A novel DTC scheme of double-star induction motors using three-level voltage source inverter

The objective of this study is to study a new control structure for sensorless Double-Star Induction Motors (DSIM) dedicated to electrical drives using a three-level Voltage Source Inverter (VSI). The output voltages of the three-level VSI can be represented by four groups: the zero voltage vectors, the small voltage vectors, the middle voltage vectors and the large voltage vectors in (d, q) plane. Then, the amplitude and the rotating velocity of the flux vector can be controlled freely. Both fast torque and optimal switching logic can be obtained. The selection is based on the value of the stator flux and the torque. Both approaches, two level control and three level control, are simulated. The results obtained show superior performances over the FOC one without need to any mechanical senso

Feedback of the input voltage in FDTC control using a three-level NPC-VSI

A new control structure for sensorless induction machine dedicated to electrical drives using a three-level voltage source inverter VSI-NPC is completely analysed. The amplitude and the rotating velocity of the flux vector could be controlled freely. Both fast torque and optimal switching logic could be achieved; the selection is based on the value of the stator flux and the torque. A novel DTC scheme of induction motors is proposed in order to develop a suitable dynamic. We proposed a DTC approach based in fuzzy logic, in witch the response of torque and flux is enhanced trough optimal switching strategies and torque ripple minimisation is achieved. However, the middle point voltage of the input DC voltages of the three-level NPC voltage source inverter presented serious problems caused by a fluctuation of the DC voltage sources UCU, UCL. As consequence to these problems, we obtained an output voltage of the inverter, which is asymmetric and with an average value different from zero. We presented one solution to minimise this fluctuation. This solution used a feedback to regulate the input voltages of a three-level inverter VSI NPC. A scheme of a fuzzy direct torque control "FDTC" with complete cascade is simulated for an induction motor. The results obtained indicate superior performance over the FOC one without need to any mechanical senso

An improved direct torque control strategy for induction motor drive

The object of this study is to study a new control structure for sensorless induction machine dedicated to electrical drives using a three-level Voltage Source Inverter (VSI). The major problem with DTC drives is the high torque ripple, to solve this problem two approaches are proposed to replace the conventional hysteresis-based controller. The output voltages of the three-level VSI can be represented by four groups: the zero voltage vectors, the small voltage vectors, the middle voltage vectors and the large voltage vectors in (d, q) plane. Then, the amplitude and the rotating velocity of the flux vector can be controlled freely. Both fast torque and optimal switching logic can be obtained. The selection is based on the value of the stator flux and the torque. Both approaches are simulated for a induction motor. The results obtained show superior performances over the conventional DTC one without need to any mechanical senso

DC-link voltage balancing algorithm using a space-vector hysteresis current control for three-level VSI applied for wind conversion system

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Performance Analysis of a Flywheel Energy Storage System

The flywheel energy storage systems (FESSs) are suitable for improving the quality of the electric power delivered by the wind generators and to help these generators to contribute to the ancillary services. In this paper, a flywheel energy storage system associated to a grid connected variable speed wind generation (VSWG) scheme using a doubly fed induction generator (DFIG) is investigated. Therefore, the dynamic behavior of a wind generator, including models of the wind turbine (aerodynamic), DFIG, matrix converter, converter control (algorithm of VENTURINI) and power control is studied. This paper investigates also, the control method of the FESS with a classical squirrel-cage induction machine associated to a VSWG using back-to-back AC/AC converter. Simulation results of the dynamic models of the wind generator are presented, for different operating points, to show the good performance of the proposed system

Study and control of three-level PWM rectifier-five-level NPC active power filter cascade by using feedback control and redundant vectors

The purpose of this paper is to develop a control and regulation method of input DC voltages of five-level Neutral Point Clamping (NPC) Active Power Filter (APF). This APF is applied for the enhancement of medium voltage network power quality by compensation of harmonic currents produced by an induction motor speed variator. In the first part, the authors present a topology of five-level NPC Voltage Source Inverter (VSI), and its simplified Space Vector Pulse Width Modulation (SVPWM) control strategy. In the second part, the control strategy of Three-level PWM current rectifier is presented. In the third part, to remedy to instability problem of the input DC voltages of the APF, the authors propose the feedback control of the three-level rectifier associate with a simplified SVPWM with redundant vectors method of five-level APF. After that, the sliding mode regulator used to control the APF is developed. The application of the proposed control algorithm offers the possibility of stabilizing the DC voltages of APF. Stable DC bus supply associated with sliding regulator of APF allows getting low-harmonic content network currents with unity power factor. In all over, the instability problem associated with use of multilevel APF is solved. The obtained results are full of promise to use the multilevel APF in medium voltage and great power application

A scheme of EDTC control using a three-level voltage source inverter for an induction motor

The object of this paper is to study a new control structure for sensorless induction machine dedicated to electrical drives using a three-level voltage source inverter (VSI). The amplitude and the rotating speed of the flux vector can be controlled freely. Both fast torque response and optimal switching logic can be achieved; the selection is based on the value of the stator flux and the torque. A novel DTC scheme of induction motors is proposed in order to develop a suitable dynamic. We propose an approach; in wich we enhance the response of torque and flux with optimal switching strategies. However, the middle point voltage of the input DC voltages of the three-level NPC voltage source inverter presents serious problems caused by a fluctuation of the DC voltage sources UcU, UcL. As consequence to these problems, we obtain an output voltage of the inverter which is asymmetric and with an average value different from zero. In this paper, we will present one solution to minimise this fluctuation. This solution uses a clamping bridge to regulate the input voltages of a three-level inverter VSI NPC. A scheme of Enhanced direct torque control "EDTC" with complete cascade is simulated for an induction motor. The results obtained indicate superior performance over the FOC one without need to any mechanical senso