(1) It depends what you mean by reasonable. Yes, this a perfectly reasonable (i.e. correct) answer to this power flow problem. No, it is not reasonable to operate this power system at this set-point, other generator set-points should be reduced to make it feasible.
(2) Again, it depends what you mean. What the result says, is that given that network, under that loading condition, with those generator set-points, you would need about 3 MW of load at that bus to achieve power balance. (3) You should not expect flows to increase uniformly throughout the system as you scale loads at all buses and generation only at the slack bus. Some may increase, some may decrease, some may even switch direction. -- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Feb 28, 2013, at 10:02 AM, TANG Difei <[email protected]> wrote: > Dear all, > > I ran 'results=runpf('case24_ieee_rts')' and found that > results.gen(12,2)==-2.9536 MW, which means the real power slack bus (Bus 13) > is a negative value. > (1) Is that result reasonable? > (2) Can the slack bus with negative PG be looked as a load? > By checking the previous thread, I knew that PG of slack bus = all loads + > all losses - all other generator real power outputs > > In my opinion, it is not reasonable. For example, I used function > 'scale_load' to scale all the real and reactive loads from 10% to 100% of > original value (I did not scale the generator output), by using > > mpc = loadcase('case24_ieee_rts'); > for i = 1 : 10 > multiple = i/10; > mpc_m(i) = mpc; > mpc_m(i).bus = scale_load(multiple, mpc_m(i).bus); > [results_m(i), success_m(i)] = runpf(mpc_m(i)); > end > > Then, I found that, for example, in the scenario of the multiple value from > 0.1 to 1, the real power injected at "to" bus end (PT) of Branch 1 is > reduced from 25.2679 MW to 11.9363 MW, and the PG of slack increase from > -2322 MW to -2.9536 MW , which is not reasonable, because with the loads > increase from 0.1 to 1, the power of each branch will increase too. > (3) Am I correct? > > Any advice from anyone will be very much appreciated. > > > Best wishes, > Difei Tang
