Hi Robert, Thank you for the information. I'll try to look into unbalanced solver for this case.
I'd also like to look into this scenario as well: What if I simplify the circuit to a single phase circuit with 1 main generator transmitting at 12kV, down the line transformer step down the voltage to 120V to serve house loads. How would the branch matrix look in this case? Thank you Thai On Fri, Jun 19, 2015 at 10:54 AM, Robert Spiewak < [email protected]> wrote: > What about all mutual couplings with other phases, neutral, ground and > ground return... Are you going to simulate each "path" separately (minimum > 25)? How are you going to combine them back together? Using supperposition > principle? It will not work. I tried that. Only solution is to have an > unbalanced solver with NR method that considers all self an mutual pedances > at the same time. > > Best Regards, > > Robert Spiewak > (Sent from Remote) > > On Jun 19, 2015, at 13:04, Thai Tran <[email protected]> wrote: > > Hi Dr.Zimmerman and Robert, > > I understand that Matpower can't work with an unbalanced three phase > circuit. For this example, I'm only working with the A phase leg of the > circuit. I'm just not sure how to setup the connection between nodes > correctly. > > Thank you > Thai > On Jun 19, 2015 4:48 AM, "Robert Spiewak" <[email protected]> > wrote: > >> Thai, >> >> You cannot aproximate unbalanced system consited of branches and loads >> with 3W+N+G (three-phase, neutral and ground) via positive sequence solver >> like MATPOWER. The principle of methodology (NR) assumes symmetry in the >> system. Symmetry in branch impedances, loads and generation sources. >> >> Best Regards, >> >> Robert Spiewak >> >> > On Jun 19, 2015, at 08:18, Ray Zimmerman <[email protected]> wrote: >> > >> > MATPOWER does not model unbalanced 3-phase systems, and without a lot >> of work to refresh my memory, I’m not comfortable commenting on the >> possibility of a good single-phase approximation in your case. >> > >> > Maybe someone else can comment. >> > >> > Ray >> > >> > >> > >> >> On Jun 18, 2015, at 8:24 PM, Thai Tran <[email protected]> wrote: >> >> >> >> Hi Dr.Zimmerman, >> >> >> >> I'm new to matpower so please excuse me if this is a silly question. >> >> >> >> I'm trying to use matpower to calculate power flow for a distribution >> grid. This circuit has power coming from a substation on 12.47 kV three >> phase line. Single phase transformers tap off the three phase line and step >> the voltage down to 120V to serve houses in the circuit. In matpower, >> transformers are modeled as a branch, how should I model the connections in >> my circuit? >> >> >> >> For example: >> >> substation is connected to transformer 1 which is then connected to 5 >> loads. In the circuit model it would be >> >> substation -> transformer >> >> transformer -> load 1 >> >> ... >> >> transformer -> load 5 >> >> >> >> Should I model this in the branch matrix as >> >> >> >> substation(node 1) -> load 1 (node 2) >> >> ... >> >> substation(node 1) -> load 5 (node 6) >> >> load 1(node 2) -> load 2 (node 3) >> >> ... >> >> etc. >> >> >> >> >> >> Also since the transformer step the voltage level from 12.47kV to >> 120V, which level should I use to calculate my p.u impedance? >> >> Thank you >> >> Thai >> > >> > >> > >> > >> >> >>
