10.3_practical implementation of microgrid control, protection, and communications_manson_sel
TRANSCRIPT
Practical Implementation of Microgrid Control, Protection, and Communications
Scott MansonTechnology Director, SEL
Control Cost, Quality, FeaturesHardware-in-the-Loop Testing
Both Mechanical and Electrical Systems Must Be Modeled Accurately!
Controller
Inputs
ControllerStatus
Controls
Dynamic Simulation
System
Outputs
0.961.0
Power (pu)
Frequency (pu)
1.0
Steady-State Droop Line
3
21
Transient Governor Behavior
Governor Frequency Set Point
Factory Acceptance Tests Improved With Hardware-in-the-Loop Testing
66
65
64
63
62
61
60
590 10 20 30 40
Time (s)
Freq
uenc
y (H
z)
Field
Simulation
Inverter-Based Generation Has Limited Overload Capacity
Short-Term Capacity Limit
Long-Term Capacity Limit
Inverter-Based Generation
Q
P
Rotating Generators
Q
P
Load Balancing Must Happen Faster With Inverter-Based Generation
Pow
er, F
requ
ency
Time
Rotating Generation Power
Rotating Generator Frequency
Power
Frequency
Load
Inverter-Based Power
Inverter-Based Frequency
FAST Load Shedding Prevents Blackouts
Grid-Tied Operation
Islanded Operation
Synchronization Systems
Automatic Decoupling
Load Shedding
Subcycle FAST
Controller
Relay
Status Trip
PF Deadband
–PF
+PF
–P +P
–PF
+PF
+Q
–QEnlargement of Origin
–100 +100
–50
+50
Deadband Control
Boundary
+28.9
PFsp1, sp2
PFactual1
PFactual1
+0.5
PF–0.5 PF
+0.5
PF –0.5 PF
Power Factor Control Limits Must Be Considered Carefully!
Frequency and Voltage Define Power System Resilience
1/f
t
f
V
V
2V
63
57
Rotating Generator
Sets
1.3 0.7
Generation Shedding
Load Shedding
Allowable Operation
65
1.2 0.8
55
Inverter Technology
A
CB2 CB157
60
63
f (Hz)
B
Reliability Improved With Several Load-Balancing Techniques
CB1 Opens:Contingency
Load Shedding Island Generator
AutobalancingAka “AGC”
CB2 Opens
Underfrequency Load Shedding
Overfrequency Generation Runback
How Much “Responsive” Generation Is Required to Ensure Stability?Step 1: Identify grid time constants
+
–
–DER Frequency/Droop Controller
Steady-State Electrical Load
Frequency
+ –
Simplification
Frequency
1JS
1R
2
R1 S
DER Frequency/Droop Controller
Power System 2 (seconds)Utility 0.5 to 1.2 Microgrid 0.25 to 2.5
How Much “Responsive” Generation Is Required to Ensure Stability?Step 2: Tabulate Incremental Reserve Margins (IRM)
DER Rating (kW) IRM (%) IRM (MW)PV 200 0 0Battery (SLOW) 1000 5 50Battery (FAST) 1000 100 1000Steam Extraction Turbine 1200 0 0CHP 900 10 90Gas Turbine 1500 40 600Diesel Genset 1000 40 400Totals 6800 31.5 2140
How Much “Responsive” Generation Is Required to Ensure Stability?Step 3: Compare Total IRM to Largest Disturbance
Event kWSmall Motor 200LCI drive 2000Large Feeder 5000Small Feeder 800Available IRM 2140
50
49.449
48
Hz
DERs will trip
Macrogrid
Power
Freq
uenc
y
Microgrid
Power
Frequency
Load
Freq
uenc
y (H
z)
474849505152535455
0 50 100 150 200 250 300Time (seconds)
Unstable Microgrid
Governor Controls must be Adapted for Changing load Composition
Load Responses Are Different for Islanded Microgrids
Intelligent Relays Are Used to Adapt DER Controllers
Turbine
Electric Generator
Valve Turbine Controller
MicrogridMacrogrid
Relay
Microgrid Controller
Relay
Relay
Relay
Relay
RelayRelay
Relay Relay
Relay
It’s an Island !
Protection Must Adapt to Changing Fault Conditions Fault levels Grounding Directions Impedances
DERt
I
Relay
20,000
20,000
2,000
2,000
Fault Current Independent Protection Schemes Are Preferred Line current differential Transformer differential
Bus differential Time domain (future)
Security for Critical Infrastructure
• Avoid OS and software• Made in the USA • Mature Processes• Vertical Integration• Cyber Security
Conclusions
Testing reduces installation and maintenance costs Fast control systems prevent outages Reliable load balancing maintains stability Adaptive protection saves lives Security in depth is mandatory