Unified Power Quality Conditioner for improving power quality using MVR with Kalman filters

This paper presents a new control design for the Unified Power Quality Conditioner (UPQC) for harmonics compensation in a power distribution system. The topology of the UPQC is based on two 3-phase voltage source inverters (VSIs) which share two de link capacitors with their midpoint grounded. A novel Multi-Variable Regulator-based (MVR) UPQC with state observers is introduced. The control strategy employs a Kalman filter to estimate the fundamental component as well as the harmonic components of the source voltage and the load current of a power distribution system. It then uses an observerbased MVR to coordinate the switching sequences for the VSIs of the UPQC. Simulation results with a 3-phase nonlinear load are presented to confirm the validity of the proposed controller. The proposed controller, though computational intensive, is fast, accurate and cost effective for practical implementation and usage.