Erkan Mese

Automatic control of excitation parameters for switched-reluctance motor drives

This paper presents a new approach to the automatic control of the turn-on angle used to excite the switched-reluctance motor (SRM). The control algorithm determines the turn-on angle that supports the most efficient operation of the motor drive system, and consists of two pieces. The first piece of the control technique monitors the position of the first peak of the phase current (/spl theta//sub p/) and seeks to align this position with the angle where the inductance begins to increase (/spl theta//sub m/). The second piece of the controller monitors the peak phase current and advances the turn-on angle if the commanded reference current cannot be produced by the controller. The first piece of the controller tends to be active below base speed of the SRM, where phase currents can be built easily by the inverter and /spl theta//sub p/ is relatively independent of /spl theta//sub m/. The second piece of the controller is active above base speed, where the peak of the phase currents tends to naturally occur at /spl theta//sub m/ regardless of the current amplitude. The two pieces of the controller naturally exchange responsibility as a result of a change in command or operating point. The motor, inverter and control system are modeled in Simulink to demonstrate the operation of the system. The control technique is then applied to an experimental SRM system. Experimental operation documents that the technique provides for efficient operation of the drive.

An approach to torque ripple reduction in fully pitched switched reluctance motors by pole tip shaping

Torque ripple is a drawback for both conventional and fully pitched SRM structures. Although there are several publications in the literature addressing the full or partial solution to the problem for conventional SRM, but not for emerging fully pitched SRM. This paper proposes a solution to a torque ripple problem in fully pitched SRM by shaping stator and rotor pole tips. The essence of the proposed method is to shape the inductance profile of the motor so that torque profile changes accordingly. Analysis has been performed with the finite element (FE) model of 6/4 3-phase fully pitched SRM with unipolar excitation. A sharp increase and decrease in torque profile existing before the proposed geometry has been smoothed out after pole tip shaping. This brings the torque ripple level from 37.2% to 13.7% for 6 A phase current.

Investigating Operating Modes and Converter Options of Dual Winding Permanent Magnet Synchronous Machines for Hybrid Electric Vehicles

Summary form only given. This paper investigates the operating modes and converter options of dual winding permanent magnet synchronous machines (DWPMSMs) that are used to drive accessories in hybrid electric vehicles. In this application, DWPMSM operate in three different modes: 1) motor-only; 2) generator-only; and 3) simultaneous motor-generator modes. Motor-only and generator-only operations can be treated independently as long as two winding sets are magnetically decoupled. Simultaneous motor-generator mode links two winding sets through a mechanical shaft. As part of this study, the impact of dual winding set usage on the machines output and performance is also investigated. Experimental results are given for each mode. The converter options of generator winding were investigated as well. These options include uncontrolled rectifier with dc-dc converter and controlled rectifier. Two converters are compared for their impacts on efficiency and generator current harmonics. The relationship between speed and converter control variable is given for various back electromotive force constant values of the DWPMSM.

Unbalanced fault analysis of doubly fed induction generator drive system for wind turbine applications

This paper presents detailed analysis of the doubly fed induction generator (DFIG), converters and step-up transformer under normal and fault conditions for wind turbine applications. 2.5 MW DFIG is modeled through finite element analysis in Ansoft-Maxwell, and the simulation is coupled to Ansoft-Simplorer and Matlab-Simulink for the drive circuit and controller implementation. Single phase to ground short circuit which has the highest probability to occur in the grid is tested through coupled simulators. The effect of short circuit stator current on the rotor currents are analyzed for rotor side converter protection. The FFT analysis of the stator and rotor fluxes in simulation during fault conditions are carried to be able to develop advanced control techniques in eliminating the harmonics and protecting the overall drive system. Experimental 7.5 HP DFIG test system has been developed to verify the simulation results. The FFT analysis of stator fluxes under fault condition from experimental results agrees well with the simulation results.

Investigating DC link current ripple and PWM modulation methods in Electric Vehicles

Batteries are one of the key components for Electric Vehicles (EVs). While batteries supply energy to output at normal working mode by converting internal chemical energy to electric energy (discharging), they restore energy at regenerative working mode as opposed to discharging (charging). During each working mode, battery current is not smooth DC and it has ripple. The ripple current influence battery lifetime negatively. Simulations which include ideal battery model and ideal DC bus capacitor model do not give realistic results about battery ripple current. This paper presents comparative investigations and evaluations about battery current waveform, battery current harmonic spectrum and the ratio of battery current harmonic components to battery average current for different modulation methods and operating states for motor (i.e. speed and torque) by using high frequency battery model and high frequency DC bus capacitor model.

Analysis of doubly fed induction generator wind turbine system during one phase-to-ground fault

This paper presents detailed analysis of doubly fed induction generator (DFIG) wind turbine electrical components during normal and unbalanced fault condition. Wind turbine components are individually modeled and then combined in a simulation process which is called coupled simulation. The coupled simulation results show that grid frequency oscillation occurs on q and d axis currents under one phase-ground fault condition. Experimental study has been done to show the effects of fault on rotor currents. Same behavior is also found in experimental rotor currents. Additionally experimental study shows that rotor currents are very sensitive to the grid fault voltage level.

A new electric accessory drive system for hybrid electric vehicles

This paper presents a new electric accessory drive system for hybrid electric vehicles. The system offers cost and space advantages. In this concept, dual winding electric machine with simultaneous motor and generator functions is used. The electric machine provides power for all accessory loads such as steering pump, compressors, and 12V loads. If the engine is on, accessory loads are driven by engine through a belt like conventional vehicle. If the engine is off, electric machines motoring action starts and provides mechanical power to accessory loads. Simultaneously, the generator windings provide power for 12 V loads. Converter options for generator were also investigated and preliminary experimental results were presented.

An adaptive predictive current control technique for permanent magnet synchronous motors

Producing the required magnitude and shape of reference current is necessary to achieve precise torque control in motor control applications. A deadbeat predictive current controller provides very good dynamic performance. In order to achieve very accurate reference current production the machine and inverter should be modeled properly with accurate parameters. Parameter changes, especially the back emf voltages and inverter delay elements, cause deadbeat current regulator performance to deteriorate significantly. This paper addresses accurate determination of permanent magnet synchronous machine parameters dynamically on-line, taking into account the delay elements such as inverter output filters, calculation time steps of the control algorithm within the DSP, and updating the current regulation accordingly. The new algorithm is simulated and experimentally tested. The simulation and experimental results of the new current regulation technique provide very good dynamic and steady state results, validating regulator performance.

Comparative design of direct drive PM synchronous motors in gearless elevator systems

In todays world electrical machines become irreplaceable for human beings to continue daily routines. Due to the features such as high efficiency, high starting torque, and silent working, permanent magnet synchronous motors (PMSM) are becoming more common in many applications. One of these applications is gearless elevator system where PMSM seems to be the best candidate so far. In this paper, comparative design of PMSM for gearless elevator has been investigated. Maxwell 2D Finite element analysis software has been used in this study. With comparative design, the influence of pole count on the machine performance is studied. Also, material consumption, weight and costs of two machines have been compared.

Design considerations for dual winding permanent magnet synchronous machines

This paper presents design and analysis performed for a dual winding electric machine. Windings of the machine are concentrated type so that electrical and magnetic isolation is maintained. For this reason, the proposed structure could be a reasonable candidate for fault tolerant applications. As required by some applications (electric accessory drive system (EADS) for hybrid electric vehicles), simultaneous motoring and generating operations can be implemented in a single housing of electric machine. Design considerations of the proposed electric machine are outlined in the paper. Also a comparison between distributed winding topology and concentrated winding topologies is performed. Finally experimental results discussed.