Research On Method Of Selective Harmonic Compensation With SAPF

The application of shunt active power filter is the main means of power quality optimization.In order to solve the problem of the insufficient capacity of the compensation device and the higher production cost in the engineering application,the selective harmonic compensation method is adopted to reduce the demand for the capacity of the DC side component.Firstly,the detection methods of selective harmonic compensation are analyzed.The effect of ip-iq specific subharmonic detection and d-q specific subharmonic detection is analyzed and compared.Simulation results show that d-q is superior to ip-iq in detecting higher harmonics,therefore,the d-q specific subharmonic detection is selected as a selective harmonic detection method.In order to solve the problem of digital processing delay in the process of d-q detection,a method of repetitive half cycle control for a particular subharmonic is adopted.This method can not only solve the delay problem caused by the high quality detection of specific subharmonic,but also shorten the computation time required for repetitive cycle control under the condition of sudden load variation,and then improve the real-time and transient characteristics of the tracking current.Secondly,in order to improve the utilization of DC side voltage,reduce the trigger frequency instability,low precision and complex triggering control process caused by hysteresis control and SVPWM control,the hysteresis SVPWM control is adopted to reduce the switching frequency and to avoid the calculation of the instruction voltage area time.At the same time,a simplified method for judging the conduction state of the hysteresis SVPWM three-phase switch tube is proposed according to the region selection of the command voltage and the error current,and the flow chart of judgment is provided.Then,in order to solve the DC side voltage fluctuation problem,the capacitance selection process of the DC side capacitor voltage and the charging process of the DC side voltage boost circuit are analyzed according to the energy flow.A voltage predictive control strategy based on data rolling optimization is proposed to keep the DC side voltage stable,so that the amplitude of the compensation current is accurate.The simulation results show that under the condition of load stability,the voltage predictivecontrol method can reduce the amplitude of capacitor voltage fluctuation caused by energy flow,and meet the requirements of Engineering design,and in the case of transient voltage fluctuation is gentle.Finally,the prototype is built and the experimental verification is carried out.Experimental results show that the proposed control strategy can compensate harmonic currents in a timely and accurate manner,and verify the effectiveness of the proposed method.