EV Charging Converter Control for Current Ripple Suppression
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Solution Overview
Problem
Existing power converters for electric vehicles experience current ripple fluctuations due to delays in switch circuit operations, leading to unpredictable duty ratios in PWM signals.
Innovation Solution
A charging device with multiple legs and a controller that monitors current fluctuations and adjusts PWM signal duty ratios based on detected fluctuations, using sampling periods other than 1/N of the carrier period to suppress ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PWM signals with fixed duty ratios are used to drive switching elements, then the power conversion process is simple, but current ripple fluctuations occur due to switch circuit operation delays
Solution Approach 1:
The patent implements a feedback mechanism where the controller monitors the actual current flowing through the power storage device and adjusts the PWM signal duty ratios dynamically. The controller calculates the fluctuation width of the monitored current and instructs the driver to apply adjusted duty ratios so that the fluctuation width is reduced, creating a closed-loop control system that compensates for switching delays and operational variations.
Solution Approach 2:
The patent transitions from fixed duty ratio PWM signals to dynamically adjustable duty ratios. The controller continuously monitors current fluctuations and adjusts the duty ratios in real-time based on the detected fluctuation width, making the control system adaptive to changing operating conditions and switching delays.
2Stability of the object's composition
If current fluctuation monitoring and dynamic duty ratio adjustment are implemented, then current stability is improved, but control system complexity increases
Solution Approach 1:
The controller monitors the measurement result of a sensor for measuring a current from the plurality of legs to the battery, and instructs the driver to apply duty ratios of the PWM signals so that a fluctuation width of the monitored current is reduced based on the fluctuation width of the monitored current.
Solution Approach 2:
The patent changes the PWM signal parameters (duty ratios) dynamically based on monitored current fluctuations. The controller calculates the fluctuation width and adjusts the duty ratios accordingly, changing the temporal characteristics of the PWM signals to optimize current stability.
3Ease of operation
If sampling is performed at 1/N of the carrier period, then measurement timing is simplified, but accurate detection of current fluctuation width becomes difficult
Solution Approach 1:
The patent makes the sampling timing dynamic rather than fixed. The controller determines sampling timings based on the carrier signal phase and the detected current fluctuation characteristics, adapting the sampling strategy to accurately capture the fluctuation width while maintaining synchronization with the PWM carrier.
Data Source
AI summary
A charging device includes: a plurality of legs including respective upper and lower arms having respective switching elements, the upper and lower arms being connected to a battery and a negative pole of a DC charger, respectively; a motor having three phases with a neutral point connected to a positive pole of the DC charger; a driver that drives the switching elements with respective PWM signals; and a controller that monitors a current from the legs to the battery, and instructs the driver to apply duty ratios of the PWM signals so that a fluctuation width of the monitored current is reduced. Further, the controller monitors the measurement result of the sensor at a period other than 1/N of a period of a carrier of the PWM signals, where N is a number of the plurality of legs used for charging the battery.