Overview

Load flow is implemented so that users can start a simulation from a steady-state condition. It is an analysis to determine the voltages, currents, real and reactive power flows under a given operating condition. Given the system admittance matrix, 4 variables (P, Q, V, theta) are associated with each bus to solve two power flow equations. Therefore, for each node, at least 2 out of the 4 variables should be known to solve the equations.

For background, see IEEE Std 3002.2™-2018 Recommended Practice for Conducting Load-Flow Studies and Analysis of Industrial and Commercial Power Systems.

For the use of different HYPERSIM components in load flow analysis, see Load Flow | Configuration of Components.

Open the Quick Start Reference Model

Launch HYPERSIM and load the model Load_Flow.ecf found under Options > Open an example model > How To.

Open

Build the Model

Ensure that all pertinent values have been entered when building the model (e.g. for voltage sources, ensure that you have defined both Base voltage and impedance values). Base power and Base voltage are important if voltage or impedance value is determined per unit.

After all the parameters are configured and all the connections are made, the model is ready for load flow execution.

Without a load flow solution, all the signals in the model would start from 0. Starting with a load flow solution initializes the model from steady-state values.

If you click on a bus in the example model where load flow has not yet been calculated, you will see default values in the load flow results tab.

Open

If you click on a generator, you will see the default values for Angular frequency, Voltage, Active power, and Reactive power.

Configure the Generation

Once the model is ready, relevant generator/source parameters must be defined so HYPERSIM can solve them in the load flow analysis.

First, choose the bus types for generators and sources, then configure the active power, voltage, and angle as required: see below.

Step 1: Determine the swing bus

There should be a source/generator that serves as the swing bus, with a given voltage and angle, to provide/absorb any mismatch between the load and generation in the system. 

Double-click on voltage source VS2, in the Load Flow tab, select the Type to be Swing. Specify Voltage to be 1 pu and Angle to be 0 deg.

Step 2: Configure the other sources

Similarly, configure the other generators/sources in the model. Usually, a generator bus is a PV bus because the generator controller regulates its terminal voltage and active power. 

Double-click on synchronous machine SM1, in the Load Flow tab, and select the Type to be PV. Specify Voltage to be 1 pu and Active power to be 30 MW.

Similarly, configure VS1, SM2 and SM3 as PV buses with the following parameters in the Load Flow tab:

Entering the Bus Voltage Level

To execute the loa’s nominal voltages, it defines the voltage of all the buses connected to each side of the transformer.

• For example, in this model, to access, click the HYPERSIM tab and click Netlist. 

• Once the Netlist window pops up, select Base Voltage from the Views drop-down menu.

• Each transformer’s primary, secondary and tertiary base voltages are already configured based on the transformers' voltage settings in the network model.

• Specify the Primary Bus Voltage and Secondary Bus Voltage accordingly. If a tertiary bus is present, configure it as well. There is a drop-down menu with common voltage levels which you can choose from.

• If the secondary buses of several transformers are connected, defining one bus will automatically define the others. After the configuration, it should look like this:

• Now if you go back to the model and double-click a bus, the nominal voltage is defined.

Step 3: Defining in Netlist - Load Flow Parameters

When there is no transformer, it means all buses are at the same voltage level. You could launch Netlist, then select Load Flow Parameters from the Views drop-down menu. 

Then you could define the Nominal voltage of all buses. Copy and paste works here!

Run the Load Flow

Open the Load flow, from the HYPERSIM Ribbon Options under Network.

Step 4: Load flow options

The Load Flow window opens. In the Load flow execution section, there are several load flow options and parameters:

Step 5: Load flow execution

Load flow execution parameters do not need to be changed for this example. Once all input parameters have been verified, proceed to perform the load flow analysis.

Hit the Load Flow button located in the upper part of the load flow window. This step also sets initial conditions for all the buses and components in the model.

You can see the result report abstract in the Output tab.

Click on the XML Report button to generate the Report. Then click on Load_Flow.exe in the report tab to see the summary and the values at each bus.

or click on the Txt Report button to display the report in the output tab:

Now, if you double-click source VS1, the Amplitude and Angle are updated.

If you double-click on SM1, the Angular frequency, Voltage, Active power and Reactive power are updated to load flow solution values.

If you double-click on a bus, the data in Load Flow Results tab are updated based on the load flow solution. Take Bus14 as an example:

The load flow parameters can also be viewed in Netlist - Load Flow Parameters.

The updated values are used by HYPERSIM once the simulation is launched to start from steady-state conditions.

Additional Information