ELEC 7313 – Renewable Energy Integration
Lab Session – Wind Turbine with DFIG
Watch the laboratory experiment video of ‘Wind Turbine with DFIG’ and use the provided
experiment results to answer the following questions. (12 marks in total)
1. Based on the experimental results in Table 2, plot the curve of active power
supplied to the grid (y-axis) with respect to the rotor speed (x-axis) and on the
same graph, plot another curve of active power loss of the MSC-LSC pathway (y-
axis) with respect to rotor speed (x-axis). Explain what is the relationship between
active power loss of the MSC-LSC pathway and the power supplied to the grid as
the rotor speed changes? (2 marks)
2. Plot a curve of reactive power supplied to the grid (y-axis) with respect to rotor
speed (x-axis) using the results in Table 3. Why does the rotor speed not affect the
reactive power? Explain the concept from ‘Wind Experiment Reading Document’.
(1 mark)
3. Why is DFIG wind machine better than Type 1 and Type 2 wind machines in terms
of active and reactive power supply to the grid? (1 mark)
4. What could be a drawback of controlling the active power to 20-30% of the DFIG
rating during super-synchronous operation? (1 mark)
5. Based on the experimental results in Table 4,
a) Draw single line diagrams of DFIG wind machine showing the active power
distribution at or near the synchronous speed. In the diagram, clearly show the
mechanical power Pm, stator power Ps, rotor power Pr and the power supplied
to the grid Pg. Explain the possible reasons why is the formula Pr = -sPs not valid
for the experimental results at synchronous speed? (2 marks)
b) Draw a graph of mechanical power Pm (y-axis) vs wind speed (x-axis) and
highlight the operational regions of the DFIG wind machine. (1 mark)
c) Draw a graph of rotor speed (y-axis) vs wind speed (x-axis) and explain why is
the rotor speed almost constant at high wind speed (>13 m/s)? Explain your
answer based on the wind turbine aerodynamics as explained in the lecture
notes. (2 marks)
d) Why does the DFIG operating point lie on the left side of MPP curve at wind
speed of 9.8 to 13 m/s? Please refer to the provided screenshots. What is your
comment about the optimum tip speed ratio in this case? Explanation should
be based on the theory learnt in the lecture. (2 marks)