Inverter Single-Phase Island Grid Operation
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Solution Overview
Problem
There is a need to ensure local energy supply to consumers during a grid failure without requiring additional inverters and batteries, as the power output from decentralized sources is often insufficient to operate all consumers simultaneously.
Innovation Solution
A method and inverter design that utilizes three bridge arms to convert DC power into AC power, switching from three-phase to single-phase operation when disconnected from the grid, allowing for the creation of a single-phase isolated grid using the same inverter components without additional devices, and adjusting voltage and frequency settings to supply essential loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional inverters and batteries are installed to ensure local energy supply during grid failure, then reliability of energy supply is improved, but device complexity and cost increase
Solution Approach 1:
The inverter is designed to perform multiple functions: it can operate in three-phase mode during normal grid operation and automatically switch to single-phase mode during grid failure. This multi-functionality eliminates the need for separate backup systems, resolving the contradiction between reliability and device complexity by making one device serve multiple purposes
Solution Approach 2:
The inverter dynamically adapts its operating mode based on grid status. It transitions from three-phase operation when connected to the grid to single-phase operation when disconnected, allowing the system to maintain reliability under varying conditions without requiring additional hardware
2Adaptability or versatility
If the inverter switches from three-phase to single-phase operation during grid failure, then adaptability is improved, but manufacturing precision and control complexity increase
Solution Approach 1:
The control system dynamically adjusts the inverter's operating parameters based on the detected grid status. When grid failure is detected, the controller automatically transitions from three-phase to single-phase control algorithms, enabling adaptability while managing control precision through programmed switching between established control modes
Solution Approach 2:
The inverter changes its operational parameters (phase configuration, switching patterns, control algorithms) based on grid availability. This parameter adaptation allows the system to maintain precision in both three-phase and single-phase modes by using optimized control strategies for each operating condition
3Device complexity
If existing inverter components are used without additional devices, then device complexity is reduced, but power output sufficiency worsens
Solution Approach 1:
During grid failure, the inverter provides partial power output in single-phase mode rather than attempting to supply full three-phase power. This partial action approach ensures that critical single-phase loads can be maintained with the available power, resolving the contradiction by accepting reduced power output in exchange for system simplicity
Solution Approach 2:
The same inverter hardware that provides three-phase power during normal operation is used to provide single-phase power during grid failure. This multi-functionality allows the system to maintain simplicity while adapting power output to match the reduced requirements of single-phase loads
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous energy supply to critical consumers during grid failures by converting DC power to single-phase AC power using existing inverter components, ensuring efficient and reliable operation without the need for extra hardware, while maintaining compliance with grid codes and minimizing changes to existing installations.
Implementation Method 1
converting DC power from a source into AC power by means of an inverter
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
A method for converting DC power from a source (2) into AC power using an inverter (1) comprising three bridge arms (4, 5, 6), each with a phase output (7, 8, 9), is described. In grid-connected operation, the bridge arms (4, 5, 6) are controlled such that the AC power is fed into a grid (10) as three-phase, grid-compliant power. In emergency operation of the inverter (1), the AC power is provided as a single-phase island grid by two of the three bridge arms (4, 5, 6) at their phase outputs (7, 8, 9), with the inverter (1) being disconnected from the grid (10).