Transformers in Photovoltaic Power Generation Systems: A Complete Technical Guide from System Architecture to Engineering Selection

Why can’t photovoltaic systems do without high-quality transformers?

Driven by the global energy transition and the goal of carbon neutrality, photovoltaic power generation has become one of the most important forms of renewable energy. Whether it is large-scale centralized photovoltaic power stations or industrial and commercial distributed photovoltaic systems, the installed capacity is continuously expanding. However, while photovoltaic modules, inverters, and other equipment are frequently discussed, the key equipment of transformers is often underestimated.

In fact, transformers are the core infrastructure equipment for photovoltaic power generation systems to achieve safe grid connection, stable operation, and efficient transmission. The volatility of photovoltaic systems, the characteristics of power electronicization, and the continuous improvement of grid connection standards have made photovoltaic transformers no longer traditional distribution transformers, but highly specialized power equipment.

This article will systematically analyze transformer technology in photovoltaic power generation systems from multiple dimensions such as system structure, technical requirements, application scenarios, and development trends.

1、 Analysis of the overall architecture of photovoltaic power generation system

A complete photovoltaic power generation system typically consists of the following components:

• Photovoltaic modules
• Combiner Box
• Inverter
• Transformer
• Grid connection and distribution system

Photovoltaic modules convert solar energy into direct current, which is then converged and fed into an inverter. The inverter outputs low-voltage alternating current (commonly 400V or 690V). Due to the fact that power grids typically use medium or high voltage levels, they must be stepped up through transformers before they can be connected to the grid.

In this process, the transformer plays a crucial role as a link between the photovoltaic power generation unit and the public power grid.

2、 The core role of transformers in photovoltaic systems

2.1Voltage level conversion

This is the most fundamental and important function of a transformer. Common boosting paths for photovoltaic systems include:

• 0.4kV → 10kV
• 0.69kV → 20kV
• 0.69kV → 35kV

Reasonable voltage conversion is not only related to grid compliance, but also directly affects system losses and transmission efficiency.

2.2Electrical isolation and system safety

Transformers achieve electrical isolation through winding structures, effectively improving system safety. This is particularly important for distributed photovoltaic projects in densely populated areas.

2.3Power quality regulation

Due to the non-linear nature of inverters, there are inevitably issues such as harmonics and voltage fluctuations in photovoltaic systems. The structural design, wiring method, and impedance configuration of transformers have a significant impact on the power quality of the system.

3、 The difference between photovoltaic transformers and traditional distribution transformers

3.1Fundamental differences in operating conditions

Traditional distribution transformers are usually designed for long-term near full load operation, while photovoltaic transformers have obvious characteristics:

• Daytime operation, no load at night
• Long term low load state
• Power changes rapidly with lighting conditions

Therefore, photovoltaic transformers place greater emphasis on low load efficiency and dynamic adaptability.

3.2Higher resistance to harmonics and impact

The high-order harmonics generated by photovoltaic inverters can cause:

• Increased additional loss of iron core
• The temperature rise of the winding increases
• Accelerated insulation aging

Photovoltaic specialized transformers usually require anti harmonic optimization design to adapt to the power electronics environment.

4、 Application of transformers in centralized and distributed photovoltaics

4.1Centralized photovoltaic power station

Large scale ground photovoltaic power plants usually adopt:

• Oil immersed step-up transformer
• Photovoltaic box type substation

Its advantages include:

• Low loss
• Superior heat dissipation performance
• Suitable for long-term outdoor continuous operation

Centralized projects focus more on full lifecycle costs and long-term reliability.

4.2Distributed photovoltaic system

In industrial and commercial rooftops, park photovoltaics, and other scenarios, more common configurations include:

• dry-type transformer
• Compact Box Transformer

Distributed systems emphasize more on:

• Fire prevention and environmental protection
• Installation flexibility
• Ease of operation and maintenance

5、 Requirements for key technical parameters of transformers in photovoltaic systems

5.1Rated capacity and efficiency curve

The power generation of photovoltaic systems varies significantly over time, so transformer selection should focus on:

• Efficiency in the 30% -70% load range
• No load loss level
• Short term overload capacity

High quality photovoltaic transformers can maintain low losses under non full load conditions.

5.2Wiring method and grid adaptability

Common wiring methods include Dyn11, Ynd11, etc. A reasonable wiring method can help:

• Suppress zero sequence current
• Improve voltage stability
• Improve grid compatibility

5.3Insulation level and environmental adaptability

Photovoltaic power plants are often built in complex environments such as deserts, plateaus, and coastal areas, which require higher requirements for transformers:

• High temperature resistance level
• Moisture proof, salt spray proof, and dust-proof design
• Strong UV and aging resistance

6、 New challenges for transformers under the trend of photovoltaic+energy storage

With the rapid development of the “photovoltaic+energy storage” system, the operation mode of transformers has undergone significant changes:

• Bidirectional power flow
• Frequent switching between charging and discharging
• More complex grid interactions

This has promoted the application of high-efficiency, low loss, and intelligent transformers.

7、 The intelligent and digital development of photovoltaic transformers

Modern photovoltaic power plants are evolving towards digitization and intelligence, and transformers are gradually becoming intelligent nodes：

• Online temperature monitoring
• Partial discharge monitoring
• Status assessment and warning
• Remote operation and maintenance management

These technologies have significantly improved system security and operational efficiency.

8、 The Development Direction of Photovoltaic Transformers from the Global Market Perspective

The continuous growth of photovoltaic investment in Europe, the Middle East, Africa, Latin America and other regions has put forward higher requirements for transformers:

• IEC/IEEE standard compliance
• Customized voltage and capacity
• High reliability and long lifespan design

In the future, truly competitive photovoltaic transformers will be part of the system solution rather than a single device.

The long-term stable operation of photovoltaic systems relies on the support of professional transformers

As photovoltaic power generation moves from “scale expansion” to “quality improvement”, the importance of transformers is constantly highlighted. Only by deeply understanding the operational characteristics of photovoltaic systems can we design and select transformers that are truly suitable for photovoltaic applications.

For photovoltaic project developers, EPC contractors, and equipment purchasers, choosing the appropriate photovoltaic transformer is one of the key decisions to ensure long-term profitability and safe operation of the project.

Luoyang Datang Energy Technology Co., Ltd. is a high-tech enterprise integrating R&D, manufacturing and supply of power equipment such as transformers, new energy components, distribution cabinets and inverters. With technological innovation as the core, we focus on creating high-reliability and high-performance power solutions to serve global customers. With a strict quality control system and international standard certification, we continue to output excellent products and enable customers to build safe and stable power systems.