SU547027A1 - Device to control single-phase stand-alone parallel inverter - Google Patents

Description

one

The invention relates to the field of converter technology and can be used in the conversion of direct current voltage into alternating current.

Single-phase parallel autonomous current inverters on thyristors are known, which contain a power circuit and a control system made in the form of a master oscillator 1. The disadvantage of these inverters is the relative complexity of their control system, which reduces the reliability of the inverters as a whole.

Self-excited inverters are also known that do not require a master oscillator, which simplifies their control circuit 2. However, peak-transformers included in an oscillating circuit deteriorate the conditions for the formation of control pulses on the thyristors.

The prototype of the invention is a device for controlling a single-phase autonomous parallel inverter on thyristors with self-excitation, containing a saturation choke with a working winding in a control circuit connected in series with resistors between the control electrodes of the thyristors 3. Such a device is not reliable enough in operation. This is due to the fact that 10 times the throttle saturation through the control of the closed thyristor electrode flows a current of small magnitude. When heated by this current, the closed thyristor may turn on prematurely, which leads to a breakdown of the inversion. In order to increase the reliability of the inverter in the proposed device, the working winding of saturation droplets is provided with taps connected via two additional resistors to the thyristor cathodes.

Such an embodiment of the device provides a negative voltage on the control electrode from the moment the thyristor is locked to the next saturation of the throttle core. Negative voltage on the control

the closed thyristor electrode prevents its accidental premature opening, which leads to an increase in the reliability of the inverter. FIG. I depicts the scheme described

devices for controlling an inverter with combined anodes; in fig. 2 is the same for controlling an inverter with combined anodes and with a magnetic choke; in fig. 3 - diagrams of the device operation.

The inverter with a control device (see Fig. 1) contains thyristors 1 and 2, saturation throttle 3 with taps 4 and 5, resistors 6 and 7, limiting thyristor control current, additional resistors 8 and 9

and the commuting cond. 10.

The control device (see Fig. 2) contains two saturation throttles with a common winding 11 nodomagnetisation, which makes it possible to regulate the frequency of the inverter.

FIG. 3 shows the graphs of the f / io pattern on the capacitor 10, the current / s of the primary winding of the throttles 3, the voltages f / 4.5 on the taps 4 and 5, the voltage of the t / y gain control by thyristors 1 and 2, and the magnetization curve of the throttles 3.

The control device operates as follows.

Suppose that the thyristor 1 is open, the thyristor 2 is closed and the voltage on the capacitor 10 has the polarity shown in FIG. 1. At the moment when the operating point of the ferromagnetic material is at point a (see Fig. 3), hock magnetization, equal to jo, flows through the resistor 9, and a voltage is applied to the primary winding of the drossel 3 with the polarity shown in FIG. 1. The melody by tapping 5 and the ends of the winding transforms the voltage f / 4,5. The voltage at the point of connection of the resistor 7 with the winding relative to the cathode of the thyristor 2 is equal to the difference in voltage between the resistor 9 and the voltage (/ 4.5. From the voltage change curve it is seen that at the moment when the working point of the ferromagnetic material is at point a the control voltage of the thyristor 2 is negative. At the time of saturation of the core of the throttle, the voltage / 7y changes polarity and increases dramatically due to the decrease in voltage drop

Drossel 3 and the disappearance of the voltage / 74.5. The current of the control electrode of the thyristor 2 is limited by the resistor 7. In the next half period, the processes are repeated for the thyristor 1.

Desoldering eliminates the accidental premature turning on of the thyristors until the core of the throttle is saturated, which leads to an increase in the reliability of the inverter.

Claims (3)

1.B. E. Kalashnikov, S. O. Krivitsky, I. I. Epshtein, “Control Systems for Autonomous Inverters,” ed. “Energie, 1974, p. 38. 2.I. V. Nezhdanov, “Inverters on thyristors, ed. “Energie, 1965, pp. 53, 54. 3. USSR author's certificate No. 213162, 1kl. 21 d2 12/03, 1962 (prototype).