Purpose

Multilevel inverter (MLI) is an established design approach for inverter applications in medium-voltage and high-voltage range of applications. An asymmetric design synthesizes multiple DC input voltage sources of unequal magnitudes to generate a high-quality staircase sinewave comprising a large number of steps or levels. However, the implications of using sources of unequal magnitudes results in the requirements of a large variety of inverter switches and higher magnitudes of the total blocking voltage (TBV) rating of the inverter, which increase the cost. The purpose of this study is to present a solution based on algorithms for establishing DC source magnitudes and other design parameters.

Design/methodology/approach

The approach used in this study is to develop algorithms that bring an asymmetric cascaded MLI (ACMLI) design close to symmetric design. This approach then reduces the variety of switch ratings and minimizes the TBV of the inverter. Thus, the benefits of both asymmetric design (generation of a large number of voltage levels in the output waveform) and symmetric design (modularity) are achieved. The proposed algorithms can be applied to a number of ACMLI topologies, including classical cascaded H-bridge (CHB). The effectiveness of the proposed algorithms is validated by simulation in Matlab-Simulink and experimental setup.

Findings

Two new algorithms are proposed that reduce the number of variety of switches to just three. The variety can further be reduced to two under a specified condition. The algorithms are compared with the existing ones, and the results are promising in minimizing the TBV rating of the inverter, which results in cost reduction as well. For a specific case of four CHBs, the proposed Algorithm-1 produced 27% and Algorithm-2 produced 53% higher levels. Moreover, the presented algorithms produced minimum values of the TBV and resulted in minimum cost of inverter.

Originality/value

The proposed algorithms are novel in structure and have achieved the targeted values of minimized switch variety and reduced TBV ratings. Due to less variety, the inverter achieves a near symmetric design, which enables to attain the added advantages of modularity and reduced difference of power sharing among the DC sources.

中文翻译：

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新算法在非对称级联多电平逆变器中的应用

目的

多电平逆变器（MLI）是在中压和高压应用范围内的逆变器应用的既定设计方法。非对称设计合成了大小不等的多个DC输入电压源，以生成包含大量阶跃或电平的高质量阶梯正弦波。然而，使用大小不等的信号源的含义是要求逆变器开关种类繁多，并且逆变器的总阻断电压（TBV）额定值也要更高，这会增加成本。本研究的目的是提出一种基于算法的解决方案，用于建立直流电源幅值和其他设计参数。

设计/方法/方法

本研究中使用的方法是开发使非对称级联MLI（ACMLI）设计接近对称设计的算法。然后，这种方法减少了开关额定值的变化，并使逆变器的TBV最小化。因此，既获得了非对称设计（在输出波形中生成大量电压电平）又获得了对称设计（模块化）的好处。所提出的算法可以应用于许多ACMLI拓扑，包括经典级联H桥（CHB）。通过在Matlab-Simulink中进行仿真和实验设置验证了所提算法的有效性。

发现

提出了两种新算法，可将各种开关的数量减少到三个。在指定条件下，品种可以进一步减少到两个。将算法与现有算法进行比较，结果有望使逆变器的TBV额定值最小化，从而也降低了成本。对于四个CHB的特定情况，建议的算法1产生27％的值，而算法2产生53％的更高的值。此外，所提出的算法产生了TBV的最小值，并使得逆变器的成本最小。

创意/价值

所提出的算法在结构上是新颖的，并且已经实现了最小化开关变化和降低TBV额定值的目标值。由于种类较少，逆变器实现了近乎对称的设计，从而可以实现模块化的附加优势，并减少直流电源之间的功率共享差异。