Abstract: It has been observed that PMSG output

Abstract: In this paper, Simulation Model for
Analysis of Permanent Magnet Synchronous Generator (PMSG) based Wind Turbine
Generation System is designed in MATLAB / SIMULINK software. The developed
model is simulated and analyzed with step response (increase/decrease) of wind
speed applied to PMSG. It has been observed that PMSG output responds similar
to the change in wind speed applied to the wind turbine controller. It has been observed that PMSG output responds similar
to the changes in wind speed. The wind turbine controller generates mechanical
torque/power (N-m) with respect of the wind speed. Mechanical torque/power used
to drive PMSG is shown in MATLAB / SIMULINK Model.

Keywords: Wind Turbine, PMSG, Perturb &
Observe, Incremental Conductance

1. Introduction:  Access to electricity is now a basic
requirement of mankind. There are still many places around the world which have
no access to electricity. International agencies report that 1.5 billion people
have no access to electricity, which is more than 20% of world’s population.
Even though many of these places might have substantial potential for energy
generation, the resources are not properly identi?ed and/or utilized. Hence,
people have to pay at high rates, if they have the ?nancial resources, for the standard
energy sources to full?ll their basic energy requirements such as lighting,
charging small equipment like radios and mobile phones, and even heating. In
many remote places, people often burn kerosene and even wood for basic lighting
and heating. Meanwhile, there is a big contradiction between the fossil fuels supply
and the global energy demand, which leads to a high oil price in the
international market recently. The energy shortage and the atmosphere pollution
have been the major limitations for the human development. Generation of
electricity through renewable energy sources such as solar, wind, and
micro-hydro could be potential options for these remote places. For an
isolated, o?-grid and stand-alone system, the energy needs to be stored whenever
available from these sources and then supplied if required. In hilly and remote
regions where renewable energy potential is high, large scale generating
systems could also be an option, but due to the complex geography and di?cult infrastructure, small scale systems might
seem more feasible.

 

1.1 Current research activities: 

Electricity is one the
most essential needs for humans in the present. Use of electricity is
increasing day by day. The electricity finds its application in all the domains.
The rapid increase in the demand for electricity and the recent change in the
environmental conditions such as global warming led to a need for a new source
of energy that is cheaper and sustainable with less carbon emissions. Among all
renewable energy resources, wind energy conversion technology has greatly
increased in the past for improvement of power crisis and global warming issues
in the world.

1.2 Problem Overview: The energy from these
renewable/natural sources tends to vary throughout the day and hence optimizing
the energy capture is a necessity. For a wind turbines, Photo-Voltaic (PV)
arrays, and micro-hydro turbines, the output power is determined by  the wind speed, irradiation and water ?ow
respectively. Hence, the control of these systems needs to behave appropriately
according to the variation of these parameters. For example, the turbine speed
for wind and micro-hydro needs to be adjusted for deferent wind speeds or water
?ow such that the generated power available is optimized and the system runs at
Maximum Power Point (MPP). Similarly, the output DC voltage and current of the
PV array systems need to be adjusted in order to run them at MPP.

 

2. Wind Turbine Generation
System Connected to Grid: Wind turbine is connected to PMSG from where we get
the voltage, current and power which will be converted into the pulsating DC
with the help of a rectifier. The output of the rectifier i.e. current, voltage
and power will be given to the DC-DC Converter where we get the output voltage,
current and power. The
inerter is used to convert the DC into AC which will show the output results in
AC. The controller is used to control the inerter which is connected to the
load.

  Fig.1 Wind Turbine Generation System Connected to
Grid                                     
 3. Control
Methodologies:

3.1 DC-DC Converter: It is an electronic device
that converts a source of direct current from one DC voltage to another. Here
we are using Boost converter with and without MPPT techniques and obtaining the
power accordingly. The output of the rectifier
is given as an input to DC-DC Converter as shown in above fig.1. The inductor
is connected from the input supply to the common node between the MOSFET and
diode. Therefore the peak MOSFET current is now nearly equal to the input
current, not the load current.

 

The
inductor and MOSFET current in CCM. If we ignore the small triangular ripple,
it is easy to see that the peak MOSFET current is nearly the same as the load
current.

Boost
regulators have a maximum duty cycle, beyond which the regulator will not boost
as shown in graph:

           

MPPT Control Trajectory
Subjected to Step Input: The experiment began by starting up the wind turbine
simulator at a wind speed of 4.5m/s to verify the tracking performance of the
developed MPPT controller. The controller would try to track the maximum peak
power as fast as possible by reducing Pe and thus resulting in an increase in
wt . When an operating point with the maximum power was found (i.e., dp/dw =0),
the controller tried to keep staying at that point. The objective of this
experiment was to track the maximum output power of the turbine. The wind
simulator was started at a wind speed of 4m/s, stepped up to 4.5, 5 and 6 m/s
respectively and run until steady state. The MPPT controller would capture
maximum powers of 260, 420, 600 and 900 W respectively. The power versus rotational
speed is shown and the output torque versus rotational speed is shown. It is
clearly seen that at the maximum output power, the aerodynamic torque are not maximum.
The relationship between cP and time obtained from the experiment. It can be
seen from the figure that in this case, the MPPT controller can manage to keep
cP at 0.4 for the four step wind speeds.

3.2 Maximum power transferred to
load is analysed using two control methods:

 

·       
Perturb & Observe Algorithm

·       
Incremental Conductance Algorithm

 

Perturb & Observe: In this
method controller adjusts the voltage by a small amount from the turbine and
measures power, if the power increases, further adjustments in that direction
is needed until power no longer increases. This is called the perturb & observe
method. It depends on the rise of cure of power against voltage below maximum
power point. The following parameters are used
for the above algorithm