Implementation of sector change detection schemes for current error space phasor hysteresis controller based Shunt Active Power Filters

Abstract

Current harmonics injected in the utility by nonlinear loads tend to deteriorate the power quality at the mains. These harmonics are compensated by Shunt Active Power Filters (SAPF). Current error space phasor based hysteresis controller for SAPF is presented in this paper, which allows precise compensation of harmonic currents produced by non-linear loads. Because of proper sector change detection logics, the proposed controller is self-adaptive in nature and does not require any particular calculation of voltage vector at the Point of Common Coupling (PCC). The controller operation is studied for two different self-adaptive logics for detection of sector changes — one with outer hysteresis band, and the other without using outer hysteresis band. The proposed controller based SAPF using outer hysteresis band compensates harmonics in supply current effectively. Distortion in supply current is further reduced by avoiding the outer hysteresis band and generating the SAPF compensating currents by synchronizing the sector change with supply frequency. The controller keeps the current error space phasor within the hexagonal boundary (fixed band) by applying SAPF voltage vectors which are adjacent to the reference voltage vector (voltage vector at the PCC). This leads to the switching of optimal voltage vector unlike the random selection of the voltage vectors in conventional hysteresis controller based schemes. Performance of the proposed controller based SAPF is analyzed for dc-link voltage regulation scheme of reference compensating current generation. The performance of controller is tested for balanced as well as unbalanced mains voltage and is found satisfactory. Experimental validations of the proposed controller based SAPF for sector change detection with and without using outer hysteresis band are presented. Detailed theoretical analysis, modelling, simulation and experimental studies are carried out and the claimed performance of the proposed controller is evident from the results presented in the paper.