Power Converter Fault Mode for Shared Transistor-Diode Current
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Solution Overview
Problem
In aerospace applications, electrical power systems with DC networks face high fault currents during faults due to the operation of electrical machines with low impedances and permanent magnets, leading to undesirable high voltages and potential thermal breakdown of power electronics components.
Innovation Solution
A controller is configured to share fault current between transistors and associated diodes in the power electronics converter by controlling their switching, minimizing conduction losses and improving thermal properties through dynamic balancing of the load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the converter operates as an uncontrolled diode rectifier during DC network fault, then the converter structure is simple and easy to control, but high fault current flows to the fault site causing thermal breakdown risk
Solution Approach 1:
The patent applies dynamic control by switching the converter operation mode from normal controlled rectification to uncontrolled diode rectifier mode upon detecting a DC network fault. This dynamic transition allows the system to automatically adapt to fault conditions, where the converter ceases active switching and allows free-wheeling current flow through diodes, thereby reducing fault current magnitude while maintaining operational simplicity during faults.
Solution Approach 2:
The patent converts the potentially harmful high fault current into a beneficial protective mechanism. By allowing the converter to operate as an uncontrolled diode rectifier during faults, the system naturally limits fault current through the inherent diode characteristics and impedance, transforming what would be a dangerous condition into a protective state that prevents thermal breakdown while maintaining system stability.
2Object-affected harmful factors
If the converter limits fault current by controlled switching, then fault current is reduced, but conduction losses increase and thermal management becomes more difficult
Solution Approach 1:
The patent employs periodic switching control during fault conditions, where the converter switches between active device conduction and diode free-wheeling modes in a periodic manner. This periodic action allows the system to limit fault current while periodically reducing conduction losses by transitioning to diode-based current paths, thereby managing thermal load more effectively during fault periods.
Solution Approach 2:
The patent changes the operational parameters of the converter during faults by transitioning from high-frequency PWM switching to lower-frequency or uncontrolled diode rectification mode. This parameter change reduces the switching losses and allows the system to operate in a more thermally efficient state during fault conditions, balancing current limitation with energy loss reduction.
3Reliability
If the converter uses over-sized components to handle maximum fault current, then reliability during faults is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements preliminary protective action by detecting DC network faults and preemptively switching the converter to a safe operating mode before excessive fault current can damage components. This preliminary action allows the use of normally-sized components rather than over-sized ones, as the system proactively prevents fault current from reaching damaging levels through controlled mode transition.
Solution Approach 2:
The patent introduces the converter control system as an intermediary between the electrical machine and the DC network during faults. This intermediary actively manages the energy flow and current distribution, mediating the fault condition by redirecting current through safe paths and preventing direct high-current flow to the fault site, thereby protecting the system without requiring oversized components.
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
Reduces the need for over-sizing components, minimizes conduction losses, and improves thermal management by distributing fault current effectively, preventing thermal breakdown of power electronics.
Implementation Method 1
the controller is further configured, responsive to a determination that there is a fault in the DC electrical network, to operate in a fault mode in which the controller controls the switching of the transistors of the converter so that a fault current is shared between the transistors and the associated diodes of the converter
Implementation Method 2
the power electronics converter comprising a plurality of transistors and associated diodes connected in anti-parallel with the transistors
Data Source
AI summary
An electrical machine with a rotor coupled to a drive shaft of an engine; a DC electrical network; a power electronics converter connected, on a DC-side, to the DC electrical network, and, on an AC-side, to the electrical machine, the power electronics converter comprising a plurality of transistors and associated diodes connected in anti-parallel with the transistors; and a controller configured to control switching of the transistors so that the converter either inverts DC power to AC power or rectifies AC power to DC power. The controller is further configured, responsive to a determination that there is a fault in the DC electrical network, to operate in a fault mode in which the controller controls the switching of the transistors so that a fault current is shared between the transistors and the associated diodes.