Dear Shuo, I'd try to simulate a simply network with 1 reference bus with 1 transformer and 1 subsequent load to test the behaviour between Matpower and netomac.
I'm not used to netomac, so can't help here directly. Nice regards, Chris 2016-05-10 13:22 GMT+02:00 Shuo Chen <[email protected]>: > Dear Chris, > > thanks for your reply, actually we are getting the same transformer data. > In my power system uk is far more larger than ur (more than 50:1), so it > can be assumed that ux = uk. > > i'm wondering whether there is any little difference between netomac and > matpower by modeling the transformer, so that even if I give them the same > input, PF results could still differ. > > best regards > Shuo > > Zitat von Chris Prokop <[email protected]>： > > Dear Shuo Chen, >> >> I'm used to similar data and calculate r and x as (ur, uk in p.u., >> base_MVA >> and S_transformer in MVA): >> - r = ur * base_MVA / S_transformer >> - x = sqrt(uk^2 - ur^2) * base_MVA / S_transformer >> - ratio = 1 (in your case, where rated = nominal voltage) >> - angle = 0 (in your case, without phase shifting) >> >> Maybe one of your problems is using uk instead of ux (uk^2 = ux^2 + ur^2)? >> >> Nice regards, >> Chris >> >> 2016-05-10 0:33 GMT+02:00 Shuo Chen <[email protected]>: >> >> >>> Dear Ray and matpower users, >>> >>> i'm writing my thesis about a data-converter for two power system >>> simulation softwares: PSSE@Netomac from Siemens and matpower. Here is a >>> problem with transformer modeling, i've read a lot in this archive but >>> still can't solve it, so i decide to post my question here. >>> >>> My goal is to get the same or a simular power flow convergency using the >>> Newton's method after converting the net topology from one to the other. >>> However, I'm stucked when I try to convert a Netomac net into a matpower >>> case. Comparing the PF results of the 2 softwares, there is always a big >>> deviation (by bus voltage magnitude, bus voltage angle and branch P/Q >>> injection). More specifically, the bus voltages in pu of matpower are all >>> lower than those of Netomac, the deviation could be up to 5%, like 0.977 >>> instead of 0.997 in Netomac. >>> >>> I simply grab all the bus/gen/branch parameters from Netomac except for >>> the transformer impedance, so I guess there might be a mistake when the >>> transformer model is built in matpower. >>> The transformers have 2-windings and no tap changer >>> >>> The parameters I could get from Netomac are: >>> >>> - Rated voltage of HV side winding (Un1) >>> - Nominal network voltage HV side (UB1? the value is equal to Un1) >>> - Rated voltage of LV side winding (Un2) >>> - Nominal network voltage LV side (UB2? the value is equal to Un2) >>> - Rated apparent power (equal to baseMVA) >>> - ur in % (may not be zero) >>> - uk in % (must be larger than ur) >>> - P0 and I0 are not given >>> - vector group YY0 >>> in matpower a transformer is treated as a transmission line, where >>> r(p.u.) >>> and x(p.u.) are needed for the power flow calculation. (b is omitted in >>> my >>> case) >>> According to the formels: >>> >>> z_pu = uk% / 100 >>> x_pu = uk% *(Un/UB).^2 * (SB/Sn) / 100 >>> r_pu = sqrt(z_pu.^2 - x_pu.^2) (here r_pu = ur%/ 100) >>> >>> Since in my case Un/UB = 1, SB/Sn = 1, so x = uk%/100, r = ur%/100, b = 0 >>> I set ratio = 1 and angle = 0, status = 1, angmin/max = +-360 >>> other values are set to 0 >>> >>> Netomac can also export a .raw file for PSSE, the conversion above will >>> generate equivalent r and x values as the exported .raw file. >>> Theoretically, with the same net topology and P/Q accuracy, the PF >>> convergency of the two simulation tools should be almost the same. >>> >>> Here is one more hint, as far as I know, the transformer impedance in >>> matpower is modeled at "to" side, while in Netomac it's modeled at "HV" >>> side (which is the "from" side), so there could be a difference between >>> the >>> two models but i got no clue how to unify them. >>> >>> >>> Has anyone ever met this kind of problem before? Or the transformer is >>> converted in a right way, but there could be something wrong in other >>> parts? >>> I know this is a tough one, hopefully I could get some hints here. Many >>> thanks for all! >>> >>> Best Regards >>> Shuo >>> >>> >>> >>> >>> > > > >
