基于多目标性能优化的模块化多电平高频直流变压器移相控制策略

高频直流变压器(high-frequency DC transformer,HDCT)是直流电网的关键设备。为了满足中高压直流电网母线互联、电压变换、功率双向传输和电气隔离的需求,两端皆为模块化多电平变换器(modularmultilevel converter,MMC)结构的模块化多电平高频直流变压器(modular multilevel DC transformer,M2DCT)尤受关注。目前,移相控制是提高M2DCT性能的有效方法之一,而现有的移相控制方法主要优化M2DCT的单一特性。因此,为了同时降低电流应力,最小化功率损耗,改善软开关特性,实现M2DCT性能的多目标综合优化,提出了一种基于多目标性能优化的双相移(dual-phase-shift,DPS)控制策略。建立M2DCT电流应力,功率损耗和软开关特性的数学模型,提出多目标性能优化DPS的控制策略。通过M2DCT样机实验结果,验证了所提策略的有效性和优越性。

Phase-shift Control Strategy of Modular Multilevel High-frequency DC Transformer Based on Multi-objective Performance Optimization

The high-frequency DC transformers(DCTs)are important equipment in DC grids.To satisfy the requirements of buses connection,voltage conversion,bidirectional power transmission and electrical isolation in MVDC and HVDC grids,the modular multilevel DC transformer(M2DCT)with modular multilevel converter(MMC)topology is developed.Currently,the phase-shift control is one of the most effective ways to improve M2DCT performance.However,the existing phase-shift strategies mainly optimize a single characteristic of M2DCT.Therefore,to reduce current stress,minimize power loss and improve soft switching characteristics,achieving the comprehensive optimization for M2DCT,a multi-objective optimization control strategy based on dual-phase-shift(DPS)scheme is proposed in this paper.The mathematical model of current stress,power loss and soft-switching performers in M2DCT are established,and the control principle and framework of proposed multi-objective optimization DPS strategy is investigated.The experimental results in M2DCT prototype are presented to verify the correctness and effectiveness of the proposed strategy.