Research On Control Strategy Of Virtual Synchronous Generator Based On Feedback Linearization

Nowadays,fossil energy is gradually exhausted,and more and more countries are beginning to pay attention to renewable energy.In distributed power generation,the form of energy with renewable energy as the main body has been applied.Policies to develop and utilize renewable energy are an important part of many national energy strategies.Through power electronic conversion technology,the electric energy generated by renewable energy can be converted into electric energy that meets the standard.However,the distributed power generation unit with renewable energy as the main body has no rotating parts,and the inertia of output electric energy is almost negligible.This can lead to oscillations in the frequency and power of microgrid systems made up of large amounts of renewable energy when disturbances occur.In view of the above problems,in order to improve the power quality of the power grid,the virtual synchronous generator(VSG)technology is used in the control strategy to provide damping and inertia to the power grid.The control method of flux linkage compensation for the excitation part of the virtual synchronous generator through feedback linearization and the nonlinear control strategy based on the virtual synchronous generator microgrid system are studied.A coordinated control strategy for multiple virtual synchronous generators is studied.The main contents of this paper are as follows:1.Firstly,the mathematical model of the three-phase voltage source inverter is introduced.By modeling the mechanical and electrical parts of the virtual synchronous generator,the overall control strategy of the virtual synchronous generator is proposed.The simulation experiment of the proposed virtual synchronous generator model is carried out,and it is verified that the virtual synchronous generator can improve the inertia and damping of the output power.2.A control strategy based on feedback linearization to compensate the flux linkage of the virtual synchronous generator excitation part is designed.Firstly,by introducing low-pass filtering,the third-order state equation of the virtual synchronous generator is obtained to obtain the nonlinear dynamic model of the system,and then the design of the controller is simplified by the linearization method.Through simulation,the ability of the proposed strategy to maintain system stability during grid-connected and off-grid processes is verified,and the influence of linear quadratic regulator(LQR)on the system is analyzed.3.The nonlinear control strategy of virtual synchronous generator based on precise feedback linearization is studied.Firstly,a large-signal nonlinear dynamic model of virtual synchronous generator is established.Then,the large-signal model is converted into a secondorder linear system by feedback linearization,and a second-order voltage controller with voltage tracking capability is designed combined with the LQR method.It is verified by simulation that the system can remain stable when the load changes.Finally,compared with PI control,it is proved that the proposed control strategy has strong robustness.4.Using distributed communication network,combined with multi-agent model and consensus algorithm,the coordinated control strategy of multiple virtual synchronous generators in microgrid is studied.Firstly,the multi-agent system is introduced,and a multivirtual synchronous generator microgrid model considering distributed communication is described.Then,through feedback linearization technology combined with LQR,a distributed controller of smart microgrid with virtual synchronous generator is designed,and the closedloop stability of the controlled system is proved by establishing the Lyapunov function.Finally,under this distributed control strategy,the ability of the system to maintain voltage and frequency stability when the load changes is verified by simulation.