Parallel Battery Row Switching Control

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Solution Overview

Problem

In parallel-connected electricity storage systems, excessive current flows occur when switching on electricity storage element rows, leading to potential breakdowns due to voltage differences caused by wiring resistance, especially during charging and discharging fluctuations.

Innovation Solution

The system employs a configuration with electricity storage element row models, state detecting devices, and a control mechanism to manage parallel connections, ensuring equal current flow by calculating and adjusting open-circuit voltages and internal resistances, and using shunt resistors for current detection, thereby preventing excessive current during reconnection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If electricity storage element rows are switched on when battery remaining powers are equal, then the system maintains balanced power distribution, but a large current flows to the switched-on electricity storage element rows due to voltage difference caused by wiring resistance

Engineering Contradiction:
Improvepower distribution balanceVSAvoidexcessive current flow
Core Design Contradiction:
Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The control device calculates the open-circuit voltage of each electricity storage element row before switching it on, and determines the optimal switching timing to minimize voltage differences. This preliminary calculation and timing adjustment prevents excessive current flow from occurring in the first place

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the switching timing of electricity storage element rows based on calculated voltage differences and current states. By changing the temporal parameter (switching timing) rather than simply switching on all rows simultaneously, the voltage difference and resulting excessive current are reduced

Inventive Principle:
Principle #35Parameter changes

2Quantity of substance

If a large number of electricity storage elements are connected in series and in parallel, then the system capacity increases, but internal short-circuits occur in parts of the electricity storage elements due to manufacturing variation and environmental differences

Engineering Contradiction:
Improvesystem capacityVSAvoidinternal short-circuit occurrence
Core Design Contradiction:
Quantity of substanceVSReliability

Solution Approach 1:

The electricity storage system is divided into multiple independent electricity storage element rows, each with its own control switch. This segmentation allows individual monitoring and control of each row, enabling early detection and isolation of rows with internal short-circuits before they affect the entire system

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The control device continuously monitors the state of each electricity storage element row and adjusts switching decisions based on real-time feedback. When voltage differences or current anomalies indicate potential internal short-circuits, the control device can prevent switching on affected rows or isolate them from the parallel connection

Inventive Principle:
Principle #23Feedback

3Productivity

If electricity storage element rows are reconnected during charging and discharging to maintain power supply, then continuous power supply is maintained, but voltage difference causes excessive current to flow during reconnection

Engineering Contradiction:
Improvecontinuous power supplyVSAvoidexcessive current during reconnection
Core Design Contradiction:
ProductivityVSObject-generated harmful factors

Solution Approach 1:

Before reconnecting an electricity storage element row during operation, the control device calculates its open-circuit voltage and compares it with the system voltage. This preliminary assessment allows determination of the optimal reconnection timing to minimize voltage difference and excessive current flow

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The control device dynamically determines the reconnection timing based on real-time system conditions including charging/discharging state, voltage levels, and current flow. Rather than using fixed timing, the system adapts reconnection moments to minimize harmful current spikes while maintaining continuous power supply

Inventive Principle:
Principle #15Dynamics

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 effectively prevents excessive current from flowing to electricity storage elements during reconnection, reducing the risk of element breakdown and maintaining stable power supply.

Implementation Method 1

using shunt resistors for current detection

Methodology Applied
Scientific EffectOhm's Law: Ohm's Law

Data Source

PatentEP2961023B1Parallel-connected electricity storage system
Publication Date: 2020.02.05 HITACHI LTD
  • EP2961023B1 patent drawingFigure 1
  • EP2961023B1 patent drawingFigure 2
  • EP2961023B1 patent drawingFigure 3

AI summary

A parallel-connected electricity storage system in which a plurality of chargeable and dischargeable electricity storage elements are connected in series as an electricity storage element row and a plurality of the electricity storage element rows are connected in parallel includes an electricity-storage-element-voltage measuring device that measures an electricity storage element voltage of each of the electricity storage elements, an electricity-storage-element-state estimating device that estimates an electricity storage element state of each of the electricity storage elements, an electricity-storage-element-current measuring device that measures an electricity storage element current of each of the electricity storage element rows, a parallel-connected switch that performs connection and disconnection to and from the parallel-connected electricity storage system for each of the electricity storage element rows, and a parallel-connected-switch control means for turning on the parallel-connected switch on the basis of the electricity storage element voltage, the electricity storage element state, and the electricity storage element current.