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In photovoltaic systems, dc–dc converters have been identified as one of the most critical and challenging subsystem in terms of failure rate. Thus, this paper proposes fault-tolerant operation of a two-stage buck/buck–boost converter under open-circuit switch failure. Remedial actions are efficient in any failure of one of the two switches of the converter. Here, a new unified approach is considered, for the overall fault-tolerant operation of the two stages of the converter. The fault-tolerant circuit we propose lies on performing redundancy by implementing the equivalent synchronous switch for the two main switches of the two stages, in offline mode. The fault-tolerant circuit results from the basic two-stage buck/buck-boost converter and its equivalent circuit with a synchronous switch, merged together to form the new dc–dc fault-tolerant circuit. Therefore, postfault operation at full power can also be performed. By using a switch fault management unit with reduced complexity, inserted between the control block and the switches, we have designed an unified, efficient, and optimized fault-tolerant control, suitable in both healthy and postfault operations. Some selected experimental tests, which all confirm the good performances of the proposed fault-tolerant approach, are presented and discussed. [ABSTRACT FROM AUTHOR]

Fault detection (FD) in power electronic converters is necessary in embedded and safety critical applications to prevent further damage. Fast FD is a mandatory step in order to make a suitable response to a fault in one of the semiconductor devices. The aim of this study is to present a fast yet robust method for fault diagnosis in nonisolated dc–dc converters. FD is based on time and current criteria which observe the slope of the inductor current over the time. It is realized by using a hybrid structure via coordinated operation of two FD subsystems that work in parallel. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. For validation, computer simulations are first carried out. The proposed detection scheme is validated on a boost converter. Effects of input disturbances and the closed-loop control are also considered. In the experimental setup, a field programmable gate array digital target is used for the implementation of the proposed method, to perform a very fast switch FD. Results show that, with the presented method, FD is robust and can be done in a few microseconds. [ABSTRACT FROM PUBLISHER]