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
------------------ Original ------------------
From:
"MATPOWER discussion forum"
<[email protected]>;
Date: Thu, Mar 25, 2021 09:03 AM
To: "MATPOWER discussion forum"<[email protected]>;
Subject: Re: Constructing IEEE second benchmark for subsynchronous
resonance using matpower
yangyang wrote:
Hi Carlos, I think there is a bus labeled 1 in the bus
field, next to the "mpc.bus" in the file, and it is a slack bus. If
there was not a slack bus, runpf() will report an error. So this
may not be the problem of my case...
Best Regards,
Yang Yang
You're right, my bad. A 5 second glance is a bad idea. I now see
a problem: you have an impossible 22.7273:1 tap ratio in branch 4,
leading to outrageous losses and reactive dispatches in the power flow
solution.
carlos.
