For the planning, operation and control of multiterminal voltage source converter (VSC) based high-voltage direct current (HVDC) (VSC-MTDC) systems, an accurate power flow formulation is a key starting point. Conventional power flow formulations assume the constant frequencies for all asynchronous AC systems. Therefore, a new feature about the complex coupling relations between AC frequencies, DC voltages and the exchanged power via VSC stations cannot be characterized if VSC-MTDC systems are required to provide cross-regional frequency responses. To address this issue, this paper proposes a comprehensive frequency-dependent power flow formulation. The proposed approach takes the frequencies of asynchronous AC systems as explicit variables, and investigates the novel bus models of the interlinking buses of VSC stations. The proposed approach accommodates different operation modes and frequency droop strategies of VSC stations, and considers the power losses of VSC stations. The effectiveness and generality of the developed approach are validated by a 6-terminal VSC-HVDC test system. The test system presents the characteristics of the coexistence of numerous VSC operation modes, the absence of slack buses in both AC and DC subsystems, and diversified grid configurations such as point-to-point integration of renewable energy sources and one AC system integrated with multiple VSC stations.

中文翻译：

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考虑跨区域一次频率响应的多端子VSC-HVDC系统的综合潮流方法

对于基于多端子电压源转换器（VSC）的高压直流（HVDC）（VSC-MTDC）系统的规划，操作和控制，准确的潮流公式化是一个关键的起点。常规潮流公式假设所有异步交流系统的频率都是恒定的。因此，如果要求VSC-MTDC系统提供跨区域的频率响应，则无法表征有关交流频率，直流电压和通过VSC站进行的交流电之间的复杂耦合关系的新功能。为了解决这个问题，本文提出了一种基于频率的综合潮流公式。提出的方法将异步交流系统的频率作为显式变量，并研究了VSC站的互连总线的新型总线模型。所提出的方法适应VSC站的不同操作模式和频率下降策略，并考虑了VSC站的功率损耗。该开发方法的有效性和通用性已通过6端子VSC-HVDC测试系统进行了验证。该测试系统展现了多种VSC操作模式并存，AC和DC子系统中都没有松弛总线以及多种电网配置（例如可再生能源的点对点集成以及一个集成了多个AC的AC系统）的共存特征。 VSC站。