Dear Ms. Agreira,
I don't think what you are seeing is related at all to the bug fix you
quoted. In fact, I don't believe it is actually a bug. It has to do
with missing features in MATPOWER. If my conjecture is correct, both
PSS/E and Powerworld have controls that are modified during the power
flow solution in order to solve for a feasible solution. In
particular, transformer taps and generator voltage setpoints may be
altered in order to avoid violating generator reactive output limits
or other constraints.
By default, MATPOWER's power flow solver does not make any such
changes. It solves the power flow equations using the data provided
even if the solution violates limits. So PSS/E and PowerWorld are not
solving exactly the same problem as MATPOWER.
MATPOWER does have a very primitive ability to enforce generator
reactive power limits which can be enabled by doing ...
opt = mpoption('ENFORCE_Q_LIMS', 1);
runpf('valor1', opt);
This simply converts all buses with violated generator Q limits from
PV to PQ buses, setting the Q output at the limit and allowing the
voltage to deviate from the setpoint in order to satisfy the power
balance equations. Then it re-runs and checks again ... continuing
until there are no more violations. In the case you provided, there
are still violations when ALL of the generator Q outputs are fixed at
their limits, which leads me to the conclude that the transformer taps
need to be changed in order to make it feasible.
I am confident that if you use the bus voltages from the PowerWorld
and PSS/E solutions as generator setpoint voltages gen(:, VG) in
MATPOWER and similarly, take the transformer tap ratios from the
PowerWorld and PSS/E solution and put it into branch(:, TAP), you will
get the same solution.
--
Ray Zimmerman
Senior Research Associate
428-B Phillips Hall, Cornell University, Ithaca, NY 14853
phone: (607) 255-9645
On Jun 20, 2008, at 7:16 AM, Cristina faustino wrote:
Dear sir,
I work with matpower software package in my PhD thesis. I developed
a new methodology for classification and raking contingencies. This
methodology is for apply in a real transmission line with 512
busbar. In version 3.2 , you said the “Fixed bug in pfsoln.m which
caused incorrect value for Qg when Qmin == Qmax for all generators
at a bus in power flow solution”, but in my case the bug in not fixed.
I simulate a Newton raphson power flow, in Powerworl and PSS/E and
the Power Flow is exactly equals, but simulated in matpower de Qg
is very different.
The result for Qg in the PSS/E or Powerworld is 1847.5 MVar . The
result in Matpower for Qg is 2562,8 MVar.
I send you my Test Power Network, and the results in PSS/E.
I appreciate if you can help me,
Best Regards and thank you for your attention,
Cristina Agreira
<valor1.m><Resultados PSSE.txt>
