Adaptive Load Sharing via AC Selection Switch
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Solution Overview
Problem
Existing DC to AC converters, such as grid-tie and standalone inverters, face challenges in efficiently utilizing solar power without connecting to the grid, requiring expensive batteries for energy storage and incurring additional costs and regulatory barriers, while current-mode inverters still need to switch off during grid outages.
Innovation Solution
A novel circuit using a two-way AC selection switch with low-pass filters and a controller to alternately select between grid and solar power sources at a high frequency, ensuring continuous load sharing without a direct electrical connection, allowing for adaptive control of current proportion based on solar energy availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a standalone inverter is used to power a home in a totally off-grid installation, then solar power can be used without connecting to the grid, but a very large and expensive battery is required to ensure the ability to bridge a period of overcast weather
Solution Approach 1:
The patent segments the power supply function by using multiple independent power sources (solar inverter, utility grid, generator) that can operate independently. The AC power source selector switch divides the power delivery path into separate channels, allowing the system to draw from different sources without requiring a large battery to bridge transitions between them.
Solution Approach 2:
The patent introduces an AC power source selector switch as an intermediary device that couples the solar inverter, utility grid, and generator to the electrical load. This mediator enables seamless transitions between power sources and allows the solar inverter to operate in voltage-mode without direct connection to the grid, eliminating the need for large batteries while maintaining off-grid capability.
2Loss of energy
If a grid-tie inverter is used to convert DC energy to AC current and feed it back into the electricity grid, then net energy consumption is reduced, but the system must be switched off if the utility is in an outage
Solution Approach 1:
The patent implements dynamic operation by enabling the solar inverter to switch between current-mode (for grid-tie operation) and voltage-mode (for standalone operation) based on grid availability. The AC power source selector switch dynamically routes power between the grid and the inverter, allowing the system to maintain reliability during grid outages while maximizing energy efficiency when the grid is available.
Solution Approach 2:
The patent changes the operating parameters of the solar inverter based on grid conditions. When the grid is available, the inverter operates in current-mode with controlled current output. When the grid fails, the inverter switches to voltage-mode, outputting a stabilized AC voltage that can power loads independently, thus maintaining reliability without requiring shutdown.
3Productivity
If a current-mode inverter is used in utility assist mode to supplement current coming from the grid, then a finer degree of matching between solar power generated and solar power used can be achieved, but the inverter must switch off if the grid is in outage unless a fast disconnect switch operates and simultaneously switches to voltage-mode DC to AC inversion
Solution Approach 1:
The patent makes the solar inverter universal by enabling it to perform multiple functions: grid-tie operation in current-mode, standalone operation in voltage-mode, and utility assist mode. The AC power source selector switch provides a unified interface that handles all these modes without requiring separate switching mechanisms, reducing device complexity while maintaining fine matching capability between solar generation and consumption.
4Adaptability or versatility
If a standalone inverter is used to power loads directly without connecting to the grid, then regulatory barriers and utility subversion issues are avoided, but expensive batteries are required for energy storage
Solution Approach 1:
The patent segments the power supply architecture by introducing an AC power source selector switch that creates independent power channels. This allows the solar inverter to operate independently from the grid in voltage-mode, achieving regulatory independence while using the grid or generator as alternative power sources when needed, thereby eliminating the requirement for large battery storage.
Data Source
AI summary
Sharing of load current in desired ratios between multiple electrical voltage sources is achieved without coupling between the sources by controlling a selection switch to select each voltage source for a proportion of the time at a high rate, the switching rate components being prevented from being seen by either the load or the sources through use of low-pass filters.