含LCC-MMC串/并联混合直流的交直流系统潮流计算方法

Power Flow Calculation of AC/DC System With LCC-MMC Series/Parallel Hybrid HVDC

混合直流输电技术方案多样,直流系统拓扑结构复杂,目前的潮流算法面对复杂直流系统时建立数学模型存在困难,为此该文基于串联型、并联型混合交直流系统潮流计算进行研究。首先分析了白鹤滩、昆柳龙工程中混合直流系统的拓扑结构及稳态控制模式。然后根据换流站与单个换流器间状态变量的数值关系,对双极、多阀组换流站进行等效,导出了基于电网换相换流器(line commutated converter,LCC)和模块化多电平换流器(modular multilevel converter,MMC)的换流站潮流模型。在此基础上,通过分析换流站潮流模型间的内在联系,给出了串联型、并联型混合直流系统潮流模型建立方法,进而提出一种LCC-MMC串/并联混合交直流系统潮流交替迭代算法。最后,通过修改的IEEE 39节点串/并联交直流系统验证了所提模型及算法的有效性。

There are various technical schemes for the hybrid HVDC transmission,and rather complex structures for the topology of the DC system.Meanwhile,it is difficult for the current power flow algorithm to establish a mathematical model in the complex DC system.Therefore,this paper studies the power flow calculation of the series and parallel hybrid AC/DC system.Firstly,the topologies and steady-state control modes of the hybrid DC systems in the Baihetan and the Kunliulong projects are analyzed.Then,according to the numerical relationship of state variables between the converter station and the single converters,the bipolar and the multi-valve converter stations are equivalent,deriving the power flow model of the converter station based on the line commutated converter(LCC)and the modular multilevel converter(MMC).On this basis,by analyzing the internal relationship between the converter station power flow models,the establishment method of the power flow models of the series and parallel hybrid DC system is given.A LCC-MMC series/parallel hybrid AC/DC system power flow alternating iterative algorithm is proposed.Finally,the effectiveness of the proposed model and algorithm is verified by the modified IEEE 39-node series/parallel AC/DC system.