Reference is now made to FIG. 6, which illustrates a method 60 performed by inverter 204 or signaling block 420 attached at the input of inverter 104. In step 601, inverter 104 is off or inverter 204 is on standby, and not converting power to its output. In decision box 603, start conditions for turning on inverter 104,204 are determined. Typically, as a safety requirement, inverter 104 delays operation (converting power to its output) until after at least 5 minutes of connection to a functioning AC-grid at its output. This safety requirement may be achieved using microcontroller 422 and at least one of relays 424 and 426 in signaling block 420. In inverter 204, a minimum voltage is required at the input to inverter 204 (e.g. if the safety output voltage of each module is 2V, and the minimal-length string allowed contains 5 modules, the inverter will wait until at least 10V are present at its DC input) and only thereafter does inverter 204 begin to charge its input, typically to a specified standard input of 400V.
