RE: Why is objective function in negative

[Rick Muth]

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From: bounce-126045400-90152...@list.cornell.edu 
[mailto:bounce-126045400-90152...@list.cornell.edu] On Behalf Of Ray Daniel 
Zimmerman
Sent: Tuesday, November 2, 2021 9:53 AM
To: MATPOWER-L <matpowe...@list.cornell.edu>
Subject: Re: Why is objective function in negative

Hi Maliha,

When using dispatchable loads, the objective function value includes a large 
“negative cost” to represent the value of serving the dispatchable load. If all 
load is dispatchable, you could think of the objective function value as the 
negative of the social welfare.

If you want to compare results between cases with and without dispatchable 
load, you will want to explicitly compute the costs of the actual generators 
(excluding those that represent dispatchable loads) for each case.

>> define_constants
>> r = runopf('case30', mpopt);
>> k = ~isload(r.gen);
>> sum(totcost(r1.gencost(k, :), r1.gen(k, PG)))

ans =

  576.8922

>> r = runopf(load2disp('case30'), mpopt);
>> k = ~isload(r.gen);
>> sum(totcost(r1.gencost(k, :), r1.gen(k, PG)))

ans =

  576.8922

I have no idea why you would get the error of "too many refrence buses making a 
connected system…” when increasing the load in the Pd column.

    Ray




On Oct 27, 2021, at 7:38 AM, MALIHA SHAH 
<mshaheep19....@student.nust.edu.pk<mailto:mshaheep19....@student.nust.edu.pk>> 
wrote:

Respected Ray

I performed simple runopf function to check the cost minimization of case 30 by 
observing objective function in dollar per hour.
Similarly, when i increased the load in Pd column it gives error of "too many 
refrence buses making a connected system..."
But when i run case 30 with dispatchable loads the opf results in negative 
objective function. What does the negative objective function means. How can it 
made positive?
The objective function is not only negative but is very different from base 
case.
Base case had 576 $/hr and dispatchable loads case has 21940$/hr (the loads are 
20% more then base case but let me know if this answer of obj fcn is feasible 
under this situation,it can be around tgis figure or its impossible and I am 
msking other mistakes ).

Thanking you in advance.

Maliha