Common Photovoltaic Inverter Classification And Its Advantages And Disadvantages Explained In Detail
May 31, 2024
Inverter is also called power regulator. According to the use of inverter in photovoltaic power generation system, it can be divided into two types: independent power supply and grid-connected. According to the waveform modulation method, it can be divided into square wave inverter, step wave inverter, sine wave inverter and combined three-phase inverter. For inverters used in grid-connected system, it can be divided into transformer inverter and transformerless inverter according to whether there is a transformer.
As an important part of photovoltaic power generation, the inverter mainly converts the direct current generated by photovoltaic modules into alternating current. At present, the common inverters on the market are mainly divided into centralized inverters and string inverters, as well as trendy distributed inverters.
1. Centralized photovoltaic inverter
As the name suggests, the centralized inverter converts the direct current generated by photovoltaic modules into alternating current and then boosts and connects to the grid. Therefore, the power of the inverter is relatively large. Centralized inverters of more than 500kW are generally used in photovoltaic power stations.
The advantages of centralized inverters are as follows:
(1) High power, small quantity, easy to manage; few components, good stability, easy to maintain;
(2) Low harmonic content, high power quality; complete protection functions, high safety;
(3) With power factor regulation function and low voltage ride-through function, the grid regulation is good.
Centralized inverters have the following problems:
(1) The MppT voltage range of centralized inverters is narrow, and the operation status of each component cannot be monitored. Therefore, it is impossible to make each component at the optimal working point, and the component configuration is not flexible;
(2) Centralized inverters occupy a large area and require a dedicated machine room, which is not flexible to install;
(3) The power consumption of the inverter itself and the power consumption of ventilation and heat dissipation in the machine room are large.
2. String photovoltaic inverters
As the name suggests, string inverters directly convert the DC power generated by photovoltaic modules into AC power, aggregate it, and then boost it and connect it to the grid. Therefore, the power of the inverter is relatively small. String inverters below 50kW are generally used in photovoltaic power stations.
Advantages of string inverters:
(1) Not affected by module differences and shadows between strings, while reducing the mismatch between the optimal working point of photovoltaic cell modules and inverters, maximizing power generation;
(2) MppT voltage range is wide, and module configuration is more flexible; on rainy days and foggy areas, power generation time is long;
(3) Small size, small footprint, no need for a dedicated machine room, flexible installation;
(4) Low self-power consumption and small impact of failures.
Problems with string inverters:
(1) Small electrical clearance of power devices, not suitable for high altitude areas; many components, integrated together, slightly poor stability;
(2) Outdoor installation, wind and sun exposure can easily cause aging of the casing and heat sink;
(3) The number of inverters is large, the total failure rate will increase, and system monitoring is difficult;
(4) Design without isolation transformer, slightly poor electrical safety, not suitable for thin-film module negative grounding system.
3. Distributed photovoltaic inverter
Distributed inverter is a new inverter type proposed in the past two years. Its main features are centralized inverter and decentralized MppT tracking. Distributed inverter is a product that gathers the advantages of centralized inverter and string inverter, achieving the low cost of centralized inverter and the high power generation of string inverter.
Advantages of distributed inverter:
(1) Compared with centralized inverter, decentralized MppT tracking reduces the probability of mismatch and increases power generation;
(2) Compared with centralized and string inverter, distributed inverter has boost function and reduces line loss;
(3) Compared with string inverter, centralized inverter has more advantages in construction cost.
Problems of distributed inverter：
(1) Little engineering experience. Compared with the first two categories, it is still a new form and is relatively less used in engineering projects;
(2) Characteristics such as safety, stability and high power generation still need to be tested in engineering projects;
(3) Because it uses centralized inversion, it occupies a large area and requires a dedicated machine room, which is also a disadvantage of distributed inverters.
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