Circuit based implementation of the Universal Line Model in Matlab/Simulink


Over the last decades the transmission grid has been transformed by an increasing use of power electronics. It is the result of the rapidly growing number of HVDC links in the AC transmission network as the renewable energies are integrated into the grid to meet climate neutrality by 2050.

Manufacturers of power converters need to develop solutions for multiterminal and multivendor MVDC and HVDC systems. Interoperability and protection strategies must be developed for reliable operations of such systems. As a result, manufacturers of power electronics need accurate and reliable simulation tools and models for their studies of electrical systems.

Electrical systems can be simulated using various commercial software tools and simulation environments, such as EMTP, PSCAD, or MATLAB/Simulink. EMTP and PSCAD provide comprehensive cable and power grid models and are thus typically used by TSOs and grid specialists for transient studies. On the other hand, MATLAB/Simulink includes low-level controls, and is thus widely used by power electronic manufacturers to model converters. MATLAB/Simulink has however less reliable and detailed models of cable and power grid compared to EMTP and PSCAD.

This paper presents an improved version of the Universal Line Model (ULM) also known as Wide-Band (WB) model. This new model has been integrated in the MATLAB/Simulink environment to achieve time domain transient simulations of electrical networks based on power electronics.

This improved ULM model is based on an electrical circuit representation of the shunt line admittance. Its efficiency is improved thanks to lower order approximations using the Rational Krylov technique. For multiconductor modeling, the characteristic admittance is represented as an equivalent two-port Y parameter system.

First, the frequency dependent multiconductor transmission line modeling is reviewed in the frequency and time domains. Then, the new implementation is described step-by-step to reach the equivalent electrical circuit. Finally, the accuracy and the numerical performance of the proposed implementation are assessed using representative application examples, and they are compared to the Electromagnetic Transient Program EMTP. Our improved ULM combines the capability of reliable transient studies while having similar performances as traditional grid simulation softwares.

Amjad Mouhaidali, Martin Henriksen, Léo Dalmar

Presented at Jicable’23