Tsinghua University, China - Medpower 2018medpower2018.com/wp-content/uploads/2018/11/2_Kang... · China has announced a series policies for CSP development, including fixed feed‐in

2018/11/14

1

Integrating High Share of Variable Renewable Energy in Bulk Power Systems

Prof. Chongqing Kang

Tsinghua University, China

The 11th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion

2

Outline

Challenges

Solutions

• Development of Power Industry

• Progress in Research

Conclusion

2018/11/14

2

3

World Energy Outlook

• The world energy industry is speeding up its transition

to be diversified, renewable and low-carbon. In 2050,

the proportion of renewable energy will be 54%.

• Electrification is an important sign of future energy

transformation. World electricity demand will

continuously increase, doubling from 2015 levels in

2050, with 72% of the growth coming from non-fossil

sources

Renewable and Sustainable Energy System

Energy Environment

World Trends in Energy

4

The development of renewable energy is a common trend in the world

• High renewable energy penetration has become a hot focus of future power system scenarios

Ireland, Denmark, ……

United States：80% renewable penetration in 2050

World Trends in Energy

2018/11/14

3

China Trends in Renewables

5

0

100000

200000

300000

400000

500000

600000

700000

2010 2011 2012 2013 2014 2015 2016 2017

Biomass Power 5500 7000 7700 9000 10700 11199 12248 14760

Solar Power 890 3500 7000 19420 28050 43180 77420 130250

Geo‐Thermal 28 30 30 30 30 30 30 30

Wind Power 44734 62364 75324 91413 114609 145362 168730 188392

Hydro Power 216060 232980 249470 280440 304860 319530 334200 348870

Installed Cap

acity / MW

Hydro Power

Wind Power

Geo‐Thermal

Solar Power

Biomass Power

Current Situation

6

Renewable Energy Curtailment in China

Renewable Resource Distribution 2017 Wind Curtailment Ratios

2017

Win

d C

urta

ilmen

t R

atio

s

Average

ProvinceLoad(GW)

Wind Capacity(GW)

Theoretical generated energy (TWh)

Energy integrated(TWh)

Energy Curtailment

(TWh)

Curtailment Ratio

Xinjiang 28.04 18.06 45.15 31.9 13.25 29%

Inner Mongolia

30.46 26.70 64.6 55.1 9.5 15%

Gansu 13.90 12.82 27.98 18.8 9.18 33%

Jilin 5.05 10.96 8.7 2.26 21%

Hebei 11.81 28.33 26.3 2.03 7%

Heilongjiang 5.7 12.55 10.8 1.75 14%

Liaoning 7.11 16.32 15 1.32 8%

Shanxi 8.72 17.6 16.5 1.1 6%

Ningxia 9.42 16.27 15.5 0.77 5%

Yunnan 8.19 20.47 19.9 0.57 3%

2018/11/14

4

7

Inflexible Generation Portfolio

China VS U.S.Large number of flexible gas‐fired generators

Compared with gas‐fired generations, the coal‐fired generations lack of flexibility, and has worse regulation performance: The minimum output of the coal‐fired generation is high; The ramp rate of the coal‐fired generation is slow;The lack of flexibility cannot fully respond to the uncertainty and intermittence of renewable energy, and thus cause wind and PV curtailment.

Coal‐fire generators: 60%‐70%

8

Bottleneck of Wind Power Accommodation

GansuTransmission

constraints

YunnanEnergy surplus on wet

season

Jiangsu• Not enough Peak-off-

peak regulation capacity in winter

Guangdong• Not enough Peak-off-

peak regulation capacity in winter

Jibei• Transmission

interface constraints

Jilin• Not enough Peak-

off-peak regulation capacity

• Transmission interface constraints

West Inner Mongolia

Minimum load constraints in heating season

QinghaiTransmission interface

constraints

GuizhouNot enough Peak-off-peak regulation capacity in wet

season GuangxiNot enough Peak-off-peak

regulation capacity

Hainan• Not enough Peak-off-peak

regulation capacity • Stability issue

2018/11/14

5

9

The whole sale prices of competitive electric

energy will not be fixed

Beneficial to traditional coal and

hydro power.

Utilization hours of large thermal power may be very high,compressing its ability to provide

reserve.

No real‐time system marginal price to give incentives for storage or other flexibility services.

Deregulating market share

Lack of day ahead and real time market

Deregulating prices

The overall utilization hour of conventional generator will not be

regulated.

All the trading are long term contract.

Impacts of the electricity reform on renewable energy

Power Sector Reforms

10

Special Section: IEEE TPWRS

CFP: Jan, 2017 Publish: May, 201824 papers(out of 300 submissions)

2018/11/14

6

11

Outline

Challenges

Solutions



Conclusion

Improving the flexibility of coal-fired thermal units by technology upgrades

2018/11/14

7

Trend of Thermal Units

13

Increasing flexibility of thermal power units

Electricity Load Demand Net‐load with large scale integration of wind power

Thermal Power Units

• Base‐load Plants• Middle‐load Plants• Peak‐load Plants• Ensuring provided energy

Thermal Power Units

High flexible Requirements • Lower minimum load

requirement• Faster load ramps • Faster start‐up/shut down• Providing firm capacity

Typical Requirements in three load segments

14

Improving the Flexibility

Introducing Oxygen‐enriched combustion technology

The power grid in northeast China is suffering severe wind curtailment problem.

Combustion‐supporting with oil under low load

Optimizing the water supply in low‐load operation

Technology upgrades:

Heat supply control in steam turbine under

low load

2018/11/14

8

15

Benefit of Flexibility Improvement

Benefits of increasing the flexibility of coal-fired power plants

--- Decreasing the minimum load

serving level of power systems

0 MW

Pmin

Pmax

0 MW

Pmax

Pmin - ∆

Performance of Technology Upgrades

16

Wind Power Capacity(GW)

Time period from 2016 Q2 to 2018 Q2 Time period from 2016 Q2 to 2018 Q2

Wind Curtailment Rate(%)

Type Before After

Thermal Power Plants 50% 30%~40%

CHP 60%~70% 40%~50%

Some advanced units 一 20%~30%

Change of Minimum Load Ratio of Thermal Units:

China

Wind Power Accommodation in Northeast China (including three provinces）

Jilin Province

Heilongjiang Province

Liaoning Province

In 2016, 17GW of thermal units were technically upgraded in China China plans to finish the flexibility improving of 220GW thermal units by 2020.

2018/11/14

9

Enhancing AC/DC links between regions and provinces

18

Uneven Distribution of Source and Load

Renewable Energy

LoadCenter

Renewable energy bases are in north/west of China The load centers are in southeast China We need long‐distance power transmission !!!

UHV AC transmission

UHV DC transmission

To satisfy the operation constraints of power systems, renewable energy needs to be controllable. That means under some conditions the renewable energy should be curtailed in these renewable energy bases in north/west of China.

2018/11/14

10

19

Planning and Operation of AC-DC Grid

The State Grid has been planning and building a huge Ultra High voltage power grid, both AC and DC. It provides a larger (national‐wide) power balancing area for renewable energy accommodation. Power grids in different provinces can provide flexibility for each other.

20

Benefits of Interconnection

North‐Western China

South‐Western China

Analyzing the benefits of connecting the northwestern with southwestern China in 2030.

Generation complementarity

The North-west

The South-west

Interconnection

Thermal

Hydro

Wind

PV

PV Thermal

Wind

Hydro

Thermal

2018/11/14

11

21

Renewable Energy Curtailment(TWh)

Curtailment Rate

Two dependent systems 227.7 8.43%

Interconnection 14.91 0.55%

Operation simulation results show that connecting the northwestern grid with the southwestern grid can significantly facilitate the accommodation of renewable energy and reduce the overall operation cost.

ConnectingCapacity（GW） 160 120 100 90 80

TransmissionUtilization Hours 2800 3770 4770 5300 6300

Exchange of energy（TWh） 477.6 477.0 477.0 477.1 472.0

Renewable Energy Curtailment Rate 0.49% 0.49% 0.49% 0.55% 3.5%

Considering the cost of transmission investment, the optimal connecting capacity is about 90-100 GW

Benefits of connecting the northwestern with southwestern China

Benefits of Interconnection

Multiple energy systems integration:Electricity and Heat

2018/11/14

12

23

Large‐sized Combined Heat and Power (CHP) units have been installed

The output power of CHP is determined by heat demand, which makes the CHP units less flexible

This leads to huge wind power curtailment

Integrated power and heat energy systems

Wind Resource Distribution

Bridging wind power with heating

coal

traditional


2018/11/14

13

25


DemandSupply

Power grid

Heating network

Coal boiler

CHP

Thermalgenerator

Power demand

Heating demand

Electrical boiler

Heat storage

Wind

Heat pump

electric thermal storage

heater(ETS)

CurtailedWind

Integration

CurtailedWind

1. Supply side：Increasing the flexibility of CHP by interacting with heat storage, electrical boiler and wind power

2. Demand side：Synergize the wind power and space heating demand, using thermal inertia to mitigate the fluctuation of wind power

Electric boiler and heat water tank

enlarge the operation zone of the

CHP power plant and make the

operation of power system and

heat supply system more flexible.


2018/11/14

14

27


Power Balance

Base

28


• Established in Taonan, Jilin in 2011, with 9 electric boilers

• 200,000 m2 heat supply

• Established in Inner Mongolia, 2014, with 20 electric boilers

• 500,000 m2 heat supply

• Decrease CO2 emission by 68,000t

The First Demo Project

The Largest Project

2018/11/14

15

Demand Response Project for Better Renewable Energy Integration

30

Demand response

Grid

Generation Consumer Load curve

P(MW)

T(h)0 12 24

Information

• Demand response would smooth the load curve, shave the peak load anddecrease the gap between max and min load.

• This would save the investment of generation capacity, improve the utilizationfactor of facilities and bring down the overall operating cost for power system.

2018/11/14

16

31

National Demand Side Management PlatformIssued on June 25, 2014http://www.dsm.gov.cn/

The maximum peak-load shifting is around 16GW.

DR Application in China

DR Pilot Project in Ningxia

Intermittent Renewable Energy Large Industrial

Customers

Trans & Dist

EV

Micro-grid

Residential

Medium Customers

Sponsored by Ministry of Science and Technology of China

2018/11/14

17


Database Server Workstation1 Workstation2

……

WorkstationN

InteractiveDispatch

Sys.Server

ApplicationServer

Front serverInteractive user dispatch serverInteractive data interface sys.

Evaluation server

Interactive Operation Platform

Router Router Router

User acquisition middle database

server

IDP server of Zone Ⅲ

D5000 Webserver of Zone Ⅲ

FirewallForward safetyisolation device

User acquisition

server

OPEN3200Server

Of Zone Ⅰ

D5000 Webserver of ZoneⅠ

Ningdong Aluminum Puhua Metallurgy Yinglite Chemicals

HaibaoCharging station

XinchengCharging station

330kVPV&battery

MG

Smart community

Heating Station

Dist. Grid

Trans. GridUser Info. Acquisition Terminal

DRTerminal

Data acquisition System

GPRS

User Info. Acquisition Terminal

DRTerminal

Forward safetyisolation device

System Configuration

Large Industrial Customers


Main System Platform

Interaction Result and Analysis

Distribution Customer Dispatch

Large Industrial Customer Dispatch

2018/11/14

18

Benefit of DR for Renewable Accommodation

By the end of 2015, wind generator

installed capacity in Ningxia is 8.22 GW,

PV installed capacity is 3.06 GW.

In 2016, sustainable energy capacity

grew at a rate of more than 30%.

In 2015, Ningxia grid generated economic benefits of 113 million RMB by accommodating renewable energy through DR pilot project. It is estimated 731 million RMB of economic benefits has been generated in 2015-2017.

Cap

acity (10 thousand kW)

Wind PV

Revenue(10 thousand yuan

)

Pilot area Extend to whole area

Environmental Benefit

Wind and PV energy curtailment was reduced by 7,230

MWh in 16 DR Event days, which equals to saving 2,895

tons of standard coal.

2018/11/14

19

Development of Concentrating Solar Power in China

38

Concentrated Solar Power (CSP)

Operation without CSP Operation with CSP

CSP can provide both renewable energy generation and operational flexibility. CSP is a unique way to accommodating renewable energy using renewable energy.

CSP firstly reflects sunlight and produce solar thermal energy which can be stored in the thermal storage system for later use.

2018/11/14

20

CSP Market

39

Solar Radiation in ChinaAccumulated Global CSP Capacity

CSP is receiving world‐wide attentions.

China has announced a series policies for CSP development, including fixed feed‐in tariff and demonstration projects.

China has invested 1.35 GW CSP by now and plans to achieve 5GW and 180GW by 2020 and 2050, respectively.

1 MW150 MW

1.5 MW

CSP projects under construction and operation in China

50 MW

285 MW

214 MW650 MW

Benefits of CSP in Gansu

40

The Same Renewable Energy Penetration Level

CSP

PV光热With CSPWithout CSP

PV

Wind

Wind

Thermal Power

PV

Wind

Hydro

Power Capacity Portfolio in 2020

Case 1: Without CSP

Case 2: With CSP to realize the same renewable penetration level

Comparing the performance between case 1 and case 2 to assess the benefit of CSP

2018/11/14

21

Benefits of CSP in Gansu

41

Gansu Provincial Power System with CSP

Gansu Provincial Power System without CSP

CSP generation share in renewables

=5% =10% =15% =20%

Reduced Wind+PV

Capacity (MW)

CSP Capacity (MW)

CSP Capacity

Substitution Rate

Levelized Benefit of

CSP ($/kWh)0.30 0.27 0.25 0.24

Renewable

Curtailment Rate8.38% 7.81% 6.49% 5.01%

Return on Investment

of CSP

Compared with the scheme of Wind+PV, investing CSP will reduce the total capacity requirement of renewable energy and help accommodating renewable energy, with a given renewable energy penetration level.

42

Outline

Challenges

Solutions



Conclusion

2018/11/14

22

Probabilistic Modeling and Analysis for High Share Renewable Integration

Modeling uncertainties

44

Proposing a Copula-based Dependent Probability Modeling Theory

• Joint probability distribution is broken down into two parts ：Marginal Distribution and correlation function

( , )= ( ), ( ) ( ) ( )XY X Y X Yf x P c F x F P f x f P

Joint probability distribution

Copula Function

Marginal Distribution

2018/11/14

23

Modeling uncertainties

45

1x 2x 3x 4x 5x

1x

2x

3x

4x

5x

1 2c ，

1 3c ，

1 4c ，

1 5c ，

1 2

,1 1 2

c

rx x x ，

3x 4x 5x

3x

4x

5x

2 3c ，

2 4c ，

2 5c ，

1 2c ，

1 3c ， 2 3c ，

2 3c，

,1rx

,1rx

Renew the Copula function

2 3c，2 4c，2 5c，

3 4c ，

3 5c ， 4 5c ，

3 4c ，

3 5c， 4 5c ，

Dimension Deflation

Sampling

0C1C

A very fast method for dependent probability calculation

46

Probabilistic Forecasting

Probabilistic Wind Forecasting

Probabilistic PV Forecasting

Conditional Forecasting Errors

2018/11/14

24

47

02000400060008000

100001200014000

0 2 4 6 8 10 12 14 16 18 20 22

Net

load

(M

W)

Hour (h)

Duck curve of Qinghai in 2020

0

2000

4000

6000

8000

10000

12000

14000

16000

0 2 4 6 8 10 12 14 16 18 20 22

Net

load

(M

W)

Hour (h)

Probabilistic Net-Load 99%90%80%70%

Expecte

Qinghai Province in 2020

Duck Curve

Probabilistic “Duck Curve”Probabilistic Ramping Requirement

Market based Strategy for Energy Storage with Renewable Integration

2018/11/14

25

49

Distributed energy storage

Load PV

prosumer

Distributed Energy Storage

• Peak Load Shifting• Demand Response• Store Renewable

Energy

Energy storage is an effective way to accommodate the fluctuations of renewable energy.

In fact a huge number of distributed energy storage has been installed.

Investment cost of DES is high

Utilization rate of DES is low

Lack of motivation of using DES

How to offer a more economical storage product/service?

50

Cloud Energy Storage

Solution


Advantages of centralized

energy storage

Advantages of centralized

energy storage

Overcome drawbacks

of DES

Overcome drawbacks

of DES

Cloud serviceCloud service

Sharing economySharing

economy

An alternative to DES

Rely on grid facilities

Use of CES is similar to use of DES

UberAirBnBMobike… …

2018/11/14

26

51


Benefit Evaluation of CES

52

Based on Ireland's user home load and electricity price data

Load profile of typical user

40 users in a day

One user in 40 days

Users’ behavior differ on the same day

The same user’s behavior differ in different days

Real-time electricity price in one year

High price

Low price

2018/11/14

27

53


‐0.15

‐0.1

‐0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

‐600

‐400

‐200

0

200

400

600

800

1000

1200

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47

Electricity price (Eu

ro)

Power (kW

)

‐0.1

‐0.05

0

0.05

0.1

0.15

0.2

‐600

‐400

‐200

0

200

400

600

800

1000

1200

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47

Electricity price (Eu

ro)

Power (kW

)

(a)

(b)

Comparison of CES operation and user's separate energy storage operation on a typical day

The peak value of theCES charging profile issignificantly less thanthe peak value of theaggregated DEScharging profile

CES is capable ofsatisfying therequirement ofdistributed users with asmaller energy storagecapacity by sharing thecapacity among theseusers

Peak charging power of CES is less than total demand of all users

Case a: peak/off‐peak price

Case b: real‐time price

54

Unit energy storage capacity investment cost

CES annual return on investment

CES profit margin

100USD/kW 300USD/kWh (100%) 5.28% 4.60%

80USD/kW 240USD/kWh (80%) 7.66% 6.53%

60USD/kW 180USD/kWh (60%) 21.38% 16.82%

40USD/kW 120USD/kWh (40%) 25.31% 20.90%

1.Compared with users using DES, CES can reduce costs and generate considerable profits under the same storage usage demands.

2.The business value of CES mainly come from two aspects: 1) lower energy storage investment cost brought by energy storage capacity multiplexing; 2) lower operating cost brought by optimized operation.

3.Investment cost of large-scale storage energy is lower than that in DES, which can increase business value of CES.

Benefit Evaluation of CES

2018/11/14

28

Big-Data Analytics for Better Integration of Renewables

56

Data Analytics for Power Systems

Explore the value behind massive smart meter data, renewable energy data, economic data, etc. It helps to: Have a better understanding and prediction of how load and generation change; Promote demand response programs and design retail market; Make optimal operation and planning decision for renewable energy accommodation.

2018/11/14

29

57

Operation Simulation

DimensionalityReduction

Clustering

Evaluation,Visualization

Massive daily operation scenarios

Unit Output Load Demand Power Flow

PC #2PC #1T-SNE、PCA

K-means、DBSCANTypical Operating Scenarios

Visualized Operation Patterns

Big data framework of system operation pattern identification

Indexes

DataPreprocessing

Bad data identification Seasonable Operation Scenarios

Application---Finding Operation Patterns

principal component (PC)

58

Power System Operation Simulation


2018/11/14

30

59

The Visualized Operation Scenarios

of Qinghai Power Systems in 2020

Increasing the renewable energy penetration


Identify the Potentials of Carbon Captured Power Plant

2018/11/14

31

61

Carbon Capture Power Plant

Development of Carbon Capture Power Plant(CCPP) in China

Shanghai

HechuanBeijing

62


Energy Flow in CCPP

Generation cycle

CO2

absorbCO2

Compress

Energy used for:

CO2

decompose

Inp

ut en

ergy

Gross output

Net output

BasicPower Plant Side

0 MW

Pmin

Pmax

0 MW

Pmax

Pmin - ∆

2018/11/14

32

63


Flexible Operation of CCPP

• Operation region of thermal power plants can be greatly expanded when equipped with a flexible carbon capture equipment.

• Deviation between net

output and gross output;

Breaking minimum

output limit; Enabling

wider range of output

adjustment

• Separate control of

power output and CO2

emission

64


Reduce wind power curtailment• Wind power output with different installed capacity of CCPPs

2018/11/14

33

65


Wind powerCCPP

Generation System

Capture System

Demand

Wind power could be supplied to capture system, enablingfully utilization of wind energy—cost effective

CO2 Capture: by using “to-be curtailed” Wind Power

66

Conclusion and Future Outlook

2018/11/14

34

67

Conclusions

The share of Renewable energy in power system will

continue growing in the world

China has been facing big challenges because of the

curtailment of renewables

It is important for power industry to take actions

Advanced models and methodologies should be

developed to address the characteristics of high share

renewable power system

68

China is still on the road……

National Key Research and Development Program of ChinaFundamental Theory of Planning and Operation for Power Systems with High Share of Renewable Energy Generationsbudget: 68 million RMB (10.6 million USD)

There are several big projects related to renewable energy integration supported by National Key Research and Development Program of China and National Science Foundation of China (NSFC).

2018/11/14

35

69

Lots of Issues to Be Further Addressed……

Efficient operation and planning methods for the power systems;

Market design and practice for renewable energy integration;

Stability analysis of inverter‐dominated power grids;

High accurate forecasting of renewable energy;

Regulation service from renewable energy itself;

Grid‐scale storage such as power‐to‐hydrogen;

……

Thank You for your attentions!

Prof. Chongqing Kang

Tsinghua University

Email: [email protected]

Documents

Tsinghua University, China - Medpower 2018medpower2018.com/wp-content/uploads/2018/11/2_Kang... · China has announced a series policies for CSP development, including fixed feed‐in