Power Converter Controller Torque Ripple Reduction
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Solution Overview
Problem
Existing motor control methods, such as indirect field oriented control (IFOC), face limitations in motor response beyond first-order lag and cause torque ripple, especially when attempting to consume regeneration energy during braking.
Innovation Solution
A controller employing dead-beat direct torque and flux control (DB-DTFC) that estimates flux vectors and calculates torque lines to directly control torque and flux, allowing for rapid energy consumption without torque ripple by maximizing loss during braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If indirect field oriented control (IFOC) is used to control current to indirectly control flux, then the control method is simple and general, but the motor response is limited by first-order lag and cannot achieve fast response
Solution Approach 1:
The patent replaces the indirect current control mechanism of IFOC with direct flux control. By directly controlling the flux magnitude through the inverter output voltage and frequency, the system eliminates the first-order lag transfer function between current and flux, achieving fast motor response without adding complex hardware.
Solution Approach 2:
The patent changes the control parameter from indirect current control to direct flux control. By controlling the flux magnitude as a direct parameter and adjusting the inverter output frequency to match the motor's natural frequency, the system achieves rapid response while maintaining control simplicity.
2Loss of energy
If frequencies other than inverter output frequency are superimposed to cause motor to consume energy, then braking is achieved, but torque ripple is caused
Solution Approach 1:
The patent converts the motor's natural frequency characteristic, which could cause resonance issues, into a beneficial feature for energy consumption. By operating the inverter at the motor's natural frequency during braking, the system maximizes energy dissipation through the motor's inherent impedance without introducing external frequency components that would cause torque ripple.
Solution Approach 2:
The patent utilizes periodic action by operating the inverter at the motor's natural frequency, which creates a periodic energy dissipation pattern that efficiently consumes regeneration energy while maintaining smooth torque characteristics through resonant damping.
3Speed
If hysteresis is provided for torque and flux control in direct torque control method, then fast response is achieved, but torque ripple is caused
Solution Approach 1:
The patent replaces the hysteresis-based direct torque control mechanism with frequency-based control. By controlling the inverter output frequency to match the motor's natural frequency during braking, the system achieves fast response through resonant energy dissipation without the torque ripple caused by hysteresis switching.
Solution Approach 2:
The patent changes the control parameter from torque and flux with hysteresis to frequency control. By directly controlling the inverter output frequency to match the motor's natural frequency, the system achieves rapid braking response while eliminating the torque ripple inherent in hysteresis-based direct torque control.
Data Source
AI summary
A controller for a power converter detects a current output from the power converter, estimates a flux vector of the motor, and calculates a torque line in a physical model resulting from mathematizing a circuit equivalent to the motor, based on the estimated flux vector. The torque line indicates a line for obtaining a desired torque in a subsequent control period. The controller calculates a stator flux command value in accordance with a loss, calculates a voltage command value based on the torque line and the stator flux command value, and controls an output voltage.