How to Classify PV Inverters

 

 

Inverter as an important part of solar powered portable generation, the main role is to send the PV module to DC into AC. At present, the market common inverter is divided into centralized inverters, string inverters and trendy distributed inverters. The three kinds of inverter to talk about their own characteristics.

First, the centralized inverter

 

Centralized inverter is the name suggests is the PV modules generated after the conversion of DC into AC voltage boost, and the network. Therefore, the inverter power is relatively large. Photovoltaic power plants generally use more than 500kW centralized inverter.

 

The advantages of a centralized inverter are as follows:

 

(1) power, the number of small, easy to manage; components less, good stability, ease of maintenance;

(2) low harmonic content, high power quality; protection function is complete, high security;

(3) there are power factor adjustment function and low voltage through function, good grid regulation.

 

The problem of the centralized inverter is as follows:

 

(1) centralized inverter MPPT voltage range is narrow, can not monitor the operation of each component of the road, it is impossible to make each component at the best working point, the component configuration is not flexible;

(2) centralized inverter covers an area of large, need a dedicated room, the installation is not flexible;

(3) Its power consumption and the room ventilation and heat dissipation power consumption.

 

Second, the string inverters

 

Group string inverter as the name suggests is the direct conversion of photovoltaic power generation components AC voltage summary after the step-up, and the network. Therefore, the inverter power is relatively small. Photovoltaic power plants in the general use of the following series of 50kW inverter.

The advantages of the string inverters:

 

(1) It is not affected by the differences between groups of modules and shadowing, and at the same time, the optimal working point of the battery pack is not matched with the inverter, for example LiFePO4 battery pack, thus maximizing the generation capacity.

(2) MPPT voltage range is wide, more flexible component configuration; in the rainy days, fog and more of the Ministry of District, power generation time is long;

(3) small size, small footprint, no special room, flexible installation;

(4) since the low power consumption, fault impact.

 

Group string inverter problem:

 

(1) power device electrical gap is small, not suitable for high altitude areas; components more integrated together, the stability of a little worse;

(2) outdoor installation, wind and sun can easily lead to aging shell and heat sink;

(3) the number of inverters, the total failure rate will increase, the system is difficult to monitor;

(4) without isolation transformer design, electrical safety slightly worse, not suitable for membrane component negative grounding system.

Third, the distributed inverter

Distributed inverter is a new form of inverter proposed in the past two years. Its main features are "centralized inverter" and "scattered MPPT tracking". Distributed inverters are a product of the advantages of a centralized inverters and a string inverters, achieving "low cost of centralized inverters, high power generation of string inverters ".

 

Advantages of Distributed Inverters:

 

(1) "centralized MPPT tracking" reduces the probability of mismatch and increases the generation capacity compared with the centralized approach.

(2) and centralized and group string comparison, distributed inverters with boost function, reducing the line loss;

(3) Compared with the group string, "centralized inverter" in the construction cost more advantages.

 

Distributed inverter problem:

 

(1) Less engineering experience. Because it is the last two years the new form. In the application of the project after all, still a minority;

(2) safety, stability, and high power generation characteristics also need to go through the test of the project;

(3) Because the use of "centralized inverter", therefore, covers an area of large, need to be dedicated room shortcomings exist in the distributed inverter.

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