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DC to AC Conversion: How does a Solar Generator do It?

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DC to AC conversion is one of the key functions of a solar generator to harvest and store solar energy. This technology paved the way for the transition and adoption of renewable energy solutions.

However, only some realize that we use two kinds of current for our daily lifestyle (Alternating Current and Direct Current) and the relevance of their conversion process.

That’s why in this article, you will learn:

  • What are AC and DC;
  • The differences between the two;
  • How a solar generator does DC to AC conversion via an inverter; and
  • Why converting DC to AC is important.

Quick recall: A basic solar generator setup consists of four major components:

  1. Solar Panel - Produces DC electric power
  2. Battery - Stores DC electric power
  3. Charge Controller - Acts as a protection device, ensuring the battery is charging/discharging safely.
  4. Inverter - Takes care of DC to AC conversion.
The essential components of a solar generator
The essential components of a solar generator

As an add-on bonus, you will also learn an enhanced DC to AC converter known as the Bidirectional Inverter.

What are AC and DC?

In a nutshell, AC and DC are two types of currents that differ in how their current flows behave. We use both types to power our daily lifestyles. For beginners, electrical professionals describe current as the flow of electric charge carriers such as electrons.

Metaphorically speaking, an electric current flowing through an electric cable is similar to water flowing through a hose.

Remembering their unique electric characteristic is easier by understanding what each abbreviation means.

What is DC

DC stands for Direct Current. The current in a DC system flows only in one direction (towards the positive). Examples of these include batteries and power banks. The current that flows from the power bank to your cellphone goes in only one direction.

What is AC

One the flip side, AC is a short term for Alternating Current. Compared to DC where the current goes in only one direction, the current for AC flows alternatively between positive and negative terminals of an electric system. Depending on where you live, the number of current flow switches falls between 50 to 60 cycles per second. In the electrical industry, this is known as Hertz (Hz).

Comparing this to our water hose metaphor, An AC current is like having a pump that alternates the flow of water 50 to 60 times per second.

Lastly, it is important to know that AC is traditionally created via a generator turbine with a spinning magnet (also known as an alternator).

Is DC to AC Conversion Limited to Current?

Before we proceed further, know that the terms DC and AC are applicable beyond the current. While this may sound confusing for first-timers, know that DC and AC can be used as adjectives for other electrical terms such as AC Voltage, DC Voltage, AC Power, and DC Power.

dc to ac conversion
dc to ac conversion - Growatt

Water in a hose metaphor for AC and DC.

DC vs. AC: Which is Better?

Most of the articles you see online nowadays put DC in a bad spot, saying that it is an older-than-a-boomer technology that should be locked in a chest and thrown into the pits of the ocean. This is mainly because of the story between Thomas Edison and Nikola Tesla, the great minds who discovered DC and AC, respectively.

But we beg to differ. From our perspective, both DC and AC have a role to play in modern electric systems. For example, DC is an innate necessity for semiconductors and power electronics.

As some of you also know, DC is easier to store than AC. That is why batteries require an inverter for their DC to AC conversion. DC, in some cases, is also more cost-effective than AC. 

Not to mention, solar panels produce DC power due to their semiconductor components. If you have heard about solar panels producing AC, they already have small DC to AC converters embedded in them, known as microinverters.

Conversely, AC is more economical when transmitted over longer distances. They are more efficient (with fewer losses) and cheaper to produce before introducing solar panels.

The bottom line, DC and AC were pitted against each other in the early days, but both have their uses in the digital age and the green energy transition.

How does a Solar Generator Perform DC to AC Conversion?

Let’s get into the meat of the topic; As we said, one of the primary components of a solar generator is the inverter which takes care of the DC to AC conversion.

But how does it exactly do this?

We’ll try our best to simplify this but know that this section is where you will need to pay more attention.

Three main processes are involved in DC to AC conversion:

  1. Switching - converting DC to rough AC
  2. Filtering - cleaning the rough AC output to make it useful to sensitive AC appliances and gadgets; and
  3. Amplify - increasing the voltage to acceptable values such as 120V or 220V, depending on where you live;
types of inverters convert DC to AC
How different types of inverters convert DC to AC

Switching

DC to AC conversion is initially done through electronic switching techniques. Without getting too much into the nitty-gritty, think of an electric wire carrying DC voltage that you can turn on and off. In engineering terms, this is called square wave conversion using a switching circuit.

dc to ac converter - GrowattA simple switching device can convert a DC voltage to a square waveform

Let’s take the DC to square wave conversion a step further. As you observed in the image above, the square bounces only between 1 and 0. However, as we have mentioned before, an AC voltage alternates between positive and negative terminals in the image below.

DC to AC conversion of a full-bridge inverter
A full-bridge inverter doing rough DC to AC conversion

This is where the full-bridge inverter comes in. It is a circuit design with diodes, transistors, and other fancy electric components. It can pull off a rough DC to AC conversion by following a sequence of switching events (see image below).

Switching operations of a full-bridge inverter

Switching operations of a full-bridge inverter

From here, the inverter circuits only become more sophisticated such as modified sine wave inverters (see image below).

modified sine wave inverters

Filtering

As circuit design complexity and cost increase, we can arrive at a pure sine wave inverter that generates a clean sinusoidal AC voltage. This involves some processes like taking your rough AC-square waveform and running it through circuit devices such as oscillators and filters.

oscillators and filters

Amplifying

Lastly, any inverter has a built-in transformer that amplifies the small AC voltage (DC voltages range from 1.5V to 24V) to a much higher voltage like 110V or 220V.

In the figure below, the small AC voltage goes through the transformer from the primary side before being amplified to usable 110V/220V on the secondary side

Amplifying

Final Thoughts on DC to AC Conversion

There you have it. A mini masterclass on how solar generators do DC to AC conversion.

To sum it up, solar generators have inverter components that take DC voltage from either solar panels or batteries and use switching techniques and filters to generate a clean, low AC voltage. In turn, this AC voltage goes through a transformer that amplifies its value to a level that household appliances can use.

What if we told you that some solar generators could perform not only DC to AC conversion but AC to DC as well? Why is that important? Our other article thoroughly explains the added benefits of solar generators with bidirectional inverters.

Read: Bidirectional Inverter Technology Explained 2023