Effect of two-level PWM sources on plant power system harmonics

Even two level PWM sources with low harmonic voltage and current distortion characteristics can affect an industrial plant´s power system in such a way that voltage sensitive electronic equipment is adversely affected. It is unwise to feed PWM sources and sensitive electronic equipment from the same substation transformer. The resulting voltage distortion is time consuming to trouble-shoot and expensive to fix. Additional filtering is needed to stop the unwanted harmonic frequencies that emanate from PWM sources from interfering with the operation of sensitive electronic equipment such as gas burner controls, robots and assembly line sensors typically used in the automotive industry. The paper describes the generation of voltage and current harmonics of two level PWM inverter sources. The level of these harmonics were measured before the application of a passive filter and serve as a guide as to the effectiveness of the passive filter in minimizing the level of voltage and current harmonics.