Smart Grid Update

7/29/2019 Smart Grid Update

1/26

1IEEE USA 5-4-2012

Smart Grid and Renewable

Energy Grid IntegrationJian Sun, Professor and Director

Department of ECSE & Center for FutureEnergy Systems


2/26

2IEEE USA 5-4-2012

How Smart Can WeMake This Grid?


3/26

3IEEE USA 5-4-2012

Smart Grid Drivers Need to Use Renewable Energy

Peak Oil; Energy Security GHG Emission; Climate Change

Electrification of Transportation Sector

Energy Storage

Demand Response; Efficient Utilization

Stronger Transmission Network Intelligent, Bidirectional Distribution System


4/26

4IEEE USA 5-4-2012

Energy is a National Priority

1

2

3

Energy

Security

Climate

Change

Green

Economy

Nuclear

Energy

R

enewable

Energy

Energy

Efficiency


5/26

5IEEE USA 5-4-2012

Role of Power Electronics

Smart Grid

Renewable

Generation

Renewable

Generation

Energy

Storage

Energy

Storage

Load

Manag.

Load

Manag.


6/26

6IEEE USA 5-4-2012

With Electric Machines With Power Electronics

t

Production of AC

B()

v(t)


7/26

7IEEE USA 5-4-2012

Traditional vs. Wind Generators

0.01 0.1 1 10 100 1000 10000Frequency (Hertz)

Prime Mover

Control

Prime Mover

Control

Excitation

Control

Excitation

ControlTraditional

Generator

SemiconductorSwitching

SemiconductorSwitchingCurrentControlCurrentControl

DC-Link

Control

DC-Link

Control

Turbine SpeedControl

Turbine SpeedControl Grid Q & VControlGrid Q & VControlLa

rgeWind

G

enerator Grid

Synchronization

Grid

Synchronization

Limited Controllability at Low

Frequencies

Complex Control & Dynamics

at High Frequencies

Limited Controllability at Low

Frequencies

Complex Control & Dynamics

at High Frequencies


8/26

8IEEE USA 5-4-2012

0.1 1 10 100 1000 10000 100000.

Grid Operation & Control

102

103

109

102 0.1 1 10 102 103 104 Hz

105

106

107

108

104

Central Control

Manual Dispatch

Control Frequency (F)

Numbe

rofUnits(N)

102

103

109

105

106

107

108

104

Fast, Autonomous Control

of Many Units


9/26

9IEEE USA 5-4-2012

Impedance is a Key Parameter

c

1

PhaseMargin

Gain

Margin

Im

Re

Partition System into a Source and a Load Subsystem

Determine Source Subsystem Output Impedance (Zs) and LoadSubsystem Input Impedance (Zl)

System is Stability ifZs/Zl Meets Nyquist Stability Criterion

+

Zs

ZlVs Vl

+

Source Load

)(

)(1

1)()(

)()()(

sZ

sZsZsZsZ

sVsV

l

ssl

l

s

l


10/26

10IEEE USA 5-4-2012

Grid-Parallel Inverter Stability

Grid-Connected Inverters are Controlled as Current Sources

Different System Model and Stability Requirement

Ratio of Grid Impedance to Inverter Output Impedance MustMeet Nyquist Stability Criterion

Voltage-Source System Current-Source System


11/26

11IEEE USA 5-4-2012

An Example Solar Inverter


12/26

12IEEE USA 5-4-2012

Grid Impedance Line + Transformer + Generator Impedance

Typically Inductive at Fundamental Frequency Focus of Traditional Power System Theory

Weak Grid

Resonance at Harmonic Frequencies

Effects of Loads; Variability with Time

Effects of Neighboring Renewable Sources Active Control; Different from Passive Impedance


13/26

13IEEE USA 5-4-2012

Inverter Output Impedance Depends on Physical Design and Control

Filter Inductors and Capacitors (L, LC, LCL) Current & Voltage Control, Grid Synchronization

Inverter Impedance Modeling

Native Circuit & Control Models are Nonlinear

Small-Signal Impedance has to be Used

Time-Varying Operation; No DC Operation Point

Traditional Linearization Methods cannot be Applied


14/26

14IEEE USA 5-4-2012

Small-Signal Modeling Phasor-Based Methods

Not Compatible with Impedance-Based Analysis Limited to Line Fundamental Frequency

DQ-Transformation Method

Impedance in DQ-Coordinate System is Difficultto Measure and Interpret

Coupling between DQ Axes Requires Generalized

Nyquist Criterion

Direct Harmonic Linearization


15/26

15IEEE USA 5-4-2012

Three-Phase Converter Modeling Decomposition Using Symmetric Components

Positive-Sequence Impedance

Negative-Sequence Impedance

Zero-Sequence Impedance Usually Open-Circuit

Single-Phase Model for Each Sequence Component

No Crossing Coupling between Positive and NegativeSequence Subsystems

va

vb

vc

ia

ib

ic

ip in+

vp

+

vp

Positive Sequence Negative Sequence

+


16/26

16IEEE USA 5-4-2012

Smart Grid System Test-Bed Need a Controllable Grid to

Emulate Different Grid Conditions

Test Analysis Method and System Theory

Demonstrate System Control Techniques

A System Test-Bed has been Developed

Grid Simulator

Programmable Voltage, Frequency, Harmonic Contents,

and Impedance

Single or Three-Phase Operation, 75 kW Power

Standalone, Grid Parallel Mode, Micro Grid


17/26

17IEEE USA 5-4-2012

Simulate

dGridwithProgrammable

SimulatedGridwithProgrammable

Volt/Freq/Impedance

Volt/Freq/Impedance

PV SimulatorsPV Simulators

CentralCentral

Inverters (3)Inverters (3)

Inverters(20)

Inverters(20

)

=~

44thth Gen Wind Turbine SimulatorGen Wind Turbine Simulator

ElectronicElectronic

LoadsLoads

~= MMMGGG

= ~

=~

=~

UtilityUtilityGridGrid

=~

Grid SimulatorGrid Simulator


18/26

18IEEE USA 5-4-2012

Single-Phase Solar InverterGrid Voltage (500V/div)

Grid Current (10A/div)

Lp = 0 mH

Grid Voltage (500V/div)

Grid Current (10A/div)

Lp = 12.8 mH


19/26

19IEEE USA 5-4-2012

Harmonic Resonance

0

1

2

3

4

5

2 7 12 17 22 27 32 37

Lp = 0 mH

Lp = 12.8 mH

Ih/I1 (%)

h


20/26

20IEEE USA 5-4-2012

Three-Phase Wind Inverter

rd

ib (5 A/div.)ia (5 A/div.) ic (5 A/div.)

Sequence Gain Margin Phase Margin

Positive 1.04 dB 5

Negative 15 dB 42

Sequence Gain Margin Phase Margin

Positive >15 dB 25

Negative >15 dB 55

PLL Bandwidth 100 Hz PLL Bandwidth 10 Hz


21/26

21IEEE USA 5-4-2012

Nature of Harmonic Resonance


22/26

22IEEE USA 5-4-2012

Inverter Impedance Shaping Grid Synchronization Methods

Current Control Loop Active Damping

Online Grid Impedance Identification

Adaptive Control

Inverter Interactions in Wind Farms


23/26

23IEEE USA 5-4-2012

HVDC for Offshore Wind Farms

Speed

Source

1600 rpm

mech

690 V

7 km

PM

Speed

Source

1600 rpm

mech

690 V

7 km

PM

SpeedSource

1600 rpm

mech

690 V

7 km

PM

Speed

Source

1600 rpm

mech

690 V

7 km

PM

Speed

Source

1600 rpm

mech

690 V

7 km

PM

400*2.5MW Turbines

33kV AC

Bus

7km Cable

Direct-Drive Technology HVDC Rectifier

(VSC or LCC)

HVDC

300 MVA

STATCOM

300 MVA

STATCOM

ACBus

Filters

ACBus

Filters

Stability & Control of AC Collection Bus


24/26

24IEEE USA 5-4-2012

Multi-Terminal HVDC

DC Output from Individual Turbines

Series and Parallel Connections

Modular Voltage-Source Converter Design


25/26

25IEEE USA 5-4-2012

=~

=~

=~

=~

=

~

=~

~=

Utility GridUtility Grid

RealReal--TimeTime

SimulatorSimulator

AC DGAC DG

TestTest--BedBedMTHVDC

MTHVDC

Hybrid AC-DC System Test-Bed


26/26

26IEEE USA 5-4-2012

Summary Renewable Energy and Electric Transportation Will

Drive Smart Grid Development

Energy Storage and Demand Management Required

Ubiquitous Use of Power Electronics

New Stability Problems at High Frequencies

New Modeling and Analysis Tools Needed

Fast, Autonomous Control are Essential

New Impedance-Based System Analysis Methods

Hardware-in-the-Loop System Test-Bed for

Validation and Demonstration

Smart Grid Update

Documents

Transcript of Smart Grid Update