An integral part of a solar power system is a string inverter, sometimes called a central inverter. It transforms solar-generated direct current (DC) electricity into proper alternating current (AC) electricity that can run buildings and commercial establishments.
How String Inverters Work?
A “string” of solar panels is created by connecting several solar panels in series using string inverters. Each panel produces DC electricity, which is supplied to the inverter to transform into AC electricity to control the flow of electricity. The string inverter ensures that the voltage and frequency are appropriate for the local power grid.
1. From DC to AC: The Core Function
When solar panels receive sunlight, they generate direct current (DC) electricity.
String inverters obtain this DC electricity from a “string” (usually six to twelve) of connected solar panels.
The inverter subsequently transforms this direct current (DC) into alternating current (AC), which powers appliances and houses.
2. Maximizing Power Output (MPPT)
Maximum PowerPoint Tracking (MPPT) is a feature that many string inverters include.
The output of solar panels might vary depending on the temperature and strength of the sun.
To guarantee that the panels are always operating at their maximum power point and optimize total energy production, MPPT continuously analyzes these variables and modifies the inverter’s operation.
3. Safety and Grid Protection
When linked to the grid, string inverters’ safety features guard against electrical failures and guarantee grid security. They can turn the system off in the event of an undervoltage, overvoltage, or ground fault.
4. Monitoring and Data Acquisition (Optional)
Advanced features like data recording and communication capability are available on certain string inverters.
This enables homeowners to track energy output, monitor system functionality, and spot possible problems.
Limitations of String Inverters
- Single Point of Failure: The complete string of linked panels will not generate electricity if a string inverter fails.
- Limited Shading Tolerance: A string’s output can be impacted if one of its panels is shaded. Microinverters may be a more advantageous choice for systems that experience shading problems.
- Less Scalability: It could be necessary to install another inverter to expand a system using a string inverter, which would increase complexity.
Installing Process of String Inverters
- Determine your solar panel’s location: Before installing a string inverter, you must select your installation location. This might be a brightly lit spot on your roof or the ground.
- Mounting the solar panels: Racking and mounting tools are used to install the solar panels on the assigned spot. This guarantees the panels are firmly fixed and oriented to get the most sunlight possible.
- Wiring the solar panels: After the panels are installed, wires and connectors must be used to wire them in a series. This produces a row of panels ready to be attached to the string inverter.
- Installing the string inverter: Usually, the string inverter is mounted close to the main electrical panel in your house. Mounting brackets allow it to be positioned on the ground or fixed on a wall.
- Connecting the panels to the string inverter: The panels are then attached to the string inverter’s input ports using connections made explicitly for outdoor use.
- Connecting to your home’s electrical system: The AC electricity generated by the string inverter is subsequently fed into your home’s wiring using a connection to the electrical system.
- Testing and monitoring: After everything is connected, the system must be checked to ensure it functions appropriately. Monitoring systems to track the string inverter’s performance and energy production are also possible.
String Inverter Design
String inverters come in various sizes, from tiny residential units to massive commercial units, and they usually have a box-like shape. They are made strong and resilient to weather-related conditions, including wind, rain, and extremely high or low temperatures.
String vs. Hybrid vs. Central vs. Microinverter
| Feature | String Inverter | Hybrid Inverter | Central Inverter | Microinverter |
| Input | DC from multiple panels (string) | DC from solar & battery | DC from the entire array |
DC from a single-panel
|
| Output | AC (grid-tie) | AC (grid-tie & battery) | AC (grid-tie) | AC (grid-tie) |
| MPPT | Yes (centralized) | Yes (centralized) | Yes (centralized) | Yes (per panel) |
| Scalability | Limited (add another inverter) | Limited (add another inverter) | Limited (increase inverter size) |
High (add more panels)
|
| Partial Shading | Poor (whole string affected) | Moderate (battery can compensate) | Poor (whole array affected) |
Excellent (each panel performs independently)
|
| Cost | Lower (per watt) | Higher | Lower (per watt) | Higher |
| Use Case | Residential solar systems | Residential with battery backup | Large commercial & utility-scale solar farms |
Residential & small commercial
|
| Centralized vs. Distributed Conversion | Centralized | Centralized (AC) with additional DC-DC conversion for battery | Centralized |
Distributed (each panel)
|
Pros and Cons of String Inverters
The advantages and disadvantages of string inverters are discussed below.
Pros:
- Lower upfront costs compared to other inverter types.
- Proven technology with a long track record of performance.
- It is compatible with most solar panel types, making it easier to find replacement parts if needed.
- It can easily be replaced or upgraded without replacing the entire system.
Cons:
- Potential power loss due to shading on a single panel affecting the entire string.
- Limited flexibility in system design as panels must be wired together in a series.
- Smaller systems may not require the total capacity of a string inverter, resulting in lower efficiency.
How to Evaluate String Inverters
There are various things to take into consideration when thinking about a string inverter for your solar power system:
- String Inverter Durability: Seek inverters made of premium, outdoor-grade materials that are resistant to weather.
- Warranties of Inverters: Check the warranty length and coverage the manufacturer offers. A longer warranty period generally indicates a more durable and reliable inverter.
- Cost of String Inverters: Compare prices from different manufacturers to find the best value for your budget.
- String Inverter Capacity: Consider the size of your solar system and choose an inverter with enough capacity to handle your energy needs.
- String Inverter Efficiency: Look for inverters with high conversion efficiency to ensure maximum output from your solar panels.
- Number of Inputs: If you have many solar panels, consider a string inverter with multiple inputs to accommodate them.
String Inverter Types
There are three types of string inverters available on the market:
- Standard String Inverters: These are the most common type and are suitable for most solar power systems.
- Optimized String Inverters: These inverters use additional technology to maximize energy output, making them more efficient than standard string inverters.
- Hybrid String Inverters: These inverters combine the features of standard and optimized string inverters. Providing both efficiency and flexibility in system design.
String Inverter Manufacturers
There are many manufacturers of string inverters.
- Fronius
- SMA
- Sun grows
- Delta
Conclusion
An essential part of every solar power system is a string inverter. The selection of string inverter solutions grows along with technology. You may select the best string inverter for your solar energy requirements by knowing how they operate, weighing their benefits and drawbacks, and considering essential variables.