1. ASC2005 Kickoff Conference Protection Systems Batteries and Protection Systems Session Daniel Bohachick

2. ASC2005 Kickoff Conference Protection System Topics System overview Fail safe concerns Reliability Real world behavior Whole system protection Implementation

3. ASC2005 Kickoff Conference System Overview 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.

4. ASC2005 Kickoff Conference System Overview(cont.) Array Power Trackers Battery Pack Motor Controller Motor Protection System Power Switch(es)

5. ASC2005 Kickoff Conference Protection System Limits* 1) Over Voltage(OV) 2) Over Temperature(OT) 3) Over Current(OC) 4) Under Voltage(UV) * Depending on Battery Chemistry Fail Safe Concerns The Culprits –Incorrect setting on power trackers or motor controller –Lack of active monitoring(telemetry or driver readouts) –Regen Braking What occurs when a fault is detected Actions afterward

6. ASC2005 Kickoff Conference System Overview(cont.) Array Power Trackers Battery Pack Motor Controller Motor Protection System Power Switch(es)

7. ASC2005 Kickoff Conference Reliability 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

8. 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

9. 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 –Internal DC/DC –Motor Winding I **Also some MPPT should be shut off before battery is disconnected.

10. ASC2005 Kickoff Conference System Overview(cont.) Array Power Trackers Battery Pack Motor Controller Motor Protection System Power Switch(es) Sequenced Power Shut Down Dynamic Braking

11. ASC2005 Kickoff Conference 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