采用下垂控制的直流配电系统高频振荡分析及控制

Analysis and Control of High-frequency Oscillation for DC Distribution System with Droop Control

针对直流配电系统的高频振荡现象,以下垂控制的辐射状直流配电系统为研究对象,建立了电压源型换流器、直流线路和恒功率负荷的频域模型,进一步建立了直流配电系统的频域降阶模型。推导了频域下系统参数对高频振荡频率影响的解析式,分析了下垂控制系数、直流线路以及负荷参数变化对系统振荡频率的影响,发现下垂控制器和恒功率负荷的负阻尼特性易引发高频振荡。据此,文中提出了基于线路参数的前馈补偿下垂控制方法和改进虚拟电阻的控制器设计方法,并对补偿前后系统的稳定性进行了比较。通过频域、时域仿真验证了理论分析的正确性以及所提方法的有效性。

Aiming at the phenomenon of high-frequency oscillation in DC distribution systems,the frequency domain models of the voltage source converter,DC line and constant power load are established regarding radial DC distribution system with droop control as the research object.And the frequency domain reduced-order model of DC distribution systems is further established.The analytical expression of the influence of system parameters on high-frequency oscillation frequency in frequency domain is derived.The influences of the droop control coefficient,DC line and load parameters change on the system oscillation frequency are analyzed.It is found that the negative damping characteristics of the droop controller and constant power load tend to cause the high-frequency oscillation.Based on this,the droop control method of feedforward compensation based on line parameters and the controller design method of the improved virtual resistance are proposed,and the stability of the system before and after compensation is compared.The correctness of the theoretical analysis and the effectiveness of the proposed method are verified by the simulations in frequency domain and time domain.