Enhancing grid-forming converters control in hybrid AC/DC microgrids using bidirectional virtual inertia support

This paper presents a new grid-forming strategy for hybrid AC/DC microgrids using bidirectional virtual inertia support designed to address weak grid conditions. The stability of hybrid AC/DC microgrids heavily relies on the AC mains frequency and the DC-link voltage, and deviations in these factors can lead to undesirable outcomes such as load curtailments and power system congestions and blackouts. This paper introduces a unique approach that leverages bidirectional virtual inertia support to enhance the stability and reliability of hybrid AC/DC microgrids under weak grid conditions. The proposed strategy employs virtual inertia as a buffer to mitigate rapid changes in DC-link voltage and AC frequency, thereby enhancing system stability margins. This strategy significantly contributes to a more stable and reliable grid operation by reducing voltage and frequency fluctuations. A standard hybrid AC/DC microgrid configuration is used to implement the bidirectional virtual inertia support, where a bidirectional interlinking converter control is adjusted to deliver inertia support to both the AC and DC subgrids. This converter utilizes the DC grid voltage and AC grid frequency as inputs, effectively managing active power balance and implementing auxiliary functions. Extensive simulations are conducted under weak grid conditions and standalone mode to validate the effectiveness of the proposed strategy. The simulation results demonstrate a remarkable improvement in frequency nadir, rate-of-change-of-frequency (RoCoF), and DC bus voltage deviation in the hybrid AC/DC microgrids. The bidirectional virtual inertia support substantially reduces voltage and frequency fluctuations, enhancing the microgrid stability and resilience. There is an improvement of over 45% and 25% in the frequency deviation and voltage deviation, respectively, achieved through implementing the proposed control strategy

Optimized Modulation Scheme for Four-Leg Quasi Z-Source Inverter: Reducing Power Loss and Improving Output Quality

This study introduces a new three-dimensional space vector modulation technique for a four-leg quasi Z-source inverter (4L-qZSI) integrating a qZSN and a two-level four-leg inverter. The proposed method encompasses three variants, namely 3DZSVM2, 3DZSVM4, and 3DZSVM8, designed to enhance steady-state operations and harmonic distortions for 4L-qZSI. One of the main contributions of this research is the establishment of a new modulation technique for the 4L-qZSI. The proposed method amalgamates the benefits of SVMs in both abc and $\alpha \beta \gamma$ coordinates. The design processes of the 3DZSVM algorithm are carried out in the newly proposed $\rho \sigma \tau$ coordinates, while the space vector diagram (SVD) of the 4L-qZSI is utilized in the $\alpha \beta \gamma$ location. The proposed algorithm is applied in a single sector, optimizing time interval calculations and pulse creation without requiring trigonometric functions. Extensive simulation studies were conducted to validate the performance of the introduced modulation scheme for the 4L-qZSI. The simulation results show excellent steady-state performance and benefit over the conventional space vector modulation with zero sequences (CZPWM), including a power loss reduction of 50% and a 50% decrease in the THD of the output voltage. In addition, applying this technique results in enhanced output current quality, reduced power loss by 40%, and decreased inductive current ripple by 50% under unbalanced load conditions. Furthermore, the proposed 3DZSVM control strategy for 4L-qZSI is experimentally verified using the TMS320F28379D kit based on the Hardware-in-the-Loop (HIL) simulator. This demonstrates the practicality and effective performance of the suggested control strategy under unbalanced load conditions

Tuméfaction du muscle pectoral révélant une tuberculose musculaire isolée

La tuberculose des parties molles représente l'une des formes rares de la tuberculose extra pulmonaire, la localisation musculaire isolée est parailleurs exceptionnelle. Nous rapportant une observation médicale originale, une tuberculose musculaire isolée intéressant le muscle grand pectoral chez un jeune patient immunocompétent. Le diagnostic a reposé essentiellement sur l'histologie. L'évolution été favorable sous traitement anti bacillaire seul. Ce cas rare est présenté avec revue de littérature.Mots clés: Tuberculose, muscle, tuméfactionEnglish Title: Swelling of the pectoralis muscle revealing isolated muscular tuberculosisEnglish AbstractSoft tissue tuberculosis is one of the rare forms of extrapulmonary tuberculosis. Furthermore, isolated muscular tuberculosis is exceptional. We here report the original case of a young immunocompetent patient with isolated muscular tuberculosis involving major pectoralis muscle. The diagnosis was mainly based on histology. The patient was successfully treated with anti bacterial therapy only. This rare case study has been combined with a literature review.Keywords: Tuberculosis, muscle, swellin