Resonant Impedance Type Hybrid Active Filter

The study is focused on RITHAF-Resonant Impedance Type Hybrid Active Filter, a novel facility for substation harmonic elimination. This dissertation expands the structure, principle and control of RITHAF, as well as passive filter optimization and output filter analysis, presenting a self-contained solution for substation harmonic elimination.After the comparison of the existing active filters, a novel RITHAF is proposed here to meet the given situation of substation harmoinc elimination. With the operation of RITHAF, power source seems to be connected with a FSRC (Fundamental Series Resonant Circuit) in series. The impedance of FSRC approximates zero at fundamental frequency and is comparatively large at harmonic frequency. So the fundamental current passes without decay, while the harmonic current is blocked and change its route into passive filters. Thus the harmonic current of power source side is removed, viz, the goal of substation harmonic elimination is reached. In addition, the passive filters included in RITHAF also have a function of reactive power compensation. Because both fundamental components of the voltage across the converter of RITHAF and the current injecting into it approximates zero, the capacity of converter decreases as well as the total budget. Based on the analysis of harmonic attenuation function defined here, the performance of RITHAF are investigated under several practical cases, such as variation of power source impedance, change of FSRC parameters, mistiming of passive filters and so on. The resonance dampping capability of RITHAF is also discussed.The generic criteria of passive filter design is induced through analysis of existing design methods in this dissertation. According to this generic criteria, a novel design method based on multi-objective optimization GA (Genetic Algorithm) is proposed. It is thoroughly considered in this new method that harmonic attenuation, reactive power compensation, mistuning, background harmonic and resonance with power line impedance. In this method, the optimal parameters of passive filters are derived by paralle search aimed three goals of cost, capability of reactive power compensation and content of harmonic. In conventional way, there is only one goal and the others are treated as restrictions. But in fact, these restrictions have their own expected boundaries. So the method proposed here is more reasonable, in which solution individuals satisfying these restrictions can also evolve towards the expected boundaries. The multi-objective eclectic selection mechanism is brought forward to reserve the good genes both of each goal and of eclectic goal. In this manner, the diversity of colony is enhanced too.The influence of output filter on hybrid active filter and its causation are revealed in the chapter 3 ofthis dissertation. The conclusion is come from the analysis of the index functions defined here of four different types output filters: LC, LCL, L and LCR. It shows that, compared with other output filters, LCR output filter can largely attenuate the amplitude of amplified harmonic components at high frequencies and simultaneously amplify the harmonic components at low frequencies in converter current so that the harmonic components at high and low frequencies in power source current are both reduced. The simulation results given in dissertation tell that LCR output filter is preferable in active filter appliances.The analysis of state of arts of acive filter control is performed in this dissertation from the point of view of classic control theory. A discrete sliding-mode variable structure control law based on approach principle and a generalized integrator based iterative control algorithm are proposed. On this foundation, a discrete ternary variable-structure control is proposed by introuducing the answer of generalized integrator based iterative control algorithm as an equivalent control of discrete sliding-mode variable structure control. In this manner, there are three alterable controller structures with three correspondi...