Research And Implementation On STATCOM With Selective Harmonic Compensation Of Control Method

With the rapid development of global energy Internet,the requirements for the power quality are higher,so it is of great significance to carry out in-depth research on it.STATCOM is a high dynamic reactive power compensator formed by a full control converter.It has the characteristics of high controllability and control precision,fast and flexible,and can compensate the reactive power of system and eliminate harmonics,compensate for three-phase unbalance,and improve power quality.In this paper,based on the shortcomings of existing methods,three-phase three-line STATCOM used as the research object,and put forward the selective harmonic compensation control method.The working principle and system structure of STATCOM are analyzed,and the mathematical model of three-phase three-line STATCOM in three-phase stationary coordinate system is established.The mathematical model of two-phase stationary and two-phase rotating coordinate system is deduced by coordinate transformation.The SVPWM modulation strategy is studied and the principle and control algorithm are analyzed.A harmonic detection method based on synchronous rotation coordinate transformation is studied,and a current detection method based on multiple synchronous rotation coordinate transformation is designed.An improved fundamental reactive power control method is proposed.The design method of current inner ring,voltage outer ring and mode selection is studied respectively.Based on the multiple synchronous rotation coordinate transformation,the mathematical model of STATCOM in multiple synchronous rotating coordinate system is established,and the design method of harmonic PI controller is studied.Combining the fundamental and the harmonic control,a STATCOM controller with selective harmonic compensatin based on PI control is designed.In view of the poor tracking effect of harmonic PI controller.In order to further improve the compensation accuracy of the selective harmonic,the composite current regulator is designed by using the harmonic PI controller and the plug-in repetitive controller.Composite current regulator can retain the advantages of the two controllers,and make up for the lacks.Then,a STATCOM controller based on repetitive control of the selective harmonic compensation is designed.Finally,a simulation model of three-phase three-line STATCOM is set up in PSCAD simulation software to verify the proposed control method.The results show that both the selective harmonic compensation control method based on PI control and repetitive control can accurately compensate the fundamental reactive power and the selective harmonic and imbalance,and the latter is more effective.