In this study, a simple carrier-based pulse-width modulation (CBPWM) method is proposed for a three-phase three-level neutral-point-clamped converter with neutral-point (NP) balancing, which can be applied to three-phase three-wire (TPTW) and three-phase four-wire (TPFW) converter systems simultaneously. First, the effect of each switching state for the NP potential in TPTW and TPFW systems is analysed in detail, and a newly NP control strategy by reconstructing the switching state and adjusting the corresponding duration time is deduced for all operation conditions, it only needs to add the offset voltage to the modulation reference voltage to guarantee the NP balance and is easy to implement. Then, under all operating conditions, the mathematical model of NP current is derived and analysed to evaluate the low-frequency voltage oscillation in the NP. Finally, the effectiveness and feasibility of the proposed CBPWM strategy are verified by the experimental results based on a 12 kVA laboratory prototype.

中文翻译：

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具有中性点平衡的三相三电平三线和四线转换器系统的基于载波的统一PWM方法

在这项研究中，针对具有中性点（NP）平衡的三相三电平中性点钳位转换器，提出了一种基于载波的简单脉宽调制（CBPWM）方法，该方法可应用于三相三线（TPTW）和三相四线（TPFW）转换器系统。首先，详细分析了每个开关状态对TPTW和TPFW系统中NP电位的影响，并推导了通过重构开关状态并调整相应的持续时间的新NP控制策略，它只需要将偏移电压加到调制参考电压上可确保NP平衡，并且易于实现。然后，在所有操作条件下，推导并分析了NP电流的数学模型，以评估NP中的低频电压振荡。最后，基于12 kVA实验室原型的实验结果验证了所提出的CBPWM策略的有效性和可行性。