Technology iteration means market change or even life and death, which is particularly impressive in the ever-changing photovoltaic industry.
It has been less than 20 years since the application of my country’s first grid-connected inverter in 2003. With the upgrading of inverter technology and changes in the terminal market, the photovoltaic inverter industry has been reshuffled several times, and enterprises have disappeared and withdrawn. Green and rising
As far as the inverter technology route is concerned, the industry is generally divided into centralized, distributed, string and micro-inverters, of which the centralized and string types occupy 90% of the market. The former is commonly known as “big inverter”. “, the latter is a “small machine”.
The war of separatism between large and small machines has not stopped. Under the new demands of the new power system, where will the technological evolution of photovoltaic inverters go?
1. Small machine counterattack
Those who are familiar with the photovoltaic industry can easily guess that the numbers at the beginning of the article are the success of string inverters. The counterattack in the market share of small machines is sometimes more artificial.
Back in 2003, Sungrow led by Cao Renxian, head of the academic school, launched my country’s first 10kW grid-connected photovoltaic inverter with independent intellectual property rights. However, until 2009, there were few inverter companies in my country. There are very few overseas brands such as Emerson, SMA, Siemens, Schneider, ABB, etc., which rely on imports for a large number of equipment.
But at the same time, the profits as high as 200~300% have also stimulated the mushrooming of domestic inverter companies. From 2011 to 2012, the number of photovoltaic inverter companies in my country surged to more than 140. Players surged, and price wars followed. Overseas brands gradually withdrew from the domestic market after this round of fierce fighting.
Next, it is the boiling moment of the domestic market. Since 2011, in order to further cultivate the demand of the domestic photovoltaic terminal market, subsidy policies have been introduced, officially opening the long-awaited “golden age” of ground photovoltaic power plants. At this time, due to cost factors, the standard configuration of ground photovoltaic power plants is large-scale centralized inverters, and domestic large-scale machine companies such as Sungrow Power and Sineng Electric are galloping in the market.
Of course, there will always be “lone brave men” in the era, and the communication giant Huawei began to focus on inverters and chose all in string inverters.
It is undeniable that the string inverter defined by Huawei subverts the tradition, integrates digital technology and power electronics technology, and uses intelligent controllers as the core to create smart photovoltaic solutions with better cost of electricity. The fanless inverter it advocates A series of concepts such as no fuse, intelligent IV diagnosis technology, “0-Touch” operation and maintenance, and SDS intelligent tracking bracket optimization algorithm maximize the value of string inverters and lead the concept of the inverter market innovation.
Led by Huawei, string inverters began to gradually squeeze into the ground power station market, and at the same time, the turning point reappeared. Since 2016, distributed photovoltaics, which have been highly favored by policies, have begun to explode. Many small machine companies working overseas Gurui Watt, GoodWe, Jinlang, etc. returned to China and quickly seized market share.
“Limited by scale and grid-connected voltage, most distributed photovoltaic power plants use string inverters.” Shangneng Electric pointed out, “And as the price of string inverters decreases year by year, the ground power station’s Competitiveness will also increase further.”
The proportion of string inverters will continue to increase, which has become the unanimous judgment of mainstream inverter companies. Huawei expects that the market share of string inverters will climb to 80% in 2022.
However, the technical school Sungrow Power tried to break through the barriers. It launched the “1+X” modular inverter last year, claiming that it is independent of the string and centralized inverters and can meet the multi-scenario applications of distributed and ground power stations.
2. Market changes?
In terms of inverter selection and adapting to the needs of different application scenarios, “adjust measures to local conditions” can be described as a general rule in the industry.
For example, the centralized inverter has a large single-unit capacity, a small number of equipment, convenient installation and maintenance, and adapts to various types of components. According to Sineng Electric, centralized inverters are still the mainstream solution in large-scale flat power stations and water surface power stations around the world.
String inverter, “Based on the inherent characteristics of multi-channel MPPT tracking, it has multiple advantages such as increased power generation, convenient intelligent operation and maintenance, and small granularity of single-unit failure during the entire life cycle of the power station.” Kehua Digital Energy Market Personnel introduction. String inverters are mainly used in distributed power plants and complex mountain applications.
The photovoltaic terminal market is also quietly changing under the strong hurricane of global carbon emission reduction. To implement the goal of carbon peaking and carbon neutrality, the country will accelerate the construction of large-scale wind power and photovoltaic bases in deserts, Gobi, and desert areas. By 2030, the planned installed capacity will reach 455GW, which will become an absolute potential market for new installed capacity in the next ten years.
“Large bases are mainly constructed in the deserts and Gobi areas of the Three Norths, with flat terrain as the main base. The application ratio of more cost-effective centralized inverters in base projects will increase.” Shangneng Electric believes.
“Not necessarily.” Han Guang, Product Director of Photovoltaic Channel Department of Shenzhen Hopewind Electric Co., Ltd., said that with the increasing capacity of string inverters, the current capacity of a single inverter has reached 300kW+, and it may reach 500kW in the future. , which will lead to a further reduction in the cost of string inverters, and the cost advantage of centralized inverters will not be so significant. In addition, in the desert environment, the IP54 protection level of the traditional centralized inverter may not be able to meet the long-term stable operation in the harsh environment of wind and sand, and the protection level of the string inverter IP65/IP66 makes it more reliable.
However, TBEA also emphasized that the company’s centralized inverters have IP65 protection capabilities, and can completely compete with string inverters in terms of environmental adaptability.
In this regard, Sungrow still emphasizes “adapting measures to local conditions and scientific design”, and the optimal solution should be selected for use in large-scale photovoltaic base scenarios such as Gobi and deserts.
Returning to the actual application scenario again, in the large clean energy base, the new energy mainly composed of wind and solar accounts for more than 60%, and the grid connection stability of the power station will undoubtedly become the main challenge. Take Qingyu DC, which transmits 100% new energy power, as an example. Due to the lack of voltage support near the DC sending end and the impact of transient overvoltage, the more new energy power generation, the smaller the Qingyu DC transmission capacity.
Therefore, the power grid puts forward higher requirements on the grid-connected characteristics of photovoltaic inverters. In December 2019, GB/T 37408-2019 “Technical Requirements for Grid-connected Inverters for Photovoltaic Power Generation” and GB 37855-2019 “Guidelines for Stability of Power Systems” were promulgated and implemented successively. The rate of change does not exceed 10%, and the latter first proposed the concept of short-circuit ratio (SCR).
In response to the higher requirements of clean energy bases for grid adaptability, Huawei supports string inverters: “Huawei introduced an AI self-learning algorithm for impedance reshaping, integrating dynamic damping adaptation algorithms, intelligent series compensation adaptive algorithms, active Various leading grid-connected algorithms, such as harmonic suppression algorithm, dynamically adjust the electrical characteristics of the power station itself to match the grid through AI self-learning, so that the grid remains stable.”
3. Long time must be combined
In fact, it is not only a clean energy base, but under the pressure of building a new power system based on new energy, photovoltaic power generation urgently needs to move from “adapting to the grid” to “supporting the grid”.
Under this proposition, as the “brain” of the photovoltaic system and the “bridge” between the photovoltaic power generation unit and the grid, the technological change of photovoltaic inverters will continue to surge.
“In 2008, the power of mainstream centralized inverters in ground power stations was 250kW, and today the power of mainstream string inverters in ground power stations is also 250kW. Long-term separation must be combined, and ‘combination’ has become a trend.” Shangneng Electric expects.
Surprisingly, not only Shangneng Electric, but also mainstream inverter companies such as Sungrow, TBEA, Kehua Shuneng and Hopewind Electric have surprisingly consistent predictions, and the technical route of future inverters will become more and more blurred.
Focusing on the core demands of high reliability, high efficiency and low cost, the technological evolution of photovoltaic inverters includes the following five major trends:
First, high pressure and high density.
System voltage increase is an important way to reduce LCOE, from 600V to 1000V to 1500V, and will move to higher voltage in the future. While the system voltage is increasing, the sub-arrays are getting bigger and bigger. At present, the domestic mainstream is still 2.5MW and 3.125MW square arrays, and it may reach 5MW, 6.25MW or even larger in the future. Larger sub-arrays can reduce inverters, transformers and collector lines. Cost, to achieve lower cost of electricity.
In Huawei’s view, with the development of root technologies such as silicon carbide, gallium nitride materials, chip heat dissipation, and topology architecture, the power density of inverters will increase by more than 50% by 2025.
Among them, for centralized inverters, Sineng Electric expects that the power of a single unit will be gradually upgraded from 3.125MW to 4.4MW and higher; and for string inverters, it has reached 300kW+ for a single unit at present, and it is possible to achieve it in the future. 500kW.
Second, the integration of light and storage.
The inverter uses the solar-storage collaborative control algorithm to realize the characteristics of synchronous machines such as virtual inertia, and the technical indicators of photovoltaic power generation are closer to thermal power, which can be stored and controlled, and further strengthen the power grid. Huawei expects that by 2025, the proportion of solar-storage symbiosis will reach more than 30%.
Third, intelligence.
The in-depth application of intelligent AI technologies such as 3D power station twinning, intelligent power prediction, intelligent IV scanning, open intelligent support tracking system, and intelligent health diagnosis of optical storage enables the system to be independently and collaboratively optimized, creating infinite possibilities.
Fourth, support the power grid.
High-throughput active power stability, high-low voltage ride-through capability, frequency adaptability… Photovoltaic inverters need to have more accurate grid-connected algorithms.
Fifth, modularization.
The modular design can realize expert-free maintenance, greatly reduce operation and maintenance costs, improve system availability, support a longer power station life cycle, and help reduce LCOE by 25%.
In addition, technological trends such as intelligent shutdown and substitution of domestic components have also been repeatedly mentioned by enterprises.
4. Latent micro-inverter and power optimizer
To ensure the maximum output power of photovoltaic arrays, the maximum power point tracking (MPPT) technology of photovoltaic inverters is regarded as the standard. Here, the advantages of microinverters and power optimizers are incomparable.
Micro-inverter, according to Kehua Shuneng, its main feature is independent MPPT tracking and inverter grid connection for each module, one board and one inverter, and it is completely free from the influence of occlusion and tendency of the module string, maximizing By using the roof area, some non-high-quality photovoltaic roof resources with shade can also be developed.
The power optimizer is also available, “Not only that, but with the large-scale development of photovoltaics, system safety issues have become more and more prominent. Roof photovoltaic high voltage brings potential risks to users and operation and maintenance personnel, and it will also cause fire and rescue in emergency situations. Obstacles. Install a power optimizer, and the voltage of photovoltaic modules can be quickly shut down to zero V, ensuring the safety of personnel and property.” Huawei added.
Of course, according to micro-inverter companies, micro-inverters still belong to the category of inverters and undertake the task of DC-AC conversion, while optimizers are not inverters. In addition, microinverters and power optimizers differ significantly in terms of module-level shutdown functionality.
At present, the application markets of micro-inverters and power optimizers are mainly concentrated overseas. For example, the United States first proposed module-level shutdown requirements, and Australia also updated the DC isolator shutdown standards. The basis for the popular application of power optimizers in corresponding countries.
Focusing on the domestic market, on the one hand, the policy of module-level shutdown and safety requirements corresponding to distributed photovoltaics needs to be introduced and enforced.
On the other hand, it is also the core, and the economy is relatively weak. “The cost per watt of a micro-inverter is more than twice that of a string inverter, and its primary task should be to reduce the cost to a reasonable range through technological innovation.” Han Guang revealed.
But the opportunity is also ready to go, “my country has increased the peak-to-valley price difference and opened up the carbon trading market and personal carbon emissions, which has increased the added value of green power. When the cost of thermal power/the added value of green power has reached a threshold, That’s when the micro-inverter breaks out.” TBEA expects.
“The application of the optimizer is not limited to distributed scenarios, but also has applications in large-scale ground power stations.” Huawei emphasized, “Components decay over time, and the attenuation between components is inconsistent, which leads to the fact that even the same model After a period of time, the power generation of the components will also vary, which may easily cause series mismatch and affect the power generation. And the components are affected by environmental changes during operation, such as weeds, side dust, etc. will affect the power generation. Optimizer Then the influence caused by the above problems can be avoided, and the power generation can be significantly increased.”
With policy adjustments, market changes, and technology collisions, the technical landscape of photovoltaic inverters is still in intense turmoil.
statement of thanks
This inverter special manuscript has received strong support from companies such as Sungrow, Huawei, Sineng Electric, TBEA, Growatt, Kehua, Hopewind, and Maitian. Due to space limitations and the logic of writing, we cannot show the wonderful replies of all enterprises one by one, please understand.
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