JPS5943914B2 - Protection method of controlled rectifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection method in the event of commutation failure in a large-capacity controlled rectifier in which a plurality of unit control rectifiers are connected in parallel to form a main circuit. be.

FIG. 1 shows a main circuit configuration diagram of a conventionally commonly used controlled rectifier.

In the figure, 1 is an AC bus, 2 is a rectifier transformer, 3 is a unit control rectifier that rectifies the secondary voltage of the rectifier transformer, and 4 is a load. The unit control rectifier 3 has a constant firing order. The U-phase, Z-phase, V-phase, X-phase, W-phase, and Y-phase are repeatedly fired in the order of rectification. When the ignition phase shifts from the U phase to the U phase, the phenomenon in which the ignition phase changes sequentially is called commutation. Now the firing angle of unit control rectifier 3 is α,
If the commutation overlap angle is u, then 1800-α-u is called commutation margin angle γ, and when γ becomes smaller than a certain value, commutation becomes impossible due to the characteristics of the control rectifying element. This phenomenon is called commutation failure. It is known that when a commutation failure occurs, the DC output voltage drops to zero, and if no protection is provided, the commutation failure may repeat and the system may not recover permanently. FIG. 2 shows a block diagram of a conventional commutation failure protection system.

In the figure, 5 is a commutation failure detection circuit, and □ is a phase control circuit, which generates the ignition timing of U phase, Z phase, V phase, X phase, W phase, and Y phase. 8 receives the inverted signal of the output from the phase control circuit T and the output from the commutation failure detection circuit 5, and outputs the signal from the phase control circuit 1 during normal operation, and when the commutation failure occurs, the output from the phase control circuit Inhibit circuit that cuts the signal from 6
determines the currently firing phase based on the signal from the phase control circuit □, determines the phase to fire in the event of commutation failure, and waits. 9 is an OR circuit that takes the OR between the output signal of the inhibit circuit 8 and the output signal of the commutation failure timing determining circuit 6. The circuit 10 is an interface.

A conventional protection system in case of failure of commutation will be explained below with reference to FIG.

When a commutation failure signal is generated from the commutation failure detection circuit 5, the firing command from the phase control circuit 7 is cut by the inhibit circuit 8, and the signal is sent to the firing phase determination circuit 6 at the time of commutation failure. An ignition command is generated in the next phase of the more regular ignition phase. The command is OR circuit 9, interface 1
0 to the gate of the controlled rectifier. For example, if a commutation failure occurs during commutation to the U phase and the starting phase, a firing command is issued to the W phase from the firing phase determination circuit 6 at the time of commutation failure,
The W phase and the Z phase are energized and enter a bypass pair state. If the output signal from the commutation failure detection circuit 5 is 0'' when normal and 1 when commutation fails, and the period during which the signal 61'' is generated from the time of commutation failure is 180 flows, then commutation Failure signal is 00''
When it returns to normal, ignition starts again according to the ignition timing from the phase control circuit, and the original state is restored. FIG. 3 shows the phase voltage waveform of the unit control rectifier and the DC output waveform in the protection operation in the event of commutation failure described above. 6 in Figure 4
The main circuit configuration diagram of a single-control rectifier in which two unit-control rectifiers are connected in parallel and performs 12-phase rectification is shown.

Components in the figure that have the same functions as those in FIG. 1 are designated by the same reference numerals. By the way, if the above-mentioned protection method for a controlled rectifier in the event of commutation failure is used in a controlled rectifier as shown in FIG. Occur.

For example, in the conventional protection system, if the unit leg rectifier 3-1 fails in commutation, the unit control rectifier 3-1 will be in a bypass pair state), and the DC output will be zero, but the unit control rectifier 3-2 will be in the so-called bypass pair state. Since an inverter voltage (negative voltage shown by the DC output waveform in FIG. 3) is generated, almost all of the load current flows to the unit control rectifier 3-1. For this reason, the current value of the rectifier increases when commutation fails, so
Even if an attempt is made to recover after a certain period of time, commutation failure occurs again, current control becomes impossible, and the unit control rectifier 3-
A problem occurs in which the bypass pair phase 1 becomes overcurrent. In particular, when the load is a large inductance or a large sink voltage is required, unit control rectifiers are connected in parallel and connected in cascade, and the firing angle is adjusted individually to improve the power factor. The problem is significant. The object of the present invention is to provide a controlled rectifier in which a plurality of unit controlled rectifiers are connected in parallel to form 12 or more phases.
An object of the present invention is to provide a protection system for a controlled rectifier that can smoothly recover from commutation failure even when one unit controlled rectifier fails in commutation. The present invention will be explained below with reference to the drawings. FIG. 5 shows a block diagram of an embodiment of the present invention.
In the figure, blocks having the same functions as those in FIG. 2 are denoted by the same reference numerals. 11-1 and 11-2 change the firing angle α from the inverse conversion area (α is 90 to 1800) to the forward conversion area (α is 00
This is a phase control circuit with an added function to shift the phase to 90%.

5-1, 5-2, 6-1, 81-86, 91-96, 1
0-1, 10-2 are 5, 6, 8, 9 and 10 in Figure 2
Since it corresponds to the function of , the explanation will be omitted.

FIG. 6 shows a block diagram of an embodiment of the phase control circuits 11-1 and 11-2 shown in FIG. 12 is a control circuit that generates a signal Ec to control the firing angle based on the deviation between the reference value and the detected value; 13 is a firing angle control signal generation circuit when commutation of another unit leg rectifier fails; 14 is a firing advance 15 is a synchronous power supply circuit; 16 is a comparator that compares the output signal of the synchronous power supply circuit 15 with the output signal of the ignition advance angle priority circuit 14 and generates an ignition timing command at a point of agreement; 17 is a comparator 16; Logic control circuit that divides the output into ignition phases,
18 is a commutation failure signal of another unit control rectifier, and 19 is an analog switch that is closed when the signal 18 is 111.

Next, the operation of the present invention will be explained with reference to FIGS. 4, 5, and 6.

For simplicity, the main circuit configuration is the unit control rectifier 2 shown in Figure 4.
Although the description will be given in the case of parallel units, the present invention can also be applied to the case where a plurality of unit control rectifiers are connected in parallel. In FIG. 5, during normal operation, the output signal of the commutation failure detection circuit is O'', and the unit control rectifiers 3-1, 3-2 are connected to the phase control circuit 11-1,
The phase is controlled by the firing timing of 11-2.
When the unit control rectifier 3-1 in Fig. 4 fails in commutation, the output of the commutation failure detection circuit of the rectifier becomes "1", and the unit control rectifier in which commutation has failed is controlled in the same manner as in the conventional protection system. It becomes a bypass spare state. At the same time, commutation failure detection circuit 5-
The output signal of 1 is the unit 1U control rectifier 3 which is in normal operation.
-2 phase control circuit 11-2. In the phase control circuit 11-2, as shown in FIG. 6, when the commutation failure signal 18 of the other unit control rectifier reaches ``1'', the analog switch 19 closes. Therefore, the ignition advance angle priority circuit 14 cuts off the output from the control circuit 12 during normal operation, selects the ignition angle control signal at the time of commutation failure, and selects the output from the control circuit 12 when the commutation fails.
7 The ignition signal is generated. If the arc angle at the time of commutation failure is set to an appropriate value smaller than 90 degrees, the commutation failure signal 1
In response to the signal from 8, the controlled rectifier 3-2 can instantly shift from the inverse conversion region to the 1 conversion region. As described in the conventional method, if the commutation failure signal is set to the normal state after a certain set time from the time of commutation failure, and is set to "O" in the present invention, the unit leg rectifier 3-2 returns to the output of the control circuit 12. The unit Fbl leg rectifier 3- is operated at the firing angle determined by the signal Ec.
1 can recover from commutation failure. FIG. 7 shows the phase voltage waveforms and DC output waveforms of the unit control rectifiers 3-1 and 3-2 when the above-described operation is performed.

FIG. 7 will be explained below. U,,L,Wl,Xl,
Yl, Zl are the phase voltages 6U2, V of the unit control rectifier 3-1
2, W2, X2, Y2, and W2 are phase voltages of the unit control rectifier 3-2. FIG. 7 shows a unit leg rectifier 3- as an example.
1 and 3-2 are operated at around the firing angle α=1500, and a commutation failure occurs during commutation from the phase to the W1 phase in the unit control flow device 3-1. In the unit control rectifier 3-1, the ignition command is input to the U1 phase, commutation occurs from the D phase to the U1 phase, and the U1 phase and X
One phase is in the energized state, so-called bypass pair state, and the direct current output voltage is zero. The unit leg rectifier 3-2 receives a commutation failure signal from the unit control rectifier 3-1, and the firing angle is 1.
You can quickly progress from 50 to 30 losses, so V2 phase,
From the 2-phase energized state, a firing command is issued to the W2 and 2 phases, but since it has already reached 300 for the U2 phase, a firing command to the U2 phase is subsequently generated, and the firing command is issued to the Y2 and U2 phases. When the power is turned on, a positive output voltage as shown in FIG. 7 is generated.

In the main circuit configuration diagram in FIG. 4, the DC output voltage of the unit control rectifier 3-1 is zero, and the DC output voltage of the unit control rectifier 3-2 is positive, so the load current is
, through the load 4 and unit controlled rectifier 3-2.
, to flow the current from 3-1 to 3-1, the unit is u
The heavy current of the control rectifier 3-1 decreases rapidly. As mentioned above, commutation failure is caused by some kind of malfunction that causes the commutation margin angle γ21 to decrease.
This occurs when 800-α-u becomes smaller than a certain value. Since the commutation overlapping angle u becomes smaller as the current flowing through the control rectifier decreases, reducing the current of the unit control rectifier 3-1 allows smooth recovery from commutation failure. Depending on the value of the voltage-time product of the output voltage value from the unit control rectifier 3-2, the unit control rectifier 3-1 may be turned off, but in this case as well, it is possible to recover from commutation failure. . As is clear from the above explanation, in addition to the conventional protection system in the event of commutation failure, simple electronics such as a firing angle setting circuit in the event of commutation failure of the unit rectifier, an analog switch, and a firing advance angle priority circuit are used. If you add a circuit and receive commutation failure signals from other unit control rectifiers, you can smoothly recover from commutation failure even in controlled rectifiers that connect multiple unit control rectifiers in parallel to form 12 or more phases. You can continue driving.

[Brief explanation of drawings]

Figure 1 is the main circuit configuration diagram of the three-phase bridge control rectifier;
The figure is a block diagram of a conventionally used control rectifier method in the event of commutation failure, and Figure 3 is a diagram of the phase voltage and DC output voltage waveforms of a unit control rectifier when the conventional protection method is used.
Fig. 4 is a main circuit configuration diagram of a controlled rectifier in which two unit control rectifiers are connected in parallel, Fig. 5 is a block diagram showing an embodiment of the present invention, and Fig. 6 is a diagram of a phase control circuit used in the present invention. FIG. 7 is a block diagram showing one embodiment, and is a waveform diagram of phase voltage and DC output voltage of a unit control rectifier for explaining the present invention. 1... AC bus, 2, 2-1, 2-2...
... Rectifier transformer, 3, 3-1, 3-2...
Unit control rectifier, 4... Load, 5, 5-1, 5
-2... Commutation failure detection circuit. 6,6-1,6-
2...Signing phase determination circuit at the time of commutation failure, 7...
...Phase control circuit, 8,8,,~86...Inhibit circuit, 9,91-96...OR circuit,
10,]0-1...Interface 11-1,
11-2...Phase leg circuit for the present invention, 1
2... Firing angle control circuit, 13... Other unit control rectifier commutation failure time firing angle control signal generation circuit, 14
...Ignition advance angle priority circuit, 16...Comparator, 17...Logic control circuit, 18
...Other unit control rectification failure signal, 19...-
・Analog switch.

Claims (1)

[Claims] 1. In a controlled rectifier in which multiple unit controlled rectifiers are connected in parallel to form 12 or more phases, when a particular unit controlled rectifier fails in commutation, the unit controlled rectifier is connected to the bypass pair, and at the same time the other unit controlled rectifiers are A protection method for a controlled rectifier, characterized in that a unit controlled rectifier in which commutation has failed is removed from a bypass pair after the firing angle of a healthy unit controlled rectifier is shifted from an inverse conversion operation area to a forward conversion operation area.