Current Limiting Strategy of Single-Phase Standalone Inverter for Direct-On-Line Starting of Induction Motor

In this paper, a simple current limiting controller is introduced for single-phase standalone inverter. When an induction motor load is connected to the standalone inverter, several times the rated current of the motor can flow through the winding, and the semiconductor switches of the inverter may be destroyed. To prevent this, the current limiting technique is necessary in the control system. In the proposed method, a magnitude-based proportional integral (PI) controller was used to regulate the output voltage of the inverter. Also, the instantaneous limit was utilized to limit the current within a threshold. Additionally, to ensure sufficient limiting performance during direct-on-line (DOL) starting of an induction motor with rapid voltage changes, a capacitor voltage feedforward path was added to the current controller. As the magnitude estimation algorithm for magnitude-domain control, an all-pass filter based orthogonal signal generator was employed. The validity of the proposed method was verified with DOL starting experiments of a 2.2kW capacitor start and run induction motor.