Recommended selection of centralized inverters and string inverters for fishery-solar hybrid photovoltaic power stations

"Fish-photovoltaic complementarity" refers to the combination of fishery farming and photovoltaic power generation. A photovoltaic panel array is set up above the water surface of the fish pond, and fish and shrimp can be farmed in the water area below the photovoltaic panels. The photovoltaic array can also provide good shielding for fish farming, forming a new power generation model of "generating electricity above and farming fish below".

At present, the most commonly used photovoltaic inverters in China are mainly centralized inverters and string inverters. As for how to choose between the two types of photovoltaic inverters, KSHIDA always recommends the principle of "adapting measures to local conditions and scientific selection", recommends the best solutions to customers, reduces customer investment costs, and increases system power generation.

For the fishery-photovoltaic complementary power station, how should we select it according to the principle of "adapting measures to local conditions and scientific selection"? Next, let's take a look at the main features of the fishery-photovoltaic complementary power station and the comparative analysis of the application of centralized inverters and string inverters in the fishery-photovoltaic complementary power station.

1) The orientation is consistent and the terrain is flat, so there is basically no mismatch problem caused by occlusion and inconsistent orientation

2) The construction cost of the power station is high, and attention should be paid to the inverter cost and system cost.

3) When the ambient humidity is high, attention should be paid to the PID attenuation of the components to avoid affecting the power generation

4) Operation and maintenance is difficult, and attention should be paid to operation and maintenance costs

Comparative analysis of the application of centralized and string inverters in fishery-photovoltaic complementary power stations

Investment cost:

From the perspective of investment cost, the centralized inverter solution (box-type inverter integrated machine) is relatively low. The cost per watt of string inverter is higher than that of conventional centralized inverter, and the cost per watt of string inverter + box-type inverter is higher than that of box-type inverter integrated machine.

Infrastructure:

The integrated box-type inverter has a higher degree of integration, and the inverter and box-type transformer only need to build one foundation. Although the string inverter does not require a foundation, the box-type transformer needs to be installed with a separate foundation.

Installation and debugging:

The roadside construction foundation installation, the number of centralized inverter equipment is small, which is convenient for installation and commissioning, and can shorten the construction period. Taking a 100MW power station as an example, according to the 1.3 over-capacity, only 25 3.125MW box inverters are needed.

There are many string inverters, which are scattered and the weight of high-power string inverters exceeds 80kg. It is difficult to install them on the water surface, which will increase the construction cost and duration. Taking a 100MW power station as an example, considering the 1.3 over-capacity, 440 175kW string inverters are needed.

Operation and maintenance:

Centralized:

(1) Roadside construction and basic installation, with a small number of equipment, convenient for future maintenance

(2) After a device fails, the faulty unit module can be replaced according to the fault point, with low maintenance cost

String type:

(1) Scattered distribution and numerous equipment make surface projects more difficult to maintain

(2) After equipment failure, some equipment needs to be replaced as a whole, which results in high maintenance costs

Scheduling management:

The number of centralized inverters is small, which is convenient for management and has a faster response and scheduling time.

There are many string inverters, which are difficult to manage and have a relatively slow response time.

Inverter performance:

Centralized:

(1) 1 or 2 MPPT paths, meeting the requirements of water power stations (2) Protection level IP54, based on a large number of domestic centralized inverter application cases, meeting the application conditions of water power stations

String type:

(1) MPPT has multiple paths, which is suitable for projects with different module inclinations and orientations, but has little advantage for water-surface power stations

(2) Protection grade IP65

Through the comparative analysis of the characteristics of the fishery-photovoltaic complementary power station and the two inverters, according to the principle of "adapting measures to local conditions and scientific selection", for power stations with large scale, flat terrain, consistent orientation and high grid connection requirements, it is recommended to adopt a centralized inverter solution and use a box-type inverter all-in-one device.

Conclusion: Centralized inverters and string inverters have their own characteristics and are used in different scenarios. For large-scale fishery-photovoltaic complementary power stations, centralized inverter solutions are the first choice, whether from the perspective of investment returns or from the perspective of maintainability, construction, and inverter characteristics.

Typical application cases of KSTAR's fish-light complementarity

Zhejiang Shuqimeng Fishery-Photovoltaic Complementary Project

The largest single-unit fishery-solar complementary project in China, with a total installed capacity of 200MW. The total investment of the project is 1.8 billion yuan, and the total water area is 4,492 mu.