Voltage magnitude initialization #392

geofjamg · 2021-12-03T10:24:16Z

Signed-off-by: Geoffroy Jamgotchian [email protected]

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What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
feature

What is the current behavior? (You can also link to an open issue here)
In some cases where we have a large grid and many transformers with a voltage ratio far from 1pu, the starting point (1pu, 0°) is not able to make the Newton Raphson converge.

What is the new behavior (if this is a feature change)?
We added a new algorithm to find a better voltage magnitude starting point.

Does this PR introduce a breaking change or deprecate an API? If yes, check the following:

The Breaking Change or Deprecated label has been added
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Signed-off-by: Geoffroy Jamgotchian <[email protected]>

# Conflicts: # src/main/java/com/powsybl/openloadflow/OpenLoadFlowParameters.java # src/test/resources/debug-parameters.json

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

annetill · 2021-12-05T15:02:35Z

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

@@ -43,6 +43,14 @@

    public static final boolean VOLTAGE_PER_REACTIVE_POWER_CONTROL_DEFAULT_VALUE = false;

+    public enum VoltageInitMode {


I understand now that it is an extension of VoltageInitMode of LoadFlowParameters, but it was not obvious the first time. So, the usage was not clear, especially with NONE. And what is happening if on LoadFlowParameters with choose PREVIOUS_VALUES and on OLFParameters we choose FULL_VOLTAGE. I think that the best solution is to put everything on LoadFlowParameters side. What do you think ?

As far as mode is not NONE, it overrides the LoadFlowParameters one.
Maybe we should rename the enum and parameter name to be more clear?
I would not add it to LoadFlowParameters as it is something that probably won't be in any other LF. Maybe also I would prefer to remove DC_VALUE and move it to LF specific parameters.

What you be the better names? For DC_VALUE, indeed as it is shared by at least two implementations, we can keep it as it is, no?

annetill · 2021-12-07T07:51:18Z

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

+                double r = 0;
+                for (LfBranch neighborBranch : neighborBranches) {
+                    PiModel piModel = neighborBranch.getPiModel();
+                    b += Math.abs(1 / piModel.getX()); // to void issue with negative reactances


You neglect B1 and B2 here, right? It could be worst righting it here.

How to mix it with 1/x ? there is no real branch model in that system. It is just a very raw and approximative proportionality law which is I think good enough to find a decent starting point.

Ok, I get that.

Be careful, we have some non impedant lines with an X equal to zero. I have met an issue on test testWith3GeneratorsAndNonImpedantBranch.

I am not sure that the good condition is piModel.getX() equals to zero. Maybe, but not sure here, we have to rely also on branch.isSpanningTreeEdge(). But it means that we can have zero impedance line that are not in the spanning tree, so another fix is needed for that branches.

annetill · 2021-12-07T07:55:28Z

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

+        //
+        // there are 2 types of equations:
+        //   for PV buses: target_v = v_i where i is the bus number
+        //   for other buses: 0 = sum_j(b_j * v_j) / sum_j(b_j) - v_i where j are buses neighbors of bus i and b is 1 / x


You miss to take into account ratios in our comment.

annetill · 2021-12-07T08:59:51Z

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

+                equationSystem.createEquation(bus.getNum(), InitVmEquationType.BUS_TARGET_V)
+                        .addTerm(v);
+            } else {
+                equationSystem.createEquation(bus.getNum(), InitVmEquationType.BUS_ZERO)


I don't understand here why we don't have any susceptance and any ratio. It seems that you use them only to compute the derivative. Why?

The InitVmBusEquationTerm equation term represents the sum at a given bus (I didn't use multiple equation term). So you will find the susceptance and ratio in the derivative calculation in this class.

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

geofjamg · 2021-12-08T21:35:12Z

@annetill I added support to non impedant branches, does it solve your issues?

It seems to only work if non impedant branch is not connected to a PV bus, otherwise PV bus voltage value is modified...

It is not working on Terna and on NGESO networks because it falls in exception Susceptance sum is zero.

Is it better now?

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

annetill · 2021-12-09T08:53:40Z

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

+    private static boolean isZeroImpedanceBranch(LfBranch branch) {
+        return branch.getBus1() != null
+                && branch.getBus2() != null
+                && branch.getPiModel().getX() == 0;


My first think here is to use better branch.isSpanningTreeEdge() to avoid cycle. It is what we have done for the AC equation system.

annetill · 2021-12-09T08:54:05Z

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

+                    variables.add(variableSet.getVariable(neighborBus.getNum(), InitVmVariableType.BUS_V));
+                }
+            }
+            if (bs == 0) { // should never happen


I fall in that with Energinet D10 network.

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

annetill · 2021-12-13T07:59:20Z

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

+
+        private final TDoubleArrayList der;
+
+        private static boolean isConnected(LfBranch branch) {


Could it be interested to move this method as a method of LfBranch ?

annetill · 2021-12-13T08:00:11Z

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

+                    && branch.getBus2() != null;
+        }
+
+        private static Map<LfBus, List<LfBranch>> findNeighbors(LfBus bus) {


Same remark with this method ?

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

sonarqubecloud · 2021-12-13T08:16:31Z

SonarCloud Quality Gate failed.

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89.0% Coverage
0.0% Duplication

geofjamg and others added 20 commits December 2, 2021 23:44

Voltage magnitude initialization

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Signed-off-by: Geoffroy Jamgotchian <[email protected]>

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Fix

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Cleanup

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Refactoring

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Refactoring

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Merge branch 'main' into init_v_mag

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Full voltage init

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Fix

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macos

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Signed-off-by: Geoffroy Jamgotchian <[email protected]>

Merge branch 'main' into init_v_mag

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# Conflicts: # src/main/java/com/powsybl/openloadflow/OpenLoadFlowParameters.java # src/test/resources/debug-parameters.json

Merge branch 'main' into init_v_mag

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Revert

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Signed-off-by: Geoffroy Jamgotchian <[email protected]>

Add unit tests

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Add doc

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Cleanup

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geofjamg changed the title ~~[WIP] Voltage magnitude initialization~~ Voltage magnitude initialization Dec 5, 2021

geofjamg requested a review from annetill December 5, 2021 12:16

geofjamg and others added 4 commits December 5, 2021 14:21

Add unit test

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Signed-off-by: Geoffroy Jamgotchian <[email protected]>

Cleanup

7a38c6c

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

Fix typo

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Merge branch 'main' into init_v_mag

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annetill reviewed Dec 7, 2021

View reviewed changes

geofjamg added 2 commits December 7, 2021 13:25

Fix doc

0afb8c0

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

Rename to VoltageInitModeOverride

38b3714

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

geofjamg requested a review from annetill December 7, 2021 13:27

geofjamg changed the title ~~Voltage magnitude initialization~~ [WIP] Voltage magnitude initialization Dec 8, 2021

geofjamg added 4 commits December 8, 2021 22:12

Fix zero impedance branch support

33f64a0

Signed-off-by: Geoffroy Jamgotchian <[email protected]>

Cleanup

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Improve unit test

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Add more unit test

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geofjamg changed the title ~~[WIP] Voltage magnitude initialization~~ Voltage magnitude initialization Dec 8, 2021

Fix Sonar issues

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Signed-off-by: Geoffroy Jamgotchian <[email protected]>

annetill reviewed Dec 9, 2021

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geofjamg and others added 8 commits December 9, 2021 13:40

Add more unit tests

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Signed-off-by: Geoffroy Jamgotchian <[email protected]>

Merge remote-tracking branch 'origin/init_v_mag' into init_v_mag

c8d62fa

Fix

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Fix

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Fix zero impedance cycle issue

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Add unit test

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Revert zero impedance equations

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Fix

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geofjamg requested a review from annetill December 13, 2021 07:23

geofjamg added 3 commits December 13, 2021 08:23

Merge branch 'main' into init_v_mag

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Fix

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Fix

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annetill reviewed Dec 13, 2021

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geofjamg requested a review from annetill December 13, 2021 08:14

annetill approved these changes Dec 13, 2021

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geofjamg merged commit cdd3e75 into main Dec 13, 2021

geofjamg deleted the init_v_mag branch December 13, 2021 08:22

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Voltage magnitude initialization #392

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sonarqubecloud bot commented Dec 13, 2021

		@@ -43,6 +43,14 @@

		public static final boolean VOLTAGE_PER_REACTIVE_POWER_CONTROL_DEFAULT_VALUE = false;

		public enum VoltageInitMode {


		private final TDoubleArrayList der;

		private static boolean isConnected(LfBranch branch) {

Voltage magnitude initialization #392

Voltage magnitude initialization #392

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