A health status-based performance evaluation method of photovoltaic system

Abstract

The large scale application of the photovoltaic (PV) systems is significantly beneficial to the mitigation of energy crisis. The quality and performance of PV systems directly influence the energy yield. It is necessary to establish more scientific and effective methods to maximize the energy yield. In this paper, the concept of health status is proposed to describe the performance of PV systems within a certain period of time. A health status based performance evaluation model is built by the Gaussian mixture models (GMM) and the empirical mode decomposition (EMD). Then, the health index (HI) of PV array is defined. Under the outdoor ambient conditions, the proposed model can sensitively detect the slight performance reduction caused by faults or partial shadings of the PV array in real-time. At last, the proposed method is verified by the simulations and experiments. Experimental results show that on the sunny day the average daily HI is 1.2 and the average performance ratio (PR) is 0.85, which both show the PV array is healthy. When one of the PV modules in the PV array is partially shaded, the PR is still approximate 0.9. However, the calculated HI is greater than the threshold and the fault is reported. The results indicate that the proposed method can sensitively identify pseudo health status that cannot be identified by the PR. The proposed evaluation method based on health status provides an alternative option to assess the performance of the PV systems. Combining with the PR, the comprehensive performance of the PV systems can be reflected more accurately.