Testing Methods for Tigo Flex MLPE Systems

A Tigo system is comprised of Energy Intelligent Module Level Power Electronics (MLPEs) with Rapid Shutdown solution. Since these MLPE units are intelligent, it's like having a tiny in-line computer attached to each PV module. For this reason, there are certain consideration on what affects the electronics of the units and whether a traditional testing method is considered applicable. 

Tigo MLPE Systems are separated into 2 families, with their possible testing methods:

Radio - Smart / Optimized	PLC - Fire Safety TS4-F
Energy Intelligent MLPE family that uses Radio Communications to transfer data and to deliver a Rapid Shutdown (RSD) response	Fire Safety MLPE family that uses Power Line Communication (PLC) to deliver an RSD response. No Data is captured or transferred.
Testing Methods: ✅ Voc Test ✅ Vmp Test ✅ Imp Test ✅ Insulation Test ❌ Isc Test ❌ IV Curve Tracing	Testing Methods: ✅ Safety Voltage ✅ Vmp Test ✅ Imp Test ❌ Isc Test ❌ Voc Test ❌ Insulation Test ❌ IV Curve Tracing

Before testing, always refer to the following:

• Know which MLPE family you are working with (and the proper testing methods that apply)
• Follow all safety and operation instructions of the insulation tester you are using 
• Follow general electrical safety practices
• Have a certified electrician perform the test
• Make sure that all wires and conductors being tested are rated to the same voltage (or higher) than the test requires. (The voltage rating of the PV cables on Tigo products are printed on them).

Smart / Optimized Systems 

Tigo Smart / Optimizer MLPE units are sold in an open position (passing full voltage / no RSD response). They are packaged in this state for ease of assembly and testing during the system build process. Once commissioned, these systems require Radio Communications to stay in active 'non-Rapid Shutdown (RSD) mode.

This is important to know because the MLPE Units' state (commissioned vs not commissioned) dictates what conditions need to be present in order for the MLPE units to pass voltage. 

• Non-Commissioned - MLPE units can be tested without any special consideration. 
• Commissioned - CCA & TAP signal must be present for MLPE Units to pass voltage to the string. 

For safety reasons: Tigo strongly suggests enacting RSD / AC Loss before and after the test. This way, the system can be safely accessed by the installer to prepare the conditions for the test. Once the installer is ready to proceed with the test, the system must be re-energized (deactivate RSD / AC Loss) so the units are able to pass voltage and/or current throughout the testing period.

• ✅ Open Circuit Voltage Test (Voc): 
  As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE Unit or string can be DC Voltage tested for Voc results using the standard methods.
  
  
• ✅ Maximum Power Circuit Voltage Test (Vmp): 
  As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE Unit or string can be DC Voltage tested for Vmp results using the standard methods.
  
  
• ✅ Operating Current (Imp):
  As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE or string can be DC Amperage tested for Imp results using the standard methods.
  
  
• ✅ Insulation (megger) Testing: 
  As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE or String can be insulation tested up to 1000 V using the standard methods.
  
  

• ❌ Short Circuit Current (Isc): 

  The Module (panel) can be tested, but the MLPE cannot. The radio family of MLPE Optimizers has built-in Short-circuit protection. If a unit is placed in a short circuit condition, the unit or string automatically goes into RSD, and the test shows zero current.
• ❌ IV Curve Tracing: 
  Unfortunately, IV Curve tracing will not work for any Tigo devices (whether RSD is activated or not). The Tigo MLPE units receive their functional power from the PV Module, and the IV Curve test will present conditions that range from Isc to Voc. This effectively starves the MLPE from its running power and (if sustained) the unit will shut down. 

Fire Safety Systems

TS4-F Fire Safety system require a constant PLC signal in order to remain in an active state (passing voltage / non-RSD). These systems must have a completed circuit in order for units to receive the signal and continue passing voltage. For this reason, standard testing procedures like Voc, Isc, Insulation (megger) and IV Curve Tracing are not possible. 

For safety reasons: Tigo strongly suggests enacting RSD / AC Loss before and after any test. This way, the system can be safely accessed by the installer to prepare the conditions for the test. Once the installer is ready to proceed with the test, the system must be re-energized (deactivate RSD / AC Loss), so the units are able to pass voltage and/or current throughout the testing period.

• ✅ Maximum Power Circuit Voltage Test (Vmp): 
  Testing for Vmp is possible with PLC signaling since the Vmp condition requires the MLPEs to be connected to an MPPT of a Charge Controller or Inverter. Since this is a completed circuit, the MPLEs will be receiving the PLC signal.
  
  
• ✅ Operating Current (Imp): Clamp Meter
  Testing for Imp is possible with PLC signaling because the Clamp Meter can be applied to the completed circuit.
  
  

• ❌ Short Circuit Current (Isc): 

  The Module (panel) can be tested, but the MLPE cannot. The PLC family of Fire Safety products has built-in Short-circuit protection. If a unit is placed in a short circuit condition, the unit or string automatically goes into RSD, and the test shows zero current. 
• ❌ Open Circuit Voltage Test (Voc): 
  Testing for Voc is not possible with PLC signaling, as the MLPEs require a closed circuit to receive the signal.
• ❌ Insulation (megger) Testing: 
  Testing for Insulation is not possible with PLC signaling, as the MLPEs require a closed circuit to receive signal. Without signal, the unit only allows safety voltage (.6 volts) per module.
  
  
• ❌ IV Curve Tracing: 
  Unfortunately, IV Curve tracing will not work for any Tigo devices (whether RSD is activated or not). The Tigo MLPE units receive their functional power from the PV Module, and the IV Curve test will present conditions that range from Isc to Voc. This effectively starves the MLPE from its running power, and (if sustained), the unit will shut down.