Half-Bridge Battery Module Control for Full-Current SOC Balancing
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Solution Overview
Problem
Existing energy storage systems face significant challenges in balancing the state of charge (SOC) of battery cells, leading to series-connection capacity loss, parallel-connection capacity loss, and parallel-connection circulation current, due to insufficient balancing ability in both passive and active balancing methods.
Innovation Solution
A full current balancing method that utilizes a half-bridge control circuit with full-controlled power electronic devices to adjust the charging and discharging of battery modules, allowing for higher balancing currents and enabling direct series-connection and parallel-connection of battery packs, thereby improving SOC balancing across multiple battery cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive balancing is used to discharge battery cells with excessive high voltages, then SOC balancing is achieved, but balancing current is only about 0.1 A which is insufficient for large-scale battery systems
Solution Approach 1:
The patent introduces a current circulation balancing device as an intermediary component that enables high-current balancing by circulating current between battery cells. This mediator allows direct current exchange between cells with different SOC levels, achieving fast balancing without relying on the limited 0.1A passive balancing current.
Solution Approach 2:
The patent replaces the traditional passive resistance-based balancing mechanism with an active current circulation mechanism. Instead of dissipating excess energy as heat through resistors, the system uses controlled current circulation to directly transfer charge between battery cells, achieving much higher balancing currents.
2Reliability
If active balancing is used to transfer energy from high SOC to low SOC battery cells, then SOC balancing is improved, but cost increases and it is not suitable for long battery clusters
Solution Approach 1:
The patent segments the battery system into modular units with individual balancing circuits for each battery cell. Each balancing circuit can independently manage current circulation for its associated cell, allowing the system to scale to large battery clusters without proportionally increasing overall system complexity and cost.
Solution Approach 2:
The current circulation balancing device serves multiple functions: it provides SOC balancing, enables high-current operation, and can be applied to battery clusters of any size. This universal solution replaces the need for complex active balancing systems while maintaining effectiveness across different system scales.
3Quantity of substance
If battery cells are connected in series to increase system capacity, then energy storage capacity increases, but series-connection capacity loss occurs due to insufficient balancing ability
Solution Approach 1:
The patent introduces current circulation paths as intermediary channels between series-connected battery cells. These intermediaries allow direct charge transfer between cells with different SOC levels, preventing the capacity loss that would otherwise occur in series connections due to inadequate balancing.
4Quantity of substance
If battery cells are connected in parallel to increase system capacity, then energy storage capacity increases, but parallel-connection circulation current occurs due to insufficient balancing ability
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors SOC levels of parallel-connected battery cells and automatically activates current circulation balancing when imbalances are detected. This feedback control prevents the development of harmful circulation currents by maintaining real-time SOC equilibrium among parallel cells.
Data Source
AI summary
A full current balancing method of SOC for an energy storage system is provided. DC output terminals of each battery pack are connected in parallel with a half-bridge control circuit to form a battery module, positive and negative electrodes of battery modules are successively connected in series to form a battery cluster. In operation, SOCs of the battery modules are sorted, battery modules with lower SOCs are put in operation first when charging, and the battery modules with higher SOCs are put in operation first when discharging, thereby achieving full current balancing of SOC among the battery packs in the battery cluster. After multiple battery clusters are connected in parallel to form a battery stack, current of the battery cluster with a low SOC is increased, and current of the battery cluster with a high SOC is decreased, thereby achieving balancing of SOC among the battery clusters.