abstract： the "tuyere" in the tuyere: Investigation on the status quo of photovoltaic inverter

"Tuyere" in tuyere: Investigation on current situation of photovoltaic inverter

Reprinted: Economic Observer

Abstract: the "tuyere" in the tuyere: Investigation on the status quo of photovoltaic inverter

Guide reading

1、 At a time when the global photovoltaic market is in a gale, the inverter, which plays the role of the "heart" of the photovoltaic power station, has also ushered in its own high light moment.

2、 In addition to the two mature inverter products of centralized and series type, various manufacturers in the industry are actively exploring the development direction of the next generation of "inverter", and micro inverter is one of the representatives.

3、 The integrated solution of light storage is more suitable for those areas with power shortage, low power and high electricity price. For domestic families or enterprises, it is really not as cost-effective to land a set of light storage power station as to directly use the market power.

4、 In the second half of last year, the "core shortage" suddenly swept the inverter industry. Leading enterprises such as sunshine power supply and goodway all made clear the supply risks of semiconductor components faced by the company in the annual report of last year.

August 7, the beginning of autumn. Qujing, a small city in Southwest China, is ushering in the longest sunshine period of the year. "Qujing in August has a sunrise at about 6:30 a.m. and a sunset at about 7:40 p.m., with a total sunshine duration of 13 hours and a peak sunshine duration of 4.5 hours. The beginning of autumn is a good time to install photovoltaic power stations." Chen Lin told reporters on the phone.

This "post-85" Chongqing girl is a sales engineer of a distributed photovoltaic enterprise in Jiangsu. August and September at the turn of summer and autumn is usually the busiest time of the year. At present, Chen Lin is following up the delivery of the largest photovoltaic power station project this year. Just a few days ago, she accompanied several heavy trucks of the company from the plant in Changzhou to Qujing, Yunnan, carrying complete sets of photovoltaic modules. "This is a 468kw industrial and commercial power station. Our company is responsible for the installation and grid connection of this project. According to comprehensive estimation, the total power generation of this power station in the first year will reach 630000 kwh, and the carbon dioxide emission reduction will be 650 tons." Chen Lin's tone is a little proud.

However, on the same day of August 7, Chen Lin and the customer still had some twists and turns in the process of checking and counting the goods on the site. "The inverter is not delivered with other components. If the inverter is missing, the project construction needs to be suspended." When it comes to inverters, Chen Lin becomes a little anxious.

Chen Lin's company is an integrated manufacturer in the photovoltaic industry, mainly engaged in one-stop photovoltaic solutions. Its business covers early stage consulting, 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 supports and cables. The inverter that Chen Lin has not yet delivered belongs to the "heart" of the whole photovoltaic power station.

01 "tuyere" in tuyere

The global photovoltaic industry is in the "tuyere", 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, including 30.88gw of new installed capacity, 11.22gw of centralized photovoltaic power stations and 19.65gw of distributed photovoltaic power stations in the first half of 2022. The newly installed capacity of household distributed PV was 8.91gw, with a year-on-year increase of 51.5%.

According to Gao Gangjie, fund manager of AXA PV ETF of Puyin, it is predicted that during the 14th Five Year Plan period, the annual average new photovoltaic installed capacity of China's photovoltaic industry may exceed 75gw.

In the overseas market, in May this year, the European Union released a draft plan called repowereu, which proposed that "by 2025, all new buildings and existing buildings with energy consumption level D or above should be installed with roof photovoltaic equipment". "The conflict between Russia and Ukraine that broke out this year has made Europe pay more attention to its own energy security, so the sales volume in the European market this year is very good." Tang Tao, sales manager of Guangdong Xindun power supply Co., Ltd., told the reporter.

The reporter inquired the data of Eurostat and found that in the first quarter of this year, the scale of PV modules exported to Europe was 16.7gw, a year-on-year increase of 145%.

During the reporter's visit to the photovoltaic enterprises, the market managers of many enterprises disclosed to the reporter that their companies have given up the domestic market strategically and are fully exploring and following up the overseas market demand. "We are now mainly engaged in overseas markets, and domestic ones are not used for consultation." Said a sales manager of Shenzhen meishile New Energy Technology Co., Ltd.

In Tang Tao's view, the growth of sales volume in the European market this year is partly due to the market-based electricity price settlement mode adopted locally. He believed that with the tight energy supply, the soaring electricity price began to make many European families consider the feasibility of photovoltaic power generation. "Different from the big cities in China, European households are very suitable for roof power generation." Tang Tao said.

In the relevant research report recently released by CITIC Securities, it is said that Europe will accelerate the construction progress of photovoltaic projects, and the overseas installed capacity will maintain a high-speed growth. In 2022, the global photovoltaic installed capacity is expected to exceed 230gw.

At a time when the global photovoltaic market is in the gale, the inverter, which plays the role of the "heart" of the photovoltaic power station, has also ushered in its own high light moment.

According to the statistics at the beginning of the year of China Commercial Industry Research Institute, the global PV inverter shipment increased rapidly from 98.5gw in 2017 to 185.1gw in 2020, with a compound annual growth rate of 22.51%. "Although the cost of inverters in the whole system is not high, it is generally 5%, but the photovoltaic power station without inverters is equivalent to (just) erecting several 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 are irradiated on the photovoltaic panel, the electrons in the silicon crystal move due to the absorption of energy, thus forming direct current." Hao Zhe, a technical engineer of a small photovoltaic enterprise in Jiaxing, explained to the reporter that for the power consumption side, the direct current generated by the solar panel can not be directly used. The role of the inverter is to convert the direct current into the power frequency alternating current, which is often referred to as the market power.

Hao zhe said that as an important equipment connecting photovoltaic modules and power grid, the inverter can not only undertake the role of DC / AC conversion, but also keep the photovoltaic panel working at maximum power through MPPT Technology (maximum 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 wind of photovoltaic, the downstream inverter manufacturers are also making a lot of money. "I'm too busy to get the list. Like picking up money, I made tens of millions of achievements in the first half of the year." Wang Fang, the sales manager of a domestic head inverter enterprise, told reporters by telephone.

​Wang Fang said that the sales volume of his company in the first half of this year had exceeded 3 billion yuan, and most of them came to consult and cooperate with customers. Now, compared with the beginning of his career, he has been "lazy" a lot. Except for a few big customers, he has rarely taken the initiative to go out to visit the customers. "Our focus now is on how to do a good job of demand docking, rather than exploring the market." Wang Fang said.

02 the rise and fall of the "three brothers"

"The current inverter market is dominated by centralized, series and micro 'three brothers'." Yi Wenliang told the reporter.

Yi Wenliang is the head of a photovoltaic integrator in Suzhou in South China. In the first half of 2022, they have done more than 20 industrial, commercial and household power station projects throughout the country. He has a lot of experience in inverter selection.

At present, photovoltaic power stations can be generally divided into large-scale ground power stations, industrial and commercial power stations and household power stations. For these three main scenarios, inverters can also be divided into three categories: centralized, string type and micro type. The distinction is mainly based on the number of connected photovoltaic strings and the maximum supporting power rate.

"You can simply understand them as plug-in. 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-scale 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 projects.

"When we plan the overall solution, we will select the inverter from the perspectives of safety, economy and reliability according to the needs of the project party, and do not stick to the theoretical applicable scenarios of various products." Yi Wenliang stressed to the reporter.

Yi Wenliang explained the inverter selection logic to the reporter with a recent project of a super large power station in China as a case. In the photo he showed to the reporter, the reporter saw rows of photovoltaic panels on the ground, forming a blue ocean. "The installed capacity of this power station has reached 1 GW, and more than 2 million photovoltaic panels have been used." Yi Wenliang said. He said that for such a super large power station, in theory, a large centralized inverter should be selected. "The construction site of this power station is located in Ganzi, Sichuan Province, in the plateau area. The terrain is complex, the centralized inverter with a large area is difficult to deploy, and the reliability is poor. Therefore, more than 5000 series inverters are selected for this project to ensure power generation by connecting to the cloud and through intelligent operation and maintenance." Yi Wenliang further explained.

The reporter learned that such cases of abandoning the "heavy" centralized inverter and embracing the "flexible" series inverter 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 basically belong to the series inverter.

According to the statistical data of China Photovoltaic Industry Association, in the domestic market, the proportion of series inverter has exceeded 50% since 2018, and has reached nearly 70% by 2021, while the market share of centralized inverter has shrunk to less than 30%.

In addition to the two mature inverter products of centralized and series type, various manufacturers in the industry are actively exploring the development direction of the next generation of "inverter", and micro inverter is one of the representatives.

"The micro inverter is mainly designed to optimize and develop the traditional inverter in terms of efficiency, safety and operation and maintenance." Zhang Xinyao, senior product manager of Hangzhou Hemai Co., Ltd., said, "on the safety level, in the traditional series inverter architecture, when a single photovoltaic module with a voltage of about 40-50 volts is connected in series, 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 is difficult to extinguish once it burns." Zhang Xinyao said.

Zhang Xinyao showed the experiment made by Hemai Laboratory for the "high voltage DC arc" fault. The reporter saw that when the DC voltage in the system reached 200 V, the two ends of the PV module line produced violent "arc flash" (arc flash phenomenon) and kept burning.

In his opinion, although many photovoltaic modules currently have relevant fire certification, the current domestic fire certification test temperature is usually around several hundred degrees, while the temperature generated by DC arc can reach eight or nine thousand degrees.

In addition, when the roof photovoltaic fire occurs, the site is still in a high-voltage state, which will also bring great safety risks to the firefighters who arrive at the site for rescue.

"Even some foreign firefighters, after arriving at the fire site of the photovoltaic power station, will wait until the fire is completely extinguished before going to rescue." Zhang Xinyao said.

Under this background, the micro inverter of the photovoltaic system is built in parallel by connecting photovoltaic modules separately, which has unique advantages in terms of safety.

The reporter learned that in the construction scheme using the micro inverter, the system voltage is a single module voltage, and when the voltage in the DC system is about 40 or 50 volts, the DC arc generated at the line end is much smaller, thus solving the potential safety problems brought by the high voltage of the roof photovoltaic at the source.

In addition to its advantages in safety, the micro inverter connected with a single module can also avoid the "barrel effect" in the series system. The power generation efficiency is usually 5% - 22% higher than that of the photovoltaic power station using the traditional inverter, and the operation and maintenance is more convenient.

Zhang Xinyao said that compared with the traditional inverter, the micro inverter can monitor the voltage, current, power and other information of a single component. Through the layout map, the fault can be accurately located and the problem can be quickly solved.

However, Yi Wenliang told the reporter that at present, there are not many manufacturers, including leading enterprises in the field of inverters, eager to enter the micro inverter circuit, and they rarely use micro inverters in their projects.

Because, in Yi Wenliang's view, the optimization of the micro inverter for the pain point of the traditional inverter is completely sorry for the price rise caused by it.

According to the reporter, in this year, the price of the centralized inverter in China is usually about 0.15 yuan / W, while the price of the mainstream series inverter is about 0.2 yuan / W. if the series inverter with the rated power of 125KW is taken as an example, the single purchase price is about 25000 yuan.

In contrast, the price of micro inverter in the domestic market is as high as 1.5 yuan / W. under this background, the price of a single micro inverter is 187500 yuan for the same 125KW inverter, which is more than seven times higher than that of the series inverter.

"As for the potential safety risks brought by DC high voltage, the traditional inverter has also adopted many ways to avoid them, such as adding a DC arc prevention detection module. As for the two points of power generation efficiency and easy operation and maintenance, each manufacturer has its own opinions. Anyway, in the project I follow up, the solution with micro inverter has not been adopted yet." Yi Wenliang said.

03 energy storage inverter "popular" overseas

In May this year, a document issued by Pingyin County, a subsidiary of Jinan, a "big city" of photovoltaic, has attracted wide attention in the market.

This document requires that the future distributed photovoltaic construction in Pingyin County should be absorbed locally. In principle, the total development scale of various types of photovoltaic should not exceed 60% of the annual maximum power load in the urban area, and reverse power transmission to 220 kV and above power grids should be avoided.

The document also pointed out that the development of distributed photovoltaic in Pingyin County should be promoted in the way of "photovoltaic + energy storage", and energy storage facilities of no less than 15% and 2 hours should be built or leased according to the specific consumption situation. In case of insufficient consumption capacity of the power grid, the proportion of energy storage configuration and the duration of charge and discharge shall be increased to ensure that the distributed photovoltaic can be locally consumed and meet the requirement of 95% utilization rate.

The release of this document has led to a "old and difficult" problem in the development of distributed photovoltaic in recent years - Photovoltaic consumption.

"A major inborn defect of photovoltaic power generation is instability. The rising and falling of the sun, whether the weather is cloudy or sunny, are all uncontrollable. Therefore, it brings great challenges to the stable operation of the power system." Hao zhe said, "and photovoltaic consumption refers to how to make full use of photovoltaic power generation to avoid waste and impact on the power grid."

In the view of Chen jiongcong, deputy director of Guangzhou Energy Research Institute of Chinese Academy of Sciences, high permeability distributed photovoltaic will test the bearing capacity of the distribution network. At present, the infrastructure level of the domestic distribution network is still difficult to meet the needs of source load interaction and energy balance.

Therefore, under the background that power grid construction still takes time, but photovoltaic construction has been accelerating, promoting the construction of "photovoltaic + energy storage" and realizing on-site consumption has become a feasible measure to solve the current consumption problem. However, the energy storage reverse specially developed by domestic manufacturers for this scenario

Common household energy storage systems now include energy storage inverters, photovoltaic modules and lithium battery energy storage modules, Chen Yong told reporters.

Chen Yong works as a sales manager in an enterprise specializing in the production of energy storage inverters in Shenzhen. According to him, in the first half of this year, he obtained many orders in the company's African, Southeast Asian and European markets, but the progress in China was not great.

"In fact, the integration of light and storage is very easy to understand. The battery is connected under the inverter. In the past, photovoltaic power generation was connected to the power grid. Now, it is self used, and it can be charged into the battery after being used up." Chen Yong said.

In his opinion, the reason why the integration of optical storage is slow in China is still due to the market's consideration of costs.

Taking a household power station project with an installed capacity of 5kW as an example, Chen Yong calculated an account with the reporter. He pointed out that in the construction of the household power station, the main cost items include photovoltaic panels, supports, grid boxes, inverters and labor.

Chen Yongjin further said that the current price of monocrystalline silicon photovoltaic panels is 4 yuan / watt, the installed capacity of 5kW needs 20000 yuan, and the matching inverter with the same power needs 10000 yuan. The total cost of the remaining supports, grid boxes and labor is about 14000 yuan, and the total installation cost is about 40000 yuan to 50000 yuan.

"If the effective light is 4 hours a day, the annual power generation of this 5kW power station can reach more than 7000 kwh, which basically meets the daily power demand of a family of three." Chen Yong said.

However, if the power station is equipped with energy storage batteries, the situation will change.

"If you want to do the integration of light and storage, you must at least have a battery that can meet your daily power demand. Now the average daily power consumption of the family is about 15 degrees, but the corresponding price of the energy storage battery is about 2000 yuan per kilowatt hour." Chen Yong said.

According to Chen Yong's calculation, taking the above 5kW household power station as an example, if an energy storage battery with a capacity of about 15 degrees is required, the user needs to pay an extra 30000 yuan. Moreover, under the background that the 5kW power station just meets the daily power consumption of the user, it is difficult to have surplus power to charge the battery.

Therefore, during the actual implementation of the project, Chen Yongtong often suggested that the customer integrate the power station into the power grid. If it is to be an off grid power station, he would also give priority to the customer to purchase ordinary inverters directly, so as to achieve the effect that the power generation can not be connected to the power grid by installing anti backflow devices. "Light storage integration is not cost-effective for small household power stations, let alone industrial and commercial power stations with larger scale." Chen Yong was somewhat helpless.

In Chen Yong's view, the integrated solution of optical storage is more suitable for those areas with power shortage, low power and high electricity price. For domestic families or enterprises, it is not as cost-effective to land a set of optical storage power station as to directly use the market power.

04 IGBT chip problems

At present, many inverter manufacturers who actively explore photovoltaic solutions under different scenarios and try to help the industry solve their problems also have their own problems.

In the second half of last year, the "core shortage" suddenly swept the inverter industry. Leading enterprises such as sunshine power supply and goodway all made clear the supply risks of semiconductor components faced by the company in the annual report of last year. "The semiconductor devices in the company's power electronic equipment mainly include power semiconductor devices and various chips. The main manufacturers are foreign enterprises. At present, there are few domestic manufacturers and there are still gaps in performance indicators. Superimposed on the impact of the global epidemic on the production capacity of manufacturers, there is a certain risk of insufficient supply and price fluctuation of semiconductor devices." Sunshine power said in the annual report of 2021.

In the 2021 annual report, goodway pointed out that the capacity of LGBT chips could not match the demand, and there were few domestic manufacturers of IGBT components. Compared with imported components, there were certain differences in product stability and technical indicators, and it is expected that import substitution will not be fully realized in the short term.

Wu Dong, the customer manager of an inverter enterprise in Shenzhen, recalled to the reporter that around November last year, their company adopted the quota sales method to supply products to customers in a fixed amount every month. These queued production orders were not digested until March this year.

"At that time, the inverter belonged to 'there was a price but no market'. Many customers could not get the goods even if they had money, so they had to wait." Wu Dong said.

This chip that makes the inverter industry collective "panic" is called IGBT, and its full Chinese name is insulated gate bipolar transistor. This chip is mainly used for power conversion and circuit control of power equipment. It is a core device for power processing and a bridge for converting DC power to AC power.

"If the inverter is the heart of the photovoltaic power station, then the LGBT chip is the heart of the inverter." Hao zhe explained to the reporter.

The well-known private equity firm Dunhe asset management once issued a document in June this year saying that the current 1GW photovoltaic installed capacity needs to consume about 4000 igbt8 inch chips, of which 3800 chips are consumed by the centralized inverter and 4200 chips are consumed by the series inverter.

Dunhe asset management believes that based on the installed capacity of 170gw of PV in 2021, IGBT can support the installed capacity of 240gw at most in 2022. If the installed capacity of PV exceeds 250gw in 2022, IGBT is likely to become a bottleneck of PV installation.

As for the current IGBT core shortage phenomenon in the inverter industry, the reporter once expressed his intention to interview several head manufacturers, but all of them were declined on the ground that the problem was sensitive.

However, according to the reporter's first-line visit to the market, compared with the end of last year, the lack of core in the photovoltaic inverter industry has been basically alleviated. Except that the production of individual high-power inverters still needs to queue up due to the impact of IGBT capacity, other products can basically ensure stable supply.

Li He, deputy general manager of a small inverter enterprise in Zhejiang, told the reporter that at present, the LGBT chips used in the company's products are mainly purchased from foreign enterprises such as Infineon, Fuji and Mitsubishi. However, his company only learned about the LGBT chips produced by domestic manufacturers in March this year.

Hao zhe told the reporter that the technical barrier of LGBT chip production is high. At present, the domestic IGBT chip can only meet the photovoltaic application scenarios within 35kw, and there is still a certain gap between the products of overseas manufacturers in performance indicators.

The reporter had an exchange with a regional manager of sungrow power on the topic of self-produced LGBT chips. The manager said that the company has no plan to research and produce LGBT chips by itself. "If chips were so easy to make, Huawei would have made them long ago." He said.

Wang Bohua, honorary chairman of China Photovoltaic Industry Association, said at a seminar in July that the localization rate of photovoltaic LGBT chips in the second quarter of this year was only 4% to 5%. According to his prediction, the localization rate of LGBT chips may rise to 10% by the end of this year.

(at the request of the interviewee, Wang Fang is an alias)