Saturation controller-based ripple reduction for direct torque controlled permanent-magnet synchronous machines

A fuzzy direct torque control (DTC) algorithm to permanent magnet synchronous motor (PMSM) with a novel space vector modulation (SVM) defuzzification is proposed. The defuzzification unit outputs a vector contains two voltage vectors as well as the duty of each vector instead of a single vector. And more voltage vectors can be obtained. A simulation model is built up, basic DTC and conventional fuzzy DTC and proposed fuzzy DTC are carried out respectively. Torque ripple, flux ripple and current distortion are compared and analyzed. The proposed fuzzy controller makes the torque and flux ripples lower and current smoother compared with basic DTC and conventional fuzzy DTC.

The direct torque control (DTC) technique for a three-phase induction and synchronous motor is receiving increasing attention due to the important advantages as the elimination of the current controllers and the low dependence on motor parameters when compared with other motor control techniques. However high torque and stator linkage magnetic flux ripples and stator voltage and, stator current harmonic contents result when using a two-level inverter with hysteresis controller. This paper presents simulation results of a three-phase permanent magnet synchronous motor (PMSM) fed from a three-level voltage-controlled inverter showing low air-gap flux and torque ripples and reduced stator current and stator voltage harmonic distortion. As far as the authors know this is the first paper showing the benefits of the use of a three-level voltage-controlled inverter in DTC scheme to control the torque and speed of PMSM with the proposed algorithm.

The objective of this paper is to design and study of duty ratio modulated modified Direct Torque Control drive, especially for Permanent Magnet Synchronous Motor (PMSM). Conventional Direct Torque Control (DTC) is typically associated with torque ripple and stator flux ripple. Duty ratio modulated direct torque control (DDTC) reduces torque ripple and stator flux ripple. For high performance applications the conventional DDTC is again modified to obtain comparatively less torque and flux ripple. In this paper the DDTC is associated with MTPA approach to obtain duty ratio calculation more effectively.

Permanent magnet synchronous motor (PMSM) is the most widely used motor in electric vehicles (EV) due to its high power density and high efficiency. Conventional direct torque control (DTC) is developed to improve the performance of speed response of the PMSM drive but it suffers from higher torque ripples. Therefore a space vector modulation (SVM) based DTC has been developed to enhance the speed response. Due to the use of flux comparator and torque comparator conventional DTC has disadvantages such as higher torque and current ripples at steady state. To improve the performance of PMSM drive a space vector pulse width modulation is used with 3 level NPCI. To improve the performance of 2 level inverter in the PMSM drive is replaced with a neutral point clamped inverter (NPCI). Also, the switching selection strategy of SVM is modified using nearest three space vector pulse width modulation to reduce the total harmonic distortion (THD) in the inverter output. The simulation outcome proves that the SVM technique implementation in DTC for 3 level NPCI yields good performance for PMSM.KeywordsElectric vehicles (EV),voltage source inverter (VSI)Direct torque control (DTC)Neutral point clamped inverter (NPCI)Permanent magnet synchronous motor (PMSM)Space vector modulation (SVM)Total harmonic distortion (THD)

This article investigates an observer-based optimal direct torque control (DTC) strategy for improving the transient and steady-state performance of surface-mounted permanent magnet synchronous motor (SPMSM) drives. Unlike conventional DTC techniques, the proposed method simultaneously controls speed, torque, and flux variables by employing the optimal control theory in the stationary reference frame. This helps achieving a simple structure along with good low-speed operation as the stator flux angle need not be estimated. Further, the feedforward control terms are designed to compensate for system uncertainties. Additionally, an in-depth stability analysis is presented through the Lyapunov theory. Comparative results via a real-time prototype SPMSM test-bed with TI-TMS320F28335 DSP indicate improved performance of the proposed optimal DTC compared to conventional PI DTC, nonlinear optimal DTC, and adaptive DTC, including less computational burden, less torque and flux ripples, more robustness to parameter uncertainty, and improved transient response under very low speed/load step-changes and speed reversal.

Direct torque control (DTC) is one of the most widely used control strategy in induction motor drives. DTC drive utilizes the hysteresis band control which is one of the simplest and popular control scheme. The major problems in the conventional DTC scheme is large torque ripple, stator current distortion and variable switching frequency. This paper presents a DTC scheme for five phase induction motor drive to achieve constant switching frquency and minimum distortion in the stator current. The proposed DTC scheme is validated by extensive simulation on a Matlab-Simulink platform.

This paper proposes 20-sector based direct torque control (DTC) scheme for dual inverter fed five phase induction motor drives with open-end stator windings powered by a single DC source. The proposed scheme utilizes 20 virtual voltage vectors that divide the space vector plane into 20 sectors, each sector spanning 18 degrees. The 20-sector based DTC scheme provides a smoother control over torque and flux compared to the conventional 10 sector-based DTC schemes for five phase induction motors. The switching scheme used in the proposed scheme eliminates the auxiliary plane harmonic voltages and provides higher DC bus utilization compared to two-level five phase voltage source inverter fed DTC schemes. The switching scheme for realization of these virtual voltage vectors does not generate any resultant common mode voltage across the stator windings and hence a single DC source is used to supply both the voltage source inverters. The proposed DTC scheme is validated by extensive simulation using MATLAB-Simulink software and experimentally verified on a laboratory prototype.

A direct torque control (DTC) scheme for five phase induction motor drives with open-end stator winding configuration is presented in this paper. The DTC scheme proposed here make use of the non-adjacent line voltage vectors that are generated as resultants of the voltages produced in the two inverters. The method of generation of voltage vectors proposed in this paper does not produce common mode voltage across the motors windings. Both the inverters can be fed from a single DC source with a common DC link without any common mode current flow. Another important aspect of the proposed scheme is that it makes the average voltage produced in the non-torque producing plane (x-y plane) zero thereby preventing the flow of large harmonic currents through the windings. Also, this scheme can reduce DC voltage requirement by 47% when compared to that of a single–end inverter fed, star connected five phase induction motor drive for the same phase voltage. The proposed DTC scheme is verified experimentally using a laboratory prototype under both steady state and transient operating conditions.

This paper presents a sliding mode controller for an interior permanent magnet (IPM) synchronous motor, in which direct torque control (DTC) concept, variable structure control and space vector modulation (SVM) are integrated to achieve high performance. In comparison with conventional DTC, the inverter switching frequency is constant and controllable by using SVM, the torque and flux ripple are significantly reduced. The fast response and robustness merits of DTC are preserved. Position and angular speed of the rotor are obtained through an extended Kalman filter (EKF).

Most of the direct and indirect torque control schemes proposed for switched reluctance motors (SRMs) consider equal rotor and stator pole arc. Leading to a linear non-saturating inductance profile. However, actually, in SRM, the rotor pole arc is kept higher than the stator pole arc. Leading to a non-linear saturating inductance profile. And not considering this in control leads to underutilization of the maximum torque producing capacity during the constant torque region. In the proposed novel direct torque control (DTC) scheme, firstly, the rotor pole arc and saturation effect are incorporated by considering it in the sector formation for every electrical cycle. Second, the flux control loop is removed, and sectors are classified based on the actual inductance profile, which is rotor position-dependent. Also, the voltage vector selection rule is modified for torque control. And the proposed voltage vector concerning the sector, allows multiple phases to conduct simultaneously. Wherein each phase conducts according to its actual inductance profile. This also ensures complete energization of incoming phase current while the outgoing phase is maintained at a constant current level. Leading to a reduction in torque ripples during commutation. The proposed DTC scheme incorporating the rotor pole arc and saturation effect improves the operating range for effectively reducing the torque ripples and facilitates a higher torque/ampere ratio.

In conventional direct torque controlled (DTC) permanent magnet synchronous motor drive, there is usually undesired torque and flux ripple. The existing literature have proposed some methods to reduce torque and flux ripple by optimizing the duty ratio of the active vector. However, these methods are usually complicated and parameter dependent. This paper first compares the performances of three duty determination methods in detail and then proposes a very simple but effective method to obtain the duty ratio. The novel method is superior to the existing methods in terms of simplicity and robustness. By appropriately arranging the sequence of the vectors, the commutation frequency is reduced effectively without performance degradation. To further improve the performance of system, a low-pass filter-based voltage model with compensations of amplitude and phase is employed to acquire accurate stator flux estimation. The proposed scheme is able to reduce the torque and flux ripple significantly while maintaining the simplicity and robustness of conventional DTC at the most. Simulations and presented experimental results validate the effectiveness of the proposed schemes in this paper.

The conventional direct torque control (DTC) method features fast dynamic response, but it also has notable drawbacks such as high torque and flux ripples, variable switching frequency and acoustic noise. The proposed DTC scheme based on model predictive control (MPC) is studied in the paper for permanent magnet synchronous machine drive. The paper aims to reduce the torque and flux ripple. Firstly one- and two-step delay MPC methods are employed with or without the torque/flux and switching frequency compensation. Furthermore linear extrapolations N-step delay MPC method is taken into account. Compared to simulation results, the two-step delay DTC scheme is better than the one-step scheme in the steady response and dynamic performance, at the same time the torque and frequency compensations can reduce switching frequency from high value to a low constant one. Simulation results are presented to validate the effectiveness of the proposed schemes in this paper.

This investigation improves the performance of a direct torque controlled permanent magnet synchronous motor (PMSM) using both genetic algorithm (GA) and fuzzy logic. In this approach electromagnetic torque error, stator flux linkage error and stator flux angle are fuzzified using three appropriate fuzzy sets. Therefore the best voltage space vector has been selected in order to minimize torque, flux and current ripples. In this paper direct torque control (DTC) of a PMSM drive is simulated using both conventional table based and fuzzy methods and the PI speed controller is tuned using GA. A comparative study between conventional DTC and proposed approach shows that not only the speed response of the controller has been improved but also torque, flux and stator current ripples have significantly been reduced without any effective change of the inverter switching frequency.

Direct torque control (DTC) systems for open-end winding permanent magnet synchronous motors (OEW-PMSM) with common DC bus generate zero sequence currents (ZSC) and large torque ripple, resulting in increased system loss and poor operating characteristics. In this paper, a DTC based on five level torque hysteresis (FLTH) is proposed to improve the system performance. Firstly, an online calculation and selection strategy based on switch table is designed to suppress ZSC. By analyzing the composition of zero sequence voltage and using the double vector method to suppress it, the ZSC can totally be suppressed in theory, without affecting the system performance. On this basis, this paper proposes to add FLTH to DTC to reduce torque ripple. FLTH can not only effectively use many voltage vectors, but also reduce torque ripple. In the case study, the torque ripple rate has been reduced by 53%. Through simulation and experiment, the conventional DTC and the FLTH DTC are compared, and the results prove the validity of the proposed strategy.

The direct torque control theory has achieved great success in the control of permanent magnet synchronous motor. A Direct Torque Control (DTC) scheme of Permanent Magnet Synchronous Motor (PMSM) is presented. Based on in-depth analysis of PMSM mathematical model in abc frame and  frame are established and the operation principle of DTC-SVPWM system, the relationships between the torque and fundamental components. A novel space vector pulse width modulation (SVPWM) method which has a feature of low harmonic is proposed. The proposed method is adopted to implement the direct torque control (DTC) of a three-phase PMSM. A large number of simulation results show that the DTC System of PMSM has fast response and good dynamic performance. Aiming at the direct torque control in PMSM Drives, in this paper explained the theoretical basis of the direct torque control (DTC) for PMSM firstly. Then explained the difference between the applications of DTC-SVPWM to PMSM. Finally the MATLAB/Simulink models were developed to examine the DTC- SVPWM for PMSM. The simulation results is presented in this paper.