An Investigative Study on Impact of Frequency Dynamics in Load Modeling

Load modeling plays a significant impact in assessing power system stability margin, control, and protection. Frequency in the power system is desired to be kept constant, but in a real sense, it is not constant as loads continually change with time. In much literature, frequency dynamics are ignored in the formulation of load models for the basic assumption that it does not affect the models.  In this paper, the composite load model was formulated with Voltage-Frequency Dependency (V-FD) on real and reactive powers and applied to estimate the load model. 2- Area network 4- machines Kundur test network was used for testing the developed model.  The model was trained with measurements from a low voltage distribution network supplying the Electrical Engineering department at Ahmadu Bello University, Zaria. Both training and testing data were captured under normal system operation (dynamics). To evaluate the V-FD model performance, Voltage-Dependent (VD) model was examined on the same measured data. The work makes use of the Feed Forward Neural Network (FFNN) as a nonlinear estimator. Results obtained indicate that including frequency dynamics in modeling active power reduces the accuracy of the model. While in modeling reactive power the model performance improves. Hence, it can be said that including frequency dynamics in load modeling depends on the intended application of the model

The Impact of Colonialism on Surgical Training Structures In Africa Part 2: Surveying Current and Past Trainees.

BACKGROUND: As a result of gradual independence from colonial rule over the course of the past century, Africa has developed and evolved 3 primary surgical training structures: an extracontinental colonial model, an intracontinental college-based model, and several smaller national or local models. There is consistent evidence of international brain drain of surgical trainees and an unequal continental distribution of surgeons; however there has not, to date, been an evaluation of the impact colonialism on the evolution of surgical training on the continent. This study aims to identify the etiologies and consequences of this segmentation of surgical training in Africa. METHODS: This is a cross-sectional survey of the experience and perspectives of surgical training by current African trainees and graduates. RESULTS: A surgeon’s region of residence was found to have a statistically significant positive association with that of a surgeon’s training structure (P CONCLUSIONS: These findings provide evidence to support the concept that the segmentation of surgical training structures in Africa, which is the direct result of prior colonization, has affected the distribution of trainees and specialists across the continent and the globe. This maldistribution of African surgical trainees directly impacts patient care, as the surgeon patient ratios in many African countries are insufficient. These inequities should be acknowledged addressed and rectified to ensure that patients in Africa receive timely and appropriate surgical care