Transcript Protection Systems - North American Solar Challenge

Protection Systems
Batteries and Protection Systems Session
Daniel Bohachick
ASC2005 Kickoff
Conference
Protection System Topics
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System overview
Fail safe concerns
Reliability
Real world behavior
Whole system protection
Implementation
ASC2005 Kickoff
Conference
System Overview
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Primarily to protect batteries
Operates whether sourcing or sinking power
Complete Electrical Isolation from other Systems
Automatic monitoring and reaction
– “Smart Fuse”
• No single correct solution
5.8.3. Protection Circuitry – Batteries must have
protection circuitry appropriate for the battery technology.
Proof is required at scrutineering that the protection system
is adequate. Protection circuitry should be primarily for the
purpose of protection.
ASC2005 Kickoff
Conference
System Overview(cont.)
Array
Protection
System
Power
Trackers
Power
Switch(es)
Battery Pack
Motor
Controller
ASC2005 Kickoff
Conference
Motor
Fail Safe Concerns
• The Culprits
– Incorrect setting on power trackers or
motor controller
– Lack of active monitoring(telemetry or
driver readouts)
– Regen Braking
Protection System Limits*
Over Voltage(OV)
• What occurs when a fault 1)
2) Over Temperature(OT)
3) Over Current(OC)
is detected
4) Under Voltage(UV)
* Depending on Battery
• Actions afterward
Chemistry
ASC2005 Kickoff
Conference
System Overview(cont.)
Array
Protection
System
Power
Trackers
Power
Switch(es)
Battery Pack
Motor
Controller
ASC2005 Kickoff
Conference
Motor
Reliability
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Verifying Set Points
Diagnostics and Fault Readout
How is protection system powered?
Sensitivity to noise(EMI/RFI)
Sense Voltage Isolation(Galvanic, Optocouplers)
Ability to impound(connectors, sense leads)
Hysteresis, Delay, Calibration
ASC2005 Kickoff
Conference
Real World Behavior
• In-house or off the shelf designs do not always
work according to spec
• Power tracker and motor controller set points can
be changed
• Human error
• Secondary system damage
– Motor Controller
ASC2005 Kickoff
Conference
Whole System Protection
• Regen on a steep down hill can cause problems due to a battery
fault conditions isolating the motors load causing a large dI/dT for
the inductance and since V = L dI/dT, then a large transient voltage
could appear on the motor controller bus causing damage to:
– MOSFET
– Main Capacitor
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– Internal DC/DC
– Motor Winding
**Also some MPPT
should be shut off
before battery is
disconnected.
ASC2005 Kickoff
Conference
System Overview(cont.)
Array
Protection
System
Battery Pack
Sequenced Power Shut Down
Power
Trackers
Power
Switch(es)
Motor
Controller
Dynamic Braking
ASC2005 Kickoff
Conference
Motor
Implementation
• Braking Resistor, Clamping Diode, or Transient
Stability Circuit on Main Bus.
• Integrate Protection System to soft shut down all
sources
• Provide telemetry to detect and prevent conditions
that result in faults
• When a fault occurs determine root cause before
continuing
• Understand effects on system when an abrupt shut
down occurs
ASC2005 Kickoff
Conference