ABSTRACT:
This
paper presents a control approach for the Permanent Magnet Synchronous
Generator (PMSG) based Wind Energy Conversion Systems (WECS) under a wide range
of wind speeds. Generally, most of the wind turbines are turned-off and
disconnected from the power grid, in case wind velocity is gone over 25 m/s. It
may cause wind power supply shortage from wind farms. This research introduces
a pitch angle controller as well as a rotational speed control system so that
the PMSG based WECS can generate power if the wind speeds are above 25 m/s. The
proposed method reduces the mechanical stress of the wind turbine by
preferential reducing of the rotational speed rather than the mechanical torque
during strong wind condition. As a result, the chance of turning-off the is
reduced compared to the conventional control system because the PMSG based WECS
can temporarily tolerate the wind speed up to 35 m/s. A 2 MW WECS with the
electrical and mechanical characteristics is modeled in the MATLAB/Sim Power Systems®
to verify the proposed research.
KEYWORDS:
1. WECS
2. PMSG
3. Pitch
angle control
4. Strong
wind conditions
SOFTWARE:
MATLAB/SIMULINK
This
paper describes a control method for the PMSG based WECS under strong wind
conditions. Conventional control method is compared with the proposed control
method considering same conditions and system parameters. In the MPPT control
area, both conventional and proposed systems have shown similar performances.
When the wind turbine is controlled at the rated power, the power fluctuation
occurs with the conventional method. This is because, it is controlled by only
the pitch angle control system with some delays. In the proposed method, both
pitch angle and rotational speed control methods are designed for the
wide-windrange of wind velocity. As a result, the output power is controlled with
high accuracy by using the proposed method. In addition, the proposed method
preferentially reduces the rotational speed rather than the mechanical torque
in order to reduce the power coefficient and the centrifugal force during the
strong wind conditions. For this reason, the allowable condition of power
generation can temporarily reach up to the wind speed of 35 m/s. Therefore, it
can be said that the PMSG based WECS with the proposed control method can avoid
a sudden cut-off from the power grid during strong wind conditions as well as
can continue to generate power in the typhoon prone area. However, if the wind
speed goes above the 35 m/s the wind turbine needs to be shut down. In doing so
it will give some time to bring appropriate load-frequency control action
rather than sudden generation curtailment.
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