Add tests

Author: YingboMa

Diff for: examples/electrical_components.jl

@@ -66,3 +66,41 @@ function Inductor(; name, L = 1.0)
           ]
     extend(ODESystem(eqs, t, [], ps; name=name), oneport)
 end
+
+@connector function HeatPort(;name)
+    @variables T(t)=293.15 Q_flow(t)=0.0 [connect = Flow]
+    ODESystem(Equation[], t, [T, Q_flow], [], name=name)
+end
+
+function HeatingResistor(;name, R=1.0, TAmbient=293.15, alpha=1.0)
+    @named p = Pin()
+    @named n = Pin()
+    @named h = HeatPort()
+    @variables v(t) RTherm(t)
+    @parameters R=R TAmbient=TAmbient alpha=alpha
+    eqs = [
+           RTherm ~ R*(1 + alpha*(h.T - TAmbient))
+           v ~ p.i * RTherm
+           h.Q_flow ~ -v * p.i # -LossPower
+           v ~ p.v - n.v
+           0 ~ p.i + n.i
+          ]
+    compose(ODESystem(
+        eqs, t, [v, RTherm], [R, TAmbient, alpha],
+        name=name,
+    ), p, n, h)
+end
+
+function HeatCapacitor(;name, rho=8050, V=1, cp=460, TAmbient=293.15)
+    @parameters rho=rho V=V cp=cp
+    C = rho*V*cp
+    @named h = HeatPort()
+    D = Differential(t)
+    eqs = [
+           D(h.T) ~ h.Q_flow / C
+          ]
+    compose(ODESystem(
+        eqs, t, [], [rho, V, cp],
+        name=name,
+    ), h)
+end

Diff for: src/structural_transformation/StructuralTransformations.jl

@@ -45,6 +45,7 @@ export sorted_incidence_matrix, pantelides!, tearing_reassemble, find_solvables!
 export tearing_assignments, tearing_substitution
 export torn_system_jacobian_sparsity
 export full_equations
+export but_ordered_incidence, lowest_order_variable_mask, highest_order_variable_mask
 
 include("utils.jl")
 include("pantelides.jl")

Diff for: test/components.jl

@@ -211,3 +211,22 @@ end
 
 @named foo = Circuit()
 @test structural_simplify(foo) isa ModelingToolkit.AbstractSystem
+
+# BLT tests
+V = 2.0
+@named source = ConstantVoltage(V=V)
+@named ground = Ground()
+N = 50
+Rs = 10 .^range(0, stop=-4, length=N)
+Cs = 10 .^range(-3, stop=0, length=N)
+rc_systems = map(1:N) do i
+    parallel_rc_model(i; name=:rc, source=source, ground=ground, R=Rs[i], C=Cs[i])
+end;
+@variables E(t)=0.0
+eqs = [
+       D(E) ~ sum(((i, sys),)->getproperty(sys, Symbol(:resistor, i)).h.Q_flow, enumerate(rc_systems))
+      ]
+@named _big_rc = ODESystem(eqs, t, [E], [])
+@named big_rc = compose(_big_rc, rc_systems)
+ts = TearingState(expand_connections(big_rc))
+@test istriu(but_ordered_incidence(ts)[1])