Technical Progress and Application Status of String Inverters

ByDr. Zhang,Chief Expert, Ginlong (Solis) Technologies

Introduction

As countries worldwide accelerate their push toward “dual-carbon” goals, photovoltaics (PV) are taking center stage in the global energy transition. In 2024 alone, around 530 GW of new PV capacity was added worldwide, with China contributing 277.6 GW — a 28.3% year-on-year increase. 

At the heart of every PV system lies the inverter, the device that converts solar power into usable electricity. Inverters are generally divided into two categories: centralized and string. Over the past decade, string inverters have emerged as the mainstream choice, offering flexibility, adaptability, and strong potential to reduce both upfront investment and the levelized cost of energy (LCOE). By 2024, string inverters accounted for roughly 80% of global shipments, far ahead of centralized units at just 20%. 

As deployment expands across residential rooftops, commercial and industrial systems, and large-scale ground plants, string inverters are evolving at an unprecedented pace. This article reviews the key technology trends and application developments shaping the market as we move into 2025.

The Core Driver: Lower Costs, Higher Efficiency 

The demand for cheaper, more efficient PV systems continues to push string inverter technology forward. Three trends stand out: 

1. High Voltage and High Power 

 Mainstream string inverters have transitioned from 1,100 V to 1,500 V DC input platforms, cutting current, raising conversion efficiency, and reducing costs. The next step is 2,000 V and beyond. Some manufacturers are already rolling out solutions in the 2,000 V / 400 kW+ range, driving down balance-of-system (BOS) costs even further. 

Alongside voltage gains, power density is rising. By 2030, large-scale string inverters are expected to reach 365 kW per unit, with power density climbing from around 2.76 kW/kg in 2024 to over 3.5 kW/kg. That means more power output at lower manufacturing cost. 

2. High DC/AC Overload Ratios 

 Pushing DC input power higher than the inverter’s rated AC power — the “overload ratio” — allows systems to maximize annual output and cut LCOE. Mainstream models now exceed 130%, while leading solutions hit 160% or more, thanks to wide MPPT voltage ranges and intelligent dynamic derating that adjusts output in real time. 

3. Topology Innovation 

 To handle higher voltages and boost efficiency, three-level topologies (such as NPC and ANPC) have become standard in high-power inverters. At 2,000 V and beyond, research is moving into five-level and multi-level designs, further improving waveform quality, reducing stress on devices, and lowering losses. 

Reliability as the Lifeline 

PV plants operate in tough, variable conditions — which means inverter reliability is non-negotiable. Advances are focusing on safety, protection, and predictive maintenance. 

1. DC Arc Fault Detection and Interruption (AFCI) 

 Arc faults are a major fire risk. The latest string inverters use advanced sensors and AI-driven algorithms to achieve near-perfect detection rates and extinguish arcs in under 500 ms. Challenges remain in long-cable and high-current scenarios, but detection accuracy is improving rapidly. 

2. Structural Safety and Explosion-Proof Design 

 Outdoor inverters typically achieve IP65 or higher protection. To address risks from internal faults, new designs combine reinforced enclosures with intelligent pressure relief — such as predefined rupture paths and venting channels — to safely release pressure without sacrificing sealing. 

3. Intelligent Monitoring and Predictive Maintenance 

 Instead of reacting after faults, inverters are shifting to predictive models. Using precise insulation monitoring, temperature sensing, and capacitor health checks, combined with edge/cloud AI algorithms, operators can identify risks early and carry out preventive maintenance. 

Value Expansion: Control and Smart O&M 

As renewable penetration rises, inverters are becoming active participants in grid stability and plant operation. 

1. Grid-Forming Capability 

 Advanced control strategies — such as Virtual Synchronous Generator (VSG), droop control, and Virtual Oscillator Control (VOC) — allow string inverters to provide inertia and damping in weak grids. Some 320 kW+ units can now operate stably at SCR ≥ 1.1 and even deliver black-start capability. The next frontier is fault ride-through and interoperability across different strategies. 

2. Power Quality and Harmonic Suppression 

 Using fast DSPs, optimized modulation, and active filtering, modern string inverters can keep total harmonic distortion (THDi) below 3%, even under complex grid conditions. 

3. AI-Driven O&M 

 AI is transforming operations: minute-level forecasting, second-level IV curve scans, and AI-based fault recognition all help operators run plants more efficiently. The challenge now is integrating diverse data sources — from weather and grid data to module imagery — into actionable insights. 

Industry Foundations: Semiconductors and Localization 

Performance gains depend on breakthroughs in core components — and in supply chain security. 

1. Silicon Carbide (SiC) 

 SiC MOSFETs boost efficiency above 99%, increase power density, and reduce cooling needs. High costs limit use to premium models today, but rapid capacity growth and cost reductions will drive broader adoption. 

2. Gallium Nitride (GaN) 

 GaN is already used in microinverters and auxiliary circuits, with engineering trials underway in higher-power applications. As costs drop and voltage handling improves, GaN will play a bigger role. 

3. Localization 

 China is rapidly closing the gap in IGBTs, SiC modules, and control chips. By 2024, localization rates hit nearly 40% for 1,500 V string inverter power modules. Domestic MCUs are also gaining traction in mid- and low-power products. Localization strengthens supply chain resilience and cost competitiveness. 

Conclusion 

The string inverter industry is in a period of accelerated innovation. High-voltage platforms, advanced control strategies, predictive O&M, next-generation semiconductors, and localized supply chains are converging to deliver higher efficiency, lower costs, and greater reliability. 

Looking ahead, string inverters will not only consolidate their dominance over centralized designs but also become central to new scenarios: commercial rooftops, residential PV, and PV-plus-storage systems. With their evolving intelligence and grid-support capabilities, string inverters are moving from passive power converters to active energy managers. 

For Ginlong (Solis) Technologies and other Chinese manufacturers at the forefront of these developments, the opportunity is clear: lead in technology, scale globally, and make a lasting contribution to the world’s clean energy transition and the achievement of dual-carbon goals.