DC Precharging Circuit for Capacitor Voltage Balance
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Solution Overview
Problem
Existing technologies face challenges in managing capacitors in DC power networks, particularly in floating systems, leading to overcurrent conditions and disconnections due to uncontrolled voltage fluctuations and imbalances.
Innovation Solution
Incorporating a switchable high ohmic path and a load control unit to manage capacitor voltages and currents, along with a balance control unit to equalize capacitor charges, ensuring symmetric voltage around ground and preventing overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If capacitors are used as energy buffers in DC power networks, then energy storage capability is improved, but overcurrent conditions occur during transition phases leading to disconnection
Solution Approach 1:
The patent implements a precharging device that charges capacitors before they are connected to the DC power network. This preliminary action ensures that capacitor voltages are equalized and match the network voltage, preventing overcurrent conditions during connection. The precharging circuit includes switching elements and current influencing means that activate before the main connection, thereby eliminating harmful inrush currents.
Solution Approach 2:
The patent introduces an intermediary precharging circuit between the capacitors and the DC power network. This intermediary device includes switching elements and current influencing means that control the charging process, acting as a mediator that prevents direct harmful current flow. The intermediary structure allows gradual voltage equalization and safe connection to the network.
2Adaptability or versatility
If series capacitors are connected to floating DC power networks, then system flexibility is improved, but voltage imbalances and floating voltage issues occur
Solution Approach 1:
The patent implements feedback control through a balance control unit that continuously monitors capacitor voltages and switching states. The control unit adjusts switching elements and current influencing means based on detected voltage imbalances, ensuring that capacitor voltages remain equal and symmetric. This feedback mechanism maintains voltage symmetry even in floating DC power networks where neither pole is grounded.
Solution Approach 2:
The patent enables the system to self-regulate voltage imbalances through automatic detection and correction mechanisms. The balance control unit automatically detects voltage differences and activates appropriate switching elements to equalize capacitor voltages without external intervention. The system serves itself by continuously monitoring and correcting its own voltage distribution.
3Reliability
If circuit breakers are used to protect DC power networks, then safety is improved, but uncontrolled voltage fluctuations cause overcurrent conditions triggering disconnection
Solution Approach 1:
The patent implements preliminary control of capacitor voltages and currents through precharging devices and balance control units before circuit breakers need to operate. By equalizing capacitor voltages and limiting currents in advance, the system prevents overcurrent conditions that would trigger circuit breaker disconnection, thereby maintaining operational continuity while preserving safety protection.
Solution Approach 2:
The patent uses feedback control through load control units and balance control units that continuously monitor voltage and current conditions. This feedback prevents overcurrent situations before they occur, allowing circuit breakers to remain closed and maintain power supply continuity. The feedback mechanism ensures safety by detecting and correcting potential problems before they require circuit breaker intervention.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An arrangement (1a..1l) with a circuit breaker (20) and a precharging device (21) is disclosed, where two series capacitors (C1, C2) are connected to a direct current power network (DC) and where the arrangement (1a.. 1l) comprises a circuit switch control unit (SCU), which is designed to open a circuit switch (Sc) in case of overcurrent and/or upon manual intervention, a load control unit (LCU), which is designed to limit a load current of the two series capacitors (C1, C2) by use of a high ohmic path (4), and a balance control unit (BCU), which is designed to measure a capacitor voltage (V1, V2) of each of the two series capacitors (C1, C2) and to avoid or limit and an imbalance of these capacitor voltages (V1, V2) by individually controlling currents through the two series capacitors (C1, C2).