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"System model requires too many VARS" when using large amount of CMLDBLU2 load models

asked 2017-10-26 17:40:20 -0600

Phyl gravatar image

I am using version PSS/E 34.2 to do dynamic simulations of the Poland test system which contains 2000+ buses. I am trying to input the CMLDBLU2 model for every load in the system. When I have greater than approximately 1500 loads with the CMLDBLU2 I get the error: "Return to dynamics terminated--system model requires too many VARS". My system will run successfully when using under 1500 dynamic load models. Then when using greater than 1500 and I get that error and I receive "NaN" in the output results. When loading the dynamic file the output is:

Generator models use: CONS 1- 3924 STATES 1- 1635

Excitation System models use: CONS 3925- 8502 STATES 1636- 2943 VARS 1- 327

Turbine Governor models use: CONS 8503- 10791 STATES 2944- 3924 VARS 328- 654

Shared Load Characteristic models use: CONS 10792-253649 ICONS 1- 3652

Shared Load Relay models use: CONS 253650-290169 ICONS 3653- 5478

Return to Dynamics terminated--system model requires too many VARS

Unshared Load models use: STATES 3925- 50040 VARS 655-249876 ICONS 5479- 87414

SUMMARY OF MODELS READ:

GENS: GENSAL 327

EXSYS: IEEET1 327

GOVS: IEEEG2 327

USER: USRLOD 3652

NEXT AVAILABLE ADDRESSES ARE: CON STATE VAR ICON 290170 50041 249877 87415

Only PSS/E supplied models in case. Compilation is not required

What is the cause of this error? And if there a way to work around it?

Thank you!

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answered 2017-10-27 08:28:51 -0600

perolofl gravatar image

You must change to a larger version of PSSE since you are running out of available VARS. I believe you are using 50 000 buses version. Try with 200 000 buses version where you can use up to 999 999 VARS.

To start PSSE from command window:

psse34.exe -buses 200000
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Thank you this worked. Now the program runs without the error, however now the output in "NaN". I have used DOCU to verify that my load models are tuned correctly. Not sure why having additional load models would cause NaN output.

Phyl gravatar imagePhyl ( 2017-10-31 17:41:41 -0600 )edit

I found the error causing the NaN, it is from having the load model on the swing bus. No errors when there are no load models on the swing bus.

Phyl gravatar imagePhyl ( 2017-11-02 14:53:31 -0600 )edit

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Asked: 2017-10-26 17:40:20 -0600

Seen: 797 times

Last updated: Oct 27 '17