Isolate and Ground
Isolate and Ground
Seems the answer is two fold:
(1) deenergize all AC circuits in the vicinity of the equipment you are working on.
(2) Ground & short all AC and DC circuits to eliminate all voltage. (Just like good practice on medium-voltage systems.)
Obviously, you cannot stop PV modules from generating current but they can be shorted to reduce the voltage to near zero. PV DC wiring is required by NEC to be sized to operate safely under a short circuit. Unless the module manufacturer prohibits shorting the DC circuit, this seems a viable way to achieve voltages below 600V.
Once LOTO and short/ground is completed using appropriate tools, there are no voltages over 600V present.