Showing papers by "Neville R. Watson published in 2018"

A Hybrid DA-PSO Optimization Algorithm for Multiobjective Optimal Power Flow Problems

Abstract: In this paper, a hybrid optimization algorithm is proposed to solve multiobjective optimal power flow problems (MO-OPF) in a power system. The hybrid algorithm, named DA-PSO, combines the frameworks of the dragonfly algorithm (DA) and particle swarm optimization (PSO) to find the optimized solutions for the power system. The hybrid algorithm adopts the exploration and exploitation phases of the DA and PSO algorithms, respectively, and was implemented to solve the MO-OPF problem. The objective functions of the OPF were minimization of fuel cost, emissions, and transmission losses. The standard IEEE 30-bus and 57-bus systems were employed to investigate the performance of the proposed algorithm. The simulation results were compared with those in the literature to show the superiority of the proposed algorithm over several other algorithms; however, the time computation of DA-PSO is slower than DA and PSO due to the sequential computation of DA and PSO.

Optimized Dispatch of Energy Storage Systems in Unbalanced Distribution Networks

Abstract: This paper presents a method to achieve optimal active and reactive power contributions from each energy storage system in an unbalanced distribution network to minimize power loss, while ensuring network current and voltage constraints are satisfied. By modeling loads as either constant current or constant impedance, the ac optimal power flow is transformed into a noniterative convex optimization problem. The application of capacity constraints, voltage constraints, and energy storage constraints in an unbalanced three-phase four-wire system is considered, addressing specific issues pertaining to unbalanced networks such as voltage unbalance and neutral voltage displacement. The proposed method is then used to demonstrate optimized dispatch of energy storage systems in a suitable four-wire unbalanced distribution test network. The contribution of losses in the neutral wire to the total losses is also determined for a test system under a range of operating conditions and various neutral earthing systems, highlighting the importance of considering this in a typical unbalanced distribution network.

Smart grid research in New Zealand – A review from the GREEN Grid research programme

Abstract: Globally, renewable generation is growing rapidly, and the next few decades are likely to see many consumers adopting new grid-connected technologies such as electric vehicles, photovoltaics and energy management systems. However, these ‘greener’ and smarter’ changes could create significant challenges for power quality, safety and other aspects of grid management. We describe how New Zealand is an ideal research environment for combining smart grid capability with integration of high levels of renewables, as it already has around 80% renewable generation, and advanced metering infrastructure in over 62% of households. Challenges for achieving a greener, smarter grid identified in the GREEN Grid research programme include managing the increased variability in supply, especially from the growing use of wind and solar generation; the potential for power quality and congestion issues from high levels of small scale distributed generation; the need for increased frequency keeping and instantaneous reserves as variability increases; and the relatively low level of consumer engagement in demand response which could ideally assist with variability. In this paper we describe the methodology and approach used in the research programme, and note some initial findings that may help address these issues, including the benefits of geographically distributed wind farms to reduce overall wind variability; the development of a hosting capacity tool for small scale distributed generation; a proposal for new ancillary services to help manage (and cover the costs of) increased variability; and the increased use of hot water cylinders for demand response. As the research programme continues to move forward with developing mechanisms for managing a smart green grid, the findings are likely to have widespread relevance to other nations that are seeking high levels of renewable generation.

A New Test Procedure to Measure Power Electronic Devices’ Frequency Coupling Admittance

Abstract: One method to model power electronic devices for harmonic emission studies is using frequency-domain models based on the frequency coupling matrices. This paper presents a new test procedure for the experimental evaluation of the frequency coupling matrix elements of power electronic devices. An automated test system is designed, realized, and characterized from a metrological perspective. Experimental tests show the tremendous increase in speed of the new test procedure in comparison to the classical test procedures present in the literature, with the same levels of accuracy of obtained results.

On the use of fourier descriptors for the assessment of frequency coupling matrices of power electronic devices

Abstract: The use of Fourier descriptors (FD) for the assessment of frequency coupling matrices (FCM) of power electronic devices is considered. After some recalls on FDs, FCM approach is discussed showing how the matrices elements can be built basing on the use of maximum two FDs under linearity hypothesis. Then, a non-linearity index that allows to check the validity of the assumed “linearity hypothesis” and to quantify the obtainable accuracy is introduced. Numerical simulations on two very simple non linear circuits are performed to show the sensitivity of the FCM elements to magnitude and phase angle variation of the background harmonic distortion using FDs and the usefulness and the behavior of the non linearity index.

Impact of reference conditions on the frequency coupling matrix of a plug-in electric vehicle charger

Abstract: Plug-in Electric Vehicles (PEVs) are progressively penetrating world markets. A significant impact on harmonic distortion in distribution networks is expected due to large-scale charging of PEVs at homes. Therefore, models that accurately predict the individual current injections are needed to perform harmonic studies, in particular frequency domain models such as those based on Frequency Coupling Matrices (FCM). In this paper, Fourier descriptors are used to estimate and compare the FCMs of a commercially available on-board PEV charger. Two models were calculated for two different supply reference conditions, namely, a sinusoidal voltage with no distortion, and a flat-top voltage. To that end, extensive laboratory measurements were carried out. Results show similar values in the parameterized admittances for both reference conditions. These results indicate a wide linear range in the coupled Norton model for this load, and should be probably attributable to the active power factor correction topology of the charger.

Statistical analysis of Australian and New Zealand Power Transformer Catastrophic Fires

Abstract: Modelling fires or explosions of power transformers is necessary to assist a utility determine the level of risk incurred from operating their network. However, a challenge is to collect enough data to establish a robust model when these events occur so rarely. Consequently, to collect such a large volume of usage data the Australian and New Zealand utilities were surveyed for information on their power transformers, and on those which had failed catastrophically (either fire or explosion). Approximately 88,000 service-years of operation were collected from 6,637 power transformers operated by 28 utilities between 2000 and 2016. Twenty-one fire or explosion events were identified over this period. Certain power transformer voltage groups appeared to be more likely to fail catastrophically as their age increased. The Poisson distribution was used to provide a method to determine in how many years a fire might be expected, as this can help plan asset replacement.