Fixed PST Flow Regulation on non impedant branch causing exception

src/main/java/com/powsybl/openloadflow/network/LfNetwork.java

@@ -482,8 +482,9 @@ public void fix(boolean minImpedance, double lowImpedanceThreshold) {
             }
         } else {
             // zero impedance controller phase shifter is not supported
+            // zero impedance controlled branch is not supported
             branches.stream()
-                    .filter(LfBranch::isPhaseController)
+                    .filter(b -> b.isPhaseController() || b.isPhaseControlled())
                     .forEach(branch -> branch.setMinZ(lowImpedanceThreshold));
         }
     }

src/main/java/com/powsybl/openloadflow/network/impl/AbstractLfBranch.java

@@ -281,6 +281,10 @@ public void setMinZ(double lowImpedanceThreshold) {
             if (piModel.setMinZ(lowImpedanceThreshold, loadFlowModel)) {
                 LOGGER.trace("Branch {} has a low impedance in {}, set to min {}", getId(), loadFlowModel, lowImpedanceThreshold);
                 zeroImpedanceContextByModel.get(loadFlowModel).zeroImpedance = false;
+            } else if (isZeroImpedance(loadFlowModel)) {
+                // For DC load flow model, the min impedance has already been set by AC load flow model but
+                // the zero impedance field was not updated.
+                zeroImpedanceContextByModel.get(loadFlowModel).zeroImpedance = false;
             }
         }
     }

src/test/java/com/powsybl/openloadflow/ac/AcLoadFlowPhaseShifterTest.java

@@ -157,6 +157,24 @@ void remoteFlowControlT2wtTest() {
         assertEquals(0, t2wt.getPhaseTapChanger().getTapPosition());
     }
 
+    @Test
+    void remoteFlowControlOnZeroImpedanceBranch() {
+        selectNetwork(PhaseControlFactory.createNetworkWithT2wt());
+        parameters.setPhaseShifterRegulationOn(true);
+        t2wt.getPhaseTapChanger().setRegulationMode(PhaseTapChanger.RegulationMode.ACTIVE_POWER_CONTROL)
+                .setTargetDeadband(1)
+                .setRegulating(true)
+                .setTapPosition(2)
+                .setRegulationTerminal(line1.getTerminal1())
+                .setRegulationValue(83);
+        line1.setR(0).setX(0).setG1(0).setG2(0).setB1(0).setB2(0);
+        LoadFlowResult result = loadFlowRunner.run(network, parameters);
+        assertTrue(result.isOk());
+        assertActivePowerEquals(100.0, line1.getTerminal1());
+        assertActivePowerEquals(0.0, line2.getTerminal1());
+        assertEquals(1, t2wt.getPhaseTapChanger().getTapPosition());
+    }
+
     @Test
     void currentLimiterT2wtTest() {
         selectNetwork(PhaseControlFactory.createNetworkWithT2wt());
@@ -621,15 +639,16 @@ void activePowerflowControlAndNonImpedantPhaseShifterTest() {
         assertActivePowerEquals(-112.019, line2.getTerminal2());
         assertEquals(2, t2wt.getPhaseTapChanger().getTapPosition());
 
-        line1.setR(0).setX(0);
+        line1.setR(0.0).setX(0.0);
         t2wt.setR(2.0).setX(100.0);
         t2wt.getPhaseTapChanger()
                 .setRegulationTerminal(line1.getTerminal1())
                 .setTapPosition(0);
+        LoadFlowResult result2 = loadFlowRunner.run(network, parameters);
 
-        assertTrue(result.isOk());
-        assertActivePowerEquals(-12.006, line1.getTerminal1());
-        assertActivePowerEquals(112.197, line2.getTerminal1());
-        assertEquals(0, t2wt.getPhaseTapChanger().getTapPosition());
+        assertTrue(result2.isOk());
+        assertActivePowerEquals(100.0, line1.getTerminal1());
+        assertActivePowerEquals(0.0, line2.getTerminal1());
+        assertEquals(1, t2wt.getPhaseTapChanger().getTapPosition());
     }
 }