海上平台新能源单元主动式虚拟直流电机技术

针对海上平台多种新能源构成的电力电子化直流微网系统具有低惯量、弱阻尼特性，以及海上新能源强的间歇性所引起的微网系统稳定性问题，在风力发电单元、光伏发电单元的接口直流变换器中，采用主动式虚拟直流发电机技术，即接口变换器的控制系统中加入直流发电机机械方程和电磁特性方程，使其具有直流发电机惯量特性与阻尼特性，减缓在风光发电单元出力突变时对母线电压冲击，以提高直流微网系统惯性。建立虚拟直流发电机控制小信号模型，分析其中惯量系数和阻尼系数对于系统稳定性影响机理，利用小信号线性模型根轨迹获得参数的优化设计准则。仿真结果表明，采用所提出的虚拟直流发电机控制方法极大弱化风光间歇性对于母线电压冲击的影响，同时提高了弱电网特性下微网稳定性，验证了该方法理论正确性与可行性，在新能源独立供电弱网条件下具有广泛的应用前景。

The Active Virtual DC Generator Technique for the New-Energy Unit in the DC Microgrid of Offshore Platform

The power-electronics-based DC microgrid system composed of multiple new energy sources on offshore platforms is with low inertia, weak damping characteristics, and the stability of microgrid systems caused by the intermittent of offshore renewable energy sources. In the interface DC converter of wind and PV power generation unit, an active virtual DC generator technology is adopted. That is, the DC converter mechanical and electromagnetic equations are added to the control system of the interface converter, so that it has the DC generator inertia and damping characteristics, which reduces the impact on the DC voltage when the output of the wind-solar power unit changes suddenly, thereby improving the inertia of the DC microgrid system. By establishing a small-signal model of virtual DC generator control, the mechanism of inertia and damping coefficients on the stability of the system is analyzed. The root locus of the small-signal linear model is also analyzed, obtaining the optimal design criteria of the parameters, and the DC microgrid Simulink model is established. The results show that the proposed virtual DC generator control method greatly weakens the impact of wind-solar intermittent on the DC voltage impact, and improves the stability of the microgrid under weak grid characteristics. Meanwhile, the stability of the microgrid under the characteristics of the weak grid is improved. The method has a wide application prospect under the condition of a weak grid independent of renewable energy supply.