| The development of demand response technology has changed the traditional role of users,which is conducive to the dynamic coordination of resources on both sides of power supply and demand.As a form of demand response,the electric vehicle is favored by its unique advantages.The dynamic characteristics of electric vehicles participating in frequency modulation refer to the relationship between the input quantity and the output quantity in the dynamic process,that is,the process of the dynamic response control command of the electric vehicle and the change of the system state quantity during the system frequency modulation process.From the perspective of system,studying the dynamic characteristics of electric vehicles participating in frequency modulation is one of the effective ways to improve system flexibility.To study the dynamic characteristics of electric vehicle frequency modulation,we must establish a dynamic model of electric vehicles participating in frequency modulation.The number of electric vehicles is large and scattered,individual parameters are difficult to count one by one.Therefore,the communication time delay,first-order link time constant,and frequency response coefficient of the dynamic model are all based on the average parameters.It is seriously deviate from the actual response.The needs of electric vehicle users are all different.These differences should be considered when scheduling electric vehicles in a form of clusters.Regarding the issues above,the dynamic model of cluster electric vehicles participating in frequency modulation is taken as the starting point.The model and strategy of traditional electric vehicles participating in frequency modulation are improved and optimized.As to the dynamic model of electric vehicles participating in frequency modulation,the first-order inertia link and time delay link are used to derive the dynamic response model of the cluster electric vehicles.The communication time delay link is set to the single-input and double-output random variables which satisfies the uniform distribution.When the variable does not satisfy the uniform distribution,it can be processed by the histogram equalization criterion which can convert it into a uniform distribution.Then a first-order time-delay dynamic model of cluster electric vehicles participating in frequency modulation is established based on the traditional power system frequency modulation model and the dynamic characteristics of the model are discussed.As to the control strategy of electric vehicles participating in frequency modulation,Monte Carlo simulation which can be used to generate the probability function of the time of electric vehicle users arriving at the company's vehicle to grid control center and the initial state of charge is used in this paper.The control strategy of cluster electric vehicles participating in frequency modulation,which takes the diversity of the difference of users' demands and travel rules into account,such as access time,off-grid time,initial state of charge and termination state of charge is proposed.The control module written by S function realizes the change of idle,one-way charging and two-way charging of electric vehicles.In summary,the rationality of the proposed control model and the feasibility of the frequency modulation strategy are verified in this paper through multi-scenario quantitative simulation of the examples.The simulation results of the third chapter show that the dynamic response of the first-order time-delay dynamic model established in this paper is closer to the actual response than the existing model.It can suppress frequency overshoot and frequency fluctuations.The simulation results in the fourth chapter show that the proposed control strategy is feasible and effective.The first-order time-delay model can be used to ensure the user's demands and suppress the frequency fluctuation. |
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