Yes you are right, the transformer is a ??-Yg (bus4-bus3) connection, and
changing the shift to around 30 degree can fix this problem. The more precise
values of tap and shift need a few more efforts to match the results in
Simulink example more accurately, but it is approximately correct. Thank you.
Best Regards,
Yang Yang
------------------ Original ------------------
From:
"MATPOWER discussion forum"
<[email protected]>;
Date: Thu, Mar 25, 2021 09:34 AM
To: "MATPOWER discussion forum"<[email protected]>;
Subject: Re: Constructing IEEE second benchmark for subsynchronous
resonance using matpower
yangyang wrote:
Thank you Carlos, I have also found it; the tap should be
the ratio of per unit voltages instead of nominal voltages. But
after changing the tap to 1, the power flow shows that all buses are 1
pu 0 degree, and it still differs from the load flow results in the
Simulink example calculated using load flow block in Simulink's
powergui, in which the angle at bus 4 is around -30 degree. I think it
is because of the tap ratio and shift; the transformer has some
resistance and inductance, and matpower manual says that the ratio has
something to do with the impedence of the transformer, but I dont know
how to calculate the tap ratio correctly based on the transformer
impedence.
Best Regards,
Yang Yang
The transformer after the generator is most likely a delta-wye
connection, which would explain the generator's voltage lagging by 30
degrees the rest of the system. Set the tap ratio to 0 or 1.0 (0 means no
off-nominal tap ratio), and the angle shift parameter to 30 degrees (SHIFT
column) and you'll get what you need.
carlos.
