Planning the Installation

PV Array Voltage and MPPT Requirements

 

 

WARNING: Shock hazard

 

 

Whenever a PV array is exposed to sunlight, a shock hazard exists at the output wires or

 

 

exposed terminals. To reduce the risk of shock during installation, cover the array with an

 

 

opaque (dark) material before making any connections, and always test for voltage before

 

 

touching exposed wiring or devices.

 

 

 

MPPT operational

The MPPT software maximizes the output energy of solar arrays as long as the

window

operating voltage is within the MPPT operational window. Ensure that the PV

 

 

array used in the system operates within the MPPT operational window.

 

 

Effects of array voltages outside of the MPPT operational window are shown in

 

 

Table 2-1.

Table 2-1MPPT Operational Window

Voltage

Effect of Array Voltage

Inverter Mode

 

 

 

Voc < 240 Vdc

Inverter not operating.

Off-line

VMPP < 240 Vdc

Operating voltage shifts to 240 Vdc; the array is not at its

On-line (low power)

(Voc > 240 Vdc)

maximum power point.

 

VMPP 240 to 550 Vdc

Maximum harvest of solar energy.

On-line (MPPT window)

VMPP 550 to 600 Vdc

Does not allow maximum harvest of solar energy.

On-line (power derating)

VMPP > 600 Vdc

Inverter stops delivering power and shuts down. Inverter

Off-line (shutdown)

(or Voc > 600 Vdc)

may be damaged.

 

Voltage

The maximum power point voltage of a string connected to the GT Inverter should

requirements

preferably be above 240 Vdc. If it is less than 240 Vdc, the inverter continues to

 

operate, but it regulates the PV voltage to 240 V. Because the array is not

 

operating at its maximum power point, this may result in lower than expected

 

energy harvest. If Voc is below 240 Vdc, the inverter remains off-line and does not

 

deliver power.

CAUTION: Equipment damage

To prevent damage to the inverter, the array voltage must never exceed 600 Voc (open circuit voltage) under any condition.

The open circuit voltage of the array under normal conditions should be above 240 Vdc.

The short circuit current (Isc) rating of the array at any temperature must not exceed the Isc rating of the inverter. For maximum solar energy harvest, it is recommended that the effective power output of the array be matched with the input power capacity of the inverter.

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