Robust model-free DC-bus voltage regulation for stand-alone solar-powered electric vehicle charging stations with experimental laboratory verification

This paper proposed an ultra-local model free control (ULM) strategy for robust DC bus voltage regulation in a stand-alone solar powered electric vehicle charging station. In this study, the system under consideration consists of a photovoltaic (PV) generator interfaced via a maximum power point tracking (MPPT) controlled boost converter, a battery energy storage system (BESS) connected through a bidirectional buck-boost converter, and a shared DC-bus supplying a DC load that emulates Electric Vehicle (EV) charging behavior without grid support. In general, the proposed control strategy is intended for DC bus voltage regulation and real-time power balancing in highly uncertain operating conditions without considering the accurate parameters of the converter and battery, which might have occurred due to temperature changes and component aging. Unlike conventional PI/PID control schemes, the proposed ULM does not require an accurate model of the system since it can estimate the system’s behavior with the help of its ultra-local representation. This approach is experimentally verified on the laboratory scale prototype implemented on the dSPACE 1104 real-time platform. The test results under rapid irradiance changes, large load steps, and inductance mismatches verify the effectiveness of the proposed ULM in achieving better performance compared to the well-tuned PID controller in terms of reduced voltage deviation by 35%, approximately 4 to 5 times faster recovery response, zero overshoot, and reduced control efforts. This verifies the effectiveness of ULM as a viable approach for reliable off grid solar powered EV charging infrastructure and the proposed DC-microgrid (DCMG).