Research And Application Of Single-phase Harmonic Detection And Phase-locked Loop Based On Iteration

With the widespread use of power electronic equipment,more and more attention has been drawn to the problem of containing harmonic pollution caused by nonlinear loads.In present harmonic control methods,active power filter is one of the most effective methods at present,and the related harmonic detection technology and phase-locked loop technology are the key links in its operation.Therefore,this paper takes the related technology of single-phase harmonic control as the research topic,and improvements are made on the technology of single-phase harmonic detection and single-phase phase-locked loop.To solve the problem that the single-phase harmonic current detection technology based on instantaneous power is affected by the low-pass filter and it is difficult to balance the detection accuracy and speed,this paper proposes an improved harmonic detection method based on the iterative principle.This method not only weakens the influence of the main two harmonic components on the low-pass filter,but also flexibly adjusts the harmonic number of iterations according to different load current conditions.The proposed method is compared with other detection methods through simulation and experiment,suggesting that the proposed method can greatly improve the accuracy of harmonic detection without the loss of dynamic performance.In order to solve the problem of high-frequency harmonic oscillation in the output phase of the traditional single-phase phase-locked loop when there is harmonic distortion in the grid voltage,this paper applies the iterative module s of harmonic detection method to the structure of the single-phase phase-locked loop,and the structure is simplified according to the situation of the grid voltage signal.The simulation results show that the iterative single-phase phase-locked loop proposed in this paper can achieve accurate phase-locking when the input voltage has harmonic distortion while ensuring dynamic performance.In order to verify whether the iterative harmonic detection method and the phase-locked loop can achieve the improvement of harmonic governance,this paper applies these two improved technologies into the control system of the single-phase parallel APF.Finally,comparison with another control scheme in MATLAB/Simulink is made,indicating that the steady state and dynamic performance of APF can be improved with these two methods.