Sir,
At nose point in P-V curve using cpf, Jacobian matrix becomes singular.
i.e. determinant of Jacobian to be zero. I am getting very high negative value
of determinant of jacobian at nose point. My question is "I doubt my
jacobian is not correct. How to get correct jacobian at nose point". I have
used following code:
define_constants; mpopt =
mpoption('out.all',0,'verbose',2,'out.bus',1); mpopt =
mpoption(mpopt,'cpf.stop_at','nose','cpf.step',0.03); mpopt =
mpoption(mpopt,'cpf.plot.bus',7,'cpf.plot.level',2); mpcb =
loadcase('case39'); % load base case mpct = mpcb; % set up target case
with mpct.gen(:,[PG QG]) = mpcb.gen(:,[PG QG])*1.35 mpct.bus(:,[PD
QD]) = mpcb.bus(:,[PD QD])*1.35 results = runcpf(mpcb, mpct,
mpopt); J=makeJac(results)
%%% determinant of J det(J)
ans =
-1.0471e+126
Thank you.
From: "Abhyankar, Shrirang G." <[email protected]>
Sent: Fri, 14 Aug 2015 02:28:21
To: MATPOWER discussion forum <[email protected]>
Subject: Re: PV curve using CPF
MATPOWER’s CPF, by default, uses a pseudo arclength parameterization that takes
a step in the tangent space of the PV curve. As such, the ‘MW' increments
depend on the steps taken along the tangent, and in turn on the slope of the
curve. If you want a
fixed ‘MW’ increase then you need to use natural parameterization instead.
(mpoption(‘cpf.parameterization’,’NATURAL’). Natural parameterization directly
uses the scaling parameter lambda and such has direct connection with MW
increments. However, note that
natural parameterization suffers from divergence near the fold point! I would
not use natural parameterization unless there is a really strong need.
Note that the step size for CPF, for natural parameterization, is given in
terms of increments of the scaling parameter lambda, where lambda = 0
represents the base case and lambda = 1 is the target case. Going from 100 MW
base case (lambda = 0) to 200
MW target case (lambda = 1) in 10 continuation steps would need a stepsize of
0.1. (mpoption(‘cpf.step’, 0.1).
Shri
From: nilesh patel <[email protected]>
Reply-To: MATPOWER discussion forum <[email protected]>
Date: Thursday, August 13, 2015 at 5:45 AM
To: "[email protected]" <[email protected]>
Subject: Re: PV curve using CPF
It mean my system base case_P is 100 MW and reaches to 200 MW at nose point in
10 steps in cpf. so step size in this case is 10 MW. Is it correct?
Thanks.
From: Jose Luis Marin <[email protected]>
Sent: Thu, 13 Aug 2015 14:05:07
To: MATPOWER discussion forum <[email protected]>
Subject: Re: PV curve using CPF
Lambda interpolates between the [P_base, Q_base] and [P_target,
Q_target] vectors of your choice, so therefore the relationship between the
lambda stepsize and the actual power increase on the buses depends on that.
--
Jose L. Marin
Gridquant España SL
Grupo AIA
On Wed, Aug 12, 2015 at 12:16 PM, nilesh patel
<[email protected]> wrote:
Sir,
If i want to increase load in continuation power flow by step of 1 MW, What
should be the step size of Lamda. My system base case load is 5000 MW. As CPF
accuracy depends on step-size.
Thanks.
From: Jose Luis Marin <[email protected]>
Sent: Mon, 10 Aug 2015 18:53:11
To: MATPOWER discussion forum <[email protected]>
Subject: Re: PV curve using CPF
Shruti is right, the value you obtain for lambda is valid for all the network,
since voltage collapse is a global phenomenon (in other words, you';;ll see a
nose point at the same value of lambda regardless of which bus you choose to
plot). Remember that lambda
represents a fraction along the vector of injections linearly iterpolating
[P_base, Q_base] to [P_target, Q_target]. The value of Lambda
at the nose point is NOT the maximum loading point for that bus; rather, it is
the maximum loading value along the path
to the particular load/gen profile chosen as a target.
Of course, one may wonder about this other problem: for a given profile
[P_base, Q_base], what is the target direction [P_target, Q_target] for which
one would obtain the shortest value of critical lambda? If this is what
you';;re thinking about, then it is
in general a hard problem. I suggest these references by Ian Dobson, on
the concept of "shortest distance" to voltage collapse:
http://www.ece.wisc.edu/~dobson/PAPERS/publications.html#loading
--
Jose L. Marin
Gridquant España SL
Grupo AIA
On Mon, Aug 10, 2015 at 6:23 AM, nilesh patel
<[email protected]> wrote:
Sir,
When we run continuation power flow for particular system, we get p-v curve for
selected bus. using this p-v curve, we can find Voltage stability Margin (in
MW) on that bus by difference of operating point to nose point lamda.
I agree lambda at nose point provides
maximum loading value but that is for that bus only for which p-v curve is
plotted.
My question is How to find Voltage Stability Margin for whole Network using P-V
curve ? I mean how to find maximum lamda for whole network using p-v
curve?
Thanks.
From: "Abhyankar, Shrirang G." <[email protected]>
Sent: Fri, 07 Aug 2015 22:31:31
To: MATPOWER discussion forum <[email protected]>
Subject: Re: PV curve using CPF
I donⴠquite understand your question, can you please elaborate.
The maximum value of loading scaling parameter ᬡmbda⠧ives a measure of how much
power can be transferred for a given transfer direction. So, lambda is also a
measure of the nose point for the whole network.
Shri
From: nilesh patel <[email protected]>
Reply-To: MATPOWER discussion forum <[email protected]>
Date: Friday, August 7, 2015 at 8:46 AM
To: matpower-l <[email protected]>, MATPOWER-L
<[email protected]>
Subject: PV curve using CPF
Dear Sir,
P-V curve solution using continuation power flow gives nose point (maximum
loading point) for individual bus.
My question is - How to get nose point for whole network (all buses) using PV
curve ? I want to find network voltage stability margin rather than
individual bus margin using CPF.
Thanks.
Nilesh Patel
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