Balanced Control for Heterogeneous Battery Systems
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Solution Overview
Problem
Retired electric vehicle batteries with varying capacities and conditions pose challenges for balanced charge and discharge in stationary energy storage systems, leading to inefficiencies and potential overcharging or overdischarging, which can reduce the overall energy storage capability and battery life.
Innovation Solution
A balanced charge/discharge control strategy that uses terminal voltage and current measurements to estimate internal parameters and maintain equilibrium among heterogeneous battery packs, allowing for continuous balancing and efficient operation in both parallel and series connections, even when packs are not initially balanced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If retired EDV batteries with varying capacities and conditions are integrated into stationary energy storage systems, then the energy storage capacity and power capacity are significantly increased, but the control complexity and difficulty of maintaining balanced operation increase
Solution Approach 1:
The patent segments the heterogeneous battery system into individually controllable modules or packs, each with its own control parameters. This allows the system to manage diverse battery characteristics (different capacities, ages, conditions) by treating them as separate controllable units rather than a monolithic system, thereby enabling complex energy storage configurations while maintaining manageable control through modular architecture
Solution Approach 2:
The patent implements dynamic control strategies that continuously adjust charge/discharge rates based on real-time battery state measurements. The control system adapts to varying battery conditions by modifying operating parameters dynamically, allowing the system to optimize performance and maintain balance across heterogeneous batteries with different characteristics, thus resolving the contradiction between high storage capacity and control complexity
2Loss of energy
If cell balancing currents are kept relatively small to avoid power loss and reduce costs, then power loss is reduced and costs are decreased, but the balancing effectiveness is limited to small cell imbalances
Solution Approach 1:
The patent performs cell balancing during idle periods (when vehicles are parked) before the batteries are put into service. By proactively equalizing small imbalances during non-operational times using small balancing currents, the system prevents these imbalances from accumulating into larger discrepancies that would require high currents to correct, thus achieving effective balancing while minimizing power loss and costs
Solution Approach 2:
The patent implements periodic balancing cycles during idle times rather than continuous balancing. This approach allows small balancing currents to be applied intermittently to correct drift in cell states, achieving sufficient balancing effectiveness for typical operating conditions while avoiding the continuous power loss and cost associated with constant high-current balancing
3Adaptability or versatility
If heterogeneous battery packs with different capacities and internal resistance are connected in series and parallel, then the system flexibility and adaptability are improved, but the risk of overcharge/overdischarge and reduced battery life increase
Solution Approach 1:
The patent applies individualized control parameters and charge/discharge rate limits to each battery pack based on its specific characteristics (capacity, internal resistance, age, condition). This localized approach ensures that each heterogeneous pack operates within its safe boundaries, preventing overcharge/overdischarge conditions while maintaining the overall system's flexibility to accommodate diverse battery types in series and parallel configurations
4Productivity
If battery systems are used continuously to support grid operations, then the productivity and grid support capability are improved, but the opportunity for cell balancing is reduced
Solution Approach 1:
The patent performs cell balancing during idle periods (when vehicles are parked and batteries are not needed for grid support) before the batteries are deployed for continuous grid operations. By proactively equalizing cell imbalances during non-operational windows, the system ensures batteries start each grid support cycle in a balanced state, maintaining balancing effectiveness without compromising continuous productivity
Solution Approach 2:
The patent implements control strategies that maintain balanced operation continuously during grid support operations by dynamically adjusting charge/discharge rates. This allows the system to achieve both continuous productivity for grid support and ongoing balancing effectiveness, as the control system continuously monitors and adjusts operations to prevent imbalance accumulation during extended use
Data Source
AI summary
A battery network includes a plurality of heterogeneous batteries coupled to at least one energy source and one energy load, a plurality of switches coupled to the heterogeneous batteries, and the switches controllable having a duty cycle between 0 and 1. A controller is configured to characterize each of the plurality of heterogeneous batteries characteristics, determine duty cycles for each of the plurality of switches based on the characterization such that a charge applied from the at least one energy source or a discharge to the at least one energy load converges to a balanced state for the plurality of heterogeneous batteries, and apply the determined duty cycles to the plurality of switches.