S.C. Srivastava, Professor Departmentof Electrical...

S.C. Srivastava, Professor Departmentof Electrical Engineering

Indian Institute of Technology Kanpur Email: [email protected]

SC Srivastava/IITK NETRA-Conference on 'Green Power-Challenges and Innovations' 9th June, 2017 NTPC-PMI, NOIDA 1

mailto:[email protected]

Contents Recent Changes in Power system Networks

Overview of Indian Power Sector

Grid Integration of Renewable Energy Sources (RES): Key Issues

System Wide Impact of Large Penetration of RES

Impact of Wind Penetration and Dynamic Loads on Stability

Planning SVC to Mitigate Instability

Decentralized Wide Area Damping Controller Development

Concluding Remarks

9 SC Srivastava/IITK NETRA-Conference on 'Green Power-Challenges and Innovations' 9th June, 2017 NTPC-PMI, NOIDA

Recent Changes in Power system Networks

• Use of New Materials - Polymeric, Composite, Nano, Superconducting materials.

• Use of Alternate and Renewable Energy Sources to address Global Environmental Concerns

• Development of New Power Electronic Devices, DSP, Sensors, Information & Communication Technology

• IT Enabled Services for maintaining system Security, Reliability and Resiliency- Modern SCADA, Wide Area Monitoring system, Smart Grid

• Regulatory Changes in the Electricity Sector – Electricity Market.


SC Srivastava/IITK NETRA-Conference on 'Green Power-Challenges and Innovations' 9th June, 2017 NTPC-PMI, NOIDA 4

PHASOR DATA CONCENTRATOR

APPLICATION SOFTWARE

SYSTEM CONTROL CENTER

MONITORING CONTROL DATABASE

PMU

GPS

PMU

PMU PMU

PDC

PDC SUPER PDC

Synchrophasor based WAMS for Smart Transmission Grid

Time synchronized phasor data with high accuracy

Provides phasors within an interval of 20/40 ms (50 Hz System)

Suitable for observing the system under dynamic conditions

Suitable for real time monitoring, control and protection


Distributed Energy Resources (DERs) Distributed Generations using Renewable Technologies

Photovoltaics

Solar thermal

Small wind systems (upto 50 kW)

Large wind systems (ranging upto 1-2 MW)

Biomass etc.

6

Storage Technologies

Mechanical (Pumped storage, Compressed air, Fly wheel)

Electrical (Super capacitor, SMES)

Chemical (Fuel cell)

Electrochemical Batteries (Lead Acid, Li-Ion, Flow, Sodium/Zinc)

SC Srivastava International Workshop on CPS 25-26 March, 2017 IIT Kanpur

An Overview of Indian Power Sector Installed Gen. Capacity as on 30th April, 2017

Source: www.cea.nic.in

Fuel MW %age

Total Thermal 220569.88 67.0

Coal 194402.88 59.0

Gas 25329.38 7.7

Diesel 837.63 0.3

Hydro (Renewable) 44594.42 13.5

Nuclear 6780.00 2.1

RES** (MNRE) 57260.23 17.4

Total 329204.53

**Renewable Energy Sources(RES) include Small Hydro, Bio-mass/gas, Urban & Ind. Waste

Sector MW %age

State Sector 104447.28 31.7

Central Sector 81167.25 24.7

Private Sector 143590.01 43.6

Total 329204.53

All India Thermal Plant Load Factor : 65.59% (April 2017)

7

http://www.cea.nic.in/

North-Eastern

Region

Western

Region

Northern

Region

Southern

Region

Eastern

Region

High Voltage Transmission Capacity (as on 30-04-17)

(220kV & above about 3,69,650 ckt. km)

Capacity MVA Circuit km

765/800 kV 170500 31616

400 kV 243307 159058

220 kV 314503 163420

HVDC 19500 15556

Map of India in Five Regions (regions are shown separated for sake of clarity)

8

Inter-regional capacity: 75,050 MW

SC Srivastava/IITK NETRA-Conference on 'Green Power-Challenges and Innovations' 9th June, 2017 NTPC-PMI, NOIDA

Non Conventional Energy In India (as on 31st March, 2017)

• 3900 MW in 2002 to 57244.23 MW in March 2017 (Grid Connected)

Wind : 32279.77 MW (Onshore potential 49130 MW)

Small Hydro : 4379.85 MW

Bio-power : 8181.70 MW (Biomass, Gasification & Bagasse)

Waste to power : 114.08 MW

SPV : 12288.83 MW (100 GW by 2022)

• Off-grid : 1468.95 MW (Source: http://www.mnre.gov.in/mission-and-vision-2/achievements/)


System Operation (at present)

10

• At regional level – Five RLDCs viz. NRLDC, SRLDC, ERLDC, WRLDC and NERLDC, and at national level NLDC.

• All regional power grids are synchronized (NEW grid)

• RLDCs and NLDCs owned by POSOCO New Delhi.

• Two exchange in operation viz. Indian Energy Exchange (IEX), and Power Exchange India Limited (PXIL)

• Frequency linked ABT for Unscheduled Interchange (UI) to improve grid discipline (at regional levels).

• Synchrophasor based WAMS being deployed in Regional grids. (URTDMS Project of PGCIL). About 1700 PMUs planned.

• NSGM to promote Smart Grid activities.


Renewable Generation: Few Technical Challenges


Intermittent generation dependent on weather, season, time of day–Need accurate forecasting & Power balancing .

Voltage and frequency control; Many of these sources do not have reactive power generation.

Sudden generation loss can lead to angle and voltage instability. Also inertia less generation, e.g. solar.

Power Quality issues-Harmonics, flicker, under voltage ride through capability (IEEE & IEC standards)

Power management and Maximum power point tracking. Requires proper converters and controls.

References: 1. Vignesh V., „Improved Load Modelling and its Impact on Stability of Power Systems having Large

Penetration of Wind Generation‟, Ph.D. Thesis, IIT Kanpur, March 2016.

2. Vignesh V, S. C. Srivastava and S. Chakrabarti, “A Robust Decentralized Wide Area Damping

Controller for Wind Generators and FACTS Controllers Considering Load Model Uncertainties”,

accepted for publication in IEEE Trans. on Smart Grid, , Early access DOI: 10.1109/TSG.2016.2552233.

Region Wise Installed Generation Capacity in

India (CEA Report, April 2017)

Region Installed Capacity in MW

RES Total

Northern 11539.36 90241.59

Western 18304.43 108418.96

Southern 26132.07 91808.36

Eastern 990.74 34752.87

North-Eastern 281.12 3930.19

Islands 12.52 52.57

TOTAL 57260.23 329204.53

12 States like Tamilnadu, Gujarat and Rajasthan have high penetration of wind generation.

Ref: POSOCO Report on “Flexibility Requirement in Indian Power System” , January 2016. 13

Ref: POSOCO Report on “Flexibility Requirement in Indian Power System” ,

January 2016. 14

Few Possible Solutions/RD&D Needs at Grid Level

Transmission planning to cater for renewable generation- Green Corridor in India.

Flexible generation/load management.

Proper planning of Flexible AC Transmission System (FACTS) controllers, SVC/STATCOM.

Regulatory mechanism to promote renewables.

Balancing mechanism, Ancillary service market development.

SCADA with renewable desk.

Synchrophasor technology based Wide Area monitoring and Control, employing Phasor Measurement Units.


Power System Stability

Frequency

Stability

Small-Signal

Stability

Transient

Stability

Short

Term

Long

Term

Large-

Disturbance

Voltage Stability

Small-

Disturbance

Voltage Stability

Voltage

Stability

Rotor Angle

Stability

Considerat-

ion for

Classification

Physical

Nature/ Main

System

Parameter

Size of

Disturbance

Time

Span

Short Term

Short

Term

Long

Term

P. Kundur, J. Paserba, V. Ajjarapu, G. Andersson, A. Bose, C. Canizares, N. Hatziargyriou, D. Hill, A. Stankovic, C. Taylor, T. V. Cutsem, and V. Vittal, "Definition and classification of power system stability IEEE/CIGRE joint task force on stability terms and definitions," IEEE Transactions on Power Systems, vol. 19, no. 3, pp. 1387-1401, Aug. 2004.

16

Study on Impact of Large Wind Penetration on System Stability

The impact of different level of wind penetration (5-20%) on system stability was first studied on NRPG system.

The NRPG system used (400 kV, 765 kV and few 220 kV buses retained) had a total generation of around 17000 MW and total load of around 16500 MW .

Wind Parks assumed at Udaipur, Jodhpur, Banswara and Bikaner of 850 MW, (5% of the total generation).

Constant MVA models for loads were first considered.

DSA tool from Power Tech was used for simulation.

The disturbance simulated was to disconnect the wind generation at these buses.

.


18

Study System-WPP Considered in Rajasthan


Generator Angles and Bus Voltages for 15 Percent

Wind Penetration

19

0 10 20 30 40 50 60 70 80 90 100-80

-60

-40

-20

0

20

40

60

Time (sec)

Ge

ne

rato

r A

ng

les

in

de

g

Generator Angles with 15% Penetration

Hardwaganj

Tanakpur

Chamera

Uri

Bhakra RL6

Bhakra RL2

Bhakra RR2

Dehar 2

Siul

Dehar 4

pong

Theing

Dadri

Paricha


0 10 20 30 40 50 60 70 80 90 1000.5

0.6

0.7

0.8

0.9

1

1.1

1.2

Time (sec)V

olt

ag

e M

ag

nit

ud

e (

p.u

.)

Bus Voltage Magnitude with 15% Penetration

Ajmer

Bhiwandi

Bhilwara

Bikaner

Bilara

Jaipur

Jodhpur

Ketri

Kota

Siron

Paricha

Generator Angles and Bus Voltages for 18 Percent

Wind Penetration

20

0 10 20 30 40 50 60 70 80 90-200

0

200

400

600

800

1000

1200

1400

1600

1800

Time (sec)

Ge

ne

rato

r A

ng

les

in

de

g

Generator Angles with 18% of Wind Penetration

Hardwaganj

Tanakpur

Chamera

Uri

Bhakra RL6

Bhakra RL2

Bhakra RR2

Dehar 2

Siul

Dehar 4

Pong

Theing

Dadri

Paricha

With 18 % penetration of the wind, after the

disturbance the generator at Paricha goes into

instability


0 10 20 30 40 50 60 70 80 900.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

Time (sec)

Vo

lta

ge

Ma

gn

itu

de

(p

.u.)

Bus Voltage Magnitude with 18% Wind Penetration

Ajmer

Bhiwandi

Bhilwara

Bikaner

Bilara

Jaipur

Jodhpur

Ketri

Kota

Siron

Paricha

Generator Angles and Bus Voltages for 13% wind penetration

and detailed load models (dynamic and static loads)

21

0 10 20 30 40 50 60 70 80-200

0

200

400

600

800

1000

Time in Seconds

Ge

ne

rato

r A

ng

les

in

de

gre

es

Generator Angles for 13% Wind Penetration with detailed load models

Paricha

Uri

BhakraRL6

BhakraRL2

Hardwaganj

Siul

Chamera

Pong

Theing

Dadri

BhakraRR2

Dehar2

Kota

Dehar4


0 10 20 30 40 50 60 70 800.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

Time in seconds

Vo

lta

ge

in

p.u

.

Voltage magnitude for 13% penetration with detailed load models

Kanpur

Allahabad

Jaipur

Noida

Kota

Ballabhgarh

Ratangarh

Auriya

Paricha

Jaisalmer

Agra

Jalandhar

Amritsar

Ludhiana

Effect of Control Actions

To restore the system stability, measures adopted are:

1. Ramp up of real power output of other generators

2. Reactive power management to mitigate voltage

stability issues.

3. Load shedding.

Initially ramp up of real power and load shedding controls were considered.

The ramp up of real power was done by changing the reference setting of the governor.

The output of generators at Thankpur, Urig, Chamra, Bhakranagal, Ropar, Dadri, Siul, Theing were ramped up.


Generator Angles and Bus voltages after Power Ramp-up

for loss of 18% wind generation

23

0 50 100 150-80

-60

-40

-20

0

20

40

Time (sec)

Ge

nra

tor

An

gle

s in

de

g

Generator angles after power ramp up

Hardwaganj

Tanakpur

Chamera

Uri

Bhakra RL6

Bhakra RL2

Bhakra RR2

Dehar 2

Siul

Dehar 4

Pong

Theing

Dadri


0 50 100 1500.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

Time (sec)

Volta

ge

Ma

gn

itud

e (

p.u

.)

Bus voltage magnitude after generator ramp up

Ajmer

Bhiwandi

Bhilwara

Bikaner

Bilara

Jaipur

Jodhpur

Ketri

Kota

Siron

Case Study-Shedding of the loads

Both real and reactive loads were shed at all the buses.

The loads were shed till the system voltage and generator angles stabilized.

It was observed that even without shedding of loads completely to compensate for 3000 MW of wind power loss (18 % of total generation), the system stabilized.

It was observed that the amount of load to be shed to stabilize the system for 18% loss of wind generation was around 1700 MW( 11% of the total load)


25

0 50 100 150-80

-60

-40

-20

0

20

40

60

80

Time in Seconds

Ge

ne

rato

r A

ng

le in

de

gre

es

Generator angles after Load Shedding

Paricha

Dehar4

Uri

Bhakra RL6

Bhakra RL2

data6

Hardwaganj

Siul

Chamera

Pong

Theing

Dadri

BHAKRA RR2

Dehar2

Tanakpur

Generator Angles and Bus Voltages after load shedding


0 50 100 1500.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

Time (sec)

Vo

lta

ge

Ma

gn

itu

de

(p

.u.)

Bus Voltage Magnitude with load shedding

Ajmer

Bhiwandi

Bhilwara

Bikarner

Bilara

Jaipur

Jodhpur

Ketri

Kota

Siron

Paricha

Bus Voltages stabilize after

the load shedding

Planning of SVCs to Mitigate Voltage Instability with High Wind Penetration

1. Static Var Compensators (SVCs) are shunt dynamic reactive power

compensators.

2. Methodologies proposed to determine the location and sizes of the

SVCs in presence of wind power plants and dynamic loads.

3. A sensitivity index for determining the effective locations of the

SVCs, to enhance the damping of the voltage modes, is proposed.

4. The optimal sizes of the SVCs were determined by a hybrid

optimization technique in order to mitigate voltage instabilities.

5. Supplementary controller for the optimally placed SVCs was

designed to improve the damping of the electromechanical modes.

6. Tested on three systems


Composite Load Model Used

Primary distribution level

Transmission level

j

Bss

LM

MM

AC motor

R+jX

2

B1 jB

Static


Steps Used:

• Determination of set of critical contingencies- damping ratio based index

• Determination of optimal locations of SVCs-sensitivity approach

• Determination of sizes of SVCs –Optimization approach

• Design of supplementary damping controller-Optimal algorithm

Simulation Studies

• The proposed method is implemented on three test systems. • The results for NRPG system is presented.

• NRPG system is a reduced network of a practical power system in India, containing 220 and 400 kV networks with 246 buses,376 branches (lines/transformers), 42 generating stations with 60 machines, and 40 reactors.

• A total wind penetration of 25 % is assumed, with the wind turbines placed at the buses 160, 161, 162, 163, 164, 165, 168, 174, 177, and, 178, each of 500 MW capacity.

• 10 critical contingencies were identified, method gave 10 optimal locations of SVCs


Table : Most critical contingencies in NRPG System

S.N0. Contingency Rank

1 Ballabgarh-Kanpur line (233-239) outage 1

2 Rihand generator outage (Bus 41) 2

3 Dadri generator outage (Bus 38) 3

4 Ballabgarh- Dadri line (233-235) outage 4

5 Ropar generator outage (Bus 13) 5

6 Agra-Kanpur line (234-239) outage 6

7 Lucknow- Sultanpur line (211-217) outage 7

8 Bhakranangal generator Outage (Bus 6) 8

9 Sitapur-Lucknow line (188-190) outage 9

10 Udaipur- Chithorgarh line (168-170) outage 10


Table: Critical eigenvalues for the outage of Agra-Kanpur line

(234-239) in NRPG System

S.N0 Eigenvalue Damping (%) Frequency(Hz)

1 0.6824+j56.86 -1.20 9.05

2 0.5852+j55.7319 -1.05 8.87

3 0.54460+57.3278 -0.95 9.18

4 0.4043+j57.8363 -0.78 8.25

5 0.2865+j55.1035 -0.52 8.77

6 0.1321+j55.0407 -0.24 8.76

7 0.0559+j55.8579 -0.10 8.89

8 -0.0802+j57.3027 0.14 9.12


Simulation Studies (without and with SVCs)- Three Phase Fault

(a) 1.5

1

0.5

0 0 5 10 15 20 25 30 35

(b) 1.2

1

0.8

0.6

0.4 0 5 10 15 20 25 30 35

Time in s

Figure: Few load bus voltages in NRPG system, following a three

phase fault in Kanpur-Ballabgarh 400 kV line (233-239).

Vo

lta

ge

in

p.u

. V

olt

ag

e i

n p

.u.


Similar results found with generator outage.

Simulation Studies without and with SVC- Wind Generators Outage

(a)

1

0.9

0.8

0.7

0.6

0.5

0.4

15 16 17 18 19

Time in s

20 21 22 23

(b) 1

0.9

0.8

0.7

0.6

0.5

0.4

0.3 0 5 10 15 20 25 30 35 40 45

Time in s

Figure : Voltage at Jaipur (Bus 40), following the outages of two wind

generators

Vo

lta

ge

in

p.u

. V

olt

ag

e in

p.u

.


Decentralized Wide Area Damping Controller Considering Load Model Uncertainties

• A decentralized wide area damping controller proposed for the

wind farms and FACTS considering uncertainties in the load parameters through the Monte-Carlo simulations..

• A robust H∞ output feedback controller is, then, designed for the uncertain fuzzy system by satisfying Linear Matrix inequalities (LMIs).

• Practical issues such as input signal latency has been considered in this work.

• Input/output signal selection using joint controllability-observability index and input time delay compensated through state prediction using Extended Kalman Filter (EKF)

• Tested on two test systems.


Figure : A typical decentralized wide area control architecture

Δω Y1 G- PMU-1 +

Y2

Exciter AVR-1

Y

1 +

WADC-1

PMU-2 DFIG WADC-2

POWER

SYSTEM

PMU-K SVC WADC-N

Y K

TDC

TDC

TDC

CPSS-1


Steps in Proposed Methodology

1. Choice of control architecture-Decentralized. 2. Wide area signal selection.

3. System reduction. 4. Controller design. 5. Non-linear simulations.

Input-Output Signals in SRPG System

Table : Critical eigenvalues in the SRPG system and input-output signals for decentralized controllers

S.N0 Eigenvalue Input Signal Output Signal

1 -0.0186+j2.324 P7361−8504 , P7351−7353 Wind Plant at 7408

2 -0.0369+j3.051 P7357−9801 , P7356−8505 TCSC in 7353-7354

3 -0.0539+j2.915 P7358−8509 , P736−921 Wind plant at 8981

4 -0.0947+j3.9458 P7368−8511 , P7408−8643 Wind plant at 9855

5 -0.1070+j3.6820 P7327−9208 , P7551−8522 SVC at 7558


Three Phase Fault

500

400

300

200

100

0

-100

-200

-300 0 5 10 15 20

Time in s

25 30 35 40

Figure : Power flow in tie line following a three-phase fault at a bus in

SRPG system (Similar results observed for most critical line outage)

Real

po

we

r fl

ow

in

tie

lin

e i

n M

W.

CPSS

CPSS+LOCAL PWADTFC


Real Time Validation on RTDS

Satellite

GPS clock

Input Signal

GTNET

PMUs

Workstation

Wide Area Damping

Figure : Software in loop implementation of the proposed controller in RTDS

RTDS

Control Signal

Delayed Signal

Extended Kalman Filter

Based Delay

Compensator

Delay Compensated

Signal

Proposed Decentralized

Controller


Impact of Time Delay Compensation

900

800

700

600

500

400

12 14 16 18 20

Time in s

22 24 26 28 30

Figure : Power flow in line 15-16 following loss of load at bus 21 in NE

39 bus system

Real p

ow

er

flo

w in

lin

e 1

5-1

6 in

MW

Without TDC

With TDC


Conclusions Future power system expansion will have large deployment of

Distributed Energy Resources containing renewable sources, predominantly solar and wind based generations.

Solar and wind generation intermittency will pose system stability challenges. This may worsen in presence of dynamic induction motor loads.

Apart from flexible generation and ample storage for system power balancing, proper controls such as use of FACTS controllers are required to improve the system stability.

Use of synchrophasor based wide area damping control will help in damping system oscillations under disturbances.


S.C. Srivastava, Professor Departmentof Electrical...

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