Research On Application Of Hybrid Energy Storage System Based On Multi-level Converter In Wind Farm

Wind energy is a new energy source that is pollution-free and renewable,and it has attracted worldwide attention since many years ago.However,the characteristics of wind energy,such as volatility and intermittency,make the power grid bring hidden troubles when the wind power is connected to the grid.The addition of energy storage systems to compensate the system can solve the problems of wind energy fluctuations and intermittency.For this reason,this paper designed a hybrid energy storage module combining a lead-acid battery and a super capacitor to suppress wind power fluctuations,and cooperated with a modular multi-level converter module to output high-quality waveforms.Solved the main problems of the current wind power grid-connected operation,meet the grid side demand,increase two reliable and stable factors for the output of the wind turbine,and improve the stability of the grid-connected wind turbine operation.First of all,the overall structure of the system was designed to suppress the power fluctuation of the wind turbine and meet the main purpose of the grid-side demand.At the outlet of the fan,modular multi-level converter module,bi-directional DC/DC converter hybrid energy storage module and equalization module are added.The principle,topology and model of the modular multi-level converter module and hybrid energy storage module are described.Second,the system control strategy was studied.Modular multilevel converter module uses double closed-loop control strategy to stabilize voltage and current to ensure the system output high-quality waveform;hybrid energy storage module uses constant power method to absorb power when the fan output is higher than the grid side demand,and the output of the fan is lower than the grid When the side demand,the power is compensated;in the lead-acid battery part,the equilibrium control strategy is used to equalize the voltage of the single cell battery.This article improves on the original equalization method and designs a set of equalization strategies that are faster,less in charge and discharge times,and extended.The service life of the battery pack makes the system more reliable.Finally,the system is verified by matlab simulation.The constructed simulation circuit mainly includes two parts: a modular multilevel converter part and a hybrid energy storage power compensation part.The modular multi-level part includes the main circuit,the PWM circuit and the SPWM phase shift,and the inverse becomes three-phase alternating current.The hybrid energy storage power compensation part includes the active response of the system during grid dispatching and the power response that triggers the control strategy when the wind turbine output fluctuates,demonstrating the effectiveness of the system's control strategy and the feasibility of the overall construction.The simulation of the equalization strategy was followed to verify the excellent effect of the secondary improvement strategy.The simulation results show that combining modular multilevel converters with hybrid energy storage can save energy and stabilize power fluctuations.It can positively respond to grid dispatch,obtain good output waveforms,and improve the operation of wind turbines connected to the grid.stability.