A simple and low cost control strategy for multilevel shunt active filters

Use of nonlinear loads, such as thyristor controlled inductors for FACTs devices, converters for HVDC transmission line and large adjustable speed motor drives, is expected to grow rapidly. All of these loads inject harmonic currents and reactive power into the power system. This paper presents a new control scheme for a 3 phase multi level parallel active filter. The presented control system is able to compensating current harmonics, reactive power and current unbalance of nonlinear loads. The conventional controllers based on pq theory need more calculations, since they need the use of Clark transformation (abc to alphabeta transformation). The proposed control system is very simple and therefore practical implementation of active filters is available. The presented simulation results carried out by Matlab/Simulink program show the validity of control strategy.