Research on adaptive control of grid-connected PV inverters in weak grid

In recent years, with the promotion and application of photovoltaic (PV) technology, research on grid-connected inverters incorporating with weak grid has become a hot field. In general, the large grid impedance will reduce the gain and bandwidth of the control system and slow down the dynamic response, or even lead to resonance and instability of the whole control system. Especially, when the grid impedance changes, the traditional PI controller with fixed parameters will lead to poor control performance. In this article, the control strategy of grid-connected PV inverter in weak grid was researched, so as to improve the adaptation of the whole control system to grid impedance. Firstly, a two harmonic injection method was used to detect the grid impedance, and then an adaptive control algorithm based on pole assignment principle was studied to adjust the current controller parameters. So the robustness of grid-connected PV inverter system is improved. At last, the simulation and experimental results verified its validity.