Scalable Fault Models for Prognosis and Diagnosis of Generators in Aircraft Electrical Systems
Prognosis and diagnosis are important aspects of any state-of-the-art aerospace application. Machine condition based monitoring and maintenance can help enhance the system performance and prevent system failures. It also helps reduce maintenance costs. Line replaceable units (LRU) are the basic components in any aerospace system that can be easily replaced during maintenance. The reliability of the system could be considerably enhanced when each of the LRUs are equipped with an automatic condition monitoring and maintenance system.
In this research work, transient stability margin is tested on a laboratory model of Wind Electric Generator (WEG), an induction generator. An important limitation of Squirrel Cage Induction Generator (SCIG) used in WEG, is that, it may run at excess speed and lose stability if terminal voltage drops heavily, besides drawing very high reactive power.
Transient Stability Margin is the predicted behavior of a system when there are sudden fluctuations in the output of an electric power generator. Improvement of Transient stability margin means larger critical clearing time of electric generator, which is the indication of better Fault Ride Through Capability (FRTC).
Currently, only switched capacitors are used to improve the reactive power compensation. In this work, STATic Synchronous COMpensator (STATCOM) with a super capacitor is used. When a sudden fault occurs in the Generator, the entire system is disconnected from the grid. This project attempts to demonstrate that a grid-connected Wind Electric Generator (WEG) will remain connected to power network during and after severe system faults.
The proposed work is a scheme by which the fault ride is improved to preserve the power system security through capability of SCIG. STATCOM can rapidly supply dynamic VARs required during system disturbances and faults for voltage support. Super capacitor is very fast responding which is needed to restore the system quickly after clearing the fault so as to maintain system stability. The proposed system consists of IGBT based Voltage Source Converter (VSC), with a DC capacitor and a super capacitor as energy storage devices, a coupling inductor connected in shunt with the power system, and control circuits. Pulse Width Modulation (PWM) technique is used for controlling the switching of VSC MOSFETs/IGBTs.