Research On Wind-storage Combined Frequency Control Of Energy Storage Type Hydraulic Wind Turbine

The flying development of the wind power industry has caused the wind power penetration rate(the proportion of wind power in the grid)to continue to increase.Because of the irregularity and variability of wind power and the loose coupling between traditional wind turbines and the grid,the anti-interference ability of the power system and the power quality are reduced.The frequency of the power system is one of the important criteria for measuring power quality.Maintaining frequency stability is a necessary way to stabilize the power system and promote the further development of the wind power industry.To improve the frequency stability under the high wind power penetration rate,this dissertation focuses on the power and frequency control of the Energy Storage Type Hydraulic Wind Turbine(ESHWT).By establishing mathematical models of various parts of the ESHWT,including the wind turbine,hydraulic transmission system,hydraulic energy storage system,and synchronous generator,the response characteristics of the ESHWT are analyzed,and a dual closed-loop power control strategy for the ESHWT is proposed.According to the frequency regulation control requirements,combined with frequency fluctuation characteristics,a variable parameter wind-storage combined frequency regulation control strategy is proposed.In view of the frequency change caused by the mismatch of power supply and demand on the grid side lead to,power control research is carried out.Starting from the analysis of the power transmission characteristics of the ESHWT when the frequency fluctuation causes the variable displacement motor speed to change,it is concluded that the small range fluctuation of the motor speed has a greater influence on the transmission power.Therefore,a dual closed-loop power control strategy for the ESHWT under the fluctuation of the motor speed is proposed.The simulation shows that the control method can accurately control the output power,which lays the foundation for the research of frequency control.For the primary frequency regulation control of the ESHWT,the wind turbine and the hydraulic energy storage system are combined to participate in the system frequency regulation control.First,it analyzes the system frequency fluctuation mechanism and the feasibility of wind turbines and energy storage systems participating in frequency regulation control.Then,according to the frequency fluctuation characteristics,the frequency regulation control method at different stages of frequency fluctuations is determined.Finally,based on the power control method,a variable parameter wind-storage combined frequency regulation control method is proposed.And the control parameters are adjusted according to the state of the wind turbine and the accumulator.Finally,a single-zone two-unit power system simulation platform including energy storage hydraulic wind turbines was established on Matlab/Simulink,and the frequency response of the system without frequency regulation control and with frequency regulation control was analyzed as the load instantly raised or reduced.The effectiveness of the wind-storage combined frequency control strategy is verified.And the feasibility of the power control method is verified by experiments on the 30 k VA wind turbine experimental platform.