A Cascade-Free Model Predictive Control Scheme for Back-to-Back Converter-Fed PMSM Drive System

In this article, a cascade-free model predictive control (MPC) scheme without the outer dc-link voltage control loop is proposed for the back-to-back converter-fed permanent magnet synchronous machine drive system. Specifically, the voltage regulation term is integrated together with the power regulation term into a newly constructed cost function so that the control of dc-link voltage as well as power can be realized by a single cost function. To predict accurately and to reduce the sensitivity to variable parameters, the expressions of dc-link voltage and power are dynamically corrected, thus enhancing the robustness. In addition to presenting no tracking deviation in steady state, the dc-link voltage also presents smaller deviation from reference and faster recovery time in dynamics. It is beneficial to enhancing the reliability of system since the voltage surge on power switches and diodes has been reduced. Besides, controllable power flow, sinusoidal phase current, and well-regulated electromagnetic torque can be achieved in the system as well. A series of experiments are carried out to test the feasibility of the proposed scheme. Performance comparisons with the classical proportional integration controller-based MPC and the modified cascade-free quasi-centralized MPC validate the improvements of the proposed control scheme.