Advanced High Switching-Frequency Cascaded H-Bridge Multilevel Inverter Based Shunt Active Filter for PV Generation: A Case Study

Abstract

This article presents a compact structure ofshunt active photovoltaic filter based on a cascaded H-bridge multilevel inverter (SAF-PV/CHB-MLI) to eliminate electrical perturbations caused by nonlinear loads and to generate MPPT of PV generators. The SAF-PV/CHB-MLI structure, while injecting the maximum current of PV generators, opts to increase the apparent switching frequency, reduces the coupling/output filter size, improves grid-side power quality, generates sinusoidal-like output stepping voltage, and minimizes voltage stresses on IGBTs devices. To achieve these objectives, the SAF-PV/CHB-MLI structure is configured for an HB module per phase/cluster, combined with an appropriate common control strategy for both active filtering and PV generation. The $p - q$ current identification algorithm is adapted/modified to include a P&O algorithm for MPPT detection and a developed PLL to ensure reliable operation under grid distortion conditions. The common control strategy comprises three complementary control loops: the injected current controller for perturbation compensation and maximum PV current injection, the individual cluster voltage balancing controller, and the overall dc voltage regulator which is incorporated within the adapted/modified p-q algorithm. Then, a multicarriers phase-shifted pulsewidth modulation is adopted to ensure the required individual and apparent switching frequencies, while reducing the sideband harmonic components’ impact. A tradeoff among the HB modules number, IGBTs rating, individual and apparent switching frequencies, and the accumulative output voltage is elaborated to create reliable and economical structure that meets industrial application recommendations. To validate the proposed structure's performance, a case study is conducted for textile industrial factory suffering from harmonic impact on its main sensitive load (SL) textile machine of almost 50 kVA; site measurements using power-quality analyzer devices are collected. A numerical model of the factory's network was developed to investigate the proposed structure performance on SL.