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Research On PV Grid-connected Control Technology Based On Virtual Synchronous Generator

Posted on:2020-09-28Degree:MasterType:Thesis
Country:ChinaCandidate:J LiuFull Text:PDF
GTID:2392330599453789Subject:Engineering
Abstract/Summary:PDF Full Text Request
With the increasing proportion of photovoltaic power generation in the grid,the impact and impact of grid-connected photovoltaic power on the grid is becoming increasingly obvious,which is not conducive to the stable operation of the grid.Because distributed generation is connected to the power grid by power electronic devices,it has a fatal disadvantage that it does not have the rotational inertia and damping components to maintain the stable operation of the system,which is the inherent characteristics of the dominant synchronous generator(SG)in the traditional power system.In this paper,a control strategy based on virtual synchronous generator(VSG)is proposed.This strategy uses a certain control algorithm to control the inverters,so that they have the same external characteristics as a synchronous generator,and have the similar frequency and voltage regulation performance of SG.The main contents of this paper are as follows:(1)The working principle of virtual synchronous generator is analyzed.The first part describes the characteristics of SG.The second part gives a brief introduction to the whole frame structure of SG.The third part clarifies the essence of SG work by combining the equivalent graph and equation.Secondly,the composition of VSG control system is explained concisely and in detail.The excitation system is related to reactive power regulation,and the governor is related to active regulation.(2)The mathematical model of virtual synchronous generator is analyzed.In the first part,the dq coordinate transformation is used to realize the decorrelation of the control variables.The second part divides the simulated prototype into two parts: rotor and stator,and builds models according to their corresponding governing equations.The third part is the model of the reactive power controller.The transfer function of the controller is determined and the control block diagram is given in combination with the relevant formulas and equations.The last part is the model of active power controller,which also builds the block diagram.(3)Modeling photovoltaic grid-connected power generation system in Matlab software.In order to prove the validity of the model,each part of the module is verified by simulation in Matlab software.It includes: main circuit,DQ converter,inverter,electrical modeling of VSG,mechanical modeling of VSG,excitation and motor modeling.(4)The simulation results of photovoltaic grid-connected generation control system are analyzed.This method is compared with droop control method in power and current,voltage and frequency of grid connection under normal conditions and system frequency fluctuation.Finally,it proves that VSG control method is effective.
Keywords/Search Tags:Photovoltaic Power Generation, Virtual Synchronous Generator, Voltage Regulation and Frequency Modulation, Virtual Inertia, Stability
PDF Full Text Request
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