Walter Issamu Suemitsu

Fuzzy logic torque ripple reduction by turn-off angle compensation for switched reluctance motors

A fuzzy-logic-based turn-off angle compensator for torque ripple reduction in a switched reluctance motor is proposed. The turn-off angle, as a complex function of motor speed and current, is automatically changed for a wide motor speed range to reduce torque ripple. Experimental results are presented that show ripple reduction when the turn-off angle compensator is used.

Torque ripple minimization in a switched reluctance drive by neuro-fuzzy compensation

A simple power electronic drive circuit and fault tolerance of converter are specific advantages of SRM drives, but excessive torque ripple has limited their use to special applications. It is well known that controlling the current shape adequately can minimize the torque ripple. This paper presents a new method for shaping the motor currents to minimize the torque ripple, using a neuro-fuzzy compensator. In the proposed method, a compensating signal is added to the output of a PI controller, in a current-regulated speed control loop. Numerical results are presented in this paper, with an analysis of the effects of changing the form of the membership function of the neuro-fuzzy compensator.

Proposition of an offline learning current modulation for torque-ripple reduction in switched reluctance motors: design and experimental evaluation

A new offline current modulation using a neuro-fuzzy compensation scheme for torque-ripple reduction in switched reluctance motors is presented. The main advantage of the proposed technique is that the torque signal is unnecessary. The compensating signal is learned prior to normal operation in a self-commissioning run, capturing the necessary current shape to reduce the torque ripple. Simulation results verify first the effects of speed and then load changes on the compensator performance. Implementation of the proposed technique in a laboratory prototype shows the feasibility and accuracy of the respective offline scheme.

Fuzzy logic control of a switched reluctance motor

This paper presents the use of fuzzy logic control (FLC) for switched reluctance motor (SRM) speed. The PLC performs a PI-like control strategy, giving the current reference variation based on speed error and its change. The performance of the drive system was evaluated through digital simulations through the toolbox Simulink of the Matlab program.

Flywheel Energy Storage System Description and Tests

This paper presents test results of a flywheel energy storage system (FESS) prototype. The bearing system is composed of a superconducting magnetic thrust bearing (SMB) and a permanent magnet bearing (PMB). The SMB was built with Nd-Fe-B magnet and YBCO superconducting blocks. The PMB has the function of positioning radially the switched reluctance machine (SRM) used as motor/generator and reduce the load over the SMB. The SRM drive is responsible to convert electrical into mechanical energy, and vice versa. The prototype still operates at low speeds, but the dynamical simulations of the SRM drive showed that the system can work at high speed, supplying the required energy during disturbances. In the tests performed with the FESS prototype, the system took or delivered energy from/to the grid when requested.

Development and Experimental Tests of a Simple Neurofuzzy Learning Sensorless Approach for Switched Reluctance Motors

Despite becoming competitive with ac and dc machines, the necessity for a shaft position transducer makes switched reluctance (SR) machines lose their low cost advantage, mainly as low power machines such as fans and pumps. Many techniques have been proposed for indirect rotor position detection for SR machines. However, their characteristics can be summed up as being based on a lookup table plus an interpolation algorithm, making them specific to a particular machine. For economic reasons and also dynamic performance, sensorless algorithms need a learning mechanism to allow them to adapt to a new SR machine or even adapt to changes in the SRM parameters. This paper presents a novel methodology for position sensor elimination for SR machines. Using the voltage from each conducting phase and the reference current signal as inputs, the rotor speed is first obtained as the output of a neurofuzzy learning system used as a “virtual” speed sensor. Then, the rotor position is determined by integrating the estimated value of speed. The effectiveness of the proposed sensorless technique was investigated through a series of real-time experiments on an SR drive system. The experimental results show that the suggested “virtual” speed sensor and corresponding rotor position can operate well in a sensorless SR speed control system.

Voltage sags compensation using a superconducting flywheel energy storage system

This paper presents a voltage sag compensator, which uses a flywheel energy storage system with superconducting magnetic axial thrust bearing (SMB) and a permanent magnet radial bearing (PMB). The SMB was built with Nd-Fe-B magnet and YBCO superconducting blocks, refrigerated with liquid Nitrogen. The magnets are assembled with magnetic flux shapers in order to increase the levitation force and the stiffness. The radial PMB is used to positioning the vertically arranged switched reluctance machine (SRM) used as motor/generator. Simulations of the power electronics and SRM show that the system can work up to 30,000 rpm supplying the required energy during disturbances.

Low-Cost Gate Drive Circuit for Three-Level Neutral-Point-Clamped Voltage-Source Inverter

This paper presents a new hardware implementation of gate drive circuits applied to low-power neutral-point-clamped (NPC) multilevel three-phase inverters. The proposed circuit is based on commercially available MOS-gate driver ICs (MGDs) for large-scale applications, which may reduce the total cost of implementation of NPC inverters. Only one DC power supply is required to feed all the gate drivers for the three-phase system. Detailed design procedures are presented, which include the protection circuits for avoiding hazardous switching states of the power switches. Experimental results of a laboratory prototype demonstrate the validity of the proposed circuit. These results also suggest that for achieving safe operation of snubberless power switches during transients, a hybrid implementation of each NPC phase leg, consisting of MOSFETs with voltage ratings at half the DC bus voltage and of insulated gate bipolar transistors rated at the total DC bus voltage, is recommended.

Development and implementation of a neuro fuzzy technique for position sensor elimination in a SRM

This article has the objective to present a brief revision of the techniques more generally used in the position sensor elimination in a switched reluctance motor. For each speed level, different techniques are indicated for a good system operation. A new technique of position sensor elimination is presented, based in intelligent techniques with neural nets and fuzzy logic. It uses only phase voltages and the reference current signals to obtain the speed/position estimation. Experimental and simulation results are presented showing its good performance.

UFRJ power electronics teaching lab: ten years

Over ten years ago, the first laboratory course on Power Electronics was introduced in the Federal University of Rio de Janeiro (UFRJ). The course was conceived in conjunction with the development of a small but consistent set of modules, which have been designed with the aim of making it easier to implement many different converter functions. After a decade of successful use, this conception has been proving so far to be very effective and versatile. Undergraduate and graduate students have developed a variety of projects with the available modules, and the whole material has evolved to a great tool for interdisciplinary work on many subjects, such as power electronics, electrical motor drives and digital control. An overview of various ways in which this teaching tool has been used is presented in this paper, along with a discussion about perspectives for the next years.