Unified Expression of Power Flow and Feasible Solution for DC Power Network with Multiple Control Strategies
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摘要: 通常计算含电压源换流器(VSC)交直流混合系统的直流潮流时,需按照直流侧VSC的控制策略列写对应的潮流方程。但是,由于控制策略的不同潮流方程会有多种表达式;随着柔性电网的发展,直流系统将形成由多种单一策略构成的混合控制策略,其表达式结构和维度均不一致;在计算基于实际情况下控制策略需要切换的潮流时,出现控制策略的切换,这些都为潮流计算带来了极大的不便。本文在分析直流侧VSC不同控制策略的基础上,通过定义新的直流节点类型,推导出含多种控制策略的直流电网潮流统一表达模型。该模型可以表征直流系统多种控制模式,形成模型的统一表达,具有统一结构和固定维度。当直流电网控制方式变化时,仅需修改少量参数,即可求出其稳态潮流,编程简单,实现方便。以含5端6线的VSC直流电网为例,验证了所提算法的准确性。最后,将此算法用于求解7端VSC-MTDC直流网络控制策略切换时的潮流,验证了其灵活性。Abstract: The DC power flow of the AC/DC hybrid system with voltage source converter (VSC) is usually calculated based on power flow equations corresponding to the control strategy of the DC side VSC. Power flow equations differ from the different control strategies. With the development of flexible grids, a hybrid control strategy of the DC system, consisting of multiple single strategies will present with the result of inconsistent power flow expression structures and dimensions. In addition, the control strategy switching in the actual situation brings great inconvenience to the power flow calculation. Based on the analysis of different control strategies of DC-side VSC, this paper deduces the unified expression model of DC grid power flow for various control strategies by defining new DC node types. The model can represent various control modes of DC system and form a unified expression of the model with a unified structure and a fixed dimension. When the DC power grid control mode switches, only a small number of parameters need to be modified. The programming is simple and convenient to implement. The accuracy of the proposed algorithm is verified by an example of VSC DC power grid with 5 terminals and 6 lines. Finally, the algorithm flexibility is verified by the 7terminal VSC-MTDC DC network in the situation of control strategy switching.
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Key words:
- voltage source converter /
- DC system /
- power flow equation /
- control strategy /
- unified expression
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