Research On Microgrid Synchronization And Stability Based On Robust Control

Nowadays,with the increase in energy demand and the waste of environmental resources and other challenges,Distributed Generation(DG)has gradually made its way into the modern power distribution system.As a small low-voltage power supply network,microgrids are now widely used which includes at least one distributed power generator.If the microgrid and the Grid are connected,the voltage and frequency of the microgrid are required to meet certain standards in order to synchronize the connection;otherwise,it will impact the stable operation of the grid system and even damage the distributed power supply and other equipment.In this paper,a comprehensive controller is used to design a robust controller to solve the problem of synchronization and stability between the microgrid and the main grid.This article first explains the basic concept of the microgrid and introduces the μ comprehensive analysis method.Classic control strategies such as PI control and PQ control rely on accurate physical models which is very difficult to deal with.The emergence of robust control theory makes up for the deficiencies of the above control strategies,and enables the control system to ensure the expected dynamic quality and stability.It can design a robust controller by taking into account the effects of various uncertainties and using function constraints,so that it can make parameter changes within a certain range to ensure the overall stability of the system.Next,the uncertainty model of the linear system,as well as the internal and external stability of the system are explained.The standard robust control theory is introduced and the μ comprehensive analysis method is detailed.Second,the microgrid system structure design and modeling with multiple power sources are carried out.A distributed power generation system based on generators and based on inverters is designed so that the it can best includes different types of power generation systems.The modules of the microgrid are elaborated in detail,and the inverter structure and the PWM technology and PLL technology required for synchronization are explained;the duty cycle represents the uncertainty of the inverter module,so the duty cycle is established as the core The mathematical model of can receive the feedback signal d through the drive circuit of the inverter.Next,the structure of the diesel generator is given.In this paper,the Heffron-Phillips model is used to design a mathematical model based on the rotor angle,rotor speed,output of the terminal voltage converter and input of the terminal voltage converter as variables.The state space equation can better show the structure of the microgrid,so the state space equation of the microgrid system is established through the simultaneous inverter module and generator module.Third,the control scheme of the microgrid system is designed.A microgrid synchronization control scheme is designed and the robust controller is solved.First,the concept and standard of synchronization are explained,and then the synchronization control scheme of microgrid system based on robust controller is designed.Taking the robust controller K as the core,the input variables are the voltage difference and frequency difference of the microgrid and the main grid respectively.The robust controller K will minimize the error signal and when the standard is reached at the same time,the microgrid can be synchronized.Then,starting from the robust performance theorem,the robust controller is designed by using the μ synthesis method.This is the innovation of this paper.It can handle the designed microgrid model.Then determine the uncertainty model of the microgrid,use linear fractional transformation to process the uncertainty parameters of the system,build a structure with perturbed parameters,and minimize the singular structure value as the goal,and obtain the solution of the robust controller.Objective function.And select the weighting function,use the iterative method as the means,set the standard,use MATLAB to perform the iterative solution,get the simulation image,and reach the required standard,and finally get the designed robust controller.Finally,the simulation was carried out.A micro-grid system based on a robust controller built using simulink is designed,and then PV modules,BESS modules,and generator modules are given separately,and the parameter setting diagrams of each module and the relationship diagram of the generator modules are also given.Next is the simulation of the microgrid composed of a robust controller and a PI controller after receiving interference synchronously.The microgrid is analyzed after four scenarios of 32 ms,200ms,500 ms network delay and resistance change of 10% The comparison chart of frequency,electrical angle difference and active power,it can be observed that the fluctuation range and peak value of the frequency,electrical angle and power deviation of the robust controller are smaller than that of the PI controller,and the recovery speed is faster.At the same time,there is more settling time,and the active power oscillation can decay faster.It fully shows that the designed robust controller has good anti-interference ability and robustness,and can meet the expected synchronization requirements of the microgrid system.