Grid voltage modulated direct power control for grid connected voltage source inverters

We propose a grid voltage modulated (GVM) direct power control (DPC) strategy for a grid-connected voltage source inverter (VSI) to control the instantaneous active and reactive powers. The GVM-DPC presents the system in d-q frame without using a phase-lock loop. In addition, the GVM method converts the system into a linear time-invariant system. The GVM-DPC is designed to obtain two separate second-order systems for not only the convergence rate of the instantaneous active and reactive powers but also the steady-state performance. In addition, the closed-loop system is exponentially stable in the whole operating range. The proposed method is verified by using MATLAB/Simulink with PLECS blockset. The simulation results show that the proposed method has not only good tracking performances in both active and reactive powers but also a lower current total harmonic distortion than that of the sliding mode control DPC method. Finally, the proposed method is validated by using a hardware-in-the-loop system with a digital signal processor. The experimental results are similar to simulation results. Moreover, the robustness to the line impedance and the grid voltage is tested and discussed.