## Please help with a loop

### Please help with a loop

Hello!

I am trying to do a simple example and I am New to GAMS.

I want to do a simple Power flow example in order to expand it later, i want GAMS to minimize the cost by choosing the cheapest generators.

My problem is that I want the load to change for every hour for my system, here is a 3 hour example and the error is marked in red.

Can you please help me and explain what i must do different?

HERE IS MY CODE:

$TITLE pflow

Set t hours per day / t1, t2, t3 / ;

parameters

L(t) Load for each

/t1 3

t2 5

t3 8/ ;

Scalar

Cost_diesel in â‚¬ per kWh / 2 /

Cost_pv in â‚¬ / 1.1 /

VARIABLES

*L(t),

X_g Diesel generator,

X_pv Domestic PV generation ,

Z Total cost of grid operation in â‚¬ per kWh for on hour;

EQUATIONS

Load_Balance Maintane a stable grid,

OBJ Objective equation total cost of grid operation in â‚¬ per kWh ;

Load_balance.. X_g + X_pv -L(t) =E= 0 ;

149 Uncontrolled set entered as constant

OBJ.. Z =E= (X_g*Cost_diesel) + (X_pv*Cost_pv);

* Upper bounds

X_g.UP = 10 ;

X_pv.UP = 2 ;

* Lower bounds

X_g.lo = 0 ;

X_pv.lo = 0 ;

* Initial point

X_g.l = 0 ;

X_pv.l = 0 ;

* Load(s).l = 0 ;

MODEL pflow / ALL / ;

OPTION LIMROW = 100;

OPTION LIMCOL = 100;

loop(t, SOLVE pflow USING LP MINIMIZING Z) ;

--

To unsubscribe from this group and stop receiving emails from it, send an email to gamsworld+unsubscribe@googlegroups.com.

To post to this group, send email to gamsworld@googlegroups.com.

Visit this group at http://groups.google.com/group/gamsworld.

For more options, visit https://groups.google.com/d/optout.

### Re: Please help with a loop

Hi,

the programming problem was very basic, see new equation definition

and alias for the loop.

Still the problem as defined is unfeasible, you might want to check

its rational definition.

$TITLE pflow

Set t hours per day / t1, t2, t3 / ;

parameters

L(t) Load for each

/t1 3

t2 5

t3 8/ ;

Scalar

Cost_diesel in â‚¬ per kWh / 2 /

Cost_pv in â‚¬ / 1.1 /

alias(t,tt);

VARIABLES

*L(t),

X_g Diesel generator,

X_pv Domestic PV generation ,

Z Total cost of grid operation in â‚¬ per kWh for on hour;

EQUATIONS

Load_Balance(t) Maintane a stable grid,

OBJ Objective equation total cost of grid operation in â‚¬ per kWh ;

Load_balance(t).. X_g + X_pv -L(t) =E= 0 ;

*149 Uncontrolled set entered as constant

OBJ.. Z =E= (X_g*Cost_diesel) + (X_pv*Cost_pv);

* Upper bounds

X_g.UP = 10 ;

X_pv.UP = 2 ;

* Lower bounds

X_g.lo = 0 ;

X_pv.lo = 0 ;

* Initial point

X_g.l = 0 ;

X_pv.l = 0 ;

* Load(s).l = 0 ;

MODEL pflow / ALL / ;

OPTION LIMROW = 100;

OPTION LIMCOL = 100;

loop(tt, SOLVE pflow USING LP MINIMIZING Z) ;

hope this helps,

Roger

http://fnu.zmaw.de/index.php?id=7179&L=3

2014-10-16 12:44 GMT+02:00 Ivan Nordnes Dahlberg :

> > Hello!

> >

> > I am trying to do a simple example and I am New to GAMS.

> > I want to do a simple Power flow example in order to expand it later, i want

> > GAMS to minimize the cost by choosing the cheapest generators.

> > My problem is that I want the load to change for every hour for my system,

> > here is a 3 hour example and the error is marked in red.

> >

> > Can you please help me and explain what i must do different?

> >

> > HERE IS MY CODE:

> >

> > $TITLE pflow

> >

> > Set t hours per day / t1, t2, t3 / ;

> > parameters

> > L(t) Load for each

> > /t1 3

> > t2 5

> > t3 8/ ;

> > Scalar

> > Cost_diesel in â‚¬ per kWh / 2 /

> > Cost_pv in â‚¬ / 1.1 /

> >

> > VARIABLES

> > *L(t),

> > X_g Diesel generator,

> > X_pv Domestic PV generation ,

> > Z Total cost of grid operation in â‚¬ per kWh for on hour;

> >

> > EQUATIONS

> > Load_Balance Maintane a stable grid,

> > OBJ Objective equation total cost of grid operation in â‚¬ per kWh ;

> >

> > Load_balance.. X_g + X_pv -L(t) =E= 0 ;

> > 149 Uncontrolled set entered as constant

> > OBJ.. Z =E= (X_g*Cost_diesel) + (X_pv*Cost_pv);

> >

> > * Upper bounds

> > X_g.UP = 10 ;

> > X_pv.UP = 2 ;

> > * Lower bounds

> > X_g.lo = 0 ;

> > X_pv.lo = 0 ;

> > * Initial point

> > X_g.l = 0 ;

> > X_pv.l = 0 ;

> > * Load(s).l = 0 ;

> >

> > MODEL pflow / ALL / ;

> > OPTION LIMROW = 100;

> > OPTION LIMCOL = 100;

> >

> > loop(t, SOLVE pflow USING LP MINIMIZING Z) ;

> >

> > --

> > "gamsworld" group.

> > To unsubscribe from this group and stop receiving emails from it, send an

> > email to gamsworld+unsubscribe@googlegroups.com.

> > To post to this group, send email to gamsworld@googlegroups.com.

> > Visit this group at http://groups.google.com/group/gamsworld.

> > For more options, visit https://groups.google.com/d/optout.

### Re: Please help with a loop

Hi,

The problem with the equation is You have to enter constant here. You can do this by summing or specifying certain for example

1. Load_balance.. X_g + X_pv -sum(t,L(t)) =E= 0 ;

2. Load_balance.. X_g + X_pv -L('t1') =E= 0 ;

Otherwise GAMS dont know which element to select from the domain t until you specify function like sum,prod etc..

Regards

The problem with the equation is You have to enter constant here. You can do this by summing or specifying certain for example

1. Load_balance.. X_g + X_pv -sum(t,L(t)) =E= 0 ;

2. Load_balance.. X_g + X_pv -L('t1') =E= 0 ;

Otherwise GAMS dont know which element to select from the domain t until you specify function like sum,prod etc..

Regards