Solar inverters make our lives easier by powering our homes with solar panels. But how do they exactly work? What makes them intake power from your solar panels and light your home?
Before we jump to how does a solar inverter work, first, you need to understand why exactly a solar inverter is needed. That will help us understand why they do what they do and how they do it.
Why Are Solar Inverters Needed?
Solar panels produce DC voltages which cannot be supplied to most of the appliances at your home as they operate at AC voltages.
You might have noticed the input voltages mentioned on the appliances say 240 VAC with a “~”; this sign means the appliance operates at only AC voltages. Similarly, if you notice the specifications of your solar panels, they have 24-48VDC output with a “=” sign which means DC voltages.
So, the output of your solar panels and the input required to power most of your home appliances do not match. If they are still connected, the appliances can immediately burn or malfunction.
This is the problem solar inverters solve. They convert the DC output of your solar panels into AC voltages and step up the voltages from 24-48 to 240 volts.
Now that you understand the function of a solar inverter let’s discuss its basic working principle.
Basic Working Principle Of A Solar Inverter
Solar inverter intakes the 24-48 VDC and converts them into 24-48 VAC. This process is called AC to DC conversion, and there are many ways to do it.
Most traditional solar inverters use an oscillator circuit to convert the power from DC to AC. Later the voltages were stepped up through a transformer. The resultant voltages were alternating and useable but did not make a pure wave. This was a major problem, affecting the appliances’ longevity and performance.
Fortunately, today, technology has advanced and design innovated. The latest MPPT and RLC filter-based solar inverters produce pure sinewave; they are far more efficient and reliable.
Since the energy has to be processed and consumed simultaneously, the inverter must also manage the flow of energy. This is why modern solar inverters are designed with far more functions.
Modern solar inverters are smart; they are equipped with a display that lets consumers track their performance. Moreover, they can connect via WIFI & GPRS, which helps monitor them over the internet.
To ensure safety, they are also equipped with telemetry systems. In case of minor issues like overheating, the inverter turns on its cooling fans and auto-cools.
But if the inverter detects any major problems like over-discharging, over-loading, or short-circuit. In that case, it isolates itself from the rest of the system, raises the alarm, and shows a corresponding error code on the inverter’s display.
These solar inverters are widely used at domestic and commercial scales; hence, they have also been designed in different specifications and packages according to need.
Accordingly, different types of solar inverters have been produced. All three designs are slight functionality and scale differences. Their working mechanism also differs in their functions.
Let’s discuss the three major classes of solar inverters and how they differ.
On-grid Solar Inverters
The on-grid solar inverters are the most widely used commercially among all types. On-grid solar inverters are connected to the grid supply and solar panels at the same time. No batteries are connected to them, and the energy is not stored but efficiently managed.
On-grid Solar Power System
Their most important function is to maintain the same frequency and voltages of the power supplied by the solar panels as the grid’s output power. Certain sensing circuits measure the frequency of the grid’s power using techniques like zero-level detection and altering the solar power’s frequency accordingly.
Another important function is the two-way power flow between the inverter and the grid. For example, suppose solar power exceeds the energy demand of the building. In that case, the inverter synchronizes the line voltage generated by the solar power with the grid’s line voltage and feeds it to the grid.
But if the solar supply does not meet the building’s power requirements (at night or on a cloudy day), the inverter switches the power input to the grid supply. This way, the inverter helps manage the energy at both ends.
Off-grid Solar Inverters
Unlike on-grid solar inverters, off-grid solar inverters are connected to the solar panels but not to the grid. Instead, a battery bank is connected to them for energy storage.
The over-charging and over-discharging can severely impact the life of a battery, and the solar panels work like a constant current source. If the charging of batteries is not controlled, the battery can deteriorate before time or even explode.
Thanks to the built-in charge controllers of off-grid solar inverters that enable regulation of battery charging. They keep track of the battery bank’s voltages to know if the battery needs charging or is draining below the minimum limit and take action accordingly.
Interestingly, the charge controller enables powering DC equipment. While at the same time, it also regulates the energy being converted to AC (through the inverter) for powering AC appliances and the energy being used to charge the batteries.
So, the off-grid inverter also helps store solar energy while converting it into AC for powering appliances in the daytime. But unlike on-grid solar inverters, it also functions at night. It collects the DC power from the battery bank and converts it to AC to run your appliances when your solar panels do not produce energy.
Hybrid Solar Inverters
Like the name says, hybrid solar inverters are a hybrid between the on-grid and off-grid solar inverters. They can be connected to the grid and batteries and simultaneously manage energy.
An essential function these inverters perform is the conversion of AC power into DC. This is useful when the solar panels are not producing enough power to charge the battery bank. In such conditions, the solar inverter intakes AC power from the grid, converts it into DC power through rectification, and feeds it to the batteries.
Given their functions, they add tremendous flexibility to the energy management of industries. These inverters are far more efficient for large-scale solar power management than the rest.
So, the three types of solar inverters and the differences in their working mechanism. But so far, I have discussed the basic DC to AC conversion, assuming we are producing only a 1-phase supply. Some AC appliances (especially in the industry) operate at a 3-phase supply. For such a scale, 3-phase solar inverters are used. Let’s discuss how they work.
How Do 3-phase Solar Inverters Work?
The 3-phase solar inverters work on the same principle as the 1-phase solar inverters, except they produce 3-phases aligned at 120 degrees. To produce a 3-phase supply, they are equipped with three coils (instead of one).
The impact of a rotating magnetic field on the coils at different intervals produces three phases; each is a sine wave that has a peak at different times. The 120 degrees that I have mentioned before is the gap between the peaks of the sine wave in all three phases.
Apparently, the only difference between 1-phase inverters and 3-phase inverters is their capability to produce 3-phases.
Since there are different kinds of solar inverters, their working mechanisms slightly differ. But the primary function of a solar inverter remains the same; it converts the DC power generated by solar panels into AC.