Check if circuit has twoport for loop and nodal analysis

doc/circuits.rst

@@ -245,8 +245,9 @@ of an ideal resistor and a noise voltage source using the
 Mesh analysis
 -------------
 
-Lcapy can output the mesh equations by applying Kirchhoff's voltage
-law around each loop in a circuit.  For example, consider the netlist:
+Lcapy can output the mesh equations for a planar circuit by applying
+Kirchhoff's voltage law around each loop in the circuit.  For example,
+consider the netlist:
 
    >>> cct = Circuit("""
    ...V1 1 0; down
@@ -323,6 +324,10 @@ The mesh currents can be found with the `solve_laplace()` method.
 This solves the circuit using Laplace transform methods and returns a
 dictionary of results.
 
+The mesh analysis implementation does not support twoport components,
+such as transformers and gyrators.
+
+
 .. _nodal-analysis:
 
 Nodal analysis
@@ -433,6 +438,8 @@ The node voltages can be found with the `solve_laplace()` method.
 This solves the circuit using Laplace transform methods and returns a
 dictionary of results.
 
+The nodal analysis implementation does not support twoport components,
+such as transformers and gyrators.  Instead use modified nodal analysis.
 
 .. _modified-nodal-analysis:
 

lcapy/analysis.py

@@ -1,7 +1,7 @@
 """
 This module collects information about a circuit.
 
-Copyright 2022--203 Michael Hayes, UCECE
+Copyright 2022--2024 Michael Hayes, UCECE
 
 """
 

lcapy/circuitgraph.py

@@ -83,6 +83,11 @@ class CircuitGraph(object):
     @classmethod
     def from_circuit(cls, cct):
 
+        if cct.twoports != []:
+            raise ValueError('Cannot create CircuitGraph with twoport components: ' + ', '.join(cct.twoports))
+            # Perhaps could split twoports into an input oneport and an
+            # output oneport?
+
         G = nx.Graph()
 
         dummy = 0

lcapy/components.py

@@ -18,6 +18,7 @@ def __init__(self, cct):
         self.open_circuits = []
         self.ports = []
         self.transformers = []
+        self.twoports = []
         self.voltage_sources = []
         self.wires = []
 
@@ -44,6 +45,12 @@ def __init__(self, cct):
             elif elt.is_wire:
                 self.wires.append(eltname)
 
+            # Note, this includes all twoport components (TP, TF, GY,
+            # etc) and not just TP.
+            if elt.is_twoport:
+                self.twoports.append(eltname)
+
+
     def __repr__(self):
 
         return str(vars(self))

lcapy/loopanalysis.py

@@ -16,7 +16,8 @@
 
 class LoopAnalysis(object):
     """This performs for loop analysis.  Currently, it uses mesh analysis
-    and so is only applicable to circuits with a planar topology.
+    and so is only applicable to circuits with a planar topology and
+    without twoport components.
 
     The API is likely to change since different invocations find
     different current loops.
@@ -51,6 +52,14 @@ class LoopAnalysis(object):
 
     """
 
+    # twoport components could be handled by splitting into
+    # input and output oneports.  In the case of an ideal transformer,
+    # an unknown voltage across the primary could be added to the mesh
+    # equations.  The voltage across the secondary is the primary voltage
+    # multiplied by N2 / N1.  An auxiliary equation is required
+    # relating the mesh currents in the primary and secondary loops:
+    # ib = -N1 / N2 ia.
+
     @classmethod
     def from_circuit(cls, cct):
 

lcapy/mnacpts.py

@@ -610,14 +610,14 @@ def is_capacitor(self):
 
     @property
     def is_oneport(self):
-        """Return True if component is a oneport."""
+        """Return True if component is any oneport (R, C, L, V, I, etc.)."""
 
         from .oneport import OnePort
         return isinstance(self.cpt, OnePort)
 
     @property
     def is_twoport(self):
-        """Return True if component is a twoport."""
+        """Return True if component is any twoport (TP, TF, GY, etc.)."""
 
         from .twoport import TwoPort
         return isinstance(self.cpt, TwoPort)

lcapy/netlistmixin.py

@@ -87,10 +87,18 @@ def analysis(self):
     @cached_property
     def branch_list(self):
         """Determine list of names of branch elements, e.g.,
-        ['C1', 'V1', 'R1', 'R2']."""
+        ['C1', 'V1', 'R1', 'R2'].
+
+        Two-port components (TF, GY, TP) are ignored.   Perhaps
+        they could be split into input and output one-ports?
+        """
 
         branch_list = []
         for key, elt in self.elements.items():
+            if elt.is_twoport:
+                warn('Ignoring twoport component ' + key)
+                continue
+
             if elt.type not in ('W', 'O', 'P', 'K', 'XX'):
                 branch_list.append(elt.name)
         return branch_list
@@ -418,6 +426,12 @@ def transformers(self):
 
         return self.components.transformers
 
+    @property
+    def twoports(self):
+        """Return list of twoports."""
+
+        return self.components.twoports
+
     @property
     def voltage_sources(self):
         """Return list of voltage_sources."""