Stability Analysis of an Autonomous Microgrid Operation Based on Particle Swarm Optimization

This paper presents the stability analysis for an inverter based Distributed Generation (DG) unit in an autonomous microgrid operation. The small-signal model of the controlled Voltage Source Inverter (VSI) system is developed in order to investigate the dynamic stability for the given operating point and under the proposed power controller. This model includes all the details of the proposed controller, while no switching actions are considered. System oscillatory modes and the sensitivity to the control parameters are the main performance indices which are considered, particularly when the microgrid is islanded or under the load change condition. In this work, the proposed power controller is composed of an inner current control loop and an outer power control loop, both based on a synchronous reference frame and conventional PI regulators. These controllers also utilize the Particle Swarm Optimization (PSO) for real-time self-tuning in order to improve the quality of the power supply. The complete small-signal model is linearized and used to define the system state matrix which is employed for eigenvalue analysis. The results prove that the stability analysis is fairly accurate and the controller offers reliable system\u27s operation

PSO algorithm for an optimal power controller in a microgrid

This paper presents the Particle Swarm Optimization (PSO) algorithm to improve the quality of the power supply in a microgrid. This algorithm is proposed for a real-time selftuning method that used in a power controller for an inverter based Distributed Generation (DG) unit. In such system, the voltage and frequency are the main control objectives, particularly when the microgrid is islanded or during load change. In this work, the PSO algorithm is implemented to find the optimal controller parameters to satisfy the control objectives. The results show high performance of the applied PSO algorithm of regulating the microgrid voltage and frequency

Optimal sizing design and operation of electrical and thermal energy storage systems in smart buildings

Photovoltaic (PV) systems in residential buildings require energy storage to enhance their productivity; however, in present technology, battery storage systems (BSSs) are not the most cost-effective solutions. Comparatively, thermal storage systems (TSSs) can provide opportunities to enhance PV self-consumption while reducing life cycle costs. This paper proposes a new framework for optimal sizing design and real-time operation of energy storage systems in a residential building equipped with a PV system, heat pump (HP), thermal and electrical energy storage systems. For simultaneous optimal sizing of BSS and TSS, a particle swarm optimization (PSO) algorithm is applied to minimize daily electricity and life cycle costs of the smart building. A model predictive controller is then developed to manage energy flow of storage systems to minimize electricity costs for end-users. The main objective of the controller is to optimally control HP operation and battery charge/discharge actions based on a demand response program. The controller regulates the flow of water in the storage tank to meet designated thermal energy requirements by controlling HP operation. Furthermore, the power flow of battery is controlled to supply all loads during peak-load hours to minimize electricity costs. The results of this paper demonstrate to rooftop PV system owners that investment in combined TSS and BSS can be more profitable as this system can minimize life cycle costs. The proposed methods for optimal sizing and operation of electrical and thermal storage system can reduce the annual electricity cost by more than 80% with over 42% reduction in the life cycle cost. Simulation and experimental results are presented to validate the effectiveness of the proposed framework and controller

Hydatidosis of the Pelvic Cavity: A Big Masquerade

We report and discuss a case of primary hydatidosis of the pelvic cavity in a woman who presented with severe weight loss and abdominal pain. This unusual presentation was initially considered as a tumor process until surgical exploration and microscopic studies confirmed the diagnosis. The gynecologists should be aware of possibility of primary hydatid cyst of the pelvic cavity and should be considered in the differential diagnosis of cystic pelvic masses, especially in areas where the disease is endemic

Causes de mortalité chez le patient cirrhotique

CAEN-BU Médecine pharmacie (141182102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

What Is the Most Appropriate Test in Detecting Prostate Cancer in Patients With Intermediate Prostate Specific Antigen Levels?

Background: Regarding the variety of tests present for detecting and also screening   prostate cancer and also bearing in mind the advantages and disadvantages of   these tests we decided to re-evaluate these tests (total prostate specific antigen and all   of its modifications) in detecting prostate cancer in men with intermediate serum   PSAlevels. Methods: Following a cross sectional study, 100 consecutive men with intermediate   serum PSA levels and normal digital rectal examination (DRE) were incorporated. Total and free PSA levels and TRUS-guided systematic prostate biopsy were   performed. PSA density, percent free PSA and percent free PSA density were calculated and compared. Statistical analysis was carried out using STATA8 SE. Results: Overall, 27 patients had prostate cancer and 73 had benign prostate pathology. PSA density had the greatest area under the curve (AUC) which was significantly higher than percent free PSA density (0.685 vs. 0.448, p<0.001). The AUC of percent free PSA density was not different between benign and malignant biopsy results nor was significantly higher than the AUC of percent free PSA (0.308) or any other screening tests. Conclusion: PSAdensity was the most accurate screening test for prostate cancer in patients with PSA levels of 4-10 ng/ml and normal DRE. The percent free PSA density was not significantly more accurate than percent free PSA and regarding the costs of transrectal ultrasonography, it can be concluded that the percent free PSA is more cost-effective and hence more appropriate than percent free PSA density to screen prostate cancer

PV self-consumption enhancement with optimal residential thermal energy management

The high penetration of renewable energy resources (RES), in particular the rooftop photovoltaic (PV) systems in power systems, causes rapid ramps in power generation to supply load during peak-load periods. In smart residential buildings, variations in rooftop PV power causes a mismatch between generation and load demand. This paper deals with shifting heat pumps loads to either the lower electricity price period or whenever PV generation is available. A strategy is proposed for managing heat pump operation based on real-time pricing tariff to minimize the operation cost of a smart building by controlling the room temperature. This is done by applying real-time temperature boundaries to increase the PV self-consumption. Simulation results demonstrate the cost benefits and effectiveness of the proposed thermal energy management strategy

A cost-effective thermal and electrical energy storage management strategy for smart buildings

In smart residential buildings, variations in rooftop photovoltaic (PV) power causes a mismatch between generation and load demand. This paper deals with combined thermal and electrical energy systems, including a heat pump coupled with a thermal storage tank, rooftop PV modules, a battery energy storage system, and the electrical and thermal loads. An integrated home energy management system with optimal operation schedule is proposed to manage different resources based on time-of-use pricing tariff to minimize the operation cost of a smart building and reduce the mismatch between generation and load. Extensive simulation results show the cost benefits and effectiveness of the proposed combined thermal and electrical energy management strategy