Capacitor Bank Pre-Charging via Dynamic Current Limiting
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Solution Overview
Problem
Conventional pre-charging techniques for capacitor banks in wind turbines are inefficient, time-consuming, and difficult to implement, necessitating a simpler, more efficient, and controllable method to manage the charging process.
Innovation Solution
A system comprising a power switch and a current limiting device, controlled by signals indicative of charge current and voltage, limits the peak charging current and ceases pre-charging when a threshold voltage is reached, using a bypass contactor to divert current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional pre-charging techniques (high power resistors, PTC thermistors, transformers) are used to limit inrush current into the capacitor bank, then the magnitude of inrush current is reduced, but the pre-charging process becomes inefficient, time-consuming, and difficult to implement
Solution Approach 1:
The patent employs a dynamic pre-charging approach using a controllable switch (such as a transistor or MOSFET) that adjusts the charging current in real-time based on the capacitor bank voltage state. The switch transitions from a closed state during pre-charging to an open state when the capacitor is sufficiently charged, enabling adaptive current control rather than fixed passive limiting. This dynamic control resolves the contradiction by maintaining high pre-charging efficiency while still limiting inrush current through active management of the charging process.
2Object-affected harmful factors
If conventional pre-charging techniques are used, then inrush current is limited, but the pre-charging process becomes time-consuming
Solution Approach 1:
The patent implements a feedback control mechanism where the pre-charging process is monitored based on capacitor bank voltage levels. A control device receives feedback about the charging state and adjusts the switch operation accordingly, transitioning from closed to open state when the capacitor reaches the desired voltage threshold. This feedback-driven approach resolves the time contradiction by enabling rapid pre-charging while preventing excessive inrush current, as the system actively responds to charging progress rather than relying on fixed-time or passive limiting methods.
3Object-affected harmful factors
If conventional pre-charging techniques are used, then inrush current is limited, but the system becomes difficult to implement
Solution Approach 1:
The patent replaces complex passive pre-charging components (high power resistors, PTC thermistors, transformers) with an active electronic switch controlled by a simple control device. This substitution dramatically simplifies the implementation while maintaining effective inrush current limitation. The control device can be integrated into existing power electronics, and the switch can be implemented using standard semiconductor devices, making the system easier to manufacture and implement compared to conventional approaches that require specialized passive 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
This approach allows for efficient and controlled pre-charging of capacitor banks, reducing current applied to the current limiting device and optimizing capacitor bank voltage, thereby enhancing the overall efficiency and simplicity of the process.
Implementation Method 1
a current limiting device coupled in series between the power switch and a capacitor bank
Implementation Method 2
a capacitor bank comprising one or more capacitor devices
Data Source
AI summary
Systems and methods of pre-charging a capacitor bank are provided. In particular, a power switch and a current limiting device can be coupled in series between a power source and a capacitor bank. Operation of the power switch can be controlled to limit a peak charging current applied to the capacitor bank during a pre-charging process. In this manner, a duty cycle of a pulse signal can be modified based at least in part on a measured current flowing into the current limiting device. In addition, a voltage at the capacitor bank can be monitored, and the pre-charging process can be ceased when the monitored voltage reaches a threshold.