A practical modeling method of VSC-HVDC and DC-grid electromechanical transient in simulating bulk grid was put forward. The principle of building, the way realizing of each element and the major function of this model were stated. The practical processing was created as follow: interfaces with different integration step lengths used by VSC-HVDC and AC grid respectively, the way controlling frequency in isolated electric island, decoupling calculation of d-axis and q-axis current on phase impedance, integration of DC-grid including property of electromagnetic transient, and measures assuring fast and smooth regulation. Flow chart of whole calculation on VSC-HVDC and DC-grid in one small step was given. Comparisons of MMC-HVDC transmission system electromagnetic transient models in PSCAD and others indicate the validity of this model.%提出一种在大规模机电暂态仿真中建立电压源型换流器和直流电网模型的实用方法.阐述建立该模型的原则、各部分实现方法以及主要功能,并通过如下步骤实现所提方法.VSC换流器模型与机电暂态网络分别采用不同积分步长的模型接口;无源孤岛的频率控制方法;换相阻抗支路d、q轴电流解耦计算;考虑电磁特性的直流网络积分处理方法以及保证调节快速平稳的措施.给出完整的VSC换流器和直流电网解算流程.最后通过与PSCAD中搭建的MMC-HVDC电磁暂态模型对比等算例证明了所提方法的有效性.
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