DC Power Bus Pre-Charge Switching for Inrush-Limited Transfer
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Solution Overview
Problem
Existing DC electric power systems face challenges in efficiently managing electrical pre-charging, particularly in systems utilizing non-rechargeable DC electric power sources like fuel cell stacks or photovoltaic panels.
Innovation Solution
A pre-charge system is introduced, comprising a high-voltage electric power bus with positive and negative bus links, a contactor with switches controlled by a controller, a pre-charge resistor, and voltage sensors. The controller activates and monitors the switches and voltage sensors to manage pre-charging based on voltage thresholds and time-rates of change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-charge system is implemented in DC electric power systems, then the safety and efficiency of power transfer is improved, but the device complexity increases due to additional components like pre-charge resistors, voltage sensors, and controlled switches
Solution Approach 1:
The system performs preliminary pre-charging action before main power transfer by activating the pre-charge resistor and second switch in advance to charge the external bus capacitance, then transitions to normal operation by closing the first switch. This preliminary action prevents inrush currents and ensures safe power transfer.
Solution Approach 2:
The pre-charge resistor acts as an intermediary element between the DC electric power source and the external bus, providing a controlled path for initial charging current. The controller serves as another intermediary that coordinates the switching actions between different circuit components to manage the pre-charge sequence.
2Loss of substance
If non-rechargeable DC electric power sources like fuel cell stacks or photovoltaic panels are used, then the loss of substance is reduced, but the ease of operation becomes more difficult due to challenges in managing pre-charging for one-way power flow systems
Solution Approach 1:
The system implements self-service through automatic controller management of the pre-charge sequence. The controller autonomously monitors voltage thresholds, controls switch activation timing, and manages the transition from pre-charge to normal operation without requiring manual intervention, making the system easy to operate despite the complexity of non-rechargeable power sources.
Solution Approach 2:
The voltage sensor provides continuous feedback to the controller about the external bus voltage state. The controller uses this feedback to determine when to activate the pre-charge circuit and when to transition to normal power transfer by closing the first switch, enabling automatic adaptation to system conditions.
Data Source
AI summary
A pre-charge system for a DC electric power system includes a high-voltage electric power bus that electrically connects to an external bus. A contactor includes a first switch arranged to control electric power through the positive bus link, and a second switch arranged to control electric power through the negative bus link. A pre-charge resistor is arranged in parallel with the first switch. A controller is operatively connected to the first and second switches, and in communication with a voltage sensor. The controller includes an instruction set to activate the second switch, periodically monitor the electrical potential, determine a time-rate of change in the electrical potential, and close the first switch when the time-rate of change in the electrical potential is less than a first threshold.