Abstract-- Hawaii Electric Light operates an autonomous
power system on the island of Hawaii with a diverse mix of
generating resources. Although the system is small, with an
annual peak in 2009 of less than 200 MW, the power system
balancing and frequency control is provided through a
conventional centralized Automatic Generation Control system.
The mix of generation resources on the Hawaii Electric Light
System has changed significantly in recent years to accommodate
a large amount of wind and, more recently, a significant amount
distributed solar photovoltaic generation. In addition to the
variable wind and solar resources, the system incorporates run of
river hydroelectric facilities and a geothermal facility which
provide a significant portion of the system energy. The
operation of the island power system provides an opportunity to
observe, through actual operating experience, issues relating to
power system frequency control and response under various
levels of variable generation and changes in the mix of thermal
generation.
The change in generation mix has had a marked and
measureable impact on the system frequency performance
during normal and disturbance conditions, as well as on the
generators providing system frequency response and control
capabilities. This report will describe system and generation
impacts found from studies and through actual operational
experiences. These impacts will include system performance
data collected during normal operation and disturbances, with
some specific event analysis. This paper will also describe
mitigation measures taken to improve the power system
frequency performance including modification of the power
system operation and control, changes to the conventional
generators, and requirements for existing and anticipated
generation facilities.