1

A Survey of Techniques Used to Control Microgrid Generation and Storage during Island Operation

Michael Angelo Pedrasa and Ted SpoonerPresented by: Saad Sayeef

AUPEC 2006

2

Presentation OutlineIntroductionIsland operation of microgridsCo-operation strategies of generators and storage devicesComparison of co-operation strategiesConclusion

3

IntroductionWhat is a microgrid?

4

Microgrid ComponentsDistributed generation (microsources)Loads

Intermediate storageController (MGCC)Point of common coupling

5

Microgrid OperationGrid Connected Island Mode

6

Island Operation of MicrogridsVoltage and frequency managementBalance between supply and demandPower qualityMicrosource issuesCommunication among microgrid components

7

Co-operation StrategiesPure droop controlInverter modes controlPrimary energy source controlReverse droop controlAutonomous controlAgent-based PQ control

8

Output Power Control of Microsources

PQ Control Droop Control

9

Pure Droop ControlGrid-connected

v0 and p0

Importing Pg and Qg

Island operationvnew and pnew

Pg = ΔP0 + ΔP1 + ΔP2

Qg = ΔQ0 + ΔQ1 + ΔQ2

10

Inverter Modes ControlMaster microsource

Shifts to droop controlSets microgrid frequency and voltage

Slave microsourceRemains in PQ control

Single master operationMulti-master operation

11

Primary Energy Source ControlAll microsources and storage are in droop controlThe droop characteristics of the microsources shift to restore frequency and voltage to pre-island values

12

Reverse Droop ControlBus voltage is controlled by the real power flow while the frequency is controlled by the reactive power

13

Autonomous ControlUnit power flow configuration

Similar to pure droop controlFeeder flow configuration

14

Agent-Based PQ Control

15

Comparison of Co-operation Strategies

Voltage and frequency variation

High for pure droop, reverse droop and autonomous control Low for inverters mode, primary energy source and agent-based control

Intermediate storage capacity

Small for inverter modes and agent-based controlLarge for pure droop, reverse droop and primary energy source control

16

Comparison of Co-operation Strategies

Communication infrastructure

Not required except for agent-based control

Intermittent sourcesInverter modes and agent-based control if installed storage capacity is small

Pure droop and reverse droop control if installed storage capacity is largeUsed feeder flow configuration is autonomous control is used

17

Comparison of Co-operation Strategies

Ownership of microgrid generators and storage

All approaches if uGrid is normally importing powerAgent-based and autonomous control of uGrid is normally exporting power

18

ConclusionSix co-operation approaches are presentedCompared with respect to

Power quality and stabilityRequired storage capacityRequired communication infrastructurePerformance with intermittent sourcesMicrogrid ownership

19

End

Thank you.