The Study On Key Techniques Of Shunt Active Power Filter For Engineering Application

The Active Power Filter (APF) with the goal of harmonic inhibition and reactive power compensation is already basically mature. At the same time, the problem of power harmonic becomes more and more severe. Therefore, it is urgent to carry out industrialized and applied research about APF. Shunt APF becomes mainstream due to its convenience in installation and maintenance. So, the industrialization of shunt APF is studied in this dissertation.The research developed by this dissertation is induced by the engineering problem that harmonic amplification occurs when a conventional shunt APF compensates harmonic current generated by electric apparatus in office building. The electric loads in office building are mainly made up of personal computers, UPSs, switching mode power supplies and ac drives which are all voltage-type harmonic sources. The dissertation starts with the analysis of voltage-source rectifier. It is analyzed the steady state currents, voltages and their spectrums of uncontrolled single-phase voltage-source rectifier compensated by shunt APF based on piecewise linearization method. The method of steady-state analysis illuminated by this dissertation is helpful to understand theoretically the working mechanism of APF compensating voltage-source rectifier and has important significance in the applied research of APF.A simplified model of APF compensating capacitive load is modeled on the base of analyzing the characteristics of electric loads inside office building. By this simplified model, it is analyzed in this dissertation that the relationship between the value of capacitor in office load and the harmonic amplification. The harmonic amplification can be overcome by a filter added to the load current sampling to get rid of the component on resonance frequency. Although the harmonic amplification is suppressed, the THD of power grid current increases rapidly as a result of delay time introduced. According to this way, the selective harmonic compensation based on fast fourier transformation (FFT) is adopted to eliminate the resonant component from the sampled load current. So, the system will work under open-loop control upon resonance frequency and keeps resilient. The selective harmonic compensation based on FFT is proved effective to suppress the harmonic amplification by field operation of shunt APF compensating harmonic current generated by electric load in office building. This part work developed by the dissertation has reference value for field operation of shunt APF.In order to meet the harmonic compensation in high power level application, this dissertation presents the multi-modular APF system for shunt compensation whose characteristics are presented as follows: modular structure and N+1 redundancy, master-slave bus architecture and master module generation, load current detection and parallel sharing scheme. Master module generation and load current detection scheme are the prominent characteristics and illuminate the innovational work developed by this dissertation. Besides, model and stability of multi-modular APF system have also been studied. According to multi-modular parallel compensation strategy, industrialization of APF has been fulfilled under the support of Zhejiang province science & technology program key project which includes general plan design, parameter determination, prototype commissioning, full power operation, performance test, field compensation of harmonic current generated by building electronic equipments or industrial electric loads, industrial prototype standardization and so on. This part of work fulfilled by the dissertation promotes the industrialized application of shunt APF greatly and some standardized industrial APF products have been hatched by the project.The contents include three aspects mentioned above and the chapters are arranged as follows: (1) In chapter one, the research progress is summarized in harmonic detection, current tracking control and topology from view of practical application. (2) In chapter two, it is analyzed the steady state currents and voltages of uncontrolled single-phase voltage-source rectifier compensated by shunt APF. (3) In chapter three, the harmonic amplification when a conventional shunt APF compensates harmonic current generated by electric apparatus in office building is analyzed. The selective harmonic compensation based on FFT method is adopted to suppress the harmonic amplification by making the system under open-loop control in resonance frequency. (4) In chapter four and chapter five, the parallel compensation strategy of multi-modular APF system is illuminated. The design procedure and experiment results are also presented. (5) In chapter six, the thesis is summarized and the prospect of future work is illuminated.