This paper presents a review of recently used direct torque and flux control (DTC) techniques for voltage inverter-fed induction and permanent-magnet synchronous motors. A variety of techniques, different in concept, are described as follows: switching-table-based hysteresis DTC, direct self control, constant-switching-frequency DTC with space-vector modulation (DTC-SVM). Also, trends in the DTC-SVM techniques based on neuro-fuzzy logic controllers are presented. Some oscillograms that illustrate properties of the presented techniques are shown.

Direct torque control of PWM inverter-fed AC motors - a survey

With the advent of more stringent regulations related to emissions, fuel economy, and global warming, as well as energy resource constraints, electric, hybrid, and fuel-cell vehicles have attracted increasing attention from vehicle constructors, governments, and consumers. Research and development efforts have focused on developing advanced powertrains and efficient energy systems. This paper reviews the state of the art for electric, hybrid, and fuel-cell vehicles, with a focus on architectures and modeling for energy management. Although classic modeling approaches have often been used, new systemic approaches that allow better understanding of the interaction between the numerous subsystems have recently been introduced.

https://www.eee.hku.hk/doc/ccchan/Electric,%20Hybrid,%20and%20Fuel-Cell%20Vehicles-%20Architectures%20and%20Modeling.pdf

Electric, Hybrid, and Fuel-Cell Vehicles: Architectures and Modeling

Doubly fed induction generators (DFIGs), often organized in wind parks, are the most important generators used for variable-speed wind energy generation. This paper reviews the control systems for the operation of DFIGs and brushless DFIGs in wind energy applications. Control systems for stand-alone operation, connection to balanced or unbalanced grids, sensorless control, and frequency support from DFIGs and low-voltage ride-through issues are discussed.

Overview of Control Systems for the Operation of DFIGs in Wind Energy Applications

This paper presents a new control strategy for the rotor-side converter (RSC) of wind turbines (WTs) based on doubly fed induction generators (DFIG) that intends to improve its low-voltage ride through capability. The main objective of this work is to design an algorithm that would enable the system to control the initial overcurrents that appear in the generator during voltage sags, which can damage the RSC, without tripping it. As a difference with classical solutions, based on the installation of crowbar circuits, this operation mode permits to keep the inverter connected to the generator, something that would permit the injection of power to the grid during the fault, as the new grid codes demand. A theoretical study of the dynamical behavior of the rotor voltage is also developed, in order to show that the voltage at the rotor terminals required for the control strategy implementation remains under controllable limits. In order to validate the proposed control system simulation, results have been collected using PSCAD/EMTDC and experimental tests have been carried out in a scaled prototype.

/pdf/rotor-voltage-dynamics-in-the-doubly-fed-induction-generator-308fc5ja1p.pdf

Rotor Voltage Dynamics in the Doubly Fed Induction Generator During Grid Faults

The use of AC electrical machines in controlled electrical drive applications is reviewed. The major types of electrical machines are briefly summarized to set the context and establish the physical basis for the control techniques used. Machine properties, which are the key to successful control, can be obscured by the necessary mathematics required for machine analysis and control scheme derivations. The main focus of this paper is on control techniques which are being applied to make AC drives a rapidly growing area. Development of the control is discussed, with concentration on recent trends suitable for practical applications in the industry with good dynamic behavior. A particular feature is the increasing importance of speed or position sensorless techniques.

/pdf/controlled-ac-electrical-drives-1ttwuo7kop.pdf

Controlled AC Electrical Drives

AC machines supplied in parallel by a common voltage source inverter are sometimes used in industrial drives and railway traction applications. This reduction of power and control electronics leads to a reduction of cost, weight, and dimensions that is very useful for on-board systems. But this common supply imposes common voltages to all machines and the possibilities of independent behavior are reduced. In this paper, a graphical modeling is suggested to model such parallel drives for a railway application. A weighted control is then systematically deduced from this modeling and different possibilities of control are highlighted. Experimental results are provided to compare two of the deduced controls

Weighted Control of Traction Drives With Parallel-Connected AC Machines

A formalism is defined to describe systems composed of several electrical machines with several electrical and/or mechanical converters. So, a first classification of multi-converter multi-machine systems is proposed in order to point out their influences on the global power conversion: cost reduction, conversion quality... Three examples are presented with this specific formalism.

Multi-converter multi-machine systems: application for electromechanical drives

The main idea developed in this paper is a novel biconverter structure to supply a doubly fed induction machine (DFIM). Two voltage source inverters (VSIs) feed the stator and rotor windings. The outputs of the two VSIs are combined electromechanically in the machine, and as a result, novel features can be obtained. For example, for high power drive applications, this configuration uses two inverters dimensioned for a half of the DFIM power. A new dual direct torque control is developed with flux model of DFIM. Two switching tables linked to VSI are defined for stator and rotor flux vector control. The satisfactory experimental and simulation results are shown, and they confirm good dynamic behavior in four quadrants of the speed-torque plane. Moreover, experimental results show the correct flux vector control behavior and speed tracking performances.

/pdf/dual-direct-torque-control-of-doubly-fed-induction-machine-15xim8pp6b.pdf

Dual Direct Torque Control of Doubly Fed Induction Machine

High speed permanent magnet synchronous motors (PMSMs) are used in electric vehicles because of their intense power density The high speed implies a significant electromotive force and requires flux weakening The usual control algorithms realize flux weakening by adding a negative $I_{d}$ current component when the voltage required by the current regulation exceeds the maximum voltage depending on the battery If the magnet can be totally defluxed, then it is better to use a maximum torque per volt strategy Furthermore, there is no speed regulation in the control and the driver gives a torque reference This reference value has to be limited by the attainable operating points; therefore, the battery power limit has to be taken into account in addition to the voltage and current limits The d–q current references are calculated to minimize the total current magnitude required to reach the reference torque This paper proposes a strategy to control a PMSM operating continuously since the speed zero up to the maximum speed without the switching algorithm, in order to take into account the different limitations (current, voltage, and power) and to expand the overspeed zone In order to validate the proposed strategy, experimental results are shown for a low power machine

Maria Pietrzak-David

Papers

Weighted Control of Traction Drives With Parallel-Connected AC Machines

Multi-converter multi-machine systems: application for electromechanical drives

Dual Direct Torque Control of Doubly Fed Induction Machine

MTPV Flux-Weakening Strategy for PMSM High Speed Drive

Control structures for multi-machine multi-converter systems with upstream coupling