Motor Control System Rectangular Wave Step-Up Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor control systems face challenges in minimizing system loss when switching between control modes, particularly during rectangular wave control, due to the inability to determine optimal timing for starting the step-up operation of the converter, leading to increased torque fluctuations and overall system losses.
Innovation Solution
A motor control system that includes a control unit capable of starting the step-up operation of the converter when the current vector or voltage phase reaches a specific threshold corresponding to equal system losses before and after the operation, allowing for optimal current or voltage phases during rectangular wave control, thereby minimizing system losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the modulation factor is kept constant at 0.78 for rectangular wave control, then switching loss is minimized, but the ability to variably control system voltage is lost
Solution Approach 1:
The control system dynamically adjusts the modulation factor based on the relationship between the modulation factor and the threshold. When the modulation factor exceeds the threshold, the system transitions to a state where the converter stops step-up operation and the modulation factor becomes variable again. This dynamic adjustment restores variable control capability while maintaining minimal switching loss during rectangular wave control operations.
2Power
If the converter continuously performs step-up operation to maintain high system voltage, then motor torque and rotation speed increase, but switching loss and overall system loss increase
Solution Approach 1:
The control unit changes the system voltage parameter dynamically by comparing the modulation factor with the threshold. When the modulation factor exceeds the threshold, the converter stops step-up operation, allowing the system voltage to be determined by the battery voltage rather than maintained at high stepped-up voltage. This parameter change reduces switching loss and overall system loss while still enabling high torque operation when needed by resuming step-up operation when the modulation factor decreases.
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
The system effectively suppresses the increase in system loss by initiating the step-up operation at appropriate timing during rectangular wave control, maintaining optimal current or voltage phases and reducing overall system losses.
Implementation Method 1
a converter (20) that is capable of stepping up a direct-current voltage supplied from a power supply (11) according to a system voltage command value
Implementation Method 2
an inverter (221) that is capable of converting a direct-current voltage which is a system voltage output from the converter (20) to alternating-current voltage
Implementation Method 3
a motor (M1) that is driven by the alternating-current voltage applied from the inverter (221)
Data Source
AI summary
A motor control system includes: a power supply; a converter; an inverter; an alternating-current motor; and a control unit that drives the motor in any one of sinusoidal PWM control, overmodulation control and rectangular wave control through operation control of the converter and the inverter. The control unit starts step-up operation of the converter when a current vector of motor current of the motor on a d-q coordinate plane becomes a current phase corresponding to motor torque, at which a system loss is equal between before and after starting the step-up operation, while the control unit supplies the direct-current voltage, supplied from the power supply, to the inverter without stepping up the direct-current voltage by the converter and performs the rectangular wave control of the motor in a state where the current phase is an optimal current phase.