Andrew Yip Pacific Gas and Electric Company (PG&E)...

Solar Forum 2013 High Penetration

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PG&E HIGH PENETRATION SOLAR PV CURRENT STATUS AND RESEARCH

Andrew Yip Pacific Gas and Electric Company (PG&E)

http://www.gosolarcalifornia.org/


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PG&E Overview Company Facts

• Fortune 200 company located in San Francisco, CA

• $14B in operating revenues in 2010

• 20,000 employees

Energy Supply • Services to 15M people:

– 5.2M Electric accounts

– 4.3M Natural Gas accounts

• Peak electricity demand: 20,000 MW

• Over 50% of PG&E’s electric supply comes from non-greenhouse gas emitting facilities

Service Territory • 70,000 sq. miles with diverse topography

• 160,000 circuit miles of electric transmission and distribution lines

• 49,000 miles of natural gas transmission and distribution pipelines



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PG&E Renewable Energy Programs

Customer-scale Utility-scale

Net Energy Metering

Utility Owned

California Solar Initiative

Available PG&E Programs

Feed-in Tariff Programs

Renewables RFO

Self Generation Incentive Program

PV RFO

System Size 1 kW 1 MW 100 MW ++ 20 MW 100 kW 3 MW

Solar Water Heating (CSI Thermal)

Renewable Auction Mech.

in regulatory proceeding



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Solar PV Programs

Note: Customer-Side Solar PV Online value includes projects associated with various customer-side incentive programs. In-development and PG&E Program Cap value only includes projects in the California Solar Initiative mass market program.

0 500 1000 1500 2000 2500 3000

Customer-Side Solar

Feed-In Tariff Programs

Renewable AuctionMechanism

Solar PV Program (PPA)

Solar PV Program (UOG)

Renewables RFO

Installed Capacity (MW)

PG&

E Pr

ogra

ms

Online

In Development

PG&E Program Cap

>1.5 MW

1-20 MW

1-20 MW

1-20 MW

<1.5 MW

<1 MW



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PG&E and Distributed PV

• PG&E is a leader in distributed PV

• > 79,000 installations

• > 802 MW (CEC AC)

• ~ 30% of US total

• PG&E serves ~5% of US population

• Over 17,000 interconnections in 2012

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

20002001200220032004200520062007200820092010201120122013

# of

Inte

rcon

nect

ions

Res

Non-Res



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PV Penetration Status

• Overall high penetration of PV in PG&E territory (relative to other utilities)

• However, feeder-level penetration is generally low (relative to feeder max demand)

• On the other hand, high concentrations of PV exist in some localized areas (i.e., on individual transformers)



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PV Penetration by Circuit

PV Penetration* on PG&E Feeders

0%

10%

20%

30%

40%

50%

60%

70%

80%

0 - 2%2 - 4%

4 - 6%6 - 8%

8 - 10%

10 - 12%

12 - 14%

14 - 16%

16 - 18%

18 -20%

>20%

% P

enet

ratio

n* 2010 2011

* % PV Penetration = PV MW (CEC AC) / 2009 Feeder Max Demand



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Currently, DG penetration is low at about 5% of System Peak

CC DA DI EB FR KE LP MI NB NC NV PE SA SF SJ SI ST YO TOTALExisting 36 38 52 33 229 37 29 59 50 74 46 31 59 19 72 63 28 40 995

Proposed 27 7 18 6 371 330 33 18 5 25 52 4 68 4 32 23 55 186 1264

0

50

100

150

200

250

300

350

400

CC DA DI EB FR KE LP MI NB NC NV PE SA SF SJ SI ST YO

Existing and Potential Distributed Generation (MW)

Existing Proposed

Penetration = installed DG as a % of total system peak (22,000MW)



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• All DG’s are studied individually for potential impact and mitigated prior to physical interconnection • Studies focus on Safety, Equipment

Loading, Voltage Fluctuation and Islanding

• For most feeders, aggregate DG is less than local load, and power flows on the feeders are still from the substation out in a radial mode

• All identified issues are mitigated to have less than significant system impacts

9

At Low Penetration, DG System Impacts are Manageable

~ DG

Voltage profile

Voltage regulator

Load center

Substation Q P

Reference voltage



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Voltage Concerns

114 V

126 V Acceptable voltage band

With DG (PV)

Without DG (PV)

Feeder

Acceptable service

voltage band

Electric Rule 2

• DG (PV) can impact the voltage profile along a given feeder, driving the service voltage outside of acceptable ranges at points – particularly in low-load conditions



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PV and the Distribution Grid: Challenges

PV can cause… • Service voltage to exceed the acceptable range

• Can lead to inverter trip-offs (potential domino effect)

• Flicker

• Due to inverter trip-offs or rapid cloud cover

In what cases? • High concentrations of PV beyond a single transformer

• Large PV on feeders

• PV at points on feeder already close to voltage limits



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Voltage Mitigations

Acceptable voltage band

Feeder

Capacitor banks

Voltage regulators

Load tap changers

Bucking transformers

Today, voltage impacts of PV on the grid are generally addressed by adjusting settings or relocating distribution system equipment, including:

In certain situations with fast voltage fluctuations due to intermittency, reconductoring may be the only effective mitigation measure. Energy storage is an alternative but has higher capital cost and market operational uncertainties



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PV and the Distribution Grid: Today

• Examples of grid problems caused by PV and mitigation strategies employed

• Generally, few impacts today despite the relatively high number of PV systems

• However, requirements for mitigation may increase in future with increased penetration of PV in localized areas

Concern Mitigation Strategy A facility’s 10-kW PV system (inverter) trips off-line when customer load is light due to high service voltage

Adjust voltage regulator settings

Generators at a facility downstream of a 1-MW PV system trip off-line due to high service voltage

Adjust capacitor bank settings



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PV and the Distribution Grid: Potential Future Strategies

• In the future, the negative impacts of PV on the grid may be mitigated in a variety of ways

Install new equipment (e.g.,

voltage regulators

Reconductor lines

Require curtailment of PV generation Distribution

Management Systems (DMS) (e.g., Volt/Var Optimization

(VVO) “Smart” inverters



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Current Research for Distributed Solar PV • Collaborative efforts

• Development and Analysis of a Progressively Smarter Distribution System (UC Irvine) • Advanced Grid-Interactive Distributed PV and Storage (Solar City/Tesla Motors/ UC

Berkeley) • PV and Advanced Energy Storage for Demand Reduction (SunPower/KEMA) • Quantification of Risk of Unintended Islanding and Re-Assessment of Interconnection

Requirements in High-Penetration of Customer-Sited Distributed PV (GE) • Screening Distribution Feeders: Alternatives to the 15% Rule (NREL/Sandia/CPR) • Tools Development for Grid Integration of High PV Penetration (BEW)

• Other research areas • Two internal studies to assess the impacts of PV on the PG&E distribution system with

separate focus on (a) 1-20 MW systems and (b) smaller (e.g., residential) systems. • A DOE SEGIS-funded, EPRI-led project involving National Grid, Excel Energy, and Detroit

Edison that will explore how utility-inverter communication can enable “smart” inverters to optimally provide grid support. PG&E is supporting this project in an advisory role.



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Q &A AND DISCUSSION

Andrew Yip [email protected] 415-973-6143


mailto:[email protected]

Andrew Yip Pacific Gas and Electric Company (PG&E)...

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