Research On Active Power Filter Used In Traction Power Supply System

Traction power supply system, whose loads are mostly rectifier load with the features of low power factor and high harmonic content, has a great impact on the power system as a special user of it. Active power filter, a power electronic device with the good performance of dynamic response and compensation, which are better than those of passive power filter, is used for harmonic and reactive compensation. Therefore, it has the theoretical significance and practical value to research the active power filter and apply it to the traction power supply system for improving the power quality.The basic principles of Active Power Filter are first introduced. The scheme and structure of single-phase hybrid filter system is then illustrated and analysis is made based on the harmonic and reactive compensation principles. Through theoretical analysis, the system has been proved to have the function of harmonic and reactive compensation.For single-phase circuit, three directive-current detecting methods are presented in this thesis. By the comparison of simulation results, it is concluded that the no phase-locked loop directive-current detecting method based on the Hilbert space can rapidly and accurately detect the directive-current of single-phase circuit.The active power filter control strategies, including current tracking control and voltage control, are researched. According to the practical requirements of the project, an improved unipolar voltage-type PWM strategy based on vector control, which can make the PWM circuit work at fixed frequency, is researched. The compensation precision can meet the requirements of the project.Through analyzing the general requirements for the design of system parameters, a relevant parameter design method of active power system is proposed.Traction power supply systems simulation model with or without single-phase hybrid filter system is established under PSCAD/EMTDC environment to verify the compensation effect of the system. The validity of the proposed approach is verified by the simulation results.