Abstract
This article considers fault detection in the case of a three-phase three-wire (3P3W) inverter, when only two current sensors are used to save cost or due to a faulty current sensor. With two current sensors, there is no current method addressing the diagnosis of both IGBT open-circuit (OC) faults and current sensor faults. In order to solve this problem, this article proposes a method which innovatively combines two kinds of diagnosis variables, line voltage deviations and phase voltage deviations. The unique faulty characteristics of diagnosis variables for each fault are extracted and utilized to distinguish the fault. Using an average model, the method only needs the signals already available in the controller. Both IGBT OC faults and current sensor faults can be detected quickly in inverter mode and rectifier mode, so that the converter can be protected in a timely way to avoid further damages. In addition, error-adaptive thresholds are adopted to make the method robust. Effects such as system unbalance are analyzed to ensure that the method is robust and feasible. Simulation and experimental results are used to verify and validate the effectiveness of the method.
Highlights
Grid-tied three-phase voltage-source inverters are widely used in renewable energy systems, electrical traction systems, etc
Many papers have been published focusing on IGBT OC fault diagnosis
The average output line and phase voltage deviations are taken as diagnosis variables
Summary
Grid-tied three-phase voltage-source inverters are widely used in renewable energy systems, electrical traction systems, etc. When a fault occurs with a current sensor in grid-tied inverters, the current will rise quickly due to the actions of the close-loop control, which may cause further damages to IGBTs and sensitive loads. There have been some reports on fault diagnosis of sensors in inverters Most of these methods are based on current analysis [24]-[26] and models [27]-[30]. A fast and general method based on a parity space and temporal redundancies is developed in [26] It is suitable for various kinds of sensor faults. The methods for IGBT fault diagnosis utilizing sampled currents may have false alarms when current sensor faults occur. The method in [33] can diagnose multiple IGBT faults and current sensor faults through stator current analysis.
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