Efficient Two-Cost-Function Predictive Control for A 10-MVA Cascade H-Bridge STATCOM System

Abstract

Static synchronous compensator (STATCOM), using cascaded H bridge (CHB) converter, is an attractive configuration for FACTS system, renewable energy integration, etc., functioning to compensate reactive power and to enhance power quality. However, conventional control methods (e.g., linear control with PI controllers and pulse width modulator (Cas-PI-PWM)) require a cascaded structure to realize the necessary current and voltage control targets, resulting high tuning efforts and relatively poor control dynamics. In this work we propose a computationally efficient model predictive control (MPC) solution for a 10-MVA STATCOM system with CHB topology, which has a very simple structure, scalable cost-function, and outperformed control dynamics in comparison with the conventional Cas-PI-PWM technique. Additionally, to cope with the weighting factor design difficulty, inherently with the classical MPC technique for multiple control-objective system, we utilize a two cost-function MPC structure. With this, the complex weighting factor design process has been simplified. Finally, offline simulation results confirm that the proposed solution outperforms the well-known Cas-PI-PWM technique, in terms of current tracking and capacitor voltage balancing, at difference testing scenarios.