Battery Charge Power Control Using Multi-Threshold Voltage Limits
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Solution Overview
Problem
Existing battery control methods experience unstable output of allowable electric power due to repeated limitations and cancellations, leading to operational instability, particularly during charging and discharging cycles.
Innovation Solution
A battery control method that uses a control unit, storage unit, and measurement unit to define allowable electric power based on predetermined voltage thresholds (first, second, and third voltage values) for partial and complete limitations, ensuring stable operation by acquiring voltage values at specified times and applying appropriate limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single threshold voltage mechanism is used to limit allowable electric power, then overcharge and overdischarge are prevented, but hunting occurs causing repeated limitations and cancellations that make the output unstable
Solution Approach 1:
The voltage threshold mechanism is segmented into three distinct thresholds: first threshold voltage (for normal operation), second threshold voltage (for partial limitation), and third threshold voltage (for complete limitation). This segmentation prevents hunting by creating clear zones for different control actions, where the battery operates normally below the first threshold, experiences partial limitation between first and second thresholds, and complete limitation above the third threshold.
Solution Approach 2:
Different control actions are applied to different voltage regions. In the normal voltage region (below first threshold), full allowable electric power is permitted. In the intermediate region (between first and second thresholds), partial limitation is applied. In the high-voltage region (above third threshold), complete limitation is applied. This local differentiation ensures appropriate responses to varying battery states and eliminates oscillatory behavior.
2Reliability
If allowable electric power is limited to ensure safety near unstable states, then overcharge and overdischarge are prevented, but the allowable electric power becomes unstable immediately after limitation due to short cycle fluctuations
Solution Approach 1:
The control mechanism performs preliminary action by establishing multiple threshold levels in advance. The first threshold voltage is set as a preliminary warning level, the second threshold as a partial limitation level, and the third threshold as a complete limitation level. This preliminary structuring of thresholds prevents the system from reaching unstable states while avoiding abrupt single-point limitations that cause oscillations.
Solution Approach 2:
The control system dynamically adjusts the allowable electric power based on the real-time battery voltage relative to the three thresholds. When voltage fluctuates, the system responds appropriately: maintaining full power below the first threshold, applying partial limitation between first and second thresholds, and applying complete limitation above the third threshold. This dynamic multi-level response stabilizes the system by preventing abrupt transitions.
Data Source
AI summary
By using a control unit that controls a battery, a storage unit that stores data of allowable electric power, and a measurement unit that measures a voltage value between a pair of electrode terminals of the battery, the allowable electric power is defined as chargeable maximum electric power which is calculated based on a predetermined upper limit voltage value and a current charged state; wherein the data includes: a first voltage value that is an upper limit value for which a limitation of the allowable electric power is not required; a second voltage value which is higher than the first voltage value and for which a partial limitation of the allowable electric power is required; and a third voltage value which is higher than the second voltage value and for which a complete limitation of the allowable electric power is required; and wherein the control unit: acquires the voltage value from the measurement unit at every specified time; performs the complete limitation of the allowable electric power when the voltage value of the allowable electric power becomes equal to or higher than the third voltage value; and performs the partial limitation or the complete limitation of the allowable electric power while the voltage value of the allowable electric power decreases to the second voltage value and then to the first voltage value. Accordingly, a battery control method which eliminates hunting and enhances reliability is provided.