Infeasible solution for Hydro Optimization Problem

Problems with syntax of GAMS
Post Reply
Posts: 1
Joined: 3 months ago

Infeasible solution for Hydro Optimization Problem

Post by priyamjain123 » 2 months ago

*Demo of Unit commitment
t time /1*12/
g plants
n maximum number of units /1*4/

Parameters Data (g,*), Demanddata (t,*), Availableunits (g,t);
$Call GDXXRW Demo.xlsx set=g RDim=1 rng=Data!a2:a4 par=Data RDim=1 CDim=1 rng=Data!a1:f20 par=Demanddata RDim=1 CDim=1 rng=Data!I1:K13 par=Availableunits RDim=1 CDim=1 rng=DC!A1:M4
$GDXIN Demo.gdx
$LOAD g Data Demanddata Availableunits

Energy (g) Total Energy of plant
Demand (t) Time block wise demand
Differential (t) Demand differential
totalnumberofunits (g) Total units in a plant
Plantcapacity (g) Capacity of plant
unitcapacity (g) Capacity of unit of a plant
P3 (g) Minimum generation limit
P4 (g) Maximum generation limit to maintain reserves
capacity (g,t,n) Capacity of all the units of a plant
P3capacity (g,t,n) P3 Capacity of all the units in a plant
P4capacity (g,t,n) P4 Capacity of all the units in a plant

*Parameter assignment

Energy(g) = Data (g, "Energy");
totalnumberofunits (g) = Data (g, "Totalunits");
unitcapacity (g) = Data (g, "Ucapacity");
Demand (t) = Demanddata (t, "Demand");
Differential (t) = Demanddata (t, "Differential");
Plantcapacity (g) = unitcapacity (g)*totalnumberofunits (g);
P3 (g) = Data (g, "P3");
P4 (g) = Data (g, "P4");

*Unit capacity, P3, P4 assignment

Loop (g,

loop ((n)$(ord(n) < totalnumberofunits (g)+1),
capacity (g,t,n) = unitcapacity (g);
P3capacity (g,t,n) = P3 (g);
P4capacity (g,t,n) = P4 (g);


display g, Energy, totalnumberofunits, Plantcapacity, unitcapacity, demand, Differential, capacity, availableunits;

positive variables
unitgeneration (g,t,n) Unit wise generation
plantgeneration (g,t) Plant wise generation

unitgeneration.lo(g,t,n) = 0;

Variable X


Energylim(g) Total energy
Plantgen (g,t) Plant Generation should be equal to sum of generation of all its units
Unitmaxgen(g,t,n) Unit maximum generation limit for units in service
Unit_outmaxgen(g,t,n) Unit maximum generation limit for units out of service
Unitmingen (g,t,n) Unit minimum



Unitmaxgen (g,t,n)$(ord(n)<availableunits(g,t)+1).. unitgeneration(g,t,n) =l= P4capacity (g,t,n);
Unit_outmaxgen (g,t,n)$(ord(n)>availableunits(g,t)).. unitgeneration(g,t,n) =e= 0;
Unitmingen (g,t,n)$(ord(n)<availableunits(g,t)+1).. unitgeneration(g,t,n) =g= P3capacity (g,t,n);
Plantgen(g,t).. plantgeneration (g,t) =e= sum (n, unitgeneration (g,t,n));
Energylim(g).. Sum(t, plantgeneration(g,t)) =e= Energy (g);
objfn.. X =e= Sum((g,t),plantgeneration(g,t)*demand(t)) + Sum((g,t),plantgeneration(g,t)*differential(t));
*objfn.. X =e= Sum((g,t),plantgeneration(g,t)*demand(t)) ;

Model POSOCO /All/;

Solve POSOCO using nlp maximizing X;

Display unitgeneration.l, plantgeneration.l;

Parameters TotalGeneration(t);

TotalGeneration(t) = Sum(g,plantgeneration.l(g,t));

EXECUTE_UNLOAD 'Summary', TotalGeneration;
EXECUTE 'GDXXRW Summary.gdx par=TotalGeneration rng=Output!A5 o=Demo.xlsx';
(13.89 KiB) Downloaded 7 times

User avatar
Site Admin
Site Admin
Posts: 11
Joined: 2 years ago

Re: Infeasible solution for Hydro Optimization Problem

Post by gamsadmin » 2 months ago


If you check your output, you will see that two of the energylim equations are limited.
You limit the total production by P4capacity, so there be at least enough capacity to produce energy(g).
However, There is no feasible solution because the maximum capacity is less than the demand

PS. Next time, please either attach your gams file or put the code between the code tags (use the "</>"-symbol to insert these tags).

Code: Select all

parameter check;

check(g) = sum((t,n), P4capacity(g,t,n)) - energy(g);
display check;

----     90 PARAMETER check  

G1   60.000,    G2 -120.000,    G3 -640.000

Post Reply