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This paper investigates single stage boost-inverter integrated electric drives for HEV applications by integrating boost function in inverters of electric drives. In the discussed systems, battery is combined with generator/motor stator windings, so inverters control generator/motor and battery to achieve their bidirectional power flows, meanwhile, boost battery voltage to a high level on de bus. A control strategy is proposed to ensure drive system with high performance. The topologies, operational principle, detailed analysis, modulation and control method included in the paper thoroughly explain this kind of boost-inverter integrated electric drive systems. A simulation example is illustrated to verify the discussed electric drives and control method.

High performance or heavy weight electric vehicles (EVs) require high power electric drive (e-drive) systems. However, availability of automotive qualified power devices with demanded high voltage and high current ratings are limited. Devices and inverters in series and/or in parallel are typical and effective solutions to achieve high power output capability. This paper investigates high power traction inverter design, from a practical point of view, through providing three options for EV applications. The three circuit topologies are described firstly. Typical modulation methods are reviewed, and optimal approaches are proposed to minimize DC bus capacitor ripple current. Inverter total loss and key components sizing are compared in detail. Simulation results verify the proposed high power traction inverter design and theoretical analysis.

Mandatory regulations worldwide are being adopted by several countries to accelerate the motor market transformation toward Premium/IE3 and Super-Premium/IE4 efficiency classes. However, besides the motor energy efficiency, there are other important operation issues in the scope of the modern industrials plants which also have to be taken into account when deciding for a high-efficiency motor, such as motor reliability, protection, maintenance, reactive power, operating speed, starting torque, and torque-speed capability. In this paper, key considerations on the reliability and operation of high-efficiency motors are presented, offering a comprehensive perspective on the advantages, drawbacks and limitations of high-efficiency industrial motors. A comparison of the lifetime expectancy of IE2-, IE3- and IE4-Class motors under unbalanced and distorted voltage supply is presented. It is also demonstrated how moving to a higher efficiency class can avoid investing in a larger motor. As far as the authors know, this is the first time this analysis on different classes of very high-efficiency motors is presented.

The quasi-Z source (qZS) cascaded multilevel inverter (CMI) (qZS-CMI) presents attractive advantages in application to photovoltaic (PV) power system. Each PV panel connects to an H-bridge qZS inverter (qZSI) to form a power generation module. The distributed maximum power point tracking and all modules' dc-link peak voltage balance can be achieved. However, it is the same with the conventional CMI that the second-harmonic (2ω) voltage and current ripples exist in each qZSI module. It is crucial for a qZS-CMI to design the reasonable qZS network parameters to limit the ripples within a desired range. This paper proposes an analytic model to accurately calculate the 2ω voltage and current ripples of each qZSI module. A qZS impedance design method based on the built model is proposed to limit the 2ω ripples of dc-link voltage and inductor current. Simulated and experimental results through using the designed 1.5-kW prototype validate the proposed analytic model and the design method. Furthermore, this paper analyzes all of the operating states for a qZSI module and calculates the power loss. The measured efficiency from the prototype verifies the theoretical calculation, and the qZS-CMI-based grid-tie PV power system is tested in practical. © 1982-2012 IEEE.

This paper proposes a new four-quadrant adjustable speed drive (ASD) system based on an induction motor fed by a three-phase quasi-Z-source direct matrix converter (QZSDMC). The quasi-Z-source (QZS) network is used to overcome the limitation of the voltage gain of the traditional direct matrix converter (DMC). The QZSDMC can provide a buck-boost operation by controlling the shoot-through (ST) duty ratio. In addition, this paper presents a four-quadrant speed control method based on vector control technique which is able to control the motor speed from zero to the rated speed with the full load torque during motoring and regenerating operation modes. The simulation results validate the proposed QZSDMC based adjustable speed drive system. The proposed ASD system overcomes the voltage gain limitation of the traditional direct matrix converter with improved efficiency and higher readability compared to the traditional back-to-back converter configuration.

Three-phase line-start permanent magnet motors (LSPMs) are a recent entrance in the marketplace. In general, such motors are designed to meet IE4/Super-Premium Class requirements. As with squirrel-cage induction motors, LSPMs can benefit in terms of efficiency and power factor from a proper magnetizing flux regulation as a function of load. This is important to improve the motor performance when it is oversized and/or driving variable-load fixed-speed applications. In this paper, an experimental study on the improvement potential of steady-state partial-load efficiency and power factor in special multi-connection LSPMs with up to six different flux levels, is presented. Some novel conclusions are offered regarding the efficiency and power factor gains and connection mode management rules, including the delta-star change in conventional 6-terminal LSPMs. With the proposed solutions, efficiency gains of 6–8 percentage points and power factor gains of 0.4–0.5 points can be obtained at light partial loads, which represents a very significant performance improvement. Moreover, it is demonstrated that reactive power injection into to the mains grid is possible with LSPMs.

The use of variable-speed drives (VSDs) is increasing fast. The operation and the output voltage quality of such devices can be significantly affected by power supply voltage sags and continuous unbalance, ultimately influencing the performance of the controlled motor. This paper presents an analysis of the impact of such power supply anomalies on VSDs with 3-phase diode rectifier and PWM voltage-source inverter, which are the most used in the low/medium power range. In VSD applications requiring ride-through capability to voltage sags, the investment in extra DC-bus capacitance can be cost-effective, particularly when the motor driven system stop leads to significant injuries, including loss of production. The extra DC-bus capacitance also improves the output voltage in VSDs fed from unbalanced power supplies.

Applications of switched reluctance motor (SRM) to direct drive robot are increasingly popular because of its valuable advantages. However, a greatest potential defect its torque ripple owing to the significant nonlinearities. In this paper, a fuzzy neural network (FNN) is applied to control the SRM torque at the goal of the torque-ripple minimization. The desired current provided by FNN model compensates the nonlinearities and uncertainties of SRM. On the basis of FNN-based current closed-loop system, the trajectory tracking controller is designed by using the dynamic model of the manipulator, where the torque control method cancels the nonlinearities and cross-coupling terms. A single link robot manipulator directly driven by a four-phase 8/6 pole SRM operates in a sinusoidal trajectory tracking rotation. The simulated results verify the proposed control method and a fast convergence that the robot manipulator follows the desired trajectory in a 0.9-s time interval.

An effective control solution for speed sensorless vector control of induction motor fed by a cascaded neutral point clamped (NPC) inverter is proposed, where the novel SPWM pulse rotation control approach provides a simple way to implement vector control for induction motor when the cascaded NPC inverter is employed. The single carrier is used in the novel pulse control, instead of the multi-carriers, which makes the voltage modulation simpler and the hardware burden decrease. It is of great benefits to the cascaded NPC inverter, i.e., the output voltages and powers of all inverter modules, and two series-capacitor dc voltages of each inverter module are perfectly balanced, and a low switch frequency of all inverter modules provides a synthesized high frequency PWM phase voltage. A rotor flux-oriented vector control is combined with back EMF-based MRAS speed estimation, which results in a speed closed-loop control. The voltage sensors together with the filters of changeable parameters ensure the precision of speed estimation for the whole frequency range. The proposed scheme is applied to control an 800kW 4160V induction motor fed by the 1MVA 6000V 17-level cascaded NPC inverter, where the controller mainly consists of one DSP and one CPLD. The experimental results verify the proposed scheme.

A 1 MW/6000 V cascaded neutral point clamped (NPC) inverter is developed for medium voltage high power induction motor drives and an effective control technique is proposed in this paper. A pulse rotation method of SPWM is implemented for a wide range of output voltage. The output voltage and power, and series-capacitor DC voltage of each module are perfectly balanced with switching at a low frequency while providing synthesized high frequency PWM phase voltage. The internal voltage drop of the inverter, due to the cascade structure of many IGBT-diode modulespsila series connection, is analyzed, which causes distorted phase voltages and currents at low speeds when the frequency and output voltage are low. The current closed-loop control compensates the distortion of phase voltages and currents. The speed closed-loop system based on the vector control is designed. The proposed scheme is applied to control an 800 kW/4160 V induction motor fed by the 1 MVA 6000 V 17-level cascaded NPC inverter. The experimental results verify the proposed scheme.

The three-phase, squirrel-cage, induction motor (IM) is the most used type of electrical motor in industry. Nowadays, energy recovering during deceleration or breaking periods is a well-explored technique in IMs fed by converters, incorporating special rectifier/inverter input stages, allowing energy to be injected back into the power grid. However, for line-fed IMs, during stopping or deceleration period, after disconnecting the power supply, the energy stored in the system inertia is, in general, not recovered. In this paper, a novel principle to recovery energy during stopping period in line-fed, multi-speed IMs, based on the stator connection change from a lower pole-number mode(s) to a higher pole-number mode(s), is proposed. The principle is described and a connection mode management strategy is proposed, on the basis of preliminary simulations. Considerations on the stator windings are made and the final prototype of an electronic device for the stator winding connection mode management is also briefly described.

In this paper, the consequences of steady-state voltage supply anomalies on the behavior, losses and operating limits of low-power, low-voltage, three-phase, squirrel-cage induction motors is presented. The study is mainly based on simulations and previously published works, but experimental results are also presented. The well-known motor derating curves proposed by NEMA are questioned. It is demonstrated that they are too general, and do not consider combined effects of voltage unbalance, magnitude deviation, and distortion. Additionally, the effects of ambient temperature and motor characteristics (e.g. rated power, frame type, rotor type and efficiency class) should also be considered. Another important issue discussed in this paper is the fact that voltage unbalance and voltage distortion definitions should be properly revised in order to eliminate ambiguities. A clear methodology to evaluate the impact of the referred power anomalies on motors is proposed. An artificial neural network-based approach for mathematical description of motor derating curves as a function of multiple variables is also proposed and validated. Several relevant considerations on motor simulation within power quality scope are presented.

Most oversized three-phase induction motors operate with low efficiency and power factor, which is by far the most important cause of poor power factor in industrial installations. In the low-load operating periods, motor performance can be improved both in terms of efficiency and power factor through stator-winding connection change from delta to star. In this paper, a new low-cost electronic device for automatic change of the stator-winding connection for efficiency and power factor improvement in variable-load three-phase induction motors is proposed and experimental results are presented. Some technical and economical considerations related to the final application of the device are discussed. The proposed device is particularly suitable for low-medium power three-phase induction motors, with significant load variation during their duty-cycle, including long, low-load operating periods. The application of the proposed device in such motors can lead to significant energy savings and to the power factor improvement, largely compensating the additional modest investment in the device. The importance of this work is highlighted by the recent concerns about the need to achieve energy savings in the industrial and in the tertiary sectors

Robust controllers which are designed by employing discrete-time reaching law control (RLC) and internal-model control (IMC) are presented for permanent magnet synchronous motor (PMSM). They are to achieve accurate control performance in the presence of uncertainties and plant parameter variation. As the powerful technique to control the nonlinear and uncertain systems, IMC is applied to PMSM current control. The synchronous-frame PI-type IMC controller greatly improves the performances of the current loop and simplifies the design procedure. The RLC-based speed controller is proposed, and the design equations are derived in the discrete time since the discrete time analysis and design is more appropriate for the digital control applications. The robustness of RLC-based speed controller is analyzed, and the bounds of control parameters that ensure the drive stable are obtained. Simulation results verify the proposed control methods for PMSM.