Open-circuit fault diagnosis in Neutral-Point-Clamped active power filters based on instant voltage error with no additional sensors

This paper proposes the use of a fault diagnosis algorithm based on instant voltage error for Neutral-Point-Clamped active power filters. This algorithm uses only signals already available to the filter controller and thus does not require any additional hardware. The algorithm is highly independent from the load and control technique. Very fast diagnostics and a high reliability are achieved by considering all possible fault conditions. The main characteristics of filter behavior under fault are analyzed as well as their impact in the studied diagnostic algorithm. Simulation results are presented to demonstrate the algorithm's performance when applied to NPC active power filters.