Simplified modelling of frequency dependent network for converter control system design

The integration of renewable generation in the energy mix has led to a massive penetration of converter-interfaced generators (CIG) in the electrical network. However, CIG's are reported to be susceptible to interactions with electrical resonances and  other equipment. It became common practice to conduct electromagnetic transient (EMT) studies to assess these risks, define the mitigation measures and design the control systems. To perform the controllers design efficiently, the EMT analysis can be complemented with an analysis of linearized systems, for which numerous efficient methods have been developed.

 The paper presents a method to construct the linearized system which is believed to be sufficiently accurate for being used for controllers tuning, and sufficiently simple to be efficiently used on real-life cases. It takes into account the frequency dependent electrical network, and is based on the approach previously used for torsional analyses, but applied to a wider spectrum. It is illustrated on a simple numerical example, demonstrating the challenges that the electrical resonances might pose on the stability margins. A comparison of the results obtained from linearized model and EMT model is presented, aiming to validate the findings from the linearized model and the proposed approach.