Booster Charger Feedback Gain Tuning for Stable EV Charging
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Solution Overview
Problem
Existing chargers for battery electric vehicles face interference issues due to the electrical characteristics of the power supply, which can lead to voltage and current fluctuations during feedback control, affecting charging efficiency and stability.
Innovation Solution
The charger incorporates a controller with a feedback module, a feedforward module, and a driver that adjusts the switching element's operation to match the target voltage, while determining a feedback gain to separate the control peak frequency from the disturbance peak frequency, thereby reducing interference from the power supply's characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback module is used to control the booster circuit voltage, then the voltage control precision is improved, but voltage and current fluctuations occur due to interference with power supply electrical characteristics
Solution Approach 1:
The controller performs frequency sweeping of the target voltage before actual charging to identify the disturbance peak frequency on the Bode diagram. This preliminary action allows the system to detect power supply electrical characteristics in advance and adjust control parameters accordingly, preventing interference issues during actual operation.
Solution Approach 2:
The controller adjusts the feedback gain parameter based on the identified disturbance peak frequency. By changing the feedback gain, the control peak frequency is shifted to avoid overlapping with the disturbance peak frequency, thereby resolving the interference between feedback control and power supply electrical characteristics.
2Speed
If the feedback gain is increased to improve control response, then the control speed is improved, but interference with power supply characteristics increases causing larger fluctuations
Solution Approach 1:
The system uses frequency response analysis through Bode diagrams to understand how the power supply characteristics affect the control system. By analyzing the disturbance transfer function and control transfer function in the frequency domain, the controller can optimize feedback gain to achieve fast response while avoiding resonant frequencies that cause interference.
3Reliability
If frequency sweeping is performed to identify disturbance peak frequency, then the ability to avoid interference is improved, but the charging preparation time increases
Solution Approach 1:
The frequency sweeping process covers only the necessary frequency range to identify the disturbance peak frequency, rather than performing a complete system characterization. This partial action approach achieves the essential goal of interference avoidance while minimizing the time required for preparation.
Data Source
AI summary
The charger includes a controller for controlling the booster circuit. The controller includes a FB module, a FF module, and a driver. The controller (1) identifies the disturbance peak frequency on the board diagram of the disturbance transfer function from the target voltage to the current flowing through the reactor by sweeping the target voltage while setting FB command to zero, and (2) determines FB gain included in FB module such that the difference between the control peak frequency on the board diagram of the control transfer function of the controller and the disturbance peak frequency is larger than the predetermined threshold frequency width when it is assumed that the ideal power supply is connected to the low voltage terminal.