# A Sensorless Rotor Position Detection Method for Permanent Synchronous Motors Based on High-Frequency Square Wave Voltage Signal Injection

## TL;DR

This paper introduces a new sensorless control method for permanent magnet synchronous motors that reduces speed and torque fluctuations using a high-frequency signal and a specialized controller.

## Contribution

A novel harmonic suppression strategy using a sixth-order QPR controller to improve sensorless control of PMSM.

## Key findings

- The proposed method significantly reduces stator current distortion and torque/ speed ripples.
- The sixth-order QPR controller effectively suppresses fifth and seventh harmonic disturbances.
- Simulation results confirm improved rotor position estimation accuracy.

## Abstract

What are the main findings?
A sensorless control strategy for permanent magnet synchronous motors (PMSM) based on high-frequency square-wave injection with multi-coordinate transformation voltage harmonic suppression using a sixth-order quasi-proportional resonant (QPR) controller is proposed, which exhibits superior harmonic interference rejection performance and significantly reduced speed and torque fluctuations.The multi-coordinate transformation architecture can effectively extract the AC components of stator current harmonics by converting them into DC components.

A sensorless control strategy for permanent magnet synchronous motors (PMSM) based on high-frequency square-wave injection with multi-coordinate transformation voltage harmonic suppression using a sixth-order quasi-proportional resonant (QPR) controller is proposed, which exhibits superior harmonic interference rejection performance and significantly reduced speed and torque fluctuations.

The multi-coordinate transformation architecture can effectively extract the AC components of stator current harmonics by converting them into DC components.

What are the implications of the main findings?
The establishment of the voltage compensation mathematical model facilitates the compensation of harmonic currents and enables real-time tracking of harmonic components.A sixth-order quasi-proportional resonant (QPR) controller, operating in parallel with the proportional-integral (PI) controller, can further suppress additional harmonics of the relevant order introduced during the compensation process.

The establishment of the voltage compensation mathematical model facilitates the compensation of harmonic currents and enables real-time tracking of harmonic components.

A sixth-order quasi-proportional resonant (QPR) controller, operating in parallel with the proportional-integral (PI) controller, can further suppress additional harmonics of the relevant order introduced during the compensation process.

To address the torque ripple and speed fluctuation issues in high-frequency square-wave injection-based sensorless control of interior permanent magnet synchronous motors (IPMSM) caused by low-order stator current harmonics (primarily the fifth and seventh), this paper proposes a harmonic voltage compensation strategy based on a sixth-order quasi-proportional resonant (QPR) controller, which effectively suppresses these specific harmonic disturbances. The proposed method, building upon conventional high-frequency square-wave injection, introduces a harmonic current extraction technique based on multiple synchronous reference frame transformations to separate the fifth and seventh harmonic components accurately; then, according to the established harmonic voltage compensation equation, generates targeted compensation voltage commands; finally, further precisely suppresses the corresponding harmonic currents through a sixth-order QPR controller connected in parallel with the current proportional-integral (PI) controller. This paper comprehensively establishes the mathematical models for harmonic extraction and voltage compensation, and conducts a detailed analysis of the parameter design of the sixth-order QPR controller. Simulation results demonstrate that the proposed strategy can significantly suppress stator current distortion, effectively reduce torque and speed ripples, and substantially improve rotor position estimation accuracy, thereby verifying the superiority of the novel harmonic-suppression-based sensorless control strategy.