Neural network-based adaptive global sliding mode MPPT controller design for stand-alone photovoltaic systems.

The increasing energy demand and the target to reduce environmental pollution make it essential to use efficient and environment-friendly renewable energy systems. One of these systems is the Photovoltaic (PV) system which generates energy subject to variation in environmental conditions such as temperature and solar radiations. In the presence of these variations, it is necessary to extract the maximum power via the maximum power point tracking (MPPT) controller. This paper presents a nonlinear generalized global sliding mode controller (GGSMC) to harvest maximum power from a PV array using a DC-DC buck-boost converter. A feed-forward neural network (FFNN) is used to provide a reference voltage. A GGSMC is designed to track the FFNN generated reference subject to varying temperature and sunlight. The proposed control strategy, along with a modified sliding mode control, eliminates the reaching phase so that the sliding mode exists throughout the time. The system response observes no chattering and harmonic distortions. Finally, the simulation results using MATLAB/Simulink environment demonstrate the effectiveness, accuracy, and rapid tracking of the proposed control strategy. The results are compared with standard results of the nonlinear backstepping controller under abrupt changes in environmental conditions for further validation.

Microvascular decompression: incidence and prevention of postoperative CSF leakage in a consecutive series of 134 patients.

Introduction: Microvascular decompression (MVD) is an established procedure for treating Trigeminal Neuralgia and Hemifacial Spasm. Postoperative CSF leakage is still a common complication after MVD.Material and Methods: We did a retrospective study of 134 patients who underwent microvascular decompression, mainly for Trigeminal Neuralgia and Hemifacial Spasm in our unit. All patients had an apparently watertight repair of the dura at the end of the operation done by our technique using Duraguard ® and Histacryl® glue.Results: Of the 134 patients, 129 (96.2%) had no postoperative CSF leakage. Only five (3.7%) of the patients experienced postoperative CSF leak.Conclusion: We conclude that dural repair using the described technique, with a dural substitute (Duraguard) and Histacryl glue is safe and effective in preventing postoperative CSF leakage following MVD.