Enhanced Co-Simulation of Wind Energy Conversion Systems: A Mechanically Equivalent Interfacing Method

Co-simulation of mechanical subsystems (MSs) and electrical subsystems (ESs) is crucial for the efficient design and analysis of wind energy conversion systems (WECSs). The interfacing method is critical to affect the accuracy of such multi-rate co-simulations, due to the inherent multi-timescale nature of WECSs. Existing studies primarily utilize the zeroorder-hold (ZOH)-based interfacing method, introducing the stepwise approximation errors for updating interfacing variables. Enhancing co-simulation accuracy via an effective interfacing method remains an open research challenge. This paper proposes a mechanically equivalent interfacing method that accurately predicts interfacing variables, thereby enhancing co-simulation accuracy. A frequency-dependent equivalent model is derived based on the frequency-domain response of the MS. A parameterfree nonlinear identification algorithm is proposed, operating independently of prior MS parameters knowledge to improve generality. Moreover, a linear parameter-varying (LPV) model is introduced to capture nonlinear behavior across the global operating region of the MS. The proposed frequency-dependent equivalent model is verified in both the frequency and time domains using the 5MW and 10MW WECSs. Furthermore, the interfacing method is compared with the ZOH-based, higher-order extrapolation interpolation-based, and waveform relaxation-based methods under both normal and fault operating conditions in offline and real-time co-simulations. Simulation results confirm the accuracy advantages of the proposed method for multi-rate co-simulation of WECSs.