Modulated Model Predictive Control With Two State Variables for Active Power Decoupling Under Unbalanced and Distorted Grid Conditions

Abstract

This paper proposes an active power decoupling (APD) control method based on modulated model predictive control (MMPC) with two state variables to reduce dc-link voltage ripple under unbalanced and distorted three-phase grid conditions. The dc-link power ripple is analyzed by considering harmonic components of the grid voltage and input current, and the APD capacitor voltage reference is derived from the ripple analysis. The proposed MMPC uses the APD capacitor voltage and inductor current as state variables for simultaneous voltage and current control. Based on the predicted states, the APD duty is directly calculated without an outer voltage control loop or an additional weighting factor. The proposed method is verified using a 3 kW prototype. The measured peak-to-peak dc-link voltage ripples are 18.1 V without APD, 8.2 V with APD under PI/PR control, and 6.5 V with APD under the proposed MMPC. The second order components are 4.65 V, 2.25 V, and 1.90 V, while the sixth order components are 1.48 V, 0.65 V, and 0.52 V. Compared with operation without APD, the proposed MMPC reduces the second and sixth components by 59.14% and 64.86%, respectively. For a step change in the APD capacitor voltage reference, the response times are $400~\mu $ s with MMPC and 1.2 ms with PI/PR control.