Parallel Battery Short-Circuit Protection via Switch Control
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Solution Overview
Problem
High-power DC voltage sources using lithium-ion electrochemical accumulator batteries face challenges in managing short-circuits due to high short-circuit currents exceeding the breaking capacity of conventional electro-mechanical circuit-breakers, leading to safety hazards and costly solutions.
Innovation Solution
An electrical installation with a circuit-breaker and DC voltage source comprising batteries connected in parallel, each with a switch and flyback diode, and a control circuit that detects short-circuits to manage current flow through the circuit-breaker, ensuring it trips and opens while preventing excessive electromagnetic disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If batteries with low internal resistance are used to achieve high power output, then power delivery capability is improved, but short-circuit current exceeds circuit-breaker breaking capacity
Solution Approach 1:
The battery system is divided into multiple parallel strings, each equipped with its own switching device. During short-circuit conditions, the control system can selectively open switches in specific strings to limit the total short-circuit current while maintaining power delivery capability through the remaining strings.
Solution Approach 2:
The switching devices are controlled dynamically based on real-time current monitoring. Under normal operation, all batteries contribute to power output. Upon detecting short-circuit conditions, the control system rapidly adjusts switch states to limit current to below the circuit-breaker's breaking capacity, enabling adaptive protection.
2Reliability
If expensive high-breaking-capacity circuit-breakers are used to handle short-circuit currents, then short-circuit protection capability is improved, but installation cost increases
Solution Approach 1:
Electronically controlled switching devices are introduced as intermediary components between the batteries and the circuit-breaker. These switches act as a first line of defense, limiting short-circuit current before it reaches the circuit-breaker, thereby enabling the use of lower-cost circuit-breakers with reduced breaking capacity.
Solution Approach 2:
The control system performs preliminary current limiting by opening switching devices before the short-circuit current can reach the circuit-breaker. This preliminary action reduces the current to a level that standard, less expensive circuit-breakers can safely handle.
3Reliability
If circuit-breaker breaking capacity is increased to handle maximum short-circuit current, then short-circuit current handling is improved, but electromagnetic disturbances and safety hazards increase
Solution Approach 1:
The control system applies preliminary anti-action by detecting short-circuit conditions and opening switching devices before the full short-circuit current can flow through the circuit-breaker. This prevents the circuit-breaker from being exposed to excessive currents that would generate harmful electromagnetic disturbances and safety hazards.
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 configuration allows for safe operation of high-power installations with existing or less expensive circuit-breakers, ensuring safety and reducing the risk of catastrophic failures, while maintaining continuity of service and minimizing electromagnetic disturbances.
Implementation Method 1
each with a switch and flyback diode
Implementation Method 2
DC voltage source comprising at least two electrochemical accumulator batteries connected in parallel
Implementation Method 3
electro-mechanical circuit-breakers are used to protect the electrical installation and electrical loads from short-circuits
Data Source
AI summary
An electrical apparatus, including: a circuit breaker having a breaking capacity and a breaking current; a DC voltage source including two batteries connected in parallel, connected in series with the circuit breaker, the sum of short-circuit currents of the batteries being greater than the breaking capacity, each battery including: a first branch including storage batteries and a switch connected in series; a second branch connected in parallel with the first branch and including a free-wheeling diode; an ammeter measuring output current; and a control circuit configured to detect a short-circuit. The control circuits simultaneously keep a majority of switches open and close one switch to apply a current passing through the circuit breaker which is higher than the breaking current and lower than the breaking capacity.