What is the on-grid inverter?
It's an inverter used to convert DC "direct current" coming from solar panels or wind turbine to AC "alternating current" and injects into the power grid.
The on-grid inverter must match grid sine wave phase and voltage, so can inject the AC current into it. The most important feature of such inverter is its ability to work without batteries, it based on solar panels or wind turbine and power grid presence only, so if the solar energy or wind energy are not sufficient to feed the load, it consumes his power requirements from the power grid.
How does the on-grid inverter work?
Simply the inverter has a computer module that senses the grid AC voltage waveform and continuously measure all its parameters instantly like voltage, frequency…etc. and then starts to inject the AC current, so that the inverter keeps its output voltage to be slightly higher than grid voltage all the time.
In the same time, the inverter must have anti islanding feature which quickly disconnect it if the grid power system shuts down for any reasons, so protect itself from feeding uncontrollable loads "may be higher capacity" and protect personnel who were sent to troubleshot the power grid.
What are on grid inverter types?
There are 3 types of inverters in the market:
- Low frequency with transformer coupling inverter.
- High frequency with transformer coupling inverter.
- Transformer-less inverter.
For the first and second type, the inverter has a transformer inside and a computer unit which schedule converting the DC power to low or high frequency and return to DC power again, then converting to final AC voltage which matches the power grid. Inverter.com offers 300W to 1000W grid tie inverters and 300W to 1400W micro solar inverters with transformer design.
For transformer-less inverter, it doesn't have transformer inside, so it converts DC to AC with high converting efficiency. Although the price of transformer type inverter is lesser than transformer-less type, but transformer-less inverter is smaller, lighter and more efficient.
One thing pertaining to transformer-less type is, it doesn't have a transformer inside, so there will be concerns about the absence of galvanic isolation between DC side and AC side, so the probability of injecting dangerous DC currents and voltages into the power grid.
Which on grid inverter type you should purchase?
We recommend to buy the most advanced and efficient transformer-less type, single phase 1500W to 10kW and three phase up to 50kW transformer-less on grid solar inverters are available here. Just check their specs in regard to DC voltage and current components injections, to be sure its within safety limits.