Robust Dichotomy Solution Based Model Predictive Control with Voltage Observer for Grid-Connected Inverters

A robust dichotomy solution-based model predictive control (DS-MPC) with a voltage observer for a three-phase grid-connected inverter (GCI) is proposed in this paper. The optimal voltage vector can be dynamically selected in the whole space vector circle plane in a very short time due to the voltage vector dichotomy solution algorithm. Therefore, the proposed DS-MPC control has not only fast dynamic performance but also good steady state performance. Meanwhile, the performance of model predictive control (MPC) usually depends on the accuracy of plant model. In weak grid case, the variation of equivalent grid impedance could impact on the performance. To improve the current control robustness, DS-MPC is combined with a grid voltage disturbance observer using the extended Kalman filter (EKF) so that the disturbance of weak grid voltages is effectively suppressed. Moreover, the grid currents are well regulated even with greatly distorted and unbalanced grid voltages. The test results verify the correctness and effectiveness of the proposed DS-MPC with EKF observer under the weak grid.