Aircraft Power Generators: Hybrid Modeling and Simulation for Fault Detection

Integrated drive generators (IDGs) are the main source of electrical power for a number of critical systems in aircraft. Fast and accurate fault detection and isolation (FDI) are necessary components for safe and reliable operation of the IDG and the aircraft. IDGs are complex systems, and a majority of the existing FDI techniques for the electrical subsystem (brushless generator) are based on signal analysis and heuristic methods derived from experience. Model-based fault diagnosis techniques are hypothesized to be more general and powerful in designing detection and isolation schemes. However, building sufficiently accurate models of brushless generators is a difficult task. dq models have been developed for single generators, but these models are not suitable to represent the complete brushless generator either in normal or fault situations, where the generator may become unbalanced. In this paper, we develop a novel hybrid dynamical model for the complete brushless ac generator. We exploit the hybrid modeling capability to accurately model different rectifier diode faults and rotor winding faults, reported as the most severe brushless generator faults. We simulate the hybrid model for nominal and different faulty conditions, and develop fault signatures for different machine faults.

I. Introduction

The Integrated drive generator (IDG) is the primary source for electrical power in the aircraft. The system draws its power from the main aircraft engines and comprises two synchronous generators that operate in a brushless configuration. It also includes a number of other subsystems that convert the mechanical energy into electrical energy at a prespecified voltage and frequency. Since the machine operates in harsh environments, different components are subject to degradations and faults that can vary in terms of their critical effects on system behavior. For the electrical subsystem of the IDG, the most critical faults are winding faults and rectifier diode failures [4]. Fast and accurate fault detection and isolation (FDI) is a necessary component for the safe and reliable operation of the IDG, and, therefore, the aircraft.