Digital implementation of an advanced static compensator for voltage profile improvement, power-factor correction and balancing of unbalanced reactive loads

Abstract

In this paper, a three-phase advanced static compensator (STATCOM) is proposed to compensate reactive power either for regulating ac supply voltage at a constant value or for unity power-factor and balancing of unbalanced reactive loads. An insulated gate bipolar transistor (IGBT) based current controlled pulse width modulated (CC-PWM) and voltage source inverter (VSI) is employed as the STATCOM. A TMS320C31 DSP is used to implement the control algorithm of the STATCOM. To regulate the instantaneous ac supply voltage across the load through shunt reactive power compensation, a sliding mode controller (SMC) over the amplitude of supply voltage is used to obtain a reactive component of the reference supply current in quadrature with the supply voltage. Another SMC over the voltage of a self-supporting dc bus of the STATCOM is used to compute an active component of reference supply current in-phase with the supply voltage. An indirect PWM current control over the reference (computed) and sensed supply current is employed to generate the gating pulses of the IGBTs of the STATCOM. Test results are presented and discussed in detail to demonstrate the reactive power compensation for terminal voltage regulation and power-factor correction along with load balancing capabilities of the proposed advanced STATCOM.