Three-Phase AC Power Supply Abnormality Detection
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Solution Overview
Problem
Existing power failure detection systems in uninterruptible power supplies face delays in detecting abrupt voltage fluctuations, leading to potential temporary drops in voltage supplied to loads during transitions from AC to DC power conversion.
Innovation Solution
A power supply device with a controller that detects abnormalities in three-phase AC voltage by estimating threshold values based on instantaneous voltage measurements, allowing for quicker detection and switching to prevent overvoltage or undervoltage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the effective value of AC input voltage is used for power failure detection, then the detection is simple and reliable, but there is a time delay between voltage fluctuation and detection
Solution Approach 1:
The system performs preliminary action by estimating future threshold values based on current voltage measurements and waveform characteristics. The abnormality detection unit calculates what the threshold should be at a future time point, allowing the system to detect abnormalities before they actually occur, thus eliminating the time delay inherent in traditional methods that wait for the effective value to cross a fixed threshold.
Solution Approach 2:
The invention applies dynamics by making the threshold value dynamic rather than static. Instead of using a fixed power failure detection level, the system continuously updates the threshold based on the actual AC voltage waveform characteristics, frequency, and phase. This dynamic threshold adapts to changing operating conditions, enabling accurate detection without the time delay caused by fixed thresholds.
2Speed
If the AC power supply voltage fluctuates abruptly, then the power supply system must respond quickly, but the inverter conversion from DC to AC power causes temporary voltage drop
Solution Approach 1:
The system detects abnormalities in advance using the estimated future threshold values before the voltage fluctuation fully develops. By detecting the abnormality condition earlier, the system can initiate the inverter conversion process proactively, reducing the response time and minimizing the duration of any voltage drop during the transition from AC to DC power.
Solution Approach 2:
The invention enables the system to skip or rush through the detection and response process by using instantaneous voltage measurements and estimated thresholds to identify abnormalities immediately. This allows the system to bypass the slower traditional effective value calculation method and respond more quickly to voltage fluctuations, reducing the time the load experiences unstable voltage during power transitions.
Data Source
AI summary
A switch is connected between an AC power supply and a load. A controller detects an abnormality of the AC power supply by detecting an instantaneous value of a three-phase AC voltage supplied from the AC power supply, when the switch is on. Based on an instantaneous value of the three-phase AC voltage detected at a first time and a first threshold value preset for a peak value of the three-phase AC voltage, the controller estimates a second threshold value for an instantaneous value of the three-phase AC voltage at a second time having a prescribed time difference from the first time. The controller detects the abnormality of the AC power supply by comparing the estimated second threshold value with the instantaneous value of the three-phase AC voltage detected at the second time. The controller turns off the switch when the abnormality of the AC power supply is detected.