Abstract
In the fault diagnosis process of a photovoltaic (PV) array, it is difficult to discriminate single faults and compound faults with similar signatures. Furthermore, the data collected in the actual field experiment also contains strong noise, which leads to the decline of diagnostic accuracy. In order to solve these problems, a new eigenvector composed of the normalized PV voltage, the normalized PV current and the fill factor is constructed and proposed to characterize the common faults, such as open circuit, short circuit and compound faults in the PV array. The combination of these three feature characteristics can reduce the interference of external meteorological conditions in the fault identification. In order to obtain the new eigenvectors, a multi-sensory system for fault diagnosis in a PV array, combined with a data-mining solution for the classification of the operational state of the PV array, is needed. The selected sensors are temperature sensors, irradiance sensors, voltage sensors and current sensors. Taking account of the complexity of the fault data in the PV array, the Kernel Fuzzy C-means clustering method is adopted to identify these fault types. Gaussian Kernel Fuzzy C-means clustering method (GKFCM) shows good clustering performance for classifying the complex datasets, thus the classification accuracy can be effectively improved in the recognition process. This algorithm is divided into the training and testing phases. In the training phase, the feature vectors of 8 different fault types are clustered to obtain the training core points. According to the minimum Euclidean Distances between the training core points and new fault data, the new fault datasets can be identified into the corresponding classes in the fault classification stage. This strategy can not only diagnose single faults, but also identify compound fault conditions. Finally, the simulation and field experiment demonstrated that the algorithm can effectively diagnose the 8 common faults in photovoltaic arrays.
Highlights
With the intensification of the energy and environment crisis, clean energy plays an integral role in restraining global warming issues and has received more and more attention in industrial circles.As a major clean energy technology, photovoltaic power generation has received worldwide attention in recent years, especially in developing countries
Gaussian Kernel Fuzzy C-means clustering method (GKFCM) shows good clustering performance for classifying the complex datasets, the classification accuracy can be effectively improved in the recognition process
These two points lead to the fault classification difficulty that some single faults and compound faults with similar characteristics cannot be discriminated by the conventional feature quantities proposed in previous papers
Summary
With the intensification of the energy and environment crisis, clean energy plays an integral role in restraining global warming issues and has received more and more attention in industrial circles. Zhao Y et al [17] developed a graph-based semi-supervised detection method for discriminating different faults including short circuits, open circuits and line-to-line faults, and so on. Some single faults and compound faults display similar features and the fault datasets acquired in the field experiment are usually accompanied by environmental and system noise These two points lead to the fault classification difficulty that some single faults and compound faults with similar characteristics cannot be discriminated by the conventional feature quantities proposed in previous papers. Compared to the traditional fuzzy C-means clustering algorithm, the GKFCM can highlight the difference of the sample characteristics by the nonlinear mapping of kernel space This method can improve the clustering ability of complex datasets and robustness of fault diagnosis effectively. Since the proposed method considers the normalization of the feature quantities and the robustness of the GKFCM, the generalization ability of the fault diagnostic algorithm can be further guaranteed
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