Modulation Signal Control Across Forbidden Duty Regions
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Solution Overview
Problem
Power electronic converters and motor drives face operational errors due to the need to avoid specific duty cycles or frequency ranges, leading to nonzero direct current errors and significant ripple when control loops transition unpredictably through forbidden regions.
Innovation Solution
A control apparatus that generates an applicable control signal by modifying a reference signal to avoid forbidden regions, using an error determination module, compensation module with noise-shaping, and an enforcer module to ensure the signal remains within or alternates between the forbidden region boundaries, seamlessly switching between nonlinear and linear regulation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control loop transitions slowly and unpredictably between the boundaries of the forbidden region to avoid specific duty cycles, then the system avoids forbidden regions, but a significant error ripple occurs and the DC error remains nonzero
Solution Approach 1:
The patent applies periodic action by using a triangular carrier wave that periodically intersects with the modulating signal. This periodic intersection pattern generates PWM pulses that naturally avoid forbidden regions while maintaining controlled transitions. The carrier wave's periodic nature ensures consistent avoidance behavior without unpredictable transitions, thereby reducing error ripple while maintaining reliability.
Solution Approach 2:
The patent employs dynamics by implementing a dynamic modulation scheme where the duty cycle is continuously adjusted based on the intersection points between the carrier wave and modulating signal. This dynamic adjustment allows the system to adaptively avoid forbidden regions in real-time while maintaining smooth transitions, preventing both nonzero DC errors and significant error ripple that would occur with static or slow transitions.
2Ease of operation
If the duty cycles of different phases are kept near one another to simplify control, then the control is simpler, but ADC sampling cannot be performed properly in single shunt configuration
Solution Approach 1:
The patent resolves this contradiction by introducing a temporal dimension to the control strategy. Instead of keeping duty cycles spatially close in the time domain (which would simplify control but prevent ADC sampling), the invention schedules duty cycle changes to occur at specific temporal intervals that coincide with ADC sampling windows. This dimensional approach allows both simple control logic and accurate ADC sampling to coexist.
Solution Approach 2:
The patent applies preliminary action by pre-scheduling duty cycle transitions to occur at optimal moments in the switching cycle, specifically timed to allow ADC sampling to complete before or after the transition. This advance planning of transition timing ensures that ADC sampling accuracy is maintained while keeping the control logic simple and systematic.
3Reliability
If the control signal is forced to avoid forbidden regions completely, then forbidden regions are avoided, but the control loop transitions slowly and unpredictably causing significant error ripple
Solution Approach 1:
The patent implements feedback by continuously monitoring the modulating signal and carrier wave intersections to determine when duty cycle transitions should occur. This feedback mechanism ensures that the control signal avoids forbidden regions systematically rather than unpredictably, maintaining stability. The feedback loop adjusts the timing of duty cycle changes based on real-time signal conditions, preventing both forbidden region entry and erratic transitions that would cause error ripple.
Data Source
AI summary
An apparatus for generating an applicable control signal, including: a control module operable to generate a reference control signal that avoids, but is effectively within, a forbidden region by alternating the reference control signal between upper and lower levels of the forbidden region; an error determination module operable to generate an error signal based on a difference between the reference control signal and the applicable control signal; and a compensation module operable to noise-shape the error signal to suppress a portion of the error signal resulting from avoiding the forbidden region, and to modify the reference control signal based on the noise-shaped error signal, wherein the modified reference control signal is output by the apparatus as the applicable control signal for generating a modulation signal.