Hybrid VAR compensator operating study under conditions of a three-wire network

Abstract

The approaches to the control of the hybrid VAR compensator are considered. A hybrid VAR compensator is a passive and active compensator connected in series. The passive part is represented by a thyristor-switched capacitor bank. The power part of the active part is implemented on the basis of an autonomous voltage inverter, connected through a voltage transformer in series with a passive part. Most of the reactive power is compensated by means of the compensator’s passive part. The hybrid compensator combines the advantages of passive (low price, reliability) and active compensators (possibility of smooth control of reactive power, operation in networks with non-sinusoidal currents). This configuration allows to significantly reduce the rated power of the active part, while maintaining the possibility of smooth control of the reactive power. Mathematical modeling of the hybrid system operation in a three-wire network is carried out. Two operating modes are checked: the reactive power compensation mode and the mode of providing the sinusoidal waveform of the network current. The first mode provides fundamental reactive power compensation only (the compensator current is sinusoidal, therefore, provides «insulation» of capacitor bank from higher harmonics) and the second mode provides limitedly non-active power compensation, including distortion power (overvoltages and exceeding the permissible currents of the capacitor bank are not allowed). When choosing a control strategy, the network configuration and the real requirements of power consumers for power quality indicators are taken into account. The efficiency of the proposed model under conditions of non-sinusoidal load current and unbalance of the main’s voltage is provided