Power Flow Improvements

[ccoffrin]

Performance

• [x] eliminate memory allocation needed by inject in warm-start feature
• [ ] explore use of complex numbers in PowerFlowData struct
• [ ] can calc_admittance_matrix_inv be improved by using a @view?
• [ ] can injection_factors_va be improved by using a @view?

Scope

• [ ] a support DC lines as a fixed injection, similar to a PV bus?
• [ ] should storage be treated as a PV bus instead of PQ?
• [ ] topology processing to support switches?

[odow]

See https://github.com/lanl-ansi/PowerModels.jl/blob/685fbb260fe1a773aef2a89dc205e0525b42a030/src/core/admittance_matrix.jl#L187-L188

[odow]

@ccoffrin there are zero tests that hit calc_admittance_matrix_inv?

And if I do

using PowerModels
data = PowerModels.parse_file("../test/data/matpower/case24.m")
am = calc_admittance_matrix(data)

the admittance matrix is ComplexF64, so is am_inv = zeros(Float64 intentional?