Two Base Frequencies in one Dynamic Simulation Case

I am performing the simulation for an HVDC connected system which has one area with system frequency of 60 Hz and other one has 50 Hz both are connected with a back to back HVDC. I want to perform the Dynamic Simulation and if I keep the case Base Frequency at 50 Hz and I run the Flat Simulation (with no disturbance) Rotor Angles of 50 Hz machines continuously increase and that of 60 Hz system decrease. This may be due to the fact the 50 Hz machines try to catch the 60 Hz machines and speed up and vice versa. Please guide me how can I handle this problem?

answered Mar 3 '1

perolofl

3452 ●1 ●9 ●20

No, you are wrong here. PSSE is using per unit speed so both system have 1 pu speed at start of simulation.

The reason for the change of rotor angles may be a very small surplus of power in the 50 Hz system or a small lack of power in the 60 Hz system. How fast are the rotor angles changing? A small change of rotor angles is acceptable at flat run simulation since there are two asynchronous power systems.

Are you plotting absolute or relative rotor angles?

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I am plotting relative angles and increase or decrease in rotor angle is slow but in 10 seconds simulation there is significant increase and decrease in angles. The major problem is that Slack bus angles are also increasing and decreasing in the same speed.

Shafqat Hussnain (Mar 3 '1)

Is the load flow solved? Are initial conditions OK? No warning messages at initialisation?

perolofl (Mar 3 '1)

There are some initial conditions suspects appearing along with some load model inner loop non-convergence message.

Shafqat Hussnain (Mar 3 '1)

INITIAL CONDITIONS SUSPECT: I DSTATE(I) STATE(I) MODEL STATE BUS# X-- NAME --X BASKV ID 22266 -4.8946 0.10000 GAST2A K 406048 RAFB2G16 15.000 91 22267 1.0401 0.23179 GAST2A K+1 406048 RAFB2G16 15.000

Shafqat Hussnain (Mar 3 '1)

CIM5BL AT BUS 391180 LOAD R1: INNER LOOP NOT CONVERGED ON OUTER ITERATION 2 CIM5BL AT BUS 391180 LOAD R1: INNER LOOP NOT CONVERGED ON OUTER ITERATION 3 CIM5BL AT BUS 391180 LOAD R1: INNER LOOP NOT CONVERGED ON OUTER ITERATION 4

Shafqat Hussnain (Mar 3 '1)

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Two Base Frequencies in one Dynamic Simulation Case

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