Research On Frequency Adaptive MAF Phase-locking Method Under Unbalanced Power Grid

With the declining fossil energy sources and the deteriorating global environment.In order to quickly and accurately obtain grid phase and frequency information under the non-ideal conditions such as voltage harmonic distortion,voltage drop,frequency jump and phase hopping,the phase locking technology under non-ideal conditions.First,the research background and status of the phase locking loop technology are introduced,and the vector analysis of the three-phase voltage under non-ideal conditions is performed.In the research background and current review of phase locking loop technology,analyzing the latest theoretical results of sliding average filter(moving average filter,MAF),laying the foundation for the frequency adaptive MAF-PLL phase locking loop by improved PID control,analyzing the three-phase voltage,the "components" affecting grid voltage imbalance,mainly the harmonic distortion,voltage drop,phase angle hopping and frequency jump,and obtaining the effective information in the base wave positive order component.Secondly,the working principle and digital implementation of three typical phase locking rings are introduced,and the controller parameters are designed respectively.The three typical phase-locking rings are the synchronous coordinate system phase-locking rings(SRF-PLL),the Tw constant MAF-PLL under traditional PI control,and the frequency-adaptive MAF-PLL phase-locking rings under modified PID control.This paper combines with the literature results on the Tw constant MAF-PLL and the digital implementation method of frequency adaptive MAF-PLL phase-locked loop of improved PID control to determine their suitable digital implementation methods.Moreover,the frequency adaptation of the improved MAF-PLL is introduced,and the PI and PID controller parameters corresponding to the two MAF-PLL phase locking technologies are designed respectively.Finally,combining the simulation model and the experimental platform,the dynamic and steady-state performance of the three classic phase-locked loops are compared and analyzed.Based on the Matlab/Simulink simulation platform,the simulation models of three typical phase-locked loops are built respectively,and the dynamic and steady-state performance of the three phase-locked loops are tested under the conditions of harmonic distortion,voltage drop,and phase jump;Improved PID-controlled frequency adaptive MAF-PLL uses frequency hopping conditions to test its frequency adaptive capability.At the same time,based on the VME bus architecture experimental platform,the same experimental conditions as the simulation model were selected to test the dynamic and steady-state performance and frequency adaptation capabilities of the three phase-locked loops.Both simulation and experimental results show that,compared with SRF-PLL and traditional PI control-based Tw constant MAF-PLL,the response speed of the improved PID control frequency adaptive MAF-PLL proposed in this paper can be increased by more than 1 times,and because With frequency self-adapting ability,it can maintain high steady-state accuracy even when the grid frequency significantly deviates from the rated power frequency.