JP2017221008A - Power conversion device and power conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a power converter, to suppress influences exerted upon a sound phase by an accident phase and to recover the power converter by exchanging only the accident phase if an accident occurs, although it is difficult to make downsizing of the power converter compatible with suppression of influences exerted upon the sound phase by the accident phase in the case of a short-circuiting accident.SOLUTION: In a power converter, one phase consists of a semiconductor switching element, a capacitor, wiring and a fuse. Multiple capacitors are connected in parallel for each phase, and the fuse is inserted into a part of wiring that connects the capacitors in parallel. Thus, the power converter can be downsized, influences exerted upon a sound phase by an accident phase in the case of a short-circuiting accident are suppressed, and the power converter can be recovered by exchanging only a component of the accident phase.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device and a power conversion method, and more particularly to a power conversion device and a power conversion method suitable for main circuit configuration and main circuit protection.

  Power converters using semiconductor switching elements are widely used in fields such as industry, home appliances, transportation, automobiles, and power / social infrastructure systems. Industrial power converters of several hundred kW or more are often composed of assemblies containing multiple semiconductor switching elements. In such a power converter, even if an accident occurs in which the semiconductor switching element is short-circuited, the accident phase is quickly separated by the protective means in the power converter, and the influence on the healthy phase is suppressed. It is desirable to reduce downtime until recovery. In response to this requirement, a protection method in which a fuse is inserted at a location where the DC circuit portion inside the power converter is connected is frequently used.

  In this way, a fuse is inserted in the DC circuit to protect the power converter, and a circuit in which a diode and a capacitor are connected in series is provided so that the fuse can be blown quickly in the event of a short circuit in the semiconductor switching element. Is described, for example, in JP-A-2014-96892.

JP 2014-96892 A

  The above prior art is a protection circuit for a configuration having a smoothing capacitor in a three-phase package. On the other hand, power converters for industrial and power / social infrastructure systems have been increased in voltage for the purpose of reducing loss. In such high-voltage power converters, components such as semiconductor switching elements have high breakdown voltage / The one with a large current is used. When a circuit is configured with three phases at once, the distance between the smoothing capacitor and the semiconductor switching element is increased to ensure the insulation distance and creepage distance. As the distance increases, the parasitic inductance of the main circuit increases. When the parasitic inductance increases, the semiconductor switching element may be damaged by the jumping voltage generated between the terminals of the semiconductor switching element when switching the semiconductor switching element. Therefore, an additional circuit for suppressing the jumping voltage such as a snubber circuit is provided. This is necessary and causes an increase in the size of the power converter.

  As described above, power converters, particularly high-voltage power converters, have a problem that it is difficult to achieve both miniaturization and suppression of the influence of the accident phase on the healthy phase in the event of a short circuit accident.

  An object of the present invention is to provide a power conversion device and a power conversion method that can reduce the size of the power conversion device and that can be easily restored when an accident occurs.

  In order to achieve the above object, the present invention has a plurality of phase circuits constituting a phase, the plurality of phase circuits partially including a common DC voltage unit, and each of the plurality of phase circuits includes: A switching circuit configured by a semiconductor switching element and performing a power conversion operation; an AC terminal connected to the switching circuit; a plurality of capacitors connected in parallel between the switching circuit and the DC voltage unit; A fuse connected between the switching circuit and the DC voltage unit is provided.

  Alternatively, each phase includes a semiconductor switching element, a first capacitor, a second capacitor, and a wiring, and a common DC circuit in which the DC circuits of the assembly are connected in parallel. One capacitor and a second capacitor are connected in parallel to the DC circuit of the assembly, the first capacitor terminal is connected in the vicinity of the semiconductor switching element of the assembly DC circuit, and the second capacitor terminal is connected to the first capacitor Compared to the above, it is connected to the common DC circuit side of the assembly DC circuit, and has a configuration in which a fuse is inserted into a part of the wiring connecting the first capacitor terminal connection location and the second capacitor terminal connection location.

  According to the present invention, it is possible to reduce the inductance of the DC circuit as expected from the semiconductor switching element, and as a result, it is possible to reduce the size of the apparatus. In addition, since the fuse can be blown by the discharge current from the capacitor in the assembly, the influence of the accident phase on the healthy phase in the event of a short-circuit accident can be suppressed, and simple recovery is possible by replacing only the accident phase.

1 is a configuration of a power converter according to a first embodiment of the present invention. FIG. 3 is a diagram for explaining a current flow in the first embodiment of the present invention. It is a figure explaining the circuit structure and current path in the case of a reference example. It is a figure explaining the circuit structure and current path of a reference example. 6 is a configuration of a power converter according to a third embodiment of the present invention. 6 is a configuration of a power converter according to a fourth embodiment of the present invention. It is a figure explaining the circuit using the semiconductor switching element in this invention. It is a figure explaining the circuit using the semiconductor switching element in this invention. It is explanatory drawing of the electric current which flows from the capacitor | condenser in this invention.

  EMBODIMENT OF THE INVENTION Below, the form for inventing is demonstrated using drawing.

  Example 1 will be described. Fig. 1 shows the circuit configuration of the power converter. In this embodiment, a three-phase two-level converter will be described as an example. The main circuit of this power converter is composed of circuits 102a, 102b, and 102c that form one phase, and the DC terminals of 102a, 102b, and 102c are a common DC circuit 100a (also referred to as a DC voltage unit (positive electrode)), 100b (also referred to as DC voltage section (negative electrode)) is connected in parallel. 102a, 102b, and 102c have a disconnection configuration (not shown) between them and a common DC circuit, and can be removed or replaced for each phase.

  The circuit (102a, 102b, 102c) that constructs one phase forms, for example, a U phase, a V phase, and a W phase, and each terminal (104a), terminal (104) of the circuit (102a, 102b, 102c) that constructs one phase 104b) and terminal (104c) are connected to the U-phase, V-phase, and W-phase terminals of the three-phase AC power machine. As a result, an AC motor (not shown) is driven, or regenerative power is converted to DC.

  For example, taking the circuit (102a) for constructing one phase as an example, the circuit (102a) for constructing one phase is connected to the switching element (401) on the positive side as the circuit (101) as shown in FIG. A pair of positive reverse diodes (402), a negative switching element (401) and a negative reverse diode (402) pair are connected in series. Via the wiring (positive electrode) (108a) connected to the circuit composed of semiconductor switching elements to the DC circuit (100a), via the wiring (negative electrode) (109a) connected to the circuit composed of semiconductor switching elements Connected to the DC circuit (100b). The connection point between the pair of the positive switching element (401) and the positive reverse diode (402) and the pair of the negative switching element (401) and the negative reverse diode (402) is input / output. Terminal (104a).

  The switching element (401) converts the DC power between the DC circuit (100a) and the DC circuit (100b) into AC power by switching such as PWM and outputs it from the terminal (104a), or the terminal (104a) AC power is converted into direct current and output to the direct current circuit (100a) and direct current circuit (100b).

  The switching element (401) performs power conversion by switching alternately up and down by a gate drive circuit and a gate control circuit (not shown). The switching element 401 is controlled by a PWM modulation system by comparing a modulated wave and a carrier wave by a PWM control circuit (not shown).

  The other circuits (102b) and (102c) for constructing one phase have the same configuration as the circuit (102a) for constructing one phase.

  In the circuit (102a) constituting one phase, the first capacitor (102a) is placed in parallel with the DC circuit (100a) and the DC circuit (100b) in close proximity to the circuit (101a) constituted by the semiconductor switching element. 103a) is installed. The circuit has the configuration shown in FIG. Although IGBT (401) is used as the semiconductor switching element in FIG. 7, it may be replaced with other semiconductor switching elements (transistor, GTO, thyristor, etc.). Thus, since the current path (C100) from the capacitor (103a) to the circuit (101a) composed of the semiconductor switching elements is reduced, the parasitic inductance of the current path can be reduced. Here, since the jumping voltage applied between the terminals when the IGBT (401) switches is determined by the parasitic inductance and the current change (di / dt), the jumping voltage can be suppressed by this configuration. Accordingly, a snubber circuit for protecting the semiconductor switching element from the jumping voltage becomes unnecessary, and the power converter can be downsized.

  The structure and mechanism for realizing the accident propagation suppression to the healthy phase using the second capacitor, which is a feature of the present invention, will be described below.

  The power converter shown in the present embodiment is provided in the assembly provided for each phase, the first capacitor (103a) provided in the immediate vicinity of the semiconductor switching element (101a), and the wiring connected to the terminals of the capacitor (103a). Aside from the fuse (105a / 106a) and the first capacitor (103a), it is installed on the common DC circuit (100a / 100b) side, between the DC circuit (100a) and the DC circuit (100b). The second capacitor (107a) is provided with a feature.

  With this configuration, when a semiconductor switching element short circuit accident occurs, it is possible to blow only the fuse in the fault phase, and it is possible to reduce the impact on the sound phase assembly (102b, 102c) .

  The current flow when the fuse is blown will be described with reference to FIG.

  The fuse (105a) is inserted so that one of the terminals of the semiconductor switching element (101a) and the DC circuit 100a are disconnected by fusing. The fuse (106a) is inserted so as to separate the other terminal of the semiconductor switching element (101a) from the DC circuit (100b) by fusing.

  When the semiconductor switching element is short-circuited, electric charge is first discharged from the capacitor (103a) adjacent to the circuit (101a) composed of the semiconductor switching element to the circuit (101a) composed of the semiconductor switching element (current path (200) ). Since the voltage between the terminals of the capacitor (103a) decreases due to the charge discharge, current flows from the capacitor (107a) through the fuse (105a), the current blows the fuse (current path (201)), and the accident phase Disconnected from the DC voltage section (100a / 100b). Since the capacitor (107a) is provided in the same assembly as the circuit (101a) composed of semiconductor switching elements, the parasitic inductance from the capacitor (107a) to the circuit (101a) composed of semiconductor switching elements is It is smaller than the parasitic inductance from the capacitor in the assembly (102b, 102c) to the circuit (101a) constituted by the semiconductor switching element of the accident phase (102a). Therefore, the current required to blow the fuse in the accident phase is supplied from the capacitor (107a). By supplying the current for fusing the fuse from the capacitor (107a), the terminal voltage of the capacitor (107a) is lowered, so that the current also flows from the healthy phase. In order to reduce the influence on the healthy phase, compared to the parasitic inductance from the capacitor (107a) to the circuit (101a) composed of semiconductor switching elements, the healthy phase generated by the wiring (L10 / L20) connecting each phase To the capacitor (107a) is desirably sufficiently large. Note that the resonance frequency determined by the capacitance of the capacitor (107a) and the parasitic inductance of the current path (201) is more than four times the resonance frequency determined by the parasitic inductance of the capacitor (103b) and the current path (203). Thus, it is desirable to select the parasitic inductance of the wiring (L10) connecting each phase and the capacitance of each capacitor. As a result, for example, as shown in FIG. 9, it is possible to blow the fuse by the current (800) flowing from the capacitor (107a) in the accident phase before the current (801) flowing from the healthy phase reaches the peak value. Become. This is a mechanism for reducing the influence on the healthy phase when the semiconductor switching element is short-circuited.

  The flow of fuse blowing when there is no capacitor (107a) closest to the fuse will be described as a comparative example with reference to FIG. Here, the leftmost phase (102a) is the accident phase, and the other phases (102b and 102c) are the healthy phases. When a short circuit of the semiconductor switching element occurs in this configuration, the charge is first released from the capacitor (103a) close to the circuit (101a) composed of the semiconductor switching element (current path (200)), and then the healthy phase ( Since the fuse is blown by discharging the electric charge from the capacitor (103b) of 102b and 102c (current path (202)), not only the fault phase (102a) but also the fuse of the healthy phase (102b and 102c) Fatigue accumulates. Therefore, when recovering from an accident, it is necessary to recover not only from the accident phase but also from other phases.

  Next, as a comparative example, a case where there is no capacitor (103a) arranged in the immediate vicinity of the circuit (101a) composed of semiconductor switching elements will be described with reference to FIG. In this configuration, in the event of a short circuit failure of the semiconductor switching element, the fuse is blown by discharging the capacitor (107a) arranged in the immediate vicinity of the fuse, so that current is supplied from other phases as in the configuration shown in FIG. Inflow is suppressed and the fuse for the accident phase only is blown. However, since the current path (C200) from the capacitor (107a) to the circuit (101a) composed of semiconductor switching elements becomes large, the parasitic inductance of the current path becomes large. Therefore, there is a concern about the jumping voltage when switching the semiconductor switching element, a protection circuit such as a snubber circuit is required, and the power converter becomes large.

  As described above, according to the present embodiment, since the inductance of the DC circuit expected from the semiconductor switching element can be reduced, it is not necessary to add a snubber circuit, and as a result, the power converter can be miniaturized. In addition, since the fuse can be blown by the discharge current from the second capacitor in the assembly, the influence of the accident phase on the sound phase can be suppressed in the event of a short circuit accident, and recovery can be achieved by replacing only the accident phase.

Figure 2 shows how to select the capacitance of the capacitor (107a) placed in the immediate vicinity of the fuse. In the second embodiment, which is a modification of the first embodiment (same in other embodiments), only different parts will be described. Therefore, the part where the description is omitted is the same as that of the first embodiment. When the semiconductor switching element (402) in the circuit (101a) composed of the semiconductor switching elements has a short circuit failure, the fuse (105a) is blown by the discharge current of the capacitor (107a) as shown in the first embodiment. The Here, the fuse is blown by the discharge current Is (A) that flows to blow the fuse and the Joule integral value Is ² t (A ² s) determined by the discharge time ts (s).

Here, Rs (Ω) is the resistance of the current path (201) at the time of the short-circuit accident, V0 (V) is the voltage before discharge of the capacitor (107a), V1 (V) is the voltage after discharge, and the capacitor (107a) If the capacitance of Cf (F) is Cf (F), the time t (s) required to discharge the capacitor voltage from V0 (V) to V1 (V) can be obtained by equation (1). That is, the time to blow the fuse at the time of a short circuit failure is determined by the characteristics of the fuse (Joule integral value Is ² t (A ² s)), the resistance at the time of the short circuit failure, and the capacitance of the capacitor (107a) for fusing the fuse. Accordingly, the capacitance of the fuse blowing capacitor (107a) is selected according to the time at which the fuse should be blown when the semiconductor switching element (402) is short-circuited. The selected component is employed.

  t (s) =-Cf × Rs × ln (V0 / V1) ... Equation (1)

  Figure 5 shows an example of a 3-phase 3-level converter. In addition to DC circuit (300a) (also referred to as DC voltage section (positive electrode)) and DC circuit (300b) (also referred to as DC voltage section (negative electrode)), DC circuit (300c) (also referred to as DC voltage section (common)) Composed. A capacitor (308a) is provided between the DC circuit (300a) and the DC circuit (300c), and a capacitor (308b) is provided between the DC circuit (300c) and the DC circuit (300b).

  The wiring (positive) (309) connected to the circuit composed of the semiconductor switching elements of the circuit (301) constructing one phase (309) and the wiring (common) (311) connected to the circuit composed of the semiconductor switching elements A capacitor (303a) is provided between the wiring (311) and a wiring (negative electrode) (310) connected to a circuit composed of semiconductor switching elements.

A fuse (305a) is connected between the wiring (309) of the circuit (301) and the DC circuit (300a), and a fuse (307a) is connected between the wiring (311) and the DC circuit (300c). 310) and a DC circuit (300b) are provided with a fuse (306a) As shown in FIG. 8, the circuit (301) constituting one phase is switched between the wiring (309) and the wiring (310). Four pairs of the element (401) and the reverse diode (402) are connected in series, the connection point between the pair of the two upper switching elements (401) and the reverse diode (402), and the two lower switching elements (401 ) And the connection point of the pair of reverse diodes (402) are connected by two diodes (501) connected in series. One of the circuits formed by connecting four pairs of the switching element (401) and the reverse diode (402) in series is connected to the DC circuit (300a) via the wiring (309), and the other is connected to the DC circuit via the wiring (310). Connected to the circuit (300b). The connection point of the two diodes (501) is connected to the DC circuit (300c) via the wiring (311). The connection point between the two upper switching elements (401) and the reverse diode (402) and the connection point between the two lower switching elements (401) and the reverse diode (402) are the input / output terminals (304). It becomes. The circuits that make up the other phase are similarly configured.

  The circuit (301) shown in FIG. 8 functions at three levels by PWM modulation, and outputs positive output, zero output, and negative output to the input / output terminal 304, or outputs AC power from the input / output terminal 304 to DC. Power conversion.

  As in the first embodiment, the circuit is configured in the order of a circuit (301) including capacitors (308a and 308b), fuses (305a, 306a, and 307a), capacitors (303a and 303b), and semiconductor switching elements. The effects and operations of this configuration are the same as in the first embodiment.

  FIG. 6 shows another embodiment of the three-phase two-level converter. Similar to the first embodiment, a first capacitor (103a) is installed in the vicinity of the circuit (101a) composed of the semiconductor switching element, and the circuit (101a) composed of the semiconductor switching element and the first capacitor ( A circuit group 103a) is defined as one circuit group (700), and the circuit group is connected in parallel to the fuses (105a and 106a). In the present embodiment, the circuit configuration of two parallels is shown, but the number of parallels may be different. The same applies to the configuration shown in the third embodiment.

100a / 300a ... DC voltage part (positive electrode), 100b / 300b ... DC voltage part (negative electrode), 101 / 101a / 101b / 301 ... Circuit composed of semiconductor switching elements, 104a / 104b / 304 ... terminal (AC output terminal) ), 105a, 106a, 105b, 106b, 305a, 306a, 307a ... fuses, 102a, 102b, 102c, 302a, 302b, 302c ... circuits constituting the phases, 103a, 103b, 107a, 303a, 303b, 308a, 308b ... Capacitors, 108, 309 ... wiring connected to a circuit composed of semiconductor switching elements (positive electrode), 109, 310 ... wiring connected to a circuit composed of semiconductor switching elements (negative electrode), 200, 201, 202, 203 ... Current path, 300c ... DC voltage section (common), 311 ... Wiring (common) connected to a circuit composed of semiconductor switching elements, 401 ... IGBT, 402 ... Diode, 700 ... Consists of semiconductor switching elements A circuit group consisting of a circuit and a capacitor, 800 ・ 801… The current that blows the fuse , C100 / C200 ... current path, L10 / L20 ... wiring to connect each phase

Claims (8)

  A plurality of phase circuits, each of which includes a common DC voltage unit, and each of the plurality of phase circuits includes a semiconductor switching element and performs power conversion operation; Switching circuit, an AC terminal connected to the switching circuit, a plurality of capacitors connected in parallel between the switching circuit and the DC voltage unit, and between the switching circuit and the DC voltage unit A power conversion device comprising a fuse to be connected.   In Claim 1, the plurality of capacitors connected in parallel are constituted by a first capacitor connected in proximity to the switching circuit, and a second capacitor connected in parallel with the first capacitor, The fuse is inserted into a wiring connecting the first capacitor and the second capacitor, and the second capacitor has a capacitance necessary to blow the fuse in a desired time. Power conversion device.   3. The power converter according to claim 1, wherein the parasitic inductance of the wiring connecting the capacitor in each phase circuit and the semiconductor switching element of the phase is smaller than the parasitic inductance of the wiring connecting the phases. .   The resonance frequency determined by the inductance between the circuit constituted by the second capacitor and the semiconductor switching element in an arbitrary phase and the electrostatic capacitance of the second capacitor according to claim 2, A power converter characterized by being at least four times the resonance frequency determined by the inductance between the first capacitors in a phase different from the phase and the capacitance of the first capacitor in the different phase.   5. The structure according to claim 1, wherein one phase is composed of the plurality of semiconductor switching elements, the capacitor, the wiring, and the fuse as one assembly, and the assembly is integrated when replacing parts. A power conversion device characterized in that it can be removed.   2. The power converter according to claim 1, wherein a capacitance of a fuse blown capacitor is selected according to a fuse blow time when the semiconductor switching element has a short circuit failure.   2. The DC voltage unit according to claim 1, wherein the DC voltage unit is a positive DC voltage unit, a negative DC voltage unit, and a common DC voltage unit, and a capacitor is disposed between the DC voltage unit and the common DC voltage unit. A capacitor is disposed between a voltage unit and the negative DC voltage unit, and a fuse is disposed corresponding to each of the positive DC voltage unit, the negative DC voltage unit, and the common DC voltage unit. Conversion device.   A control method for a power converter having a plurality of phase circuits constituting a phase, wherein the plurality of phase circuits partially include a common DC voltage unit, wherein each of the plurality of phase circuits includes semiconductor switching The power is converted by a switching operation of an element, and a jumping voltage of the semiconductor switching element is absorbed by a plurality of capacitors connected in parallel between the switching circuit and the DC voltage unit. Power conversion method that cuts off with a fuse connected between the two.

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