Kalman filter based high speed measurement and control of AC voltages for UPS applications

A scheme is proposed for high speed measurement and processing of AC voltages encountered in offline uninterruptible power supplies (UPSs) based on the design of a Kalman filter with an internal model of the sinusoidal waveform. The proposed scheme provides a common framework to monitor the UPS mains input supply, to sense its out-of-specification voltage and frequency conditions, and to measure the UPS inverter output voltage for its feedback control. Issues related to the accuracy of measurement with finite wordlength implementation are addressed. The superior performance of the scheme is demonstrated through a practical implementation of a high power quality UPS design used onboard ships to supply critical loads