One-cycle Controlled Unified Power Quality Conditioner for load side voltage sag compensation

Voltage quality is an important factor of the power quality of distribution systems, while voltage sags/dips are the most common voltage quality problems. Voltage sags/dips may originate both from the source side and the load side. Without proper regulation, utility customers connected to the same bus could be disturbed. This paper studies the load side voltage sags caused by the resistive load disturbance and the current source type disturbance. The One-cycle Controlled Unified Power Quality Conditioner (OCC-UPQC) can effectively compensate both the load side and the source side voltage sags under the resistive load disturbance. When the current source type disturbance is experienced, the load side voltage shows more significant improvement than the source side. The OCC-UPQC features constant switching frequency, simple circuitry, fast transient response, high precision, and excellent stability. The compensation strategies for load side voltage sags are analyzed and verified to be effective by experiments.