Sometimes it looks like matpower automatically chooses the reference bus
(slack bus). Is it true? For instance, if I increase the power demand of
one of the buses in my two-bus island, the generator increases its power
generation as well, even though it is not marked as slack bus. Please look
at the two cases, in the second case I increased the power demand, and
hence generation increased too to reduce the imbalance. Another question:
does slack bus substitute for increasing PG. In other words, is it the same
when one *introduces slack bus* or *increases the PG* to meet the PD? If
not, which one is better?
*Summary 1:*
Bus Voltage Generation Load
# Mag(pu) Ang(deg) P (MW) Q (MVAr) P (MW) Q (MVAr)
----- ------- -------- -------- -------- -------- --------
1 1.000 0.000 436.05 158.45 - -
2 0.950 -7.136 170.00 0.00 600.00 98.61
-------- -------- -------- --------
Total: 606.05 158.45 600.00 98.61
================================================================================
| 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 2 436.05 158.45 -430.00 -98.61 6.052
60.52
--------
--------
Total: 6.052
60.52
*Summary 2:*
Bus Voltage Generation Load
# Mag(pu) Ang(deg) P (MW) Q (MVAr) P (MW) Q (MVAr)
----- ------- -------- -------- -------- -------- --------
1 1.000 0.000 747.87 276.69 - -
2 0.924 -12.657 170.00 0.00 900.00 98.61
-------- -------- -------- --------
Total: 917.87 276.69 900.00 98.61
================================================================================
| 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 2 747.87 276.69 -730.00 -98.61 17.873
178.73
--------
--------
Total: 17.873
178.73
Thanks,
Bijay
On Mon, Mar 2, 2015 at 10:24 PM, Ray Zimmerman <[email protected]> wrote:
> It appears you are using an older version of MATPOWER. Could you try it
> with the latest released version and see if you still get an error.
>
> Ray
>
> On Mar 1, 2015, at 3:46 PM, Bijay Hughes <[email protected]> wrote:
>
> Hi All,
>
> When I remove some branches in case5, two islands are formed. First island
> with slack bus (bus_type 3) and second island with no slack bus. I want to
> extract the second island extract_islands(mpc,2) and run power flow. It
> doesn't work obviously because there is imbalance in load and supply due to
> the lack of slack bus. However, I try to change the bus type of one of the
> busses in second island to 3 to have the slack bus, but my power flow still
> doesn't work. It gives me the following error message:
>
> Subscript indices must either be real positive integers or logicals.
>
> Error in ext2int (line 185)
> as = bs(n2i(mpc.areas(:, PRICE_REF_BUS)));
>
> Error in runpf (line 130)
> mpc = ext2int(mpc);
>
> Error in rough (line 12)
> results=runpf(ccr)
>
> Am I missing something here? Does all islands need to have slack bus
> (bus_type 3) to run power flow? Why does my island still not run power flow
> even though I made one of the buses into the slack bus? Could anyone please
> help me out?
>
> Thanks,
>
> Bijay
>
>
>
