Slow-Scale Nonlinear Control of a H-Bridge Photovoltaic Inverter

Abstract

Aiming at the slow-scale nonlinear behaviors of a dual-loop control H-bridge photovoltaic inverter, a slow-scale nonlinear control method based on time-delay feedback control is proposed. Firstly, a feedback signal is formed by the difference between the current error signal and its own delay, and the feedback signal is made to pass through a proportion link so as to obtain a time-delay control signal. Then, based on the necessary conditions of the stability criterion, the value range of the delay feedback proportional coefficient is quickly determined, and the best delay time is chosen by determining the variation curve of the largest Lyapunov exponent. Finally, based on the double-loop PI regulation, the time-delay control signal is added to the original control signal to form the final control signal applied to the inverter. The results obtained show that the slow-scale nonlinear behaviors in the system can be absolutely eliminated, and the stable operation domain of the inverter can be remarkably expanded. When the sun irradiance and temperature change, the proposed control method still has a good control effect and shows strong robustness. In addition, the complex calculation in determining the control coefficient and delay time can be avoided by the method.