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Multiobjective optimal power flow for static voltage stability margin improvement
No full textWorldwide, utilities are aiming to increase the stability of modern power systems during system disturbances. Optimizing generation scheduling can improve system security in contingency and stressed conditions while lowering losses and generation costs. An efficient operating strategy for maintaining power system stability is proposed in this work. The paper focuses on incorporating a Voltage Collapse Proximity Index (VCPI) in the traditional optimal power flow problem for multiobjective optimization (MO). Different case studies are assessed to evaluate the impact on the control variables. A Preference Selection index (PSI) is utilized to determine the best-case study for optimal system operation. The effectiveness of the proposed approach is tested on standard IEEE 30-bus and IEEE 57-bus during normal, contingency, and stressed conditions using MATPOWER. During normal conditions, the MO voltage stability constrained optimal power flow (VSC-OPF) increases the system stability by 28.13 % higher than the single objective (SO) case. Furthermore, the transmission losses are lowered by 14.69% with the proposed MO approach. During line outage contingency conditions, the voltage stability enhancement and loss reduction are higher in the MO than in the SO case by 13.60% and 23.19%. However, the loss minimization and stability improvement during normal and contingency conditions come at a slightly higher generation cost of 5.05% in both systems. On the other hand, during stressed conditions, the SO performs better in voltage stability improvement (by 8.77%) and loss reduction (by 6.97%) than in the MO voltage stability constrained OPF. Additionally, PV Curve analysis for the two systems indicates that voltage stability in MO OPF problems provides a more significant margin enhancement of 9.00%, 118.95% in normal and contingency, respectively, higher than the SO case. However, the SO case increases the load margin by 12.36% more than the MO case in stressed conditions. Consequently, the PSI ranks the multiobjective optimization of the three objectives as the most optimal way for operating the systems in normal and line outage contingency conditions. However, during increased load conditions, the system performance is better if a singular objective function is considered. This is due to the lack of adequate reactive power generation during stressed conditions, and hence a singular objective focus is sufficient to assure system stability. Therefore, the proposed approach is an effective preventive control measure for possible voltage collapse in typical power systems. The resulting improvement also brings about a sufficient system stability margin, causing the system to become more secure
A Systematic Review On The Impact Of Educational Robots In Teaching Secondary School STEM Related Subjects
No full textRobots are interdisciplinary in nature. Research in Educational robotics in the education sector has grown tremendously. The robots have been used as teaching tools in STEM subjects. However, even though research interest on educational robots is on the rise, it seems that enough attention has not been paid to the impact they have in students' interest in STEM. This study presents a systematic review of literature on the impact of educational robotics in teaching these subjects to Secondary School Students. The purpose of the review is to i) Synthesize findings from studies that provide learning experiences through educational robotics ii) Identify the possible impact of integration of educational robotics to teaching of Sciences. In this review 25 research studies were included through search and review processes. A synthesis of the studies was done based on matching characteristics and for this case how the educational robots contribute to STEM education in secondary school level. The review show that educational robotics plays an active role in STEM education; however, in some situations no significant improvement in students' sciences and mathematical learning. The results of the review will help curriculum developers in introducing educational robotics in pre-college levels for teaching STEM related subjects. Additionally, it will help researchers in identifying other areas that require more attention
