Uninterruptible Power Supply DC Component Detection
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Solution Overview
Problem
Conventional uninterruptible power supplies with an input transformer between the AC power supply and converter can experience abnormal operation due to magnetic bias caused by a DC component in the AC current, which is not effectively detected and addressed, leading to potential system failures.
Innovation Solution
Incorporating a current detector and processors to extract the DC component from the AC current and stop the converter operation when the DC component exceeds a threshold, preventing magnetic bias in the input transformer, and implementing a controlled restart mechanism to manage power supply efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a DC component is included in the AC current flowing through the input transformer, then the transformer can operate with simplified current waveform, but magnetic bias occurs causing abnormal operation
Solution Approach 1:
The system performs preliminary detection of DC components in the AC current before they cause magnetic bias in the transformer. The controller continuously monitors the current waveform and identifies DC offsets, taking preventive action by switching to battery power before abnormal operation occurs.
Solution Approach 2:
The system uses feedback from current detection to control the power supply mode. The controller detects DC components in the AC current and adjusts the power supply strategy accordingly - switching to battery power when DC components are present and excessive, and returning to AC power when conditions normalize.
2Duration of action of stationary object
If the converter operates continuously to maintain power supply, then uninterrupted power is provided to the load, but magnetic bias accumulates causing distortion and potential failure
Solution Approach 1:
The system implements periodic switching between AC power and battery power based on detected DC component levels. When DC components exceed thresholds, the system periodically switches to battery power, allowing the transformer to rest and magnetic bias to dissipate, then returns to AC power when conditions improve.
Solution Approach 2:
The system prepares battery power as a cushioning backup before AC power causes harmful magnetic bias. By having battery power ready and switching to it proactively when DC components are detected, the system prevents transformer damage while maintaining continuous power supply.
3Reliability
If the system stops operation when overcurrent is detected to prevent damage, then transformer safety is protected, but normal operation with small DC components is unnecessarily interrupted
Solution Approach 1:
The system changes the detection parameter from simple overcurrent threshold to DC component magnitude analysis. By specifically measuring and comparing DC component levels against thresholds, the system can distinguish between harmful DC offsets causing magnetic bias and normal AC current variations, avoiding unnecessary shutdowns.
Solution Approach 2:
The system applies different response thresholds and detection criteria to different operational conditions. It monitors DC components continuously but only triggers protective actions when DC levels exceed specific thresholds, allowing normal operation with minor fluctuations while protecting against significant magnetic bias.
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
Prevents abnormal operation of the uninterruptible power supply by eliminating magnetic bias and optimizes power consumption by controlled restarts, ensuring reliable operation and reduced power consumption from the DC power supply, particularly when using a battery with limited capacity.
Implementation Method 1
an input transformer connected to an input node that is configured to be connected to an AC power supply so as to transform AC voltage from the AC power supply
Implementation Method 2
a converter receiving the transformed AC voltage to convert the transformed AC voltage to DC voltage
Implementation Method 3
an inverter that converts the DC voltage from the converter to AC voltage for supplying to a load
Implementation Method 4
a current detector that detects current flowing between the AC power supply and the converter
Data Source
AI summary
An uninterruptible power supply includes a main uninterruptible power supply unit including a converter, an inverter, and a battery, as well as an input transformer which is arranged between an AC power supply and the converter and transforms the AC voltage from the AC power supply. The uninterruptible power supply further includes a DC component extraction unit that extracts a DC component from current flowing between the AC power supply and the converter, as well as a CPU which, when the DC component extracted by the DC component extraction unit is greater than a threshold current, stops operation of the converter and causes DC voltage from the battery to be supplied to the inverter.