Identification Of Inertia And Damping Parameters Of Grid Inverter

In recent years,due to the consumption of nonrenewable energy and environmental pollution,the development of distributed generation technology has been widely concerned.With the continuous penetration of distributed generation,the power grid lacks the regulation of inertia and damping characteristics,which makes the balance of power and frequency fluctuation difficult to be smoothed in a short time.By applying the inertia and damping characteristics of synchronous generator to the inverter reasonably,the frequency fluctuation of power grid can be effectively suppressed and the frequency quality can be improved.Based on the external characteristics of grid-connected inverters with unknown models,quantitative identification of inertia and damping size is of great practical significance and application value for evaluating the inertia and damping of the whole power network.the paper proposes a unified VSG control strategy model by analyzing the governor and rotor motion equations of various VSG control strategies,and quantitatively identifies the inertia and damping of VSG by recursive least square method and genetic algorithm,respectively.The main contents of this paper are as follows:1.This paper introduces the background and significance of the research,and the research status of virtual synchronous generator technology and its inertia and damping parameters identification are described in detail.2.A unified VSG control strategy is proposed to equivalently simulate the gridconnected inverter of unknown model.Starting from the two modules of the virtual governor algorithm and the torque characteristic algorithm,the different implementation methods of VSG are elaborated,and the condition that the grid-connected inverter droop control strategy is equivalent to the VSG control strategy is discussed.And the unified grid-connected VSG model with static damping characteristics,to achieve the model equivalent of grid-connected inverter devices with inertia and damping characteristics,and to provide a model structure for grid-connected inverter inertia and damping.3.A recursive least square method is used to identify the parameters of inertia and damping of the unified VSG model in an ideal grid environment.the overall framework for parameter identification of grid-connected inverters is designed based on four aspects: excitation signal,external characteristic data acquisition,identification structure and identification algorithm.a VSG small signal model between active power and instruction power is established.the main parameter inertia and damping parameters in the VSG are identified by recursive least square method.the feasibility and effectiveness of the identification method are verified by MATLAB simulation.4.For non-ideal grid environment,the parameter identification of inertia and damping of the unified VSG model with PLL is carried out by genetic algorithm.Discusses the limitation of recursive least square method in identifying the parameters of unified VSG model including PLL,and establishes the state space model of unified VSG control strategy including PLL,which selects genetic algorithm for identification;To solve the problem of inaccurate identification of PLL PI parameters,the influence of different PLL bandwidth on the dynamic performance of the system is analyzed.The VSG system including PLL is reduced by using the principle of high order system.