Study On Harmonic-Mitigation Technology Of Electric Equipment For Material Manufacture

With the development of power electronics, electric equipments have beenwidely used in the field of material manufacture today. Due to their nonlinearity, alot of harmonic pollution has been brought to power systems and results in a seriesof power quality and reliability problems of power system. At the same time, theharmonics existing in input current, give limit to advance the power factor further,and result in a low efficiency, which means an enormous waste of capacity ofpower system. In little more than ten years, the electricity power quality has grownfrom obscurity to a major issue and the limits have been proposed in the newinternational standards,so the solution to the problem about harmonic pollution isimperative under the situation in the near future. There are mainly two types of electric equipments in material manufacture.One of them is those equipments use SCR to regulate the output voltage, whichinput circuit is an inductor as filter after bridge SCR rectifier and injects harmonicsas a current source. The others are various inverters, which input circuit is acapacitor as filter after a diode bridge rectifier and injects harmonics as a voltagesource. In recent years, the inverters are more and more popular, so it is meaningful,to some degree, to solve the harmonic pollution problem arisen by the use ofinverters. Generally, there are mainly two ways to solve the harmonic pollution, that iscompensation method or correction method. The compensation method is tocompensate the harmonics through compensation equipment, such as Active PowerFilter. The correction method is to change the equipment not to induce harmonics,such as Power Factor Correction. For different harmonic sources and with differentmethods, the performance is quite different. The correction method must deal withall energy needing to transfer, but compensation method just deal with a part of allenergy and it can be used to compensate a group of load. Therefore, theoretically,compensation method is more ideal compared with correction one. The second chapter gives an analysis to the two types of harmonic sources inmaterial electric manufacture. The relation between the input performance and theparameter of typical circuit is given via theoretical analysis and simulation. Theresults can be used as a reference to select the parameter on the balance of inputand output performance. The third chapter mainly introduces a feedback harmonic detection method,which is based on frequency analysis of IRP (Instantaneous Reactive Power III北京工业大学工学博士学位论文Theory) The design method and DSP realization to this method is proposed. Theexperiment and simulation results show the feedback detection is more accuratethan the conventional open-loop one. So the harmonic feedback detection can meetthe high requirement of APF (Active Power Filter)control system . The forth chapter analyzes the mathematical model of 3-phase VSI andinvestigate the current detection methods for APF. When the source currentdetection method is adopted,there might be an unstable phenomenon. A correctionmethod is proposed to solve the unstable problem. The DC side control of APFimposes the direct effect on the performance and the stable running of APF system.Based on intensive analysis of the DC control of APF, the correction of DC voltageloop is proposed, and the simulation and test results are shown. From the theory ofDC voltage regulation, a novel control method, based on the active power balancetheory, is proposed. Only two current sensors and one voltage sensor are needed inthis method. At the same time, this method can be generalized to the control ofPWM Rectifier. The simulation and test results verify the method proposed above. In the fifth chapter, research has been done on the unstable phenomenon,which occurs in the compensating system where shunt active power filter (SAPF)is used to compensate the...