Does Vensim embed loop intervals?

Use this forum to post Vensim related questions.
Post Reply
kong17
Senior Member
Posts: 60
Joined: Wed May 30, 2018 1:12 pm
Vensim version: PRO

Does Vensim embed loop intervals?

Post by kong17 »

Hi,
I am working on a model that simulate the long-term investment behavior for electricity market. In order to betwer simulate this behavior, I need to calcualte the profit by simulating the price under different demand load for each hour of the year. So, I need to build the load duration curve, it is defined as the variation of a certain load in a downward form such that the greatest load is plotted in the left and the smallest one in the right. On the time axis, the time duration for which each certain load contiunues during the day is given.
load duration curve.png
load duration curve.png (45.47 KiB) Viewed 2878 times
To avoid unnecessary complexity in the exemplary calculations , a linear LDC with an initial peak load and a minimum load at the start of the simulations is adopted. it can be analytically expressed as:
L(t) = (Lmin(t) - Lmax(t))*d + Lmax(t).
load.png
load.png (5.48 KiB) Viewed 2878 times
My question is if I define t as years, then d as load duration is hour of year. At each time t, there will be a LDC.
and taking into account other factors, the Lmin and Lmax will also change over time.
We can simply understand d as an interval [0,1] (Analogy [0, 8760]),
Does vensim have any function to solve it?
or, this question is needed to build two models to interconnect each other?
Thank you for your attention!
kong17
Senior Member
Posts: 60
Joined: Wed May 30, 2018 1:12 pm
Vensim version: PRO

Re: Does Vensim embed loop intervals?

Post by kong17 »

I am so sorry that I ask the question twices.
I resubmitted the question due to typographical erros.
Say sorry again to everyone.
tomfid
Administrator
Posts: 3806
Joined: Wed May 24, 2006 4:54 am

Re: Does Vensim embed loop intervals?

Post by tomfid »

No problem - we can delete one. Is this the better copy?
kong17
Senior Member
Posts: 60
Joined: Wed May 30, 2018 1:12 pm
Vensim version: PRO

Re: Does Vensim embed loop intervals?

Post by kong17 »

tomfid wrote: Wed Dec 11, 2019 11:59 pm No problem - we can delete one. Is this the better copy?
Yes, it is the better one.
Please help me to delete the another one.
Thank you
tomfid
Administrator
Posts: 3806
Joined: Wed May 24, 2006 4:54 am

Re: Does Vensim embed loop intervals?

Post by tomfid »

I think the thing to do is to discretize the LDC into a number of segments, represented by an array dimension. Then you can compute utilization of each plant type in each segment. Then the price is the highest-cost plant with nonzero utilization in the segment. (The allocation functions might make this really easy.)

Then you can SUM() over the array to find each plant's utilization, revenue, etc. over the year.
kong17
Senior Member
Posts: 60
Joined: Wed May 30, 2018 1:12 pm
Vensim version: PRO

Re: Does Vensim embed loop intervals?

Post by kong17 »

tomfid wrote: Thu Dec 12, 2019 2:48 am I think the thing to do is to discretize the LDC into a number of segments, represented by an array dimension. Then you can compute utilization of each plant type in each segment. Then the price is the highest-cost plant with nonzero utilization in the segment. (The allocation functions might make this really easy.)

Then you can SUM() over the array to find each plant's utilization, revenue, etc. over the year.
Hi, thank you for your reply.
From your suggestion, I build an example model in the attachment, just focus on the discretize the LDC.
I set the load duration(d) to days, so I get 365 line and the software has begun to become sluggish. I am not sure if the software can work normally if the d is set to hours and the time step is set small.
Example.mdl
(7.52 KiB) Downloaded 150 times
tomfid
Administrator
Posts: 3806
Joined: Wed May 24, 2006 4:54 am

Re: Does Vensim embed loop intervals?

Post by tomfid »

Does it make sense to have a small time step in a long-term capacity model? Or if it does, could you then dispense with the array and observe actuals?
Post Reply