Common photovoltaic inverter classification Inverter, also known as power regulator, can be divided
Common photovoltaic inverter classification
As an important part of photovoltaic power generation, the inverter is mainly used to convert the direct current generated by photovoltaic modules into alternating current. At present, the common inverters on the market are mainly divided into centralized inverters, string inverters, and trendy distributed inverters.
The centralized inverter, as the name implies, converts the DC power generated by photovoltaic modules into AC power, and then boosts and connects to the grid. Therefore, the power of the inverter is relatively large. In photovoltaic power plants, centralized inverters of more than 500kW are generally used.
The advantages of a centralized inverter are as follows:
(1) The power is large, the quantity is small, and it is easy to manage; the components are few, the stability is good, and the maintenance is easy;
(2) Less harmonic content and high power quality; complete protection functions and high safety;
(3) It has power factor adjustment function and low voltage ride-through function, and the grid regulation is good.
Central inverters have the following problems:
(1) The MppT voltage range of the centralized inverter is narrow, and the operation of each component cannot be monitored, so it is impossible to make each component in the best working point, and the component configuration is inflexible;
(2) The centralized inverter occupies a large area, requires a dedicated computer room, and is inflexible in installation;
(3) The power consumption of itself and the ventilation and heat dissipation of the computer room are large.
The string inverter, as its name implies, directly converts the direct current generated by photovoltaic modules into alternating current, and then boosts the voltage and connects to the grid. Therefore, the power of the inverter is relatively small. Generally, string inverters below 50kW are used in photovoltaic power plants.
String inverter advantages:
(1) It is not affected by module differences between strings and shadows, and at the same time reduces the mismatch between the best operating point of photovoltaic cell modules and the inverter, and maximizes power generation;
(2) The MppT voltage range is wide, and the component configuration is more flexible; in cloudy and rainy days, in areas with much fog, the power generation time is long;
(3) Small size, small footprint, no need for a dedicated computer room, and flexible installation;
(4) Low self-consumption power and small fault impact.
There are problems with string inverters:
(1) The electrical clearance of power devices is small, which is not suitable for high-altitude areas; there are many components, integrated together, and the stability is slightly poor;
(2) Outdoor installation, wind and sun exposure can easily lead to aging of the shell and heat sink;
(3) The number of inverters is large, the total failure rate will increase, and the system monitoring is difficult;
(4) Without the design of isolation transformer, the electrical safety is slightly worse, and it is not suitable for the negative grounding system of the thin film module.
Distributed inverter is a new inverter form proposed in the past two years, and its main features are centralized inverter and decentralized MppT tracking. The distributed inverter is a product that combines the advantages of the centralized inverter and the string inverter, and achieves the low cost of the centralized inverter and the high power generation of the string inverter.
Distributed inverter advantages:
(1) Compared with centralized, decentralized MppT tracking reduces the probability of mismatch and increases power generation;
(2) Compared with the centralized type and the string type, the distributed inverter has the boost function, which reduces the line loss;
(3) Compared with the string type, the centralized inverter has more advantages in terms of construction cost.
Distributed inverter problem;
(1) Less engineering experience. Compared with the first two categories, it is still a new form and has relatively few applications in engineering projects;
(2) Characteristics such as safety, stability and high power generation also need to be tested by engineering projects;
(3) Because of the centralized inverter, the disadvantage of requiring a dedicated machine room is also present in the distributed inverter.