Grid integration

Grid Integration

Modeling and Simulation of offshore renewable generation and integration into the power system

Traditional power systems have been designed with generation plants based on large rotating synchronous generators. New renewable generation plants are based mainly on generators connected though power electronic converters. There is a problem when replacing generation plants with conventional synchronous generators by generation plants connected through full converter machines and asynchronous generators. This issue is shared by any distributed power generation but is especially relevant with high power penetration as in offshore renewable farms. The total inertia of the system decreases and the response to frequency variation worsens.

Power electronics-based systems have faster response times than traditional systems providing extra degree of controllability. However, they can also exhibit dynamic interactions at higher frequencies. This makes it necessary to develop specific models for stability analysis. Moreover, the rapid dynamics of the power electronics control system and the interaction with the electrical system can influence critical eigenvalues associated with relatively low frequencies. As a result, oscillations are generated at frequencies not typical (50*n). To tackle this problem proper tuning of the power electronics control loops, PLLs and implementation of damping algorithms is necessary.

Therefore, the design and analysis of offshore delivery systems in HVDC and HVAC is essential. In HVAC, the losses and reactive power compensation (static and dynamic) must be considered. In HVDC, controls and specific models for multi-terminal and point to point grids, to carry out grid integration and stability studies, are designed. The controls assure the correct performance of the HVDC link itself and allow grid connection and Grid Code compliance.

The main origin of these problems has aroused with the high penetration of large offshore renewable energy farms. In this sense, the research is focused on the integration of renewable generation into power systems from the development of models of renewable generation systems and power system integration studies, especially through the following activities:

  • Dynamic user models of renewable and distributed generation, including storage, with high-level controls for normal and perturbed operation.
  • Integration of models into commercial power system analysis tools.
  • Power system studies (EMT, dynamic and steady state) for evaluating technical and economic issues due to the interconnection of renewable generation. From detailed evaluation of specific renewable plant project to large system integration studies.
  • Stability studies and propagation of harmonics are carried out through impedances and modal analysis in order to propose solutions to mitigate these issues.

Contact and more information: Pablo Eguia