Motor Control Device Switching Pulse Modes for Railway Motors
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Solution Overview
Problem
Motor controlling devices for permanent magnet synchronous motors in railway electric cars face challenges in maintaining stable inverter output voltage and positive/negative symmetricity, leading to current oscillations and torque ripples due to changes in output torque and rotation speed, and high switching frequencies result in noise and oscillations.
Innovation Solution
A motor controlling device that switches between synchronous and asynchronous pulse modes based on inverter output state quantities, including the number of pulses in a cycle of the output voltage fundamental wave, to maintain voltage symmetricity and prevent oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optimal controlling methods are used to regulate torque component current and magnetic flux component current according to rotation speed and output torque, then motor efficiency and torque performance are improved, but inter-terminal voltage changes greatly causing instability
Solution Approach 1:
The patent applies dynamics by making the inverter output voltage dynamically adjustable based on motor operating conditions. The control device calculates the required inverter output voltage according to the permanent magnet synchronous motor voltage equation, considering rotation speed and output torque variations, and adjusts the voltage accordingly to maintain stability while enabling optimal control performance.
2Measurement precision
If high switching frequencies are used in the inverter, then control precision and response speed are improved, but noise and oscillations increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the inverter output voltage magnitude based on actual motor operating conditions (rotation speed and output torque). Instead of using fixed high voltage, the system calculates the precise voltage needed and adjusts parameters accordingly, reducing unnecessary high-frequency switching noise and oscillations while maintaining control precision.
3Object-generated harmful factors
If inverter output voltage is reduced to avoid noise, then harmful oscillations decrease, but voltage symmetricity becomes difficult to maintain
Solution Approach 1:
The patent applies feedback by continuously monitoring motor operating conditions (rotation speed, output torque) and using this information to calculate and adjust the inverter output voltage. The control device incorporates feedback from current detectors and voltage detectors to maintain voltage symmetricity while adapting voltage levels to minimize oscillations and noise.
Data Source
AI summary
In a controlling device for a permanent magnet synchronous motor, an asynchronous pulse mode is switched to a synchronous pulse mode in a situation where a modulation factor has become equal to or larger than a first set value or in a situation where an inverter output frequency has become equal to or higher than a second set value. The synchronous pulse mode is switched to the asynchronous pulse mode in a situation where the modulation factor has become smaller than the first set value, and also, the inverter output frequency has become lower than the second set value. By setting the second set value so that the number of pulses included in a half cycle of an output voltage fundamental wave of the inverter is equal to or larger than a predetermined value, it is possible to inhibit current oscillations and torque ripples from occurring in the motor.