Distributed generation interconnection and power quality improvement by smart control

Sami Repo and Jarmo AhoCleen Summit 7.4.2011

Contents1. Distributed generation (DG)

• Trends• Interconnection

2. Smart control in medium voltage networks• Loss-of-Mains protection• Island operation• Island operation• Voltage rise• Active network management

3. Static synchronous compensator (STATCOM) • Technology• STATCOM system• Demonstrator

4. Hybrid STATCOM and SVC

DG technology trends

Distributed generation interconnection• Connection principle

– Normally network customers have firm network capacity available– Non-firm network capacity >> firm capacity

• The amount of DG to be connected and operated under normal network conditions will be increased

• Production curtailment or constraints in extreme conditions• Production curtailment or constraints in extreme conditions• The probability of extreme conditions should be low enough

Loss-of-Mains protection

-1

-0.5

0

0.5

delta

Q =

Qlo

ad -

Qdg

[MVa

r]

0.50.7

11.52

-0.5 0 0.5 1

-1

deltaP = Pload - Pdg [MW]

delta

Q =

Qlo

ad -

Qdg

[MVa

r]

-0.5 0 0.5 1

-1

-0.5

0

0.5

deltaP = Pload - Pdg [MW]de

ltaQ

= Q

load

- Q

dg [M

Var]

0.3

0.50.711.52

Island operationProtection• In automatic islanding LOM need to know what to do• Protection in island mode might be a challenge (low

fault currents)Control and automation• Black starting• Black starting• Frequency and voltage• ResynchronizationNetwork planning• Adequate DG capacity and controllability• SAIDI improves

– Island operation may replace backup connections– Permanent islands may allow to remove lightly

loaded frequently faulted MV branches

Voltage control – Voltage rise

DG unit may contribute to control• Power factor control• Local voltage control• Co-ordinated control (controller • Co-ordinated control (controller

parameter resetting)• Production curtailment

Co-ordinated voltage control

110 / 20 kVAVRVoltage measurement

Setting point

AMRDMSSCADA

State estimationCo-ordinated voltage controletc.RTU

ACAC

20 / 0.4 kV

Settingpoint

AMR

AQR

Settingpoint

AVR

Settingpoint

RTU

Benefits of co-ordination

2000

2500

3000

Net

wor

k tra

nsfe

r cap

abili

ty [k

W]

Unity power factor

0

500

1000

1500

364 473 572 690 825 992 1174

Loading of feeder [kW]

Net

wor

k tra

nsfe

r cap

abili

ty [k

W]

Unity power factorLocal voltage controlCo-ordinated control

Active network management

Enterprise Application Integration

DMS MDS CISNIS…

Substation automation

SCADA NIS

IEDRTU

Substation automation

Smart meter

ThermostatTemperature

MV/LV automation

EVDG DER PQ monitoring

Mains switch

Home energy management

MV/LVautomation

PQ monitoring IED

IEDRTU

MV/LV automation

RTU

Smart meter

Smart meter

Active network management

MV/LV automation

Aggregator

SOAP

Meter reading system

Substation automation /

SCADA / DMS

SCADA protocolsIEC 61850

Home Energy Management

Agent

HTTP APIApplication 1

Application n

HTTP

AMRconsentratorRTU

AMI

DLMS/COSEM

User interface

DG

EV

DER

Introduction to STATCOM developmentA number of different multilevel VSC topologies for high-power medium voltage applications has emerged as results of development work related to power semiconductors.

Multilevel converters include in general an array of power semiconductors which are arranged in such a way that they are able to add capacitor voltages stepwise to the output of the able to add capacitor voltages stepwise to the output of the converter.

The 3-level converter topology (3L-NPC-VSC) described in this paper offers a good compromise in terms of:• Performance,• Efficiency,• Quality of harmonics spectrum,• Complexity,• Costs.

Three-Level, Neutral Point Clamped, Voltage Source Converter

The bus voltage is split in two by the connection of equal series-connected bus capacitors.

Diodes are connected to the mid-point of the

Figure 1. 3-level neutral point clamped voltage source converter schematics.

Each phase leg contains four IGBT and additionally two so called clamp diodes.

Diodes are connected to the mid-point of the dc bus to insure that the voltage across any single IGBT never exceeds one half of the total dc bus voltage.

STATCOM system

The STATCOM system consists of a Master Controller and one or several parallel Power Modules.

The Master Controller captures the measurements from the network and calculates the required reference values for the compensation currents. for the compensation currents.

Figure 2: STATCOM block and communication diagram

These values are transformed into a serial data stream and transmitted via fiber optic links to the Slave Controllers of the Power Modules.

The Master Controller communicates also with a common user interface (HMI, SCADA or Web server).

STATCOM system

• 3L-NPC-VSC with IGBTs

• DC capacitor bank

• LCL-Filter for AC currents

Figure 4 STATCOM Power Module

STATCOM modules can be switched in parallel and connected to the power system via a step up transformer to any voltage level.

STATCOM system (cont.)

The efficiency and the power quality in the distribution network can be improved using STATCOM by:

• Compensating harmonics and reactive power,• Compensating harmonics and reactive power,

• Eliminating negative sequence currents,

• Reducing voltage flicker,

• Stabilizing the voltage level,

• Improving the network recovery during line fault.

Demonstrator: STATCOM for Dunneill Windfarm

Alstom Grid delivered a 6Mvar STATCOM to Dunneill windfarm in Ireland as demonstrating system related to ADINE project. The STATCOM is installed in a container and commissioned in september 2010.

Figure 3: Single line diagram of the power grid

SC

AD

A

com

mun

icat

ion

Figure 4: STATCOM in a container

Single line diagram and block diagram for RTDS simulations in hybrid SVC simulations for SGEM

Figure 5: Single line diagram

Figure 6: Signalisation block diagram of RTDS simulation

Flicker value improvement using hybrid SVCFlicker values without compensation

Flicker values using SVC (1)Flicker values using SVC and STATCOM (2)

1

Figure 7: Flicker reduction for different reactive power comp. topologies

1

2

1

2

Thank you!

ADINE is a project co-funded by the European Commission

www.adine.fi