Motor Inverter Dead Time Compensation Under RF Voltage Injection
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Solution Overview
Problem
Existing motor control systems face challenges in accurately performing dead time compensation and noise reduction due to the influence of superimposed radio-frequency voltage, leading to potential noise and torque ripple, and increased power loss.
Innovation Solution
An electric motor control device and method that estimates radio-frequency current using an inverse model of the motor, incorporating this estimation into dead time compensation to ensure accurate phase delay compensation and minimize noise, thereby enhancing reliability and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If radio-frequency voltage is superimposed for noise reduction control, then noise is reduced, but dead time compensation cannot be appropriately performed
Solution Approach 1:
The patent separates the current into two distinct components: fundamental wave current (for torque) and radio-frequency current (for noise reduction). By estimating the radio-frequency current separately using an inverse model, the system can compensate for dead time effects on each component independently, preventing the radio-frequency current from interfering with dead time compensation accuracy while maintaining noise reduction benefits.
Solution Approach 2:
The patent introduces an inverse model as an intermediary mechanism that estimates the radio-frequency current generated by the superimposed radio-frequency voltage. This estimated current serves as a mediator that allows the control system to account for and compensate the dead time effects specifically on the radio-frequency current component, thereby maintaining accurate dead time compensation despite the presence of noise reduction control.
2Reliability
If reactive current is caused to flow for dead time compensation, then dead time compensation accuracy is improved, but power loss increases
Solution Approach 1:
The patent employs sensorless control where the system uses its own operational data (voltages and currents) to estimate the radio-frequency current through an inverse model. This self-service approach eliminates the need for additional sensors or external measurement devices, achieving accurate dead time compensation without increasing system complexity or energy consumption.
Solution Approach 2:
The patent changes the approach from directly injecting reactive current to mathematically estimating and compensating for radio-frequency current effects. By transforming the problem from a physical current injection approach to a computational parameter adjustment approach, the system achieves accurate dead time compensation without the energy losses associated with flowing additional reactive current.
3Device complexity
If sensorless control is applied for rotation angle estimation, then device complexity is reduced, but measurement precision of rotation state may be affected
Solution Approach 1:
The patent implements a feedback mechanism where the estimated radio-frequency current is continuously fed back into the dead time compensation calculation. This feedback loop ensures that the rotation angle estimation and control parameters are continuously refined based on the actual system state, maintaining high measurement precision without requiring additional physical sensors.
Data Source
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AI summary
Provided are an electric motor control device and an electric motor control method with high reliability capable of performing noise reduction control (or sensorless control) by superimposing a radio-frequency voltage and capable of performing compensation of a dead time of an inverter with a minimum necessary configuration. The electric motor control device includes: a radio-frequency voltage superimposing unit that adds a radio-frequency voltage command value to a fundamental wave voltage command value and outputs a voltage command value; a radio-frequency current estimation value calculation unit that estimates a radio-frequency current value from the radio-frequency voltage command value; a dead time compensation current estimation value calculation unit that adds a radio-frequency current estimation value estimated by the radio-frequency current estimation value calculation unit to a fundamental wave current command value; and a dead time compensation voltage calculation unit that compensates an output voltage of an inverter according to a dead time compensation current estimation value calculated by the dead time compensation current estimation value calculation unit.