improving stability and giving hints about possible problems

src/pandapipes/component_models/heat_consumer_component.py

@@ -8,9 +8,9 @@
 from pandapipes.component_models import (get_fluid, BranchWZeroLengthComponent, get_component_array,
                                          standard_branch_wo_internals_result_lookup)
 from pandapipes.component_models.junction_component import Junction
-from pandapipes.idx_branch import (MDOTINIT, QEXT, JAC_DERIV_DP1, JAC_DERIV_DM,
+from pandapipes.idx_branch import (MDOTINIT, QEXT, JAC_DERIV_DP1, JAC_DERIV_DM, FROM_NODE,
                                    JAC_DERIV_DP, LOAD_VEC_BRANCHES, TOUTINIT, JAC_DERIV_DT,
-                                   JAC_DERIV_DTOUT, LOAD_VEC_BRANCHES_T, ACTIVE, FLOW_RETURN_CONNECT)
+                                   JAC_DERIV_DTOUT, LOAD_VEC_BRANCHES_T, FLOW_RETURN_CONNECT)
 from pandapipes.idx_node import TINIT
 from pandapipes.pf.internals_toolbox import get_from_nodes_corrected
 from pandapipes.pf.pipeflow_setup import get_lookup
@@ -76,7 +76,18 @@ def create_pit_branch_entries(cls, net, branch_pit):
         mdot = net[cls.table_name()].controlled_mdot_kg_per_s.values
         hc_pit[~np.isnan(mdot), MDOTINIT] = mdot[~np.isnan(mdot)]
         treturn = net[cls.table_name()].treturn_k.values
-        hc_pit[~np.isnan(treturn), TOUTINIT] = treturn[~np.isnan(treturn)]
+        mask_tr = ~np.isnan(treturn)
+        if np.any(mask_tr):
+            node_pit = net["_pit"]["node"]
+            fn = hc_pit[:, FROM_NODE].astype(int)
+            mask_err = treturn + 15 >= node_pit[fn, TINIT]
+            if np.any(mask_err):
+                logger.warning(r'The initial temperature of the following heat consumers %s '
+                               r'are below or close to their controlled return temperature. '
+                               r'This might cause a pipeflow failure. '
+                               r'Please adapt the initial temperature accordingly.'
+                               % net.heat_consumer.loc[mask_tr & mask_err].index.tolist())
+        hc_pit[mask_tr, TOUTINIT] = treturn[mask_tr]
         hc_pit[:, FLOW_RETURN_CONNECT] = True
         mask_q0 = qext == 0 & np.isnan(mdot)
         if np.any(mask_q0):
@@ -169,7 +180,7 @@ def adaption_after_derivatives_hydraulic(cls, net, branch_pit, node_pit, idx_loo
             t_out = hc_pit[:, TOUTINIT]
 
             df_dm = - cp * (t_out - t_in)
-            mask_equal = t_out == t_in
+            mask_equal = t_out >= t_in
             mask_zero = hc_pit[:, QEXT] == 0
             mask_ign = mask_equal | mask_zero
             hc_pit[mask & mask_ign, MDOTINIT] = 0

src/pandapipes/pf/pipeflow_setup.py

@@ -795,7 +795,8 @@ def check_infeed_number(node_pit):
         node_pit[slack_nodes, INFEED] = True
     infeed_nodes = node_pit[:, INFEED]
     if np.sum(infeed_nodes) != np.sum(slack_nodes):
-        raise PipeflowNotConverged(r'The number of infeeding nodes and slacks do not match')
+        return False
+    return True
 
 
 class PipeflowNotConverged(ppException):

src/pandapipes/pipeflow.py

@@ -286,13 +286,15 @@ def solve_temperature(net):
     calculate_derivatives_thermal(net, branch_pit, node_pit, options)
     for comp in net['component_list']:
         comp.adaption_after_derivatives_thermal(net, branch_pit, node_pit, branch_lookups, options)
-    check_infeed_number(node_pit)
-
-    jacobian, epsilon = build_system_matrix(net, branch_pit, node_pit, True)
 
     t_init_old = node_pit[:, TINIT].copy()
     t_out_old = branch_pit[:, TOUTINIT].copy()
 
+    if not check_infeed_number(node_pit):
+        return [branch_pit[:, TOUTINIT], t_out_old, node_pit[:, TINIT], t_init_old], [np.nan]
+
+    jacobian, epsilon = build_system_matrix(net, branch_pit, node_pit, True)
+
     x = spsolve(jacobian, epsilon)
 
     node_pit[:, TINIT] -= x[:len(node_pit)] * options["alpha"]