The adequacy of the present practice in dynamic aggregated modelling of wind farm systems

Large offshore wind farms are usually composed of several hundred individual wind turbines, each turbine having its own complex set of dynamics. The analysis of the dynamic interaction between wind turbine generators (WTG), interconnecting ac cables, and voltage source converter (VSC) based High Voltage DC (HVDC) system is difficult because of the complexity and the scale of the entire system. The detailed modelling and modal analysis of a representative wind farm system reveal the presence of several critical resonant modes within the system. Several of these modes have frequencies close to harmonics of the power system frequency with poor damping. From a computational perspective the aggregation of the physical model is necessary in order to reduce the degree of complexity to a practical level. This paper focuses on the present practices of the aggregation of the WTGs and the collection system, and their influence on the damping and frequency characteristics of the critical oscillatory modes. The effect of aggregation on the critical modes are discussed using modal analysis and dynamic simulation. The adequacy of aggregation method is discussed

Model order reduction of wind farms: linear approach

This paper presents three types of linear model order reduction (MOR) technique, namely singular value de- composition (SVD)-based, Krylov-based, and modal truncation- based type applied to large-scale wind farm models. The first type includes a Balanced Truncation (BT) and Alternating Direction Implicit (ADI)-based BT method, while the second type encompasses a Rational Krylov (RK), and Iterative Rational Krylov Algorithm (IRKA) method. In the third type, a Subspace Accelerated MIMO Dominant Pole Algorithm (SAMDP) method is used. The effectiveness of these methods are tested on practical- sized wind farms with 90, 120 and 210 doubly-fed induction generators (DFIGs). Merits and demerits of each method are discussed in detail. The reduced order model (ROM) of wind farm is validated against the full order model (FOM) in term of frequency domain indices and waveform agreement at the point of common coupling (PCC)

Electrical oscillations in wind farm systems: analysis and insight based on detailed modeling

This paper presents modeling and analysis of electrical oscillations in a wind farm system. The detailed modeling and modal analysis of a wind farm system are presented in this paper. The approach to modeling uses detailed representation of a wind turbine generator and collection system including high-voltage direct-current (HVDC) power converter system control, facilitating a comprehensive analysis of the wind farm system. Various modes are classified according to the frequency of oscillation. The detailed modal analysis is used to characterize the critical modes. Time-domain simulation also confirms the presence of these modes. The effect of wind farm operating conditions and voltage source converter control tuning on critical oscillatory modes are also assessed and discussed in detail