9 Power Flow
9 Power Flow
Cimphony contains a balanced power flow engine that can analyse a network and perform a Newton- Raphson based power flow calculation. It currently supports CIM 14-16 with support for exporting the results as CIM State Variable data
9.1 Building a Power Flow Model
- From the main menu select Analysis and Run Power Flow…
- Select the IEEE 14 Bus Network from the Local Repository→IEEE Test Networks folder and click Next.
- For the power flow input parameters we can select from differentinputs: the steady state hypothesis values (i.e. the default values for CIM14-15 or the new steady state values added in CIM16); any SCADA measurement data if available; or an existing solution defined as state variables. Select the Steady State Hypothesis.
- The network can use either the pre-computed Topological Nodes (Bus/Branch) or Connectivity Node (Node/Breaker) data, with the option of computing the Bus/Branch model from the Connectivity Nodes at runtime. Select the Topological Nodes.
- There are no Energy Sources in the data so the option of converting them to Generators can be ignored.
- No existing islands exist in the data so this option is disabled.
- Click Build Power Flow Model to calculate the network and starting conditions for the power flow calculation.
- When this is complete the Next button will become active and a green tick will appear next to the Build Power Flow Button. Click Next.
9.2 Running the Power Flow
The Power Flow Starting Condition screen shows the computed Buses and Branches along with a summary of the number of islands and total load, generation and shunts on the system.
When the network produces multiple islands, multiple tabs are created for each island with a summary for each. The user can choose whether to include each island in the power flow calculation or to ignore it. If the island is not energised (i.e. has no input generation or negative loads) it will be disabled by default.
- Click on the Bus Name column to sort the buses by their name. Check that Bus 1 HV has its type set as Swing.
- Leave the Flat Start and Automatic Swing disabled as we should be able to solve without requiring a flat start and a swing bus is already defined so we do not have to automatically determine the best one.
- Click Run Power Flow to execute the power flow calculation.
- If the calculation converged then a green tick will appear in the tabof the island. The Bus and Branch views will be greyed out. Click the View Log button to see the calculation log.
- This shows how many iterations were required and the maximum PQDelta at each iteration (and which bus this was on). Click OK to closethis window.
- Click Next to load the Power Flow Results window showing thecalculated values for the buses and branches. This shows the voltage magnitudes and angles and all calculated real and reactive power generation.
The results should show that the swing bus, Bus 1 HV was held at a per-unit voltage of 1.0 and its angle held at 0.0 degrees. Its real and reactive generation will have changed to solve the network. For the PQ nodes the voltage magnitude and angle will both have varied and for PV buses the voltage will be at its initial starting value with a change to the angle and reactive generation
The Branches view shows the real and reactive power flows at each side of the branch and the resulting losses. The summary at the top sums these losses to show the overall loss in the system
- Click Next to get to the Power Flow Result Export page. Here different outputs can be generated
- Click Export Excel... and select a location on disk for an Excel file with the output results.
- Select Create State Variables to create the CIM State Variable results data.
- Select Create Headers to ensure the data is written out with the correct headers as defined by IEC 61970-552.
- Click Next for the file output page. Select the Open Grid Systems project and its networks folder. Set the file name to ieee14-sv.xml.
- Click Finish to generate this state variables data and write the file to disk.