现有的电力电子变压器(power electronic transformer,PET)拓扑所需高频变压器数目较多,体积大,为了解决该问题,采用一种高功率密度的 PET 结构,其仅需一台高频变压器可实现 PET 的高度集成.为保证所提拓扑稳定运行,通过分析模块化多电平变换器子模块电容电压波动机理,提出了模块化多电平变换器在超高调制比下降低子模块电容电压波动的方法;同时,针对模块化多电平直流变换器中桥臂间均压控制存在内移相角与桥臂间交换功率的相关性受功率移相角影响的问题,在考虑控制安全运行域的基础上,提出了桥臂电感的参数设计方法,可以降低该控制的复杂度.并在MALTAB/Simulink中搭建了仿真模型,以此验证了文中所提出的方法可以降低电容电压波动以及全工况下实现电压均衡.
Topological Structure and Control Strategy of Power Electronic Transformer Based on Integrated High-frequency Transformer
The existing topology of power electronic transformer(PET)demands a considerable number of high-frequency transformers and a large volume.To address this issue,we adopt a high-power-density PET structure,which merely requires one high-frequency transformer to achieve a high degree of PET integration.To guarantee the sta-ble operation of the proposed topology,we analyze the mechanism of capacitor voltage fluctuation of the submodules of the modularized multilevel converter and propose a method to reduce the capacitor voltage fluctuation of the submodules under the ultra-high modulation ratio.Meanwhile,aiming at the issue that the correlation between the internal phase shift angle and the exchanged power between the bridge arms is influenced by the power phase shift angle in the modularized multilevel DC converter,we put forward a parameter design method of the bridge arm inductance,which can lower the complexity of the control.Moreover,a simulation model is constructed in MATLAB/Simulink to verify that the proposed method can be adopted to reduce capacitor voltage fluctuation and achieve voltage equalization under all working condi-tions.The results verify the effectiveness of the proposed method.
power electronic transformermodular multilevel converterDC transformervoltage balance controlcir-culating current restrainmain circuit parametric design
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