Changing the load will change the voltage angles, but not in arbitrary ways,
only within the sub-space of feasible power flow solutions. So, if you only
want to deal with changes in voltage angles that still satisfy the power flow
equations, then simply multiply the B_bus matrix from (3.27) in the manual by
your vector of voltage angle changes to get the changes in nodal injections
(loads). If you want to handle arbitrary voltage angle updates, I suspect you
may be approaching your problem from the wrong angle.
Ray
> On Mar 22, 2019, at 4:19 AM, Arkan Arkan <[email protected]> wrote:
>
> Dear Ray,
>
> As you mentioned previously there is no way to change the voltage angles to
> change the output cost. I am wondering is it possible to change the load
> values in the case file to get the desired change in voltage angles? For
> example, if PD is 60 MW, the correspondent voltage angle is -6.5. Now is it
> possible to change PD in such a way that the value of the phase angle will be
> -6.82 or -6.17 (5% decrease/increase). I mean changing PD and PQ in such a
> way that we get a specific amount of change in voltage angles (in the output
> of PF and OPF). I ask this because I need to know the output cost value based
> on defined values of voltage angles.
>
> If it is not possible, is there any other values in the case file which by
> changing them (input values) we could change the output phase angle value (a
> specific amount of decrease/increase). Overall, how could we do that by
> changing just the case file values?
>
> Thank you for your time and consideration.
>
> Kind regards,
> Arkan
>
> On Wed, Mar 20, 2019 at 11:18 PM Arkan Arkan <[email protected]
> <mailto:[email protected]>> wrote:
> Thank you very much for your help and time. I very much appreciate it.
>
> On Wed, Mar 20, 2019 at 11:02 PM Ray Zimmerman <[email protected]
> <mailto:[email protected]>> wrote:
> You cannot modify voltage angles independently and maintain feasibility
> (respect the power balance constraints). In order to maintain feasibility you
> must modify voltage angles and generator injections together along the
> surface of power flow solutions.
>
> If you modify the voltage angles along the power flow surface, that is, while
> maintaining feasibility, it will imply changes in generation which will
> result in changes in cost.
>
> Ray
>
>
>> On Mar 20, 2019, at 1:25 PM, Arkan Arkan <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>> I see. Thank you for your clarification. So, is there any trick and solution
>> to be able to change the output cost though manipulating the voltage angles?
>>
>> Thanks.
>>
>> On Wed, Mar 20, 2019 at 7:33 PM Ray Zimmerman <[email protected]
>> <mailto:[email protected]>> wrote:
>> Ok, so you just want to evaluate the objective (or cost) function of the DC
>> OPF at a given solution. The issue is that the cost function depends only on
>> the generator injections, which are related to the voltage angles through
>> the constraints. So if you take a DC PF solution and make changes to the
>> voltage angles, without changing the generator injections, the result will
>> be only infeasible power balance constraints with no change in the cost
>> function.
>>
>> Simply put, manipulating the voltage angles will affect feasibility, but not
>> cost.
>>
>> Ray
>>
>>
>>> On Mar 19, 2019, at 10:03 AM, Arkan Arkan <[email protected]
>>> <mailto:[email protected]>> wrote:
>>>
>>> Dear Ray,
>>>
>>> Thank you so much for your response. I very much appreciate it. What I mean
>>> is a little bit different. Based on my understanding, I exactly need DC
>>> for my work. This is my understanding. When we run "rundcopf", after some
>>> calculations, the phase angles are obtained and then fed into the OPF
>>> function which finally gives us the total cost and the whole process is
>>> done as a function. Now, after computing the phase angles through PF and
>>> before feeding into OPF function to calculate the cost, I need to somehow
>>> change the values of calculated phase angles a little bit so that the final
>>> cost will be based on the manipulated (my values) phase angles. I tried to
>>> change the values of phase angles in different steps of the function but
>>> wasn't effective and the final calculated cost is like before change.
>>> Please let me know your thoughts on this.
>>>
>>> Thanks.
>>>
>>> Kind regards,
>>> Arkan
>>>
>>> On Tue, Mar 19, 2019 at 6:21 PM Ray Zimmerman <[email protected]
>>> <mailto:[email protected]>> wrote:
>>> I’m not sure I understand what you want to do.
>>>
>>> Let’s start with the DC OPF. It sounds like you’re saying you need to run a
>>> DC OPF where you are directly specifying (constraining to a specific value)
>>> some of the voltage angles. Is that correct? The problem is that there are
>>> very few degrees of freedom in the voltage angles due to the power balance
>>> constraints. I suspect that manipulating (constraining) the voltage
>>> magnitudes directly will very quickly result in an infeasible OPF.
>>>
>>> But, you’re welcome to try. You can add user-defined linear constraints (A,
>>> l and u) to restrict the voltage angles. The first nb columns of A
>>> correspond to the voltage angles. See section 6.3 and Chapter 7 in the
>>> User’s Manual for more details. Simply use the VMIN and VMAX columns of the
>>> bus matrix to restrict voltage magnitudes.
>>>
>>> Ray
>>>
>>>
>>>
>>>
>>>> On Mar 19, 2019, at 8:26 AM, Arkan Arkan <[email protected]
>>>> <mailto:[email protected]>> wrote:
>>>>
>>>> Dear All,
>>>>
>>>> I hope this note finds you well. I need to run optimal power flow (both DC
>>>> and AC) while the input values for phase angles and voltage magnitudes are
>>>> manipulated. In other words, how could I run OPF with desired values of
>>>> phase angles and voltage magnitudes? I know that I should change the
>>>> values on the way and in the middle of code but I wasn't able to find the
>>>> right place in MATPOWER.
>>>>
>>>> I would be so grateful if you could, please, help me in this regard.
>>>>
>>>> Thank you for your time and consideration.
>>>>
>>>> Kind regards,
>>>> Arkan
>>>
>>
>
