27-07-2012, 10:48 AM
Optimization of a Wind Turbine using Permanent Magnet Synchronous Generator (PMSG)
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Abstract:
This paper proposes strategies for a Wind Turbine with a Voltage Source Converter (VSC) in the
case of a 200-300kW Permanent Magnet Synchronous Generator (PMSG). This control allows the
synchronous generator to operate at an optimal speed. To show its effectiveness, a mathematical model of a
variable speed wind energy conversion system is developed. The mathematical model is used to calculate the
response of the wind energy conversion and to determine the maximum power operating point. This paper
also provides the theoretical background of this method. Simulation of the system using Matlab / Simulink /
SimPower System was performed to illustrate the advantages of this control strategy.
INTRODUCTION
The realization of a wind turbine as a source of
clean, non-polluting and renewable energy may
depend on the optimum design of the system and
the control strategies of the different possible
parameters that can operate efficiently under
extreme variations in wind conditions. The
general goal of this paper is to optimize the
electromechanical energy conversion of the wind
turbines, developing suitable strategies of control
[1].
Optimum wind energy extraction is achieved by
running the Wind Turbine Generator (WTG) in
variable speed because of the higher energy gain
and the reduced stresses. Using the Permanent
Magnet Synchronous Generator (PMSG) the
design can be even more simplified. However, the
recent advancements in power electronics and
control strategies have made it possible to regulate
the voltage of the PMSG in many different ways.
In the proposed system a VSI converter is
preferable [2,3].
The converter.
Two different types of converter can be
implemented: the Voltage Source Inverter (VSI
or VSC) and the Current Source Inverter (CSI).
The first has a capacitor in the DC circuit and
works with a relative constant DC tension; the
second has a winding in the DC circuit and works
with a relative constant DC current. The power
production of the turbine is controlled by current
control of the generator and it is necessary that the
generator current go fast. A chopper can be used
to change the DC voltage and to keep it constant;
it provides also an extra way to control our wind
energy conversion system. For theses reasons, a
VSI converter is preferable.
WIND ENERGY CONVERSION
The mechanical power that the turbine extracts
from the wind, Pm, is inferior to Pw. This is due to
the fact that the wind speed after the turbine isn’t
zero (the air needs to be carried of after the
turbine). So, the power coefficient of the turbine
Cp can be defined.
CONCLUSIONS
The paper tries to optimize and to maximize the
yield of a wind turbine, using permanent magnet
synchronous generator (PMSG). First, variable speed has been chosen because of
the higher energy gain and the reduced stresses.
A gearbox is not necessary when a synchronous
PMSG is used. The chopper has been added to
the system to improve the dc voltage. This allows
energy gains, even for lower wind speeds.
In the second part, a controller is designed. The
pitch wind turbine model is changed to a stall
wind turbine model by adding a PI controller for
the attack angle. A controller for the chopper
voltage has been developed. The developed
inverter controller is an all or nothing controller
which is a very basic controller.