Advanced Materials Research Vols. 181-182 (2011) pp 557-562
Online available since 2011/Jan/20 at www.scientific.net
© (2011) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.181-182.557
The Research and Design of Vertical-shaft Water Turbine Power
Generation Device
Yang Yong1, a, Hao Long1,b, Guo Jian1,c and Zhang Liang2,d
1
College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin, China
2
College of Shipbuilding Engineering, Harbin Engineering University, Harbin, China
a
b
c
yyong_2010@163.com, haolong84@163.com, gjian_2006@163.com,
d
zhangliang@hrbeu.edu.cn
Keywords: Tidal Energy; Vertical-shaft Water Turbine; Maximum Power
Abstract. Under the circumstances of global climate becoming warm, the development of tidal
energy which is a reproducible clean energy attracts great attention.And the effective usage of
developed tidal energy is the critical problem of developing the tidal energy.Presently, the utilization
rate of tidal energy is improved mostly by changing water turbine’s structure, which is under research.
And the refinement of already built tidal energy generating set is restricted by cost.The electronics and
electric device of water turbine are designed by taking certain control strategy under the structure of
water turbine unchanged. So the water turbine is run at maximum efficiency. And the tidal energy can
be applied as far as possible. After experiment, the designed experimental device is up to the control
requirements.
Introduction
China has long coast line and the tidal movement is fierce. The amount of tidal energy of China is
considerable.Comparing with conventional water power resource, tidal energy doesn’t need dam,
causing little influence to hydrology and ecological environment.Power generation with tidal energy
dated from 1970’s. With researchers’ great efforts, it went through principle researching stage and
experiment stage, and has become a practicable new resource technology with perspective future [1].
Traditionally, there are two types of water turbine: vertical-shaft water turbine and horizontal-shaft
water turbine.There are two types of vertical-shaft water turbine—lateral axis type and vertical axis
type, which are different in the angle between rotation axis and horizontal plane. The direction of
rotation axis of lateral axis type is parallel to water flow, whereas that of vertical axis type is
vertical.The amount of absorbing energy of horizontal-shaft water turbine’s blades is affected by
water-flow direction, and yaw mechanism is needed. Mostly, the output torque of it can’t be directly
used. So the application of it is relatively fewer.Comparing with horizontal-shaft water turbine, the
amount of absorbing energy of vertical-shaft water turbine’s blades is not affected by water-flow
direction, and the output torque of it can be directly used. So the application of it is relatively more
[1,2,3].
Because of the random change of tidal energy with time and space, and the structural limit of water
turbine, inevitably there is volatility in output voltage and power while water turbine normally
operates, which is undesirable for later energy transformation and storage. Meanwhile, it is hoped that
water turbine can capture the most of tidal energy, to realize the maximum usage of resource.To reach
this goal, it is necessary to adjust the external load of water turbine continuously, to stabilize its output
voltage and power, making it always operates with maximum power.Present tidal energy generation
device generally adopts electronics and electric controller to stabilize output voltage and power and
obtain the maximum output power.Because the research of water turbine and related accessory
devices is still in process, and the operating environment of it is relatively harsh, the modification in
machinery is restricted by technology and cost. Comparing with machinery, the electronics
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Advanced Materials Science and Technology, ICMST 2010
technology is relatively mature, is of high flexibility, easy installation and distance control, which
make its application in tidal energy generation device possible [4,5,6].
This experimental device takes vertical-shaft water turbine as research target. Focusing on the
problems such as big volatility in output voltage and power, and failure in constant maximum power
output, a solution is proposed and the control principle is given, under which the hardware is
designed. Finally the experiments were carried out, proving the practicability of the solution.
Control Parameters and Principles
Power Utilization Coefficient C p of Water Turbine. The average power utilization coefficient of
water turbine is calculated as Eq.1 [3].
Cp =
Qω
0.5 ρ DbVA3
(1)
Where: Q--torque（Nm）; ω --angular velocity (rad/s); ρ --density (Kg/m3); D—diameter of track
circle (m); b --expanded length of blade(m); VA --velocity of approaching water flow (m/s).
Velocity ratio λ is defined as Eq.2.
λ = ωR
(2)
VA
Where: ω --angular velocity (rad/s); R—radius of track circle (m); VA --velocity of approaching
water flow (m/s).
According to Eq.2, Eq.1 can be changed into
Qλ
.
ρ bVA2
Influences of each factor to C p are described as follows:
Cp =
(3)
Velocity ratio, defined as the ratio of velocity of rotor’s rotating and that of approaching water
flow, is one of the important factors influencing water turbine’s power performance. Once the
structure of water turbine is fixed, it directly influences the relative velocity and angle of different
position, consequently influences the performance of water turbine.
Velocity of approaching water flow, is also the important factor influencing water turbine’s
performance. The difference in water turbine’s performance is quite obvious, and the power
utilization rate increases as it rises.
From the formula of C p , it can be got that C p is only related to velocity ratio and torque once
water turbine parameters and hydrology condition are set.Once the velocity of approaching water flow
is set, the relationship between velocity ratio and C p can be found via changing torque of water
turbine. From that relationship, the maximum absorbing power of water turbine can be reached via
tuning its external load dynamically. Based on this strategy, an electronics and electric device is
designed to dynamically tune water turbine’s load and look for the maximum power point via
calculating the output power of water turbine power generation device, which is carried out
real-timely by gauging its output current and voltage.
Control Principle and Diagram. The principle of the control system is showed in Fig. 1.
Principle and operating procedure of the control system: water turbine drives power generation device
to rotate; once it starts operating, firstly the discharge resistor is used to look for the maximum power
point of present condition; then the rotation rate of water turbine is gauged via encoder real-timely;
after that the set-value and feedback-value are compared , and the difference is used for PID
calculation to control the PWM output of discharge resistor circuit; finally the load of water turbine is
changed, stabilizing its speed at set-value.
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Once the speed is stabilized, the output voltage and discharge current of power generation device
are gauged real-timely via AD converting. Then the power of it is calculated. After multiple sampling
and calculation, the average value is got. Finally the rotation speed and power value under this speed
are stored. After this sampling, the set-value of rotation speed is changed. Repeat the above
procedures of sampling, calculation and storage, until the sampled power and voltage cannot satisfy
the charging condition of batteries. The output power value of different speed can be obtained. Find
the maximum power point and the corresponding speed via calculation. Then the process of finding
maximum power point under present condition is over. Once the maximum power point is found and
the minimum voltage of charging batteries is reached, the discharge resistor circuit is gradually closed
whereas the charge resistor circuit is gradually opened, to charge the batteries. If batteries' condition
permits, the discharge resistor circuit is fully closed to concentrate all the power on batteries charging.
During charging process, the system is protected via real-time voltage and current detection, and
certain measures are carried out when fault occurs. During the operating process of power generation
device, its load is increased or reduced by fixed step-length real-timely. The output voltage and
current are gauged to calculate the power, which is then compared with last one to determine the new
maximum power point. This process promises the power generation device always operates with
maximum power, absorbing the most of the energy of tidal energy.
Fig.1 Diagram of control system
The Hardware Circuit Design of Control System
The control system is consist of two parts, which are control board and power amplifier board. In
order to increase the system expandability, the chip TMS320LF2406 of TI company is used as the
control chip of control board. The rest parts of control board are the digital display circuit, keystroke
circuit and logic circuit of the system at normal state. The power amplifier board is made of switching
power supply based on UC3844 chip, 3-channel sampling circuit of analog, 1-channel interface
circuit of encoder, 2-channel drive circuit of IGBT and relay. Hall sensor of Carson electronic
company is used to measure current and voltage. The chip model of IGBT is K25T1202. And the
drive chip of IGBT is 1ED020I12 of Infineon Technologies AG. The partial circuit design is showed
from Fig. 2 to Fig. 4.
Since the output voltage of generator is not stable. In order to reliably supply power to control
source, switching power supply based on UC3844 chip is used to supply power to the whole control
system. And it is showed in Fig. 2. It has five-road outputs in all. Through the experiment, the output
of switch power supply can completely satisfy the demand of power supply of the whole control
system.
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Advanced Materials Science and Technology, ICMST 2010
Fig.2 Electric schematic diagram of switching power supply
The A/D convert circuit is showed in Fig. 3. Interference immunity of A/D convert is increased by
taking voltage follower. At the same time the analog input can be adjusted by changing the numerical
value of sample resistance.
Fig. 3 The circuit of A/D convert
The drive circuit of IGBT is showed in Fig. 4. In order to improve the reliability of drive circuit,
there is another spare circuit of charge and discharge circuit. When any one circuit fault the system
can automatically is switched to spare circuit and control system can work normally.
Fig. 4 The drive circuit of IGBT
The Experiment of Dynamic Load
According to the situation of actual rotate speed, voltage and current, the external load is changed
dymaicly to remain constant of rotate speed and voltage. It is called dynamic load.
Without electric control system, the external load of water turbine is changed only by changing the
resistence value of slide rheostat manually. In the process of experiment, at the constant conditions of
Advanced Materials Research Vols. 181-182
561
hydrology and water turbine, and at the low speed ratio condition, the speed fluctuation of water
turbine is serious. When the load is becoming greater, the water turbine is stopped suddenly. The
curve of this condition is showed in Fig. 5.
0.45
0.45
0.40
0.40
Cp
0.30
0.25
0.25
0.20
0.20
0.15
0.15
0.10
0.10
0.05
0.05
0.00
0.00
1.00
2.00
3.00
4.00
Cp
0.35
0.30
Cp
Cp
0.35
5.00
0.00
0.00
6.00
1.00
2.00
λ
3.00
λ
4.00
5.00
6.00
Fig. 5 The curve of Cp without electric control Fig. 6 The curve of Cp at the control of electricity
When the eletric control system is added to the system, the rotate speed and voltage of water
turbine is real-time detected, and then the load of water turbine is real-time changed without human
intervention. At this condition, the adjustable time is short and the precise adjust is got. So the speed
ratio of water turbine can be further reduced. The curve of experiment is showed in Fig. 6.
The analysis result of experment: from the curve of Cp of Fig. 5, the energy utilization rate is max
at the point of speed ratio being 3.0. Under the condition without the electric control system, if the
speed ratio is less than 3.0, the rotate speed of water turbine is not stable and at final the water turbine
stalls with the speed ration being reduced sharply. The curve of energy utilization rate is not measred
at the condition of speed ratio being less than 3.0. From the Fig. 6, the electric control system is added
to the system. If the speed ratio is less than 3.0, the voltage is real-time detected and the load is
dynamicly adjusted. So the curve of water turbine characteristics is got at the condition of the speed
ratio being less than 3.0. The water turbine can be stopped at any rotate speed by changing real-time
external load through the experiment of dynamic load. The feasibility of water turbine working at
maximum power is poved.
The devices of storage battery and discharge resistance are joined to the control system. The
experiment of maximum power can be done.
In the process to define the maximum power point, the curve of detection is showed in Fig. 7. From
the curve, the maximum power point is found through the discharge resistance at the beginning of
device working. And the rotate speed which is relative to the maximum power point is saved. If the
output power and voltage are not satisfied the condiiton of charge, the behavior of finding the
maximum power point is stopped.
0.45
0.45
0.40
Cp
0.35
0.35
0.30
0.30
0.25
0.25
Cp
Cp
0.40
0.20
Cp
0.20
0.15
0.15
0.10
0.10
0.05
0.05
0.00
0.00
1.00
2.00
3.00
λ
4.00
5.00
0.00
0.00
2.00
4.00
6.00
t
8.00
10.00
12.00
Fig. 7 The curve of finding maximum power point Fig. 8 The operation curve of maximum power
The operation curve of maximum power is showed in Fig. 8. When the water turbine is working,
despite the wave of tide is existed in time and space, the water burbine is always working at the nearby
maximum power point through dynamic adjusting load. The result of experiment is up to the expected
goals and plan.
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Advanced Materials Science and Technology, ICMST 2010
Summary
To sum up, the conclusions got are showed as follows:
(1) through the theoretical analysis and experiments the feasibility of project is proved.
(2) the running of water turbine is near the maximum power point all the time by adjusting
dymamicly external load. So the energy of tide flow is absorbed at maximum degree. The utilization
factor of energy can be improved.
(3) In the process of finding the maximum power points by adjusting machine, the water turbine is
at the invalid state for a period of time.
(4) The energy of generator is stored at maximum degree by adjusting machine. The energy
absorptivity of tidal energy is not improved primarily. The deflection control of water turbine can be
considered later. And the energy absorption rates can be improved further.
Acknowledgment
This work is partially supported by National 863 Project (Grant No: 2007AA05Z450), Science and
Technology Support Program (Grant No: 2008BAA15B04), Ocean Public Benefit Industry Special
Research (Grant No: 200805040), Natural Science Foundation of China (Grant No: 50706008) and
Zhejiang Province Major Scientific and Technological Special (Grant No: 2008c14039).
References
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[2] L.B. Wang. Theoretical and Experimental Study on Hydrodynamic Performances of
Vertical-Axis Tidal Turbine. Dissertations by Doctoral Candidates of Harbin Engineering
University, Harbin, China (2005).
[3] J.Y. Ji. Experimental Study on the Performance of Controlled Vertical-axis Variable-pitch
Turbine. Master's Thesis of Harbin Engineering University, Harbin, China (2008).
[4] Q.Z. Dai. Tidal Power Generation and Tidal Power Generation Devices. The Orient Motor
(2010), p. 51-66.
[5] D.W. Qian and H.Q. Chen. An Intelligent Control Strategy for Hydro-turbine Regulation System.
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Advanced Materials Science and Technology, ICMST 2010
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The Research and Design of Vertical-Shaft Water Turbine Power Generation Device
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