Accurate rotor position information is important for the high-performance operation of position sensorless permanent magnet synchronous motor drives. However, during steady-state operation and variable speed conditions, traditional sliding mode observer with phase-locked loop (PLL) causes position estimation error. In this paper, an observer designed in rotary reference frame is proposed to reduce position estimation error during steady-state operation. Besides, a PLL with speed compensation is proposed to suppress the position estimation error caused in variable speed conditions. Experiments and simulation results verify the effectiveness of these two methods for position estimation error suppression.

A novel position estimation strategy for high-frequency (HF) pulsating injection based position sensorless permanent magnet synchronous machine (PMSM) drives is proposed in this paper. The method performs the inverse tangent of HF response currents to realize the decoupling of current information and the extraction of position tracking error can be obtained simply, which reduces the use of low-pass filters. In addition, there is no need to introduce additional demodulation signals, which simplifies the adjustment process. Finally, the feasibility and effectiveness of the proposed scheme are verified on a 2.2-kW sensorless PMSM drive.

Electrolytic capacitors are usually most seriously affected by aging in power electronic systems and it is necessary to timely indicate the degradation status of the electrolytic capacitor for ensuring the safe operation of the system. An online estimation method of the DC-link capacitance based on impedance analysis for permanent magnet synchro-nous motor (PMSM) drives with the boost power factor correction (PFC) converter is proposed, which does not need any additional signal injection or DC-link capacitor current sensor. Based on the principle of area equivalence, the capacitor current can be reconstructed by the inductor current and the duty ratio in the boost PFC converter. The bandpass filter (BPF) is applied to extract the 100Hz ripples from DC-link voltage and capacitor current. Through analyzing the capacitor impedance characteristics, the DC-link capacitance can be estimated by the 100Hz ripple voltage and the 100Hz ripple current. The experimental results verified the effectiveness of the estimation method.

In order to expand the modulation index of the single DC-link shunt permanent magnet synchronous motor drive and improve the motor's operating frequency and load capacity, an improved overmodulation strategy is proposed in this paper. A phase current reconstruction strategy based on vector phase shifting is applied to both modulation linear and nonlinear region. To improve the stability of the motor at high speed, an improved flux weakening strategy based on the voltage angle control method is applied, which can effectively reduce the current harmonics. In addition, this paper proposes a dual-mode overmodulation strategy considering the influence of vector phase shift, and the analysis shows that this strategy can effectively improve the modulation index. Finally, the experimental results show the effectiveness of the proposed method in different operation conditions.

The control accuracy of PMSM depends largely on the inductance. In the traditional inductance identification methods, the ideal PMSM mathematical model is applied, where d-axis and q-axis are assumed completely decoupled. In this case, only the d-axis and q-axis inductances are considered. However, the cross-coupling effect exists in the actual model of PMSM, which leads to the mutual inductance between d-axis and q-axis. In this paper, a high-frequency (HF) equivalent impedance model of PMSM under virtual axis is proposed. According to the HF signal injection, the inductance matrix of PMSM considering the cross-coupling effect can be accurately identified. The experimental results show the effectiveness of the proposed method under different PMSM operation conditions.

The space vector modulation-based direct torque control (SVM-DTC) based permanent magnet synchronous motor (PMSM) suffers from large speed ripples due to the periodic fluctuation of load torque. An adaptive load torque feedforward compensation method is proposed based on the observation of the periodic pulsation component in the load torque. The reference torque in the torque loop is compensated according to the torque feedforward. This method can effectively reduce the speed ripples and improve the steady-state performance meanwhile maintaining the advantages of the conventional SVM-DTC. The effectiveness of the proposed method is verified by conducting experiments on the 1.5kW air conditioning compressor.

In the high frequency boost power factor correction (PFC) converter, it is necessary to obtain the phase of the grid side voltage. However, in some cost-sensitive applications, there is only a sensor to detect the rectified voltage. This paper proposes a digital phase locked loop (PLL) scheme with a frequency predistortion digital bandpass filter to obtain the rectified voltage phase. Based on analyzing the frequency domain response characteristics of the digital bandpass filter, the continuous bandpass filter is digitized by bilinear transformation with frequency predistortion. On this basis, the rectified voltage is filtered to obtain its fundamental component as the PLL input. Then the grid side voltage phase is obtained at the output side, so the in-phase PFC reference current signal can be generated. Experiments have been carried out on the platform of the 70kHz PFC converter to verify the effectiveness of the strategy.

An accurate inertia identification is particularly important for the controller self-tuning to achieve high-performance permanent magnet synchronous motor (PMSM) drives. In this paper, a variable-period inertia identification strategy based on Landau adaptive method is proposed to improve the identification accuracy under low-acceleration conditions. According to the speed measurement rule of low-resolution encoder, the speed updating period of the Landau adaptive inertia identification method is redesigned and auto-adjusted under low-acceleration conditions. Finally, the proposed method is verified on a 2.2-kW PMSM drive platform.

The slim film capacitor driving mode can prolong the operating life of the PMSM system and reduce the system volume. However, the small DC-link capacitor and the grid-side filter inductor are prone to LC resonance. Many stability control methods have been investigated, but they cannot work well under the situation of the grid impedance change. An adaptive stability control strategy is proposed to improve the power quality of the grid side for the electrolytic capacitor-less motor drive in this paper. Through the analysis of the phenomenon of the LC resonance on the grid side, the active damping control strategy based on DC-link voltage feedback is designed with the detection of the THD of the grid current. and the control parameters are adaptively changed. Then, the harmonics of the gird currents can be suppressed effectively. Finally, the simulation results verify the feasibility of the strategy.

Permanent magnet linear synchronous motor (PMLSM) has many superior advantages, but the unique structure leads to the large end force. And PMLSM is also affected by other disturbance forces such as the cogging force and friction force. These forces result in the large thrust ripples, which seriously reduce the performance of PMLSM drives. Firstly, the dynamic model and thrust ripple characteristics of PMLSM are analyzed. On this basis, a thrust ripple suppression method based on the Fourier transform compensator cascaded an improved extended state observer (ESO) is proposed. The Fourier transform compensator extracts the amplitude of the 2nd harmonic of the speed ripple, and outputs the feedforward compensation to suppress the detent force in the thrust ripples. The improved ESO observes and compensates other harmonic components. These two parts adopt cascade structure to comprehensively suppress the thrust ripples of PMLSM. Finally, experiments are carried out on a 750W PMLSM drive platform to verify the effectiveness of the proposed suppression method.

High frequency (HF) signal injection is commonly used in sensorless permanent magnet synchronous motor (PMSM) drives at low speeds and standstill. However, the extra acoustic noises caused by additional signal injection impose restrictions on its further applications. To address this issue, a pseudo-random frequency pulse voltage injection scheme is proposed for sensorless PMSM drives at low speeds. Compared with the pseudo-random signal injection, the proposed pseudo-random frequency pulse voltage injection scheme with pulse width adjustment can make all the discrete harmonics in the noise spectrum disappear, thus achieving effective noise attenuation. The signal injection design is performed via current power spectral density (PSD) analysis. According to the form of the injected signals, the signal demodulation procedure is designed to obtain estimated rotor position. The validity of the proposed scheme is verified on 2.2-kW IPMSM platform.

To achieve high-performance sensorless control of interior permanent magnet synchronous motor (IPMSM) drives, this paper proposes an extended flux observer by using the current model to modify the voltage model. The current model is set to correct the voltage model through the PI regulator to form closed-loop control. The proposed closed-loop control method effectively suppresses the DC offsets and integral saturation in the voltage model, which greatly improves the stability and accuracy of sensorless control. On this basis, for the 5th and 7th harmonics caused by the inverter nonlinearity, this paper proposes a filter network composed of multiple second-order generalized integrators (Multiple SOGIs), and uses the integral characteristic of the second-order generalized integrator to replace the pure integral of the voltage model. Multiple SOGIs greatly filter out the high-order harmonics in the back electromotive force (EMF) and improve the accuracy of sensorless control. The effectiveness of the proposed scheme is verified on a 2.2kW IPMSM drive platform.

Motor drives with reduced DC-link capacitance may face grid current distortion or even instability under weak grid condition. In this paper, the small signal model of reduced DC-link capacitance drive system under weak grid condition is derived and analyzed. On this basis, an impedance reshaping method is proposed to suppress the harmonics of the grid-side current. By extracting DC-link harmonics near the LC resonant frequency and reconstructing the virtual admittance of the drive, the active damping voltage control signal is generated to suppress the harmonic of the grid-side current at the specific frequency. The THD of the grid-side current was reduced from 53% to 39%. The experiment was carried out on a 5.5kW permanent magnet motor drive platform with reduced DC-link capacitance, and the effectiveness of the control strategy was verified by experiments.

In order to avoid the failure of electrolytic capacitor due to the influence of ambient temperature, film capacitors are applied in the DC-link of permanent magnet synchronous motor (PMSM) drive systems. In this paper, an online estimation method of DC-link capacitance is proposed for the electrolytic capacitorless motor drive system. The power signals of the drive system are analyzed, and the characteristic frequency of the DC-link capacitance power is determined. The instantaneous capacitor power is obtained by the sampled grid input power and the reconstructed inverter power, which is determined by the DC-link voltage and inverter input current. The components of capacitor power and the result of multiplication of DC-link voltage and its derivative at the expected frequency are obtained to calculate the DC-link capacitance by a band-pass filter. The estimation process can be carried out when the system operates normally, and no additional sensors are required. The experimental results verify the effectiveness of the proposed method.

During the past few years, finite control set predictive current control (PCC) method has attracted more and more attention in research and industry applications. However, PCC method could be improved by considering two points. First, the current reference used in the cost function of PCC control scheme is usually produced by a proportional and integration speed controller. Confront with load torque and time-varying system parameters, it is a better solution to design a disturbance estimation based feed-forward compensated controller. In this way, the current reference could be generated faster and more accurate. Second, the PCC method is model-based method which means the accuracy of the model parameters are essential. In real system, time-varying parameters existed almost always. This paper investigates a generalized proportional integral observer based PCC approach for dealing with load torque disturbance, time-varying parameter uncertainties. The effectiveness of the proposed method has also been confirmed by simulation and a lab-constructed experimental prototype.

Compared with wye-connected winding machine, the delta-connected shows merits in wider constant power speed range (CPSR) and higher efficiency because of the full utilization of terminal voltage, which is promising for electric vehicles (EVs), industries and domestic appliances, etc. However, circulating loss caused by triple-order harmonics impedes the application of delta-connected winding in permanent magnet synchronous machines (PMSMs). This paper discusses the advantages of delta-connected winding, and proposes an optimal design methodology on interior permanent magnet (IPM) rotors to minimize the triple-order harmonics, aiming to arouse the awareness of adopting delta connection in PMSMs for higher performance. A 22kW IPMSM prototype with delta-connected winding is manufactured, and the minimized triple order harmonics and super premium efficiency (IE4) are verified by experiments.

Incremental encoders are popular for detecting angular position and speed. However, the conventional incremental encoder-based methods for estimating speed are prone to poor performance at low speed where the encoder output rate is correspondingly low, leading to a number of research efforts in improved low-speed detection algorithms. To improve speed control performance, a speed detection method based on reduced-order observer is presented in this paper. The observer can interpolate speed and position which is the integration of speed and compared with real data from the encoder when the encoder pulse is detected between encoder pulses. Furthermore, inertia identification based on recursive extended least square algorithm is presented to reduce sensitivity of the speed estimation. Experimental results show that low speed control performance using the reduced-order order is superior to that of conventional one