Grid Codes with respect to Distributed Generation · Wind power Small hydro power (1 - 10 MW) Small hydro power (

Project: Analysis of Indian distribution systems for the integration of high shares of rooftop PV

INTEGRATION OF RENEWABLE ENERGIES IN THE INDIAN ELECTRICITY SYSTEM (I-RE)

Final Workshop, 29 August 2017

Dr. Thomas Ackermann

Dr.-Ing. Eckehard Tröster

Grid Codes with respect to

Distributed Generation

Day 1, 2:45pm, 30 mins

DISTRIBUTED GENERATION EXAMPLE: DEVELOPMENT IN GERMANY

2

Unbundling of power systems and increasing shares of decentralized generation are major drivers of grid code development.

around 30.000 plants around 1.500.000 plants around 220.000 plants

2000 2006 2014

Wind Photovoltaics Biomass

Source: 50Hertz Source: 50Hertz Source: 50Hertz

0 10,000 20,000 30,000 40,000 50,000 60,000

53.0

52.0

51.5

51.0

50.5

50.3

50.2

49.7

49.5

49.0

48.0

47.5

47.0

MW

Fre

qu

en

cy t

hre

sh

old

fo

r d

isco

nn

ecti

on

Biogas Photovoltaic

Wind power Small hydro power (1-10 MW)

Small hydro power (<1 MW) Combined Heat & Power

The 50.2 HZ Problem in Germany: Several thousand megawatts of installed renewable capacity disconnect at unfavorable frequency thresholds

Germany

as of end 2010

Source:

EEG-registry of TSOs (1997-2008) and

Federal Netzwork Agency (2009-2010)

Reasons

• Underestimation of DG

development

• Slow grid code updating

• Missing coordination

between DSOs and TSOs

Continental EU India

COMPARISION EU - INDIA

4

Continental EU

Total Net Generation

India

2612 TWh 1231 TWh 2371 TWh 4773 TWh

2016

2022

2040

Government Ambitious Scenario

* *

*

Share of generation by Wind + PV

12.42% about 5% 12.2% 25%

2016 2022 2040

** **

today

excl. CSP *

today

Each of these challenges comes with its own set of technical issues for system planning and operation:

• Variable availability must be incorporated into system adequacy, dispatch and scheduling, as well as short-time balancing and reserve provision schemes.

• Distributed generation includes generator facilities of widely varying scales (power ratings), where also different services are necessary, useful and feasible.

• Power converter control schemes need to incorporate response characteristics to voltage and frequency changes, similar to the inherent characteristics of synchronous machines.

The technical solutions for these issues require research, development, and implementation. The resulting costs should be optimized, and the distribution of costs should be agreed on between generator manufacturers, generator owners, and system operators.

BACKGROUND:

IDENTIFYING THE CHALLENGES

5

THE MAIN SYSTEM CHALLENGE:

HIGH INSTANTANIOUS PEAK PENETRATION

6

RULE OF THUMB:

Hourly peak penetration can be 4 times higher than annual

average penetration

Example Germany India:

18,5 %

today

Average Wind+PV Penetration

Around 70 %

Peak Hourly Wind+PV Penetration

40-50 %

2022

Estimated Hourly Peak Penetration

from Wind+PV

Around 70 %

Regional hourly Peak Penetration will reach 100%

The technical challenges of VRE integration do not only require technical solutions, but also have operational, economic, and regulatory implications.

Grid codes exist for systems with and without VRE. In case of systems with VRE, the grid codes provide the rules within which the VRE challenges are addressed. Due to the scope of the implications, grid codes also cover a wide range of aspects. These are often divided as follows:

• Market Codes govern the rules of the power market, connecting market operation and the technical needs and constraints of system operation.

• Planning Codes lay out the principles of network planning and the network-relevant aspects of generator (connection) planning.

• Connection Codes specify minimum technical requirements for generators to be connected to the power system. Connection codes may also cover, or exist for, other actors such as demand control facilities, storage, HVDC, etc.

• Operating Codes describe operational procedures and requirements concerning data exchange and scheduling, response to operational disturbances, and behaviour in emergency situations.

CLEAR RULES TO ADDRESS THE CHALLENGES

7

Hence, different types of grid codes facilitate the increasing operational flexibility required and offered by increasing VRE generation with the needs of operational stability, security and quality of supply, and well-functioning wholesale markets.

CLEAR RULES TO ADDRESS THE CHALLENGES

8

The function of a grid connection code is to provide clear rules and technical requirements for generator facilities when connecting to an electricity system.

The technical requirements in grid connection codes are determined by the need to enable a sustainable growth of VRE and to maintain the reliability, security, and quality of the power supply:

• The electrical power needs of all consumers must be met reliably;

• Voltage and frequency must be maintained within set limits to avoid damaging equipment connected to the grid;

• The system must be able to recover quickly from system disturbances;

• At all times the system must operate without endangering the public or operating personnel.

GRID CONNECTION CODES

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By applying at the boundary between power system and generator facility, technical requirements in grid connection codes affect different stakeholders in unbundled power systems: technology suppliers (generator manufacturers), investors (generator owners), system operators, and often also regulators.

Grid codes are a means to achieve fair and transparent treatment of these system actors and enable efficient coordination.

GRID CONNECTION CODES

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Distribution

Grid Owners Transmission

Grid Owners

Grid

Operators

Conventional

Generator

Operators

Generator

Manufacturers Policymakers

/ Legislators

Renewable /

Decentralized

Generator Operators

UNBUNDLING AND THE NEED TO COORDINATE SYSTEM ACTORS

11

Traditional power system • Centralized generation • Utility owns grid and

generators • Internal rules and

requirements

Unbundled power system • Decentralized generation • Separated ownership • Need for grid code

governance

ADEQUATELY STRICT REQUIREMENTS

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Requirements too stringent: No VRE are installed (cost!)

Requirements too lenient: System security may be compromised.

Grid codes are a major driver of technology development as manufacturers

have to adjust to new requirements…

… but a bad grid code can also be a major show stopper!

The process of determining the requirements involves studies investigating the needs of the power system. Requirements must consider the capabilities of available generator systems in order not to hinder the process of VRE adoption.

The following studies are usually needed:

• Load flow study to investigate the needed reactive power capabilities of generators, consulting manufacturers to identify the capabilities of existing products and evaluate potential cost of extended capabilities,

• Static and dynamic short circuit studies for evaluating protection and LVRT requirements,

• Load frequency control studies for reserve requirements and gradient limitations, ideally including frequency stability study.

This list only includes studies in the context of VRE grid code parameterization and should be added to the studies that need to be performed for system planning and operation purposes.

DETERMINING TECHNICAL REQUIREMENTS

13

The most important driver for necessity of certain technical requirements for VRE generators is the VRE share in the power system:

TECHNICAL REQUIREMENTS, AND WHEN ARE THEY NEEDED?

14

VR

E Sh

are

Protection

Fully-Fledged Frequency Control

Fully-Fledged Voltage Control

Synthetic Inertia

Operating Reserves

Active Power Gradient Limitation

Simulation Models

Communication

Low Voltage Ride Through

Reactive Power Capability

Power Reduction at Overfrequency

low

h

igh

Power Quality

Active Power Management

LIMIT INVERTER SIZE / CURTAILMENT

15

Reduce worst feed-in peaks with very little loss of energy.

REQUIREMENT EXAMPLE: LVRT

16

LVRT requirements from different grid codes

In fault cases that cause a voltage drop, such as short circuits, VRE must

support the grid for a certain time without disconnecting.

VRE connection codes govern only the minimum technical capabilities VRE generators must provide. Many requirements directly satisfy some operational necessity. However, certain requirements have a connection to higher-level use cases. The scale to which extent these capabilities are actually used depends on the scope of the requirement, which in some cases involves legislation, regulation, and market design:

• System balance and frequency control is usually procured by the TSO through reserve power markets. This use case relates to remote controllability of power control mode and set-point, which is typically enforced on the grid code level for all relevant generators.

• Reactive power and voltage control may be obtained by a reactive power market or directly by voltage control requirements in the grid code. Grid Codes usually require the availability of reactive power control modes, and a remote control interface.

• Active power control may be required by the grid code, actual participation of VRE in congestion management is often subject to renewable energy law.

MAKING USE OF VRE GENERATOR CAPABILITIES

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Active Power Control:

• Balance Control

• Delta Control

• Power limiter

• Automatic frequency control

Reactive Power Control:

• Reactive power Control

• Automatic voltage control

Fault Ride Through

Inertia Supply

ANCILLARY SERVICE OPTIONS (WIND+PV)

18

PRIMARY AND SECONDARY CONTROL WITH PV

19

PV START/STOP CONTROL

20

• In the traditional generation mix with fossil fuels, solar eclipses were not a big deal for power

system operators

• This changed with the increasing share of solar generation: An eclipse takes away huge

amounts of potentially produced electricity out of the system, within seconds

• The 20 March 2015 solar eclipse was thus first of its kind event: a true stress test, passed

successfully

Solar Eclipse in Germany on 20th March 2015

21 Source : The successful stress test of Europe’s power grid – more ahead, own diagram, last downloaded on 28.09.2015

Figure: Progression of the solar eclipse in South-Bavaria, Germany. Source: „Animation partielle sonnenfinsternis“ von Sgbeer - Eigenes Werk. Lizenziert unter CC-BY-SA 4.0 über Wikimedia Commons

Solar Eclipse on 20th March 2015 – Eclipse Impact: Dropdown in GW

22 Source: The successful stress test of Europe’s power grid – more ahead, Solar Power Europe, ENTSO-E, own diagram, last downloaded on 28.09.2015

Figure: Continental Europe installed PV capacity in GW (IC) and estimated eclipse impact ( x GW drop)

Aggregated PV Feed-In during Solar Eclipse

23 Source: The successful stress test of Europe’s power grid – more ahead, Solar Power Europe, ENTSO-E, own diagram, last downloaded on 28.09.2015

Figure: Aggregated PV feed-in from a subset of European TSOs.

This slope is considered “extreme“ today, but with 80% of VRES this situation

may be considered “normal“

Enforcing technical requirements in VRE grid codes require mechanisms for verification of compliance with the codes. There are different strategies with differing costs and degrees of feasibility depending on the country context.

These mechanisms include, for example:

• On-site inspections,

• Use of certification systems,

• Verification of plants instead of units,

• Requiring manufacturer statements of conformance,

• Post-disturbance evaluation of system event recordings and revocation of grid access if non-compliance with grid code requirements is identified for a generator.

An effective and reliable certification system may come with the highest level of trust per required effort. However, it is infeasible for small system regulations due to significant organizational overhead.

Harmonization of requirements and resource sharing between countries can make it feasible!

CERTIFICATION AND VERIFICATION OF TECHNICAL REQUIREMENTS

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COMPLIANCE TESTING

25

On-site measurements are costly and complicated

Compliance mechanisms and certificates can be

a) Adapted from larger countries

b) Set up regionally, bundling resources

GRID CODE UPGRADE PROCESS

26

All stakeholders involved in grid code issues should take part in the consultation: • Policy makers • generator owners/operators • network operators • regulators • Generator and grid asset

manufacturers • Depending on scope:

consumers A predictable and reliable revision process is important for network and generator planning!

GERMAN GRID CODE IN INDIA:

INDIA CAN BENEFIT FROM THE LESSONS

LEARNED IN GERMANY

27

Due to Germany being the world leader in rooftop PV for years, many inverters available on

the market are compliant with the German distribution grid codes!

The current German grid codes have been revised multiple times. Germany has some of the most

advanced requirements in the world for units connected to LV and MV level.

Installations found in Bhopal and

Delhi.

• Power factor can be varied between 0.8

lagging and 0.8 leading

• VDE-AR-N 4105 is the German low

voltage grid connection code

Recommendations for stakeholders:

• Harmonize requirements and share resources! This makes it easier to use certification systems for verification, and reduces the cost of market access for generator manufacturers.

• Design a predictable and reliable grid code revision process! This increases reliability and security by coordinating system change with technical development, and makes system planning significantly easier.

• Consult with all relevant stakeholders! VRE integration targets can be reached more easily without sacrificing system security and reliability when the burden of changes is shared fairly between all involved parties.

• Anticipate requirements of a changed system! When your targets are reached, the system will work differently than it does today, and has different requirements. System change might even be faster than you expect!

• Avoid the mistakes from other countries! Communicate, identify best practices, and consider experiences made by others. Considering that a lot of progress has been made in technical development, many capabilities are now available at low cost that were not available when the pioneering countries started.

CONCLUSIONS

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IRENA REPORT

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Link: http://www.irena.org/DocumentDownloads/Publications/IRENA_Grid_Codes_2016.pdf

(or google “IRENA Grid Codes”)