论文部分内容阅读
在基于电压源型换流器的柔性高压直流输电(voltagesourced converter based high voltage direct current,VSC-H-VDC)场合,由半桥和全桥子模块构成的混合型模块化多电平变流器(modular multilevel converter,MMC)因具备直流短路故障自清除能力,引起了广泛的研究.而大容量MMC子模块电容的质量、体积大,成本较高,逐渐成为其取得更广泛应用的限制因素.分析并建立了混合型MMC子模块电容电压基频纹波系数与桥臂负电压以及功率因数之间的函数关系.根据该函数,提出一种混合型MMC的参数设计方法使子模块电容最小,在提高MMC功率密度的同时降低了子模块的成本和体积.同时,对比传统的桥臂参考电压始终为正的混合型MMC,在直流电压和桥臂电流有效值相等的情况下,建立了桥臂参考电压存在负电压的混合型MMC的功率传输特性函数,并求出了函数的最优解.最后,通过+160 kV混合型MMC的对比仿真验证了所提设计方法的正确性和有效性.“,”Modular multilevel converter (MMC) mixed with half-bridge submodules and full-bridge submodules (SMs) has attracted extensive research due to its dc short circuit fault handling capability in voltage source converter based high voltage direct current (VSC-HVDC) transmission systems.The bulky and expensive SM capacitance is one of the major drawbacks of the large capacity MMC.The functional relation between the fundamental ripple factor of the SM capacitor voltage and the negative part of the arm reference voltage,power factor was investigated in this paper.Additionally,this paper proposed a circuit parameter design method in order to minimize the SM capacitance of the hybrid MMC according to the function.The size and costs of the hybrid MMC can be reduced to a certain extent.Compared with the hybrid MMC with positive arm reference voltage,this paper set up the power transmission characteristics function of the hybrid MMC with negative arm reference voltage under the same dc voltage and RMS of arm currents conditions.The optimum solution of the function is also established.Finally,the validity of the proposed design method is verified by a +160 kV hybrid MMC comparative simulation.