斜坡式重力储能系统的并网控制研究

Research on Grid Connection Control of Slope Gravity Energy Storage System

重力储能是利用高度差以重力势能进行能量存储的系统,具有成本低、储能容量大、使用寿命长、对环境无污染、安全可靠等优点。斜坡式重力储能尤其适合在多山地且温差较大的地区进行规模化建设,拥有较高的转化效率。重力储能的存储介质是离散的重物块,会引起电机重复启动和停止,为了平滑斜坡式重力储能系统运行中重物块的间断切换所造成的并网功率波动,有必要研究重力储能系统经变流器并网的控制策略。根据斜坡式重力储能系统的工作原理和能量转换过程,构建相应的数学模型。考虑到斜坡式重力储能在风能和太阳能发电并入电网中的有功功率控制需求,采用通过背靠背双PWM变流器实现并网的方案。该方案中,机侧和网侧变流器分别采用基于定子电流d轴分量id=0、电压定向控制的双闭环控制策略,以达到控制重力储能系统在发电工况和电动工况过程中的并网功率,从而实现新能源发电并网后电力系统的稳定运行。利用Matlab/Simulink软件构建重力储能系统的并网仿真模型,通过分析仿真结果中的输出功率和电网侧电压、电流的波形,验证了所提出并网方案的有效性。

Gravity energy storage is a system that uses height difference to store energy by gravitational potential energy.It has the advantages of low cost,large energy storage capacity,long service life,no pollution to the environment,and high safety and reliability.Slope gravity energy storage is especially suitable for largescale construction in mountainous areas with large temperature differences,and has high conversion efficiency.The storage medium of gravity energy storage is discrete heavy blocks,which will cause the motor to start and stop repeatedly.In order to smooth the grid-connected power fluctuation caused by the intermittent switching of heavy blocks during the operation of slope gravity energy storage system,it is necessary to study the control strategy for grid connection of gravity energy storage system through converter.According to the working principle and energy conversion process of slope gravity energy storage system,the corresponding mathematical model is constructed.Considering the active power control requirements of the slope gravity energy storage when wind and solar power are integrated into the grid,a scheme of grid connection through back-to-back dual PWM converter is adopted.In this scheme,the double closed-loop control strategy based on stator current D-axis component id=0 and voltage directional control is adopted for the converters on the machine side and the grid side respectively to control the grid-connected power of the gravity energy storage system in generator operating mode and motor operating mode,so as to realize the stable operation of power system after new energy generation is connected to the grid.The grid connection simulation model of gravity energy storage system is built by Matlab/Simulink software.The effectiveness of the grid connection scheme is verified by analyzing the output power and the wave forms of voltage and current on the grid side in the simulation results.