Fault Diagnostic System for Cascaded H-Bridge Multilevel Inverter ...

The magnitude can be used to determine the fault types (open or short circuit) by setting
the threshold value: threshold values are usually based on experiment or simulation. The
average angle can be used to identify a fault location as shown in Table 2.1.
Second, Peuget used the slope of trajectory in the orthogonal space to identify fault
locations. The trajectory of input motor current is transformed by modifying (2.2) and
(2.3). It should be noted that (2.3) assumes a balanced load. Equations (2.2) and (2.3) can
be rewritten in terms of line currents as:
i
i
α
β
= i
=
a
,
1
3
30
( i
b
− i ).
Table 2.1. Interval of θ av to identify fault locations
Switch locations Open circuit fault Short circuit fault
S1
S2
S3
c
150 o < θ av < 210 o 330 o < θ av < 30 o
210 o < θ av < 270 o 30 o < θ av < 90 o
270 o < θ av < 330 o 90 o < θ av < 150 o
S4 330 o < θ av < 30 o 150 o < θ av < 210 o
S5 30 o < θ av < 90 o 210 o < θ av < 270 o
S6 90 o < θ av < 150 o 270 o < θ av < 330 o
(2.7)