Fix zero impedance subgraph (#718)

Signed-off-by: Geoffroy Jamgotchian <geoffroy.jamgotchian@gmail.com>

src/main/java/com/powsybl/openloadflow/OpenLoadFlowProvider.java

@@ -28,17 +28,12 @@
 import com.powsybl.openloadflow.dc.DcLoadFlowResult;
 import com.powsybl.openloadflow.graph.EvenShiloachGraphDecrementalConnectivityFactory;
 import com.powsybl.openloadflow.graph.GraphConnectivityFactory;
-import com.powsybl.openloadflow.network.LfBranch;
-import com.powsybl.openloadflow.network.LfBus;
-import com.powsybl.openloadflow.network.LfNetwork;
-import com.powsybl.openloadflow.network.LfNetworkStateUpdateParameters;
+import com.powsybl.openloadflow.network.*;
 import com.powsybl.openloadflow.network.impl.LfNetworkLoaderImpl;
 import com.powsybl.openloadflow.network.impl.Networks;
 import com.powsybl.openloadflow.network.util.ZeroImpedanceFlows;
 import com.powsybl.openloadflow.util.*;
 import com.powsybl.tools.PowsyblCoreVersion;
-import org.jgrapht.Graph;
-import org.jgrapht.alg.interfaces.SpanningTreeAlgorithm;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -161,9 +156,10 @@ private LoadFlowResult runAc(Network network, LoadFlowParameters parameters, Ope
     }
 
     private void computeZeroImpedanceFlows(LfNetwork network, boolean dc) {
-        Graph<LfBus, LfBranch> zeroImpedanceSubGraph = network.getZeroImpedanceNetwork(dc).getSubGraph();
-        SpanningTreeAlgorithm.SpanningTree<LfBranch> spanningTree = network.getZeroImpedanceNetwork(dc).getSpanningTree();
-        new ZeroImpedanceFlows(zeroImpedanceSubGraph, spanningTree, dc).compute();
+        for (LfZeroImpedanceNetwork zeroImpedanceNetwork : network.getZeroImpedanceNetworks(dc)) {
+            new ZeroImpedanceFlows(zeroImpedanceNetwork.getGraph(), zeroImpedanceNetwork.getSpanningTree(), dc)
+                    .compute();
+        }
     }
 
     private LoadFlowResult runDc(Network network, LoadFlowParameters parameters, OpenLoadFlowParameters parametersExt, Reporter reporter) {

src/main/java/com/powsybl/openloadflow/ac/AcTargetVector.java

@@ -15,7 +15,6 @@
 import com.powsybl.openloadflow.network.*;
 
 import java.util.Objects;
-import java.util.Optional;
 
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
@@ -24,11 +23,9 @@ public class AcTargetVector extends TargetVector<AcVariableType, AcEquationType>
 
     private static double getBusTargetV(LfBus bus) {
         Objects.requireNonNull(bus);
-        double targetV = bus.getShuntVoltageControl().filter(dvc -> bus.isShuntVoltageControlled())
-                .map(ShuntVoltageControl::getTargetValue)
-                .orElse(bus.getTransformerVoltageControl().filter(dvc -> bus.isTransformerVoltageControlled())
-                        .map(TransformerVoltageControl::getTargetValue)
-                        .orElse(getVoltageControlledTargetValue(bus).orElse(Double.NaN)));
+        double targetV = bus.getHighestPriorityVoltageControl()
+                .map(Control::getTargetValue)
+                .orElseThrow(() -> new IllegalStateException("No active voltage control has been found for bus '" + bus.getId() + "'"));
         if (bus.hasGeneratorsWithSlope()) {
             // take first generator with slope: network loading ensures that there's only one generator with slope
             double slope = bus.getGeneratorsControllingVoltageWithSlope().get(0).getSlope();
@@ -37,19 +34,10 @@ private static double getBusTargetV(LfBus bus) {
         return targetV;
     }
 
-    private static Optional<Double> getVoltageControlledTargetValue(LfBus bus) {
-        return bus.getGeneratorVoltageControl().filter(vc -> bus.isGeneratorVoltageControlled()).map(vc -> {
-            if (vc.getControllerElements().stream().noneMatch(LfBus::isGeneratorVoltageControlEnabled)) {
-                throw new IllegalStateException("None of the controller buses of bus '" + bus.getId() + "'has voltage control on");
-            }
-            return vc.getTargetValue();
-        });
-    }
-
     private static double getReactivePowerDistributionTarget(LfNetwork network, int busNum) {
         LfBus controllerBus = network.getBus(busNum);
         double target = (controllerBus.getRemoteVoltageControlReactivePercent() - 1) * controllerBus.getTargetQ();
-        for (LfBus otherControllerBus : controllerBus.getGeneratorVoltageControl().orElseThrow().getControllerElements()) {
+        for (LfBus otherControllerBus : controllerBus.getGeneratorVoltageControl().orElseThrow().getMergedControllerElements()) {
             if (otherControllerBus != controllerBus) {
                 target += controllerBus.getRemoteVoltageControlReactivePercent() * otherControllerBus.getTargetQ();
             }

src/main/java/com/powsybl/openloadflow/ac/equations/AcEquationSystemUpdater.java

@@ -10,18 +10,31 @@
 import com.powsybl.openloadflow.lf.AbstractEquationSystemUpdater;
 import com.powsybl.openloadflow.network.*;
 
+import java.util.List;
+import java.util.Objects;
+
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
  */
 public class AcEquationSystemUpdater extends AbstractEquationSystemUpdater<AcVariableType, AcEquationType> {
 
-    public AcEquationSystemUpdater(EquationSystem<AcVariableType, AcEquationType> equationSystem) {
+    private final AcEquationSystemCreationParameters parameters;
+
+    public AcEquationSystemUpdater(EquationSystem<AcVariableType, AcEquationType> equationSystem,
+                                   AcEquationSystemCreationParameters parameters) {
         super(equationSystem, false);
+        this.parameters = Objects.requireNonNull(parameters);
+    }
+
+    private void updateVoltageControls(LfBus bus) {
+        bus.getGeneratorVoltageControl().ifPresent(voltageControl -> AcEquationSystemCreator.updateGeneratorVoltageControl(voltageControl.getMainVoltageControl(), equationSystem));
+        bus.getTransformerVoltageControl().ifPresent(voltageControl -> AcEquationSystemCreator.updateTransformerVoltageControlEquations(voltageControl.getMainVoltageControl(), equationSystem));
+        bus.getShuntVoltageControl().ifPresent(voltageControl -> AcEquationSystemCreator.updateShuntVoltageControlEquations(voltageControl.getMainVoltageControl(), equationSystem));
     }
 
     @Override
     public void onGeneratorVoltageControlChange(LfBus controllerBus, boolean newVoltageControllerEnabled) {
-        controllerBus.getGeneratorVoltageControl().ifPresent(voltageControl -> AcEquationSystemCreator.updateGeneratorVoltageControl(voltageControl, equationSystem));
+        updateVoltageControls(controllerBus.getGeneratorVoltageControl().orElseThrow().getControlledBus());
         controllerBus.getReactivePowerControl().ifPresent(reactivePowerControl -> AcEquationSystemCreator.updateReactivePowerControlBranchEquations(reactivePowerControl, equationSystem));
     }
 
@@ -32,12 +45,12 @@ public void onTransformerPhaseControlChange(LfBranch controllerBranch, boolean n
 
     @Override
     public void onTransformerVoltageControlChange(LfBranch controllerBranch, boolean newVoltageControllerEnabled) {
-        AcEquationSystemCreator.updateTransformerVoltageControlEquations(controllerBranch.getVoltageControl().orElseThrow(), equationSystem);
+        updateVoltageControls(controllerBranch.getVoltageControl().orElseThrow().getControlledBus());
     }
 
     @Override
     public void onShuntVoltageControlChange(LfShunt controllerShunt, boolean newVoltageControllerEnabled) {
-        AcEquationSystemCreator.updateShuntVoltageControlEquations(controllerShunt.getVoltageControl().orElseThrow(), equationSystem);
+        updateVoltageControls(controllerShunt.getVoltageControl().orElseThrow().getControlledBus());
     }
 
     @Override
@@ -74,9 +87,7 @@ public void onDisableChange(LfElement element, boolean disabled) {
                 equationSystem.getEquation(bus.getNum(), AcEquationType.BUS_TARGET_V)
                         .orElseThrow()
                         .setActive(false);
-                bus.getGeneratorVoltageControl().ifPresent(voltageControl -> AcEquationSystemCreator.updateGeneratorVoltageControl(voltageControl, equationSystem));
-                bus.getTransformerVoltageControl().ifPresent(voltageControl -> AcEquationSystemCreator.updateTransformerVoltageControlEquations(voltageControl, equationSystem));
-                bus.getShuntVoltageControl().ifPresent(voltageControl -> AcEquationSystemCreator.updateShuntVoltageControlEquations(voltageControl, equationSystem));
+                updateVoltageControls(bus);
                 bus.getReactivePowerControl().ifPresent(reactivePowerControl -> AcEquationSystemCreator.updateReactivePowerControlBranchEquations(reactivePowerControl, equationSystem));
                 break;
             case BRANCH:
@@ -96,4 +107,41 @@ public void onDisableChange(LfElement element, boolean disabled) {
                 throw new IllegalStateException("Unknown element type: " + element.getType());
         }
     }
+
+    private void recreateDistributionEquations(LfZeroImpedanceNetwork network) {
+        for (LfBus bus : network.getGraph().vertexSet()) {
+            bus.getGeneratorVoltageControl()
+                    .filter(voltageControl -> voltageControl.getMergeStatus() == VoltageControl.MergeStatus.MAIN)
+                    .ifPresent(voltageControl -> AcEquationSystemCreator.recreateReactivePowerDistributionEquations(voltageControl, equationSystem, parameters));
+            bus.getTransformerVoltageControl()
+                    .filter(voltageControl -> voltageControl.getMergeStatus() == VoltageControl.MergeStatus.MAIN)
+                    .ifPresent(voltageControl -> AcEquationSystemCreator.recreateR1DistributionEquations(voltageControl, equationSystem));
+            bus.getShuntVoltageControl()
+                    .filter(voltageControl -> voltageControl.getMergeStatus() == VoltageControl.MergeStatus.MAIN)
+                    .ifPresent(voltageControl -> AcEquationSystemCreator.recreateShuntSusceptanceDistributionEquations(voltageControl, equationSystem));
+        }
+    }
+
+    @Override
+    public void onZeroImpedanceNetworkSplit(LfZeroImpedanceNetwork initialNetwork, List<LfZeroImpedanceNetwork> splitNetworks, boolean dc) {
+        if (!dc) {
+            // TODO
+            // only recreate distribution equations if controllers buses are redistributed on the different
+            // split networks (should be a rare case) and not only ate the end on only one of the split network
+            for (LfZeroImpedanceNetwork splitNetwork : splitNetworks) {
+                recreateDistributionEquations(splitNetwork);
+            }
+        }
+    }
+
+    @Override
+    public void onZeroImpedanceNetworkMerge(LfZeroImpedanceNetwork network1, LfZeroImpedanceNetwork network2, LfZeroImpedanceNetwork mergedNetwork, boolean dc) {
+        if (!dc) {
+            // TODO
+            // only recreate distribution equations if controllers buses are merged (should be a rare case)
+            // so we have to check here that controllers were spread over network1 and network2 and were not
+            // already only on network1 or network2
+            recreateDistributionEquations(mergedNetwork);
+        }
+    }
 }

src/main/java/com/powsybl/openloadflow/ac/outerloop/IncrementalShuntVoltageControlOuterLoop.java

@@ -161,12 +161,14 @@ public OuterLoopStatus check(OuterLoopContext context, Reporter reporter) {
                 .filter(LfBus::isShuntVoltageControlled)
                 .forEach(controlledBus -> {
                     ShuntVoltageControl voltageControl = controlledBus.getShuntVoltageControl().orElseThrow();
-                    double diffV = voltageControl.getTargetValue() - voltageControl.getControlledBus().getV();
-                    List<LfShunt> sortedControllers = voltageControl.getControllerElements().stream()
-                            .filter(shunt -> !shunt.isDisabled() && shunt.hasVoltageControlCapability())
-                            .sorted(Comparator.comparingDouble(LfShunt::getBMagnitude).reversed())
-                            .collect(Collectors.toList());
-                    adjustB(voltageControl, sortedControllers, controlledBus, contextData, sensitivityContext, diffV, status);
+                    if (voltageControl.getMergeStatus() == VoltageControl.MergeStatus.MAIN) {
+                        double diffV = voltageControl.getTargetValue() - voltageControl.getControlledBus().getV();
+                        List<LfShunt> sortedControllers = voltageControl.getMergedControllerElements().stream()
+                                .filter(shunt -> !shunt.isDisabled() && shunt.hasVoltageControlCapability())
+                                .sorted(Comparator.comparingDouble(LfShunt::getBMagnitude).reversed())
+                                .collect(Collectors.toList());
+                        adjustB(voltageControl, sortedControllers, controlledBus, contextData, sensitivityContext, diffV, status);
+                    }
                 });
         return status.getValue();
     }

src/main/java/com/powsybl/openloadflow/ac/outerloop/IncrementalTransformerVoltageControlOuterLoop.java

@@ -208,22 +208,24 @@ public OuterLoopStatus check(OuterLoopContext context, Reporter reporter) {
 
         controlledBuses.forEach(controlledBus -> {
             TransformerVoltageControl voltageControl = controlledBus.getTransformerVoltageControl().orElseThrow();
-            double diffV = getDiffV(voltageControl);
-            double halfTargetDeadband = getHalfTargetDeadband(voltageControl);
-            if (Math.abs(diffV) > halfTargetDeadband) {
-                controlledBusesOutsideOfDeadband.add(controlledBus.getId());
-                List<LfBranch> controllers = voltageControl.getControllerElements();
-                LOGGER.trace("Controlled bus '{}' ({} controllers) is outside of its deadband (half is {} kV) and could need a voltage adjustment of {} kV",
-                        controlledBus.getId(), controllers.size(), halfTargetDeadband * controlledBus.getNominalV(), diffV * controlledBus.getNominalV());
-                boolean adjusted;
-                if (controllers.size() == 1) {
-                    adjusted = adjustWithOneController(controllers.get(0), controlledBus, contextData, sensitivityContext, diffV, controlledBusesWithAllItsControllersToLimit);
-                } else {
-                    adjusted = adjustWithSeveralControllers(controllers, controlledBus, contextData, sensitivityContext, diffV, halfTargetDeadband, controlledBusesWithAllItsControllersToLimit);
-                }
-                if (adjusted) {
-                    controlledBusesAdjusted.add(controlledBus.getId());
-                    status.setValue(OuterLoopStatus.UNSTABLE);
+            if (voltageControl.getMergeStatus() == VoltageControl.MergeStatus.MAIN) {
+                double diffV = getDiffV(voltageControl);
+                double halfTargetDeadband = getHalfTargetDeadband(voltageControl);
+                if (Math.abs(diffV) > halfTargetDeadband) {
+                    controlledBusesOutsideOfDeadband.add(controlledBus.getId());
+                    List<LfBranch> controllers = voltageControl.getMergedControllerElements();
+                    LOGGER.trace("Controlled bus '{}' ({} controllers) is outside of its deadband (half is {} kV) and could need a voltage adjustment of {} kV",
+                            controlledBus.getId(), controllers.size(), halfTargetDeadband * controlledBus.getNominalV(), diffV * controlledBus.getNominalV());
+                    boolean adjusted;
+                    if (controllers.size() == 1) {
+                        adjusted = adjustWithOneController(controllers.get(0), controlledBus, contextData, sensitivityContext, diffV, controlledBusesWithAllItsControllersToLimit);
+                    } else {
+                        adjusted = adjustWithSeveralControllers(controllers, controlledBus, contextData, sensitivityContext, diffV, halfTargetDeadband, controlledBusesWithAllItsControllersToLimit);
+                    }
+                    if (adjusted) {
+                        controlledBusesAdjusted.add(controlledBus.getId());
+                        status.setValue(OuterLoopStatus.UNSTABLE);
+                    }
                 }
             }
         });

src/main/java/com/powsybl/openloadflow/ac/outerloop/ReactiveLimitsOuterLoop.java

@@ -10,8 +10,8 @@
 import com.powsybl.openloadflow.ac.OuterLoop;
 import com.powsybl.openloadflow.ac.OuterLoopContext;
 import com.powsybl.openloadflow.ac.OuterLoopStatus;
-import com.powsybl.openloadflow.network.LfBus;
 import com.powsybl.openloadflow.network.GeneratorVoltageControl;
+import com.powsybl.openloadflow.network.LfBus;
 import com.powsybl.openloadflow.util.PerUnit;
 import com.powsybl.openloadflow.util.Reports;
 import org.apache.commons.lang3.mutable.MutableInt;

src/main/java/com/powsybl/openloadflow/ac/outerloop/SecondaryVoltageControlOuterLoop.java

@@ -47,8 +47,9 @@ private static boolean isValid(LfBus bus) {
 
     private static List<LfBus> getControllerBuses(LfBus controlledBus) {
         return controlledBus.getGeneratorVoltageControl()
+                .filter(voltageControl -> voltageControl.getMergeStatus() == VoltageControl.MergeStatus.MAIN)
                 .orElseThrow()
-                .getControllerElements()
+                .getMergedControllerElements()
                 .stream().filter(SecondaryVoltageControlOuterLoop::isValid)
                 .collect(Collectors.toList());
     }

src/main/java/com/powsybl/openloadflow/ac/outerloop/TransformerVoltageControlOuterLoop.java

@@ -11,6 +11,7 @@
 import com.powsybl.openloadflow.ac.OuterLoopStatus;
 import com.powsybl.openloadflow.network.LfBranch;
 import com.powsybl.openloadflow.network.LfBus;
+import com.powsybl.openloadflow.network.VoltageControl;
 import org.apache.commons.lang3.mutable.MutableObject;
 
 import java.util.ArrayList;
@@ -79,14 +80,16 @@ public OuterLoopStatus check(OuterLoopContext context, Reporter reporter) {
             for (LfBus bus : context.getNetwork().getBuses()) {
                 if (!bus.isDisabled() && bus.isGeneratorVoltageControlled() && bus.getNominalV() <= maxControlledNominalVoltage) {
                     var voltageControl = bus.getGeneratorVoltageControl().orElseThrow();
-                    voltageControl.getControllerElements().forEach(controllerBus -> {
-                        if (controllerBus.isGeneratorVoltageControlEnabled()) {
-                            controllerBus.setGenerationTargetQ(controllerBus.getQ().eval());
-                            controllerBus.setGeneratorVoltageControlEnabled(false);
-                            contextData.getBusesWithVoltageControlDisabled().add(controllerBus);
-                        }
-                    });
-                    status.setValue(OuterLoopStatus.UNSTABLE);
+                    if (voltageControl.getMergeStatus() == VoltageControl.MergeStatus.MAIN) {
+                        voltageControl.getMergedControllerElements().forEach(controllerBus -> {
+                            if (controllerBus.isGeneratorVoltageControlEnabled()) {
+                                controllerBus.setGenerationTargetQ(controllerBus.getQ().eval());
+                                controllerBus.setGeneratorVoltageControlEnabled(false);
+                                contextData.getBusesWithVoltageControlDisabled().add(controllerBus);
+                            }
+                        });
+                        status.setValue(OuterLoopStatus.UNSTABLE);
+                    }
                 }
             }
             for (LfBranch branch : getControllerBranches(context.getNetwork())) {