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THE OPERATIONAL STUDY OF A DARRIEUS WIND TURBINE GENERATOR FOR APPLICATION DEMONSTRATION
Session 3.2.
1833
THE OPERATIONAL STUDY OF A DARRIEUS WIND TURBINE GENERATOR FOR APPLICATION DEMONSTRATION Wang Cheng xu Dept. of Electrical Engineering, Tsinghua Univ. Beijing, China
ABSTRACT This paper describes an application demonstration study of a Darrieus wind turbine generator which can be connected to the local network or operated in stand alone condition. The study includes system layout, control strategy and performance test. KEYWORDS Darrieus wind turbine generator; system layout; grid connected operation; stand alone operation; control strategy; AC/AC con verter; load regulator; performance test. INTRODUCTION In recent years, the wind energy utilization have been paid more attention in China, up to now most of the islands along the sea shore and in the remote countryside, grassland where are no electricity at all or lack of it.On the other hand, in these districts the renewable energy, including solar and wind energy, are rich, so using wind energy for electricity generation is getting more and more attractive. Based on this situation a joint study of wind energy conversion system have been carried out between Dornier System GmbH ( Fed eral Germany )and Tsinghua University ( China ). The study shows that using AC/AC converter or using load regu lator both two different operation system can be realized in steady and safety by adopting suitable control strategies. The performance testing shows a satisfactory results. Based on the performance data and technical-economic evaluation, the app lication prospect of such Darrieus wind turbine generator in windy areas is promising. CONSTRUCTION OF WTG
1834
Session 3.2.
The Darrieus WTG1 s construction is shown in Fig.1« Anemometer Vibration sensor
Top bearing Guy wire
SpoilerRotor blade — \
Lower bearing Support structure Synchronous generator D.C.start motor Concrete fundation Fig.1.
Construction of Darrieus WTG
The Darrieus rotor has three aluminium extruded blades. The swept area of the rotor is HOmnf . The profile of blade is 634021 and the cord length of the blade is 300mm. The gearbox, synchronous generator, disc brake, lower bearing and starting motor are all assembled inside a steel made support structure which are fixed above the concrete foundation. The rated revo lving speed of the alternator is 1500 rpm. The gear ratio be tween the alternator and Darrieus rotor is 16.78. An anemometer is installed on the top of the mast, it provides the signals to start the rotor. A vibration sensor is also installed on the top of the mast. When the vibration of the mast becomes severe, the sensor will give out a signal to stop the WTG automatically. In order to limit the overload and overspeed of the alternator, three spoilers had been assembled on three blades to absorb the extra wind energy during high wind speed running period. Three guy wires are fixed on three concrete foundations.The prestress of each guy wire is about 3KN. The total weight of the WTG is about 3 tons. OPERATION MODE
1835
Session 3.2. The operation mode scheme is shown in Pig. 2, Darrieus WTG
Control cabinet
Load switch
—
,
"a re tTa <Ã* <÷ Transforme tof* ^ ^ r*ï râ*9 10000/380V
Load
Î Battery 24V T
Fig.2.
I
Converter
380V 50Hz Existing Grid
Operation Mode Scheme
Stand Alone Operation Mode In this operation mode, the load switch could be switched in with load according to the frequency. The frequency and volt age of the alternator are proportional to its revolving speed, i.e, to wind speed. For experimental purpose at first stage a set of 20kw electric heaters which war divided into 2,4,8,12, I6,20kw steps were installed and tested. To minimize the variation of the frequency while the WTG is run ning with load, another load regulator for stand alone operation had been developed and tested. It consists of SCR, frequency/ voltage converter, consumer's load, dump load, alternator and wind turbine simulator. All these components form a speed-fre quency-power close loop control system. In this system, the regulation process is automatically continuous and the frequen cy could be kept in constant. Grid Connected Operation Mode In this operation mode, the A.C. power with variable frequency from alternator goes into the converter, and the A.C. power with constant frequency can be obtained at the output side of the converter. This means it permits to extract more energy from the wind. In addition, using AC/AC converter between the alternator and network makes the alternator independent of the grid, so it alleviates the synchronisation problem. The shortcoming of this operation mode is the relatively high cost of the AC/AC converter. In spite of this fact, it is still
Session 3.2.
1836
attractive while considering the advantage above mentioned and the direct drive capability of using a low speed alternator. CONTROL STRATEGY The control strategy of the WTG is shown in Fig. 3. Automatic S t a r t I Start Motor starts
^ ^ m e r genere. w < ^ Switch J^~ | c l o s e | ^ ^ \ C 1o se d^^ ♦Ye g
üTircuix* Breaker Closed
< Yes No cut Yes 1 S t a r t Delay Switch in toad Switch AC/AC Converter
1 Start
1 Open t he Brake
Existing Network
Consumer's Load
->Hr.max.
Yes
[No
WTG STOP Check
"emp.geri^
e >
Location of trouble Indication
^emp. 'batt. aatt.mir
Yes
No "Vibration^ Acceleration >1g
Reset
Automatici Manual Start Start
[No Pig.3·
1 JManual
Control Logic Plow Chart
1837
Session 3.2.
OPERATIONAL PERFORMANCE According to the design data, the cut in wind speed is 4.5m/s, the rated wind speed is 10m/s, corresponding to 20kw electric power output and the cut out wind speed is 15m/s. Fig.4. is the operational characteristic which represents the electric power of the WTG as a function of wind speed. From the measured points it is obvious that the expectant effect had been reached.
30 i
Electric Power Output,KW 30
25
<'·//""
ί *« *
20
»
* I
÷** ÷
< **
«
15
Electric Power Output ,KW
25
X
*
X X X* XX
20
*
15
»/*
10
Wind „Direction: 10 r "* . east + south c # "Î .'·' * 5 t ,'/.\: * north
**X X X A
++\\
5i I
■ .
5
,
■
- r\
10 15 Wind Speed,M/S Fig.4. Electric Power Output at Different Wind Speed
X
V
X
500 1000 1500 Rotation Speed of Generator,rpm Fig.5. Characteristic of Electrie Power Versus Rotating Speed of the Alternator
The maximum electric power output depends on the rated power of the alternator and its ability for short time overloads. The rated power of the alternator in this wind energy conversion system is 20KW. To limit the power output within 20KW and keep this power output as the wind speed goes up and higher than 10m/s, the spoilers open at 1300 rpm of the alternator. This based on the characteric of electric power versus rotating spe ed of the alternator, see Fig.5. REFERENCE DANIEL M.SLMM0NS.(1975). Wind Power. NOYES DATA CORPORATION. J.P.MOLLY. (1978). Windenergie in Theorie und Praxis, Verlag C F . Müller Karlsruhe. V.D.HUNT.(1981). Wind Power. VAN NOSTRAND REINHOLD COMPANY. R.J. TEMPLIN and R.S.RANGI. Vertical-Axis Wind Turbine Develop ment in Canada, IEE PROCEEDINGS, Vol.130,Pt.A,No.9,December 1983 A.FRETZSCHE,K.SPEIDEL, WANG CHENG XU. Technical-Economic Evalu ation of Vertical Axis Wind Turbine of 30-50kw, Report, Dornier System, Tsinghua University, 1986.
1833
THE OPERATIONAL STUDY OF A DARRIEUS WIND TURBINE GENERATOR FOR APPLICATION DEMONSTRATION Wang Cheng xu Dept. of Electrical Engineering, Tsinghua Univ. Beijing, China
ABSTRACT This paper describes an application demonstration study of a Darrieus wind turbine generator which can be connected to the local network or operated in stand alone condition. The study includes system layout, control strategy and performance test. KEYWORDS Darrieus wind turbine generator; system layout; grid connected operation; stand alone operation; control strategy; AC/AC con verter; load regulator; performance test. INTRODUCTION In recent years, the wind energy utilization have been paid more attention in China, up to now most of the islands along the sea shore and in the remote countryside, grassland where are no electricity at all or lack of it.On the other hand, in these districts the renewable energy, including solar and wind energy, are rich, so using wind energy for electricity generation is getting more and more attractive. Based on this situation a joint study of wind energy conversion system have been carried out between Dornier System GmbH ( Fed eral Germany )and Tsinghua University ( China ). The study shows that using AC/AC converter or using load regu lator both two different operation system can be realized in steady and safety by adopting suitable control strategies. The performance testing shows a satisfactory results. Based on the performance data and technical-economic evaluation, the app lication prospect of such Darrieus wind turbine generator in windy areas is promising. CONSTRUCTION OF WTG
1834
Session 3.2.
The Darrieus WTG1 s construction is shown in Fig.1« Anemometer Vibration sensor
Top bearing Guy wire
SpoilerRotor blade — \
Lower bearing Support structure Synchronous generator D.C.start motor Concrete fundation Fig.1.
Construction of Darrieus WTG
The Darrieus rotor has three aluminium extruded blades. The swept area of the rotor is HOmnf . The profile of blade is 634021 and the cord length of the blade is 300mm. The gearbox, synchronous generator, disc brake, lower bearing and starting motor are all assembled inside a steel made support structure which are fixed above the concrete foundation. The rated revo lving speed of the alternator is 1500 rpm. The gear ratio be tween the alternator and Darrieus rotor is 16.78. An anemometer is installed on the top of the mast, it provides the signals to start the rotor. A vibration sensor is also installed on the top of the mast. When the vibration of the mast becomes severe, the sensor will give out a signal to stop the WTG automatically. In order to limit the overload and overspeed of the alternator, three spoilers had been assembled on three blades to absorb the extra wind energy during high wind speed running period. Three guy wires are fixed on three concrete foundations.The prestress of each guy wire is about 3KN. The total weight of the WTG is about 3 tons. OPERATION MODE
1835
Session 3.2. The operation mode scheme is shown in Pig. 2, Darrieus WTG
Control cabinet
Load switch
,
"a re tTa <Ã* <÷ Transforme tof* ^ ^ r*ï râ*9 10000/380V
Load
Î Battery 24V T
Fig.2.
I
Converter
380V 50Hz Existing Grid
Operation Mode Scheme
Stand Alone Operation Mode In this operation mode, the load switch could be switched in with load according to the frequency. The frequency and volt age of the alternator are proportional to its revolving speed, i.e, to wind speed. For experimental purpose at first stage a set of 20kw electric heaters which war divided into 2,4,8,12, I6,20kw steps were installed and tested. To minimize the variation of the frequency while the WTG is run ning with load, another load regulator for stand alone operation had been developed and tested. It consists of SCR, frequency/ voltage converter, consumer's load, dump load, alternator and wind turbine simulator. All these components form a speed-fre quency-power close loop control system. In this system, the regulation process is automatically continuous and the frequen cy could be kept in constant. Grid Connected Operation Mode In this operation mode, the A.C. power with variable frequency from alternator goes into the converter, and the A.C. power with constant frequency can be obtained at the output side of the converter. This means it permits to extract more energy from the wind. In addition, using AC/AC converter between the alternator and network makes the alternator independent of the grid, so it alleviates the synchronisation problem. The shortcoming of this operation mode is the relatively high cost of the AC/AC converter. In spite of this fact, it is still
Session 3.2.
1836
attractive while considering the advantage above mentioned and the direct drive capability of using a low speed alternator. CONTROL STRATEGY The control strategy of the WTG is shown in Fig. 3. Automatic S t a r t I Start Motor starts
^ ^ m e r genere. w < ^ Switch J^~ | c l o s e | ^ ^ \ C 1o se d^^ ♦Ye g
üTircuix* Breaker Closed
< Yes No cut Yes 1 S t a r t Delay Switch in toad Switch AC/AC Converter
1 Start
1 Open t he Brake
Existing Network
Consumer's Load
->Hr.max.
Yes
[No
WTG STOP Check
"emp.geri^
e >
Location of trouble Indication
^emp. 'batt. aatt.mir
Yes
No "Vibration^ Acceleration >1g
Reset
Automatici Manual Start Start
[No Pig.3·
1 JManual
Control Logic Plow Chart
1837
Session 3.2.
OPERATIONAL PERFORMANCE According to the design data, the cut in wind speed is 4.5m/s, the rated wind speed is 10m/s, corresponding to 20kw electric power output and the cut out wind speed is 15m/s. Fig.4. is the operational characteristic which represents the electric power of the WTG as a function of wind speed. From the measured points it is obvious that the expectant effect had been reached.
30 i
Electric Power Output,KW 30
25
<'·//""
ί *« *
20
»
* I
÷** ÷
< **
«
15
Electric Power Output ,KW
25
X
*
X X X* XX
20
*
15
»/*
10
Wind „Direction: 10 r "* . east + south c # "Î .'·' * 5 t ,'/.\: * north
**X X X A
++\\
5i I
■ .
5
,
■
- r\
10 15 Wind Speed,M/S Fig.4. Electric Power Output at Different Wind Speed
X
V
X
500 1000 1500 Rotation Speed of Generator,rpm Fig.5. Characteristic of Electrie Power Versus Rotating Speed of the Alternator
The maximum electric power output depends on the rated power of the alternator and its ability for short time overloads. The rated power of the alternator in this wind energy conversion system is 20KW. To limit the power output within 20KW and keep this power output as the wind speed goes up and higher than 10m/s, the spoilers open at 1300 rpm of the alternator. This based on the characteric of electric power versus rotating spe ed of the alternator, see Fig.5. REFERENCE DANIEL M.SLMM0NS.(1975). Wind Power. NOYES DATA CORPORATION. J.P.MOLLY. (1978). Windenergie in Theorie und Praxis, Verlag C F . Müller Karlsruhe. V.D.HUNT.(1981). Wind Power. VAN NOSTRAND REINHOLD COMPANY. R.J. TEMPLIN and R.S.RANGI. Vertical-Axis Wind Turbine Develop ment in Canada, IEE PROCEEDINGS, Vol.130,Pt.A,No.9,December 1983 A.FRETZSCHE,K.SPEIDEL, WANG CHENG XU. Technical-Economic Evalu ation of Vertical Axis Wind Turbine of 30-50kw, Report, Dornier System, Tsinghua University, 1986.