the middle portions of the positive wiring and the negative wiring.

According to this configuration, the wiring lengths of the bus bars 201 and 202 from the capacitor 102 to the semiconductor module 108 are equal to the wiring lengThs of the bus bars 201 and 202 from the capacitor 103 to the semiconductor module 109, and the wiring lengths of the bus bar 201 and 202 from the capacitor 102 to the semiconductor module 109 are equal to the wiring lengths of the bus bars 201 and 202 from the capacitor 103 to the semiconductor module 108. That is, the parasitic inductance between the semiconductor module 108 and the two capacitors 102 and 103 is equal in value to the parasitic inductance between the semiconductor module 109 and the two capacitors 102 and 103.

[0024] FIG. 12 illustrates a comparative example. Referring to FIG. 12, on the positive wiring and the negative wiring, the points of connection with the electrodes of the semiconductor modules are not connected between the points of connection with the electrodes of the two capacitors 102 and 103 but are connected to the capacitors at one end of the wiring and are connected to the semiconductor modules at the other end of the wiring. When being connected in such a configuration, the semiconductor module 109 is positioned closer to the capacitors on the circuit than the semiconductor module 108, which causes biases among parasitic inductances in the wiring.

[0025] FIG. 6 illustrates capacitors 102 and 103 used in the single-phase power conversion device 4 according to the first example of the present invention. As illustrated in FIG. 5, the positive wiring and the negative wiring are configured in flat plate form and are arranged at a distance almost in parallel to each other. Accordingly, the same amount of electric current flows in mutually opposite directions, and the magnetic flux is canceled out to reduce the wiring inductance and the surge voltage.

[0026] In addition, the two capacitors 102 and 103 are configured to have electrodes on the surfaces opposite to the opposed surfaces. By providing the electrode arrangement surfaces as illustrated in FIGS. 4 and 5, the capacitors 102 and 103 can be adjacent to each other to form the capacitors 102 and 103 into one capacitor module.

[0027] Taking the capacitor 103 as an example, the capacitor 103 has positive electrodes 301 to 304 and negative electrodes 305 to 308 on the surface opposite to the surface opposed to the capacitor 102. In the present invention, the eight capacitor electrodes 301 to 308 are provided. However, at leas7_ one each positive electrode and negative electrode may be provided. In this example, when the capacitors 301 to 308 are unevenly arranged on the electrode arrangement surface of the capacitor 103, an imbalance occurs between currents output from the capacitors 102 and 103, which results in deterioration and breakdown of the capacitors 102 and 103. To solve this problem, in the present invention, the electrodes of the capacitors 102 and 103 are arranged at equal spaces on the electrode arrangement surfaces. By connecting the positive electrodes 301 to 304 of the capacitors 102 and 103 to the positive bus bar 201 and connecting the negative electrodes 305 to 308 of the capacitors 102 and 103 to the negative bus bar 202, it is possible to unify the current distributions in the positive bus bar 201 and the negative bus bar 202, and suppress concentration of current on and around the capacitor electrodes 301 to 308.

In addition, by arranging the negative electrodes 301 to 304 and the negative electrodes 305 to 308 in a zigzag pattern, the opposed areas of the positive bus bar 201 and the negative bus bar are equal to improve the effect of cancelling out the magnetic fields resulting from the currents flowing in the positive bus bar 201 and the negative bus bar 202, and contribute to reduction in the parasitic inductances 104 and 105. [Example 21 [0028] FIG. 8 illustrates a single-phase power conversion device according to a second example of the present invention. In general, to increase the capacity of a power conversion device, a plurality of semiconductor modules is connected in parallel to increase the current capacity. FIG. 8 is a configuration when a plurality of the semiconductor modules is connected. The capacitors 102 and 103 are configured in the same manner as the single-phase power conversion device 4 in the first example such that the points of connection with the electrodes of semiconductor modules 203 to 210 on the positive wiring and the negative wiring are positioned between the points of connection with the electrodes of the two capacitors 102 and 103. [0029] The semiconductor modules 203 to 210 are connected in parallel. It is assumed that the semiconductor modules 203 to 206 and the semiconductor modules 207 to 210 constitute one each leg of the power conversion device. When the lengths of the wiring from the capacitors 102 and 103 to the semiconductor modules 203 to 210 are different, the problem of variations in the surge voltage occurs as described above.

[0030] Accordingly, the bus bars 201 and 202 in the first example are used to connect the pluralixy of capacitors 102 and 103 and semiconductor modules 203 to 210. In this example, the high-potential electrodes and the low-potential electrodes of the semiconductor modules 203 to 206 are aligned in the same directions, and the high-potential electrodes and the low-potential electrodes of the semiconductor modules 207 to 210 are aligned in the same directions. According to this configuration, the wiring length of the bus bar connecting the capacitor 102 and the semiconductor modules 203 to 206 is equal to the wiring length of the bus bar connecting the capacitor 103 and the semiconductor modules 207 to 210, and the wiring length of the bus bar connecting the capacitor 102 and the conductor modules 207 to 210 is equal to the wiring length of the bus bar connecting the capacitor 103 and the semiconductor modules 203 to 206. That is, the parasitic inductances are equal to cause no variations in the surge voltage.

[Third Example]

[0031] FIG. 9 is a circuit diagram of a three-phase power conversion device 5 as the power conversion device 1 according to another embodiment of the present invention. The three-phase power conversion device 5 is composed of the capacitors 102 and 103 and semiconductor modules 108 to 110. The three-phase power conversion device 5 is configured to convert DC power of the DC power source 101 to AC power and drive a three-phase motor 311. In this example, the operations of the switching element Q1 are the same as described above and thus descriptions thereof will be omitted. As in the case of the single-phase power conversion device 4, the positive electrodes of the capacitors 102 and 103 and the positive electrodes of the semiconductor modules 108 to 110 are electrically connected by the use of the bus bar 201, and the negative electrodes of the capacitors 102 and 103 and the negative electrodes of the semiconductor module 108 to 110 are electrically connected by the use of the negative bus bar 202, and parasitic inductances 104 to 106 reside in the wiring. The parasitic inductances 104 to 106 depend on the wiring shape. When the values of the parasitic inductances 104 to 106 are different, there arise variations in the surge voltages generated in the semiconductor modules 108 to 110, which results in deterioration and breakdown of the three-phase power conversion device 5.

[0032] FIG. 10 is a bird's-eye view of the three-phase power conversion device 5 according to the second example of the present invention. As in the case of the single-phase power conversion device 4, the capacitors 102 and 103 are configured such that the points of connection with the electrodes of the semiconductor modules 108, 109, and 110 on the positive wiring and the negative wiring are positioned between the points of connection with the electrodes of the two capacitors 102 and 103. The semiconductor modules 108 to 110 are aligned in parallel on the same plane. According to this configuration, the wiring length of the bus bar connecting the capacitor 102 and the semiconductor module 108 is equal to the wiring length of the bus bar connecting the capacitor 103 and the semiconductor module 109. In this example, the wiring length of the bus bar connecting the capacitor 102 and the semiconductor module 110 is physically longer than the wiring length of the bus bar connecting the capacitor 102 and the semiconductor module 108 by the size of the semiconductor module 108. However, the positive bus bar 201 and the negative bus bar 202 form a parallel-flat plate structure. The direction of current flowing in the positive bus bar 201 and the direction of current flowing in the negative bus bar 202 are mutually opposite, and the magnetic fields are thus cancelled out and the absolute values of the parasitic inductances 104 7_o 106 are as small as several nH. That is, the difference between the parasitic inductance 105 and the parasitic inductance 106 becomes very small so there will be no problem of variations in the surge voltage. Similarly, the wiring length of the bus bar connecting the capacitor 102 and the semiconductor module 109 is equal to the wiring length of the bus bar connecting the capacitor 103 and the semiconductor module 108, whereas the wiring length of the bus bar connecting the capacitor 103 and the semiconductor module 110 is shorter than the wiring length of the bus bar connecting the capacitor 102 and the semiconductor module 109 with reduction in the parasitic inductance. As in the foregoing case, the parallel-flat plate structure causes a very small difference between the parasitic inductances to cause no problem of variations in the surge voltage.

[Fourth Example]

[0033] FIG. 11 illustrates a single-phase power conversion device as the power conversion device 1 according to another example of the present invention. Although in the first example, the electrode arrangement surfaces of the two capacitors are on mutually opposite sides, the electrode arrangement surfaces may be on the same plane as Illustrated in FIG. 11. In this case, as in the other examples, the points of connection with the electrodes of the semiconductor modules 108 and 109 on the positive wiring and the negative wiring are positioned between the points of connection with the electrodes of the two capacitors 102 and 103.

Reference Signs List [0034] 1 power conversion device 2 overhead line 3 rail 4 single-phase power conversion device three-phase power conversion device 11 surge voltage Ql to Q6 switching element D1 to D6 diode 101 DC power source 102, 103 capacitor 104 to 106 parasitic inductance 108 to 110 semiconductor module 111 single-phase motor 112 capacitor module 201 positive bus bar 202 negative bus bar 203 to 210 small-capacitance semiconductor module 301 to 304 positive electrode of capacitor 305 to 308 negative electrode of capacitor 311 three-phase motor