Method for detecting fault in relay of three-level grid-connected converter

Abstract

The invention discloses a method for detecting a fault in a relay of a three-level grid-connected converter. The method specifically comprises: under different states of a relay, opening auxiliary pipes of an inverter bridge arm of the converter, and detecting current passing through the relay in real time; if the relay is closed and the current is detected, determining the relay is normally closed, and otherwise, determining the relay has an open-circuit fault; and if the relay is in a disconnected state and the current isn't detected in a preset time, determining the relay is normally disconnected, and otherwise, determining the relay has a short-circuit fault. According to the method, open-circuit and short-circuit faults of the relay can be accurately detected, and addition of excess detection values isn't needed. The system is suitable for a single-phase, three-phase three-wire, or three-phase four-wire system, has characteristics of simplicity, accurate determination, and good versatility, and is suitable for detecting the fault in the relay of a grid-connected converter.

Description

technical field [0001] The invention relates to the technical field of relay fault detection, in particular to a relay fault detection method for a three-level grid-connected converter. Background technique [0002] With the continuous improvement of people's requirements for clean energy and power quality, more and more power electronic equipment, such as photovoltaic inverters and active power filters, have begun to be incorporated into the grid. In order to ensure the safe operation of the power grid, most power electronic equipment will be connected to the grid through one or more physical switches, such as relays, contactors, circuit breakers, etc. Therefore, timely and accurate detection of such switch failures is crucial to the safe and stable operation of the equipment important. At present, the detection of switches such as relays, contactors, and circuit breakers is mainly through the change of the voltage at both ends of the auxiliary contact before and after clo...

AI Technical Summary

Problems solved by technology

For some switches without auxiliary contacts, the method of judging by auxiliary contacts is invalid; to detect the voltage at both ends of the switch before and after closing needs to add an additional voltage detection circuit; to detect changes in the bus voltage of uncontrolled rectification may be affected by grid voltage fluctuations, grid impedance Misjudgment caused by the interference of factors such as changes

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