| The energy transition is a severe challenge and a major demand for sustainable development of China.Now,renewable energy development of China is in full swing and has become a key driving force for the energy transition.However.the continuous increase in the proportion of wind and solar power generation has led to a significant reduction in the inertia level of the system,and system stability has become prominent,which puts forward higher requirements for the inertia support of wind farms and photovoltaic power plants.The virtual synchronous generator(VSG)control technology emerged at the historic moment,which utilizes flexible and controllable converters to simulate the dynamic equations of synchronous generators to provide the system with excellent characteristics such as inertia and damping.Therefore,applying the virtual synchronous generator control technology to the wind and solar power generation system,and studying its stability to optimize the control parameters,has great value and practical significance for further improving the absorption capacity of wind and solar power generation and ensuring the safe and stable operation of the system.While the virtual synchronous generator control introduces inertia to improve the system stability,it also makes the system’s small signal stability more complicated.Thus,in this paper the small signal stability of PV-VSG and PMSG-VSG integrated power system is studied.And a parameter optimization design method is proposed.Then a stochastic small signal stability analysis method of PV-VSG and PMSG-VSG under the influence of stochastic power source is proposed.All this will be conducive to the safe and stable operation of the system.Firstly,taking into account the dynamic link of the wind and solar power source.the virtual synchronous generator control method is introduced into the PV and PMSG generation system,namely PV-VSG and PMSG-VSG.and its detailed mathematical model is established.Further establish its detailed electromagnetic model on the ADPSS platform,and use the electromagnetic-electromechanical hybrid simulation technology to realize the simulation of PV-VSG,PMSG-VSG and the actual system electromechanical model.Then,the small signal stability of the PV-VSG and PMSG-VSG integrated systems is analyzed through the linear model,and the influence of the VSG control parameters on the system stability is analyzed by eigenvalue trajectory.On this basis.a global optimization design method for VSG parameters is proposed.The results of small signal stability analysis are used to construct a quantitative model to reflect the comprehensive benefits of different parameter combinations.The optimization solution method of generalized search is used to optimize the the controller parameters under the complex condition of the constrained space.The time-domain simulation results of the single generator system and the actual system show that PV-VSG and PMSG-VSG with optimized parameters can provide sufficient inertia and damping under complex operating conditions.Finally,considering the influence of the random power source in the system,a stochastic small signal stability analysis method of the PV-VSG and PMSG-VSG integrated power system is proposed.The wind and solar integrated power system is described as a kind of Ito differential equation with random coefficients and incentives.Then the moment stability of the stochastic differential equation is considered,and the second-order moment stability is introduced on the basis of the linearized stochastic differential equation.The moment equation is derived through the Fokker-Planck equation related to the Ito differential equation,and the stochastic small signal stability of the system is analyzed through the second moment stability.The time-domain simulation shows that the proposed analysis method can fully take into account the effects of stochastic processes and obtain more accurate results. |
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