JPS5918932B2 - DC power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a small and economical semiconductor DC switchgear for use in a DC substation.

Conventionally, a DC power supply circuit has been used in which a plurality of sets of DC power supply circuits having semiconductor shear breakers are connected to a common DC power supply circuit to supply DC power to different loads. That is, a conventional DC power supply circuit as shown in FIG. 1 will be explained. 1 is a rectifier, and its AC side is connected to an AC power supply 3 having a power supply reactance 2.

The DC positive side of the rectifier 1 is connected to a common power supply circuit 4 such as a DC bus.
The DC negative electrode side is connected to a load circuit (not shown). Reference numerals 5a, 5b, and 5c indicate DC feeder circuits, respectively, which are used in semiconductor DC switchgear devices such as semiconductor shear circuit breakers 6a, 6b.
, 6c, each of which is configured to supply DC power to a separate load (not shown).

The semiconductor shear breaker 6a is connected in parallel to the main thyristor T with a commutation circuit 11 consisting of a commutation capacitor 8, a reactor 9, and an auxiliary thyristor 10 connected in series. Freewheeling diodes 12a, 12b, 12c are connected between the output sides of the semiconductor shear disconnectors 6a, 6b, 6c and the negative electrode side of the rectifier 1 so that the negative electrode side becomes the anode side. Next, the operation of such a conventional circuit will be explained based on FIG.

When cutting off the current Id of the feed circuit 5a with the semiconductor shear breaker 6a, the commutating capacitor 8 is charged in advance to the polarity shown in the figure, and at the same time the gate signal of the main thyristor T is stopped by the shear cutting signal. An ignition signal is sent to the auxiliary thyristor 10 to make it conductive. As a result, the discharge current of commutating capacitor 8 flows through the circuit consisting of commutating capacitor 8 - reactor 9 - auxiliary thyristor 10 - main thyristor 1 - commutating capacitor 8, and extinguishes the main thyristor 7. The current Id that has been flowing is commutated to the commutation circuit 11 and charges the commutation capacitor 8 to a polarity opposite to that shown in the figure. When the commutating capacitor 8 is charged with a polarity opposite to that shown in the figure and becomes equal to the DC voltage of the rectifier 1, the free-wheeling diode 12a becomes energized.
Since the energy stored in the reactance of the load circuit (not shown) is released, the load circuit reactance becomes irrelevant to the charging of the commutating capacitor 8. However, due to the energy stored in the power supply reactance 2, the commutation circuit 11 continues to be energized, and the commutation capacitor 8 is overcharged. For this reason, commutation capacitor 8
requires sufficient capacity to absorb the energy stored in the current circuit reactance. Especially when cutting off overcurrent, the power supply reactance 2
The current flowing through the capacitor 8 is large, and therefore its energy is naturally large, and the commutating capacitor 8 needs to have a large capacity. On the other hand, in the conventional system, the semiconductor shear breaker 6a,
6b and 6c each require a commutating capacitor capacity large enough to absorb the energy of the power supply reactance 2 independently, so as the number of feeder circuits 5 increases, the total capacitance of commutating capacitors becomes enormous, and the equipment The size and cost have become very large. The present invention is aimed at solving such drawbacks, and provides a DC power supply circuit comprising a plurality of sets of DC feed circuits each having a semiconductor shear disconnector connected to a common DC power supply circuit.
The purpose is to provide a DC power supply circuit with a small total capacitance of commutating capacitors.

The embodiment of the present invention shown in FIG. 2 will be described in detail below.

Each of the numerals 1 to 12 in FIG. 2 represents the same components as those in the conventional device shown in FIG. 1, and the circuit connections and configurations are also the same as in the conventional device shown in FIG. Next, in the present invention, a surge voltage absorber 15 is provided between the anode side 13 and the cathode side 14 of the common DC power supply circuit of each feeder circuit 5a, 5b, 5c.
Connect. The surge voltage absorbing device 15 is composed of, for example, a series body of a capacitor and a resistor, or a non-linear resistor. The surge voltage absorber 15 is a feeder circuit shear breaker 5a.
, 5b, 5c operate, the energy stored in the power supply reactance 2 is absorbed and the common power supply circuit 4 is activated.
The capacitor should have enough capacity to suppress abnormal voltage rise. In the present invention, a case where, for example, a capacitor is used as the surge voltage absorbing device 15 will be explained in more detail.

Now, if the semiconductor shear breaker 6a cuts off the DC current 1d, the power supply reactance at this time is 2×(-LcId2
) However, Lc is the value equivalent to 1 of power supply reactance 2, that is, Lc
This means that energy Id2 is stored in the power source.

Therefore, if the DC voltage immediately before shearing is interrupted by the semiconductor shear breaker 6a is EdOl, and the allowable DC voltage after shearing is Edl, then LcId2 is obtained if the capacitor capacity C1 of the surge absorber 15 is selected to be greater than the value given by The DC voltage increase due to energy is below Fdl-FdO, and the voltage of the common power supply circuit 4 is suppressed below Fd.

Therefore, the capacitor 8 of the shear disconnector 6a is connected to the main thyristor 7.
It is sufficient that the current is commutated to the commutation circuit 11 and the capacity is large enough to ensure the turn-off time of the main thyristor 7.
Since there is no need to consider overcharging due to energy 1cId2 on the power supply side, a small capacity is sufficient. On the other hand, surge absorber 1
The required capacitance of capacitor 5 is determined by the power supply reactance 2 and the maximum shear current, and is therefore not related to the number of feeder circuits 5. Therefore, even if the number of feeder circuits increases, there is no need to increase the capacitor capacity of the surge absorber 15, and only the number of small-capacity capacitors 8 increases, and the total capacitor capacity as a whole does not need to be very small. I'm done. On the other hand, in the conventional device, a capacitor with a capacitance of 15 according to the present invention was used for the capacitor 8 of each shear disconnector, so as the number of feeder circuits increased, the total capacitor capacity of the entire DC power supply circuit became enormous, resulting in increased cost. However, the present invention solves all of these problems. As described above, according to the present invention, in a DC power supply circuit formed by connecting a plurality of sets of feeder circuits each having a thyristor switch having a commutation circuit having a commutation capacitor and a reactor to a common DC power supply circuit, It is possible to obtain a small, low-cost DC power supply circuit in which the total capacitance of current capacitors is greatly reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional device, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. Note that the same reference numerals in the figures indicate the same or corresponding parts. 1... Rectifier, 2... Power supply reactance, 3... AC power supply, 4... Common power supply circuit, 5a, 5b, 5c...・DC feeding circuit, 6
a, 6b, 6c... Semiconductor switchgear, 7...
...Main thyristor, 8... Commutation capacitor,
9...Reactor, 10...Auxiliary thyristor, 11...Commuting circuit, 12a, 12b,
12c... Freewheeling diode, 13...
Common power supply circuit anode side, 14...Common power supply circuit cathode side, 15...Surge voltage absorber.

Claims (1)

[Claims] 1. In a DC power supply circuit formed by connecting multiple sets of feeder circuits each having a thyristor switch having a commutation circuit having a commutation capacitor and a reactor to a common DC power supply circuit,
A surge voltage absorbing device consisting of a series body of a capacitor and a resistor for suppressing abnormal voltage during the opening operation of the semiconductor DC switchgear is connected between the positive and negative terminals of the common DC power supply circuit. Capacity of capacitor C_
1 to [2LcId^2]/[Ed^2_1-Ed^2_
0] (However, Lc is the value of the power supply reactance, Id is the DC current value at which the thyristor switch is cut off, Ed_1, E
A DC power supply circuit characterized in that d_0 is selected to be greater than or equal to a value given by a DC voltage value immediately before being cut off by a thyristor switch and an allowable DC voltage value after being cut off by a thyristor switch.