Intelligent Models of Long-Term Security Correction in Energy Conversion Dispatching

doi:10.4236/epe.2013.54B1120

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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

Email: chchluo@ 163.com, [email protected], chenqq@ hnepc.com.cn

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:

T1,1 1

tgl

WW WW







(1)

where

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;

N represents the total

number of units; t represents the number of contact

lines, represen ts the number of load nodes.

Similarly, the following formula can be obtained from

the power balance of zone B:

111

tlg

WWWW



 



(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

TT T

WWSS WW

WWWSSWW





 









(3)

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

dWd



, B



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

(







，

，

)

W

)

(5)

(

SWW







,

，

(6)

where , min

g represents the maximal and mi-

nimal power respectively.

Amax

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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