Dynamic performance enhancement of a grid-connected wind farm using doubly fed induction machine-based flywheel energy storage system

This paper presents the dynamic performance enhancement of a wind farm connected to an IEEE-39 bus New England test system using doubly-fed induction machine (DFIM)-based flywheel energy storage system (FESS). The variable wind speed causes fluctuations in the output power of the wind farms. The use of FESS smoothes the power of the wind farm and improves the dynamic response of the system during fluctuating wind speeds. A DFIM-based FESS is proposed in this study which works on an effective control technique. The cascaded black-box optimization technique based proportional-integral (PI) control strategy is implemented on the FESS. The PI controllers are used to control the insulated gate bipolar transistor (IGBT) based rotor side converter (RSC) and the grid side converter (GSC) of the DFIM. The PI controller In-depth modeling and control strategy of the system under study is presented. The effectiveness of the proposed system is tested under real-time wind speed data. The validity of the system is verified by the simulation results which are carried out using PSCAD/EMTDC

Transient stability enhancement of a gridconnected wind farm using an adaptive neurofuzzy controlled-flywheel energy storage system

With the rapid growth of the wind energy systems in the past years and their interconnection with the existing power system networks, it has become very significant to analyse and enhance the transient stability of the wind energy conversion systems connected to the grid. This study investigates the transient stability enhancement of a grid-connected wind farm using doubly-fed induction machine-based flywheel energy storage system. A cascaded adaptive neuro-fuzzy controller (ANFC) is introduced to control the insulated gate bipolar transistor switches-based frequency converter to enhance the transient stability of the grid-connected wind farm. The performance of the proposed control strategy is analysed under a severe symmetrical fault condition on both a single-machine infinite bus model and the IEEE-39 bus New England test system. The transient performance of the system is investigated by comparing the results of the system using the proposed ANFCs with that of the black-box optimisation technique-based proportional-integral controllers. The validity of the system is verified by the simulation results which are carried out using PSCAD/EMTDC environment

Three Essays on CEO Compensation, Partisanship and Capital Structure

This dissertation consists of three essays. In the first essay, I construct a CEO pay complexity index based on grant-level compensation data to test whether compensation complexity is consistent with optimal contracts or agency problems. Complexity may represent board effort to contract optimally or a means by which the CEO camouflage agency issues and rent extraction. I find evidence supporting the agency view by showing how complexity is negatively related to firm value, profitability, and CEO turnover performance sensitivity. I also examine the relationship between complexity and CEO investment behavior and find mixed results. Overall, the findings relate to shareholders' dissatisfaction with the increased complexity of CEO compensation. The second essay studies how customer concentration affects the use of relative performance evaluation (RPE). Customer concentration increases the potential benefit of RPE in compensation contracts to ease the higher systematic risk CEOs face and provide proper incentives. However, such concentration may make RPE costly and less appealing because of the limited availability of peers or the possible disruption to major customers' relationships. I find that the sensitivity of CEO compensation to systematic performance is higher for firms with significant customers (less RPE). Examining why these firms rely less on RPE, I show that the positive sensitivity of pay to systematic performance disappears once a firm has enough informative peers. Further evidence indicates that the lack of RPE is not related to other explanations such as the possibility of disruption to the relationship with significant customers, CEO power, industry strategic interactions, or less incentive pay for risky firms. The third essay examines the relationship between CEOs' political leanings and the speed of adjustment to target leverage. While most CEOs' political views do not affect movement towards the target, we find that partisan Democrat CEOs of under-levered firms have significantly slower adjustment speeds. After the exogenous shock of the 2017 Tax Cut and Jobs Act (TCJA), these firms are even slower to make adjustments. We find that the post-TCJA inertia of partisan Democrats reflects a reduction in share repurchases, consistent with the Democratic Party views on the use of windfall corporate profits

Speed Control of a Three Phase Induction Motor Fed from a Single Phase Supply

This paper describes a novel and cost effective arrangement of controlling the speed of a three phase induction motor fed from a single phase supply. Theoretical analysis is supported by experimental results. Speed control of a three phase induction motor by stator voltage variation is straightforward, simple, economical and as such increasingly employed in low to medium power applications, especially where the load torque varies as the square of the motor speed. This paper describes an alternative arrangement for the conventional scheme used to implement this technique of speed control. The proposed scheme requires single phase supply and two thyristors as opposed to the three phase supply and six thyristors in the conventional scheme. A single capacitor-phase balancer is used to adapt the motor to the supply. An optimum value for the capacitance of the balancer is chosen to give nearly minimum unbalance between the motor voltages. Experimental results confirm the superiority of the proposed scheme

Capacitance requirements for three phase self-excited reluctance generators

A direct method to find the capacitance requirements for a three phase self-excited reluctance generator under any load or speed is introduced. Expressions for the load angle as well as for the minimum value of the excitation capacitance are derived. It has been found that there is a cut off speed, above which no excitation is possible no matter what the terminal capacitance value. Expressions for the value of this speed under open circuit, resistive and pure inductive loads are also derived and presented.IEE

Developing a Balanced Scoreboard (BSC) for Evaluating the Safety Performance of Saudi Public Schools

Since a number of school fire accidents occurred in 2002, the Saudi Arabian government has realised that providing school safety regulations is necessary in order to avoid accidents in the nation’s schools. The Saudi Ministry of Education has been actively seeking to develop applicable regulations to measure the safety performance of each school. Nowadays, school safety has become an important topic for all Saudi parents, especially parents of children who are just starting school for the first time; it also has become an important priority for the Saudi Minister of Education. For this reason, the Minister, in 2012, issued an important decision to develop an administrative unit, under the name of Schools Security and Safety Administration, to achieve the following goals: provide a safe and healthy environment in schools; prevent accidents or injuries during school hours; control school accidents and emergencies; provide necessary information and instructions to know the risks that students and staff may face at school and guide them on methods of prevention; contribute to educating students on the safety aspects in their schools; and finally, document accidents and injuries for the purpose of evaluating school safety processes. Kaplan and Norton (1992) developed an innovative performance management system that includes three core subsystems, namely, a measurement system, a strategic management system and a communication system. This performance management system, called a balanced scorecard (BSC), showed great potential to be adapted to enable the Saudi Ministry of Education to meet its need for effective safety performance at each school. Therefore, the study’s key aim was to develop a BSC, which includes diverse perspectives for evaluating the various leading and lagging indicators of safety performance in Saudi schools.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EngineeringScience, Environment, Engineering and TechnologyFull Tex