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Breaking the 1:1 rigid limit, fully liberalizing the photovoltaic capacity ratio

Views: 5     Author: Qi Yan     Publish Time: 2020-11-03      Origin: GUANGFU.BJX

On October 23, the National Energy Administration approved the official issuance of 502 energy industry standards including the "Technical Specifications for Real-time Monitoring System for Ecological Flow of Hydropower Projects". The above-mentioned standards will be implemented from the date of issuance of the document.

It is worth noting that the standard includes the "Photovoltaic Power Generation System Efficiency Specification" (hereinafter referred to as the "Code") organized and compiled by the State Hydropower Institute. It is understood that a series of efficiency parameters are proposed in the "Specifications", including: key equipment parameters (module efficiency, double-sided module bifacial ratio, inverter efficiency, etc.), photovoltaic system parameters (capacity ratio, DC power loss, AC power loss, on-grid power, comprehensive occupancy rate, etc.), comprehensive evaluation parameters of power station (occupation area of power generation system, installed capacity per unit area, on-grid power, power generation revenue, economic revenue, external revenue, etc.).

Among them, the highly anticipated photovoltaic capacity ratio in the industry was officially released. According to a new report from Industrial Power, the "Specification" recommends a maximum capacity ratio of 1.8:1.0. This means that the photovoltaic power station capacity ratio has finally broken the 1:1 rigid limit and fully liberalized.

The so-called power station capacity ratio usually refers to the ratio of the sum of the power of the photovoltaic modules connected to the inverter in the photovoltaic power station to the rated capacity of the inverter. According to previous standards, the photovoltaic power station capacity ratio should not exceed 1:1, that is, the maximum DC input power allowed by the inverter should not be less than the actual maximum DC output power of the corresponding photovoltaic array.

It is understood that the current capacity ratio of power stations in the overseas photovoltaic market is basically above 1.4:1, and the power stations in Japan are even more than twice as large, while the general capacity ratio of power stations in my country is around 1.05 to 1.3.

In fact, increasing the capacity ratio to a certain extent can increase the equipment utilization of inverters and box-type substations, reduce the engineering cost of inverters and box-type substations, and at the same time can dilute the investment costs of public facilities such as booster stations and transmission lines. It is of positive significance to the decline of LCOE. On the other hand, with the increase in capacity ratio, the power variation range of photovoltaic power plants is also reduced simultaneously, the output of power plants is smoother and more stable, and the friendliness of the grid is improved accordingly.

Industry professionals said that the liberalization of the photovoltaic capacity ratio has higher requirements for the flexible matching ability and reliability of the inverter. "Previously, the maximum capacity ratio of photovoltaic power plants was around 1.2~1.3. If the capacity ratio is increased to 1.8, this requires that the matching ability of each stage of the inverter is the best."

"On the other hand, after the photovoltaic capacity ratio is increased, the number of full power hours of the power station will increase, which means that the inverter will run at full load for longer, which has stricter requirements for inverter derating and failure rate. From this perspective, improving the reliability of the inverter is more important than improving the efficiency of the inverter."

On the other hand, the increase in photovoltaic capacity ratio will bring about an increase in subsidies and an increase in the abandonment rate, which is one of the reasons why the photovoltaic capacity ratio has not been liberalized.

In accordance with the latest policies, my country's photovoltaic power plants are subsidized according to the number of hours in their life cycle, and the power grid company will check the capacity of the power station. Once it is found to be "overloaded", the subsidy funds will be reduced by 2 times of the non-compliant capacity. From this point of view, the liberalization of the "capacity matching ratio" policy does not apply to stock bidding projects, which is more favorable for photovoltaic parity projects.

From the perspective of abandonment, the current abandonment rate of photovoltaic power plants in my country is the highest at 5%. After increasing the capacity ratio, the abandonment rate of most power stations will exceed 5%. The above-mentioned industry insiders pointed out that “to solve the problem of high abandonment rate, it is necessary for photovoltaic power plants to configure energy storage, and DC-coupled energy storage should be added. Because the photovoltaic power station increases the DC side current after the capacity ratio is increased, the DC power is directly charged. In the energy storage system, it can solve the problem better than AC coupling."

On the whole, the liberalization of the capacity ratio meets the requirements of the era of photovoltaic parity, and is of great significance for increasing the demand for modules, reducing the cost of photovoltaic power stations, and accelerating photovoltaic parity. It should be noted that the higher the photovoltaic capacity ratio is not the better, the enterprise still needs to design according to the actual project.

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