Energy and Power Engineering, 2013, 5, 621-624
doi:10.4236/epe.2013.54B120 Published Online July 2013 (http://www.scirp.org/journal/epe)
Intelligent Models of Long-Term Security Correction in
Energy Conversion Dispatching
Chaochun Luo1, Dunnan Liu2, Qingqi Chen1, Xinming Liu2
1Power Exchange Center, Hunan Electric Power Company, Changsha, China
2School of Economics and Management, North China Electric Power University
Received January, 2013
ABSTRACT
This paper is research on the dispatching models for monthly generation plan which is manage the congestion consid-
ering the security constrains of the power grid. Since the monthly generation plan is the result of vary monthly power
exchange, including long-term power contract, power exchange among provinces and generation constitution exchanges,
The application of monthly secu rity constrained dispatching is with significant meaning for the security and stability of
power grid. This paper brings forward the purpose and contents of security dispatching and introduces the working
procedure and mathematic models. At last, the practical example of the Hunan Province power grid is introduced to
explain the models.
Keywords: Intelligent Models; Congestion Management; Electricity Market; Monthly Generation Plan
1. Introduction
In recent years, environmental protection and climate
change have become the world’s most important issue of
common concern. Energy conservation, the improvement
of energy efficiency and the development of renewable
energy sources have become the basic energy policies.
China’s “Eleventh Five-Year Plan” made it clears that to
the year 2010 the energy consumption of unit GDP and
total emissions of major pollutants will reduce by 20%
and 10%.respectively compared to the year 2005.
The power industry is the key area of energy saving
and pollution reduction with great energy-saving poten-
tial. In view of this, the National Development and Re-
form Commission formulated the “energy generation
scheduling (Trial)[1], and has submitted it to the State
Council for approval in ear ly 2007. In June of 2007, with
“on energy conservation scheduling the implementation
of alternative electricity generation guidance” issued by
Economic and Trade Commission of Hun an Province[2],
Hunan Electric Power Company developed the “Hunan
power grid to carry out energy-saving scheduling imple-
mentation details the implementation of alternative elec-
tricity generation”, to achieve the goals of energy-saving
and emission reduction through the market-oriented
means.
Middle and long-term energy security checking is an
important guarantee for the Implementation of generation
energy-saving scheduling. The scheduling of Hunan
Province needs to consider the power generation capacity
of plants, peaking capacity, safe operation of power net-
work, net loss and other factors, determine whether the
transaction of alternative power generation is effective,
and is responsible for the implementation of effective
transaction of alternative power generation. Middle and
long-term security checking refers to the security con-
straint adjustments in terms of power plans, and its main
function is to test and adjust the plans of monthly elec-
tricity consumption, so as to meet inter-regional security
constraints, where the monthly electricity consumption
includes annual contracts decomposed to every month,
contracts of external transmitting power and bidding
power of alternative generation. The imple mentation and
operation of middle-long term security checking is es-
sential to ensure the safety operation of power network
and improve the enforceability of power plans [3,4].
In view of the characteristics of monthly power in-
cluding wide time span and strong uncertainty, this paper
will use the tie-line stability limit of the average family
as the security constraints between areas. To present
processes and algorithms of middle-long tern security
checking under energy generation scheduling model to
verify the actual network data.
2. The Main Transaction Process
In order to better describe the relative functions of the
middle-long term security checking, it is necessary to
introduce the transaction process of alternative genera-
tion and power bidding rules briefly. Alternative power

C. C. LUO ET AL.
622
generation refers to trading tools to promote the substitu-
tion of low-capacity and high-energy generating units for
generating units with high capacity and high energy effi-
ciency, to achieve energy saving and emission reduction
through the market-oriented means. The main transaction
process is as follows:
1) Electricity Trading Center releases the centralized
transaction reporting notification about monthly alterna-
tive power on 16th of each month, and clarifies trading
days.
2) Before 17:00 in the first 2 working days of trading
days, the power Trading Center releases the next month's
monthly pre-power projects of trading unit, and trading
unit involved in alternative power generation focused on
transactions monthly maximum transfer/transferee power
of monthly alternative power centralized transaction.
3) Trading subjects participating in the centralized
transactions of monthly alternative power generation
confirm the transferors/transferees’ status through tech-
nical support systems of alternative power generation
transactions to the power grid electricity trading center in
Hunan, and submit the transaction declarations from
9:00pm in the trading day; 9: 00-12:00 am in the trading
day is a free reporting period; 12:00 in the trading day is
a deadline for reporting, and technical support system
will match the clearing according to the final effective
transaction d eclarat i o n s .
4) The power trading center will hand over the pre-
liminary results of monthly alternative power generation
centralized transaction to Hunan Electric Power Dis-
patching and Communication Center before 17:00 in the
transaction day.
5) Dispatching and Communication Center will com-
plete the safety check of the transaction preliminary re-
sults, and feedback the checking suggestions to the elec-
tricity trading center before 17: 00 in the third working
days after the transaction day.
6) The power trading center will make the necessary
adjustments for the preliminary results of the transaction,
until the security check is passed and the centralized
trading results of monthly alternativ e power generation is
formed. Additionally, the power trading center power
generation releases and issues transaction notice to the
relevant transaction subjects through technical support
systems about alternative power generation trading be-
fore 17:00 in the fourth working day after the trading
days.
7) Dispatch communications center is responsible for
the implementation of centralized trading results of
monthly alternative power generation.
3. The Main Process of Security Checking
According to the orders about security and stability
and existing scheduling and running system, on the basis
of the appropriate partition of the entire power grid and
the formation of multiple independent security zones,
security checking software regards the average stable
limits of the contact line as constraints to test and adjust
the monthly power plan, so as to meet the needs of secu-
rity and stability of inter-regional power transmission.
Figure 1 shows the basic model o f the middle-long term
safety checking, the power grid by consists of two safety
zones labeled by A and B, contact line is denoted with T.
According to the power balance relationship after
safety partition of A zone, the flow of contact line T can
be calculated by the following fo rmula:
AA
T1,1 1
g
tl
N
NN
tg
tgl
WW WW



A
l
(1)
where
g
W denotes the monthly planning power of unit
g; t dentes the flow of contact line t; l
W denotes
load capacity of the month;
W
g
N represents the total
number of units; t represents the number of contact
lines, represen ts the number of load nodes.
N
l
Similarly, the following formula can be obtained from
the power balance of zone B:
N
BB
Tt
111
g
tl
N
NN
l
tlg
WWWW

 

B
g
T
B
(2)
with the consideration of the upper and lower space of
generation output of each partition, and the flow con-
straints of contact line groups, the amount of planning
power adjustments can be expressed in the following
formula:
,maxA B,max
,minA B,min
min{(),,} ,
dmin{ (),,},
TTT T
A
TT T
WWSS WW
WWWSSWW


 




(3)
A
ddWW (4)
where is the adjusting amount of planning power
of zone A; is the amount of power adjustments;
T is the flow of contact line groups; ,maxT
W is the
upper flow limits multiplied by upper stable limits of
contact line groups, the average load rate and adequacy
factors; ,minT is the lower flow limits multiplied by
lower stable limits of contact line groups, the average
load rate and adequacy factors; the up-regulated space of
security zone A
A
dWd
W
B
W
S
W

, B S

refers to the increased power
with the biggest possibility of generation plants within
Figure 1. The basic model of the middle-long term safety
checking.

C. C. LUO ET AL. 623
the security zone; the down-regulated space of security
zone A, B refers to the decreased power with the
biggest possibility of generation plants within the secu-
rity zone. We take zone A as example, and present the
calculating formulas as follows:
SS
A
Am ax
1A
(
g
N
g
gg
SW



，
，
A
)
g
W
in
)
(5)
AA
Am
1A
(
g
N
gg
gg
SWW



,
，
A
(6)
where , min
g represents the maximal and mi-
nimal power respectively.
Amax
g
W，W，
In summary, middle-long term safety checking in-
cludes the following processes [4,5]:
1) Reading and pre-processing the raw data of trading
center.
2) According to actual operation situations of power
network and protocols for security and stability security
zone partition is made.
3) The upper and lower flow limits of contact line
groups are calculated from stable limits.
4) Carry out power balance from (1) and (2) partition.
5) Calculating the flow cross-border situation of con-
tact line groups.
6) With the consideration of generation capacity, the
flow cross-border situation, the net losses and other fac-
tors, proposing some adjusting suggestions and feeding
them back to the trading center.
4. Case Analysis
4.1. Safety Division of Hunan Power Grid
The indices to reflect the generators’ status in the market
can be obtained by comparing the capacity of different
market suppliers and the market demand. Many indices
in this class, such as RSI [2, 3] and MRR [4] have been
studied by many researchers. Here we introduce two
representative indices.
1) After years of construction, Hunan power grid has
built the main grid with 500 kV lines and the regional
backbone grid with 220 kV lines connected through 500
kV back lines with the Eastern grid. Among them, the
Huai River coal bases concentrate 56.1% generating ca-
pacity of the main power plants of the whole province,
the rest of the main thermal power plants are distributed
along the area of Yangtze River. As part of Eastern
power grid and an important energy-output province of
East China Power Grid, Hunan power grid ensures its
own electricity supply and bears the important task of
transmitting electricity to economically developed areas.
2) According to the characteristics of geographical
distribution of Hunan power grid and procedures of sta-
bility and security, Hun an power grid can be divided into
A, B, C, D, E, F, G, H, I, a total of nine security parti-
tions, each partition contains a certain amount of gener-
ating units and system load, the topology connection is
shown in Figure 2.
4.2. The Adjusting Processes of Monthly Power
Transactions
Let’s take zone A of Hunan power grid for example,
carry out for a comprehensive validation for middle-long
term safety checking algorithms, and ultimately give the
adjusting effects of middle-long term security checking
under the modes of energy scheduling. In July 2008, ac-
cording to the given definition of safety area and contact
line groups, we follow the idea of zoning regulations to
give the power balance plan of zone A before adjust-
ments, Table 1.
Through the power balance to generating cap acity, the
total load, the upper flow limit of contacting line groups
we can see that, the planned trading power of area A is
too high, and the monthly planned generation is far
greater than the sum of total power generation capacity
and the contact line groups. The actual implementation
has some difficulties. Table 2 shows the adjusted balance
of power balance plans of area A after adjustments.
Figure 2. Security partition diagram of Hunan power net-
work.
Table 1. Power balance plan of area A before adjustments.
GenerationTotal
load
Contact line
Group1
Upper limit
Contact line
Group 2
Upper limit
Contact line
Group 3
Upper limit
18.92 10.312.75 2.47 2.23

C. C. LUO ET AL.
624
Table 2. Power balance plan of area A after adjustments.
Generation Total
load
Contact line
Group 1
Upper limit
Contact line
Group 2 Upper
limit
Contact line
Group 3
Upper limit
17.76 10.31 2.75 2.47 2.23
Judging from the actual operation situation of the grid,
the revised electricity plans have strong operational qual-
ity, which guarantees the safe and reliable operation of
the grid with the high opinions of operating personnel
alike.
5. Conclusions
Middle-long term security checking is the key problem
about energy generation scheduling. This paper describes
the functions, features and its major processes of alterna-
tive power trading, and on this basis puts forward ma-
thematical models and algorithms about electricity safety
checking of partition. Hunan grid’s application examples
show that the proposed algorithms can provide important
criterions for power trading plans, and are essential to
maintain open, fair, equitable principles of the alternative
power generation electricity market, to ensure safe op-
eration of power grid.
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