University Documentation
http://localhost:8080/xmlui/handle/123456789/204
This collection includes the University's publications, photographs, events (conferences, lectures, speeches, etc)2024-03-28T22:52:00ZTesting the Weak-Form Efficiency Market Hypothesis on the Ghana Stock Exchange: A Sectoral Analysis
http://localhost:8080/xmlui/handle/123456789/808
Testing the Weak-Form Efficiency Market Hypothesis on the Ghana Stock Exchange: A Sectoral Analysis
Asiedu, E. L.; Mireku-Gyimah, D.; Kamasa, K; Otoo, H.
Testing the efficiency of the financial market is of much importance to investors who wish to hold diversifiable assets. This paper analysed the weak form market efficiency hypothesis for five sectors of the Ghana stock exchange using monthly returns of their respective stock market capitalisation as the information generating event. The paper investigated the weak form market efficiency in the framework of random walk hypothesis for the sectors of Ghana stock exchange by using the Run and the Lo-MacKinlay Variance Ratio tests. The results revealed that the sectors - consumer staples, financials and pharmaceuticals do not follow random walk and thus imply these sectors are not weak form efficient. The results also revealed contradictory results on the mining and the petroleum sectors, hence the issue of whether or not the random walkhypothesis holds for the two sectors is inconclusive.
2020-09-01T00:00:00ZCascaded Loop Control of a Three-Phase Grid-Connected PV Inverter System
http://localhost:8080/xmlui/handle/123456789/803
Cascaded Loop Control of a Three-Phase Grid-Connected PV Inverter System
Asiedu-Asante, A. B.; Ofosu, R. A.
Owing to the advantages Photovoltaic (PV) systems possess over other renewable energy sources, more resources have been diverted into their advancement in recent years. These advantages combined with the increasing energy demand of the world have led to the commercialisation of PV power generation. One way of achieving large-scale utilisation of PV sources is through grid-connection. This paper focuses on the control of a three-phase grid connected PV inverter system that comprises a regulated boost DC-DC converter and a Heterojunction with Intrinsic Thin Layer (HIT) PV array. Perturb and Observe (P&O) Maximum Power Point Tracking (MPPT) Algorithm was used in the control of the boost converter and the Sanyo HIP-215NKHE5 solar module was chosen and simulated for system verification. For grid integration, a three-phase voltage source inverter was modelled together with an LCL filter. The inverter control used was a voltage-current cascade loop control scheme that employed Proportional Integral (PI) controllers in conjunction with a Phase Lock Loop (PLL) and the synchronous d-q frame control. The optimal PI gains were obtained using the Ziegler-Nichols method and the system was simulated in MATLAB/Simulink. With this control, the input to the inverter was maintained constant irrespective of the changing PV output voltage. The amount of current injected into the grid was regulated. The inverter system output was successfully synchronised with the grid in terms of phase and frequency, thereby improving power factor control. Thoughrelatively not robust, this control strategy was relatively simple, easy to implement and efficient
2020-09-01T00:00:00ZPrediction of Weather-Related Electric Power Interruptions on the 33 kV Bonsa Feeder Using Artificial Neural Networks
http://localhost:8080/xmlui/handle/123456789/802
Prediction of Weather-Related Electric Power Interruptions on the 33 kV Bonsa Feeder Using Artificial Neural Networks
Normanyo, E.; Dadzie, G.
The objective of this study is to establish the relationship between weather parameters such as rainfall, temperature, wind speed and relative humidity and power interruption of a 33 kV feeder and to develop an Artificial Neural Network (ANN) model for the prediction of these weather-related power interruptions. Four years data spanning 2013 to 2016 on the weather parameters for the geographical area and number of recorded outages on the feeder were taken. These data were used to develop the prediction model. The data were used to train, validate and test the performance of the network and that of 2016 were used to predict the number of outages. The Levenberg Marquardt algorithm was used to train the network. Different models were developed to predict the occurrences of the outages based on a total of nine scenarios. This was also done to investigate which parameters had the most influence on the outage events. The weather data for 2016 were used as new inputs (sample) to the networks, and all the networks were simulated to predict the number of outages. The results showed that the ANN model was able to predict the number of outages with a reasonable level of accuracy. Rainfall and wind speed were established as the critical causes of the outage events while temperature and humidity had minimal influence on the outage events.
2020-09-01T00:00:00ZOscillation Studies on Replacement of Phase–Wound Induction Motors of a SAG Mill Drive with Permanent Magnet Synchronous Motors
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Oscillation Studies on Replacement of Phase–Wound Induction Motors of a SAG Mill Drive with Permanent Magnet Synchronous Motors
Normanyo, E.; Amo-Aidoo, K.
The primary objective of every industry is to optimise production at preferably lower costs. These industries make use of electric motors for their operations and the mining industry is no exception. Often is the notion to replace the Semi-Autogenous (SAG) mill drive phase-wound induction motor with an equivalent synchronous motor. This paper evaluated the correctness or otherwise of the motor replacement from the point of view of oscillations. The SAG mill drive motor was modelled and simulated using Matlab/Simulink software to ascertain the level of oscillation at start and in running mode. Both motors gave same responses at an average load of 291.385 tonnes, where they delivered same power, speed and drew the same amount of current. At maximum load of 328.571 tonnes, the Permanent Magnet Synchronous Motor (PMSM) delivered more electrical power than the PWIM, both motors exhibited a constant speed characteristic and the current drawn by the Phase-Wound Induction Motor (PWIM) was higher than that of the PMSM resulting in additional power draw of value 208.3 kW. Oscillations of the PMSM on the whole were better than those of the PWIM. The PWIM is subject toreplacement in SAG mill drive systems.
2020-09-01T00:00:00Z