hvdc in csg challenges and solutions - national...

HVDC in CSGChallenges and Solutions

LI, Licheng [email protected]

1

LI, Licheng [email protected], Peng [email protected]

China Southern Power Grid Co., LtdJune 2013

PDF created with pdfFactory trial version www.pdffactory.com

mailto:[email protected]



http://www.pdffactory.com

Outline

I. Overview of CSGII. Overview of HVDC&UHVDC in CSGIII. Challenges & solutions for AC//DC

© CSG 2013. All rights reserved. 2

III. Challenges & solutions for AC//DC IV. Innovation on HVDC V. Conclusion



I. I. Overview of CSG




Overview of CSG

December 29, 2002

Power transmission, distribution, and supply in Guangdong, Guangxi, Yunnan, Guizhou, and Hainan, a total area of 1.02 million square kilometers

Date of EstablishmentDate of Establishment

ServicesServices Xinjiang

National power gridNational power grid

TibetEast

ChinaCentral China

North China

Northeast China

Northwest China


kilometers

A total population of 230 million, accounting for 17.8% of the national population

As of the end of 2012, 562.9 billion yuan, ranked 152 in Fortune Global 500

Population ServedPopulation Served

AssetsAssets

Southern power gridSouthern power grid

Central China



Overview of CSGuIn 2012, the installed generation capacity within CSG is about 200 GW.

730 750

108.7257.17%

4.20

4.052.13%

6.123.22%

67.0835.27% Thermalpower

pumpedstoragewind powernuclearpowerHydroelectric power

GW


78.1388.86

95.90104.36

113.23 118.08

2007 2008 2009 2010 2011 2012

44785272

58596708

7307 7500

2007 2008 2009 2010 2011 2012

119.6

Average annual peak load growth rate of 8.6% in the past five years

Average annual electricity consumption growth rate of 10.9% in the past five years

447527

585670

730 750

GWTWh

4.202.21%



YunnanGuizhou

9.11GW

Three Gorges

8 AC + 5 DC from west to east

Overview of CSG


Guangdong

Hainan

pp Long DistanceLong Distance

pp Ultra High VoltageUltra High Voltage

pp Bulk CapacityBulk Capacity

pp Hybrid Operation of AC/DCHybrid Operation of AC/DC

Guangxi

24.43GW

9.54GW

1/3 of GD Load



III. III. Challenges & solutions for AC//DC


AC//DC



III. Challenges & solutions

HVAC

power

Interaction in AC//DC systems

HVDC block lead to power shift to AC systems and make it more intense.


HVDC HVAC

voltageabnormal ac voltage lead to HVDC commutation failure or block

A blackout from ac/dc interaction




Challenge 1: DC power shiftBulk power will shift from HVDC to HVAC during:

□ HVDC Block or ESOF□ HVDC Line fault□ HVDC Power reduction

Bulk power shift may lead to :

DC BLOCK or ESOF


Bulk power shift may lead to :

□ Voltage drop□ AC line overload□ Relay malfunction□ System instability□ Blackout

DC power reduction

AC power increase

Dc line fault--recovery--success

Dc line fault--recovery--fail

Power Shift

DC

AC

AC//DC




Challenge 2: Commutation Failure of multi infeed HVDC linksConcurrent commutation failure of 5 HVDC links will be caused by AC fault in 500kV substations or 220kV substations within GD area.

Simultaneous commutation failure of multi-HVDC will cause sharp power reduction of HVDC and bulk power shift to HVAC.

If the AC fault couldn’t be cleared fast, continuous


If the AC fault couldn’t be cleared fast, continuous commutation failure may lead to Multi HVDC Block.

Power ShiftAC

AC//DC

Bulk power flow transfer to AC SYS, may cause blackout




Challenge 3: Simulation of AC/DC hybrid system

Exact simulation of AC/DC hybrid system is the basis for system analysis and control.

□ Traditional simulation tools developed for bulk power systems, such as PSS/E and BPA, can’t deal


power systems, such as PSS/E and BPA, can’t deal with interaction between AC and DC exactly. For example, they are not able to simulate commutation failures in DC and consequent dynamics in AC systems.

□ Tools for HVDC simulation, such as EMTDC, can only deal with small systems.




Solution 1: Wide Area SPS

è Detecting HVDC bipolar block, N-2 outages and some N-3 outages

è Start remote generation shedding, or HVDC modulation, or load shedding, run back/up of HVDC

è Communication by fiber-optical

Goal:

to keep system integrity after a severe contingency


è Communication by fiber-optical channel

è Redundancy to enhance reliability

L L

500kV grid

MS

SS

SS

MS

Ø Prevent CSG from blackout in case of several cascading faults

Ø Increase transmission capability

Ø Prevent CSG from blackout in case of several cascading faults

Ø Increase transmission capability




Solution 2: Coordination between AC and DC

AC SPS

Solution 2.1: Coordination on protection & control coordination of AC and DC system

100Hz protection27DC protection

© CSG 2013. All rights reserved.

13

DC P/C

AC Relay SPScoordination

Ø to avoid HVDC block during AC fault

Ø to avoid HVDC block during AC fault

81DC protection 87DCM protection

… …





Solution 2.2: Optimization parameters of HVDC control (e.g. VDCOL considering recovery requirement of AC system after fault clear in receiving end of HVDC; DC line fault recovery sequence, etc).


Ø To enhance the system performance.

Ø To enhance the system performance.

CC

CIACEA

CC

VDCOL

最小电流限制

最小α

限制

Id

Vd

Im

逆变器

整流器





è A closed-loop control system based on WAMS

è Coordinated damping control for three HVDC links

è Commercial Operating since 2008

Solution 2.3: Wide-area damping control system


è Commercial Operating since 2008

0 5 10 15 20 25 30 35 404

4.5

5

5.5

6

time (s)

Out

put o

f Con

trol U

nit (

V)

XingRen Control Unit

投入

退出Ø Develop WAMS to WACSØ Increasing damping and

transfer capacity




Solution 3: Countermeasures to commutation failure

3.1 Fast fault clear with high reliability

□ Redundancy of all Protection System Elements in all station of 220 kV and above.

□ Special maintenance of important protection and circuit


□ Special maintenance of important protection and circuit breakers.

3.2 Distribution of converter stations in GD

□ Proposed new index to evaluate interaction between converter stations and to weak the interaction through proper distribution of sites.




Solution 3: Countermeasures to commutation failure

3.3 STATCOM

□ Installation of more than 800 MVAR STATCOM in some key stations to support transient voltage.





Solution 4: Hybrid simulation

□Established the world largest RTDS lab, with 33 RACKs, connected with protection and control systems, to simulate dynamics of bulk power system involved HVDC.

□Developed electromagnetic and electromechanical transient hybrid simulation. HVDC models in the simulation is the same as


hybrid simulation. HVDC models in the simulation is the same as EMTDC, and it can deal with dynamic of bulk AC systems as well.



IV. IV. Innovation on HVDC




IV. Innovation on HVDC

Innovation 1: VSC-MTDC for wind power integration

p Wind farms in NanAo Islandn By 2011, total capacity is 143MWn In 2013, more 25MW; In 2015, offshore 50MW (Tayu)

n VSC-MTDC project in Nanao Islandn Three sending converter stations, One receiving inverter stationn Voltage ±160kVn Capacity 200 MW


n Capacity 200 MWn Distance:20km

Solve key technical issues for a number of large-scale wind farms integration into grid friendly

Operating in end 2013




Innovation 2: Islanded Operation of UHVDC-- background

No Power Shift

DC

AC

DC Islanded

Power Shift

DC

AC

AC//DCLarge-capacity HVDC power transmission system working in islanded operation, may reduce the effect of power shift on the AC system due to HVDC trip.


HVDC trip.

Because the supporting power plants are far away from the converter station, new problems on overvoltage control appear under the islanded operation mode of YG UHVDC.




Innovation 2: Islanded Operation of UHVDC—overvoltage controlOvervoltage control is the biggest problem for islanded operation:

pFast tripping of AC filter/capacitor banks by DC control system (overvoltage protection is the backup). And the ferromagnetic saturation characteristics of converter transformers can be used to limit power-frequency overvoltage .


limit power-frequency overvoltage .

pTwo-column arresters for AC busbar at converter stations are used .




Innovation 2: Islanded Operation of UHVDC—frequency controlFrequency control is another problem for islanded operation:

□ Even primary frequency control (PFC, set dead zone as ±0.15Hz) of generators and frequency limit control (FLC, set the dead zone as ±0.1Hz) of HVDC are both running, the HVDC control is much faster, and the FLC plays the key role.


faster, and the FLC plays the key role. □ The frequency of islanded system will be kept within 49.9 to 50.1Hz, which is reasonable.

Frequencyin Paralleloperation

Frequencyin Islanded operation




Innovation 3: Back to Back HVDC

□ CSG plan to replace the AC tie-lines between YN and rest of CSG with Back to Back HVDC around 2020, to control the size of synchronized power systems, and to mitigate power shift influence of multi DC.

□ 3000 MW + 1500 MW BTB DC lines and VSC technology are


□ 3000 MW + 1500 MW BTB DC lines and VSC technology are under considering.

YN

GZ

GX GD



More HVDC links of CSG before 2030

CSG will run 20 HVDC links by 2030




V. V. Conclusion




V. Conclusion

□ HVDC play a very important role in CSG.

□ CSG adopted different technical strategies. HVDC//HVAC is a proper choice in initial stage to develop long distance transmission systems. Up to now, CSG is continuing optimizing the hybrid system.


continuing optimizing the hybrid system.

□ There are still many works to do to keep the security and stability of AC/DC hybrid systems.

□ CSG is tracing the technical trend and intends to use the HVDC technology more extensively in the future.



Together we keep our lights on!


Thanks for your attention!And welcome to CSG!



hvdc in csg challenges and solutions - national...

Documents