Imperial College London

DrOnyema SundayNduka

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Visiting Researcher
 
 
 
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Contact

 

onyema.nduka12

 
 
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Location

 

1105Electrical EngineeringSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

8 results found

Yu Y, Nduka O, Pal B, 2020, Smart control of an electric vehicle for ancillary service in DC microgrid, IEEE Access, Vol: 8, Pages: 197222-197235, ISSN: 2169-3536

This article presents a two-stage framework for optimal Electric Vehicle (EV) charging/discharging strategy for DC Microgrid (MG) with Distributed Generators (DGs). A multi-objective optimisation task aimed at minimising system losses and EV battery degradation with Vehicle-to-Grid (V2G) peak shaving service has been realised. This coordinated EV integration into the DCMG was formulated as a directed weighted single source shortest path problem that was solved using a modified Dijkstra’s algorithm. The weights of the edges were obtained using primal-dual interior point method. The proposed framework has been experimentally verified using simulations with a test DCMG system with practical IEEE European low voltage test feeder load profiles. Results show realisation of peak demand shaving leveraging on EV discharge with minimal on-board battery degradation as well as reduced system losses. It is also shown that the proposed two-stage framework reduces the battery state of charge (SOC) sample space requirements in the analysis, thus, reducing the computational burden.

Journal article

Nduka O, Yu YUE, Pal BC, Okafor ENCet al., 2020, A robust augmented nodal analysis approach to distribution network solution, IEEE Transactions on Smart Grid, Vol: 11, Pages: 2140-2150, ISSN: 1949-3053

The ambition to decarbonize the source of energy for heat and transport sector through electricity from renewable energy has led to significant challenge in the way power distribution networks (DNs) are planned, designed and operated. Traditionally, DN was put in place to support the demand passively. Now with renewable generation, storage and demand side management through automation, provision of network support services have transformed the character of the DNs. Active management of the DN requires fast power flow analysis, state estimation, reactive power support etc. This paper proposes a method of power flow analysis which incorporates the challenges of distributed generator (DG) characteristics, demand side management and voltage support. The proposed approach reformulated the Jacobian matrix of the well-known modified augmented nodal analysis (MANA) method; thus, improving the robustness and solvability of the formulation. Reactive powers of the DGs, node voltages and currents of ‘non-constitutive’ elements were the chosen state variables. The performance of this method is compared with the MANA. Results are discussed and the effectiveness of the proposed approach is demonstrated with two example case studies.

Journal article

Nduka OS, Kunjumuhammed L, Pal B, Majumdar A, Yu Y, Maiti S, Ahmadi Aet al., 2019, Field trial of coordinated control of PV and energy storage units and analysis of power quality measurements, IEEE Access, Vol: 8, Pages: 1962-1974, ISSN: 2169-3536

Trends support low voltage distribution networks will soon experience significant uptake of customer-owned low-carbon technology (LCT) devices especially rooftop photovoltaics (PVs) and small-scale energy storage (SSES) systems. This paradigm shift will introduce some significant challenges in modern distribution network planning and operations owing to the temporal nature of modern demand.Therefore, it became relevant to investigate the UK low voltage (LV) network operations considering high uptake of PVs and SSESs through both field measurements and desktop studies. The aim was to validatethrough field trials, the flexibility benefits of peak demand reduction and reverse power flow mitigation through smart control of customer-owned SSESs. It was shown that peak demand of up to 60% could beachieved in UK distribution network through the smart control of these devices. In tandem with the demand reduction, the study revealed that type-tested SSES power interface units do not pose significant powerquality risks even for 100% customer penetration.

Journal article

Ayiad M, Martins H, Nduka O, Pal Bet al., 2019, State estimation of low voltage distribution network with integrated customer-owned PV and storage unit, 2019 IEEE Milan PowerTech, Publisher: Institute of Electrical and Electronics Engineers (IEEE)

The growing integration of rooftop photovoltaics (PVs) and energy storage units (ESUs) in customer households has resulted in changes in the customer load profiles. This is likely to influence the accuracy of state estimation (SE) carried out based on previously assumed load profiles. In this paper, a statistical model for modern low voltage (LV) customers was developed using Gaussian mixture model (GMM). The resulting model was subsequently applied to SE using weighted least squares (WLS) algorithm. LV network with high penetration of customer-owned PV and ESUs have been simulated. Different scenarios which include load profiles: with PVs integrated but without ESUs, ESUs alone, and with hybrid systems (combination of PVs and ESUs) have been considered. The results are presented and discussed.

Conference paper

Pal B, Nduka O, 2018, Harmonic Domain Modeling of PV System for the Assessment of Grid Integration Impact, 2018 IEEE Power & Energy Society General Meeting (PESGM), Publisher: IEEE

Conference paper

Nduka O, Pal BC, 2018, Quantitative evaluation of actual loss reduction benefits of a renewable heavy DG distribution network, IEEE Transactions on Sustainable Energy, Vol: 9, Pages: 1384-1396, ISSN: 1949-3029

Modern distribution network architectures havegreatly changed due to the increasing proliferation of the networkwith power converters of renewable distributed generators(RDGs) and switching electronic loads. While these RDGs mayoffer benefits to the distribution network operator (DNO) interms of network loss reduction, the quantification of suchbenefits are usually investigated on the basis that harmonicsfrom the power converters are negligible. In this work, theelectrical power losses in a network with significant penetrationof photovoltaics (PVs) is assessed. The harmonics from the powerconditioners of the PVs and network background distortions havebeen taken into account in the analysis. Technical insights fromstudy of practical distribution networks are presented.

Journal article

Nduka O, Pal BC, 2017, Harmonic domain modelling of PV system for the assessment of grid integration impact, IEEE Transactions on Sustainable Energy, Vol: 8, Pages: 1154-1165, ISSN: 1949-3037

In this paper, a comprehensive harmonic domainreference frame (HDRF) model of a voltage source converter(VSC) grid interactive photovoltaic (PV) system is presented.The model is useful for assessing the harmonic coupling betweenthe PV system and the network. Different components of the PVsystem such as inverter, LCL filter and interconnecting trans-former have been incorporated in the model. Using this model,harmonic currents from PV system connected to both distortedand undistorted networks have been quantified. Also, the modelhas been deployed in investigating resonance occurrence in amedium-voltage distribution network (MVDN) where the resultsprovide interesting technical insight and understanding.

Journal article

Nduka OS, Pal BC, 2016, Harmonic characterisation model of grid interactive photovoltaic systems, 2016 IEEE International Conference on Power System Technology (POWERCON), Publisher: IEEE

This paper presents an alternative model of a grid interactive photovoltaic (PV) system which can be used for characterising the harmonics from a PV system when connected to a distorted and undistorted network respectively. The approach uses an orthogonal series function in modelling the different sections of a practical PV system thus yielding a complete harmonic domain model. The proposed model accurately handles the harmonic cross-coupling between the PV system and the network. Both single and three phase grid interactive single-stage transformerless PV systems are presented. Simulation results show the effectiveness of the proposed model.

Conference paper

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