JP6365724B1 - DC breaker - Google Patents

Abstract

In a DC interrupter, a bidirectional DC current is reliably interrupted. A mechanical circuit breaker CB is connected between a + terminal of a first DC system 1 and a + terminal of a second DC system 2. A first capacitor C1 is connected between the + terminal of the first DC system 1 and the common connection point of the mechanical circuit breaker CB and the-terminals of the first and second DC systems 1 and 2. The first semiconductor switching element T1 is connected between the positive terminal of the second DC system 2 and the common connection point of the mechanical circuit breaker CB and the first capacitor C1. A second capacitor C2 is connected between the + terminal of the second DC system 2 and the common connection point of the mechanical circuit breaker CB and the-terminals of the first and second DC systems 1, 2. The second semiconductor switching element T2 is connected between the positive terminal of the first DC system 1 and the common connection point of the mechanical circuit breaker CB and the second capacitor C2. [Selection] Figure 1

Description

  The present invention relates to a direct current interrupting device that is capable of interrupting bidirectional direct current with low power loss during normal operation.

  Patent Document 1 discloses an example of a conventional DC cutoff device. Unlike the alternating current, a zero point does not occur in the direct current, and therefore there is a problem that the arc generated when the mechanical circuit breaker is opened cannot be extinguished. Patent Document 1 creates a zero point by diverting the current when the mechanical circuit breaker is opened to the auxiliary circuit, and extinguishes the arc.

  The DC interruption device of Patent Document 1 has a configuration corresponding to unidirectional current interruption. In the future, the spread of renewable energy is considered, and in a networked DC transmission / distribution system, there are cases where bidirectional current flows through one path, and bidirectional current interruption technology is required.

JP 2016-28378 A

  The auxiliary circuit that bypasses the current in Patent Document 1 is required to have as low impedance as possible. Otherwise, a voltage drop occurs as current passes through the auxiliary circuit, and a voltage equal to the voltage drop is applied to the mechanical circuit breaker. If the voltage is greater than the arc maintenance voltage, the arc is not extinguished and the current continues to flow through the opened mechanical circuit breaker, failing to interrupt the current.

  The auxiliary circuit is composed of a capacitor and a diode, but a constant voltage drop that does not depend on the passing current occurs in the diode. In addition, there are parasitic resistance and parasitic inductance components. In particular, the inductance causes a voltage drop proportional to the slope of the current change. Therefore, if the short circuit current, which is a large current, is bypassed, the voltage drop also increases.

  FIG. 15 shows a problem operation. FIG. 15A is a circuit diagram in which only elements that are relevant when the short-circuit current of the second DC system 2 is interrupted are extracted from the DC interrupter, and parasitic inductance is added to the auxiliary circuit.

  FIG. 15B is a time chart showing waveforms when the voltage drop and inductance of the diode in the auxiliary circuit are ignored. When the mechanical circuit breaker CB is opened at time t1, only the capacitor voltage is applied to the voltage Vcb across the mechanical circuit breaker, and is zero at time t1. Therefore, no arc is generated and all current is bypassed to the auxiliary circuit, and the current can be cut off.

  FIG. 15C is a time chart showing waveforms when the voltage drop and inductance of the diode in the auxiliary circuit are taken into consideration. At time t1, the sum of the voltage drop of the diode and the parasitic inductance voltage is applied to the mechanical circuit breaker voltage Vcb in addition to the capacitor voltage of the auxiliary circuit. Further, the auxiliary circuit current Iaux increases with a finite slope due to the parasitic inductance, and the mechanical circuit breaker passing current Icb also decreases with the same slope.

  After time t1, the capacitor C is charged by the auxiliary circuit current Iaux, and the voltage Vcb across the mechanical circuit breaker further increases. Here, if the mechanical circuit breaker voltage Vcb exceeds the arc holding voltage before the mechanical circuit breaker passage current Icb becomes sufficiently small (at time t2 in FIG. 15), the arc cannot be extinguished and the current is lost to the mechanical circuit breaker CB. Will continue to pass and will fail to shut down. Further, when a plurality of diodes D are connected in series for a high voltage system, the risk of exceeding the arc holding voltage increases.

  As a countermeasure, there is a method of increasing the capacitor capacity of the auxiliary circuit. However, this only reduces the increase amount of the mechanical circuit breaker voltage Vcb after time t1 in FIG. 15, and has no effect of reducing the increase of the mechanical circuit breaker voltage Vcb at time t1. Further, when the capacitor capacity is increased, there is a problem that the cost and the apparatus volume increase.

  As described above, in the DC interrupting device, it is a problem to surely interrupt bidirectional DC current.

  The present invention has been devised in view of the conventional problems, and one aspect thereof is a mechanical circuit breaker connected between the + terminal of the first DC system and the + terminal of the second DC system, A first capacitor sequentially connected in series between a positive terminal of the first DC system and a common connection point of the mechanical circuit breaker, and a positive terminal of the second DC system and a common connection point of the mechanical circuit breaker; A first reactor and a first semiconductor switching element, or a first reactor and a first capacitor and a first semiconductor switching element; a positive connection terminal of the second DC system; a common connection point of the mechanical circuit breaker; and the first DC The second capacitor and the second reactor and the second semiconductor switching element, or the second reactor and the second capacitor and the second semiconductor, which are sequentially connected in series between the positive terminal of the system and the common connection point of the mechanical circuit breaker. Switching element A common connection point between the first reactor and the first semiconductor switching element, or a common connection point between the first capacitor and the first semiconductor switching element, and a negative terminal of the first and second DC systems. A first impedance connected to the second reactor and a common connection point of the second reactor and the second semiconductor switching element, or a common connection point of the second capacitor and the second semiconductor switching element, and the first and second And a second impedance connected between the negative terminal of the DC system.

  As one aspect thereof, the first impedance and the second impedance are resistors.

  As one mode, the first and second semiconductor switching elements are self-extinguishing elements, and a diode is connected in series to the first and second semiconductor switching elements.

  As another aspect, the first and second semiconductor switching elements are thyristors.

  Further, as one aspect thereof, the semiconductor device includes a third semiconductor switching element connected between the first and second resistors and a negative terminal of the first and second DC systems, or the first resistor and the first resistor A third semiconductor switching element connected between the negative terminal of the first and second DC systems, and a fourth semiconductor switching connected between the second resistor and the negative terminal of the first and second DC systems. And an element.

  As another aspect, the first impedance and the second impedance are a third reactor and a fourth reactor, and between the third and fourth reactors and a negative terminal of the first and second DC systems. A third semiconductor switching element connected to the third semiconductor switching element, or a third semiconductor switching element connected between the third reactor and a negative terminal of the first and second DC systems, the fourth reactor, and the second 1, a fourth semiconductor switching element connected between the negative terminal of the second DC system, an anode connected to a common connection point of the third reactor and the third semiconductor switching element, and a cathode connected to the first semiconductor A first diode connected to a common connection point of the switching element and the + terminal of the second DC system, the fourth reactor, the fourth semiconductor switching element, or An anode is connected to the common connection point of the third semiconductor switching element, and a cathode is connected to the common connection point of the second semiconductor switching element and the positive terminal of the first DC system. It is characterized by.

  In one embodiment, the first and second semiconductor switching elements are thyristors.

  Further, as one aspect thereof, when a current flows from the first DC system to the second DC system, and an accident occurs in the second DC system, the second semiconductor switching element is turned on, and the machine After the current flowing through the circuit breaker falls below a predetermined value, the mechanical circuit breaker is shut off, current flows from the second DC system to the first DC system, and an accident occurs in the first DC system. In this case, the first semiconductor switching element is turned on, and the mechanical circuit breaker is interrupted after a current flowing through the mechanical circuit breaker becomes a predetermined value or less.

  According to the present invention, it is possible to reliably interrupt bidirectional DC current in a DC interrupter.

FIG. 2 is a circuit diagram showing a DC interrupter in Embodiment 1. The figure which shows the direct current | flow interrupting device of the steady state in Embodiment 1. FIG. The figure which shows the DC interruption | blocking apparatus when the accident generate | occur | produces in the 2nd DC system side in Embodiment 1. FIG. The figure which shows the direct current | flow interruption | blocking apparatus after the arc interruption | blocking in Embodiment 1. FIG. The figure which shows the DC interruption | blocking apparatus at the time of re-injecting the 2nd DC system in Embodiment 1. FIG. The time chart which shows each waveform at the time of the short circuit current interruption | blocking of the 2nd DC system in Embodiment 1. FIG. FIG. 5 is a circuit diagram showing a DC interrupter in Embodiment 2. FIG. 5 is a circuit diagram showing a DC interrupter in Embodiment 3. FIG. 6 is a circuit diagram showing a DC interrupter in Embodiment 4. The figure which shows the DC interruption | blocking apparatus at the time of the 3rd, 4th semiconductor switching element ON in Embodiment 4. FIG. The figure which shows the DC interruption | blocking apparatus at the time of the 3rd, 4th semiconductor switching element OFF in Embodiment 4. FIG. The figure which shows the DC circuit breaker when the accident generate | occur | produces in the 2nd DC system side in Embodiment 4. FIG. The figure which shows the direct-current interrupting device after the arc interruption in Embodiment 4. The figure which shows the DC interruption | blocking apparatus at the time of re-introducing the 2nd DC system in Embodiment 4. The figure which shows each waveform of the conventional DC circuit breaker.

  Hereinafter, Embodiments 1 to 4 of the DC interrupter according to the present invention will be described in detail with reference to FIGS.

[Embodiment 1]
FIG. 1 shows a main circuit configuration of the first embodiment. As shown in FIG. 1, the DC breaker 3 of Embodiment 1 includes a mechanical breaker CB, first and second semiconductor switching elements T1 and T2, first and second diodes D1 and D2, and a first , Second capacitors C1, C2, first and second reactors L1, L2, and first and second resistors R1, R2.

  A mechanical circuit breaker CB is connected between the + terminal of the first DC system 1 and the + terminal of the second DC system 2.

  The first capacitor C1, the first reactor L1, the first terminal are connected between the + terminal of the first DC system 1 and the common connection point of the mechanical circuit breaker CB and the-terminals of the first and second DC systems 1, 2. A resistor (first impedance) R1 is sequentially connected in series. (The order of connection between the first capacitor C1 and the first reactor L1 may be reversed.) One end of the first semiconductor switching element T1 is connected to the common connection point between the mechanical circuit breaker CB and the + terminal of the second DC system 2. Is connected. The other end of the first semiconductor switching element T1 is connected to the anode of the first diode D1. The cathode of the first diode D1 is connected to the common connection point of the first reactor L1 and the first resistor R1.

  Between the positive terminal of the second DC system 2 and the common connection point of the mechanical circuit breaker CB and the negative terminals of the first and second DC systems 1 and 2, there are a second capacitor C2, a second reactor L2, and a second resistor. (Second impedance) R2 are sequentially connected in series. (The order of connection of the second capacitor C2 and the second reactor L2 may be reversed.) The common connection point of the mechanical circuit breaker CB and the positive terminal of the first DC system 1 has one end of the second semiconductor switching element T2. Is connected. The other end of the second semiconductor switching element T2 is connected to the anode of the second diode D2. The cathode of the second diode D2 is connected to the common connection point of the second reactor L2 and the second resistor R2.

  Note that the semiconductor switching elements T1 and T2 of the first embodiment are switching elements capable of self-extinguishing. In FIG. 1, an IGBT is used, and the collector terminal of the first semiconductor switching element T1 is connected to a common connection point between the positive terminal of the first DC system 1 and the mechanical circuit breaker CB. Further, the collector terminal of the second semiconductor switching element T2 is connected to the common connection point of the positive terminal of the second DC system 2 and the mechanical circuit breaker CB. The emitter terminals of the first and second semiconductor switching elements T1 and T2 are connected to the anodes of the first and second diodes D1 and D2.

  The first and second semiconductor switching elements T1, T2, and the first and second diodes D1, D2 may be replaced with a self-extinguishing switching element having a reverse blocking capability such as a reverse blocking IGBT.

  Next, the operation of the DC interrupter in Embodiment 1 will be described.

  FIG. 2 shows the DC cutoff device in the steady state according to the first embodiment. In the steady state, the mechanical circuit breaker CB is in a closed state, and current flows in both directions. At this time, a charging current flows through the first capacitor C1 via the first reactor L1 → the first resistor R1. A charging current flows through the second capacitor C2 via the second reactor L2 → second resistor R2.

  When the first and second capacitors C1 and C2 are charged up to the system voltage, the charging current becomes zero. Since the current passes only through the mechanical circuit breaker CB at a constant time, there is almost no power loss.

  FIG. 3 shows the DC interrupter 3 of the first embodiment when an accident occurs on the second DC system 2 side. When an accident occurs, the second semiconductor switching element T2 is turned on, and the discharge current from the second capacitor C2 is supplied as an auxiliary circuit current via the mechanical circuit breaker CB → second semiconductor switching element T2 → second diode D2 → second reactor L2. Then flow. This auxiliary circuit current cancels the short-circuit current flowing through the mechanical circuit breaker CB to create a zero point of the current, opens the mechanical circuit breaker CB, and extinguishes the arc.

  The magnitude of the auxiliary circuit current is determined by the second reactor L2 and the second capacitor C2. Therefore, the magnitude | size of the 2nd reactor L2 and the 2nd capacitor | condenser C2 is determined so that the maximum value of the assumed short circuit current can be negated.

  FIG. 4 shows the DC interrupter 3 of the first embodiment after arc extinguishing. The auxiliary circuit current flows through the second semiconductor switching element T2, the second diode D2, the second reactor L2, the second capacitor C2, and charges the second capacitor C2 in the direction opposite to that in FIG. When the charging of the second capacitor C2 is completed, the current on the second DC system 2 side becomes zero, and the interruption of the current is completed.

  At this time, a current unnecessary for the cutoff operation flows through the second semiconductor switching element T2 → the second diode D2 → the second resistor R2, and a loss occurs. The resistance value of the second resistor R2 needs to be increased so that this current becomes sufficiently small. The same applies to the first resistor R1. When the reverse charging of the second capacitor C2 is completed and the interruption of the current is completed, the second semiconductor switching element T2 is turned off.

  FIG. 5 shows the DC interrupter 3 of the first embodiment when the current interrupt is completed and the second DC system 2 is turned on again. When the mechanical circuit breaker CB is closed, the current flows through the mechanical circuit breaker CB → second capacitor C2 → second reactor L2 → second resistor R2, and the second capacitor C2 that has been charged in the opposite direction passes through the second capacitor C2. Recharge in the correct direction. When charging is completed, the state returns to the state shown in FIG.

  The direction of current flow and the current value when an accident occurs are monitored using a host controller, and the mechanical circuit breaker CB is opened and closed and the first and second semiconductor switching elements T1 and T2 are turned on and off.

  FIG. 6 shows a waveform when the short-circuit current on the second DC system 2 side is cut off. A short circuit occurs at time t1, and the mechanical circuit breaker passage current Icb increases. When the second semiconductor switching element T2 is turned on at time t2, the discharge current flows from the second capacitor C2 as the auxiliary circuit current Iaux, and the mechanical circuit breaker passing current Icb is canceled.

  At this time, the auxiliary circuit current Iaux becomes a resonance current having a frequency determined by the second capacitor C2 and the second reactor L2. If the resonance frequency is too high, resonance ends before the mechanical circuit breaker CB opens, and the mechanical circuit breaker passing current Icb returns to its original magnitude. On the other hand, if the resonance frequency is too low, the increase rate of the mechanical circuit breaker passage current Icb due to the short circuit becomes larger than the increase rate of the auxiliary circuit current Iaux, and a zero point cannot be created in the mechanical breaker passage current Icb. Therefore, it is necessary to set the resonance frequency to be the same as or slightly longer than the mechanical circuit breaker CB operation time.

  When the mechanical circuit breaker passage current Icb becomes small to some extent, the mechanical circuit breaker CB is opened. There are two possible methods for determining the timing for opening the mechanical circuit breaker CB. The first is a method of detecting the mechanical circuit breaker passage current Icb with a current sensor and opening the contact when the detected value is less than or equal to an allowable value. The second is a method of calculating the time when the auxiliary circuit current Iaux is maximized from the values of the second reactor L2 and the second capacitor C2 and opening the mechanical circuit breaker CB at that timing.

  It should be noted that there is a time delay from when the mechanical breaker CB receives a break designation until it is actually opened. When it is described as blocking in this specification, it indicates the actual opening time.

  In FIG. 6, the mechanical circuit breaker CB is opened at time t3. At time t3, a slight arc is generated because the mechanical circuit breaker passing current Icb remains, but the mechanical circuit breaker passing current Icb becomes zero thereafter by the auxiliary circuit current Iaux, so that the arc can be extinguished.

  Thereafter, the voltage Vc2 of the second capacitor C2 is charged in the opposite direction by the resonance current and the short-circuit current. When the voltage Vc2 reaches the negative system voltage Vdc, the charging is completed, and the auxiliary circuit current Iaux becomes zero and the interruption is completed.

  In this Embodiment 1, although the interruption | blocking method when the accident generate | occur | produced on the 2nd DC system 2 side was described, also when the accident generate | occur | produces on the 1st DC system 1 side, interruption | blocking is possible. In this case, by turning on the first semiconductor switching element T1 instead of the second semiconductor switching element T2, the short-circuit current passing through the mechanical circuit breaker CB is canceled using the discharge current of the first capacitor C1.

  As described above, according to the first embodiment, a zero point is created in the mechanical circuit breaker passing current Icb by the capacitor discharge current of the auxiliary circuit, and the bidirectional DC current can be reliably interrupted.

  Furthermore, since the mechanical circuit breaker CB is always energized at the normal time, there is almost no power loss. Further, immediately after the first and second semiconductor switching elements T1 and T2 are turned on, the first and second reactors L1 and L2 increase from zero current with a slope (see Iaux in FIG. 6B), so that the turn-on is performed. The loss is very small. Furthermore, the first and second semiconductor switching elements T1 and T2 do not cut off the short-circuit current, and turn off when the short-circuit current becomes zero due to reverse charging of the first and second capacitors C1 and C2. There is almost no loss.

  Further, the capacitor capacity of the auxiliary circuit may be small, and the size can be reduced. Further, a slight increase in the parasitic impedance component of the auxiliary circuit can be allowed. In addition, the DC current can be repeatedly interrupted and turned on again.

[Embodiment 2]
FIG. 7 shows the main circuit configuration of the second embodiment. In the second embodiment, the first and second semiconductor switching elements T1 and T2 of the first embodiment are replaced with switching elements having a reverse blocking capability that cannot be self-extinguishing, such as thyristors. Further, the first and second diodes D1 and D2 of the first embodiment are omitted.

  The operation of the second embodiment is exactly the same as that of the first embodiment. However, since the unnecessary current flows through the second semiconductor switching element T2 and the second resistor R2 by turning on the second semiconductor switching element T2 after the mechanical circuit breaker CB is opened as shown in FIG. Without the capability, the second semiconductor switching element T2 cannot be turned off by a command signal from the host controller.

  However, a normal thyristor is turned off when the gate current is zero and the forward current is less than the holding current. Therefore, the values of the first and second resistors R1 and R2 are increased, and the unnecessary current flowing through the first and second resistors R1 and R2 when the first and second semiconductor switching elements T1 and T2 are ON is smaller than the holding current. As a result, the first and second semiconductor switching elements T1 and T2 can be replaced with thyristors.

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment can be obtained. The thyristor has a smaller voltage drop than the IGBT, and a high withstand voltage / high current product is also easily available. In addition, since the thyristor has components with higher withstand voltage than the IGBT, the number of series connections may be smaller than that of the IGBT. For this reason, it is possible to increase the breakdown voltage and current at a smaller size and at a lower cost than the IGBT, and to reduce loss and heat generation at the time of interruption.

[Embodiment 3]
FIG. 8 shows a main circuit configuration of the third embodiment. In the third embodiment, a third semiconductor switching element T3 capable of self-extinguishing is provided between the first and second resistors R1 and R2 of the second embodiment and the negative terminals of the first and second DC systems 1 and 2. In addition, unnecessary current can be cut off.

  Hereinafter, the operation of the DC interrupter 3 in the third embodiment will be described. In the steady state, the third semiconductor switching element T3 is turned ON, and the first and second capacitors C1 and C2 are charged in the same state as in FIG. When a cut-off command is received due to completion of charging or a short circuit accident, the third semiconductor switching element T3 is turned off.

  Completion of charging is performed on the condition that the voltage across the first and second capacitors C1 and C2 is detected and becomes equal to the system voltage. Alternatively, the time constant is obtained from the product of the first capacitor C1 and the first resistor R1, the second capacitor C2 and the second resistor R2, and is sufficiently longer than the time constant from the mechanical circuit breaker CB closing (for example, about 10 times). It may be determined that charging is complete with the progress of.

  After arc extinguishing, the third semiconductor switching element T3 is OFF, and unlike FIG. 4, the unnecessary current flowing through the second semiconductor switching element T2 and the second resistor R2 is blocked by the third semiconductor switching element T3. .

  As described above, according to the third embodiment, the same operational effects as those of the first and second embodiments can be obtained. Further, the loss after the current interruption can be made zero. Moreover, even if the resistance values of the first and second resistors R1 and R2 are small, no unnecessary current flows, so that the first and second thyristors T1 and T2 can be reliably turned off. As an advantage of reducing the resistance values of the first and second resistors R1 and R2, the recharging speed of the first and second capacitors C1 and C2 when the system is re-input in FIG. 5 is improved. Therefore, it is possible to shorten the time required to complete the preparation for shutting down.

  The third semiconductor switching element T3 may be divided into a semiconductor switching element T3 for charging the first capacitor C1 and a semiconductor switching element T4 for charging the second capacitor C2. In this case, the first resistor R1 and the semiconductor switching element T3 are connected. Further, the second resistor R2 and the semiconductor switching element T4 are connected. Moreover, the command signal from the host controller of the semiconductor switching element T3 and the semiconductor switching element T4 may be shared.

[Embodiment 4]
In the first to third embodiments, the first and second capacitors C1 and C2 of the auxiliary circuit are charged in advance, the current at the time of opening the mechanical circuit breaker is canceled using the capacitor discharge current, and the zero is created to extinguish the arc. Arc. However, since the charging currents of the first and second capacitors C1 and C2 flow through the first and second resistors R1 and R2 as shown in FIG. 2, there is a problem that power loss occurs in each resistor.

  Hereinafter, the DC cutoff device 3 according to Embodiment 4 will be described with reference to FIG. The DC circuit breaker 3 in the fourth embodiment includes a mechanical circuit breaker CB, first and second capacitors C1 and C2, first to fourth semiconductor switching elements T1 to T4, and first to fourth reactors L1 to L4. And first and second diodes D1 and D2.

  A mechanical circuit breaker CB is connected between the + terminal of the first DC system 1 and the + terminal of the second DC system 2.

Between the positive connection terminal of the first DC system 1 and the mechanical circuit breaker CB and the negative terminals of the first and second DC systems 1 and 2, a first capacitor C1, a first reactor L1, and A third reactor (first impedance) L3 and a third semiconductor switching element T3 having a self-extinguishing capability are sequentially connected in series. (The order of connection of the first capacitor C1 and the first reactor L1 may be reversed.)
In FIG. 9, the third semiconductor switching element T3 is an IGBT, the collector terminal is connected to the third reactor L3, and the emitter terminal is connected to the negative terminal side of the first and second DC systems 1 and 2.

  The anode of the first semiconductor switching element (thyristor in FIG. 9) T1 having reverse blocking capability is connected to a common connection point between the + terminal of the second DC system 2 and the mechanical circuit breaker CB. The cathode of the first semiconductor switching element (thyristor) T1 is connected to the common connection point of the first and third reactors L1, L3.

  The anode of the first diode D1 is connected to the common connection point of the third reactor L3 and the third semiconductor switching element T3. The cathode of the first diode D1 is connected to a common connection point between the first semiconductor switching element (thyristor) T1 and the + terminal of the second DC system 2.

Between the positive connection terminal of the second DC system 2 and the mechanical circuit breaker CB, and the negative terminal of the first and second DC systems 1 and 2, a second capacitor C2, a second reactor L2, and A fourth reactor (second impedance) L4 and a fourth semiconductor switching element T4 having a self-extinguishing capability are sequentially connected in series. (The order of connection of the second capacitor C2 and the second reactor L2 may be reversed.)
In FIG. 9, the fourth semiconductor switching element T <b> 4 is an IGBT, the collector terminal is connected to the fourth reactor L <b> 4, and the emitter terminal is connected to the − terminal side of the first and second DC systems 1 and 2.

  The anode of the second semiconductor switching element (thyristor in FIG. 9) T2 having reverse blocking capability is connected to the common connection point of the positive terminal of the first DC system 1 and the mechanical circuit breaker CB. The cathode of the second semiconductor switching element (thyristor) T2 is connected to the common connection point of the second and fourth reactors L2 and L4.

  The anode of the second diode D2 is connected to the common connection point of the fourth reactor L4 and the fourth semiconductor switching element T4. The cathode of the second diode D2 is connected to a common connection point between the second semiconductor switching element (thyristor) T2 and the + terminal of the first DC system 1.

  The first and second semiconductor switching elements T1 and T2 do not need self-extinguishing capability but need reverse blocking capability. You may replace with other switching elements, such as a series circuit of IGBT and a diode, or reverse blocking IGBT.

  Hereinafter, the operation of the DC cutoff device 3 according to the fourth embodiment will be described. In the steady state, the mechanical circuit breaker CB is in a closed state, and current flows in both directions. In this steady state, the first and second capacitors C1 and C2 are charged by switching the third and fourth semiconductor switching elements T3 and T4.

  FIG. 10 shows a state when the third and fourth semiconductor switching elements T3 and T4 are turned on. The capacitor charging current flows through the first capacitor C1, the first reactor L1, the third reactor L3, and the third semiconductor switching element T3, and the first capacitor C1 is charged. At the same time, the capacitor charging current flows through the second capacitor C2, the second reactor L2, the fourth reactor L4, and the fourth semiconductor switching element T4, and the second capacitor C2 is charged.

  FIG. 11 shows a state when the third and fourth semiconductor switching elements T3 and T4 are turned off. The magnetic energy stored in the third reactor L3 when the third semiconductor switching element T3 is ON circulates through the first diode D1, the first capacitor C1, the first reactor L1, and the first capacitor C1 is charged.

  Further, the magnetic energy stored in the fourth reactor L4 when the fourth semiconductor switching element T4 is turned on circulates through the second diode D2, the second capacitor C2, and the second reactor L2, and the second capacitor C2 is charged. The

  When the charging is completed, the third and fourth semiconductor switching elements T3, T4 maintain the OFF state. Since the current passes only through the mechanical circuit breaker CB at a constant time, there is almost no power loss.

  The completion of charging is determined by detecting the voltage across the first and second capacitors C1 and C2 and reaching a predetermined voltage. As another method, the time until the first and second capacitors C1 and C2 are fully charged is calculated in advance from the constants of the first to fourth reactors L1 to L4 and the first and second capacitors C1 and C2. When the time is reached, the third and fourth semiconductor switching elements T3 and T4 may be turned off.

  FIG. 12 shows the DC interrupter 3 of the fourth embodiment when an accident occurs on the second DC system 2 side. When an accident occurs, the second semiconductor switching element T2 is turned ON, so that a discharge current flows from the second capacitor C2 as an auxiliary circuit current via the mechanical circuit breaker CB → second semiconductor switching element T2 → second reactor L2. This auxiliary circuit current cancels the short-circuit current flowing through the mechanical circuit breaker CB to create a zero point of the current, opens the mechanical circuit breaker CB, and extinguishes the arc.

  FIG. 13 shows the DC interrupter 3 of the fourth embodiment after arc extinguishing. The auxiliary circuit current flows via the second semiconductor switching element T2 → second reactor L2 → second capacitor C2, and charges the second capacitor C2 in the direction opposite to that in FIG. When the charging of the second capacitor C2 is completed, the current on the second DC system 2 side becomes zero, and the interruption of the current is completed.

  Unlike the first and second embodiments, no unnecessary current flows in the DC interrupter 3 of the fourth embodiment. Therefore, even if the second semiconductor switching element T2 does not have a self-extinguishing capability (even if the holding current is large), it can be reliably turned off.

  FIG. 14 shows the DC interrupting device 3 of Embodiment 4 when the current interrupting is completed and the second DC system 2 is turned on again. When the mechanical circuit breaker CB is closed, a resonance circuit is formed in the path of the second capacitor C2, the second reactor L2, the fourth reactor L4, the second diode D2, and the mechanical circuit breaker CB. C2 is recharged in the original direction.

  When the charging of the second capacitor C2 is completed, the resonance current is blocked by the second diode D2, reaches a steady state, and the preparation for interruption is completed. If the charging of the second capacitor C2 is incomplete, the second capacitor C2 can be charged by turning on the fourth semiconductor switching element T4.

  The direction of current flow and the current value when an accident occurs are monitored using a host controller, and the mechanical circuit breaker CB is opened and closed and the first and second semiconductor switching elements T1 and T2 are turned on and off.

  In this Embodiment 4, although the interruption | blocking method when the accident generate | occur | produced in the 2nd DC system 2 side was described, also when the accident generate | occur | produces in the 1st DC system 1 side, interruption | blocking is possible. In this case, by turning on the first semiconductor switching element T1 instead of the second semiconductor switching element T2, the short-circuit current passing through the mechanical circuit breaker CB is canceled using the discharge current of the first capacitor C1.

  The third semiconductor switching element T3 and the semiconductor switching element T4 may be shared. In this case, the common semiconductor switching element has the same connection configuration as the third semiconductor switching element T3 in FIG.

  The fourth embodiment has the same effects as the first to third embodiments. Further, in the DC interrupter 3 of the fourth embodiment, the capacitor charging current does not flow through the resistor, and power loss due to the resistor does not occur, so that loss during charging can be reduced.

  In addition, when the system is turned on again, recharging of the first and second capacitors C1 and C2 is completed only by closing the mechanical circuit breaker CB.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... 1st DC system 2 ... 2nd DC system 3 ... DC circuit breaker CB ... Mechanical circuit breaker C1, C2 ... 1st, 2nd capacitor T1-T4 ... 1st-4th semiconductor switching element R1, R2 ... 1st , Second resistors L1 to L4 ... first to fourth reactors D1, D2 ... first and second diodes Iaux ... auxiliary circuit current Icb ... mechanical circuit breaker energization current Vcb ... voltage across the mechanical circuit breaker

Claims (8)

A mechanical circuit breaker connected between the + terminal of the first DC system and the + terminal of the second DC system;
A first capacitor sequentially connected in series between a positive terminal of the first DC system and a common connection point of the mechanical circuit breaker, and a positive terminal of the second DC system and a common connection point of the mechanical circuit breaker; A first reactor and a first semiconductor switching element, or a first reactor and a first capacitor and a first semiconductor switching element;
A second capacitor sequentially connected in series between the positive terminal of the second DC system and the common connection point of the mechanical circuit breaker, and the positive terminal of the first DC system and the common connection point of the mechanical circuit breaker; A second reactor and a second semiconductor switching element, or a second reactor and a second capacitor and a second semiconductor switching element;
Between a common connection point of the first reactor and the first semiconductor switching element, or a common connection point of the first capacitor and the first semiconductor switching element, and a negative terminal of the first and second DC systems. A connected first impedance;
Between the common connection point of the second reactor and the second semiconductor switching element, or the common connection point of the second capacitor and the second semiconductor switching element, and the negative terminal of the first and second DC systems. A connected second impedance;
DC circuit breaker characterized by comprising   2. The DC interrupter according to claim 1, wherein the first impedance and the second impedance are resistors.   3. The DC interrupter according to claim 2, wherein the first and second semiconductor switching elements are self-extinguishing elements, and a diode is connected in series to the first and second semiconductor switching elements.   3. The DC interrupter according to claim 2, wherein the first and second semiconductor switching elements are thyristors.   A third semiconductor switching element connected between the first and second resistors and a negative terminal of the first and second DC systems; or the first resistor and the first and second DC systems A third semiconductor switching element connected between the second terminal and a fourth semiconductor switching element connected between the second resistor and the negative terminal of the first and second DC systems; The direct current circuit breaker according to claim 4. The first impedance and the second impedance are a third reactor and a fourth reactor,
A third semiconductor switching element connected between the third and fourth reactors and a negative terminal of the first and second DC systems; or a third semiconductor switching element and the first and second DC systems; A third semiconductor switching element connected between the terminal and a fourth semiconductor switching element connected between the fourth reactor and the negative terminal of the first and second DC systems;
A first diode having an anode connected to a common connection point of the third reactor and the third semiconductor switching element, and a cathode connected to a common connection point of the first semiconductor switching element and a positive terminal of the second DC system; ,
An anode is connected to a common connection point of the fourth reactor and the fourth semiconductor switching element or the third semiconductor switching element, and a cathode is a common connection point of the second semiconductor switching element and the + terminal of the first DC system. A connected second diode;
The direct current circuit breaker according to claim 1, further comprising:   7. The DC circuit breaker according to claim 6, wherein the first and second semiconductor switching elements are thyristors. When a current flows from the first DC system to the second DC system and an accident occurs in the second DC system, the second semiconductor switching element is turned ON, and the current flowing through the mechanical circuit breaker is predetermined. After the value falls below the value, shut off the mechanical circuit breaker,
When a current flows from the second DC system to the first DC system, and an accident occurs in the first DC system, the first semiconductor switching element is turned ON, and the current flowing through the mechanical circuit breaker is predetermined. The DC circuit breaker according to any one of claims 1 to 7, wherein the mechanical circuit breaker is interrupted after the value becomes equal to or less than a value.

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