Battery Cluster Equalization to Reduce ESS Bucket Effect
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Solution Overview
Problem
Energy storage systems using electrochemical cells face capacity attenuation issues, leading to reduced available capacity over time, and phased battery capacity calibration methods result in a 'bucket effect' where batteries with lower State of Health (SOH) are fully charged or discharged faster, causing waste due to shutdowns by the Battery Management System (BMS).
Innovation Solution
An energy storage system with a battery cluster, direct current converter, and controller that includes independent operation of battery clusters with first equalization circuits to balance electricity quantities and allocate operating power, allowing for flexible phased deployment and improved equalization performance, reducing the impact of the bucket effect and maximizing battery capacity utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phased battery capacity calibration is implemented to reduce initial capacity requirements, then initial costs are reduced, but bucket effect occurs where batteries with lower SOH are fully charged or discharged faster causing capacity waste
Solution Approach 1:
The patent segments the battery system into multiple independent battery clusters, each with its own DC converter and control unit. This allows independent management of each cluster's charging/discharging cycles, preventing the bucket effect where one battery's lower SOH limits the entire system. Each cluster can be calibrated and operated independently based on its specific capacity and SOH characteristics.
Solution Approach 2:
The controller dynamically adjusts operating parameters (charging/discharging power, voltage, current) for each battery cluster based on real-time SOH, capacity, and load conditions. This parameter optimization ensures that batteries with different SOH levels can operate simultaneously without the lower-SOH battery prematurely reaching full charge/discharge, thereby eliminating the bucket effect and maximizing overall capacity utilization.
2Adaptability or versatility
If battery clusters with different SOH are operated together in a parallel configuration, then system flexibility is improved, but the bucket effect causes shutdowns by BMS reducing effective capacity
Solution Approach 1:
The patent divides the battery system into multiple independent clusters, each managed separately by its own control unit. This segmentation allows the system to accommodate batteries with different SOH levels without causing bucket effect, as each cluster operates independently. The system maintains flexibility through modular architecture while ensuring reliability through isolated control of each cluster's charging/discharging cycles.
Solution Approach 2:
The controller continuously monitors SOH, capacity, and operating status of each battery cluster, and dynamically adjusts control strategies based on this feedback. When a battery approaches full charge or discharge, the controller receives feedback and modifies the operating parameters to prevent premature shutdown, thereby maintaining system stability while supporting flexible configurations of batteries with varying SOH levels.
3Duration of action of stationary object
If sufficient capacity margin is provided in initial design to compensate for battery capacity attenuation, then long-term capacity requirements are met, but initial costs greatly increase
Solution Approach 1:
The patent implements dynamic capacity management where the controller continuously monitors battery SOH and capacity attenuation over time, and adjusts operating parameters (power, voltage, current) accordingly. This dynamic adjustment allows the system to extend service life by optimizing battery usage patterns, reducing stress on aging batteries, and preventing premature failure, thereby meeting long-term capacity requirements without over-provisioning initial capacity.
Solution Approach 2:
The system changes operating parameters based on battery age and SOH degradation. As batteries age and capacity attenuates, the controller adjusts charging/discharging rates, voltage thresholds, and power limits to extend usable life. This parameter optimization enables the system to maintain adequate capacity over extended service periods without requiring excessive initial capacity margin, thus reducing initial costs while meeting long-term requirements.
Data Source
AI summary
An energy storage system includes a battery cluster, a direct current converter, a controller, and at least one power conversion system. The energy storage system includes at least one direct current branch. The direct current branch includes a battery cluster and a direct current converter that are connected to each other. The direct current converter performs direct current conversion on a direct current provided by the battery cluster. Each battery cluster includes at least two energy storage modules that are connected in series. The controller controls the first equalization circuit, to balance electricity quantities of battery modules in the battery cluster, and allocates operating power to the power conversion system and the direct current converter. In this solution, impact of bucket effect on the energy storage system is reduced, so that a battery capacity can be more fully utilized.