01-introduction to vsc
DESCRIPTION
introduction to voltage source converterTRANSCRIPT
ECE 636– B2
Dynamics and Control of Voltage Source Converters (VSCs)
Winter 2013
Instructor: Dr. Yasser Mohamed Electrical and Computer Engineering Dept. University of Alberta Office W2-014 – ECERF email: [email protected]
1
Lecture 1 – Introduction
Outline
• What is a Voltage Source Converter?
• The importance of Voltage Source Converters in modern energy systems
• Course Organization
2
What is a Voltage Source Converter? A Voltage Source Converter can be seen as a
Flexible Power Electronic-Based Voltage Source
- Similar to a synchronous machine, which is is a key component in power systems, VSCs are key components in future distribution and power system. A VSC can be seen as flexible synchronous machine (motor or generator). 3
gI
V
LV
E
Two-way power flow
fRgLi fL
fC
gRgidcV
DC
Sy
stem
PWM
v+
-
e+
-
Grid
AC system
AC-side filter (LC)
VSC
Control
signal
))()(cos()( ttttVv mc
Control and signal
processing
MeasurementsMeasurements
Semiconductor
switching cells
vo
lta
ge
harmonic order
1
h n
Pulse width modulation
(PWM)carrier and sideband
harmonics
What is a Voltage Source Converter?
The frequency behavior of VSCs
- - The VSC can operate at wide range of frequencies, multiple
frequencies can be intentionally included in the control signal.
1 h n
. . . .
Unwanted harmonics!
Fundamental
component Injected harmonics
(for specific control
functions)
4
gI
V
LV
E
gI
V
LV
E
gI
V
LV
E
The importance of VSCs Flexible AC Transmission Systems (FACTs)
High voltage DC (HVDC) transmission system based on VSC ABB – HVDC Light up to 1,200 MW at ± 500kV dc (modular VSCs)
VSC HVDC system is utilized in - Connecting wind farms to power grids - Underground power links - Connecting asynchronous grids - City center in-feed - Increasing power carrying capability versus transient stability - “Firewall” connection in large AC systems
Rectifier
station
Inverter
station
5
The importance of VSCs
High voltage DC (HVDC) transmission system based on VSC
330 MW HVDC light converter
station.
Source: ABB 6
The importance of VSCs
separate control loops active and reactive power active power control
one station controls the active power other station controls the DC-link voltage
reactive power control reactive power or AC side voltage
HVDC based on PWM grid converter offers . .
7
The importance of VSCs
Multi-terminal VSC-based Network 8
Average
Model of
Ideal
Three
Phase VSC
Vnull
PLL
abc to dq ρ ρ
Vsq
Vsd
R+ron ia
ib
ic
L
L
L
R+ron
R+ron
+Vsa-
iqid
ia ib icmcmbma
Vta
Vtb
Vtc
iLoss C
iDCiext
-
V
DC
+
PextPDC
Pt Ps and Qs
+Vsb-
+Vsc-
VSC-m
Average
Model of
Ideal
Three
Phase VSC
Vnull_2
PLL
abc to dq
ρNVsq
Vsd
R+ron ia
ib
ic
L
L
L
R+ron
R+ron
+Vsa-
iqid
ia ib icmcmbma
Vta
Vtb
Vtc
iLoss
iDC
-
V
DC
+
Ps and Qs
+Vsb-
+Vsc-
VSC-PQ
K (s)+-
Id _ ref V DC2
_ ref
++
G-1
i (s)
P f (s ) G N -i (s)e(t)
(.)2
V DC _ ref
(.)2
V DC _ ref
Id _ ref
+-PI
Controller
I d
V sd
Iq _ ref PI
Controller
I q
V sq
+-
-2 / Vdc
2 / Vdc
m d
m q
K (s)+-
V DC2
_ ref
++
G-1
i (s)
P f (s ) G N -i (s)e(t)
(.)2
V DC _ ref
(.)2
V DC _ ref
Ps
Id _ ref
+-PI
Controller
I d
V sd
Iq _ ref PI
Controller
I q
V sq
+-
-2 / Vdc
2 / Vdc
m d
m q
dq to abc
m qm d
m cm bm a
Sequence Analyzer
and
Phase - Locked - Loop ( PLL )
V sa V sb V sc V ta V tb V tc
V sd+ V sd
- V sq+ V sq
- V td+ V td
- V tq+ V tq
-
Dual - Sequence Current -
Command Generator
Id- Iq
+ Iq-
Qs _ ref
Proposed DC -Voltage Control System
Zone I: VSC-m: DC-Voltage Power Port connected to Grid1
L1
CLVL
S1
S2
iL1iESS
Average
Model of
Ideal
Three
Phase VSC
abc to dq ρ
ron
ron
ron
iqid
ia ib icmcmbma
CW
PMSG
CH
Zone II: PQ VSC
connected to grid 2
Zone IV: DC Micro-grid with
Energy Storage System (ESS)
Id_ref
+-Current
Controller
Id ωLs
Σ
Vsd
Iq_ref Current
Controller
Iq ωLs
Σ
Vsq
+-
-2/Vdc
2/Vdc
md
mq
Wind Turbine Current Controller:
VL
VL_Ref+-
PI
ControllerPWM
S2
iL1
iL_Ref+-
PI
ControllerPWM
S1
S1=0
S2=0
Bidirectional DC-DC Converter:
Voltage Controller; buck mode
Current Controller; boost mode
Ccable
Grid 1
Grid 2
PDCPt
DC Energy
Pool
Main
Breaker
VCap_Charger
Interlocked
breaker #1
ρωL
ωL
Zone III: Full-Scale Wind Turbine
with AC/DC VSC Positive-sequence
current controller
Dual Sequence Current
Controller
Ps_ref
and
PLL
Vsa Vsb Vsc Vta Vtb Vtc
Vsd+ Vsd
- Vsq+ Vsq
- Vtd+ Vtd
- Vtq+ Vtq
-
Dual-Sequence Reference-
Current Generator
Id+ Id
- Iq+ Iq
-
Qs_ref
Sequence Analyzer
Rcable
Lcable
Rcable
Lcable
Rcable
Lcable
Rcable
Lcable
RDC
Mode 2:
Buck Mode
Mode 1:
Boost Mode
+
VL
-
Σ
Σ
VSC-W
Energy
storage
DC-micro-
grid load
ρN
The importance of VSCs VSC STATic Compensator (STATCOM) for reactive
power compensation or voltage regulation
Flexible wide range capacitive/inductive reactive power control AC voltage control at the point of common coupling
to support the transmission system
9
STATCOMPCCVLV
GV
q
Holly STATCOM – Austin –Texas – Source: ABB.
The importance of VSCs VSC STATic Compensator (STATCOM) for reactive
power compensation or voltage regulation
10
Field measurement of STATCOM response during a transmission line fault (Austin,Texas, 2004): a) Three VSC phase currents b) DC voltage c) VSC reactive current reference calculated by the control system d) 138 kV system line-to-ground voltages.
The importance of VSCs
Distributed Power Grids
11
Future Power System
Less central power plants and more Distributed Power Generation Systems
VSCs are the main interfacing medium for renewable/clean generation units and modern loads
Current Power System
The importance of VSCs
Interfacing Renewable/Clear Energy Resources
12
Rotor
Power conversion &
power controlPower transmission
Gearbox (obtional) Generator
Power conversion
Power converter
(obtional)
Power conversion &
power control
Supply grid
Power transmission
Wind power
Mechanical power Electrical power
Electrical control
Power control
Pref Qref
Consumer
Wind systems require optimized grid converter at high power New turbines go up 7.5 MW with full scale power converter (VSC)
The importance of VSCs
Interfacing Renewable/Clear Energy Resources
13
Doubly-fed is the most adopted soltion in wind systems
PM-synchronous
Generator
Multi-pole
Pitch
GridDC
AC
AC
DC
Pref Qref
Gear
Induction
generator
Pitch
DC
AC
AC
DC
Pref Qref
Gear
Doubly-fed
induction generator
Pitch
Grid
DC
AC
AC
DC
Pref Qref
Full power converter can be used either with asynchronous generator or synchronous generator (multipole permanent magnet gearless solution is the most promising)
The importance of VSCs
Interfacing Renewable/Clear Energy Resources
14
PV Panels
String
dc-dc
boost
LCL
Low pass
filter
C
VPV
IPV
+
-
L
N
Trafo
&
Grid
Anti-Islanding
Protections
Grid /PV plant
Monitoring
Ig
Vg
dc-ac
PWM-VSI
VdcPWM PWM
MPPT
Active filter
controlGrid support
(V,f,Q)
Ancillary functions
PV specific functions
Basic functions (grid conencted converter)
Current
Control
Vdc
Control
MicroGrid
Control
Grid
Synchronization
Photovoltaic systems require high-efficient and multi-functional grid converters
The importance of VSCs
15
Power Quality Conditioners A
CT
IVE
FIL
TE
R
load
AC
TIV
E
FIL
TE
R
load
LVGV
Series and parallel (or hybrid series/parallel) active power conditioners enhance grid power quality compensating voltage sag, harmonic, reactive power, etc .
The importance of VSCs
16
Converter Interfaced Loads
PCCVLVGV
ACTIVE
RECTIFIER
p
load
load Active rectifier is adopted as
active front-end for medium and high power loads like multi-drive systems and single drives working frequently in regenerative operation like cranes, elevators . .
Motor drive load
The importance of VSCs
17
Converter-Based Machine Drives Loads
Induction motor drive
The importance of VSCs
18
Converter-Based Machine Drives Loads
Permanent-magnet motor drive
The importance of VSCs
19
Distributed Generation Micro-grids AC Micro-grid
Local-generation to meet the load demand Higher efficiency and power quality High reliability by providing backup power during utility supply outage
The importance of VSCs
20
Distributed Generation Micro-grids
Hybrid AC/DC Micro-grid
Vin Iin
Cdc
Lf Rf
Cf
vo io
Utility Grid
L g Rg
i
Lf R f
Cf
vo iov i
Feeder Feeder
AC-
Loads
AC-Bus
AC-BusVSC-1
VSC-2
DC Bus
Microturbine
Fuel Cell
Storage
dc-load Direct
dc-load
DC Micro-grid
Utility Grid
Interface
AC micro-grid
Interface
vg
Islanded Micro-grid
Utility Grid interfacingDG Park
Idc
DC Bus
v
Common
DC-Link
PMSM
M
Vdc
SW
Yload1
Yload2
Yload3
Ysource Idc1
Idc2
Idc3
The importance of VSCs
21
Hybrid Electric and All-Electric Vehicle
High efficiency energy conversion by VSCs
Two-way power flow (motoring, generation)
Fast low-level control for robust and fast high-level energy management and control
Course Scope and Content Voltage source converters (VSCs) are gaining increased acceptance and importance in energy systems. This course presents key Modeling, Analysis and Control aspects of VSCs. Key topics include: 1) DC/AC Half-Bridge Converter 2) Control of DC/AC Half-Bridge Converter 3) Space Phasors and Two-Dimensional Frames 4) Two/Three-Level 3-phase VSC 5) Control of Grid-Connected VSC in Stationary Reference Frame 6) Control of Grid-Connected VSC in Rotating Reference Frame 7) Control of VSC in Autonomous Mode (isolated micro-grid mode) 8) Variable-Frequency Control of VSC 9) Applications: 1) Static Compensator (STATCOM) 2) ) HVDC 3) Distributed Generation Micro-grids 4) Active Power Filters 5)Wind Energy Conversion Systems
Course Organization
22
Course Objectives
Course Organization
• Review fundamentals (circuit construction, principle of operation and modeling) of half-bridge, 2-level VSCs and multi-level VSCs
• Understand different operation modes of VSCs (current-controlled, voltage-controlled, grid-connected, isolated micro-grid, variable frequency, etc.)
• Understand and implement switched and average models of VSCs
• Understand and design simple and effective control algorithms for VSCs
• Understand VSC converter operation and control in key applications
23
Course Prerequisites
Course Organization
24
• Basic understanding of power electronic converters, power systems and control theory.
• Familiarity with a programming language and/or a simulation package such as MATLAB/Simulink or EMTDC/PSCAD.
A. Yazdani and R. Iravani, Voltage-sourced converters in power systems, Modeling, Control, and Applications, John Willy, 2010, ISBN 978-0-470-52156-4.
ECE636 Lectures Notes (slides). Will be available on eClass.
Main Teaching Materials
Other References
Course Organization
25
M. P. Kazmierkowski, R. Krishnan, F. Blaabjerg, “Control in Power Electronics”,
Academic Press, 2002, ISBN 0-12-40277205. B. Bose, “Modern Power Electronics and A.C. Drives”, Prentice Hall, 2001, ISBN
013016743 Background references: N. Mohan, T. M. Undeland and W. P. Robbins, “Power Electronics: Converters,
Applications, and Design” Wiley, 2002, ISBN-10: 0471226939 B. Kuo, Digital Control Systems., Oxford University Press, New York, NY, USA,
1992. Chi-Tsong Chen, Linear Systems Theory and Design, - Oxford University Press,
1999 – ISBN 0195117778
Reading Assignment (25%)
Simulation Project (25%)
Final Exam (50%)
Grading Scheme
Course Organization
26
Reading Assignment (25%)
A well-written report detailing a comprehensive critical survey on an application related to VSCs. Report should be based on a fair number of IEEE journal papers (at least 10~15 papers) related to the reading topic.
Simulation Project (25%)
Reproduction of results reported in a journal paper by simulation. One of the papers used in the reading assignment can be used for a simulation project. Softcopy of developed models should be submitted with your simulation project report.
Final Exam (50%)
Based on a good understanding of course topics; this is a grad-course!
Grading Scheme Description
Course Organization
27
One page Abstract on proposed reading topic and project for Instructor’s approval: Jan. 31, 2013
Reading Assignment Report and Simulation Project Report: April 18, 2013
20-minute presentation summarizing Reading Assignment and Simulation Project findings: (Last 3 lectures)
Final Exam: Date: TBD
Important Dates
Course Organization
28
Grid interfacing system for photovoltaic arrays
Doubly-fed induction generator-based wind turbine system.
Full-scale permanent-magnet synchronous generator-based wind turbine system
Grid interfacing system for fuel cells
Grid interfacing system for micro-turbines
VSC-based high voltage DC transmission (HVDC) system
Multi-level VSCs in renewable energy applications
Multi-converter distributed generation AC micro-grid
Multi-converter DC micro-grid
Parallel operation of VSCs
Fault-ride-through control of doubly-fed-based wind turbines
Reading Assignment/Simulation Project Topics
Course Organization
29
VSC-based unified power quality conditioner
VSC-based dynamic voltage restorer
Coupled inductor VSCs
Modeling and real-time simulation of VSCs
VSC for energy storage applications
VSC-based STATCOM (or distribution STATCOM – DSTATCOM)
Mechanical-sensorless VSC-fed induction motor drive
Mechanical-sensorless VSC-fed permanent-magnet synchronous motor drive
Flexible VSC-based distributed generation
VSC versus Z-source converter
VSC versus current source converter
Reading Assignment/Simulation Project Topics
Course Organization
30
Notes: Reading Assignment/Simulation Project
Cannot be something that you have already done.
Must have a strong VSC modeling and control components.
New ideas and justified improvement suggestions have higher weights.