Research On Distortion Detection Algorithm Of Unified Power Quality Controller

As a secondary energy source,electric energy has become the most dependent form of energy for humans because of its advantages of cleanness,high efficiency,wide transmission range,fast propagation speed,and convenient use.Due to the rapidity of power transmission and the convenience of use,its use has spread across various fields and institutions and is an integral part of human life.Therefore,the user's requirements for power quality are also increasing.The Unified Power Quality Controller(UPQC),as a comprehensive power quality control device,can centralize the voltage and current problems that occur in the power grid,and has become a hot topic of research.This paper firstly introduces the working principle and topology of UPQC,and studies three kinds of topology structures: single-phase UPQC,three-phase three-wire system and three-phase four-wire system.It establishes a mathematical model for its series and parallel compensation units and analyzes UPQC.The operating characteristics and its internal power flow under different voltage conditions.Secondly,the traditional signal detection algorithms and control strategies in UPQC are analyzed and compared.For the traditional phase-locked loop in the case of voltage distortion,the voltage cannot be phase locked accurately.The paper uses decoupled double synchronous coordinate transformation to lock the phase.The ring is improved to eliminate the influence of the negative-sequence component in the distortion voltage,and the voltage can be phase-locked accurately under adverse voltage conditions.Thirdly,the traditional harmonic detection method has a complex calculation process,which involves multiple coordinate transformations and only a single defect detection of voltage or current distortion.In this paper,a comprehensive detection method based on RMS is proposed.In the traditional RMS harmonic current detection method,harmonic voltage detection is added,and the compensation module is designed for the error caused by theapproximate calculation,which improves the detection.Accuracy realizes synchronous detection of current and voltage.Finally,under the condition of voltage distortion,the comprehensive detection method of effective value designed in this paper was simulated and compared with the traditional detection method.The simulation results show that under the bad voltage conditions,using the detection method proposed in this paper,UPQC can achieve stable compensation for distortion in the power grid.Based on the simulation study,the software and hardware in-loop tests were performed on the detection algorithms respectively,which further verified the feasibility of the detection algorithm.