Harmonic interaction between nonlinear loads in electric power systems

Hamid Reza Majlesein, Louisiana Tech University


Conventional ac power systems are designed to operate with sinusoidal voltages and currents. However, nonlinear loads cause distortion in the steady state ac voltage and current waveforms. Periodic steady state distortion can be studied by examining the components of a Fourier series representation of the waveforms.

Harmonic distortion can cause problems in meter accuracy, communications, machine and transformer heating, and relay operation. Voltage and current waveform distortion in power systems is becoming more universal because of the greater usage of high efficiency solid-state devices and other nonlinear loads. Metering accuracy in the presence of harmonics is of great concern. In some cases, harmonic levels are high enough to also cause damage to utility distribution equipment.

This research investigates the interactions between different types of nonlinear loads in power distribution systems. With the present number and size of nonlinear loads connected to the electric grid and the projected future increases of such loads, now is an appropriate time to study such interactions. Extensive computer simulations are conducted, including the design and analysis of harmonic filters. The importance to utilities of developing economic incentives for customers generating harmonics is also explored.