Inverter Generator Overcurrent Control via PWM Feedback
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Solution Overview
Problem
Existing inverter generators with overcurrent limiter circuits repeatedly drop output current to zero when the current exceeds the tolerance limit, leading to inefficient overcurrent limitation and a preference for limiting overcurrent at a lower level than set.
Innovation Solution
An inverter generator with a current detector, direct current voltage detector, alternating current voltage detector, output voltage corrector, and PWM signal corrector that adjusts the PWM signal based on detected voltages to maintain the alternating current below a threshold value, allowing for reliable overcurrent limitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the overcurrent limiter circuit makes the PWM signal zero when current exceeds the tolerance limit, then overcurrent is prevented, but the output current is made zero repeatedly causing inefficient operation
Solution Approach 1:
The patent implements a feedback control mechanism where the output current is continuously detected and compared against a threshold value. When the current exceeds the threshold, the output voltage is adjusted based on the detected DC voltage to reduce the current back below the threshold, creating a closed-loop control system that prevents overcurrent without completely shutting down the output.
Solution Approach 2:
The patent changes the output voltage parameter dynamically in response to current conditions. When overcurrent is detected, the output voltage is corrected based on the detected DC voltage, which in turn reduces the output current. This parameter adjustment allows continuous operation at reduced capacity rather than complete shutdown.
2Reliability
If the tolerance limit is set to a relatively high value, then the switching elements are protected, but overcurrent cannot be limited at a lower preferred level
Solution Approach 1:
The feedback mechanism continuously monitors the output current and adjusts the output voltage accordingly. This allows the system to maintain current at a precise level just below the threshold, rather than allowing it to exceed a high tolerance limit. The feedback loop provides fine-grained control that enables precise current limitation.
Solution Approach 2:
The system dynamically adjusts the output voltage based on real-time current detection. This dynamic control allows the current limitation level to be flexible and responsive to actual operating conditions, enabling precise limitation at lower levels rather than relying on a fixed high tolerance limit.
3Reliability
If the PWM signal is repeatedly made zero to limit overcurrent, then the current is controlled, but a series of the same events is repeated causing instability
Solution Approach 1:
The patent maintains continuous operation of the inverter by avoiding complete shutdown of the PWM signal. Instead, it continuously adjusts the output voltage to control the current, ensuring the useful action of power conversion continues without interruption or repeated on-off cycles that would cause instability.
Solution Approach 2:
The feedback control creates a stable equilibrium by continuously adjusting the output voltage in response to current measurements. This prevents the repeated oscillation between overcurrent and shutdown that occurs with conventional limiters, as the system actively maintains current below the threshold through continuous small adjustments rather than periodic large corrections.
Data Source
AI summary
In an inverter generator having an engine generator unit, a converter that converts generated alternating current to direct current, an inverter that converts the direct current to alternating current with switching elements to supply to an electrical load, an inverter driver that drives the switching elements with a PWM signal and makes the alternating current of a predetermined frequency, the alternating current supplied to the electrical and voltages of the direct and alternating currents are detected, the detected voltage of the alternating current is corrected as a predetermined value based on a coefficient (DCgainA) set based on the detected voltage of the direct current, when the detected alternating current is greater than a threshold value, and the PWM signal is corrected by the predetermined, thereby limiting overcurrent.