微型逆變器是組件級控制觀念的呈現(xiàn)

逆變器是光伏發(fā)電系統(tǒng)的心臟。不僅承擔將太陽能光伏產(chǎn)生的直流電轉換為交流電的重要角色，在完成最大功率點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集中式逆變器的直流輸入端，完成最大功率點跟蹤后，再統(tǒng)一并網(wǎng)。組串式逆變器對數(shù)串光伏組件單獨進行最大功率追蹤，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逆變器只對應少數(shù)光伏組件，實現(xiàn)對每塊光伏組件單獨的最大功率點跟蹤，在逆變轉化之后單獨并入交流電網(wǎng)。

微型逆變器運行效率更高、安全性更好   主要應用于戶用發(fā)電場景

微型逆變器作為組件級電力電子設備可以對每塊光伏組件的輸出功率進行精細化調節(jié)及監(jiān)控，在遇到部分陰影遮擋和個別組件性能出現(xiàn)故障的情況下，能夠提升光伏系統(tǒng)整體的運行效率。同時比起集中式、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，微逆的單瓦價格較高，當下的應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結構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已經(jīng)日益成為全球主要經(jīng)濟體的政策共識；（ 2）近年來全球通脹導致的大宗商品價格高企使得太陽能作為一種能源具備了相當?shù)慕?jīng)濟性。因此我們推斷光伏在未來將進一步提升其在全球電力結構中的占比。

1 、 組件價格高企   分布式漸成光伏裝機主力

在全球光伏裝機需求持續(xù)高增下，產(chǎn)業(yè)鏈上游原材料多晶硅料價格出現(xiàn)了劇烈的上漲，從而帶動組件價格出現(xiàn)了飆升。以 2021年1 月6日為基點，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% 。高價組件降低了集中式光伏項目的收益率。以一個100MW ，組件成本為 1.95元 /W ，項目初始投資成本為4.58 元 /W 的集中式光伏電站項目為例。根據(jù)開源證券測算，在年利用小時數(shù)為 1300h ，上網(wǎng)電價為0.37 元 /kWh 的情況下，項目收益率僅為 6.4% 。高昂的組件價格對當前集中式電站業(yè)主的裝機意愿產(chǎn)生了較大的影響。

2 、 對組件價格敏感性更低   分布式電站漸成光伏裝機主力

通過對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于組件價格的敏感性相對更低，對高價組件的接受度更高。

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

從2020到 2022上半年，中國的分布式光伏裝機占比已經(jīng)從32.2%提升到了65.5%，其中戶用光伏裝機占比更是從  2016 年的 1.7%提升到了 2021年的  39.4%。同時，在全球范圍內的分布式光伏裝機占比也實現(xiàn)了大幅提升。從逆變器出貨統(tǒng)計口徑看，全球分布式光伏裝機占比從 2020 年的  38.9%上升到了  2021 年的 47.9%，其中戶用光伏裝機占比更是連續(xù) 5年實現(xiàn)提升，到  2021 年已經(jīng)達到了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)存在短板效應會大幅下降發(fā)電功率。短板效應即木桶效應，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。在電站實際應用中，陰影遮擋、云霧變化、污垢積累、組件溫度不一致等內外部不理想條件，都會造成組件內部各光伏單元輸出功率不一致，進而導致各組輸出功率不一致，從而導致整個系統(tǒng)組件失配，整個系統(tǒng)的發(fā)電功率都隨之下降。

微型逆變器能克服短板效應，最小化個別組件的影響。微逆多路獨立的 MPPT輸入設計，可將每塊組件的輸出優(yōu)化在最大功率點附近，系統(tǒng)發(fā)電量是所有組件發(fā)電量總和。此外，微逆啟動功率更低，決定了其工作時間更長，從質和量兩方面貢獻更高的發(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。

組件級監(jiān)控，提高運維效率，節(jié)約故障維修成本。

基于高轉換效率和低運維成本，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.

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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.

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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%.