JP2002034267A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily protect a power converter by controlling a short-circuit current when a fault such as short-circuit of arm is generated. SOLUTION: A current limiting device 6 consisting of an n-type silicon semiconductor is connected in series to a DC capacitor 5 in a voltage type power converter including semiconductor switching elements 2a, 2b and a DC capacitor 5 for converting an alternate current to a direct current or a direct current to an alternate current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor power converter, and more particularly to a power converter capable of suppressing a short-circuit current flowing when a circuit is short-circuited.

[0002]

2. Description of the Related Art FIG. 9 is a circuit diagram showing a conventional general voltage type power converter. In FIG. 9, reference numeral 21 denotes a converter for converting AC to DC, reference numeral 22 denotes a DC capacitor, and reference numeral 23 denotes a converter for converting DC to AC. Inverter. Here, one phase of the converter circuit 21 will be described as an example. 24a, 24
b is an upper and lower arm gate turn-off thyristor, 25a and 25b are anode reactors connected in series to gate turn-off thyristors 24a and 24b, respectively, and 26a and 26b are anode reactors 25 respectively.
a, a reflux diode connected in parallel to 25b, 27a,
27b is a gate turn-off thyristor 24a,
Reflux diodes connected in anti-parallel to 24b, 28a, 2
8b is a fuse.

In FIG. 9, when the upper and lower arms become conductive due to element damage, erroneous signals, etc., an arm short circuit occurs. In the conventional circuit shown in FIG. 9, the short-circuit current flowing from the DC capacitor 22 when the arm is short-circuited is limited by blowing the fuse to protect the gate turn-off thyristors 24a and 24b from accidents such as breakage.

FIG. 10 is a circuit diagram showing a conventional power converter disclosed in Japanese Patent Application Laid-Open No. 9-233833. In FIG. 10, reference numeral 29 denotes a power conversion device including a bridge-connected semiconductor switch element, reference numeral 30 denotes a DC capacitor, reference numeral 31 denotes a current limiting device using the critical current characteristic of the superconductor shown in FIG. 11, and reference numeral 32 denotes a transformer. .

[0005] In FIG. 10, a current equal to or less than the critical current of the current limiting device 31 flows in the current limiting device 31 at normal times, and the current limiting device 31 is energized in a superconducting state. When the arm is short-circuited or the upper and lower arms are simultaneously energized, a large short-circuit current flows from the DC capacitor 30, and when the short-circuit current exceeds the critical current of the current limiting device 31, the current limiting device 31 enters a normal conduction state. As shown, the short-circuit current is suppressed, and the semiconductor switch element is protected.

[0006]

Since the conventional power converter is constructed as described above, in the first example, since the semiconductor switch element is protected by blowing the fuse, the capacity of the DC capacitor is large. Sometimes, or when the DC voltage is high, there is a problem that the protection coordination between the fuse and the semiconductor switch element cannot be achieved.

Further, in order to suppress the short-circuit current, an anode reactor is required, and a circuit for consuming the energy stored in the anode reactor is required, so that the apparatus becomes expensive and the efficiency of the apparatus is impaired. There was a problem.

In the power converter disclosed in JP-A-9-233833, since a superconductor is used as a current limiting device, liquid helium or the like is used to keep the superconductor in a superconductive state. There is a problem that the used cooler is required and the apparatus becomes expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and when a failure such as a short-circuit of an arm of a power converter occurs, a short-circuit current is suppressed and the device is easily protected. It is intended to do so.

[0010]

According to a first aspect of the present invention, there is provided a power converter comprising a converter for converting a direct current into an alternating current and an inverter for converting an alternating current into a direct current. And a circuit in which a DC current capacitor and a DC capacitor are connected in series, are connected in parallel to the converter and the inverter.

According to a second aspect of the present invention, there is provided a power converter in which a plurality of circuits in which a current limiting device and a DC capacitor are connected in series are connected in parallel to a converter and an inverter.

According to a third aspect of the present invention, a power converter includes a diode connected in parallel with a current limiting device.

According to a fourth aspect of the present invention, there is provided a power conversion device, comprising: a voltage monitoring circuit for monitoring a voltage generated in the current limiting device; and determining a short-circuit state based on a voltage value of the voltage monitoring circuit exceeding a predetermined value. And a control circuit for stopping the apparatus in response to a command from the abnormality determination circuit.

A power converter according to a fifth aspect of the present invention is a power-type three-level power converter comprising a converter for converting DC to AC and an inverter for converting AC to DC, wherein two DC capacitors are provided. Is connected in parallel to the converter and the inverter, and a current limiting device made of an n-type silicon semiconductor is connected in series between the upper DC capacitor and the neutral point. A current limiting device comprising a current limiting device connected in series between the lower DC capacitor and the neutral point, and monitoring a voltage generated at both ends of the two current limiting devices, and a voltage value of the voltage monitoring circuit being a predetermined value. An abnormality determination circuit that determines a short circuit state when the value is exceeded, and a control circuit that stops the apparatus in response to a command from the abnormality determination circuit are provided.

A power converter according to a sixth aspect of the present invention is a power type three-level power converter comprising a converter for converting direct current to alternating current and an inverter for converting alternating current to direct current. A circuit in which a current limiting device made of an n-type silicon semiconductor is connected in series is connected in parallel to the converter and the inverter,
Connect the diode so that the anode is located at the middle point of the upper DC capacitor and the current limiting device, and the diode is located at the neutral point of the cathode, and the cathode is located at the middle point of the lower DC capacitor and the current limiting device.
A diode is connected so that the anode is connected to the neutral point

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram showing a power converter according to Embodiment 1 of the present invention. In the figure, a power converter (converter) 1 includes semiconductor switching elements 2a and 2b and a freewheel diode 3a connected in anti-parallel thereto. , 3b. Reference numeral 4 denotes an inverter device, which is also constituted by a semiconductor switch element and converts DC into AC, and FIG. 1 shows one phase. 5 is a DC capacitor for storing DC power, and 6 is a current limiting device made of an n-type silicon semiconductor.

In FIG. 2, the current limiting device 6 has a low resistance in a low voltage region (Vr <Vp) and a low resistance (Vd>Vr> Vp) in a high voltage region due to the drift velocity of electrons generated at a certain voltage (electric field). Has a non-linear characteristic of high resistance. When the temperature Tj of the current limiting device 6 increases, the resistance value of the current limiting device 6 has a positive temperature coefficient.

FIGS. 3 (a) to 3 (d) are graphs showing operation waveforms of respective parts in the power converter.
The difference of the load current flowing to the side flows. The current flowing during normal operation is set to be equal to or less than Ip, and the voltage Vr generated in the current limiting device 6 is small.

On the other hand, when the arm is short-circuited due to element breakage or the like, or when the arms are simultaneously energized, a short-circuit current flows. In this case, a short-circuit current flows through the current limiting device 6, and the voltage Vr of the current limiting device 6 gradually increases. When the short-circuit current exceeds Ip, the current limiting device 6 reaches the high-resistance region and the voltage Vr (> V
p) rises and suppresses short-circuit current.

As shown in FIG. 1, by connecting a current limiting device 6 made of an n-type silicon semiconductor to the DC capacitor 5 in series, a short-circuit current can be suppressed and the semiconductor switching element can be protected. With the above-described configuration, it is possible to suppress element breakage and short-circuit current flowing during simultaneous energization, and it is possible to easily protect the device even during short-circuit.

Embodiment 2 FIG. FIG. 4 is a circuit diagram showing a power converter according to a second embodiment of the present invention. In the figure, reference numeral 7 denotes a voltage monitoring circuit that monitors a voltage Vr applied to a current limiting device 6, and 8 denotes a short-circuit abnormality. The abnormality determination circuit 9 to be determined is a control circuit. When a short circuit occurs, it is determined that Vr has exceeded a predetermined voltage Vcl, and the control circuit 9 stops the device. As shown in FIG. 4, when a short circuit occurs, the voltage of the current limiting device 6 is monitored, a short circuit state is determined, and a device for stopping the device is provided.

Embodiment 3 FIG. FIG. 5 is a circuit diagram showing a power converter according to Embodiment 3 of the present invention. In the figure, 5a and 5b are DC capacitors connected in parallel, and 6a and 6b are connected to DC capacitors 5a and 5b. Each is a current limiting device connected in series. FIG. 5 shows an example of two parallel arrangements, but more than two arrangements may be used. As shown in the figure, a plurality of DC capacitors 5 connected in parallel
By connecting the current limiting devices 6a and 6b in series with the a and 5b, respectively, the shunt current between the DC capacitors 5a and 5b can be equalized. Further, resonance due to wiring inductance between the DC capacitors 5a and 5b and the DC capacitors can be suppressed.

Embodiment 4 FIG. 6 is a circuit diagram showing a power converter according to Embodiment 4 of the present invention. In the figure, a diode 10 is connected in parallel with current limiting device 6. By connecting the diode 10 in the opposite direction to the discharge path in this way, the current for charging the DC capacitor 5 in the normal state flows through the diode 10, so that the current limiting device 6
, Only the current in the direction of discharging the DC capacitor 5 flows.

On the other hand, when a short circuit occurs, the current in the direction of discharging the DC capacitor 5 passes through the current limiting device 6, so that the short circuit current can be suppressed. Therefore, the current limiting device 6 is normally used.
Current flowing through the current limiting device 6 can be reduced.

Embodiment 5 FIG. FIG. 7 is a circuit diagram showing a power converter according to Embodiment 5 of the present invention. In the figure, a voltage type three-level power converter 11 includes four semiconductor switch elements 2a to 2d connected in series, and The freewheel diodes 3a to 3d connected in anti-parallel to the semiconductor switch elements 2a to 2d, the midpoints of DC capacitors 5a and 5b connected in series, and the semiconductor switch elements 2a and 2b,
Clamp diode 12 connected to the center of
a, and a clamp diode 12b connected between the midpoint of the DC capacitors 5a and 5b and the midpoint of the semiconductor switch elements 2c and 2d.

The current limiting device 6a is connected between the DC capacitor 5a and the neutral point C, and the current limiting device 6b is connected between the DC capacitor 5b and the neutral point C. 7
Is a circuit for monitoring the voltage VR generated at both ends of the current limiting devices 6a and 6b, and 8 is an abnormality determination circuit for determining a short circuit abnormality. Reference numeral 9 denotes a control circuit that stops the apparatus in response to an abnormal signal.

As shown in the figure, in the voltage type three-level power converter, when a short-circuit current flows, a voltage monitoring circuit 7 is provided at both ends of the current limiting devices 6a and 6b connected in series to provide one monitoring. The short circuit state can be determined by the circuit. That is,
When the semiconductor switch elements 2a, 2b and 2c are simultaneously turned on, the short-circuit current flows from the DC capacitor 5a → the semiconductor switch elements 2a, 2b and 2c → the clamp diode 12b → the current limiting device 6a. Is suppressed.

The semiconductor switch elements 2b, 2c, 2d
Are conducted at the same time, the short-circuit current is
The current flows through the current limiting device 6b, the clamp diode 12a, and the semiconductor switching elements 2b, 2c, and 2d. Since the current limiting device 6b is provided, the short-circuit current is suppressed. Further, when the semiconductor switching elements 2a, 2b, 2c, 2d are simultaneously turned on, the short-circuit current is changed from the DC capacitor 5a to the semiconductor switching element 2a,
2b, 2c, 2d → DC capacitor 5b → Current limiting device 6
a, 6b, and the current limiting devices 6a, 6b suppress the short-circuit current. In the above, the voltage type three-level power converter has been described, but a power converter having three or more levels can be similarly configured.

Embodiment 6 FIG. FIG. 8 is a circuit diagram showing a power converter according to Embodiment 6 of the present invention. In the figure, a voltage type three-level power converter 11 includes four semiconductor switch elements 2a to 2d connected in series, and Reflux diodes 3a to 3d and clamp diodes 12a and 12 connected in anti-parallel to semiconductor switch elements 2a to 2d.
b and DC capacitors 5a and 5b connected in series. FIG. 8 shows one phase. Reference numeral 6 denotes a current limiting device made of an n-type silicon semiconductor, which is connected between the DC capacitors 5a and 5b. Reference numeral 13a denotes an anode at the midpoint of the current limiting device 6 and the DC capacitor 5a, and a neutral point C.
A cathode is connected to the midpoint of the current limiting device 6 and the DC capacitor 5b;
Is connected to the anode.

In FIG. 8, the semiconductor switching elements 2a,
In any of the short-circuit paths in which the semiconductor switching elements 2b, 2c and 2d conduct simultaneously, the semiconductor switching elements 2b, 2c and 2d conduct simultaneously, and the semiconductor switching elements 2a, 2b, 2c and 2d conduct simultaneously. Since the current limiting device 6 is provided as in the case of mode 5, the short-circuit current is suppressed. In the present embodiment, the diodes 13a, 1
By providing 3b, the number of current limiting devices 6 can be reduced.

[0031]

According to the power converter according to the first aspect of the present invention, the power converter comprises a converter for converting DC to AC, and an inverter for converting AC to DC, wherein n
Since a circuit in which a current limiting device made of a silicon semiconductor and a DC capacitor are connected in series is connected in parallel to the converter and the inverter, it is possible to suppress element shortage and short-circuit current flowing at the same time.

According to the power converter of the second aspect of the present invention, since a plurality of circuits in which a current limiting device and a DC capacitor are connected in series are connected in parallel to the converter and the inverter, wiring between the DC capacitors is provided. Resonance due to inductance can be suppressed.

According to the third aspect of the present invention, since the diode is connected in parallel with the current limiting device,
Normally, the current flowing through the current limiting device can be reduced,
The loss of the current limiting device can be reduced.

According to the power converter of the fourth aspect of the present invention, a voltage monitoring circuit for monitoring a voltage generated in the current limiting device, and a short-circuit state due to the voltage value of the voltage monitoring circuit exceeding a predetermined value Is provided, and a control circuit for stopping the apparatus in accordance with a command from the abnormality determination circuit is provided.

According to the power converter according to claim 5 of the present invention, there is provided a power type three-level power converter comprising a converter for converting DC to AC and an inverter for converting AC to DC. A circuit in which a DC capacitor is connected in series is connected in parallel to the converter and the inverter, and a current limiting device made of n-type silicon semiconductor is connected in series between the upper DC capacitor and the neutral point, and another n-type is connected. A voltage monitoring circuit that connects a current limiting device made of a silicon semiconductor in series between a lower DC capacitor and a neutral point and monitors a voltage generated at both ends of the two current limiting devices, and a voltage value of the voltage monitoring circuit. Is provided with an abnormality judgment circuit for judging a short circuit state when the value exceeds a predetermined value, and a control circuit for stopping the apparatus in accordance with a command from the abnormality judgment circuit. It can be constant.

According to the power converter of claim 6 of the present invention, there is provided a power type three-level power converter comprising a converter for converting DC to AC and an inverter for converting AC to DC. A circuit in which a current limiting device made of an n-type silicon semiconductor is connected in series between a DC capacitor is connected in parallel to the converter and the inverter, and an anode is provided at a middle point between the upper DC capacitor and the current limiting device. The diode is connected so that the cathode is located at the center, and the diode is connected so that the cathode is connected to the lower DC capacitor and the midpoint of the current limiting device, and the diode is connected so that the anode is connected to the neutral point. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power converter according to a first embodiment of the present invention.

FIG. 2 is a graph showing characteristics of a current limiting device.

FIG. 3 is a graph showing an operation waveform of each unit.

FIG. 4 is a circuit diagram showing a power converter according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a power converter according to Embodiment 3 of the present invention.

FIG. 6 is a circuit diagram showing a power converter according to a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a power converter according to a fifth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a power converter according to Embodiment 6 of the present invention.

FIG. 9 is a circuit diagram showing a conventional power converter.

FIG. 10 is a circuit diagram showing a conventional power converter.

FIG. 11 is a graph showing the operation of a conventional power converter.

[Explanation of symbols]

1 converter, 4 inverters, 5 capacitors, 6
Current limiting device, 7 Voltage monitoring circuit, 8 Abnormality judgment circuit, 9
Control circuit, 10, 13a, 13b Diode.

Claims (6)

[Claims] 1. A power converter comprising a converter for converting direct current to alternating current and an inverter for converting alternating current to direct current, wherein a circuit in which a current limiting device made of an n-type silicon semiconductor and a DC capacitor are connected in series is connected to the converter. And a power converter connected in parallel to the inverter. 2. The power converter according to claim 1, wherein a plurality of circuits in which a current limiting device and a DC capacitor are connected in series are connected in parallel to the converter and the inverter. 3. The power conversion device according to claim 1, wherein a diode is connected in parallel with the current limiting device. 4. A voltage monitoring circuit for monitoring a voltage generated in a current limiting device, an abnormality determining circuit for determining a short circuit state when a voltage value of the voltage monitoring circuit exceeds a predetermined value, and The power converter according to any one of claims 1 to 3, further comprising a control circuit that stops the device according to a command. 5. A power type three-level power converter comprising a converter for converting direct current to alternating current and an inverter for converting alternating current to direct current, wherein a circuit in which two DC capacitors are connected in series is connected to the converter and the inverter. And a current limiting device made of n-type silicon semiconductor is connected in series between the upper DC capacitor and the neutral point, and another current limiting device made of n-type silicon semiconductor is connected to the lower DC capacitor. And a voltage monitoring circuit that is connected in series between the neutral point and monitors the voltage generated at both ends of the two current limiting devices, and a short-circuit state occurs when the voltage value of the voltage monitoring circuit exceeds a predetermined value. An electric power conversion device comprising: an abnormality determination circuit for determining; and a control circuit for stopping the device in response to a command from the abnormality determination circuit. 6. A power type three-level power converter comprising a converter for converting direct current to alternating current and an inverter for converting alternating current to direct current, wherein a current limiter comprising an n-type silicon semiconductor between two DC capacitors. A circuit in which the devices are connected in series is connected in parallel to the converter and the inverter, and an anode is connected to the middle point of the upper DC capacitor and the current limiting device, and a diode is connected so that the cathode is located at the neutral point, A power converter characterized in that a diode is connected so that a cathode is connected to a middle point of the lower DC capacitor and the current limiting device, and an anode is connected to a neutral point.