Sliding Mode Controller with Integral Action for DC-Link Voltage Control of Grid-Integrated Domestic Photovoltaic Systems

Abstract

The grid integration of photovoltaic systems is preferred over the islanded mode of operation as the former does not require additional storage element, hence less maintenance and no chemical pollution. To regulate power exchange between the grid and the photovoltaic system, a robust DC-link voltage controller capable of withstanding the intermittent nature of solar energy and sudden variations in load is inevitable. A proportional–integral controller is used for DC-link voltage control, exhibiting oscillations during steady state and overshoot during transients. However, the conventional sliding mode controller reduces the overshoot at the expense of increased steady-state error. This paper proposes a robust sliding mode controller for DC-link voltage control to reduce steady-state error by incorporating integral action to the conventional sliding mode controller. The harmful effect of chattering phenomenon is minimised by limiting the error in the control variable using a signum function. The added features of the work include an incremental conductance method for obtaining maximum power from the photovoltaic system, instantaneous pq theory-based self-tuning filter for the extraction of fundamental component and inverter switching pulse generation using hysteresis current control technique. The grid-integrated photovoltaic system along with all features is modelled and simulated in MATLAB/Simulink platform. The results of numerical simulations carried out for various system conditions illustrate that the proposed controller provides superior performance when compared to proportional integral controller and conventional sliding mode controller in terms of harmonic compensation, power flow balance and speed of response at all system conditions.