Design and operation of very slow-speed generators for a Bristol cylinder sea wave generating device

Abstract

Abstract-This paper describes the operation of a direct-drive brushless generator for a Bristol cylinder ocean wave device. This is a very low speed device so the pole number and diameter is very large. While the machine may be large the pole pitch and axial length is low. The application is described and simulated using analytical and finite element analysis techniques. A 248 pole design with surface rotor magnets is developed with both surface and slotted windings. An analysis of the control is put forward.

Grid-integrated permanent magnet synchronous generator based wind energy conversion systems: A technology review

“…Both methods have their own advantages and drawbacks. For instance, insensitivity to machine parameter variation, elimination of rotor position sensor, no current regulation loop, faster torque response and reduced computation time are the various advantages; whereas high ripples in torque, flux and current; the variation in switching frequency with load torque and rotor speed; and two hysteresis comparators' bandwidth are some of the disadvantages of DTC compared to FOC [14,25,39,129,[134][135][136][137]. However, both of these strategies allow torque and flux to be decoupled for independent control of the active and reactive powers handled by the generator [126,138,139].…”

“…field-oriented control (FOC) and direct torque control (DTC) are used at the machine-side and have almost similar dynamic responses [126][127][128][129][130][131]. The FOC is one of the most established strategies for generator speed control which involves dual loop control structure -an outer speed control loop and an inner current control loop usually based either on hysteresis control in natural reference frame or on PI control in synchronous reference frame [132].…”