Frequency spectrum shaping using finite control set MPC with LQ lookahead

Abstract

Finite control set model predictive control (FCS-MPC) has been shown to be a very effective approach to control of power electronics and ac drives. It can address even demanding tasks such as frequency shaping of the current spectrum. However, its accuracy is limited by one-step ahead optimization of the cost function, neglecting long-term consequences of the control action. LQ lookahead is a technique of approximate dynamic programming that designs an approximation of the optimal cost-to-go function that is added as an additive term to the FCS-MPC cost function. We study the effect of this technique on the problem of frequency spectrum shaping of a three-phase voltage source inverter with RL load. We demonstrate in simulation and laboratory experiment that the proposed LQ lookahead approach offer a better compromise between spectrum shaping and current tracking error.