This paper details the methodology and development of an isolated wind-battery system in the lab. The full-scaled prototype was built using commercial components along with the assistance of a hardware-in-the-loop system. The integration and characterisation of a wind energy conversion system in an off-grid power system are also elaborated. Droop-based inverters interfacing batteries were used to form the isolated grid whilst a fixed speed wind turbine was employed as the main source of power generation. The former is known to be autonomous and function without communication system whilst the latter employs a squirrel cage induction generator which is robust, simple to operate and requires minimal maintenance. They were selected with the aim to reduce the technical problems which may be faced by the communities where technical assistance is scarce. We have shown that the proposed methodology presents a more controlled environment for system testing and integration whilst reproducibility of measurements can be achievable in parallel. The performance and electrical dynamics of the isolated wind-battery system are analysed with simulations and experiments. Finally, we present the capability of the test-rig in emulating the non-ideal tower shadow effect of a wind energy system.

Air-cored machines offer benefits in terms the elimination of magnetic attraction forces between stator and rotor. With no iron in the stator there is not a good thermal conduction path for heat generated by Joule losses in the stator winding. Results from both models and experimental tests are provided in this paper to investigate different methods of cooling air-cored windings, including natural air-cooling, direct liquid cooling, and the use of heat pipes.

This paper investigates the effect of the inlet configuration on cooling for an air-cooled axial-flux permanent-magnet (AFPM) machine. Temperature rises in the stator were measured and compared with results predicted using computational fluid dynamic (CFD) methods linked to a detailed machine loss characterization. It is found that an improved inlet design can significantly reduce the stator temperature rises. Comparison between the validated CFD model results and the values obtained from heat transfer correlations addresses the suitability of those correlations proposed specifically for AFPM machines.

A proper maximum power tracking algorithm for a Wind Energy Conversion Systems (WECS) requires all the relevant losses to be modelled, especially copper and core losses. Such accurate loss modelling is not a simple task when the machine operates connected to a power converter. In this paper we validated an equivalent circuit for a novel air-cored PM generator by comparing the results from a transient-non- linear Finite Element Model (FEM) of the generator and by experimental testing on a 20-kW prototype. Finally we present the benefits of a proper integrated optimisation in terms of annual energy yield and average losses. We suggest that a detailed loss modelling is desirable at a design stage for an optimum matching between machine and rotor blades.

The power electronic rectifying stage (DC to AC) in a variable speed generator compromises the generator efficiency and its lifetime. However, this effect in a PMSG might need to be quantified in a design stage for energy output yield calculations. We have conducted an in-depth efficiency analysis of a 20kW direct drive PMSG by the implementation of an equivalent circuit aided by a 2D-Finite Element Model. Copper and core losses due to non-sinusoidal currents have been analyzed when two options of common rectifier topologies are used in the AC to DC power stage: a diode and an active (PWM) rectifier. Simulation results show that the active rectifier does not exhibit a considerable advantage in terms of energy output. So far, for medium-power applications, a diode rectifier can be a cost-effective solution.