This paper concerns the issue of unbalanced output power among cells in cascaded H-bridge multilevel (CHBM) converters with conventional staircase modulation techniques under low modulation signals. This is a common condition in high-voltage/frequency hybrid power amplifiers (HPAs) consisting of a CHBM converter in series with a linear power amplifier (LPA). The online implementation of a modulation technique called split-voltage first-in first-out (SV-FIFO) that mitigates this issue is presented in this study. Differently from conventional techniques, it needs to take into consideration the magnitude and frequency of the reference voltage to generate the gating signals of the CHBM converter. This paper also introduces a design procedure for a series-type HPA and a means for generating online the gating signals of the CHBM converter, with SV-FIFO, and the reference signal for the LPA in closed loop with a mixed signal controller. Experimental results for a series-type HPA with a six-cell CHBM converter and a commercial LPA are provided to validate the design procedure of the HPA and demonstrate the enhanced (active) power balance of SV-FIFO and the effectiveness of the proposed control scheme for the HPA under transient and steady-state conditions.

中文翻译：

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一种提高混合功率放大器级联 H 桥多电平单元中功率平衡的新算法

本文涉及在低调制信号下采用传统阶梯调制技术的级联 H 桥多电平 (CHBM) 转换器中单元之间的不平衡输出功率问题。这是由 CHBM 转换器与线性功率放大器 (LPA) 串联组成的高压/频率混合功率放大器 (HPA) 中的常见情况。本研究介绍了一种称为分压先进先出 (SV-FIFO) 的调制技术的在线实现，该技术可缓解此问题。与传统技术不同的是，CHBM转换器的门控信号产生需要考虑参考电压的幅值和频率。本文还介绍了串联型 HPA 的设计过程和在线生成 CHBM 转换器门控信号的方法，使用 SV-FIFO，以及带有混合信号控制器的闭环中 LPA 的参考信号。提供了带有六节 CHBM 转换器和商用 LPA 的串联型 HPA 的实验结果，以验证 HPA 的设计程序并证明 SV-FIFO 的增强（有源）功率平衡和所提出的控制方案的有效性对于瞬态和稳态条件下的 HPA。