Chair of Power Electronics

Stability Analysis and Control of a Distribution Grid with High Penetration of Wind Energy

In the last years, the legacy power grids, which are dynamically dominated by centralized power plants, are progressively evolving into power electronic based power systems, driven by the large-scale adoption of electronic power converters. This evolution paves the way towards a huge improvement on sustainability and flexibility, but the hosting capacity of the grid for renewable energy is limited by the grid infrastructure. Moreover, the continuous increase of renewable energy sources in the grid poses new challenges, such as the stability of the grid without the centralized power plants. More precisely, for distribution grids dominated by renewable energy sources, the problem of Harmonic Instability can arise and needs to be considered. [read more]

Harmonic Instability is a variety of small-signal instability that induces a waveform distortion in different frequency ranges and can result in the instability of the system. Voltage oscillations affected by these phenomena may even destroy loads connected to the grid. Systems like photovoltaic and wind farms (low SCR) are more prone to this problem, that for this reason must be addressed with high priority to allow the development of modern renewable energy grids. Northern Germany, in particular Schleswig-Holstein, as a land between the seas is continuously increasing the extension of wind energy, whereby in 2016 onshore wind energy is already accounted for covering nearly 76,1% of the Schleswig-Holstein energy consumption.


For enabling a further increase of the hosting capacity for renewable energies without excessive and expensive grid extension, the Smart Transformer (ST), which is a power electronic based transformer with control and communication capability, is a potential solution. That lays the foundation for the realization of a modern, intelligent and efficient energy generation system based on renewable energy. This research is focused on the control of a Smart Transformer fed Micro Grid in order to ensure Harmonic Stability.


An example of Harmonic Instability

Title Stability Analysis and Control of a Distribution Grid with High Penetration of Wind Energy
Coordinator Prof. Marco Liserre
Contact Person M. Sc. Federico Cecati (
Type Doctroral Scholarship (Funded by EKSH)
Funding -
Partners Aalborg University
Duration 01.06-2018 - 31.05.2021
Keywords Smart Transformer, State Space, Stability Analysis, Micro Grid

  • Our research is focused on the design of high efficient and reliable PWM-based power converter architectures (single-cell, multi-cell, multilevel), their modelling and control to exploit commercial as well as new power semiconductor devices with minimum over design.
    We develop controllers for electric drives and we are particularly skilled in the integration of renewable energy systems into the electric grid.
    Please discover our expertise looking to our recent projects.

    HEART - The Highly Efficient And Reliable smart Transformer
    Further Research Projects