三相固态变压器功率平衡控制策略研究

Research on Three-phase Modular Cascaded Solid State Transformer Power Balance Control

固态变压器作为现代智能电网的关键设备之一,得到国内外电力电子与电力系统等领域学者的广泛关注与研究。低电压/功率等级的模块级联型结构减小了在高电压/功率的传输时开关管电压电流应力。然而,这种拓扑结构引入模块之间电压/功率不平衡问题,可能产生开关管过压、过流及电网电流谐波增加等影响。分析了一种新颖的整流级共同占空比控制、中间级电压跟随控制、逆变级PR控制的三相固态变压器均压均功率系统控制策略以及可能影响电压及功率平衡的模块参数,理论与仿真验证该系统控制策略有效性。三相15 kW原理样机验证控制策略可实现输入侧单位功率因数、电压功率平衡及能量双向传输功能。

Solid state transformer(SST),one of the key equipment in smart grid,has got great attention and resear-ch in both the areas of power electronics and power systems.The topology of modular cascaded SST decreases the voltage and current stresses,but it may cause issues such as overvoltage or overcurrent in each module and even the increase of grid current harmonics.This paper focuses on the model analysis of a systematic three-phase SST balance control strategy that the common-duty-ratio control,voltage feedback control and PR control is applied to rectifier,dual active bridge(DAB)and inverter stages,respectively.The power balance influenced factors,obtained from model analysis,has been studied in both theory and simulation.A15kW experimental prototype is designed and built to prove the functions of PFC,voltage/power balance and bi-directional power flow.