Search found 148 matches

by RWTH_FCN
Tue Sep 17, 2019 5:10 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16686

Re: sensitivity analysis (vensim)

1- Can we do these sentivity analysis in a model which has external function? I am asking this becasue I get this errors: {ERROR: Yearly Depreciation Factor not found or wrong type must be constant. ERROR: No sensitivity inputs marked in sensitivity file} These errors are nothing to do with externa...
by RWTH_FCN
Tue Sep 17, 2019 4:51 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 16686

Re: sensitivity analysis (vensim)

Hi, I have two questions regarding sensitivity analysis and stochastic programming in Vensim: 1- Can we do these sentivity analysis in a model which has external function? I am asking this becasue I get this errors: {ERROR: Yearly Depreciation Factor not found or wrong type must be constant. ERROR: ...
by RWTH_FCN
Wed Aug 21, 2019 11:04 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

I've attached two models, neither of which is really right, but both in the ballpark. DEMAND AT PRICE elec 2.mdlDEMAND AT PRICE elec 1.mdl #1 implements what I originally suggested, which is that everyone bids close to MAX( marg cost, expected price ). That actually implements collusion, and the pr...
by RWTH_FCN
Wed Aug 21, 2019 9:56 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

I mentioned noise for the following reason. If the auction is structured so that bids reveal true marginal costs, and that information is disclosed, then everyone has a pretty good idea what the aggregate supply curve looks like. Therefore they can do a pretty good job of anticipating the clearing ...
by RWTH_FCN
Wed Aug 21, 2019 8:07 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

It seems like this should result in an outcome much like a single clearing price, but with a little more noise. If I'm running unit X, I don't want to bid my marginal cost. I want to figure out where the market is likely to clear next period, and bid just below that. However, the price in the next ...
by RWTH_FCN
Wed Aug 21, 2019 7:55 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

Ah ... so the problem is more game theoretic. Each plant has to choose a bid that maximizes profit, subject to everyone else doing the same. We know the bid has to lie above marginal cost, and below a price cap (set by regulator?). Is the capacity constraint loose, in the sense that they want to ru...
by RWTH_FCN
Wed Aug 21, 2019 7:46 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

Does your capacity constraint imply that A generates 100 to 300 or 0 ? That probably can't be done with the alloc functions. Not sure it could be done with FIND ZERO or even an LP either. It makes this more of a mixed integer programming problem, right? Sorry, it should be (0<Capacity of A<300). If...
by RWTH_FCN
Wed Aug 21, 2019 7:19 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

Doesn't everyone who supplies > 0 get paid at the (single) market clearing price, rather than their bid price? No, they get paid exactly their bid. So bidders bid at their individual cost with a margin on top. However uniform auction can help me but my main concern is modeling this maximization rat...
by RWTH_FCN
Wed Aug 21, 2019 6:51 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

The FIND ZERO example model in the Help system is already pretty close to what you need. I'll see if I have something better. Have you explored the allocation functions? That would be an even easier solution. Yes but maybe I did not use it correctly. I used "Allocation by priority", in th...
by RWTH_FCN
Wed Aug 21, 2019 2:29 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 32
Views: 14906

Re: Integrating time step of optimization problem

The one thing you can't do is run the Vensim optimizer at intervals within the simulation. OTOH you can do some kinds of optimization with FIND ZERO - I've used that before to dispatch power plants in a model. Can you please describe or send a sample model how to model economic dispatch with Find Z...
by RWTH_FCN
Mon Jul 22, 2019 5:27 pm
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

tomfid wrote: Sat Jul 20, 2019 8:52 pm A possible workaround would be to create a macro that implements a pulse train.
Can you describe it a little bit
by RWTH_FCN
Mon Jul 22, 2019 4:01 pm
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

For debugging we really need the exact variables in the big model copy-pasted into a test model, with exactly the same time settings. Otherwise there are too many possible causes of variation. (However, if the copy-pasted version works for you, this probably won't help us diagnose.) Other things to...
by RWTH_FCN
Mon Jul 22, 2019 3:58 pm
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

Do they work in the large model if it's not compiled? (Note that if you've previously compiled it, you either have to change the model or delete the .dlls to run interpreted.) No, it is not related to compilation because it does not work with or without compilation. I was just wondering which time ...
by RWTH_FCN
Sat Jul 20, 2019 7:35 pm
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

Can you copy the parameters "pulse", "eeg start", "eeg repeat time", "eeg duration" and "eeg end time" and paste them into a blank model? I have attached the equations of the function. As you can see I have used very simple equations and they work i...
by RWTH_FCN
Sat Jul 20, 2019 6:54 pm
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

tomfid wrote: Sat Jul 20, 2019 6:40 pm Can you post or email the model?
Unfortunately, I cannot send the model, it has also huge input files and external files which make sending hard.
Attached you can find my time setting and formula for repeat time of PULSE TRAIN. The rest of variable for this function are as simple as repeat time.
by RWTH_FCN
Sat Jul 20, 2019 6:27 pm
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

tomfid wrote: Fri Jul 19, 2019 8:21 pm Any chance the variable type is set to INITIAL?
Changing variable type to initial does not help. It works well when I use a PULSE TRAIN function in a compiled small test model but it still does not work in my large scale model.
by RWTH_FCN
Fri Jul 19, 2019 3:29 pm
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

Hard to say. I'd recommend copy-pasting your equation into a standalone model for testing. Be sure the time bounds are the same as the original. Also, be sure SAVEPER=TIME STEP; otherwise you might not see the pulses in the output. I checked all your suggestions. When I open another vensim file and...
by RWTH_FCN
Fri Jul 19, 2019 10:08 am
Forum: Vensim
Topic: Somebody help me please!! ramp and pulse train combination
Replies: 33
Views: 14492

Re: Somebody help me please!! ramp and pulse train combination

Hi,
What kind of mistakes can cause a failure in PULSE TRAIN. I am using a PULSE TRAIN in a large-scale model but it produces nothing, although all 4 inputs of this fuction seems to be correct.
by RWTH_FCN
Wed Jul 03, 2019 3:36 pm
Forum: Vensim
Topic: demand and supply at price
Replies: 29
Views: 12649

Re: demand and supply at price

"No priority" = "priority vector with all values the same" would be one option. You can't change the type of an argument from a vector to a single value. Another, simpler option would be to use one of the one-sided ALLOC functions. In other words, add up the demands to a single ...
by RWTH_FCN
Wed Jul 03, 2019 2:37 pm
Forum: Vensim
Topic: demand and supply at price
Replies: 29
Views: 12649

Re: demand and supply at price

Hi,

How can I use FIND MARKET PRICE(dq,dp,sq,sp) when I have only multi suppliers and no priority for demanders?
I get this error: Argument 2 of FIND MARKET PRICE must be a normal variable
by RWTH_FCN
Sat May 11, 2019 2:54 pm
Forum: Vensim
Topic: demand and supply at price
Replies: 29
Views: 12649

Re: demand and supply at price

tomfid wrote: Mon May 06, 2019 5:56 pm I'd have to see the relevant equations.
The problem is that, this ranking is being done for a subrange. However, these functions are not suitable for ranking subrange. Do you have any idea how to rank subranges?
by RWTH_FCN
Mon May 06, 2019 5:42 pm
Forum: Vensim
Topic: demand and supply at price
Replies: 29
Views: 12649

Re: demand and supply at price

You could use a stock or SAMPLE IF TRUE to identify the winner and set their quantity to 0, or priority very low, for future auctions. Thanks. I still get this error for a part of model which is related to ALLOCATE AVAILABLE function: "Error in ALLOCATE_AVAILABLE/FIND_MARKET_PRICE - subscript ...
by RWTH_FCN
Mon May 06, 2019 3:29 pm
Forum: Vensim
Topic: demand and supply at price
Replies: 29
Views: 12649

Re: demand and supply at price

It sounds like we need something like an "ALLOC IF" function that's switchable, so it only executes when a flag is true. I just multiplied pluse train with allocation function. Do you have any suggestion for filtering the winner and looser of each auction. I want that looser can be able t...
by RWTH_FCN
Mon May 06, 2019 1:35 pm
Forum: Vensim
Topic: demand and supply at price
Replies: 29
Views: 12649

Re: demand and supply at price

You'll need to create a variable that is zero or one at those three times of the year. Then use SAMPLE IF TRUE to hold the winning value until the next round. VECTOR RANK can be used to work out which is the winner at each auction round. The thing is that I want the winners will be able to sell for...
by RWTH_FCN
Sat May 04, 2019 4:33 pm
Forum: Vensim
Topic: demand and supply at price
Replies: 29
Views: 12649

Re: demand and supply at price

My model is an hourly based model which simulates electricity market for 35 years. I want to model the auction of technology X only three times per year and winners of auction X can be able to sell their energy for 10 years. Looser of auction X will sell their energy without any premuim, but they ha...