Investigations on STATCOM using current error space phasor based modified hysteresis current controller

Abstract

A STATCOM that employs a nearly constant switching frequency hysteresis current controlled VSI is presented in this paper. Hysteresis controller enhances the dynamic performance of STATCOM. The switching frequency variations associated with the conventional hysteresis current controller is reduced by using a variable hysteresis boundary. Variable hysteresis boundary is predetermined by the current error, based on the sampled magnitudes of the reference voltage vector. This makes the switching frequency nearly constant and switching vector selection optimal. As a result, a voltage FFT profile similar to that of a space vector modulated STATCOM is obtained. Choosing a space vector based reference voltage vector keeps the current error within the pre-calculated boundaries and improves the current tracking capability of STATCOM. The systematic method of selecting a switching sequence avoids random switching. Effectiveness of the proposed method for the control of grid-connected STATCOM is experimentally verified and compared with a voltage-controlled space vector modulated voltage source inverter based STAT-COM. The hardware implementation of the controller for grid-connected STATCOM is carried out in OPAL-RT real-time simulator platform and experimentally validated for a three-phase balanced load of 5 kVA.