Research On Harmonic Compensation Device APF Of Low-voltage Distribution Network Based On Compound Control

With the rapid increase in the use of power electronic devices,high-end processors and high-power equipment has been widely used in industrial and mining enterprises,which improves the power efficiency and the working conditions,but systemharmonicalso bring the test of power quality.Thus,on the basis of controlling the amount of nonlinear load generated by harmonics,we should rely on advanced technology and adaptive devices to detect and control harmonic in electric network.In recent years,parallel APF methods have been commonly used to control harmonics,domestic and foreign scholars has also made breakthrough in the study of active power filter.According to the operation principle and composition of APF device,the main circuit adopts a four-arm topological model in structure,that is,the compensation for the neutral current is completed by the fourth pair of arms separately.On this basis,established corresponding mathematical model and analyzed the selection basis of the relevant parameters of the main circuit.The detection methods and control algorithms are studied and verified based on the above analysis.For the design of the APF device detection section,according to the theory of the instantaneous reactive power,to analyze the composition characteristics of the instantaneous active,reactive,and zero-sequence currents in the low-voltage three-phase four-wire circuit,and verify the applicability of the power supply system.And the improved ip-iq method that using mean module instead of low-pass filter is selected,which improves the speed and accuracy of harmonic detection.This thesis focuses on the current tracking strategy of APF devices.Aiming at the shortcomings of traditional single control strategies exist,such as fast response speed but precision is not high,the repetitive control can avoid this problem but one cycle delay,this thesismake use of parallel compound control method to make up.this algorithm solves the problem that accuracy and speed are not unified in a large extent,but this parallel model still exists some errors in the track of command signal effect.In order to compensate for the lack of compensation performance of the hybrid controller,a modern control method of the adaptive parallel hybrid controller is used.The original controller is modified by the BP neural network to improve the anti-disturbance performance and response speed of the device.Through research on the topology,detection method and control strategy,build three-phase four wire active power filter test system simulation model on the MATLAB platform,detect the performance of active power filter and build an experimental platform,comparing and analyzing system performance of traditional control methods,proved that the adaptive parallel composite control system to improve the quality of power supply in power system is reasonable and practical.