Inverter Control Sampling Frequency Dynamics for Motor Current Precision
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional 12-sample phase control techniques for motor inverters are limited by degraded current control performance and reduced freedom of control, especially at high speeds due to fixed duty cycles and insufficient sampling frequency relative to rotor rotation frequency.
Innovation Solution
An apparatus that increases sampling frequency by dynamically computing and adjusting the sampling frequency based on the voltage vector phase and rotor rotation period, allowing for multi-sampling beyond 12 samples per cycle, and implementing high gain over voltage modulation with minimum distance overmodulation control to enhance current control performance and prevent unnecessary switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional 12-sample phase control is used, then the control structure is simple, but current control performance is degraded and freedom of control is limited
Solution Approach 1:
The patent implements dynamic sampling frequency adjustment based on rotor speed. At low speeds, 12-sample phase control is used for simplicity. At high speeds, the sampling frequency is increased to maintain adequate sampling density, transforming the fixed control structure into a dynamic one that adapts to operating conditions.
Solution Approach 2:
The patent changes the sampling frequency parameter based on rotor speed conditions. By computing the sampling frequency as a function of rotor speed and adjusting it dynamically, the system achieves better current control performance at high speeds while maintaining simplicity at low speeds.
2Ease of operation
If fixed duty cycle is used in 12-sample phase control, then the control implementation is simple, but freedom of control is limited
Solution Approach 1:
The patent introduces dynamic duty cycle adjustment based on the position of the voltage command vector relative to hexagon vertices. Instead of fixed duty cycles, the duty cycle is computed dynamically to achieve minimum distance overmodulation, enabling the system to adapt to different operating points while maintaining implementation feasibility.
Solution Approach 2:
The patent segments the voltage vector control space into multiple regions based on hexagon vertices and sides. Different control strategies are applied in different segments: 12-sample phase control in some regions, and increased sampling with dynamic duty adjustment in others, providing flexibility across the entire operating range.
3Productivity
If 12-sample phase control is used, then the sampling frequency is low, but current control performance degrades at high speed
Solution Approach 1:
The patent implements dynamic sampling frequency adjustment where the sampling frequency is computed as a function of rotor speed. At low speeds, 12 samples per cycle are sufficient. At high speeds, the sampling frequency is increased proportionally to maintain adequate sampling density, ensuring current control performance across the entire speed range.
Solution Approach 2:
The patent changes the sampling frequency parameter based on rotor speed conditions. By computing the sampling frequency dynamically and adjusting it according to speed, the system achieves both high productivity at low speeds and maintained control performance at high speeds.
4Manufacturing precision
If increased sampling frequency is implemented, then current control performance improves, but device complexity increases
Solution Approach 1:
The patent implements conditional dynamic sampling where the sampling frequency is adjusted based on rotor speed thresholds. Below a certain speed threshold, 12-sample control is used for simplicity. Above the threshold, increased sampling is activated. This dynamic switching minimizes complexity while maintaining performance where needed.
Solution Approach 2:
The patent applies different control qualities to different operating conditions. At low speeds, simpler 12-sample control with fixed duty cycles is sufficient. At high speeds, more complex dynamic duty adjustment and increased sampling are applied. This local differentiation optimizes the balance between performance and complexity.
Data Source
AI summary
An apparatus for controlling an inverter to drive a motor includes: a current control processor generating a voltage command for generating d/q axis current detection values, which are obtained by measuring current supplied to the motor, to follow a d/q axis current command for driving the motor, the current control processor converting the voltage command, which is sampled according to a sampling frequency generated based on a voltage vector phase of the voltage command, into a voltage vector corresponding to a point on each vertex and each side of a hexagon in a voltage vector diagram to apply a resulting value to the inverter driving the motor; and a sample frequency computing processor computing the sampling frequency based on the voltage vector phase of the voltage command and a reference number of sampling times during one rotation period of the motor.