摘要
作为电能变换的关键环节,高电压大功率交交变流器在海上风电、远距离分频输电及海底输配电系统建设等低频输配电场合具有非常重要的作用。文中提出一种新的Y型大功率模块化多电平变流器(Y modular multilevel converter,Y-MMC)拓扑,只需6个等效桥臂即可实现直接交交功率变换,输出电压波形质量和功率特性均表现良好,其结构简单对称,且不存在环流。针对Y-MMC拓扑建立其dq坐标下的动态数学模型,实现了系统输入输出两种交流频率分量的解耦,在此基础上给出相应的控制策略,包括内环电流控制和外环功率控制,其物理概念清晰、控制结构简单、控制性能良好。进一步,在控制方案中引入无功分配系数,推导其与桥臂稳态调制度之间的解析关系式,并给出在对应优化目标下分配系数的最优解。Matlab/Simulink平台下的一系列仿真结果验证了所提出Y-MMC拓扑和数学模型的正确性及其控制策略的有效性。
As the key equipment for power conversion, a new high-power direct AC/AC modular multilevel converter topology in Y configuration, which is called Y-MMC, suitable for low frequency power transmission and distribution applications was proposed. Y-MMC can realize direct AC/AC power conversion with only 6 equivalent branches and has a satisfying performance in both output voltage quality and power characteristics. Y-MMC enjoys a simple and symmetric structure and has no circulating current problem. The dynamic mathematical model of the Y-MMC system in dq coordinates was deduced, where AC components with two different frequencies are decoupled completely. Corresponding control strategy was thoroughly discussed, including the inner loop current control and the outer loop power control. This paper also lays the emphasis on the optimization of reactive power distribution between main branches and assistant branches by introducing the reactive power distribution coefficients kl and k2 into the system control scheme. The analytical expressions between k~, k2 and the modulation degree of the Y-MMC branches were detailed deduced and the optimal solution was also provided. The validity of the Y-MMC topology and the control strategy as well as the theoretical analysis proposed in this paper was verified by computer simulation results.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2017年第6期1764-1776,共13页
Proceedings of the CSEE
基金
国家电网公司科技项目(52094016000C)~~
关键词
Y-MMC
低频输配电系统
数学模型
控制策略
无功优化
Y-MMC
low frequency power transmissionand distribution system
mathematical model
control strategy
reactive power optimization
