Inverter AC Frequency Signaling for Load Shedding Control
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Solution Overview
Problem
Existing load shedding systems for inverter-based power sources, particularly portable devices, face challenges due to the steady AC frequency not changing with load, making frequency-based detection methods ineffective and costly, and requiring complex communication systems that are difficult to install and prone to reliability issues.
Innovation Solution
The system controls the frequency of AC power provided to loads in response to the amount of power consumed, using a frequency measurement circuit to prevent or alleviate overloads by disconnecting loads or limiting power consumption, and communicates this information through the AC power frequency, eliminating the need for additional communication channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency-based detection methods are used for load shedding, then load management accuracy is improved, but device complexity and installation difficulty increase due to requiring complex communication systems
Solution Approach 1:
The system uses the inverter's own AC power frequency as the communication medium to convey load information, eliminating the need for separate communication channels. The inverter automatically modulates its output frequency based on load conditions, and the load control device detects these frequency variations to determine power source status, making the system self-sufficient without external communication infrastructure.
Solution Approach 2:
The AC power frequency serves dual purposes: it simultaneously provides electrical power to loads and communicates power source loading status. This multi-functionality eliminates the need for dedicated communication systems, reducing device complexity while maintaining accurate load detection capability through frequency measurement.
2Loss of information
If additional communication channels are added for load control, then information transmission capability is improved, but ease of installation deteriorates due to complex wiring and setup
Solution Approach 1:
The existing AC power conductors are used for both power delivery and information communication. The inverter modulates its output frequency to encode load status information, which is naturally transmitted through the same wires already present in the system, eliminating the need for additional communication wiring and simplifying installation.
Solution Approach 2:
The patent combines power transmission and information communication functions into a single AC power channel. By encoding load status information in the frequency of the power signal itself, the system merges two separate functions (power delivery and data communication) into one unified medium, reducing installation complexity.
3Reliability
If voltage reduction is used for overload protection, then power source protection is improved, but harmful effects increase due to voltage drop damaging to loads
Solution Approach 1:
The system dynamically adjusts the AC power frequency based on load conditions rather than using static voltage reduction. When overload is detected, the inverter modifies its output frequency to signal the load control device, which then disconnects or reduces non-critical loads. This dynamic frequency-based control protects the power source while maintaining stable voltage for connected loads, avoiding the harmful effects of voltage drop.
Solution Approach 2:
The system implements a feedback loop where the inverter continuously monitors its output load and adjusts its frequency accordingly. The load control device detects these frequency changes and responds by managing load disconnection. This closed-loop feedback mechanism enables precise overload protection without the need for aggressive voltage reduction that could harm connected equipment.
Data Source
AI summary
A method and apparatus is described for conveying the amount of loading of a power source to a load control device by controlling the frequency of the AC power output from that power source in a manner that controlled frequency represents the loading. At a different location in the power system, the frequency is measured and the corresponding loading of the power source is used to prevent or alleviate a power source overload.