Battery String Control for Accurate SOH Estimation Under Load
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Solution Overview
Problem
Existing power storage systems face challenges in accurately estimating the state of health (SOH) and state of charge (SOC) of storage batteries due to varying current demands, which can disrupt the estimation process and limit input/output operations.
Innovation Solution
A storage battery control device that identifies target batteries, determines a buffer string to manage power, and measures discharge or charge currents and voltages independently of system requests, allowing for continuous and accurate SOH and SOC estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the storage battery control device performs SOH estimation by measuring polarization recovery time, then the SOH estimation can be completed, but the input and output operations of the power storage system must be limited or stopped during the measurement period
Solution Approach 1:
The power storage system is divided into multiple storage battery strings (first string, second string, third string, etc.). During SOH estimation of a target battery in one string, other strings can continue to perform input and output operations. This segmentation allows parallel operation of estimation and power delivery, resolving the contradiction between measurement accuracy and system productivity.
2Adaptability or versatility
If the current of storage batteries changes according to power supply requests, then the power storage system can respond to load demands, but the SOH estimation cannot be accurately performed
Solution Approach 1:
A buffer battery (or buffer string) is introduced as an intermediary component. The buffer battery absorbs current fluctuations and provides a stable electrical environment for the target battery during SOH estimation. This mediator allows the target battery to maintain constant current conditions for accurate measurement while the power storage system continues to respond to external power supply requests through other strings and the buffer battery.
3Measurement precision
If the power storage system limits input and output operations during SOH estimation, then accurate SOH measurement can be achieved, but the system availability and responsiveness are reduced
Solution Approach 1:
The system is segmented into multiple independent battery strings, allowing the SOH estimation process to be isolated to a specific string without affecting the operational status of other strings. This enables continuous system availability while performing maintenance measurements on individual components.
Solution Approach 2:
The buffer battery is pre-charged or pre-prepared to ensure it has sufficient capacity to maintain constant current conditions during the SOH estimation period. This preliminary preparation allows the estimation process to proceed without interrupting external power operations.
Data Source
AI summary
The present disclosure relates to a storage battery control device, a power storage system, and a storage battery control method. The storage battery control device controls a power storage system including storage battery strings each including storage batteries and connected with each other by a power line, the storage batteries being connected in series, and power converters each provided between the storage battery string and the power line and converting an input and output voltage of the storage battery string. The storage battery control device discharges a target storage battery to a buffer string or an outside of the power storage system to measure a discharge current or a voltage of the target storage battery, and estimates a state of the target storage battery based on the measured discharge current or the measured voltage of the target storage battery.