直流配电网的暂态稳定判据与电压分级协同控制研究

If the flexible DC voltage inertia and damping is considered as two major standard indicators for transient stability of distribution networks, the system stability can be significantly improved by various control methods. In DC distribution networks, the virtual capacitor obtained from the reserved energy of wind turbines and energy storing devices is calculated firstly, and then the control mechanisms of the voltage inertia and damping at various network levels are further analyzed. Following that, according to the transient stability criterion of multi-level DC distribution networks, the relationship between the controlled DC voltage inertia and damping, as well as the effect of their interaction on system stability margin are discussed. Then, based on the analysis of the system operating range adapted for regulation of the above two parameters, the cooperative control strategy of the voltage inertia and damping between multi-level DC distribution networks is proposed. Finally, this project will implement simulation and prototype platforms of a six terminals DC network containing wind turbines and energy storing devices, to verify the presented control strategy.

灵活可控的直流电压惯性及阻尼特性作为衡量直流配电网暂态稳定的主要指标，系统稳定性会因具有了多元调节方法而得到显著提高。本课题首先研究利用直流配电网内风电、储能隐含的储备能量获得虚拟电容的计算方法，进而分析各级配网电压的惯性与阻尼控制机理。其次，以多级直流配网的暂态稳定判据为依据，分析风电、储能具备的可控电压惯性、阻尼与系统稳定裕度间的相互影响，研究适于电压惯性与阻尼调整的运行范围及两种控制的结合方法，提出直流配电网多级电压惯性与阻尼的协同控制策略。最后，本课题将搭建含风、储的六端直流动模实验平台，对所提出的控制策略进行分析与验证。

灵活可控的直流电压惯性及阻尼特性作为衡量直流配电网暂态稳定的主要指标，系统稳定性会因具有了多元调节方法而得到显著提高。本课题首先基于常规发电机组的固有惯量定义，研究了利用直流配电网内风电、储能隐含的储备能量获得虚拟电容的计算方法，利用换流器的快速有功控制，虚拟出直流配电网可控的惯性响应，理论分析在不同运行情况下惯性控制策略所能提供的虚拟惯性裕度。其次，研究了直流配电网的暂态稳定特性，分析负载功率及直流电压波动后系统运行点的移动轨迹，阐述直流配电网的稳定运行机理，提出了直流配电网在暂态稳定恢复中应遵循的等电量原则，该原则可用于评估故障后系统的稳定运行能力，根据电压安全裕度内电容器最大允许的放电电量，计算直流电网稳定极限和直流故障切除时间，获得了直流电网的暂态稳定判据。再次，研究了直流配电网中换流站的功率控制模式在扰动中表现出的负阻抗特性增加了系统振荡失稳的风险，推导含恒功率负荷的直流配电网的小扰动线性化状态方程，理论分析了换流器出口振荡电压、电流作为可调节控制参数对直流配电网振荡特性的影响机理，并以直流电压与电流为状态反馈变量，提出了阻尼直流配电网振荡的控制策略，并通过系统极点配置，实现参数优化设计。最后，本课题搭建了含风、储的多端直流动模实验平台，对所提出的控制策略进行分析与验证。