In many countries the supply of mains electricity is not assured all the time in all locations. As demand for power is overtaking supply it is common for some locations to endure scheduled loss of supply. In locations with an old and fragile infrastructure, loss of service can also occur for technical or natural reasons.
A grid back-up system can simply comprise a diesel generator with a mains failure auto-start function. The generator is started automatically when the mains fails. However, if this is due to a temporary loss of power for a short time, ie minutes rather than days, then the generator may be regularly started, only to run for just a short time. This is not good for the generator diesel engine. Also, with such a system there is a time delay between when the mains power fails and when the generator is running and its power is available. Both these situations can be avoided as the power supply can be supported temporarily from stored battery energy using modern Multi-Function Inverter-Chargers. Conventional UPS systems are inherently limited and cannot offer the benefits of a MFIC solution.
A grid back-up solution has similar components to an off-grid system, but as they are not required to provide all the power all the time, we may choose to size the system differently and use different features of the power management components to focus on critical needs.
A back-up system may comprise some or all of the components of an off-grid system with the exception that it always includes the central MFIC (intelligent switching and supply of inverted mains) and a battery bank (the energy store).
Typically we can support the power requirement fully with instantaneous transfer switching to prevent connected loads losing power. The system can also ‘load shed’ which means turn off supply to unnecessary loads and thus reduce demand on batteries and prevent unnecessary diesel generator runs (if installed).
Back-up systems can be in single phase, 3-phase and even combinations of both.
The MFIC is so flexible that we can, for instance, provide a single phase back-up to a 3-phase building where the critical systems are located only on one phase. This reduces cost and complexity of a back-up system.
The back-up system can also be a way to overcome shortfalls in the grid supply, letting you have more powerful consumers in your development than would otherwise be possible with grid supply alone. Back-up systems also work well with renewables, extending the time power is available from batteries when the grid is down.