P R E S E N T E D B Y

Sandia National Laboratories is a multimission

laboratory managed and operated by National

Technology & Engineering Solutions of Sandia,

LLC, a wholly owned subsidiary of Honeywell

International Inc., for the U.S. Department of

Energy’s National Nuclear Security

Administration under contract DE-NA0003525.

Battery and PV Based Inverters

S ig i f r edo Gonza lez

1SAND2019-6656 PE

Outline

•Inverter types

•Inverter Utility Interconnection Changes and Requirements

•Inverter Ride-Through Capabilities

•Inverter Utility Support Functions

•Battery + PV (Hybrid) Inverters

•Inverter in Grid-Forming Mode

2

Residential Battery-based Inverters3

Module level micro-inverter

And storage systemResidential inverter

And storage system

Residential inverter

And storage system

Large “AC” Battery Inverters4

Hybrid Type Residential Inverter5

Inverter DC Input

• Battery input

• PV input

Inverter AC Output

• Grid and loads

• Critical loads

• Transfer switch

Hybrid Type Residential Inverter One-Line Diagram6

Inverter safety features

• Array qualification before use

• Residual current monitoring

• Rapid shutdown

Inverter Grid-Tied and Off-Grid

• Export energy to the grid

• Achieve “no” export if required

• Operates off-grid is needed

Utility Interconnection Requirements

Trans i t ion ing to h igh pene t ra t ion o f d i s t r ibuted energ y r esources

8

Evolution of the IEEE 1547

IEEE Std

1547-2003

IEEE Std

1547a-2014Amendment 1

IEEE Std

1547-2018

• Shall NOT actively regulate voltage

• Shall trip on abnormal voltage/frequency

• May actively regulate voltage

• May ride through on abnormal

voltage/frequency

• May provide frequency response

• Shall be capable of actively regulating

voltage

• Shall ride through abnormal

voltage/frequency

• Shall be capable of frequency regulation

9 Sandia’s Distributed Energy Technologies Laboratory (DETL) Facilities

10

IEEE 1547-2018 requires inverter manufacturers to meet minimum stated accuracy on key parameters

11

Inverter Mandatory Voltage Ride-Through Requirements12

Inverter Mandatory Frequency Ride-Through Requirements13

Low Voltage Ride-Through < 50% of nominal14

RegionVoltage

(% Nominal Voltage)

Ride-Through

UntilOperating Mode

Maximum

Trip Time (s)

Low Voltage 3

(LV3)

V < 501 sec.

Momentary

Cessation2.0 sec.

Momentary

cessation within

.0833 seconds

Achieves > 80%

of pre-event current

level within 0.4 sec.

Low Frequency Ride-Through 15

RegionFrequency (Hz)

(% Nominal Voltage)

Ride-Through

UntilOperating Mode

Maximum Trip

Time (s)

Low Frequency 2

(LF2)57.0 ≤ f < 58.8 299 sec. Continuous operation 300.0 sec.

Frequency drops to

57.2 Hz and remains

for 299 seconds.

Rate of change of

frequency (ROCOF)

should not exceed

3.0Hz/sec for EUT

to remain exporting

Frequency returns to

60.0 Hz and EUT delivered

rated current over entire

duration of frequency

excursion

Utility Support Requirements

Trans i t ion ing to h igh pene t ra t ion o f d i s t r ibuted energ y r esources

Utility Voltage Support Functions per IEEE 1547-2018 17

Autonomous

Functions

Commanded

Functions

Autonomous functions may have to be enabled to operate

Commanded functions must be set/adjusted to operate as intended

Voltage and Frequency Support Functions18

Volt-Var Voltage Support Function Implementation19

Current lags voltage and

lowers voltage with

absorbing reactive current

Current leads voltage and

increases voltage with

injection of reactive current

20 Voltage regulation functions can expedite implementation

Freq-Watt Frequency Support Function Implementation21

Utility Outage Support Requirements

Hybrid PV/Energy Storage Systems Address Outages

Hybrid Inverters can solve Red Flag Power Outage Concerns23

Inverter design can operate autonomously

from the utility and takes PV and battery

energy to meet local and utility demands

Inverter can perform the following:

• Export PV energy to the utility

• Achieve net zero export

• Charge battery from PV, generator, and

the utility

• Automatic generator start/control

• Supply critical sub panel/loads during

utility outage

Grid Connected and Grid-Following Inverter transitioning to Grid-forming and off grid

24

Another Hybrid PV/Battery System that addressesRed Flag induced Blackout Conditions

25

Communication

portal

PV inverter

Energy storage

inverter

Development of Continuous Grid-Forming Inverters 26

Grid-Following Characteristics Grid-Forming Characteristics

need well-defined terminal voltage Regulates instantaneous voltage

PLL estimates voltage/current angle Regulates frequency

Current-control loop regulates

injection into grid

Operate autonomously from grid

PF commands- inverter adheres to

constant PQ

Droop control—active-frequency and

Q-V (reactive-voltage)

Grid-forming (GFM) inverters eliminate the dropout during transitioning from grid-connected

To standalone (micro-grid) operation. Challenges remaining to be addressed are:

• Power quality

• Dynamic response

• Unintentional islanding

• Low voltage and frequency ride-through

Thank You27

Questions?

Supplemental slides28

Unintentional Islanding Methods29

IEEE 1547 2018 requires all utility interconnected DER to be type tested with ride-through and utility

Support functions enabled at their most aggressive adjustments.

Each method listed above has an evaluation procedure in draft IEEE P1547.1 test procedure.

30 Frequency Regulation Function Capabilities

31 Smart Electricity Grid Communications

32 Communications/Control Architecture

Battery and PV Based Inverters