Open-loop-based Island-mode Voltage Control Method for Single-phase Grid-tied Inverter with Minimized LC Filter

This paper proposes an island-mode voltage control method using an open-loop control that applies a high-gain disturbance observer (DOB) for a single-phase inverter with a low-capacitance output filter. The output voltage is distorted with low capacitance obtained from the conventional method that consists of a PID regulator for an automatic voltage regulator and a PI regulator for an automatic current regulator. To compensate for the output voltage distortion, the high-gain DOB for the output voltage is applied for open-loop-based voltage control. DOB is implemented into a field-programmable gate array with high-speed sampling. In the LC filter of a 1-kW prototype, the impedance of the inductor is minimized to 1.0% of the normalized inverter impedance, whereas the admittance of the capacitor is reduced to 0.25% of the normalized inverter admittance. Using the proposed method, the inverter output voltage total harmonic distortion is reduced by 82.4% even with the diode rectifier load compared to conventional voltage control, whereas the constant output voltage is achieved regardless of load conditions.