How do you install a solar inverter?

Many people are a little confused when in comes to installing a solar inverter, how does it work?

Solar inverters have a cable in but no cable out?
There are various types of inverters so you need to pay attention to what inverter you have.
If you have a grid in and grid out then you may have an off grid inverter. You may see a grid in and EPS out or you may see just grid.

EPS is a island power which does NOT connect to the grid side. – this is like an off grid power supply which works when the grid is down. it needs to be “on its own”.

Grid is a in and out AC power.

How does the inverter work then?
Power is made up of voltage and current so the inverter reads the grid power voltage, and adds a little bit of voltage to push current into your home that it makes. the power you use in your home is not voltage but current also known as amps, so the inverter is making amps that it adds to the wiring of your home. Current/Amps are electrons, tiny bits of matter that float around atoms, these electrons are exactly electricity.

How Grid-Tied Inverters Work: A Technical Deep Dive

Grid-tied inverters are essential components of solar power systems, converting the direct current (DC) generated by solar panels into alternating current (AC) that can be fed back into the utility grid. To understand how they work, let’s delve into the technical aspects:  

Core Functionality

1. DC to AC Conversion: The primary function of a grid-tied inverter is to convert the DC power generated by solar panels into AC power that is compatible with the utility grid. This involves several stages:
   • Power Conditioning: The DC power from the solar panels is first conditioned to ensure it is within acceptable voltage and current ranges for the inverter’s input.  
   • Inverter Stage: The conditioned DC power is then fed into the inverter’s power electronics, where it is converted into AC power. This typically involves high-frequency switching techniques to efficiently control the output waveform.  See H Bridge below.
   • Output Transformer (Optional): Some inverters use a transformer to isolate the output from the grid and provide impedance matching. Transformerless inverters are becoming more common due to their higher efficiency.  
     
2. Grid Synchronisation: The inverter must synchronise its output with the grid’s voltage and frequency. This is crucial to ensure the safety of both the system and utility workers. Synchronization is typically achieved through:
   • Phase-Locked Loop (PLL): A PLL circuit continuously monitors the grid’s voltage waveform and adjusts the inverter’s output to match its phase and frequency.  
   • Voltage and Frequency Sensors: These sensors measure the grid’s voltage and frequency, providing feedback to the inverter’s control system.  
3. Maximum Power Point Tracking (MPPT): MPPT algorithms are used to maximize the power output from the solar panels. These algorithms constantly adjust the inverter’s input impedance to match the solar panels’ operating point, ensuring maximum power extraction under varying conditions.  

Key Features and Considerations

• Efficiency: Modern grid-tied inverters typically have efficiencies exceeding 95%, meaning they can convert a large portion of the DC power into usable AC power.  
  
• Safety Features: Grid-tied inverters are equipped with various safety features, including:
  • Islanding Protection: This prevents the inverter from continuing to operate if the grid connection is lost, ensuring the safety of utility workers.  
  • Overvoltage and Overcurrent Protection: These features protect the inverter and grid from damage due to excessive voltage or current.  
  • Ground Fault Protection: This detects ground faults and disconnects the inverter to prevent electrical hazards.  
    
• Monitoring and Communication: Many grid-tied inverters have built-in monitoring and communication capabilities, allowing users to track their system’s performance and energy production.  

How a Grid-Tied Inverter Uses an H-Bridge

A grid-tied inverter, a crucial component of solar power systems, employs an H-bridge circuit to convert the direct current (DC) generated by solar panels into alternating current (AC) that can be fed back into the utility grid.  

Understanding the H-Bridge

An H-bridge is a fundamental circuit configuration consisting of four power electronic switches, typically MOSFETs or IGBTs, arranged in a diamond-like pattern. These switches can be controlled to either connect or disconnect the DC supply from the output, allowing the inverter to generate an AC waveform.  

Operation in a Grid-Tied Inverter

1. DC Input: The DC power generated by the solar panels is fed into the H-bridge.
2. Switch Control: The switches in the H-bridge are rapidly turned on and off in a specific sequence, determined by a control algorithm. This creates a square wave output.
3. Pulse Width Modulation (PWM): To generate a sinusoidal AC waveform, the switches are controlled using PWM. By varying the width of the on-time pulses, the average voltage across the load can be modulated to produce a sinusoidal output (a sine wave).  
4. Filtering: The square wave output from the H-bridge is typically filtered using an LC filter to remove high-frequency harmonics and produce a smooth sinusoidal waveform.  
5. Grid Synchronization: The inverter’s output must be synchronized with the grid’s voltage and frequency. This is achieved using a phase-locked loop (PLL) circuit that continuously monitors the grid voltage and adjusts the inverter’s output accordingly.  

Key Points:

• The H-bridge is a fundamental building block for many power electronic converters, including grid-tied inverters.  
• The control algorithm for the H-bridge is crucial in determining the output waveform’s shape and frequency.
• Grid synchronization is essential to ensure the safety and stability of the grid.

THE ANSWER:
Installing solar inverters that work in parallel with the grid need to be compliant with the relative regulations, G99, G98. if they are NOT they cannot be connected to the grid and your homes power. Unless they are off grid of course.
Most inverter working with the grid have one cable that is the IN and OUT.

in BS7671 – Delving into BS 7671: Section 712 and Solar Panel Systems — RenewSolar we wrote the “guidelines” of solar installations and they are a power source and therefore should protected.
They should NOT be installed on the Wrong side of a RCD.

All inverters have to be “commission tested”
The installation has to comply with a lot of rules and regulations. which includes isolation and protection as well as Wiring and safety.
This is extended with Solar and Battery Storage (BESS)