String Inverter
Central inverter that converts the direct current from one or more series-connected module strings into alternating current.
Also known as: String-Inverter, Central Inverter
What Is a String Inverter?
A string inverter is the most commonly used inverter type in residential rooftop photovoltaic systems. It converts the direct current (DC) from one or more series-connected module strings into grid-compliant alternating current (AC).
How It Works
The solar modules are connected in series to form a string, with voltages adding up. The inverter receives the direct current at typically 300—600 V and converts it into 230 V alternating current. Integrated MPP trackers ensure that each string always operates at its optimal working point.
Advantages and Disadvantages
| Advantages | Disadvantages |
|---|---|
| High efficiency (96—98%) | Power loss from partial shading |
| Proven, affordable technology | One failure affects the whole string |
| Simple installation | Less flexible for complex roofs |
| Good monitoring | Modules must face the same direction |
Application
String inverters are particularly suited for uniformly oriented roof surfaces without shading. Modern devices have two or more MPP trackers, allowing different roof surfaces to be connected.
Practical Tip
For shading issues or significantly different module orientations, combining with power optimisers or using microinverters may be more effective.
Related Terms
Microinverter
Small inverter mounted directly on a single solar module, converting DC to AC on a per-module basis.
Hybrid Inverter
Inverter that combines PV electricity generation, battery storage, and grid feed-in in a single device.
MPP Tracker
Electronic control in the inverter that continuously finds and optimises the Maximum Power Point of the solar modules.
Efficiency
Ratio of usable electrical energy to incident solar energy -- indicates the effectiveness of a solar cell or system.
AC/DC (Alternating Current/Direct Current)
AC (Alternating Current) is the mains electricity from the grid, DC (Direct Current) is produced by solar modules and batteries.