Fix SA Exception not same number of equations and variables (#1321)

Signed-off-by: Damien Jeandemange <[email protected]>
Co-authored-by: PRABAKARAN Sylvestre <[email protected]>

Author: jeandemanged

src/main/java/com/powsybl/openloadflow/equations/EquationSystemIndex.java

@@ -326,11 +326,11 @@ public void onEquationArrayChange(EquationArray<V, E> equationArray, int element
                             addVariables(variables);
                         }
                     }
-                    for (var singleTerm : equationArray.getSingleEquationTerms(elementNum)) {
-                        if (singleTerm.isActive()) {
-                            List<Variable<V>> variables = singleTerm.getVariables();
-                            addVariables(variables);
-                        }
+                }
+                for (var singleTerm : equationArray.getSingleEquationTerms(elementNum)) {
+                    if (singleTerm.isActive()) {
+                        List<Variable<V>> variables = singleTerm.getVariables();
+                        addVariables(variables);
                     }
                 }
                 equationsIndexValid = false;

src/test/java/com/powsybl/openloadflow/network/VoltageControlNetworkFactory.java

@@ -1523,4 +1523,23 @@ public static Network createFourBusNetworkWithSharedVoltageControl() {
                 .setTargetV(1.2);
         return network;
     }
+
+    public static Network createThreeBuses() {
+        Network network = Network.create("three-buses", "code");
+
+        Bus b1 = createBus(network, "B1", 400.);
+        Bus b2 = createBus(network, "B2", 400.);
+        Bus b3 = createBus(network, "B3", 400.);
+        createGenerator(b1, "GEN1", 150., 400.);
+        createGenerator(b3, "GEN3", 150., 400.)
+            .newMinMaxReactiveLimits().setMinQ(-1).setMaxQ(1).add();
+        createLoad(b1, "LOAD1", 100., 30.);
+        createLoad(b2, "LOAD2", 100., 30.);
+        createLoad(b3, "LOAD3", 100., 30.);
+        createFixedShuntCompensator(b3, "SC3", 1e-8, 1e-5);
+        createLine(network, b1, b2, "l12", 3.00);
+        createLine(network, b2, b3, "l23", 3.00);
+
+        return network;
+    }
 }

src/test/java/com/powsybl/openloadflow/sa/OpenSecurityAnalysisTest.java

@@ -4737,4 +4737,18 @@ void testDoubleBus() {
         });
 
     }
+
+    @Test
+    void testContingencyDisconnectingPqBlockedBus() {
+        Network network = VoltageControlNetworkFactory.createThreeBuses();
+
+        // Contingency disconnects/isolates B3 with 1 load, 1 gen blocked PQ, and one fixed shunt.
+        List<Contingency> contingencies = List.of(new Contingency("l23", new LineContingency("l23")));
+
+        List<StateMonitor> monitors = List.of(new StateMonitor(ContingencyContext.all(), Set.of("l12"), Collections.emptySet(), Collections.emptySet()));
+
+        SecurityAnalysisResult result = assertDoesNotThrow(() -> runSecurityAnalysis(network, contingencies, monitors));
+        assertEquals(50., result.getPreContingencyResult().getNetworkResult().getBranchResult("l12").getP1(), DELTA_POWER);
+        assertEquals(100., result.getPostContingencyResults().getFirst().getNetworkResult().getBranchResult("l12").getP1(), DELTA_POWER);
+    }
 }