模块化多电平储能单元改善并网风电场稳定性研究

Research on Stability of Grid-connected Wind Farms Improved by Modular Multilevel Energy Storage Unit

由于风能的随机性,风电场存在输出功率和连接点电压波动的问题,为提高风电并网稳定性,提出一种基于模块化多电平变流器(modular multilevel converter,MMC)拓扑和超级电容结合的储能单元结构。利用拟合函数建立风机数学模型,分析了基于异步发电机风电系统的运行特性;利用逆系统方法将MMC变流器等效电路模型进行线性解耦,对于解耦后子系统设计了以平滑有功功率和稳定接入点电压为目标的控制器。在Matlab/Simulink中搭建了在随机风波动时的仿真模型。仿真结果表明,基于MMC和超级电容的储能单元具有快速的有功和无功补偿能力,电网吸收的有功功率维持恒定,接入点电压稳定在额定值,从而降低了风速变化对电网的冲击,提高了风电并网的稳定性。

The randomicity of wind energy leads to the problem of fluctuation for both wind power and voltage.In order to enhance the stability of a grid-connected wind farm,a kind of energy storage unit based on modular multilevel converter（MMC） and super capacitor is presented.After establishing the mathematical model of wind turbine,the operation characteristics of wind power based on induction generator are analyzed.Inverse system method is developed to decouple the modular multilevel converter model and design the controllers for smoothing the output active power and stabilizing the voltage of the connected point.A simulation model is established with Matlab/Simulink.The simulation results show that the energy storage unit can rapidly compensate active power and reactive power of wind power.The power absorbed by the grid maintains constant and the voltage is kept at the setting value,which greatly enhances the power quality and the stability of wind power grid integration.