In the photovoltaic power generation system, an inverter is one of the most important core equipment.Among them, micro inverters and series inverters are two common types, and they differ from each other in many ways.
1.Working principle
Micro-inverter
The micro inverter separately performs MPPT for each photovoltaic module, and the DC generated by the module is directly converted to AC and then fed into the grid.Each micro-inverter works independently and does not interfere with the others.
As it were, the rooftop system with several PV modules installed, even if one component is shaded or fails, the other components can still output electricity at maximum power through their respective micro-inverters, thereby maximizing the overall power generation efficiency of the system.
Series-inverter
A series inverter is a series of several photovoltaic modules into a series, the whole series of maximum power point tracking.Then, the direct current generated by the series is converted into alternating current and fed into the power grid.
If one component in the string has any problems, like blockage or damage, it would have an effect on the output power of the whole string and thus affect the efficiency of power generation of the system.
 
2.System structure
Micro-inverter
Small and compact, it can usually be installed directly on the back or side of the photovoltaic module without additional installation space.This integrated design makes the system more simple and beautiful but also reduces the complexity of wiring.
By using a micro-inverter for an installation at home rooftop photovoltaic systems, are very convenient, will not occupy too much space, and have perfect matches a variety of different types of photovoltaic modules.
Series inverter
The volume is relatively large and needs to be installed in a special inverter indoor or outdoor cabinet.The series inverter and the photovoltaic module need to be connected through a long DC cable, which increases the installation cost of the system and line losses.
Several inverter rooms are set up in a large photovoltaic power station, and series inverters are installed in the central to achieve unified management and maintenance.
 
3.Performance Characteristics
Generation Efficiency
Micro-inverter: Due to the independent MPPT of each component, it can adapt better to different lighting conditions and shadow occlusion.Therefore, the power generation efficiency is higher in a complex environment.  Even if some components are affected by the shadow, other components can still work normally, and there is no barrel effect.
String-inverter: Although MPPT can also be realized because the whole string is tracked, once some components in the string have reduced or blocked performance, the output power of the whole string will be affected, thus reducing the overall power generation efficiency of the system.  Reliability
Micro-inverter: Each micro-inverter works independently;even if one fails, the rest will continue working normally.Moreover, microinverters are based on advanced electronic technology, including a heat dissipation design which makes them highly reliable and stable.
String-inverter: In the case of a fault, perhaps the whole string may not be able to generate normally, affecting the reliability of the system.Also, series inverter debugging and maintenance are relatively complex and require professional and technical staff to operate.
Micro-inverter: The output is low-voltage AC, generally 220V or 110V, which greatly reduces the safety risk caused by DC high voltage.Meanwhile, the micro-inverter also has perfect protection functions, such as overvoltage protection, overcurrent protection, short circuit protection, etc., to ensure the safe operation of the system.
Series-inverter: The output is a high voltage direct current, so there are certain security risks.If the DC cable is damaged or grounded incorrectly, accidents such as electric shock or fire may occur.
4.Application Scenarios
Micro-inverter
Applied to small distributed photovoltaic systems, such as the roofs of private residences, roofs of commercial buildings, and so on.Under these conditions, the installation site of the photovoltaic module is dispersed, and lighting conditions are different.It is here that micro-inverters can play their advantages more strongly to enhance the power generation efficiency and reliability of the system.
For places with higher aesthetic requirements, the integrated design of micro inverters will also meet the needs of users.
Series-inverter
Suitable for large-scale ground photovoltaic power plants and Industrial and commercial rooftop photovoltaic systems.In these scenarios, the installation scale of photovoltaic modules is large, and the series inverter can better meet the power needs of the system and reduce costs.
For areas with relatively flat terrain and relatively consistent lighting conditions, series inverters can also play a better performance.
 
5. Cost analysis
Initial investment cost
Micro-inverter: Because of its high technical content and complex production process, the price is relatively high.In addition, because each component needs to be equipped with a micro-inverter, the initial investment cost will be higher when the system is small.
Series-inverter: The price of series inverters is relatively low, especially in large-scale applications, and the cost advantage is more obvious.
 
Operation and maintenance cost
Micro-inverter: Thanks to its high reliability and low failure rate, the operation and maintenance costs are relatively low.In addition, the micro inverter can be monitored and managed remotely through the network, which is convenient and fast.
Series-inverter: The cost of operation and maintenance is relatively high.Especially when there is a failure, professional and technical personnel need to investigate and repair it, which consumes time and labor costs.

In general, micro inverters and string inverters have a lot of different and obvious features in working principle, system structure, performances, application scenarios, and cost.Inverter selection shall take into comprehensive consideration specific application scenarios and needs for the optimal performance and economic benefit of the system.