基于改进虚拟同步发电机的构网型并联储能逆变器控制研究

Research on VSG control of grid-structured parallel fed inverter based on improved virtual synchronous generator

针对构网型变换器预同步过程时电力系统频率电压稳定性低导致变换器并网失败的问题,提出一种基于改进线性自抗扰控制(LADRC)的构网型变换器预同步控制策略。首先,采用无锁相环(PLL)控制策略,通过相位偏差的反馈控制对网侧电压的相位和幅值进行快速同步追踪,可避免因PLL精度较低和响应速度慢而引起的电力系统稳定性降低的问题。在此基础上,在有功频率支路模块的角频率输出端引入LADRC,这可以有效解决预同步控制过程中变换器输出电压频率存在过冲的问题,从而确保构网型变换器预同步控制顺利进行最终实现成功并网。最后,在MATLAB/Simulink仿真平台中搭建基于改进LADRC的构网型变换器预同步控制模型并进行仿真验证,结果表明所提控制策略可以有效抑制系统频率震荡,并能够加速系统预同步进程,确保构网型变换器安全运行最终实现成功并网,仿真结果验证了所提方法的有效性。

With the high proportion of new energy connected to power grid,multi-machine parallel coordinated control of energy storage inverter has become a key problem.Virtual synchronous generator(VSG)algorithm can provide damping,inertial support and stable voltage frequency for grid-forming energy storage system.However,the parallel synchronization,stability,state of charge(SOC)of each stack and impedance of each line should be considered in the coordinated control of parallel operation of multiple energy storage inverters.To solve this problem,a parallel mathematical model of energy storage inverter is established,the methods of reactive power allocation considering virtual impedance and active power allocation considering SOC are analyzed,and an improved VSG control strategy combining self-adaptive virtual impedance and SOC equalization is proposed.Finally,a model is built on the MATLAB/Simulink simulation platform,and the coordination control of each energy storage inverter is analyzed under the discharge condition with the all vanadium redox flow battery pack as the energy storage system.The validity of the improved VSG control strategy is verified,and the problem of over-discharge caused by voltage drop,reactive power and SOC difference caused by impedance difference is solved effectively,the utilization efficiency of the battery and the energy storage inverter is improved,and the life loss of the battery is reduced.