There is a certain amount of current harmonics in interior permanent magnet synchronous motor. In order to accurately control the current harmonic, this article focuses on three aspects: establishing current harmonic calculation model, extracting current harmonic, and designing current harmonic regulator. A current harmonic calculation model, which considers the effect of voltage harmonics induced by current controllers and digital control delay on the initial phase angle of voltage harmonics, is established for the first time. With the help of multiple synchronous rotating frame transformation, a current harmonic extraction method more suitable for motor drive field, which aims to extract the current harmonic characteristics of d -axis and q -axis currents, is proposed. On this basis, the controlled quantity and control quantity are unified in d–q coordinate frame for analyzing the coupling relationship of current harmonic characteristics. And then a PI current harmonic regulator, including current harmonic decoupling and voltage harmonic initial phase angle compensation, is constructed, so as to realize the effective control of current harmonics. Finally, the effectiveness and superiority of the proposed method are verified by simulation and experiments.

The high-frequency (HF) square-wave voltage injection sensorless control method will bring additional HF torque ripple to interior permanent magnet synchronous motor (IPMSM). Focused on this problem, this paper analyzes the relationship between the HF response current and the HF torque ripple resulting from HF square-wave voltage injection. It is concluded that when the fluctuation direction of HF response current is vertical to the stator current vector direction at the maximum torque per ampere (MTPA) operating point, the resulting HF torque ripple reaches its the minimum. Based on this conclusion, a novel HF square-wave voltage injection sensorless control method is proposed in this paper, which can realize the sensorless control and minimize the HF torque ripple at the same time. The injection angle of HF square-wave voltage in the estimated synchronous rotating reference frame (SRF) is adjusted in real time according to the operating conditions, so that the HF response current always fluctuates along the vertical direction of the stator current vector at the MTPA operating point. Besides, the corresponding demodulation method of the rotor position estimation error is illustrated. Finally, the experiments are performed on a 20kW IPMSM platform and the results verify the effectiveness of the proposed method.

In this article, a variable structure sliding mode observer (VS-SMO) for load torque observation is designed by adding a decoupling term to the structure of the traditional sliding mode observer. The VS-SMO can remove the coupling relationship between the parameter to be estimated and the derivative of the estimated speed error, as well as the chattering signal in the estimated load torque. Then, a variable structure extended sliding mode observer (VS-ESMO) is designed on this basis, with the moment of inertia used as an extension, to achieve simultaneous identification of the load torque and the moment of inertia. This article analyzes the estimation errors and the impact of measurement noise on estimation errors. The stability of the VS-ESMO is proved by backstepping control theory. An experiment is carried out on a 3.1 kW surface-mounted permanent magnet synchronous motor to validate the identification performance. The experimental results demonstrate that the VS-ESMO has a high estimation accuracy and fast convergence speed, and the identification value does not contain a chattering signal. Using the inertia and load torque identified by VS-ESMO for parameter tuning and compensation can improve system dynamic performance and anti-interference performance to the load.

The coupling between the rectifier and inverter makes the modulation of the indirect matrix converter (IMC) relatively complicated. A novel modulation method is proposed in this letter, where a space vector modulation without a zero-voltage vector, which is only responsible for adjusting the phase of the output voltage vector, is used for the inverter, and a novel delta-sigma method (ΔΣM) to modulate the input current vector phase and dc-link voltage is adopted by the rectifier. Duty cycles of the inverter are obtained by looking up the table of reference output voltages and updated at a 5-kHz carrier cycle, while switching states of the rectifier change once per cycle at a 40-kHz sampling frequency. By decoupling the rectifier and inverter, modulation of the IMC is greatly simplified. Methods that optimize the selection of rectifier switching states under various output/input voltage transfer ratios are also discussed. Simulations and experimental results are presented to validate the proposed method.

In view of the disadvantages of the traditional high-frequency square wave signal injection method in the low-speed operation of high-power interior permanent magnet synchronous motor (IPMSM), such as the large error of rotor position calculation and delay of position update, a method based on high-frequency square wave signal injection is proposed to obtain an effective vector action current through oversampling. When the vector is zero, the current changes to not zero, but when the vector is effective, the current changes greatly. In the traditional sampling and calculation methods, the change of the zero-vector is ignored, resulting in errors, especially in the case of small power, and the errors are more obvious. Through the method of oversampling the current of the effective vector, the high-frequency response current of the effective vector is obtained. Through the reasonable demodulation method, the high-frequency response current of the effective vector is extracted, and then the rotor position information is obtained through the phase-locked loop. On this basis, the influence of the inherent nonlinear characteristics of the motor system and the sampling delay on the calculation of the rotor position is analyzed, and the error is compensated to obtain a more accurate rotor position.

The dq-axis inductance parameter value of the Internal Permanent Magnet Synchronous Motor (IPMSM) will change with the dq-axis current. The Virtual Constant Signal Injection Method (VCSIM)-based Maximum Torque Per Ampere (MTPA) control ignores the partial derivative term of the dq-axis inductance to the dq-axis current when extracting the partial derivative information of the torque to the dq-axis current. This will cause the current to deviate from the MTPA point, which will have a certain impact on the output capacity and efficiency of the motor torque. To solve the above problems, this paper proposes a simple and feasible compensation method by solving the partial derivative information between the dq-axis inductance and the dq-axis current. The experimental results show that the motor efficiency and torque output capability are significantly improved after applying the proposed strategy.