SU1737673A1 - Clock generator for controlling frequency converter - Google Patents

Description

The signal at the output of such a filter is established in tens, or even hundreds of periods of the input signal. Therefore, the speed of the control systems by the mean value is mainly determined by the integration time loss in the input filter.

The closest in technical essence to the present invention is a device in which time-pulse measurement of an analog input signal takes place with the help of an integrator equipped with a reset circuit controlled by a microprocessor. The output of the microprocessor in digital form can be used for control purposes. In order to control the average value of the input signal of a variable form, an input unit containing a measuring transducer of alternating current to direct current voltage is applied in the known device.

Rectifier-filter converters have low speed, which makes them unsuitable for use in control systems based on the average value of a periodic input signal for a number of technological processes that use thyristor frequency converters. In particular, such are the processes using induction heating ( isothermal stamping, optical glass melting, semiconductor epitaxi, single crystal growth). A convenient parameter for controlling the process using induction heating is the average value of the voltage across the load of the thyristor converter.

The use in control systems of the mean value of rectifier-filter type meters makes them ineffective due to low speed.

The purpose of the invention is to increase the speed of control.

The goal is achieved by the fact that a clock pulse generator for controlling a frequency converter, comprising a controlled clock generator, the first control input of which is used to connect the control voltage, a switch, a converter output voltage sensor and a first integrator with a reset input, is provided with a second integrator a reset input, two keys, two differentiating circuits with an IT trigger, and the output voltage of the output voltage sensor through the first and second keys is connected respectively to moves of the first and second integrators, the outputs of which are connected to the first and second inputs of the switch, the output of which is connected to the second control input of the clock generator, the output of which is used as the driver output and connected to the input of the T-flip-flop, the direct and inverse outputs of which are connected to the control inputs of the switch and through the corresponding differentiating

circuit - to the reset input of the corresponding integrator. In addition, the converter output voltage sensor is in the form of a rectifier.

FIG. 1 shows a functional diagram of the device; in fig. 2 - timing diagram of the analog part of the device. FIG. 1 shows the input unit (rectifier) 1, keys 2 and 3, integrators 4 and 5

with reset inputs; differentiating circuits 6 and 7; trigger 8, multiplexer 9, controlled 10 clock pulse generator, frequency converter 11.

The device works as follows.

The input voltage 1) n, proportional to the voltage on the load of the converter, is applied to the input rectifier 1 and through the keys 2 and 3, working in antiphase under the control of the trigger 8, is fed to the inputs of the integrators 4 and 5.

Let the output of the trigger 8 is a high level voltage (interval

 in fig. 2, Us diagram, therefore, key 2 is on, and key 3 is off. The voltage from the output of the rectifier 1 - Ui is applied to the input of the integrator 4. The storage capacitor of the integrator 4 in front of

this is discharged - when the key of integrator 4 is closed at the time of the leading edge of the signal Q, the time of closure of the key of integrator 4 is no more than the switching time of trigger 8;

chain 6.

The capacitor of the integrator 4 in the interval tcrti is charged from the applied voltage Ui. The output voltage of the integrator at the site to the end of the interval is equal to

50

U4 jЈUidt. (one)

At the time ti, the trigger 8 is switched by the pulse of the generator 10. At the same time, at the output Q of the trigger 8, the voltage becomes low, and at the output Q - high. At the time q, the switching time of the trigger 8 closes the key of the integrator 5, preparing the latter for operation (the previously accumulated charge on the capacitor of the integrator 5 is reset). Key 3 in the interval ti-t2 is closed and

the output voltage of the rectifier Ui is applied to the input of the integrator 5, which in the interval ti-t2 works similarly to the integrator 4. At the output of the integrator 4, the voltage stored in the interval is equal to (1). For the interval, the voltage at the output of the integrator 5 becomes equal to

. (2)

At time t2, the trigger 8 is again switched by the pulse of the generator 11. In this case, the voltage on the integrator 4 is reset, and the integrator 5 retains the accumulated value during the interval t2-t3.

The multiplexer 9 is controlled by the output voltage of the trigger 8 in such a way that the output voltage of that integrator 4 or 5, which stores the accumulated voltage at this interval, is connected to the input of the generator 10. Thus, we can write that the voltage applied to the input of the generator 10 in any time interval,

U9 JJ Uidt-, (3)

where i is the current time interval equal to the period of the output pulses of the generator 10, i.e. converter control period T.

As the control frequency of converter 11 increases, the voltage amplitude across the load UH increases. Therefore, the voltage Ug increases, as shown in FIG. 1, starting with the interval.

The frequency of the output pulses of the oscillator 10 depends on the magnitude of the reference signal Uzad and the magnitude of the signal of the meter Ug (3). The generator 10 maintains the frequency of the control pulses of the converter 11 such that Ug and 3ad. If this equality is violated due to a change in voltage or voltage on the load due to a change in its parameters, generator 10 corrects the frequency of the control pulses of the converter 11 until the equal Ug and voltage occurs.

By definition, the average value of a periodic signal is the signal integral over a period divided by the period T value. Therefore

.

If, for control purposes, it is the average value that is needed, then in generator 10 it is necessary to divide the input value Ug (3) by the period of output pulses T of generator 10. This can be done if generator 10 is performed on the basis of a digital timer, signal Ug (3) convert to digital form using the ADC, and divide by the value of the period and timer programming using a microprocessor. In that

In the case of ADC, a timer and a microprocessor are part of the generator 10.

In most cases, for the purpose of regulation, it is sufficient only the magnitude of the integral of the monitored signal

0 period. In this case, the generator 10 can be made analog.

The invention is made on the layout of the process unit using a thyristor converter power

5 100 kW, frequency 10 kHz, operating at a resonant load. Voltage on the load circuit is used as the control parameter. The system is based on a single-chip microcomputer K 1816 BE 48. The K 580 VI 53 chip is used as a timer, K 111EPV1A as the ADC, and K590 KN2 multiplexer.

Compared to the control system,

5 having an integrating filter with a rectifier as a mean value meter, the proposed device shows significantly smaller overshoot values and a settling time.

0 voltage on the load. There is no oscillatory process of setting the controlled parameter, which is observed in the system with the rectifier-filter meter with large changes in the given value of the control parameter.

Claims (2)

Claims 1. Clock driver for 1 frequency converter control, 0 containing a controlled clock generator, the first control input of which is used to connect a control voltage, a switch, a converter output voltage sensor and 5, the first integrator with a reset input, characterized in that, in order to increase the control speed, it is provided with a second integrator with a reset input, two keys, two differentiators 0 chains and T-trigger, the output voltage sensor output through the first and second keys are connected respectively to the inputs of the first and second integrators, the outputs of which are connected to the first and second inputs of the switch, the output of which is connected to the second control input of the controlled generator clock pulses, the output of which is used as a driver output and connected to the input of a T-flip-flop, the direct and inverse outputs of which are connected to the control inputs of the switch and through the corresponding differentiating center Chain to the reset input of the corresponding integrator. 2. A shaper according to claim 1, wherein the sensor is in such a way that the sensor of the output voltage of the converter is made in the form of a rectifier.