JP7250266B1 - DC current interrupter - Google Patents

Abstract

Kind Code: A1 A hybrid switch in which a metal contact and a plurality of IGBTs are connected in parallel for DC current is controlled to reduce the input current, and the current is interrupted without arcing. A current of a metal contact 1 is commutated to a parallel IGBT 4 by an arc voltage when the contact is opened, and a signal of an auxiliary contact 2 interrupts the current by the IGBT 4. are connected in series to provide negative feedback to the gate voltage to correct the current diversion of the parallel IGBT 4, and the gate of the IGBT 4 is PWM-controlled to reduce the inrush current even when the power is turned on. [Selection diagram] Fig. 1

Description

The present invention relates to a direct current interrupting device, and more particularly, in a hybrid switch configuration in which a metal contact and a semiconductor switch are connected in parallel, a direct current interrupting device capable of interrupting a large direct current by connecting a plurality of semiconductor switches in parallel. Regarding the device.

In the present invention, the metal contact switch has no current loss, but when the DC current is interrupted (when the metal contact is opened), an arc is generated and it is difficult to interrupt the current. It relates to a hybrid switchgear that commutates and cuts off.

In order to control a large current with a semiconductor switch, it is necessary to connect the semiconductor switches in parallel. When using a MOSFET, parallel connection is easy because the voltage-current characteristics of pure resistance are linear when conducting. Not suitable for relatively large currents. Therefore, an insulated gate bipolar transistor (hereinafter referred to as "IGBT"), which is a semiconductor switch capable of conducting large currents, is used. The so-called parallel shunt has a difficult property.

Conventional DC hybrid switchgear uses semiconductor switches such as power MOSFETs and IGBTs with insulated gates, and the arc voltage between the contacts when the contacts are opened automatically transfers the arc current to the semiconductor switch. After flowing, it was possible to cut off the current at the gate of the semiconductor switch, but in order to drive the semiconductor switch in parallel to control the large current, it is necessary to ensure equal current division of the parallel-connected IGBTs. There is a need to.

In order to further apply the hybrid switchgear of metal contacts and semiconductor switches such as MOSFETs to high-current direct current, the present invention connects IGBTs with non-linear forward characteristics in parallel, which are capable of carrying high current, to achieve high direct current. It is intended to be applied to the breaking device of

Japanese Patent No. 6713660

Electric Discharge Handbook Publishing Committee Edition "Discharge Handbook" The Institute of Electrical Engineers Edition 6.4.5 "Contact Arc"

In the direct-current switchgear disclosed in Patent Document 1, the semiconductor switch starts energization by opening the b-contact before the a-contact is closed, and the a-contact is closed. When the contact is closed, current is passed through the a-contact, and no current flows through the semiconductor switch because the contact resistance is sufficiently low.
In particular, the IGBT has a threshold voltage of about 1V to 2V in the ON state, but the voltage between the metal contacts is lower than this, so no current flows through the IGBT.
Next, in the case of disconnection, when the a-contact opens first, the semiconductor switch is already in the ON state at that time, so current flows through the semiconductor switch and the voltage between the metal contacts is determined by the semiconductor switch. According to Non-Patent Document 1, in order to generate an arc between metal contacts, a voltage between the contacts of about 10 V to 20 V and a current of several A or more are required to maintain the arc plasma under atmospheric pressure.
When the current flows through the semiconductor switch and the voltage of the semiconductor switch circuit is 10V or less, the current flows through the semiconductor switch in a short time, the commutation is completed in the time of inductance × current ÷ 10V, after all, the arc cannot be maintained for a short time. to disappear.
After that, several ms to 10 ms after the opening of the a-contact advances, the gate voltage of the semiconductor switch is reduced by closing the b-contact (interlocking) as the timing of completion of opening of the a-contact, and the direct current is interrupted. be able to.

FIG. 2 shows the characteristics of the collector current Ic with respect to the gate voltage V _GE of the IGBT. Since the IGBT has a negative temperature characteristic, parallel connection requires some contrivance. When the current increases, the threshold voltage drops due to heat generation, and when the current concentrates and the temperature rises, the threshold voltage drops further and the current concentrates further (so-called "thermal runaway"). However, in order to use IGBTs in parallel, it is necessary to devise strong heat removal.

The present invention has been made in view of the above points, and in a hybrid switch configuration in which a metal contact and a semiconductor switch are connected in parallel, it is possible to cut off a large direct current by connecting a plurality of IGBTs, which are semiconductor switches, in parallel. It is an object of the present invention to provide a DC current interrupting device that

The present invention relates to a direct current interrupting device inserted between a direct current power supply and a load, and the object of the present invention is to provide a first terminal connected to the direct current power supply and a second terminal connected to the load. Between the first terminal and the second terminal, a metal contact that is an a-contact is connected, and in parallel with the metal contact, a plurality of insulated gate bipolar transistors (hereinafter "IGBT ), the collector of each IGBT is connected to the first terminal, the emitter of each IGBT is connected to the second terminal via a shunt resistor, and the gate of each IGBT is connected to the first terminal via a gate resistor. is connected to a gate control circuit, and the gate control circuit is connected to an auxiliary contact, which is a b-contact that interlocks with the metal contact,
When the auxiliary contact is opened, the gate control circuit supplies a voltage for turning on the IGBT to the gate of each IGBT through the gate resistance of each IGBT, and then the metal contact associated therewith is closed. When the metal contact is opened, the current flowing through the metal contact is commutated to each of the IGBTs, and then when the associated auxiliary contact is closed, the gate The control circuit cuts off the current flowing between the first terminal and the second terminal by supplying a voltage for turning off each IGBT to the gate of each IGBT to turn off each IGBT. This is achieved by a DC current interruption device that features.

IGBTs with high short-term current-carrying capacity are used in parallel with a direct-current interrupter that uses metal contacts and semiconductor switches to initiate conduction prior to the closing of the high-current contacts, generating an interrupting arc when the contacts are opened. By suppressing , contact wear is prevented, the metal contact current is commutated to the parallel-connected IGBTs in a short period of time, and finally the DC current is simultaneously interrupted by IGBT gate control, thereby interrupting large currents and high voltages. becomes possible.

1 is a configuration diagram of a DC current interrupting device in which a plurality of IGBTs of the present invention are connected in parallel; FIG. FIG. 4 is a diagram showing conducting current characteristics (temperature characteristics) of a semiconductor switch IGBT; It is a figure which shows the time sequence of the injection|throwing-in of the DC current interruption|blocking apparatus of this invention, and interruption|blocking. FIG. 4 is a diagram showing characteristics of a collector voltage and a collector current with the gate voltage of an IGBT as a parameter; 1 is an embodiment of a gate control circuit for a DC current interrupter according to the present invention; It is an application example in which a plurality of DC current interrupting devices of the present invention are connected in series. This is an embodiment for avoiding inrush current resonance using the DC current interrupting device of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration example of a DC current interrupting device according to the present invention. A DC current interrupting device includes a first terminal (positive terminal) connected to the positive side of a DC power supply and a second terminal (negative terminal) connected to the positive side of a load.
Between the positive terminal and the negative terminal, a metal contact 1 which is a contact is arranged, and in parallel with the metal contact 1, an IGBT 4 has a positive terminal on the collector side and a shunt resistor (hereinafter referred to as an "emitter resistor") on the emitter side. .) 5 to the negative terminal. Also, the gate of the IGBT 4 is connected to the gate control circuit 9 via the gate resistor 6 . A plurality of IGBTs 4 are connected in parallel to the metal contact 1 in the same manner.
The emitter resistors 5 connected in series with the emitters of the parallel-connected IGBTs 4 play a role of correcting the current division of the parallel IGBTs by negatively feeding back the voltage drop generated in the resistors to the gate voltage.

In addition, the gate control circuit 9 is provided with an auxiliary contact 2 which is a b-contact.
The resistance value of the emitter resistor 5 is preferably low, and a voltage higher than the threshold voltage varies with temperature is applied by the resistor. Typically, the change is 1V. The resistance value of the emitter resistor 5 is approximately 0.01Ω to 0.1Ω, but can be changed according to the design.
As an example of the metal contact 1, the structure of a double-break circuit breaker is shown here. There is an effect that the recovery of the withstand voltage of is accelerated, and an effect that the opening speed is substantially doubled.

The opening and closing operations of the metal contact 1 and the auxiliary contact 2 are interlocked by an interlocking mechanism 3 (not shown), and the operation thereof will be described later.
Furthermore, a CR surge absorber 7 consisting of a resistor and a capacitor and a varistor 8 are connected in parallel to the metal contact 1 . The varistor 8 is an element having voltage-current characteristics (current non-linearity) in which current suddenly flows at a certain voltage. A CR surge absorber 7 consisting of a varistor 8, a capacitor, and a resistor is connected in parallel to the metal contact 1 to suppress the rise rate of the recovery voltage after the metal contact 1 is cut off, and further suppress the recovery voltage to the breakdown voltage of the varistor 8. , the breaking current can be passed through the varistor 8, and the overvoltage during series connection can be suppressed and the current can be reduced.
In the hybrid switch, the energization time is short and it is thought that there is no repetition, so the IGBT 4 and the emitter resistor 5 do not need heat removal measures such as heat sinks.
The IGBT is a gate control structure with a large current carrying capacity and has self-extinguishing ability, but when multiple IGBTs with negative temperature characteristics are connected in parallel and applied to a hybrid switchgear, commutation from the metal contact is required. As long as the on-voltage is low relative to the arc voltage, it is possible to add a large shunt resistor to the emitter of the IGBT, which is energized for a short time. A DC hybrid interrupter for current is provided.
That is, since the semiconductor switch circuit only needs to be energized for a short time of about 10 ms and the arc voltage is 10 V or less, even if an emitter resistor that shares several volts is used, there is no problem of heat generation, and even distribution of current is stabilized. It is possible.

FIG. 3 is a diagram showing the time sequence of current application (circuit connection) and current interruption of the DC current interruption device of the present invention.
When the metal contact 1 starts to be closed, the interlocking auxiliary contact 2 first starts to open. When an electric signal for opening the auxiliary contact 2 is sent to the gate control circuit 9 , the gate control circuit 9 turns on the IGBT 4 . Current then flows through the IGBT 4 and the emitter resistor 5 from the positive terminal to the negative terminal. After several ms to 10 ms, the interlocking mechanism 3 reaches the metal contact 1, and when the voltage between the contacts of the metal contact 1 becomes a metal contact short-circuit state, the current of the IGBT 4 reaches the emitter resistor 5 in series with the ON voltage of the IGBT. Since the voltage of is about 5V, it is stopped. Although the gate voltage of the IGBT 4 may not be applied during the subsequent period, the gate of the IGBT 4 is maintained in the ON state, but the current does not flow and the contacts generate little heat, so there is no need for cooling.

At the time of interruption, after the transition time from the start of opening of the metal contact 1 until the opening gap length is obtained, which is about several ms to 10 ms, until the auxiliary contact 2 is closed, the IGBT gate control circuit Since the gate voltage is supplied from 9 and the IGBT is turned on, even if the voltage V of the emitter resistor 5 for shunting is added, it is lower than the two series arc voltages of the metal contact 1, so the current of the metal contact 1 is commutated to parallel IGBT4. The parallel-connected IGBT 4 conducts the entire current for about several ms to 10 ms until the gate voltage is lowered by closing the auxiliary contact 2 and the IGBT 4 is turned off.

In order to interrupt the current with the direct current interrupting device according to the present invention, first, the metal contact 1 starts to open, but the gate of the IGBT 4 is already in the ON state, and the ON voltage of the IGBT 4 is about 5 V, which is the arc voltage. less than The direct-current arc voltage in the atmosphere is described in Patent Document 1 above, but is 10 V to 20 V regardless of the gap length, and does not change even if the arc current is 10 A to several kA. The arc current is commutated to the IGBT 4 within a short period of time (several μs) when it is generated. The arc of the metal contact 1 becomes less than the arc sustaining current and is naturally extinguished, and then the contact opens without arcing. The opening operation of the metal contact 1 takes about several ms to 10 ms, and when the auxiliary contact 2 closes, the gate controller 9 receives the signal and reduces the total gate voltage of the parallel-connected IGBTs 4 to zero to cut off all currents. be.

In order to finally cut off the current, the current of the metal contact 1 is commutated to the IGBT 4 connected in parallel. Then, it is also conceivable to reduce the current by using the constant current characteristic of the IGBT 4 . In that case, the limit of the IGBT 4 may be exceeded and the junction of the IGBT 4 may be fused, but the varistor 8 also starts operating to stop the current. The varistor 8 is a zinc oxide (ZnO) semiconductor element, and has an energy absorption amount of several kJ, and commutates from the IGBT 4 at its operating voltage to reduce the current. It can also be expected to have the capability of current reduction breaking as a fault current circuit breaker.

FIG. 4 is a diagram showing the relationship between the collector current and the collector voltage with the gate voltage of 600V-85A of IGBT "RJH60F6DKP" Renesas Electronics Corporation as a parameter. It can be seen that the current is saturated by showing the characteristics. It is possible to cut off the fault current by controlling the gate voltage of the IGBT.

[Embodiment of gate control circuit: FIG. 5]
FIG. 5 is a diagram showing an embodiment of the gate control circuit 9 according to the present invention.
The voltage of the collector of the IGBT 4 is connected to the gate of the IGBT through a gate resistor 6, here Rg=100Ω as an embodiment, with a capacitor 10 of 0.05 μF as an embodiment, but it is appropriately selected by the IGBT 4. FIG. Furthermore, a resistor 11 , here Rs=100Ω, short-circuits the gate voltage via the auxiliary contact 2 . A direct-current power supply 14 (insulated voltage source) is connected to the auxiliary contact 2 via a backflow prevention diode 13 . An output current limiting resistor 15 (1 kΩ) and an insulated voltage source 14 are connected to the common emitter of the IGBT 4 . The insulated voltage source 14 is short-circuited by the closing of the interlocking auxiliary contact 2, and the collector voltage rises with the time constant CR of the capacitance Cs of the capacitor 10 and the resistance value Rs of the resistor 11, and the gate voltage can be zero. That is, when the auxiliary contact 2 is closed, the gate voltage becomes almost zero.

A capacitor 10 and a resistor 11 connected to the collector form an integration circuit for the gate voltage of the IGBT 4, and when the auxiliary contact 2 is closed and the gate is cut off, the voltage of the IGBT rises with an integration time constant CR. This determines the rise rate of the recovery voltage of the DC current interrupter after interruption, and when multiple DC current interrupters are connected in series, it has the effect of reducing the difference in the partial voltage against the variation in series interruption timing. play.

[Second Embodiment: FIG. 6]
FIG. 6 shows an embodiment in which the DC current interrupting device of the present invention is used as one unit and connected in series in multiple stages to increase the voltage.
Simultaneity of turn-on/turn-off timing is important when increasing the voltage with series multi-stage connection, and if even one delay occurs, the voltage sharing will be disturbed. If one unit cuts off first due to the presence of the varistor 8, it is maintained at the varistor voltage to protect against overvoltage, but must wait for other series-connected units to cut off. During this period, the amount of energy absorbed by the varistor is taken into consideration when selecting, but there is uncertainty in that period because there is a range of variation in the mechanical operation of the contact switch, ie, jitter.
In FIG. 6, a sequence control device 16 is provided for receiving the b-contact signal of each DC current interrupter and simultaneously controlling the gate voltage of all the DC current interrupters by the NAND signal. , the sequence control device 16 confirms the closed/open state of the b contacts of all units connected in series, and then simultaneously sends a gate signal to the semiconductor switches (IGBTs) of all the DC current interrupters connected in series. , allows simultaneous switching of currents without the effects of jitter on the contacts. As a result, the heat resistance capacity and absorbed energy of the varistor 8 can be reduced.

[Third Embodiment: FIG. 7]
Fig. 7 shows a conceptual diagram for avoiding inrush current when a DC distribution system is turned on. When the distribution route is several kilometers long, the line inductance becomes several milliseconds and resonance appears, and the voltage on the supply side drops below 50%. I have a problem stopping it. When the power is turned on, the sequence controller (not shown) measures the current, and if there is an overcurrent, the current is intermittently supplied in pulses by controlling the gate of the IGBT to eliminate resonance with the capacitor on the load side. can be avoided.

In a DC distribution system, a DC voltage of about 400 V is used to connect power supplies with electrolytic capacitors of several thousand μF to both sides through several kilometers of DC distribution lines with switches. There is a problem that an inductance of mH causes a potential oscillation, the voltage on the supply side drops, and the operation stops. This is the so-called inrush current.
When the IGBT 4 is turned on and off at several kHz by a PWM (Pulse Width Modulation) control circuit (not shown) before the metal contact 1 is closed, the oscillation of the inrush current can be stopped. Substantially the same current waveform as resistance input is possible. Since the vibration frequency is about 50 Hz even if the distribution line is 4 km long, a stepped current waveform can be obtained by PWM control for about 10 ms.

A voltage is applied to the drive electromagnetic coil of the metal contact 1 according to the closing command of the metal contact 1, and it takes 10ms to 30ms until the contact is closed. The inrush current attenuates until the entire current flows to the metal contact 1, and finally the current is commutated from the IGBT 4 to the metal contact 1 having a low on-voltage.

In this manner, the load voltage and current can be controlled by high-speed PWM control of the on/off of the IGBT 4, which is a semiconductor switch, when the current is turned on and off. Power-up rush current can be avoided with PWM control of the gate voltage of the series hybrid switch. It is possible to turn on/off the multi-stage hybrid switch IGBT 4 by a program to gradually increase or decrease the current.

A high-current DC hybrid circuit breaker is provided by using IGBTs with high overcurrent resistance in parallel. Furthermore, by connecting them in series, a high-voltage, high-current hybrid circuit breaker is formed. Inrush current can be avoided by controlling the semiconductor switch not only for breaking without arcing but also for closing.

1: Metal contact (a contact)
2: Auxiliary contact (b contact)
3: Interlocking mechanism 4: IGBT
5: Emitter resistor Re (shunt resistor)
6: Gate resistance Rg
7: CR surge absorber 8: Varistor 9: Gate control circuit 10: Capacitor 11: Resistor Rs
12: Reverse voltage protection diode (Diode2)
13: Backflow prevention diode (Diode1)
14: Insulated voltage source 15: Output current limiting resistor

Claims (4)

A DC current interrupting device inserted between a DC power supply and a load, the DC current interrupting device comprising:
A first terminal connected to the DC power supply side and a second terminal connected to the load side, wherein between the first terminal and the second terminal is a metal contact that is an a contact is connected and
In parallel with the metal contact, a plurality of insulated gate bipolar transistors (hereafter referred to as "IGBTs") are connected to the first terminal by the collector of each IGBT and the emitter of each IGBT by the shunt resistor. each connected to a second terminal,
A gate of each IGBT is connected to a gate control circuit via a gate resistor, and an auxiliary contact, which is a b-contact interlocking with the metal contact, is connected to the gate control circuit,
When the auxiliary contact is opened, the gate control circuit supplies a voltage for turning on the IGBT to the gate of each IGBT through the gate resistance of each IGBT, and then the metal contact associated therewith is closed. applying a current to the metal contact as a pole,
When the metal contacts are opened, the current flowing through the metal contacts is commutated to the respective IGBTs, and when the associated auxiliary contacts are closed thereafter, the gate control circuit causes the gates of the IGBTs to be connected to the respective IGBTs. A direct-current interrupting device, which cuts off a current flowing between the first terminal and the second terminal by supplying a voltage for turning off the IGBT to turn off each of the IGBTs. The gate control circuit is
A series connection circuit of a capacitor (10), a resistor (11), a backflow prevention diode (13), and a DC insulated voltage source (14) is provided,
A connection point between the capacitor (10) and the resistor (11) is connected to the gate resistor (6), and
A connection point between the resistor (11) and the cathode of the diode (13) is connected to one end of the auxiliary contact, and the other end of the auxiliary contact is connected to the negative side of the isolated voltage source (14). and
When the auxiliary contact is opened, a voltage for turning on the IGBT is supplied from the insulated voltage source (14) to the gate of each IGBT through the gate resistor (6) of each IGBT, and the auxiliary contact is closed. 2. The DC current interrupting device according to claim 1, wherein when the voltage is turned off, the isolation voltage source (14) is short-circuited to supply the gate of each IGBT with a voltage for turning off each IGBT. A CR surge absorber consisting of a capacitor and a resistor and a varistor are connected in parallel with the metal contact to suppress the rise rate of the re-electromotive voltage after opening of the metal contact, and further reduce the re-electromotive voltage to the breakdown voltage of the varistor. 2. The DC current interrupting device according to claim 1, wherein the current is reduced by flowing the current through the varistor while suppressing the current. Further, a PWM control circuit for PWM-controlling the gate voltage of the IGBT is provided, and by PWM-controlling the gate voltage by the PWM control circuit, the inrush current and the load voltage at the time of power-on are controlled to reduce the current. A DC current interrupting device according to any one of claims 1 to 3.

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