Secondary Frequency Regulation Strategy With Fuzzy Logic Method Of The Battery Storage In AGC

Challenges such as the increasing demand for energy and the problems of environment protection require us to take advantage of renewable energy,the volatility and uncertainty of renewable energy put pressure on power grid as large-scale renewable energy is connected to the grid.If only thermal generation sets are used for frequency regulation,too much action will result in the fatigue and wear of the sets.Furthermore,generator sets often find it difficult to meet grid frequency requirements.Rapid developments in battery storage technology,have been widely used in peeling and filling the valley and supporting for new renewable energy access,can provide a new means for controlling the frequency quality of a grid connected with large-scale renewable energy sources,with respect to frequency regulation,the battery storage system used here has a faster power regulation speed,which can respond more quickly to the load variation of the system than the generator set.The characteristics of the battery storage are more suitable for frequency regulation in a power system.Firstly,this paper analyzed two common control modes of the battery storage involved in secondary frequency regulation;the modes were based on the area control error(ACE)signal and the area regulation requirement(ARR)signal.The ACE control mode is beneficial to quickly recover the deviation of the transient frequency,but doing so can restrain the recovery of the steady-state frequency deviation.The ARR control mode can improve the recovery ability of the steady-state frequency deviation,but more capacity is required.Than,this paper developed an integrated control strategy and defined the switch timing and the output depth of battery storage.That is,when the system frequency is deteriorated and the frequency deviation |?f| is large,according to the fuzzy logic method,the output of the battery storage is smoothened on the basis of the state of charge(SOC)When the system is in good condition,the frequency deviation |?f| is small.The remaining frequency regulation capacity of generators can be used to improve the SOC,the experimental results show that the proposed strategy takes into account the advantages of reducing the maximum frequency deviation and the steady-state frequency deviation.A further comparison with the ARR control mode shows that the capacity and power requirements of the battery storage are smaller.Moreover,a further comparison with the ACE control mode shows that the effect of frequency regulation is better and the utilization rate of generators is higher.This control strategy can promote secondary frequency regulation.Finally,different from the conventional strategy in frequency regulation,signals are allocated to energy storage systems and conventional units in a fixed proportion.In this paper,according to empirical mode decomposition method,the frequency regulation demand signals are decomposed into high frequency and low frequency parts to be borne by energy storage and conventional units,respectively.and the use of empirical mode decomposition(empirical mode decomposition,EMD)will demand FM signal into high frequency and low frequency respectively by the energy storage and conventional unit commitment.On the basis of existing single fuzzy control,the innovative double-level fuzzy control method not only plays a role in smoothing the stored energy response power,but also adaptively adjusts the EMD filter order online according to the real-time SOC and the response power.The example shows that the proposed control strategy can smoothen the fluctuation of energy storage and reduce the coordination demand of energy storage capacity,and improve the economy of energy storage participation in frequency regulation.