| The survival and development of mankind are inseparable from energy,especially the rapid development of industry requires a large amount of energy support.At the same time,energy shortages and environmental pollution have become increasingly serious.The government vigorously advocates the development and utilization of clean energy,of which wind energy occupies an important position in the field of renewable energy.However,the power of wind power is volatile and unpredictable,and the grid’s voltage and frequency fluctuate frequently,which poses a huge challenge to the stability of the power system.The rapid development of energy storage technology provides new solutions to improve the power system’s ability to absorb wind power.With its flexible,fast,and controllable two-way energy through put capability,battery energy storage systems have broad application prospects in dealing with frequency and voltage fluctuations caused by the disturbance in grid-connected wind power.Based on PSASP,using its user-defined modeling function,the electromechanical transient model of the battery energy storage system was established.In the power grid with wind farms,the influence of the battery energy storage system on the frequency and voltage fluctuations caused by wind turbine disturbances was analyzed.Firstly,the structure and mathematical models of three wind turbine systems: squirrel cage asynchronous wind turbine,doubly-fed induction wind turbine,and direct-drive permanent magnet synchronous wind turbine were studied.The wind turbine model including blade model,mechanical transmission model and pitch angle control model were established.Wind speed model:Weibull distribution model and combined wind speed model were established.The analysis software PSASP used in the simulation and its own wind turbine model were introduced.Secondly,based on in-depth analysis of battery energy storage system’s structure,an electromechanical transient model of the battery energy storage system that can reflect the characteristics of the active power adjustment dead zone,the charge and discharge power limit,and the inverter reactive power support limit was established.In the 36-bus system,it was simulated that the established energy storage model could restrain the increase of frequency and voltage when the system had a load shedding failure.The validity of the model was verified.Thirdly,the established wind farm model was connected to the system,and the system frequency changes caused by gusts,gradual winds and random wind disturbances under different wind speeds were simulated and analyzed.The established battery energy storage system model was connected to the power grid containing wind farm,and the wind farm was set to be disturbed by wind speed to study the impact of energy storage on frequency changes.It was mainly aimed at comparing and analyzing the battery energy storage system under different active power and different access positions.Finally,for the purpose of improving the voltage stability of the power system,the voltage stability analysis function in PSASP was used to calculate the area with weak voltage stability in the power system containing wind farms.This area was used as the connection location of the battery energy storage system.The simulation verified that when the power grid containing wind farms experienced load reduction and wind power cut-off failures,the energy storage connected to the weak nodes could effectively suppress voltage fluctuations and enhance voltage stability.Moreover,the voltage suppression effect of energy storage access to weak nodes was better than access to other nodes. |
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