Proportional Integral Control Realized in Stationary and Synchronous Reference Frames for a Single-Phase UPS Inverter System: A Comparative Study

Abstract

ABSTRACTVoltage regulation of the single-phase UPS inverter has design challenges in terms of dynamic performances and control complexity. Widely used conventional integral controllers, such as proportional integral and proportional resonant in stationary frame (SF) of reference have limitations of either steady state error or implementation difficulties. Although a mature technique in three-phase applications, the synchronous reference frame (SRF) control scheme has not been exhaustively investigated for single-phase UPS inverters due to complex multiple transformations. This paper suggests a voltage control scheme which can be alternatively used in both stationary and synchronous reference frames. Three integral controllers namely, SF-proportional integral (SF-PI), SF-proportional resonant (SF-PR) and SRF-proportional integral (SRF-PI) are comparatively evaluated for steady state and transient performances. A systematic procedure for the design of control parameters with stability analysis in the frequency domain for the closed loop control system is also presented. Respective controllers are simulated in discrete time frame using MATLAB/Simulink and experimentally implemented using the TMS320F2812 Digital Signal Processor based laboratory prototype.