Energy and Power Engineering, 2013, 5, 646-650
doi:10.4236/epe.2013.54B125 Published Online July 2013 (http://www.scirp.org/journal/epe)
Multiple Dispatching Reactive Power and Voltage
Coordinated Control Method
Ting Yu1, Tianjiao Pu1, Wei Wang 2, Zhaoyu Jin3, Ning Yang4
1China Electric Power Researc h I n s t itute, Beij i n g, China
2Gansu Electric Power Corporation, Lanzhou, China
3North China Electric Power University, Beijing, China
4Northeast China Grid Company, Shenyang, China
[e-mail], [e-mail]
Received January, 2013
ABSTRACT
This paper studies the reactive power and voltage coordinated control scheme. According to the characteristics of Hu-
nan power grid, the coordinated schemes about Hunan power grid with Central China Power Grid, as well as Changsh a
power grid are proposed. At the same time, this paper builds a two-way interactive and multiple dispatching reactive
power and voltage coordinated control mode, and can be successfully applied in Hunan power grid. The operation re-
sults show that this control scheme fulfills the ab ility of large power grids in optimal allocating of resources, effectively
integrates the reactive power resources of the entire grid, achieves the purpose of reducing power grid loss, improving
voltage quality, reducing the operating numbers of the reactive power equipment.
Keywords: Coordinated Control; Power Grid Loss; Voltage Quality; Operating Numbers
1. Introduction
In recent years, the scale of state grid is gradual expand-
ing, but each dispatching center (area dispatching, pro-
vincial dispatching, regional dispatching) only adminis-
ters a local part of the entire power grid. If these dis-
patching control centers are independent in the imple-
mentation of voltage and reactive power control, it will
not take full advantage of the power grid in resource op-
timal allocation, resulting in unnecessary waste of energy
and the overall optimal control result is not satisfactory.
Even may be appearing the situatio n which the regulated
effect is contrary between the interconnected grids, re-
sulting in repeated adjustment of the control device. It
not only affects the life of the equipment, but also can
not ensure the quality of the voltage. Therefore, it need
coordinated control of reactive power and voltage
through the exchange of information between different
dispatching con trol centers an d different power grid at all
levels, to ensure the whole grid voltage and reactive
power integrated operation, to achieve optimal distribu-
tion of voltage and reactive power, to meet the requests
of bus voltage qualified, the gateway power factor rea-
sonable, power grid loss minimum and so on [1-6].
This paper is aimed at the provincial grid, studies the
coordinated control method of reactive power and volt-
age among provincial grid, regional grid, area gr id. Then ,
taking Hunan power grid for example, verifying the ef-
fectiveness of the coordinated control according to this
method.
2. Province and Region Coordinated Control
This coordination means that the optimal coordinated
control of the reactive power and voltage between pro-
vincial power grid and regional power grid. It is realized
by the information exchange of Automatic Voltage Con-
trol (AVC) system between the provincial dispatching
and the regional dispatching. For the selection of the co-
ordinated variables, because the regulation of reactive
device in provincial power grid and regional power grid
may have impact on the gateway bus voltage, so it is not
a good choice to select the bus voltage as coordinated
variable. As for gateway power factor, when it is light
load in power grid, the slight change of active power or
reactive power are likely to cause substantial fluctuation
in power factor [7-9]. In this view, the gateway reactive
power and the gateway bus voltage are chosen as the
coordinated variables together will be a good choice, but
according to the different functions of each dispatching
department, it also needs differentiate specifically. In the
area of northwest China, provincial dispatching adminis-
ters the 330 kV power plants and substations, while re-
gional dispatching administers the 110 kV substation, so

T. YU ET AL. 647
here the medium-voltage side reactive power and me-
dium-voltage side bus voltage of 330 kV gateway substa-
tion are chosen as coordinated variables. In other areas,
provincial dispatching administers the 220 kV power
plants and the high-voltage side bus of substations, while
regional dispatching administers the 110 kV substation
and the reactive power device of the 220 kV substation,
so the high-voltage side reactive power and high-voltage
side bus voltage of the 220 kV gateway substation are
chosen as coordination variables.
Due to regional dispatching administering discrete re-
active devices which include capacitors, reactors and
transformers tap and so on, it is unable to achieve the
precise regulation of the gateway reactive power, so pro-
vincial dispatching needs issue the gateway reactive
power range to regional dispatching, rather than the ga-
teway reactive power precise value. In order to further
clarify the coordinated goals of provincial dispatching,
and avoid frequently regulating the discrete devices of
regional grid, provincial dispatching needs also issuing
compensation direction instruction to regional dispatch-
ing at the same time. Specific coordinated method as
follows:
Based on the information provided by regional dis-
patching, provincial dispatching implements the reactive
power optimal calculation of the whole grid, issues the
gateway exchanging reactive power range and the de-
sired regulate direction of reactive power compensation
to regional dispatching.
Regional dispatching provides information to provin-
cial dispatching including that the AVC system operation
state, the compensation capacity of the gateway, the de-
sired gateway voltage range and so on. On the premise of
meeting the control requirements of provincial dispatch-
ing, based on its own security and economic needs, re-
gional dispatching calculates the control strategy, adjusts
the capacitors, reactors and transformer taps and other
equipment.
Provincial dispatching gets the coordinated time from
the information supplied by regional dispatching, and
calculates the difference between coordinated time and
current time. If the time difference is more than 15 min-
utes, it is judged that the information exchange is inter-
rupted, and exits the online coordination with regional
dispatching. When the time difference is less than 15
minutes, provincial dispatching resumes the online coor-
dination wit h r egi o nal dis pat ching.
Regional dispatching obtains the command time from
issued information supplied by provincial dispatching,
and calculates the difference between this time and the
current time. If the time difference is more than 15 min-
utes, it is judged that the information exchange is inter-
rupted, exits on-line coordination. When the time differ-
ence is less than 15 minutes, regional dispatching
resumes the online coordination with provincial dis-
patching.
The coordinated process is shown in Figure 1.
3. Area and Province Coordinated Control
This coordinated control means that the optimal coordi-
nated control of the reactive power and voltage between
area power grid and provincial power grid. Addition to
Northwest area of China (area dispatching administers
750 kV power grid, provincial dispatching administers
the 330 kV power grid), area dispatching administers the
500 kV power grid, provincial dispatching administers
the 220 kV power grid, so the essence of coordination is
the optimal control between the 500 kV power grid and
the 220 kV power grid, to realize th e local eq uilibrium o f
reactive power. However, many provincial dispatching
still administers a part of 500 kV plant or station, so the
specific coordinated program depends on the provincial
dispatching whether administers the 500 kV plant and
station. The coordinated example is shown in Figure 2.
Figure 1 Coordinated process.
Figure 2 Coordinated diagram.
When provincial dispatching administers the 500 kV

T. YU ET AL.
648
power grid, area dispatching AVC system selects the
high-voltage side reactive power and high-voltage side
bus voltage of the 500 kV gateway substation as coordi-
nated variables. In the side of area dispatching, through
the AVC system, calculates the optimum distribution of
the voltage and reactive power of the entire 500 kV grid,
and sends the optimal range of the coordinated variables
to provincial dispatching AVC system. Provincial dis-
patching AVC system calculates the 500 kV power grid
and 220 kV power grid together, taking coordinated vari-
ables optimum range issued by area dispatching as con-
straints, and implementing the optimal computation, to
ensure the optimal distribution of voltage and reactive
power of 220 kV grid is matched with the optimal distri-
bution of 500 k V grid that area dis pat chi n g d e sired.
When provincial dispatching does not administer
500kV grid, area dispatching AVC system selects me-
dium-voltage side reactive power and the medium-volt-
age side bus voltage of 500 kV gateway substation as
coordinated variables. Thus area dispatching gets the
voltage and reactive power optimal distribution of the
entire 500 kV grid through optimal calculation, and then
issues the optimal range of the coordinated variables to
the provincial dispatching AVC system. Provincial dis-
patching AVC system controllable range only covers 220
kV grid, taking the optimal range of coordinated vari-
ables issued by area dispatching as constraints, to ensure
the optimal distribution of voltage and reactive power of
220 kV grid is matched with the optimal distribution of
500 kV grid that area dispatching desired, in order to
achieve the objective of coordination between 220 kV
power grid and 500 kV power grid.
In short, regardless of provincial dispatching whether
administers the 500 kV grid or not, the responsibility of
area dispatching is achieving the optimal distribution of
voltage and reactive power of the entire 500 kV grid.
And set this as goals, one side area dispatching directly
controls its own plants and stations, at the same time it
needs issuing the desired target value of the coordinated
variables to provincial dispatching. The responsibility of
provincial dispatching is matched with area dispatching,
realizes the optimal distribution of voltage and reactive
power of 220 kV grid, and ensures that the 500 kV grid
and 220 kV grid can be synchronously optimized
[10-12].
4. Coordinated Method
Taking Hunan power grid for example, the control bound-
ary of Hunan provincial power grid and regional power
grid is 220 kV substation, while the control boundary
with central China power grid is 500 kV substation. So
the 220 kV gateway high-voltage side reactive power and
high-voltage side bus voltage are chosen as coordinated
variables between Hunan power grid and regional power
grid, while the 500 kV gateway medium-voltage side re-
active power and medium-voltage side bus voltage are
chosen as coordination variables between Hunan power
grid and central China power grid.
4.1. The Information Supplied by Regional
Dispatching
During the process of coordinated control, regional dis-
patching should periodically supply information to pro-
vincial dispatching. If 220 kV bus bars are parallel oper-
ating, regional dispatching sends the whole substation
station data to provincial dispatching, while 220 kV bus
bars are separated operating, regional dispatching sends
the main transformer data to provincial dispatching, the
illustrations are as follows:
Coordinated time: the time of regional dispatching
supplies the data to pro vincial dispatching;
Coordinated symbol: if regional dispatching partici-
pates in coordinated control, AVC system marks “1”,
else AVC system marks “0”;
Available symbol: if regional dispatching AVC system
is available marks “1”, else marks “0”;
Real compensation capacity: the reactive power com-
pensation capacity belo w the main transformer of su bsta-
tion;
Total maximum compensation capacity: the total ca-
pacity of the capacitive reactive compensation below the
main transformer of substation;
Total minimum compensation capacity: the total ca-
pacity of the inductive reactive power compensation be-
low the main transformer of substation;
Security compensation capacity upper limit: the max-
imum available compensation capacity below the main
transformer of substation in the conditions that 10 kV bus
voltage is qualified;
Security compensation capacity lower limit: the mini-
mum available compensation capacity below the main
transformer of substatio n in the conditions that 10kV bus
voltage is qualified;
Voltage coordinated requests: when the regulation ca-
pacity of regional dispatching is insufficient, making an
application to provincial dispatching, to expect that pro-
vincial dispatching regulates 220 kV bus voltage at a
certain range.
When the online coordination between provincial dis-
patching and regional dispatching is exited more than 15
minutes, provincial dispatch ing will automatically cancel
the coordination with regional dispatching, and no longer
issue control command to regional dispatching. When
communication is normal, provincial dispatching will
automatically restore online coordination with regional
dispatching.

T. YU ET AL. 649
4.2. The Command Issued by Provincial
Dispatching
According to the information supplied by regional dis-
patching, provincial dispatching implements the whole
grid reactive power optimal calculation, and gives the
real-time coordinated command as follows:
Command time: the time of provincial dispatching is-
sues command to regional dispatching;
220 kV bus voltage: the lower and upper limit of 220
kV bus voltage;
Gateway substation high-voltage side reactive power:
the lower and upper limit of the gateway substation high-
voltage side reactive power;
Compensation direction: provincial dispatching re-
quires for reactive power compensation switching direc-
tion of regio nal dispatchi n g power grid;
Increase compensation: exiting the inductive reactive
compensation equipment, or pu tting into capacitive reac-
tive compensation equipment;
Maintain compensation: neither putting into nor exit-
ing the reactive power compensation equipment;
Reduce compensation: exiting the capacitive reactive
compensation equipment, or putting into the inductive
reactive compensation equipment.
When the online coordination of provincial dispatch-
ing and regional dispatching is exited more than 15 min-
utes, regional dispatching will automatically cancel the
coordination with provincial dispatching, and imple-
ments local control. When communication is normal,
regional dispatching will automatically restore online
coordinatio n with provincial dispatching.
4.3. The Information Supplied by Provincial
Dispatching
This coordinatio n is similar to the above process, provin-
cial dispatching should periodically supply the following
information to the area dispatching:
Available status signal: it indicates that whether or no t
provincial dispatching AVC system is available, when
more than one generator of provincial power grid par-
ticipate in closed-loop control, AVC system is available,
otherwise is unavailable;
Remote/local signal: it indicates that provincial dis-
patching whether or not adopts area dispatching coordi-
nated control command, remote indicates adopting, oth-
erwise is not;
Supplying data time: it indicates the time which pro-
vincial dispatching AVC system sends information to
area dispatching, according to this time, area dispatching
determines provincial dispatch ing information is whether
or not available;
Controllable generator information: it includes the
generator reactive power measurement, active power
measurement, reactive power upper limit, reactive power
lower limit;
Gateway voltage information: it includes the gateway
voltage measurement, voltage upper limit, voltage lower
limit.
4.4. The Command Issued by Area Dispatching
In the process of this coordination, area dispatching
needs to issue command to provincial dispatching as fol-
lows:
Command time: it indicates the time which area dis-
patching issues command to provincial dispatching, ac-
cording to this time, provincial dispatching determines
area dispatching command is whe ther or not a va i lable;
Gateway reactive power command: it includes that
gateway substation medium-voltage side reactive power
upper and lower limit;
Gateway voltage command: it includes that gateway
substation medium-voltage side voltage upper and lower
limit.
5. Practical Application
Hunan power grid AVC system has been successfully put
into closed-loop operation in August 2009, and realized
the control of all directly dispatched power plants. With
AVC systems of Central China Power Grid and Hunan
regional grid are on-line operating, it has provided the
conditions of implementing the reactive power and volt-
age coordinated control. Hunan Power Grid, Central
China Power Grid and Changsha power grid are selected
to implement coordinated control, and the power grid
loss and voltage fluctuation rate of area dispatching, the
power grid loss and voltage qualification rate of provin-
cial dispatching, the equipment action numbers and vol-
tage qualification rate of regional dispatching are re-
coded before and after coordinated control, and the data
is shown in Tables 1- 3:
Table 1. The coordinated control results of central china
power grid.
Central China
power grid Daily average power grid loss(MW) Daily average voltage fluctuation rate (%)
Before coordination773.5 4.8
After coordination 771.9 3.3
Table 2. The coordinated control results of hunan power
grid.
Hunan power gridDaily average power
grid loss(MW) Daily average voltage qualification rate (%)
Before coordination184.66 99.2
After coordination183.87 100

T. YU ET AL.
650
Table 3. The coordinated control results of changsha pow er
grid.
Changsha power grid Daily equipment
action times Daily average voltage qualification rate (%)
Before coordination 149 98.9
After coordination 141 99.8
In the view of the comparative results, the coordinated
control scheme can fulfill the capability of the large
power grid in the resources optimal allocation, effect-
tively reduce power g rid loss, i mprove voltage qu alifica-
tion rate, reduce equipment action numbers and reduce
the voltage fluctuation rate.
6. Conclusions
This paper studies the reactive power and voltage coor-
dinated control scheme among area power grid, provin-
cial power grid and regional power grid. And according
to the characteristics of Hunan power grid, proposed the
detailed coordinated control method. The actual coordi-
nated control effect shows that: implementing reactive
power and voltage online coordinated control among area
grid, provincial grid and regional grid can fully integrate
the reactive power resources of the entire network, stabi-
lize voltage fluctuations, improve voltage quality and
reduce power grid loss according to this scheme. And it
has great significance to achieve secure, stable, graceful
and economic operation of state grid.
REFERENCES
[1] G. Radman, A. Pama, J. Powell, et al., “Ynamic Voltage
Stability Improvement Using Coordinated Control of
Dynamic Var-sources,” P Symposium-Bulk Power System
Dynamics and Control, Revitalizing Operation Reliability,
Charleston, SC, USA, 2007.
[2] S. Coris, M. Pozzi, C. Sabelli, et al., “The Coordinated
Automatic Voltage Control of the Itanlian Transmission
Grid,” IEEE Trans on Power Systems, Vol. 19, No. 4,
2004, pp. 367-371.
[3] C. Sandro, P. Massimo, S. Ca rlo, et al. “The Coordinated
Automatic Voltage Control of the Italian Transmission
Grid—Part I: Reasons of the Choice and Overview of the
Consolidated Hierarchical System,” IEEE Trans on
Power Systems, Vol. 19, No. 4, 2004, pp. 1723-1732.
doi:10.1109/TPWRS.2004.836185
[4] T. Yu and W. Wang, “Coordinated Scheme for Automati c
Voltage Control of Hunan Power Grid,” Power System
Technology, Vol. 35, No. 4, 2011, pp. 82-86.
[5] J. X. Su, H. L. Liao, W. Q. Yuan and J. H. Chen, “Muti-
layer United Controlling by the Region and County’s
AVC,” Rela y, Vol. 36, No. 10, 2008, p. 36239.
[6] X. Y. Wei, “Study on Large-scale Power Networks
Real-time Reactive Power Optimal Control Method,”
Zhejiang University, 2010.
[7] X. Y. Wei, “Study on Large-scale Power Networks
Real-time Reactive Power Optimal Control Method,”
Zhejiang University, 2010.
[8] T. Yu and R. P. Guo, “Control Scheme for Voltage Reac-
tive Power of Regional Power Grid Based Load Fore-
cast,” Power System Protection and Control, Vol. 40, No.
12, 2012, pp. 121-124.
[9] G. H. Zou, Y. J. Guo, Z. X. Yao, et al., “Study on the
Implement of Coordinated Automatic Voltage Con-
trol(AVC),” Electric Power, Vol. 41, No. 12, 2008, pp.
6-9.
[10] Q. L. Guo, B. Wang Bei, W. Y. Ning, et al., “Application
of Automatic Voltage Control System in North China
Power Grid,” Automation of Electric Power System, 2008,
Vol. 32, No. 5, pp. 95-107.
[11] B. Wang, Q. L. Guo, H. B. Sun, B. M. Zhang and W. C.
Wu, “Automation Voltage Control Among Muti Control
Centers,” Power System Technology, Vol. 34, No. 12,
2010, pp. 53-57．
[12] J. L. Chen, W. D. Tang, X. G. Xiao, et al., “Coordinated
Voltage Control for Central China Power Grid,” Electric
Power Automation Equipment, Vol. 31, No. 8, 2011, pp.
47-51.