Three-Phase AC Voltage State Detection Using Instantaneous Sum of Squares
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Solution Overview
Problem
Conventional techniques for detecting phase interruptions in three-phase AC power supplies are complex and fail to accurately determine abnormal states, leading to potential equipment damage due to inadequate detection of instantaneous voltage drops and power failures.
Innovation Solution
A system that measures instantaneous voltages of three-phase AC power and determines the state of the power supply by comparing the sum of n-th powers of these voltages to reference values, using a determination unit to switch between power sources based on predefined criteria, including time windows and reference values, to prevent equipment damage and ensure continuous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ripple detection using differentiating circuit is used, then phase interruption can be detected, but the configuration becomes complicated and detection accuracy is insufficient
Solution Approach 1:
The patent extracts the essential detection function from the complex differentiating circuit configuration and implements it through a simplified calculation approach. By calculating the sum of squares of instantaneous voltages and comparing it with a reference value, the system achieves accurate phase interruption detection without requiring complex analog differentiating circuits, thus reducing configuration complexity while maintaining detection accuracy.
Solution Approach 2:
The patent replaces the mechanical/analog differentiating circuit with a digital calculation and comparison system. Instead of using physical capacitors and resistors in a differentiating circuit, the system uses computational operations (squaring instantaneous voltages, summing them, and comparing with reference) to achieve the same detection function, thereby simplifying the overall configuration.
2Device complexity
If simple voltage comparison is used, then configuration is simple, but instantaneous voltage drops and power failures cannot be accurately determined
Solution Approach 1:
The patent changes the parameter used for comparison from simple instantaneous voltage to the sum of squares of instantaneous voltages of all three phases. This parameter transformation enables the system to accurately detect abnormal states such as phase interruptions and voltage drops, as the sum of squares relationship (Vline1² + Vline2² + Vline3² = constant) provides a more sensitive indicator of power supply abnormalities while maintaining configuration simplicity.
3Measurement precision
If detection threshold is set low, then sensitivity increases, but false detection increases
Solution Approach 1:
The patent establishes a feedback mechanism where the detection result (abnormal state determination) triggers power source switching, and the system continuously monitors the switched power source. This feedback loop allows the system to adapt to changing conditions and prevents false detections from causing unnecessary switching, thereby improving reliability while maintaining detection sensitivity through the appropriate reference value comparison.
Data Source
AI summary
A conventional technique makes a configuration complicated. Provided is an apparatus including: a voltage measuring unit configured to measure each of instantaneous voltages of three-phase AC voltage; and a determination unit configured to determine a state of a power supply source of the three-phase AC voltage based on a result of comparison between a comparison target value corresponding to a sum of n-th powers (n is a positive even number) of the instantaneous voltages of the three-phase AC voltage and a reference value.