Renewable Energy Generation:

Challenges and Practices

CHEN Guoping

State Grid Corporation of China (SGCC)

Sep 7, 2018

Contents

2

1. Developments of Renewable Energy in SGCC

2. Challenges on Large-scale Wind and Solar

Power Integration

3. Work carried out and proposed by SGCC

Introduction of SGCC

SGCC is the world’s largest public utility company which serves over 1.1 billion people and

covers 88 % of the Chinese territory.

By July 2018, the total generating capacity installed in SGCC’s service area had reached 1427 GW.

The maximum load in SGCC’s service area reached a historical high at 810 GW on July 25, 2018.

3

Generating capacity by energy source (July 2018)

Coal

799GW, 56.9%

(▲3.6%)

Hydro

225GW, 16.0%

(▲2.0%)

Wind

137GW, 9.8%

(▲11.5%)

Nuclear

23GW, 1.6%

(▲10.1%)

Solar

142GW, 10.1%

(▲41.9%)

Gas

60GW, 4.2%

(▲7.7%)

Other thermal

42GW, 3.0%

(▲10.5%)

Load curve on July 25, 2018GW

550

600

650

700

750

800

850

0:00 4:00 8:00 12:00 16:00 20:00 24:00

Promoting UHV Power Transmission

China’s coal, wind and solar energy resources concentrate in the Three-North areas, while hydro power

resources are mainly located in the southwest. However, over 70% of electrical load resides in Central

and East China. SGCC actively promotes the ultra-high voltage (UHV) power transmission to facilitate

large-scale, long-distance allocation of energy resources. It has constructed 11 UHV DC projects with a

total length of over 40,000 km, and the interregional transmission capability exceeds 96 GW.

4

HVDCUHVDC

From Russia

To South China

Northeast

NorthNorthwest

East

SouthwestCentral

Northwest coal,

wind & solar

power base

North and

Northeast coal

and wind power

bases

Southwest hydro

power base

Load

center

The ongoing Changji-Guquan

project is the world's state-of-

the-art UHV DC project with

the highest voltage (±1100 kV),

the largest capacity (12 GW)

and the longest transmission

distance (3324km).

北京天津

重庆

冀南山西

辽宁

吉林

黑龙江

江苏

浙江

安徽

福建

江西

山东

河南

湖北

湖南

广东

海南

四川

贵州

云南

陕西甘肃

青海

台湾

蒙西

广西

西藏

宁夏

新疆

上海

蒙东

冀北

Renewable Power Generation

In 2011~2017, the average annual growth of hydro, wind and solar power generating

capacity were 6%, 24% and 93%, respectively. By July 2018, SGCC has 504 GW of

renewable power generation installed in its service area (225 GW hydro, 137 GW wind,

142 GW solar with 39 GW distributed PV).

5

0~20

20~50

50~100

100~200

>200 Unit: GW

Renewable power generation in SGCC

156169

185199

208 216224 225

3547

7088

103117

129 137

2 315

2436

67

115

142

0

30

60

90

120

150

180

210

240

2011 2012 2013 2014 2015 2016 2017 2018

Hydro/水电 Wind/风电 Solar/光伏

GWWind & solar power in provincial grids

Wind & Solar Energy Consumption

In 2011~2017, the average annual growth of wind and solar energy consumption were

26% and 134%, respectively. In 2018, wind and solar energy accounted for 8.4% of the

total electricity generation in SGCC by August; the growth rate of wind and solar energy

consumption (38.4%) was much higher than that of total electricity consumption.

6

5779

129145

166183

233

1 3 823

3856

101

0

50

100

150

200

250

2011 2012 2013 2014 2015 2016 2017

Wind/风电 Solar/光伏

GWhRenewable energy generation in SGCC

Contents

7

1. Developments of Renewable Energy in SGCC

2. Challenges on Large-scale Wind and Solar

Power Integration

3. Work carried out and proposed by SGCC

Difficulties on Load Following

The volatility of wind power output results in difficulties on load following. In 2017, the total wind

power output in SGCC varied from 63 to 7.9 GW, and the maximum intraday variation reached 32 GW.

China heavily relies on coal power with limited regulation capability, while flexible power sources

contributes a very small portion. The grid regulation capability further reduces during heating period.

8

Load

(GW)

Wind

(GW)

Load and wind power in Northwest China, March 2018

In March 2018, the wind power

output in Northwest China grid

varied from 2 to 31 GW, and the

maximum intraday variation reached

17.72 GW.

0

5

10

15

20

25

30

35

50

55

60

65

70

75

80

85

0:00 4:00 8:00 12:00 16:00 20:00

Challenges from Power Electronics

Wind and solar power generation is integrated into the system via power electronic

components, which lacks active/reactive power regulation abilities. As conventional

generators are replaced by wind and solar power, the system presents weaker inertia,

damping and robustness to grid disturbances. This is a large challenge to the security and

stability of the system.

9

The evolution of power system in China

Inertia from

conventional

generators

Grid in the past Present and future grid

100% conventionalConventional<70%

Wind & solar>30%

Inertia from

conventional

generators

Lost inertia

Intolerance to Grid Disturbances

Wind and solar power generation lacks tolerance to grid disturbances such as high frequency and

high/low voltage. It may be off the grid after a grid fault and worsen the situation.

In January 2014, the transient overvoltage (128%Un) caused by a Tianshan-Zhongzhou UHVDC fault resulted in the

loss of 25 wind turbines by overvoltage protection in Qiaowan wind farm which is 400km away from Tianshan

station.

10

Comparison of tolerance levels of wind turbines and

coal-fired generators

Wind Coal-fired

Overvoltage 1.1 p.u. 1.3 p.u.

Overfrequency 50.2Hz 51.5Hz

Primary frequency

responseNone 6%

Power factor0.95 leading

~0.95 lagging

0.95 leading

~0.85 lagging

Overvoltage caused by Tianshan-Zhongzhou UHVDC

fault (PMU recordings)

128%Un

Grid Oscillation Problems

Multi-form sub/super-synchronous oscillations (SSOs) are likely to occur in a

weak grid with high wind power penetration.

Since 2015, more than 100 SSOs have happened near Tianshan-Zhongzhou UHVDC

converter stations and wind farms in Hami, Xinjiang.

11

至汗海

照阳河牧场

鹿原

白龙山

长青

博丰

华锦东山

乌登山

国华佳鑫

麒麟山义缘站

韩家庄

金阳

永发

宏达东湾

坝头

察北站中宝

九龙泉

沽源

至太平

恒泰

冰峰

莲花滩

桦树岭

秋林

风电场

500kV变电站

200kV变电站

固定串补

500kV线路

200kV线路

Wind power oscillations in Guyuan, Hebei SSOs triggered by wind power in Hami, Xinjiang

Contents

12

1. Developments of Renewable Energy in SGCC

2. Challenges on Large-scale Wind and Solar

Power Integration

3. Work carried out and proposed by SGCC

Analyzing Grid Characteristics

SGCC performs researches and innovations on basic theory, grid control and simulations,

which improves the recognition of grid characteristics.

Construct the world’s largest hybrid analog/digital real-time power system simulation platform

and the first 900-Tflops supercomputing platform designated for power system simulation.

Conduct hybrid electro-mechanical/electro-magnetic transient simulations to accommodate the

trend of power-electronization of power systems.

13

Supercomputer center Verification of UHV DC simulation models

Enhancing and Utilizing Transmission

Continuously strengthen the grid to improve long-distance power transmission capability.

Establish market mechanisms to reduce the number of online fossil-fuel power units and give full

play to their regulation capabilities.

Closely monitor and effectively utilize the grid regulation capabilities and the available transmission

capacity of tie-lines to consume renewable energy to the maximum extent.

14

Real-time grid balance monitoringProspective interregional grid in 2030

Improving Regulation Capability

Support the upgrade of coal-fired generators to allow lower minimum load levels for wider ranges

of power output adjustments.

Promote grid-scale energy storage and expedite the construction of pumped-hydro plants. Over

24 GW of pumped hydro is expected to be in service by 2020.

Establish power balancing mechanism with distributed energy storage and demand response, and

make room for renewable energy through markets of generation rights and ancillary services.

15Minimum load level of coal-fired generators Power balance affected by demand-side management

Wind + solar

Load without demand-

side management

Load with

demand-side

management

Load/Generation

Time

0%

20%

40%

60%

80%

100%

China/中国 Denmark/丹麦 Germany/德国

Promoting Grid-friendly Wind & Solar Power

Revise the grid code compliance to include high/low voltage ride-through (LVRT/HVRT)

requirements for wind turbines, and construct testbeds to support the upgrade of wind turbines

for LVRT/HVRT capabilities.

Conduct researches on primary frequency response (PFR) capability of wind turbines and wind

farms, and carry out experiments in Northwest China grid.

Promote virtual synchronous generator (VSG) control of wind turbines and PV units to enable

grid-friendly capabilities including inertia, damping, PFR and reactive voltage regulation.

16

Frequency Pper

49.4

49.6

49.8

50.0

50.2

50.4

50.6Hz

150

200

250

300

350

400

450

500

550

600

650

700kW

0 5 10 15 20 25 30 35 40 45 50 55

sFref Pact Pref

49.75

49.80

49.85

49.90

49.95

50.00

50.05

50.10Hz

16.5

17.0

17.5

18.0

18.5

19.0

19.5

20.0

20.5MW

0 10 20 30 40 50 60

s

PFR test on wind turbines and

wind farms

VSG control of PV inverters

130%Un_500ms

125%Un_1s

120%Un_10s

115%Un_10s

110%Un_∞

Revised requirements on LVRT/HVRT

of wind turbines

PI

Udc

Umppt

Pm

E0

Pmppt

kqEref

无功调节

有功调节

AVR

kf

ua

ub

uc

Qref

Uac

Q

ωref

ω

Uac_ref

定子电流闭环及调制

P

功率计算

Pref

1/s-+

-1/Js

+0

D

sin

sin( 2 / 3)

sin( 2 / 3)

1/Ls

R

uabc

+

--

P、Q

VSG本体模型

Eabc

Pprim

Conclusion and Outlook

By 2030, wind and solar power in SGCC is expected to make up 30% of generating capacity

and 16% of electricity generation; the proportion will further rise to 50% and 30% by 2050.

SGCC will dedicate to a next generation power system with better connectivity, intelligence,

flexibility and safety, and actively promote the development of renewable power to

support China’s transformation towards clean and low carbon economy.

17

60% 54%39% 33%

17%

11% 21%

30% 37%52%

0%

20%

40%

60%

80%

2015 2020 2030 2035 2050

Fossil fuel/火电 Wind + solar/新能源

66% 64%54% 47%

29%

4% 9%16%

20%

34%

0%

20%

40%

60%

80%

2015 2020 2030 2035 2050

Fossil fuel/火电 Wind + solar/新能源

Generating capacity 2015~2050 Electricity generation 2015~2050

18

Thank you for attention!