This article presents a free-harmonic ac/dc/ac converter structure using a novel modulation approach for asymmetrical cascade H-bridge multilevel inverter and, conventional rectifiers combined with a shunt active filter, for grid integration. The novel approach SMT-SHE combines two modulation techniques: the staircase modulation technique (SMT); and the selective harmonics elimination (SHE). SMT-SHE approach achieves a sinusoidal-like output stepping voltage with variable output voltage amplitude and free of wideband or/and specific harmonics to fulfill the sensitive loads’ specifications; by determining the appropriate SHE switching angles. The precalculated switching angles are optimized to minimize the number of H-bridge modules and lower the dc capacitor rating. Furthermore, a restriction on the switching angles is proposed to prevent the appearance of undesired harmonics (zeros, even) and, consequently, overcome the limitation of the SHE algorithm applicability. Finally, a real case study in the textile factory is conducted, using real measurements provided by power quality analyzer measuring devices, to validate the proposed ac/dc/ac converter supplying a sensitive load of 50 kVA, given by an asynchronous motor drive.

中文翻译：

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开发基于并联有源滤波器的 AC/DC/AC 转换器结构和用于非对称级联 H 桥多电平逆变器的高级调制方法

本文介绍了一种自由谐波交流/直流/交流转换器结构，该结构使用一种新颖的调制方法，用于非对称级联 H 桥多电平逆变器，以及与并联有源滤波器相结合的传统整流器，以实现电网集成。新颖的 SMT-SHE 方法结合了两种调制技术：阶梯调制技术 (SMT)；和选择性谐波消除（SHE）。SMT-SHE 方法实现了类似正弦的输出步进电压，具有可变的输出电压幅度，并且不含宽带或/和特定谐波，以满足敏感负载的规格；通过确定适当的 SHE 切换角度。预先计算的开关角度经过优化，可最大程度地减少 H 桥模块的数量并降低直流电容器额定值。此外，还提出了对开关角度的限制，以防止出现不需要的谐波（零、偶数），从而克服 SHE 算法适用性的限制。最后，利用电能质量分析仪测量设备提供的实际测量结果，对纺织厂进行了实际案例研究，以验证所提出的交流/直流/交流转换器，该转换器可提供由异步电机驱动器提供的 50 kVA 敏感负载。