Abstract
With the extensive use of power electronic equipments, a large amount of harmonics may inject into the utility grid to reduce the power factor and worsen the electric power quality. Recently, the active power filter is increasingly developed and employed to replace the conventional passive LC filter. Although a lot of researches have been made during the past years, there are still many issues being worthy of studying such that the performance and application occasions of active power filter can be further promoted. The major purpose of this thesis is to study the development of modular active power filter and its controller. Firstly, a single-phase single-module active power filter is designed and implemented. Through properly designing the current and voltage control loops, it possesses close current tracking characteristic and quantitative voltage regulation response. By connecting the developed power filter in parallel with the nonlinear load, its distorted line drawn current can be compensated to be sinusoidal with low distortion and near unity power factor. Then based on the high-performance single-phase single-module active power filter, two studies are further carried out : (i) a single-phase multimodular parallel active power filter system is developed. The proper control is made to let it possess good current sharing control characteristic and power filtering control performance; (ii) three or two single-phase single modules are arranged to form a three-phase active power filter, the desired active power filtering control properties are also successfully achieved by the designed controllers. The circuit analysis, dynamic modeling and controller the design of each type of active power filter are described in detail in this thesis. After confirming the validities of the designed circuits and controllers by simulations, hardware implementations are performed and some results are provided to further demonstrate the performances of the proposed active power filters.