JPH035141B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output switching device for an uninterruptible power supply having a plurality of inverters.

Conventionally, there has been one shown in FIG. 1 as an example of an uninterruptible switching type uninterruptible power supply having a plurality of inverters. In the figure, 1 and 2 are inverters, 3
0 and 40 are forced commutation type thyristor switches for switching the output of the inverter, and 20 is a load. FIG. 2 shows an example of the circuit of the forced commutation type thyristor switch shown in FIG. 31 is a main thyristor, 32 is a main diode, 33 and 34 are commutation capacitors and commutation reactors necessary for forced commutation, and 35
is an auxiliary thyristor, and 36 is a diode, the anode of which is connected to the input terminal R1 of the forced commutation type thyristor switch 30. R2 is the output terminal of the thyristor switch 30, and S1 and S2 are the input terminal and output terminal of the thyristor switch 40.

Next, the operation of the conventional device will be explained with reference to the waveform diagram in FIG. Now, the inverters 1 and 2 are operating normally and the thyristor switch 30 is on (Fig. 3a).
Assuming that the thyristor switch 40 is off (FIG. 3d), the load 20 is supplied with power from the inverter 1. If the inverter 1 fails at time t1 in FIG. 3, the gate signal of the main thyristor 31 of the thyristor switch 30 is turned off (FIG. 3b) and the auxiliary thyristor 35 is turned on (FIG. 3c) at the same time. At t2, the main thyristor 31 is quickly turned off. At the same time, the main thyristor switch (not shown) of the thyristor switch 40 is turned on to switch the inverter from 1 to 2 without interruption.
Power is supplied from the inverter 2 to the load 20.

The reason why forced commutation type thyristor switches 30 and 40 as shown in Fig. 2 must be used as the output switching device of the inverters 1 and 2 is that when one inverter fails, the other normal inverter is switched to the failed inverter. This is to quickly disconnect the faulty inverter from the load in order to prevent the inverter itself, which is normally operating, from causing a failure due to current flowing to other inverters.

Conventional uninterruptible switching type uninterruptible power supplies using multiple inverters are configured as described above, so the circuit configuration of the forced commutation type thyristor switch for output switching is complicated, making it difficult to operate in the event of a failure. The circuit configuration for timing the thyristor gate signals also becomes complicated. Furthermore, if a short-circuit accident occurs on the load side, all inverters may stop.

The purpose of this invention is to eliminate the drawbacks of the conventional device as described above, and its configuration is as follows:
In addition to multiple inverters, a commercial backup power source is installed.
It is characterized by the provision of a natural commutation type thyristor switch that performs instantaneous switching between inverters via a commercial standby power source.

Next, one embodiment of the present invention will be explained with reference to FIG. In the figure, 1 and 2 are inverters, 3 is a commercial backup power source, 11 to 13 are natural commutation type thyristor switches for switching the outputs of the inverters 1 and 2 and the commercial backup power source 3, and 20 is a load. Natural commutation type thyristor switches 11 to 13 have a configuration in which main thyristors 41 and 42 are connected in antiparallel.

Next, the operation of the present invention will be explained using the waveform diagram shown in FIG. Currently, inverters 1 and 2 and commercial backup power supply 3
is normal, natural commutation type thyristor switch 11 is on, natural commutation type thyristor switch 12, 13
is off, power is supplied from the inverter 1 to the load 20. When the inverter 1 fails at time t1 in FIG. 5, the thyristor switch 13 is turned on (FIG. 5b) and the thyristor switch 1
1 gate signal is turned off. As a result, at time t2 when the load current of the inverter 1 crosses zero, the thyristor switch 11 is turned off (FIG. 5a), and the faulty inverter 1 is switched to the commercial standby power source 3 without momentary interruption.
Power is supplied to the load 20 from the commercial backup power source 3. When power is supplied from the commercial backup power source 3 to the load 20, some loads may require high-quality power, so after switching to the commercial backup power source 3, the time At time t3, the thyristor switch 12 is turned on (FIG. 5c), and at the same time the thyristor switch 13 is turned off, and at time t4, the commercial backup power source 3 is switched to the normal inverter 2 without any interruption, and power is supplied from the inverter 2 to the load 20. .
In the present invention, switching between inverters is performed indirectly via the commercial standby power source 3, so a naturally commutated thyristor switch can be used as the output switching device.

That is, in general, if a current of about 130% of the rated current flows through an inverter, even momentarily, the inverter will malfunction, but a commercial power source can instantly flow a current of about 500% of the rated current.

Therefore, even if a fault current flows into the commercial backup power source when switching from the faulty inverter to the commercial backup power source, the commercial backup power source can normally supply power. Also,
When switching from the commercial standby power source to the normal inverter, the inverter is operating normally, so power can be normally supplied to the inverter.

Therefore, when switching the inverter via the commercial standby power source, there is no need to instantly disconnect the power source, so it is possible to use a naturally commutated thyristor switch, which takes about one cycle to switch.

In the above embodiment, a case has been described in which two inverters and one commercial backup power source are used, but the numbers of inverters and commercial backup power sources are not limited to those in the embodiment.

As explained above, the present invention provides another commercial backup power source for a plurality of inverters, and provides a natural flow type thyristor switch that performs switching between inverters via the commercial backup power source, so the control timing circuit of the thyristor switch The configuration becomes simple and a complicated forced commutation type thyristor switch is not required. Furthermore, even if a short-circuit accident occurs on the load side, all inverters can be prevented from failing by supplying a short-circuit current from a commercial standby power source to eliminate the fault in a short time.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional uninterruptible switching type uninterruptible power supply, Figure 2 is a circuit diagram of the forced commutation type thyristor switch of Figure 1, and Figure 3 is an operating waveform diagram of Figures 1 and 2. , FIG. 4 is a circuit diagram showing an embodiment of the present invention,
FIG. 5 is an operational waveform diagram of FIG. 4. 1, 2... Inverter, 3... Commercial backup power supply,
11-13...Natural commutation type thyristor switch,
20... Load, 30, 40... Forced commutation type thyristor switch, 41, 42... Main thyristor. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A non-interruption system characterized by connecting a naturally commutated thyristor switch between a plurality of inverters, each of a commercial backup power source, and a load to perform instantaneous interruption switching between inverters via a commercial backup power source. Switchable uninterruptible power supply.