Effect of Inertia Constant on Generator Frequency and Rotor Angle

Ngyarmunta Alan Audu

doi:10.11648/j.eas.20180301.12

Abstract

Inertia constant of a rotating system describes the initial transient, frequency and rotor angle behavior of that system when subjected to a real power disturbance. Therefore, the inertia constant of a system can be a useful tool when investigating the frequency and rotor angle stability of a system. The use of the swing equation gives us a viable method for estimating the inertia constant, if a measurement of that can provide time stamps measurements of the frequency and power dynamics during a disturbance. In this project work, effect of inertia constant of synchronous generator (machine constant) on its frequency and rotor angle is investigated. Swing equation is used for modeling the dynamics of the system. It is then built and simulated using MATLAB. The analysis is done by observing how the frequency and rotor angle changes when the inertia constant is varied while keeping all system parameters constant. The study is extended to investigate the dynamics of such system with very high and those with very low inertia constant and the results show that the higher the value of the inertia constant, the higher the settling time and of course the maximum overshoot.

Highlights

A Power System consists of the generating machines and transmission network in which the generating machine includes turbine, alternator and excitation system [1]
Results obtained for variation in inertia constant shows different waveforms of the rotor angle and frequency as depicted in Figure 2 and Figure 4 respectively
It can be inferred from the waveform of the rotor angle that the settling time and maximum overshoot are proportional to the values of the inertia constant

Summary

Introduction

A Power System consists of the generating machines and transmission network in which the generating machine includes turbine, alternator and excitation system [1]. Inertia is an inherent property of synchronous generators, and frequency dynamics of the system within the first seconds after a disturbance is governed by inertial response of the rotating machines. Since inertia level defines the rate of frequency deviation in the first seconds after a disturbance, reduced inertia results in faster frequency dynamics [9 - 11]. One of the measures to mitigate the effects of reduced inertia is implementation of faster primary frequency control Another possible solution is provision of artificial rotational inertia in the system. 2. Frequency stability refers to the ability of a power system to maintain steady frequency following a severe system upset resulting in a significant imbalance between generation and load. 3. Rotor angle stability is defined as the ability of synchronous machine of an interconnected power system to remain in synchronism after being subjected to a disturbance. Whether a system remains stable or not after a large disturbance, depends on the initial state of this system and the severity of the disturbance

Aim and Objectives

Modeling and Simulation

Results and Discussion

Conclusion