Modified symmetrical sinusoidal integrator and instantaneous reactive power theory-based control of shunt active filter

Abstract

Instantaneous reactive power theory (IRPT) based control of shunt active filter (SAF) is designed to work with balanced load currents and balanced as well as undistorted supply voltages. This can be overcome by individually pre-processing the supply voltages and load currents through the modified symmetrical sinusoidal integrator (MSSI) for the extraction of the respective positive sequence fundamental components, which can be further processed by the IRPT for the reference current generation. MSSI can reject harmonics and dc offset and extract the fundamental component. For proper functioning of MSSI, it is important that the coefficients of its transfer function are properly selected. This paper presents IRPT based control of SAF with pre-processing of supply voltages and load currents by MSSI. In this work, the coefficients for the MSSI are determined by comparing its characteristic equation with that of the standard third order system. The coefficients are selected such that the real poles of MSSI are closer to imaginary axis as compared to the complex conjugate poles. This results in system operating as a first order system with reduced settling time and peak overshoot, which is evident from the steady state and dynamic performance of the MSSI with selected coefficients. SAF operation with this MSSI for pre-processing the input signals for the IRPT based control, results in improved dynamic and good steady state response of SAF even under non-ideal grid conditions.