With the rapid penetration of power electronic (PE) devices in the system, large network wide dynamic stability simulations conventionally performed using Root Mean Square (RMS) type simulations may not capture the correct system dynamic response. Electromagnetic transient (EMT) simulation can accurately capture the changing dynamic of the network. However, it requires a significant data modelling effort and has limitations when simulating large systems. Thus, a more effective and flexible future power system modelling approach is required to meet future modelling needs.
This project aims to develop an innovative co-simulation modelling approach between Digsilent PowerFactory (RMS type) and PSCAD (EMT type) which can effectively maintain the benefits to both types of mathematical platforms, reduce the data modelling effort for EMT modelling and efficiently perform reliable simulation studies.
Benefits
The developed co-simulation approach in this project will reduce the modelling efforts and improve the efficiency of the simulation on system dynamic analysis for large networks. It will also improve the accuracy of the modelling and reduce the risk in planning and design. Based on our cost benefit analysis, the estimated benefits of the project by 2030 in NPV (Net Present Value) will be around £272k if the project is successful.
Learnings
Outcomes
The co-simulation uses a master/slave architecture as described by the Functional Mock-Up Unit Interface (FMI) 2.0.4 specification. One process uses PSCAD/EMTDC to run pre-identified portion/s of the network in EMT domain. Another process (PF Slave) uses PowerFactory to run the rest of the network in RMS domain.
The PowerFactory processes were configured for co-simulation using the Co-Simulation Interface Module. PF Master is a PowerFactory instance configured to run as the simulation master in a Co-Simulation with external application. It is assumed that the communication between the PF Master and PF Slave exchange data through an FMI compliant interface, which has been prepared using the Co-simulation Interface module.
A PowerFactory instance is configured to run as an FMU (Functional Mock-Up Unit) Agent. FMU files are generated during preparation, which define the voltage and current signals to be transmitted. The FMU files also contain executable code to implement tool coupling described in the FMI standard. The RMS FMU is coupled to PowerFactory.
An EMT FMU has been developed, which is coupled to EMTDC. PSCAD/EMTDC uses a communication interface to transmit data through Transmission Control Protocol/Internet Protocol (TCP/IP) connections. EMTDC will act as a server and establish communication channels for a given port. The TCP/IP client is implemented as a dynamic link library, which is encapsulated in the EMT FMU. During the calling sequence, input/output values representing voltage and current are exchanged between the EMT and RMS networks.
The communication link between EMT and RMS is verified (by using the example case shown in Figure 2) and proven to be functioning properly. The FMUs input/output signals were in accordance with the FMI standard and the electrical signals were being correctly transmitted between EMT and RMS networks. Furthermore, output signals from the EMT network and output signals from the RMS network were analysed to identify any delays that resulted from the co-simulation run.
It was observed that the co-simulation was able to proceed with the RMS and EMT regions running at different time steps i.e. the RMS subsystem simulated at 10 ms time step while the EMT subsystem simulated at 50 µS. During each communication point, the RMS and EMT simulations were able to exchange voltage and current signals through the master.
Further investigations exhibited that the PowerFactory co-simulation implementation supports the parallel data exchange algorithm (RMS and EMT sub-systems exchange the latest available information without waiting for the other to complete time step calculation) between RMS and EMT sub-systems. Alternatively, a serial data exchange algorithm (RMS and EMT sub-systems exchange information once each side completes time step calculation) may also be supported by PowerFactory co-simulation implementation.
Recommendations for further work
Recommendations for further work can be realised once further development and testing of the co-simulation approach is conducted.
Lessons Learnt
Further development of co-simulation is required before lessons for future projects can be realised.
Dissemination
Dissemination activities will be arranged after the completion of the project.
