Evaluation and reduction of harmonic distortion in power systems

Abstract

Harmonic distortion in electric power systems affects the whole system environment, often at large distances from the original sources. Like may other forms of pollution, harmonics are a form of electrical pollution in the power system. Harmonic distortion in power systems is increasing with the wide use of nonlinear loads in solid state power devices. Thus it is important to analyze the various harmonic problems, to evaluate the harmonic level and to eliminate harmonics prior to their becoming a serious problem. This paper describes methods of harmonic evaluation and reduction. Establishment of frequency dependent models for various system components is briefly covered. The modeling of harmonic sources and methods of harmonic elimination are also briefly discussed. The technique of analyzing the propagation of characteristic harmonic currents in an AC system utilizes steady-state AC analysis by means of direct solution of the system impedance matrix at each harmonic frequency. Harmonic distortion in two different AC systems is studied using the developed methodology. One of the systems is a transmission system with a number of generators and loads totalling 4000 MW. The other system is a radial distribution system with shunt compensation at various load locations. Both systems are modeled to evaluate harmonic penetration at different locations. The system responses to harmonic distortion due to individual components and different operating conditions are studied. The location and size of shunt capacitor banks in the system are among the important factors that affect harmonic resonances and could result in a high level of harmonics in the system. Strategies of harmonic reduction are also discussed.