Electric Power Conversion Device Duty Ratio Control
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Solution Overview
Problem
Conventional electric power conversion devices with duty ratio limitations and feedback control require a significant amount of time to reach a steady state, particularly extending battery charging time due to restricted duty ratio adjustments.
Innovation Solution
An electric power conversion device employing proportional plus integral control with two operation limits, where the second limit is set higher than the first, to manage the duty ratio and reduce convergence time to a target value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the duty ratio is limited by a prescribed upper limit to secure the safety and controllability of a semiconductor switching element, then the reliability of the semiconductor switching element is improved, but the time required for the electric power conversion to reach a steady state increases
Solution Approach 1:
The patent applies dynamics by making the upper limit of the duty ratio adjustable rather than fixed. The control part dynamically changes the upper limit value based on the operating state - setting it to a first value during normal operation and a second value (higher than the first) during startup or transient states. This allows the system to adapt the duty ratio constraints to different operational phases, enabling faster convergence during transients while maintaining safety during normal operation.
Solution Approach 2:
The patent changes the parameter of the duty ratio upper limit based on the operating state of the electric power conversion device. By switching between a first upper limit value and a second upper limit value (where the second is higher than the first), the system optimizes the balance between safety and convergence speed. This parameter change allows larger duty ratio adjustments during startup to reduce settling time, while maintaining stricter limits during normal operation to ensure component safety.
2Manufacturing precision
If feedback control is carried out to minimize the difference between the calculated duty ratio and the duty ratio target value, then the manufacturing precision of the voltage control is improved, but the time required for the duty ratio to converge to the target value increases
Solution Approach 1:
The control part dynamically adjusts the upper limit of the duty ratio based on the operating state. During startup or transient states, a higher second upper limit value is applied to allow larger duty ratio adjustments and faster convergence. Once the system reaches normal operation, it switches to a stricter first upper limit value to maintain precise voltage control. This dynamic adjustment resolves the contradiction by applying different control strategies at different stages.
Solution Approach 2:
The patent applies preliminary action by pre-setting different upper limit values for different operational phases. Before the system reaches steady state, the control part uses a higher duty ratio upper limit to enable rapid convergence. This preliminary configuration of relaxed constraints during the transient phase allows the system to reach the target voltage faster, after which normal precision control is restored.
3Loss of energy
If the duty ratio target value is set close to the upper limit, then the power conversion efficiency is improved, but the ability to obtain a large difference from the target value for feedback control is reduced
Solution Approach 1:
The patent makes the duty ratio upper limit dynamic rather than fixed. During normal operation, the first upper limit value is set close to the optimal duty ratio for high efficiency. During transient states or when rapid adjustment is needed, the control part switches to a second upper limit value that is higher than the first, providing more headroom for feedback control adjustments and enabling faster response to changing conditions.
Data Source
AI summary
Electric power conversion devices carry out feedback control, so that a difference between a duty ratio and a duty ratio target value may approach zero, while a duty ratio, which becomes the origin of a drive signal of a semiconductor switching element, is limited by a prescribed upper limit.The control part issues a first operation result, which is limited by a first upper limit, with respect to an operation value which is on an operation process for controlling an output electric power, and further a second operation result which is limited by a second upper limit, which is set as a value higher than the first upper limit, with respect to an operation value. In addition, the control part is configured to carry out the proportional plus integral control, by a difference between the second operation result and a target value of the second operation result.