JPH0343837Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field of the Invention> The present invention relates to a control device for a voltage source inverter with parallel redundancy, and particularly to a protection circuit.

<Prior Art> Uninterruptible power supply systems include a power switching type that switches between an inverter and a commercial power supply, and a standby inverter switching type that switches to a standby inverter. In these power source switching type uninterruptible power supply devices, power source switching is performed by synchronizing both power sources and temporarily connecting both power sources in parallel to supply power to a load. There is also an uninterruptible power supply that supplies power to a load by operating multiple inverters in parallel, and even if one inverter fails, the other healthy inverter continues to supply power.

In uninterruptible power supplies that provide parallel redundancy in which multiple power supplies are connected in parallel, conventional protection measures in the event of a failure in a power supply with an inverter configuration include an AC switch such as a thyristor on the AC output side of the inverter. There is a system in which a fault inverter is isolated from other parallel power supplies and loads by controlling the AC switch to open when a fault is detected.

This conventional method requires an AC switch and its control circuit in the inverter, which has the problem of increasing the cost and size of the device.

Another conventional method uses self-extinguishing elements such as transistors and GTOs in the inverter main circuit switch, and disconnects it from other parallel power supplies by controlling the entire main circuit switch to extinguish upon failure detection. . This method eliminates the need for the above-mentioned AC switch, but in the event of a failure due to short-circuit damage to the main circuit switch, the bypass current from the normal power supply will flow through the faulty switch and the feedback diode, and the normal power supply side will also stop due to overcurrent. The system may go down.

<Purpose of the invention> The object of the invention is to provide a control device that can prevent power from being diverted from a normal power source even in the event of a short-circuit failure of the main circuit switch without providing an AC switch.

<Summary of the invention> This invention detects an inverter failure, stops normal control operation, and fires the high-voltage side switch of the main circuit for a short period of time, and then fires the low-voltage side switch for a short period of time, thereby removing the damaged switch. In some cases, the series fuse is blown, and each switch on the high-voltage side and the low-voltage side is put into an extinguished state to create a disconnected state from other healthy power sources.

<Embodiment> FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and shows the case of a transistor type single-phase inverter. The inverter main circuit 3 has on the input side a DC rectified by a rectifier 1 and smoothed by a capacitor 2.
As each phase arm of U, V, 6
A bridge is constructed with X and 6Y. The AC side of the inverter main circuit 3 is connected in parallel to the output side of another power source 9 via an AC filter of a reactor 7 and a capacitor 8, and a parallel redundant structure is formed in which a load 10 is connected to this parallel connection point.

Each phase transistor switch 4U, 4V, 4X, 4Y of the inverter main circuit 3 is connected to the control circuit main body 11.
The control pulses U, V,
Controlled off.

The OR gates 12 U, 12 V, 12 The short circuit protection circuit 14 includes a current transformer 15 that detects the discharge current of the smoothing capacitor 2, a comparator 16 that detects that this detected current exceeds the setting value of the overcurrent setting device 16A, and this comparator 16. is triggered by the detection signal of the OR gate 12 to obtain a pulse of a certain time width.
A unitary constant multivibrator 17 whose gate inputs are U and 12V, and a monostable multivibrator 18 which is triggered by the trailing edge of the output of this multivibrator 17 to obtain a pulse with a constant time width and which is used as a gate input of OR gates 12X and 12Y. Consists of.
The detection output of the comparator 16 is also given to the control circuit main body 11, and the control operation of the control circuit main body 11 is stopped and its outputs u, v, x, y are inactive (logic "0").
Make it.

In such a configuration, when the main circuit 3 becomes in a mode where PN is short-circuited for some reason, for example, due to a short-circuit accident in one of the transistor switches, the U-X phase and the V-Y phase start firing at the same time. At this time, a short circuit current flows from the electrolytic capacitor 2. When this short-circuit current Ic exceeds the set value Is of the setting device 16A, as shown in _FIG . By applying the output of the vibrator 17 to the transistor switches 4U, 4V through the OR gate 12U, 12V and the gate amplifier 13U, 13V during the output period T ₀ (the time required to blow the fuse), the U, V of the high voltage side arm is
Ignite the phase. Similarly, after the time limit of the monostable multivibrator 17 (time t ₂ ), the output of the monostable multivibrator 18 ignites the X and Y phases of the low-pressure side arm for the time limit (T ₁ ).

Due to this control operation, if the phase element on the low voltage side is short-circuited, the monostable multivibrator 1
During the output period T ₀ of 7, the short-circuit current passed through both switches 4U and 4V causes the fuse connected in series to the short-circuit damaged element to melt. Conversely, when a phase element on the high voltage side is short-circuited, the fuse connected in series to the damaged element is blown during the output period _T1 of the monostable multivibrator 18. As a result, the bypass current from the normal power supply 9 through the short-circuit damaged element is blocked by the blown fuse, and the voltage of the load bus can be maintained normally.

In addition, when a signal that shorts between PN is generated due to a malfunction of the control device main body 11, that is, when the transistor switches 4U, 4V, 4X, and 4Y are all normal and the mode is momentarily shorted between PN, the output of the comparator 16 After the control is stopped, the subsequent firing of the high-pressure side arm and then the firing of the low-pressure side arm do not result in a short circuit between PN, and normal control can be restored after time _t3 without damaging the switch or blowing out the fuse.

<Effects of the invention> According to the invention, in order to stop the control device main body due to an overcurrent on the DC side of the inverter main circuit and fire the high-voltage side arm and the low-voltage side arm sequentially instead of the control device main body, the main circuit switch This has the effect of reliably preventing leakage from other normal power sources without providing an AC switch in case of a short circuit in the main circuit due to a short circuit failure or control malfunction. Furthermore, in the event of a malfunction of the control device, normal operation can be restored without damaging the main circuit switch, fuses, etc.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a time chart for explaining the operation of FIG. 1. 3...Inverter main circuit, 4U, 4V, 4X,
4Y...transistor switch, 6U, 6V, 6
X, 6Y...fuse, 9...power supply, 10...load, 11...control device body, 13U, 13V, 1
3X, 13Y... Gate amplifier, 14... Short circuit protection circuit, 16... Comparator, 16A... Overcurrent setting device, 17, 18... Monostable multivibrator.

Claims (1)

[Scope of utility model registration request] A fuse is connected in series to the high-voltage side and a low-voltage side, and a plurality of these series-connected bodies are connected in parallel, and the arms are connected in series to the high-voltage side and the low-voltage side. an inverter main circuit that outputs alternating current from each bridge point of the low-voltage side arm; and a control circuit main body that generates on/off control pulses for switch elements of each phase arm to control the alternating current output of the inverter main circuit. , in a voltage source inverter in which the AC output side of the inverter main circuit is connected in parallel with another AC power source to supply power to the same load, detects a state in which the DC input side current of the inverter main circuit exceeds an overcurrent setting value. a comparator that stops generation of on/off control pulses of the control circuit main body based on the detection signal;
a first monostable multivibrator that is triggered by the detection signal of the comparator and generates a pulse with a time width necessary for blowing the fuse as an ON signal for the switch element of the high voltage side arm of each phase; and a second monostable multivibrator that is triggered by the trailing edge of the output pulse of the vibrator and generates a pulse with a time width necessary to blow out the fuse as an ON signal for the switch element of the low voltage side arm of each phase. A voltage source inverter control device with special features.