Research On Hybrid Energy Storage System To Suppress The Wind Farm Power Fluctuations

Rich deposits of wind energy as a clean and renewable energy, is an effective way to solve the current energy crisis and environmental degradation, the wind power technology more and more attention around the world. Wind power grid directly will adversely affect safe and stable operation of the power system, even lead the collapse of power grid, because of the wind's strong stochastic volatility. With large-scale energy storage technologies become more sophisticated, the installation of some capacity storage system is an effective means to solve wind power fluctuation problem in wind farms. A single type of storage mode is hard to combine the advantages of high power density and high energy density. Hybrid energy storage system composes of batteries and supercapacitors can learn from each other and play their respective advantages, the effection of wind power fluctuations stabilize is better. The research on hybrid energy storage system model founding, batteries and supercapacitors capacity configuration and coordination control strategy is of great significance.Firstly, briefly introduces the energy storage principle and properties of leadacid batteries and supercapacitors. On the basis of comparison of various existing equivalent model, the paper lead-acid batteries selection of PNGV equivalent circuit model, supercapacitors choose the classic equivalent circuit model. Build a single simulation model of batteries and supercapacitors in Matlab, the simulation results show the validity of the model.Then, propose a capacity configuration method of batteries and supercapacitors. According to a wind farm measured wind power data Fourier transform to spectral analysis, obtain the frequency distribution of wind power fluctuations as a basis for hybrid energy storage system power distribution. Considering wind power grid fluctuations requirements and storage capacity allocation of economic issues, get the best layer wavelet packet on wind power data and propose optimization wavelet function choice based on the Law of Entropy. Select three groups typical representative wind power data, with the wavelet packet decomposition to the optimum level by best wavelet function to get the desired grid power and each different frequency fluctuation component. The fluctuation component is divided into low frequency fluctuation part and high frequency fluctuation part as stabilize target to the two energy storage elements based on the batteries' high energy density and supercapacitors' high power density, and then we get the capacity configuration result after analysis and calculation.Finally, the paper put forward a hybrid energy storage system coordinated control method based on the SOC optimization. The work area of the energy storage element is divided into five parts according to the value of its SOC, and then the working status of the energy storage element is divided into the normal working state and non-normal working condition combined with the real-time charging and discharging state. Analysis all the non-normal working condition that may arise when the two storage elements cooperate with each other. By the real-time monitoring of the SOC, reallocates the charging and discharging reference power when the energy storage element under non-normal working condition to ensure that the SOC is within a normal range. This control method can ensure the smoothing effection as far as possible to extending the life of the energy storage device at the same time.