5715ch9 - 9 Switched Reluctance Generators and Their...

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© 2006 by Taylor & Francis Group, LLC 9 -1 9 Switched Reluctance Generators and Their Control 9.1 Introduction . ...................................................................... 9 -1 9.2 Practical Topologies and Principles of Operation. .......... 9 -2 The kW/Peak kVA Ratio 9.3 SRG(M) Modeling. ............................................................. 9 -9 9.4 The Flux/Current/Position Curves. ................................. 9 -10 9.5 Design Issues . ................................................................... 9 -12 Motor and Generator Specifications Number of Phases, Stator and Rotor Poles: m , N s N r Stator Bore Diameter D is and Stack Length The Number of Turns per Coil W c for Motoring Current Waveforms for Generator Mode 9.6 PWM Converters for SRGs. ............................................. 9 -18 9.7 Control of SRG(M)s . ....................................................... 9 -21 Feed-Forward Torque Control of SRG(M) with Position Feedback 9.8 Direct Torque Control of SRG(M) . ................................ 9 -25 9.9 Rotor Position and Speed Observers for Motion-Sensorless Control. ....................................... 9 -30 Signal Injection for Standstill Position Estimation 9.10 Output Voltage Control in SRG. ..................................... 9 -31 9.11 Summary. .......................................................................... 9 -33 References. ................................................................................... 9 -35 9.1 Introduction Switched reluctance generators (SRGs) are double-saliency electric machines with nonoverlapping stator multiphase windings and with passive rotors. They may also be assimilated with stepper motors with position-controlled pulsed currents. Multiphase configurations are required for smooth power delivery and eventual self-starting and motoring, if the application requires it. SRGs were investigated mainly for variable speed operation as starter/generators on hybrid electric vehicles, as power generators, on aircraft and for wind energy conversion. They may also be considered for super-high-speed gas turbine generators from kilowatt to megawatt (MW) power range per unit. As SRGs lack permanent magnets (PMs) or rotor windings, they are low cost, easy to manufacture, and can operate at high speeds and in high-temperature environments.
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© 2006 by Taylor & Francis Group, LLC 9 -2 Variable Speed Generators In vehicular applications, an SRG is required to perform over a wide speed range to comply with the internal combustion engine (ICE) that drives it. For wind energy conversion, limited speed range is needed to extract additional wind energy at lower mechanical stress in the system. Aware of the very rich literature on SRMs [1, 2], we will treat in this chapter the following aspects deemed as representative: • Practical topologies and principles of operation • Characteristics for performance evaluation • Design for wide constant power range • Converters for SRG motor (M) • Control of SRG as starter/generator with and without motion sensors The existence of a handful of companies that fabricate and dispatch SRMs [3] and vigorous recent proposals of SRGs as starters/alternators for automobiles and aircraft (up to 250 kW per unit) seem sufficient reason to pursue the SRG study within a separate chapter such as this one. 9.2 Practical Topologies and Principles of Operation A primitive single-phase SRG(M) configuration with two stator and two rotor poles is shown in Figure 9.1a and Figure 9.1b. It illustrates the principle of reluctance machine, where torque is produced through magnetic anisotropy. The stored magnetic energy ( W e ) or coenergy ( W c
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5715ch9 - 9 Switched Reluctance Generators and Their...

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