Quasi‐Z based adaptive sliding mode control for three‐phase photovoltaic grid‐connected system

Abstract

Abstract Considering the non‐linear characteristics of both the input and output of photovoltaic (PV) modules and quasi‐Z‐source inverters, as well as the unpredictable natural factors such as large disturbances caused by changes in illumination and temperature, an average state model for the PV quasi‐Z‐source inverter is established. This paper uses the output current of photovoltaic module, DC‐link capacitor voltage and its integral as state variables, then an adaptive reaching law with second‐order sliding mode characteristics is designed by combining with power reaching law and variable speed reaching law. By using the sliding mode controller based on the adaptive reaching law to control the stability of the DC‐link voltage of the quasi‐Z‐source inverter and the small capacitor voltage ripple, the photovoltaic system can operate stably at the maximum power point when the temperature and illumination conditions change abruptly, and the grid‐connected effect is improved. Through SIMULINK and RT‐LAB real‐time simulation, the effectiveness of the proposed adaptive sliding mode control strategy is verified when the environment changes, which effectively improves the dynamic response speed and grid‐connected effect of the system, and ensures the global robustness of the grid‐connected system.

Keywords

• adaptive sliding mode control law
• quasi‐Z‐source inverter
• three‐phase photovoltaic grid‐connected