SU750697A1 - Method of cutting-off inverter power-diodes - Google Patents

Description

The invention relates to electrical engineering and can be used in static conversion devices with a DC link that converts electrical energy of direct or alternating current. Known inverters, network-driven, in which the locking valves produces with the EMF load, for example, iQ synchronous motor. In these inverters, the switching of the gates is performed in an incremental manner by periodically shorting the adjacent phases of the load along the circuit of the main gates of the inverter. In this case, the phase of the current at the output of the inverter must be advanced. The pulsations of the load current are limited by a choke in the DC link. The disadvantages of this method of locking the valves include significant commutation distortion of the output voltage curve, which is the greater, the greater the load current and its switching reactance, the relatively low use of converter valves and synchronous control, low speed. There is also a known method of locking the inverter valves without the use of F2J capacitors, which consists in supplying pulses to the main valves of each half-wave of each phase, and then firing pulses of this half-wave of this phase are supplied. This method is the closest in technical essence to this method. The disadvantages of this method are the distortion of network voltage and load and the ability to control the frequency only discretely. In addition, the method is applicable only under load with lagging ccsV. The circuit of the invention is to reduce the load voltage distortion. This is achieved by the fact that, in a known method, first, pulsing pulses are applied to the switching valves of each half-wave of each phase, and then unlocking pulses are applied to the main valves.

and this popuvnopnye this phase, moreover, the valve gates are produced using DC load.

FIG. 1 shows one of the possible inverter circuits implementing this method of locking the valves; in fig. 2 potential diagrams and voltage current curves.

1-6 - main valves of the inverter, 7-bridge rectifier, 8 - supply transformer, 9, 10 - group switching valves, 11-16 - individual switching valves, 17 19 potent diagrams of the inverter external leads built around the midpoint of the secondary winding transformer, 20-22 are load curves, 23 is the EMF curve of phase A, 24 and 25 are linear voltage curves.

The current and emf curves are constructed to supply the motor with a synchronous reactance equal to 0.7, active resistance equal to zero, and a current advance factor equal to

Let the stationary periodic process be established in the system and at the moment conduct the valves 1, 2, 3. At this time, the instantaneous value of the EMF of the motor exceeds the voltage at the input of the inverter and the phase current decreases. By the time t, the current I d becomes equal to zero and the valve 1 begins to restore its valve properties due to the reverse voltage and -5 Un where ooo} - the voltage of the direct current link. If by this moment I apply a trigger pulse to the valves 13 and 14, then they will open, since with respect to them the same voltage will be direct. The current in phase A will change direction and will flow through the circuit of the switching valves to the phase B of the A-14-13-B load. The current of the ventip 3 decreases by the magnitude of the current i. At time 1 ", an unpulsing pulse is applied to the valve 10 and the valve 13 is closed by a reverse voltage equal to UdJ / 2-Tokg. Now flows through the chain of 14-10. At time t. an unlocking impulse is applied to the valve 4. In hospitals 14 and 10, they are locked by the same voltage UcS / 2. From now on

the inverter conducts valves 2, 3, 4. By the time t, when the current of the phase Ci drops to zero, unlocking pulses are applied to the valves 14 and 15 and they conduct current from the moment when the current of the previous half-wave of the current drops to zero. Current i changes direction and flow along the C-14-15-A circuit. Valve 4 is discharged by the amount of current. Further operation of the converter valves is similar.

When the valves 1-6, 9, 10 are locked, the voltage of the inverter changes abruptly, as shown in FIG. 2. The shape of the voltage curve is practically independent of the magnitude of the load current (it depends only to the extent that the voltage drop in the supply network changes). Switching valves relieve the main valves 1-6 by current. The stable voltage waveform provides higher engine utilization. In contrast to the known device, the frequency of the inverter can be adjusted arbitrarily smoothly and exceed the frequency of the mains supply.

invention formula

A method of locking the inverter valves with two-step commutation, which consists in triggering opening impulses on the main valves of each half-wave of each phase, and then triggering pulses of this half-wave of this phase, characterized in that, in order to reduce the load voltage distortion, the first unlocking pulses to the switching valves of each half-wave of each phase, and then serving unlocking pulses to the main valves of this half-wave of this phase, and the valves are closed with the help of EMF load.

Sources of information taken into account in the examination

1.Schilling V. Tpristorna Technique M., Energie, 1971, p. 84-97.

2. USSR author's certificate number 345571, cl. H O2 M 5/42, 1968.

uei

Claims (1)

Claim A method of locking the valves of an inverter with a two-stage switching, which consists in sending gate pulses to the main valves of each half-wave of each phase, and then applying gate pulses of this half-wave of this phase, characterized in that, with a circuit to reduce distortion of the load voltage, first the pulses unlocking them to the switching valves of each half-wave of each phase, and then the unlocking pulses are supplied to the main valves of this half-wave of this phase, and the valves are locked using the EMF load .