The main goals and research objectives of this project are to study the stability of power systems dominated by a large number of grid-connected converters, develop stable and reliable control algorithms to guarantee their secure operation in an interconnected network, and outline models and tools that can improve and facilitate system-level analysis and planning.

In the initial phase of the project development, a comprehensive review of the state-of-the-art literature and currently available technical standards will be conducted to assess the foundations and challenges of the fields of interest. The literature survey will help to define the mathematical framework and methodologies for analysis, investigate the current research result, and define specifications and performance metrics that will be used for quantitative assessment of project findings and results.

Then, analytical modeling and numerical simulations will be carried out, both on a single converter level and on a system level. To achieve these tasks, we plan to use readily available tools for time-domain and phasor-domain simulation of power electronic devices and larger power systems (e.g., MATLAB-Simulink, DIgSILENT PowerFactory). Frequency and voltage control algorithms will be developed, taking also advantage of the results from previous research activities.

Experimental validation of the project findings will be finally conducted at the University of Zagreb’s Smart Grid Laboratory (SGLab) facility. SGLab is equipped for conducting the stated research activities. SGLab includes a real-time simulator (dSPACE SCALEXIO), synchronous generating units (2x20 kVA), converter-based generating units and loads (6x VARTA Neo Pulse 2.5 kW battery, 80 kW solar PV plant, PowerTech Systems 18 kW battery, 5 kW supercapacitor), and a low-voltage microgrid emulating a realistic distribution system (13 node CIGRE benchmark with reconfigurable line parameters). Additionally, the specification and procurement of an open and custom designed power electronic converter are planned to integrate it into the existing Smart Grid Laboratory for conducting research.

Research goals and objectives are:

• Characterization of power system dynamic behavior in the presence of a high share of heterogeneously controlled converter-interfaced equipment
• Development of reduced-order models of converter-interfaced equipment suitable for large-scale power system analysis with the focus on grid frequency control
• Experimental verification of developed control algorithms on a laboratory-scale power system
• Definition of a set of key technical requirements for future grid codes based on conducted system level and component-level analysis