Introduction: The Superstar of Solar Technology

Hybrid inverters are currently the superstars of solar technology. Apart from the solar modules themselves, they handle all tasks of a complete solar system. Whether power conversion or energy management – everything in one compact device.

What a Hybrid Inverter Can Do:

A hybrid inverter combines numerous functions in a single device. The following overview shows the tasks it performs:

Function	Description
DC→AC conversion	Direct current from modules to alternating current
Voltage adjustment	Boosting and bucking DC voltage
Battery management	Charge and discharge control
Energy management	Optimised energy distribution
MPPT	Maximum Power Point Tracking
Data acquisition	Voltage, current, temperature
Communication	Wi-Fi, LAN, app connectivity
Safety technology	Overvoltage protection, fuses

Structure of a Hybrid Inverter

A hybrid inverter consists of several integrated components:

1. Inverter (DC→AC)

The primary interface between solar modules and the internal system:

• Converts direct current to alternating current
• Can feed power directly into the household grid
• Or forward internally to the DC-DC converter

This component is the namesake and fulfils one of the main functions.

2. DC-DC Converter

The interface to the battery:

• Adjusts the solar module voltage for the battery
• Increases or decreases voltage as required
• The charging electronics determine the optimal voltage

Note: Some hybrid inverters have an integrated battery. This article considers the variant without an integrated battery.

3. Maximum Power Point Tracker (MPPT)

The core of the control system:

• Extracts maximum power regardless of weather or load
• Often already integrated in the inverter
• Measures generated voltage and adjusts it optimally

4. Energy Management System

Answers critical questions:

• When should the battery charge/discharge?
• What should the power output be?
• When to use solar power, when grid power?

5. Sensors and Measurement Technology

Continuously monitors:

• Current and voltage
• Temperature
• Additional operating parameters

The measurement data is processed internally and forwarded to the communication module.

6. Communication Module

Modern hybrid inverters offer:

• Wi-Fi/LAN connectivity
• Real-time app control
• Smart home integration
• Remote monitoring and maintenance

7. Safety Technology

Integrated protective devices against:

• Overvoltage
• Short circuit
• Overload
• Temperature issues

Advantages and Disadvantages

Advantages

The integration of all components in one device offers numerous benefits:

Advantage	Explanation
All in one device	Fewer components, simpler installation
Space-saving	One device instead of several separate ones
Optimised coordination	All components perfectly matched
Simple operation	One app for everything
High efficiency	Fewer conversion losses
Future-proof	Often expandable (additional batteries)

Disadvantages

Despite the many advantages, some aspects require consideration:

Disadvantage	Explanation
Higher acquisition cost	More expensive than simple inverters
Complexity	If defective, the whole system fails
Less flexibility	Components not individually replaceable
Manufacturer dependency	Often only compatible with batteries from the same manufacturer

Single-Phase vs. Three-Phase

The choice between single-phase and three-phase hybrid inverters has far-reaching implications.

Single-Phase Hybrid Inverter

The direct current is converted into one AC phase.

Advantages:

Single-phase devices excel particularly with smaller systems:

Advantage	Explanation
Simple construction	Only two cables required
More affordable	Simpler technology
Compatibility	Many devices use only one phase

Disadvantages:

The limitations become apparent particularly with larger systems:

Disadvantage	Explanation
Limited power	Usually only up to 3–6 kWp
Asymmetric loading	Can cause grid issues
Not for large consumers	Heat pumps, EV chargers often need three-phase power

Three-Phase Hybrid Inverter

The direct current is converted into three symmetrical AC phases.

Advantages:

Three-phase inverters are designed for larger systems and offer corresponding benefits:

Advantage	Explanation
Higher power	For systems from 6 kWp upwards
Better load distribution	Higher currents across three phases
Symmetrical feed-in	More grid-friendly
Large consumers	Compatible with heat pumps, EV chargers

Disadvantages:

The higher performance capability comes at a cost:

Disadvantage	Explanation
Higher costs	More complex construction
More complex installation	Additional safety precautions

Recommendation

The choice between single-phase and three-phase depends primarily on system size and connected consumers:

System Size	Recommendation
Up to 3 kWp	Single-phase sufficient
3–6 kWp	Depends on consumers
From 6 kWp	Three-phase recommended
With heat pump/EV charger	Three-phase

Integration into the Solar System

With hybrid inverter systems, there is no strict distinction between AC-coupled and DC-coupled systems. All components converge at the hybrid inverter.

Typical Configuration

Solar modules
    ↓ DC
Hybrid inverter
    ├── Battery (DC)
    ├── Household grid (AC)
    └── Public grid (AC)

The Power Flow

1. Sunny day, low consumption:

   • Modules → Hybrid inverter → Battery charging
   • Surplus → Grid feed-in

2. Evening, high consumption:

   • Battery → Hybrid inverter → Household grid

3. Night, battery empty:

   • Grid → Hybrid inverter → Household grid

4. Cheap night-time tariff:

   • Grid → Hybrid inverter → Battery charging

Software Makes the Difference

Beyond hardware, software is essential for control:

Software Tasks

The software is the central control element and handles diverse tasks:

Function	Description
Control	Close cooperation with MPPT
Data acquisition	Digital management of all measurements
Communication	Between all components
Monitoring	Fault detection
Forecasting	Yield predictions
Smart home	Integration with home automation

App Functions of Modern Devices

• Real-time monitoring of generation and consumption
• Historical data and statistics
• Remote control and settings
• Push notifications for faults
• Yield forecasts based on weather data

Conclusion

How to optimally configure your solar system is shown in the article AC or DC? System Topologies for Solar Systems.

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The Complete Article Series "Energy Storage for Solar Systems"

1. From Frog Legs to Batteries: How Does an Energy Storage System Work? – Fundamentals
2. Lithium vs. Lead: Which Battery for Solar? – Technology comparison
3. Power Electronics: Inverters and DC-DC Converters – Power conversion
4. The All-Rounder: Hybrid Inverters – You are here
5. AC or DC? System Topologies for Solar Systems – System concepts

Sources

• SMA: Solar Inverter Basics
• HTW Berlin: Hybrid Inverter Efficiency
• Optivolt: Single-Phase vs. Three-Phase Inverter
• Energie-Experten: Phase Inverters