HVDC Bus Coupling Circuit Inductor Pre-Charge
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Solution Overview
Problem
Current methods for adding a high voltage DC source to a DC bus in aircraft systems often result in large current spikes, which can damage contactors and reduce their lifespan, especially when dealing with busses with significantly different voltages, and require complex sensor systems and diodes with conduction losses.
Innovation Solution
The system connects two high voltage DC sources in parallel using a bus coupling circuit with series-connected inductors and contactors, allowing the natural resistance of inductors to equalize capacitor voltages and avoid current spikes without diodes, enabling parallel connection of busses with different voltages without inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional methods are used to connect HVDC sources in parallel, then the connection can be established, but large current spikes occur that damage contactors and reduce their lifespan
Solution Approach 1:
The auxiliary contactor is closed before the main contactor to pre-charge the capacitor and equalize voltages between the two HVDC sources. This preliminary action prepares the circuit to avoid large current spikes when the main contactor is subsequently closed, thereby protecting the contactors from damage and extending their lifespan.
Solution Approach 2:
The auxiliary contactor acts as an intermediary element that facilitates the gradual equalization of capacitor voltages before the main power connection is established. By introducing this intermediate switching stage, the system avoids direct connection of unequal voltage sources that would cause harmful current spikes.
2Loss of energy
If traditional connection methods are used, then parallel connection can be achieved, but complex sensor systems and diodes are required with conduction losses
Solution Approach 1:
The invention removes diodes and complex sensor systems from the parallel connection circuitry. By using only auxiliary and main contactors with inherent capacitor equalization, the system eliminates components that cause conduction losses and add complexity, achieving a simpler and more efficient power distribution architecture.
Solution Approach 2:
The capacitor voltages equalize automatically through the auxiliary contactor connection without requiring external sensors or control systems. The system uses its own inherent electrical properties to achieve voltage balance, eliminating the need for additional monitoring and control components that would increase complexity and energy losses.
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 approach reduces or eliminates current spikes during parallel connection, extends contactor life, and minimizes power losses by eliminating diodes, allowing for smoother power distribution and increased electrical capacity for larger loads like electric propulsion systems.
Implementation Method 1
allowing the natural resistance of inductors to equalize capacitor voltages and avoid current spikes
Data Source
AI summary
A system for connecting first and second high voltage direct current (HVDC) sources in parallel to a bus includes one or more contactors connecting the first HVDC source to the bus. The system also includes a bus coupling circuit located between the second HVDC source and the bus that utilizes inductors to couple, in operation, couples the second HVDC source to the bus such that first and second HVDC sources are in parallel with the second positive output is connected to the positive rail and the second negative output connected to the negative rail. The inductors are first connected to the bus though auxiliary contactors and, after a predetermined time, main contactors are closed that provide a path around the inductors.