The tuyere in the tuyere: a survey of the status quo of photovoltaic inverters
The global photovoltaic industry is in the "wind", showing a "blowout" development.
Guided reading
One || When the global photovoltaic market is in the midst of a big wind, the inverter, which plays the role of the "heart" of photovoltaic power plants, has also ushered in its own highlight moment.
Ⅱ||In addition to the relatively mature inverter products of centralized type and string type, various manufacturers in the industry are also actively exploring the development direction of the next-generation "inverter", and micro-inverter is one of them. one of the representatives.
3|| The integrated solution of solar energy storage is more suitable for those areas with power shortage, low electricity and high electricity price. For domestic families or enterprises, it is indeed better to use a set of solar energy storage power station directly than to use mains electricity. cost-effective.
Four || In the second half of last year, the "chip shortage" suddenly swept the inverter industry. Leading companies such as Sungrow and GoodWe all clarified the supply risks of semiconductor components faced by the company in their annual reports last year.
On August 7, the beginning of autumn. Qujing, a small town on the southwestern border of my country, is ushering in the longest period of sunshine of the year. "In August, Qujing sunrise at around 6:30 in the morning and sunset at around 7:40 in the evening, the total sunshine duration can reach 13 hours, and the peak sunshine duration is 4.5 hours. The beginning of autumn is the time when photovoltaic power plants are installed. Good time." Chen Lin told reporters on the phone.
This "post-85" Chongqing girl is a sales engineer for a distributed photovoltaic company in Jiangsu. August and September at the turn of summer and autumn are usually her busiest time of year. Right now, Chen Lin is following up on the delivery of her first photovoltaic power station project this year. Just a few days ago, she set off from the factory in Changzhou with several of the company's heavy-duty trucks, carrying a complete set of photovoltaic modules, over the mountains. Ling came to Qujing, Yunnan. "This is a 468kW industrial and commercial power station. This project is carried out by our company from installation to grid connection. According to comprehensive estimates, the total power generation of this power station in the first year can reach 630,000 kWh, and achieve 650 tons of carbon dioxide emission reduction." Chen Lin There was a hint of pride in his tone.
However, on August 7, when Chen Lin and the customer checked and counted the goods together on the spot, there were still some small twists and turns. "The inverter was not delivered with the other components. If the inverter is missing, the project construction (just) needs to be postponed." When it comes to the inverter, Chen Lin became a little anxious.
Chen Lin's company is an integrated manufacturer in the photovoltaic industry. It mainly provides one-stop photovoltaic solutions. Its business covers pre-project consultation, system design and operation and maintenance monitoring.
However, the company itself does not have the ability to produce photovoltaic modules including solar panels, distribution boxes, photovoltaic brackets and cables, and the inverter that Chen Lin said has not been shipped yet belongs to the entire photovoltaic power station. The "heart" in it.
The "window" in the tuyere
The global photovoltaic industry is in the "wind", showing a "blowout" development.
On July 29, the National Energy Administration announced the construction and operation of photovoltaic power generation in the first half of 2022. Among them, in the first half of the year, the newly installed photovoltaic capacity was 30.88GW, the centralized photovoltaic power station was 11.22GW, and the distributed photovoltaic was 19.65GW. The newly installed capacity of household distributed photovoltaics was 8.91GW, a year-on-year increase of 51.5%.
According to Gao Gangjie, the fund manager of Puyin AXA Photovoltaic ETF, recently predicted that during the 14th Five-Year Plan period, my country's annual average new photovoltaic installed capacity may exceed 75GW.
In terms of overseas markets, in May this year, the European Union released a draft plan called REPowerEU, which proposed: "By 2025, all new buildings and existing buildings with energy consumption class D or above should be installed with rooftop photovoltaics. equipment". "The Russian-Ukrainian conflict that broke out this year has made Europe pay more attention to its own energy security, so the sales in the European market this year are very good." Tang Tao, sales manager of Guangdong Xindun Power Co., Ltd., told reporters.
The reporter checked the data of Eurostat and found that in the first quarter of this year, the scale of domestic photovoltaic modules exported to Europe was 16.7GW, a year-on-year increase of 145%.
During the reporter's visit to photovoltaic companies, the market managers of many companies revealed to reporters that their companies have strategically abandoned the domestic market and are trying their best to tap and follow up on overseas market demand. "We are mainly engaged in overseas markets now, and domestic ones are not used for consultation." A sales manager of Shenzhen Mercer New Energy Technology Co., Ltd. said.
In Tang Tao's view, the sales growth in the European market this year is partly due to the market-based electricity price settlement model adopted locally. He believes that in the context of tight energy supply, soaring electricity prices have begun to make many European households consider the feasibility of photovoltaic power generation. "Unlike the big cities in China, the type of residential houses in Europe is very suitable for roof power generation." Tang Tao said.
According to a recent research report released by CITIC Securities, Europe will speed up the construction of photovoltaic projects, overseas installed capacity will maintain a relatively rapid growth, and the global photovoltaic installed capacity is expected to exceed 230GW in 2022.
At a time when the global photovoltaic market is in a big blow, the inverter, which plays the role of the "heart" of photovoltaic power plants, has also ushered in its own highlight moment.
According to statistics from the China Business Industry Research Institute at the beginning of the year, the global PV inverter shipments have risen rapidly from 98.5GW in 2017 to 185.1GW in 2020, with a compound annual growth rate of 22.51%. "Don't look at the cost of the inverter in the entire system, which is generally 5%, but a photovoltaic power station without an inverter is equivalent to (just) setting up a few empty boards." Chen Lin told reporters.
"Photovoltaic power generation mainly uses the 'photoelectric effect' learned in middle school, that is, when the photons in the sunlight hit the photovoltaic panel, the electrons in the silicon crystal move due to absorbing energy, thereby forming direct current." Jiaxing family Hao Zhe, a technical engineer of a small photovoltaic enterprise, explained to reporters that for the electricity side, the direct current generated by the solar panels cannot be used directly. The function of the inverter is to convert the direct current into power frequency alternating current, which is what we often say Mains electricity.
Hao Zhe said that the inverter, as an important device connecting photovoltaic modules and the power grid, not only undertakes the role of DC-AC conversion, but also enables the photovoltaic panels to work at maximum power through MPPT technology (*power point tracking). "In addition to being like the 'heart', it is also like the 'brain' of a photovoltaic power station." Hao Zhe said.
At present, with the increasingly fierce photovoltaic wind, downstream inverter manufacturers are also earning "plenty of money". "I am too busy to receive orders. It's like picking up money. I made tens of millions in the first half of the year." Wang Fang, a sales manager of a domestic head inverter company, told reporters on the phone.
Wang Fang said that the sales of his company in the first half of this year have exceeded 3 billion yuan, and most of them are customers who come to consult and cooperate on their own initiative. Now he is much "lazy" compared to the beginning of his career. Except for a few big customers, he has rarely taken the initiative to go out to visit customers. "Our focus now is how to do a good job in meeting demand, rather than opening up the market." Wang Fang said.
The rise and fall of the "Three Brothers"
"The current inverter market is dominated by centralized, string and micro 'three brothers'." Yi Wenliang told reporters.
Yi Wenliang is the head of a photovoltaic integrator in Suzhou in southern China. In the first half of 2022, they have done more than 20 industrial, commercial and household power station projects across the country. He has a lot of experience in the selection of inverters.
At present, photovoltaic power plants can be roughly divided into large-scale ground power plants, industrial and commercial power plants and household power plants. For these three main types of scenarios, inverters can also be divided into three categories: centralized, string and micro. The main difference lies in The number of connected PV strings and the maximum supported power.
"You can simply understand them as sockets. The centralized inverter has the most jacks and can connect the most photovoltaic modules, while the micro-inverter has only one jack and can only connect one photovoltaic module." Yi Wenliang said .
The reporter learned that in common photovoltaic power generation scenarios, centralized inverters are mainly used in large photovoltaic power plants with a total power of more than 1 MW, while string inverters are often used in small and medium-sized distributed photovoltaic power plants. in photovoltaic projects.
"When we plan the overall solution, we will select inverters from the perspectives of safety, economy and reliability according to the needs of the project party, and are not bound by the theoretical application of various products. Scene." Yi Wenliang emphasized to reporters.
Yi Wenliang used a recent project of a super-large power station in China as a case to explain the logic of inverter selection to reporters. In the photo he showed to reporters, the reporter saw rows and rows of photovoltaic panels merged into a blue ocean on the ground. "The installed capacity of this power station has reached 1 GW, and more than 2 million photovoltaic panels are used." Yi Wenliang said. He said that for such a super-large power station, a large centralized inverter should theoretically be used. "The construction site of this power station is located in Ganzi, Sichuan, in the plateau area. The terrain conditions are complex, and the deployment of centralized inverters with a large area is difficult and the reliability is poor. Therefore, more than 5,000 string-type inverters were finally selected for this project. The inverter, by connecting to the cloud, ensures power generation through intelligent operation and maintenance." Yi Wenliang explained further.
The reporter learned that such cases of abandoning "clunky" centralized inverters and embracing "flexible" string inverters are the epitome of the development trend of the inverter industry in recent years. In the current market , The products of various mainstream inverter manufacturers are basically string inverters.
According to the statistics of China Photovoltaic Industry Association, in the domestic market, since 2018, the proportion of string inverters has exceeded 50%, and by 2021, it will be close to 70%, while the market of centralized inverters has exceeded 50%. The proportion has shrunk to less than 30%.
In addition to the relatively mature inverter products of centralized type and string type, various manufacturers in the industry are also actively exploring the development direction of the next-generation "inverter", and micro-inverter is one of the representatives .
"Micro-inverters are mainly developed to optimize the development of traditional inverters in terms of efficiency, safety, and operation and maintenance." said Zhang Xinyao, senior product manager of Hangzhou Hemai Co., Ltd. In the string inverter architecture of 2019, after connecting a single photovoltaic module in series with a voltage of about forty or fifty volts, there is a high voltage of about 300v-1500v in the whole system."
"In the DC high voltage system, if there is a fault arc in the line, it will be difficult to extinguish once it burns." Zhang Xinyao said.
Zhang Xinyao showed the experiment done by Hemai Laboratory for the "high voltage DC arcing" fault. The reporter saw that when the DC voltage in the system reached 200 volts, a violent "arc flash" occurred at both ends of the photovoltaic module line. (arc flash phenomenon) and continued to burn.
In his view, although many photovoltaic modules have relevant fire protection certification, the current domestic fire certification test temperature is usually around a few hundred degrees, while the temperature generated by the DC arc can reach eight or nine thousand degrees.
In addition, when a roof photovoltaic fire occurs, because the scene is still in a high voltage state, it will also bring great safety hazards to firefighters who arrive at the scene for rescue.
"There are even some foreign firefighters who, after arriving at the fire scene of the photovoltaic power station, will wait until the fire is completely extinguished before going to rescue." Zhang Xinyao said.
In this context, by connecting photovoltaic modules individually and constructing micro-inverters of photovoltaic systems in parallel, it has unique advantages in terms of safety.
The reporter learned that in the construction scheme using the micro-inverter, the system voltage is the voltage of a single component, and when the voltage in the DC system is around forty or fifty volts, the DC arc generated at the line end is much less, so At the source, the hidden safety hazards caused by the high voltage of rooftop photovoltaics are solved.
In addition to its advantages in safety, micro-inverters connected with a single module can also avoid the "cask effect" in string systems, and the power generation efficiency is usually 5% higher than that of photovoltaic power plants using traditional inverters- 22%, and operation and maintenance are also more convenient.
Zhang Xinyao said that compared with traditional inverters, micro-inverters can monitor the voltage, current, power and other information of a single component, and can accurately locate faults and solve problems quickly through the layout diagram.
However, Yi Wenliang told reporters that, including leading companies in the inverter field, not many manufacturers are eager to enter the micro-inverter track, and they themselves rarely use micro-inverters in their projects.
Because, in Yi Wenliang's view, the optimization of micro-inverters for the pain points of traditional inverters is completely sorry for the price increase it brings.
According to the reporter's understanding, this year, the price of centralized inverters in China is usually about 0.15 yuan/W, while the price of mainstream string inverters is about 0.2 yuan/W. Take a string inverter as an example, the purchase price of a single unit is about 25,000 yuan.
In contrast, the price of micro-inverters in the domestic market is as high as 1.5 yuan / watt. In this context, the same 125kW power inverter, the price of a single micro-inverter needs 187,500 yuan yuan, which is more than 7 times higher than that of string inverters.
"For the potential safety risks brought by DC high voltage, traditional inverters have also adopted many methods to avoid them, such as adding an anti-DC arcing detection module, and for power generation efficiency and ease of operation and maintenance, each manufacturer has its own There is a saying, anyway, in the projects I follow up, the solution with micro-inverter has not been adopted yet." Yi Wenliang said.
Energy storage inverters are "popular" overseas
In May of this year, a document issued by Pingyin County, a subsidiary of Jinan, the "big city" of photovoltaics, has attracted widespread market attention.
This document requires that the future construction of distributed photovoltaics in Pingyin County should be absorbed locally. In principle, the total development scale of various photovoltaics should not exceed 60% of the annual maximum electricity load in its urban area. reverse transmission.
The document also pointed out that the development of distributed photovoltaics in Pingyin County should be promoted in accordance with the "photovoltaic + energy storage" method, and energy storage facilities of not less than 15% and 2 hours should be built or leased according to the specific consumption situation. When the capacity of the grid is insufficient, the proportion of energy storage configuration and the duration of charging and discharging should be increased to ensure that distributed photovoltaics can be consumed locally and nearby to meet the 95% utilization rate requirement.
The release of this document has brought out a "big problem" faced by the development of distributed photovoltaics in recent years - photovoltaic consumption.
"One of the congenital defects of photovoltaic power generation is instability. The rise and fall of the sun, whether the weather is cloudy or sunny, are all uncontrollable, so this brings great challenges to the stable operation of the power system." Hao Zhe Said, "The photovoltaic consumption refers to how to make full use of photovoltaic power generation, neither waste, but also avoid impact on the power grid."
According to Chen Jiongcong, deputy director of the Guangzhou Institute of Energy Research, Chinese Academy of Sciences, distributed photovoltaics with high penetration rate will test the carrying capacity of the distribution network. At present, the level of domestic distribution network infrastructure is still difficult to meet the needs of source-load interaction and power balance.
Therefore, in the context of grid construction still taking time, but photovoltaic construction has been accelerating, promoting the construction of "photovoltaic + energy storage" and realizing local consumption has become a feasible measure to solve the current consumption problem, while domestic manufacturers The energy storage inverter specially developed for this scenario has also begun to come to the forefront.
Common household energy storage systems include energy storage inverters, photovoltaic modules, and lithium battery energy storage modules.