Documentation Center

  • Trial Software
  • Product Updates

Wind Turbine Induction Generator (Phasor Type)

Implement phasor model of squirrel-cage induction generator driven by variable pitch wind turbine

Library

Renewable Energy/Wind Generation

Description

The wind turbine and the induction generator (WTIG) are shown below. The stator winding is connected directly to the grid and the rotor is driven by the wind turbine. The power captured by the wind turbine is converted into electrical power by the induction generator and is transmitted to the grid by the stator winding. The pitch angle is controlled in order to limit the generator output power to its nominal value for high wind speeds. In order to generate power the induction generator speed must be slightly above the synchronous speed. But the speed variation is typically so small that the WTIG is considered to be a fixed-speed wind generator. The reactive power absorbed by the induction generator is provided by the grid or by some devices like capacitor banks, SVC, STATCOM or synchronous condenser.

Pitch Angle Control System

The wind turbine model uses the Wind Turbine block of the Renewable Energy/Wind Generation library. See documentation of this block for details.

A Proportional-Integral (PI) controller is used to control the blade pitch angle in order to limit the electric output power to the nominal mechanical power. The pitch angle is kept constant at zero degree when the measured electric output power is under its nominal value. When it increases above its nominal value the PI controller increases the pitch angle to bring back the measured power to its nominal value. The control system is illustrated in the figure below:

Dialog Box and Parameters

The WTIG parameters are grouped in two categories: Generator data and Turbine data». Use the Display listbox to select which group of parameters you want to visualize.

Generator Data Parameters

Nominal power, line-to-line voltage and frequency

The nominal power in VA, the nominal line-to-line voltage in Vrms and the nominal system frequency in hertz.

Stator [Rs, Lls]

The stator resistance Rs and leakage inductance Lls in pu based on the generator ratings.

Rotor [Rr', Llr']

The rotor resistance Rr' and leakage inductance Llr', both referred to the stator, in pu based on the generator ratings.

Magnetizing inductance Lm

The magnetizing inductance Lm in pu based on the generator ratings.

Inertia constant, friction factor and pairs of poles

Combined generator and turbine inertia constant H in seconds, combined viscous friction factor F in pu based on the generator ratings and number of pole pairs p.

You may need to use your own turbine model, in order for example, to implement different power characteristics or to implement the shaft stiffness. Your model must then output the mechanical torque applied to the generator shaft. If the inertia and the friction factor of the turbine are implemented inside the turbine model you specify only the generator inertia constant H and the generator friction factor F.

Initial conditions

The initial slip s, electrical angle Θ in degrees, stator current magnitude in pu and phase angle in degrees.

Turbine Data Parameters

Refer to the Wind Turbine for a detailed documentation.

External mechanical torque

If this parameter is checked, a Simulink® input named Tm appears on the block, allowing to use an external signal for the generator input mechanical torque. This external torque must be in pu based on the nominal electric power and synchronous speed of the generator. For example, the external torque may come from a user defined turbine model. By convention for the induction machine, the torque must be negative for power generation.

Display wind turbine power characteristics

If this parameter is checked, the turbine power characteristics at the specified pitch angle are displayed for different wind speeds.

This parameter is not visible when the External mechanical torque parameter is checked.

Nominal wind turbine mechanical output power

This parameter is not visible when the External mechanical torque parameter is checked.

The nominal turbine mechanical output power in watts.

Base wind speed

This parameter is not visible when the External mechanical torque parameter is checked.

The base value of the wind speed, in m/s, used in the per unit system. The base wind speed is the mean value of the expected wind speed. This base wind speed produces a mechanical power which is usually lower than the turbine nominal power.

Maximum power at base wind speed

This parameter is not visible when the External mechanical torque parameter is checked.

The maximum power at base wind speed in pu of the nominal mechanical power.

Base rotational speed

This parameter is not visible when the External mechanical torque parameter is checked.

The rotational speed at maximum power for the base wind speed. The base rotational speed is in pu of the base generator speed.

Pitch angle controller gain [Kp Ki]

This parameter is not visible when the External mechanical torque parameter is checked.

Proportional and Integral gains Kp and Ki of the pitch controller. Specify Kp in degrees/(power deviation pu) and Ki in degrees/(power deviation pu)/s. The power deviation is the difference between actual electrical output power and the nominal mechanical power in pu of the generator nominal power.

Maximum pitch angle (deg)

This parameter is not visible when the External mechanical torque parameter is checked.

The maximum pitch angle in degrees.

Maximum rate of change of pitch angle

This parameter is not visible when the External mechanical torque parameter is checked.

The maximum rate of change of the pitch angle in degrees/s.

Inputs and Outputs

A B C

The three terminals of the WTIG.

Trip

Apply a simulink logical signal (0 or 1) to this input. When this input is high the WTIG is disconnected. Use this input to implement a simplified version of the protection system.

Wind (m/s)

This input is not visible when the External mechanical torque parameter is checked.

Simulink input of the wind speed in m/s.

Tm

This input is visible only when the External mechanical torque parameter is checked.

Simulink input of the mechanical torque. Tm must be negative for power generation. Use this input when using an external turbine model.

m

Simulink output vector containing 8 WTIG internal signals. These signals can be individually accessed by using the Bus Selector block. They are, in order:

Signal

Signal Names

Definition

1

Vabc (cmplx) (pu)

Phasor voltages (phase to ground) Va, Vb, Vc at the WTIG terminals in pu based on the generator ratings.

2

Iabc (cmplx) (pu)

Phasor currents Ia, Ib, Ic flowing into the WTIG terminals in pu based on the generator ratings.

3

P (pu)

WTIG output power in pu based on the generator ratings. A positive value indicates power generation.

4

Q (pu)

WTIG output reactive power in pu based on the generator ratings. A positive value indicates reactive power generation.

5

wr (pu)

Generator rotor speed (pu)

6

Tm (pu)

Mechanical torque applied to the generator in pu based on the generator ratings.

7

Te (pu)

Electromagnetic torque in pu based on the generator ratings.

8

Pitch_angle (deg)

Blade pitch angle in degrees.

Example

See the power_wind_igpower_wind_ig example, which illustrates the steady-state and dynamic performance of the WTIG. Three WTIG blocks are used to simulate a 9 MW wind farm connected in a 25 kV, 60 Hz, system. Voltage regulation is performing by a 3 Mvar STATCOM.

References

[1] Siegfried Heier, "Grid Integration of Wind Energy Conversion Systems," John Wiley & Sons Ltd, 1998, ISBN 0-471-97143-X

Was this topic helpful?