Hi there, I have some generator data- LV MVAr Limit: Lag = 409, Lead = -187. Is this the data which would go in columns 4 and 5 generator input?
thanks, shane. Quoting Ray Zimmerman <[email protected]>: > That is the correct field to enter the generation info. But, if bus 1 > is set as the slack bus, the entered value for gen 1 will be ignored > and replaced by the computed value (equal to load minus losses minus > sum of other generation). If you want to specify the generation at > bus 1 and allow one of the other generators to be the slack, just > change the type of bus 1 to 2 and change one of the other generator > buses to type 3. > > Hope this helps, > > Ray > > On Mar 23, 2007, at 11:37 AM, [email protected] wrote: > > > > > Ray, > > > > Yes that makes sense to me, but i'm till struggling with the idea > > of this > > 'slack' for the real power, because if the generator info is not > > entered in that > > field then how does MATPOWER know the generator output? > > > > thanks. > > > > shane. > > > > > > > > > > > > > > > > > > > > > > > > Quoting Ray Zimmerman <[email protected]>: > > > >> On Mar 22, 2007, at 4:32 PM, Prof. Jose Roberto Camacho wrote: > >> > >>> I didn't have the case9 here, but running a power-flow (a non- > >>> linear set of equations) you can > >>> leave your power generation at zero (active and reactive) in the > >>> slack bus (reference bus), in > >>> matpower you can have more than one. As an iterative process, on a > >>> slack bus (reference > >>> bus) you specify voltage (1 pu) and angle (zero), generator active > >>> and reactive powers in the > >>> slack bus will be function of the voltages obtained in other bars > >>> and the losses. In agreement > >>> with all the equations of your non-linear system describing the > >>> system. > >>> > >>> Run your case9 model, and look if the powers remains the same after > >>> convergence (at the > >>> end of the routine). > >> > >> Just one small additional clarification. There are two separate > >> concepts here that are often combined, and in fact they are combined > >> in the MATPOWER implementation of the power flow. > >> > >> (1) Voltage angle reference bus -- Since the power flow equations > >> essentially only deal with angle differences, a single arbitrary > >> reference is necessary in each "island" in the network to uniquely > >> solve for the remaining voltage angles. Normally, you would only want > >> to specify more than one angle reference if you have multiple > >> unconnected islands. > >> > >> (2) Real power slack -- When computing the power flow for an N-bus > >> system, where Q is specified at all load buses and V is specified at > >> the remaining buses and a reference angle is specified at the > >> reference bus, specifying P at every bus would leave us with 2N > >> equations [a] and 2N-1 unknowns [b]. A simple approach to solve this > >> is to allow P at a single bus to be a variable that takes up the > >> "slack". Conceptually, this could be any generator bus. I does not > >> have to be the same bus used for (1). It is also possible to allow P > >> to be free at multiple buses if we include additional equations > >> defining how the slack is to be distributed. Again this is > >> independent of (1). > >> > >> One more point, an optimal power flow formulation needs (1) but not > >> (2), and in MATPOWER's implementation the reference bus is exactly > >> that. The power flow problem, on the other hand needs both (1) and > >> (2), and in the MATPOWER implementation the reference bus serves as > >> both. > >> > >> > >> [a] P and Q balance at each bus > >> [b] V at load buses, Q at remaining buses and angle at all buses > >> except the reference > >> > >> > >> -- > >> Ray Zimmerman > >> Senior Research Associate > >> 428-B Phillips Hall, Cornell University, Ithaca, NY 14853 > >> phone: (607) 255-9645 > >> > >> > >> > >> > >> > > > > > > > > > > > > >
