196 Open and Short Circuit Switches Fault Detection of Voltage Source Inverter Using Spectrogram
Fig.12. Parameter Estimation for short-circuit fault Upper
a Instantaneous Average Current, Iavet b Instantaneous RMS Current, Irmst
c Instantaneous RMS Fundamental Current, Irmst
d Instantaneous Total Waveform Distortion, TWDt
5.4 Short Circuit Switches Fault in VSI Lower Fault
Fig. 13a shows the signal short-circuit faults of the lower switch where switch at phase A fault at 0.2-0.3s. The
current momentary decrease and for phase B and C have certain distortion. According TFR shows harmonics and
interharmonics that occurred as represented Fig. 13b. As previous results, faults occurred at dc component and at 60
Hz.
Short-circuit Faults of the Lower Switch Signal
Fig.13. a Signal of Short-Circuit Fault Lower b
Spectrogram Short-Circuit Fault Lower The parameter that estimated from TFR with the
instantaneous average current for phase A is lower than phase B and C as shows Fig. 14a. But for the RMS
current value, phase A is higher while phase B and C is lower, respectively as Fig. 14b. For the instantaneous
RMS fundamental current on Fig. 14c, phase A is lower than phase B and C. Besides that, instantaneous waveform
distortion as shows in Fig. 10d, where faults signal occur at DC component, there TWD gives 1.42 percent but phase
B and C is below then 1 percent.
0.1 0.2
0.3 0.4
0.5 0.6
0.5 1
1.5
Phase A
Phase C
Phase B
Instantaneous Total Waveform Distortion, TWDt
P erc
en tag
es,
Time s d
P ha
se C
0.1 0.2
0.3 0.4
0.5 0.6
-3 -2
-1 1
2 3
0.1 0.2
0.3 0.4
0.5 0.6
-3 -2
-1 1
2 3
0.1 0.2
0.3 0.4
0.5 0.6
-3 -2
-1 1
2 3
Cu rre
n t,
A
Time s a
P ha
se A
P ha
se B
Instantaneous Average Current, Iavet
0.1 0.2
0.3 0.4
0.5 0.6
-0.5 0.5
1
Cu rr
e n
t A
Time s a
Phase A
Phase B Phase C
Cu rre
n t,
A
Fre q
u en
cy ,
Hz
Time Frequency Representation
Time s b
0 Hz 60 Hz
0.1 0.2
0.3 0.4
0.5 0.6
0.8 1
1.2 1.4
1.6
Instantaneous RMS Current, Irmst
Time s b
Cu rre
n t,
A
Phase A Phase B
Phase C
0.1 0.2
0.3 0.4
0.5 0.6
0.8 0.9
1 1.1
1.2 Instantaneous RMS Fundamental Current, Irmst
Cu rre
n t,
A
Time s c
Phase A Phase B C
N. S. Ahmad , A. R. Abdullah and N. Bahari 197
Fig. 14. Parameter Estimation for short-circuit fault
lower a Instantaneous Average Current, Iavet
b Instantaneous RMS Current, Irmst c Instantaneous RMS Fundamental Current,Irmst
d Instantaneous Total Waveform Distortion According all results that shows four patterns which is
open circuit fault upper, open circuit fault lower, short circuit fault upper and short circuit fault lower, the
parameter that estimate gives information for detect type of fault. Fig. 15 shows the bar graph indicates that error of
current detection for VSI faults can be known from the parameter estimation by applying TFD. The condition of
each fault can be identifying according to the result as a bar graph below. The details of each fault are shows in table 1
and 2
In order to find out the relation between parameter to detect condition of the VSI faults have been conducted.
Analysis results were made based on current parameter estimation from spectrogram. Table 1 shows general of
current error during fault detected. Next, Table 2 shows overall observation of current error from parameter
estimation. From the observation of average current, that found the value of I
B
is equal I
C
but less than 0.5 and other of current is I
B
equal with I
C
. Both of current is greater than 0.5 and less than zero. Next, the open-circuit lower can be
detect with I
A
below than 1, respectively is greater than zero. For this condition IA is greater than 1 but IA less than
zero. higher than zero for open circuit fault upper. Besides that, the current error at phase A is greater than 1 when
short circuit fault upper detected. But other IA is less than 1. When short-circuit lower, I
A
less than -1 and other I
A
is greater than -1. On the other hand, the error of rms current
when open circuit fault either upper and lower, value IA is equal I
C
but for short-circuit is I
A
different IC. During short circuit fault upper detected, value of I
B
is greater than IC and other fault I
B
is greater than I
C
. Then, open circuit fault can be detected during RMS fundamental current I
A
is greater than IB and IC, where both of current are equal. But,
short circuit fault can be detected IA is greater than IC and greater then I
B
. Lastly, table 2 give summaries of characteristic for each fault cased on error current where
average current is important used to detect type of faults. The rules based on error current detection during fault are
used to detection the faults event instanteously are summaries in Table 1.
Table 1. General of current error during fault
Switch Type of fault
Current Observation
Upper Open
Average I
A
I
B =
I
C
I I 0
RMS I
A
= I
C
I
B
Short Average
I
A
I
B =
I
C
I I 0
RMS I
A
= I
C
I
B
Lower Open
Average I
A
I
B =
I
C
I I 0
RMS I
A
I
B
I
C
Short Average
I
A
I
B =
I
C
I I 0
RMS I
A
I
C
I
B
Cu rre
n t,
A
Instantaneous Average Current, Iavet
0.1 0.2
0.3 0.4
0.5 0.6
-1 -0.5
0.5 1
Time S
Cu rr
e n
t A
Time s a
Phase B Phase C
Phase A
Cu rre
n t,
A
0.1 0.2
0.3 0.4
0.5 0.6
0.8 1
1.2 1.4
1.6
Instantaneous RMS Current, Irms t
Time s b
Phase A Phase B
Phase C
Phase B C
0.1 0.2
0.3 0.4
0.5 0.6
0.8 0.9
1 1.1
1.2
Cu rre
n t,
A
Instantaneous RMS Fundamental Current, Irmst
Times c
Phase A Phase B C
0.1 0.2
0.3 0.4
0.5 0.6
0.5 1
1.5
P erc
en tag
e,
Instantaneous Total Waveform Distortion, TWDt
Time s d
Phase C Phase A
Phase B
198 Open and Short Circuit Switches Fault Detection of Voltage Source Inverter Using Spectrogram
Fig. 15. The bar graph for error of current detection Table 2. Characteristic for each fault detection
based on parameter estimation
Parameter Type of fault
Observation Average
Current Open Upper
Others I
B
= I
C
0.5 I
B
= I
C
0.5 I
B
= I
C
Open Lower Others
I
A
1 but I
A
I
A
1 I
A
Short Upper Others
I
A
1 I
A
1 Short Lower
Others I
A
-1 I
A
-1 RMS
Current Open
Other I
A
= I
C
I
A
= I
C
Short Upper Other
I
B
I
C
I
B
= I
C
Short Lower Other
I
C
I
B
I
C
=I
B
RMS Current
Open I
A
I
B
= I
C
Short I
A
I
C
I
B
6. Conclusion
