DC Conversion Circuit Control for Low-Load Battery Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In uninterruptible power supplies, when the mains supply is out of range, the boost circuit modules frequently switch between charging and discharging due to small load conditions, leading to increased temperature and reduced service life of the energy storage apparatus.
Innovation Solution
A dual-loop control method is implemented for direct current conversion circuits, including an external voltage control loop and internal current control loop, with full-bridge circuit modules disconnected when the current reference value is below a threshold, and a predetermined startup duty cycle is used to prevent negative current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the boost circuit modules operate under small load conditions, then the power supply can meet the load requirements, but the modules frequently switch between charging and discharging causing increased temperature and reduced service life
Solution Approach 1:
The patent introduces a threshold current reference value as an intermediary parameter to mediate between the power supply capability and the reliability of the energy storage apparatus. When the current reference value falls below this threshold, the system switches to a special control mode that prevents negative current changes, thereby eliminating the harmful frequent charging-d discharging cycles while maintaining adequate power supply for small loads.
Solution Approach 2:
The patent changes the control parameter behavior by introducing a threshold value for the current reference value. When this parameter exceeds the threshold, different control strategies are applied: above the threshold, normal power supply control is used; below the threshold, a protective mode is activated that constrains the full-bridge circuit current to prevent negative values, thus changing the system's operational characteristics to protect the energy storage apparatus.
2Power
If the full-bridge circuit module operates with PWM control, then the voltage can be regulated, but negative current flow occurs when the current reference value is low
Solution Approach 1:
The patent applies preliminary anti-action by predicting when negative current might occur (when the current reference value is below the threshold) and taking preventive measures before the harmful effect manifests. The control system monitors the current reference value and, upon detecting it falls below the threshold, preemptively adjusts the duty cycle of the full-bridge circuit to prevent negative current flow, rather than waiting for the negative current to actually occur.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the current reference value and comparing it against the threshold. Based on this feedback, the system dynamically adjusts the operating mode of the full-bridge circuit module. When the feedback indicates the current reference value is below the threshold, the system modifies the PWM duty cycle to prevent negative current, thereby using feedback to eliminate the harmful effect.
Data Source
AI summary
A control method for a direct current conversion circuit is provided. The direct current conversion circuit is connected between an energy storage apparatus and direct current buses, and includes at least one buck/boost circuit module and at least one full-bridge circuit module that are connected in parallel. The control method includes an external voltage control loop and an internal current control loop. Each of the at least one buck/boost circuit module and the at least one full-bridge circuit module corresponds to one internal current control loop. The control method includes: obtaining a voltage error based on a predetermined bus reference voltage and an actual bus voltage; obtaining a current reference value for the internal current control loop based on the voltage error; and disconnecting the at least one full-bridge circuit module when the current reference value is less than a threshold.