3 Phase unbalanced PQ load

I am trying to model 3ph unbalanced constant PQ load. Constant PQ load can be modeled using dynamic load and there is 3ph dynamic load in Simpower system, it is just not unbalanced. I have used 3 1ph dynamic load and connected them in Wye but the system does not converge.

It would be helpful if anyone can direct me in right direction?

Answer 1

[Shashank]

Hi Pawan...I am trying to do exactly the same thing. What i have done so far---used 3 nos 3 phase dynamic load models with all constants set to zero so that it works as constant PQ (I used matlab 2009b which does not have 1 phase dynamic load block). Each DL block for me is one phase of the unbalanced 3 phase system-----hence P1 = total power of 1st phase and same for other 2 blocks....then i have connected the measuerement output of dynamic load blocks to a demux---used a divide block to create P/V----used this as input signal to a controlled current source----and then connected these 3 controlled current sources in wye. created a subsystem out of it...but connected only the 1st input terminals of each block to the corresponding phase. Please find a .mdl file..it is running the simulation in my ieee 13 node feeder model but is not showing required characteristics...see and tell.

Answer 2

[Shashank]

PFA a const PQ block...plz try to connect 3 such in star but please add high parallel R across the 3 current sources...

[Rubron]

Hi Shashank, but by connecting the resistance in parallel, they are consuming power, from what the power they absorb are additional to the power set point of each PQ block (single phase load block).

Answer 3

[Craig Breaden]

Hi

I'm also looking at modelling the IEEE 13 Node feeder. Out of curiosity, what did you use as RG60 (the regulator)?

[Shashank]

Hi Craig!

If the question is for me, then let me tell you that the voltage regulator has not been modeled in the feeder since repeated attempts to model it have not yielded results. Since i am connecting a PV inverter at one point, i can assume that the inverter characteristics can cause problems to the static controls of the regulator like reverse-power flow etc. which confuses the regulator. I have tried using 3 phase auto transformer block and used node 671 voltages (measured by a 3 phase VI block) as the regulating reference voltages but the problem is modeling the line drop compensator if you want to externally control the auto transformer controls. So i have attached the ieee 13 node model only without the RG 60 block. Also the PQ load model blocks are changed from above answer. They are inspired from: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6038989&queryText%3DModeling+of+a+Small+Distribution+Grid+with+Intermittent+Energy+Resources+Using+MATLAB%2FSIMULINK and http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=5762948&queryText%3DMafra+STATCOM.

Please see and tell. Please use in discrete mode with 5e-5 sample time

Answer 4

[Hasan Ismaiel]

Dear, I have the same question, if you have any information please tell me. I need to program unbalanced load flow but I don't know how!

[Pawan]

For unbalanced load use the single phase dynamic load from the Matlab example and then connect the single phase load in delta or Wye configuration. These loads can also be configured as any ZIP load.

[Rubron]

Hi Pawan, but connecting the 3 single phase dynamic loads in Wye, the system does not converge. Have you found a solution to that? Help please!