RU38253U1 - SYNCHRONOUS PULSE EXCITATION DEVICE - Google Patents

Description

Synchronous machine pulse excitation device

The utility model relates to electrical engineering and can be used in excitation systems of synchronous machines. Analogs of the device include;

1. A device for controlling a thyristor rectifier. USSR copyright certificate No. 551796 class. H02P 13/16. publ. in BI, 1977, No. 11.

2. Kuznetsov I.E. Kulakov Yu.P., Relin A.B. Analysis of switching processes and increasing the power factor of the thyristor excitation device of a POWERFUL synchronous motor. - Electrotechn. industry. Ser. Converting Technology, 1975, no. 7 (66). from. 18-22.

3.Abramovich B.N. et al. Electromechanical complexes with a synchronous motor and thyristor excitation St. Petersburg: Science. 1995.S. 149. 150.209.

4.Suvorov P.A. Static exciter with a high power factor. - Industrial Energy, 1980, No. 12, p. 23-25.

In analogue 1, a thyristor exciter of synchronous motors containing a three-phase AC voltage source, a thyristor rectifier, the input circuit of which is connected to the specified three-phase voltage source, and the output DC circuit to the excitation winding of a synchronous machine, is shown. To increase the power factor of the pathogen with deep voltage regulation, an additional controllable valve connected between the zero output is introduced into the analog circuit

H02P9 / 14

a three-phase voltage source (secondary winding of the transformer) and one of the poles of the thyristor rectifier. A disadvantage of device 1J is an increase in circuit complexity due to the introduction of an additional valve and a control circuit for said valve.

In analogue 2, a thyristor exciter is shown, in which, in order to increase the power factor, the field winding is shunted by valves that increase the power factor of the converter by about 30%. The disadvantage of device 2 is the increased complexity of the circuit due to the introduction of additional valves.

Analogue 3 shows a thyristor exciter of a synchronous motor containing a three-phase AC voltage source, a thyristor rectifier, the input circuit of which is connected to the specified three-phase voltage source, and the output DC circuit to the excitation winding containing the damping circuit of the rotor field. Field blanking is performed by transferring the thyristor rectifier into inverter mode. The disadvantage of this device is a violation of the invert mode and an increase in the damping time of the rotor field when the three-phase voltage source is disconnected from the AC mains. because in this case, the current generated by the inductive load, the excitation winding, closes through the last thyristor turned on, and the current decay time increases tens of times compared with the invert mode.

The closest in composition and energy indicators to the described device is a thyristor pathogen, given in

In the prototype 4 shows a diagram of a static pathogen with high

the value of cos f is 0.958. To obtain such energy indicators, an additional three-phase boost winding is introduced into the power transformer, the zero points of which are closed using three thyristors equipped with a control circuit, and three additional diodes are introduced into the power rectifier. Thus, the rectifier has two bridges connected in series: controlled and uncontrolled, and the middle group of valves is an integral part of both bridges. The disadvantage of prototype 4 is the complexity of the rectifier and transformer and the need to introduce control circuits for additional thyristors. IN

the exciter according to scheme 4, as in analogues 1 - 3. The inversion mode stops when the supply voltage is turned off, and the decay time of the excitation current increases many times (more than 10 times).

The purpose of the utility model is to simplify the hardware base of the device, increase the power factor and obtain the mode of quick damping of the field when the power supply is turned off, as well as the effective reduction of rotor oscillations at a sharply variable load.

The goal is achieved in that the converter is made of a diode rectifier: a power transistor switch, for example, a transistor IGBT module, connected in series with the field winding and the output circuits of the specified rectifier; a diode connected in series with the resistor and connected in parallel to the field winding by the cathode to the positive terminal of the field coil; a thyristor connected in parallel to the specified diode; software control systems are a key element.

The figure shows a block diagram of the device.

The device contains an AC voltage source 1; rectifier 2; power transistor switch 3, made, for example, in the form of a transistor IGBT module; a program control system consisting of an automatic excitation controller (ARV) 7, a relay switching unit for a pulse frequency 8, a pulse generator with an adjustable duty cycle 5, driver 4; the excitation current sensor 6, made, for example, based on the Hall sensor.

At the input of blocks 7, 8 are connected the output circuit of the sensor 6, the measuring circuit of the current 11 and voltage 10 of the stator of the synchronous machine 13; the rotor field damping unit 9, comprising a resistor 17 and a diode 16 and a thyristor 14 connected in series with a resistor 17, a block 9 is connected in parallel with the field winding 12. A power transistor switch 3 and a current sensor 6 are connected in series with the field winding 12 and are connected to the + and - outputs rectifier 2.

The device operates as follows;

The power transistor switch 3 operates in a pulsed mode and supplies a series of pulses of a fixed frequency, for example, f 6 kHz, with a constant amplitude equal to the voltage of the diode bridge 2 and with varying duty cycle determined by the automatic excitation regulator 7 and

driver 4. Since the pulse repetition period T is small in comparison with the electromagnetic constant of the excitation winding, the average voltage value for the period practically does not change. It fluctuates around the average value, which depends on the duty cycle of the control pulses Ои ТЛи, or, what is the same, on the duty cycle of pulses Кз 1 / Ои 1иЯ. A change in the latter within the limits of О Кз 1 depending on the magnitude of the control signal allows one to obtain a corresponding change in the excitation current from zero to the maximum value.

High efficiency of a pulsed excitation device is achieved due to the fact that the power transistor switch 3, for example, a transistor module, in a pulsed mode of operation has only two states - saturation and cutoff. In the first of them, the current of the transistor module is maximum, and the voltage drop across it is small (1 - 1.5 V), in the second - vice versa. As a result, the heat loss in the transistor module is relatively small. They are determined by the residual voltage drop in saturated mode and the leakage current of the closed transistor module. The relay switching unit of the frequency 8 comes into operation with significant load drops, providing quasi-optimal damping of the rotor vibrations due to the relay change in the frequency of the control pulses of the pulse generator 5.

The device provides a device power factor value close to unity, because when the power transistor switch 3 is operating in pulse-width regulation mode with a high frequency many times higher than the frequency of the supply network, there is no phase shift between the current and voltage at any rectified current values.

The rotor field is suppressed when the power transistor switch 3 is turned off, which occurs either by an external signal or when the power of the source 1 is turned off. At the same time, terminal 15 is closed in the thyristor 14 control circuit. When terminal 15 is closed, the thyristor 14 is turned on, the field circuit 12 having a large inductance, closes through the thyristor 14 to the resistor 17. When the resistance value of the resistor 17 is equal to 10 times the resistance of the field winding 12, the process of damping the rotor field occurs during a time equal to or close to the inverter blanking time.

New in the utility model is the use of a power transistor switch 3 operating as an AC / DC converter operating in pulse-width regulation mode with a frequency that is significantly (more than 100 times) higher than the frequency of the supply network and connected in series with the diode rectifier output with field winding. The excitation current is controlled by an adjustable duty cycle pulse generator, to the input of which the output circuits of the automatic excitation controller and the pulse switching relay block are connected, which provides damping of the rotor oscillations.

Compared with thyristor converters, the device has a high (close to unity) power factor, field blanking is performed at high speed when the supply voltage is turned off.

Claims (1)

A pulsed excitation device of a synchronous machine containing an AC voltage source, an adjustable AC to DC converter, the output of which is connected to the poles of the field winding, a starting resistor connected through a diode-thyristor switch parallel to the field winding, an automatic field controller, characterized in that the AC converter DC voltage is made in the form of a diode rectifier and a power transistor switch, for example transistor IGBT-m a module connected in series with the field winding and DC output circuits of the rectifier specified, the diode-thyristor switch is made in the form of a diode connected in series with a starting resistor and connected in parallel to the field winding by the cathode to the positive terminal of the field winding, and a thyristor connected in opposite to the specified diode , an adjustable duty cycle pulse generator, wherein the power transistor switch control circuits are connected to the output circuits of said pulse generator c, and the output circuit of the automatic excitation controller and the relay switching unit are connected to the control input of the adjustable duty cycle pulse generator.