Zero impedance flows. Specific solution for open Loadflow

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

@@ -19,7 +19,6 @@
 import com.powsybl.loadflow.LoadFlowProvider;
 import com.powsybl.loadflow.LoadFlowResult;
 import com.powsybl.loadflow.LoadFlowResultImpl;
-import com.powsybl.loadflow.resultscompletion.z0flows.Z0FlowsCompletion;
 import com.powsybl.math.matrix.MatrixFactory;
 import com.powsybl.math.matrix.SparseMatrixFactory;
 import com.powsybl.openloadflow.ac.nr.NewtonRaphsonStatus;
@@ -33,11 +32,20 @@
 import com.powsybl.openloadflow.graph.GraphDecrementalConnectivityFactory;
 import com.powsybl.openloadflow.network.LfBranch;
 import com.powsybl.openloadflow.network.LfBus;
+import com.powsybl.openloadflow.network.LfNetwork;
 import com.powsybl.openloadflow.network.impl.LfNetworkLoaderImpl;
 import com.powsybl.openloadflow.network.impl.Networks;
 import com.powsybl.openloadflow.util.*;
+import com.powsybl.openloadflow.network.util.ZeroImpedanceFlows;
+import com.powsybl.openloadflow.util.Markers;
+import com.powsybl.openloadflow.util.PerUnit;
+import com.powsybl.openloadflow.util.PowsyblOpenLoadFlowVersion;
+import com.powsybl.openloadflow.util.ProviderConstants;
 import com.powsybl.tools.PowsyblCoreVersion;
-import net.jafama.FastMath;
+
+import org.jgrapht.Graph;
+import org.jgrapht.alg.interfaces.SpanningTreeAlgorithm;
+import org.jgrapht.alg.spanning.KruskalMinimumSpanningTree;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -116,8 +124,10 @@ private LoadFlowResult runAc(Network network, LoadFlowParameters parameters, Rep
                                                 parameters.isPhaseShifterRegulationOn(),
                                                 parameters.isTransformerVoltageControlOn(),
                                                 parameters.isDistributedSlack() && parameters.getBalanceType() == LoadFlowParameters.BalanceType.PROPORTIONAL_TO_CONFORM_LOAD,
-                                                parameters.isDistributedSlack() && (parameters.getBalanceType() == LoadFlowParameters.BalanceType.PROPORTIONAL_TO_LOAD ||
-                                                    parameters.getBalanceType() == LoadFlowParameters.BalanceType.PROPORTIONAL_TO_CONFORM_LOAD) && parametersExt.isLoadPowerFactorConstant(), parameters.isDc());
+                                                parameters.isDistributedSlack() && (parameters.getBalanceType() == LoadFlowParameters.BalanceType.PROPORTIONAL_TO_LOAD || parameters.getBalanceType() == LoadFlowParameters.BalanceType.PROPORTIONAL_TO_CONFORM_LOAD) && parametersExt.isLoadPowerFactorConstant(), parameters.isDc());
+
+                // zero or low impedance branch flows computation
+                computeZeroImpedanceFlows(result.getNetwork(), parameters.isDc());
             }
 
             LoadFlowResult.ComponentResult.Status status;
@@ -144,20 +154,17 @@ private LoadFlowResult runAc(Network network, LoadFlowParameters parameters, Rep
                                                                             result.getDistributedActivePower() * PerUnit.SB));
         }
 
-        // zero or low impedance branch flows computation
-        if (ok) {
-            new Z0FlowsCompletion(network, line -> {
-                // to be consistent with low impedance criteria used in DcEquationSystem and AcEquationSystem
-                double nominalV = line.getTerminal1().getVoltageLevel().getNominalV();
-                double zb = nominalV * nominalV / PerUnit.SB;
-                double z = FastMath.hypot(line.getR(), line.getX());
-                return z / zb <= LfBranch.LOW_IMPEDANCE_THRESHOLD;
-            }).complete();
-        }
-
         return new LoadFlowResultImpl(ok, Collections.emptyMap(), null, componentResults);
     }
 
+    private void computeZeroImpedanceFlows(LfNetwork network, boolean dc) {
+        Graph<LfBus, LfBranch> zeroImpedanceSubGraph = network.createZeroImpedanceSubGraph(dc);
+        if (!zeroImpedanceSubGraph.vertexSet().isEmpty()) {
+            SpanningTreeAlgorithm.SpanningTree<LfBranch> spanningTree = new KruskalMinimumSpanningTree<>(zeroImpedanceSubGraph).getSpanningTree();
+            new ZeroImpedanceFlows(zeroImpedanceSubGraph, spanningTree).compute(dc);
+        }
+    }
+
     private LoadFlowResult runDc(Network network, LoadFlowParameters parameters, Reporter reporter) {
         OpenLoadFlowParameters parametersExt = OpenLoadFlowParameters.get(parameters);
         OpenLoadFlowParameters.logDc(parameters, parametersExt);
@@ -186,6 +193,9 @@ private LoadFlowResult.ComponentResult processResult(Network network, DcLoadFlow
                     parameters.isTransformerVoltageControlOn(),
                     parameters.isDistributedSlack() && parameters.getBalanceType() == LoadFlowParameters.BalanceType.PROPORTIONAL_TO_CONFORM_LOAD,
                     false, true);
+
+            // zero or low impedance branch flows computation
+            computeZeroImpedanceFlows(pResult.getNetwork(), true);
         }
 
         return new LoadFlowResultImpl.ComponentResultImpl(

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

@@ -109,6 +109,8 @@ default List<LfLimit> getLimits2(LimitType type) {
 
     void updateState(boolean phaseShifterRegulationOn, boolean isTransformerVoltageControlOn, boolean dc);
 
+    void updateFlows(double p1, double q1, double p2, double q2);
+
     boolean isPhaseController();
 
     boolean isPhaseControlled();

src/main/java/com/powsybl/openloadflow/network/impl/AbstractFictitiousLfBranch.java → src/main/java/com/powsybl/openloadflow/network/impl/AbstractImpedantLfBranch.java

@@ -1,5 +1,5 @@
 /**
- * Copyright (c) 2021, RTE (http://www.rte-france.com)
+ * Copyright (c) 2022, RTE (http://www.rte-france.com)
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
@@ -18,76 +18,81 @@
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
  */
-public abstract class AbstractFictitiousLfBranch extends AbstractLfBranch {
+public abstract class AbstractImpedantLfBranch extends AbstractLfBranch {
 
-    protected Evaluable p = NAN;
+    protected Evaluable p1 = NAN;
 
-    protected Evaluable q = NAN;
+    protected Evaluable q1 = NAN;
 
-    protected Evaluable i = NAN;
+    protected Evaluable i1 = NAN;
 
-    protected AbstractFictitiousLfBranch(LfNetwork network, LfBus bus1, LfBus bus2, PiModel piModel) {
+    protected Evaluable p2 = NAN;
+
+    protected Evaluable q2 = NAN;
+
+    protected Evaluable i2 = NAN;
+
+    protected AbstractImpedantLfBranch(LfNetwork network, LfBus bus1, LfBus bus2, PiModel piModel) {
         super(network, bus1, bus2, piModel);
     }
 
     @Override
     public void setP1(Evaluable p1) {
-        this.p = Objects.requireNonNull(p1);
+        this.p1 = Objects.requireNonNull(p1);
     }
 
     @Override
     public Evaluable getP1() {
-        return p;
+        return p1;
     }
 
     @Override
     public void setP2(Evaluable p2) {
-        // nothing to do
+        this.p2 = Objects.requireNonNull(p2);
     }
 
     @Override
     public Evaluable getP2() {
-        return NAN;
+        return p2;
     }
 
     @Override
     public void setQ1(Evaluable q1) {
-        this.q = Objects.requireNonNull(q1);
+        this.q1 = Objects.requireNonNull(q1);
     }
 
     @Override
     public Evaluable getQ1() {
-        return q;
+        return q1;
     }
 
     @Override
     public void setQ2(Evaluable q2) {
-        // nothing to do
+        this.q2 = Objects.requireNonNull(q2);
     }
 
     @Override
     public Evaluable getQ2() {
-        return NAN;
+        return q2;
     }
 
     @Override
     public void setI1(Evaluable i1) {
-        this.i = Objects.requireNonNull(i1);
+        this.i1 = Objects.requireNonNull(i1);
     }
 
     @Override
     public Evaluable getI1() {
-        return i;
+        return i1;
     }
 
     @Override
     public void setI2(Evaluable i2) {
-        // nothing to do
+        this.i2 = Objects.requireNonNull(i2);
     }
 
     @Override
     public Evaluable getI2() {
-        return NAN;
+        return i2;
     }
-
 }

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

@@ -9,7 +9,6 @@
 import com.powsybl.commons.PowsyblException;
 import com.powsybl.iidm.network.*;
 import com.powsybl.openloadflow.network.*;
-import com.powsybl.openloadflow.util.Evaluable;
 import com.powsybl.openloadflow.util.PerUnit;
 import com.powsybl.security.results.BranchResult;
 import org.slf4j.Logger;
@@ -19,29 +18,15 @@
 import java.util.List;
 import java.util.Objects;
 
-import static com.powsybl.openloadflow.util.EvaluableConstants.NAN;
-
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
  */
-public class LfBranchImpl extends AbstractLfBranch {
+public class LfBranchImpl extends AbstractImpedantLfBranch {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(LfBranchImpl.class);
 
     private final Branch<?> branch;
 
-    private Evaluable p1 = NAN;
-
-    private Evaluable p2 = NAN;
-
-    private Evaluable q1 = NAN;
-
-    private Evaluable q2 = NAN;
-
-    private Evaluable i1 = NAN;
-
-    private Evaluable i2 = NAN;
-
     protected LfBranchImpl(LfNetwork network, LfBus bus1, LfBus bus2, PiModel piModel, Branch<?> branch) {
         super(network, bus1, bus2, piModel);
         this.branch = branch;
@@ -147,66 +132,6 @@ public boolean hasPhaseControlCapability() {
                 && ((TwoWindingsTransformer) branch).getPhaseTapChanger() != null;
     }
 
-    @Override
-    public void setP1(Evaluable p1) {
-        this.p1 = Objects.requireNonNull(p1);
-    }
-
-    @Override
-    public Evaluable getP1() {
-        return p1;
-    }
-
-    @Override
-    public void setP2(Evaluable p2) {
-        this.p2 = Objects.requireNonNull(p2);
-    }
-
-    @Override
-    public Evaluable getP2() {
-        return p2;
-    }
-
-    @Override
-    public void setQ1(Evaluable q1) {
-        this.q1 = Objects.requireNonNull(q1);
-    }
-
-    @Override
-    public Evaluable getQ1() {
-        return q1;
-    }
-
-    @Override
-    public void setQ2(Evaluable q2) {
-        this.q2 = Objects.requireNonNull(q2);
-    }
-
-    @Override
-    public Evaluable getQ2() {
-        return q2;
-    }
-
-    @Override
-    public void setI1(Evaluable i1) {
-        this.i1 = Objects.requireNonNull(i1);
-    }
-
-    @Override
-    public Evaluable getI1() {
-        return i1;
-    }
-
-    @Override
-    public void setI2(Evaluable i2) {
-        this.i2 = Objects.requireNonNull(i2);
-    }
-
-    @Override
-    public Evaluable getI2() {
-        return i2;
-    }
-
     @Override
     public BranchResult createBranchResult(double preContingencyBranchP1, double preContingencyBranchOfContingencyP1, boolean createExtension) {
         double flowTransfer = Double.NaN;
@@ -255,10 +180,7 @@ public List<LfLimit> getLimits2(final LimitType type) {
 
     @Override
     public void updateState(boolean phaseShifterRegulationOn, boolean isTransformerVoltageControlOn, boolean dc) {
-        branch.getTerminal1().setP(p1.eval() * PerUnit.SB);
-        branch.getTerminal1().setQ(q1.eval() * PerUnit.SB);
-        branch.getTerminal2().setP(p2.eval() * PerUnit.SB);
-        branch.getTerminal2().setQ(q2.eval() * PerUnit.SB);
+        updateFlows(p1.eval(), q1.eval(), p2.eval(), q2.eval());
 
         if (phaseShifterRegulationOn && isPhaseController()) {
             // it means there is a regulating phase tap changer located on that branch
@@ -277,4 +199,12 @@ public void updateState(boolean phaseShifterRegulationOn, boolean isTransformerV
             checkTargetDeadband(rtc);
         }
     }
+
+    @Override
+    public void updateFlows(double p1, double q1, double p2, double q2) {
+        branch.getTerminal1().setP(p1 * PerUnit.SB)
+                .setQ(q1 * PerUnit.SB);
+        branch.getTerminal2().setP(p2 * PerUnit.SB)
+                .setQ(q2 * PerUnit.SB);
+    }
 }

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

@@ -19,7 +19,7 @@
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
  */
-public class LfDanglingLineBranch extends AbstractFictitiousLfBranch {
+public class LfDanglingLineBranch extends AbstractImpedantLfBranch {
 
     private final DanglingLine danglingLine;
 
@@ -81,12 +81,13 @@ public List<LfLimit> getLimits1(final LimitType type) {
 
     @Override
     public void updateState(boolean phaseShifterRegulationOn, boolean isTransformerVoltageControlOn, boolean dc) {
-        if (this.isZeroImpedanceBranch(dc)) {
-            danglingLine.getTerminal().setP(-getBus2().getP().eval() * PerUnit.SB);
-            danglingLine.getTerminal().setQ(-getBus2().getQ().eval() * PerUnit.SB);
-        } else {
-            danglingLine.getTerminal().setP(p.eval() * PerUnit.SB);
-            danglingLine.getTerminal().setQ(q.eval() * PerUnit.SB);
-        }
+        updateFlows(p1.eval(), q1.eval(), Double.NaN, Double.NaN);
+    }
+
+    @Override
+    public void updateFlows(double p1, double q1, double p2, double q2) {
+        // Network side is always on side 1.
+        danglingLine.getTerminal().setP(p1 * PerUnit.SB)
+                .setQ(q1 * PerUnit.SB);
     }
 }

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

@@ -20,7 +20,7 @@
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
  */
-public class LfLegBranch extends AbstractFictitiousLfBranch {
+public class LfLegBranch extends AbstractImpedantLfBranch {
 
     private final ThreeWindingsTransformer twt;
 
@@ -147,8 +147,7 @@ public List<LfLimit> getLimits1(final LimitType type) {
 
     @Override
     public void updateState(boolean phaseShifterRegulationOn, boolean isTransformerVoltageControlOn, boolean dc) {
-        leg.getTerminal().setP(p.eval() * PerUnit.SB);
-        leg.getTerminal().setQ(q.eval() * PerUnit.SB);
+        updateFlows(p1.eval(), q1.eval(), Double.NaN, Double.NaN);
 
         if (phaseShifterRegulationOn && isPhaseController()) {
             // it means there is a regulating phase tap changer located on that leg
@@ -157,7 +156,7 @@ public void updateState(boolean phaseShifterRegulationOn, boolean isTransformerV
 
         if (phaseShifterRegulationOn && isPhaseControlled() && discretePhaseControl.getControlledSide() == DiscretePhaseControl.ControlledSide.ONE) {
             // check if the target value deadband is respected
-            checkTargetDeadband(p.eval());
+            checkTargetDeadband(p1.eval());
         }
 
         if (isTransformerVoltageControlOn && isVoltageController()) { // it means there is a regulating ratio tap changer
@@ -169,4 +168,11 @@ public void updateState(boolean phaseShifterRegulationOn, boolean isTransformerV
             checkTargetDeadband(rtc);
         }
     }
+
+    @Override
+    public void updateFlows(double p1, double q1, double p2, double q2) {
+        // Star bus is always on side 2.
+        leg.getTerminal().setP(p1 * PerUnit.SB)
+                .setQ(q1 * PerUnit.SB);
+    }
 }