The Structure and Operation of CSG Integrated Low ... · The Structure and Operation of CSG...

The Structure and Operation of CSG Integrated

Low Frequency Oscillation Defense System

Liang Zhifei, Xiao Ming, Zhang Kun

CSG Power Dispatching Control Centre, Guangzhou, China

Outline

I. Introduction

II. The dynamic stability situation in CSG

III. The structure of Integrated Low Frequency Oscillation Defense System

IV. Discussion of Improving the Defense Line

V. Conclusion

I. Introduction

China Southern Power Grid (CSG) is a typical power grid with ultra-high voltage level,

long-distance transmissions, large capacity and hybrid AC/DC operation mode. Since its

establishment in 2002, CSG started to face a complicated dynamic stability problem

represented by low frequency oscillation. Since 2005, dynamic problem became the

threshold of transmitting electricity from the western areas to East China

This paper reviewed current dynamic stability situation in CSG, introduce the structure

and operation experiences of CSG integrated low frequency oscillation defense system,

give out success application cases in 2010 and 2011. Finally suggestions for improving

the performance of present defense system are proposed.

Outline

I. Introduction




V. Conclusion


Over 1600kM

Yunnan

Guizhou

Guangxi Guangdong

Hainan


Yunnan-Guizhou Oscillation Mode

0.55Hz~0.60Hz

Yungui-Guangdong Oscillation Mode

0.40Hz~0.45

Guizhou 500kV grid

Yunnan 500kV grid

Guangdong 500kV grid

Hainan-Main Grid Oscillation Mode

0.70~0.78Hz

Moreover, there are

several inter-area

oscillation modes that

depend on local power

flow hard to analysis

and control.

Outline

I. Introduction




V. Conclusion


The 1st defense line

The 2ed defense line

The 3ird defense line

Oscillation monitoring and warning

applications based on WAMS and SCADA

HVDC/UHVDC additional control function

represented by fast DC power modulation and

the coordinated HVDC damping control

system .

The centralized and decentralized dispatching

control system based on

integrated emergency response plan

oscillation warming application based on SCADA



Oscillation time duration over 20s;

Power swings around base value;

Oscillation amplitude over threshold value；

Power swings similarly on input and output terminal of

the device.

(1)Voice alarm;

(2)The device that occurred power oscillation firstly

Warning output

(1)Voice alarm;

(2)The device that occurred power oscillation firstly;

(3) dormitory frequency, maximum variation amplitude

oscillation warming application based on WAMS



Oscillation criterion:

Dumpling level calculated by continues twice Prony

analysis less than threshold value ；

Warning output

On-line Prony analysis with

10s interval

HVDC/UHVDC additional control function


The 2ed defense line

For single HVDC/UHVDC: Fast DC power

modulation ;

For multi-HVDC/UHVDC: The coordinated HVDC

damping control system.

Oscillation control operations


Oscillation control operations by the 2ed defense line

Assumed serious N-2

500kV lines trip

Fast DC power modulation

Yungui-Guangdong Oscillation Mode

Guizhou 500kV grid

Yunnan 500kV grid

Guangdong 500kV grid

Xing-An HVDC

Gao-Zhao HVDC


The coordinated HVDC damping control system

Control substation

Master Control Station

2M Channel for order

Luodong

Baoan

Dispatching Center

Gaopo substation

Anshun

Xingren substation

Luoping

Xingan DC

Pole Control

System

Gaozhao DC

Pole Control

System

2M Channel

for data



Continuous

feedback

control system

Inter-area frequency

difference caused by system

disturbance

500kV AC lines trip

Large capacity generators

trip

Mono-polar or bipolar block

of DC transmission

systems

modulated DC power output

Modulated power output of Xinan pole I(MW)

Time(s)

dead area 0~0.0017Hz

Control

substation

Modulation command




28 30 32 34 36 38 40 42 44 46

-0.01

0

0.01

??

(H

z)

? ? ( ? )

28 30 32 34 36 38 40 42 44 46

4.7

4.8

4.9

5

5.1

5.2

5.3

??

??

?(

V)

? ?

? ? ? ? ?

Frequency

difference(Hz)

Time(s)

output(V)


At 00:02:30 of Nov,8,

2009, during the

process of blocking

pole2 of Gaopo-

Zhaoqing HVDC,

pole1 tripped.

The centralized and decentralized dispatching control system based on

integrated emergency response plan


The 3rd defense line

The 1st and 2ed defense lines mainly designed to dealing with weak/negtive

dumpling oscillations in 500kV grid. However, these defense lines could not

cover two oscillation types.

Oscillations under 500kV grid Forced Oscillations

1) lack of RTU and PMU under 500kV

grid.

2) HVDC power modulation in 500kV

grid could not change power flow and

dumping level under 500kV grid.

1) Locating oscillation source is

supposed to be more complex.

2) Conventional control strategies

show no positive performance.


The 3rd defense line

Generation

plants

Converter

Stations Substations

Grid

dispatchers

integrated emergency

response plan

Centralized control

Decentralized Control

Oscillation information communication

• Forced oscillation control strategy in the 3rd defense line

1) stabilize AGC target value or switch to manual control.

2) stabilize generation unit valve

3) Other necessary operation suggested by emergency response plan.

1)Increase voltage level of oscillation area; 2)Regulate DC power to strength electric connection between different provincial grids. 3) Other necessary operation suggested by emergency response plan.

Disconnect generation unit from power gird if oscillation expands


Generation plants Grid dispatchers

Decrease generation unit out put to minimum level

• Oscillation control strategy for grid under 500kV in the 3rd defense line

1)Locate the oscillation device by

the first defense line.

2)Give suggestions to dispatchers

of grid under 500kV.

3)Other necessary operation

suggested by emergency

response plan.

1) Search for oscillation source

based on the PRELIMINARY location

result by Dispatchers of 500kV gird.

2) Other necessary operation

suggested by emergency response

plan.


Dispatchers of 500kV gird Dispatchers of grid under 500kV

Outline

I. Introduction




V. Conclusion


Improve the 1st defense line by transient energy flow method

t

iijPEi dtPtV0

t

jjiPEj dtPtV0

Transient energy flow

Oscillation source generator

The transient energy give out a clear way to locate forced oscillation source: the source generator always outputs transient energy to grid and can be located by searching backward along the transient energy flow.


Improve the 1st defense line by transient energy flow method

0.026MJ

0.014MJ

0.030MJ

0.112MJ

0.017MJ

Generation plant A

Generation plant B

Generation plant C

10s after forced oscillation started

Oscillation source

Generation plants Converter Stations Substations

Fast Regulation commands

Grid Fault Information

Integrated emergency

response plan database

The First Defense Line

Conform and issue

manually


Improve the 3rd defense line by FCNC（Fast control & network command）

Outline

I. Introduction




V. Conclusion

V. Conclusion

During ten years development, CSG has established an integrated low

frequency oscillation defense system .The defense system shows effective,

precise and sensitive performance in practical operations.

The first defense line could provide valuable warning signal and preliminary

analysis result. The second defense line could cover most inter-area low

frequency oscillation modes. The third defense line shows strong flexibility and

has successfully handled several low frequency oscillation incidents so far.

The defense system is still being developed nowadays. New technologies

and research achievements such as the oscillation source locating method

based on transient energy flow and rapid dispatch command system are

introduced to make it a more powerful and accurate one.

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