Motor Control Device Modulation Mode Switching
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Solution Overview
Problem
Existing electric motor control devices for electric vehicles and hybrid electric vehicles do not effectively reduce power losses during high-speed rotation, as they continue to use SVpwm and Dpwm modes even in high-speed regions, leading to increased losses.
Innovation Solution
The control device determines a secondary-side target voltage to operate in a first region with PWM power for low-speeds, a third region with reduced PWM power for field weakening, and a second region with one-pulse rectangular-wave power, optimizing voltage gradients to minimize power losses and eddy current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM power is applied to at least two phases in high-speed regions, then torque control precision is maintained, but power losses and iron losses increase
Solution Approach 1:
The patent dynamically switches between different modulation modes (PWM mode for low-speed, one-pulse mode for high-speed) based on the rotation speed of the electric motor. This dynamic adaptation allows the system to maintain torque control precision at low speeds while reducing power losses at high speeds by transitioning to a modulation mode better suited for high-speed operation.
Solution Approach 2:
The patent changes the modulation mode parameter based on rotation speed. By switching from PWM modulation (with its associated switching losses and iron losses) to one-pulse modulation at high speeds, the system alters the electrical parameters to minimize energy losses while maintaining adequate torque control.
2Speed
If field weakening control is performed with PWM power, then rotation speed increases, but power loss due to field weakening current increases
Solution Approach 1:
The patent dynamically switches to one-pulse modulation mode when field weakening control is required at high speeds. This dynamic mode switching allows the system to achieve the necessary rotation speed increase while minimizing the power loss associated with field weakening current by using a modulation mode more efficient for high-speed field weakening operation.
3Loss of energy
If one-pulse mode is used in high-speed regions, then power losses are reduced, but torque control precision deteriorates
Solution Approach 1:
The patent dynamically selects the appropriate modulation mode based on rotation speed. At low speeds where precise torque control is critical, PWM mode is used. At high speeds where power loss reduction becomes more important, the system transitions to one-pulse mode. This dynamic switching optimizes the trade-off between torque control precision and power loss reduction across the entire operating range.
4Force
If converter voltage is increased to maintain torque at high speeds, then torque output is maintained, but converter power loss increases
Solution Approach 1:
The patent changes the modulation mode parameter at high speeds to one-pulse mode, which allows for more efficient voltage utilization. This parameter change enables the system to maintain the necessary torque output while reducing the converter power loss that would otherwise occur with continuous voltage increase in PWM mode.
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 approach significantly reduces power losses and iron losses in high-speed regions by enhancing the one-pulse mode, suppressing eddy current generation and maintaining efficient torque control across a wide rotation speed range.
Implementation Method 1
a voltage increasing power supply device (25, 26, 29) that increases a voltage of the primary-side DC power supply to a secondary voltage (Vuc) to supply the secondary voltage to the inverter
Implementation Method 2
a regenerative power supply device (27) that reversely supplies regenerative power from the inverter to the primary-side DC power supply
Implementation Method 3
an inverter (19m) that supplies an output of a primary-side DC power supply (18, 22) to an electric motor (10m) to control driving of the electric motor (10m)
Implementation Method 4
electric motor control means (30m) for controlling the inverter on the basis of a target torque (T*) and a rotation speed (ω) of the electric motor and the secondary voltage (Vuc) such that an output torque of the electric motor becomes the target torque
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A primary-side DC voltage is increased to a secondary voltage by a converter (30c), and converted by an inverter (19) into three-phase AC, which is applied to an electric motor (10m). Regenerative power from the electric motor is reversely supplied to a primary-side DC power supply (18, 21). A secondary-side target voltage, which sets the secondary voltage to be applied to the inverter, is determined such that the electric motor is driven on the basis of one of a first region in a modulation mode in which PWM power is applied to at least two phases and in which field weakening control is not performed, a third region in a modulation mode in which PWM power at a voltage lower than a maximum voltage (Vmax) that can be output by the converter is applied to at least two phases and in which field weakening control is performed, and a second region (FIG. 4) in a one-pulse mode in which rectangular-wave power at a voltage lower than the maximum voltage of the converter is applied to all the phases and in which field weakening control is performed. A converter control device (30v) controls the secondary voltage to the secondary-side target voltage.