Harmonic Torque Ripple Research Articles

Dual Converter Operating With Floating Capacitors Connecting Open-End Winding Doubly-Fed Induction Generator to the DC Microgrid

This paper presents a novel configuration to connect a three-phase doubly-fed induction generator (DFIG) to the dc microgrid. The proposed topology connects an uncontrolled con- verter and a full-controlled converter in series with the generator stator windings in an open-end winding (OEW) configuration. The full-controlled converter is connected to an independent dc link based on floating capacitors. The paper discusses the converter operating principles, pulse-width modulation (PWM), DFIG power control, and the floating capacitors' voltage reg- ulation. The work compares the proposed and conventional systems regarding current harmonic distortions, torque ripple, and semiconductor losses. Simulations and experiments show steady-state and transient results for a 0.56-kW DFIG operating at the rated power. Finally, it was verified that the proposed topology presents lower power losses and low-distorted voltages and currents over the DFIG stator windings.

A New Closed Loop Constant v/f Control of Induction Motor with Torque Control Based on DPWM

An easy sensor-less scalar control algorithm is described in this article as a method for controlling the speed of an induction motor. For developing a closed-loop v/f control of the induction motor drive, a torque controller with PI is implemented. The torque command was estimated by utilizing the voltage command, the feedback current, and a torque estimator. Additionally, a torque reference was provided for the Torque PI controller. Considering this, the purpose of this work is to investigate the closed-loop PI-based torque control of an induction motor drive that applies DPWM. In addition to this, it provides a description of a PI-based closed-loop torque control that works in conjunction with v/f control and tries to discover the most effective method for driving an induction motor based on an examination of Total Harmonic Distortion (THD) and torque ripple. To evaluate the performance studies of open- and closed-loop strategies with DPWM techniques for induction motor driving, the MATLAB/Simulink environment has been deployed. Experimental results have been validated.

Harmonic Injection-Based Torque Ripple Reduction of PMSM With Improved DC-Link Voltage Utilization

This letter proposes an improved scheme for torque ripple reduction of permanent-magnet synchronous machines (PMSMs) considering dc-link voltage utilization. Different from the previous methods, both <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis harmonic currents are optimized and injected. Specifically, the appropriate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis harmonic current reference is obtained through harmonic analysis of PMSM. Furthermore, the harmonic voltage control loop is included to generate the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis harmonic current reference, which can ensure that the magnitude of the voltage vector satisfies the maximum output voltage circle under the voltage constraint. The virtual signal and multiple reference frame-based proportional-integral (PI) controllers are employed to regulate the harmonic components. The effectiveness of the proposed method is validated by experimental results.

A New Closed Loop Constant v/f Control of Induction Motor with Torque Control Based on DPWM

An easy sensor-less scalar control algorithm is described in this article as a method for controlling the speed of an induction motor. For developing a closed-loop v/f control of the induction motor drive, a torque controller with PI is implemented. The torque command was estimated by utilizing the voltage command, the feedback current, and a torque estimator. Additionally, a torque reference was provided for the Torque PI controller. Considering this, the purpose of this work is to investigate the closed-loop PI-based torque control of an induction motor drive that applies DPWM. In addition to this, it provides a description of a PI-based closed-loop torque control that works in conjunction with v/f control and tries to discover the most effective method for driving an induction motor based on an examination of Total Harmonic Distortion (THD) and torque ripple. To evaluate the performance studies of open- and closed-loop strategies with DPWM techniques for induction motor driving, the MATLAB/Simulink environment has been deployed. Experimental results have been validated.

A Variable Switching Frequency Space Vector Pulse Width Modulation Control Strategy of Induction Motor Drive System With Torque Ripple Prediction

The constant switching frequency space vector pulse width modulation (CSFSVPWM) generates high-frequency harmonics with integer multiples of the switching frequency, making it fail to fully exploit the potential of pulse width modulation (PWM) technique. In this paper, a variable switching frequency space vector pulse width modulation technique with the function of torque ripple prediction is proposed for induction motor drive system, which could optimize the high-frequency harmonic current distribution and torque ripple. The mathematical correlation between inverter average voltage and instantaneous voltage under the space vector pulse width modulation (SVPWM) is first analyzed, followed by the analysis of current ripple in a switching cycle using the typical seven-segment SVPWM, thus the torque ripple of induction motor during this period can be predicted. The switching period is dynamically adjusted according to the magnitude of predicted torque ripple, and the average switching frequency is maintained to be the same with that of CSFSVPWM. The effectiveness of the proposed method in suppressing high-frequency current harmonics and torque ripple is fully verified by experimenting on a 2.2 kW induction motor drive system, and a comprehensive comparison with CSFSVPWM and random PWM modulation is implemented.

Electromagnetic Torque Analysis and Structure Optimization of Interior Permanent Magnet Synchronous Machine with Air-Gap Eccentricity

Interior permanent magnet synchronous machine with air-gap eccentricity (AGE-IPMSM) has the advantages of low torque ripple and low noise. However, air-gap eccentricity will lower the power density of the machine to a certain extent. In this paper, an 18-slot/8-pole interior permanent magnet synchronous machine with air-gap eccentricity is taken as the research object. According to the magnetic circuit method, the no-load and load air-gap magnetic field analytical models are calculated, respectively. Then, by Maxwell’s tensor method, the variation law of radial and tangential air-gap magnetic density harmonic amplitudes and phase angle difference cosine values are analyzed, and it is concluded that the electromagnetic torque can be improved by increasing phase angle difference cosine values of the magnetic density harmonic, which produces the driving torque after eccentricity. On this basis, in order to improve the output characteristics of the machine, the eccentricity and the angle between the V-type permanent magnets are optimized with the total harmonic distortion (THD), electromagnetic torque, and torque ripple as the optimization goals, and then the optimal structure size parameters of the machine are finally determined. Finally, a prototype is manufactured on the basis of the optimal parameters, and the experimental results of the prototype verify the validity and correctness of the theoretical analysis and finite element analysis (FEA).

Influence of slot/pole number combinations and pole shaping on electromagnetic performance of permanent magnet machines with unbalanced north and south poles

AbstractThe influences of slot/pole number combinations on electromagnetic performances, including flux linkage, inductance, and torque ripple harmonic components etc., resulting from unbalanced characteristics between north and south poles in concentrated winding permanent magnet (PM) machines with symmetrical and asymmetric rotor pole shaping methods are theoretically analysed and experimentally validated in this paper. It shows that for the PM machines with odd number of coils per phase per submachine, including consequent pole (CP) and surface‐mounted PM (SPM) machines, the influences of unbalanced pole characteristics can lead to additional torque ripple harmonics due to additive effects in windings, but can be cancelled in other machines. Compared with symmetrical pole shaping method, asymmetric pole shaping method can result in lower torque ripple for CPPM machines with odd number of coils per phase per submachine, while symmetrical and asymmetric pole shapes have similar effects on torque ripple reduction for other CPPM machines and all the SPM machines. The findings have been validated by finite element analyses on 12‐slot/8‐pole, 12‐slot/10‐pole, 9‐slot/6‐pole, and 12‐slot/14‐pole machines, and by experiments with 12‐slot/8‐pole and 12‐slot/10‐pole CPPM prototypes.

A Single Inductor Multi-Port Power Converter for Electric Vehicle Applications

This research presents a non-isolated multi-port power converter feasible to hybridize energy alternatives in electric vehicles. Due to the hybridization of the various input sources, there are several advantages in load power distribution in the system. Flexible control of discharging as well as the charging process concerning the energy sources can be achieved. The developed converter can able to boost the voltage levels with dual inputs such as a renewable solar PV and the other input as a battery and provides dual outputs with various voltage levels, which can able to suit the converter fed for several loads like motor drive and the low-rated loads like lighting and other auxiliary supplies in electric vehicles. Also, as the various voltages appear at the output, this converter can be interfaced with multilevel inverters fed electric vehicle drivetrain. The utilization of multilevel inverters reduces the total harmonic distortion and torque ripples in motor drives in electric vehicles. The proposed converter consists of less number of components making the circuit simple and cost-effective. With one inductor, two various modes are obtained for charging and discharging states concerning the energy storage units. A state-space analysis is designed for all the converter operating modes along with its control design. The proposed multi-port DC-DC converter is designed in MATLAB/Simulink and tested in a laboratory environment with a hardware setup.

Vector Proportional Integral Control with Delay Compensation for Stator Excited Doubly Salient Synchronous Motors

This paper proposes a novel current control technique to solve the problem that the special doubly salient structure of the studied stator excitation doubly salient synchronous motor (SEDSSM) causes the motor back EMF to cause large harmonic current and torque ripple. Based on the space vector pulse width modulation sinusoidal drive method, a vector proportional-integral controller with delay compensation (VPIC) is introduced into the current loop to replace the traditional PI controller to control the motor. The SEDSSM stator current under the current loop control mode of conventional PI controller is analyzed, and it is found that its waveform is obviously affected and disturbed by the third harmonic current, which will cause torque pulsation. Therefore, additional resonance items are considered to be introduced into the controller to suppress its harmonic. At the same time, considering that the digital delay in the application of the digital system will lead to an unstable state of the control system under the vector proportional-integral controller, the vector proportional-integral controller with delay compensation is introduced for this purpose. Experimental data tested on a 12/8 SEDSSM prototype show that the VPIC controller can significantly reduce stator current ripple and motor torque ripple compared to the existing PI controller.

Finite Control Set Model Predictive Field-Oriented Control For Three-Phase Induction Motor Drives

Field-oriented control is one of the well-established vector control strategies for induction motor drives. However, its cascaded structure and requirement of a modulator for constant switching frequency operations makes it complex and computationally expensive. Model predictive control (MPC) is a novel control strategy used for AC motor drives. In this paper, a finite control set model predictive control (FCS-MPC) based field-oriented control (FOC) is presented. The Finite control set model predictive field-oriented control (FCS-MPFOC) utilizes a cost function that quantifies the error between the reference and anticipated current values for all the potential voltage vectors of the voltage source inverter. The voltage vector that generates the lowest value of the cost function is directly implemented on the inverter to produce the drive voltage. The efficiency of the proposed method is authenticated by using a three-phase induction motor, fed via a two-level three-phase voltage source inverter in the MATLAB/Simulink environment under various speeds, load torque, and model parameter mismatch situations. In order to authenticate the performance of the proposed strategy, it is compared with traditional model predictive torque control. Simulation results show that the proposed method performed significantly well in total current harmonic distortion, flux and torque ripples, switching frequency, and parameter variations.

Half-Controlled Converters Connecting Open-End Doubly Fed Induction Generator to a DC-Microgrid

This article presents a novel system to connect a three-phase doubly fed induction generator (DFIG) to a dc-microgrid. The proposed topology is based on two three-phase half-controlled converters connected in series with the generator stator windings, in an open-end winding configuration. The converters operating principles, pulsewidth modulation, power and air-gap flux controls, and zero-sequence current minimization strategies are discussed. The proposed system is compared with conventional systems in terms of current harmonic distortions, torque ripple, and semiconductor losses. Simulations and experiments were also performed, showing steady-state and transient results for the DFIG generating 500 W. Finally, it was verified that the proposed system can operate with lower power losses and maintain low-distorted voltages and currents over the DFIG stator windings.

Correction of Field Orientation Inaccuracy Caused by Resolver Periodic Error and Rotor Time Constant Variation for Indirect Field-Oriented Control Induction Motor Drives

This article proposes an algorithm correcting the field orientation inaccuracy caused by resolver periodic error and rotor time constant variation. It is found that the periodic error brings harmonic current vectors and torque ripples while the rotor time constant variation makes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> currents deviate from the reference values. The cross-product of fundamental and harmonic current vectors contains the information of resolver periodic error. The gradient descent method with a variable step is introduced to compensate the periodic error. During the process, the cross-product is minimized. A new form of cross-product calculation is derived to reduce the computation time. The rotor time constant is identified by the reactive-power based model reference adaptive system (MRAS). Voltages and currents in the stationary reference frame are used in the reference model to avoid the influence of resolver periodic error. Appropriate parameters of the MRAS are selected to guarantee the stability. The algorithm is integrated with an induction motor drive which is based on indirect field-oriented control. The feasibility of the proposed algorithm is verified by simulation results and experiments.

Unipolar sinusoidal current excited switched reluctance motor control based on a 3D space vector modulation

This paper reports on a novel unipolar current excited control scheme for the asymmetric bridge converter (ABC)-based switched reluctance drive (SRD), where the 3D space vector modulation under three modes is developed to reduce the total harmonic distribution (THD) and torque ripple. Firstly, two different 3D vector distributions, namely, the small voltage amplitude mode and large mode are presented based on the asymmetric converter. For both distributions, the zero-sequence voltages generated by the effective vectors are considered. Additionally, zero-sequence vectors (1,1,1) and (−1,−1,−1) are no longer treated as null vectors and involved in the control of zero-sequence current. Then, the duty cycles of both two modes are obtained by the combination of the zero-sequence and two adjacent active vectors. Moreover, based on the large modulation mode, a novel method combined with the small mode is proposed to further optimise the switching costs and torque ripples. The effectiveness of the proposed modes is verified through the simulation in MATLAB and the experiment on a dSPACE-1103-based prototype. Compared with the conventional switched reluctance motor vector control, the proposed scheme delivers better performances of THD, efficiency and torque ripple reduction.

Harmonic suppression and road feeling control of steer-by-wire system with permanent magnet synchronous motor

In this paper, a hierarchical control strategy is proposed to improve the quality of road feeling control of a steer-by-wire system. The upper layer proposed a road feeling torque control method of uncertain system, and the lower layer suppresses the current harmonics produced in the road feeling control process. Firstly, the dynamic model of the steer-by-wire system and the vehicle are established. Secondly, considering the influence of uncertain system parameters, uncertain harmonic torque ripple, and uncertain sensor noise on the road feeling torque control, a road feeling torque control strategy based on mixed H2/H∞ robust control theory is designed. Then, a current harmonic suppression strategy based on the extended Kalman filter is proposed in the lower layer to suppress the current harmonics of all frequencies. Finally, the simulation is conducted using MATLAB/Simulink, and the experimental verification is carried out on the steer-by-wire experimental platform. Simulation and experimental results show that the proposed road feeling control strategy is robust to nonlinear system uncertainties, and the proposed current harmonic suppression strategy can suppress current harmonics in all frequency ranges.

Finite element and analytic equivalent circuit models for MSIM feeded by MPI controlled by SVPWM strategy to minimise circulation harmonic current

This article deals with the determination of the multi-stars induction machine (MSIM) equivalent circuit parameters based on the geometrical and electrical data using two methods namely analytic and finite element method (FEM). Additionally, this paper proposes a general dynamic study of MSIM. This latter is fed by a multi-phase inverter (MPI) controlled by a space vector pulse width modulation (SVPWM) and a sinusoidal pulse width modulation (SPWM). However, when this machine is fed by the voltage inverter for the case of 30° electrical shift between stator stars, large harmonic currents are observed. Thus, the main goal of this paper is to reduce the effect of these harmonic currents. Therefore, to overcome these issues, the machine stars number has been increased to three and four and the inverter has been controlled by the SVPWM. The effectiveness of this association and its capability to reduce the effect of the output harmonic current and electromagnetic torque ripple has been proved by simulation results.

30° Discontinuous PWM-Based Closed Loop Volts/Hz Control of Induction Motor Drive with Slip Regulation

This paper proposes 30° discontinuous PWM-based closed loop volts/Hz control of induction motor drive with slip regulation. The voltage source inverter is carried out with various pulse width modulation (PWM) schemes such as continuous PWM (CPWM) and discontinuous PWM (DPWM) schemes. The inverter's performance is affected by these PWM schemes. Therefore, this paper investigates the PWM schemes for the inverter. It aims to identify a best PWM scheme based on the total harmonic distortion and torque ripple analysis for constant volts/Hz induction motor drive amongst the various PWM schemes in open loop and closed loop and also proposes a 30° DPWM-based closed-loop control. The performance investigations of various PWM schemes based on inverter-fed induction motor have been evaluated analytically and using MATLAB/Simulink environment. Experimental results have been validated. The combination of 30° DPWM with PI control and slip regulation for induction motor makes the speed control system robust and ideal for low-accuracy applications.

Dual Converter Connecting Open-End Doubly Fed Induction Generator to a DC-Microgrid

This article presents a novel system to connect a three-phase doubly fed induction generator (DFIG) to a dc-microgrid. The proposed system uses a three-leg rectifier at each side of the stator windings, in an open-end winding configuration. Usually, these legs are composed of insulated gate bipolar transistors (IGBTs). To reduce the number of controlled switches and costs, one of the rectifiers has its IGBT switches replaced by diodes. The converters operating principles, pulsewidth modulation, power control, and zero-sequence current minimization strategies are discussed. The proposed system is compared with two conventional systems in terms of current harmonic distortion, torque ripple, and semiconductor losses. Simulations and experiments were also performed, showing steady-state and transient results for a 0.56-kW DFIG operating at constant torque. Finally, it was verified that the proposed system maintains balanced voltages and currents over the DFIG stator windings, with no significant torque oscillations.

Torque Ripple-Minimizing Control of IPMSM With Optimized Current Trajectory

In an interior permanent-magnet synchronous machine (IPMSM) for higher torque density, there would be undesirable torque ripples due to spatial harmonics. This article analyzes the torque ripple based on the actual torque map, which is more practical and accurate than the torque model-based analyses. Based on the analysis, a torque ripple-minimizing scheme is proposed for practical IPMSMs. In addition, an experimental identification method of torque map is proposed. The identified torque map is used not only for the proposed torque ripple-minimizing method, but also for the torque reconstruction in experiments. Simulation and experimental results are provided to verify the proposed method. It is confirmed that the harmonic torque ripple under target has been reduced by over 90%.

Torque ripple suppression strategy of asynchronous motor for electric vehicle based on random pulse position space vector pulse width modulation with uniform probability density

AbstractA random modulation strategy is proposed to suppress the torque ripple of asynchronous motor for electric vehicle in this article. First, the models of harmonic torque and torque ripple are established. The reason of harmonic generation and its effect on torque are analysed. Second, the random position pulse width modulation (PWM) strategy with different random quantities is introduced. The problem of the increasing harmonic content near the integer multiple of the switching frequency in the modulation process is solved. Subsequently, the influences of different random quantity distributions and random number ranges on harmonic suppression are studied. The different structures of random pulse position space vector PWM strategy based on uniform probability density are designed. The specific harmonic content is dispersed and the torque ripple is suppressed. Finally, the precise test platform based on cSPACE is established. The influence of different random PWMs on motor at various speeds is compared. Experimental results verify the validity of the proposed approach.

A Sequential Direct Torque Control Scheme for Seven-Phase Induction Machines Based on Virtual Voltage Vectors

The traditional direct torque control (DTC) strategy utilizes the largest 14 voltage vectors for a seven-phase induction machine (7PIM), which is directly extended from the three-phase counterparts. This method suffers from the issues of severe harmonic currents and torque ripple for multiphase ones. This article first puts forward the concept of virtual vectors for a 7PIM. This can efficiently eliminate the third- and fifth-order harmonic currents. However, the DTC strategy based on the virtual voltage vector has insignificant effect on reducing the torque ripple. Then, the torque ripple caused by these virtual vectors in different torque and speed conditions is investigated. Analysis shows that there are some additional degrees of freedom while choosing the applied voltage vector. A novel sequential strategy integrated with duty ratio optimization algorithm is proposed to select the optimal voltage vector that can significantly alleviate the torque ripple. Experimental results verified that the proposed method can effectively reduce the dynamic and steady-state torque ripple as well as the harmonic current.This article utilizes a 7PIM for an illustration, but it should be mentioned here that the proposed strategy is applicable for multiphase machines with any number of phases.