Dynamic Duty Ratio Limits for Boost Converter Current Response
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Solution Overview
Problem
The existing voltage conversion control systems face challenges in achieving high response of the output current from the electricity storage apparatus, leading to a significant difference between the electrical power output and the required power by the rotating electrical machine, especially during transient periods, due to the limitations imposed by constant upper and lower limit values of the duty ratio.
Innovation Solution
A voltage conversion control apparatus that calculates a duty ratio to reach a target output current, with a limit relaxing device adjusting the allowable range based on current deviations, allowing for dynamic control of the upper and lower limit values to enhance the response time and reduce the capacitance requirements of the smoothing condenser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If constant upper and lower limit values of duty ratio are used, then the control system is simple, but the response time of output current is slow
Solution Approach 1:
The patent applies dynamics by making the duty ratio limits variable rather than constant. The upper and lower limit values of the duty ratio are dynamically adjusted based on the absolute value of current deviation |Δi|. When |Δi| exceeds a threshold, the limits are relaxed to allow faster response; when |Δi| is within the threshold, the limits are maintained to ensure stability. This dynamic adjustment resolves the contradiction by enabling fast response only when necessary.
Solution Approach 2:
The patent changes the parameters of the duty ratio limits based on operating conditions. Specifically, the upper limit Du and lower limit Dl are modified according to the current deviation |Δi|. When |Δi| > Δi_th, the limits are expanded (Du increased, Dl decreased) to permit larger duty ratio variations for faster current response. This parameter change strategy allows the system to achieve high response speed without permanently increasing control complexity.
2Speed
If the duty ratio limits are relaxed to improve response, then the response time decreases, but the difference between output power and required power increases during transient periods
Solution Approach 1:
The patent uses dynamic adjustment of duty ratio limits that are activated only when |Δi| exceeds the threshold. During transient periods when fast response is needed, the relaxed limits enable quicker current response. Once the current returns to the acceptable range (|Δi| ≤ Δi th), the limits are restored to their normal values, preventing excessive power mismatch. This temporal dynamics ensures fast response only when necessary.
Solution Approach 2:
The patent applies partial relaxation of duty ratio limits only when the current deviation exceeds the threshold. The relaxation is not continuous but conditional, providing just enough additional duty ratio range to achieve acceptable response time without allowing excessive power mismatch to develop. This partial action approach balances response speed with power matching accuracy.
3Volume of moving object
If the capacitance of the smoothing condenser is reduced to downsize it, then the device size decreases, but the delay of response of electrical power increases
Solution Approach 1:
The patent implements feedback control by continuously monitoring the current deviation |Δi| and using this information to dynamically adjust the duty ratio limits. This feedback mechanism allows the system to compensate for the reduced capacitance effect by actively adapting the control parameters. When the smaller condenser causes larger power fluctuations, the feedback loop detects increased |Δi| and relaxes the duty ratio limits to enable faster correction, effectively compensating for the reduced energy storage capacity.
Solution Approach 2:
The patent changes the control parameters (duty ratio limits) in response to the reduced condenser capacitance. By making the limits variable based on |Δi|, the system can tolerate larger short-term deviations that result from the smaller condenser, while still maintaining overall stability. This parameter adaptation allows the use of a smaller condenser without permanently degrading the response performance.
Data Source
AI summary
A voltage conversion control apparatus is a voltage conversion control apparatus which controls a voltage converter having an upper switching element and a lower switching element, and has a calculating device which calculates duty ratio such that output current of an electricity storage apparatus reaches target value and the duty ratio is within predetermined allowable range; a limit relaxing device which relaxes at least one of upper limit value and lower limit value of the allowable range on the basis of magnitude relationship between predetermined threshold value and current deviation which is obtained by subtracting the output current from the target value; and a controlling device which controls the upper switching element and the lower switching element to perform a switching control on the basis of the duty ratio which is calculated by the calculating device.