Series-connected multi-half-bridge modules converter for integrating multi-megawatt wind multi-phase permanent magnet synchronous generator with dc grid

In this study, a new transformerless wind energy conversion system to integrate high-power multi-phase permanent magnet wind generators to medium-voltage local grids is presented. The proposed converter topology consists of multi-half-bridge modules with a high ac-direct current (dc) boosting capability. Each phase of an open winding multi-phase generator is connected to the ac side of a half-bridge module, whereas the dc sides of the halfbridge modules are connected in series forming the high-voltage dc-link output. The proposed architecture facilitates the employment of semiconductor switches with a relatively low-voltage rating, which equals the dc-link voltage divided by the number of generator phases. A detailed analysis of the proposed architecture along with the required closed-loop control is presented. The proposed architecture is simulated under different operating conditions using a typical 2 MW system, while the experimental validation is carried out using a low-scale prototype converter.