DC To AC Conversion: How Do Inverters Convert DC To AC?

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Since the War of the Currents unofficially ended in the 19th century, Alternating Current (AC) became the definitive winner as major contracts were given to AC developers.

However, the end of the war did not mark the end of Direct Current (DC), since this current still exists in different electronics: batteries, photovoltaic (PV) systems – practically everywhere.

Homes using battery banks or PV systems require inverters that convert DC into AC. The DC to AC conversion is one of the most important subjects in PV residential, commercial, and even industrial systems.

In this article, you will learn about the relationship between DC and AC, how they differ, and why they are necessary.

Additionally, you’ll learn about the best inverters out there.

Foreword
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DC vs. AC: What Are The Differences?

There are two forms of electricity – alternating current (AC) and direct current (DC). One is not better than the other as both are necessary.

Here we will explain each of them and how they differ from one another.

How Does DC Work?

DC is a linear type of electrical current – it moves in a straight line/flows in one direction.

This current moves from the positive pole to the negative pole, while electrons produce electricity while moving from negative to positive.

For DC, the positive and negative poles always remain the same.

A graph showing the movement of direct current.
Figure 1. Form of the DC – Source: AC & DC Physics Lovers

DC powers appliances with delicate electronic circuits that require a simple and steady current flowing in one direction.

Nowadays, this type of current powers cellphones, computers, and most other electronics.

How Does AC Work?

AC is a current that constantly changes its flow between positive and negative terminals.

This means that electrons also change their flow, following the negative to positive end as the polarity changes.

The speed at which AC changes polarity and completes several cycles in one second is called frequency, and it is measured in Hertz (Hz).

A diagram depicting AC waveforms
Figure 2. AC Waveforms – Source: The Basic Quantities of AC Waveform – EEWeb

AC can come in different forms, as seen in the figure above. There are triangular, square, sine, and complex waves.

Standard AC found at U.S. homes, is a 120V amplitude pure sine wave with a 60Hz frequency.


Differences Between DC vs. AC

DC and AC are quite different. While the positive and negative terminals remain the same for DC, it is not the same for AC, since the polarity constantly changes from positive to negative.

DC energy is unidirectional and does not vary in time, while AC is bidirectional, with the direction and magnitude of the wave varying in time.

Most DC appliances work at low voltages of 5V, 12V, or up to 24V, while AC devices usually operate at higher voltages of 120 – 240V.


How Does DC To AC Conversion Work?

Understanding how DC to AC conversion works is important to fully comprehend how your PV system operates.

PV modules generate DC energy and solar batteries also store energy in DC. To use this energy, you need to convert DC into AC, which is the required current by your appliances.

In the past, inverters converted DC into AC by switching the polarity for the output from positive to negative back and forth very rapidly, creating a square wave.

Inverters first increase the DC voltage using a DC to DC converter, and then they created the square wave. The output wave has an increased voltage with a reduced current, maintaining a power output similar to the input.  

Diagram depicting square wave in alternating current.
Figure 3. Square Wave in AC – Source: Alternating Current (AC) vs Direct Current (DC)

AC square waves are very abrupt and can end up damaging some delicate electronics in your home.

To solve this, manufacturers invented rectification devices that modify the wave, creating what is known as a modified sine wave (MSW).

The MSW is more subtle with regular appliances and can power them without causing any damage.

While MSW is better than a square wave, it is still not a pure sine wave, which is required to power certain delicate electronics.

Further developments in the industry allowed for the creation of rectification circuits, giving way to the creation of pure sine waves.  

Diagram illustrating different types of AC waves
Figure 4. Different types of AC waves. Source: Inverters – ExplainThatStuff

With DC to AC pure sine wave inverters, solar technology was finally able to convert DC generated and stored energy, into fully usable AC energy to power your appliances.

By creating a pure sine wave with a 110 – 120V amplitude, solar inverters can provide you with the same type of AC energy you get from your electrical utilities, but using 100% renewable energy.


Why Is DC To AC Conversion Necessary?

Fundamentally, DC to AC conversion is necessary because your appliances require a 120V sine wave to work. Most devices are just designed like this since AC has been the norm for several decades.

In the 19th century, DC tried to take over, but AC provided more advantages and ended up winning in the end. This is because transporting and converting AC energy costs less than DC, which is why it became the global standard.

Nowadays, some appliances use both DC and AC, but you regularly require AC to power your appliances. This is why you must have the right DC to AC converter at home, allowing you to power all your appliances with the right voltage and AC wave.


What Inverters Convert DC To AC The Best?

Finding the best DC to AC inverters takes time and effort.

To help you choose, we’ve picked the top 5 options and reviewed them for you.

Renogy 1,000W 12V Battery Power Inverter

The Renogy 1,000W pure sine wave inverter is a very light and robust inverter, which can be used with 12V batteries. This inverter has an efficiency of over 90%, delivering a 115V pure sine wave at 60Hz. This inverter can deliver a constant power output of 1,000W and a surge output of 2,000W.

The inverter includes 2 x AC sockets and 1 x USB port. The equipment features a system that protects against Low Voltage Disconnection (LVD), High Voltage Disconnection (HVD), AC overload, and over-temperature. The inverter also includes a Ground-fault circuit interrupter (GFCI) protection.

Most Relevant Features/Specs

  • Optimized for 12VDC systems.
  • Protection against LVD, HDV, AC overload, and over-temperature.
  • GFCI protection.
  • It can deliver a power peak of 2,000W.
  • Includes 2 x AC pure sine wave outlets (115V).
  • Additional Renogy remote control included.
  • 1-Year Warranty.

Krieger 1,500W Power Inverter

The Krieger KR1500 is a very light and compact DC to AC inverter. This model outputs a modified sine wave, delivered through 2 x AC outlets that operate at a maximum constant power of 1,500W with an additional 10W for the USB ports.

This device handles output currents of 13A, operating with an efficiency of 90%. The inverter is very silent because of the usage of a thermal fan. The Krieger inverter is protected against power overload, DC short-circuit, low voltage, high voltage, voltage overload, and over temperature.

Most Relevant Features/Specs

  • It can operate at 10.5 – 15.5 VDC.
  • Includes 2 x AC modified sine wave outlets (115V/13A).
  • Remote control included.
  • Ultra Silent inverter.
  • Handles a maximum peak power output of 3,000W.
  • 3-Year warranty.

Renogy 2,000W 12V Battery Power Inverter

Manufactured by one of the best brands, the 2,000W Renogy power inverter is suitable for high-capacity batteries. This inverter can be used to power a wide variety of devices, delivering a constant power output of 2,000W or a surge output of 4,000W.

This model is very light, robust, and compact considering its capacity. This 2,000W inverter is very secure to use since it includes the following protection systems: LVD, HVD, AC overload, over-temperature, and GFCI protection. This model includes 1 x USB port and 3 x AC sockets with a 115V pure sine wave.

Most Relevant Features/Specs

  • Suitable for 12VDC systems.
  • Protection against LVD, HDV, AC overload, and over-temperature.
  • GFCI protection.
  • It can deliver a peak power output of 4,000W.
  • Includes 3 x AC pure sine wave outlets (115V).
  • Additional remote control included.
  • 1-Year Warranty.


Giandel 2000W DC to AC Pure Sine Wave Power Inverter

The 2,000W Giandel DC to AC pure sine wave inverter is a very lightweight device with silent functioning. This inverter is ideal for installing with battery banks and small PV systems. The equipment can deliver a power output of 2,000W and a peak power surge of 4,000W.

This Giandel DC to AC pure sine wave inverter has a very low Total Harmonic Distortion (THD) of under 3% and overall efficiency of 90%. The model includes protection against AC overload, over-temperature, and it has LVD and HVD.

Most Relevant Features/Specs

  • Optimized for 24VDC systems.
  • It can deliver peak surges of 4,000W.
  • Includes 2 x AC pure sine wave outlets (110 – 120V).
  • Includes protection against AC overload, over-temperature, LVD, and HVD. 
  • GFCI protection.
  • 18-Month Warranty.

Growatt 3000W (SPF 3000TL LVM-24P)

The Growatt 3,000W power inverter is a 120VAC pure sine wave inverter with a 93% efficiency. This equipment can deliver a high constant power output of 3,000W and a peak power of 6,000W. This model does not only operate as a power inverter, it also works as a charge controller for self-consumption applications. This makes it ideal for both grid-tied and off-grid homes.

You can configure this inverter to prioritize grid power or solar input, depending on your needs. This equipment can be monitored using Wi-Fi or a GPRS network. This solar inverter has a parallel capacity, meaning that it can be installed with several other Growatt 3,000W power inverters to either increase the power output or provide two or three phases at your home.

Most Relevant Features/Specs

  • Parallel capacity.
  • Integrated MPPT charge controller.
  • You can prioritize a grid or solar input.
  • Monitoring through Wi-Fi/GPRS.
  • Delivers a peak power surge of 6,000W.
  • It can operate with a maximum PV array of 2,000W.
  • MPPT operating voltage of 30 -115VDC.
  • 5-Year Warranty.

Final Thoughts

DC to AC conversion is vital for PV systems and homes with energy storage banks. Having the right solar power inverter will allow you to power your appliances with the right pure sine wave inverter.

These should have a 120V amplitude and 50–60 Hz – required for most home appliances.

When picking a solar inverter for your home, you should consider the different features, specifications, and nominal capacity, compared to the cost and the power needs of your home.

We recommend you purchase the Renogy 1,000W or the 1,5000W Krieger inverter for small-medium systems, and the 2,000 – 3,000W options for larger systems.

Carlos Huerta, B. Eng

Carlos is a qualified Electrical Engineer with a background in solar PV designs for residential and commercial projects as well as power systems development. He is also a featured technical writer for many papers and articles. In his spare time, he enjoys conducting research on related topics to sustainability, especially solar power.

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