An effective fault detection technique for a quasi-Z-Source based grid-tied PV system

In high performance grid-connected PV systems, deploying a power electronics converter capable of operating effectively in the presence of any single point of failure is essential. One of the main advantages of Cascaded H-Bridge (CHB) Multilevel Inverter (MLI) is the modularity. Moreover, the association of a quasi Z-Source (qZS) network with a CHB MLI was deeply investigated in the last decade for grid-tied PV systems. This structure is considered as a single-stage DC/AC topology having the capability of boosting the DC input voltage with high-quality multilevel AC voltage, independent DC-link voltage compensation, and control of the power transfer with high reliability. Thus, this topology suits well fault-tolerant PV systems due to the modularity of the CHB inverter and the flexibility of the qZS network in controlling the DC-link voltage even under faults. However, the effective operation of the MLI needs a continuous monitoring to detect abnormalities and faults to provide more effective and less interrupted energy supplies. The Exponentially Weighted Moving Average (EWMA) method has been proved to be among the most effective univariate techniques to detect small and moderate faults. Thus, this paper presents an effective EWMA based fault detection technique for a 3-phase 3-cell qZS-CHB MLI. Simulation results show the effectiveness of the proposed technique in detecting faults compared to the conventional Generalized Likelihood Ratio Test (GLRT) technique.