fix docs issues (#349)

* fix powerflow

* update network switch

docs/src/perturbations.md

@@ -30,6 +30,12 @@ Triping one circuit can be modeled by doubling the impedance, i.e., dividing by
 new_yb = [0.0 - 10.0im 0.0 + 10.0im
           0.0 + 10.0im 0.0 - 10.0im]
 ```
+To apply a Network Switch, we require to use a sparse matrix, so we can do this by simply:
+
+```julia
+using SparseArrays
+new_yb = sparse(new_yb)
+```
 
 Then, this perturbation ocurring at ``t = 1.0`` seconds can be included as:
 ```julia
@@ -47,6 +53,7 @@ new_yb2 = [10000.0 - 20.0im  0.0 + 20.0im
 Then, this perturbation ocurring at ``t = 1.0`` seconds can be included as:
 
 ```julia
+new_yb2 = sparse(new_yb2)
 ns2 = NetworkSwitch(1.0, new_yb2)
 ```
 
@@ -60,6 +67,7 @@ new_yb3 = [0.0 - 10.0im 0.0 + 10.0im
 and the perturbation as:
 
 ```julia
+new_yb3 = sparse(new_yb3)
 ns3 = NetworkSwitch(1.05, new_yb3)
 ```
 

docs/src/tutorials/tutorial_inverter_modeling.md

@@ -146,7 +146,7 @@ add_component!(sys, storage)
 A good sanity check it running a power flow on the system to make sure all the components are properly scaled and that the system is properly balanced. We can use `PowerSystems` to perform this check. We can get the results back and perform a sanity check.
 
 ```@repl inv_sys
-res = run_powerflow(sys)
+res = solve_powerflow(ACPowerFlow(), sys)
 res["bus_results"]
 ```