This document summarizes a distributed power system with wind power and biogas generation presented at the IEEE T&D Asia 2009 conference. The system aims to provide steady electricity to remote communities using renewable energy sources. It combines an uncontrolled wind power generator with a controlled biogas generator to balance the intermittent wind output. The biogas generation allows controlling the system's total power output to meet electricity demand. Power flow and the sizing of the biogas capacity to stabilize output are discussed.

1. IEEE T&D Asia 2009
Renewable Energy Distributed Power System With
Wind Power and Biogas Generator
Zhang Yanning1, Kang Longyun1, Cao Binggang2, Huang Chung-Neng3, Wu Guohong4
(1. School of Electric Power, South China University of Technology, Guangdong key laboratory of Clean energy technology, 510640 Guangzhou
China;2. Institute of Mechanical Engineering, Xi’an Jiao Tong University, Xi’an 710049,china; 3.National University of Tainan, Tainan City, Tainan
700, Taiwan; 4.Electrical Engineering and Information Technology at Tohoku Gakuin University,985-8537, Japan)
large local communities. When DPS generate more power than
Abstract: The energy shortage and environment pollution is receivers and local energy storage systems require, they is on
attracting more and more attention with the social development. grid-connected to provide surplus power to the grid. Obviously,
Hence it is important to develop new energy and renewable the major aim of DPS is to supply remote, off-grid
energy that are bio-energy, wind energy, solar energy, small communities where the costs of connection to the
waterpower, tide energy, terrestrial heat energy, and hydrogen long-distance transmission or distribution grid are too high.
energy and so on. The research of distributed power system with DPS use few technologies connected with power generation
the solar and wind power is the leading domain. It is known to all such as different power generation devices, different energy
that the wind generation system is enslaved to the weather, the storage technologies and advanced microprocessor control
micro net composed by them don’t supply the steady electricity. supervision systems.
The biogas is produced from anaerobic biodegradation of organic The renewable energy distributed power systems are
material in the absence of oxygen and the presence of anaerobic cooperated by renewable energy; they contain two or more
microorganisms. The plant, animal dejecta, and rubbish are the power generation sources in order to balance each other’s
source, so the biogas can be gotten very easily. The biogas strengths and weaknesses [3]. There are many types DPS such
generation can be supplying the steady electricity and the output as: DPS with wind power and solar; DPS with wind power and
power can be control. Thus the authors present the wind-biogas fuel cell; DPS with wind power, solar, fuel cell [4-9]. These
renewable energy distributed power system, and the biogas sources are environmentally friendly and use primary energy
generator is employed to balance the output power of the system. carriers such as solar, wind and biogas, biomass etc. The
This system can keep the constant output power under control. sources mentioned above can be divided into two groups:
controlled sources and uncontrolled sources. Controlled
Key Words: Renewable Energy, Distributed Power System, sources mean that the output power can be easily controlled to
Wind Power, Biogas Generator the goal power; for example biogas. It is obvious that output
power from uncontrolled sources is unpredictable and
1. INTRODUCTION independent of human action. Solar and wind power plants are
There are many definitions of Distributed Power System. environmentally uncontrolled sources.
Our definition of DPS is as follows [1,2]: small set of For the user, electricity should be produced exactly at the
co-operating units, generating electricity or electricity and heat, time it is needed. Wind power does not meet this requirement.
with diversified primary energy carriers (renewable and So, special kind of power plants should be built to avoid
non-renewable), while the co-ordination of their operation shortages of wind power. The biogas is introduced to balance
takes place by utilisation of advanced power electronics the electricity of wind power.
systems.
Mostly DPS are connected to the power grid; furthermore 2 THE WIND-BIOGAS RENEWABLE ENERGY SYSTEM
they can also work independently feeding separated receivers, The wind power is influenced by the weather; the output
from one or several homes/farms, small industrial plants to power is determined by the wind speed. It is known to all that

2. the wind speeds are changed with the time and space. The DPS Thus
with the wind power system is not satisfied to the user need.
PG 0 (2)
Biogas is produced from anaerobic biodegradation of organic
material in the absence of oxygen and the presence of
Where, P , PB , PE , PL , P are the powers of wind, biogas,
W G
anaerobic microorganisms. The biogas generation is developed
with the biogas usage. The biogas produced by the waste of battery, load and grid, It means that the DPS provide the
industry, agriculture and town is fired to drive the engine to electricity to the grid. When the relation is shown as:
generate electricity.
Pw PB PE PL (3)
The biogas generation is under control and can provide
electricity to balance the output power of wind generation, the The battery gets the electricity from the DC bus or gives the
DPS with wind and biogas is shown as fig1. electricity according to the user load.
When the relation is shown as
Pw PB PE PL (4)
Thus
PG 0 (5)
It means that the DPS can’t satisfy the need of the user and
get the right electricity from the grid. The DPS under control is
shown above.
2.2 Capacity of Hybrid System
Fi The hybrid system of wind generator and biogas generator
g 1 wind-biogas DPS is a good choice for the remote user. It is known to all that the
output power of wind generator is varied with the wind speeds
2.1 Power Flow of System change. Thus the output power is varied from the power of
The output current of the wind generation is transformed to starting wind speed to the rating power. The output power
the DC current by AC/DC and is connected to the DC bus, the range is big, which is not good for the user. To keep the
biogas generation is connected to the DC bus with AC/DC. constant power out the capacity of biogas must be right for the
These generators controllers are connected to the system hybrid system.
controller. The current of output power is described as fig2. The start working wind speed is v1 and the rating power is
PE at the rating wind speed vE. The relation between the wind
speed and the output power is shown as
P Kv3 (6)
Where, K is a parameter which is a constant at a speed. It is
concluded that the output power is third order direct ratio to
the wind speed. The minimal power of wind generator can be
easily gotten by equation
Fig2 current of output power
v1
P1 PE (7)
vE
There are three cases according to the relations between these
powers. When the relation is shown as: The output power of wind generator on whole day is
presented as
Pw PB PE PL (1)

3. main idea behind this method is to control the reaction torque
0 P PE (8)
of the generator via changing the winding voltage and the
The biogas generator is usually composed by the motor and output current.
gas engine. The efficiency of engine is high from a power
point to rating output power. Assuming that the output power
of biogas generator is Pb, it is shown as
Ps Pb PbE (9)
Where, Ps is the start power with the high efficiency, PbE is the
rating power of biogas generator.
Assuming that the load is Pl, it is shown as
Fig3 VSCF wind turbine
0 Pl PlE (10)
The stable electricity supply is important to the user; hence the For the fixed pitch wind turbine, the torque produced by the
relation between the capacity of wind generator, biogas wind energy could be described as follows:
generator and load is shown as Pf 1 3
Tf Cp R2
Pl Pb P (11) g 2 g
(14)
Comparing these relations the capacity of biogas generator is 1 Cp
R3 2
presented as 2
Where p is the density of the air, R is the radius of the blade; V
Ps PlE (12)
is the wind speed; Cp is the coefficient.
The dynamic performance of wind turbine could be
3 CONTROLLER DESIGN described as follows:
The wind-biogas system is a complex system which the
d g
whole model is difficult to exactly get, thus the control design Jg Tf Tg B g (15)
is the key to the good electricity. The controller of the system
dt
is separated to two parts, one of which is the controllers of
Where Tg is described as follows:
wind generator and biogas generator, and the other is the chief
controller. The controller of wind generator is designed to get
Tg p ig k g igq (16)
the max energy from the wind, the controller of biogas
generator is designed to get the need power by adjusting the Where k is the ratio of boost-bucker converter, and igq is the
mass of the input biogas. current of DC bus.
3.1 Wind Generator 3.2 Biogas Generator
The wind speed input model of wind generation is shown The controller is also designed to track the maximum output
as: power and keep the constant output voltage. The biogas
1 3 generation is shown as fig4.
p v1 SC p
2 (13)
In the (13) is the air density, v1 is the up wind speed, s is the
area that the wind past through the wind turbine vane, Cp is
the coefficient of wind energy use.
The rotor speed of the wind turbine is controlled through the
adjustment of ration of Boost-bucker, as shown as fig3. The Fig 4 biogas generation

4. The instantaneous power is shown as
K1 c (25)
pVni
Pi 17
120
Where, i is number of gas vat. The output torque is described 4 SIMULATIONS
as: The hybrid system of wind generator and the biogas
generator is made up and the research on how to track the max
9550 Pi m
Ttq point of wind generator and the research on how to make the
n
30 output power follow the order quickly have being already done.
n 18
But the whole system controller is on designing. The
d simulations are done first to validate the control ways. The
dt capacity of hybrid system is confirmed by 2.2. The rating
Where, m is the availability efficiency. power of wind generator is 7Kw; the rating power of biogas
The control model of biogas generation is described as generator is 20Kw.
d The reference wind speed is 15m/s, the radius of wind
J Ttq Te Tf (19)
dt turbine is 10m, and the moment of inertia is 1270. The control
From the (19) it is also shown as result with the wind speed of 15m/s is shown as fig5.
d2 d
J Ptq Pe B (20)
dt 2 dt
3.3 ADRC
The ADRC of wind turbine is designed as follows.
(1)TD of this system is presented as:
x1 rfal ( x1 v, a, ) (21)
Where, v is the input signal, x1 is the tracking signal.
(2) The ESO of first order system is presented as
z1 z2 1 fal ( z1 , a, ) u (t )
(22) Fig 5 rotor speed controlled by ADRC
z2 2 fal ( z1 , a, )
Where, z1 is tracking the real rotor speed , z2 is detecting The gas engine simulation at the rotor speed 1500 r/min is
g
shown as fig 6.
the wind input torque.
(3)The NLSEF of first order system is presented as
e1 v z1
u0 K1 fal (a, , e1 ) (23)
u u0 z3
The linear model is also first considered and is proposed as
e1 v z1
u0 K1e1 (24)
u u0 z3
Normally the K1 is also calculated by the transfer function
Fig6 result of simulation
and follow the rules of TD gains r, the gains K1 is proposed as

5. The dc load is 15Kw, the output power of wind generator, The dc voltage is little vibrated at 400V. The simulations
the output power of biogas and the dc voltage is shown as prove that the hybrid system of wind generator and biogas
fig7 fig8 and fig9. generator provides the stable electricity to the user.
5 CONCLUSIONS
The renewable energy is attracting more and more attention
for its clean. The biogas is produced by waste and dead plant.
The wind generator is widely applied in the world and many
other generators are introduced to combine. The biogas
generator is only restricted by the marsh gas pond. It is
controllable and the capacity can be planed. The hybrid system
of wind generator and biogas generator keep the stable output
electricity by simulations.
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Fig8 output power of biogas generator
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BIOGRAPHIES
Zhang Yan-ning was born in Ningxia Province of
China, on January, 1978. He received the Bachelor
from Xi’an University of Technology, Xi’an, China,
in 2000, and the Master in 2003. He is a graduate
student of Xi’an JiaoTong University; his main
research is renewable energy usage and control
theory. The telephone is (o) +086+029-82665331;
the mobile phone is (m)+086+13488358928; the Email is
zhangyn96@sina.com; the Address is No.28 Xian Ning West Road, Shanxi,
Xi’an, China and Post code is 710049.
Fig9 dc voltage

6. Kang Long-yun was born in Jiling province of china experts who programs the development of universities belonging to ministry
on 1961. He is an advisor of doctor students, is a of education, and a member of experts commission of Science Chinese since
professor of School of Electric Power, South China Nov. 2001
University of Technology. He received the Bachelor
from Yanbian University CN in 1982, Master and Chung-Neng Huang Chung-Neng Huang (M 04) received the B.S.E.E. from
Doctor from Engineering Department of Kyoto National Taiwan University of Science and Technology, Taipei, Taiwan, in
University, in 1996 and 1999. He is addressing on the 1992, and the M.S.E.E. and PH.D. degrees from Tohoku University, Sendai,
renewable energy, such as distributed power system, photovoltaic automobile. Japan, in 1997 and 2000, respectively. He is an associate professor at National
University of Tainan, Tainan City, Taiwan. His main research interests are
Cao Bing-gang was born in Gansu Province of mechatronic system, hybrid-power control, and vehicular electronics.
China on 1953, He is an advisor of doctor students ,
dean of Mechanical Engineering School of Xi'an WU GUO-HONG Guohong Wu was born in Tianjin, China,on 26 September
Jiaotong University, a director of Research 1969. He received his B.S. and M.S. degree in electrical engineering from
Development Center of Electric Vehicle, is dean of Tianjin University,China in 1989 and 1994, respectively. In 1998, he reeived a
Center of Vehicle Engineering in Xi'an Jiaotong University as well as head of joint-supervised Ph.D.degree from the University of Tokyo, Japan and Tianjin
Research Institute of System Monitoring & Diagnostics. He has been a vice University. He was with the University of Tokyo from 1995 to 2001, as a Ph.D
director of Electric Vehicle in Shannxi Province and a member of Editorial student, a research associate and a postdoctoral fellowship, respectively. From
Board of Journal of Xi'an Jiaotong University and Asian 2001 to 2005, he worked with Tohoku University, Japan. He is currently an
Information-Science-Life which is an international journal. Furthermore, he is associate professor of Electrical Engineering and Information Technology at
one of experts who recognise name-brand products in Xi'an City, one of Tohoku Gakuin University, Japan. Dr. Wu is a member of IEEE and IEEJ.