| The rapid development of wind power technology brings economic and environmental benefits.However,due to the intermittent,volatility,randomness and uncertainty of wind energy,it also brings many problems to the power system break it's safe and high-quality operation,especially the frequency stability problem is more prominent in the high wind power permeability system,and the traditional frequency control method can no longer meet the system frequency stability requirements.Based on the analysis of the system structure,operation mode,operation characteristics and control mode of the doubly-fed induction generator and battery energy storage system,the frequency control characteristics,control system and control strategy of the two systems are studied systematically,and the relevant models are established.In order to realize the frequency control,DFIG is added with frequency response unit,which participates in the frequency modulation of the system through rotor kinetic energy control or loaded reduction operation.BESS adopts droop control,and its active power output can be quickly adjusted to respond to the change of system frequency.By analyzing the frequency control characteristics of DFIG,BESS and thermal power unit,the three are complementary in terms of frequency modulation speed and frequency modulation capacity,that is BESS has fast frequency modulation speed and small frequency modulation capacity,the thermal power unit has slow frequency modulation speed and large frequency modulation capacity,and DFIG has medium frequency modulation speed and frequency modulation capacity.Aiming at the primary frequency modulation of the system,a frequency control strategy based on the principle of frequency division is proposed to determine the active power output of the three elements.Aiming at the secondary frequency modulation of the system and considering the capacity demand,based on regional control criteria proposed a joint frequency control strategy,which takes into account are thestandby size,economy,safety and regional control requirements,to reduce the burden of thermal power units and is conducive to rapid restore the frequency stablility.On the MATLAB/Simulink platform,a simulation model of the combined system is established,and a simulation study is carried out.The results show that the proposed combined frequency control strategy is more suitable for the power system with high wind power permeability.About capacity optimization of BESS,this paper puts forward comprehensive considerate FM technology demands and economy in order to realize the objective function minimum energy storage capacity,based on grid frequency stability index and economy index established multi-objective mathematical model to optimize the capacity of BESS.To avoid falling into local optimal solution,using non-dominated sorting genetic algorithm with elitist strategy to achieve optimal capacity,and its effectiveness is verified by an example. |
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