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Research On Improved Repeated Control Technology For Parallel APF

Posted on:2021-02-18Degree:MasterType:Thesis
Country:ChinaCandidate:J L ZhenFull Text:PDF
GTID:2392330602491032Subject:Agricultural Electrification and Automation
Abstract/Summary:PDF Full Text Request
With the development of power electronics technology in the industry,the massive use of nonlinear devices has resulted in a large amount of harmonics and reactive currents being injected into the grid.Parallel Active power filters are widely used as common devices for controlling reactive and harmonic currents.This paper focuses on the filtering and current compensation techniques of higher harmonics:In this paper,the main circuit topology of the three-level Active power filter is briefly summarized.By comparing the three main circuit topologies,the diode clamp type is selected as the main circuit topology.The DC side capacitor parameters are optimized from the DC side voltage fluctuation principle.In addition,the LCL filter parameters are designed according to the maximum ripple current limit of the inverter and the regulation of the harmonic current into the network.For the resonance problem of the LCL filter,the resonant passive damping method is used to suppress the resonance peak and improve the stability of the system.Secondly,the main circuit of the threelevel Active power filter is mathematically modeled,and the mathematical model of the system in the abc stationary coordinate system is derived,and the equivalent transfer function of the threelevel Active power filter is obtained.For the subharmonics generated by three-phase non-linear loads,the principle of basic repetitive control is introduced.For the deficiencies of the controller,an improved repetitive control strategy in the static coordinate system is proposed,and the internal recurrence delay of the basic repetitive control strategy is shortened to 1/6.The composite controller with P+ improved repetitive control improves the dynamic response by improving the negative gain characteristics of the repetitive controller through the proportional controller.At the same time,the high frequency compensation and low frequency compensation links of the system control object are designed to further optimize the control bandwidth of the parallel Active power filter.In order to improve the characteristics of the internal model delay link in the repeated control is not an integer,the Langrange interpolation FIR filter with Farrow structure is introduced to approximate the fractional delay characteristic,which improves the system's steady state performance and compensation accuracy.Then,the DC side voltage stability is designed by the PI controller to maintain the DC side voltage stability.Finally,the Matlab test simulation model and the 2k VA test platform are built to compare and analyze the compensation effect and dynamic performance of the Active power filter.The experimental results show that the proposed P+ improved repetitive control can effectively track system harmonics and has good transient performance.
Keywords/Search Tags:Passive damping, Voltage feedforward, Repetitive control, Fractional delay, Active power filter
PDF Full Text Request
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