Diesel generators are an integral component of remote islanded microgrids in rural Alaska. As inverter-based generation is integrated in these microgrids, adequate transient modeling will be necessary as dynamic and transient stability issues can arise with significant contributions of inverter-based generation. A complete transient model of a diesel generator includes models of the machine, exciter, governor, and any relays or other limiting components. Few studies compare the adequacy of various types of diesel generator governor or exciter models or include a volts/hertz (V/Hz) limiting functionality commonly found in diesel generators deployed in such remote islanded microgrids. This paper introduces and compares diesel generator models in response to two load steps against responses from the ACEP PSI lab 400 kVA diesel generator which represents a realistic diesel generator found in remote islanded Alaskan microgrids. A simplified governor model is introduced and compared to the traditional DEGOV governor model, and the functionality of a V/Hz limiter added to a DC4B exciter is demonstrated.

Alaska has over 200 communities operating remote islanded microgrids that are not connected to each other or to the North American electric grid. These communities range in size from a few dozen to a few thousand residents and rely heavily on fossil fuels-primarily imported diesel-to generate electricity. This has resulted in some of the highest energy costs in the nation (over $1/kWh in some locations) and a strong incentive to invest in renewable energy as a strategy for reducing these costs. This article explores technical challenges and associated mitigation strategies of renewable energy integration, including lessons learned from the implementation of over 70 renewable-diesel hybrid microgrids in Alaska utilizing a wide range of resource and technology solutions. This article also reviews the underlying socio-political and economic landscape that has allowed Alaska to emerge as an early adopter of microgrid-enabling technologies and includes a discussion of Alaska's energy programs and policies and how they impact project development. The results of this article show that the primary technical hurdles for renewable energy integration in Alaska's remote islanded microgrids include management of distributed energy resources and design for reliable and resilient operation with intermittent high-penetration renewable generation. Additionally, economic drivers include extremely high energy costs, a highly deregulated utility market with dozens of certificated utilities, state investment in infrastructure, and modest subsidies that create a technological niche where renewable energy projects are cost-competitive at current market prices. Many of the evolving technical strategies and lessons learned from renewable integration projects in Alaska's remote islanded microgrids could help inform project development in other markets, despite differences in climate and geography.