I see, that's interesting. Thanks!
2017-05-22 10:00 GMT+02:00 Jose Luis Marín <[email protected]>:
>
> 1. Yes, VM VA are used both for input and output. Note one subtle point,
> though: in runpf.m (Lines 177--183) the initial seed for the iteration is
> first set to the values [VM VA] provided as input, but for
> voltage-controlled buses (with active generators), the value of VM is
> replaced by the setpoint VG of their respective bus generator(s) (the value
> of VA is preserved). This makes sense because it guarantees that the seed
> will be closer to the solution.
>
> 2. What you see here is to be expected. Basically, what happens is that
> the basins of attraction of low-voltage volutions are usually smaller than
> those of the operating solution. Also, note that there are *many* (for N
> buses, somewhat of the order of 2^N) low voltage solutions, so chances are
> that the iteration will converge to a solution that's different from the
> one you followed by homotopy (CPF). Even homotopy methods can encounter
> this same problem if their step-size is not small enough.
>
>
> Here's some refs on the fractal nature of the problem:
>
> @INPROCEEDINGS{KlumpOverbye00b,
> author={Klump, R.P. and Overbye, T.J.},
> booktitle={Power Engineering Society Summer Meeting},
> title={A new method for finding low-voltage power flow solutions},
> publisher={IEEE},
> year={2000},
> volume={1},
> pages={593--597},
> doi={10.1109/PESS.2000.867653},
> ISSN={}
> }
>
> @INPROCEEDINGS{ThorpNaqavi89,
> author={Thorp, J.S. and Naqavi, S.A.},
> booktitle={Proceedings of the 28th IEEE Conference on Decision and
> Control},
> title={Load flow fractals},
> year={1989},
> volume={2},
> pages={1822--1827},
> doi={10.1109/CDC.1989.70472}
> }
>
> @INPROCEEDINGS{ThorpNaqaviChiang90,
> author={Thorp, J.S. and Naqavi, S.A. and Chiang, H.-D.},
> booktitle={Decision and Control, 1990., Proceedings of the 29th IEEE
> Conference on},
> title={More load flow fractals},
> year={1990},
> month={dec},
> volume={6},
> pages={3028--3030},
> doi={10.1109/CDC.1990.203339}
> }
>
> @ARTICLE{ThorpNaqavi97,
> author={Thorp, J.S. and Naqavi, S.A.},
> journal=IEEE_M_CAP,
> title={Load-flow fractals draw clues to erratic behaviour},
> year={1997},
> month={jan},
> volume={10},
> number={1},
> pages={59--62},
> doi={10.1109/67.560872},
> ISSN={0895-0156}
> }
>
> @INPROCEEDINGS{Mori00,
> author={Mori, H.},
> booktitle={IEEE International Symposium on Circuits and Systems (ISCAS)},
> title={Chaotic behavior of the Newton-Raphson method with the optimal
> multiplier for ill-conditioned power systems},
> year={2000},
> volume={4},
> pages={237--240},
> doi={10.1109/ISCAS.2000.858732}
> }
>
>
> --
> Jose L. Marin
> Grupo AIA
>
>
>
>
> 2017-05-19 11:30 GMT+02:00 Elis Nycander <[email protected]>:
>
>> Hi all matpower users!
>>
>> I have two questions:
>>
>> 1. In the bus matrix, the columns VM and VA are used both for the initial
>> guess when solving the power flow, and to store the resulting voltages?
>>
>> 2. When solving a cpf, I get lam_max which corresponds to the nose point,
>> i.e. maximum load/generation increase before "voltage collapse" happens. I
>> can also find the power flow at the nose point just by running an ordinary
>> power flow with flat start and conditions corresponding to the maximum
>> load. However, I have tried to do the same thing for the lower part of the
>> PV curve but failed to reproduce the solutions from the cpf. Basically I
>> thought I could get the lower part of the PV curve by just solving a power
>> flow using initial conditions which are close to the "unstable"/lower
>> solutions from the cpf (instead of a flat start), but I get different
>> solutions.
>>
>> Thanks,
>> Elis
>>
>
>
