Fuzzy grey predictor compensated time-varying variable structure controller for solar inverters

Abstract

In this paper, a fuzzy grey predictor (GP) compensated time-varying variable structure controller (TVVSC) is developed and applied to solar inverters. TVVSC can shorten the reaching phase and ensure the sliding mode occurrence from an arbitrary initial state. However, while loading is a severe nonlinear condition, the TVVSC may suffer from chattering and steady-state error problems, thus deteriorating solar inverter performance. A GP is thus devoted to alleviate the chattering when the system uncertainty bounds are overestimated, and to reduce the steady-state error when the system uncertainty bounds are underestimated. However, the GP with a fixed forecasting value causes long rise time or large overshoot of the system response. Thus, fuzzy logic (FL) is applied to obtain flexible forecasting values to improve the system performance. With the proposed controller, the robustness of the solar inverter system can be enhanced, and a high-quality solar inverter sinusoidal output voltage with low voltage harmonics and fast dynamic response can be obtained, even under nonlinear loading. The theoretical analysis, design procedure, computer simulations, and digital signal processing (DSP)-based experimental implementation for solar inverters are presented to verify the efficacy of the proposed controller.