AC Load Transfer Using Predicted Zero-Crossing Switching
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Solution Overview
Problem
Existing methods for switching between on-board and off-board AC power sources in vehicles result in inconvenient power interruptions, potential device damage, and inefficiency due to the need for manual shutdown and synchronization, which can be costly and environmentally harmful.
Innovation Solution
A system and method using solid-state switching circuits controlled by a microprocessor to seamlessly transfer AC loads by predicting synchronous zero crossings and accounting for actuation delays, allowing for automatic switching without shutting down generators or devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual shutdown and restart procedure is used to switch between power sources, then power source switching can be completed, but power interruption occurs and devices may be damaged
Solution Approach 1:
The control system predicts future synchronous zero crossings in advance and schedules the switching operation to occur at these predetermined optimal moments. By performing the switching action at the predicted zero crossing point, the system ensures seamless transition without power interruption or device damage.
Solution Approach 2:
The system continuously monitors the actual zero crossing timing and compares it with the predicted timing. Based on this feedback, the control system adjusts future predictions to account for actuation delays and timing variations, ensuring accurate switching at the correct moment while preventing power interruptions.
2Reliability
If frequency synchronization is performed before switching, then seamless transition can be achieved, but the process becomes complex and expensive
Solution Approach 1:
The invention extracts and eliminates the complex frequency synchronization step from the power source switching process. Instead of synchronizing frequencies before switching, the system directly switches at the predicted zero crossing moment, achieving seamless transition without requiring frequency matching or complex synchronization hardware.
Solution Approach 2:
The system replaces the mechanical/electrical frequency synchronization mechanism with a computational approach using zero crossing prediction algorithms. This substitution eliminates the need for complex synchronization hardware and reduces system complexity while maintaining seamless transition capability.
3Reliability
If on-board generators are run continuously, then power supply is maintained, but energy consumption increases and environmental pollution occurs
Solution Approach 1:
The system dynamically switches between on-board generator and external power source based on real-time conditions and predicted zero crossings. This dynamic switching allows the generator to be shut down when external power is available, reducing fuel consumption and emissions while maintaining power supply reliability through automated transitions.
Solution Approach 2:
The control system automatically manages the power source switching without requiring continuous generator operation. By implementing self-service switching at predicted zero crossings, the system eliminates the need for continuous generator running, thereby reducing energy loss and environmental pollution while ensuring power availability.
4Device complexity
If switching is performed without accounting for actuation delay, then control is simplified, but timing accuracy deteriorates causing power interruption
Solution Approach 1:
The control system performs preliminary compensation for the known actuation delay by advancing the trigger signal timing. The predicted zero crossing time is adjusted backward by the actuation delay amount, so that the actual switching occurs at the correct zero crossing moment, preventing power interruption while maintaining relatively simple control logic.
Data Source
AI summary
Methods for switching the power source supplying an alternating current (AC) electrical load from a first AC power supply to a second AC power supply comprising: (a) determining, during a time period, the zero voltage crossings of at the first and second AC power supplies; (b) estimating for a future time period, based on information obtained in said determining step (a), the times at which a series of future current zero-crossings of said AC load and at least the current zero-crossing of the second power supply; (c) based on said estimating step (b), determining whether during said future time period the time of said zero-crossing of said load current and the zero-crossing of the second power supply are within about 0.1 microseconds of each other; and (d) for a time period during which said zero crossings are estimated to be within 0.1 microseconds of each other, switching said load to said second power supply at said time at which said zero crossings are estimated to be within 0.1 microseconds of each other, wherein said switching: (i) uses a solid-state switching system and microprocessor-based control system for actuating said solid-state switching circuit; and (ii) accounts for any known actuation delay between the actuation signal from said microprocessor and the occurrence of said switching.