Fault Mechanism Analysis And Ride-Through Strategy of Adjustable Speed Drive to Voltage Sag

Voltage sag and voltage interruption are common power quality disturbances in modern industry, which affects the performance of adjustable speed drives (ASDs). This paper analyzes the waveforms of the DC voltage and output current of ASD, motor torque and speed during voltage sag. It is concluded that the DC side voltage fluctuation is the key factor that causes the ASD to stop. In addition, a low-voltage ride-through strategy based on flywheel energy storage system (FESS) is proposed, which is suitable for large-capacity ASD. The strategy can effectively reduce the impact of voltage sag on ASD by ensuring that the DC side voltage of ASD is constant. Compared with the current common voltage sag mitigation equipment, FESS has the advantages of long service life, high efficiency, less maintenance, good stability and fast response speed. And the simulation method is used to verify the effectiveness of the strategy.