Sensor-less Motor Starting of Grid Connected Small Wind
Mohamed Aner firstname.lastname@example.org
Ahmed Ali email@example.com
Edwin Nowicki firstname.lastname@example.org
David Wood email@example.com
International Conference on Recent Advances in Energy
and Power Systems, RAEPS 2012
2. Proposed System
3. Wind Turbine Description
4. Proposed Control Technique.
5. Backward operation of VSMC
• Small wind turbine takes longer time for starting due to the lake of pitch adjustment.
• When the turbine starts under the aerodynamic torque, it takes turbine takes 13 sec to reach it optimal tip
speed ration at rated wind speed while at cut-in wind speed it take around 45 sec. for 5kW wind turbine.
• Due to the intermittence of the wind, the wind turbine system needs to increase the conversion efficiency
to extract the max. possible energy.
• If the turbine can reach faster to its optimal speed, the turbine can extract more energy especially at higher
• small wind turbines are being grid connected which can use grid power for rapid acceleration in order to
reach to the optimal tip speed ratio fast.
Starting of 5 kW wind turbineStarting of 5 kW wind turbine
3.3. Wind Turbine DescriptionWind Turbine Description
6 5 4 3 2
6 5 4 3 2 1 0
= + + + + + +
P AC U
C a a a a a a a
λ λ λ λ λ λ
4.4. Proposed Control TechniqueProposed Control Technique
• According to the dynamic equation of the turbine rotor , the rotor can be accelerated if the
generator is operated as a motor.
• The turbine rotor can operate near its optimal tip speed ratio if the generator torque
matches the aerodynamic torque
a gT T J d dt B− = Ω + Ω
4.1 Motoring Mode4.1 Motoring Mode
• When wind turbine starts, the turbine speed has to be increased to establish operation at
maximum power coefficient , The turbine speed can be quickly increased, if the
aerodynamic torque is assisted by operating the generator as a motor using grid power
and the bidirectional power flow feature of the VSMC.
• In order to reach the maximum acceleration, the generator torque is set to its rated value
by injecting the rated quadrature current component to the generator in the positive
1.5 ( )= −e m qT P Iλ
4.2 MPPT Mode4.2 MPPT Mode
• When the turbine reaches to 60% of optimal tip speed ratio λopt, the MPPT control
takes over to maintain operating around λopt.
0.5=mvir P virP AC Uρ
• Rotor speed can be estimated from the space vector angle of the generator voltage
( )2 /3 2 /32
∠Θ = + +J J
a b cSV V V e V eπ π
5.5. Backward operation of VSMCBackward operation of VSMC
VSMC Control:VSMC Control:
Rectifier stage control aspects:Rectifier stage control aspects:
Switching frequency Fs should be higher than Fo and Fi.
Only two switches should be turned on at the same time “one from upper and the
other from lower switches” to insure current continuity.
The rectifier should be switched at zero current.
The switching should provide a max DC link voltage.
The switching should provide a unity input displacement power factor “DPF”.
Control Technique LayoutControl Technique Layout
Modulation of Input PhasesModulation of Input Phases
Inverter stage controlInverter stage control
7. Conclusion7. Conclusion
• The proposed control technique allows faster starting.
• The proposed motor starting control technique produce more energy than
• The proposed Control technique has significant increase in conversion efficiency
• The proposed starting technique can start the turbine at any wind speed even below
the cut-in wind speed.