Voltage-Regulated Solar PV String Inverter with LC Filter for Islanded Operation

Efficient conversion of photovoltaic (PV) energy is essential for the smooth operation of inverters and reliable power supply to electrical appliances. This paper highlights the LC filter design and implementation of PV inverter operation in islanded mode. A PI controller along with a two-level PWM controller is used to generate the gate pulses for the inverter. The LC filter minimises voltage ripples and harmonics, ensuring smooth power delivery. The analysis shows the system's competence in maintaining a stable constant output voltage under varying weather conditions. On top of that, during sudden load changes, whether withdrawals or reconnections, the system sustains consistent voltage levels, proving its efficacy and reliability. The analysis shows that for a 100 kW PV system, the inverter voltage THD remains below 1.3%, and the peak voltage stays constant at 500 V, even when the phase-to-phase voltage is set to 360 V and load or irradiance conditions change. These findings highlight the suitability of this system for standalone renewable energy applications, particularly in DC-based load systems.