Power Conversion Device Input Current Control
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Solution Overview
Problem
Conventional power conversion devices for electric vehicles struggle to maintain efficient charging by preventing excessive current from flowing into the charging cable, especially when there are abnormalities in the input current sensor, leading to potential overheating and incomplete charging.
Innovation Solution
A power conversion device equipped with input and output sensors, along with a controller that monitors and adjusts the input current to ensure it does not exceed the allowable value, while diagnosing abnormalities in power conversion efficiency to prevent excessive current flow and optimize charging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum output value is calculated based on the expected minimum conversion efficiency, then the input current does not exceed the allowable current value even when conversion efficiency lowers, but the power conversion device can only accept a current value smaller than near the allowable current value when conversion efficiency is high
Solution Approach 1:
The controller performs preliminary diagnosis of the input current sensor by comparing the detected input current with the calculated input current (derived from output current and conversion efficiency) before normal charging operation. This preliminary action identifies sensor abnormalities in advance, allowing the system to switch to alternative control methods that maintain both current safety and charging speed.
Solution Approach 2:
The system uses feedback control by continuously monitoring the relationship between detected input current, output current, and conversion efficiency. When the input current sensor is diagnosed as normal, the controller accepts input current near the allowable value. When abnormality is detected, the controller switches to using output current and conversion efficiency as feedback parameters to calculate and control input current, ensuring safety while maintaining optimal charging speed.
2Productivity
If feedback control is performed so that input current does not exceed the allowable current value without setting maximum output value, then output power can be increased and charging period can be shortened, but excessive current exceeding the allowable current value would flow into the charging cable if abnormality arises in the input current sensor
Solution Approach 1:
The controller performs preliminary diagnosis of the input current sensor by comparing the detected input current with the calculated input current (derived from output current and conversion efficiency) before normal charging operation. This preliminary action identifies sensor abnormalities in advance, allowing the system to switch to alternative control methods that maintain both current safety and charging speed.
Solution Approach 2:
When input current sensor abnormality is detected, the controller uses the output current sensor and conversion efficiency data as intermediary parameters to indirectly monitor and control input current. This intermediary approach allows the system to maintain safe operating limits without relying on the faulty input current sensor, preventing excessive current flow while preserving high charging speed.
3Reliability
If the power conversion device controls output power so that output power does not exceed the maximum output value, then safety is ensured, but the input current value cannot reach near the allowable current value even when conversion efficiency is high
Solution Approach 1:
The controller performs preliminary diagnosis of the input current sensor by comparing the detected input current with the calculated input current (derived from output current and conversion efficiency) before normal charging operation. This preliminary action identifies sensor abnormalities in advance, allowing the system to switch to alternative control methods that maintain both current safety and charging speed.
Solution Approach 2:
The system dynamically adjusts its control strategy based on the diagnosis result. When the input current sensor is normal, the controller uses direct input current control allowing operation near the allowable current value. When abnormality is detected, the controller dynamically switches to using output current and conversion efficiency as control parameters, maintaining safety while optimizing charging speed according to actual operating conditions.
Data Source
AI summary
A power conversion device includes an input current sensor, an input voltage sensor, a power converter, an output voltage sensor for detecting an output voltage from the power converter, an output current sensor for detecting an output current value from the power converter, and a controller for controlling the power converter. The controller obtains an allowable current value that can be accepted from an external alternating current power source, and, controls the power converter so that the input current value does not exceed the allowable current value based on an input current value detected by the input current sensor. The controller detects an abnormality in the power conversion device based on the input current value, the input voltage, the output current value, the output voltage, and power conversion efficiency of the power converter.