In recent years, electrical generators based on renewable energies have been massively deployed in electrical distribution systems. These generators are connected by using electronic power converters instead of the traditional electrical rotating machines. This change in the operation paradigm is negatively affecting the power system, which was design to work with rotating machines, exclusively. On the one hand, the operating principles of electrical rotating machines cannot be modified since their response is mainly based on the physical characteristics of the machine itself (inertia, friction, impedance values, etc.). On the other hand, the operation principles of electronic power converters are highly flexible since the response can be configured by adapting the control system (i.e. the software). Therefore, an efficient solution to simplify the integration of both technologies is to emulate the dynamic characteristics of electric rotating machines with the control system of power converters. If power converters emulate electrical machines, the original machines will “see” other machines, and therefore both technologies can operate together, seamlessly. A converter that emulates an electrical machine is commonly known as a “virtual synchronous machine” (or VSM). However, the development and design of this type of control system is complex and requires more research effort in order to implement it in real systems.
The Electrical Systems Unit of IMDEA Energy Institute has developed a design procedure for virtual synchronous machines*. The main benefit of this procedure is that the design can be standardized. In order to develop these design rules, the converters and their control systems were modelled and analyzed in detail. By following the proposed steps, converters and electrical machines can be operated together in a robust and stable way.
(*) Rodriguez-Cabero, A., Roldan-Perez, J., Prodanovic, M. Virtual Impedance Design Considerations for Virtual Synchronous Machines in Weak Grids (2020) IEEE Journal of Emerging and Selected Topics in Power Electronics, 8 (2), art. no. 8693833, pp. 1477-1489, DOI: 10.1109/JESTPE.2019.2912071
More information: Javier Roldán, Postdoctoral Researcher, Electrical Systems Unit firstname.lastname@example.org
Electrical and control system diagram of an electronic power converter connected to a grid. (a) control System, (b) virtual impedance (it is used to adjust the VSM response) and (c) hardware elements.
Main results obtained during the design procedure. (left) Frequency response of the system, (ctr) eigenvalues and (right) transient response of active and reactive power.