The Key Technologies Research And Engineering Application Of Injection Type Active Power Filter

Nowadays, people pay more attention to the harm of harmonic. However, the harmonic pollution in power grid is getting worse, and power quality requirement is becoming stricter by users. The advanced dynamic compensation device, APF(Active Power Filter), may reduce harmonic and synthetically control power quality in industrial enterprises, which will bring the remarkable economic and social benefit.This dissertation focused on the research of harmonic suppression and large-capacity reactive power compensation in industrial substations. According to the harmonic elimination project at the 10kV side of a 110kV substation in a JiangXi copper-foil enterprise, a novel HSHIAPF (High-capacity Shunt Hybrid Injection Type Active Power Filter) was proposed, and some key problems of HSHIAPF were emphatically discussed, such as topology structure, work principle, filter performance, harmonic detection algorithm, current tracking control algorithm and so on. Based on HSHIAPF, an integrated harmonic analysis and elimination scheme was realized. Finally, HSHIAPF was operated and obtained good results in the industrial field, which produced great economic and social benefit for the copper-foil enterprise.In the HSHIAPF structure, active part was firstly connected with a FSRC (Fundamental Series Resonant Circuit) in parallel, and then linked in series with an injection circuit, finally connected in parallel with passive power filters and injected into power grid directly. Because of the functions of FSRC and injection circuit, the active part's fundamental-wave voltage and fundamental-wave current were very small, and even close to zero. Therefore, the topology structure of HSHIAPF was very suitable for harmonic suppression in high voltage and large capacity situations, and the initial investment was also small. Moreover, the passive part of HSHIAPF could also provide much reactive power. Meanwhile, the control equation of HSHIAPF was established in this dissertation. According to the theory, that the output of voltage source inverter would be determined by load harmonic current, a kind of basic control strategies was chose for HSHIAPF. Both theoretical analysis and simulation research have been done under the situations of load harmonic current fluctuation, power source harmonic voltage fluctuation, power grid impedance fluctuation, and power grid frequency fluctuation. All the results have shown that HSHIAPF can get perfect harmonic elimination effect.To satisfy the demands of the real-time detection and high precision of harmonic current reference signal, and the characters of easy realization and less calculation of harmonic current detection algorithm, a sliding-window and iterative harmonic current detection algorithm was proposed based on DFT (Discrete Fourier Transform). Regarding DFT as a type of FIR band-pass filters, the proposed algorithm set the corresponding fundamental-wave frequency or harmonic frequency as the FIR filter's center frequency to meet the demands of current frequency-division detection. A sliding window was used to iteratively compute the FIR filter's coefficients and the sliding window's width equaled the sampling times in one power-grid cycle. Simulation results have proved that good detection effect can be obtained by the algorithm even under the abrupt changes of fundamental-wave current or harmonic current. In addition, each order of harmonic current could be detected quickly by extending the algorithm. The algorithm could not only decrease the detection calculation greatly, but also be directly applied in three-phase three-wire, three-phase four-wire and single-phase systems. Moreover, the algorithm was fit for software programming and could ensure the consistency of good detection precision and perfect response speed with DSP (Digital Signal Processor) and some high speed devices.The mathematical model of HSHIAPF was built in this dissertation. On the one hand, because the voltage source inverter of HSHIAPF was a natural variable structure system, it would bring extremely obvious advantages in fast control with discrete sliding-mode variable structure control algorithm. On the other hand, because control reference signal was a periodic parameter, it could eliminate system steady error well with recursive integral PI control algorithm. Combining the merits of above two algorithms, a novel compound control algorithm was proposed. In the proposed algorithm, the output of recursive integral PI control algorithm was introduced as an equivalent control of sliding-mode variable structure control algorithm. In this manner, there were three alterable controller conditions with three corresponding switching modes—inside a limit band and either outside of the limit band. Sliding-mode control law would be put into use when the tracking error of reference current was out of the limit band. In this way, the tracking error would be reduced rapidly. When the tracking error entered into the limit band, it would be diminished to zero by recursive integral PI control algorithm. Consequently, this novel controller could provide fast respond and high accuracy. In addition, the switching harmonic could be eliminated easily by the output filter.In order to obtain better filter performance and less investment, a whole set of optimal design methods has been established including the design of some important parameters in main circuit, the choice of some key components, application experience and so on. Based on these proposed design methods and simulation results, HSHIAPF had been testified its feasibility and validity for industrial applications. Furthermore, an advanced integrated system based on HSHIAPF was proposed to realize harmonic analysis and suppression better in the industrial field. The integrated system had forceful dynamic harmonic suppression abilities and large-capacity reactive power compensation abilities, however, the inverter's capacity could be limited to a small range and the cost was also less. Besides, the integrated system had excellent harmonic analysis abilities, friendly human-machine interfaces and reliable harmonic-data share abilities. Therefore, it could not only provide enterprise managers with necessary information of industrial power-grid, but also send actual power quality data to some upper power departments. Finally, all the developing and debugging tasks have been finished, and the integrated system has been put into use in the industrial field. In essential, the integrated system was equivalent to a layered distributed system which gathered many functions together, such as harmonic watch, data analysis, harmonic suppression, and so on. Furthermore, these proposed design methods, software, hardware and network design ideas, and engineering experience of HSHIAPF would be very useful for large-capacity active power filters' research and applications in china.