Fault tolerant SVM strategy for 3-level NPC inverter

Reconfiguration of NPC Multilevel Inverters to Mitigate Short Circuit Faults Using Back-to-Back Switches

“…In SVM, when device failure happens, some voltage vectors cannot be achieved, thus redundant vectors are utilized to compensate for the lost vectors [14], [15]. An effective way to tolerate device failure is to tie the phase which contains the failed component to the neutral point, change the control strategy and operate the two remaining healthy phases to achieve the balanced phase-to-phase voltage [16]- [21]. Another way is by changing the diodes D 1 to D 2 in Fig.…”

“…Tying the whole phase leg which contains only one failed device to the neutral point is not cost effective [16]- [21]. For example, if S 1 in Fig.…”

“…The SVM-based method [14], [15] has more complex control in the reconfigured condition, and utilizing the redundant vector means more switching actions are assigned to the remaining healthy devices which causes extra stress on these devices. The method of isolating a faulty phase leg (IFPL) [16]- [21] has the drawbacks of reduced output voltage peak and unbalanced per-phase voltages, since the MLI is operated with only two phases. The ANPC fault-tolerant inverter [22] has the same drawbacks of IFPL and since it has additional switching devices, the control complexity is increased.…”

Multilevel Power Converters: A Survey

“…SVPWM arises from the vectorial description of the switching states of power converters. Since those switching states constitute a discrete set of space vectors, the continuous reference vector must be approximated by the time averaging of a space vector sequence [101][102][103][104]. The SVPWM technique is used to determine this sequence and to calculate the time interval corresponding to each vector.…”