AC Motor Controller Mode Switching via Modulation Factor
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Solution Overview
Problem
Existing AC electric motor control systems face complexity in determining whether to switch between PWM and rectangular wave control modes, as decisions are based on modulation factor and q-axis current, leading to complicated processes.
Innovation Solution
A controller for AC electric motors that includes a current detector, pulse width modulation control unit, rectangular wave voltage control unit, voltage deviation calculating unit, modulation factor calculating unit, and mode switching determination unit, which simplifies the decision-making process by calculating control values and determining necessary mode switches based on these values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If switching between PWM control and rectangular wave control is determined based on modulation factor and q-axis current, then control accuracy is improved, but determination process complexity increases
Solution Approach 1:
The patent extracts the q-axis current parameter from the switching determination process, using only the modulation factor for mode switching decisions. This simplifies the determination process while maintaining control accuracy through alternative control strategies in each mode.
Solution Approach 2:
The patent changes the determination parameter from a combination of modulation factor and q-axis current to solely modulation factor. By adjusting the control strategy within each mode rather than using multiple parameters for switching, the complexity is reduced while effectiveness is maintained.
2Reliability
If switching determination uses multiple parameters (modulation factor and q-axis current), then control effectiveness is improved, but control process complexity increases
Solution Approach 1:
The patent removes q-axis current from the switching determination criteria, simplifying the control process to use only modulation factor for mode switching decisions, thereby improving ease of operation.
Solution Approach 2:
The patent implements feedback control within each operating mode to maintain effectiveness. By using modulation factor for switching and incorporating current feedback within modes, the system achieves reliable control with simplified switching logic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution simplifies the determination of inverter control mode switches, avoiding complexity and ensuring efficient operation of AC electric motors by determining mode changes based on calculated control values.
Implementation Method 1
a pulse width modulation control unit generating, based on a current deviation between a motor current detected by the current detector and a current command corresponding to an operation command of the AC electric motor, an AC voltage command causing the AC electric motor to operate in accordance with the operation command; the pulse width modulation control unit generating, by pulse width modulation control based on a comparison between the AC voltage command and a carrier wave, a control command for the inverter
Implementation Method 2
a rectangular wave voltage control unit generating the control command for the inverter, by the rectangular wave voltage control controlling the applied voltage such that the applied voltage comes to be a rectangular wave voltage having a phase in accordance with the operation command
Implementation Method 3
a voltage deviation calculating unit calculating, by executing an operation of substituting the current deviation to a voltage equation of the AC electric motor, a voltage deviation between a first voltage command corresponding to the AC voltage command when the rectangular wave voltage control is executed and a second voltage command corresponding to the AC voltage command when the pulse width modulation control is executed
Data Source
Figure 1
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Figure 4
AI summary
An AC electric motor (M1), an inverter (14) and a controller (30) are mounted on an electric powered vehicle. The controller (30) includes a voltage deviation calculating unit (320), a modulation factor calculating unit (340), and a mode switching determination unit (360). The voltage deviation calculating unit (320) calculates a voltage deviation between a first voltage command when the rectangular wave voltage control is executed and a second voltage command when pulse width modulation control is executed, by inputting a current deviation to a voltage equation of the AC electric motor. Modulation factor calculating unit (340) calculates the modulation factor based on the first voltage command and the voltage deviation. The mode switching determination unit (360) determines whether or not control mode of the AC electric motor (M1) from the rectangular wave voltage control to the pulse width modulation control is necessary, based on the modulation factor.