Field Verification of Autonomous Anti-Islanding Schemes and Grid Support Functions of an Inverter-Based Microturbine Distributed Generator

Abstract

Canada-wide climate change plans have been put in place in the form of legislation and emission reduction programs. As part of these measures, reduced amounts of natural gas can be vented, incinerated, or flared. These programs have a direct impact on the Canadian oil and gas industry. Other measures mandate the decommissioning of high-emission thermal power plants, such as coal-fired generation. At the same time, governments are encouraging the wide-scale adoption of distributed energy resources (DERs). Because of these changes, natural gas fired DERs have been proliferating in oilfields to consume the byproduct natural gas and most major oil and gas companies are diversifying their portfolio to include generation assets. It is a more sustainable and environmentally friendly scenario as compared to the previous status quo. From an electric utility standpoint, this represents a change in paradigm, because distribution systems are traditionally planned to be radial and only experience power flowing from the substation to the load centers. This change requires utilities to adapt to new concerns and requirements, which span from operation to health and safety hazards. Among these, anti-islanding is likely the most important concern to allow the safe and reliable operation of a distribution system. The standard method to avoid unintended islanded operation is the direct transfer trip. Under exceptional circumstances, the utility may waive this requirement if an alternative acceptable method is in use. This article addresses existing anti-islanding schemes and covers in detail an alternative anti-islanding method native to many inverters. This article contains the philosophy of such method and measurement results captured during commissioning of a DER containing the scheme. Furthermore, this article highlights the evolution of inverter-based generator technologies and how the revision of applicable standards (IEEE 1547) can improve the reliable operation of such DERs.