Controller design of power quality-improving appliances

This paper presents an innovative solution to power quality problems using power quality-improving (PQI) appliances. PQI appliances conduct currents that supplement and correct the sum of the other load currents within a premise. From the utility side, the premise housing a PQI appliance thus becomes an improved, if not ideal, utility customer. The PQI appliance improves both harmonic power quality and power factor while performing its normal function, such as heating water. In this paper, the water heater PQI appliance is used as an example to demonstrate the control circuit design and function. Both computer simulation results and laboratory experiment results are presented to demonstrate the effectiveness of the approach. The estimated costs of the PQI controller and of harmonic compensating filters are compared to show that the PQI appliance may be an economic way to provide power quality improvement at the building level.