Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
Contents lists available at SciVerse ScienceDirect
Renewable and Sustainable Energy Reviews
journal homepage: www.elsevier.com/locate/rser
Operation challenges for fast-growing China’s hydropower systems and
respondence to energy saving and emission reduction
Chun-Tian Cheng a,∗ , Jian-Jian Shen a , Xin-Yu Wu a , Kwok-wing Chau b
a
b
Institute of Hydropower System & Hydroinformatics, Dalian University of Technology, Dalian, China
Department of Civil & Structural Engineering, Hong Kong Polytechnic University, Hong Kong, China
a r t i c l e
i n f o
Article history:
Received 10 February 2011
Accepted 29 January 2012
Keywords:
Large-scale
Optimal operation
Hydropower systems
a b s t r a c t
During the past two decades, in particular the past decade, there has been a rapid rate of development
of hydropower in China. It is foreseeable that the same rate of development will be maintained in the
next decade. The total installed generation capacity of hydropower in China has now surpassed 200 GW
and ranks first in the world. The unprecedented rate of expansion, development scale, emergence of
large number of hydro plants with high head and huge capacity, and electric power transmission have
led to significant changes in management and operation of large-scale hydropower systems which have
become one of the significant factors in constraining the security and economic operation of power grid
in China. This article gives an overview of the China’s hydropower, analyses the new challenges that it
faces, highlights the key scientific and technological issues that need to be solved, and pinpoints that the
solution of these problems will be the key to the realization of energy saving and emission reduction by
China in 2020.
© 2012 Elsevier Ltd. All rights reserved.
Contents
1.
2.
3.
4.
5.
6.
7.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2387
An overview of China’s hydropower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2387
Characteristics of China’s hydropower systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2388
Relationship with energy-saving and emission reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2389
New challenges facing optimal operation of hydropower in China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2390
5.1.
Multi-level coordination problem for large-scale hydropower energy transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2390
Operation problem on the multiple vibration zones for plants with huge capacity and high head in
5.2.
large-scale cascaded hydropower system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2390
5.3.
Problem of peak regulation of hydropower in multi-power grids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2390
Impact of extreme climate on safe operation of hydropower and power grids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2391
5.4.
Problem on solution of hydropower systems and operating efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2391
5.5.
Key scientific and technical problems to be solved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2391
6.1.
Modelling large-scale complicated hydropower systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2391
Parallel computation of optimal operation of hydropower systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2392
6.2.
Knowledge management of optimal operation of hydropower system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2392
6.3.
6.4.
Uncertainty analysis of optimal operation of hydropower system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2392
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2392
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2392
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2392
∗ Corresponding author.
E-mail address: ctcheng@dlut.edu.cn (C.-T. Cheng).
1364-0321/$ – see front matter © 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.rser.2012.01.056
C.-T. Cheng et al. / Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
1. Introduction
Hydropower’s low cost, near-zero pollution emissions and ability to quickly respond to peak loads make it a valuable energy
source. In past years, hydropower occupied about 15% of Chinese
total electricity generation and about 22% of total installed capacity. Now it is the most widely used renewable resource for electric
power generation in the China. According to the proposed “Twelve
‘Five Year’ Electrical Plan in China” that will be released soon,
hydropower will be placed in the first priority amongst all types
of development of electricity generation and it is recognized as the
most stable and reliable approach to reduce the proportion of nonfossil energy to one-time energy consumption in China to 15% in
2020 and 40−45% carbon emission.
Up to the end of 2010, 213.4 GW of hydropower generation
capacity in China, with approximately 22.2% of total generation
capacity, has been reached, which is the result of rapid development of hydropower and power grid during the past two decades,
in particular the past decade. It is foreseeable that the same
rate of development will be maintained in the next decade. The
hydropower installed capacity will reach 330 GW in 2020. More
than 45,000 hydropower plants exist in China, which include about
400 ones with more than 50 MW generation capacity, 85 ones
with more than 300 MW and 32 ones with more than 1000 MW.
The largest hydropower plant in the world, the Three Gorges
with the total capacity of 22.4 GW and an annual production of
84.7 trillion Wh, is a typical example.
At present, the total generation capacity has reached 962.19 GW
in China, about 73.4% of generation capacity is from thermal power
plants, 22.2% from hydropower plants, a very small percentage from
other energy. About 70% thermal plants are using coal for electric
power generation in China. However, about 82 of coal deposits
are concentrated in the north and southwest regions. About 70%
of hydro resources are in 5 southwestern provinces, cities or
autonomous regions, including Sichuan, Yunnan, Tibet, Guizhou,
Chongqing, and Guangxi. However, the majority of electricity consumption is required in the eastern and the southern coastal regions
as well as some part of the central region. Long distance and large
scale electric power transmission is necessary for effective utilization of hydropower resources. In the past 10 years, the total length
of high-voltage transmission lines of 35 kV and above increased
by 69%, and total substation storages increased by 2.3 fold. 750 kV
UHV AC, 1000 kV UHV AC and ±800 kV UHV DC have been put
into operation successfully. By the end of 2009, the total length
of high-voltage transmission lines of 220 kV reached 399,400 km.
Now, most of regions are connected by interconnected national
grids. The power systems of China have the capacity of transporting
a massive amount of electricity over the geographic span of huge
country. The operation and management of hydropower systems in
China are characterized by large scale, trans-basin, trans-province,
and trans-region. The operation and management of large-scale
hydropower systems have become one of the significant factors
in constraining the security and economic operation of power grid
in China. The challenges to the operation management of the large
scale hydropower systems are tremendous. New problems, which
have direct impacts and relations to the attainable efficiency of the
hydropower systems comprising the commissioned plants as well
as those large-scale plants under construction, have emerged and
become the technical bottleneck in operation and management of
systems of hydropower stations in China.
2. An overview of China’s hydropower
China is endowed with large hydro potential. The exploitable
hydro capacity is 542 GW and the corresponding annual
2387
Table 1
Ranking of country (top 20 in the world) in terms of hydropower installed capacity
(2007, unit: GW).
Rank
Country
Capacity (GW)
Rank
Country
Capacity (GW)
1
2
3
4
5
6
7
8
9
10
China
USA
Brazil
Canada
Russia
India
Norway
Japan
France
Sweden
145.26
77.885
76.871
73.439
46.062
35.209
27.832
21.824
20.829
16.592
11
12
13
14
15
16
17
18
19
20
Venezuela
Italy
Switzerland
Turkey
Mexico
Spain
Argentina
Columbia
Austria
Paraguay
14.597
13.573
13.465
13.395
13.143
13.025
9.94
8.525
8.429
8.13
Table 2
Ranking of country (top 20 in the world) in terms of hydropower generation (2007,
unit: trillion Wh).
Rank
Country
Generation
Rank
Country
Generation
1
2
3
4
5
6
7
8
9
10
China
Brazil
Canada
USA
Russia
Norway
India
Venezuela
Japan
Sweden
486.7
370.3
364.7
247.5
175.3
132.6
122.6
83.0
73.3
65.5
11
12
13
14
15
16
17
18
19
20
France
Paraguay
Columbia
Austria
Turkey
Switzerland
Italy
Argentina
Vietnam
Pakistan
57.6
53.2
41.4
35.6
35.5
34.9
32.5
30.2
29.6
28.4
generating production 2470 trillion Wh, ranked first in the world.
The development process of hydropower in China has lasted for
100 years or so. Tables 1 and 2 respectively list the top 20 countries in the world in terms of total installed capacity of hydropower
and generation by the end of 2007. The two tables show that China
ranked first from both two indexes. Table 3 shows the total installed
Table 3
Total hydropower installed capacity in GW and generation in trillion Wh.
Year
Capacity
Annual
generation
Year
Capacity
Annual
Generation
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
0.36
0.36
0.38
0.39
0.53
0.61
0.70
0.91
1.02
1.22
1.62
1.94
2.33
2.38
2.43
2.68
3.02
3.64
3.84
4.39
5.05
6.24
7.80
8.70
10.30
11.82
13.43
14.66
15.77
17.28
19.11
1.20
1.32
1.49
1.83
2.55
3.20
3.40
4.71
4.82
4.11
4.36
7.41
7.41
9.04
8.69
10.60
10.41
12.62
13.14
11.50
16.01
20.46
25.06
28.82
38.90
41.44
47.63
45.64
47.65
44.63
50.12
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2031.8
21.93
22.96
24.17
25.60
26.42
27.54
30.19
32.70
34.58
36.05
37.88
40.68
44.89
49.06
52.18
55.58
59.73
65.07
72.97
79.35
83.01
86.07
94.90
105.24
117.39
128.57
145.26
172.60
196.29
213.40
58.21
65.55
74.40
86.36
86.78
92.37
94.48
100.23
109.18
118.45
126.35
124.84
131.47
151.60
166.79
186.77
186.92
194.56
204.30
212.93
243.13
261.11
274.57
281.33
330.99
396.40
416.70
486.70
565.55
571.68
2388
C.-T. Cheng et al. / Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
capacity and generation of hydropower in China since 1949. The
installed capacity has jumped more than 593% compared with
1949, and generation more than 476% (based on 2009 data). Specially, the average annual increment is more than 10 GW from 2003
whilst the annual increment in 2009 reached 23.69 GW, which is
even more than the total installed capacity of Japan (rank number 8 in the world). Referred to the most recent data by the end
of 2010, the hydropower installed capacity in China has reached
213.4 GW whose amount is 2.74 times that of the second ranked
USA (based on 2007 data) (Table 1). However, the current proportion of hydropower in China is not high, i.e. only 37%, which is far
less than over 80% in the western countries such as USA, France,
Norway, etc.
According to the proposed “Twelve ‘Five Year’ Electrical Plan in
China” that will be released soon, hydropower will be placed in
the first priority amongst all types of development of electricity
generation. Emphasis will be highlighted on the development of
6 hydropower bases scattered in the western region, i.e., Jinshajiang River, Yalongjiang River, Daduhe River, Lancangjiang River,
Nujiang River and the upper main stream of Yellow River. Development will further be made towards basins in Tibet such as
Yarlung Zangbo River. According to the aforementioned plan, the
hydropower installed capacity will reach 284 GW and 330 GW in
2015 and 2020, respectively. It is projected that, in that time, the
scale of hydropower installed capacity in China will be equivalent
to the summation of hydropower installed capacities of the other
top seven countries in the world (based on data of 2007 in Table 1).
This rate of expansion and scale of construction are very rare in
the world history. The challenges of operations and management
of hydropower systems in China are tremendous and unique.
3. Characteristics of China’s hydropower systems
More than 60% of hydropower resources in China are focused
on the main stream of several largest rivers and they have been
planned as 13 large hydropower bases [14]. Their total capacity of
cascaded plants on the main stream of these largest rivers has been
planned to reach 227.96 GW which occupies about 42% of the whole
exploitable hydro capacity. The followings are the most distinct
features of China’s hydropower systems.
Super scale: We have mentioned above that the current capacity of hydropower is 2.74 times that of the second ranked USA. By
the end of 2020, the scale of hydropower capacity in China will be
equivalent to the summation of one of the other top seven countries in the world. Now, amongst the top ten hydro plants under
construction or commission in the world, four of them are located
in China. They are respectively the Three Gorges, Xiluodu, Xiangjiaba and Longtan, with the total capacity from 6.3 GW to 22.4 GW,
ranked 1, 3, 7 and 9, respectively.
Huge unit: In recent decades, the unit generation capacity of
hydro turbines in China has been steadily enhanced. The 300 MW,
400 MW and 550 MW of unit capacity have been widely used in
recently developed projects in China. The Three Gorges project is
a milestone that 700 MW of unit capacity of hydro turbine is first
adopted. On its heels, other projects with huge capacity, such as
the Longtan and Xiaowan, also adopted 700 MW of unit hydro turbine. Furthermore, 1000 MW and above of hydro turbines are being
developed and will be employed by Xiluodu, Xiangjiaba and other
new projects.
Large scale cascaded hydropower plants: There are a lot of hydroelectric power plants on the main stream of rivers in 13 hydro
bases. Table 4 shows the generation information related to the
13 hydropower bases. The priority of developing hydropower is
given to the Wujiang River, the Nanpanjiang–Hongshuihe River,
the Yangtze River Upper Reaches, the Lancangjiang River, the
Table 4
General information of the 13 of largest hydropower bases in China.
Name
Capacity
(GW)
Annual
generation
(trillion Wh)
Number of
cascaded plants
on the main
stream
Jinshajiang
Yangtze River Upper Reaches
Yalongjiang
Lancangjiang
Daduhe
Nujiang
Yellow River Upper Reaches
Lanpangjiang–Hongshuihe
East Regiona
Fujian, Zhejiang and Jiangxia
Wujiang
West Hulana
Middle Yellow River
Summation
62.25
28.84
25.7
25.11
24.92
21.99
20.93
14.30
13.26
12.20
11.22
10.81
64.30
277.96
292
128
125
140
113.6
103.7
75
63.5
35.5
31.5
39.6
37.8
17.8
1203
13
8
21
14
16
13
16
18
11
8
a
An aggregative name that includes a lot of cascaded hydropower plants distributed in different basins. Correspondingly, their number of cascaded plants on
the main stream is vacant.
Jinshajiang River, the Yalongjiang River, the Daluhe River and the
Nujiang River in recent two decades or next decades. The total
capacity of cascaded hydropower plants for the eight bases aforementioned varies from 11.22 GW to 62.25 GW, the total generation
from 39.6 trillion Wh to 292 trillion Wh, and the number of cascaded plants from 8 to 21. Specifically, all hydroelectric power
plants on the main stream of the Hongshuihe River and the Wujiang
River have been developed and are being implemented into operation. The Three Gorges plant, being the largest hydroelectric plant
in the world and one of the cascaded hydropower plants on the
main stream of the Yangtze River Upper Reaches, has been put into
production since 2008.
High-head: There are more than 100 developed and developing hydropower plants whose installed capacity is more than
1000 MW. This is contributed greatly by plants under development
or in planning, most of which are of high head. Parts of them are
above 100 m or even 200 m. Table 5 lists parts of plants whose
installed capacity is more than 1000 MW and the highest head
is above 100 m. Most plants are located in the Jinshajiang River,
Yalongjiang River, Daduhe River, Lancangjiang River, Hongshuihe
River and the upper main stream of Yellow River that are the priority of hydropower development in the past two decades and the
future.
Long-distance of electric power transmission: As mentioned
above, most of the energy resources are in the western and northern regions, whereas the majority of electricity consumption is
required in the eastern and the southern coastal regions as well
as some part of the central region. Hence, a national strategy of
electricity transmission from western to eastern China has been
formulated. One of the main objectives of the strategy is thus
to exploit the abundant hydro-power resources in Guizhou, Yunnan and Sichuan provinces and transfer electricity eastward to
southern, central and northern China. The economically prosperous
eastern areas, such Shanghai, Jiangsu, Zhejiang, Beijing, Tianjin will
be benefited from the project. There are three transmission corridors from the west to east. Two corridors are related to hydropower
energy transmission. The central corridor is to transmit power from
hydro plants including the Three Gorges and Xiluodu along Jinshangjiang River to central and eastern China via both AC and
DC lines. The southern corridor will transmit the hydropower distributed in the Lancanjiang River, Hongshuihe River, Wujiang River
and Nujiang River in the Yunnan, Guizhou and Guangxi provinces
and the thermal power in the Guizhou province to the Guangdong
C.-T. Cheng et al. / Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
2389
Table 5
Part of hydroelectric plants whose capacity is over 1000 MW.
Name of Base
Plant
Capacity (MW)
Annual generation
(trillion Wh)
Turbine (MW)
(capacity × units)
Highest head
(m)
Jinshajiang
Jinshajiang
Jinshajiang
Jinshajiang
Jinshajiang
Jinshajiang
Yangtze River Upper Reaches
Yalongjiang
Yalongjiang
Yalongjiang
Yalongjiang
Yalongjiang
Daduhe
Wujiang
Wujiang
Yangtze River Upper Reaches
Yangtze River Upper Reaches
Yellow River Upper Reaches
Yellow River Upper Reaches
Yellow River Upper Reaches
Hongshuihe
Hongshuihe
Hongshuihe
Nanpanjiang
Lancangjiang
Lancangjiang
Lancangjiang
Lancangjiang
Lancangjiang
Jinanqiao
Guanyinyan
Wudongde
Baihetan
Xiluodu
Xiangjiaba
Three Gorges
Lianghekou
Jinping-I
Jinping-II
Guandi
Ertan
Pubugou
Wujiangdu
Goupitan
Shuibuya
Geheyan
Laxiwa
Lijiaxia
Gongbaixia
Tianshengqiao-I
Tianshengqiao-II
Longtan
Guangzhao
Gushui
Wulonglong
Huangden
Xiaowan
Manwan
2400
3000
8700
1400
13,860
6400
22,600
3000
3600
4800
2400
3300
3300
1250
3045
1600
1200
4200
2000
1500
1200
1320
6300
1040
2600
1200
1600
4320
1670
9.23
10.60
31.74
49.53
57.12
28.88
84.70
11.69
17.40
21.08
8.71
17.00
14.58
4.06
9.35
3.92
3.04
10.22
6.06
5.14
5.15
8.20
15.67
2.70
10.52
4.51
6.62
19.81
7.78
120
117
130
220
220
113
113
278
233
317
124
185
178
131
200
203
121.5
220
135.6
106.6
143
204
179
165
261
126
142
251
100
Lancangjiang
Luozhadu
5850
23.91
600 × 4
600 × 5
870 × 10
875 × 16
770 × 18
800 × 8
700 × 32
500 × 6
600 × 6
600 × 8
600 × 4
550 × 6
550 × 6
250 × 5
609 × 5
400 × 4
300 × 4
700 × 6
400 × 5
300 × 5
300 × 4
220 × 6
700 × 9
260 × 4
650 × 4
400 × 3
400 × 4
720 × 6
300 × 1 + 250 × 5
+120 × 1
650 × 9
province in Southern China. The project has speeded up the links
of the entire power system in China.
4. Relationship with energy-saving and emission reduction
Generally, reservoirs (hydroelectric plants) can be served for the
multiple goals of electricity generation, flood control, water supply,
irrigation, ecology, environment, navigation, etc. The main objectives of operation and management of hydropower systems are
to determine the optimal hydro generation that satisfies various
complicated constraints including power grid security, environmental protection, energy saving, economical operation, and
so on.
Owing to the uneven spatial and temporal distribution of
runoff and varying comprehensive demands of electricity generation, water supply and other usages, the optimal operation
of hydropower systems can be classified into various scales, i.e.,
long-term, mid-term, short-term and real-time, which are all complicated tasks. The complexity of optimal operation of hydropower
system mainly lies on the uncertainty of runoff and electricity loads.
Under the present scientific and technological level, water flow
process and electricity loads cannot be accurately predicted. The
problem of optimal operation of hydropower systems has not been
resolved satisfactorily.
Research on optimal operation for hydropower system began in
1940s [11]. The strong influence of operational research theory and
computer science technologies in the area can be observed. A big
leap in this topic came in 1950s and 1960s. It entered into the golden
development stage in 1970s and 1980s [19–21]. Following more
than 70 years’ effort, many research and application outcomes were
proposed, mainly comprising linear programming, non-linear programming, dynamic programming, Lagrangian relaxation, network
flow method, large-scale system decomposition-coordination, etc.
[16,17,1,21,13]. Since 1990s, various artificial intelligence algorithms, such as artificial neural networks, simulated annealing
215
algorithm, genetic algorithm, chaos optimization algorithm, ant
colony algorithm, particle swarm optimization algorithm, etc., have
been applied to optimal operation of hydropower (reservoir) systems [15,5,6,8,9,10,12,18].
It is widely recognized that the optimal operation of hydrothermal systems is an important approach to reduce the utility of
fossil fuels by substantially improving efficiency in a mixed power
system [23,24]. Currently, the energy sources of power grids in
China are mainly constituted by hydropower and thermal power.
With the increasing occurrence of global warming and extreme climate, the difference between peak and valley becomes bigger and
bigger, which in turn poses difficulties on peak regulation of most
power grids. There is a pressing need to enhance the composition
of energy sources in power grids and to introduce high quality
hydropower resources. On the other hand, with the heavy national
investment on new energy sources such as wind energy and solar
energy, problems arise on how to absorb these new energy sources
through the installation of pumped-storage power plants and their
joint operation with hydropower systems. Many previous local and
international research and application studies demonstrated that
optimal operation of hydropower systems via rational scientific
methods can increase power generation of systems of cascade
hydropower systems by 1.5–15% [2]. According to our experiences,
taking the power grids at South-Western regions of China with
higher proportion of hydropower as an example, the potential
increase of power generation via the regional grid platform will be
even more and will exceed 15%. Even if a conservative value of 1.5%
is taken, for the annual national electricity generating capacity of
571.68 billion kWh in 2009, an increase of 8.58 billion kWh will
be attained. It exceeds one-tenth of the annual design electricity
generating value of the Three Gorges which is 84.7 billion kWh.
A saving of 3.432 million tonnes of standard coal and a reduction
of carbon dioxide emission of 855.4 tonnes can be accomplished.
The effect on energy-saving and emission reduction will be quite
substantial.
C.-T. Cheng et al. / Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
139
146
153
22:00
132
20:00
125
Gross head/m
18:00
119
16:00
112
14:00
106
Vibration zones
12:00
0
99
10:00
150
08:00
300
06:00
450
Daily schedules
800
700
600
500
400
300
200
100
0
04:00
Vibration zones
02:00
Expected generation curve
00:00
600
Generation(MW)
Generation / MW
2390
Time
Fig. 1. Problem of multi-vibration zones with huge capacity and high head.
5. New challenges facing optimal operation of hydropower
in China
5.1. Multi-level coordination problem for large-scale hydropower
energy transmission
Currently, hydropower resources are mainly concentrated in
economically underdeveloped southwestern China whilst the
major electricity load is around Yangtze River delta and Pearl
River delta. In order to cater for this unbalanced energy structure, the strategic plan of “transmission of electricity from the
west to the east” was fully implemented in 2000, with the construction of main hydropower works around Three Gorges and
Longtan. This, together with the construction of the ultra-high voltage transmission grid during the past decade, basically realizes
nationwide power network connection. The connections in Southwestern China, Southern China, Eastern China and Central China
together constitute the largest hydropower and electricity network
system in the world. Through the power system reform, the electrical industry is now developed into a multi-level hydropower
operation and management system. The national, regional, provincial, and local control centres (substations) are responsible for the
balance and coordination of electricity resources amongst regional,
inter-provincial, and intra-provincial power grids, respectively.
The key characteristics of the operation of hydropower system in
China are large-scale, large areal extent, long distance, trans-region,
trans-province, and trans-basin. It is an extremely complicated
optimal operation and management problem.
5.2. Operation problem on the multiple vibration zones for plants
with huge capacity and high head in large-scale cascaded
hydropower system
Many dams in the main stem of several large rivers in Southwestern China are more than 100 m high. Even those with
200–300 m high are not rare. The installed capacity of a single plant
and a cascade hydropower system can be very large and shoulder a
more complicated optimal operation task. The unit vibration zones
have great effect on the security of hydropower plant and power
grids [3,22]. Generally, the vibration zone is closely related to the
generating water head, power output and power generating flow.
If, during the continuous operation process of the station, the power
output exceeds the specified range, it will pass through multivibration zones and will have related impact on its operation during
subsequent periods. In such cases, it may sometimes be difficult
to determine an appropriate regulation mode and may aggravate the difficulties on optimal operation of hydropower plant. If
multi-vibration zones exist simultaneously in several downstream
cascade hydropower stations, it will be even more difficult to
determine a feasible unit generator commitment within a limited
range of period. From mathematical point of view, it is a multidimensional discontinuous optimization problem and cannot be
solved by conventional optimization techniques. Novel techniques
are entailed for its solution.
Fig. 1 is a practical example about multiple vibration zones for
the Longtan plant with huge capacity and high head. The Longtan
plant is the largest one in the Hongshui River, with 9 generators
of 700 MW each and total capability of 6.3 GW. Three vibration
zones exist for each generator. Dynamic variation of the generating
water head often happens for regulating system loads. Frequently,
a variation of water head of 1–2 m may trigger variation in the
unit vibration zone. In some cases, several vibration zones may be
surpassed and may have mutual influence between different time
periods. For the Longtan plant, there are two upper hydropower
plants, i.e., the Upper Tianshengqiao plant, and the Lower Tianshengqiao plant and multiple vibration zones also exist for them.
The operations for the cascaded hydropower system will be more
complicated because of the hydraulic connection between the
upstream and downstream. The multi-vibration zones with huge
capacity and high head are a distinct operation problem of large
quantity of large-scale cascade hydropower systems in commission and to be commissioned soon in China. The left side of Fig. 1
shows the unit vibration zone of Longtan Hydropower plant whilst
the right side of Fig. 1 represents a real case of planned operation
in the Upper Tianshengqiao plant. It can be observed that from the
figure that, during the operation process, the unit needs to surpass
several vibration zones, which becomes an inevitable problem.
5.3. Problem of peak regulation of hydropower in multi-power
grids
Following the extension of the scale of hydropower and power
grid, the system networks will impose a more distinct need on
peak regulation, frequency regulation and emergency reserve of
hydropower plants. The operations and management of large-scale
hydropower systems will be completely different from the medium
or small ones built previously. An obvious change to the operation modes of single hydropower plants and hydropower systems
is the emergent demand for peak regulations for multiple grids.
The problems include electricity transmission to different provincial power grids by plants located at upstream and downstream
of the same river, as well as that by a single hydropower plant
to several provincial power grids. Fig. 2 shows a case example of
electricity transmission by cascaded hydropower system in the
Hongshui River. The distribution of electricity includes 4 provinces,
i.e., Yunnan, Guizhou, Guangdong and Guangxi. The Yunpeng and
Lubuge plants at the upstream convey electricity to Yunnan whilst
Guangzhao and Dongqing plants provide power to Guizhou. The
Upper and Lower Tianshengqiao plants and Longtan plant convey
electricity to Guangdong and Guangxi simultaneously whilst other
plants at the main stream and tributaries are mainly responsible to
provide electricity to Guangxi. The total power load, peak, and difference between peak and valley at different receiving power grids
are quite different, which can be up to a few folds. The load variation and periods of peak and valley may not be consistent. Whilst
C.-T. Cheng et al. / Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
2391
Fig. 2. An example of peak regulation under multi-power grids.
hydropower plants in the river basin have intimate hydraulic
connections, they also have mutually related as well as conflicting power connections. The complicated application demands of
various power grids need to be considered in short-term peak regulation of hydropower systems. This is substantially different from
the peak regulation problem for hydropower systems under a single
power grid.
5.4. Impact of extreme climate on safe operation of hydropower
and power grids
At present, the structure of energy sources in China mainly
relies on thermal and hydropower: thermal installed capacity occupies 74.6%, hydropower occupies 22.5%, and other energy sources
including nuclear, wind, solar, etc. occupy 2.9%. It is anticipated
that, after 2020, the proportion of hydropower installed capacity in
the Southern provincial power grids, such as Yunnan and Sichuan,
will occupy more than 70% inside the region itself. The Southern
China power grid, with the highest proportion of hydropower, has
a potential hydropower capacity of 148 GW and occupies 27% of
the country. It is forecasted that its hydropower installed capacity
will be increased from the current 48.5 GW to 100 GW in 2015, the
corresponding proportion inside the grid from 33% to 38%, and the
corresponding proportion of total hydropower installed capacity
within the nation from 25% to 38%. As the scale of the hydropower
becomes larger and larger, the impact of uncertain runoff quantity
on hydropower and power grids will become more significant. The
impact of the extreme climate on the operation of hydropower stations will be even more. The drought at southwestern region of the
country in 2008 exhibits an important warning.
coupling constraints. As an example, the multiple vibration zones
for plants with huge capacity are in fact a complicated practical need. With the more refined operations and management of
power grid, the demands for peak regulation, generation, release
and level of hydropower plants are becoming higher. For instance,
for plants with better regulation capability and higher installed
capacity, there are mandatory demands on partitioning of peak
regulation, depth of peak regulation, variation of unit power output. The power output is then specified certain fixed value and
the depth of peak regulation should be consistent to the variation of power load curve. Another example is the demand on some
plants to adopt or refer to previous scheme of real operation, in
accordance with real engineering practice. Other example such
as electricity transmission constraints on sectional area and output limit of transmission channels amongst power grids, based
on security and safety reasons, will also impose higher demand
on hydropower operations. Hence, the operations of hydropower
systems are the optimal problems with high-dimensional, nonlinearity, multi-stage, stringent constraints. The ever expansion
of hydropower systems render hydraulic and electricity connections amongst plants and cascaded systems more complicated. The
engineering practical needs impose a more complicated and difficult solution to the refinement demands of the optimal operation.
The computation effort and time during the solution process will
increase with the number of plants and number of constraints. It is
crucial to ensure the solution efficiency and quality of large-scale
hydropower system so that the optimization results can be applied
to suit engineering practical needs. There are strong demands on
novel methods and techniques in order to solve these problems.
6. Key scientific and technical problems to be solved
5.5. Problem on solution of hydropower systems and operating
efficiency
6.1. Modelling large-scale complicated hydropower systems
The rate of expansion and scale of construction of hydropower
in China are unprecedented in the world history. On the other
hand, the operations of hydropower systems involve a complicated
set of constraints, in particular a large amount of spatiotemporal
Reservoir (hydropower) systems involve power generation,
flood control, water supply, irrigation, ecology and other comprehensive purposes [5,6]. During recent six decades, optimal
operations of hydropower systems have been addressed by many
2392
C.-T. Cheng et al. / Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
researches [21,2,15]. It is most popular from 1970s to 1990s, with
the development of various models including linear programming,
non-linear programming, dynamic programming, network flow
programming, large-scale system decomposition, etc. During the
past two decades, artificial intelligent algorithms, such as artificial neural network, genetic algorithm, ant colony optimization,
were also applied. Dynamic programming was the most popular optimization technique in hydropower system. Amongst them,
incremental dynamic programming (IDP), discrete differential
dynamic programming (DDDP), incremental dynamic programming successive approximation (IDPSA), differential dynamic
programming (DDP), progressive optimality algorithm (POA) and
dynamic analytical (DA) method, which are employed to address
the curse of dimensionality, are studied and applied extensively.
However, on the whole, these methods have some drawbacks and
the curse of dimensionality was not totally solved. There are two
strategies to enhance the original dynamic programming. The first
strategy is to reduce the number of state discretization, which
occurs in IDP, DDDP and IDPSA. The overall concept is the successive
iteration approximation. Each iteration is searched within a limited
range of state-space. Another strategy is to replace discretization
of state variable with certain analytical iterative solution, which
is adopted by DDP, POA and DA. Hence, in order to pinpoint the
current and prospective large-scale hydropower systems, the key
scientific problem needed to be solved is to propose a general,
practical and quick optimization method in order to address different optimization objectives, complicated security and operating
constraints, spatial–temporal hydraulic and electricity connections
during the optimization process, etc.
6.2. Parallel computation of optimal operation of hydropower
systems
model construction and thus to facilitate the solution of complicated engineering problems.
6.4. Uncertainty analysis of optimal operation of hydropower
system
The uncertainty of runoff is the key factor affecting the feasibility of any hydropower system scheduling, in particular for mid- to
long-term optimal operation of power system. The occurrences of
more frequent extreme climate in recent years also aggravate the
difficulties of operation and management of hydropower systems.
An important research direction remains to predict runoff of various scales, to enhance the prediction accuracy and forecast period,
and to develop theory on uncertainty analysis of optimal operation
of hydropower system based on uncertain runoff values at different
confidence levels.
7. Conclusions
Hydropower is currently the largest renewable energy resources
in China. It is the key to attain the target to reduce the proportion of non-fossil energy to one-time energy consumption in
China to 15% in 2020. In order to accomplish this goal, it not only
requires continuing substantial development of hydropower, but
also needs to investigate emerging new problems on optimal operation and management of hydropower systems of ever-increasing
scales. The objective is to furnish more effective scientific methods
and decision-support tools to support the operation and management of current and prospective large-scale hydropower systems
in China.
Acknowledgements
For large scale and complicated hydropower systems, the
computation efficiency not only affects the feasibility, but also
determines the utilization of the method. It is particularly true for
short-term and real-time optimal operation. For complicated and
large-scale optimal operation problems such as the hydropower
systems, an effective way is to employ parallel computation in the
solution process for enhancement of the solution speed and efficiency [7]. For hydropower system in region-oriented or provincial
power grid, the attribute of natural spatial distribution of stations
and the coordination management of optimal operation of intraregional and inter-regional power systems are suitable for the
solution by the parallel computation. Hence the introduction of the
parallel computation to optimal operation analysis of hydropower
system is a feasible and practical way to enhance the solution efficiency problem of complicated hydropower system.
6.3. Knowledge management of optimal operation of hydropower
system
It will be a complicated task to build models for large scale
hydropower systems. With the ever expansion of the scale of
hydropower systems, more factors have to be considered so that the
complexity and difficulty of model construction will be escalated
in a non-linear manner. For operation problem of hydropower systems with strong engineering attributes, adequate simplifications
are useful and necessary in order to enhance the solution efficiency
and feasibility of the system. During the past decade, it is feasible to
introduce intelligent techniques, such as knowledge management,
for large-scale complicated models [4]. This technique is able to
make induction based on the existing engineering knowledge, to
depict and systemize the model construction process employing
knowledge representation technique, to automatically direct the
This research was supported by the National Natural Science
Foundation of China (No. 51025934) and Central Research Grant of
Hong Kong Polytechnic University (G-U861).
References
[1] Allen RB, Bridgeman SG. Dynamic programming in hydropower scheduling. Journal of Water Resources Planning and Management-ASCE
1986;112(3):339–53.
[2] Barros MTL, Tsai FTC, Yang SL, Lopes JEG, Yeh WWG. Optimization of largescale hydropower system operations. Journal of Water Resources Planning and
Management-ASCE 2003;129(3):178–883.
[3] Catalao JPS, Mariano SJPS, Mendes VMF, Ferreira LAFM. Scheduling of headsensitive cascaded hydro systems: a nonlinear approach. IEEE Transactions on
Power Systems 2009;24:337–46.
[4] Chau KW, Chuntian Cheng, Li CW. Knowledge management system on flow and
water quality modeling. Expert Systems with Applications 2002;22(4):321–30.
[5] Cheng C. Fuzzy optimal model for the flood control system of upper and middle
reaches of the Yangtze River. Hydrological Sciences Journal 1999;44(4):573–82.
[6] Cheng C, Chau KW. Fuzzy iteration methodology for reservoir flood
control operation. Journal of the American Water Resources Association
2001;37(5):1381–8.
[7] Cheng C, Wu X, Chau KW. Multiple criteria rainfall-runoff model calibration
using a parallel genetic algorithm in a cluster of computer. Hydrological Sciences Journal 2005;50(6):1069–88.
[8] Cheng C, Wang W-C, Xu D-M, Chau KW. Optimizing hydropower reservoir operation using hybrid genetic algorithm and chaos. Water Resources Management
2008;22:895–909.
[9] Cheng C, Liao S, Wu X, Chau KW. Two stage particle swarm optimisation for
long-term operation of a hydroelectric power system. The HKIE Transactions
2009;16(3):8–14.
[10] Cheng C, Liao S, Tang Z, Zhao M. Comparison of particle swarm optimization
and dynamic programming for large scale hydro unit load dispatch. Energy
Conversion and Management 2009;50(12):3007–14.
[11] EL-Hawary ME, Christensen GS. Optimal economic operation of electric power
systems. New York/San Francisco/London: Academic Press; 1979.
[12] Fu Guangtao. A fuzzy optimization method for multicriteria decision making: an application to reservoir flood control operation. Expert Systems with
Applications 2008;34(1):145–9.
C.-T. Cheng et al. / Renewable and Sustainable Energy Reviews 16 (2012) 2386–2393
[13] Howson HR, Sancho NGF. New algorithm for the solution of multi-state
dynamic programming problems. Mathematical Programming 1975;8(1):
104–16.
[14] Huang H, Yan Z. Present situation and future prospect of hydropower in China.
Renewable and Sustainable Energy Reviews 2009;13(6–7):1652–6.
[15] Labadie JW. Optimal operation of multireservoir systems: state-of-theart review. Journal of Water Resources Planning and Management-ASCE
2004;130(2):93–111.
[16] Momoh JA, El-Hawary ME, Adapa R. A review of selected optimal power flow
literature to 1993. Part I. Nonlinear and quadratic programming approaches.
IEEE Transactions on Power Systems 1993;14(1):96–104.
[17] Momoh JA, El-Hawary ME, Adapa R. A review of selected optimal power flow
literature to 1993. Part II. Newton, linear programming and interior point methods. IEEE Transactions on Power Systems 1993;14(1):105–11.
[18] Qin H, Zhou J, Lu Y, Wang Y, Zhang Y. Multi-objective differential evolution with adaptive Cauchy mutation for short-term multi-objective optimal
[19]
[20]
[21]
[22]
[23]
[24]
2393
hydro-thermal scheduling. Energy Conversion and Management 2010;51(4):
788–94.
Simonovic SP. Reservoir systems analysis: closing gap between theory and practice. Journal of Water Resources Planning and Management
1992;118(3):262–80.
Wurbs RA. Reservoir-system simulation and optimization models. Journal of
Water Resources Planning and Management 1993;119(4):455–72.
Yeh WW-G. Reservoir management and operations models: a state-of-the-art
review. Water Resources Research 1985;21(12):1797–818.
Yi JL, John W, Steven S. Dynamic optimal unit commitment and loading in
hydropower systems. Journal of Water Resources Planning and ManagementASCE 2003;129(5):388–98.
Yuksel I. Hydropower for sustainable water and energy development. Renewable and Sustainable Energy Reviews 2010;14(1):462–9.
Yuksel I. As a renewable energy hydropower for sustainable development in
Turkey. Renewable and Sustainable Energy Reviews 2010;14(9):3213–9.