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]<mailto:[email protected]>> Reply-To: MATPOWER discussion forum <[email protected]<mailto:[email protected]>> Date: Thursday, August 13, 2015 at 5:45 AM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[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]<mailto:[email protected]>> Sent: Thu, 13 Aug 2015 14:05:07 To: MATPOWER discussion forum <[email protected]<mailto:[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]<mailto:[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]<mailto:[email protected]>> Sent: Mon, 10 Aug 2015 18:53:11 To: MATPOWER discussion forum <[email protected]<mailto:[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<http://www.ece.wisc.edu/~dobson/PAPERS/publications.htmlloading> -- Jose L. Marin Gridquant España SL Grupo AIA On Mon, Aug 10, 2015 at 6:23 AM, nilesh patel <[email protected]<mailto:[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]<mailto:[email protected]>> Sent: Fri, 07 Aug 2015 22:31:31 To: MATPOWER discussion forum <[email protected]<mailto:[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]<mailto:[email protected]>> Reply-To: MATPOWER discussion forum <[email protected]<mailto:[email protected]>> Date: Friday, August 7, 2015 at 8:46 AM To: matpower-l <[email protected]<mailto:[email protected]>>, MATPOWER-L <[email protected]<mailto:[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. 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