International Conference on Automatic control, Telecommunications and Signals (ICATS15) University BADJI Mokhtar - Annaba - Algeria - November 16-18, 2015
Control of a Permanent Magnets Synchronous Generator based vertical axis wind turbine using a Pulse Width Modulated inverter K. Kerbouche Electronic Department, Faculty of Sciences and Technology University of Jijel Jijel, Algeria
[email protected]
S. Haddad, A. Mellit Electronic Department, Faculty of Sciences and Technology University of Jijel Jijel, Algeria
[email protected],
[email protected]
Abstract— This paper discuss the control of a direct driven vertical axis wind turbine based on permanent magnet synchronous generator using an uncontrolled rectifier and a PWM inverter. The state of the art and advantages of vertical axis wind turbines is discussed first. Then the proposed system components and the control technique are analyzed and simulation results are presented. The simulation results proves the simplicity and effectiveness of the studied wind energy conversion system.
II. VERTICAL AXIS WIND TURBINES Vertical axis wind turbines are currently experiencing a renewed interest in small-scale urban applications, this interest is driven by a list of advantages, mainly: Ease and low manufacturing cost for smaller turbines. Low noise levels. Suitable in building mounting in urban environment.
Keywords—Vertical axis wind turbine (Vawt) ; Permanent magnets synchronous generator (PMSG); PWM inverter.
Ability to handle the “dirty” wind seen in urban environments.
I. INTRODUCTION
Ability to capture wind from different directions without using yaw
The energy consumption of the world is increasing dramatically with the rapid increase of population. With the increasing concern of global warming and the depletion of fossil fuel reserves, many are looking at sustainable energy solutions to preserve the earth for the future generations. Recently, renewable energy sources such as PV arrays, wind generators and fuel cells are gaining more and more attention due to their advantage of being abundant in nature and causing zero-emissions [1]. Over the last few years renewable energy generation system based on wind, solar, fuel cell or geothermal power have drawn a great attention in the industries Among renewable energy systems wind energy systems are much cheaper compared to other power generation systems [2]. Small VAWTs use in the urban environment has been significantly increased due to their ease and low manufacturing cost, its low maintenance costs due to the absence of yaw system and gearboxes, and its low level noise.
The electrical components that require maintenance are normally positioned on the supporting platform. More scalable and can be installed at a lower elevation above the ground. Low maintenance costs. Low start up wind speeds. Ability to handle much higher turbulence and varied wind speeds compared to HAWTs [3], [4].
Direct driven PMSG based VAWTs: Permanent Magnet Synchronous Generator (PMSG) are becoming very popular in wind power applications specially for gearless drive systems with advantages such as small size, less weight, flexible design and attractive low cost , when compared with other rotating machines with similar ratings. For small scale wind applications (some kilowatts) low speed multi-pole PMSG are certainly the most convenient technology since they have a better reliability and increased efficiency without gearboxes or external excitation systems. In addition, PMSG are well adapted for variable speed operation since they have a high power
In this paper we present a small scale wind energy conversion system consist of permanent magnets synchronous generator direct driven vertical axis wind turbine controlled by a simple pulse width modulated inverter. The aim of this paper is then to study the feasibility of the overall system using such control techniques. The above section will detail advantages of the VAWTs.
1
International Conference on Automatic control, Telecommunications and Signals (ICATS15) University BADJI Mokhtar - Annaba - Algeria - November 16-18, 2015 density, high performance at low speed applications and low maintenance cost [5].
1 Pt .Cp ( , ). . A.V 3 2
III. SYSTEM DESCRIPTION AND MODELLING A wind turbine can only convert just a certain percentage of the captured wind power. This percentage is represented by Cp (λ,β) which is a function of the wind speed, turbine speed, and the blade pitch angle, like the figure 2 shows.
The proposed system illustrated by the figure 1 consist of a small direct driven PMSG based vertical axis wind turbine coupled to an uncontrollable rectifier. The diode rectifier is mounted in cascade with a three phase PWM controlled inverter feeding the three phase load.
In case of the VAWTs, there is no pitch angle. Then the power coefficient is a function of wind speed and turbine speed only. B. PMSG Model [7]: The modeling of PMSG type electrical equipment is made through the following equations, represented by d-q reference frame.
Fig. 1.
A wind turbine is a series of blades connected to a central rotor and angled to move when struck by sufficiently strong winds. Basically, as wind turns the blades, which spin a shaft, it produces mechanical energy, which connects to a generator and makes electricity
e Ld id em
The electrical torque is obtained through the following equation:
The aerodynamic power of the wind through a wind disk of radius R is given by:
Where
dt
Vd and Vq are d and q components of stator voltages (V) id and iq are d and q components of stator currents (A) Rs is stator resistance (ohms) L d and Lq are machine inductances (H) ωe is the electrical speed (rad/s) ϕm is the magnetic flux (wb).
A. Turbine model [6]:
1 . . A.V 3 2
diq
did e Lq i q dt
Where:
The whole WECS.
Pwind
Vq Rs iq Lq
Vd Rs id Ld
Te
represents the air density ( =1,235 kg/m3) A is the swept area in m2. V is the wind velocity in m/s.
2 p.( m iq ( Ld Lq )i d iq ) 3
The mechanical power, which is converted by a wind turbine Pt, is dependent on the power coefficient Cp (λ,β).
It is given by:
Fig. 2. Typical power coefficient curves
2
International Conference on Automatic control, Telecommunications and Signals (ICATS15) University BADJI Mokhtar - Annaba - Algeria - November 16-18, 2015
Tm Te B r J
d r dt
(6)
Where : B is the rotor friction (kgm2/s) J is the rotor inertia (kgm2), ωr is rotor speed (rad/s) . Tm is the mechanical torque produced by wind (Nm). The machine dynamics can be simplified by assuming: (Ld = Lq = 0). Fig. 3. System control scheme.
C. Power converters control scheme: IV. OVERALL SYSTEM SIMUALTION. The most important objective of the control system used in this paper is controlling the load voltage and frequency using a PWM voltage source inverter (PWM-VSI) control.
In order to investigate the feasibility of the WECS and the effectiveness of the PWM inverter in the control of the VAWT detailed models presented earlier are implemented in Matlab Simulink® package software as shown in fig.4.
The used control scheme is illustrated by the fig.3. In this scheme, detection of the R.M.S. value of the inverter output voltage is necessary to control the modulation ratio to the target value. However, output voltage of the PWM inverter is AC voltage, therefore it is difficult to detect the R.M.S.Value from the instantaneous value of the inverter output voltage. Modulation ratio m of the PWM inverter is determined with feedback control which is calculated from PI controlled value of the error e which is the difference of Vrms and Vref . Here, m is obtained from the ratio of carrier wave amplitude and modulating wave amplitude. R.M.S. value of PWM inverter output voltage is adjustable by using m.
The simulated model contains a wind data blocks which generates variable wind speeds, Permanent magnets synchronous generator based vertical axis wind turbine, a diode rectifier and the PWM controlled voltage source inverter in addition to filters and measurements devices. The inputs of this simulation are the wind speed, the VAWT and PMSG parameters, the PWM pulses frequency, the filter passive elements values, while the outputs are: The Vawt rotor speed and developed mechanical torque, the DC voltage in addition to the inverter and load voltages. The input parameters and the results discussion are detailed in the next section.
Fig.3. Overall system implemented in Simulink.
3
International Conference on Automatic control, Telecommunications and Signals (ICATS15) University BADJI Mokhtar - Annaba - Algeria - November 16-18, 2015 V. SIMUALTION RESULTS DISCUSSION
400
350
In order to check the feasibility of the proposed PWM controlled VAWT, the overall system is simulated under variable wind speeds.
300
DC voltage(V)
250
Fig.5 shows the wind speed, fig.6 and fig.7 present the VAWT turbine rotor speed and developed mechanical torque respectively.
Figure 1 200
150
The results shows that the developed mechanical torque is influenced by the wind speed variations while the turbine rotor speed remain quasi-stable. This can be explained by the high machine inertia.
100
50
0
0
0.5
1
1.5
2
2.5 Time(s)
3
3.5
4
4.5
Fig.8. DC voltage
16
14
12
Wind spees(m/s)
10
8
6
4
2
0
0
0.5
1
1.5
2
2.5 Time(S)
3
3.5
4
4.5
5
Fig.5. wind speed 39.5
39.4
39.3
VAWT rotor speed (rad/sec)
39.2
39.1
39
38.9
38.8
38.7
38.6
38.5
0
0.5
1
1.5
2
2.5 Time(s)
3
3.5
4
4.5
5
Fig.9. Inverter output voltage.
Fig.6. VAWT rotor speed 50
Fig.8 shows DC voltage while fig.9 and fig.10 present the inverter output and the load voltages respectively.
40
A zoom on the figure is associated with the last two figures in order to show the signals more clearly.
Mechnanical torque (N.m)
30
The results presented by the three figures shows that the voltages are kept constant independently from the variations in the wind speed.
20
10
The table.1 summarize the input parameters used to simulate the previously described wind energy conversion system.
0
-10
0
0.5
1
1.5
2
2.5 Time(s)
3
3.5
4
4.5
5
Fig.7. Mechanical torque
4
5
International Conference on Automatic control, Telecommunications and Signals (ICATS15) University BADJI Mokhtar - Annaba - Algeria - November 16-18, 2015 Table 1. Simulation parameters
VI. CONCLUSION In this paper we analyzed the possibility to control a wind energy consisting of a permanent magnets synchronous generator based vertical axis wind turbine and a rectifier using a simple PWM inverter. The simulation results under unsteady wind shows the effectiveness of such converter in controlling small scale vertical axis wind turbines. Moreover, the results affirm the feasibility, reliability and simplicity of the overall wind conversion system studied to feed a load independently to the weather conditions.
REFERENCES [1]
[2]
Fig.10. Load phase to phase voltage
[3] [4]
Simulation input parameters Parameter name
value
unit
[5]
Vertical axis wind turbine Rotor diameter
1.78
m
Rotor height
2.5
m
[6]
Swept area
4.45
m2
[7]
3
/
Number of blades
[8]
Permanent magnets synchronous generator Quadratique inductance Lq
45
mH
Direct inductance Ld
21
mH
Stator resistance Rs
1.75
𝛺
Permanent magnets flux
0.63
Wb
Rated speed
300
rpm
Inertia
50
Kg.m2
Pairs of poles
21
/
2000
W
[9]
Three phase load Active power
5
S.Ramya, T.Manokaran, “A novel multi input DC-DC converter for integrated wind, PV renewable energy generated system” International Journal of Engineering Research and Development Volume 4, Issue 4 (October 2012), PP. 62-68 G. Chun, P. Ganeshkumar, A. Ahmed and J. Park, “Design of MPPT Controller for Small Scale Wind Power System with PMSG”. S. Tullis, A. Fiedler, K. McLaren, S. Ziada, “Medium-solidity Vertical Axis Wind Turbines for use in Urban Environments”. Ashraf Ahmed, ,Li Ran, , Jim R. Bumby, “New Constant Electrical Power Soft-Stalling Control for Small-Scale VAWTs” IEEE transactions on energy conversion, VOL. 25, NO. 4, December 2010 J. M. Rodrigues, F. O. Resende, C. L. Moreira , “Contribution of PMSG based Small Wind Generation Systems to Provide Voltage Control in Low Voltage Networks”. Djamila Rekioua, Wind Power ElectricSystems:Modeling, Simulation and Control, Springer-Verlag London 2014. Krishi Sanskriti, Impending Power Demand and Innovative Energy Paths, Excellent Publishing Services, New Delhi – 110070. Andoni Urtasun * , Pablo Sanchis, Idoia San Martín, Jesús López, Luis Marroyo, “Modeling of small wind turbines based on PMSG with diode bridge for sensorless maximum power tracking” Renewable Energy 55 (2013) 138e149. T.F. Ishugah, Y. Li , R.Z. Wang , J.K. Kiplagat, “Advances in wind energy resource exploitation in urban environment: A review” Renewable and Sustainable Energy Reviews 37 (2014) 613–626.
