Multi-Power-Supply Bus Control for Battery SoC Load Sharing
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Solution Overview
Problem
Uneven wear on batteries in battery systems of electric and hybrid-electric propulsion systems leads to inefficiencies and challenges in load distribution, necessitating a control scheme to balance the state of charge (SoC) and optimize power sharing among multiple power supplies.
Innovation Solution
A power balancing control scheme that adjusts the power share among multiple independent DC/DC converters connected to a common power bus, using bias commands to balance the SoC of batteries while considering system constraints, allowing for integral control and avoiding voltage droop and bus collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple independent DC/DC converters are used to supply power to a common bus, then system capacity and power availability are improved, but uneven wear on batteries and load distribution challenges occur
Solution Approach 1:
The system dynamically changes the power share parameter allocated to each DC/DC converter based on real-time battery state-of-charge levels. When one battery has lower SoC, its associated converter receives a reduced power share command, thereby reducing its contribution to the load and allowing other batteries to discharge more, balancing the wear across all batteries over time.
Solution Approach 2:
The control scheme implements feedback by continuously monitoring the state-of-charge of each battery and using this information to adjust the power share commands sent to each DC/DC converter. This closed-loop control ensures that the system responds to changing battery conditions and maintains balanced operation, preventing any single battery from being over-discharged or overcharged.
2Reliability
If power share is dynamically adjusted among multiple DC/DC converters, then battery SoC balancing is improved, but control complexity increases
Solution Approach 1:
The control system is segmented into independent modules, with each DC/DC converter having its own controller that receives power share commands and independently adjusts its operation. This modular approach allows the complex control logic to be distributed across multiple simple units rather than centralized in a single complex controller, making the system easier to implement and maintain.
Solution Approach 2:
The supervisor controller acts as an intermediary that receives high-level balancing objectives and translates them into specific power share commands for each DC/DC converter. This intermediary layer simplifies the control architecture by separating the decision-making logic (supervisor) from the execution logic (individual converter controllers), reducing overall system complexity.
3Speed
If bias commands are used to control power sharing, then response speed to load changes is improved, but communication requirements increase
Solution Approach 1:
Each DC/DC converter controller independently processes the power share bias command and autonomously adjusts its output without requiring continuous high-speed communication for control decisions. The bias command provides the necessary guidance, and each converter self-manages its control actions, reducing the communication burden while maintaining fast response capabilities.
Data Source
AI summary
A power system operable to implement a power balancing control scheme is provided. In one aspect, a power system includes multiple independent power supplies with independent batteries feeding onto a common power bus. The power supplies regulate the voltage on the common power bus at the same time. The power balancing control scheme, when implemented, causes the load on the common power bus to be shared among the individual power supplies with a specified load distribution. The specified load distribution can be set or determined to balance the State of Charge (SoC) of the batteries over time whilst taking into account the constraints or limits of the elements of the power system.