MATLAB 2012 Simulation Model for Direct-Drive Wind Power Generation

Direct-drive wind power generation systems feature a design that directly connects the wind turbine to the generator without a gearbox, offering advantages of simple structure and low maintenance costs. When constructing simulation models for such systems in MATLAB 2012 environment, several core modules require special attention: Wind Turbine Model Simulates aerodynamic characteristics of the rotor, focusing on converting wind speed into mechanical torque. Typically employs Blade Element Momentum (BEM) theory to calculate wind energy capture efficiency, with nonlinear conversion achieved through Cp (power coefficient)-λ (tip speed ratio) curves. Implementation requires polynomial fitting of Cp-λ curves using MATLAB's polyfit function or lookup tables. Permanent Magnet Synchronous Generator (PMSG) Direct-drive systems commonly use PMSGs, requiring construction of dq-axis mathematical models in Simulink including stator voltage equations, electromagnetic torque equations, and mechanical motion equations. Magnetic saturation effects must be considered (requires manual addition of saturation blocks in 2012 version). Key implementation involves proper parameterization of the PMSG block from SimPowerSystems library. Maximum Power Point Tracking (MPPT) Controls generator speed to maintain operation in the Cp-max region, commonly implemented through "hill-climbing search" methods or lookup-table approaches based on wind speed estimation. In 2012 version, this requires custom S-function programming or PID controller implementation with rate limiters to prevent excessive torque fluctuations. Grid-Connected Inverter Control Features double-loop control for machine-side and grid-side converters: machine-side regulates rotational speed while grid-side maintains DC-link voltage stability and achieves unity power factor grid connection. Note that Space Vector PWM modules in 2012 version must be called from SimPowerSystems library, with proper carrier frequency setting typically between 2-10 kHz. Wind Speed Model Recommended to use combined inputs of step wind, gust wind, or random wind to test system dynamic response. Random components can be generated using Band-Limited White Noise blocks with appropriate noise power settings and seed values for reproducible results. Simulation Key Points - Step size should be properly set (recommended ≤50μs) to avoid numerical oscillations - PMSG parameters in 2012 version require manual input with attention to unit conversions (e.g., inertia should use kg·m² rather than per-unit values) - For comparison with actual data, export waveforms to Workspace and use MATLAB scripts to calculate THD, efficiency metrics, and other performance indicators through functions like fft for harmonic analysis and mean for efficiency calculations The model can be extended to study low-voltage ride-through (LVRT) capabilities or participate in wind farm cluster simulations, though note that 2012 version has limited support for multi-machine parallel computation, requiring potential model partitioning for large-scale simulations.