By suppressing or controlling harmonic currents and voltages of the motor to overcome torque ripple, this system improves the efficiency and torque performance of an AC motor, especially permanent magnet synchronous motors (PMSM), which are very popular in industry due to high efficiency and small volume compared to other types of motors. Many PMSMs use a concentrated winding for the benefit of simple manufacturing and low cost, and they have large spatial harmonics. PMSMs are controlled by conventional vector control drives, but voltages and current harmonics present in the motor can deteriorate accuracy and efficiency. Compared to conventional vector control, this technique further improves efficiency and torque performance by reducing the harmonics.

This technique can be used in many types of equipment, including trucks and other vehicles, elevators, washing machines, air conditioners, machine tools, robotics, and industrial equipment where quick response and accuracy in speed or position control are required. The technique is simple to implement, and may be applied to existing equipment.

A block diagram of the Multi-Vector Electronic Control system.

The technology improves efficiency in PMSM electric motors in such a way that two potential outcomes can be realized. First, less expensive motors that do not use complex windings can be made to perform as well as more expensive equipment, and second, more expensive motors already optimized for conventional controllers can be made to perform at peak efficiency approaching their theoretical best performance. Such performance is not achievable using conventional controllers.

For battery-powered or hybrid equipment (such as industrial tugs), the controller improvement extends equipment range, extends equipment life, and reduces maintenance costs. Heat loss from the motor is minimized. For equipment that uses small, high-RPM electric motors (machine tools, for example), the technology offers high efficiency and better accuracy.

The technology suppresses harmonic current flowing to a 3-phase AC motor by means of harmonic current regulation in dh-qh coordinate systems by commanding zero harmonic current components. In order to further reduce torque ripple, non- zero harmonic current commands can be issued to optimize the torque response. As harmonic current is controlled at the synchronized dh-qh coordinate system, harmonic current can effectively be controlled to a high speed, compared to other harmonic current control strategies that suffer in harmonic control at high speed.

The technology controls harmonic currents even at high RPMs. It may be implemented in circuitry or software, and applied to existing equipment.

This technology was developed by Nissan Motor Co. and is offered by yet2.com. For more information, view the yet2.com TechPak at http://info.hotims.com/45611-130 .


Motion Control & Automation Technology Magazine

This article first appeared in the December, 2013 issue of Motion Control & Automation Technology Magazine.

Read more articles from this issue here.

Read more articles from the archives here.