Types of DFIG VSC converter

Depending on the range of frequencies to be represented, three simulation methods are currently available in Specialized Power Systems to model VSC based energy conversion systems connected on power grids.

The detailed model (discrete) such as the one presented in this example. The detailed model includes detailed representation of power electronic IGBT converters. In order to achieve an acceptable accuracy with the 1620 Hz and 2700 Hz switching frequencies used in this example, the model must be discretized at a relatively small time step (5 microseconds). This model is well suited for observing harmonics and control system dynamic performance over relatively short periods of times (typically hundreds of milliseconds to one second).

The average model (discrete)  In this type of model the IGBT Voltage-sourced converters (VSC) are represented by equivalent voltage sources generating the AC voltage averaged over one cycle of the switching frequency. This model does not represent harmonics, but the dynamics resulting from control system and power system interaction is preserved. This model allows using much larger time steps (typically 50 microseconds), thus allowing simulations of several seconds. Simulink commands for average model (discrete)  power_wind_dfig_avg model in the Renewable Energy in examples library.

The phasor model (continuous) such as the one presented in the "power_wind_dfig" model in the Renewable Energy examples library. This model is better adapted to simulate the low frequency electromechanical oscillations over long periods of time (tens of seconds to minutes). In the phasor simulation method, the sinusoidal voltages and currents are replaced by phasor quantities (complex numbers) at the system nominal frequency (50 Hz or 60 Hz).This is the same technique which is used in transient stability software. Simulink commands for phasor model (continuous) power_wind_dfig model in the Renewable Energy in examples library.