Research On APF Control Optimmization And Multi-machine Parallel Resonance Suppression Strategy

With the continues increase of non-linear load in the distribution network,the problem of harmonic pollution in the power grid becomes increasingly serious.In order to solve the problem of harmonic pollution,Active Power Filter(APF)is widely used as a new type of efficient filtering device.However,in terms of eliminating high-order harmonic pollution and resisting disturbances in the power grid,APF performance based on traditional control methods is not satisfactory.At the same time,with the continuous increase of the nonlinear load capacity in the distribution network,the compensation capacity of a single APF can no longer meet the harmonic compensation requirements of the power system.Therefore,APF multi-machine parallel operation is required to complete the harmonic compensation task.However,theoretical research and field experiments prove that when the APF multi-machine is operated in parallel,the resonance secondary current in the filter capacitor is too large due to the resonance of the machine network,which makes the whole APF parallel system operate abnormally and may cause damage to the filter capacitor,rotating motor and transformer.This passage studies the APF control optimization and the multi-machine parallel system resonance suppression strategy based on the industrial distribution network.Firstly,the background of harmonic pollution and the origin of the problem are expounded.The development history of APF,the research status at home and abroad and the problems existing in the current research are introduced.Secondly,the basic working principle and typical application types of APF are analyzed.The components of parallel APF system are described in detail.At the same time,the advantages and disadvantages of APF traditional control methods are expounded and analyzed.Then,aiming at improving the compensation performance of APF multi-machine parallel system,starting from the optimization of APF control performance,an indirect current control strategy based on(Proportional Integral and Vector Proportional Integral)PI-VPI controller is designed based on traditional PI control.The VPI controller can not only detect the highfrequency harmonic components contained in the load current,but also significantly improve the response speed of the APF.At the same time,the design scheme of each component of the PIVPI controller is clearly given.Theoretical analysis The proposed optimal control strategy and simulations verify the controller's steady-state performance and dynamic response capability under various operating conditions.Finally,for the ARF multi-machine parallel system,due to the resonance secondary overcurrent problem caused by parallel resonance,the Norton equivalent simplified circuit model of the equivalent circuit and circuit of APF multi-machine parallel system is established.Through the quantitative analysis of the resonance peak distribution,The mathematical expression of the system resonance frequency is proposed and applied to the APF multi-machine parallel system resonance suppression.The influence of the active damping parameters on the system resonance suppression effect is deeply studied.The theoretical analysis and simulation prove that the optimization has the source damping parameter reduces the probability of resonance in the APF multi-machine parallel system.