Development of a Small-Scale Generator Set Modelfor Local Network Voltage and FrequencyStability Analysis
G. Qui˜nonez-Varela and A. Cruden
Abstract—The integration of numerous small-scale generatorsinto existing local networks (e.g., a microgrid) is anticipated to impact their operation, control, and protection. In particular, maintaining voltage and frequency stability within the defined limits is more onerous and requires investigation. The effect of protective
limiters and characteristics such as the genuine inertia of the generation set must be taken into consideration in stability studies in order to accurately represent the overall dynamic characteristics of local distributed generators. This paper focuses on three fundamental aspects: 1) the development of a reciprocating engine
generator set model; 2) the laboratory testing of an experimental test rig; and 3) the influence of a volts-per-hertz ratio (volts-per-hertz ratio) limiter on the generator dynamic response. The experimental procedures used to determine the genuine inertia of the test rig are described and the system responses under different scenarios are used to validate the developed model. This emphasizes the significance of excitation protective limiters such as volts-per-hertz ratio, during the stability analysis. Index Terms—Dispersed storage and generation, power system
dynamic stability, synchronous generator excitation, synchronous generator stability, voltage control.
I. INTRODUCTION
THE emergence of small-scale distributed and other new
generators together with the present tendency to consider
smaller power systems have created new opportunities for
the operation of on-site power generation. As a consequence,
the prospects for the operation of “islands” of small parts of the
network and microgrid systems, either totally or temporarily
isolated, are steadily emerging [1]–[3].
To efficiently and securely integrate an escalating number
of distributed, on-site generators into the existing local power
systems, a number of issues need to be investigated and the implications/
requirements clearly understood, especially when operated
in the autonomous mode [4]. For example, in the United
Kingdom, revision of the “islanded” stability limits and protection
constraints in Engineering Recommendations P2/5 and
G59 is being considered [5], [6], and the examination of novel
procedures for coordinating “island” operation of distribution
Manuscript received May 28, 2004; revised January 19, 2005.