I want to add a 10MW generator to bus 7

[iman]

Dear All,

I have a quick question about MATPOWER.

>From MATPOWER documentation we know if  we want to load the 30-bus system
data from case30.m,increase its real power demand at bus 2 to 30 MW, then
run an AC optimal power flow with default options, this could be
accomplished as follows:

>> define_constants;
>> mpc = loadcase('case30');
>> mpc.bus(2, PD) = 30;
>> runopf(mpc);

Now I want to add a 10MW generator to bus 7 and run pf (not opf) for 14 bus
system so I write:

>> define_constants;
>> mpc = loadcase('case14');
>> mpc.gen (7, PG) = 10;              //add 10MW to bus 7
>>mpc.bus (7, BUS_TYPE) = 2;    // changes the type of bus 7 to PV
>> runpf(mpc);

but I recieve this error:

??? Subscript indices must either be real positive integers or logicals.

Error in ==> ext2int at 230
            gs = ( mpc.gen(:, GEN_STATUS) > 0 & ... %% gen status

Error in ==> runpf at 131
mpc = ext2int(mpc);

Do u know what is wrong with my code?

Thanks