Research On Resonant Control Based On Fast Current Detection And Development Of Active Power Filter

With the rapid development of national economy,the load type of the user side of the power grid system has increased rapidly,in order to adapt to different user load demand,various power electronic transform equipment and the non-linear load with front end rectifier are applied in the power grid.At the same time,these devices also inject a lot of harmonics and reactive currents,causing other electronic devices to work abnormally.APF(Active Power Filter)has become a hotspot in the field of harmonic and reactive currents which can compensate for many non-linear loads.The traditional active power filter uses Low-pass filter to remove all harmonics except the fundamental wave in the current detection link,so it is necessary to set the cut-off frequency low,which determines its narrow bandwidth and slow dynamic response.The resonant controller is often used in the current control process.In general,the fundamental currents and harmonic currents are controlled together,the proportional integral resonant controller is composed,the DC side voltage will drop at a certain amplitude when the nonlinear load is abrupt,or the control strategy of the fundamental harmonic current of the network is collected,although the algorithm does not need to separate the fundamental and harmonic currents,However,the simultaneous existence of harmonic reactive currents cannot be addressed simultaneously.In order to solve the above problems and improve the dynamic response and compensation performance of active power filter,a resonant control strategy based on fast current detection is proposed in this paper.Current detection,in response to the traditional harmonic current detection in the bandwidth and response speed limitations,using the combination filter of the special harmonic notch filter and Low-pass filter,the special harmonic notch filter removes 5,7,11,13 times low harmonics,the Low-pass filter has a wide frequency band,fast response,and filters high harmonics,The combination of the two can effectively solve the problems of traditional filters.In order to solve the disadvantage of the traditional resonant controller,the improved vector resonant control strategy under DQ coordinate system is adopted in the current control.The harmonic currents are controlled separately from the fundamental currents to ensure that the DC side voltage is stabilized when the non-linear load is abrupt,and the tracking accuracy is achieved.Which,the Pi control of the fundamental current loop,the harmonic current loop adopts the vector resonant control,and the influence of the system's line inductance is decoupled,and the control parameters are analyzed and designed in Z-field,so as to avoid the deviation introduced in the process of digitalization,so as to achieve better control effect.On the premise of verifying the Matlab/simulink simulation model,the paper designs the software and hardware of the system in detail,and sets up the experimental platform of APF with TMS320F28335 digital signal processor as the control chip.Experiments on the platform,such as start-up,variable nonlinear load and selective compensation harmonics,show that the combination filter and the improved vector resonant controller can respond quickly when the nonlinear load is abrupt,maintain the voltage stability of the DC side,and the compensation precision is high,The effectiveness of the resonant control strategy based on fast current detection is validated by the high frequency selective performance and the effective compensation of harmonic reactive current.