PSCAD/EMTDC-Based Modeling and Analysis of a Gearless Variable Speed Wind Turbine

Abstract

This paper presents dynamic modeling and simulation of a grid connected variable speed wind turbine (VSWT) using PSCAD/EMTDC, a widely used power system transient analysis tool. The variable speed wind system with a direct-drive generator and power electronics interface is modeled for dynamic analysis. Component models and equations are addressed and their implementations into PSCAD/EMTDC are described. Controllable power inverter strategy is intended for capturing the maximum energy from varying wind speed and maintaining reactive power generation at a pre-determined level for constant power factor or voltage regulation. The component models and entire control scheme are constructed by user-defined function provided in the program. Simulation studies provide control performance and dynamic behavior of a gearless VSWT under varying wind speeds. In addition, the system responses to network fault conditions have been simulated. This modeling study can be employed to evaluate the control scheme, output performance and impacts of a VSWT on power grid at planning or designing stage. Index Terms-Gearless wind generator, grid connection, maximum power capture, power electronics interface, reactive power control, variable speed wind turbine (VSWT). LIST OF SYMBOLSλ Tip speed ratio ω M Mechanical speed of wind turbine [rad/s] R Blade radius [m] V WIND wind speed [m/s] P M Mechanical power from wind turbine [kW] ρ Air density [kg/m 3 ] C P Power coefficient T M Mechanical torque from wind turbine [N · m] f B Electrical base frequency of generator [Hz] N P Number of poles RPM TUR Rated speed of wind turbine [rpm] H i Inertia constant of ith mass [s] K Shaft spring constant [Nm/rad] T E Electrical torque of generator [N · m] θ i Mass angle of ith mass (reference on generator) ω M Mechanical speed of generator [rad/s] ω E Electrical speed of generator [rad/s] E f Field voltage of exciter [V] I f Field current of exciter [A] V dc DC link voltage [V] α IGBT switching signal P inv , Q inv Measured real and reactive power [kW], [kVar] V inv , I inv Measured voltage and current of inverter [V], [A] V d , V q d-and q-axis voltage at VSWT terminal [V]

State-of-the-art review on frequency response of wind power plants in power systems

“…Different control methods for maximum power point tracking (MPPT) operation are implemented in the rotor-side converter of VSWTs, consisting of torque-based, active power-based and rotor speed-based converter control [10,[12][13][14][15][16]. To make VSWTs properly perform the frequency regulation function following specific frequency regulation requirements, supplementary controllers should be designed and integrated into both the existing converter power control loop and the pitch angle control loop to manipulate the corresponding reference set points of torque, active power or rotor speed [12][13][14][15][16][17][18][19].…”

Complementary Power Control of the Bipolar-type Low Voltage DC Distribution System

“…The WT system is operated to produce the maximum power in this paper. Detailed mathematical expression and flowchart of the WT controller are described in [4,21,22].…”

“…All cases are simulated using PSCAD/EMTDC software. Detailed mathematical descriptions and models are available in [4,19,21]. The system configuration and parameters are represented in Fig.…”

Application of Individual Pitch Controller for Flicker Reduction on Variable Speed Wind Turbines

“…Vector-control technology has been developed for direct-drive generators using back-to-back PWM converters [12]. Since the study interest is not concentrated on the switches of the PWM converter but for the flicker calculation that requires a long simulation time, an average model without switches is used so that the simulation can be carried out with a larger time step resulting in a simulation speed improvement [13].…”