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与传统的等压级联拓扑相比，混合级联多电平逆变器能以较少的功率器件和隔离直流电源，输出较多的电平数，在增加功率密度、减小体积和降低成本等方面具有明显优势，因此在中高压大功率领域具有较大的应用价值和发展前景。然而，当采用常规的混合调制方法时，在部分调制比区间内，低压单元存在功率倒灌问题，使得其直流侧电压持续上升。为了避免这个问题，低压单元直流侧需采用能量可以双向流动的可控整流器，这使得系统的复杂性和成本大大增加。该文提出一种单极性载波层叠脉宽调制方法，可以在任意调制比的情况下避免功率倒灌问题，因此低压单元直流侧仍可以采用二极管不控整流器。仿真和实验结果验证了该方法的可行性和理论分析的正确性。“,”The hybrid cascaded multilevel converters, compared with the traditional cascaded ones, can generate more output levels with less switch devices and isolated sources, which have obvious advantages of increasing power density, reducing the size and cost of the system. However, with the general hybrid modulation, it appears that the high-voltage cell feeds power into the low-voltage cell in some modulation ratio interval, making the dc-bus voltage boost of the low-voltage cell. To avoid the problem, a bidirectional controlled rectifier is employed, increasing the complexity of the equipment and limiting its applications. A unipolar level-shifted pulse width modulation (LS-PWM) strategy was presented. With this strategy, the problem of reverse power can be avoided at any modulation ratio, and the diode rectifier is also available. Computer simulations and experimental verification based on this strategy were presented.