Survey of Practices Europe & US Julia Matevosyan, ERCOT.

Survey of Practices Europe & US

Julia Matevosyan , ERCOT

Outline

• PV capacity world-wide• Challenges with integration of PVs.

Experience in Europe.• Grid connection requirements, Grid Codes• German Grid Code• ENTSO-E Grid Code• Conclusions• US survey, storage integration into US

electricity markets

PV capacity world-wide

Country

PV Capacity Installed in 2011 (MW)

PV Capacity Installed in 2011 (% of country's total by the end of 2011)

Cumulative PV Installed Capacity, 2011 (MW)

1 Germany 5,500 24% 22,6932 Italy 10,300 75% 13,7943 Japan 1,100 23% 4,7224 Spain 400 10% 4,1845 USA 1,600 39% 4,1286 China 200 7% 2,8937 France 1,500 59% 2,5258 Belgium 550 36% 1,5109 Australia 700 58% 1,204

10 United Kingdom 700 91% 76611 Geece 350 63% 55612 Canada 300 60% 50013 Slovakia 350 71% 49514 India 300 65% 46015 Isael 130 65% 20016 Ukrane 140 100% 140

Rest of the World 1,015 17% 5,823Total 25,135 66,593

Challenges with PVs

• Installed at low voltage levels• Many installations but small size ≤ 100kW• Example: in Germany: − 80% of all PVs are connected to LV networks (≤1

kV);− of those 50% are ≤ 10 kW

• No controllability or observability for network operators (at distribution or transmission level)

Problem of disconnection at under/over frequency

• Prior to April 2011 PVs were required to disconnect at 50.2 Hz (1.004 pu)

What can happen?

• On a sunny day in summer in Italy and Germany, PVs can potentially produce up to 70% of the capacity = 0.7·35GW =24.5 GW

• Due to a sudden 200mHz frequency deviation, e.g. 50% of the PVs would trip.

• As a result an outage of more than 10GW in Central Europe, the disturbance reserve is only 3GW.

• During the ENTSO-E discussions this topic was raised and a common letter was sent to all the other TSOs indicating the importance of fixing this issue for future installations.

• Retrofitting existing PVs is a very expensive option. In Germany the costs are estimated at $84-229 million.

Connection requirements of wind power plants to the network. Grid

Codes

The relationships between the network operator with all users of the network (generators, customers etc.) are set out in Grid Codes. The objectives of the Grid Code are to secure efficient operation network reliability and security of power supply, to regulate rights and responsibilities of the entities acting in the electricity sector.

Development of Grid Codes

Requirements in Grid CodesUsually the requirements concern:

• Active power control

• Frequency tolerance/ frequency control

• Reactive power / Voltage regulation

• Fault-ride-though capability and dynamic grid support

• Communication and controllability

• Tests and documentation (incl. model requirements).

Grid Code Harmonization Efforts

• The grid codes differ between countries both in the grid code structure and in the technical requirements.

• The latter calls for different technical solutions and thus impose higher costs on generation.

• The requirements are also subject to continuous revision and changes.

• There was a need for grid code harmonization so that manufactures could provide more manageable and cost-efficient solutions to meet grid code requirements.

• Two grid code harmonization examples: Nordic Grid Code (2007) and ENTSO-E Grid Code (2012)

German Grid CodesThere are 3 guidelines developed by stakeholders' associations:

•LV ≤ 1kW , “Guideline for generating plants’ connection to and parallel operation with the low-voltage network”, April 2011

•1kV < MV ≤ 60 kV, “Guideline for generating plants’ connection to and parallel operation with the medium-voltage network”, 2008•HV and EHV > 60 kV, Transmission Code, 2007

•Guidelines should be complied with (certification) to receive feed-in tariff. •DNO and TSO may develop their own requirements, should be complied with to connect to respective DNO/TSO.

•The guidelines apply to all generators but requirements differ for:

─Type 1 generating unit – a synchronous generator directly connected to the network.─Type 2 generating unit – any other (incl. PV, Storage(?)).

Overview of German Requirements

Grid Code FRT Reactive Power Supply Frequency BandActive Power Decrease

EHV/HV (>60 kV) Yes

MethodU, cos, Q

LimitationsQ/Pn and voltage level (3

different variants)

47.5 Hz 51.5 Hz

P=0.4·Pa(50.2-fa),

50.2 ≤fa≤ 51.5 Hz

Pa prod. @ 50.2 Hz

(for >30 minutes)

MV (> 1kV & ≤60 kV) Yes

MethodsQ(U), cosfix, Qfix, cos(P)

Limitationscos=from 0.95un to 0.95ov

47.5 Hz 51.5 Hz

LV (≤1kV) No

Methodcosfix, cos(P)

Limitationsfrom 0.95un to 0.95ov if ≤13.8

kVAfrom 0.9un to 0.9ov if >13.8

kVA

47.5 Hz 51.5 Hz

Source: T. Ackermann, Energinautics

Active Power Control (EHV,HV,MV,LV)

• A reduction of active power to a certain set point must be possible in steps of 10%

• The network operator sends a new setpoint in case of:

– Risk of unsafe system operation– Risk of congestions– Risk of unwanted islanding– Risk of grid instability– Repairs or constructions

Power reduction in case of over- frequency (EHV,HV,MV,LV)

Static voltage support at MV

Voltage support under normal operation. Provide reactive power:•cosφ = 0.95 underexcited to 0.95 overexcited

Setpoint can be fixed or adjustable (determined by NO):•Fixed cosφ, should be capable to change target value based on remote signal •Fixed reactive power in MVArs, should be capable to change target value based on remote signal•Variable cosφ(P), should adopt automatically within 10 seconds •Variable reactive power Q(U), should adopt automatically within 10 s to 1 minute.

Static voltage support, example of a cos ϕ (P)-characteristic (at MV,

<60kV)

Static voltage support (EHV/HV, i.e. 420, 220, 110 kV)

Q/Pn

U/Un

Applies at normal frequency range 49.5-50.5 Hz

0.975

0.950.9250.9

0.925

0.950.975

underexcited overexcited

Static voltage support at EHV/HV

The operating point is defined in the grid connection agreement depending on the requirements of the grid. The definition refers to one of the following three possibilities:

•Power factor (cos ϕ);

•Reactive power level (Q in Mvar);

•Voltage level (U in kV), if necessary with tolerance band;

The operating points are defined by the following possibilities:

•Agreement of a value or, if necessary, a schedule;

•Online setpoint value specification;

In the case of online setpoint value, a new specifications for the reactive power operating point must be realized at the grid connection point after ≤ 1 minute.

Voltage ranges, EHV

German requirement to Fault ride through MV

German requirements to Fault ride through, HV, EHV

Dynamic reactive power support, HV/EHV

Grid Codes, harmonization efforts

• The European Network of Transmission System Operators for Electricity (ENTSO-E) started in July 2009, with the aim of the TSO coordination

• ENTSO-E represents all TSOs in the EU and others connected to their networks.

• In 2009 European Commission requested ENTSO-E to undertake grid code harmonisation effort

• ‘Network code for requirements for grid connection applicable to all generators’ (down to 0.8 kW) (finalised 07/2012).

• TSOs will have a period of two years to adjust their national grid codes to fulfil the requirements of the ENTSO-E Grid Code.

What is covered in ENTSO-E code?

• ENTSO-E code covers connection requirements for generation, procedures for connection, compliance testing and compliance simulations

• Requirements are irrespective of generation technology

− Some requirements differs between synchronous generation (incl. pumped-storage) and other (incl. other storage in generating mode)

− Difference in requirements depending on plant size and connection voltage, 4 plant types.

• Requirements were developed in cooperation with national stakeholders => neither more onerous nor least onerous compared to national requirements.

Difference in Requirements in ENTSO-E Grid Code

Type Size Voltage Requirements (cumulative)

Type A ≥0.8 kW* <110 kV Freq. tolerance, Active power response capability (at overfreq.)

Type B ≥1 MW <110 kV Static voltage support, Protection, Dynamic reactive power support, FRT

Type C ≥50 MW <110 kV Active power response capability (at over/under freq.), Rate of change of active power, Wider static voltage support, Synthetic inertia (possible).

Type D ≥75 MW ≥ 110 kV Wider voltage operation range, FRT different between synch. Generators and others.

* Size ranges are for Central Europe, other ranges apply in Nordic area, GB, Ireland and Baltic countries.

Conclusion

• European Grid Codes have been “reactive” adding more requirements as amount of RES and DG grew.

• “Late” enforcement of certain requirements, e.g. FRT for wind or freq. range for PV is compromising security of the system and calls for expensive retrofit.

• If large share of DG is installed even at distribution level it can effect transmission system operation.

• Too stringent requirements at the very beginning may impede developments new generation facilities.

• From discussions with inverter manufacturers most of the capabilities required in European grid codes can be delivered, if taken into account in the development stage of a plant.

PV inverter capabilities

• Example of Danfoss 15kW PV inverter, that meets most of European GCs;

• Voltage operating range low/high: BDEW requirements asks 100% reactive power support during FRT, so low voltage is not a limitation. Higher voltages are limited due to component ratings.

• Operating frequency: Can cover a wide range +/- 5 Hz • Reactive power: components are rated in terms of

current, so 100% reactive power support is possible (this would curtail active power, so financial implications would have to be considered)

• Power factor: wider than +/-0.85 is feasible

Proposals in other ISO’s - CAISO

• Proposal to integrate Limited Energy Storage Resources into MRTU markets– Limited Energy Storage resources can in principle participate in any of the

A/S markets (Regulation Up, Regulation Down, Spinning Reserve, and Non-spinning Reserves) as well as in the Energy market.

– CAISO considering how to change, their A/S market rules to remove existing barriers that affect the ability of energy storage resources to provide A/S, such as due to limited energy.

– The existing CAISO A/S market rules were designed for the operating characteristics of generators

Proposals in other ISO’s - CAISO

• Proposal to integrate Limited Energy Storage Resources into MRTU markets – Required 4 s telemetry– Maximum Operating Limit (MW); – Minimum Operating Limit (MW); – Resource Instantaneous Output(MW); – Resource Charge/Load Pickup Ramp Rate (MW/min); -- Optional – Resource Discharge/Load Drop Ramp Rate (MW/min); -- Optional – Resource Connectivity Status (On/Off); – Resource AGC Control Status (Remote/Local); – State of Charge (SOC), represents the actual stored energy (MWh) – Curtailment Energy limit(CEL) in MWh for DR only

• Additional information is described in ISO website:

• http://www.caiso.com/thegrid/operations/gcp/index.html

Proposals in other ISO’s - MISO

• Proposed Stored Energy Resource – SER

– The Stored Energy Resource will be able to offer and supply Regulating Reserve, Spinning Reserve and Supplemental Reserve;

– Operating parameters unique to this new Resource type are proposed: Hourly Energy Storage Loss Rate, Hourly Full Charge Energy Withdrawal Rate, Hourly Maximum Energy Charge Rate, Hourly Maximum Energy Discharge Rate and Hourly Maximum Energy Storage Level.

– Requirements imposed on other Resources to be able to deploy Operating Reserves for a continuous period of 60 minutes or more have been removed for Stored Energy Resources.

– Maximum amount of Operating Reserve that may be supplied by Stored Energy Resources will be limited to a MW level equal to the Regulating Reserve requirement for that Hour.

Pilot at New England ISO• The purpose of the Alternative Technologies Regulation Pilot Program is

to provide a temporary platform for evaluation resources with a wide range of performance characteristics that did not qualify to provide Regulation under the existing market rules.

• The Pilot Program allows the ISO to validate the performance claims of these alternative technologies;

• 5 participants providing regulation services Beacon, Vcharge, A123 Systems, Open energi, Demansys Energy.

• These 5 participants provide, or are preparing to provide, regulation service representing a wide range of technologies, including

– flywheel storage, – plug-in vehicle load response (so-called “smart charging” or “v1g”), – plug-in vehicle distributed storage/generation that can discharge energy back

onto the grid (so-called “vehicle-to-grid” or “v2g”), – residential heating demand response, – real-time commercial-scale load management, and – nano-phosphate battery storage.