微型逆變器是組件級(jí)控制觀念的呈現(xiàn)

逆變器是光伏發(fā)電系統(tǒng)的心臟。不僅承擔(dān)將太陽能光伏產(chǎn)生的直流電轉(zhuǎn)換為交流電的重要角色，在完成最大功率點(diǎn)跟蹤后還要將電能并入電網(wǎng)或用于家用電器。作為分布式電源與電網(wǎng)的接口，逆變器性能將直接影響到光伏發(fā)電系統(tǒng)的發(fā)電效率及運(yùn)行穩(wěn)定性。

逆變器主要分為集中式逆變器、組串式逆變器和微型逆變器。工作原理方面，集中式逆變器是將大量并行的光伏組串連接到同一臺(tái)集中式逆變器的直流輸入端，完成最大功率點(diǎn)跟蹤后，再統(tǒng)一并網(wǎng)。組串式逆變器對(duì)數(shù)串光伏組件單獨(dú)進(jìn)行最大功率追蹤，在經(jīng)過逆變單元后并入交流電網(wǎng)。微型逆變器則是每個(gè)逆變器只對(duì)應(yīng)少數(shù)光伏組件，實(shí)現(xiàn)對(duì)每塊光伏組件單獨(dú)的最大功率點(diǎn)跟蹤，在逆變轉(zhuǎn)化之后單獨(dú)并入交流電網(wǎng)。

微型逆變器運(yùn)行效率更高、安全性更好   主要應(yīng)用于戶用發(fā)電場景

微型逆變器作為組件級(jí)電力電子設(shè)備可以對(duì)每塊光伏組件的輸出功率進(jìn)行精細(xì)化調(diào)節(jié)及監(jiān)控，在遇到部分陰影遮擋和個(gè)別組件性能出現(xiàn)故障的情況下，能夠提升光伏系統(tǒng)整體的運(yùn)行效率。同時(shí)比起集中式、組串式逆變器輸入端的1000V直流高壓，微型的最大輸入電壓僅為 60V，很大程度上降低了電站的安全隱患，在安裝和調(diào)試方面也更為簡單。不過相比集中式逆變器和組串式逆變器，微逆的單瓦價(jià)格較高，當(dāng)下的應(yīng)用場景主要以戶用光伏電站為主。

一、 需求端：三重滲透下的百億市場

作為清潔能源的太陽能在電力裝機(jī)結(jié)構(gòu)中的滲透率正在提升。其主要原因在于（1）加快以光伏為代表的新能源建設(shè)已經(jīng)日益成為全球主要經(jīng)濟(jì)體的政策共識(shí)；（ 2）近年來全球通脹導(dǎo)致的大宗商品價(jià)格高企使得太陽能作為一種能源具備了相當(dāng)?shù)慕?jīng)濟(jì)性。因此我們推斷光伏在未來將進(jìn)一步提升其在全球電力結(jié)構(gòu)中的占比。

1 、 組件價(jià)格高企   分布式漸成光伏裝機(jī)主力

在全球光伏裝機(jī)需求持續(xù)高增下，產(chǎn)業(yè)鏈上游原材料多晶硅料價(jià)格出現(xiàn)了劇烈的上漲，從而帶動(dòng)組件價(jià)格出現(xiàn)了飆升。以 2021年1 月6日為基點(diǎn)，截至 2022年8 月10日，多晶硅料漲幅超過了 260.2%，  166/182/210  組件漲幅分別為17.7% 、 15.9%、 15.9% 。高價(jià)組件降低了集中式光伏項(xiàng)目的收益率。以一個(gè)100MW ，組件成本為 1.95元 /W ，項(xiàng)目初始投資成本為4.58 元 /W 的集中式光伏電站項(xiàng)目為例。根據(jù)開源證券測算，在年利用小時(shí)數(shù)為 1300h ，上網(wǎng)電價(jià)為0.37 元 /kWh 的情況下，項(xiàng)目收益率僅為 6.4% 。高昂的組件價(jià)格對(duì)當(dāng)前集中式電站業(yè)主的裝機(jī)意愿產(chǎn)生了較大的影響。

2 、 對(duì)組件價(jià)格敏感性更低   分布式電站漸成光伏裝機(jī)主力

通過對(duì)比地面光伏電站和分布式屋頂光伏電站的投資成本可以看出，相比地面電站，分布式電站當(dāng)中非組件成本更低，初始投資成本相比地面電站也更加低廉，這使得分布式電站對(duì)于組件價(jià)格的敏感性相對(duì)更低，對(duì)高價(jià)組件的接受度更高。

2021年全球分布式光伏占比已達(dá) 47.9%，其中戶用光伏占比26%，份額連續(xù) 5年提升。高昂的組件價(jià)格直接降低了下游業(yè)主的裝機(jī)意愿，而相對(duì)初始投資成本更低的分布式光伏的裝機(jī)滲透率正在提升，其中尤以戶用光伏裝機(jī)為甚。

從2020到 2022上半年，中國的分布式光伏裝機(jī)占比已經(jīng)從32.2%提升到了65.5%，其中戶用光伏裝機(jī)占比更是從  2016 年的 1.7%提升到了 2021年的  39.4%。同時(shí)，在全球范圍內(nèi)的分布式光伏裝機(jī)占比也實(shí)現(xiàn)了大幅提升。從逆變器出貨統(tǒng)計(jì)口徑看，全球分布式光伏裝機(jī)占比從 2020 年的  38.9%上升到了  2021 年的 47.9%，其中戶用光伏裝機(jī)占比更是連續(xù) 5年實(shí)現(xiàn)提升，到  2021 年已經(jīng)達(dá)到了26%。

3 、 兼具高效與安全性的微型逆變器是戶用光伏的最優(yōu)選

組串式發(fā)電系統(tǒng)存在短板效應(yīng)會(huì)大幅下降發(fā)電功率。短板效應(yīng)即木桶效應(yīng)，指一只水桶能盛多少水取決于木桶最短的那塊木板，光伏系統(tǒng)中的木桶效應(yīng)則是指系統(tǒng)輸出的電流往往取決于系統(tǒng)中電流最小的那塊組件。在電站實(shí)際應(yīng)用中，陰影遮擋、云霧變化、污垢積累、組件溫度不一致等內(nèi)外部不理想條件，都會(huì)造成組件內(nèi)部各光伏單元輸出功率不一致，進(jìn)而導(dǎo)致各組輸出功率不一致，從而導(dǎo)致整個(gè)系統(tǒng)組件失配，整個(gè)系統(tǒng)的發(fā)電功率都隨之下降。

微型逆變器能克服短板效應(yīng)，最小化個(gè)別組件的影響。微逆多路獨(dú)立的 MPPT輸入設(shè)計(jì)，可將每塊組件的輸出優(yōu)化在最大功率點(diǎn)附近，系統(tǒng)發(fā)電量是所有組件發(fā)電量總和。此外，微逆啟動(dòng)功率更低，決定了其工作時(shí)間更長，從質(zhì)和量兩方面貢獻(xiàn)更高的發(fā)電效率。

微逆的主要優(yōu)勢

微逆可以最小化遮擋物的影響，穩(wěn)定系統(tǒng)輸出。

微型逆變器生命周期更長，省去二次安裝成本。

組件級(jí)監(jiān)控，提高運(yùn)維效率，節(jié)約故障維修成本。

基于高轉(zhuǎn)換效率和低運(yùn)維成本，微型逆變器的LCOE（度電成本）至少可降低 10%。

Micro inverter is the presentation of component - level control concept

Inverter is the heart of photovoltaic power system. It not only plays an important role in converting direct current generated by solar PV to alternating current, but also integrates the energy into the grid or uses it in household appliances after completing the maximum power point tracking. As the interface between distributed power supply and power grid, the performance of inverter will directly affect the power generation efficiency and operation stability of photovoltaic power generation system.

Inverters are mainly divided into centralized inverters, group series inverters and micro inverters. In terms of working principle, the centralized inverter connects a large number of parallel photovoltaic groups to the DC input terminal of the same centralized inverter, completes the maximum power point tracking, and then unified grid connection. The cluster series inverter is used to track the maximum power of the logarithmic series of photovoltaic modules separately, and is incorporated into the AC grid after passing through the inverter unit. The micro inverter is that each inverter corresponds to only a few photovoltaic modules, which can track the maximum power point of each photovoltaic module separately, and be incorporated into the AC grid separately after the inverter transformation.

The picture

Micro inverters have higher operating efficiency and better security. They are mainly applied to household power generation scenarios

As a component-level power electronic equipment, the micro inverter can finely regulate and monitor the output power of each PV module. In the case of partial shadow occlusion and performance failure of individual modules, it can improve the overall operating efficiency of the PV system. At the same time, compared with the 1000V DC high voltage at the input of the centralized and group series inverters, the maximum input voltage of the micro is only 60V, which greatly reduces the potential safety risks of the power plant and is simpler in installation and commissioning. However, compared with centralized inverter and cluster inverter, the single watt price of micro inverse is higher, and the current application scenario is mainly household photovoltaic power station.

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I. Demand side: 10 billion market under triple penetration

As a clean energy, the penetration of solar energy in the installed power structure is increasing. The main reasons are as follows: (1) accelerating the construction of new energy represented by photovoltaic has increasingly become the policy consensus of the world's major economies; (2) High commodity prices caused by global inflation in recent years have made solar energy quite economical as a source of energy. Therefore, we infer that PV will further increase its share in the global power structure in the future.

The picture

1. The distributed component with high price has gradually become the main force of photovoltaic installation

In the global demand for photovoltaic installations continues to increase, the price of polysilicon, the raw material in the upstream of the industrial chain, has risen sharply, which leads to a surge in the price of components. Based on January 6, 2021 as a basis point, as of August 10, 2022, polysilicon materials increased by more than 260.2%, 166/182/210 components increased by 17.7%, 15.9%, 15.9%, respectively. High-priced modules reduce the yield of centralized PV projects. Take a 100MW centralized photovoltaic power station project with module cost of 1.95 yuan /W and initial project investment cost of 4.58 yuan /W as an example. According to the open source securities calculation, in the annual utilization hours of 1300h, the on-grid price is 0.37 yuan /kWh, the project yield is only 6.4%. The high component price has a great influence on the installation intention of the current centralized power station owners.

2. Distributed power stations with lower sensitivity to module prices have gradually become the main force of photovoltaic installation

By comparing the photovoltaic power station on the ground and distributed rooftop photovoltaic power plant investment cost as you can see, compared with the ground station, the components of the distributed power station cost is lower, the initial investment cost is also cheaper than the ground power station, which makes the sensitivity of the distributed power station for a component prices are relatively low, willingness to accept high component is higher.

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In 2021, the global distributed PV accounted for 47.9%, among which household PV accounted for 26%, and its share increased for five consecutive years. The high module price directly reduces the downstream owners' willingness to install, while the installed penetration rate of distributed PV with lower initial investment cost is increasing, especially for household PV.

From 2020 to the first half of 2022, the proportion of distributed PV installed in China has increased from 32.2% to 65.5%, and the proportion of household PV installed has increased from 1.7% in 2016 to 39.4% in 2021. At the same time, the proportion of distributed photovoltaic installed worldwide has also achieved a significant increase. From the perspective of inverter shipment statistics, the proportion of global distributed photovoltaic installed capacity increased from 38.9% in 2020 to 47.9% in 2021, among which the proportion of household photovoltaic installed capacity increased for 5 consecutive years and reached 26% in 2021.

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3. The micro inverter with high efficiency and safety is the best choice for household PV

The short - board effect of cluster - series power generation system will greatly reduce the power generation. The short board effect is the barrel effect, which means that how much water a bucket can hold depends on the board with the shortest barrel. The barrel effect in a photovoltaic system means that the current output of the system often depends on the component with the smallest current. In power station actual applications, cloud shadows shade, change does not agree, dirt accumulation, components, temperature and other internal and external not ideal conditions, can cause the component within the photovoltaic cell power output, resulting in each output power, which leads to the whole system component mismatch, with the decrease of the power of the whole system.

The micro inverter can overcome the short board effect and minimize the influence of individual components. Microinverse multi-channel independent MPPT input design can optimize the output of each component near the maximum power point, and the system energy generation is the sum of the energy generation of all components. In addition, the micro-inverse start-up power is lower, which determines its longer working time and contributes higher generation efficiency in terms of both quality and quantity.

The main advantages of microinverse

Microinverse can minimize the influence of occlusions and stabilize the system output.

Micro inverter life cycle is longer, save the cost of secondary installation.

Component level monitoring, improve the efficiency of operation and maintenance, save the cost of fault maintenance.

Based on high conversion efficiency and low O&M cost, the LCOE (cost per kilowatt-hour) of micro inverters can be reduced by at least 10%.