Advancement in Renewable Generation Harmonic Models to address evolving power system standards

With the growing penetration of renewable power sources, network and wind power plant stability analysis is becoming more important, specifically converter-driven stability analysis becomes indispensable. A well-established method is to assess the frequency domain stability by precompiled harmonic models representing positive and negative sequence impedance together with the harmonic source (Thevenin or Norton) as a function of the frequency.With the increasing importance of stability studies, the industry requires more detailed models, with validated confidence. The recent standard VDE 4131 sets high requirements for frequency resolution, power setpoints (active and reactive), and potentially other operation points, and modes, such as network voltage level and specific control modes. Although such models will lead to higher granularity of stability studies it challenges the wind turbine OEMs as each turbine variant with each configuration of control parameters requires exhaustive use case simulation validated against measurements. As simulation models are requested early in planning of new wind power plant connections – possibly even before the wind turbine product is developed – validation of simulation models can often not be solicited by measurements.This paper addresses the main challenges driven by the increased requirements, and therefore a new approach to harmonic model generation is proposed. A recursive model development procedure is proposed that starts with a minimum base model and gradually enhances the model until the required impedance rate of change or operating point granularity is achieved. This ensures high model accuracy while reducing the model size as well as field test and computational effort.