Aircraft Starter Generator MOSFET Bridge Control
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Solution Overview
Problem
Conventional aircraft starter generator systems face challenges in efficiently controlling wide band gap devices for consistent power generation, particularly in providing excitation current at low speeds and managing different power sources for start and generate modes.
Innovation Solution
A MOSFET-based bridge configuration with a digital controller using Space Vector Pulse Width Modulation (SVPWM) and reverse conduction based inactive rectification, along with a dual functional exciter stator and sensorless rotor position estimation, to efficiently drive the starter/generator in both start and generate modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If wide band gap devices are used in high voltage DC system, then switching losses and conduction losses are reduced, but control complexity increases to achieve consistent efficiencies
Solution Approach 1:
The patent applies Space Vector Pulse Width Modulation (SVPWM) technique which changes the control parameters and methodology for driving wide band gap devices. This advanced modulation strategy optimizes the switching patterns and voltage vectors to minimize losses while maintaining consistent efficiency across varying operating conditions, thereby resolving the control complexity issue associated with wide band gap device utilization.
Solution Approach 2:
The patent implements a digitally controlled inverter/converter/controller with sensorless rotor position estimation that uses feedback mechanisms to continuously monitor and adjust operating parameters. This feedback system ensures consistent efficiency achievement by dynamically optimizing control parameters based on actual system state, addressing the control complexity challenge while maximizing the benefits of wide band gap devices.
2Loss of energy
If conventional starter generator systems are used, then system simplicity is maintained, but efficiency and temperature capability are limited
Solution Approach 1:
The patent replaces conventional mechanical control systems with a digitally controlled inverter/converter system that uses electronic switching of wide band gap devices. This substitution enables superior energy conversion efficiency and high temperature capability by utilizing advanced power electronic control strategies (SVPWM and reverse conduction based inactive rectification) instead of traditional mechanical or simple electronic controls, accepting increased system complexity as a trade-off for performance gains.
Solution Approach 2:
The patent employs a hybrid control approach combining SVPWM for start mode and reverse conduction based inactive rectification for generate mode. This composite control strategy integrates multiple technical approaches within a single system, enabling the starter/generator to achieve high efficiency across both motoring and generating operations while utilizing the superior properties of wide band gap semiconductor materials.
3Power
If excitation current is provided at low speeds, then starting capability is improved, but control difficulty increases due to sensorless rotor position estimation
Solution Approach 1:
The patent uses an intermediary sensorless rotor position estimation algorithm that indirectly determines rotor position without requiring physical sensors. This intermediary approach processes electrical signals and system parameters to infer rotor position, enabling excitation current provision at low speeds and improving starting capability while avoiding the complexities of direct sensor-based measurement in challenging low-speed conditions.
Solution Approach 2:
The digitally controlled system implements feedback-based sensorless rotor position estimation that continuously monitors system responses and adjusts control parameters accordingly. This feedback mechanism enables accurate rotor position determination even at low speeds where traditional methods fail, facilitating improved starting capability through proper excitation current provision without requiring additional sensors or complex mechanical structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables efficient energy conversion and management, achieving low switching and conduction losses, high temperature capability, and reliable rotor position estimation across the entire speed range, thereby improving power density and torque density.
Implementation Method 1
converts AC power, obtained from the starter/generator after the prime mover have been started, to DC power in a generate mode
Implementation Method 2
generates AC power to drive the starter/generator in a start mode for starting a prime mover of the aircraft
Implementation Method 3
utilize the aircraft engine after it has started in a generate mode, to thereby provide electrical energy to power systems on the aircraft
Data Source
AI summary
An aircraft starting and generating system includes a starter/generator and an inverter/converter/controller (200) that is connected to the starter/generator and that generates AC power to drive the starter/generator in a start mode for starting a prime mover of the aircraft, and that converts AC power, obtained from the starter/generator after the prime mover have been started, to DC power in a generate mode of the starter/generator. A four leg inverter is coupled with a DC power output (452) of the starter/generator and has an inverter/converter/controller (ICC) (580) with a four leg MOSFET-based bridge configuration that drives the starter/generator in a start mode for starting a prime mover of the aircraft, and converts DC power to AC power in a generate mode of the starter/generator. A four leg bridge gate driver (560) is configured to drive the four leg MOSFET-based bridge (580) during start and generate mode using bi-polar pulse width modulation (PWM).