Research On Detection And Control Technologies For Active Power Filter And The Application

The rapid development of power electronics technology, on one hand, made power energy transformation and application conveniently, and on the other hand, led to the serious power quality problems in the power system, such as harmonic currents pollution, reactive power issue, voltage fluctuation or unbalance. APF(Active Power Filter) has been a key project in power electronics application technology, as the most effective method to solve harmonic and reactive power currents pollution, and improve the power quality. But APF has not reached the mature stage in the domestic applications, and has many problems to more study and improve. Compared with passive filter, APF still stays in less important position in actual application. For this purpose, in this thesis, the detecting, control and realization technologies are studied deeply, the research on which is of great importance to the early industrialization application of APF.Various harmonic current detecting motheds in common use are analyzed. These detecting methods are aimed at three-phase circuit, and can not apply directly to single-phase circuit and four-phase circuit, have certain defect in general application. Therefore, one kind of universal harmonic current detecting method is proposed, on the basis of further perfecting the definitions of FBD method, which is able to apply directly to the harmonic current detecting of single-phase circuit, three-phase circuit and four-phase circuit broadly. Besides, the active power fundamental current, reactive power fundamental current, fundamental negative sequence current, harmonic current and any harmonic current can be detected by the extended research of the detecting method. Specifically for these kinds of circuits, the realization block diagrams of detecting principle are given respectively, and at the same time, the design of low pass filter is studied which affects the accuracy and dynamic behaviour of detecting method.In order to improve the current tracking performance of APF, in this thesis, two current control methods for APF are proposed. (1) The hysteresis current control method for APF based on voltage space vector. This method gives the best suitable switching of voltage vector using the space distribution of current error vector and reference voltage vector, and then controls the current error below the hysteresis width. Voltage space vector is introduced into the control system to eliminate the phase interference, and it can be realized simply without complicated vector transform. (2) The voltage space vector predictive current control method for APF. This method predicts the instruction current of next sampling instant at current sampling instant, calculates APF's reference voltage of next sampling instant, and then the corresponding control switching signals are get out using the voltage space vector modulation, lastly the objective of current tracking control is reached. The simulation results show that the two proposed current control methods have better current control effect than the traditional hysteresis current control method.In this thesis, the basic principle and control method of APF's main circuit DC bus voltage has been discussed. On the basis of PI control method for DC bus voltage, a novel control method is brought forward, which has integrated the fuzzy control with PI control. This method combines the merits of PI control and fuzzy control, has rapid dynamic response, small overshoot and small static state error, and is realized simply, which satisfies the control request of DC bus voltage under various conditions of changing loads.Thorough research has been carried out for 100kVA parallel APF's main circuit and its peripheral circuit. The Choice of main circuit switching components, and the design of snubber circuit and drive protection circuit are discussed detailedly; the selecting method of DC bus voltage value, DC bus capacitance and AC side filtering inductance value are given, using the method of integration of theoretical analysis with simulated experiment. And, the detailed design parameters of concrete main circuit components and peripheral components for 100kVA parallel APF are calculated according to above-mentioned analysis method.Finally, in this thesis, the system structure for 100 kVA parallel APF has been introduced, and the realization scheme of full digital conrol system based DSP (digital signal processor) + CPLD (complicated programming logic component) has been discussed, and the hardware circuit and software design of control system have been studied. Representative experiments have been carried out on 100kVA parallel APF model machine, and the experimental data and waves have verified the research work in this thesis.