New approaches to mitigate harmonics: Development of active power filters and converters embedded with harmonic filtering functions

Modern power electronic converters such as adjustable speed drives (ASD), uninterruptible power supplies (UPS), induction heating systems, and telecommunication rectifier equipment, etc., normally employ diodes or silicon-controlled rectifiers (SCR) to interface with the electric utility. The rectifier type utility interface causes significant harmonic currents resulting in poor input power factor and high total harmonic distortion (THD). The proliferation of rectifier loads deteriorates the quality of voltage and current waveforms: further, harmonic currents can lead to equipment overheating, malfunction of solid-state equipment, and interference with communication systems.; Active filtering of harmonics via a power electronic converter termed as “Active Power Filter” is an effective method to address this issue. This dissertation proposes several new approaches to mitigate harmonics via the development of active power filters and converters embedded with harmonic filtering functions. The proposed approaches mainly focus on improving the total harmonic distortion of the input current under varying load conditions. The first part of the dissertation focuses on improving rectifier generated harmonics in a typical telecommunication power system. An improved harmonic current control algorithm is developed utilizing synchronous reference frame analysis to actively cancel rectifier generated harmonics. A feed-forward controller is introduced to obtain a fast control response. Harmonic reference current generators are proposed to address balanced and unbalanced utility inputs.; To improve performance further, this dissertation examines a hybrid active power filter. A new hybrid active power filter topology is proposed and analyzed. It is shown that a higher VA, low switching frequency inverter combines with a high switching frequency, lower VA inverter and this approach has many distinctive advantages. Analysis, simulation and experimental results of this scheme are discussed.; Next, a matrix converter L-C network controlled as an active filter is examined. It is shown that smaller size ac L-C components can replace bulky dc-link type energy storage in an active filtering system.; Finally, a rectifier boost converter system embedded with harmonic filtering function and implementation of such a system are shown. The control of a boost PFC stage is altered to filter harmonics generated by other non-PFC converters connected in parallel. Experimental results are shown.