Modeling And Simulation Of VSC-HVDC Converter Station Based On Virtual Synchronous Generator Control

With the depletion of traditional fossil energy,new renewable energy has been paid more and more attention in life.Distributed generation technology has been greatly developed in recent years.The requirement of distributed energy interconnection and the problem of land resources occupied by transmission line corridors are becoming increasingly prominent.China's new energy bases such as wind power and photovoltaics are mainly distributed in the "three north" areas Due to insufficient local consumption,large-scale new energy needs to be transported to power load centers such as central and eastern China.HVDC technology has become an effective way to solve the problem of cross-regional,stable and efficient transmission of electric energy.Flexible HVDC transmission system based on voltage source converter(VSC)can realize independent control of active and reactive power,can better meet the dispatching requirements of power grid,and has the advantage of no commutation failure problem,so it has been widely used.However,VSC-HVDC based on power electronic conversion circuit has the characteristics of insufficient damping and inertia.Virtual Synchronizer Control Technology is an effective means to solve this problem Therefore,the study of VSC-HVDC virtual synchronous generator control is of great significance to the safe and stable operation of the power grid,which can realize primary frequency regulation,provide frequency support to the system,improve the overall inertia of the system,and realize fast adjustment without error.Under the background of fully understanding VSC-HVDC transmission,this paper introduces the principle of synchronous generator interconnection,analyses the process of converter station equivalence to synchronous motor,and focuses on the mechanical-electromagnetic equation of virtual synchronous generator(VSG)algorithm.Through reasonable control strategy design,the converter unit can provide inertia and frequency support for the system,and then verify the designed control strategy on the experimental simulation platform of Matlab/Simulink.The main contents of this paper are as follows:1)The basic topological structure of VSC-HVDC transmission system is given.Analysis of two-terminal converter station and its remaining parts and establishment of mathematical model.At the same time,the similarity between the mathematical model of synchronous generator and converter station is analyzed.Through mathematical deduction,it is concluded that one-side converter station is equivalent to virtual synchronous generator.2)The mechanism of mechanical and electrical characteristics of common synchronous generators is expounded.Comparing the similarities and differences between virtual synchronous generator and synchronous motor,and analyze the existing common VSG power frequency,excitation and current control strategies.On this basis,the control strategies of VSC-HVDC inverter side and rectifier side are proposed respectively.3)The function of virtual moment of inertia and virtual damping coefficient in flexible system is qualitatively analyzed,and the parameter tuning method is studied under relevant restrictions.According to different virtual inertia and damping coefficients,the possibility of using VSC-HVDC converter station controlled by virtual synchronous generator to participate in dynamic regulation of power grid and provide inertia support is studied..The control algorithm of virtual synchronous generator for two-terminal converter station is simulated and validated respectively.The simulation results show the effectiveness and feasibility of the proposed control strategy.