EV Inverter Current Detection Correction for Filter Delay
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Solution Overview
Problem
In electric vehicle systems, the deviation between detected and actual currents in three-phase inverters is significant due to noise removal filters with small time constants, leading to inaccurate torque control and potential damage to the inverter and motor, especially in motors with low inductance values.
Innovation Solution
An inverter control device that corrects current detection values or command values based on a current detection unit's output, accounting for the delay time of the filter element to minimize the deviation between detected and actual currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a noise removal filter is provided in the current detection unit, then noise is removed from the detection signal, but a delay element is introduced causing deviation between detection current and actual current
Solution Approach 1:
The invention performs preliminary action by calculating the deviation between detection current and actual current in advance, then using this calculated deviation to correct the torque command value before it is executed. This prevents the deviation from affecting control accuracy while maintaining the noise removal function.
Solution Approach 2:
The invention introduces feedback by calculating the deviation based on the relationship between detection current and actual current, then feeding this deviation information back to correct the torque command. This closed-loop approach compensates for the delay introduced by the noise removal filter.
2Speed
If filters with small time constants are used to reduce delay, then response speed improves, but noise removal capability is insufficient causing detection current slope to shift from true value
Solution Approach 1:
The invention uses feedback to calculate the deviation between detection current and actual current, then applies this deviation information to correct the torque command. This allows the use of fast-response filters while maintaining accuracy through active compensation.
Solution Approach 2:
The invention changes the parameter being controlled from filter time constant to torque command correction. By adjusting the torque command based on calculated deviation rather than trying to optimize filter parameters, the system achieves both fast response and high accuracy.
3Measurement precision
If current detection accuracy is improved to achieve requested acceleration performance, then torque control accuracy improves, but device complexity increases
Solution Approach 1:
The invention replaces the need for additional physical sensors or complex hardware by using calculation-based deviation determination. The deviation is computed from existing detection data and system parameters, substituting mechanical/sensor complexity with computational simplicity.
Solution Approach 2:
The system performs self-service by using its own existing detection current data and known system parameters to calculate the deviation and generate correction values. No external sensors or additional measurement devices are required, as the system determines its own deviation and corrects it autonomously.
Data Source
AI summary
A deviation between a detection result of an output current of an inverter and an actual current is suppressed. A current detection unit 7 detects a three-phase AC current output from an inverter 3 or input to the inverter 3. An inverter control device 1 controls the inverter 3 based on a current detection value based on a detection result of the three-phase AC current by the current detection unit 7 and a predetermined current command value. The inverter control device 1 corrects the current detection value so as to correct a detection error of the three-phase AC current generated due to a delay time of a filter 72 which is a filter element provided in the current detection unit 7.