So, the only difference between the two cases are the voltage constraints at the slack bus? If so, I would expect the losses (and therefore the generation) to be greater in the case with the lower voltage.
-- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Feb 23, 2012, at 11:24 AM, Silvio Miceli wrote: > Practically I don't have OLTC. According to your comments to my posts: "1) > Exclude bus GSP and the OLTC from the model and let Tx be the slack bus with > a dummy generator and VMIN = VMAX = 1.078." So, when I compare the results > considering OLTC, i.e. constraints of voltage at the slack bus , and without > any constraint, i.e. Vmax=Vmin=1.06. In my idea, in the case with OLTC and > lower and limits the capacity should be higher that without constraint? Am I > right? > > Regards > > Silvio > > > > On Thu, Feb 23, 2012 at 17:16, Ray Zimmerman <[email protected]> wrote: > It's probably due to a difference in losses. There may be losses in the OLTC > itself depending on the parameters and if the voltage profile is different > the losses in the rest of the network will be different as well. > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > On Feb 23, 2012, at 11:00 AM, Silvio Miceli wrote: > >> Dear Ray, >> >> As far as I know when we have an OLTC, the generated capacity is more than >> that in the case without OLTC (i.e. Vmin=Vmax=1.06 p.u.). When I running an >> OPF or runmarket, for example in the case57, I get more generated capacity >> in the case without OLTC compared to with OLTC. >> >> Best Wishes >> >> Silvio >> >> >> On Mon, Feb 13, 2012 at 16:09, Silvio Miceli <[email protected]> wrote: >> Thank you so much for your helpful comments. >> >> Best Wishes >> >> Silvio Miceli >> >> >> >> On Mon, Feb 13, 2012 at 15:27, Ray Zimmerman <[email protected]> wrote: >> I don't know what you mean by the first solution with and without the OLTC. >> In the first solution, I am assuming that the OLTC maintains the voltage at >> Tx at your target, so it is not in the model. I suppose if by "without OLTC" >> you mean that the OLTC is not keeping the voltage at the target, then you >> can simply set the VMIN and VMAX to 1.0 p.u. Or you could use the setup for >> the 2nd option, and simply run it once with the taps at the nominal setting. >> >> -- >> Ray Zimmerman >> Senior Research Associate >> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >> phone: (607) 255-9645 >> >> >> >> >> On Feb 13, 2012, at 9:19 AM, Silvio Miceli wrote: >> >>> Dear Prof. Zimmerman, >>> >>> I want to use first solution. It is much more easier than the second one. >>> In this case, how can I compare the results with and without OLTC? >>> >>> Kind regards >>> >>> S.M. >>> >>> >>> On Mon, Feb 13, 2012 at 15:07, Ray Zimmerman <[email protected]> wrote: >>> So it seems you could model it two different ways in MATPOWER. >>> >>> 1) Exclude bus GSP and the OLTC from the model and let Tx be the slack bus >>> with a dummy generator and VMIN = VMAX = 1.078. >>> 2) Include GSP and the OLTC, with a dummy generator at GSP (the slack bus), >>> with VMIN = VMAX = 1.0. In this case, you would have to iteratively run the >>> OPF, then update the tap setting until the voltage at Tx is close enough to >>> your target. I suppose you could use VMIN = VMAX = 1.078 at Tx and then >>> adjust the tap ratio until you get a feasible solution. You may need to >>> leave a small epsilon difference between VMIN and VMAX at GSP or Tx in >>> order to get feasibility. >>> >>> I expect the results for the rest of the system to be (at least nearly) >>> identical in the two cases. >>> >>> -- >>> Ray Zimmerman >>> Senior Research Associate >>> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >>> phone: (607) 255-9645 >>> >>> >>> >>> >>> On Feb 10, 2012, at 8:32 PM, Silvio Miceli wrote: >>> >>>> >>>> >>>> The information of the network is as follows: >>>> >>>> The one-line diagram of a typical rural section of the Irish 38-kV >>>> distribution network was shown in above Figure. The feeders are supplied >>>> by one 31.5-MVA 110/38-kV transformer (capable of handling reverse power >>>> flows). The voltage at the grid supply point is assumed to be nominal. In >>>> the original configuration (no DG), the on-load tap changer at the >>>> substation has a target voltage of 1.078 pu (41 kV) at the busbar, well >>>> within the +-10% nominal voltage limits of Irish practice. >>>> >>>> Best Wishes >>>> >>>> Silvio Miceli >>>> >>>> >>>> On Fri, Feb 10, 2012 at 23:07, Ray Zimmerman <[email protected]> wrote: >>>> You haven't said which bus is your slack bus. Can I assume that it would >>>> be the one labeled GSP? I don't see a slack generator at that bus. Is the >>>> OLTC the *only* voltage control you have in the network? Is the voltage at >>>> GSP fixed? >>>> >>>> -- >>>> Ray Zimmerman >>>> Senior Research Associate >>>> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >>>> phone: (607) 255-9645 >>>> >>>> >>>> >>>> >>>> On Feb 10, 2012, at 2:51 PM, Silvio Miceli wrote: >>>> >>>>> I want to have an OLTC at slack bus only in order to control centrally >>>>> the network voltage (active network) as below figure. How can I compare >>>>> the results with and without OLTC? with changing tap ratio or with >>>>> changing voltage setpoints? >>>>> >>>>> <image.png> >>>>> >>>>> Best Wishes >>>>> >>>>> Silvio Miceli >>>>> >>>>> >>>>> On Fri, Feb 10, 2012 at 20:43, Ray Zimmerman <[email protected]> wrote: >>>>> In order to understand clearly what you are trying to compare, I would >>>>> need to see the network topology. >>>>> >>>>> But, it both cases include the OLTC in the topology and in one case you >>>>> are modifying the tap ratio to control voltage and in the other you are >>>>> simply modifying the generator voltage setpoints, then the two solutions >>>>> will not be equivalent. >>>>> >>>>> -- >>>>> Ray Zimmerman >>>>> Senior Research Associate >>>>> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >>>>> phone: (607) 255-9645 >>>>> >>>>> >>>>> >>>>> >>>>> On Feb 10, 2012, at 10:46 AM, Silvio Miceli wrote: >>>>> >>>>>> Dear Ray, >>>>>> >>>>>> As far as I know, taking into account the voltage at slack bus as >>>>>> optimization variable is equal to have an OLTC. So, how can I compare >>>>>> the results with and without voltage control at slack? Can it be done >>>>>> either by changing the tap ratio or voltage limits? >>>>>> Best Wishes >>>>>> >>>>>> Silvio Miceli >>>>>> >>>>>> >>>>>> On Thu, Feb 9, 2012 at 18:57, Silvio Miceli <[email protected]> >>>>>> wrote: >>>>>> Dear Ray, >>>>>> >>>>>> 1. Can I say MATPOWER's OPF considers the power factor angle of >>>>>> generators as optimization variable? If not, how can I consider as >>>>>> optimization variable? >>>>>> >>>>>> 2. Also, according to one of your replies to a post with regards to >>>>>> considering the slack bus voltage as optimization variable, why you want >>>>>> to implement OLTC in MATPOWER? In my idea, considering the slack bus as >>>>>> optimization variable is equal to have an OLTC and consequently >>>>>> considering the secondary voltage as optimization variable. Because >>>>>> usually the OLTC is used in order to control the voltage of slack bus >>>>>> and in MATPOWER is already considered as optimization variable. If I am >>>>>> not right, please let me know? >>>>>> >>>>>> Best Wishes >>>>>> >>>>>> Silvio >>>>>> >>>>>> >>>>>> >>>>>> On Wed, Feb 8, 2012 at 17:47, Ray Zimmerman <[email protected]> wrote: >>>>>> On Feb 8, 2012, at 10:01 AM, Silvio Miceli wrote: >>>>>> >>>>>>> 1. What kind of generator has been taken into account in MATPOWER in >>>>>>> Section 5.4.3 of MANUAL in order to consider the capability curve? >>>>>> >>>>>> It is simply intended to be a piecewise linear approximation to the kind >>>>>> of capability curve exhibited by many types of conventional generators, >>>>>> such as this one from Figure 2 in [1]. >>>>>> >>>>>>> 2. I want to minimize losses instead of maximizing social welfare >>>>>>> considering offers and bids. How can I do it in MATPOWER? >>>>>> >>>>>> The answer to this one is readily available in the list archives ... >>>>>> e.g. >>>>>> http://www.mail-archive.com/[email protected]/msg00817.html >>>>>> >>>>>>> 3. How can I maximize profit for generators in MATPOWER instead of >>>>>>> maximizing Social welfare? >>>>>>> Also, by which formula I can obtain profits (for generators), revenue >>>>>>> and cost in MATPOWER? Could you please address it? >>>>>> >>>>>> I'm not aware of a method to maximize profits, since that would involve >>>>>> an objective that is a function of price, a very unconventional type of >>>>>> optimization problem. You can compute revenue directly as the product of >>>>>> quantity and price, and the cost is available in the dispatch matrix >>>>>> returned by runmarket. See help idx_disp for a description of each >>>>>> column of the dispatch matrix. >>>>>> >>>>>> - Ray >>>>>> >>>>>> [1] >>>>>> http://www.hydroworld.com/index/display/article-display/353952/articles/hydro-review/volume-28/issue-2/feature-articles/system-protection/coordinating-generator-protection-and-controls-an-overview.html >>>>>> >>>>>> -- >>>>>> Ray Zimmerman >>>>>> Senior Research Associate >>>>>> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >>>>>> phone: (607) 255-9645 >>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>> >>>> >>> >>> >> >> >> > >
