Proven Strategies and Key Concepts to Develop Successful

Microgrid Control Systems

Abdel Rahman Khatib, PhD, PE, IEEE SMSenior Power System EngineerSEL Engineering Services, Inc.

Proven Methods Help Ensure Success

HIL Testing Adaptive Protection

Proven Methods Help Ensure Success

Fast Control SimplificationSecurity &

Communication

Proven Strategy #1 Hardware-in-the-Loop (HIL) Testing

• SEL POWERMAX® microgrid controller

• High-speed interface electronics

• SEL-751 Feeder Protection Relays and programming

• Model ported to HIL test system

• Pullman factory acceptance tests (FATs)

• Integration support for MIT LL HIL Simulator

SEL’s Contribution to the MIT Lincoln Laboratory Symposium

MIT HIL Architecture

DMS

Modbus

Modbus

Woodward easYgenWoodward easYgen EPC InverterEPC Inverter

HIL Model

Macrogrid

Banshee

Microgrid

Loads

LoadsLoads LoadsLoads LoadsLoadsPV +

BESS

PV +

BESS

SDG CHP

PCC1 PCC2 PCC3

HIL System

MGC System

DER Interface High-Speed

HIL Interface

SEL-3555

ModbusSEL-751SEL-751

SEL-2440

24 V

TTL

24 V

TTL

SEL-2440

24 V

TTL

Proven Strategy #2 Protective Relaying

Protective Relay at PCCProvides ~50 Percent of Control Functionality

Grid reconnection

Unintentional islanding

Protection for expensive assets

IEEE 1547 compliance

Metering

Pass-through control

Macrogrid

Microgrid

SEL-751

Trip / ClosePCC

DERs SEL-3555

Microgrid

Control System

Trip / CloseTrip / CloseTrip / Close

Macrogrid

Microgrid

SEL-751

Trip / ClosePCC

DERs SEL-3555

Microgrid

Control System

Loads

• Load shedding

• Intentional islanding

• PCC dispatch

• PF control

• Voltage regulation

• Frequency regulation

Microgrid Controller Load Shedding, Dispatch, and Islanded Regulation

Grid-Tied

Operation

Islanded

Operation

Controller

ReconnectionUnintentional

Islanding

PCC Relay

Relays and Controllers Work Together

DERt

I

Relay

Protection Systems Must Adapt When Islanded

20,000

20,000

2,000

2,000

Normal

Loading

PCC

V

– pf)

I

I

(+0.8 pf)

Loads

High Current

Low Voltage

Normal Load Angle

Trip PCC

Fast (67)

Example: Directional Current Protection (67)Opens PCC During Short-Circuit Conditions

ImportExport

– pf)I

I (+0.8 pf)

FaultFAULTI

Trip PCC

Fast (67)

LoadsLoads

LoadsLoads

PCC

SEL-751

MIT LL Simulated Utility Disconnection Event What the Relay Recorded!

Fault

Starts

Relay

Trips Load Current

Interrupted

Frequency Recovers!

MGC

Sheds

Load

CB

Opens

Proven Strategy #3 Fast Control

Microgrid Resiliency Requires FAST Load Shedding

Problem to Mitigate Load-Shedding Speed

Frequency collapse FAST

Voltage collapse FAST

DERs out of step FAST

DER overload SLOW

Synchronization assist SLOW

PCC curtailment SLOW

PCC demand charge avoidance SLOW

Subcycle

(faster than 16 ms)

Slow

(~1 second)

Make Sure Your Controller Is Up to the Task

1,000160

120

80

40

01 10 100 1,000 10,000

Quantity of IEDs

Lo

ad

-Sh

ed

Tim

e (

ms)

Microgrid Controllers

Programmable

Logic Controller

(PLC) Solutions

Process Control Systems

Macrogrid

Microgrid

Loads

LoadsLoads LoadsLoads LoadsLoadsPV +

BESS

PV +

BESS

SDG CHP

PCC1 PCC2 PCC3

The Ultimate: Triple Seamless Islanding Event!Only Possible With Integrated Relays and Controllers

59.84

59.88

59.92

59.96

60

60.04

12000 14000 16000 18000 20000

Fre

q (

Hz)

VAB (rms)

V vs. Hz

Proven Strategy #4 Cybersecurity and Communication

Defense in Depth Helps

Ensure Security

Visualization, Economic

Optimization, Engineering Tools

Gateway / Firewall

Microgrid Controller

Current and

Voltage Transformers

Circuit

Breakers

Power Generation

Controllers

Protective

RelaysRemote I/O

Metering and

Power Quality

Level 0: Physical

Level 1: Protection

Level 2: Automation

Level 3: Access

Level 4: SCADA

Firewall Level 5: Perimeter

Business Systems Level 6: People

Security Requires More Than Just Layers

Operating system

Minimal software

Mature processes

Vertical integration

Cybersecurity

Proven Strategy #5 Simplification

Simple Architecture

Maximize use of protective relay

Reduce wiring

Select proper protocol

MacrogridMacrogrid

MicrogridMicrogrid

SEL-751

SEL-3555

DERDER

DV, Slip

Dispatch

Simple Grid Reconnecting MethodWorks With All DERs

δ (slip)

δ

V

VMACROGRID

VMICROGRID

Simple Feedforward (FF) Techniques

More Microgrid Use Cases

Community Microgrid With Energy StoragePresidio, Texas

Challenges

Needed energy storage to prevent blackouts

Required international coordination between Mexico and U.S.

Solutions

Fast control enabled better power quality and reliability

Automated resource sharing scheme developed between Mexico and U.S.

Innovative Approach for Community Microgrid

Courtesy of U.S. Army Corps of Engineers

Resilient and Reliable Power in the Bering SeaSaint Paul Island, Alaska

Rugged and Economical for Restricted Budgets

Challenges

Mixture of DERs

Potential for catastrophic effects from misoperation

Cost-effective solution in line with DOE requirements

Solutions

Validated models

HIL testing of all scenarios

Commercial, off-the-shelf, utility-grade hardware

Campus-Wide Energy AssuranceUniversity of California, San Diego

Courtesy of UC San Diego Publications

Challenges

Keeping critical research facilities online

High penetration of energy storage and renewables

Campus-wide monitoring and synchronization

Solutions

Seamless islanding with subcycle control

Extensive resource modeling and testing

SCADA and integrated synchrophasors

Perfect Fit for a Turnkey Solution

Questions?