Chapter 8 tutorial on microgrids

distribution systems containing loads and distributed energy resources, such as distributed generators, storage devices, or controllable loads that can be operated in a controlled, coord

Introduction to MicroGrids-

Integration of Renewable Energy

Nguyen Huu Phuc

Email: nhphuc@hcmut.edu.vn ; nhphuc123@yahoo.com ;

Klipsch School of Electrical- Computer Engineering

New Mexico State University

0

Microgrid Definitions

electricity sources and loads that normally operates connected to and synchronous with the traditional centralized grid (macrogrid), but can disconnect and function autonomously as physical and/or economic

conditions dictate

distribution systems containing loads and distributed energy resources, (such as distributed generators, storage devices, or controllable loads) that can be operated in a controlled, coordinated way either while

connected to the main power network or while islanded 1

2

What is a Microgrid?

That Was Then… …This is Now

What is Microgrid?

•It is connected to both the local generating units and the utility grid thus preventing power outages

•Excess power can be sold to the utility grid

•Size of the Microgrid may range from housing estate to

Microgrid – Islanding Mode Microgrid – Grid-Connected Mode

What is a Microgrid?

4

5

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8

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Comparison

How does this differ from a backup system, like what a campus has?

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Microgrid Generation

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MiroGrid Loads

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Basic �G Architecture

The basic architecture of a �G

system is presented in Figure

1, which shows that a �G

system generally consists of

distributed generation (DG)

resource, storage systems,

distribution systems, and

communication and control

systems

53

Figure 2: �G system with PV, diesel, and storage

55

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Figure 4: DC microgrid system

58

Distribution Systems The distribution network can be

classified as three types:

(i) DC line,

(ii) 60/50Hz AC line (line frequency),

(iii) high-frequency AC (HFAC)

In HFAC �G, the DERs are connected to a common bus.The electricity

generated by the DERs is transformed to 500Hz AC by power electronics

devices and is transmitted to the load side; it is again converted to 50Hz AC

by an AC/AC converter

60

61

mGrid Operation and Control

Georgia Institute of Technology

© 2001 University of Wisconsin Board of Regents

University of Wisconsin and Georgia Institute of Technology

Micro-Grid Operation and Control

Wisconsin A.P.Sakis Meliopoulos Georgia Institute of

Technology Giri Venkataramanan University of

Wisconsin

R.H.Lasseter University-of-Wisconsin PSERC

4 Operation and Control of Micro-Grids

R.H.Lasseter University-of-Wisconsin PSERC

Power Generation Applications

•Peaking •Back-up power units: •Local power & heat

•Cost •Isolated site deferrals: •Local voltage support

•Voltage •Cost reduction support: •Load management

Micro Grid

University-of-Wisconsin

kWs

PSERC

Micro-Turbine Basics

Recuperator Turbine

Compressor

Generator

Power electronics

Air

R.H.Lasseter University-of-Wisconsin PSERC

70kW Micro turbine

•Installed at $1000/kW (target is $350/kW)

•Efficiency 30%

•Air foil bearings

•expect in excess of 40,000 hours of

reliable operation

•Operation speed 90,000-100,000 RPMs

R.H.Lasseter University-of-Wisconsin PSERC

Fuel cell System

R.H.Lasseter University-of-Wisconsin PSERC

Automotive Influence on Fuel Cell

Ballard PEM Fuel Cell

R.H.Lasseter University-of-Wisconsin PSERC

7 kW Plug Power System

PEM Fuel Cell/water heater

QuickTime™ and a Photo - JPEG decompressor are needed to see this picture

R.H.Lasseter University-of-Wisconsin PSERC

Distributed Generation

Business Characterization

Hybrid Fuel cell CCTG

Gas

Turbine

Old steam

R.H.Lasseter University-of-Wisconsin PSERC

Factors Impacting Grid

Transmission > 66 kV Sub transmission 24-66 kV Distribution 4-16 kV

Rating Small Fault Current Islanding

Voltage Control

University-of-Wisconsin PSERC

Micro Source Dynamics

• Response of “Prime Mover”

R.H.Lasseter University-of-Wisconsin PSERC

20 sec

R.H.Lasseter University-of-Wisconsin PSERC

Load Tracking Problem

R.H.Lasseter University-of-Wisconsin PSERC

Quality of Power Perspectives

UTILITIES

second

70%

R.H.Lasseter Universit problems n PSERC

Micro-grid concept assumes:

R.H.Lasseter University-of-Wisconsin PSERC

Load Control using a

Load control

Pload

Control P set point

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Next

1 Problems and Issues related to

2 Power Electronics Sources

R.H.Lasseter University-of-Wisconsin PSERC

mGrid Operation and Control

Problems and Issues Related to

Distribution Systems

A P Sakis Meliopoulos Georgia Institute of Technology

Tutorial 14 HICSS-34 Jan 3, 2001

PSERC Georgia Tech

The mGRID Concept - Distribution System Backbone

Photovoltaics

Interface Protection

Micro-Grid Management System

Data Control Aqcuisition

RTU Converter

RTU

Sensitive Load

Variable Speed Drives

Interface Protection

Interface Protection

Converter Microturbine / Generator PSERC

Distribution System Backbone Issues

Stray Voltages and Currents

Electromagnetic Compatibility Issues

Non-autonomous/Autonomous Operation

PSERC

0 20 40 60 80 100

Body Weight (kg)

The Electrocution Parameters

Applicable Standards (IEEE & IEC):

Non-Fibrillating Body Current as a Function of Shock Duration

PSERC

Earth Current / GPR / Worst Case Condition

PSERC

Power Quality

Disturbances

Lightning Switching Power Faults Feeder Energization inrush currents, Motor Start

EMI

Impact on End User

Voltage Distortion, Sags, Swells, Outages and Imbalances

Design Options

Configuration Grounding Overvoltage Protection (arresters), Fault Protection

Lightning Caused Voltage Sags, Swells and Outages

Lightning Caused Voltage Sags, Swells and

Outages

PSERC

Voltage Sags & Swells and Grounding

Voltage Sags & Swells During a Ground Fault

The Data of the Figure can

1.50 2.25 3.00 3.75 Distance (miles) BUS50

Statistical Distribution of Voltage Sags/Swells

1 PHASE ENERGIZED

Capacitive/Inductive Impedance Ratio

Resonance Between the Inductance of a Steel Core and the Circuit Capacitance

Harmonic Resonance

BUS100 BUS90

System May Be Vulnerable When Resonance Coincides with a Harmonic Frequency

When Problem is Known, Solution is Very Simple - Detuning

334.5

Magnitude (Ohms)

334.5

Magnitude (Ohms)

872.1

Table Impedance Phase

334.5

Phase (Degrees)

Phase (Degrees)

Close

Pro gram WinIGS - Fo rm FSCAN _RES Pro gram WinIGS - Fo rm FSCAN _RES PSERC

Reliability

Reliability Indices for Distribution Systems

(Utility Perspective)

SAIFI: System Average Interruption Frequency Index

(interruptions/year and customer)

Total Number of Customer Interruptions per Year

SAIFI =

Total Number of Customers Served

SAIDI: System Average Interruption Duration Index

(hours/year and customer)

Total Number of Customer Interruptions Durations per Year

Voltage Sags Voltage Swells

Momentary Outages

Load Interruption EMI

SAIDI =

Total Number of Customers Served Comments

CAIDI: Customer Average Interruption Duration Index

(hours/interruption)

Total Number of Customer Interruption Durations per Year

Good Methods for Utility Applications Exists

CAIDI =

Total Number of Customer Interruptions

(Markovian)

ASAI: Average Service Availability Index

Total Customer Hours Service Availability per Year End User/DER Methods

ASAI =

Customer Hours Service Demand Needs Further Research

(NonMarkovian Processes) PSERC

Cost of Reliability

Example

Power requirements: 3000 VA power

Average power consumption is 2000 Watts

Power utility reliability: SAIFI = 1.5, SAIDI = 45, Momentary = 30

Sector customer damage function: commercial per Table Below

Calculations

MWhrs consumed: 17.52

Cost of two 20 minute outages: (3.0)(17.52)(2) = 105.12

Cost of five 1 minute outages: (1.0)(17.52)(5) = 87.60

Cost of momentary: (1.0)(17.52)(30) = 525.60

Annual cost of interruptions: 718.32

Comments

Cost of utility power (assuming $0.10 pwr kWhr): $1,752 per year

Sector\Duration Mom 1 Min 20 min 1 hr 4 hr 8 hr 24 hrs

64.0 106.0 135.0 3.0 4.0 5.0 PSERC

Reliability Research Issues

Protection

Conductors

PSERC

180 660

1140 1620 2100 Frequency (Hz)

PSERC

Induction Motor Response to Unbalance/Asymmetry

BUS100 Case: System Asymmetry and Imbalance Example

BUS90 BUS80

MCLOAD1_B Vb

MCLOAD1_C Vc

RGROUND Ref Currents

Combined Effects of System

Component Asymmetry and

Imbalanced Loads

Important Factors:

Configuration Transformers Load Balancing

Georgia Tech

Pro gram WinI GS - Fo rm FDR_M ULTIM ETER

PSERC

21

Stray Voltages and Currents

Comments

Electromagnetic Compatibility Issues

SOURCE

BUS10 BUS100

G Magnetic Field Near Nonmagnetic Conduit Enclosed Circuit

Plot Circle Radius Plot Along Straight Line Return

Plot Along Conduit Centered Circle

BUS200

0.00 0.00 90.0 180 270 360

56.0 0.00

Magnetic Field

90.0 180 270 360 Angle (Degrees)

Zoom In Zoom Out Zoom All Angle 244.1 F ield 75.81

Pro g ra m GEM I - Form EM F_CI RCLE performance PSERC

WEMPEC

Inverters in Microgrids

Giri Venkataramanan Department of Electrical and Computer Engineering

WEMPEC

Outline

• Description of inverter types and characteristics

• Inverter control objectives

• Inverter dynamic modeling

• Summary

• All the three phase voltages

could have an average Vdc/2

common mode voltage

• Causes a neutral shift

• Will cancel out in the line-line

voltages

WEMPEC

Three Phase Current Source Inverter

• Two Pole Three Throw Switches

factor load

Three phase a voltages

1P3T

WEMPEC

3 wire direct output

• DC voltage level has to

be bigger than peak line voltage

line-• No path for zero sequence currents frominverter

• Zero sequence currents

on star side circulateswithin the loop of the deltaside

• Reactive power injection

• POL voltage control

• Voltage imbalance correction

Operation under sag

(Reduced real power to

grid)

WEMPEC

Voltage imbalance correction

• Input voltage - Brown

• Output voltage - Cyan

• Phase currents - Green

• Note increase in currentstress on phases withlarge sag

WEMPEC

Key Control Issues

WEMPEC

Modeling objectives

• Need to model dynamic properties

• Control input and real power flow or power

Current feedback

-

Flux feedback

λi

Converter and

WEMPEC

Key control variables

Magnitude and Phase angle

Instantaneous phase quantities are projections of the

rotating vectors on appropriate axes

WEMPEC

Steady state operating condition

Classical phasor solution

WEMPEC

Perturbations in time domain

200

Voac(t , 1000 ) Voa(t , 1000)

Ioa(t , 1000 ) Ioac(t , 1000)

60

40

20 Im(Iocomplex(t , 500)) 0

WEMPEC

Properties of the dynamic model

Eigen frequencies of small signal model

−313.396 + 629.17i

−313.396 − 629.17i

−313.396 + 509.17i

−313.396 − 509.17i

Eigen frequencies of LC filter = 569 Hz

(incl damping effects)

WEMPEC

Dynamic interaction issues

droop, etc.)

z EMI filter interactions

WEMPEC

Summary

microgrid design

decouples prime mover dynamics

vectors

state

determined, (esp angle and frequency)

Operation and Control of

Micro-grid concept assumes:

• Close to loads with possible CHP

applications

R.H.Lasseter University-of-Wisconsin

PSERC

Micro Grid

open

• Solid state breaker

• Generation & storage

Control of P &Q using PWM

Basic P & Q Response

Micro Grid connected to T/D Grid

Micro-Sources Provide

• Control of local bus voltage

• Control of base power flow

Fast Load tracking is provided by the grid

Micro Grid: Dispatchable load to the grid

R.H.Lasseter University-of-Wisconsin

PSERC

Micro Grid • P control

Isolated Micro Grid

Issues

R.H.Lasseter University-of-Wisconsin

PSERC

P V Controller with Droop

E

E 0 1

Q E

P & Q Calculation V

Eo

s

Flux Vector

+ _

Island

Micro Grid

open

• Solid state breaker

• Generation & storage

Voltage on Buses 8 & 9

PSERC

Injected P & Q Buses 8 & 9

R.H.Lasseter University-of-Wisconsin

PSERC

Frequency at bus 8

Time seconds

R.H.Lasseter University-of-Wisconsin

PSERC

Sensitive loads

(Quality & Service )

Power Quality is the attribute of

electric power which enables

electronic equipment to operate

as intended

R.H.Lasseter University-of-Wisconsin

PSERC

Shunt current injection

Premium Power Micro Source

Voltage Sag Regulator

Micro Grids & Premium Power

• Generation Close to loads

Further Research Needs

1 Clear interfaces/functions to the

Grid

2 Micro-Grid protection

3 Plug & play controls

4 Placement tools including CHP

R.H.Lasseter University-of-Wisconsin

PSERC

1

Standard for Interconnecting Distributed Resources with Electric Power Systems

IEEE SCC21 1547 Series of Interconnection Standards

Distributed Resources with Electric Power Systems

Guide for Networks

P1547.3

Draft Guide for Monitoring,

Information Exchange and

Guide for Impacts

Design, Operation, and Integration of Distributed Resource Island Systems with Electric Power Systems

P1547.1

Draft Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power DP Specifications and Performance Electric Power

Systems (includes modeling) Systems

The above identifies existing IEEE SCC21 standards development projects (1547 series)

and activities under discussion by SCC21 Work Group members

IEEE P1547.5 Project

Title P1547.5 Draft Technical Guidelines for Interconnection of

Electric Power Sources Greater than 10MVA to the Power

Transmission Grid

Scope This document provides guidelines regarding the technical

requirements, including design, construction, commissioning

acceptance testing and maintenance /performance requirements, for interconnecting dispatchable electric power sources with a capacity of more than 10 MVA to a bulk power transmission grid

Purpose The purpose of this project is to provide technical information

and guidance to all parties involved in the interconnection of

dispatchable electric power sources to a transmission grid about the various considerations needed to be evaluated for establishing

acceptable parameters such that the interconnection is technically

correct

Sponsor: SCC21 - Fuel Cells, Photovoltaics, Dispersed Generation, and

Energy Storage

Sponsoring Committee Chair: Dick DeBlasio

PAR approved by IEEE September 2004 (project authorization request);

ballot to be completed by December 2007

3

Content

¾ IEEE Standards

¾ 1547 Series of Standards

• ANSI/IEEE Std 1547 (2003): Standard for interconnection

system & interconnection test requirements for

interconnecting DR with Electric Power Systems (EPS)

• P1547.1 Standard for interconnection test procedures

• P1547.2 Guide to 1547 standard

• P1547.3 Guide for information exchange for DR

interconnected with EPS

• P1547.4 Guide for DR island systems

• P1547.5 Guide for interconnection to transmission grid

4

Communications - Information Flow, Data

Management, Monitor & Control Interconnection

Distributed Generation Combined Heat

& Power

sensors

Interconnecting Power Systems

The overall power system is traditionally viewed in terms of

7 layers; each performing its function from central station 6

generation supplying power out to customers