Which design approaches are used to implement UPS systems?

The most common design approaches are the following:
1- Standby
2- Line Interactive
3- Standby on-line hybrid
4- Standby-Ferro
5- Double Conversion On-Line
6- Delta Conversion On-Line

1- Standby:
The Standby UPS mostly used for Personal Computers.

2- Line Interactive:
The Line Interactive UPS, is mostly used for small business, Web, and departmental servers. In this design, the battery-to-AC power through the converter (inverter) is always connected to the output of the UPS.

3- Standby on-line hybrid:
This type is used for UPS under 10kVA ( labeled "on-line.), The standby DC to DC converter from the battery is switched on when fault the AC power,

4- Standby-Ferro:
Standby ferro UPS systems are often shown as on-line units, although they have a transfer switch, the inverter operates in standby mode, and has a transfer characteristic during an AC failure.

5- Double Conversion On-Line:
In this type, the failure of the AC input does not cause the transfer switch to be activated because the AC input is not the primary source, but the backup source. Therefore, on-line operation does not result in a transmission time during an input AC power failure.

The online operating mode has a transfer time when the power from the primary battery charger / battery / inverter power path fails. This can occur if one of the blocks in this current path fails. The inverter power may also fail for a short time, resulting in a transfer if the inverter is subject to sudden load changes or internal control problems.

Double conversion On-line UPS systems have a transfer time, but under conditions other than a standby or line interactive UPS. While a standby and line interactive UPS has a transfer time when a blackout occurs, a dual conversion online UPS shows a transfer time when a large charging step or an inrush current occurs. This transfer time is the result of the transfer of the load from the UPS inverter to the bypass line. In general, this bypass line is built with Dual Silicon Controlled Rectifiers (SCRs). These solid state switches are very fast, so similar to the standby and line interactive UPS, the transfer time is very short, less than 4 milliseconds.

Both the battery charger and the inverter convert the total load power flow in this design, resulting in reduced efficiency and increased heat generation.

6- Delta Conversion On-Line:
in this new technology introduced to remove the disadvantages of the double conversion on-line design and is in the range of 5kva to 1mw. Similar to the Double Conversion On-line design, the Delta conversion online UPS always has the inverter that supplies the load voltage. The additional delta converter also contributes to the inverter output. Under conditions of alternating current failures or faults, this design has a reaction behavior identical to the double conversion on-line.