Research On Parallel APF Harmonic Detection And Control Strategy

With the progress of society and the development of industry,a large number of power electronic equipment is put into use,resulting in increasingly serious harmonic pollution of the power grid.Shunt Active Power Filter(SAPF),as a very effective harmonic pollution control method,has received extensive attention and research.Generally,a typical SAPF system can be divided into 4 parts: phase-locked loop(PLL),harmonic detection,output current control,and DC-side voltage control.Most traditional software phase-locked loops(SPLL)can only lock accurate voltages in the forward order,but not in the reverse order.In combination with the principle of phase-locked loop voltages discussed,voltage vectors The nature of the angular reverse order change is analyzed,and the cause of this phenomenon is analyzed.An adaptive phase-locked loop is designed for the reverse order,which can complete the phase lock under the correct positive sequence voltage and reverse sequence voltage.Using the characteristics of artificial neural network(ANN)with strong self-adaptability and ability to approximate any non-linearity,a harmonic current detection method based on BP neural network is proposed.An additional amount is added to the input of the neural network.The phase load current and the virtual magnetic chain space position angle are used as input to the neural network system to improve the detection performance and accuracy of the neural network.In order to solve the problem that the traditional model prediction algorithm is conservative,this paper presents a multi-step prediction algorithm to improve the accuracy of the prediction.Based on the PI control of the DC voltage of the traditional active power filter,a new parameter self-tuning fuzzy PI control method is designed.Compared with the traditional PI control method,under the parameter self-tuning fuzzy PI control,the DC side voltage overshoot is smaller and the response time is shorter,which can meet the DC side voltage control requirements under sudden load.And when using parameter self-tuning fuzzy PI control to control the DC voltage,the suppression ability of the voltage loop to the second harmonic is stronger than that when the PI control controls the DC voltage.