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This article presents a simplified model predictive control (MPC) method for single-phase four-level hybrid-clamped converters (1P-4L-HCCs), achieving high-quality current control and strong capacitor voltage balancing. Different from a conventional MPC, the proposed method aims to dramatically reduce switching states (control voltage vectors) in the cost function optimization of MPC. It utilizes only 16 switching states, compared to 64 in conventional methods, resulting in reduced execution time and significantly increased control bandwidth. Steady-state and dynamic performances are evaluated by simulated and experimental test, and the main results are provided to verify the effectiveness of the proposed MPC method.

This work deals with the sizing of submodule capacitors for modular multilevel converters (MMCs) used for variable speed drives for medium voltage and high voltage electric machines. Variable speed drives are required to run over a wide frequency range from zero to a few hundred Hz or even over 1 kHz. Under low frequency operation (

This article presents the design and development of a 7-kV dc bus, 1-MVA, 0–1000 Hz modular multilevel converter (MMC) prototype for high speed medium-voltage variable frequency drives. The system is designed based on 1.7-kV silicon carbide (SiC) mosfet s. First, the full in-depth design of the prototype is provided, including the submodules, arm inductors, and system integration. Then, the unique control scheme and the control hardware design are presented to achieve the full-frequency range operation. The power loss based on Si and SiC devices is analyzed. Finally, experimental results are presented to demonstrate the performance of both the SiC-based submodule and the full-scale MMC system. Compared with the traditional Si-based solution, the established SiC MMC can reduce the drive system volume by 75% and achieve 325% power density, and the peak energy efficiency reaches around 99.35%.

When a four-level hybrid clamped converter (4L-HCC) operates at low frequencies, the high load current causes significant voltage fluctuations among the capacitors in the dc link. A mathematical model is developed to clarify the mechanism of excessive capacitor voltage fluctuations. An improved common-mode voltage injection algorithm is proposed and integrated to the overall control method. With the applied algorithm, the voltage fluctuation minimization of the dc-link capacitors and the dynamic voltage balancing capability are investigated. Both simulation and experimental results validate the effectiveness of the proposed algorithm, with a voltage fluctuation reduction over 50%. The 4L-HCC with the proposed algorithm achieves much faster dynamic response to converge the unbalanced capacitor voltages and the reduced output current harmonics compared with the conventional common-mode voltage injection algorithm.

An optimized model predictive control (MPC) method is proposed based on the selected switching states to control the four-level hybrid-clamped converter. The proposed method utilizes 64, instead of 512, switching states, compared with a conventional MPC, which greatly eases the calculation burden while achieving the high-quality regulation of output currents and the balance of capacitor voltages. The steady-state performance at both high and low frequencies is investigated, and results are compared with those by the traditional carrier phase-shifted pulsewidth modulation method. The dynamic response to the current or frequency step change is also evaluated. Both simulation and experimental results validate the feasibility and effectiveness of the optimized MPC method.

The internal capacitor voltages of a four-level hybrid clamped converter (4L-HCC) can have serious instability issues without proper control, limiting its application in variable speed drives for transportation electrification. This article presents a new integrated control scheme for an electrical machine drive fed by the 4L-HCC. Compared with the traditional PWM control, the proposed method effectively minimizes the ac voltage fluctuations and dc voltage deviations for all dc-link and flying capacitors. The advantages of the proposed control method include easy implementation, accurate current and speed control, and strong capacitor-voltage-balancing capability. Four-quadrant operation with a high dynamic response is achieved over the full-speed range of the system. Simulation and experimental results are presented to validate the effectiveness of the proposed integrated method.

Low frequency operation in the modular multilevel converters (MMCs) is enabled by applying a reference common mode voltage and circulating currents at a frequency much higher than the desired output frequency. The frequency of injected common-mode signals is limited for maintaining a good performance in the circulating current control. Firstly, this paper theoretically analyzes the effect of increasing the frequency of injected common-mode signals by evaluating the error between reference and actual circulating currents. Secondly, we introduce an additional parameter in the reference circulating current to enhance the suppression of MMC's capacitor voltage fluctuations. Intensive computer simulations are developed for a seven-level MMC driving a medium-voltage induction motor drive system to verify the circulating current error analysis and assess the capacitor voltage fluctuations. Finally, the proposed technique for suppressing the capacitor voltage fluctuations is experimentally validated on a 600-V three-level MMC feeding an inductive load. The voltage fluctuations are reduced by more than 50% (63.6%) when the proposed technique is applied with a high common-mode frequency.

In this article, a double-vector-based model predictive control (MPC) method with efficient computation for single-phase five-level active neutral-point clamped (5L-ANPC) converters is proposed. It uses double voltage vectors per control cycle rather than the single in the conventional MPC method, resulting in reduced output current ripples and fixed switching frequency. First, the MPC method based on the Lyapunov function is optimized to select two voltage sectors rather than 25, reducing the calculation complexity significantly. Then, two current tracking algorithms based on double voltage vectors are presented, which are using the current cost function and current slope, respectively. Finally, a fast voltage balancing scheme for the dc-link and flying capacitors is developed and embedded in the MPC method. Both simulated and experimental results are used to validate the correctness and feasibility of the proposed MPC method.

Without active control, the voltage fluctuations of the dc-link and flying capacitors in a 4-level hybrid-clamped converter (4L-HCC) become excessively large in low-frequency operation. This paper studies the switching state redundancy inherent in a 4L-HCC and proposes a new capacitor voltage balancing and stabilizing method to minimize the dc-link and flying capacitor voltage fluctuations. A straightforward algorithm is developed based on a logic table to select the suitable switching states. Verified by simulation and experimental testing results, the new method and algorithm virtually eliminate all the big voltage fluctuations of capacitors at low and zero frequencies, greatly enhancing the robustness and reliability of a 4L-HCC. The capacitor size can be reduced by more than 80% compared with the conventional method.

A procedure to calculate maximum torque operating conditions for the inverter-fed induction machine is proposed in this paper. The proposed procedure minimizes the finite-element analysis computation load by identifying the variation range of stator current and slip frequency for the entire torque-speed map. Thus, the total calculation time for machine steady-state performance estimation can be significantly reduced. The effectiveness of the proposed procedure is validated by an experiment.

A 30-kVA SiC inverter has been developed for investigating challenges in harsh environment power electronics. In this design, operating temperature of both gate driver and power circuit is targeted at 180 °C ambient temperature. Specifically, the design is to achieve outstanding high-temperature (HT) performance at an affordable cost by taking full advantage of commercial components and applying the latest HT gate drive and protection circuit. The inverter has been evaluated at full power for hours in a thermal chamber. Experimental results of HT operation are provided to support the exciting success of the prototype and the promising future of HT power electronics. Meanwhile, comprehensive reviews on the challenges are presented along with the development process. The reviews cover the HT components in this design and the latest research on HT device characterization and packaging technique. At the end, the achievements and remaining challenges are summarized.

This paper proposes a double-end sourced layout for multichip SiC MOSFET power module adopting conventional wire-bonded packaging technology. The unique design provides each MOSFET with two parallel commutation loops by incorporating a symmetrical pair of dc-bus terminals into the power module. This new layout provides symmetrical equivalent power loops to each paralleled MOSFET and thus enables consistent switching performances and equal dynamic current sharing for the paralleled MOSFETs. Compared to the conventional design, the proposed design reduces the equivalent power-loop stray inductance by more than 50% and achieves improved dynamic current sharing among devices. By mitigating the imbalance of the switching current, the new module design demonstrated reduced temperature differences among devices and decreased near-field radiation noise level compared to the conventional layout. These features can further help to improve the power module density by shrinking the heat sink and integrating the gate driver board with the power modules. In this paper, an analytic model has been proposed for fast prediction of the near-field radiation from the power module. Detailed design procedures and experimental validations are also included in this paper.

Asymmetries in permanent magnet synchronous machines (PMSM) can result from manufacturing tolerances or optimization techniques that deliberately introduce them on rotor, stator, or both. This paper analyzes the impact of such unbalance on the air gap pressure, that is radial and tangential to the direction of motion, by means of Maxwell Stress Tensor; also, their consequences on torque pulsations and unbalanced magnetic pulling. Neglecting the manufacturing variations in the analysis of high power density PMSMs underestimates the resultant torque ripple. Additionally, new vibration modes occur due to unbalanced radial pressure. On the other hand, a geometry optimized to minimize torque ripple through controlled asymmetry is investigated, the approach compensates harmonics in torque effectively, but such compensation does not have the same effect on radial forces. Finite element analysis and experimentation are used to support the analysis and it is found that an asymmetric PMSM with low torque ripple will not necessarily produce lower vibrations and noise.

This paper presents a high-temperature (HT) gate drive and protection circuit for Silicon-Carbide (SiC) power mosfets entirely built from commercial off-the-shelf HT discrete components. To estimate cost reduction, a brief comparison was made between the proposed circuit and a commercial circuit using silicon-on-insulator integrated circuits. To evaluate performance, power tests were conducted up to 180°C in a thermal chamber. Eventually, the proposed circuit achieved a 90% cost reduction, and all functions were validated by experiments at 180°C. This demonstrated that the proposed circuit is a cost-effective solution for contemporary HT applications.

In the production of surface-mounted permanent magnet machines, manufacturing tolerances also contribute to torque ripple. Additional harmonics of low electrical orders are created in the torque spectrum. Slight manufacturing variations develop asymmetry conditions in the rotor as well as in the stator. Finite element models can be used to analyze the magnitude of pulsating torque generated due to these asymmetries. However, due to its random nature, lack of periodicity, and symmetry, it is time consuming to study the problem with numerical methods for its uneven geometry that does not allow reduced geometrical models. Moreover, the experimental verification of all possible variations would be very challenging as it would require part dimensioning and part sorting a large quantity of motor builds and finally testing of all samples. Therefore, in this paper an analytical model is presented to study the effect of such imbalance on the torque ripple. The model shows an agreement against finite element models and also with experimental results when predicting torque harmonics that come from asymmetries.

In a mass production environment, due to the manufacturing tolerances, additional orders of cogging torque are created in addition to the fundamental components. The tolerances lead to asymmetry conditions both in the rotor as well as in the stator. Finite-element models can be used to analyze the cogging generated due to these asymmetries. However, it is extremely time consuming to study this uneven geometry numerically since periodicity and symmetry conditions cannot be used to reduce the model. Moreover, the experimental verification of all possible variations would be very challenging, as it would require part dimensioning, part sorting, a large quantity of motor builds, and finally testing of all samples. Therefore, in this paper, an analytical model is presented to study the effect of such imbalance on the cogging torque. The model is validated against finite-element models and also with experimental results.

Power conversion from ultravoltage direct current (UVdc) to ultravoltage alternating current (UVac) is the biggest challenge facing industrial power application companies. Converting UVdc transmission systems with 2200 kV dc and distance up to 3000 km into UVac is the most challenging issue associated with transmitting power by UVdc transmission systems. This paper proposes an approximated arm energy control algorithm for a modular multilevel converter with a large scale of submodules per arm to convert UVdc of 2200 kV and more into UVac in order to achieve total harmonics distortion for UVac systems of $N$ ) is derived first. Second, the flooring switching pulsewidth modulation is explained in order to generate the number of inserted and bypassed submodules per arm. Third, submodules’ selections are proposed and verified by the simulations. Fourth, a set of simulation results for a dc bus of 2200 kV and 481 levels for the output voltage conducted in the MATLAB/Simulink environment are presented to verify the proposed algorithm. Finally, the proposed algorithm is experimentally verified by the hardware and software designs of the prototype.

Application of electric machines in the traction and transmission systems of hybrid/electric vehicles has been studied for many years. The hybrid vehicle based on dual mechanical port (DMP) electric machine has gained more and more attention, because it eliminates the need for planetary gear and combines the motor and the generator into a compact electric machine. The DMP machine with a squirrel-cage outer rotor (SCDMP) is investigated in this paper. Due to its unique electromagnetic characteristics, control algorithms for conventional machines cannot be applied to the SCDMP machine. The methods to calculate the correct current commands and estimate the outer rotor flux position are proposed. Based on these two methods, a control algorithm for the SCDMP machine is proposed and estimated by simulation. The results show that the proposed control algorithm is able to independently control the torque productions and the flux levels of the two rotors of the SCDMP machine.

A new type of electric machine with two free rotating rotors [dual mechanical port (DMP)] is investigated in this paper. Since this DMP machine has a squirrel-cage outer rotor, it is named as SCDMP machine. First, the electromagnetic characteristic of the SCDMP machine is analyzed. Then, the transient model and steady-state model of the SCDMP machine are derived. The proposed machine models are verified by finite element method and simulation. The results show that the proposed models accurately represent the unique electromagnetic characteristics of the SCDMP machine.

This paper focuses on a novel modeling method for interior permanent-magnet (IPM) synchronous machines. This modeling method is based on a stator winding flux linkage table that is obtained from experimental testing. As indicated by the comparison between computer simulation and dyno testing, this modeling approach can model the nonlinear behavior of IPM synchronous machines with high fidelity without adding significant computational loads.

An optimally designed ferrite permanent magnet (PM)-assisted synchronous reluctance machine (PMaSynRM) is presented to demonstrate its feasibility in electric vehicle applications. The Prius rare-earth interior PM machine is used as the benchmark, and through theoretical study and experimental testing, it is verified that the optimally designed PMaSynRM can achieve performance very close to that of the benchmark PM machine with much lower costs.

In power electronics drive systems, dead time is used to prevent shoot-through over power devices. However, dead time can lead to distortion of ac output voltages and currents. Various compensation methods have been proposed to overcome this drawback. However, most strategies assume the power switches as ideal switches and the transition from ON to OFF or vice versa is infinitely fast. In this paper, effects of inverter snubber and parasitic capacitance to the switching instants are investigated when doing dead-time compensation. A new dead-time compensation method is presented with the capacitance being considered. It is verified that the compensation becomes more accurate and effective for the specific application after the modification. It is also shown that the proposed compensation can make the inverter system stable and robust. This proposed approach is validated by the experimental results.

The capabilities of peak power and continuous power are the main concerns for electrified vehicles. To achieve good acceleration on uphill climbing, improved peak power density is necessary. The motor's peak power is determined by the maximum allowable temperature of the motor package. If the temperature at peak output power can be kept low, then a higher peak power is achieved. The major purpose of thermal management is to control both the heat generation and dissipation. Therefore, to maximize the interior permanent magnet (IPM) motor peak power capability, the losses or heat generation among the various key components, such as the windings, stator core, and magnets, should be reasonably distributed.

With the proposed dual-current-loop control algorithm, the torque and air-gap flux of a doubly fed induction motor are controlled directly. Compared to the singly fed permanent magnet and induction motors, the torque-speed operation region for electric vehicle/hybrid electric vehicle applications is nearly doubled with the proposed dual-current-loop control algorithm for a given battery voltage. Computer simulations and experimental results are provided to verify the proposed control algorithm.

In the widely applied non-direct driven wind power generation system, a gearbox is connected between the wind turbine and the high speed doubly-fed induction generator (DFIG) so that the system could be smaller and supply power with constant voltage and constant frequency as the wind turbine speed varies. However, the multi-level mechanical gearbox is rather vulnerable and poses many difficulties to maintain. Electrical variable transmission (EVT), an electrical continuous variable gearbox, is a very competitive alternative for vulnerable constant speed-ratio mechanical gearbox. In this paper, the application of EVT in wind power generation system with its unique power conversion characteristics is presented. EVT machine structures and the main principles of the EVT-based wind power generation system are introduced. Unique power conversion characteristics of the EVT-based system are investigated and compared among the conventional DEIG system and direct-driven permanent magnet generator (PMG) system. A controller without maximum power point tracking (MPPT) control to the outer rotor is implemented in Matlab/Simulink and speed sensorless control of the inner rotor is tested. The operational principle and the operation modes are evaluated by computer simulation and system experiments.

A 1000 kW/19 200 rpm wound-rotor synchronous machine has been designed as a draft based on 2-D transient finite-element method (FEM). The magnetic fields distribution, the iron losses, the electromagnetic torque and the terminal characteristics of the prototype machine are investigated in this paper by using 2-D finite element analysis. The d-axis inductance Ld and the q-axis inductance Lq of the sample machine are predicted in analytical models. All studies indicate that the wound-rotor synchronous machine is potential to apply in high speed generator or motor application.

This paper introduces a new method to solve the sensorless control problem for a grid-connected doubly fed induction machine (DFIM). The proposed method is based on high-frequency signal injection and the fact that the rotor of a DFIM can be seen as the rotating secondary of an induction transformer. The commonly used sensorless technique based on stator-flux linkage, aside from being parameter sensitive, does not work during fault ride through (FRT) conditions. Nevertheless, the proposed method is parameter independent and remains fully functional during FRT conditions. Moreover, as opposed to other high-frequency injection methods, the proposed method does not require rotor saliency. The mathematical principle of the proposed technique and its implementation are presented. Computer simulations and initial experimental results are also included for verification.

Indirect field-oriented control, direct field-oriented control, and direct torque control are the most widely used instantaneous torque control techniques for the drive system of alternative energy vehicles (AEVs). This paper evaluates three candidate alternating-current machines and investigates the suitability of different control techniques for the drive systems of battery-powered electric vehicles, hybrid electric vehicles, and integrated starter alternators. Accurate flux and torque estimation is the core of any opted control technique for all types of AEV drive systems. Therefore, an accurate closed-loop voltage model flux and torque estimator that is insensitive to stator resistance variation has been designed. This paper also analyzes loss model control and search control (SC) techniques for the drive system's efficiency optimization and proposes an offline SC efficiency optimization technique. Experimental results are presented to demonstrate the performance of the proposed flux and torque estimator and efficiency optimizer.

This paper analyzes critical control issues associated with the deep field weakening operation of interior permanent magnet (IPM) synchronous machines. The singlecurrent-regulator control algorithm is reviewed, which controls the d-axis current actively and gives a fixed q-axis voltage command. To achieve better operational efficiency and performance, improvements are made to choose an optimal q -axis voltage for variable-speed and variable-load conditions. The control algorithm is implemented on a 50-kW IPM machine. Test results, including 7:1 constant power speed ratio operation, are presented to verify the theoretical analysis.

Low power density is an obstacle of linear switched reluctance machines (LSRMs) to be competitive candidates for the wave energy conversion, which is increasingly a potential source of renewable energy. Meanwhile, the strong coupling and nonlinearity of LSRMs and drives make it very difficult to derive a comprehensive mathematical model for the behavior of the system. This paper presents a new excitation winding configuration to improve the power density and proposes a new method to model the LSRM and drive based on the matrix and tensor approach. The accuracy of the model has been evaluated by comparison to the simulation result from the finite element analysis tool.

Dual mechanical port (DMP) machine, a continuous electrical variable transmission, is a very competitive alternative for vulnerable constant speed-ratio mechanical gearbox. In this paper, an optimal design method of a double-layer permanent magnet (PM) DMP machine for wind power application with random low wind turbine speed input and constant high synchronous speed output is proposed. With the stator efficiency and the cooling effect of the inner rotor as reference, an analytical model is built for the initial design of the machine and the finite element analysis (FEA) is investigated for optimization. Then, FEA results are given and the over-load capability of the machine is evaluated. Finally, a 10 kW DMP prototype machine with the cooling system is designed.

In this article, the various possible structures of a dual mechanical port (DMP) electric machine are explored and operation features discussed. Further, dynamic modeling of the DMP electric machine is presented. In particular, the salient features and suitability of DMP machine to hybrid electrical vehicles (HEVs) are discussed.

A new sensorless field-oriented control of direct-drive permanent-magnet synchronous motors based on ldquosliding moderdquo has been studied and applied to domestic washing machine drives. To achieve speed control requirements for the application, a novel sliding-mode observer has been developed by applying the technique of feedback of the ldquoequivalent control.rdquo Armed with the developed algorithms, this observer is able to minimize the estimation error of rotor position at low speeds and guarantee fast convergence of the observer at high speeds in the flux-weakening region. As such, this sensorless control is suitable for domestic washing machine drives demanding wide-speed-range operation. The proposed sensorless control algorithms are implemented in a cost-effective digital controller and tested in a selected prototype washing machine. Both computer simulation and experimental results are illustrated for verification.

In an advanced full hybrid electrical vehicle (HEV), the small IC engine runs only in a narrow speed range for the highest energy efficiency. A continuous variable transmission (CVT) based on planetary gear set is used to integrate the IC engine and two electric machines into the drive train so that the engine can be always at the highest efficiency speed while the vehicle is allowed to run at any desired speeds. However, the two electric machines and a planetary gearbox plus two power inverters make the HEV drive train much complicated and bulky in size. In this paper, the newly invented dual mechanical port (DMP) electric machine with multi-operational modes and control strategies are presented for HEV use. This single DMP machine realizes full functions of a conventional hybrid electrical vehicle traction system without the planetary gear set. The novel control algorithms are evaluated by computer simulation and prototype design.

This paper discusses the problems of current decoupling control and controller tuning associated with sensorless vector-controlled induction-motor (IM) drives. In field-oriented control, the d-q synchronous-frame currents should be regulated to have independent dynamics such that the torque production of the IM resembles that of a separately excited dc motor. However, these currents are not naturally decoupled, and decoupling compensators should be used. Current loop tuning is an additional problem, since controller gains obtained by theoretical methods or simulation, quite often, do not work well on the real system. This paper proposes a new approach for current control that uses integral-sliding-mode (ISM) controllers to achieve decoupling. The synchronous-frame control voltages are synthesized as the sum of two controller outputs: a traditional one (PI) that acts on an ideal plant model and an ISM controller. The ISM controller decouples the d-q currents and compensates the parameter variations in the current loops of the machine. Simulations and experimental tests on a 0.25-hp three-phase induction machine show satisfactory results.

High-frequency current responses of a permanent magnet synchronous machine (PMSM), with and without considering eddy current effects, are significantly different. This paper investigates the eddy current effects on rotor position estimation. A compensation method is developed to improve the high-frequency-injection-based rotor position estimation of a PMSM at zero and low speeds. The paper also contributes to an improved magnetic pole identification based on space vector pulse width modulation for an arbitrary initial rotor position. The estimation and sensorless control method of PMSM, considering eddy current effects, has been verified by experimental results.

This paper presents sliding mode pulsewidth modulation (SMPWM) control methodologies for a current-controlled inverter. Discussion begins with circuit analysis and the selection of proper references. Based on this formulation, switching methodologies are developed. Two novel approaches adopting the sliding mode concept are proposed to make the system tracking reference inputs. Phase currents and the neutral point voltage are controlled simultaneously. Optimization of different operational criteria is offered by SMPWM via the control of neutral point voltage. Simulations and experiments are carried out to confirm the effectiveness of proposed control algorithms.

This paper contributes to the AC small signal modeling and analysis of Z source converter (ZSC) in continuous conduction mode. The AC small signal model considers the dynamics introduced by Z network uniquely contained in ZSC. AC small signal model of ZSC is derived and computer simulation results are used to validate the small signal modeling method. Various applications of the AC small signal models to ZSC design and experimental verifications are presented.

This letter presents a current control technique for fast transient-current response in a sensorless vector-controlled permanent magnet synchronous motor. Pontryagin's maximum principle is employed to derive the time-optimal voltage solution. Based on this principle, the technique can guarantee the current vector transition from one operating point to another with minimum time. Compared to a proportional-integral controller, the current response by using the time-optimal controller is much faster, even under a limited dc bus voltage. Experiments are carried out to substantiate the proposed technique

This paper proposes fault tolerant operation strategies for three-level neutral point clamped pulsewidth modulation inverters in high power, safety-critical applications. Likely faults are identified and fault tolerant schemes based on the inherent redundancy of voltage vectors are presented. Simulation verification is performed to show fault handling capabilities. Prototyping and principle investigation are performed on a 150-KW inverter and testing results are presented.

Sensorless direct field-oriented (SDFO) control of three-phase induction motors based on "sliding mode" has been studied and applied to domestic washing-machine drives. In this paper, three related techniques, sliding-mode flux observer, sliding-mode speed controller, and direct rotor-speed estimator are presented for the application of SDFO "sliding mode" in induction-motor control system. Specifically, the investigations focus on how improving speed regulation, system robustness, and some special technical issues in washing-machine drives. The complete control schemes have been developed and implemented in a low-cost digital signal processor-based electronic controller. Through a variety of system performance validation tests, it has been proved that the developed SDFO control not only achieves satisfied steady as well as a dynamic performance, but also is robust for washing-machine driving applications.

This paper presents an improved method of flux estimation for sensorless vector control of induction motors based on a phase locked loop (PLL) programmable low-pass filter (LPF) and a vector rotator. A PLL synchronized with the voltage vector is used for stator frequency estimation. The pure integration of the stator voltage equations is difficult to implement and LPFs with a fixed cutoff provide good estimates only in the relatively high frequency range-at low frequencies, the estimates fail in both magnitude and phase. The method proposed corrects the above problem for a wide range of speeds. Simulations and experimental results on a 0.25-hp three-phase induction machine verify the validity of the approach.

This paper presents two novel sliding mode (SM) model reference adaptive system (MRAS) observers for speed estimation in a sensorless-vector-controlled induction-machine drive. Both methods use the flux estimated by the voltage model observer as the reference and construct SM flux observers that allow speed estimation. Stability and dynamics of the two proposed SM flux observers are discussed. The observers are compared with the classical MRAS observer. The proposed estimators seem very robust and easy to tune. Unlike the classical MRAS, the speed-estimation process is based on algebraic calculations that do not exhibit underdamped poles or zeros on the right-hand plane. Simulations and experimental results on a 1/4-hp three-phase induction machine confirm the validity of the approaches.

An adaptive sliding mode flux observer is proposed for speed sensorless vector control of induction motors. Two sliding mode current observers are used in the method to make flux and speed estimation robust to parameter variation. Adaptive speed estimation is derived from the stability theory. The stability of adaptive flux observer is guaranteed by Lyapunov stability theory. The system is first simulated by MATLAB and HIL (hardware-in-the-loop). Then it is implemented based on TMS320F2812, a 32-bit fixed-point DSP controller. Simulation and experimental results are presented to demonstrate the potentials and practicality of the approach.

A novel approach for sensorless control of PM machines down to zero speed without signal injection or special PWM techniques is developed in this paper. Taking advantage of the low inductance, the current ripples of a PM machine under a conventional PWM excitation are measured to derive the information about the rotor position by inductance calculation or back-EMF estimation. This approach can be used to estimate the rotor position at standstill if the rotor saliency exists. No prior knowledge about the machine parameters is needed and no special detecting signal is injected to the machine in this approach. Sensorless control of a PM machine based on the proposed strategy has been investigated by comprehensive computer simulation. The experimental testing results verify the effectiveness of the proposed approach.

A new closed loop current model flux observer is designed to estimate the rotor flux, position and velocity of an induction machine. The current observer includes carefully designed sliding mode functions which are derivative of the fluxes along the /spl alpha/ and /spl beta/ axes. Therefore, when the estimated current converges to the measured one, the flux estimation is a mere integration of the sliding mode function. The rotor speed can then be derived from the sliding mode functions and the estimated flux. In the current and flux observers all of the terms that contain the rotor time constant and the rotor speed have been replaced by the sliding mode functions, thus making the proposed current and flux estimations completely insensitive to the rotor time constant variation and any error in the estimated speed. Simulations and experiments are performed under a variety of conditions to validate the effectiveness of the proposed algorithm.

In this letter, a new sliding-mode-sensorless control algorithm is proposed for the field-oriented induction machine drive. In the proposed algorithm, the terms containing flux, speed, and rotor time constant, which are common in both current and flux equations, in the current model of the induction machine are estimated by a sliding function. The flux and speed estimation accuracy is guaranteed when the error between the actual current and observed current converges to zero. Hence, the fourth-order system is reduced to two second-order systems, and the speed estimation becomes very simple and robust to the parameter uncertainties. The new approach is verified by simulation and experimental results.