Research Publications (Engineering and Built Environment)
Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215
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Item A lightweight based data aggregation scheme for smart grid power systems(2022-08-20) Khumalo, Philani; Nleya, BakheTo accomplish data aggregation securely and efficiently, it is necessary to design a scheme that is low in both computational as well as communication overheads. Thus in this paper, we propose and analyze a novel secured data aggregation scheme that ensures both privacy preservation as well as data integrity. The scheme is centered on forecasting power consumption demands for a particular neighborhood, and overall, because most attacks occur, during the transmission of data across the ICT subsystem, it thus focuses on limiting that. It does so by first forecasting its demands, and only links with the utility operator when adjustments have become necessary. The scheme utilizes a lightweight efficient noninteractive authentication mechanism in the generation and sharing of session keys. Overall, both the security analysis and performance evaluation demonstrate its efficacy in guaranteeing both privacy and security in addition to minimizing computational and communication overheads.Item Power demand and supply optimization in islanded microgrids with distributed generation(IEEE, 2022-01-25) Chidzonga, Richard; Nleya, Bakhe; Khumalo, PhilaniIn the power sector, a shift from the present fossildominated generation to renewable as well as energy-efficient generation and distribution is firmly underway. The transition is mostly driven by the digitalization of the energy systems to what has been coined ENERNET meaning energy network. Numerous benefits for both utility and consumers accrue. Digitalization enables more activity in the power trading market and a large amount of consumer data becomes available in the sector. Overall, strides are being made in the integration of Demand-Side Management (DSM) in the planning of Isolated/Islanded Microgrids (IMGs) as these will potentially reduce total OPEX costs at both customer and utility levels as well as increase renewable energy utilization. However, there is paucity in literature regarding distributed generators (DGs) non-convex cost function. Notably, not much has been covered regarding microgrid optimal load-dispatching especially with regards to optimizing algorithms. In this paper, we focus on formulating the day-ahead dispatch problem of microgrids with DGs subject to non-convex cost function and load dynamics. We first propose an operational framework that addresses the DG's 'valve point' loading effect as well as optimizing its performance. The impact of DSM on convex and non-convex EMS problems with different load participation levels is investigated. Further, the day-ahead scheduling horizon of fifteen-minute resolution time is considered to examine the effect of load dynamics in the microgrid. A Quantum Particle Swarm based approach is employed to solve non-convex DGs cost optimization. It is demonstrated that the proposed algorithm efficiently solves the non-convex EMS problem. Simulation results yield a 5% reduction in OPEX costs without compromising customer satisfaction.Item Balancing between demand and trading in microgrids(IEEE, 2020-01) Gomba, Masimba; Chidzonga, Richard; Nleya, Bakhe; Khumalo, PhilaniThe envisaged future generation power or smart grid (SG) will incorporate ICT technologies as well as innovative ideas for advanced integrated and automated power systems. The bidirectional information and energy flows within the envisaged advanced SG together with other aiding devices and objects, promote a new vision to energy supply and demand response. Meanwhile, the gradual shift to the next generation fully fledged SGs will be preceded by individual isolated microgrids voluntarily collaborating in the managing of all the available energy resources within their control to optimally serve both demand and distribution. In so doing, innovative applications will emerge that will bring numerous benefits as well as challenges in the SG. This paper introduces a power management approach that is geared towards optimizing power distribution, trading, as well as storage among cooperative microgrids (MGs). The initial task is to formulate the problem as a convex optimization problem and ultimately decompose it into a formulation that jointly considers user utility as well as factors such as MG load variance and associated transmission costs. It is deduced from obtained analytical results that the formulated generic optimization algorithm characterizing both aggregated demand and response from the cooperative microgrids assist greatly in determining the required resources hence enabling operational cost viability of the entire system.Item Intermediate node buffering-based contention minimization scheme(TELKOM, 2019-09-01) Khumalo, Philani; Nleya, Bakhe; Mutsvangwa, Andrew; Boysen, GysOptical burst switching (OBS) is a candidate switching paradigm for future backbone all-optical networks. However, data burst contention can be a major problem especially as the number of lightpath connections as well as the overall network radius increases. Furthermore, the absence of or limited buffering provision in core nodes, coupled with the standard one-way resources signalling aggravate contention occurrences resulting in some of the contending bursts being discarded. In this paper we propose and analyze a restricted intermediate Node Buffering based routing and wavelength assignment scheme (RI-RWA) scheme in which intermediate buffering provisioning is implemented for contending data bursts have already propagated more than half the network’s diameter. The aim is not to discard such bursts as they would have already utilized a considerable amount of available network resources. We comparatively evaluate the scheme’s performance in terms of performance indicators such as fairness, load balancing as well as throughput.Item Quality of transmsision aware routing and wavelength assignment algorithm for blocking minimization in translucent optical networks(IEEE, 2020-08) Khumalo, Philani; Nleya, Bakhe; Mutsvangwa, Andrew; Chidzonga, RichardIn Optical Transport networks, the optical reach is defined as the maximum distance (number of hops) a lightpath connection can span before the intelligence of the sig-nal it is carrying to unrecoverable state as a result of the degra-dation in the signal to noise power ratios. When the signal to noise ratio has degraded below a certain acceptable threshold, regeneration is necessary. Optical Transport networks will nor-mally incorporate optical repeaters throughout to facilitate sig-nal reach for all the lightpath connection establishments. Such networks are classified as being Translucent. The role of the sparsely spaced optical repeaters is to refresh the degraded op-tical signals so that an acceptable quality of transmission (QoT) can be guaranteed by the network operator. The deployment of such units where necessary throughout the network leads to an escalation to both capital as well as operational expenditures. It is however necessary that network designers strike a balance be-tween the network operating costs versus renderable quality of service (QoS) to end users. In light of this challenge, in this pa-per we propose and analyze a QoT-Aware routing and wave-length assignment algorithm (QARWA) that seeks to minimize blocking of data bursts traversing the network. The QoT block-ing considers the effects of various linear as well as nonlinear impairments. The proposed model can be infused with other al-gorithms that attempt to calculate wavelength blocking per route and also per available layer. We also further enhance the same algorithm’s efficacy by introducing its QoT aware guar-anteed RWA (QGRWA) equivalent. The novelty of the scheme is in taking into account physical layer impairments, as well as signal quality when computing candidate routes for a given source to destination pair. The proposed algorithm’s overall promising performance is validated via analytical and simula-tion means.