JPS6220772B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply system using a power converter comprising a plurality of load groups each connected to the output of the power converter via a disconnector.

2. Description of the Related Art Power supply systems in which a single power converter supplies power to a plurality of load groups via respective disconnectors are widely used. In particular, static power converters generally have a relatively small overload capacity, so if a short circuit occurs in one of the multiple load groups, an overload trip of the power converter will cause other healthy load groups to shut down. In order to prevent this from happening, a so-called selective disconnection method is often used in which each load group is provided with a semiconductor disconnector that can quickly disconnect a load group in which a short circuit has occurred.

FIG. 1 is a block diagram showing the configuration of a power supply system using a static inverter device, which is an application example of the above-mentioned power supply system. In the figure, 1 is a stationary inverter device, 13, 23, 3
3 is an independent load group; 11, 21, and 31 are semiconductor wire disconnectors for quickly limiting and disconnecting overcurrent caused by a short circuit occurring in each load group; 12, 2;
2 and 32 are CTs that detect the load current of each load group;
14, 24, and 34 are shield circuit breaker control circuits for controlling on/off of each semiconductor shield circuit; 15, 25, and 35;
is an overcurrent detection circuit that detects that the current in each load group exceeds a predetermined level (determined by the overload capacity of the static inverter device 1) and issues a trip command to the corresponding semiconductor circuit breaker.

For example, if a short circuit accident occurs in the load group 13,
The overcurrent detection circuit 15 detects an overcurrent via the CT 12 and gives a trip command to the semiconductor shingle breaker 11, which quickly cuts off the fault current, thereby converting the static inverter. The commutation failure of No. 1 is prevented and power is continued to be supplied to the other healthy load groups 23 and 33. In this case, the detection level I of the overcurrent detection circuits 15, 25, and 35 is required to quickly detect and disconnect short-circuit accidents in each load group and to facilitate coordination with the overload capacity of the static inverter device 1.
It is desirable to set _T1 , I _T2 and I _T3 as low as possible.

However, if the load group 13 in which a short-circuit accident has occurred is separated by the semiconductor shear disconnector 11, the load on the static inverter device 1 will change in the direction of becoming lighter by the amount of the separated load group. ,
With this load fluctuation, the static inverter device 1
The output voltage E ₀ fluctuates in an upward direction. If the other healthy load groups 23 and 33 include loads such as capacitors and transformers through which rush current flows due to a sudden voltage increase, the current in the load groups 23 and 33 increases rapidly due to this voltage fluctuation. When starting up such a load, inrush current is usually suppressed by sequential starting or current limiting starting by a current limiting circuit (not shown).

FIG. 2 is an operational waveform diagram for explaining details of the operation in this case. That is, time t ₁
When a short circuit accident occurs in the load group 13, as soon as the current _I1 of the load group 13 exceeds the set level I _T1 of the overcurrent detection circuit 15, the overcurrent detection circuit 15 immediately issues a trip command to the semiconductor circuit breaker 11. The load group 13 is disconnected by the semiconductor sheath disconnector 11. Due to this disconnection operation, the output voltage E ₀ of the static inverter device 1 increases as described above, and due to this voltage increase, the currents I ₂ and I ₃ of the other healthy loads 23 and 33 rapidly increase. Overcurrent detection circuit 16, 2
As mentioned above, the detection levels I _T2 and I _T3 of No. 6 are set as low as possible in order to promptly detect the short-circuit accident that occurs in each load group.
The currents I ₂ and I ₃ of 3 and 33 reach the detection levels I _T2 and I _T3 , and the overcurrent detection circuits 25 and 35 give a trip command to the semiconductor circuit breakers 24 and 34, causing the semiconductor circuit breakers to disconnect. Due to the disconnection operation of the devices 24 and 34, the healthy load groups 13 and 23 are also disconnected, and there is a risk that the entire system will go down.

The present invention has been made in view of the above-mentioned points, and the present invention consists of a plurality of load groups connected to each output of a power conversion device through a shield disconnector that has a function of detecting overcurrent and disconnecting it quickly. In the supply system, when a short-circuit accident occurs in one of the load groups, the increase in output voltage of the power converter, which is determined by the disconnection operation of the corresponding load group, causes the semiconductor circuit breakers of other healthy load groups to overshoot. It is an object of the present invention to provide a power supply system using a power conversion device that prevents the problem of current tripping.

An embodiment of the present invention will be described below with reference to FIG. In this figure, the same reference numerals as those in FIG. 1 represent the same elements, so the explanation thereof will be omitted. 16, 26, 36 are 15, 2 in Figure 1
Similarly to 5 and 35, an overcurrent detection circuit detects overcurrent in each load group and issues a trip command to each semiconductor shield circuit breaker; 41 is an overcurrent detection circuit 16, 26, 36;
42 is an OR circuit that takes the logical sum of the signals output when an overcurrent is detected, and 42 is an overcurrent detection circuit 16, 2 that detects an
This is an overcurrent detection blocking circuit that blocks the overcurrent detection operations of 6 and 36 for a predetermined period of time.

The present invention is designed to prevent other healthy load groups, including loads through which inrush current flows, from increasing when the output voltage of the static inverter device 1 increases due to the disconnection operation of the load group that has caused a short-circuit accident using a semiconductor circuit breaker. By blocking current detection for a predetermined period of time, overcurrent tripping of semiconductor circuits and circuit breakers of other healthy loads is prevented. For example, if a short circuit occurs in load group 13, the same situation as in the system shown in Figure 1 will occur.
The overcurrent detection circuit 16 connects load group 1 via CT12.
Detecting that the current I ₁ of 3 exceeds the set level I _{T 1} and giving a trip command to the semiconductor circuit breaker 11,
Load group 13 is triggered by tripping of semiconductor circuit breaker 11.
Separate. By disconnecting the load group 13, the second
As shown in the operating waveform diagram in the figure, the output voltage E ₀ of the static inverter device fluctuates in an upward direction, and this causes the currents I ₁ , I ₂ also increases. on the other hand,
The overcurrent detection circuit 16 connects the overcurrent detection signal to the overcurrent detection blocking circuit 42 via the overcurrent detection signal OR circuit 41 of the load group 13.
send to In response to this overcurrent detection signal, the overcurrent detection blocking circuit 42 switches the overcurrent detection circuit 16 of each load group,
A command is given to 26 and 36 to block overcurrent detection for a predetermined period of time. Due to this overcurrent detection block operation, the currents I ₂ and I _{3 of the healthy load groups 23 and 33} are transferred to the overcurrent detection circuit 2 as shown in the operating waveform diagram of FIG.
Even if the detection levels I _T2 and I _T3 of 6 and 36 are exceeded, a trip command is not given to the semiconductor circuit breakers 21 and 31, and the power supply to the load groups 23 and 33 is interrupted. The period during which the output voltage E ₀ of the static inverter device 1 increases and the currents I ₂ and I ₃ of the load groups 13 and 23 increase is usually 3 to 4 cycles or less, and the blocking time by the overcurrent detection and prevention circuit 42 is 100 msec. It is enough. Also, when a short-circuit accident occurs in the load group 23, the overcurrent detection blocking circuit 42 generates an overcurrent detection block signal based on the overcurrent detection signal from the overcurrent detection circuit 26, as described above.

In this way, when a short-circuit accident occurs in one load group, the power supply according to the present invention blocks overcurrent detection of other healthy load groups for a predetermined period of time using an overcurrent detection signal from an overcurrent detection circuit. In this method, when the output voltage of the static inverter device 1 increases when a load group is disconnected due to a short-circuit accident, other healthy loads, including the load through which an inrush current flows, detect an overcurrent and trip. The problem will be resolved. Therefore, the original purpose of the selective disconnection method can be achieved even if loads in which inrush current flows in each load group are included.

Next, FIG. 4 shows another embodiment of the present invention. In the same figure, 17, 27, 37 are overcurrent detection circuits, 5
1 is an OR circuit that takes the logical sum of the overcurrent detection signals of each overcurrent detection circuit, and 52 is a detection level that shifts the detection level of the overcurrent detection circuits 17, 27, and 37 in the direction of increasing the detection level according to the output of the OR circuit 51. It is a shift circuit. That is, in this embodiment, when a short-circuit accident occurs in one of a plurality of load groups, the overcurrent detection output of the corresponding load group blocks overcurrent detection of other healthy load groups for a predetermined period of time. Instead, system failure is prevented by shifting the detection levels of overcurrent detection circuits for other healthy load groups. For example, when a short-circuit accident occurs in the load group 13, the overcurrent detection circuit 17
At the same time, an overcurrent detection signal is applied to the detection level shift circuit 52 via the OR circuit 51. This overcurrent detection signal causes the detection level shift circuit 52 to control the overcurrent detection circuits 17, 27,
37 is given a command to shift the detection level for a predetermined time, and the detection level of each overcurrent detection circuit is set to I.
Shift from _T1 , I _T2 , I _T3 to I _T1 ′, I _T2 ′, I _T3 ′ (I _T1 < I _T1 ′, I _T2 < I _T2 ′, I _T3 < I _T
3 ′).

In addition, the power converter is affected by load fluctuations not only when the load group in which a short-circuit accident occurs is disconnected due to an overcurrent trip of the semiconductor circuit breaker, but also when the semiconductor circuit breaker turns off due to normal switching operations. As a result, output voltage fluctuations occur, and as in the case of the overcurrent trip described above, there is a possibility that other load groups will undergo an overcurrent trip due to the inrush current.

FIG. 5 shows still another embodiment of the present invention which also takes into account malfunctions associated with the opening and closing operations of such ordinary semiconductor circuit breakers. In the same figure, 18, 28, 38
61 is a circuit breaker control circuit that controls turning on and off of each semiconductor circuit breaker, and 61 is a logical OR with the overcurrent detection signal of each overcurrent detection circuit and the off command of each circuit breaker. The OR circuit 62 is an overcurrent detection blocking circuit that, like 42 in FIG. It is. That is, the overcurrent detection blocking circuit 62 blocks the detection of each overcurrent detection circuit for a predetermined period of time even during normal off-operation other than the overcurrent trip of each semiconductor circuit breaker. Similar effects can be obtained by providing a detection level shift circuit in place of the overcurrent detection blocking circuit 62 and shifting the overcurrent detection level for a predetermined period of time as in the embodiment shown in FIG.

Although the above description describes one power converter and a plurality of load groups, the same effect can of course be obtained in a parallel system of a plurality of power converters and a power supply system using a plurality of load groups.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of a power supply system using a conventional power conversion device, and Figure 2 is a block diagram showing an example of a power supply system using a conventional power conversion device.
An operation waveform diagram for explaining the operation of each part when a short-circuit accident occurs in one of the load groups in the system shown in the figure, and FIG. 3 is a block diagram showing an example of the power supply system using the power converter according to the present invention. Figure, 4th
5 and 5 are block diagrams showing other different embodiments of the present invention. 1...Static inverter device, 11, 21, 3
1... Semiconductor circuit breaker, 12, 22, 32...
CT, 13, 23, 33...Load group, 14, 2
4, 34...Shiya breaker control circuit, 15, 25, 3
5... Overcurrent detection circuit, 16, 26, 36... Overcurrent detection circuit, 17, 27, 37... Overcurrent detection circuit, 18, 28, 38... Shade breaker control circuit,
41, 51, 61...OR circuit, 42, 62...
Overcurrent detection prevention circuit, 52...detection level shift circuit.

Claims (1)

[Scope of Claims] 1. In a power supply system consisting of a plurality of load groups connected via wire disconnectors each having a function of detecting overcurrent and quickly disconnecting the output of a power conversion device, the load When a short circuit occurs in one of the load groups, overcurrent is immediately detected and the load group in which the short circuit occurred is tripped and disconnected. A power supply system using a power conversion device characterized by blocking current detection. 2. A patent claim characterized in that when one of the load groups is disconnected by turning off a breaker, the breaker is turned off and, at the same time, overcurrent detection of other load groups is blocked for a predetermined period of time. A power supply system using the power conversion device according to item 1. 3. In a power supply system consisting of a plurality of load groups connected via shield disconnectors each having a function of detecting overcurrent and quickly disconnecting the output of a power conversion device, when one of the load groups is short-circuited. When an accident occurs, it immediately detects overcurrent and trips the circuit breakers of the load group where the short circuit occurred to disconnect it, and at the same time shifts the overcurrent detection level of other healthy load groups for a predetermined period of time. A power supply system using a power conversion device characterized by: 4. A patent characterized in that when one of the load groups is disconnected by turning off a breaker, the overcurrent detection level of the other load groups is shifted for a predetermined time at the same time as the breaker is turned off. A power supply system using the power conversion device according to claim 3.