Sizing Optimization Methodology of Tidal Energy Conversion Chain Based on Double Stator Permanent Magnet Generator

Abstract

This paper presents a variable speed direct drive generator optimization methodology for tidal current energy application based on double stator permanent magnet generator. Maximizing annual energy output and minimizing the generator-converter system cost are the two objectives of the optimization. Generator-converter system cost includes the generator raw material cost, structure cost and converter cost. Particle swarm optimization algorithm is adopted for this multi-objectives optimization. The generator torque-speed operating profile is obtained from the predictable tidal current source and turbine characteristics. 16 parameters including machine geometry and power electronic converter size are optimized over the full operation range rather than only for rated condition. The two stators of the generator are controlled in parallel with dq axis currents which minimize the total power losses of generator and converter. Constraints are introduced to guarantee that optimization solutions are realizable and will not reach electrical limitations, magnetic saturation and thermal limit over the whole operating torque speed profile. Comparing with single stator generator by using the same optimization process, double stator generator is proved more interesting for tidal energy application due to the machine volume is sharply reduced.