Low Frequency Inverter Or High Frequency Inverter,how to choose?

Firstly lets talk what Inverter is .

An inverter is a device that converts direct current (DC) into alternating current (AC) to meet the power demands of AC loads. Based on their topology, inverters can be categorized into high-frequency inverters and low-frequency inverters.

Low-Frequency Inverter

A Low-frequency inverter directly converts DC into low-voltage AC at line frequency, which is then stepped up to 220V, 50Hz AC through a low-frequency transformer for load use.

Its advantages include a simple structure, as various protection functions can be implemented at lower voltages. Due to the presence of a low-frequency transformer between the inverter and the load, it operates stably and reliably, with strong overload capacity and resistance to power surges. Additionally, it effectively suppresses high-order harmonics in the waveform. However, low-frequency transformers are bulky, expensive, and less efficient. Small-scale low-frequency inverters currently available typically have a rated load efficiency of no more than 90%. Moreover, since the core loss of the transformer remains nearly constant under both full and light loads, the no-load loss during light-load operation is significant, further reducing efficiency.

High-Frequency Inverter

A high-frequency inverter first utilizes high-frequency DC/DC conversion technology to transform low-voltage DC into high-frequency, low-voltage AC. This is then stepped up via a high-frequency transformer before being rectified and filtered into high-voltage DC, typically above 300V. Finally, a low-frequency inverter circuit converts it into 120V or 220V AC for powering loads.

Weight Comparison Between High-Frequency and low-frequency Inverters

For inverters of the same power rating, low-frequency inverters are significantly heavier than high-frequency inverters. High-frequency inverters are compact, lightweight, and efficient, with low no-load losses. However, they cannot handle full inductive loads and have weaker overload capabilities.

Since high-frequency inverters use compact and lightweight high-frequency magnetic core materials, they achieve much higher power density, resulting in minimal no-load losses and improved efficiency. Typically, high-frequency inverters used in small to medium PV systems can reach peak conversion efficiencies exceeding 90%.

Working Principle Comparison

High-frequency inverters have more complex circuitry, usually consisting of an IGBT high-frequency rectifier, a battery converter, an inverter, and a bypass. The IGBT's switching—controlled by gate drive signals—operates at frequencies ranging from several kilohertz to tens or even hundreds of kilohertz, far exceeding those of low-frequency inverters, hence the name "high-frequency inverter."

low-frequency inverters are designed based on traditional analog circuit principles, comprising a thyristor (SCR) rectifier, an IGBT inverter, a bypass, and a low-frequency step-up isolation transformer. Since both the rectifier and transformer operate at the standard 50Hz line frequency, they are aptly named low-frequency inverters.

Conversion Efficiency Comparison

The low-frequency inverters are less efficient than high-frequency inverters. The latter replaces complex hardware analog circuits with microprocessor-controlled software algorithms, significantly reducing size while improving conversion efficiency.

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