Research On Load Frequency Control And Optimization Considering Electric Vehicles Participating

At present,large-scale load and distributed generation are increasing.Its strong randomness and uncontrollability bring great challenges to the stable operation of power systems,especially affecting frequency.The increasing popularity of electric vehicles(EVs)has brought new solutions to grid frequency stability,because of EV's characteristics: fast responsibility,flexible and so on.The EVs can provide peak-to-valley,frequency-modulated and voltage-regulating services for the power grid through the vehicle to grid(V2G).However,there are many problems when electric vehicles participate in power grid frequency modulation: Ensuring the user's power demand,the effect between electric vehicles and load frequency control,the communication delay of the system and the uncertainity of electric vehicles are the key of electric vehicle participating in frequency regulation.It will determine the performance of frequency regulation directly.Therefore,it is significantly worthy to conduct research on these issues.The paper mainly includes the following contents:(1)An equivalent model and charging and discharging strategy for electric vehicles participating in frequency regulation is established.Firstly,the advantages of electric vehicle auxiliary power grid frequency regulation are analyzed.Based on the characteristics of electric vehicle distribution,a multi-level centralized management mode is established to uniformly charge and discharge electric vehicle.Then,in order to study the electric vehicle auxiliary frequency regulation in depth,based on the electric vehicle power battery circuit model,considering its charging and discharging characteristics,the transfer function equivalent model of the electric vehicle auxiliary power grid frequency regulation is established.Finally,considering the electricity demand of the electric vehicle owner,based on the elliptic function method,based on the state of the electric vehicle's expected state of the electric vehicle,a charging and discharging strategy for the auxiliary frequency regulation of the electric vehicle that can ensure the demand of the vehicle owner is established.(2)A coordinated optimization control strategy that considers both the auxiliary frequency regulation and the load frequency control of electric vehicles is proposed.Firstly,the traditional power system load frequency control model and electric vehicle participating in frequency regulation are chosen as research objective,and the multi-area control model of electric vehicle auxiliary frequency regulation in multi-level centralized control mode is established.Then based on this model,the battery characteristics of electric vehicle and the effective working range of secondary frequency regulation of power system are considered.The regional frequency deviation is combined with the integral of the time multiplied absolute value of the error(ITAE)as the objective function,and the optimization model of the controller is established and solved by the optimization algorithm.Finally,based on interconnected system,and simulating the random fluctuation of load,the above optimization control method is simulated and verified the proposed charge and discharge strategy that can maintain the state of charge of the electric vehicle.(3)A robust proportional-integral-derivative(PID)controller considering the communication delay of power system and the uncertainty of electric vehicles participating in frequency regulation is proposed.The multi-region interconnected power system model with communication delay and considering the uncertainty of the number of electric vehicles are chosen as research objective.After establishing the state space model of the system,the robust performance of the system is analyzed,and the controller gain,communication delay time and robustness are established.The functional relationship between performance indicators,followed by a mathematical proof of system stability.The optimization model of the system frequency controller is obtained,and the controller gain is solved by the optimization algorithm.Finally,in interconnected power system,the communication delay is added to the load frequency and the uncertainty of the number of electric vehicles is considered.The above controller is simulated and verified.