Gravitational-Search Algorithm for Optimal Controllers Design of Doubly-fed Induction Generator

Recently, the Gravitational-Search Algorithm (GSA) has been presented as a promising physics-inspired stochastic global optimization technique. It takes its derivation and features from laws of gravitation. This paper applies the GSA to design optimal controllers of a nonlinear system consisting of a doubly-fed induction generator (DFIG) driven by a wind turbine. Both the active and the reactive power are controlled and processed through a back-to-back converter. The active power control loop consists of two cascaded proportional integral (PI) controllers. Another PI controller is used to set the q-component of the rotor voltage by compensating the generated reactive power. The GSA is used to simultaneously tune the parameters of the three PI controllers. A time-weighted absolute error (ITAE) is used in the objective function to stabilize the system and increase its damping when subjected to different disturbances. Simulation results will demonstrate that the optimal GSA-based coordinated controllers can efficiently damp system oscillations under severe disturbances. Moreover, simulation results will show that the designed optimal controllers obtained using the GSA perform better than the optimal controllers obtained using two commonly used global optimization techniques, which are the Genetic Algorithm (GA) and Particle Swarm Optimization (PSO)

Modeling and Simulation of TCSC- Operated Single-Phase Induction Motor

As single-phase induction motor (SPIM) is not a self-starting motor, it has been a common practice to add an auxiliary component to the motor circuit to establish a starting torque. Traditionally, two capacitors are used in SPIM to establish and improve its starting torque and to enhance its running performance. As the Thyristor-Controlled Series Compensator (TCSC) is a control device that considerably alters impedance of the circuit in which it is inserted to be capacitive or inductive, it can be utilized for starting and running purposes in SPIM. This paper explores the representation of the TCSC as a variable impedance and investigates its valuable impacts, when it is operated in its capacitive mode, on the transient behavior of SPIM. It presents a state-space model of the TCSC-inserted SPIM and shows that inserting the TCSC in the auxiliary winding of the SPIM introduces more benefits compared to the traditionally used methods of starting and running the SPIM. The simulation results of the test cases presented in the paper, which include comparisons between the presented approach and the traditional approaches, emphasize that incorporating TCSC with the SPIM brings advantageous features to start and run the motor. The paper will show that controlling the firing angle of the TCSC may attain the desired electromagnetic torque and speed characteristics. The simulation results presented in the paper indicate that the TCSC can effectively replace the traditional auxiliary component and the accompanying mechanical centrifugal switch, which in turn may reduce the size and cost of the SPIM

Outcome of Outpatient Autologous Hematopoietic Stem Cell Transplantation in Patients with Multiple Myeloma and Relapsed and Refractory Hodgkin Lymphoma. The Experience of King Fahad Specialist Hospital in Dammam, Saudi Arabia

Background: Autologous hematopoietic stem cell transplants (HSCT) is the standard of care for transplant-eligible patients with newly diagnosed multiple myeloma (MM) and patients with relapsed and refractory Hodgkin lymphoma (R/R-HL) who achieve chemosensitivity after salvage therapy. Although autologous HSCT is routinely performed in an  inpatient setting, the procedure can safely be performed in an  outpatient setting.Methods and materials: A retrospective study of patients with MM and R/R- HL who received outpatient autologous HSCT at King Fahad Specialist Hospital (KFSH) in Dammam, Saudi Arabia between the first of April 2017 and the 31st of January 2022 was performed.Results: Over the study period of 4 years and 10 months, a total of 90 outpatient autologous HSCTs were performed for 79 patients (54 patients with MM; 4 of them received planned tandem autografts and 7 other myeloma patients received second autologous HSCTs for relapsed or progressive disease; and 25 patients with R/R-HL) at our institution. The median ages of patients with MM and those with R/R-HL at HSCT were 50.4 years and 27.8 years respectively.At the presentation of their MM, the following high-risk (HR) features were encountered: stage II and III diseases according to the revised international scoring system (RISS) in 53.7%; adverse cytogenetics in 42.6% and extensive bone involvement in 53.7% of patients. In patients with HL at presentation, 48% of patients had stage IV disease according to Ann Arbor staging classification and 84% of patients had B symptoms.Survival for 100 days post-HSCT for all patients with MM and HL who received outpatient autologous transplants was 100%. For patients with MM, the overall survival (OS) rates at 3 years and 4 years post-HSCT were 80% and 67%, while the progression-free survival (PFS) rates over 3 years and 4 years were 58% and 38% respectively. For patients with HL, the OS at 6 years post-HSCT was 95% while the PFS rates at 3 years and 6 years post-HSCT were 84% and 62% respectively.Conclusion: Outpatient autologous HSCT for patients with MM and HL is safe, and feasible and can lead to short-term as well as long-term outcomes that are comparable to autologous transplantation performed in an  inpatient setting. Additional benefits of outpatient autologous include saving beds and reducing hospital costs