Investigations on Current Error Space Phasor Based Self Adaptive Hysteresis Controller Employed for Shunt Active Power Filter with Different Techniques of Reference Compensating Current Generation

Abstract

Current harmonics, which are injected in the utility by nonlinear loads, cause major problems that tend to deteriorate the power quality at the mains. To reduce such harmonics, Shunt Active Power Filters (SAPF) are commonly employed. This paper presents a current error space phasor based hysteresis controller for SAPF, which allows precise compensation of harmonic currents produced by nonlinear loads. The proposed controller is self-adaptive in nature and does not require any particular calculation of Point of Common Coupling (PCC) voltage vector (E) because of proper sector change detection logics used. Detailed Modelling and performance analysis of the proposed controller for SAPF with different compensating current generation methods, along with simulation results, is presented in the paper. The controller operation is studied for two different self-adaptive logics for detection of sector changes. 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 point of common coupling i.e. E). This leads to the switching of optimal voltage vector unlike the random selection of the voltage vectors in conventional hysteresis controller based schemes. Region detection logic enables switching of SAPF voltage vector which keeps the current error well within the prescribed hexagonal boundary. The versatile nature of the controller is proved by analyzing its performance for three different reference compensating current generation techniques. The performance of controller for SAPF is tested for balanced as well as unbalanced mains voltage and is found to be satisfactory. Effect of dc-link voltage variations on the performance of the controller is also analyzed. Under steady-state and transient conditions controller performance is found fast and precise. Hence the proposed current controller gives generalized solution for any method of reference compensating current generation. The SAPF based on the proposed controller provides adequate compensation for mitigation of harmonics. Detailed theoretical analysis, modelling and simulation studies are presented in the paper and the claimed performance of the proposed controller is evident from the simulation results provided in the paper.