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EPE 2003 - Topic 09e: Adjustable Speed Drive Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2003 - Conference > EPE 2003 - Topic 09: ELECTRICAL MACHINES AND ADJUSTABLE SPEED DRIVES > EPE 2003 - Topic 09e: Adjustable Speed Drive Systems
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	A five-phase two-machine vector controlled induction motor drive supplied from a single inverter   By E. Levi; M. Jones; S.N. Vukosavic; H.T. Toliyat	[View]   [Download]
Abstract: Application of power electronics in electric drives enables utilisation of AC machines with a phase number higher than three. It is shown in the paper that an increase of the stator phase number to five enables completely independent vector control of two five-phase machines that are supplied from a single current-controlled voltage source inverter. In order to achieve such an independent control it is necessary to connect five-phase stator windings of the two machines in series and perform an appropriate phase sequence transposition. The concept is equally applicable to any five-phase AC machine type and its major advantage, compared with an equivalent two-motor three-phase drive, is the saving of one inverter leg. Instead of six inverter legs, only five are required. Detailed verification of the novel five-phase two-motor drive configuration is provided by simulating the operation in the torque mode and speed mode, using indirect rotor flux oriented control principles. The concept can be extended to higher number of phases in a simple manner. Its main drawbacks are addressed as well.
	Acoustic noise radiated from vector controlled induction motor drives   By D. Martínez-Muñoz; J. C. S. Lai; D. W. J. Pulle	[View]   [Download]
Abstract: The acoustic behaviour of vector controlled drives at transient operation is studied. Vector control allows independent modulation of the currents controlling the flux and the torque, thus providing a dynamic performance capability hitherto only possible with a d.c. motor drive. These currents have been modulated with high frequency noise signals, in order to study the impact of radial and tangential forces on the acoustical performance of small electrical machines, and the influence of transient operation on the noise emission from vector controlled drives. Sound pressure and sound intensity measurements were conducted at load and no load. The results indicated that, for the same amplitude and frequency of the harmonic, modulating the flux produces more noise than the torque by up to 7 dB, and the noise emissions are reduced at load by up to 13 dB compared with no load.
	A MRAS-Luenberger sensorless speed control of a doubly fed induction machine   By R. Ghosn; C. Asmar; M. Pietrzak-David; B. de Fornel	[View]   [Download]
Abstract: In this paper a combination with MRAS and Luenberger speed observer is proposed to control DFIM system. In according to previous work, based on MRAS observation strategy, this mixed method gives better results in sensorless operation and especially at very low speed.
	A simple stator flux oriented induction motor control   By F. Cupertino; G.L. Cascella; L. Salvatore; N. Salvatore	[View]   [Download]
Abstract: This paper presents a novel stator flux oriented induction motor (IM) control scheme. It utilises a sliding-mode controller in the stator flux control loop. The existence condition of sliding mode control is derived, and chattering suppression at steady-state is also considered. A proportional (P) controller is used in the torque control loop so to simplify the control scheme without compromising performances. Design formula are given for the controller parameters. They are not based on the mathematical IM model but only need rated parameters. Experimental results are shown to prove the effectiveness of the control strategy.
	Suppressing low frequency resonance oscillations of a two-mass system by active damping   By D. Alders; R. Kennel; J. Onno Krah; J. Quan	[View]   [Download]
Abstract: Mechanical couplings between electrical motors and mechanical loads or processes usually provide rather low stiffnesses. This situation often results in resonance problems due to the interdependencies between the inertias of motors and loads coupled by elastic couplings. This paper describes the possibility of suppressing low frequency resonance oscillations by an active method instead of mechanical damping equipment. A special filter is integrated into the drive control loop. This paper shows the optimisation of the filter parameters to obtain good damping of the mechanical system.
	Design and optimazation of the DC-link capacitor of PWM voltage source inverter with active frontend for low-voltage drives   By M. Winkelnkemper; S. Bernet	[View]   [Download]
Abstract: In most of the ac-dc-ac-converters for low voltage drives aluminium electrolythic capacitors are used for the energy storage in the dc-link. The main design criteria for this type of capacitor is its ripple current capability. In this paper a full investigation of the influence of converter parameters like modulation strategy, grid and load angle, dc-link voltage etc. on the ripple curent is represented. The results are used to minimize the size and the capacity of the dc-link capacitor of a PWM rectifier - dc voltage link - PWM inverter configuration substancially.
	High performance space voltage vector controlled inverter considering voltage saturation for speed servo system of induction motor   By T. Kanmachi; R. Endo; K. Ohishi	[View]   [Download]
Abstract: This paper proposes a new high performance space voltage vector controlled inverter for speed servo system of induction motor. The proposed system carries out a fine anti-windup control on voltage saturation for vector controlled induction motor. The effectiveness of proposed method is verified by the numerical simulation results and the experimental results.
	Direct speed estimation based on back EMF of induction motors - its equivalent MRAS representation and stability analysis -   By S. Sangwongwanich; U. Nittayatareekul; P. Magyar	[View]   [Download]
Abstract: Difficulties in the stability analysis and design of several back EMF based speedsensorless induction motor drives arise for lack of an explicit MRAS structure. To overcome this problem, an equivalent MRAS representation of the speed estimator is given, using which stability conditions are analytically derived. A new design strategy is then proposed to guarantee the stability for the whole operation including the regenerating mode in the low speed region. Validity of the theoretical results is verified by simulation and experiment.
	Polyphase systems for high-power controlled AC drives. Specifics of their parameters and control   By D. Beliaev; A. Weinger; B. Ingram; F. DeWinter	[View]   [Download]
Abstract: Advantages of 2*3-phase, 3*3-phase and 4*3-phase motors are known for high-power controlled AC drives. But model of such system is more complicate. Solutions are proposed for parameters choice of a frequency converter and for special control. Investigation proved that proposed solutions provide realization of advantages of poly-3-phase system. This is confirmed by simulation results for a 3*3-phase synchronous drive on the base of current source inverter (CSI) with pulse-width modulation (PWM).
	Zero-speed sensorless direct torque control of induction machine drives. A sliding mode approach   By C. Lascu; I. Boldea; F. Blaabjerg	[View]   [Download]
Abstract: A new variable structure, direct torque controlled, sensorless induction machine drive is presented, in which the principles of Variable Structure Control (VSC) and Direct Torque Control (DTC) are combined to ensure high-performance operation, both in the steady state and under transient conditions. The drive is directly controlled on the basis of torque and flux errors, using Variable Structure Control and Space Vector Pulse Width Modulation. Classical DTC transient merits are preserved, while the steady-state behavior is significantly improved. The novel full-order state observer is of Sliding Mode type and it does not require the rotor speed adaptation. A new stator resistance adaptation scheme is proposed. The proposed solution allows wide speed range sensorless operation, including very low and zero speed, full load. Extensive experimental results confirm the robustness, accuracy, quickness, and low-chattering, sensorless operation.
	Discrete-time triggering method for a voltage source inverter with input LC filter used in an induction machine drive   By M. Petkovsek; V. Ambrozic; P. Zajec; D. Voncina; J. Nastran	[View]   [Download]
Abstract: The paper introduces a new concept of a sensorless induction machine (IM) drive supplied with the impressed stator voltage. In order to reduce side effects of conventional sensorless drives relying on impressed stator currents (i.e. thermal stress, noise and parasitic capacitive currents that stress the insulation system,…), a new inverter topology with controlled sinusoidal output voltage is proposed. Its power stage consists of a three-phase Voltage Source Inverter (VSI) and an output LC filter combined into a unique controlled voltage source. This is accomplished with the applied feedbackfeedforward voltage control loop whose main attraction is the control of filter capacitor current. In this way, output voltage is attained indirectly through an impressed filter capacitor current. In the case of a cosinusoidal capacitor current, the output voltage is sinusoidal and therefore no longer of a pulsed shape, which is the main drawback of the conventional inverter. In the same manner, the frequency and load dependance of output voltage are reduced while its dynamics compared to other known solutions with passive LC filter is increased. In addition, it is shown that the implementation of the speed-sensorless control with the proposed inverter has become an easy attainable feature. Firstly, upon mathematical expressions of current and voltage fed IM, a model for calculation of the IM speed ù and frequency of the magnetizing current vector ùmR is defined. Additionally, a Field-Oriented Control (FOC) scheme of the microcomputer controlled IM drive is presented. The proposed concept has been verified through experimental tests using a laboratory three-phase VSI and exhibits very promising results.
	High performance sensorless solutions for induction motor control   By V. Bostan; M. Cuibus; C. Ilas; R. Magureanu	[View]   [Download]
Abstract: The paper presents a comparison between four sensorless solutions for high performance induction motor control. The solutions are developed around two classical schemes based on direct flux oriented control (DFOC). The first is based on the Luenberger rotor flux observer and the second one on the model reference adaptive scheme (MRAS) with voltage-current (UI) and current-speed (Iù) as rotor flux observers. For both cases have been tested the classical methods to obtain the estimated rotor speed (LNBPI), (MRASPI). In addition for Luenberger based scheme have been tested an original method to obtain the estimated rotor speed (LNBG), and for the MRAS based scheme a neural network have been developed in order to perform the estimation tasks (MRASNN). All four methods have been implemented and tested using a fix-point Motorola DSP56F805.
	Flatness based control of non-linear textile multimachine process   By S. Charlemagne; A. Bouscayrol; I. Slama-Belkhodja; J.P. Hautier	[View]   [Download]
Abstract: A multimachine textile process is modelled with the energetic macroscopic representation (EMR). Then a control structure is deduced from this modelling, using specific inversion rules. This yields an uncoupled control of the unwinder-rewinder system: so the control of tension and velocity of the wire are decoupled. But as the process has time-varying parameters, the initial control structure is modified by using the flatness theory. The robustness of both controls is evaluated by simulation.
	Experimental characterization of insulation systems for high voltage inverter-fed traction motors   By L. Egiziano; V.Tucci; M. Di Lorenzo del Casale; G. Pizzella; A. Masucci	[View]   [Download]
Abstract: Increasing efficiencies and improved performances in pulse width modulation (PWM) based adjustable speed drives (ASD) are obtained owing to the continuous enhancements in working frequencies and slew rates (dv/dt) of new generations switching devices, such as MOSFET or IGBT. These advancements have beneficial consequences particularly in ASD for high power, high voltage motors, as those adopted in traction motors. However, some undesirable side effects arise, such as shaft voltages and bearing currents, EMI, overvoltages and uneven voltage distribution in the coils. In particular, both thermal and electrical ageing of the motor insulation is faster due to the enhanced stresses associated with steep fronted waveforms, as compared to that arising under sinusoidal voltages. In this paper the results of an experimental investigation carried out on some candidate insulation systems for adjustable speed drive, high voltage, traction motors are presented. The effects of the applied voltage wave-shapes parameters, such as the slew rate and frequency, are analysed. The characteristic parameters of partial discharges (PD) are analysed under sinusoidal and quasi square voltages wave shapes in order to compare the performances of the insulation systems. The results of PD test are examined and cross checked with the life curves of the insulation systems in order to gain a widespread knowledge of the degradation mechanisms affecting the motor insulation as close as possible to those taking place in real operating conditions.
	High dynamic performance of a PWM current source converter induction machine drive   By A. Klönne; F. W. Fuchs	[View]   [Download]
Abstract: The dynamic performance of a drive with induction machine fed via a pulse width modulated current source converter is investigated. The goal is to obtain a high dynamic performance of the drive. Therefore, suitable control methods are selected. These are the state feedback control on the line side, the field oriented control at the machine side and basic PI control for the dc link. The converter is controlled by means of space vector modulation with high pulse frequencies. Compared to other strategies a dc link reactor with relatively small inductivity is used to achieve fast control, while also minimizing weight and costs. Furthermore, the overall strategy aims to reduce the on-state losses in the power semiconductor modules by keeping the dc link current to a minimum level. The basic control performance in the dc link depending on the inductivity in the dc link is analysed. The dynamic performance of the drive when applying all these methods is investigated by means of simulations of a 20 kW and measurements of a 7,5 kW test drive. Thus, a torque step response time approaching that of PWM voltage source converter induction machine drives has been achieved.
	Speed sensorless control of an induction motor using the extended EMF estimation   By K. Jezernik; G. Edelbaher; M. Rodiè	[View]   [Download]
Abstract: Induction motor speed sensorless control, allowing operation at low and zero speed, optimizing torque response and efficiency, is proposed. The magnitude and orientation angle of the rotor flux of the induction motor are determined by the output of the closed-loop rotor flux observer based on the extended electromotive force of machine. A smooth transition into the field weakening region and the full utilization of the inverter current and voltage capability are thus made possible. The produced torque is a continuous output variable of control. The reference tracking performance is demonstrated by simulations and experiments.
	Natural field orientation (NFO) for sensorless control of the AC induction motor   By R. Jönsson; O. Glenberg; H. Hemark; R. Johansson	[View]   [Download]
Abstract: The basic idea of the invention “Natural Field Orientation” (NFO) is described. NFO permits sensorless operation in four quadrants at all speeds. The main purpose of NFO is to create a correct field orientation. Then the complete motor control system with current control loops and different kinds of external control loops can be designed in field coordinates. Estimation of rotor speed and motor torque is described. NFO is designed according to the “internal model principle” and consequently it is important to have accurate parameter values in the model, especially during low speed operation. Two different methods for parameter adaptation are described. One example with simulation and experimental results is presented.
	Comparison of instantaneous power control and field orientated control of induction machines   By T. Summers; R.E. Betz	[View]   [Download]
Abstract: Recently instantaneous power control (IPC) has been proposed as an alternative to field oriented control (FOC) and direct torque control (DTC) for high performance induction machine drives. This paper presents issues related to implementing the IPC algorithm on a drive system and preliminary experimental results which demonstrate the IPC algorithm’s performance. This performance is tempered though by the affect that inaccurate back-emf estimates have on refer- ence current generation. A technique for overcoming this limitation is proposed and simulation results are presented.
	Compact single-phase integrated motor drive with sinusoidal input current and bi-directional power flow capability   By C. Klumpner; F. Blaabjerg; P. Thøgersen	[View]   [Download]
Abstract: A standard configuration of an Adjustable Speed Drive (ASD) consists of two separate units: an AC motor, which runs with fixed speed when it is supplied from a constant frequency grid voltage and a frequency converter, which is used to provide the motor with variable voltage-variable frequency needed to adjust the speed of the motor. The integrated motor drive concept is a result of merging the two units in order to achieve the following benefits [1]-[3]: reducing the design and the commissioning time in complex industrial equipments, no need for a cabinet to host the frequency converter, no need for shielded cables to reduce RFI, no need for cables for the speed transducers or for other sensors for industrial process control (e.g. pressure). This solution is currently available up to 7.5 kW being not used in the medium and high power range due to a low-density integration of the converter caused by the large size of the passive components (electrolytic capacitors and iron chokes) and vibration of the converter enclosure.
	Reactive power compensation in induction motor drive system based on sine-wave voltage source inverter   By R. Seliga; W. Koczara	[View]   [Download]
Abstract: The paper describes the development of a sine-wave inverter for an AC induction motor drive application. It is shown that the proposed control method of the PWM inverter with the low-pass LC filter effectively reduces high frequency harmonics providing variable frequency and amplitude sinewave voltage to the motor terminals. The arrangement of the LC filter reduces also reactive power flow through the inverter demanded by the induction motor. Experimental verification of the sinewave voltage source inverter operation feeding 15kW laboratory drive system with the conventional cage induction motor is presented.
	Torque capability of a field oriented induction motor drive under voltage sag conditions   By K. Stockman; F. D'hulster; R. Belmans	[View]   [Download]
Abstract: This paper describes the torque capability of a field oriented induction motor drive under three fase balanced voltage sag conditions. Starting from the general description of the field oriented induction motor with main flux saturation, the maximum steady-state torque capability under reduced dc bus voltage is calculated. Both inverter current limit and voltage limit are considered and the optimal reference currents to maximize torque are given. From the steady-state analysis, a strategy to adjust the under-voltage protection level on the dc bus is proposed in order to increase the ride-through of the drive. The typical field oriented control scheme is modified to supply the flux and current controllers with the correct reference values for maximum torque. When considering the slow rotor flux dynamics, the maximum torque of the saturated machine can only be obtained with a dynamic flux controller quickly adjusting the rotor flux reference
	Line side and motor side filters for NPC medium voltage drive: Rating method   By A. Scaglia; V. Vaccaro.	[View]   [Download]
Abstract: This paper deals with the rating of suitable low-pass filters to be used together with Medium Voltage NPC IGBT inverters in certain voltage distortion sensitive applications. It will provide the rating criteria of such line side and motor side filters. In these two cases different is the goal to reach and different are the proposed solutions. The authors start from the analysis of output voltage spectrum of NPC inverters that implement a given modulation strategy [1] and describe all steps necessary to define a suitable rating of filter components. The inverter output voltage spectrum is clearly the basis to define the filter characteristics. The paper shows, besides, as also other factors influence the characteristics of the inverter-filter system. In fact, in particular for high power drives, where the size of filter components is large, the Q-factor results to be, with good reason, comparatively high, and the Qfactor has a direct influence on the damping coefficient of the system. Other conditions that impact on the filter rating can be related to the control algorithms used for the application. Finally, the paper shows how the goals were met by records taken from tests done on a 6MVA NPC IGBT inverter.
	Performance of a high speed induction motor sensorless drive   By E. Lorenzani; G. Franceschini; C. Tassoni; Y. De Mari	[View]   [Download]
Abstract: A low-cost, high reliability drive without mechanical sensor is described. The application concerns a wash machine system that, in spite of the simple, but effective solution, implemented in a fixed point DSP, presents a good dynamic performance and good steady-state speed accuracy in a very wide operating speed range. Motor phase current reconstruction is performed suitably sampling the voltage across three shunt resistances put in series to the IGBT emitters while, as far as phases voltage measurement is concerned, bus voltage is sampled and then motor phase voltages are reconstructed inside the DSP using PWM duty cycle and dead-time correction strategy. Drive performances, as far as torque production is concerned, have been tested using a dynamometer in a speed range up to 12000 rpm and compared with the torque produced with the usual constant Volt per Hertz (V/f) method. The proposed sensorless control in spite of hardware simplicity that, obviously, translates in low cost, comparable with the open loop solution, presents superior dynamical performances, higher torque per ampere, and then efficiency.
	Measuring with only one current sensor all the load currents in a multiple drive system based on a two-stage direct power electronic conversion topology   By C. Klumpner; F. Blaabjerg	[View]   [Download]
Abstract: A two-stage multi-drive Direct Power Conversion (DPC) topology suited for multi-drive application is proposed, having an input port for a three-phase power supply and several output ports to connect three-phase loads, which are independently controlled. This has similar behavior as a matrix converter with no need of energy storage components (electrolytic capacitors) in the main power flow path, sine wave in and sine wave out operation and the same disadvantage of a voltage transfer ratio lower than unity. This is a cost effective topology compared to a standard matrix converter because the multiple loads share the cost of the controlled rectification stage. A new technique to produce the command signals for the power switches is proposed, making it possible to measure with only one current transducer mounted in the dc-link, the phase currents of all the separate loads. This technique is validated by experiments on a realistic laboratory prototype.
	Analysis on the influence of transient voltage variations in ground wire due to inverter supplied induction machines in insulated grids   By D. Putman; J. Desmet; R. Belmans	[View]   [Download]
Abstract: It is known that the steep voltage changes caused by IGBT frequency inverters can cause overvoltage problems at motor terminals and in the motor winding [1,2,3]. Moreover, due to the distributed phase capacities of the cable, these voltage changes cause a voltage variation in the ground wire [4], which can only be partially eliminated by introducing filters that limit the rate of change of the voltage [5]. These voltages induced in the ground wire can initiate sparks when connected to a grounded system, thus representing a substantial danger when operating in an explosive atmosphere. The paper provides an analysis of the influence of cable parameters, cable length, grounding resistance and motor impedance.
	Vector and scalar PWM to six-phase voltage source inverters   By M.B.R. Corrêa; C.B. Jacobina; C.R. da Silva; A.M.N. Lima; E.R.C. da Silva	[View]   [Download]
Abstract: Improved PWM control of six-phase voltage source inverters fed split-phase induction motors is presented in this paper. The approach is based on space vector modulation and designed to improve the performance of the system in terms of THD and DC bus utilization. Simulation and experimental results are presented to demonstrate the feasibility of the proposed solution.
	Drive system with three-level inverter for high-speed applications   By S. Beineke; L. Hebing; A. Bünte	[View]   [Download]
Abstract: High-speed drive systems, applied for vacuum pumps, laser cooling vacuum blowers or high-speed cutting, have to fulfill some specific requirements. Since cooling of the rotor is a fundamental problem in these applications, permanent magnet synchronous motors have been chosen for the proposed drive system. Combined with the specific speed controlled inverters and LC-output filters, optimized solutions for high-speed applications are achieved. Due to its high switching frequency up to 64 kHz, the proposed three-level inverter topology facilitates sinusoidal currents with very small ripple at very high output frequencies. This new drive system offers an increasing performance regarding the dynamic of the control and the rotor losses, and at the same time the volume and costs of the filters and the overall system are reduced.