适用于高压大容量MMC-HVDC系统的改进低开关频率均压控制策略

发布时间：2018-05-05 21:42

本文选题：高压直流输电 + 模块化多电平换流器　；参考：《中国电机工程学报》2017年05期

【摘要】：模块化多电平换流器(modular multilevel converter,MMC)应用于柔性高压直流输电(voltage sourced converter based high voltage direct current,VSC-HVDC)系统时,具有功率模块数量多、桥臂电流大等特性,导致换流阀开关损耗高、开关器件散热困难。传统排序均压算法功率模块投切为随机过程,开关频率很高,难以满足实际工程需求。首先分析MMC功率模块的充放电规律,分析功率模块投切对电容电压均衡控制的影响机理;在此基础上,推导传统电压排序均压算法的开关频率上下限解析式。对现有的一种固定功率模块轮换数的低开关频率均压算法,分析开关频率和均压效果的优缺点。然后,通过推导功率模块轮换数与均压特性的关系式,提出一种改进的低开关频率均压策略。该策略在开关频率下限解析式的基础上,通过闭环控制每个控制周期功率模块轮换个数,实现MMC均压特性和开关频率的优化控制。最后,利用±350 k V 1000MW MMC-HVDC系统实时硬件在环(real-time hrdware in the loop,HIL)仿真测试系统,对两种低开关频率均压策略进行对比验证。
[Abstract]:The modular multilevel converter / converter (Modular multilevel converters) is used in the flexible HVDC / voltage sourced converter based high voltage direct current VSC-HVDCC system, which has the characteristics of large number of power modules and high current of the bridge arm, which results in high switching loss of the converter valve and difficulty in the heat dissipation of the switching device. The power module of the traditional equalization algorithm is a random process, and the switching frequency is very high, so it is difficult to meet the practical engineering requirements. Firstly, the charge-discharge rule of MMC power module is analyzed, and the influence mechanism of power module switching on capacitor voltage equalization control is analyzed. On this basis, the analytical formula of switching frequency upper and lower limits of traditional voltage sorting and voltage equalizing algorithm is derived. The advantages and disadvantages of switching frequency and voltage equalizing effect are analyzed for a low switching frequency equalizing algorithm with fixed power module rotation number. Then, by deducing the relationship between the rotation number of power modules and the voltage sharing characteristics, an improved low switching frequency voltage sharing strategy is proposed. Based on the analytical formula of the lower limit of switching frequency, the optimal control of MMC voltage sharing and switching frequency is realized by controlling the rotation number of power modules in each control cycle in closed loop. Finally, two low switching frequency voltage-sharing strategies are compared and verified by using 卤350kV 1000MW MMC-HVDC system real-time hrdware in the loopHILs.
【作者单位】：电力电子与电气驱动重点实验室(中国科学院电工研究所);
【基金】：国家自然科学基金项目(51541706)~~
【分类号】：TM721.1;TM46

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