Dear Ray and Others,
There is a bus-indexing problem in matpower for islands. For example, in
case5.m when I remove branches 1 and 5, the system parts into two islands.
I take one islands for example (the biggest one with 3 buses with indices
1,4 and 5). I want to calculate the complex current injected from bus 4
into branch 3, I do the following:
*define_constants;*
*mpc = loadcase('case5.m');*
*mpc.branch(1,BR_STATUS)=0;*
*mpc.branch(5,BR_STATUS)=0;*
*ccr=extract_islands(mpc,1)*
*results=runpf(ccr)*
*Sf = results.branch(3, PF) + 1j * results.branch(3, QF);*
*Vf = results.bus(4, VM) * exp(1j * results.bus(4, VA));*
*If = abs(conj( Sf / Vf )) %% complex current injected into branch k at bus
f*
The System Summary is:
Bus Voltage Generation Load
# Mag(pu) Ang(deg) P (MW) Q (MVAr) P (MW) Q (MVAr)
----- ------- -------- -------- -------- -------- --------
1 1.000 0.000 -63.66 10.96 - -
4 1.000 -3.046 0.00 183.35 400.00 131.47
5 1.000 0.879 466.51 -38.81 - -
-------- -------- -------- --------
Total: 402.85 155.49 400.00 131.47
================================================================================
| Branch Data
|
================================================================================
Brnch From To From Bus Injection To Bus Injection Loss (I^2 *
Z)
# Bus Bus P (MW) Q (MVAr) P (MW) Q (MVAr) P (MW) Q
(MVAr)
----- ----- ----- -------- -------- -------- -------- --------
--------
1 1 4 173.51 -13.03 -172.59 21.58 0.920
9.20
2 1 5 -237.18 23.99 237.54 -23.48 0.364
3.64
3 4 5 -227.41 30.30 228.97 -15.34 1.564
15.64
However, I get the following error message for current calculation:
Attempted to access results.bus(4,8); index out of bounds because
size(results.bus)=[3,13].
Error in rough (line 12)
Vf = results.bus(4, VM) * exp(1j * results.bus(4, VA));
As you can see in the summary current is clearly injected from Bus 4 to
branch 3, but still I get error. So what I was thinking was when Islanding
happens, the indexes of Buses are shuffled. So bus indices 1,4 and 5 are in
fact 1, 2 and 3. How do I see this? I see this because if I put Vf =
results.bus(3, VM) * exp(1j * results.bus(3, VA)), it works just fine. So
basically, the indices cannot be more than the number of buses in Islands,
but that is quite weird for me. I thought indices was fixed. Does it solve
my problem if I take my buses indices in the new island as 1,2 and 3 for 1,
4 and 5 (check out the bus table)? Would it give me the right result? How
do I map old indices to new indices? Any help is appreciated.
Regards,
Manish
