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Create and Simulate Expanded Balanced and Unbalanced Three-Phase Models

This procedure shows you how to modify a model that you built in Build and Simulate Composite Resistive and Reactive Three-Phase Models to create:

  • A three-phase load expanded into individual phases

  • An expanded three-phase load that does not have equal resistance in each phase

In this procedure, you change the original model and save the changes as new models. You then simulate the new models and analyze the results.

Create an Expanded Balanced Three-Phase Model

  1. Open Simple Three-Phase Model.

  2. Delete the RLC block.

  3. Drag two copies of the Phase Splitter block into the model from the Simscape > Power Systems > Simscape Components > Connections library.

  4. Flip one of the Phase Splitter blocks horizontally. Right-click the block and select Rotate & Flip > Flip Block > Left-Right.

  5. Drag a Resistor element into the model from the Simscape > Foundation Library > Electrical > Electrical Elements library.

  6. To create space for more components, hide the Resistor element label. Right-click the resistor and select Format > Show Block Name to clear this option.

  7. Make two more copies of the Resistor element.

  8. Connect the components as shown.

  9. Save this version of the modified model using the name simplethreephasemodel_expanded_balanced.

    This model name reflects that the load previously modeled by the RLC block is now expanded into individual phases. The load is still balanced, that is, there is equal resistance in each phase.

Create an Expanded Unbalanced Three-Phase Model

  1. Unbalance the load by changing the resistance in one phase. Double-click one of the resistor elements. Change Resistance to 2.

  2. Save this version of the modified model using the name simplethreephasemodel_expanded_unbalanced.

    This model name reflects that the three-phase load previously modeled by the RLC block is expanded into individual phases. The load is unbalanced, that is, the resistance in one of the phases is higher than in the other two.

Simulate the Models and Analyze Results

  1. Simulate the simplethreephasemodel_expanded_balanced model. In the menu bar of the Simulink® Explorer, click the Run button.

  2. View the simulation results. Double-click the Scope block.

  3. To scale the scope axes to the data, click the Autoscale button .

    In Build and Simulate Composite Resistive and Reactive Three-Phase Models, the Component structure parameter of the RLC block specifies that the three-phase load is purely resistive. In this version of the model, the load is expanded into an individual resistive element for each phase, but the resistance in each phase is unchanged. For each phase of the three-phase system, the voltage and current remain in phase with each other. Because the resistance in each phase is 1 Ω, the magnitude of the phase voltage is equal to the magnitude of the phase current.

    Comparing these results with the results for the three-phase resistive model shows that a block with composite three-phase ports (the RLC block in the original model), produces results with the same fidelity as that of expanded phases.

  4. Open the simplethreephasemodel_expanded_unbalanced model.

  5. Simulate the model. Autoscale the scope axes.

    In this version of the model, one phase of the three-phase load has twice the resistance of the other two. Therefore, half as much current flows in that phase, as the second plot shows. However, because the load remains purely resistive, the voltage and current remain in phase with each other.

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