Recent improvements in semiconductor technology make efficient switching possible at higher frequencies, which benefits the application of wireless inductive energy transfer. However, a higher frequency does not alter the magnetic coupling between energy transmitter and receiver. Due to the still weak magnetic coupling between transmitting and receiving sides that are separated by a substantial air gap, energy circulates in the primary transmitting side without being transferred to the secondary receiving side. This paper introduces an energy control method that reduces energy circulation in the primary to zero. The method makes use of the fact that energy can be stored in a magnetic field by the primary side, and absorbed by the secondary side. Furthermore, the secondary side converter topology is modified in order to boost the damping as seen by the primary converter at required times. Essentially, the control method realizes an energetic coupling factor of 1 between the air coils of the wireless transformer. The working principle of the control method has been verified with an experimental setup.

Abstract This paper describes experimental results obtained from a sliding-mode quantum controller implementation applied to a laboratory setup of a series-resonant converter. The motive for the design of the latter controller has been to achieve maximum operational efficiency. The newly formulated sliding surface indeed assures active minimization of the system energy loss in any arbitrary chosen full power range, while also assuring stable operation. The control method has a simple analogue implementation that has been verified in the laboratory.

The objective of this paper is to compare five different generator systems for wind turbines, namely the doubly-fed induction generator with three-stage gearbox (DFIG3G), the direct-drive synchronous generator with electrical excitation (DDSG), the direct-drive permanent-megnet generator (DDPMG), the permanent-magnet generator with single stage gearbox (PMG1G), and the doubly-fed induction generator with single-stage gearbox (DFIG1G). The comparison is based on cost and annual energy yield for a given wind climate. The DFIG3G is a cheap solution using standard components. The DFIG1G seems the most attractive in terms of energy yield divided by cost. The DDPMG has the highest energy yield, but although it is cheaper than the DDSG, it is more expensive than the generator systems with gearbox.