Insular Grids Research Articles

Solar Radiation Gridded Satellite data comparison in Gran Canaria Island

During the last years solar energy has been increasing the percentage of the total energy production around the world and it is expected it persists growing notably [1]. In insular grids, such as Canary Islands, the knowledge of solar radiation behaviour is one of the most important variables in order to ensure the stability for power systems. In this paper we study the suitability of Gridded Satellite data for modelling solar radiation for both PV and CSP purposes. The analysis and comparison is performed using hourly Global and Direct Solar radiation from the satellite model CM SAF database and four ground measurement stations in Gran Canaria. This study could give us a better knowledge of solar radiation behavior in a wide spatial and temporal coverage. Moreover, an accurate satellite radiation data could improve solar radiation forecasting for power systems manage systems [2].

Innovative Power Smoothing Technique for Enhancing Renewable Integration in Insular Power Systems Using Electric Vehicle Charging Stations

The reliance on imported fuels for electricity generation and internal transportation in insular electrical systems has historically posed a significant challenge due to their geographic isolation. The vulnerability of insular ecosystems to pollution has driven the need to transition toward renewable energy sources. Despite their inherent variability, wind and solar energy have gained acceptance. Integrating these renewable technologies into insular grids presents technical challenges that impact the quality of the power supply, particularly with the increasing presence of electric vehicles. Nevertheless, the batteries of these vehicles provide an opportunity to enhance network performance. This article introduces an innovative power smoothing technique that utilizes electric vehicle batteries to optimize self-consumption and reduce power fluctuations. The proposed method is an enhanced version of the ramp-rate energy smoothing method, incorporating adaptability through real-time control of the ramp-rate using fuzzy logic. It employs an aggregated model of lithium-ion batteries with a bidirectional power electronic converter. Experimental validation is carried out in the Micro-Grid Laboratory of the University of Cuenca, Ecuador. Experimental results demonstrate a significant 14% reduction in energy generation variability, resulting in a more stable electrical supply profile. Additionally, there is a marginal improvement in energy delivery, with an additional injection of 0.23 kWh compared to scenarios without the participation of electric vehicle batteries in power smoothing tasks. These findings support the effectiveness of the proposed approach in optimizing the integration of intermittent renewable generators and electric vehicle charging in insular energy systems.

Stochastic Generation Scheduling of Insular Grids with High Penetration of Photovoltaic and Battery Energy Storage Systems: South Andaman Island Case Study

Insular grids are fragile owing to lower inertia and the absence of interconnection with other grids. With the increasing penetration of non-dispatchable renewable energy sources, the vulnerability of such insular grids increases further. The government of India has proposed several projects to improve the photovoltaic systems (PV) penetration in the Andaman and Nicobar Islands’ grid. This paper investigates joint stochastic scheduling of energy and reserve generation for insular grids fed from diesel and gas-based generators, PV, and battery energy storage systems (BESS). The proposed stochastic scheduling model considers a wide range of probabilistic forecast scenarios instead of a deterministic model that assumes a single-point forecast. Hence, it provides an optimal solution that is technically feasible for a wide range of PV power forecast scenarios. The striking feature of the model developed in this work is the inclusion of stochastic constraints that represent (i) the coordination between PV and BESS, (ii) reserve constraints, (iii) battery charging/discharging limit constraints, and (iv) non-anticipatory constraints that ensure technical viability of scheduling decisions. The proposed model is validated on the dataset for South Andaman Island. Results reveal the applicability and feasibility of the proposed stochastic dispatch model for different generation mix scenarios.

Influence of Load Dynamics on Converter-Dominated Isolated Power Systems

The operation of isolated power systems with 100% converter-based generation requires the integration of battery energy storage systems (BESS) using grid-forming-type power converters. Under these operating conditions, load dynamics influences the network frequency and voltage following large voltage disturbances. In this sense, the inclusion of induction motor (IM) load models is required to be properly considered in BESS power converter sizing. Thus, this paper presents an extensive sensitivity analysis, demonstrating how load modeling affects the BESS power converter capacity when adopting conventional control strategies while aiming to assure the successful recovery of all IM loads following a network fault. Furthermore, this work highlights that generators with converter interfaces can actively contribute to mitigate the negative impacts resulting from IM loads following a network fault. Thereby, two distinct control strategies are proposed to be integrated in the power electronic interfaces of the available converter-based generators: one to be adopted in grid-following converters and another one suitable for grid-forming converters. The proposed control strategies provide an important contribution to consolidating insular grid codes, aiming to achieve operational scenarios accommodating 100% penetration of converter-based generation with a significative percentage of the IM load composition without resorting to a significative increase in BESS power converter sizing.

Comparing electricity storage technologies for small insular grids

The objective of this article is to investigate the technically and economically optimum electricity storage technologies for small, insular, autonomous electrical grids, integrated with Renewable Energy Sources (RES) power plants. Three autonomous Greek islands are investigated as case studies: Symi, Astypalaia and Kastelorizo, with annual peak demand at 4.0 MW, 2.2 MW and 0.9 MW respectively. All three islands exhibit excellent wind and solar potential, with ideal sites for the installation of seawater Pumped Hydro Storage (PHS). Two different approaches are investigated, regarding the electricity storage plants: PHS systems (for the two largest islands) and electrochemical storage, alternatively realized with lead acid or lithium-ion batteries. Wind parks and photovoltaic stations are considered as the potential RES units. Relevant operation algorithms are introduced. The dimensioning of the examined plants is optimized with a common target: the achievement of RES annual penetration percentage higher than 70%, ensuring the investments’ economic feasibility, with electricity selling prices lower than the existing specific production cost. Given the favorable land morphology for PHS installations, it is shown that wind-PHS still remains a competitive alternative for Symi and Astypalaia, despite their relatively small size, while for Kastelorizo, a wind-photovoltaic-batteries features as the optimum option. 100% annual RES penetration can be achieved only with the PHS support. With electrochemical storage systems, the RES annual penetration can be between 80 and 90%. The economic feasibility is ensured with electricity selling prices between 200 and 350 €/kWh. The investments’ payback periods are estimated between 6 and 10 years.

Comparing electricity storage technologies for small insular grids

This article investigates the technically and economically optimum electricity storage technologies for small, insular, autonomous electrical grids, integrated with Renewable Energy Sources (RES) power plants. Three autonomous Greek islands are investigated as case studies: Symi, Astypalaia and Kastelorizo, with annual peak demand at 4.0 MW, 2.2 MW and 0.9 MW respectively. All the investigated islands exhibit excellent wind and solar potential, with ideal sites for the installation of seawater Pumped Hydro Storage (PHS).Two different approaches are investigated, regarding the electricity storage plants: PHS systems (for the two largest islands) and electrochemical storage, alternatively realized lead acid or lithium-ion batteries. Wind parks and photovoltaic stations are considered as the potential RES units. The dimensioning of the examined plants is optimized with a common target: the achievement of RES annual penetration percentage higher than 70%, maintaining the electricity selling price lower than the existing specific production cost. The study is integrated with the economic evaluation of the examined systems.Given the appropriate land morphology for PHS installations, it is shown that wind-PHS still remains a competitive alternative for Symi and Astypalaia, while for Kastelorizo, a wind-p/v- batteries features as the optimum option. 100% annual RES penetration can be achieved only with the PHS support, while with the electrochemical batteries the RES annual penetration can be between 80 and 90%. The economic feasibility is ensured with electricity selling prices between 200 and 350 €/kWh, leading to payback periods between 5 and 9 years.

Analysis of satellite derived solar irradiance in islands with site adaptation techniques for improving the uncertainty

Electrical energy production using renewable energies is one of the most important challenges in recent years. Among renewable energies, it is worth highlighting photovoltaic and thermoelectric systems due to their adaptation to the Canary Islands. One of the most important issues to ensure the stability for solar power systems, mostly in insular grids as Canary Islands, is the precise knowledge of solar radiation. In this paper, we focus in Gridded Satellite data suitability for modelling Global Horizontal Irradiation (GHI) in islands with complicated orography, as Canary Islands. Solar radiation data retrieved from CM SAF and McClear model were analysed and compared with 22 ground measurement stations in Canary Islands. Moreover, this analysis presents the results of including a site-adaptation methodology for improving satellite suitability. We used different procedures to perform this site adaptation depending on the solar radiation conditions (clear sky or cloudy sky hours), the location of the measurement station (we establish two clusters according to the climate conditions) and the season. This study could provide information about satellite models suitability in islands and a better knowledge of solar radiation behavior. Furthermore, accurate satellite radiation data for wide spatial and temporal coverage could improve solar radiation modelling and forecasting.

Optimization of the operation of a flywheel to support stability and reduce generation costs using a Multi-Contingency TSCOPF with nonlinear loads

Multi-Contingency Transient Stability Constrained Optimal Power Flow (MC-TSCOPF) models optimize the economic dispatch of power systems while ensuring their stability after a series of reference incidents. This paper proposes a MC-TSCOPF model that represents the power balance at each node of the system and at each sample time. The proposed model includes non-linear loads, synchronous generators, a windfarm, and a Flywheel Energy Storage system (FESS). The model is written on GAMS and solved using a standard Interior Point algorithm. This study focuses on the Fuerteventura-Lanzarote insular grid in Spain, where stability problems and load shedding cause high additional costs due to the low inertia of the system. A FESS has been recently installed in the system to improve its stability, taking advantage of its high-power capacity and rapid response. The proposed TSCOPF model has been applied to optimize the operation of the FESS to support stability in the event of a contingency. The results of the study show that 1) a proper model of non-linear loads is essential in TSCOPF studies; 2) the proposed MC-TSCOPF provides a tool for minimizing the generation costs while ensuring transient and frequency stability; and 3) it is possible to further reduce the generation costs by using the proposed model to calculate an optimal dynamic response of the FESS.

Innovative impact assessment of electric vehicles charging loads on distribution transformers using real data

Widespread adoption of Electric Vehicles (EVs) could bring social and economic benefits. The effort of promoting the use of EVs in transportation is indispensable to meet the climate change related targets and to reduce the dependency on the ever unstable prices of diminishing fossil fuels. However, there are still many uncertainties in the market regarding the acceptability of EVs by the final consumers. As a new contribution with respect to earlier studies, this paper assesses the impact of EV charging load on the dielectric oil deterioration of two real Power Distribution Transformers (PDTs), one residential and one industrial, located in the insular grid of São Miguel. A PDT thermal model is used to estimate the hot-spot temperature given the load ratio. Real data are used for the main inputs of the model, namely, the daily residential load curve, the daily private industrial client load curve, the PDT parameters, time-of-use rates and EV parameters.

Spatial and Temporal Variability of PV Output in an Insular Grid: Case of Reunion Island

Some small territories, such islands, actually experience a high penetration rate of PV inside a small electricity grid. In this context, the variability of the PV output is an issue for the supply-demand balance. The spatial and temporal smoothing of the variability of the PV production is an important information for the grid operator.Previous works on this topic were mainly done for large-scale continental grids. They pointed out the relation between the production variability with the number and the dispersion factor of the PV systems. This paper presents an analysis of the variability of PV output for a small insular territory: Reunion island. This island has a large variety of microclimates and a strong penetration rate of PV (almost 30% of the installed power). For this little grid, the spatial and temporal effects on the variability of the PV output differ slightly with previous works.