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Fix DcEquationSystem with disabled non impedant branch #663

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merged 5 commits into from
Nov 30, 2022
Merged

Fix DcEquationSystem with disabled non impedant branch #663

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147e38b
Add a test that shows the bug.
annetill Nov 29, 2022
307d1a0
Fix proposal.
annetill Nov 29, 2022
00199b2
Merge branch 'main' into fix-disabled-non-impedant-branch
geofjamg Nov 29, 2022
b1c41d1
Merge
geofjamg Nov 29, 2022
07f5c7e
Fix
geofjamg Nov 29, 2022
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1 change: 1 addition & 0 deletions src/main/java/com/powsybl/openloadflow/dc/DcLoadFlowEngine.java
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,7 @@ public static void initTarget(Equation<DcVariableType, DcEquationType> equation,
break;

case BUS_TARGET_PHI:
case DUMMY_TARGET_P:
targets[equation.getColumn()] = 0;
break;

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15 changes: 10 additions & 5 deletions src/main/java/com/powsybl/openloadflow/dc/equations/DcEquationSystem.java
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Expand Up @@ -51,19 +51,24 @@ public static void createNonImpedantBranch(EquationSystem<DcVariableType, DcEqua
equationSystem.createEquation(branch.getNum(), DcEquationType.ZERO_PHI)
.addTerm(equationSystem.getVariable(bus1.getNum(), DcVariableType.BUS_PHI).createTerm())
.addTerm(equationSystem.getVariable(bus2.getNum(), DcVariableType.BUS_PHI).<DcEquationType>createTerm()
.minus());
.minus()).setActive(!branch.isDisabled());
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I really don't understand why but this first setActive is not needed in AcEquationSystem. So I don't know if this fix is the good one.

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EquationSystem.createEquation has 2 overloads:

  • initial one just take an element num
  • newest one take directly the LfElement and so on is able to internally disable equation according to LfElement status

DcEquationSystem had unfortunately not been migrated to new one


// add a dummy active power variable to both sides of the non impedant branch and with an opposite sign
// to ensure we have the same number of equation and variables
var dummyP = equationSystem.getVariable(branch.getNum(), DcVariableType.DUMMY_P);
equationSystem.getEquation(bus1.getNum(), DcEquationType.BUS_TARGET_P)
.orElseThrow()
.addTerm(equationSystem.getVariable(branch.getNum(), DcVariableType.DUMMY_P)
.createTerm());
.addTerm(dummyP.createTerm());

equationSystem.getEquation(bus2.getNum(), DcEquationType.BUS_TARGET_P)
.orElseThrow()
.addTerm(equationSystem.getVariable(branch.getNum(), DcVariableType.DUMMY_P).<DcEquationType>createTerm()
.minus());
.addTerm(dummyP.<DcEquationType>createTerm().minus());

// create an inactive dummy active power target equation set to zero that could be activated
// on case of switch opening
equationSystem.createEquation(branch, DcEquationType.DUMMY_TARGET_P)
.addTerm(dummyP.createTerm())
.setActive(branch.isDisabled()); // inverted logic
} else {
throw new IllegalStateException("Cannot happen because only there is one slack bus per model");
}
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3 changes: 2 additions & 1 deletion src/main/java/com/powsybl/openloadflow/dc/equations/DcEquationType.java
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Expand Up @@ -17,7 +17,8 @@ public enum DcEquationType implements Quantity {
BUS_TARGET_PHI("bus_target_\u03C6", ElementType.BUS), // slack bus voltage angle target
BRANCH_TARGET_P("branch_target_p", ElementType.BRANCH), // phase shifter active flow control
BRANCH_TARGET_ALPHA1("branch_target_\u03B1", ElementType.BRANCH), // phase shifter constant shift
ZERO_PHI("zero_\u03C6", ElementType.BRANCH); // zero impedance branch, voltage angle equality
ZERO_PHI("zero_\u03C6", ElementType.BRANCH), // zero impedance branch, voltage angle equality
DUMMY_TARGET_P("dummy_target_p", ElementType.BRANCH);

private final String symbol;

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37 changes: 35 additions & 2 deletions src/test/java/com/powsybl/openloadflow/dc/DcLoadFlowTest.java
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Expand Up @@ -6,6 +6,7 @@
*/
package com.powsybl.openloadflow.dc;

import com.powsybl.commons.reporter.Reporter;
import com.powsybl.ieeecdf.converter.IeeeCdfNetworkFactory;
import com.powsybl.iidm.network.Line;
import com.powsybl.iidm.network.Network;
Expand All @@ -17,15 +18,20 @@
import com.powsybl.math.matrix.DenseMatrixFactory;
import com.powsybl.openloadflow.OpenLoadFlowParameters;
import com.powsybl.openloadflow.OpenLoadFlowProvider;
import com.powsybl.openloadflow.network.FourBusNetworkFactory;
import com.powsybl.openloadflow.network.SlackBusSelectionMode;
import com.powsybl.openloadflow.dc.equations.DcEquationSystemCreationParameters;
import com.powsybl.openloadflow.network.*;
import com.powsybl.openloadflow.network.impl.LfNetworkList;
import com.powsybl.openloadflow.network.impl.Networks;
import com.powsybl.openloadflow.util.LoadFlowAssert;
import com.powsybl.openloadflow.util.PerUnit;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.usefultoys.slf4j.LoggerFactory;

import java.util.Collections;
import java.util.List;
import java.util.Set;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;
Expand Down Expand Up @@ -259,4 +265,31 @@ void shuntCompensatorActivePowerZero() {
loadFlowRunner.run(network, parameters);
LoadFlowAssert.assertActivePowerEquals(0, sc.getTerminal());
}

@Test
void testDisabledNonImpedantBranch() {
Network network = NodeBreakerNetworkFactory.create3Bars();
network.getSwitch("C1").setOpen(true);
LoadFlowParameters parameters = new LoadFlowParameters();
parameters.setDc(true);
LoadFlow.run(network, parameters);
LoadFlowAssert.assertActivePowerEquals(400.0, network.getLine("L1").getTerminal1());
LoadFlowAssert.assertActivePowerEquals(100.0, network.getLine("L2").getTerminal1());
LoadFlowAssert.assertActivePowerEquals(100.0, network.getLine("L3").getTerminal1());

LfNetworkParameters lfNetworkParameters = new LfNetworkParameters().setDc(true).setBreakers(true);
LfNetworkList lfNetworks = Networks.load(network, lfNetworkParameters, Collections.emptySet(), Set.of(network.getSwitch("C1")), Reporter.NO_OP);
LfNetwork largestNetwork = lfNetworks.getLargest().orElseThrow();
largestNetwork.getBranchById("C1").setDisabled(true);
DcLoadFlowParameters dcLoadFlowParameters = new DcLoadFlowParameters(lfNetworkParameters,
new DcEquationSystemCreationParameters(true, true, false, true),
new DenseMatrixFactory(),
true,
parameters.getBalanceType(),
false);
new DcLoadFlowEngine(List.of(largestNetwork), dcLoadFlowParameters).run(Reporter.NO_OP);
assertEquals(400.0, largestNetwork.getBranchById("L1").getP1().eval() * PerUnit.SB, LoadFlowAssert.DELTA_POWER);
assertEquals(100.0, largestNetwork.getBranchById("L2").getP1().eval() * PerUnit.SB, LoadFlowAssert.DELTA_POWER);
assertEquals(100.0, largestNetwork.getBranchById("L3").getP1().eval() * PerUnit.SB, LoadFlowAssert.DELTA_POWER);
}
}