Quasi - two-level converter operation strategy for overvoltage mitigation in long cable applications

This paper focuses on a Quasi-Two-Level (Q2L)converter topology and its use in long cable application, where overvoltage at the motor terminals due to wave reflection threatens the motor and cable insulation. Two operation strategies are proposed to mitigate such undesired effect, by taking advantage of the Q2L multilevel structure. In the first one, the drive works without any output filter, which results in a compact converter design, as capacitance is minimized, while enabling the use for longer cable lengths than those in applications where a dv/dt filter is commonly used. In the second one, a modified dv/dt filter is used in combination with the Q2L operation, when the first operation would require too high accuracy in the converter control. In both of the cases, the aim is to provide a compact solution that does not require the footprint and cost of multilevel converters, nor that of sine filters, and can thus be deployed in long cable applications with particular space constraints.