Sliding Mode Controller and Simplified Space Vector Modulator for three phase Shunt Active Power Filter

A Sliding mode approach is developed to control a three phase three wire voltage source inverter operating as a shunt active power filter. The novelty of the proposed approach is that the sliding mode switching functions are chosen in such a way that the multivariable coupled system is controlled as a whole. Hence, no need to divide the system model developed in the synchronous 'dq' reference frame into two separate loops. Furthermore, the proposed control strategy allows a better stability and robustness over a wide range of operation. When sine PWM is used for generation of pulses for the switches, a variable switching nature is exhibited. The pulses for the active filter are fed by a Space Vector Modulation in order to have a constant switching of converter switches. But, the conventional space vector modulation, if implemented practically, needs a complicated algorithm which uses the trigonometric functions such as arctan, sine and cosine functions which in turn needs look up tables to store the pre-calculated trigonometric values. In this paper, a very simplified algorithm is proposed for generating Space vector modulated pulse for all six switches without the use of look up tables and only by sensing the voltages and currents of the voltage source inverter acting as shunt active filter. The simulation using PSIM software verifies the results very well.