提高MMC高效电磁暂态模型仿真精度的方法

对基于戴维南等效原理的模块化多电平换流器（modular multilevel converter， MMC）桥臂电磁暂态仿真详细模型的数学原理进行了分析，发现当仿真过程中发生故障或开关动作等引起网络结构变化时，由于电容电流会发生突变，当采用梯形积分法计算时会引入计算误差。为了解决这一问题，提出了一种通过求解突变后的非状态变量来消除计算误差的方法，在PSCAD/EMTDC下对比分析了误差消除前后在开关变化时刻的电容电压，验证了本方法的正确性和有效性。同时，搭建了单端101电平MMC-HVDC仿真系统，验证了本文提出的改进计算模型的正确性。

Improvement of High-Efficiency Electromagnetic Transient Model Simulation Precision of MMC

This paper analyzes the mathematical principle of the electromagnetic transient simulation detailed model of modular multilevel converter （MMC） arm based on the Thevenin's equivalent principle. It is found that when the network structure changes caused by fault or switch of breakers during simulation process， the calculation error may be introduced when using trapezoidal integration method because of the mutation of the capacitor current. To solve the problem， this paper proposes a method to eliminate the calculation error through solving the non-state variable after the mutation. We compare the capacitor voltage before and after the elimination of the calculation error at the moment of switch changing in PSCAD/EMTDC， and verify the correctness and validity of the method. Meanwhile， we establish a single-terminal 101-level MMC-HVDC simulation system， whose results verify the correctness of the proposed improved calculation model.