features and protection - energy
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© SEL 2020
Challenges and Solutions in Microgrid Controls and Protection
Scott Manson
SEL ES Technology Director
Complexity
TimeInvention
Features
added
Reset
Recent microgrid advancements
Conventional solution
Advanced relay solution
Self-configuring communications
No tuning controls
Meter
Relay 25
Meter
Relay 25
Utility
Genset
Battery
PLC
LS
AVRGOV
ControllerPCPLC
Microgrid
controller
PCInverter
Meter
Relay
HMI
Microgrid controller
Recent microgrid advancements
Conventional solution
Advanced relay solution
Self-configuring communications
No tuning controls
Utility
Genset Inverter
Battery
Advanced
relay
Advanced
relay
Advanced
relay
Recent microgrid advancements
Conventional solution
Advanced relay solution
Self-configuring communications
No tuning controls
Hi! I’m a generator.
Great! Send me data.
Generation
relay
PCC relay
Tactical Microgrid Standard
Recent microgrid advancements
Conventional solution
Advanced relay solution
Self-configuring communications
No tuning controls
Tactical Microgrid Standard
Recent microgrid advancements
Conventional solution
Advanced relay solution
Self-configuring communications
No tuning controls
Frequency
(Hz)
Power
(kW)
60
58
56
30
0
15
Antiquated controlsState-space energy
packet controls
0 50 100 150 200250 30047
49
51
53
55
Isochronous mode
Generator tripAutomatic synchronization start
Circuit breaker open
Underfrequency Level 1
shed 0.93 MW
Oscillation start governor
Time (seconds)
Fre
qu
ency (
Hz)
Power (MW)
10 14 18
Microgrid instability caused by load efficiency improvement project
1 /
R (
MW
/ H
z)
0
Gain
0.02
0.04
0.06
0.08
1 10 100 1,000
Grid size (MW)
10,000
STG-A, -B, and -C
(50-fold)
STG-D
1
10
100
1,000
1 10 100 1,000
Grid size (MW)
10,000
Small grid
Large grid
Utility gridObserved
Predicted
Curve fit
Microgrid instability caused by load efficiency improvement project
PI
Variable load compositions negatively impact microgrid resiliency
Topology R –R DOL
1 60% 0% 40%
2 50% 50% 0%
P = V • IR =
I
V
Inverters create “twitchy” power systems
Power
Frequency
LoadPower,
frequency
Time
Rotating generation frequency
Rotating generation power
Inverter-based power
Inverter-based frequency
Mea
sure
d fre
quen
cy (
Hz)
60.04
60.02
60.00
59.98
59.96
59.94
Power (kW)
– 0 20 40– 60
Power (kW)
– 0 20 40
Synthetic inertia makes inverters difficult to dispatch
Correct behavior Actual behavior
Inverters produce less fault current than generators
Silicon limit time Stop commutation time
Inverter fault currents produce inconsistent Clark, Parks, and Sequence components
Inverter fault currents are restricted by inverter and battery health
Battery SoC
dynamic limits
Battery SoC
dynamic limits
Power systems are safer when inverters are controlled by programmable relays
Recording shows “day in the life of a relay”
Loads
Loads
PCC
SEL-751
655 15 25 35 45 55Time (cycles)
–
5,000
0Voltage (V)
–
500
0Current (A)
Recording shows “day in the life of a relay”
Recording shows “day in the life of a relay”
0.8 10.60.40.20Time (seconds)
59
60
Frequency
(Hz)
VAB
voltage
(kV rms)
0
20
0
700
IA
current
(A rms)
Relay trips
Fault starts
Breaker
opens
Microgrid controller
sheds load
Load current
is interrupted
Frequency recovers!
5 6 7 8 9 10
50.5
49.5
49
50
51
Time
Frequency
(Hz)
Nonresilient power systemcHIL simulation
Island 1
Island 2
Island 3Island 6
Island 5
Island 4
Same power system with SEL relay controlcHIL simulation
34 35 36 37 38 39
50.5
49.5
49
50
51
Time
Frequency
(Hz)
cHIL testing improves microgrid ROI
0 10 20 30 40 50 60–20K
–15K
–10K
–5K
0
5K
USD
Iteration
SDN simplifies security for critical infrastructure
Whitelisting
Minimal software
U.S. manufacturing
Mature processes
Vertical integration
Policy, plan, and procedure
SEL-2742S SDN Switch Additional SEL devices
Connect with us
info@selinc.com
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