基于共载波调制的功率复合型模块化多电平固态变压器

Power integrated modular multilevel solid-state transformer with common carrier modulation

整体功率密度低、成本高是制约现有固态变压器(SST)在配电网进一步发展和应用的关键因素。提出一种功率复合型模块化多电平固态变压器(PI-MMSST)拓扑结构,将传统SST输入级和中间级进行功率复合,整个装置的功率变换级数从3级减少为2.5级,装置体积减小,功率密度有效提高;相较于现有混频调制SST拓扑,PIMMSST对功率分配方式进行改进,大大减少滤波器使用,节约了装置成本。此外,提出双层式子模块(SM)电容电压均衡控制策略,采用高频和基频目标信号共载波的方法进行调制,满足PI-MMSST正常工作需求。最后,通过Matlab/Simulink仿真验证该新型SST拓扑及其双层式均衡控制策略的可行性和有效性。

Low power density and high cost are the key factors that prevent the solid-state transformer(SST) from further application in the distribution network. Therefore,a novel power integrated modular multilevel solid-state transformer(PIMMSST) is proposed,aiming at reducing the device volume and increasing the overall power density through power integrating the input stage and intermediate stage of the conventional three-stage SST. Furthermore,as compared to the recently proposed mixed-modulation SST topologies,the PI-MMSST reduces the use of filters and saves the cost of whole system with the help of the new power distribution concept. Based on the common carrier modulation,the working principle of the topology is analyzed,and a dual-layer control strategy is proposed to achieve the voltage balance of the submodule capacitors. Simulation results from Matlab/Simulink validate the feasibility and effectiveness of the PI-MMSST topology and dual-layer control strategy.