Hi,
I'm using Matpower (v5.0b1, but the same holds for v5.1) for a 220 kV/110
kV/20 kV-grid quite a while. The grid has 1 reference bus (220 kV), 2
PV-buses (220 kV) and >100 PQ-buses (110 kV & 20 kV). So far calculating
the grid using runpf with Newton has never been a problem.
Now I've tried to change a 20 kV PQ-bus to a PV-bus with the Q-limits +0.7
for Q_max and -0.45 for Q_min (considering mpopt =
mpoption('pf.enforce_q_lims', 1)). If I set Vg of the generator to 1.05 I
get the error:
"All 4 remaining gens exceed their Q limits : INFEASIBLE PROBLEM"
whereas when using 1.00 as Vg there is no problem (then the generator is at
its lower Q-limit, hence converted to PQ). If the problem is infeasible the
result of pfsoln in runpf are Q-values of all 4 PV generators (Slack+3 PV)
that are out of their limits. Why is there such a big difference between
the case V=1.05 and V=1.00?
As a info: the Slack has a Q-Limit of +-10000, both of the already existing
PV buses +720/-290, according to case_info the total generation is -300
MW+j10 Mvar, the total load 300 MW-j50 Mvar, but I've tried several
scenarios which are no problem when using the PQ instead of the PV-bus (or
the Vg=1).
Does anybody experience a similar problem/has an idea how to fix it?
Nice regards,
Chris
