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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.

Offline parameter identification of permanent magnet synchronous machines (PMSMs) is of great importance for general-purpose drives with sensorless control. This paper proposes an amplitude-auto-adjusting signal injection (ASI) method for the parameter self-learning of PMSMs at standstill considering inverter nonlinearities and the digital time-delay effect. The ASI method achieves the inductance identification process under various dq -axis currents and at the same time prevents the unexpected rotor rotation during the self-commissioning process. For the test PMSM, the spatial inductance maps of dq -axes and abc -phases concerning the magnetic saturation and cross-coupling effects are identified along with the stator resistance. To enhance the estimation accuracy, an error model of the inverter nonlinearities in dq -axes is established, and a compensation method independent of inverter parameters is proposed based on the Hermite interpolation. In addition, the influence of the digital time-delay effect is analyzed and compensated based on the transient model of the circuits. The effectiveness of the proposed parameter self-learning scheme is confirmed on a 2.2-kW PMSM drive. The accuracy of the experimental results is validated by finite element analysis on the test machine.

Beat phenomenon is an important concern in the reduced dc-link capacitance motor drive system. In previous research works, the topic is mainly concentrated on the beat phenomenon caused by the interaction of the fluctuated dc-link voltage and the motor phase voltage. In this paper, another form of the beat phenomenon generated by the fluctuated dc-link voltage and the severely fluctuated load torque is investigated. The effect of the beat phenomenon on the grid current and the motor speed is analyzed, which fluctuate with the low-frequency oscillation. In order to improve the drive system performance, a power balancing controller is proposed to suppress the grid current fluctuation, and a resonant controller is utilized to regulate the periodic power signals. Meanwhile, the applied fluctuated torque suppression method could improve the performance of the motor speed, which is only sensitive to the frequency of the fluctuated load torque. Experimental results are provided to verify the effectiveness of the proposed method.

The instability issue is an important concern in the reduced dc-link capacitance motor drive system, which is caused by the interaction of the LC resonance and the negative impedance of the constant power load (CPL). Harmonics of the grid current also need to be concerned to meet the requirement of the application standards. In this paper, the impedance model of the drive system is established considering the dc-link voltage fluctuation, which is applied to evaluate the drive system stability. The grid current harmonics issue could also be analyzed by the grid input impedance model. A novel grid current feedback based stabilization control method is proposed to stabilize the drive system, which could formulate the Nyquist plot of the drive system. Besides, the grid current harmonics could also be suppressed effectively by adopting the proposed stabilization control method. Experimental results are performed to verify the effectiveness of the proposed method.

The acoustic noises caused by the fixed-frequency signal injection scheme limit the applications of saliency tracking based sensorless control methods for interior permanent magnet synchronous machine (IPMSM) drives at low-speed operation. In this paper, a pseudorandom-frequency sinusoidal injection (PRFSI) considering the sample and hold effect in practical applications is proposed to reduce the undesired acoustic noises. Since the power spectral density (PSD) of the excited high-frequency (HF) current could be dispersed and continuously distributed with PRFSI, the additional HF acoustic noises can be reduced. Through the comparative analysis of HF response currents PSD results for PRFSI and fixed-frequency sinusoidal injection (FFSI), the principle of acoustic noises reduction with PRFSI is analyzed theoretically. Furthermore, the optimal selection of the injection signals is derived considering the sample and hold effect. Whereby, a comparative evaluation of the proposed PRFSI versus FFSI is carried out on a 2.2-kW position sensorless IPMSM drive, in terms of position estimation and PSD results, which verifies the effectiveness of the proposed scheme.

Pulsating high-frequency (HF) signal injection is a common saliency-based sensorless control method applied for synchronous reluctance motor (SynRM) drives. However, the accuracy of the rotor position estimation deteriorates due to severe cross-coupling effect and voltage fluctuations. To solve this problem, a measured reference frame HF voltage injection (MHFVI) method is proposed in this paper. A total of two discontinuous pulsating square-wave voltage signals are injected along with two measured axes, and position information is extracted with a cross-coupling factor (CCF) introduced, which can inherently account for the estimation error caused by the cross-coupling effect. The signal processing scheme of the proposed MHFVI method is further developed to be robust to voltage errors, meanwhile has less fluctuation in the position estimation error. The position estimation error is investigated and analyzed based on the finite element analysis results and the introduced CCF is calculated based on the SynRM current–flux characteristics models. Finally, the proposed method is verified by experiments on a 3-kW SynRM drive platform.

Reduced dc-link capacitance interior permanent magnet synchronous motor (IPMSM) drives have many advantages, such as longer lifetime, reduced cost, and higher power density. However, due to the dc-link voltage fluctuation, the dc-link voltage utilization rate and the torque ripples are two major issues in flux-weakening operation region. It is important to consider these two issues comprehensively when a flux-weakening control method is adopted. In this paper, the IPMSM torque ripples caused by the dc-link voltage fluctuation and the overmodulation are analyzed in depth. In order to reduce the torque ripples and increase the utilization rate of the dc-link voltage, a novel adjustable maximum voltage based voltage closed-loop flux-weakening method is proposed. By switching between the minimum dc-link voltage control mode and the extended dc-link voltage control mode, the torque ripples can be reduced effectively and a nearly maximum utilization of the dc-link voltage can be realized. The proposed flux-weakening control method only depends on the dc-link voltage and the stator current vector reference. Experimental results on a 2.2-kW IPMSM drive platform are provided to verify the effectiveness of the proposed method.

The LC resonance between the line inductor and the dc-link film capacitor is an important concern in the reduced dc-link capacitance interior permanent magnet synchronous motor drive system. In this paper, an active damping method based on the virtual damping resistor is applied to suppress the LC resonance and improve the drive system stability. The performance of the damping resistor is analyzed in a systematic level, and possible configurations have been analyzed to obtain the optimal solution, which is proved to be the inductor current feedback (ICF) damping method. In order to realize the equivalent damping effect, the dc-link voltage feedback is applied to emulate the ICF-based active damping method by a step-by-step approach. Meanwhile, the grid voltage distortion will stimulate additional harmonics of the grid current in the reduced dc-link capacitance motor drives. Hence a feedforward compensation method is applied to suppress the grid current distortion arising from the distorted grid voltage, which has not been investigated in the previous related researches. Harmonics of the grid current are reduced and requirements of EN61000-3-2 can be satisfied by applying the proposed method. Experiments on a compressor drive platform equipped with the reduced dc-link capacitance are performed to verify the effectiveness of the proposed method.

This paper proposes an enhanced system-delay-tolerant signal processing method for high-frequency (HF) signal injection based position sensorless interior permanent magnet synchronous machine (IPMSM) drives. To reduce the acoustic noises induced by the HF response current using the conventional fixed-frequency sinusoidal injection based method, the pseudorandom-frequency sinusoidal injection strategy is proposed and comparatively evaluated in terms of the power spectral density of the phase current. Furthermore, the position estimation degradation caused by the system delay effects due to the pulsewidth modulation (PWM) update delay and the hardware delay using the common signal processing method, especially with the injection frequency increasing, is analyzed. On this basis, an enhanced system-delay-tolerant signal processing strategy is proposed. Through the normalization process for the HF response current and coordinate transform, the terms related to plant parameters and system delays can be cancelled. Therefore, the reliable saliency based method with a higher injection frequency can be achieved. The comparative evaluation on a 2.2-kW position sensorless IPMSM drive is carried out, which verifies the effectiveness of the proposed scheme.

This paper proposes a new sensorless control scheme of interior permanent magnet synchronous motors (IPMSMs) using high-frequency (HF) orthogonal square-wave voltage injection into a stationary reference frame (SRF). This method is an improvement on the conventional HF rotating sinusoidal voltage injection into the SRF. First, discrete sequences of the HF currents are applied to establish the whole signal process. Then, a position estimation method without low-pass filters is proposed, and the phase shifts caused by high-pass filters are also reduced. Therefore, the proposed sensorless control method would not be adversely affected by digital filters, which can solve the common drawbacks of the current SRF-based injection methods. Furthermore, the digital delay in drive systems is considered, and its negative influence can be eliminated as well. The sensorless control method is verified by experiments on a 2.2-kW IPMSM drive platform.

High-frequency (HF) signal injection methods have been widely employed in the sensorless control of interior permanent magnet synchronous motor (IPMSM) drives from zero to low speed. However, the control performance will be deteriorated severely when the motor subjects to the disturbance. To cope with this issue, an enhanced linear active disturbance rejection control (LADRC)-based HF pulse voltage signal injection method is proposed in this paper. The cascaded extended state observer is established to guarantee relatively timely and accurate estimation of the total disturbance. The linear control law is generated to compensate for the total disturbance in a feedforward way, which reduces the plant to approximate a canonical first-order integral. The tracking performance and the stability of the enhanced LADRC are analyzed theoretically. Maximum torque per ampere control is adopted to reduce the estimation burden by making full use of the reluctance torque, which helps to further improve the tracking performance of the enhanced LADRC. Finally, the validity of the proposed sensorless control scheme is verified on a 2.2-kW IPMSM drive platform.

Although high-frequency circulating current exists in parallel-operated inverters, it has not attracted as much attention as low-frequency circulating current, and thus has not been analyzed in detail previously. In this paper, a mathematical model and analysis are presented, which reveal the spectrum components and their changing trends of the circulating currents caused by carrier phase differences. The impact of carrier phase difference on high-frequency circulating current is also analyzed and verified. A closed-loop control scheme is proposed to suppress the switching frequency circulating current caused by carrier phase difference. In addition, the deadbeat and closed-loop control are combined to suppress the low- and high-frequency circulating currents simultaneously, to improve the overall performance of circulating current suppression. The effectiveness of the proposed scheme is verified by the simulation and experimental results acquired from a laboratory platform.

Beat phenomenon is an important issue for the practical application of electrolytic capacitorless motor drives. In this study, the characteristics of stator current harmonics caused by the voltage sampling delay are analyzed. Further, the beat phenomenon generated from the interaction between the harmonics and the fundamental currents is investigated, and the envelope feature of the stator current is derived mathematically. For the purpose of suppressing the beat phenomenon, a voltage reconstruction strategy is proposed to reduce the influence of dc-link voltage sampling delay at the six times of grid frequency. By utilizing the reconstructed dc-link voltage for calculation of PWM duty ratio, the beat phenomenon can be attenuated significantly. The proposed method can be integrated into motor control system easily. Experimental results show the effectiveness of the proposed strategy in a prototype of electrolytic capacitorless permanent magnet synchronous motor drive.

Beat phenomenon is an important concern in the application of the reduced DC-link capacitance IPMSM drives, which leads to the low-frequency oscillation of the motor speed and current. In the previous literature, the beat phenomenon could be divided into two types: one is the interaction of DC-link voltage and inverter output voltage, and the other one is caused by the negative impedance of the voltage control loop. In this paper, another type of the beat phenomenon caused by the fluctuated DC-link voltage and the load torque is analyzed from the view of the interaction between two different frequency sinusoidal current signals. In order to mitigate the low-frequency oscillation of the motor speed and current, the motor harmonic current corresponding to the fluctuated load torque is suppressed by the resonant controller applied in parallel to the current controller. The effectiveness of the proposed method is verified by experimental results.

Signal injection methods have been highly applied in sensorless control system of interior permanent magnet synchronous motor (IPMSM) drives. However, there are inherent disadvantages of signal injection methods which are additional torque ripple and high frequency audible noise. In this paper, a rotor position estimation method is proposed by detecting the derivative of phase currents. The rotor estimation based on rotor saliency-tracking technology shows a good performance in the low-speed motor operation region. Compared with the signal injection method, the proposed method is more suitable for a noise-free working environment.

In sensorless vector control of Permanent Magnet Synchronous Motor (PMSM) drives, it is important to obtain accurate rotor position. High-frequency (HF) voltage injection method is usually used to estimate the rotor position of the motor at low speed. However, the use of the digital filter reduces the estimation accuracy of the rotor position. In this paper, an improved signal processing method based on the HF square-wave voltage injection method is used to obtain the rotor position error signal. A third-order extended state observer (ESO) is used to estimate the rotor position and speed. Compared with the traditional sensorless control strategy, the proposed method reduces the use of the digital filter, simplifies the signal processing, eliminates the influence of the inverter nonlinearity on the accuracy of rotor position estimation and improves the dynamic performance of the system. Experimental results are provided to verify the effectiveness of the proposed method.

Overmodulation strategies can be used to increase the DC-link voltage utilization rate, which enhances the output torque ability. In practice, the motor can operate beyond linear modulation region, even enter the six-step operation by implementing effective overmodulation strategies.

Permanent magenent synchronous machine (PMSM) has been widely developed in the industry and household applications for its high-power density, high efficiency, high power factor, and excellent control performance.

The instability of the drive system is caused by the interaction of the LC resonance and the constant power load (CPL), hence the active damping methods have been applied to damp the resonance and stabilize the drive system.

Large volume electrolytic capacitors are usually utilized at the DC-link of PMSM drives to buffer and store energy, which can stabilize the DC-link voltage and supply power for the inverter. Meanwhile, the power factor correction (PFC) circuit is necessary to improve the power factor and reduce the total harmonic distortion (THD) of the grid input current.

The DC-link may suffer from overvoltage during motor transient process due to the use of slim film capacitors in the diode rectifier front end.

The beat phenomenon is an important issue in the reduced DC-link capacitance motor drive system and other power electronic converters, including the resonant switching converter, the inverter with low switching frequency, the distributed power systems, and the matrix converter.

The harmonic of the grid current is an important issue in the reduced DC-link capacitance motor drive system. An input inductor has been applied in the grid side to improve the grid current quality.

Reduced DC-link capacitance permanent magnet synchronous motor (PMSM) drives have many advantages, such as longer lifetime, reduced cost and higher power density. However, due to the DC-link voltage fluctuation, the DC-link voltage utilization rate and the torque ripples are two major issues in flux-weakening operation region.

The speed of surface-mounted permanent magnet synchronous motors (SPMSMs) is limited by the DC bus voltage. The fluctuation of voltage circle in field weakening area also has negative effects on motor control. To extend the operating speed, an alternative dual-mode overmodulation (OVM) algorithm with less computation is presented combined with a sensorless field weakening strategy based on the voltage estimation. The error between d-q axes current is introduced to improve the motor operation stability. A sensorless position observer is used to estimate the speed and position in medium and high speed. Simulation results of a high-speed SPMSM during the accelerating and decelerating process show that the fast speed response and high voltage utilization can be guaranteed.

The conventional high-frequency (HF) voltage injection method can accurately extract rotor position for interior permanent magnet synchronous motor (IPMSM) drives at low and zero speed ranges. However, the fixed injection frequency will produce a loud audible noise. To solve this problem, a pseudo-random phase-switching fixed-frequency (PRPSFF) signal injection method is proposed in this paper. Based on the principle of phase selection for the PRPSFF injection scheme, the dc bias problem in the induced HF current can be diminished by setting a limitation in the injected voltage. Then a corresponding signal processing method is investigated to deal with the signal delay in the HF current extraction. Besides, the current power spectra density (PSD) for PRPSFF injection is analyzed, and a comparison between PRPSFF and the pseudo-random frequency-switching fixed-phase (PRFSFP) injection schemes is also introduced. The results show that the discrete harmonic spectrum in current PSD can be offset, and the continuous spectrum is smoother than that of PRFSFP injection. Finally, the effectiveness of the sensorless control method is verified by experiments on a 2.2-kW IPMSM drive platform.

Phase-locked loop (PLL) is commonly used for three-phase grid-connected inverters to obtain the information of grid synchronization, and PLL dynamics are the key factors for stable operation of the inverters. Under weak grid conditions, the coupling between PLL and grid impedance can result in harmonic resonance, or even instability in the system. In this paper, the effect of PLL dynamics and grid impedance on the stability of three-phase grid-connected inverters is studied with the d – q impedance model. Besides, the variable transfer relationship is used to analyze the influence of PLL perturbations on output current under weak grid conditions. To suppress low-order harmonics of the network current caused by PLL perturbations under weak grid conditions, a novel feedforward control method is proposed to compensate PLL perturbations and revise the output impedance, where the operation of the inverter and PLL dynamics have been taken into account in the design process. By analyzing the impedance characteristic of the system, it can be demonstrated that the proposed method can enhance the stability of grid-connected inverters under weak grid conditions and reduce the impact of PLL perturbations on grid-connecting current. The experimental results indicate that the low-order harmonics of the network current can be suppressed effectively, which verifies the analysis.

High-frequency signal injection methods have been widely used in sensorless control of permanent-magnet synchronous motor (PMSM) drives. However, the acoustic noise and torque ripples caused by the injected high-frequency signal limit the application of the methods. To avoid these drawbacks, this paper proposes a position estimation method that combines derivative calculations of current and zero-voltage-vector (ZVV) injection, which is especially effective for zero- and low-speed operation of sensorless PMSM drives. This investigation mainly focuses on the extraction of rotor position from ZVV period and the improvements of the accuracy of estimated position. The PMSM equation is developed in the stationary frame when ZVV is applied. The proposed $d$ -axis current allocation scheme ensures the application of the proposed method from no load to rated load. A modified space vector pulse width modulation (SVPWM) control strategy and a ZVV extension scheme are employed to improve the accuracy of estimated position, which also makes the method more realizable. Further, a novel current sampling method that selects two suitable phase currents for derivative calculation according to the voltage sector location is proposed, which can help reduce current derivative ripples and decrease position estimation errors. Finally, the effectiveness of the proposed position estimation strategy is verified on a 1.0-kW interior PMSM (IPMSM) drive platform.

In high-frequency injection-based sensorless interior permanent magnet synchronous motor (IPMSM) drives, digital filters and position tracking observers are used for signal processing, but deteriorate the dynamic performance of the drive system. To address this problem, an active disturbance rejection control (ADRC) strategy-based sensorless control scheme for IPMSM drive is proposed in this paper. The influence of digital filters and Luenberger observer on the speed-loop bandwidth and the stability are analyzed. A modified position tracking observer based on the model prediction method is presented to increase the speed-loop bandwidth. To improve the stiffness performance, an ADRC strategy is proposed by adopting an extended state observer and a nonlinear error feedback controller, which can estimate and compensate for the total disturbance of the sensorless drive system. The proposed sensorless control scheme was adopted on a sensorless IPMSM drive, and the experimental results confirmed that the expected dynamic performance could be achieved.

Although the conventional deadbeat predictive current control (DPCC) can theoretically provide fast current dynamic responses for induction machine (IM) drives, it suffers from problems of steady state current error and stability due to a detrimental model mismatch. To solve these problems, this paper proposes static-errorless DPCC using a second-order sliding-mode disturbance observer (DO). The IM parameter variation and other unmodeled dynamics are regarded as lump disturbance in the modeling of IM. Based on this model, a second-order sliding-mode DO is constructed to estimate lump disturbance, and then the estimated disturbance is applied as feed-forward compensation to correct the steady state current error. Moreover, the designed second-order sliding-mode DO effectively alleviates the chattering effect caused by the switching control. Since the designed DO works in parallel with the DPCC, the fast dynamic responses of the DPCC is retained. Experimental results confirmed the validity of the proposed scheme.

In order to mitigate harmonics of the grid input current, passive filters are applied widely in the power electric systems. The LC resonance and the negative input impedance are important concerns in the reduced dc-link capacitance motor drive system. In this paper, an active damping control method is proposed to suppress the LC resonance by the direct damping current approach, which can formulate the pole distribution of the drive system. Different control laws have been analyzed, and the stability analysis is evaluated by the Routh–Hurwitz criterion. Meanwhile, the active damping control method is realized by the voltage command, which can overcome the limited bandwidth of the current controller. Since the generation of the direct damping current only depends on the dc-link voltage, the proposed active damping control method is robust. Compared with the virtual impedance methods, parameters can be accurately optimized by Bode diagrams after adopting the proposed active damping method. Simulation and experimental results are provided to verify the effectiveness of the proposed method.

DC-link electrolytic capacitor critically affects the lifetime of the motor drive system. This paper proposes an inverter power control strategy based on dc-link voltage regulation for the electrolytic capacitor-less interior permanent magnet synchronous motor drive system. The dc-link electrolytic capacitor is replaced by a small film capacitor and the power factor correction circuit is also eliminated. Hence, the inverter power should be regulated effectively to achieve high input power factor and low grid current harmonics. The inverter power control loop based on proportional resonant (PR) controller is established to regulate the inverter power into sinusoidal wave. The PR controller can be designed to achieve a high gain at the desired frequency and the parameters are easy to design due to the simple structure. In addition, a power compensation method based on the dc-link voltage regulation is used to diminish the error of inverter power control, which does not depend on the precise calculation and is easy to realize. The effectiveness of the proposed method is demonstrated by the experimental results on an air conditioner. The input power factor can reach 0.992 and the harmonics of grid current are considerably lower than the requirement of EN61000-3-2 standard.

High-frequency (HF) signal injection has been widely used in the sensorless control of interior permanent magnet synchronous motor (IPMSM) drives for zero- and low-speed operation. However, the audible noise pollution caused by induced HF current has restricted its application. To solve this problem, a low-frequency (LF) pulse voltage injection scheme is proposed in this paper. Different from the traditional LF injection methods, by separating the injection and the control periods, it is easy to extract the fundamental and the induced currents without digital filters, which makes the position estimation more realizable. Since the accuracy of position estimation decreases, an enhanced vector-tracking observer based on the harmonic analysis of the discrete position signal is proposed. Then, the stability of the proposed observer is analyzed. The negative effects of estimation errors on position estimation are investigated, and notch filters are adopted to achieve further harmonic reduction. Finally, this sensorless control method is verified by experiments on a 2.2-kW IPMSM drive platform.

Permanent magnet synchronous motor (PMSM) drives are finding expanded use for industrial and domestic drive applications. With the distinguished characteristics such as reduced cost and increased reliability and robustness, position sensorless (self-sensing) control techniques have been good candidates for reliable and costless PMSM drives. The saliency-tracking based techniques further bring the expansion of applications with the extended controllable sensorless operating speed range. This paper presents a review on state of the art techniques for position sensorless drives using the saliency-tracking based methods. The signal injection methods and the future scope of research including the dynamic bandwidth improvement and the acoustic noise reduction are discussed.

Rotor position estimated with high-frequency (HF) voltage injection methods can be distorted by voltage errors due to inverter nonlinearities, motor resistance, and rotational voltage drops, etc. This paper proposes an improved HF square-wave voltage injection algorithm, which is robust to voltage errors without any compensations meanwhile has less fluctuation in the position estimation error. The average position estimation error is investigated based on the analysis of phase harmonic inductances, and deduced in the form of the phase shift of the second-order harmonic inductances to derive its relationship with the magnetic field distortion. Position estimation errors caused by higher order harmonic inductances and voltage harmonics generated by the SVPWM are also discussed. Both simulations and experiments are carried out based on a commercial PMSM to verify the superiority of the proposed method and the investigations in this paper.

This paper proposes a complex-vector based discrete-time synchronous-frame full-order observer for position sensorless interior permanent magnet synchronous motor (IPMSM) drives with a low-pulsewidth modulation (PWM) to operating fundamental frequency ratio, a situation common for middle- and high-power applications as well as high-frequency permanent magnet synchronous motor drives. A complex-vector based discrete-time domain zero-order hold equivalent model of IPMSM is developed explicitly incorporating with the stationary frame voltage latch effect of a PWM voltage source inverter. Whereby, a full-order observer is designed and implemented using direct pole assignment in the discrete-time domain to guarantee the stability and dynamic performance with low-frequency ratios. The proposed scheme was verified on a sensorless IPMSM drive. Experimental results confirm both the design methodology and the expected performance attained by the proposed control strategy with low-frequency ratios.

This paper presents robust predictive current control (RPCC) with online disturbance estimation to achieve high- performance current loop for induction machine (IM) drives. The disturbance caused by parameter variations and other unmodeled dynamics is considered in modeling of IM. Based on this model, the control law of the proposed scheme is derived, where a discrete Luenberger observer is designed to estimate the future values of stator current and disturbance. The selection of the designed observer gain is a compromise between the system control bandwidth and robustness. Compared with the conventional RPCC, the proposed scheme removes the steady-state current error caused by the system disturbance. Experimental results on an industrial induction machine drive show that the proposed scheme provides fast and static-errorless current tracking even with mismatched machine parameters.

This paper presents a novel filtering method for speed measurements to improve the low-speed performance of the direct-drive permanent magnet traction machines for elevators. Based on the theory of nonlinear tracking differentiator (NTD), this method, which can act as a high performance filter of a raw speed signal, obtains a more accurate speed feedback signal when applying a low-resolution encoder. In addition, it can relieve the interference caused by the position derivative for speed sampling. By analyzing the frequency response of the NTD, the influence of its parameters on the performance of the speed filtering is investigated. Compared with different types of low-pass filters, the proposed method shows a shorter time delay and a stronger ability in terms of noise suppression when the parameters are selected carefully. In addition, when using the measured speed signal through a nonlinear tracking differentiator as the feedback of the system, the motor runs more steadily at low speeds. As a result, the riding comfort of a direct-drive elevator can be improved. The feasibility of the proposed strategy was verified on an 11.7kW elevator traction machine using a commercial inverter.

The fixed-frequency signal is employed in conventional high-frequency (HF) signal injection-based sensorless control schemes for interior permanent magnet synchronous motor (IPMSM) drives, which causes significant electromagnetic and acoustic noises. In order to diminish the additional noises, a novel pseudorandom HF (PRHF) signal injection method is investigated in this paper. Comparative analysis of the power spectra density of the induced HF currents is carried out among three different schemes: fixed-frequency HF, full-period-switch (FPS) PRHF, and half-period-switch (HPS) PRHF square-wave voltage injection. The principles and the spectral characteristics of the three PRHF injection schemes are described. Both theoretical analysis and experimental results are provided, which can agree with each other well. A theoretical basis of frequency determination is presented. Comparison of the spectral performance shows that the HPS–PRHF scheme has continuous spectra and the electromagnetic and acoustic noises can be suppressed significantly. The method is verified via a 2.2-kW IPMSM drive platform.

Affine projection algorithm (APA) has been used to estimate the parameters of interior permanent magnet synchronous motor (IPMSM). However, there is not a strict guideline of choosing the stepsize of this algorithm to make sure that the results of parameter estimation are convergent. In order to solve such problem, self-adaptive stepsize affine projection algorithm for parameter estimation of IPMSM is proposed in this paper. Compared with traditional affine projection algorithm, this method can obtain the stepsize automatically based on the operation condition, which can ensure the convergence and celerity of the process of parameter estimation. Then, on the basis of self-adaptive stepsize affine projection algorithm, a novel parameter estimation method based on square-wave current injection is proposed. By this method, the error of estimated parameter caused by stator resistance, linkage magnetic flux and dead-time voltage can be reduced effectively. Finally, the proposed parameter estimation method is verified by experiments on a 2.2-kW IPMSM drive platform.

Direct-drive traction systems applying the permanent magnet synchronous motor have become the trend of modern gearless elevators. To estimate and reject the non-linear and uncertain load disturbance effectively during the elevator startup, a novel active disturbance rejection control (ADRC) strategy adopting extended state observer (ESO) and non-linear error feedback (NLEF) controller is proposed to attenuate the elevator car sliding without using weight-transducer. By using the weight-transducerless control strategy, the sliding distance and speed can be suppressed to the extent that it could ensure the riding comfort. The proposed ADRC scheme will also accelerate the dynamic response and enhance the system robustness. Both the parameter selection and the stability of ESO are analysed according to the application requirements, and the contrastive analysis of the functions selected in NLEF controller is performed via Lyapunov theory. The feasibility of the proposed strategy is verified by the experimental results on an 11.7 kW elevator traction machine.