This paper presents a comprehensive study on the state-of-the-art and emerging wind energy technologies from the electrical engineering perspective. In an attempt to decrease cost of energy, increase the wind energy conversion efficiency, reliability, power density, and comply with the stringent grid codes, the electric generators and power electronic converters have emerged in a rigorous manner. From the market based survey, the most successful generator-converter configurations are addressed along with few promising topologies available in the literature. The back-to-back connected converters, passive generator-side converters, converters for multiphase generators, and converters without intermediate dc-link are investigated for high-power wind energy conversion systems (WECS), and presented in low and medium voltage category. The onshore and offshore wind farm configurations are analyzed with respect to the series/parallel connection of wind turbine ac/dc output terminals, and high voltage ac/dc transmission. The fault-ride through compliance methods used in the induction and synchronous generator based WECS are also discussed. The past, present and future trends in megawatt WECS are reviewed in terms of mechanical and electrical technologies, integration to power systems, and control theory. The important survey results, and technical merits and demerits of various WECS electrical systems are summarized by tables. The list of current and future wind turbines are also provided along with technical details.

High-Power Wind Energy Conversion Systems: State-of-the-Art and Emerging Technologies

An electric traction vehicle is described herein which may be used to provide power to off-board electric power-consuming systems or devices. The electric traction vehicle may provide 250 kilowatts or more of three phase AC power to an off-board electric power consuming system. The electric traction vehicle may also include an electrical power storage device which can be selectively discharged to allow the vehicle to be serviced.

Control system and method for electric vehicle

The Matrix Converter (MC) evolved from the forced commutated cycloconverters and has been extensively investigated for more than thirty years. In this publication, the milestones in research on MCs in academia and industry are reviewed and presented chronologically and thematically ordered. The major contributions in the fundamental topic areas such as the development of the topology, topological extensions, commutation, modulation, loss calculation, control, or filtering and EMC are compiled and then expanded with examples of the latest activities in the corresponding field of research. In addition, an overview of the publicly reported research on MCs in industry is provided and the development of the commercialized MCs is briefly summarized. This review concludes with a comparison of the MC with the Voltage DC-Link Back-to-Back Converter (V-BBC) and a discussion of the current status of the MC technology and its future potential. The key contributions in the development of the MC can be summarized as follows: the investigation of the basic MC concept by Venturini in 1980 [19], the development of the multi-step commutation by Burany and Oyama et al in 1989 [64,65] to solve the commutation problem of the bidirectional switches, and finally the space vector representation of the modulation by Huber and Boroyevich in [80] to enable a consistent mathematical description of the converter system from the source to the load. With these fundamental features, the MC (CMC) is operational and can be used as a direct ac-ac converter with variable voltage and frequency transformation capability. The world’s first commercial MC was presented by the Japanese drive manufacturer Yaskawa in 2005 with the product name “Varispeed AC”. This converter series is based on the CMC topology and is implemented with RB-IGBTs. One year later in 2006, Fuji Electric announced also a new MC product, the Frenic-MX, which, however, is currently not anymore part of Fuji’s product portfolio. Meanwhile, Yaskawa extended their matrix converter product line with a medium voltage MC series. Despite intensive research for the last three decades, MCs have until now only achieved low market penetration with Yaskawa Electric as the only drive manufacturer currently offering MCs as commercial products. The reason for the low usage of the MC technology in industry is mainly due to the intrinsic, physical limitations given by the MC concept, such Fig. 1. Basic three-phase Matrix Converter topologies: (a) single-stage half-bridge or Conventional (direct) Matrix Converter (CMC) and (b) two-stage Indirect Matrix Converter (IMC)

Milestones in Matrix Converter Research

This paper proposes a new type of converter called a single-phase Z-source buck-boost matrix converter. The converter can buck and boost with step-changed frequency, and both the frequency and the voltage can be stepped up or stepped down. In addition, the converter employs a safe-commutation strategy to conduct along a continuous current path, which results in the elimination of voltage spikes on switches without the need for a snubber circuit. The operating principles of the proposed single-phase Z-source buck-boost matrix converter are described, and a circuit analysis is provided. To verify the performance of the proposed converter, a laboratory prototype was constructed with a voltage of 40 Vrms/60 Hz and a passive RL load. The simulation and the experimental results verified that the converter can produce an output voltage with three different frequencies 120, 60, and 30 Hz, and that the amplitude of the output voltage can be bucked and boosted.

A Single-Phase Z-Source Buck–Boost Matrix Converter

This paper is concerned on investigations in implementations of the Single-Phase Matrix Converter (SPMC) as a direct AC-AC converter subjected to passive load conditions. The output voltage was synthesized using the well-known Sinusoidal Pulse Width Modulation (SPWM) technique. A Xilinx Field Programmable Gate Array (FPGA) was used to implement the controlling algorithm with IGBTs as power switching device. Prior to hardware implementation, simulations were performed to predict the behaviour. A laboratory model test-rig of the SPMC was then developed to experimentally verify the result. Good agreement was obtained between simulations and experiments.

Implementation of Single-Phase Matrix Converter as a Direct AC-AC Converter with Commutation Strategies

A topology of a single-phase AC/AC direct power converter is presented. The circuit, composed from four ideal power switches, is used as a frequency step-up converter. The equations of the proposed converter are developed, its switching angle pattern is calculated and the dynamic behaviour of the system is simulated. Using a power MOSFET and four Schottky diodes, the basic power switch is assembled and a power converter fed from 50 V (RMS), 50 Hz, supplying a passive R, L load operated at 100 Hz, was constructed. Satisfactory agreement between simulated and laboratory results was observed.

Single-phase matrix converter

The theory of the three-phase to three-phase matrix converter is dealt with and its switching angles equations are presented. Matrix converter operation is based on the calculated switching angles. Modelling and numerical simulations of converter loaded with passive (R, L) and active (induction motor) loads are performed. Simulation results are presented.

Simulation of three-phase loaded matrix converter

The theory of three-phase AC/AC converters, known also through their modern name, the matrix converter is presented. Analysis of the three-phase converter loaded by a passive R,L load and by an induction motor follows. The analysis was performed by means of the software package "Simulink", a dynamic system simulation tool. This simulation environment was found suited for straight forward modeling and simulation of the electronic converter and the electric drive. The switching angles needed to control the electronic converter are calculated within the same environment by means of "MATLAB". According to our knowledge this is the first time that such simulations are performed.

http://ieeexplore.ieee.org/iel3/3899/11328/00514173.pdf

Matrix converter-theory and simulation

The speed control concept of closed-loop A.C. drive systems comprising current source induction motor is presented. A mathematical model of the squirrel-cage induction motor -- represented through space phasors - is given and its standard state form is obtained by a certain selection of the state variables. Based on this model, the control concept is defined: keeping a constant rotor flux linkage in the motor with bounded slip frequency, and controlling the electromagnetic torque by means of one stator component of the currents space phasor. In accordance with these basic rules, different control strategies are described: slip frequency control (SFC), torque angle control (TAC), synchronous control (SC), field oriented control (FOC) and field acceleration method (FAM). All strategies are accompanied by appropriate schematic block diagrams.

A. Zuckerberger

Papers

Single-phase matrix converter

Simulation of three-phase loaded matrix converter

Matrix converter-theory and simulation

Speed Control Concept in Closed Loop A.C. Drive Systems