Robust Constant Switching Frequency Predictive Current Control with a Dichotomy Solution for Three-Phase Grid-Connected Inverters

Abstract

A robust constant switching frequency predictive current control (CSF-PCC) with a dichotomy solution for a three-phase grid-connected inverter (GCI) is proposed in this paper. Based on a voltage vector dichotomy solution approach, the optimal voltage vector is dynamically selected in the whole space vector circle plane in a very short time. Therefore, the proposed current control has not only fast dynamic performance but also good steady state performance. Meanwhile, the performance of model predictive control (MPC) 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, CSF-PCC is combined with a proportional voltage feedforward control 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 current control.