Hybrid Passive Filter Design for Distribution Systems with Adjustable Speed Drives

Drive systems inject significant low order harmonics currents into distribution system and deteriorate the quality of electric power. This paper models variable frequency and PWM adjustable speed drives as harmonic current sources and performs power flow analysis before filtering to identify highly distorted buses and the spectrum of harmonic frequencies with unacceptable THD levels as specified by IEEE-519 standard. The IEEE 30-bus system with penetration of nonlinear adjustable speed drive loads is used to study the effectiveness of passive filters and to investigate the impact of their location and tuning frequencies on the quality of voltage and current waveforms. Simulation results before and after the installations of filters are presented, compared and analyzed for different nonlinear loading and filter configurations. It is shown that the number, locations and tuning frequencies of filters have major impacts on the overall quality of the distribution system.