JPH1169822A - Controller of thyristor rectifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably operate a thyristor rectifier, without failing in commutation even in the case the impedance of an AC power source is large. SOLUTION: This controller controls a DC voltage by converting AC into DC through a thyristor bridge 1 connected to an AC power source 2 and consisting of plural thyristors and controlling the phase of ignition of the thyristor. In this case, this possesses a zero cross means 4 which detects the zero-cross phase of an AC voltage inputted into a thyristor bridge 1 and outputs a zero- cross signal, an ignition control means 5 which generates an ignition signal, based on this zero-cross signal and gives that ignition signal to the thyristor, an AC impedance detection means 6 which detects the impedance of the AC power source, and ignition phase changing means 7 and 8 which give the ignition control means 5 a change signal, based on this power impedance, so as to change the ignition phase of the thyristor of the thyristor bridge 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thyristor which is connected to an AC power supply, converts AC into DC by a thyristor bridge composed of a plurality of thyristors, and controls a DC voltage by controlling the phase of ignition of the thyristor. Regarding the control device of the rectifier, especially when the impedance of the AC power supply is large, even-order harmonics are superimposed on the voltage waveform of the AC power supply, and there is an imbalance between the positive side and the negative side of the AC voltage waveform. However, the present invention relates to a control device for a thyristor rectifier that stably operates a thyristor rectifier without a commutation failure.

[0002]

2. Description of the Related Art Conventionally, the main circuit of various devices such as industrial machines and railway vehicles, for example, the drive circuit of a DC motor such as a thyristor leonard, converts AC into DC by using a thyristor bridge composed of a plurality of thyristors. A thyristor rectifier control device that controls the DC voltage by controlling the phase of the ignition of the thyristor is used.

In this control device for a thyristor rectifier, a zero-cross phase of an AC voltage input to a thyristor bridge is detected, and a firing signal for controlling a firing phase of the thyristor is provided based on the detected zero-cross phase. Like that.

FIG. 3 is a block diagram showing an example of such a conventional thyristor rectifier control device. In FIG.
The thyristor bridge 1 has a plurality (six in the figure) of thyristors connected in a bridge, and performs power conversion from AC to DC by phase control based on a firing signal.

The thyristor bridge 1 has a three-phase AC power supply 2 connected to its AC side, and a load 3 such as a DC motor connected to its DC side. The system of the three-phase AC power supply 2 has a power supply impedance.

On the other hand, a phase control device for controlling the firing phase of the thyristor of the thyristor bridge 1 includes a zero-cross detection circuit 4 and a firing control circuit 5.

[0007] The zero-cross detection circuit 4 is provided with an AC voltage (phase voltage or line voltage:
In the figure, a line voltage is input, a zero-cross phase of the AC voltage (a time when the line voltage becomes zero) is detected, and a zero-cross signal is output.

Further, the ignition control circuit 5 generates an ignition signal based on the zero-cross signal output from the zero-cross detection circuit 4, and supplies the ignition signal to the thyristor of the thyristor bridge 1.

That is, the firing control circuit 5 outputs a firing signal of the thyristor of the thyristor bridge 1 with a delay of a predetermined phase from the time when the zero cross is detected by the zero cross detecting circuit 4.

At this time, the control angle is given by fixing the maximum value of the control angle in advance so as to leave a constant commutation allowance angle.
Thus, the phase control device operates the thyristor bridge 1 by sequentially supplying the firing signals to the thyristors after the time corresponding to the firing angle has elapsed from the zero crossing of the AC voltage.

At this time, when the thyristor of the other phase fires, a voltage in the opposite direction is applied to the thyristor that has been fired so far, and the thyristor is extinguished. This is called commutation. The commutation margin angle indicates the minimum period of the reverse voltage necessary for commutating the thyristor.

The thyristor rectifier has a voltage fluctuation on the AC side,
The DC current or the voltage is controlled by changing the firing angle of the thyristor according to the fluctuation of the load on the DC side. This is called phase control.

[0013]

In the thyristor rectifier control device as described above, if the firing angles of the six thyristors are constant in a steady state, the harmonics flowing out of the thyristor rectifier to the AC side will be described. The waves are only odd harmonics such as the fifth and seventh harmonics.

However, during transitions such as when the AC voltage changes or the DC current changes, the firing angles of the six thyristors change sequentially. That is, the firing angles of the positive (upper) thyristor and the negative (lower) thyristor change sequentially. At this time, the thyristor rectifier outputs even-order harmonics to the AC side in addition to odd-order harmonics.

Since the AC side, that is, the power system has a certain impedance, it generates a harmonic voltage determined by the product of the outgoing harmonic current and the impedance at the frequency.

When even-order harmonics are superimposed on the three-phase AC power supply 2, a waveform as shown in FIG. This waveform is mainly when the fourth harmonic is superimposed. When such a waveform appears in the line voltage, the following problem occurs in the conventional thyristor rectifier control device shown in FIG.

That is, in the waveform as shown in FIG. 4, the positive side and the negative side of the voltage are asymmetric. This means that there is a difference between the zero cross phase detected at the rising edge of the AC voltage waveform and the zero cross phase detected at the falling edge of the waveform.

In the control device of the thyristor rectifier, if the commutation is not delayed beyond the commutation margin angle for the commutation of the thyristor, the commutation fails, that is, even if another thyristor is fired, There is a problem that the thyristor that has been fired does not extinguish.

If the commutation fails, the upper and lower thyristors are simultaneously fired, causing an overcurrent due to a short circuit between the positive side and the negative side. Furthermore, if an error occurs in the phase detected as the zero cross, that is, if commutation fails, the operation of the six thyristors of the thyristor bridge 1 becomes non-uniform. It will contain harmonics.

This harmonic voltage is further increased when the impedance of the three-phase AC power supply 2 is large. Furthermore, when trains, cranes, etc. move while being supplied with AC,
The impedance changes depending on the power supply position, and even with the same change in the DC current, the error of the zero-crossing phase changes depending on the position.

Particularly, in a place where the impedance is large,
The possibility of occurrence of commutation failure due to a sudden current change is increased. The object of the present invention is that even when the impedance of the AC power supply is large, even harmonics are superimposed on the voltage waveform of the AC power supply, and even when there is an imbalance between the positive side and the negative side of the AC voltage waveform, An object of the present invention is to provide a control device for a thyristor rectifier capable of operating a thyristor rectifier stably without a commutation failure.

[0022]

In order to achieve the above object, according to the present invention, a thyristor bridge comprising a plurality of thyristors is connected to an AC power supply to convert AC to DC and control the phase of ignition of the thyristor. In a thyristor rectifier control device that controls a DC voltage by
A zero-crossing detector for detecting a zero-crossing phase of the AC voltage input to the thyristor bridge and outputting a zero-crossing signal; and generating a firing signal based on the zero-crossing signal output from the zero-crossing detecting means. To change the ignition phase of the thyristor of the thyristor bridge based on the power supply impedance detected by the AC impedance detection means. Firing phase changing means for providing a signal to the firing control means.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an example of a control device for a thyristor rectifier according to the present embodiment. The same elements as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here.

That is, the control device of the thyristor rectifier of the present embodiment comprises, as shown in FIG. 1, an AC impedance detecting circuit 6, a margin angle changing circuit 7 and a subtraction circuit 8, which are ignition phase changing means. The configuration is added to FIG.

The AC impedance detection circuit 6 detects the impedance of the three-phase AC power supply 2. In addition, the margin angle changing circuit 7 changes the firing phase of the thyristor of the thyristor bridge 1 based on the power supply impedance detected by the AC impedance detection circuit 6, and outputs the changed commutation margin angle signal β. .

Further, the subtraction circuit 8 subtracts the commutation margin angle signal β output from the margin angle changing circuit 7 from the reference control angle command (α ^* ) 9 to fire the thyristor of the thyristor bridge 1. The angle signal α is supplied to the ignition control circuit 5.

As described above, the firing phase of the thyristor of the thyristor bridge 1 is changed according to the power supply impedance. Next, the operation of the thyristor rectifier control device according to the present embodiment configured as described above will be described.

In FIG. 1, an input AC voltage (line voltage) of the thyristor bridge 1 is input to a zero cross detection circuit 4. Next, the zero-cross phase of the input AC voltage is detected by the zero-cross detection circuit 4, and the zero-cross signal is input to the ignition control circuit 5.

Next, an ignition signal is generated by the ignition control circuit 5 based on the zero-cross signal from the zero-cross detection circuit 4, and the ignition signal is given to the thyristor of the thyristor bridge 1.

Thus, after a time corresponding to the firing angle has elapsed from the zero crossing of the AC voltage, the firing signal is sequentially applied to the thyristors of the thyristor bridge 1 to operate the thyristor converter.

On the other hand, the AC impedance detecting circuit 6 detects the impedance of the three-phase AC power supply 2. Next, the margin angle changing circuit 7 obtains a commutation margin angle signal β that changes the firing phase of the thyristor of the thyristor bridge 1 in accordance with the power supply impedance detected by the AC impedance detection circuit 6.

Then, the subtraction circuit 8 subtracts the commutation margin angle signal β obtained by the margin angle changing circuit 7 from the reference control angle command (α ^* ) 9, and outputs the firing angle signal of the thyristor of the thyristor bridge 1. is supplied to the ignition control circuit 5.

That is, the AC impedance detection circuit 6
If the power supply impedance detected in step (1) is large, the value of the commutation margin angle signal β is increased in proportion to the power supply impedance. In other words, the maximum value of the firing angle signal α of the thyristor of the thyristor bridge 1 is reduced. Is supplied to the ignition control circuit 5.

Then, the ignition control circuit 5 generates an ignition signal based on the zero-cross signal from the zero-cross detection circuit 4 and the ignition angle signal α (= α ^* −β) from the subtraction circuit 8, This firing signal is given to the thyristor of the thyristor bridge 1.

Thus, even if the impedance of the three-phase AC power supply 2 to which the thyristor converter is connected is large, the commutation margin angle β can be increased, and the AC voltage waveform is shifted to the positive side and the negative side due to harmonics and the like. Even when there is an imbalance (when an asymmetric AC voltage waveform is obtained), the reverse voltage required for commutation can be secured, and commutation failure can be prevented, and the thyristor bridge 1 can operate stably.

FIG. 2 is a conceptual diagram showing an example of an operation state of the thyristor of the thyristor bridge 1. In FIG. 2, the thyristor conducts after a lapse of the firing angle α, and the phase control is realized by changing the firing angle α by a predetermined range. The maximum value that the firing angle α can take is a value smaller than the commutation margin angle β shown in FIG. The commutation margin angle β indicates a reverse voltage necessary for commutating the thyristor.

In this case, normally, the upper limit of the firing angle α is determined on the assumption that the commutation margin angle β is constant. However, in this embodiment, when the detected impedance of the three-phase AC power supply 2 is large, The value of the commutation margin angle β is increased in proportion to the impedance.

That is, the even-order harmonic current flowing out of the thyristor rectifier increases, and the harmonic voltage determined by the impedance of the three-phase AC power supply 2 increases. As a result, the even-order harmonic component included in the AC voltage waveform causes Even if the detection error of the zero-cross phase becomes large and the commutation margin angle β cannot be secured, the maximum value of the firing angle α is reduced by detecting the impedance of the three-phase AC power supply 2. The reverse voltage required for the current can be secured, and the commutation failure can be prevented.

As described above, in the control device of the thyristor rectifier of the present embodiment, when the impedance of the three-phase AC power supply 2 is detected and the power supply impedance is large, the commutation margin angle is proportional to the power supply impedance. By increasing the value of β (decreasing the maximum value of the firing angle α), the phase of the firing of the thyristor of the thyristor bridge 1 is changed, so that the AC voltage waveform becomes an asymmetric waveform due to harmonics and the like. Even at the time, the reverse voltage necessary for commutation can be secured, and the thyristor bridge 1 can be operated stably without failure of commutation.

Further, when a train, a crane, or the like moves while being supplied with alternating current, the value of the commutation margin angle β is increased at the power supply position where the impedance is large even when the impedance differs depending on the power supply position (the ignition angle α is increased). By reducing the maximum value), the phase of the firing of the thyristor of the thyristor bridge 1 can be changed, so that the reverse voltage required for commutation can be secured, and the thyristor bridge 1 can operate stably without commutation failure. Becomes possible.

[0041]

As described above, the control device for a thyristor rectifier of the present invention is connected to an AC power supply, converts AC to DC by a thyristor bridge composed of a plurality of thyristors, and controls the phase of the thyristor firing. In the control device of the thyristor rectifier that controls the DC voltage, the zero-cross phase of the AC voltage input to the thyristor bridge is detected, and the zero-cross signal is output from the zero-cross signal. Based on the power supply impedance detected by the ignition control means for generating a firing signal based on the thyristor, the AC impedance detecting means for detecting the impedance of the AC power supply, and the AC impedance detecting means, Thyristor firing phase of thyristor bridge A change signal that changes by and a ignition phase changing means that they provide to the ignition control means is obtained by configuration.

Therefore, when the impedance of the AC power supply is detected and the power supply impedance is large, the value of the commutation margin angle is increased (the maximum value of the firing angle is reduced) according to the power supply impedance. )) Since the phase of the firing of the thyristor of the thyristor bridge is changed, the reverse voltage necessary for commutation can be secured even if the AC voltage waveform is asymmetric due to harmonics, etc. The thyristor rectifier can be operated stably.

Also, when a train, a crane, or the like moves while being supplied with alternating current, even when the impedance differs depending on the power supply position, the value of the commutation margin angle is increased at the power supply position where the impedance is large (the value of the commutation margin angle is increased (the ignition angle is increased). By reducing the maximum value), the phase of the firing of the thyristor of the thyristor bridge 1 can be changed, so that the reverse voltage required for commutation can be secured, and the thyristor rectifier can operate stably without commutation failure. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a control device of a thyristor rectifier according to the present invention.

FIG. 2 is a conceptual diagram showing an example of an operation state of a thyristor of a thyristor bridge in the thyristor rectifier control device of the embodiment.

FIG. 3 is a configuration diagram showing an example of a conventional thyristor rectifier control device.

FIG. 4 is a diagram showing an example of an AC line voltage waveform when even-order harmonics are superimposed.

[Description of Signs] 1 ... Thyristor bridge, 2 ... 3-phase AC power supply, 3 ... Load, 4 ... Zero cross detection circuit, 5 ... Ignition control circuit, 6 ... AC impedance detection circuit, 7 ... Margin angle changing circuit, 8 ... Subtraction circuit, 9: Reference control angle command (α ^* ).

Claims (1)

[Claims] 1. A control device for a thyristor rectifier connected to an AC power supply, converting AC into DC by a thyristor bridge including a plurality of thyristors, and controlling a DC voltage by controlling a phase of a firing of the thyristor, A zero-crossing detecting unit that detects a zero-crossing phase of the AC voltage input to the thyristor bridge and outputs a zero-crossing signal; and generates a firing signal based on the zero-crossing signal output from the zero-crossing detecting unit. Firing control means for giving the thyristor the following: AC impedance detecting means for detecting the impedance of the AC power supply, the phase of the firing of the thyristor of the thyristor bridge based on the power supply impedance detected by the AC impedance detecting means A change signal that changes Control device for a thyristor rectifier, wherein the ignition phase changing means that they provide the Kitenko control means, by comprising comprises a.