apresentaÇÃo do inesc porto - microgrids microgrids.p… · campus da feup rua dr. roberto frias,...

Campus da FEUP

Rua Dr. Roberto Frias, 378

4200 - 465 Porto

Portugal

T +351 222 094 000

F +351 222 094 050

[email protected]

www.inescporto.pt

© 2009

Multi-Microgrids

coordinated voltage and frequency control,emergency functions and ancillary services

J. A. Peças Lopes

[email protected]

(Director of INESC Porto)

2010 Jan 29

© 2009 2

PV

Wind Gen

MV

LV

MicroGrid: A Flexible Cell of the Electric Power System

Microturbine

Fuel Cell

Storage

DeviceMGCC

MC

MC

MC

MC

MC

LC

LC

LC

LC

LC

MG Hierarchical Control:

• MGCC, LC, MC

• Communication

infrastructure

© 2009

Multi-microgrids – MV distribution network of the future

• Microgrids

• Storage device-VSI

• Large DFIM

• Mini-Hydro

• CHP

• Small Diesel

• Sheddable Loads

HV Network

VSI

Diesel

Wind

generator

MicroGrid

MicroGrid

MicroGrid

Capacitor

Bank

Miini-

Hydro

CHP

Sheddable

Loads

Storage

3

© 2009 4

The concept: Multi Microgrids

• Integration of several Microgrids in MV networks

• Active Management of microgrids, DG units and loads for

– Normal Steady-state Operation or

– Emergency Conditions

DMS

CAMC

RTU

MGCC

~

~

MGCC

MGCC

CAMCRTU

HV

MV

HV

MV

LV

LV

LV

DG

DG

© 2009 5

Multi-MicroGrids: Interaction of MGCC and DMS

DMS

CAMC

MCOLTCSVC Load LC

MGCC

DG

Control Level 1

Control Level 2

Control Level 3

Control Scheme of a Multi-MicroGrid System

DMS

CAMC

RTU

MGCC

~

~

MGCC

MGCC

CAMCRTU

HV

MV

HV

MV

LV

LV

LV

DG

DG

© 2009 6

Multi-MicroGrids: Definition of Ancillary Services offered to the MV

Network

• Energy / Services… to be provided in each operating mode

(Normal and Emergency)

• Different services can be provided by these agents regarding

MicroGrids and Distribution / Transmission Network Operators

• A list of new DMS functionalities

• List of needed data was identified

© 2009 7

Management of the Multi-MicroGrid

• Existing DMS functionalities need to be adapted to Multi-MicroGrid operation

• The management of the Multi-MicroGrid will be performed through the CAMC

using an Hierarchical Control Architecture, which requires new functionalities

like:

– Local State Estimation

– Coordinated Voltage Support and Flow Control

– Peak shaving

– Coordinated Frequency Support

CAMCLocal

Measurements

Remote Terminal

Units

State EstimationEmergency

Functions

Control Scheduling

(Markets)

Voltage VAR

Support

Coordinated

Frequency Support

Network Data,

Pseudo

Measurements

Constraints

Contracts and Bids

MGCCs

OLTCs

Capacitors

SVCs

DG Units

Loads

© 2009

Control and Management Architecture

• Communication Scheme of a Multi-MicroGrid System

DMS

CAMC

MC

OLTCSVC Load

RTU

LC

MGCC

DG

8

© 2009 9

Local State Estimation

• Traditional State Estimation routines for DMS can be adapted to the new paradigm of Multi-MicroGrid systems

– New algorithms for Distributed State Estimation in order to minimize the amount of data required

– Fuzzy State Estimation approaches

© 2009 10


Estimation of bus voltages (both

module and phase), power injections

for each bus and power flows and

current in each branch

FUZZY STATE ESTIMATION

Type of Fuzzy Information considered on the MicroGrids

Membership Functions for the Measurements and for the

Results of the Voltage Magnitude in the Buses 2 and 20

Membership Functions for the Measurements and for the

Results of the Active and Reactive Power injected on Bus 42

© 2009 11


DISTRIBUTED STATE ESTIMATION

Each area is governed by a

Local State Estimator that is

responsible for estimating its

own state

The areas exchange

information through

communication links to a

Coordination State Estimation

© 2009 12

Coordinated Voltage Support and Control

• Two types of tools for the Coordination of Volt/VAR Control:

– Tools based on a local control approaches (using conventional

techniques)

– Tools based on a global coordinated approach (using meta-heuristics –

EPSO)

• The developed approaches make full use of the control

capabilities provided by MicroGrids, DG Units, OLTC

Transformers and Capacitor Banks

© 2009


• High DG penetration may cause voltage rise problems, especially in the case

of weak distribution networks

• The effects of voltage rise may propagate to the LV side

• From the power flow equations (in LV networks where R<<X does not apply):

• In conclusion, high DG and microgeneration penetration will require the

development of an effective voltage control scheme based on active and

reactive power control

cos12

2

2

R

VV

R

VPinj

R

V1

V2

MV Network

MicroGrid

Pinj

13

© 2009


Voltage/Control in Distribution Systems integrating

MicroGrids becomes a hierarchical optimization problem

that must be analyzed in a coordinated way between LV

and MV levels

Given the characteristics of the networks, both Active and

Reactive Power Control is needed

14

© 2009

Coordinated Voltage Support and Control ControlGeneral

• Forms of Control

– Generation curtailment

– Reactive power

(Droop control)

– OLTC

V1 V2

R+jX

P+jQ Local

Generation

Load

Transformer

Network

LineShunt

Compensator

Q generation

Vmax

Vmin

V0

Q absorbtion

DVmax

iM SQ

iM S maxQ

iM S max

Q

iM SV

15

© 2009 16

Coordinated Voltage Support and Flow Control

0,9

0,95

1

1,05

1,1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Vo

ltag

e (

pu

)

Hours (h)

Initial

Final

0

0,02

0,04

0,06

0,08

0,1

0,12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Act

ive

Po

we

r (M

W)

Hours (h)

Initial

Final

In order to maintain voltage profiles within admissible

limits, Microgeneration Shedding was required

A Neural Network was used to emulate

the behavior of the LV MicroGridGlobal Approach

Optimizing distribution

network operation in

interconnected mode, when

dealing simultaneously with

DG connected directly to

the MV grid and

microgeneration installed

at the LV side

Controls:

• OLTC Transformer taps

• Reactive power provided

by DG Sources and

Capacitor Banks

• Active power control at the

MicroGrid level in extreme

scenarios (using

Microgeneration Shedding)

© 2009 17

Flow Control and Peak Shaving – Optimization at the MV Level

iLcP

iLncP

iLP

iGc

Pi

GncP

iG

P

Optimization problem within the MMG:

Controlled from the CAMC

© 2009 18

Coordinated Frequency Support

• Effective frequency support can be obtained exploiting decentralized

control strategies together with a Hierarchical Approach housed at

CAMC and MGCC

• Coordination with Load Curtailment is required

• Dynamic Equivalents of MicroGrids may be needed

• The feasibility and profitability of Ancillary Services provision (namely

regarding frequency control) from Multi-MicroGrid should be

addressed at different levels:

– By contributing to general system frequency control (primary and

secondary):

– By allowing islanding operation and black start

© 2009 19

Development of Equivalents of MicroGrids

Boundary

bus PV

PV

Microturbine

Fuel cell

Wind

generator

Microturbine

Storage device

Boundary

bus

MG slow dynamics

reduced model

VSI

IdR; IqR

Vd; Vq

Study

subsystem

External

subsystem

MicroGrid

Dynamic equivalent

© 2009

Coordinated Frequency Support (Microgrids)

• MicroSources providing no

frequency response

• MicroSources providing primary

response using special VSI control

solutions

• MicroSources providing primary

and secondary responses,

exploiting P,Q controlled inverters

together with central control

f0

fMG

Primary

response fp

2MSP

2ref

MS

P

2p

MS

P

2m

ax

MS

P

Primary

response

Secondary

response f0

fMG

fp

3MSP3ref

MS

P

3p

MS

P

3m

ax

MS

P

20

© 2009

Coordinated Frequency Support (Microgrids)

• Flywheel

– Inertia

– Short circuit current

– Initial frequency support

• Frequency target of the flywheel

0

f0

fMG

Primary

response

Secondary

response

FWP

pF

WP

max

FW

P

21

© 2009 22

Coordinated Frequency Support – Multimicrogrid

CHP

MicroGrid

Hydro

DFIMVSI

Diesel

TEST SYSEM

© 2009 23

Coordinated Frequency Support

0 10 20 30 40 50 60 70 80 9048.5

49

49.5

50

50.5

Time (s)

Fre

qu

ency

(H

z)

With Hierarchical Control

Without Hierarchical Control

0 10 20 30 40 50 60 70 80 90

0

0.2

0.4

0.6

0.8

1

Time (s)

Ou

tpu

t P

ow

er (

pu

)

MGCC 3

Hydro

CHP

Frequency Deviation following Islanding of

the Multi-MicroGrid System

Active Power Set-Points sent by the CAMC to

the DG Units and MicroGrids

Local secondary frequency control should be designed such that load shedding is also managed

© 2009 24

Emergency Functions – Islanding with several MicroGrids

0 10 20 30 40 50 60 70 80 9047

47.5

48

48.5

49

49.5

50

50.5

Time (s)

Fre

qu

ency

(H

z)

With Load-Shedding

Without Load-Shedding

8 9 10 11 12 13 14 150

1

2

3

4

5

6

7

8

Time (s)

Po

wer

(M

W)

In some extreme situations, Load

Shedding may be needed to prevent

long frequency excursions and even

System Collapse

Load Shedding Steps

ISLANDINGSystem Collapse

© 2009

Centralized Load-Shedding (acting as secondary reserve)

• Controllable loads help to reach rated frequency faster and

economically (integrated in an optimal allocation algorithm)

• But are not able to avoid large initial frequency variations.

0 10 20 30 40 50 60 70 80 9048.5

49

49.5

50

50.5

Time (s)

Fre

qu

ency

(H

z)

With Load Shedding

Without Load Shedding

0 10 20 30 40 50 60 70 80 900

0.2

0.4

0.6

0.8

1

Time (s)

Lo

ad (

MW

)

Loads NMVCHP

Loads NMVCHP2

25

© 2009

Using MicroGrids for Service Restoration

• Black-Start is a sequence of events controlled by a set of rules

– A set of rules and conditions are identified in advance and

embedded in MGCC software

– These rules and conditions define a sequence of control actions

to be carried out during the restoration stages

– The electrical problems to be dealt with include:

• Building LV network

• Connecting microgenerators

• Connecting controllable loads

• Controlling frequency and voltage

• Synchronization with the MV network (when available)

26

© 2009

MicroGrid Black Start – Test System

20 kV

0.4 kV

Appartment

building

Appartment

building

15 kW wind

generator

30 kW SSMT

30 kW SSMT

10 kW PV

Group of 4

Residences

10 kW PV

MG Main

Storage

Industrial

Load

2x30 kW SSMT

The fast transients associated to the

initial stages of the MG restoration

process were analysed using an

EMTP-RV tool, being the long term

dynamics evaluated using the MatLab

Simulink simulation platform

27

© 2009

Results from Simulations – Long Term Dynamics

• Development of the Service Restoration Procedure

90 100 110 120 130 140 150 160 170 180 190 200 210 22049.6

49.8

50

50.2

50.4

Fre

qu

en

cy (

Hz)

90 100 110 120 130 140 150 160 170 180 190 200 210 220-20

0

20

40

Ac

tiv

e P

ow

er

(kW

)

90 100 110 120 130 140 150 160 170 180 190 200 210 220

0

20

40

60

Time (s)

Ac

tiv

e P

ow

er

(kw

)

MG main storage

SSMT 1

SSMT 2

SSMT 3

load connection

PVs connectionWG connection

Motor load start up

28

© 2009 29

Emergency Functions –Black Start

10 15 20 25 30 35 40 45 500.9

0.95

1

1.05

Time (s)

Vol

tage

(p.

u.)

Diesel

CHP1

CHP2

0 100 200 300 400 500 600 700 800 900 1000

49.8

50

50.2

50.4

Time (s)

Fre

quen

cy (

Hz)

A Bottom-Up Strategy is

followed for rebuilding the

Multi-MicroGrid network

comprising two main stages:

1. MV network energization

and synchronization of

small islands

2. Load supply and

integration of generation

BLACKSTART

© 2009 30

Ancillary Services Markets

• An Ancillary Services Markets can developed for Voltage Support and Reserves for Normal and Emergency Operation (separated from the main Energy Market)

• An Optimization Algorithm was developed for setting controllers response characteristics in both Energy and Ancillary Services Markets simultaneously

• Functions (existing and new) incorporated in the MGCC and information exchange between CAMC and MGCC regarding Ancillary Services were studied and MicroGrid contribution to voltage violation management has been investigated

© 2009 31

Ancillary Services Markets

0

0,5

1

1,5

2

2,5

Good Citizen Ideal Citizen

VA

R D

em

and

[M

VA

R]

Microgrid Policy

HV BUS

CHP

DIESEL

DFIM

µG5

µG4

µG3

µG2

µG1

Selected VAR Bids (“Good Citizen” Policy vs. “Ideal Citizen” Policy)

Normal Interconnected Operation

VAR MARKET

Normal and Emergency Mode

Import required No Import required

© 2009

Microgrids and Plugged in Electric Vehicles

• PEV are: controllable charges and mobile storage devices that

need to be controlled and managed.

33

© 2009 34

Final Remarks

• The main issues to be dealt with in the future are the deployment of Smart Metering as a mean of pushing forward the development of MicroGrids (MG) as an integrated part of the general Smart Grid concept

• Massive integration of Distributed Storage, based on mobile storage (Electrical Vehicles) or on stationary storage (fuel cells, regenerative fuel cells, ion-lithium batteries, etc.) needs to be further studied

• A full assessment of active demand side management strategies (managed by the DSO) should also be carried out.

• Integrated management of MicroGrids allows the integration of flexible DG, flexible consumption (including EV battery charging – smart charging) and flexible storage. Flexibility

• Regulatory issues need to further addressed (quantity of needed flexibility and value of flexibility) for system operation in normal and emergency modes.

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