Controller Design of Power Quality-Improving Appliances PNNL-SA D. J. Hammerstrom, N. Zhou, and N. Lu Pacific Northwest National Laboratory 902 Battelle Blvd., P. O. Box 999 Richland, WA USA (509)

time current Excessive PQI current correction Perfect PQI current correction Inadequate PQI current correction Non-PQI currents Let one load improve the power quality and power factor for an entire premise Power Quality-Improving Appliances

33 Premise current before PQI PQI current Sum of premise and PQI currents PQI appliances are like filters, but they can only consume energy. Where the energy can be put to good use, the PQI is, in theory, 100% efficient. V I Premise I Premise+PQI

Measure and Improve Current at Premise Service Panel

Controller Input Signals Gain Rectified ac voltage Rectified premise current Note: PQI controller design can be greatly simplified by using an inexpensive power factor control chip.

A Simple, Nearly Failsafe Power Circuit Most circuit failure modes would result in normal, rated appliance conduction.

Floating Driver Circuits Optically coupled PWM signal Adjustable positive and negative drive bias Same circuit works for both power switches Same PWM signal sent to both switches

Prototype Hardware Driver and Power Circuits Test Stand and Load

Same Premise I RMS ; PQI Load is Active Only When Needed PQI Appliance Inactive PQI Appliance Active

Effect of PQI Gain Input Too Low Active Too High

Effect of PQI Load Impedance High Z; Low PQI Load Low Z; High PQI Load

Conclusions PQI appliances are an undiscovered opportunity Simple effective circuit designs Comparable to, but less expensive than, filters Improve premise power quality and power factor while performing useful tasks like heating water Theoretically high effective efficiency