| With the widespread application of power electronic devices,the power system harmonic pollution is becoming more and more serious.Harmonic pollution is harmful for power system operation,power generation and transmission.Using active power filter to control harmonic pollution is one of the most effective methods at present.This thesis has done the following research on active power filter.Based on the instantaneous reactive power theory,this paper analyzes the principle of p-q detection method and ip-iq detection method,and analyzes the application conditions and limitations of the two methods.Under the condition of asymmetrical three-phase voltage,by rotating vector theory derivation analysis was carried out on the ip-iq detection method,ip-iq detection method to the fundamental positive sequence active component has a certain error,an improved detection method is proposed.Under the distortion voltage,the p-q detection method and ip-iq detection method are simulated,and the validity of the theoretical analysis of the two methods is verified by simulation results.Then,in the case of three-phase voltage asymmetry,the p-q detection method,ip-iq detection method and improved detection method are simulated,and the correctness of the improved detection method is verified by simulation results.Finally this paper introduces the current control method of active filter,the main two methods of hysteresis current control and triangular wave control,analyzed the principle and set up a simulation model of triangle wave comparison way,validated by the simulation results.In view of the traditional hysteresis control method,because the cause of the retaining ring width,switch on-off frequency change is bigger,so aiming at the intrinsic defects of ring width,the hysteresis control hysteresis comparator ring width designed ring width,ring width of hysteresis control principle are analyzed,basic structure,and ring width of circuit design.The simulation model of the two hysteresis current control is built and compared.The improved hysteresis control switch is also improved,and the compensation precision of variable ring wide hysteresis loop current control is better. |
