Post on 12-Apr-2018
Power Electronics for Distribution Grid and WBG Opportunities
Fred Wang University of Tennessee and Oak Ridge National Lab
NIST/DOE Workshop on MV WBG Power Electronics for Advanced Distribution Grids
NIST, Gaithersburg, MD April 15, 2014
Power Grid Wide Area Control of
Power Grid with High RES Penetration
Measurement &Monitoring
Communication
Actuation
Communication
FDR PMU
Storage
HVDC
Wind Farm
FACTS
Solar Farm
Responsive Load
CURENT Vision
2
Smart and Flexible Microgrid
PCC
PCC
PCC
Local protective devices
Local controllers
Microgrid central controller
System control
Normal open smart switch Normal closed smart switch
Electrical network Communication and control network
3
Power Electronics for Distribution Grid – Custom Power
• Power system conditioning and compensation
• Power flow control/interruption
SSTS SSCB SSFCL
• Active filters
SVC TCVR DSTATCOM DVR
Shunt AF UPQC 6
Power Electronics for Distribution Grid – Emerging Needs
• Microgrid (AC or DC)
• RES Interface
• Energy Storage/Charging
7
Power Electronics for Distribution Grid – More Recent Development
Solid-state Transformer Controllable Network Transformer
Continuously Variable Series Reactor 8
HV WBG Devices in MV Applications
Applications should take advantages of • Low loss • Fast switching speed • High frequency application
Benefits of HV SiC can be realized in several ways • Direct substitution – improved efficiency and power density
• Simplified topology – further loss reduction and increased power density
• Enable new capability and functionality for system-level
• Enable new applications or replace the non-PE equipment
Wide band-gap (WBG) vs. Silicon • High breakdown electric field, high voltage rating, low conduction loss • Fast switching speed, high switching frequency • Superior thermal characteristics
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Impact of DC Breaker Speed
10
With Fast DC Breaker
0.9 1 1.1 1.2 1.3 1.4-2
0
2
Cur
rent
(p.u
.)
0.9 1 1.1 1.2 1.3 1.4-2
0
2
Cur
rent
(p.u
.)
0.9 1 1.1 1.2 1.3 1.4-2
0
2
Cur
rent
(p.u
.)
0.9 1 1.1 1.2 1.3 1.4-2
0
2
Time(s)
Cur
rent
(p.u
.)
VSC 3
AC Grid I
VSC 1
VSC 4 VSC 2
AC Grid II
Wind Farm I
Wind Farm II
DC cable 1
DC cable 2
DC
cable 4
DC
cable 3
With Slow DC Breaker VSC 1 AC Currents
VSC 2 AC Currents
VSC 3 AC Currents
VSC 4 AC Currents
0.9 1 1.1 1.2 1.3 1.4-2
0
2
Cur
rent
(p.u
.)
0.9 1 1.1 1.2 1.3 1.4-2
0
2
Cur
rent
(p.u
.)
0.9 1 1.1 1.2 1.3 1.4-2
0
2C
urre
nt (p
.u.)
0.9 1 1.1 1.2 1.3 1.4-2
0
2
Time(s)
Cur
rent
(p.u
.)
VSC 1 AC Currents
VSC 2 AC Currents
VSC 3 AC Currents
VSC 4 AC Currents
Impact of Switching Frequency on Stability
is
it
vt
+
−
Yoc
Zg vg
+
−
Inverter Grid
196° (unstable)
162° (stable)
Passive region
Inverter admittance Yoc (with fsw = 10 kHz)Grid admittance Yg
Inverter admittance Yoc (with fsw = 20 kHz)
Frequency [Hz]
Phas
e [D
egre
e]M
agni
tude
[dB
]
Time [s]
Grid current
Inverter current
[A]
[A]
Time [s]
Grid current
Inverter current
[A]
[ A]
fsw = 10 kHz
fsw = 20 kHz
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WBG Potential Applications in Distribution Grid
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• Improve the performance of the existing PE equipment Efficiency improvement for all; density improvement for some;
performance improvement (e.g. CB)
• Replace non-PE equipment SST
• Enhance functionality/capability Smart inverter
• Enable new applications DC grid high bandwidth conditioner direct-tied PV inverter
12
Potential Research Needs • A benchmark study to understand the system benefits of HV SiC
for distribution grid applications and help to identify the potential early adopters and killer applications.
• System architecture, topology and control of the identified applications
• Identify the required performance characteristics of HV SiC and associated components and subsystems for grid applications:
Required and/or desired SiC device characteristics and performance (normal and abnormal conditions)
Control and protection
Passive components and filters (for dv/dt, di/dt, EMI etc.)
Thermal management
Standardization/building block for cost and reliability?
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