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Abstract In the isolated power system, consumers are traditionally supplied with electricity produced by diesel generators. Conventional diesel generators demonstrate robust and efficient operation when connected to electrical grids with slowly varying loads. With the introduction of intermittent and stochastic renewable energy sources, such generators may not be responsive enough to retain the stability and reliability of the system. The problem becomes especially acute in cases when diesel generators are required to operate at a low load. Regulating devices (e.g. energy storage systems and/or dump load) used to improve the system reliability, increase system complexity and incur additional expenses or energy losses. This paper investigates low load diesel technology as a potential solution to high level renewable energy penetration. The focus is made on the engine time delay and the generator inertia constant that should be considered during the design of the isolated hybrid power system. [ABSTRACT FROM AUTHOR]

Abstract Remote communities increasingly integrate renewable source generation to reduce the environmental and economic impact of diesel generation. Despite benefits scaling proportionally with the level of renewable penetration, most systems restrict renewable utilisation to below 30% of annual production. Identifying system complexity as a key barrier to renewable uptake, this paper investigates methodologies to simplify integration of high renewable penetrations. Three approaches are considered, via three Australian case studies; King Island, Tasmania (approach one), Flinders Island, Tasmania (approach two), and Rottnest Island, Western Australia (approach three). Approach one details a methodology for wind plus storage integration. Approach two details a methodology for wind, solar PV, plus storage integration. Approach three details a methodology for wind and solar PV integration, without storage. All approaches facilitate high renewable penetrations, with each island majority renewable supplied. Approach one benchmarks system performance, with King Island one of the worlds' earliest high penetration renewable islands. Approach two explores benefit via renewable diversification. Approach three investigates rationalisation of energy storage via low load diesel and demand management technology substitution. For approach three a 32% reduction in capital cost was observed, identifying commercial justification for the approach via deferral of energy storage integration. Highlights • High penetration renewable energy power systems using diesel engine were studied. • Annualised system behaviour was investigated for multiple isolated power systems. • The role of enabling technologies/methodologies was compared across case studies. • Battery storage rationalisation can effectively reduce system capital cost. • Advanced diesel technologies substitute for battery storage without major penalty. [ABSTRACT FROM AUTHOR]

The increasing penetration of distributed and renewable generation presents power systems with a challenge of accommodating multiple inverter-based generators. Distributed generators (DGs), capable of operating in the islanded mode, are often installed in microgrids. However, a control system for operating multiple DGs in the islanded mode using voltage-sourced converters is a real challenge under uncertainties in load parameters, unbalanced phase conditions, and transients. This paper proposes a novel approach to decentralized control of multiple DGs. This approach is based on a combination of a voltage controller using model predictive control and a fast current controller using a discrete-time sliding-mode controller for limiting the inverter currents under overload conditions. Performance of the proposed control system is compared with a robust servomechanism program controller. The proposed control strategy provides fast tracking, robustness, and fast transient recovery in voltage and current under: 1) short-circuit conditions; 2) load transients; and 3) unbalanced loads. Various scenarios including reference signal tracking and robustness against the load perturbations are considered. Results are presented and discussed. [ABSTRACT FROM PUBLISHER]

Traditional engine load limits restrict a diesel engine's range and its ability to load share. Accordingly, to achieve high renewable penetrations, diesel generation is conventionally turned off, positioning diesel in competition with variable renewable generation. While this approach maximises renewable penetration (environmental gain), it is uneconomic, requiring costly and complex enabling technologies such as battery storage. For many isolated communities the commercial, technical and social barriers associated with storage integration prove insurmountable. A stalemate results, with owners unable to transition to renewable generation due to inflexible diesel technologies. In this respect, it is easy to view diesel generation as an obstacle to renewable integration. Thankfully, modified diesel technologies can offer improved flexibility without the cost or complexity of energy storage. This paper details the development and testing of both low load and variable speed technologies, each able to improve the performance of diesel generation. Two isolated power system case studies are modelled, with Cape Barren island increasing renewable penetrations to between 41.3% to 58.0% compare to conventional penetrations of 7.7% to 10.1%. For Lady Elliot island the modelled range is 26.7% to 28.5% in comparison to a base of 5.3%. The results serve to recommend modified diesel application as a precursor to battery storage integration. • Low load and variable speed diesel technologies are experimentally investigated. • Variable speed hybrid approach is developed to mitigate converter losses. • Benefit is identified for modified application in battery-less systems. • The approach permits high renewable energy penetrations without storage. [ABSTRACT FROM AUTHOR]

Isolated communities are progressively integrating renewable generation to reduce the societal, economic and ecological cost of diesel generation. Unfortunately, as renewable penetration and load variability increase, systems require greater diesel generation reserves, constraining renewable utilisation. Improved diesel generator flexibility can reduce the requirement for diesel reserves, allowing increased renewable hosting. Regrettably, it is uncommon for utilities to modify diesel generator control during the integration of renewable source generation. Identifying diesel generator flexibility and co-ordination as an essential component to optimising system hosting capacity, this paper investigates improved diesel generator flexibility and coordination via low-load diesel application. Case study comparisons for both high- and low-penetration hybrid diesel power systems are presented in King Island, Australia, and Moloka'i, Hawai'i, respectively. For King Island, the approach details a 50% reduction in storage requirement, while for Moloka'i the application supports a 27% increase in renewable hosting capacity. [ABSTRACT FROM AUTHOR]

One-quarter of the world's population lives without access to electricity. Unfortunately, the generation technology most commonly employed to advance rural electrification, diesel generation, carries considerable commercial and ecological risks. One approach used to address both the cost and pollution of diesel generation is renewable energy (RE) integration. However, to successfully integrate RE, both the stochastic nature of the RE resource and the operating characteristics of diesel generation require careful consideration. Typically, diesel generation is configured to run heavily loaded, achieving peak efficiencies within 70–80% of rated capacity. Diesel generation is also commonly sized to peak demand. These characteristics serve to constrain the possible RE penetration. While energy storage can relieve the constraint, this adds cost and complexity to the system. This paper identifies an alternative approach, redefining the low load capability of diesel generation. Low load diesel (LLD) allows a diesel engine to operate across its full capacity in support of improved RE utilization. LLD uses existing diesel assets, resulting in a reduced-cost, low-complexity substitute. This paper presents an economic analysis of LLD, with results compared to conventional energy storage applications. The results identify a novel pathway for consumers to transition from low to medium levels of RE penetration, without additional cost or system complexity. [ABSTRACT FROM AUTHOR]

In the revolution of green energy development, microgrids with renewable energy sources such as solar, wind and fuel cells are becoming a popular and effective way of controlling and managing these sources. On the other hand, owing to the intermittency and wide range of dynamic responses of renewable energy sources, battery energy-storage systems have become an integral feature of microgrids. Intelligent energy management and battery sizing are essential requirements in the microgrids to ensure the optimal use of the renewable sources and reduce conventional fuel utilization in such complex systems. This paper presents a novel approach to meet these requirements by using the grey wolf optimization (GWO) technique. The proposed algorithm is implemented for different scenarios, and the numerical simulation results are compared with other optimization methods including the genetic algorithm (GA), particle swarm optimization (PSO), the Bat algorithm (BA), and the improved bat algorithm (IBA). The proposed method (GWO) shows outstanding results and superior performance compared with other algorithms in terms of solution quality and computational efficiency. The numerical results show that the GWO with a smart utilization of battery energy storage (BES) helped to minimize the operational costs of microgrid by 33.185% in comparison with GA, PSO, BA and IBA. [ABSTRACT FROM AUTHOR]