A Direct-Drive Wind Turbine Control for a Wind Power Plant with an Internal DC Distribution System

In this paper, a torque control algorithm of a Permanent Magnet Synchronous Generator (PMSG) for Direct Drive Wind Turbines (DDWTs) is proposed. In particular, a twelve-phase PMSG with four independent three-phase output subsystems has been considered with the aim of improving the DDWT torque management, energy efficiency, power generation and reliability; these goals are achieved by means of the decoupled control of each three-phase subsystem which the generator is split in. Hence, a novel coordinate transformation and the synthesis of the proposed master control algorithm are introduced: this last one allows the independent management of the reference currents of each subsystem and, thus, permits the development of an efficient variable speed wind turbine control. In addition, using the proposed DDWT, a novel topology of Continuous Medium Voltage Distribution system (CMVD) for a wind power plant is presented. In particular, the DC subsystems power outputs are connected by means the proposed CMVD to a centralized cascaded H-Bridge inverter structure, which is the only interface between the electric power transmission network and the wind power plant. The goodness of the proposed control algorithm is verified by means of a simulation study carried out in the Matlab Simulink environment, whose results are presented in the paper.