# Re: Regarding assigning initial values for load flow analysis in NR method in runpf() function

```Beg your pardon the missing snippet from the previous mail is as follows:
```
```
%% initial state

%V0    = ones(size(bus, 1), 1);            %% flat start

V0  = bus(:, VM) .* exp(sqrt(-1) * pi/180 * bus(:, VA))

vcb = ones(size(V0));           %% create mask of voltage-controlled
buses

vcb(pq) = 0;                    %% exclude PQ buses

k = find(vcb(gbus));            %% in-service gens at v-c buses

V0(gbus(k)) = gen(on(k), VG) ./ abs(V0(gbus(k))).* V0(gbus(k));

*SAYANDEV GHOSH*
Assistant Professor
Electrical Engineering Department
Chaibasa Engineering College, Chaibasa, Jharkhand
Mob. No. - 7292880077 / 9748509620

On Tue, Aug 8, 2017 at 1:31 PM, Sayandev Ghosh <sayande...@gmail.com> wrote:

> Hello,
> I am Sayandev Ghosh, presently teaching power system in an undergraduate
> engineering college. I have done my M.Tech on Energy Science from Jadavpur
> University. I have been using MATPOWER for load flow analysis of till 118
> bus by Newton Raphson method. While doing that I am not able to understand
> the following area:-
>
>
>  In the runpf() function while using Newton Raphson method  the initial
> values of voltage magnitude and voltage angle have been assigned by the
> following lines (line 177 - 183):
>
>                               [image: Inline image 2]
>     I am having a bit problem in understanding this section. Why are we
> considering the final values of Voltage magnitude and Voltage angle as the
> initial guess? In the case files for eg. 'case57' the Vm and Va are
> probably the final voltage magnitudes and voltage angles.
>
> Shouldn't it be like assigning all the voltage magnitudes of PQ bus as 1.0
> pu and voltage angles of all PV and PQ bus as 0 degree for a flat start.
>
> Depending on the answer of this question I would like to convey my other
> doubts/questions.
>