add some safegueards for numerical issues in TDPF

CHANGELOG.rst

@@ -39,6 +39,7 @@ Change Log
 - [CHANGED] cim2pp: extracted getting default classes, added generic setting datatypes from CGMES XMI schema
 - [ADDED] function :code:`getOTDF` to obtain Outage Transfer Distribution Factors, that can be used to analyse outages using the DC approximation of the power system
 - [ADDED] function :code:`outage_results_OTDF` to obtain the matrix of results for all outage scenarios, with rows as outage scenarios and columns as branch power flows in that scenario
+- [FIXED] add some safeguards for TDPF to avoid numerical issues in some cases
 
 
 [2.13.1] - 2023-05-12

pandapower/pf/create_jacobian_tdpf.py

@@ -115,7 +115,7 @@
     2019, pp. 1-6, doi: 10.1109/EEEIC.2019.8783234.
     """
     t_rise_pu = a0 + a1 * i_square_pu + a2 * np.square(i_square_pu) - t_air_pu
-    r_theta_pu = t_rise_pu / p_loss_pu
+    r_theta_pu = t_rise_pu / np.where(p_loss_pu == 0, 1e-6, p_loss_pu)
     return r_theta_pu
 
 

pandapower/pypower/newtonpf.py

@@ -298,7 +298,8 @@
 
         if tdpf:
             # update the R, g, b for the tdpf_lines, and the Y-matrices
-            branch[tdpf_lines, BR_R] = r = r_ref_pu * (1 + alpha_pu * (T - t_ref_pu))
+            # here: limit the change of the R to reflect a realistic range of values for T to avoid numerical issues
+            branch[tdpf_lines, BR_R] = r = r_ref_pu * (1 + alpha_pu * np.clip(np.nan_to_num(T - t_ref_pu), -50, 250 / T_base))
             # todo expansion with SSC and VSC (that are not controllable)
             Ybus, Yf, Yt = makeYbus(baseMVA, bus, branch)
             g, b = calc_g_b(r, x)