Those are certainly some crazy Mvar injections! Just checking: are you sure you reversed the signs of P properly when switching the type of that bus from PQ (load) to PV (gen with neg real power), also taking care of making the corresponding changes in the bus row and adding a new gen row?
If you could share your case file I could try to give you a quick diagnostic. -- Jose L. Marin Grupo AIA On Thu, Apr 28, 2016 at 5:19 PM, Chris Prokop <[email protected]> wrote: > Thanks for your responses. > > @ Ray Zimmerman: > I can't find the problem here. If I set Q=+0.7 Mvar (cap.), the voltage at > this bus is about 1.04 p.u., with Q=-0.7 Mvar (ind.) it decreases to 1.02 > p.u., the power flow converges as expected (+the result is as expected). > Only converting this bus into a PV-bus results in the problem mentioned > above (with or without limits). I don't get why the Newton Power Flow > returns for example 1e3 Mvar for this bus as a result, as only <1 Mvar > should have been enough reactive power. > Before solving the case the reactive power of the generators at the > PV-buses are (variable gen in runpf): > - Reference bus: 0 Mvar > - PV-Bus1: 0 Mvar > - PV-Bus2: 64.4 Mvar > - PV-Bus3 (the problematic one): 0.1 Mvar > after solving it (after pfsoln), the variable gen is filled with: > - Reference bus: 1e6 Mvar > - PV-Bus1: 2.7e4 Mvar > - PV-Bus2: 9.6e3 Mvar > - PV-Bus3 (the problematic one): -600 Mvar > whereas the next most reactive power intensive gen&bus has less than 5e2 > Mvar. I don't understand where the power comes from/goes to... > > @ Jose Luis Marin: > If I use the voltage from the PQ-calculation (e.g. 20.6668/20 p.u.) there > remains the same problem. Also without Q-limits I get the the problem... > Vg=1 p.u. actually works as a PV-bus, Vg=1.01 or Vg=1.02 etc. don't. > > > Nice regards, > Chris > > 2016-04-28 16:04 GMT+02:00 Ray Zimmerman <[email protected]>: > >> It sounds like the voltage at that bus may be very sensitive to the >> reactive power injection. One thing you might try to get some idea of this >> is to change that bus back to PQ with the reactive at the lower limit, then >> try running a few cases with slightly perturbed values of the reactive >> power at that generator and see how the voltage at the bus changes. >> >> Ray >> >> >> On Apr 28, 2016, at 8:40 AM, Chris Prokop <[email protected]> >> wrote: >> >> 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 >> >> >> >
