Hi Ray, thanks for your input, however, the question remains
unaddressed. We are not seeing only the system summary as the values are
rounded. We must compare those values with the ones found "by hand" via
branches and buses. We have some questions below.
Using the formula you described, and based only on the system summary
report, everything goes well:
*Active* | Generation + Shunt_Inj = Loads + Losses
| 5.4 – 0.1 = 4.900 + 0.39
*Reactive *| Generation + Shunt_Inj + Transf_Inj = Loads + Losses | -4.3
+ 3.6 + 2.3 = /0.036/ + 1.56
(reactive load added by hand - the summary was rounding it to 0)
However, when analyzing it "by hand" via *powerflow.bus*, we are not
understanding the differences:
get_losses gives us the active and reactive losses via
*Active Losses* /sum(abs(real(losses)))/ 0.3894
/sum(real(losses))/ 0.3894
*Reactive Losses* /sum(abs(imag(losses)))/ 1.5598
/sum(imag(losses))/ 1.5598
powerflow.gen gives us the Generation (both Active and Reactive)
powerflow.bus gives us the Loads and Shunts
*Active Generation* /powerflow.gen(1,2)/ 5.3664
*Reactive Generation* /powerflow.gen(1,3)/ -4.3127
*Active Shunts* /sum(powerflow.bus(:,5))/ 0.0865
*Reactive Shunts* /sum(powerflow.bus(:,6))/ 4.3080
*Active Loads* /sum(powerflow.bus(:,3))/ 4.8820
*Reactive Loads*** /sum(powerflow.bus(:,4))/ 0.0360
When comparing this values with the system summary, the shunts values
are different, _*why?*_
*System Summary* *sum in powerflow.bus*
*Active Shunts* -0.1 0.0865
*Reactive Shunts* 3.6 4.3080
*Active* | Generation + Shunt_Inj = Loads + Losses | 5.3664 +
0.0865 = 4.8820 + Act_Losses | *Act_Losses = 0.5709 != **0.3894 (Why?)
*
*Active**_Alt *| Generation + Shunt_Inj = Loads + Losses | 5.3664 -
0.0865 = 4.8820 + Act_Losses |*Act_Losses = 0.3979 **!=**0.3894 *
**(Why?)**
*Reactive *| Generation + Shunt_Inj + Transf_Inj = Loads + Losses |
-4.3127 + 4.3080 + ? = 0.0360 + React_Losses | *Is it possible **to
check the Transf_Inj Manually?*
---------------
Also, when summing the branches PF/PT and QF/QT, the results are
inconsistent:
PF+PT = sum(powerflow.branch(:,14))+sum(powerflow.branch(:,16)) = 0.3894
= active_losses_by_get_losses
QF+QT = sum(powerflow.branch(:,15))+sum(powerflow.branch(:,17)) =
-0.7085 != reactive_losses_by_get_losses
INESC TEC
*José Paulos*
Centro de Sistemas de Energia
Centre for Power and Energy Systems
*INESC TEC*
Campus da FEUP
Rua Dr Roberto Frias
4200-465 Porto
Portugal
T +351 91 424 1519
F +351 22 209 4050
[email protected] <mailto:[email protected]>
www.inesctec.pt <http://www.inesctec.pt>
On 10-Dec-18 17:04, Ray Zimmerman wrote:
The shunts are not included in the loss numbers, so everything does
add up.
Generation = 5.4 MW
Loads = 4.9 MW
Losses = 0.4 MW
Shunt Inj = –0.1 MW
Generation + Shunt Inj = Loads + Losses
5.4 – 0.1 = 4.9 + 0.4
Ray
On Nov 29, 2018, at 10:06 AM, José Paulos <[email protected]
<mailto:[email protected]>> wrote:
Hi Ray, thanks for your input.
In fact, we weren't considering that. However:
When analyzing the case_info we get:
Shunt Injections
active (MW) -0.1
reactive (MVAr) 3.6
I'm assuming that those are simplified values, but in our network, we
have:
Sum of the GS Shunt Conductances = *0.0865 MW*
Difference between calculated losses vs. get_losses = *0.095 MW
*(that were supposedly due to the missing GS values)
Resulting a difference of *0.0085 MW *(even this is different from
the *-0.1 MW* active shunt injections).
INESC TEC
*José Paulos*
Centro de Sistemas de Energia
Centre for Power and Energy Systems
*INESC TEC*
Campus da FEUP
Rua Dr Roberto Frias
4200-465 Porto
Portugal
T +351 91 424 1519
F +351 22 209 4050
[email protected] <mailto:[email protected]>
www.inesctec.pt <http://www.inesctec.pt/>
On 27-Nov-18 20:03, Ray Zimmerman wrote:
You are missing contribution of the shunt elements defined in the GS
and BS columns of the bus matrix. These also contribute to the
overall power balance. Have a look at …
case_info(powerflow)
… after running your test_file.
Ray
On Nov 27, 2018, at 11:53 AM, José Paulos <[email protected]
<mailto:[email protected]>> wrote:
Hi,
We have a network with the following configuration:
*%% system MVA base*
mpc.baseMVA = 100;
*%% system voltage levels (kV)*
mpc.V_levels = [
0.4 15.0 30.0 60.0
];
*%% system summary*
% number of buses: 41 (1 REF | 1 PV)
% number of branches: 41 (8 transformers)
% number of loads: 21 (including Pd/Qd = 0)
% number of generators: 2
% number of capacitors: 2
We use get_lossses, in this case:
%%% *compute the losses*
losses = get_losses(powerflow);
%%% *the active losses*
active_losses = sum(abs(real(losses)));
The balance between the injected active power and the Loads/Gen's
is not equal to the result of the get_lossses procedure described.
Follows attached the case (run test_file.m with test_network.mat in
the same dir)
Thanks in advance,
--
INESC TEC
*José Paulos*
Centro de Sistemas de Energia
Centre for Power and Energy Systems
*INESC TEC*
Campus da FEUP
Rua Dr Roberto Frias
4200-465 Porto
Portugal
T +351 91 424 1519
F +351 22 209 4050
[email protected] <mailto:[email protected]>
www.inesctec.pt <http://www.inesctec.pt/>
<test_file.m><test_network.mat>
