Research Of Active Filter For Radial Field Power System Of HL-2A

HL-2A device radial field coil is supply by the125MVA generator, and its effect is tocontrol the vertical position of the plasma. Power supply of the radial field should provideDC voltage for the radial field coil; the AC voltage must be converted into a DC voltagethrough rectifier. Phase-controlled rectifier device will produce large amounts of harmoniccurrents in the system AC side; harmonic currents will bring larger line losses, accelerateaging of equipment, affect the stability of the system and cause a series of hazards.Therefore a filter is needed to be designed to control harmonic current of the radial fieldcoil power supply.According to the characteristics of the power supply system of the HL-2A device，specific analysis should be done about the filtering device in different environment.According to the basic system and experimental data of the system, a detailed analysisshould be done about the radial field power system, which is about frequency of powersystem, voltage harmonic and current harmonic. And a decision is made by the result ofanalyses; in this decision the appropriate filtering system should be selected. Finally it’sdecided the parallel active filter will be used.In order to have a better understanding and design of parallel active filter, manyworks should be done. Based on principle of active filter, the mathematical model of theparallel active filter can be built in time-domain and dq0rotating system. The design ofactive filter system can be carried out based on the analyses of the system, the parametersof the APF can also be calculated; such as the filter capacity, the DC-side for energystorage capacitor. This article describes several common harmonic detection methods andanalyzes the advantages and disadvantages of the various methods, and ultimatelydetermines the harmonic detection method based on instantaneous reactive power theory.Control strategy plays a decisive role in the actual effect of the active filter, the analysis of hysteresis control principle points out the problems of traditional hysteresis control.A system simulation model is built by using the MATLAB/SIUMLINK simulationsoftware. Throughout the result of the simulation, it can be observed whether the parallelactive filter in a variable-frequency power can work out correct. According to thesimulation result, the PLL of APF can fast track the change of system frequency, so thatthe harmonic detection can get the accurate harmonic current, it makes that the APF caninject compensation current into the system, and complete the filtering task well.