Battery Capacity Estimation Using AC Power and SoC
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Solution Overview
Problem
Conventional techniques struggle to accurately estimate the effective capacity of secondary batteries in storage battery systems, particularly for virtual power plants and power business operators, as they lack direct information about the AC side before the DC-AC converter, making it difficult to assess capacity deterioration.
Innovation Solution
A battery capacity estimation device that acquires AC power or energy input and output via a DC-AC converter, along with the state of charge (SoC), to estimate battery capacity based on AC power and SoC, using techniques like Kalman filters and table reference methods, and considers conversion efficiency to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional techniques use DC current side information for capacity estimation, then measurement precision is improved, but device complexity and cost increase due to requiring direct access to DC side
Solution Approach 1:
The patent introduces an intermediary approach by using AC side power information as a mediator to estimate battery capacity without direct DC side measurement. The capacity estimation unit uses AC power data from the power supply/discharge control unit, combined with SoC information, to calculate capacity through integration over time, thereby avoiding the need for direct DC current sensors while maintaining estimation accuracy
Solution Approach 2:
The patent replaces the mechanical/electrical measurement system (DC current sensors and direct DC side monitoring) with a computational system that uses AC side electrical information. By substituting physical DC measurement with AC-based calculation methods involving power integration and SoC tracking, the system reduces hardware complexity while achieving capacity estimation
2Reliability
If virtual power plants and power business operators want to estimate battery capacity, then capacity deterioration monitoring is improved, but device complexity increases due to lack of direct DC side access
Solution Approach 1:
The patent makes the power supply/discharge control unit perform multiple functions: it not only controls power flow between the storage battery system and external power sources but also serves as a capacity estimation unit. By integrating the capacity estimation function into the existing control unit using AC side power information, the system achieves capacity deterioration monitoring without adding separate complex measurement devices
Solution Approach 2:
The storage battery system performs self-diagnosis and self-monitoring by using its own AC side power information and SoC data to estimate its capacity. The capacity estimation unit within the control unit automatically calculates capacity deterioration using readily available operational data, enabling the system to monitor its own health without external intervention or additional sensing infrastructure
3Measurement precision
If additional power detection devices are installed for accurate capacity estimation, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent uses AC side power information as an intermediary measurement that already exists in the system. Instead of installing additional DC side power detection devices, the invention leverages the AC power measurements taken by the power supply/discharge control unit, combining this with SoC data to derive capacity information through calculation rather than direct measurement
Solution Approach 2:
The patent creates a virtual copy or model of the battery capacity by calculating it from AC side power integration and SoC information. Rather than physically measuring DC current with additional sensors, the system creates a computational representation of capacity based on available AC side data, effectively copying the measurement function through software calculation
Data Source
AI summary
A battery capacity estimation device in an embodiment includes one or more hardware processors configured to: acquire an alternating current power or an alternating current energy that is input to and output from a storage battery system via a direct current-alternating current converter, the storage battery system being capable of controlling charge and discharge; acquire a state of charge (SoC) of the storage battery system; and estimate a battery capacity of the storage battery system based on the acquired alternating current power or the acquired alternating current energy and the acquired SoC.