Question about the add_start_vrvi!() function

[toddleif]

I’m a new PowerModelsDistribution.jl user, so my apologies if this is a basic question!

I’m trying to optimize a simple three-phase distribution network that includes a three-phase transformer. In my code, I’m running into an issue with the add_start_vrvi!() function to initialize the voltages on the transformer nodes. The issue seems to be replicated with the ut_trans_2w_yy.dss input file located in the PowerModelsDistribution.jl>test>data>opendss folder.

The code I wrote is:

const PMD = PowerModelsDistribution
data_eng = PMD.parse_file("string containing the location of ut_trans_2w_yy.dss on my computer”)
PMD.add_bus_absolute_vbounds!(data_eng, phase_lb_pu = 0.95, phase_ub_pu = 1.05, neutral_ub_pu = 0.1)
data_math_mn = PMD.transform_data_model(data_eng, multinetwork=true)
add_start_vrvi!(data_math_mn)
pm = instantiate_mc_model(data_math_mn, LPUBFDiagPowerModel, build_mn_mc_opf)

(I have additional code that adds an objective function and runs the optimization)

The issue happens when I run add_start_vrvi!(data_math_mn) to initialize the voltage values. I get the following error:

DimensionMismatch: arrays could not be broadcast to a common size; got a dimension with lengths 2 and 3

The error appears to be caused by line 107 in the initialization.jl file, which is part of the calc_start_voltage() function and is part of the code that initializes voltages for transformers.

Interestingly, the optimization solves when I remove the add_start_vrvi!(data_math_mn) line. Is it possible that add_start_vrvi!() is not applicable to three-phase networks with three-phase transformers? Is there another way I should be initializing the voltages?

[juanjospina]

Hi @toddleif,

I think the problem is that you are trying to solve a test case that is not 'Explicit Neutral' (en) and the default for the function add_start_vrvi!(data_math_mn) is to consider explicit neutrals (or treat the case as explicit neutral).

See:

PowerModelsDistribution.jl/src/data_model/transformations/initialization.jl

Lines 228 to 229 in 3014d49

	explicit_neutral=true
	)::Dict{String,Any}

I tried your case, using the following code instead:

add_start_voltage!(data_math_mn, coordinates=:rectangular; explicit_neutral=false)

and it seems to work fine. I am having issues running the add_start_vrvi!(data_math_mn) directly, that is why I used add_start_voltage instead. (This might be an issue).

Let me know if that works for you.

FYI: I did not validated the outputs, but the error disappeared.