Proportional Resonance Control Application for Photovoltaic Grid-connected Inverters

This paper applies an adaptive method for regulating the proportional resonance (PR) controller for frequency and phase synchronization in 500 kW photovoltaic grid-connected inverter. First, this paper determines the mathematical model of the three-phase voltage source inverter (VSI) in the coordinate system, and presents an automatic way for parameter tuning in proposed PR controller framework. Second, the frequency variation is detected via minimizing the error signal using a frequency locked loop (FLL) mechanism which consists of a resonant adaptive filter and a perturbation-based extreme seeking (PES) method. Unlike the widely used proportional-integral (PI) controller and phase locked loop (PLL)-based frequency detection, the proposed adaptive PR (APR) controller shows high performance in items of steady-state error of current, frequency fluctuation tracking, phase shift error, and harmonic order compensation. At last, the simulation and experimental results demonstrate that the photovoltaic grid-connected inverter embedded with APR controller realizes the static-free tracking adjustment more quickly, and has stronger grid voltage anti-disturbance capability than the traditional PI-based voltage/current loop applications.