Certainly, testing with a small system is the only way to find out what the internal model *really* is (since you can't inspect the code in this case). Anyway, I would add another suggestion: export from Netomac to PSS/E RAW format, and inspect the transformer records very carefully. Read the specs of the RAW format (the specific version of the format used), and have a look at the internal model used by PSS/E (I'd assume that Netomac uses the same, but who knows). You can find it here:
http://w3.usa.siemens.com/datapool/us/SmartGrid/docs/pti/2009July/PDFs/Modeling_of_two_winding_voltage_regulating_transformers.pdf Compare this model with the one use by MATPOWER (page 22 of the PDF manual). You'll see they're not exactly the same. You said you're not using magnetizing branches (Bs), which simplifies things a lot. But pay attention to the tap ratios (both sides!), just in case. -- Jose L. Marin Grupo AIA 2016-05-10 13:50 GMT+02:00 Chris Prokop <christophprok...@gmail.com>: > 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 <shuo.c...@st.ovgu.de>: > >> 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 <christophprok...@gmail.com>： >> >> 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 <shuo.c...@st.ovgu.de>: >>> >>> >>>> 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 >>>> >>>> >>>> >>>> >>>> >> >> >> >> >
