Currently, the contribution of renewable energy resources, such as wind power, in power systems is increasing in large, interconnected systems. However, the intermittent nature of renewable energy poses a profound challenge to power system operation and planning. Using energy storage systems can facilitate wind power integration in isolated systems. Pumped hydro energy storage (PHES) plants are by far the most established technology for energy storage on a large-scale. In dry coastal areas, seawater PHES can be used to facilitate the integration of large scale renewable energy resources. In Oman, the potential of renewable energy resources has not been exploited yet. This article presents a techno-economic evaluation case study of using a combined wind power and PHES power plant to highlight its economic feasibility. PHES systems can enable higher penetration of renewable energy in isolated systems, therefore reducing the dependency on fossil fuels.

https://www.ijrer.com/index.php/ijrer/article/download/6099/pdf

Seawater PHES to Facilitate Wind Power Integration in Dry Coastal Areas – Duqm Case Study

Currently, the contribution of renewable energy in isolated power systems are not fully exploited. The intermittent nature of renewable energy resources limits renewable energy contribution in electricity supply mix. This paper presents an overview of wind power intermittency and potential solutions. A case study about a combined wind Pumped Hydro Energy Storage (PHES) power plant in an isolated power system is presented. The study demonstrates that combined wind-PHES is economically attractive compared with other fossil fuel options.

Using PHES to facilitate wind power integration in isolated systems — Case study

Planning the development of an electrical power grid is a sophisticated multilevel process, which involves putting into practice different relevant methods of analysis, models, software packages, standards etc. The inputs and criteria for different planning levels may also vary. Planning of the transmission grid greatly depends on decision making on a higher level of hierarchy, influencing electrical power supplies of large areas. Development of a medium voltage (MV) grid, on the other hand is affected by locally generated inputs, such as local load shift. The business as usual approach is to separately derive development plans for transmission and distribution systems. This article examines one of the possible methods for creation of a combined long term (with a 15 year perspective) transmission and distribution systems' contact level (35–110 kV in current case) electrical power grid development plan, centered around grid optimization through primary distribution substations and their feeding lines location. The method proposed aims to minimize joint costs of transmission and distribution system operators (TSO-s and DSO-s) for electrical power grid development on a given planning horizon. It is shown that a co-operative approach can result in lower costs of electrical power grid development for the society as a whole. The results are applicable to practical usage.

Basis and method for electrical power grid development planning

The prevalence of cabled infrastructure associated with wind farms, combined with the increase in power-electronic interfaces in wind turbines and reactive power plant, has highlighted the pervasive nature of harmonics on electricity networks. Insufficient consideration is given to the effects of harmonics through the low prioritisation of power quality in the Front-End Engineering and Design stage and a lack of awareness of the obligations of the respective parties involved. The resulting designs are incompatible with the requirements of the relevant Grid Codes. This can lead to delays, commercial exposure, restricted network access and subsequent loss of revenue. The obligations of the Transmission Owner (TO), System Operator (SO) and wind farm developer are discussed with respect to Grid Code requirements and the responsibilities of each party in ensuring compliance. The technical aspects of assessing harmonic compliance are described in the context of the design considerations which are made at the various stages of the project development. These include the shift in resonances within the host network, the modification of existing harmonic distortion and the propagation of injected harmonics into the network and through to the extra high voltage, high voltage and medium voltage substations. The ensuing challenges associated with ensuring compliance through filter design are discussed in the context of relevant international standards, including UK ER G5/4-1, IEEE 519, EN 50160 and IEC 61000-3-6. The results indicate that shifts in resonances are more problematic to resolve, compared to the propagation of injected harmonics: injected harmonics are readily absorbed through local filtering and thus the emissions are typically low; in contrast, the effects of shifts in resonances must be transferred back to the point of common coupling, resulting in complex local filtering. Early selection by the developer of appropriate transmission infrastructure and technology can lower the filtering requirement necessary to meet the harmonic specification issued by the host TO.

Ensuring Grid Code Harmonic Compliance of Wind Farms

The sensitivity and the highly connected modern power systems make Power quality problems a priority in these systems. Both utilities and consumers have essential role in dealing with these problems. It is utilities responsibility to provide a clean and reliable power. On the other hand, it is consumer’s responsibility to draw power with acceptable indices. In this Paper, the type of the consumer’s facility is chosen as a basis for managing power quality indices. In this paper, comprehensive power quality in Jordan Low-Voltage Electrical Power Grid is measured. The loads are divided into five categories: : (i) industrial loads, (ii) commercial loads, (iii) hospital loads, (iv) residential loads, and (v) office loads. Assuming each category will affect the grid in similar way, which will facilitate prediction of power quality problems. Also, this methodology will help proposing new regulation that governs the relation between utilities and consumers. The power quality indices considered in this paper are; THD, Crest factor, K-factor, Power factor, Harmonic to active power ratio, Voltage imbalance, and Frequency variations. The results show similar results for the loads with the same type. Also, the results show the correlation between the current total harmonic distortion and utility voltages and neutral-to-ground voltage, and between voltage and current imbalance.

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Investigation of Power Quality Indices in Jordanian Distribution Grid

This paper investigates factors which influence the power quality performance of the Dhofar Power Grid, based upon the first 50MW wind farm project connection. The wind farm consists of 20×2.5 MW wind turbines and will be integrated into the 132kV Dhofar network which is connected with the Maim Interconnected System via the Petroleum Development of Oman grid. As this is the first wind farm project in Oman, a review of fundamental aspects which influence power quality for connecting the wind farm is presented, as well as an initial view on Grid Code performance. The power quality assessment is required as part of the license obligation for a transmission operator and is vital to a wind farm developer for their filter design and compensation sizing. The paper addresses power quality topics such as voltage unbalance, flicker and harmonic compliance, in relation to network changes and potential future non synchronous connections. Simulation studies are carried out in DIgSILENT software and are presented in the paper.

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Power quality of Dhofar network with 50 MW wind farm connection

The objective of this paper is to present the methodology, approach and results of the demand forecast analysis used in the Transmission Master Plan of Oman 2014–2030. Oman Electricity Transmission Company and Tractebel Engineering analyze the challenges and review the existing load demand forecast studies used in Oman. Different studies analyze load forecasting at short to medium term. A spatialization of the long term load forecast is required in the Transmission Master Plan (2014–2030) of Oman in order to correctly address the transmission expansion plan. Several approaches are proposed to review and challenge existing studies and to spatialize the load demand forecast. The approaches are called global and areabased forecasting methods. Each approach is complimentary and allows to cross-check the adequacy of the method to the peculiarities of the local load demand and the accuracy of the data available. The global method allows linking the electricity consumption to the various economic indicators through mathematical regression relating the electrical energy consumption to socio-economic indicators. The area-based based method aims to spatialize the load forecast taking into account the consumption at regional level and the local characteristics of each area in the Sultanate. The results of the load demand forecast analysis defined the area with very high growth, the amount of generation required in the firm of the Transmission Master Plan and accordingly the least cost transmission network development plan.

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S. Mirza

Papers

Power quality of Dhofar network with 50 MW wind farm connection

Development of demand forecast model for the transmission system master plan of Oman (2014–2030)