Pergamon 0360-5442(95)00045-3 Energy Vol 20, No. 10, pp. 1027-1036, 1995 Copynght © 1995 Elsevier Sctence Ltd Pnnted m Great Britain All nghts reserved 0360-5442/95 $9 50 + 0 00 GENERIC ALGORITHM TO SELECT BUILDING-LIGHTING TECHNOLOGIES FOR MINIMIZING TOTAL HARMONIC DISTORTION M. A. CHOUDHRY and S. RAHMANI" Center for Energy and the Global Environment, Bradley Department of Electrical Engmeering, Vtrgima Polytechmc Institute and State Umversity, Blacksburg, VA 24061, U S.A (Received 28 December 1994) Abstract--The proliferation of nonlinear loads has raised new concerns about the power quahty in commercml buildings. Higher cost of repair, and the reduction in average life of equipment, both on the supply and demand sides, as a result of poor power quality cannot be overlooked or ignored. As lightmg loads are the largest fraction of the load in most commercial buildmgs, a small increase in their harmonic distorUon levels may jeopardize the other loads in the building or loads connected to the same utility bus. In this paper, we present a generic algorithm to select energy-efficient hghting technologies that will minimize harmonic distortion levels m a building. Results from the algorithm are validated on a building-load model to test its accuracy. 1 INTRODUCTION Recent developments m power electronic teechnology have changed the requirements of electricity customers. A significant number of loads draw nonlinear current from the electric utility source and inject harmonics at the point of common connection (PCC). Emanuel ~ has reported forecasts of nonlin- ear loads on some typical feeders in the northeastern U.S.A. By the year 2000, these feeders will carry 60-73% nonlinear loads as they serve commercial buildings. The forecast shows that the ratio of nonlin- ear to total load is consistently increasing. There are a number of factors that contribute to the increase in nonlinear loads. The explosion of information technology and proliferation of personal computers and their peripherals have contributed most to the harmonic distortion problem. In many countries, legislation to promote energy conservation and electric utility energy-saving programs are also contribu- ting to the harmonic distortion level in the distribution network. Energy consumption in office equipment was the fastest growing end-use for electricity in the commercial sector during the last decade. 2 This means that more harmonics at the utility bus and failure of equipment in the distribution system will become a norm of life if the issue of harmonic distortion is not addressed in a proper manner. It is necessary to understand the phenomena of harmonic suummation, interaction, and cancellation in the presence of multiple harmonic sources before trying to correct the problem. Lehtonen 3 has summarized some of the previous work on harmonic summation and has proposed a general solution to this problem using a probabilistic approach. However, such an approach does not provide much help in selecting lighting technologies that keep the harmonic level low in buildings. As an alternative, we have investigated the problem at the individual harmonic frequency level. We suggest a generic algorithm to select lighting technologies for specific building environments. Results obtained from the algorithm are compared with actual measurements. Variability between these results is explained on the basis of random behavior of phase angles of individual harmonic frequencies because loads controlled by power electronic circuits draw nonsinusoidal currents from the source and inject multiple harmonic frequencies into the system. The individual harmonic currents generated by each of the harmonic sources can be viewed as phasors with random amplitudes and phase angles. The total harmonic current injection at the point of common connection is the sum of these random phasors in each harmonic order. The randomness of these phasors results in a large amount of vectoral cancellation. The proposed algorithm provides a method for evaluation of the impacts of various lighting technologies at individual harmonic levels. tTo whom all correspondence should be addressed. 1027