Re: Different results with MATPOWER and PSAT

[Jose Luis Marin]

I'll add my 2 cents. I don't know PSAT, but I can attest to the difficulty
in reproducing exactly the same powerflow solution in two different
software tools, in general.  First you have to find out how many features
are implemented and enabled/disabled in each tool; but more importantly,
you have to know the internals of how certain devices are modeled.

Here's a number of things to check:

   - Implemented in MATPOWER:
  - VAR limits in PV.  As Shruti points out, different algorithms for
  bus-type switching do indeed yield different solutions (few
people realize
  that, in general, limits may induce multiple possible solutions; and I'm
  not talking about low-voltage solutions here)
  - the modeling of transformers and phase-shifters (yes, there could
  be differences even here!)
  - the modeling of HV DC links
  - Not implemented in MATPOWER but typically implemented in other
   tools:
  - "Jumpers" (i.e. fusing buses connected by branches with very low
  impedance)
  - Automatic transformer taps (OLTC), regulating either voltage or
  MVAR flow.  Discretized vs. continuous change.
  - Automatic switched shunts. Discretized vs. continuous change.
  - Generators, transformers, and shunts regulating remote V-setpoints
  - Automatic inter-area exchange constraints
  - Simulation of primary regulation ("governor" powerflow)
  - ... and many others I'm probably forgetting about


For instance, we have been able to replicate MATPOWER's results with our
in-house powerflow, but we could only get the two solutions to agree to
very high precision after we realized that MATPOWER's basic model for the
transformer is slightly different to the one given in most textbooks. The
differences are not big, but they do affect the behavior of the tap changer
in the admittance matrix (I can provide the details, it has to do with the
location of the tap with respect to the Bshunt parameters).  Once we
adopted the same internal models, the solution matched to full precision.

Hope it helps,

-- 
Jose L. Marin
Gridquant España SL
Grupo AIA


On Fri, Nov 20, 2015 at 7:37 AM, Shruti Rao  wrote:

> If the system parameters are the same, it could be because the tolerance
> levels that were set for the different software were different i.e. the
> default power balance mismatch tolerances are not always the same in all
> software. Also probably if the VAR limits are active for PV buses,
> different software often have slightly different algorithms for bus-type
> switching and that could affect the solution maybe? Hope this helps.
>
> Shruti
>
> On Thu, Nov 19, 2015 at 9:12 PM, Yogess H Singh 
> wrote:
>
>> Dear Fellow Member,
>>
>> I ran load flow analysis on a IEEE-14 bus system using MATPOWER, PSAT and
>> PowerWorld. Voltage magnitudes as well as phases have slightly different
>> values in all three tools. However, the difference is not much but I want
>> to know what causes difference among results obtained with different
>> software tool even if all the parameters are exactly same?
>>
>>
>> Best Regards,
>>
>> *Yogesh Kumar*
>> *Graduate Research Assistant*
>> *NE 2042, EECS Department*
>> *University of Toledo, OH 43507*
>> *+1 (419)530-8295 <%2B1%20%28419%29450-2217>*
>>
>
>
>
> --
> Regards,
> Shruti Dwarkanath Rao
>
> Graduate Research Assistant, Arizona State University
> Vice Chair: IEEE PES ASU Student Chapter
> Tempe, AZ, 85281
> 650 996 0116
>

Re: Different results with MATPOWER and PSAT

[Yogess H Singh]

Shruti and Jose,

Thank you so much, that helped a lot.




Best Regards,

*Yogesh Kumar*
*Graduate Research Assistant*
*NE 2042, EECS Department*
*University of Toledo, OH 43507*
*+1 (419)530-8295 <%2B1%20%28419%29450-2217>*

On Fri, Nov 20, 2015 at 11:37 AM, Jose Luis Marin 
wrote:

>
> I'll add my 2 cents. I don't know PSAT, but I can attest to the difficulty
> in reproducing exactly the same powerflow solution in two different
> software tools, in general.  First you have to find out how many features
> are implemented and enabled/disabled in each tool; but more importantly,
> you have to know the internals of how certain devices are modeled.
>
> Here's a number of things to check:
>
>- Implemented in MATPOWER:
>   - VAR limits in PV.  As Shruti points out, different algorithms for
>   bus-type switching do indeed yield different solutions (few people 
> realize
>   that, in general, limits may induce multiple possible solutions; and I'm
>   not talking about low-voltage solutions here)
>   - the modeling of transformers and phase-shifters (yes, there could
>   be differences even here!)
>   - the modeling of HV DC links
>   - Not implemented in MATPOWER but typically implemented in other
>tools:
>   - "Jumpers" (i.e. fusing buses connected by branches with very low
>   impedance)
>   - Automatic transformer taps (OLTC), regulating either voltage or
>   MVAR flow.  Discretized vs. continuous change.
>   - Automatic switched shunts. Discretized vs. continuous change.
>   - Generators, transformers, and shunts regulating remote V-setpoints
>   - Automatic inter-area exchange constraints
>   - Simulation of primary regulation ("governor" powerflow)
>   - ... and many others I'm probably forgetting about
>
>
> For instance, we have been able to replicate MATPOWER's results with our
> in-house powerflow, but we could only get the two solutions to agree to
> very high precision after we realized that MATPOWER's basic model for the
> transformer is slightly different to the one given in most textbooks. The
> differences are not big, but they do affect the behavior of the tap changer
> in the admittance matrix (I can provide the details, it has to do with the
> location of the tap with respect to the Bshunt parameters).  Once we
> adopted the same internal models, the solution matched to full precision.
>
> Hope it helps,
>
> --
> Jose L. Marin
> Gridquant España SL
> Grupo AIA
>
>
>
> On Fri, Nov 20, 2015 at 7:37 AM, Shruti Rao  wrote:
>
>> If the system parameters are the same, it could be because the tolerance
>> levels that were set for the different software were different i.e. the
>> default power balance mismatch tolerances are not always the same in all
>> software. Also probably if the VAR limits are active for PV buses,
>> different software often have slightly different algorithms for bus-type
>> switching and that could affect the solution maybe? Hope this helps.
>>
>> Shruti
>>
>> On Thu, Nov 19, 2015 at 9:12 PM, Yogess H Singh 
>> wrote:
>>
>>> Dear Fellow Member,
>>>
>>> I ran load flow analysis on a IEEE-14 bus system using MATPOWER, PSAT
>>> and PowerWorld. Voltage magnitudes as well as phases have slightly
>>> different values in all three tools. However, the difference is not much
>>> but I want to know what causes difference among results obtained with
>>> different software tool even if all the parameters are exactly same?
>>>
>>>
>>> Best Regards,
>>>
>>> *Yogesh Kumar*
>>> *Graduate Research Assistant*
>>> *NE 2042, EECS Department*
>>> *University of Toledo, OH 43507*
>>> *+1 (419)530-8295 <%2B1%20%28419%29450-2217>*
>>>
>>
>>
>>
>> --
>> Regards,
>> Shruti Dwarkanath Rao
>>
>> Graduate Research Assistant, Arizona State University
>> Vice Chair: IEEE PES ASU Student Chapter
>> Tempe, AZ, 85281
>> 650 996 0116
>>
>
>

Different results with MATPOWER and PSAT

[Yogess H Singh]

Dear Fellow Member,

I ran load flow analysis on a IEEE-14 bus system using MATPOWER, PSAT and
PowerWorld. Voltage magnitudes as well as phases have slightly different
values in all three tools. However, the difference is not much but I want
to know what causes difference among results obtained with different
software tool even if all the parameters are exactly same?


Best Regards,

*Yogesh Kumar*
*Graduate Research Assistant*
*NE 2042, EECS Department*
*University of Toledo, OH 43507*
*+1 (419)530-8295 <%2B1%20%28419%29450-2217>*

Re: Different results with MATPOWER and PSAT

[Shruti Rao]

If the system parameters are the same, it could be because the tolerance
levels that were set for the different software were different i.e. the
default power balance mismatch tolerances are not always the same in all
software. Also probably if the VAR limits are active for PV buses,
different software often have slightly different algorithms for bus-type
switching and that could affect the solution maybe? Hope this helps.

Shruti

On Thu, Nov 19, 2015 at 9:12 PM, Yogess H Singh  wrote:

> Dear Fellow Member,
>
> I ran load flow analysis on a IEEE-14 bus system using MATPOWER, PSAT and
> PowerWorld. Voltage magnitudes as well as phases have slightly different
> values in all three tools. However, the difference is not much but I want
> to know what causes difference among results obtained with different
> software tool even if all the parameters are exactly same?
>
>
> Best Regards,
>
> *Yogesh Kumar*
> *Graduate Research Assistant*
> *NE 2042, EECS Department*
> *University of Toledo, OH 43507*
> *+1 (419)530-8295 <%2B1%20%28419%29450-2217>*
>



-- 
Regards,
Shruti Dwarkanath Rao

Graduate Research Assistant, Arizona State University
Vice Chair: IEEE PES ASU Student Chapter
Tempe, AZ, 85281
650 996 0116