UPS Ground Fault Detection Using Filter Circuit Voltage Sensing
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Solution Overview
Problem
Traditional ground fault detection methods in three-phase uninterruptible power systems face challenges such as increased power consumption, heat dissipation, and false detection due to high common-mode voltage, and require additional hardware circuits, which complicate detection and increase costs.
Innovation Solution
A ground fault detection apparatus and method that utilize a detection circuit with a first and second detection end, coupled to filter circuits between the AC/DC and DC/AC conversion circuits and the equipment grounding point, allowing for the determination of ground faults and their location based on detection voltage without additional hardware, reducing power consumption and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional hardware detection circuit is added to detect ground fault, then ground fault detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent reuses existing filter circuit components (capacitors and inductors) in the power conversion system for dual purposes: their primary function for electromagnetic interference filtering and their secondary function as detection elements for ground fault detection. By monitoring voltage changes across these existing components, the system achieves ground fault detection without adding dedicated detection hardware, thus resolving the contradiction between detection capability and device complexity.
2Use of energy by moving object
If voltage monitoring is performed using existing filter circuits, then power consumption is reduced, but detection precision may be affected by high common-mode voltage
Solution Approach 1:
The patent introduces a differential amplifier as an intermediary component that receives the voltage signal from the filter circuit and amplifies the differential voltage component while rejecting the common-mode voltage. This intermediary stage enables precise ground fault detection by isolating the useful detection signal from the interfering high common-mode voltage, thus maintaining detection precision while using the low-power existing filter circuits.
Data Source
AI summary
A ground fault detection apparatus is used to detect a ground fault of a three-phase UPS apparatus. The UPS apparatus includes a first filter circuit, an AC/DC conversion circuit, a DC bus, a DC/AC conversion circuit, and a second filter circuit coupled in sequence. The ground fault detection apparatus includes a detection circuit having a first detection end and a second detection end. The first detection end is coupled to the first filter circuit and the second filter circuit, and the second detection end is coupled to an equipment grounding point. The equipment grounding point is coupled to a neutral point of a three-phase power source, and the three-phase power source is coupled to the first filter circuit. The detection circuit indicates whether the UPS apparatus has a ground fault and a location where the ground fault occurs according to a detection voltage between the first detection end and the second detection end.