Current Source Generator–Converter Topology for Direct-Drive Wind Turbines

Permanent magnet synchronous generator (PMG) based direct-drive wind turbines (DDWTs) have recently drawn the attention of the wind power market given their low operation and maintenance cost, reliability, and longer lifetime. In this paper, a zero dc-link impedance topology for DDWT-PMG systems is presented. The proposed topology eliminates the use of the failure-prone dc bus capacitor by replacing the grid-side converter with a phasor pulse-width modulation (PPWM) boost current source inverter (CSI), also referred to as indirect boost matrix converter. Furthermore, the novelty of the proposed topology lies in utilizing the synchronous inductance of the PMG as the dc-link inductor required by the boost-CSI, thus decreasing the overall system weight and size. In addition, the PPWM boost-CSI enables a high voltage-boosting ratio, which allows the design of a low-voltage PMG. As a result, the PMG size, weight, and high-cost PM material volume can be decreased. The feasibility of the low-voltage generator is investigated through finite-element computations using as a base for comparison an existing 1.5-MW DDWT-PMG. This comparison demonstrates a reduction in the generator volume, PM material, and the total weight of the generator. Finally, the proposed topology is validated through simulations and experiments.