How can I solve this problem? Best Wishes
Roberto On Mon, Mar 14, 2011 at 16:44, Ray Zimmerman <[email protected]> wrote: > But you are over-specifying the problem and it will not have a solution. > You can't specify all of the power factors exactly and expect the power flow > equations to be satisfied. > > -- > Ray Zimmerman > Senior Research Associate > 211 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > On Mar 14, 2011, at 11:39 AM, Roberto Carvalini wrote: > > Because I want to have PF=0.9 or 0.95 for all generators. As you know, it > is very important > > On Mon, Mar 14, 2011 at 16:36, Ray Zimmerman <[email protected]> wrote: > >> You need a row of A for each generator, each one with QPratio in the >> column corresponding to Pg(i) and -1 in the column corresponding to Qg(i) >> ... >> >> mpc.A = sparse([1:ng; 1:ng], [2*nb+(1:ng); 2*nb+ng+(1:ng)], >> [QPratio*ones(ng,1); -ones(ng,1)], 1:ng, 2*nb+2*ng); >> >> As I said, this is likely to make the OPF infeasible, so I'm not sure why >> you'd want to do it. >> >> -- >> Ray Zimmerman >> Senior Research Associate >> 211 Warren Hall, Cornell University, Ithaca, NY 14853 >> phone: <%28607%29%20255-9645>(607) 255-9645 >> >> >> >> >> On Mar 14, 2011, at 11:17 AM, Roberto Carvalini wrote: >> >> Thank you very much. >> >> Is it possible for you to give an example, for example case9, for all >> generators? I will be appreciate if you do it. >> >> Best Regards >> >> R. Carvalini >> >> On Mon, Mar 14, 2011 at 16:08, Ray Zimmerman <[email protected]> wrote: >> >>> The *A* matrix is from equation (5.25) in the User's >>> Manual<http://www.pserc.cornell.edu/matpower/manual.pdf>. >>> As I mentioned, the coefficients need to go in the columns corresponding to >>> Pg(1) and Qg(1). So, Pg(1) is in the first column following the voltage >>> angles (1st nb columns) and magnitudes (next nb columns), so it's in column >>> 2*nb+1. For Qg(1) it's the first column after the Pg columns, so 2*nb (for >>> the voltage angles and magnitudes) plus ng columns for Pg. >>> >>> Yes, if you wanted to do this for all generators, you need to include a >>> row in *A* for each. Be careful though, this will likely over-constrain >>> the problem and make it infeasible. If all generators have a fixed power >>> factor, then balancing the real power output to match the load will mean a >>> specific reactive power output as well, which will not necessarily match the >>> reactive power load. >>> >>> -- >>> Ray Zimmerman >>> Senior Research Associate >>> 211 Warren Hall, Cornell University, Ithaca, NY 14853 >>> phone: <%28607%29%20255-9645> <%28607%29%20255-9645>(607) 255-9645 >>> >>> >>> >>> On Mar 11, 2011, at 11:40 AM, Roberto Carvalini wrote: >>> >>> Thank you very much. >>> >>> I have read the manual but I didn't understand by which formula you >>> computed this matrix (highlighted) >>> >>> mpc.A = sparse([1; 1], *[2*nb+1; 2*nb+ng+1]*, [QPratio; -1], 1, >>> 2*nb+2*ng); >>> >>> and if want to define the same PF for all generators, must I repeat this >>> for all or it depends on the type buses (PV or Slack)? >>> >>> Regards >>> >>> R. Carvalini >>> >>> On Fri, Mar 11, 2011 at 16:27, Ray Zimmerman <[email protected]> wrote: >>> >>>> Dirk's suggestion is fine for a simple power flow. But if you want to >>>> run an OPF, where the generator dispatch is to be determined by the >>>> optimization, but subject to a constant power factor constraint, then you >>>> will need to supply an additional user-defined linear constraint. For >>>> example, if you want to run case9 with a constant power factor constraint >>>> of >>>> 0.95 on the first generator, you could do it like this ... >>>> >>>> define_constants; >>>> mpc = loadcase('case9'); >>>> nb = size(mpc.bus, 1); >>>> ng = size(mpc.gen, 1); >>>> pf = 0.95; >>>> QPratio = sqrt(1/pf^2 -1); >>>> %% add constraint that QPratio * Pg(1) - Qg(1) = 0 >>>> mpc.A = sparse([1; 1], [2*nb+1; 2*nb+ng+1], [QPratio; -1], 1, >>>> 2*nb+2*ng); >>>> mpc.l = 0; >>>> mpc.u = 0; >>>> r = runopf(mpc); >>>> resulting_pf = r.gen(1, PG) / sqrt(r.gen(1, PG)^2 + r.gen(1, QG)^2) >>>> >>>> The important part here is defining the A matrix properly, where the >>>> columns correspond to voltage angles, voltage magnitudes, generator real >>>> injections, and generator reactive injections (2*nb + 2*ng columns in all). >>>> So the coefficients for our constraint co in the columns corresponding to >>>> Pg(1) and Qg(1). >>>> >>>> -- >>>> Ray Zimmerman >>>> Senior Research Associate >>>> 211 Warren Hall, Cornell University, Ithaca, NY 14853 >>>> phone: <%28607%29%20255-9645> >>>> <%28607%29%20255-9645><%28607%29%20255-9645>(607) >>>> 255-9645 >>>> >>>> >>>> >>>> On Mar 11, 2011, at 9:50 AM, Dirk Van Hertem wrote: >>>> >>>> You model your generator as a load, so it is not represented in your >>>> gen matrix. Of course, if you want model your generator in a unit >>>> commitment, this may not be trivial... >>>> >>>> Dirk >>>> >>>> On 03/11/2011 12:32 PM, Roberto Carvalini wrote: >>>> >>>> Thank you >>>> >>>> How can I add? my problem is this >>>> >>>> Best Wishes >>>> >>>> Roberto >>>> >>>> >>>> On Fri, Mar 11, 2011 at 12:22, Dirk Van Hertem <[email protected] >>>> > wrote: >>>> >>>>> You can just define them as a PQ bus with negative power... (negative >>>>> load) >>>>> >>>>> Dirk >>>>> >>>>> >>>>> On 03/11/2011 12:11 PM, Roberto Carvalini wrote: >>>>> >>>>>> Hi >>>>>> >>>>>> How can I define constant power factor in MAPOWER for example, for >>>>>> generators PF=0.9? >>>>>> >>>>>> Please help me >>>>>> >>>>>> Regards >>>>>> >>>>>> Roberto >>>>>> >>>>>> >>>>>> >>>>> >>>>> -- >>>>> Dirk Van Hertem [email protected] >>>>> Electrical Engineering Department http://www.esat.kuleuven.be/electa >>>>> K.U. Leuven, ESAT-ELECTA GSM: +32-(O)498-61.74.98 >>>>> 10, Kasteelpark Arenberg, B-3001 Heverlee fax: >>>>> <%2B32-16-32.19.85> <%2B32-16-32.19.85> >>>>> <%2B32-16-32.19.85><%2B32-16-32.19.85> >>>>> +32-16-32.19.85 >>>>> >>>>> >>>>> >>>> >>>> >>>> -- >>>> Dirk Van Hertem [email protected] >>>> Electrical Engineering Department http://www.esat.kuleuven.be/electa >>>> K.U. Leuven, ESAT-ELECTA GSM: +32-(O)498-61.74.98 >>>> 10, Kasteelpark Arenberg, B-3001 Heverlee fax: <%2B32-16-32.19.85> >>>> <%2B32-16-32.19.85> <%2B32-16-32.19.85>+32-16-32.19.85 >>>> >>>> >>>> >>>> >>> >>> >>> >>> >> >> >> >> >> > > > Best Wishes > > Roberto > > >
