| With the rapid development of new energy generation technology,the frequency stability of power grid is threatened.At the same time,the electric energy storage technology is becoming mature,and the research of electric energy storage becomes popular what is used in the frequency regulation of the power grid.Battery energy storage technology has become an important means of frequency modulation in power system due to its advantages such as low construction cost,relatively mature technology and fast response ability.Based on the existing achievements,this paper makes the following studies:Firstly,the research status of battery energy storage participating in power grid frequency modulation is analyzed.Aiming at the shortcomings of the existing research,a control strategy of power grid frequency modulation considering the state of energy storage battery is proposed.The core content of this paper is mainly divided into two parts.First,a State of Charge(SOC)estimation method for energy storage battery based on equivalent circuit model is proposed.In order to improve the estimation accuracy of battery SOC and avoid the algorithm being too complicated and occupying too many hardware resources,the first-order RC equivalent circuit model of battery is improved in this paper,and the hysteretic voltage of battery in the process of charge and discharge is extracted as a parameter variable for online identification.Then,the Iterative Smooth Variable Structure Filter(ISVSF)was used to estimate the SOC with the state space equation of the circuit model.Finally,the simulation results proved the effectiveness of the proposed estimation method.Secondly,a comprehensive frequency modulation Control strategy is proposed.The strategy is based on area control error(ACE)and area regulation requirement(ARR)to allocate the output of conventional generating set and energy storage battery.Then the comprehensive control parameters are set according to the state parameters of each energy storage battery pack estimated in the above research,so as to achieve the effect of controlling the power output of each battery group according to the battery state of each group.Due to the ACE frequency modulation control method can quickly restore the transient frequency deviation and cannot effectively restore the steady-state frequency deviation,and ARR frequency modulation control method can effectively restore the steady-state frequency deviation but cannot fastly recovery transient frequency deviation,so this paper uses two kind of frequency modulation mode between sensitivity and frequency deviation to the size of the switching frequency modulation control method,The power grid frequency can be restored quickly and stably.Finally,this paper set up the simulation based on the comprehensive frequency adjustment control strategy by MATLAB/SIMULINK,and the economy of the energy storage system is analyzed based on the simulation results.Simulation and economic analysis results show that,compared with ACE or ARR control methods,the proposed integrated control strategy can not only effectively reduce the frequency deviation,but also reduce the total output peak of the energy storage battery,optimize the output of each battery,prolong the life of the battery,and reduce the operating cost.Therefore,the control strategy is of great significance to the safe and economic operation of the energy storage power station. |
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