JPS6112478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching scheme between a forward converter and a reverse converter in a thyristor Leonard device without circulating current.

First, a configuration example of a thyristor Leonard device without circulating current to which the present invention is directed will be explained with reference to FIG.

For reversible operation of the DC motor 1, a forward converter 2 and a reverse converter 3 are connected in antiparallel to each other on the DC output side with respect to the motor armature circuit. Both converters each consist of a three-phase bridge-connected thyristor, for example, and are connected in parallel to each other on the AC input side and connected to a three-phase system power supply via a power transformer. For closed-loop control of the motor speed, a speed regulator 5 is provided, which is supplied with a speed setpoint value n ^* and is fed with a speed actual value n detected by the speed detection generator 4. be guided. In the minor loop of this speed control loop, the current regulator 6 performs current closed loop control. That is, the output signal of the speed regulator 5 is given to the current regulator 6 as the current target value I ^* , and the current regulator 6 converts the armature current actual value I detected by the current detector 7 into the current target value. The control input signal V _S for the firing angle regulator 8 is formed to match. In this case, if the current detector 7 outputs an actual current value signal corresponding to the absolute value of the armature current regardless of its polarity, the current value signal is sent from the speed regulator 5 to the current regulator 6 in response to this. The current target value should be an absolute value signal. The firing angle regulator 8 sends a firing angle control pulse to a pulse amplifier 9 or 1 according to the control input signal given from the current regulator 6.
0 to either converter 2 or 3. The converter to be operated each time is specified by the switching command signal A given to the firing angle regulator 8. The control pulses applied by the firing angle regulator 8 via the pulse amplifiers 9 or 10 to the individual thyristors in the transducer 2 or 10 correspond to the thyristors having a phase delay of 60° with respect to the original single pulse that determines the firing angle. This is a so-called double pulse type control pulse that is a combination of single pulses. With double pulsing, when a firing pulse is given to a thyristor of either phase in one bridge half of a thyristor bridge, a firing pulse is always given to the thyristor of the other phase in the other bridge half at the same time. Therefore, current can be reliably passed through the converter. On the other hand, with a single pulse, the converter can only be operated when the DC side current is in a continuous state, and the converter cannot be started. For this reason, double pulses are used as control pulses for the converter.

The switching command signal given to the firing angle regulator 8 is determined by determining the desired torque polarity each time based on the polarity of the output signal (output signal before absolute value conversion) B of the speed regulator 5. It is formed. However, in order to prevent circulating currents from occurring between the two converters even during the switching process of the converters 2, 3, it is necessary to , without immediately inverting the switching command signal A, an additional input signal is first given to the current regulator 6, so that the control input signal from the current regulator 6 to the ignition angle regulator 8 is V _S is shifted to a level that brings the firing angle to the maximum lag angle in the inverse conversion operating region, and then the control pulse of one transducer, which has been operating until now, is blocked when it is determined that the current has gone to zero. and then only after a predetermined time the generation of control pulses of the other converter starts.

In the conventional converter switching control method as described above,
In order to provide the current regulator with an additional input signal to shift the firing angle to the maximum retard angle as soon as the desired torque polarity reversal is detected, it is switched back on again immediately after the desired torque polarity reversal is detected. There is a drawback that the control system may be disturbed by a short-term torque disturbance such as a return. Torque disturbances such as those described above, which have periods shorter than the time required for normal switching between transducers, do not require a firing angle shift for switching without a response; If this is done, not only will it take time for the current to once become zero and then return to a normal value, but also disturbances may occur in the control system due to current fluctuations.

An object of the present invention is to provide a thyristor Leonard converter switching system without circulating current that can prevent disturbances in the control system caused by torque disturbances as described above.

According to the invention, this object is achieved by switching the control pulse of the converter from a double pulse during normal operation to a single pulse upon detection of a desired torque polarity reversal;
Only upon detection of zero current, an additional input signal is applied to the current regulator that shifts the firing angle, and then after a predetermined time the control pulses of one transducer, hitherto active, are blocked and then the control pulses of the other transducer are switched on. This is accomplished by starting to apply control pulses.

According to such a configuration, when a short-term torque disturbance occurs as described above, the control pulse only temporarily switches from a double pulse to a single pulse, and virtually no switching operation is performed, so that the current It is possible to prevent disturbances in the control system without causing any oscillations. Furthermore, when a switching operation is required, the double pulse is switched to a single pulse and the system waits for zero current detection, which provides the advantage that zero current detection can be performed accurately without delay. This is because, in the case of double pulses, the converter can operate with intermittent current, whereas in the case of single pulses, once the current reaches zero, it cannot flow again. This is because a single pulse allows current zero to be detected more quickly and reliably.

Hereinafter, the method of the present invention will be explained while comparing it with the conventional method with reference to the operational waveform diagrams of FIGS. 2 and 3.

FIG. 2 shows a time chart for a normal converter switching operation, where the solid line waveform is for the present invention and the broken line waveform is for the conventional case. Since n ^* < n with the positive converter 2 in operation, the desired torque polarity (output signal B of the speed regulator ₅
Assume that the polarity of (polarity) has switched from positive to negative. In the present invention, a command signal D is given to the ignition angle regulator 8 to immediately switch the double pulse to a single pulse due to the polarity reversal at time _t0 (conventionally, the double pulse was left unchanged as shown by the broken line). ).
By forming the current target value I ^* according to the speed control deviation (n ^* -n) by the speed regulator 5 and by controlling the current actual value I according to the current target value I ^* by the current regulator 6, the current actual value I is decreasing. At the instant t ₁ when the actual current value I reaches the zero detection level of the current detector, which is not shown in FIG. A signal C is given. As a result, the control input signal V _s given from the current regulator 6 to the firing angle regulator 8 indicates that the firing angle α is the maximum delay angle αmax
(=maximum advance angle βmin) (Conventionally, as shown by the broken line, signal C was already applied at time _t0 to perform such a level shift.) Then, at time _{t2 ,} after the time T1 for current zero confirmation has elapsed, a command signal _A1 is given which turns off the control pulse for the positive converter 2. At time _t3 , after a predetermined time _T2 taken for safety has elapsed, a command signal _A2 is given which turns on the control pulse for the negative converter 3. At this point in time _t3 , the signal C for shifting the firing angle and the single-pulse switching command signal D are simultaneously released. As a result, the negative side converter 3 starts operating and begins to flow current, and the zero current detection signal disappears at time _t4 , thereby completing the initial conversion process. Regarding the operation of the above-mentioned normal switching process, there is no essential difference between the present invention and the conventional one. However, the present invention is advantageous in that it is easy to detect zero current because it waits for zero current detection with a single pulse.

However, as shown in FIG. 3, there is an essential difference between the present invention and the conventional method in the operation when a torque disturbance occurs in which the desired torque polarity (the polarity of the speed regulator output signal) has a shorter period than the switching operation time. occurs.
In other words, when the desired torque polarity reverses and immediately returns to its original polarity, according to the control method of the present invention, as shown by the solid line, the double pulse is simply replaced by a single pulse for that period. The control system will overcome the torque disturbance on its own without any influence. On the other hand, in the case of the conventional control method, as soon as the desired torque polarity is reversed, the firing angle shift command signal C is issued and the control input signal V _S is given from the current regulator 6 to the firing angle regulator 8. is shifted to the equivalent of α = α _nax , resulting in unnecessary current narrowing,
The actual current value I fluctuates greatly as shown by the broken line, and in some cases, an unacceptable disturbance phenomenon may even occur in the control system.

As for the device for implementing the control method according to the present invention, in the firing angle regulator, it is only necessary to add a switching logic that can directly output a single pulse to a logic circuit that forms a double pulse from a single pulse, and other devices. This requires only a slight change in the sequence of the switching command circuit, and there is almost no increase in equipment costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of a thyristor Leonardo without circulating current, and FIGS. 2 and 3 are time charts for explaining the present invention. 1... DC motor, 2... Positive side converter, 3...
Negative side converter, 5... Speed regulator, 6... Current regulator, 8... Firing angle regulator.

Claims (1)

[Claims] 1. For the circulating current-free control of a thyristor Leonard device consisting of two converters each consisting of a polyphase bridge-connected thyristor and connected in anti-parallel to each other on the DC output side to the DC motor armature circuit, the motor A control pulse is applied only to the converter that corresponds to the desired torque polarity at each time determined based on the output signal polarity of the speed regulator that performs closed-loop control. After confirming the no-current state of one converter, the control pulse of that one converter is turned off and then the control pulse of the other converter is turned on. A converter switching scheme in which an additional input signal is applied to a current regulator forming a control loop during the converter switching process in order to shift the firing angle of the converter control pulse to a predetermined maximum delay angle. A circulating current characterized in that the converter control pulse is switched from a normal single pulse to a double pulse immediately upon a desired torque polarity reversal, and then the additional input signal is applied to the current regulator only when zero current is detected. No thyristor Leonard device converter switching method.