Basic principle operation of PV grid connected system

• When the light strikes the PV modules, DC power will be produced. The DC current will flow through string cable to an Array Junction Box (AJB).
• All the current in each string are combined together in the AJB i.e all the strings cables are combined and terminate in a box called Array Junction Box (AJB).
• Each string is protected by a string fuse and circuit breaker.
• From AJB, the DC current flow to grid inverter through array cable. Here, the current is converted to AC current and transfer to grid.
• The array cable is also equipped with DC breaker to break the DC circuit when required. A surge protection device (SPD) is installed to this line to protect from lightning surge. The lightning surge induces from the PV side divert to the ground through SPD thus protect the inverter.
• The main function of gid inverter is to convert DC power to AC power. This is the special kind of onverter which different from an ordinary standalone inverter. This inverter works with grid only. It cannot be used to power AC load directly. The AC power produced by the inverter feed to grid supply through direct or indirect connection. Direct connection means connection is made at the main fuse link of grid whereas indirect connection makes connection at the distribution board.
• To measure the total amount of energy generated from the PV array, an additional meter which is known as export meter is usually installed. This is important for monitoring and billing purposes.