Solar inverters are fast replacing generator sets (petrol, diesel, kerosene, and all other types of gen-sets) as the go-to alternative for backup power supply. Households, industrial factories and facilities, commercial companies, educational institutions, restaurants, and all other businesses are opting for solar inverters as an (alternative) power source. Solar Inverters fall into 3 major categories; Grid-tie Inverters, Stand-alone Inverters & battery back up Inverters.
#1. Grid-Tie Inverters
Grid-tie inverters convert DC electrical power into AC power suitable for injecting into the electric utility company grid. The grid-tie inverter (GTI) must match the phase of the grid and maintain the output voltage slightly higher than the grid voltage at any instant. A high-quality modern grid-tie inverter has a fixed unity power factor. This means its output voltage and current are perfectly lined up, and its phase angle is within 1 degree of the AC power grid. The inverter has an onboard computer that senses the current AC grid waveform and outputs a voltage to correspond with the grid.
#2. Stand-Alone Inverters
These types of inverters are not directly connected to the energy source like PV panels. Instead, they take the DC from batteries that, in their turn, can be charged by solar panels or any other energy sources like hydro/wind turbines and so on. Some of these inverters employ battery chargers to chargeback the batteries from an AC source if available.
Battery Backup Inverters
Battery backup inverters draw the energy from the batteries and can charge them back later using onboard chargers if needed. When the batteries are fully charged, they provide the surplus to the grid. During a blackout, they are able to provide AC power to select electrical devices. Because these inverters interact with the grid, they need to implement anti-islanding.
What is Anti-Islanding?
Anti-islanding shuts down the inverter when the grid is down. Inverters may still provide electricity to the grid after it is down, so anti-islanding is a safety precaution for that case. If not for this feature, an electrician may get shocked if working to repair grid failure. Secondly, transformers and other components of the grid system shut down automatically when the grid is down. Forcing electricity into the grid in this situation may cause severe damage. Grid-tie and
Battery backup inverters include anti-Islanding because they interact with the grid.