Motor Inverter PWM Control Using Divided Phase for RF Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing motor control device described in PTL 1 struggles to make the switching frequency of the inverter a radio frequency due to synchronization requirements between calculation devices, limiting the cycle of the PWM signal.
Innovation Solution
The proposed motor control device includes a current control unit, a carrier wave generation unit, a phase calculation unit, a divided phase calculation unit, and a PWM control unit, which allow for the calculation of voltage commands and the generation of PWM pulse signals with a shorter cycle than the current control calculation cycle, enabling a radio frequency switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency of the inverter is made a radio frequency, then the iron loss of the motor is reduced, but the switching loss of the inverter increases
Solution Approach 1:
The patent changes the switching frequency parameter from conventional frequencies to radio frequency range, fundamentally altering the operating parameters of the inverter-motor system. This parameter change enables the iron loss reduction benefit while managing the switching loss through advanced control methods and semiconductor device selection.
2Speed
If two calculation devices perform current control calculation and magnetic pole position calculation in synchronization, then high-speed high-response motor control is achieved, but the PWM signal output cycle cannot be made shorter than the calculation cycle
Solution Approach 1:
The patent segments the calculation functions into two independent calculation devices: one dedicated to current control calculation and another to magnetic pole position calculation. This segmentation allows the PWM signal generation to be decoupled from the calculation cycle, enabling the PWM output cycle to be shortened independently while maintaining high-response control performance.
Solution Approach 2:
The patent introduces a new dimension of control by separating the calculation timing from the PWM output timing. The current control calculation and magnetic pole position calculation can proceed in synchronization for high-response control, while the PWM signal generation operates on a separate, shorter cycle through the divided phase calculation mechanism, effectively adding temporal dimensionality to the control architecture.
3Loss of energy
If a semiconductor switching element using silicon carbide is adopted in the inverter, then the switching loss is suppressed to some extent, but the iron loss reduction at radio frequency cannot be fully achieved
Solution Approach 1:
The patent employs a composite approach by combining silicon carbide semiconductor switching elements with advanced control algorithms including divided phase calculation and radio frequency switching. This composite solution leverages the material properties of SiC for reduced switching loss while using control strategies to optimize motor operation at radio frequencies, achieving both objectives simultaneously.
Data Source
AI summary
A motor control device includes: a current control unit that calculates a voltage command with respect to a d-axis and a q-axis of a motor at every predetermined calculation cycle; a carrier wave generation unit that generates a carrier wave; a carrier wave frequency adjustment unit that adjusts a frequency of the carrier wave; a phase calculation unit that calculates a voltage phase of an inverter based on a rotation position of the motor; a divided phase calculation unit that calculates a divided phase in which the voltage phase is divided for every predetermined division number of two or more; a three-phase voltage conversion unit that converts the voltage command into a three-phase voltage command based on the divided phase; and a PWM control unit that performs pulse width modulation on the three-phase voltage command using the carrier wave and generates a PWM pulse signal for controlling operation of the inverter.