SU838960A1 - Reversible compensated dc converter with separate control - Google Patents

Description

one

The invention relates to power converter technology and can be used in electrolysis, in electric drives or other branches of the national economy, where reversible conversion of alternating current into constant current is required.

A non-compensated converter with separate control of forward and reverse valve bridges is known. This converter, which contains a transformer, as well as direct and reverse sets of valves, provides any current pattern with reversible power supply by the consumer with rectified current 1,

The disadvantage of it is the low coefficient of madness). In addition, it is desirable to increase the stability of the inverter operation in the invert mode, since an inversion failure can lead to a severe accident.

A non-reversible co-sensing converter is known about a single voltage frequency across capacitors, containing a three-phase power transformer, each phase of the secondary winding of which is connected via a capacitor to the corresponding phase

three phase rectifier bridge having a high power factor of 2.

The closest to the proposed is a reversible compensated DC converter with separate control, consisting of a p-phase supply transformer with primary and secondary windings,

0 direct and reverse n-phase valve bridges connected in parallel to the output, each phase of the direct valve bridge being connected to the secondary winding of the transformer via

5 capacitor.

The purpose of the invention is to increase the stability of the inverter in the inverter mode with the optimum degree of reactive power compensation in the rectifying mode of operation.

The goal is achieved by the fact that each phase of the return valve bridge is connected to the corresponding supply phase of the bridge

5 direct current through the additionally introduced capacitor.

The drawing shows a three-phase converter.

The converter contains three-phase transformer 1, three-phase

a rectifying bridge 2 of one current direction, a three-phase rectifying bridge 3 of a different direction of current, a main three-phase capacitor battery 4 and an additional capacitor battery 5.

The operation of the converter is carried out as follows.

During the period of time when the load is powered by the rectified current in one direction, bridge 2 and a capacitor battery 4 work in the rectifying or inverter mode. Control impulses on bridge 3 do not apply the valves of this bridge do not conduct current Therefore voltage on all phases of the capacitor battery . 5 is equal to zero. The voltage on the phases of the capacitor bank 4 is different from zero, since the valves of bridge 2 conduct current. These voltages vary with a single frequency, i.e. the frequency of the voltage applied to the primary winding of the transformer 1, are included in the switching circuits of the valves of bridge 2 and carry out their artificial KoiviMyTa. To supply the load with current of another direction, the pulse-phase control system reduces the current of bridge 2 to zero. In this case, the voltages at all phases of the capacitor battery 4 also decrease to zero. Then, after the necessary pause, control pulses are applied to bridge 3, whose operation is carried out in the inverter mode (if bridge 2 was operating in an approximate mode) or rectifying mode (if bridge 2 was operating in an inverted mode). The load starts to flow around the current in another direction. Artificial commutation of the gates of bridge 3 is carried out by both capacitor banks 4 and 5, the voltage on which, in this case, changes with a single frequency. Next, the pulse-phase control system of bridge 3 reduces the current to zero, the voltage on the capacitor batteries x 4 and 5 also becomes zero, the control pulses are removed from bridge 3 and after the necessary dead time, pulses are applied to bridge 2. The pulse-phase control of bridge 2 the required current of the opposite direction is established, etc. Both bridge 2 and bridge 3 operate with artificial cocmutation valve. therefore, with a fairly high power factor.

In the well-known non-reversible compensated converter with a single voltage frequency on capacitors, choosing an appropriate capacitor capacitance value can achieve either the optimal degree of reactive power compensation or the optimum increased stability of the converter in the inverter mode with variations in the AC system voltage and load current variations.

The above two properties of the converter (optimum compensation and optimum improved stability) occur at various capacitance capacitor bank values. In the reverse transform | Töle, the bridge operating in the rectifying mode is in operation considerably longer than the bridge operating in the inverter mode. For example, in a reverse electrolysis, the operating time of the bridge performing the rectifying mode is ten times longer than the operating time of the bridge implementing the inverter mode. In this case, it is advisable to provide optimum compensation of reactive power during operation of the bridge performing the rectifying mode. The capacitance of a capacitor battery of this bridge should be chosen - out of the condition of optimal compensation of reactive power, based on the specific operating conditions of the converter. Taking into account the severity of the accident that occurs when the inverter is disrupted, as well as the very short time of the inverter mode, the capacitance of the capacitor battery of the bridge performing the inverter mode should be chosen from the optimal increased stability of its operation. In this case, due to a slight decrease in the degree of compensation of reactive power, the inverter operation is highly reliable in inverter operation.

The inclusion of capacitor banks in the proposed converter provides various values of capacitors capacitance, which carry out artificial switching of the valve in bridges of different current directions.

Claims (2)

1. Barsky V.A. Separate control of reverse thyristor converters. M., Energie, 1973, p. 10, fig. 1-1. 2. Neuman L.R. et al. Direct current power transmission as an element of energy systems. M-L., Academy of Sciences of the USSR, 1962, p. 127, fig. 28 MlP Tf i s