Space Vector Modulation Direct Torque Control Research Articles

Design and Xilinx Virtex-field-programmable gate array for hardware in the loop of sensorless second-order sliding mode control and model reference adaptive system–sliding mode observer for direct torque control of induction motor drive

This article aims first to propose an improved space vector modulation–direct torque control in order to enhance the induction motor performance using: (1) a super-twisting controller and (2) a novel model reference adaptive system based on a sliding mode observer. Second, due to the complexity of the suggested control algorithm, this article deals also with a hardware implementation on a field-programmable gate array board. Indeed, the field-programmable gate array is mainly chosen to reduce the execution time, thanks to its parallel processing which significantly improves the quality of the control system by reducing the sampling period, and consequently the delays in the control loop. Besides, the super-twisting controller is proposed to enhance the speed regulation loop which is a second-order sliding mode control technique that uses a continuous control law to prevent the chattering phenomenon induced by the first-order sliding mode control technique. Moreover, the high performance control requires information about the rotor speed which can be obtained by a sensor. Generally, the use of the speed sensor increases the system cost and size, and reduces its system reliability. Therefore, a combination between a model reference adaptive system observer and a sliding mode observer is suggested for speed estimation and overcoming the sensitivity of the classical model reference adaptive system observer against uncertainties and stator resistance variations. The performance of the proposed space vector modulation--direct torque control--super-twisting controller with the model reference adaptive system--sliding mode observer algorithm of an induction motor is verified through simulation, hardware co-simulation and experimental validation utilizing a field-programmable gate array Virtex-5-ML507 board. The performance of the suggested sensorless control method is compared also with other recent published schemes.

A Stand-Alone PV-PEMFC System based SM-ANN-MPPT Controller: Solar Pumping Application using PMSM

Maximum Power Point Tracking (MPPT) is a tool to optimize the use of the produced power in renewable energy systems, particularly in photovoltaic (PV) systems. Many algorithms have been developed and reviewed in the literature. In this work, a Sliding Mode-Artificial Neural Network-based MPPT (SM-ANN-MPPT) technique is proved. A comparison is made with one of the simplest MPPTs in the literature Perturb and Observe (P&O). It has been found that the minimization of the PV power ripples and the dissipated energies have been gained using the SM-ANN-MPPT controller. The proposed controller is applied for a standalone PV system with a Proton Exchange Membrane Fuel Cell (PVPEMFC) considering variable irradiation and temperature. The application of the system is dedicated to a solar pumping system using a three-phase Permanent Magnet Synchronous Motor (PMSM). The control of the PMSM is ensured by a Direct Torque Control-Space Vector Modulation (DTC-SVM) approach. Two cases are tested: with imposed speed profile, and with a solar daily profile. Two cases of load profiles are also treated: constant and variable loads. The control behaviour is simulated and the results are revealed justifying the feats of the DTC-SVM PMSM drive. Results show improvement in robustness and stability under real daily climatic conditions.

A Low Torque Ripple Direct Torque Control Method for Interior Permanent Magnet Motor

This paper proposes a simple method to generate stable voltage commands for permanent magnet synchronous motors to achieve low torque ripple based on space vector modulation direct torque control (SVM-DTC). The relationship between applied voltage and electromagnetic torque is first analyzed and the effect of the voltage and flux linkage on torque ripple is discussed. Then, the new method is developed to reduce torque ripple by giving low-fluctuation voltage commands to the voltage source inverter. The magnitude of the voltage command is calculated by avoiding the effect of flux linkage angle that can be estimated inaccurately during motor operation. Therefore, the fluctuation of the voltage command can be significantly reduced. In order to validate the proposed method, Simulink is first used for simulation and the performance of the proposed method is evaluated. It is found that the torque ripple can be substantially reduced while keeping a low switching frequency and improving system response. Then, a hardware-in-the-loop (HIL) technique is applied to test the developed algorithm that is written into a Texas Instruments microcontroller. This validates the simulation results and the proposed method.

Speed Estimation Technique Using Modified Stator Current Error-Based MRAS for Direct Torque Controlled Induction Motor Drives

This paper uses a stator current error-based model reference adaptive system (MRAS) to estimate the speed of an induction motor drive. Usually, speed error signal uses the cross product of stator current error vector and flux linkage vector for the estimation of speed. However, this speed error signal has limitations, such as speed tracking error and instability (at regenerative mode) under loaded conditions at low speeds. To mitigate these issues, a modified MRAS speed estimation algorithm is proposed in this paper. In the proposed method, the adaptive model state variables are formulated in terms of flux linkages (stator and rotor) in order to alleviate the impact of current noise in the flux linkage estimation. Moreover, a compensator is added to reduce the speed error tracking in the reference model. Furthermore, the stability of the drive is kept by using the dot product of stator current error vector and the rotor flux linkage vector during the regenerative mode of operation. The analysis of the proposed algorithm is presented and validated experimentally on the laboratory setup with direct torque control-space vector modulation technique for a wide operating range including the dynamic performance.

Fuzzy Logic Enhanced Direct Torque Control with Space Vector Modulation

Over the past few years, multiple types of modifications have been proposed onto the Direct Torque Control (DTC) scheme. Among others is the implementation of Space Vector Modulation (SVM). In this paper, two new control strategies are proposed onto an SVM-DTC. Instead of using PI torque and flux controllers, a fuzzy logic control method is implemented in the proposed modification to achieve a more constant switching frequency while minimizing the torque error. The fuzzy logic controller controls the voltages in direct and quadratic reference frame (Vd, Vq). This approach fully utilizes the switching capability of the inverter and thus improving the overall system performance. To overcome issues in open loop stator flux such as DC drift and saturation, a closed loop estimation method of stator flux is also proposed based on voltage model and low pass filter. The performance of the proposed control strategy is benchmarked with that of a conventional DTC–SVM. Simulations and experiments were carried out and the results show that the proposed method outperforms the conventional DTC-SVM in terms of DC-offset elimination and overall system robustness. <p class="MsoNormal" style="text-align: justify; text-indent: 36.0pt;"><span style="font-size: 9.0pt; font-family: 'Arial','sans-serif'; color: black;" lang="EN-US">Over the past few years, multiple types of modifications have been proposed onto the Direct Torque Control (DTC) scheme. Among others is the implementation of Space Vector Modulation (SVM). In this paper, two new control strategies are proposed onto an SVM-DTC. Instead of using PI torque and flux controllers, a fuzzy logic control method is implemented in the proposed modification to achieve a more constant switching frequency while minimizing the torque error. The fuzzy logic controller controls the voltages in direct and quadratic reference frame (V<sub>d</sub>, V<sub>q</sub>). This approach fully utilizes the switching capability of the inverter and thus improving the overall system performance. To overcome issues in open loop stator flux such as DC drift and saturation, a closed loop estimation method of stator flux is also proposed based on voltage model and low pass filter. The performance of the proposed control strategy is benchmarked with that of a conventional DTC–SVM. Simulations and experiments were carried out and the results show that the proposed method outperforms the conventional DTC-SVM in terms of DC-offset elimination and overall system robustness. </span></p>

A novel DTC-SVM approach for two parallel-connected induction motors fed by matrix converter

AC machines fed by a single inverter are widely used in industries such as railroad electrification systems where speed synchronization does not have to be exact. The low cost and volume and the small number of power electronic components are attractive aspects of single-inverter multi-motor systems. This paper proposes a novel approach to controlling the speed and torque of two induction motors connected in parallel and fed by a matrix converter under unbalanced load condition. This single-inverter dual-motor (SIDM) drive uses average and differential values of speed and torque together with stator and rotor flux parameters based on the flux dead-beat scheme. An advantage of the proposed approach, compared with the conventional direct torque control (DTC) method, is that it eliminates the lookup table and lowers the torque and current ripple through the use of the PI controller instead of hysteresis blocks. Combining DTC and space vector modulation (SVM) with a matrix converter (MC) and achieving the unit input power factor are other advantages of the present study. The main purpose of this study was to propose a new drive system with an MC for two parallel-connected induction motors using the DTC method and SVM consisting of a flux dead-beat scheme.

Reduction of Torque and Flux Ripples in Space Vector Modulation-Based Direct Torque Control of Asymmetric Permanent Magnet Synchronous Machine

In this paper a study is presented about the reduction of electromagnetic interference (EMI) in Direct Torque Control (DTC) method by the means of chaotic space vector modulation. Space Vector Modulated Direct Torque Control (SV-DTC) is a method developed to reduce current and moment fluctuations which stem from the hysteresis controllers used in classical DTC method. The switching frequency amplitude was changed chaotically in a Space Vector Modulated Direct Torque Control (FFSV-DTC) having a Fixed switching frequency, and Chaotic Space Vector Modulated Direct Torque Control (CAFSV-DTC) method having chaotic amplitude modulated switching frequency was obtained. CAFSV-DTC method was suggested to reduce EMI, acoustic noise and current harmonics which occur in FFSV-DTC method. For this purpose, the proposed CAFSV-DTC method, using a Permanent Magnet Synchronous Motor (PMSM) drive, is compared to Random Amplitude Frequency method (RSV-DTC) and FFSV-DTC. Simulation results indicate that the proposed method yields better results. DOI: http://dx.doi.org/10.5755/j01.eee.22.1.14097

Second-order Sliding-mode Control Approaches to Improve Low-speed Operation of Induction Machine under Direct Torque Control

Direct torque control is a powerful approach widely used for the control of electrical machines. However, this approach is sensitive to several problems, such as the stator flux demagnetization phenomenon and the appearance of undesirable torque ripples, especially at low-speed operation. To overcome these problems, a variable structure control approach for a direct torque control–space vector modulation system, with a constant switching frequency, is proposed in this article. The proposed sliding-mode direct torque control–space vector modulation method can (i) enhance the system robustness, (ii) reduce the torque ripples, and (iii) prevent the demagnetization problem, which penalizes the stator flux regulation. To reduce the chattering phenomenon that appeared on the control law, a second-order sliding-mode approach, which is a new second-order procedure, has been proposed. Simulation results dealing with low-speed operation of the induction motor under variable structure control direct torque control–space vector modulation strategy is presented and compared to those yielded by the direct torque control–space vector modulation strategy using hysteresis controllers.

Reduction of EMI with Chaotic Space Vector Modulation in Direct Torque Control

In this paper a study is presented about the reduction of electromagnetic interference (EMI) in Direct Torque Control (DTC) method by the means of chaotic space vector modulation. Space Vector Modulated Direct Torque Control (SV-DTC) is a method developed to reduce current and moment fluctuations which stem from the hysteresis controllers used in classical DTC method. The switching frequency amplitude was changed chaotically in a Space Vector Modulated Direct Torque Control (FFSV-DTC) having a Fixed switching frequency, and Chaotic Space Vector Modulated Direct Torque Control (CAFSV-DTC) method having chaotic amplitude modulated switching frequency was obtained. CAFSV-DTC method was suggested to reduce EMI, acoustic noise and current harmonics which occur in FFSV-DTC method. For this purpose, the proposed CAFSV-DTC method, using a Permanent Magnet Synchronous Motor (PMSM) drive, is compared to Random Amplitude Frequency method (RSV-DTC) and FFSV-DTC. Simulation results indicate that the proposed method yields better results. DOI: http://dx.doi.org/10.5755/j01.eee.22.1.14097

Direct torque control of multilevel SVPWM inverter in variable speed SCIG-based wind energy conversion system

Direct torque control (DTC) theory has been successfully used in a variety of high performance industrial AC drives. This paper presents the application of DTC space vector modulation (DTC-SVM) to two and three level voltage source inverter (VSI) to improve the energy efficiency of a variable speed wind energy conversion system. Three different topologies are proposed to control the torque and flux of a squirrel-cage induction generator (SCIG) driven by a variable speed wind turbine. The main objective of this study is to improve the quality of energy of the wind energy conversion system by reducing torque ripples in the SCIG. Simulation results have shown that the proposed DTC-SVPWM with two or three levels inverter produced improved transient responses and reference tracking performance of the voltage in the generator and grid sides as well as the DC link. The overall simulation models have been implemented using Simulink and SimPowerSystems toolboxes.

Direct torque controlled space vector modulated method for line start permanent magnet synchronous and induction motors

This paper presents a thorough comparison of Direct Torque Controlled Space Vector Modulated (DTC-SVM) method for a three-phase four-pole Induction Motor and its equal Line-Start Permanent Magnet Synchronous Motor (LSPMSM), which is amended from an actual induction motor. For this reason, both nominal voltage and voltage sag conditions are tested for line-fed and voltage source inverter-fed of both motors, and a comparison between induction motor and LSPMSM behavior shows that synchronization problems of LSPMSM during line-fed conditions are obviated by DTC-SVM method. In addition, a superior transient and steady-state performance of the LSPMSM drive is observed rather than an induction motor, especially for voltage sag conditions.

Back-stepping Adaptive SVM Direct Torque Control of SPMSM Drive system

A novel back-stepping adaptive control strategy is proposed to direct torque control (DTC) of surface permanent magnet synchronous motor (SPMSM) in order to solve some problems existed in conventional DTC, such as high flux , torque and current ripple, variable switching frequency, and acoustic noises. PI speed regulator and two hysteresis regulators in the conventional DTC system are substituted by the proposed back-stepping adaptive controller respectively. The output of the designed controller makes space vector modulation (SVM) possible, which further ensures the inverter switching frequency to be fixed. The stability of the controller is verified via Lyapunov stable theory.Simulation results show that the presented control strategy can solve these problems effectively and show strong robust to external disturbance and noise.

Performance Analysis of DTC-SVM Sliding Mode Controllers-Based Parameters Estimator of Electric Motor Speed Drive

This paper is concerned with a framework which unifies direct torque control space vector modulation (DTC-SVM) and variable structure control (VSC). The result is a hybrid VSC-DTC-SVM controller design which eliminates several major limitations of the two individual controls and retains merits of both controllers. It has been shown that obtained control laws are very sensitive to variations of the stator resistance, the rotor resistance, and the mutual inductance. This paper discusses the performances of adaptive controllers of VSC-DTC-SVM monitored induction motor drive in a wide speed range and even in the presence of parameters uncertainties and mismatching disturbances. Better estimations of the stator resistance, the rotor resistance, and the mutual inductance yield improvements of induction motor performances using VSC-DTC-SVM, thereby facilitating torque ripple minimization. Simulation results verified the performances of the proposed approach.

Analysis of Cascaded H-Bridge Multilevel Inverter in DTC-SVM Induction Motor Drive for FCEV

In this paper, analysis of cascaded H-bridge multilevel inverter in DTC-SVM (Direct Torque Control-Space Vector Modulation) based induction motor drive for FCEV (Fuel Cell Electric Vehicle) is presented. Cascaded H-bridge multilevel inverter uses multiple series units of H-bridge power cells to achieve medium-voltage operation and low harmonic distortion. In FCEV, a fuel cell stack is used as the major source of electric power moreover the battery and/or ultra-capacitor is used to assist the fuel cell. These sources are suitable for utilizing in cascaded H-bridge multilevel inverter. The drive control strategy is based on DTC-SVM technique. In this scheme, first, stator voltage vector is calculated and then realized by SVM method. Contribution of multilevel inverter to the DTC-SVM scheme is led to achieve high performance motor drive. Simulations are carried out in Matlab-Simulink. Five-level and nine-level inverters are applied in 3hp FCEV induction motor drive for analysis the multilevel inverter. Each H-bridge is implemented using one fuel cell and battery. Good dynamic control and low ripple in the torque and the flux as well as distortion decrease in voltage and current profiles, demonstrate the great performance of multilevel inverter in DTC-SVM induction motor drive for vehicle application.

A novel direct torque control for induction motor drive system with low torque ripple and current distortion utilising FPGA

The conventional Direct Torque Control (DTC) is known to produce quick and robust response in ac drives. However, during steady state, notable torque and current pulsations occur. They are refl ected in speed estimation, torque response and also produce acoustic noise. In this paper, a novel Space Vector Modulated Direct Torque Control (SVM-DTC) with Low Pass Filter (LPF) for induction motor drive system is proposed, which features low torque ripple, low current distortion and fixed switching frequency. The proposed scheme has been implemented on the Xilinx Spartan 3E FPGA, both simulation and experimental results show that the proposed system can dramatically improve the steady state performance while preserving the dynamic performance of the conventional DTC.

A Novel Dynamic Overmodulation Strategy of Direct Torque Control

The direct torque control-space vector modulation (DTC-SVM) is well-known for achieving excellent dynamic overmodulation. However, the method uses complicated predictive stator flux vector control and requires high precision stator flux vector to define overmodulation mode. This paper proposes a straightforward dynamic overmodulation method and constant switching frequency controller without SVM to obtain a faster dynamic torque response in DTC for induction machines. To perform this method, the flux error status produced from the flux hysteresis comparator during dynamic condition is modified slightly before being fed to the look-up table. The verification of proposed method was performed using MATLAB/Simulink simulation package. The effects of different switching and operating condition on dynamic torque performance are analyzed. The result shows that a faster torque response is achieved in proposed dynamic overmodulation DTC method. The main benefit of the proposed method is its simplicity since only minor modification is made to the basic DTC hysteresis-based structure.

Dynamic Performance Comparison of IRFO and SFO-SM Controlled Drives in Field-Weakening Region Using Variable-Saturation Regulators

This paper proposes to use variable-saturation regulators for Induction Motor (IM) drives operating in field-weakening region, and presents a comparative dynamic-performance analysis between the traditional Indirect Rotor Field Oriented (IRFO) control scheme and a new Stator Flux Oriented – Sliding Mode (SFO-SM) control scheme. The traditional IRFO control scheme has the d-axis current component, torque, rotor flux, and speed loops with four PI-type controllers. The SFO-SM control system is a Direct Torque Control – Space Vector Modulation (DTC-SVM) scheme with closed loops of torque and stator flux without current PI-type controllers. Both control schemes use regulators with variable-saturation in such a way that maximum dc-bus voltage utilization is reached and overcurrent problems are prevented. The experiments are carried out using dSPACE digital controllers and comparative results show that the SFO-SM controlled IM drive and IRFO one are characterized by similar dynamic responses in spite of structural simplicity of the SFO-SM control scheme.