a) Stand Alone System

A standalone system is the one which is not connected to the power grid. It usually have a provision of energy storage or deficit energy produce by the PV source in grid connected systems is supply or drawn from the grid. As standalone system is not connected to the grid, it must have battery support to supplement the load requirements during the night hours or otherwise. A standalone system can be divided into five categories which are given below:

i) DC Coupled PV System

It is the simplest possible standalone configuration where PV panels are directly connected to the load. The capacity of the PV panels is designed in such a way that it is sufficient to run the load during sunshine hours. As power available to the load varies according to the weather condition, this is called an unregulated system. There is no arrangement for the energy storage to have night time load operation. A figure below describes such system.

DC coupled PV System


ii) Standalone System with DC Load

The block diagram of the configuration is given below. It is similar to unregulated PV system except that the electronic control circuitry is inserted between load and PV panel. This circuitry can be a voltage or current regulator or a maximum power point tracker. In order to achieve the smooth operation of load this circuit is introduced.

Standalone system with DC load

iii) Standalone System with Battery and DC Load

This type of PV system configuration is used when night time operation of the load is required. It requires energy from the battery to operate. The block diagram of such system is given below.

Standalone System with Battery and DC Load

Batteries in a PV system contribute to the recurring cost as the life of the batteries is significantly shorter than the life of the PV modules. The battery life is affected by the manner it is used like overcharging or over discharging reduced the life of battery.

iv) Standalone with AC/DC Load

It is similar to the standalone system with battery and dc load, the only difference is that now AC load is connected with the system. The block diagram of such system is shown below.

Standalone with AC/DC Load
In this configuration an inverter is used in order to convert DC power to AC power which is coming from battery. This type is suitable for domestic and commercial applications.

v) Hybrid System with AC/DC Load

The block diagram of this type of configuration is given below. Whenever there is more than one type of power source connected in a system, the configuration is known as hybrid PV system.

Hybrid System with AC/DC Load

If the load is operated during the night time, when the sunlight is not available, large battery bank will be required to store enough energy. Supplying the load with wind or biomass will be much more economical because no energy storage is required.