UPS Control Method for Inrush Current Reduction
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Solution Overview
Problem
Conventional uninterruptible power supplies face issues with power utilization efficiency and risk of burn-down due to inrush current when dealing with inductive or motorized loads under abnormal input voltage conditions, particularly when peak voltage, frequency, or phase differences are significant.
Innovation Solution
A control method for uninterruptible power supplies that determines abnormal input voltage conditions and switches between bypass routing and inverter output based on peak voltage, frequency, and phase differences, ensuring synchronous variation of output with input parameters to minimize inrush current and prevent burn-down, utilizing an AC/DC converter, inverter, charger circuit, bypass route, switch, and controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the static transfer switch switches the power delivery route to provide inverter output voltage for the load when input voltage is abnormal, then power quality is improved, but inrush current occurs causing device burn-down
Solution Approach 1:
The controller performs preliminary detection of input voltage parameters (peak voltage, frequency, phase difference) before switching the power delivery route. This preliminary action allows the system to identify abnormal conditions and prepare appropriate responses, preventing inrush current by avoiding switching under unfavorable conditions and ensuring power quality through timely switching when necessary.
2Reliability
If the inverter continuously converts DC voltage to AC voltage during normal operation, then power quality is maintained, but power conversion efficiency decreases
Solution Approach 1:
The controller implements periodic detection of input voltage parameters and dynamically switches between bypass mode and inverter output mode based on detected conditions. During normal operation, the bypass route provides power directly (high efficiency), while the inverter activates periodically when abnormal conditions are detected (maintaining power quality). This periodic switching optimizes the balance between power quality and energy efficiency.
3Reliability
If the system detects abnormal peak voltage, frequency, or phase difference, then power quality is protected, but switching complexity increases
Solution Approach 1:
The controller monitors three key parameters (peak voltage, frequency, phase difference) and compares them against predetermined thresholds. When any parameter exceeds its threshold, the controller switches the power delivery route. This parameter-based control approach provides systematic protection against abnormal conditions while maintaining relatively simple control logic through clear threshold comparisons.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for stable power delivery to loads, even under abnormal conditions, by synchronizing output voltage with input voltage, reducing inrush current and enhancing power efficiency, thus protecting the supply from burn-down and ensuring continuous operation.
Implementation Method 1
an AC/DC converter for receiving the first AC voltage from the power input terminal and converting the first AC voltage into a DC voltage
Implementation Method 2
an inverter for converting the DC voltage into a second AC voltage
Data Source
AI summary
An uninterruptible power supply and method for controlling same are disclosed. The controlling method includes the steps of bypassing the first AC power to the output terminal via the bypass loop and the switch and converting a second AC power having a voltage, phase and frequency substantially equal to that of the first AC power by an inverter when the first AC power is normal; and switching the second AC power to the output terminal via the switch when the phase or frequency of the first AC power is changed so as to generate a difference value between the first AC power and the second AC power and the difference value is larger than a predetermined difference value.