UPS Failure Detection Using Instantaneous Current Comparison
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Solution Overview
Problem
Existing uninterruptible power supply (UPS) systems operating in parallel redundancy conditions face challenges in quickly identifying and isolating a failed unit without affecting other 'good' UPSs and the load device, as current methods require a cycle time of 1/50 or 1/60 seconds to determine failure, which is too long for immediate selective tripping.
Innovation Solution
A UPS system that converts DC voltage to AC and includes a control unit for failure determination using instantaneous internal voltage and current values, with an inverter unit and filter circuit, and a trip switch for immediate isolation based on deviations between actual and simulated inductor current values, allowing for faster failure detection and selective tripping within a shorter time frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional failure detection methods using one cycle-delay signals are used, then failure determination can be made with sufficient accuracy, but the response time is too long (one cycle time of AC output frequency) for immediate selective tripping
Solution Approach 1:
The patent pre-calculates and stores lookup tables containing expected voltage and current waveforms under normal operating conditions. During operation, the control unit directly compares real-time measured values against these pre-prepared reference values, eliminating the need for real-time complex calculations and one-cycle delay signal generation, thus achieving immediate failure detection without sacrificing accuracy
Solution Approach 2:
The patent replaces the conventional mechanical timing-based failure detection method (using one cycle-delay signals) with an electronic comparison method using pre-stored lookup tables. This substitution allows instantaneous comparison of measured values against expected values, achieving both high reliability and rapid response time
2Power
If UPSs operate in parallel redundancy condition, then sufficient power source capacity is available, but a single failure can cause chain reaction affecting other good UPSs and the entire power source system
Solution Approach 1:
The patent extracts the failed UPS unit from the parallel system by immediately tripping its trip switch upon failure detection. This isolation prevents the failure from propagating through the bus lines to affect other good UPSs, while the remaining UPSs continue to operate and maintain sufficient power source capacity for the load device
Solution Approach 2:
The patent implements a feedback mechanism where each UPS independently monitors its own operating status and immediately communicates failure information to the control unit. This rapid feedback enables immediate selective tripping of the failed unit, maintaining system stability while preserving the redundancy benefit of parallel operation
3Ease of operation
If each UPS determines failure independently using internal information only, then selective tripping can be achieved without affecting other UPSs, but the detection speed must be increased below one cycle time
Solution Approach 1:
The patent pre-calculates and stores lookup tables containing expected voltage and current waveforms under normal operating conditions. During operation, the control unit directly compares real-time measured values against these pre-prepared reference values, eliminating the need for real-time complex calculations and one-cycle delay signal generation, thus achieving immediate failure detection without sacrificing accuracy
Solution Approach 2:
Each UPS independently monitors its own internal voltage and current using its own sensors and control unit, comparing these values against pre-stored reference patterns. This self-service approach enables each UPS to autonomously determine its own failure status without relying on information from other UPSs, achieving both independence and rapid detection
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
Enables independent failure determination and immediate selective tripping of a UPS within a time shorter than one cycle of the AC output frequency, minimizing the impact on other 'good' UPSs and the load device.
Implementation Method 1
an uninterruptible power supply (UPS) that converts a DC voltage to an AC voltage and that supplies the AC voltage to a load device
Data Source
AI summary
Performance failure in an uninterruptible power supply (UPS) is determined independently by itself. A selective tripping can be done within a shorter time than one cycle of an AC output. A UPS converts a DC voltage to an AC voltage and supplies the AC voltage to a load device. A UPS has a control unit conducting a failure determination by using an instantaneous value of an internal voltage and current. It is preferred that a UPS includes an inverter unit and a trip switch. The inverter unit includes a semiconductor bridge circuit generating a sinusoidal AC voltage by modulating a DC voltage with voltage instruction values, and a filter circuit inserted between the semiconductor bridge circuit and the load device. The trip switch connects and trips a connection between the inverter unit and the load device according to the failure determination of the control unit.