Contactless power coupling system
- Authors: Nicolae, Dan-Valentin , Van Rensberg, J. F. J. , Case, M. J.
- Date: 2004
- Subjects: Contactors (Generator parts) , Power supply
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22548 , uj:16208 , Citation: Nicolae, D.V., Van Rensburg, J.F.J. & Case, M.J. 2004. Contactless power coupling system. 9th International Conference on Optimization of Electrical and Electronic Equipment, OPTIM ’04, Brasov, Romania, 20-24 May 2004
- Description: Abstract: In this paper, a new application of the Rogowski coil, used to extract small amounts of power from HVAC transmission lines, is studied; the output voltage for single and three-phase is estimated. Practical results on a small-scale experimental model in the milliwatt range are presented which verify the theoretical studies
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Generalised voltage control for a multi-purpose switching mode converter
- Authors: Nicolae, Dan-Valentin , Case, M. J. , Machmoum, M.
- Date: 2004
- Subjects: Voltage detectors , Electric circuit breakers
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/22583 , uj:16213 , Citation: Nicolae, D.V., Case, M.J. & Machmoum, M. 2004. Generalized voltage control for a multi-purpose switching mode converter. SAIEE Transactions, 94(3):165-170.
- Description: Abstract: In this paper, a single-phase switching mode converter acting as a unity power factor rectifier and/or as active power filter with no alteration in the topology is studied. A generalised voltage control taking in consideration the output power of the DC bus is developed. To demonstrate the improved response of the voltage regulator, a battery charger as “unknown dc load” is used
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Power transfer through multi-purpose switching-mode converters
- Authors: Nicolae, Dan-Valentin , Hofsajer, I. , Jandrell, I. R.
- Date: 2004
- Subjects: Electric converters , Electric circuit breakers
- Language: English
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/367451 , http://hdl.handle.net/10210/22596 , uj:16214 , Citation: Nicolae, D.V., Hofsajer, I. & Jandrell, I.R. 2004. Power transfer through multi-purpose switching-mode converter. Quantum - The Journal for Professionals, April 2004
- Description: Abstract: In this paper, the power transfer through a multi-purpose switching-mode converter is studied. Many authors presented the separate functions of the switching mode converters as active power filters, reactive power compensator and unity power factor rectifier. In this paper we present the simultaneity of those three functions and the capability of power transfer is discussed in detail. The results of this research are intended to be a guideline for application designers
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Rogowski coil power application
- Authors: Nicolae, Dan-Valentin , Van Rensburg, J. F. J. , Case, M. J
- Date: 2004
- Subjects: Rogowski coil , Tapping tools
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22571 , uj:16211 , Citation: Nicolae, D.V., Van Rensburg, J.F.J. & Case, M.J. 2004. Rogowski coil power application. EPE-PEMC 2004 Conference, Riga, Latvia, 2-4 September 2004
- Description: Abstract: In this paper, a new application of the Rogowski coil, used to extract small amounts of power from HVAC transmission lines, is studied; the output voltage for single and three-phase is estimated. Practical results on a small-scale experimental model in the milliwatt range are presented which verify the theoretical studies.
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A study of insulation failure in a high voltage current transformer
- Authors: Jimoh, A. A. , Mahlasela, V. S. , Nicolae, Dan-Valentin
- Date: 2005
- Subjects: Electric power transmission
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22348 , uj:16190 , ISBN: 9075815085 , Citation: Jimoh, A.A., Mahlasela, V.S. & Nicolae, D.V. 2005. A study of insulation failure in a high voltage current transformer. EPE 2005 Conference, Dresden, Germany, 11-14 September 2005. DOI:10.1109/EPE.2005.219752
- Description: Abstract: The ageing and deterioration of insulation in high voltage (HV) plants have been a source of concerns to utilities. Breakdown of insulation leads to failures of HV equipment. The ageing and eventual failure of insulation in a high voltage curTent transformer (JHVCT) is the subject of investigation in this paper. A lumiiped parameter model ofHVCT is developed. This model is used to study the influlence of deteriorating and failed iinsulation on the state variables of the HVCT. Somie possible scenarios that could lead to a CT failure are investigated in this paper. For all the scelarios considered, steady alid transient equations relating the state variables of the mlodel have been developed and analyzed. The objectives of these analyses are to establish the behavioural claracteristics of the state variables, establish the interactions between these variables, and investigate the possible generations of harmonics under the various scenarios of deteriorating and outright failure of insulation in the CT. The paper concludes with a discussion of the results obtained
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Alternating current source to voltage source converter
- Authors: Case, M. J. , Van Rensburg, J. F. J. , Nicolae, Dan-Valentin
- Date: 2005
- Subjects: Voltage-frequency converters , Direct-current transmission
- Language: English
- Type: Conference proceedings
- Identifier: http://ujcontent.uj.ac.za8080/10210/388929 , http://hdl.handle.net/10210/21562 , uj:16150 , Citation: Nicolae, D.V., Van Rensburg, J.F.J. & Case, M.J. 2005. Alternating current source to voltage source converter. IPST’05 Conference, Montreal, Canada, June 2005, Paper# 05IPST081-22c
- Description: Abstract: A direct alternating current source to voltage source converter, which does not employ energy storage components, is presented. Conversion is done by a current steering mechanism in the form of a current transformer with two secondary windings. The direct conversion concept, basic circuit, simulation and experimental results of a reduced scale model are presented.
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Current transformer used as a voltage source
- Authors: Nicolae, Dan-Valentin , Van Rensburg, J. F. J. , Case, M. J.
- Date: 2005
- Subjects: Voltage detectors , Electric energy transmission
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22470 , uj:16204 , ISBN: 9536037432 , Citation: Nicolae, D.V., Van Rensburg, J. F. J. & Case, M. J. 2005. Current transformer used as a voltage source. EDPE 2005 Conference, Dubrovnik, Croatia, 26-29 September 2005.
- Description: Abstract: A direct alternating current source to voltage source converter, which does not employ energy storage components, is presented. Conversion is done by a current steering mechanism in the form of a current transformer with two secondary windings. The direct conversion concept,basic circuit, simulation and experimental results of a reduced scale model are presented.
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Overview of tapping methods from high voltage transmission lines
- Authors: Nicolae, Dan-Valentin , Jimoh, A. A. , Van Rensburg, J. F. J. , Case, M. J.
- Date: 2005
- Subjects: Tapping tools , High-voltage accelerators
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22415 , uj:16200 , ISBN:9536037432 , Citation: Nicolae, D.V., Siti, M.W. & Jimoh, A.A. 2005. Overview of tapping methods from high voltage transmission lines. EDPE 2005 Conference, Dubrovnik, Croatia 26-29 September 2005.
- Description: Abstract: This paper takes an overview of various electric energy tapping methods from high voltage transmission lines.Some of these have been studied and implemented previously, some of them are in advance stage of implementation and other new methods have just been started and they are at the initial stage of modeling and simulation. this paper briefly covers the tapping methods for ac transmission lines including two new methods that are at the final stage of research. Dc transmission presents a more challenging situation, but this paper manages to present a few new methods for energy tapping.
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Strategy for power quality improvement and maximum demand smoothing
- Authors: Siti, Willy M. , Jimoh, Adisa A. , Nicolae, Dan-Valentin
- Date: 2005
- Subjects: Electric power transmission , Data transmission modes , data switching methods
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/21725 , uj:16154 , ISBN;0780392531 , Citation: Siti,W.M., Jimoh, A.A. & Nicolae, D.V. 2005. Strategy for power quality improvement and maximum demand smoothing,“IECON’05 Conference”, Raleigh, USA, November 2005. 31st Annual conference of IEEE. pp6. DOI:10.1109/IECON.2005.1568907
- Description: Abstract: In this paper, a distributed strategy for improving the power quality and maximum demand smoothing is presented. Many authors have presented the power quality improvement as a centralized issue, which implies high power capability of compensators. Based on multi-functionality of specific switching-mode converters, a decentralised model is presented. A discussion of simultaneity of different functions is presented in details. The results of this paper are intended to be a guideline for application designers
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The use of multi agent system for monitoring and control of the smelting process in the mining metallurgical sector
- Authors: Siti, M. , Jordaan, J. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2005
- Subjects: Metallurgy , Power energy , Voltage detectors
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22052 , uj:16160 , ISBN: 0780393279 , Citation: Siti, M. et al. 2005. The use of multi agent system for monitoring and control of the smelting process in the mining metallurgical sector. IEEE PES 2005 Inaugural Conference and Exposition in Africa, South Africa, 11-15 July, 2005:326-331.
- Description: Abstract: This paper is focusing on the development of intelligent agent technology and application of that technology to the mining and metallurgical sector.We have shown how networks of communicating and cooperating intelligent software agents can be used to implement complex distributed systems. in the mining and metallurgical industries there are processes which cannot tolerate interruption, such as some sequential line chemical processes.
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A study of improving the power factor of a three-phase induction motor using a static switched capacitor
- Authors: Jimoh, Adisa A. , Nicolae, Dan-Valentin
- Date: 2006
- Subjects: Three-phase machines , Induction motors , Reactive compensation , Power factor correction
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22367 , uj:16193 , ISSN: 1-4244-0121-6 , Citation: Jimoh, A.A. & Nicolae, D.V. 2006. A study of improving the power factor of a three-phase induction motor using a static switched capacitor. EPE-PEMC, 12th International Power Electronics and Motion Control, September, 2006, Portorož, Slovenia.
- Description: Abstract: In this paper a static switched capacitor with an auxiliary three-phase stator winding, which is only magnetically coupled to the stator main winding, is explored for improving the starting and operating power factor of a three-phase induction motor. The scheme improves the power factor of the motor without compromising significantly on other performances. Important advantages of the scheme include preventing harmonics in the line current, and eliminating regeneration possibility as well as preventing high inrush currents at starting.
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A study of the impact of broken neutral in a distribution system
- Authors: Xivambu, M. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2006
- Subjects: Electric wiring , Neutral density filters
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22058 , uj:16153 , Citation: Xivambu, M., Jimoh, A.A. & Nicolae, D.V. 2006. A study of the impact of broken neutral in a distribution system. IASTED, September, 2006, Gaborone, Botswana.
- Description: Abstract: In this paper a study of the impact of the neutral conductor in a distribution system is presented. The causes which determine faults of the neutral conductor together with its effects are presented. The paper proposes a solution which will minimize the impact of the neutral failure.
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Active power control for capacitive divider tapping method
- Authors: Nicolae, Dan-Valentin , Jimoh, Adisa A. , Britten, Anton C.
- Date: 2006
- Subjects: Power systems , Captive divider systems , Tapping electric power
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22404 , uj:16197 , ISSN: 1-4244-0121-6 , Citation: Nicolae, D.V., Jimoh, A.A. & Britten, A.C. 2006. Active power control for capacitive divider tapping method. EPE-PEMC, 12th International Power Electronics and Motion Control, 30 August-1 September, 2006, Portorož, Slovenia.
- Description: Abstract: Capacitive divider systems for tapping electric power from high voltage transmission lines are known to exhibit certain detrimental problems of stability, sub-resonance harmonic oscillations, and ferroresonance when coupled with non-linear loads. On the other hand, they can improve reactive power flow, power factor and contribute to improved harmonic filtration of the larger power system. This paper, therefore, proposes a controlled power flow conditioner as an essential integral component of a capacitive divider system to control power transfer between the high voltage transmission line, capacitive divider system, and the load. The ultimate objective of this conditioner is to mitigate or minimize the attendant problems associated with coupling the system to the load, and optimize the derivable benefits to the larger network.
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Controlled power flow capacitive divider for electric power tapping
- Authors: Jimoh, A. A. , Munda, J. , Britten, A. C. , Nicolae, Dan-Valentin
- Date: 2006
- Subjects: Electric power systems , Capacitance meters
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/15982 , uj:15724 , ISBN: 1-4244-0121-6 , Citation: Jimoh, A.A. et al. 2006. Controlled power flow capacitive divider for eletric power tapping. In: Proceedings of the 12th International Power Electronics and Motion Control Conference, 30 August-1st September, 2006, Portoroz. DOI: 10.1109/EPEPEMC.2006.4778611-1477
- Description: Abstract: Capacitive divider systems for tapping electric power from high voltage transmission lines are known to exhibit certain detrimental problems of stability, sub-resonance harmonic oscillations, and ferroresonance when coupled with non-linear loads. On the other hand, they can improve reactive power flow, power factor and contribute to improved harmonic filtration of the larger power system. This paper, therefore, proposes a controlled power flow conditioner as an essential integral component of a capacitive divider system to control power transfer between the high voltage transmission line, capacitive divider system, and the load. The ultimate objective of this conditioner is to mitigate or minimize the attendant problems associated with coupling the system to the load, and optimize the derivable benefits to the larger network.
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LV and MV distribution networks reconfiguration for minimum losses
- Authors: Siti, Willy M. , Nicolae, Dan-Valentin , Jimoh, Adisa A.
- Date: 2006
- Subjects: Distribution networks , Electricity supply
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22442 , uj:16202 , ISSN: 1-4244-0121-6 , Citation: Siti, W.M., Nicolae, D.V. & Jimoh, A.A. 2006. LV and MV distribution networks reconfiguration for minimum losses. EPE-PEMC, 12th International Power Electronics and Motion Control, 30 August-1 September, 2006, Portorož, Slovenia.
- Description: Abstract: The reconfiguration of the distribution network feeders can be defined as the restructuring of the feeders through the changing of the open/close states of the sectionalizing and tie switches. This creation of a new distribution network topology is normally required to improve the performance of the network, and thus sometimes the efficiency of the electricity supply. For optimum loss reduction, feeder reconfiguration is often considered as an option. This, however, requires the implementation of an appropriate switching control strategy. It would be desirable for the switching to be automatic, that is to follow the connected load situation of the feeder. The proposed optimal reconfiguration of the phase balancing using the heuristic method proves to be robust compared to neural network method, to turn ON and OFF the different switches, allowing the three phases supply of the transformer to the end-users to be balanced. This paper presents the application examples of the proposed method using the real data.
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Performance analysis of a three-phase induction motor with capacitance injection
- Authors: Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2006
- Subjects: Three-phase machines , Induction motors , Reactive compensation , Power factor correction
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22554 , uj:16209 , Citation: Jimoh, A.A. & Nicolae, D.V. 2006. Performance analysis of a three-phase induction motor with capacitance injection. OPTIM, 10th International Conference on Optimization of Electrical and Electronic Equipments, 17-20 May, 2006, Brasov, Romania.
- Description: Abstract: In this paper a static switched capacitor with an auxiliary three-phase stator winding, which is only magnetically coupled to the stator main winding, is explored for improving the starting and operating power factor of a three-phase induction motor. The scheme improves the power factor of the motor without compromising significantly on other performances. Important advantages of the scheme include preventing harmonics in the line current, and eliminating regeneration possibility as well as preventing high inrush currents at starting.
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Controlled capacitance injection into a three-phase induction motor through a single-phase auxiliary stator winding
- Authors: Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Fusion power plants , Electromagnetic induction , Reactor fuel reprocessing
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/18755 , uj:16039 , Citation: Jimoh, A.A. & Nicolae, D.V. 2007. Controlled capacitance injection into a three-phase induction motor through a single-phase auxiliary stator winding.IEEE International Electric Machines and Drives Conference, Antalya, Turkey, May 03-05, 2007:1183-1188. DOI:10.1109/IEMDC.2007.383598
- Description: Abstact: In this paper a controlled static switched capacitor three-phase auxiliary winding fed by a three-phase PWM with single-phase auxiliary winding, which is only magnetically inverter is proposed with some positive results. This solution coupled to the stator main winding, is explored for improving the is, however, complex and there are some doubts about the starting and operating power factor of a three-phase induction controller presented. Other solution presented in [7, 8] is motor. The scheme improves the power factor of the motor applicable only to a wound rotor machine, as the rotor is without compromising significantly on other performances. Important advantages of the scheme include preventing required to be connected to an external circuit. harmonics in the line current, and eliminating regeneration In this paper a single-phase stator auxiliary winding that is possibility as well as preventing high inrush currents at starting
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DC current source to voltage source CT-based converter
- Authors: Nicolae, Dan-Valentin , Jimoh, A. A. , Van Rensburg, J. F. J.
- Date: 2007
- Subjects: Energy storage , Transformer substations
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/20504 , uj:16106 , Citation: Nicolae, D.V., Jimoh, A.A. & Van Rensburg, J.F.J. 2007. DC current source to voltage source CT-Based converter,International Aegean Conference on Electric Machines and Power Electronics & Electromotion Joint Conferences, Bodrum, Turkey, September 10-12, 2007:665-670. DOI10.1109/ACEMP.2007.4510587
- Description: Abstract: As generally known there is no energy transfer between a dc current and a current transformer. After a brief overview of other methods for tapping energy from the high voltage direct current transmission line, this paper presents the concept of a new dc to ac current source converter utilizing a current transformer. The advantage of this converter is that it is connected in series to the dc line and that at any moment in time the current flow is kept continuous. This paper presents the concept of the converter and simulation results.
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Distribution Feeder Phase Balancing using Newton-Raphson Algorithm-based Controlled Active Filter
- Authors: Siti, M.W. , Nicolae, Dan-Valentin , Jordaan, J.A. , Jimoh, A.A.
- Date: 2007
- Subjects: Phase transformations , Controlled fusion , Electric circuit analysis
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/21218 , uj:16127 , ISSN:03029743 , Citation:Siti, M. W.et al.2007.Distribution feeder phase balancing using Newton-Raphson algorithm-based controlled active filter,ICONIP 2007, Neural Information Processing_Lecture Notes in Computer Science, Volume 4985, pp. 713-720, 2007.Spriger-Verlag Berlin Heidelberg , DOI:10.1007/978354069162474
- Description: Abnstract: The distribution system problems, such as planning, loss minimization, and energy restoration, usually involve the phase balancing or network reconfiguration procedures. The determination of an optimal phase balance is, in general, a combinatorial optimization problem. This paper proposes a novel reconfiguration of the phase balancing using the active power filter control and the combinatorial optimization-based Newton-Raphson algorithm to solve the unbalance problem. By utilizing the load switches as state variable, a constant Jacobian matrix can be obtained. The model developed in this paper uses combinatorial optimization techniques to translate the change values (kVA) into a number of load points and then selects the specific load points. It also performs the inter-changing of the load points between the releasing and the receiving phases in an optimal fashion. Application results balancing a distribution feeder network in South Africa for domestic loads are presented in this paper.
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Dynamic and steady state behaviour of a synchronous reluctance machine with leading reactive power through an auxiliary winding
- Authors: Ogunjuyigbe, Ayodeji Samson , Jimoh, Adisa A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Electric machinery , Electric transformers
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/15599 , uj:15680 , Citation: Ogunjuyigbe, A.S., Jimoh, A.A. & Nicolae, D.V. 2007.Improving synchronous reluctance machine performance by direct capacitance injection through an auxiliary winding. Proceedings of the International Conference on Electrical Machines and Systems ICEMS 2007, paper IMP-05:1055-1060.
- Description: In attempt to improve the performance of synchronous reluctance machine the structure of the machine is modified to include an additional winding on the stator and injection of capacitance. This paper examines the dynamic and steady state behaviour of the modified machine based on its mathematical model and experiments performed on a practical prototype. The experimental results corroborate the solutions of the mathematical model as obtained through simulation. The modified machine shows significant improvement in performance over the conventional one.
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