抑制电流纹波的模块化多电平直流变换器移相调制策略

模块化多电平直流变换器在采用传统载波移相脉宽调制时,如果各模块的输入及输出电压不一致,就会在电感上产生更大的电流纹波,增大电感的损耗,同时也不利于滤波器件的优化设计.针对这种情况,文中通过对电流纹波的频域分析,揭示了传统移相调制技术存在的问题,并确定了电流纹波幅值、各模块输入/输出电压与载波移相角之间的关系.以电流纹波中开关频率次谐波幅值最小为目标计算各模块的载波移相角,根据不同的工况调整移相角的算法,进而实现了一种电流纹波抑制的调制策略.对三模块级联的模块化多电平直流变换器进行了软件仿真和实验测试,仿真和实验结果都表明在各模块输入及输出电压不相等工况下,所提控制策略能够有效地抑制电流纹波,从而验证了所提控制策略的正确性和实用性.

Phase-shifted Modulation Strategy of Modular Multilevel DC/DC Converter for Current Ripple Suppression

In the modular multilevel DC/DC converter, the traditional phase-shifted carrier pulse width modulation (PWM) leads to the larger inductor current ripple when the modules have different input and output voltages. As a result, the inductor loss increases and the optimal design of filter devices are difficult as well. Aiming at this problem, through the frequency-domain analysis of current ripple, this paper reveals the problems of traditional phase-shifted modulation technique. In addition, the relationship among the current ripple, input and output voltages of modules and carrier phase-shifting angles are analyzed. The carrier phase-shifting angle of each module is calculated with the goal of minimizing the switching frequency harmonic amplitude in the current ripple. The calculation method of the phase-shifting angle is adjusted according to different conditions, and a modulation strategy for current ripple suppression is realized. Finally, the software simulation and experimental test of the modular multilevel DC/DC converter with three cascaded modules are carried out. Both simulation and experimental results show that the proposed control strategy can effectively reduce the current ripple when the input and output voltages of each module are unequal, which verifies the correctness and practicability of the proposed control strategy.