Submarine Battery String Connection Unit for Overcharge Protection
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Solution Overview
Problem
Submarine drive systems face challenges in preventing overcharging and exhaustive discharging of battery strings, particularly with lithium-ion batteries, which can lead to irreversible damage and reduced service life.
Innovation Solution
The implementation of a string connection unit with a bidirectional voltage converter and a switching device allows for selective connection and disconnection of battery strings from the DC power supply system, enabling adjustment of charging and discharging currents to prevent overcharging and exhaustive discharging, while also providing galvanic isolation and independent control of string voltages and currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If battery strings are connected directly to the DC power supply system, then the system structure is simple, but overcharging and exhaustive discharging cannot be prevented
Solution Approach 1:
A string connection unit is introduced as an intermediary device between the battery string and the DC power supply system. This unit includes a voltage converter and switching device that mediates the connection, enabling current adjustment and protection functions while maintaining system modularity and managing complexity.
Solution Approach 2:
The control unit continuously monitors the state of charge of the battery string and adjusts the charging/discharging current accordingly. When the battery reaches full charge or complete discharge states, the control unit automatically interrupts current flow, providing real-time feedback-based protection against overcharging and exhaustive discharging.
2Reliability
If a string connection unit with current adjustment is implemented, then battery protection is improved, but device complexity increases
Solution Approach 1:
The string connection unit is designed to perform multiple functions: voltage conversion, current adjustment, galvanic isolation, and protection against overcharging/exhaustive discharging. By consolidating these functions into a single integrated unit, the system manages complexity while achieving comprehensive battery protection.
Solution Approach 2:
The battery system is divided into multiple independent battery strings, each equipped with its own string connection unit. This segmentation allows independent control and protection of each string, improving reliability while maintaining modular architecture that simplifies overall system management.
3Productivity
If lithium-ion batteries are used to increase energy density, then productivity is improved, but susceptibility to overcharging and exhaustive discharging increases
Solution Approach 1:
The control unit is configured to prevent harmful effects before they occur by continuously monitoring battery state and interrupting charging/discharging currents at critical thresholds. This preliminary action protects lithium-ion batteries from overcharging and exhaustive discharging, which would cause irreversible damage and exothermic breakdown reactions.
Solution Approach 2:
The string connection unit acts as a protective intermediary between the DC power supply system and the lithium-ion battery string, filtering and regulating current to eliminate harmful charging/discharging patterns that could damage the high-energy-density batteries.
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 solution effectively extends the service life of battery modules and increases the availability of the drive system by preventing unwanted charging and discharging, limiting short-circuit currents, and allowing for efficient energy management, especially with lithium-ion batteries.
Implementation Method 1
a bidirectional voltage converter, by means of which a system voltage on a DC power supply system side is transformable into a string voltage on a battery string side
Implementation Method 2
via which the battery string can be selectively connected to the DC power supply system or disconnected from the DC power supply system
Data Source
AI summary
A drive system for a submarine may include a DC power supply system for supplying electrical energy to a drive of the submarine and a plurality of battery strings, which each may comprise a plurality of series-connected battery modules. The battery strings may each be connected to a string connection unit via which the battery string can be selectively connected to or disconnected from the DC power supply system. The string current flowing in the battery string can be adjusted by the string connection unit. The present disclosure also concerns corresponding methods for operating the drive system of the submarine.