三相七电平H桥换相有源钳位变流器

可用于中压系统的少元件型多电平变流器具有广阔的应用前景,通过将半桥单元嵌入传统的三相H桥三电平变流器的直流母线,演绎了一种新颖的三相七电平变流器拓扑,该少元件型有源中点钳位多电平拓扑利用H桥的开关网络实现换相和电平倍增,获得了对称结构,规避了中点电压偏移问题,并拥有足够的冗余模态,便于实现直流母线电容的均压控制。详细分析了其工作原理,深入揭示了该拓扑的结构特点,设计了两层复合均压控制策略,并给出了一种新型的基于目标波—状态矢量函数的多电平脉宽调制(PWM)算法,用于新拓扑的驱动脉冲的生成。最后,建立了3.3kV/5 MW并网变流器MATLAB/Simulink仿真模型,仿真结果验证了工作原理、调制算法、均压控制策略的正确性。

Three-Phase Seven-level H-bridge Commutated Active Clamped Converter

To acquire a multi-level converter with reduced device count applied in the three-phase mid-voltage system, two half-bridge power electronic building blocks(PEBB)are inserted into the DC side of a typical three-phase H-bridge converter, a novel seven-level converter is demonstrated. By using the H-bridge as a level doubling network, the natural point voltage imbalance of the conventional natural-point clamped converter(NPC)is bypassed. Moreover, because of the symmetrical structure, a rational control scheme for the DC voltage balancing is adopted to facilitate active current superposition and switching states selection. The operation principle is analyzed in detail and the structure characteristics of the topology are deeply revealed while a two-layer compound control strategy for DC voltage balancing is designed. A novel multi-level pulse-width modulation(PWM)algorithm based on objective wave-state vector function is proposed for use in drive pulse generation in the novel topology. The MATLAB/Simulink model of 3. 3 kV /5 MW grid-connected converter is built to verify the validity of the operation principle, modulation algorithm and voltage balancing control strategy. This work is supported by National Natural Science Foundation of China(No. 51177147)and Zhejiang Key Science and Technology Innovation Group Program(No. 2010R50021).