Battery Management System Hierarchical Control for Pack Precision
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Solution Overview
Problem
Existing battery systems with multiple packs face challenges in managing and controlling them as a single component while ensuring precise control for each pack, as this requires balancing scalability with individual pack management to prevent changes in control logic and reduce communication load.
Innovation Solution
A battery system comprising multiple packs connected via a DC line, with a controller sending control commands and each pack equipped with a bidirectional power supply circuit and battery management unit, where one pack has a central management function to coordinate control commands, failure detection, and state monitoring, distributing limits to ensure unified and precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a controller controls multiple battery packs as a single component, then communication load is reduced and control logic remains stable, but precise individual pack control becomes difficult
Solution Approach 1:
The system segments control functions into two levels: a central controller that manages overall system coordination and sends aggregate control commands, and individual battery management units (BMUs) that each pack has, which handle precise local control of their respective packs. This segmentation allows the central controller to treat packs as a single component while BMUs ensure precise individual control.
Solution Approach 2:
The battery management unit (BMU) in each pack acts as an intermediary between the central controller and the battery pack itself. The BMU receives control commands from the central controller and translates them into precise local control actions, while also reporting detailed pack status back to the central controller. This intermediary structure resolves the contradiction by enabling both centralized simplicity and decentralized precision.
2Measurement precision
If a controller controls each battery pack individually, then precise control for each pack is achieved, but communication load increases and control logic becomes complex
Solution Approach 1:
Control functions are segmented between a central controller that handles high-level coordination and sends fewer aggregate commands, and distributed BMUs that handle detailed local control. This reduces communication load on the central controller while maintaining precise individual pack control through the local BMUs.
Solution Approach 2:
Each battery pack's BMU is equipped with autonomous decision-making capability to perform local control functions without requiring constant communication with the central controller. The BMU can independently adjust charging/discharging parameters based on real-time pack conditions, reducing communication requirements while ensuring precise individual control.
3Adaptability or versatility
If multiple battery packs are combined to provide huge capacity, then scalability is achieved, but coordination and control of all packs becomes complex
Solution Approach 1:
The system uses a hierarchical control structure where a central controller manages overall system coordination and scalability, while each battery pack has its own BMU that handles local control independently. This segmentation allows the system to scale by simply adding more packs with their own BMUs without increasing the complexity of inter-pack coordination, as each BMU autonomously manages its pack.
Solution Approach 2:
The BMU design is universal and can be applied to any battery pack in the system, providing the same control functions regardless of the total number of packs. This multi-functionality allows the system to scale from a few packs to many packs without requiring different control strategies, as each BMU performs the same set of functions for its respective pack.
Data Source
AI summary
The controller calculates a first limit based on received information about the battery packs and the schedule for charging and discharging plan, and supplies the first limit which serves as a control command to a master battery management unit (BMU), a master BMU receives the first limit. The master BMU sets and distributes the second limit to each one of local battery management function blocks in the battery packs. As a result, each BMU receives the second limit respectively. Then, the each BMU supplies the third limit to a bidirectional power source circuit, respectively, based on failure information FAIL and capacity information SOC of the battery in the battery pack.