Renewable energy sources like wind, sun, and hydro are seen as a reliable alternative to the traditional energy sources such as oil, natural gas, or coal. Distributed power generation systems (DPGSs) based on renewable energy sources experience a large development worldwide, with Germany, Denmark, Japan, and USA as leaders in the development in this field. Due to the increasing number of DPGSs connected to the utility network, new and stricter standards in respect to power quality, safe running, and islanding protection are issued. As a consequence, the control of distributed generation systems should be improved to meet the requirements for grid interconnection. This paper gives an overview of the structures for the DPGS based on fuel cell, photovoltaic, and wind turbines. In addition, control structures of the grid-side converter are presented, and the possibility of compensation for low-order harmonics is also discussed. Moreover, control strategies when running on grid faults are treated. This paper ends up with an overview of synchronization methods and a discussion about their importance in the control

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Overview of Control and Grid Synchronization for Distributed Power Generation Systems

The recently introduced proportional-resonant (PR) controllers and filters, and their suitability for current/voltage control of grid-connected converters, are described. Using the PR controllers, the converter reference tracking performance can be enhanced and previously known shortcomings associated with conventional PI controllers can be alleviated. These shortcomings include steady-state errors in single-phase systems and the need for synchronous d-q transformation in three-phase systems. Based on similar control theory, PR filters can also be used for generating the harmonic command reference precisely in an active power filter, especially for single-phase systems, where d-q transformation theory is not directly applicable. Another advantage associated with the PR controllers and filters is the possibility of implementing selective harmonic compensation without requiring excessive computational resources. Given these advantages and the belief that PR control will find wide-ranging applications in grid-interfaced converters, PR control theory is revised in detail with a number of practical cases that have been implemented previously, described clearly to give a comprehensive reference on PR control and filtering.

Proportional-resonant controllers and filters for grid-connected voltage-source converters

This paper reviews the power electronic applications for wind energy systems. Various wind turbine systems with different generators and power electronic converters are described, and different technical features are compared. The electrical topologies of wind farms with different wind turbines are summarized and the possible uses of power electronic converters with wind farms are shown. Finally, the possible methods of using the power electronic technology for improving wind turbine performance in power systems to meet the main grid connection requirements are discussed.

A Review of the State of the Art of Power Electronics for Wind Turbines

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

This paper reviews the relative merits of induction, switched reluctance, and permanent-magnet (PM) brushless machines and drives for application in electric, hybrid, and fuel cell vehicles, with particular emphasis on PM brushless machines. The basic operational characteristics and design requirements, viz. a high torque/power density, high efficiency over a wide operating range, and a high maximum speed capability, as well as the latest developments, are described. Permanent-magnet brushless dc and ac machines and drives are compared in terms of their constant torque and constant power capabilities, and various PM machine topologies and their performance are reviewed. Finally, methods for enhancing the PM excitation torque and reluctance torque components and, thereby, improving the torque and power capability, are described

Electrical Machines and Drives for Electric, Hybrid, and Fuel Cell Vehicles

PRINCIPLE OF OPERATION OF THE SWITCH RELUCTANCE MOTOR (SRM) Introduction Background Elementary Operation of the Switch Reluctance Motor Principle of Operation of the Switched Reluctance Motor Derivation of the Relationship Between Inductance and Rotor Position Equivalent Circuit SRM Configurations Linear Switched Reluctance Machines References DERIVATION OF SRM CHARACTERISTICS Introduction Data for Performance Computation Analytic Method for the Computation of Machine Characteristics Computation of Unaligned Inductance Computation of Aligned Inductance Computation of Inductance vs. Rotor Position vs. Excitation Current Comparison of Measured, Analytic and Finite Element Results References DESIGN OF SRM Introduction Derivation of Output Equation Selection of Dimensions Design Verification Operational Limit Selection of Number of Phases Selection of Poles Ratio of Pole-Arc to Pole-Pitch Selection of Pole Base Selection of Pole-Arcs Measurement of Inductance Calculation of Torque Design of Linear Switched Reluctance Machine (LSRM) References CHAPTER 4: CONVERTERS FOR SRM DRIVES Converter Configurations Asymmetric Bridge Converter Asymmetric Converter Variation Single Switch per Phase Converters m Switches and 2m Diodes m Switches and 2m Diodes with Independent Phase Current Control (m+1) Switch and Diode Configurations One Common Switch Configuration Minimum Switch Topology With Variable DC Link Variable DC Link Voltage with Buck Boost Converter Topology 1.5m Switches and Diodes Configuration Comparison of Some Power Converters Two Stage Power Converter Resonant Converter Circuits for Switched Reluctance Motor Drives References CONTROL OF SRM DRIVE Introduction Control Principle Closed Loop Speed Controlled SRM Drive Design of Current Controllers Flux Linkage Controller Torque Control Design of the Speed Controller References MODELING AND SIMULATION OF SRM DRIVE SYSTEM Introduction Modeling Simulation References ACOUSTIC NOISE AND ITS CONTROL IN SRM Introduction Sources of Acoustic Noise in Electrical Machines Noise Sources Noise Mitigation Qualitative Design Measures to Reduce Noise Measurement of Acoustic Noise and Vibrations Future Directions Appendix-1: Derivation of First Mode Frequency of SRM References SENSORLESS OPERATION OF SRM DRIVES Introduction Current Sensing Rotor Position Measurement Methods Rotor Position Estimation References APPLICATION CONSIDERATIONS AND APPLICATIONS Introduction Review of SRM Drive Features for Application Consideration Applications Emerging applications References

Switched reluctance motor drives : modeling, simulation, analysis, design, and applications

PART I: Introduction to Permanent Magnets and Machines and Converters and Control Chapter 1 Permanent Magnets and Machines Permanent Magnets Arrangement of PMs Magnetization of PMs PM ac Machines Fundamentals of Synchronous Machines Fundamental Synchronous Machine Relationships Core Losses Resistive Losses Initial Machine Design Cogging Torque Basic Types of PMSMs Based on Flux Paths Vibration and Noise Chapter 2 Introduction to Inverters and Their Control Power Device DC Input Source DC to ac Power Conversion Real Power Reactive Power Need for Inverter Control Pulse Width Modulation Hysteresis Current Control Space Vector Modulation Inverter Switching Delay Input Power Factor Correction Circuit Four-Quadrant Operation Converter Requirements PART II: Permanent Magnet Synchronous Machines and Their Control Chapter 3 Dynamic Modeling of Permanent Magnet Synchronous Machines Real-Time Model of a Two-Phase PMSM Transformation to Rotor Reference Frames Three-Phase to Two-Phase Transformation Zero Sequence Inductance Derivation Power Equivalence Electromagnetic Torque Steady-State Torque Characteristics Models in Flux Linkages Equivalent Circuits Per Unit Model Dynamic Simulation Small-Signal Equations of the PMSM Evaluation of Control Characteristics of the PMSM Computation of Time Responses Space Phasor Model Chapter 4 Control Strategies for a Permanent Magnet Synchronous Machine Vector Control Derivation of Vector Control Drive System Schematic Control Strategies Chapter 5 Flux-Weakening Operation Maximum Speed Flux-Weakening Algorithm Direct Flux Weakening Parameter Sensitivity Model-Free (Parameter-Insensitive) Flux-Weakening Method Six-Step Voltage and Constant Back EMF Control Strategies for PMSM Direct Steady-State Evaluation Flux Weakening in SMPM and IPM Synchronous Machines Chapter 6 Design of Current and Speed Controllers Current Controller Speed Controller Chapter 7 Parameter Sensitivity and Compensation Introduction Parameter Compensation through Air Gap Power Feedback Control Parameter Compensation by Reactive Power Feedback Control Chapter 8 Rotor Position Estimation and Position Sensorless Control Current Model Adaptive Scheme Sensing by External Signal Injection Current Model-Based Injection Scheme Position Estimation Using PWM Carrier Components PART III: Permanent Magnet Brushless DC Machines and Their Control Chapter 9 PM Brushless DC Machine Modeling of PM Brushless DC Motor Normalized System Equations The PMBDCM Drive Scheme Dynamic Simulation Chapter 10 Commutation Torque Ripple and Phase Advancing Commutation Torque Ripple Phase Advancing Dynamic Modeling Chapter 11 Half-Wave PMBDCM Drives Split Supply Converter Topology C-Dump Topology Variable DC Link Converter Topology Variable Voltage Converter Topology with Buck-Boost Front-End Chapter 12 Design of Current and Speed Controllers Transfer Function of Machine and Load Inverter Transfer Function Transfer Functions of Current and Speed Controllers Current Feedback Speed Feedback Design of Controllers Chapter 13 Sensorless Control of PMBDCM Drive Current Sensing Position Estimation Chapter 14 Special Issues Torque Smoothing Parameter Sensitivity of the PMBDCM Drive Faults and Their Diagnosis Vibration and Noise

Permanent Magnet Synchronous and Brushless DC Motor Drives

The application of vector control to the PMSM (permanent-magnet synchronous motor) is described, and complete modeling, simulation, and analysis of the drive system are presented. State-space models of the motor and speed controller and real-time models of the inverter switches and vector controller are included. Performance differences due to the use of pulsewidth-modulation (PWM) and hysteresis current controllers are also examined. Particular attention is paid to the motor torque pulsations and speed response. Some experimental verification of the drive performance is also given. >

Modeling, simulation, and analysis of permanent-magnet motor drives. I. The permanent-magnet synchronous motor drive

Part I: PWM Converters: Topologies and Control 1 Power Electronic Converters 2 Resonant dc Link Converters 3 Fundamentals of the Matrix Converter Technology 4 Pulse Width Modulation Techniques for Three-Phase Voltage Source Converters Part II: Motor Control 5 Control of PWM Inverter-Fed Induction Motors 6 Energy Optimal Control of Induction Motor Drives 7 Comparison of Torque Control Strategies Based on the Constant Power Loss Control System for PMSM 8 Modeling and Control of Synchronous Reluctance Machines 9 Direct Torque and Flux Control (DTFC) of ac Drives 10 Neural Networks and Fuzzy Logic Control in Power Electronics Part III: Utilities Interface and Wind Turbine Systems 11 Control of Three-Phase PWM Rectifiers 12 Power Quality and Adjustable Speed Drives 13 Wind Turbine Systems Index

Control in Power Electronics: selected problems

For ptI see ibid, vol25, no2, p265-73 (1989) The authors develop a phase variable model of the BDCM (brushless DC motor) and use it to examine the performance of a BDCM speed servo drive system when fed by hysteresis and pulsewidth-modulated (PWM) current controllers Particular attention was paid to the motor large-signal and small-signal dynamics and motor torque pulsations The simulation included the state-space model of the motor and speed controller and real-time model of the inverter switches Every instance of a power device turning on or off was simulated to calculate the current oscillations and resulting torque pulsations The results indicate that the small- and large-signal responses are very similar This result is only true when the timing of the input phase currents with the back EMF (electromotive force) is correct The large-signal and small-signal speed response is the same whether PWM or hysteresis current controllers are used This is because, even though the torque pulsations may be different due to the use of different current controllers, the average value which determines the overall speed response is the same >

R. Krishnan

Papers

Switched reluctance motor drives : modeling, simulation, analysis, design, and applications

Permanent Magnet Synchronous and Brushless DC Motor Drives

Modeling, simulation, and analysis of permanent-magnet motor drives. I. The permanent-magnet synchronous motor drive

Control in Power Electronics: selected problems

Modeling, simulation, and analysis of permanent-magnet motor drives. II. The brushless DC motor drive