The Past, Present, and Future of Inverter Technology: What Will the Inverters of Tomorrow Look Like?

Yusuf Kaan Yıldız | yk.yildiz@gmail.com

For those who prefer a short summary:

On the DC input side of inverters, the main focus over the last 15 years has been transformer-less design, higher DC voltage levels (moving from 1000 V toward 3000 V), multilevel topologies, and increased efficiency and power density. Today, 1500 V DC input voltage has become the new standard, accelerating the evolution of power modules.

On the battery side, the main focus over the last 5 years has been bidirectional power conversion systems (PCS), grid-forming inverter capabilities, and more advanced protection features.

1) What Was an Inverter, and What Has It Become?

In the past, a classical PV inverter was simply a box that converted DC to AC. Today, it has become a much more advanced power electronics system.

Modern inverters now:

• Comply with grid codes (reactive power control, voltage/frequency support, fault ride-through, harmonic limits).

• Include protection, communication, and cybersecurity features.

• Can form or shape the grid (grid-forming) when combined with batteries.

2) Evolution of Inverters from Past to Present

1980s–2000s: Transformer-based central systems. These systems used large 50/60 Hz transformers for galvanic isolation. They were safe and robust but heavy, bulky, and less efficient.

2000–2015: Transformer-less and string architectures became common. Efficiency improved, systems became more compact, and multilevel topologies reduced switching losses and harmonics.

2015–2025: 1500 V DC architecture became the standard in many utility-scale PV projects. This reshaped power module and topology design. Three-level topologies (such as NPC derivatives) became widely used in central inverters.

After 2026: The industry is moving toward 3 kV DC strings, medium-voltage AC outputs, and material minimization. DC input voltage levels may double, and AC outputs could move toward 1.2 kV as a new standard.

3) Evolution of Battery Inverters / PCS

On the battery side, inverters and PCS systems focus more on energy management and grid stability.

• Bidirectional power flow is now standard. Modern PCS systems manage both charging and discharging on the same platform.

• The shift from grid-following to grid-forming is accelerating. Instead of only following the grid reference, inverters can now create and stabilize the grid.

4) Future Technologies for Solar + Battery Systems (Next 10 Years)

Key technology blocks shaping the next generation:

Wide Bandgap Semiconductors (SiC and GaN):

• These technologies enable higher switching frequency, lower losses, higher temperature operation, and greater power density. SiC will play a major role, especially in voltage classes of 3.3 kV and above. GaN will be more common in lower-voltage, high-frequency applications such as residential and compact systems.

Commercialization of Multilevel Topologies:

• Multilevel topologies create a smoother sine wave and reduce stress on components. With NPC, ANPC, and MMC structures, voltage stress per switching element decreases, harmonics improve, and filter sizes can be reduced.

Medium-Voltage PV Architecture

• Higher DC voltage reduces cable cross-sections and conductor usage, and lowers the number of transformers and switchgear components.

Grid-Forming Inverters:

• As system inertia decreases, the need for frequency and voltage stability through power electronics is increasing.

Hybrid Systems: DC-Coupled and Multiport Inverters

• The goal is to integrate PV, battery, EV charging, and generators with fewer conversion stages.

Smarter Protection, Monitoring, and Software-Based Grid Code Compliance:

• Grid codes are becoming stricter. Event recording, diagnostics, remote updates, and cybersecurity will be standard product features.

Solid-State Transformers (SST) and Multi-Terminal DC (MCDC):

• Solid-state transformers use semiconductors instead of traditional magnetic cores. MCDC refers to multi-terminal DC grids. While promising, cost, reliability, protection, and standardization challenges mean they require more time for large-scale adoption.

5) Which Technologies Will Move Forward?

In the next 3 years:

• 1500 V DC architecture will continue due to reliability.

• Grid-forming capability will become a common option in BESS projects.

• MV-PV (such as 3 kV DC input) will gain field experience through pilot projects.

In 5–10 years:

• MV-PV and higher DC voltage systems may become dominant in utility-scale projects.

• Grid-forming capability will expand beyond BESS into PV inverters as well.

6) Expected Benefits

CAPEX and OPEX may decrease as higher voltage levels reduce equipment density.

Efficiency and power density will increase. With SiC/GaN and multilevel designs, losses will decrease and high-temperature operation will improve.

Grid services will expand. BESS combined with grid-forming capability will provide stronger frequency and voltage support, especially in microgrids and low-inertia systems.

Explanations

1) What is a Transformer-Based Inverter?

Transformer-based inverters (often called “Low Frequency” inverters) are more rugged and heavy-duty compared to modern lightweight devices.

Unlike today’s compact inverters, these systems contain a large copper-wound transformer inside.

Conversion Process

The 12V or 24V DC current coming from the battery is first switched on and off very rapidly using electronic switches (first transistors, later MOSFETs). This creates a low-voltage AC waveform.

The Role of the Transformer

This 12V or 24V AC current is then fed into a large iron-core transformer. Using the principle of electromagnetic induction, the transformer steps this low voltage up directly to 220V.

These devices operate at grid frequency, meaning 50Hz or 60Hz. The transformer must carry energy at this low frequency. According to the laws of physics, the lower the frequency, the larger and heavier the iron core and copper windings must be to transfer that energy.

That is why in the 1980s, a 1000W inverter could be the size of a small suitcase and weigh 15–20 kg. In contrast, today’s transformer-less (high-frequency) models weigh only a few kilograms.

What Changed?

Since the mid-2000s, “High Frequency” (HF) technology has become dominant. In these systems, the DC voltage is first converted into very high frequencies (20kHz+). This allows the use of small ferrite-core transformers instead of massive iron-core ones.

You might wonder: how can DC have frequency? In DC-to-AC conversion, we do not convert DC into pure AC directly—we simulate AC using switching techniques. Therefore, frequency is still essential in the process.

2) What Are Multilevel Topologies?

A 3-level topology is a method developed to process electricity more gently and more efficiently, especially at high voltages such as 1500V.

Let’s explain the difference from a classic 2-level inverter using a staircase example.

2-Level Inverter

It has only two options: +1500V or –1500V. To create the output waveform, it constantly switches sharply between these two extremes. This creates significant electrical stress on the device and generates a high amount of harmonic distortion.

3-Level Inverter

It adds a third option: 0V (neutral point). Now the steps become +1500V, 0V, and –1500V.

What is NPC (Neutral Point Clamped)?

NPC stands for “Neutral Point Clamped.” This topology includes additional diodes and switches at its core.

Why Is 3-Level NPC Preferred?

Semiconductor Protection:

1500V DC is a very high voltage. Applying 1500V directly across a single transistor (IGBT) can damage it. In a 3-level structure, the voltage is divided into two parts. Each switching device handles only about 750V. This allows the use of more standard and reliable semiconductor components.

Cleaner Waveform (Lower Harmonics):

Because the number of voltage steps increases, the output sine wave becomes much closer to a true sine wave. As a result, harmonic distortion is naturally reduced.

Smaller Filters:

Since the waveform is cleaner, there is less need for large copper filter inductors (LCL filters). This makes the inverter both more efficient and lighter.

In Summary

The 3-level NPC topology is the art of managing a massive voltage like 1500V by dividing it into smaller steps instead of handling it directly. As a result, devices operate cooler, experience fewer failures, and deliver higher-quality (lower-harmonic) power to the grid.