A Single DC-Link Current Sensor Drive Technology of Three-Phase Permanent Magnet Synchronous Motor

In recent years, permanent magnet synchronous machine (PMSM) has been widely used in servo drive, rail transit, new energy power generation, and other fields for high power density, high efficiency, good reliability, and fast dynamic response. Three-phase PMSM drive systems usually require at least two phase current sensors to obtain accurate stator current signals. However, in harsh working conditions, the current sensor is prone to various faults or is affected by noise interference, resulting in inaccurate current signals collected. Inaccurate stator current feedback can cause the deterioration of the control performance. Therefore, this paper proposes a three-phase permanent magnet synchronous motor drive method based on a single DC-link current sensor, which reduces the number of current sensors in the drive system.Firstly, the method uses a PI regulator to control the motor speed, and uses the bus current signal and the inverter switching state to reconstruct the stator current as current feedback. The principle of stator current reconstruction is the series effect of DC-link current and three-phase current. Secondly, the method uses the two-step model prediction algorithm to obtain the reference voltage of the next cycle instead of the current cycle. In the current cycle, the control system can simultaneously obtain the reference voltage of the current cycle and the next cycle through the two-step predictive control. Finally, tristate pulse width modulation (TSPWM) selects the appropriate starting and ending voltage vector to modulate the reference voltage of the current cycle according to these two sets of the reference voltage. When the TSPWM selects the appropriate starting and ending voltage vector, the area of the stator current reconstruction dead zone is greatly reduced, and the reconstruction dead zone is all located at the edge of the sector. Therefore, TSPWM can effectively eliminate the influence of the reconstruction dead zone, a tricky problem of traditional space vector pulse width modulation. The simulation results show that the error between the reconstructed current and the measured current is small, which proves that the current reconstruction method has high accuracy in both transient and steady states. When the load of PMSM is set to 4 N m, and the given speed is switched back and forth between 200 r/min and 600 r/min, the drive system can complete the speed adjustment within 10 ms. The actual speed of the motor can quickly follow the given speed, and the overshoot is small. When the load is abruptly changed, the motor speed will not fluctuate greatly. The simulation results show that the motor speed fluctuates only 1.25 % when the load torque is abruptly changed, and it quickly returns to the given speed within 20 ms. In addition, in the steady state of the system, the stator current of the proposed driving method has a high sinusoidal, and the output torque is stable. These simulation results prove the performance of the driving method. Compared with the simulation results, the performance of the control system in the experiment decreases. It is mainly caused by non-ideal factors such as inaccurate motor parameters, inverter voltage losses, and sensor measurement noise.The following conclusions can be drawn from the simulation and experiment. (1) Using TSPWM effectively eliminates the influence of the current reconfiguration dead zone. (2) Compared with other single-bus current sensor driving methods, the proposed method has fixed current sampling points and a lower CMV peak-to-peak value. (3) The method can effectively reconstruct the stator current signal using the DC-link current sensor and has good driving performance in both transient and steady states of PMSM. (4) The method performs better than vector control and traditional single DC-link current sensor driving method. © 2023 Chinese Machine Press. All rights reserved.