A Novel Repetitive Controller Assisted Phase-Locked Loop with Self-Learning Disturbance Rejection Capability for Three-Phase Grids

The synchronization between the power grid and distributed power sources is a crucial issue in the concept of smart grids. For tracking the real-time frequency and phase of three-phase grids, phase-locked loop (PLL) technology is commonly used. Many existing PLLs with enhanced disturbance/harmonic rejection capabilities, either fail to maintain fast response or are not adaptive to grid frequency variations or have high computational complexity. This article, therefore, proposes a low computational burden repetitive controller (RC) assisted PLL (RCA-PLL) that is not only effective on harmonic rejection but also has remarkable steady-state performance while maintaining fast dynamic. Moreover, the proposed PLL is adaptive to variable frequency conditions and can self-learn the harmonics to be canceled. The disturbance/harmonic rejection capabilities together with dynamic and steady-state performances of the RCA-PLL have been highlighted in this article. The proposed approach is also experimentally compared to the synchronous rotation frame PLL (SRF-PLL) and the steady-state linear Kalman filter PLL (SSLKF-PLL), considering the effect of harmonics from the grid-connected converters, unbalances, sensor scaling errors, dc offsets, grid frequency variations, and phase jumps. The computational burden of the RCA-PLL is also minimized, achieving an experimental execution time of only 12 μs

Classification and Management of Pontecerebellar-Petrosal Bridging Veins

The risks and benefits of coagulating intradural venous elements during a retrosigmoid approach for trigeminal neurovascular decompression has not been accurately established. The objectives of this study were to identify the veins that drain into the superior petrosal sinus, classify them in relation to the suprameatal tubercle, and determine the implication of their coagulation

Power Flow Management by Active Nodes: A Case Study in Real Operating Conditions

The role of distributor system operators is experiencing a gradual but relevant change to include enhanced ancillary and energy dispatch services needed to manage the increased power provided by intermittent distributed generations in medium voltage networks. In this context, the paper proposes the insertion, in strategic points of the network, of specific power electronic systems, denoted as active nodes, which permit the remote controllability of the active and reactive power flow. Such capabilities, as a further benefit, enable the distributor system operators to provide ancillary network services without requiring any procurement with distributed generation systems owners. In particular, the paper highlights the benefits of active nodes, demonstrating their capabilities in reducing the inverse power flow issues from medium to high voltage lines focusing on a network cluster including renewable energy resources. As a further novelty, this study has accounted for a real cluster operated by the Italian distributor system operator Areti. A specific simulation model of the electrical lines has been implemented in DigSilent PowerFactory (DIgSILENT GmbH–Germany) software using real operating data obtained during a 1-year measurement campaign. A detailed cost-benefit analysis has been provided, accounting for different load flow scenarios. The results have demonstrated that the inclusion of active nodes can significantly reduce the drawbacks related to the reverse power flow

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

A Novel Phase-lock Loop with Feed-back Repetitive Controller for Robustness to Periodic Disturbance in Three-phase Systems

While power networks evolve towards the new concept of smart grids, with the proliferation of power electronics embedded systems and distributed generation, the insurgence of system unbalance and voltage harmonic distortion, become more and more frequent. Also, often a noisy voltage sampling system can produce offsets in measurements. Such imperfections bring challenges to the phase identification using a traditional phase-lock loop (PLL), utilized in the control of all grid connected converters. However, since the imperfections lead to periodic harmonics in the corresponding dq-axis voltages, the repetitive controller (RC) can be useful for harmonic suppression. This paper presents a three-phase PLL using a feed-back RC. Specially, a novel running mean filter has been added to minimize the interaction between RC and the Proportional-Integral (PI) controller in the PLL. Simulation results show that the proposed PLL can track the phase of the three-phase voltage without being influenced by harmonic distortion

Single-Stage Complete Removal of Dumbbell-Shaped Trigeminal Schwannoma: 3-Dimensional Operative Video

Intracranial trigeminal schwannomas are rare tumors that may extend into multiple cranial compartments and may emerge from the root, ganglion, or intracranial portion of any of its branches.1-6 The aim of this 3-dimensional operative video is to present a single-stage complete removal of a dumbbell-shaped trigeminal schwannoma through a pretemporal approach (Video 1). Informed consent was given by the patient for use of images and the surgical video. We describe the case of a 43-year-old female presenting with chronic headaches and left facial pain in the trigeminal territory of V2 and V3. Magnetic resonance imaging showed a tumoral lesion located within the cerebellopontine angle, petroclival region, and middle fossa. Due to the patient's symptoms, tumor size, and growth on sequential imaging, single-stage surgical removal was determined through a frontotemporal approach. There were no adverse outcomes posterior to the surgery, and the patient evolved favorably without neurologic deficits. Postoperative imaging showed complete resection of the tumoral lesion. Presurgical planning is essential for an effective and safe surgical strategy. For cases of trigeminal schwannomas with extension to the middle and posterior fossa, single-stage surgery is feasible for complete and safe removal

Supracerebellar Transtentorial Approach for Posterior Temporomesial Cavernoma: 3-Dimensional Operative Video

The temporomesial region is a frequent site of neurosurgical lesions such as tumors, cavernomas, or arteriovenous malformations. This region has been divided into 3 regions: anterior, middle, and posterior.1-4 The objective of Video 1 is to present the case of a posterior temporomesial cavernoma resection through a supracerebellar transtentorial approach, highlighting the surgical technique. The case is a 50-year-old female with history of temporomesial bleeding, headaches, and seizures refractory to medical treatment. In the neuroimaging studies a posterior temporomesial image was diagnosed. We selected a paramedian supracerebellar transtentorial approach in semisitting position for the surgery. With the use of neuronavigation guidance, the cavernoma was located and removed in 1 piece. The patient evolved favorably, without neurologic deficit, improving the symptoms after surgery. The approach is an excellent alternative for exposing the temporomesial region, and the semisitting position facilitates the retraction by gravity of the cerebellum, maintaining a clean surgical field during the microsurgical procedure.3-5

Piggyback Stacking and Booster Clipping Technique: A Technical Note

In certain cases, the closing force of a single vascular clip is not sufficient for complete aneurysmal occlusion, and the use of multiple clips, or clip stacking, is required. Many stacking techniques have been described in the literature, such as in tandem stacking and overstacking. However, these may not be feasible during procedures with limited exposure or narrow corridors. Clip reinforcement with a second high-pressure booster clip, also known as the piggyback technique, is an alternative for these cases along with anatomically complex aneurysms or aneurysms demonstrating atypical morphological features. Although this technique has been cited as a potential resource for certain aneurysms, descriptions of its characteristics and advantages are scarce. The purpose of this technical note was to discuss our experience with the piggyback clipping technique and use of a booster clip for a partially embolized and recanalized saccular posterior communicating artery aneurysm in a 50 year-old patient

Virtual preoperative planning and 3D tumoral reconstruction with Horos open-source software

Background: Presurgical three-dimensional (3D) reconstructions allow spatial localization of cerebral lesions and their relationship with adjacent anatomical structures for optimal surgical resolution. The purpose of the present article is to present a method of virtual preoperative planning aiming to enhance 3D comprehension of neurosurgical pathologies using free DICOM image viewers. Case description: We describe the virtual presurgical planning of a 61-year-old female presenting a cerebral tumor. 3D reconstructions were created with the "Horos®" Digital Imaging and Communications in Medicine viewer, utilizing images obtained from contrast-enhanced brain magnetic resonance imaging and computed tomography. The tumor and adjacent relevant structures were identified and delimited. A sequential virtual simulation of the surgical stages for the approach was performed with the identification of local gyral and vascular patterns of the cerebral surface for posterior intraoperative recognition. Through virtual simulation, an optimal approach was gained. Accurate localization and complete removal of the lesion were achieved during the surgical procedure. Virtual presurgical planning with open-source software can be utilized for supratentorial pathologies in both urgent and elective cases. Virtual recognition of vascular and cerebral gyral patterns is helpful reference points for intraoperative localization of lesions lacking cortical expression, allowing less invasive corticotomies. Conclusion: Digital manipulation of cerebral structures can increase anatomical comprehension of neurosurgical lesions to be treated. 3D interpretation of neurosurgical pathologies and adjacent anatomical structures is essential for developing an effective and safe surgical approach. The described technique is a feasible and accessible option for presurgical planning

Contralateral Interhemispheric Transfalcine Approach for Supratentorial Extraventricular Ependymoma Resection

Extraventricular supratentorial ependymomas are rare entities. Most ependymomas are located at the infratentorial and intraventricular level, and only in a small group of cases they do not present continuity with the ventricular system. This is a case report of a patient with an atypical location of a cerebral ependymoma, which required the implementation of a complex and infrequent approach for its complete microsurgical removal