When working on photovoltaic systems i found my self using a two stage topology in Simulink (dc/dc with MPPT and dc/ac with PLL and PI controllers).
This structure is widely documented and a lot of work has been done in the literature using it especially on matlab simulink.
Now for power system studies, there is a generic model proposed in WECC modeling guidelines (regc_a, reec_b and repc_a).
What's the difference/relationship between the detailed models used in matlab and the one proposed in the WECC guidelines ?
Thank you in advance for your answers
The WECC models are specifically developed for what is called transient stability (or system stability) studies, while this Matlab/Simulink model you mention seems to be a detailed three-phase representation of the inverter and its controllers.
The key difference: transient stability (system studies) are usually based on models for the whole interconnected system. The WECC system is represented by more than 50,000 buses, spanning the entire West Coast of North America, from Southern California to British Columbia and Alberta, and then East to Utah, Arizona and Idaho and Montana, etc.
The transient stability model is based on fundamental-frequency, positive-sequence model of the electrical network (Y-bus matrix, algebraic model). The system stability studies are usually simulations of 10 to 30 seconds after a large system disturbance (fault, protection action, fault clearing and change in network topology due to the tripping of elements to clear such fault). These simulations are usually performed with integration steps of 1/4 of a cycle of 60 Hz (about 4 ms).
The detailed model you talk about, detailed representation of the inverter and the firing of the individual IGBTs (or whatever equivalent electronic switch you might be considering) is what is called an EMTP-type model. It requires a 3-phase dynamic model for the network (RLC dynamic model or similar) and integration time steps compatible (at minimum) with the switching frequencies of the firing control on your inverter (PWM, I presume, so perhaps around kHz?).
These studies would require integration steps one or even two orders of magnitude smaller than what is used for transient stability, with a way more detailed (and complex) representation of the network.
As far as I know, despite many claims to the contrary, I've never seen the results of an EMTP-type simulation representing the whole WECC region and simulating the usual events from transient stability studies, ie, running simulations for 10 to 30 seconds after the applied disturbance.
By the way, forgot to mention: there are many related activities being developed under the Power System Dynamic Performance Committee, of the Power and Energy Society of the IEEE.
In particular, you might want to reach out to the Task Force on Modeling and Simulation of Large Power Systems with High Penetration of Inverter-Based Generation.
https://site.ieee.org/pes-psdp/
dear L.T.G. Lima and Mohamed Azab
Thank you for your answers they were really helpful.
But how is the PV model in the WECC guidelines developed ?
Starting from the EMTP model we should be able to get to the simplified or generalized transient stability model ?
I know that the solar source and the MPPT are neglected, so it represents only the inverters and the controllers dynamics. But i found no source on how the WECC model is derived (nor the previous PV1D model).
Thank you again for you time.
PS : I wish you both a happy new year.
I believe you'd have to refer back to the model specification documents. Some (if not all) of these documents are posted in the WECC website, under their Model Validation Working Group.
https://www.wecc.org/RAC/Pages/MVWG.aspx
Some of these models were originally proposed/developed by EPRI, particularly for the wind turbines. I'm not 100% sure about the specific models for PV, but I believe that these models were developed based on whatever was previously done for the Type 4 (full inverter wind turbine).
I am greatly thankful L.T.G. Lima
The WECC link is a gold mine of information, i'll try to get the most out of it.
The PV model is actually the same used for type 3 and type 4 wind turbines.
Unfortunately the EPRI reports are not freely available unlike the WECC reports.
Thanks to you i managed to dig up a CIGRE file that details the dynamic models of inverter based generation systems.
http://cired.net/uploads/default/files/727-web.pdf
The model is similar to the WECC model which makes sense since only the inverter's dynamics are considered in power systems studies.
Again, thank you very much for your time.
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