Converter Duty Control Using Parallel Voltage and Current Loops
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Solution Overview
Problem
Conventional converter control methods face challenges in achieving a wide upper range of control band and stable control performance, especially when dealing with rapidly changing loads, due to resonance issues caused by hardware characteristics, leading to limited transient response and increased risk of over-voltage/overcurrent.
Innovation Solution
A device and method that utilize two controllers to generate duties for a switching element, with a duty determination unit deriving a final duty based on errors between predetermined reference values and measured output variables, allowing for independent control of output current and voltage, thereby avoiding dependency between inner and outer loops and enhancing band design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional cascade control is used to achieve stable control, then control stability is improved, but the control band range is limited and transient response is slow
Solution Approach 1:
The patent divides the single cascade control loop into two independent parallel control loops: a voltage control loop and a current control loop. Each loop operates independently with its own controller, allowing the voltage loop to achieve wide control band while the current loop provides fast transient response. This segmentation eliminates the dependency between inner and outer loops that limits conventional cascade control performance.
2Speed
If the inner loop control band is shifted upward to achieve faster response, then transient response is improved, but resonance occurs due to hardware characteristics
Solution Approach 1:
By separating voltage and current control into independent parallel loops, the patent allows the current loop to handle fast transient response without being constrained by the voltage loop's resonance issues. The independent structure enables each loop to be optimized separately, avoiding the resonance problem that occurs when the inner loop band is shifted upward in conventional cascade control.
3Reliability
If conventional control methods are used to limit output, then over-voltage/overcurrent is prevented, but the control band is restricted and transient response deteriorates
Solution Approach 1:
The patent implements independent feedback control in both voltage and current loops, with each loop continuously monitoring its respective parameter and adjusting the duty cycle accordingly. This dual feedback mechanism ensures reliable over-voltage and over-current protection while maintaining fast transient response, as each loop can independently react to disturbances without being constrained by the other loop's bandwidth limitations.
Data Source
AI summary
A device for controlling a converter has a first output variable and a second output variable adjusted by a duty of a switching element. The device includes a first controller that generates a first duty based on a first error between a predetermined limitation reference value corresponding to a reference value limiting a size of the first output variable and a measurement value of the first output variable measured at a load of a converter. A second controller generates a second duty based on a second error between a predetermined reference value of the second output variable and a measurement value of the second output variable measured at the load of the converter. A duty determination unit derives a final duty of the switching element based on the first duty and the second duty.