Active Rectifier Control Voltage Ramp for Transient Overshoot
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Solution Overview
Problem
Conventional active rectifiers often experience transient voltage overshoots during the start of voltage regulation, which can potentially damage the load, and existing systems require supplemental circuitry to mitigate this issue.
Innovation Solution
A method of controlling active rectifiers by generating an over-modulated rectifier switch control voltage using a pulse width modulator, with a decreasing gain factor during a ramp interval to reduce transient voltage overshoots, and seamlessly transitioning between passive and active rectification modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active rectification begins with standard voltage regulation control, then the rectifier can convert AC voltage to DC voltage, but the output DC voltage overshoots the commanded value causing potential load damage
Solution Approach 1:
The system performs preliminary action by detecting the start of regulation before active rectification begins and initiating a ramp interval with reduced gain factor. This preparatory measure limits the modulation index during the critical transition period, preventing voltage overshoot before it can occur while still enabling subsequent normal operation.
Solution Approach 2:
The system applies dynamics by dynamically adjusting the gain factor based on operating conditions. During the ramp interval at the start of regulation, the gain factor is reduced to limit over-modulation effects. Once the ramp interval completes or over-modulation detection occurs, the gain factor returns to normal values, allowing the system to adapt its control characteristics to different operational phases.
2Reliability
If supplemental circuitry is added to mitigate voltage overshoot, then load protection is improved, but device complexity and cost increase
Solution Approach 1:
The system implements feedback by continuously monitoring the modulation index and detecting over-modulation conditions. When over-modulation is detected or the ramp interval completes, the system adjusts the gain factor accordingly. This closed-loop feedback mechanism provides load protection through intelligent control rather than additional hardware circuitry.
Solution Approach 2:
The system replaces mechanical/hardware-based protection circuitry with electronic control mechanisms. Instead of using supplemental circuitry rated for higher voltage to protect against overshoot, the invention uses software-based detection and dynamic gain adjustment to prevent overshoot conditions, substituting electronic intelligence for hardware redundancy.
3Productivity
If over-modulation is used to improve voltage regulation response, then rectification speed is improved, but transient voltage overshoot increases
Solution Approach 1:
The system applies parameter changes by dynamically modifying the gain factor based on the operational phase. During the ramp interval, the gain factor is set to a reduced value to limit over-modulation and prevent overshoot. After the ramp interval or upon over-modulation detection, the gain factor changes to normal operating values, allowing the system to optimize performance for different operational requirements.
Data Source
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AI summary
A method (200) of controlling a rectifier includes receiving a gain factor, receiving a ramp interval, and generating a rectifier switch control voltage. The rectifier switch control voltage is an over-modulated rectifier switch control voltage generated by a pulse width modulator using the gain factor. The amount of over-modulation in the rectifier switch control voltage is decreased during the ramp interval for reducing transient voltage overshoot events at the start of active rectification.