特高压直流分层接入工程主回路稳态参数的分析与计算

Analysis and Calculation of Main Circuit Steady-State Parameters of UHVDC Transmission System with Hierarchical Connection Mode

在高压直流工程规划设计初期,需要对主回路稳态参数进行计算。首先把特高压直流分层接入系统简化为2个单层系统,归纳了单层工程主回路稳态参数计算方法。分析证明了低功率情况下提高换流器无功消耗的2种方法,相应地提出2种无功校验算法。在低功率情况下,分层工程若一个系统由于无功要求需提升直流电流,则会导致各系统无功校验后的直流电流不一致。针对此问题,提出了层间计算的解决方法。取各层系统直流电压的最低值作为层间控制电压,用此电压调整换流器的其他控制参数。调整后关断角、理想空载直流电压和换流器无功消耗的变化规律用M atlab分析给出。最后,用算例进行了稳态运行特性分析,验证了本文提出算法的合理有效性。

It is necessary to calculate the main circuit steady-state parameters at the beginning of the planning and design of HVDC projects. Firstly, this paper simplifies UHVDC transmission system with hierarchical connection mode into two single-layer systems, and concludes the method of main circuit steady-state parameters calculation for single-layer system. Then we analyze two ways to increase the reactive power of converters during low power transmission and present the corresponding reactive power validations. If the DC current increases due to its reactive power requirement in one system, the DC current through the hierarchical systems after reactive power validation will be different in low power condition. Aiming at this problem, we propose calculation between layers as a solution. The lowest DC voltage across the converters of hierarchical systems is selected to be the control voltage between layers, the other control parameters of the converters are adjusted according to this voltage. We analyze the changing characteristics of extinction angle, ideal no-load DC voltage, as well as the reactive power consumption of converter after adjustment with using Matlab. At last, we analyze the steady-state operating characteristics with an example, while verifying the reasonability and effectiveness of the proposed algorithm.