Flying Start of a Permanent Magnet Wind Power Generator Based on a Discontinuous Converter Operation Mode and a Phase-Locked Loop

Flying start of a wind generator is a common requirement in wind turbine applications. This paper proposes a novel method for allowing the flying start of a permanent magnet generator (PMG). The proposed method is based on the discontinuous mode of operation of the converter and the phase-locked loop (PLL). During the discontinuous mode of operation, a series of zero-voltage pulses is applied to the generator, causing the occurrence of the short-circuit current, and thereby employing the PLL structure to estimate the rotor speed and angle. Also, a short-circuit current control structure with automatic adjustment of the reference value is proposed. The input signal to a PLL structure is adequately selected in order to enable a continuous mode of operation of the PMG. Simulation results demonstrate the applicability of the proposed method on the surface and interior PMGs, as well as on low- and high-power PMGs. The estimation accuracy does not depend on changes in the PMG parameters. The proposed method was implemented in a digital control system and experimentally verified on a 375 kW interior PMG. Experimental responses referring to the flying start of the PMG demonstrate the effectiveness of the proposed method.