A new multi-port active DC-link for PMG-based WECSs

This paper presents the development and performance evaluation of a new active multi-port dc-link for applications in permanent magnet generator (PMG)-based wind energy conversion systems (WECSs). The proposed dc-link is developed as a mid-stage between a three phase (3φ) multilevel ac-dc generator-side power electronic converter (PEC) and a 3φ 6-pulse dc-ac grid-side PEC. The design of the dc-link is based on a multi-port converter (MPC) topology with two dc-dc PECs, which have their outputs connected in parallel. Each dc-dc PEC is operated and controlled independently, in order to achieve separate voltage-transfer ratios, along with the possibility of processing continuous or discontinuous input dc voltages. The performance of the MPC active dc-link is evaluated in experiments for a 7.5 kW PMG-based WECS under different operating conditions. Test results show that the proposed dc-link is capable of producing a high quality regulated dc voltage over a wide range of wind speeds, and increasing the extracted power from the PMG. Performance results also demonstrate that the operation of the MPC active dc-link has minor impacts on the harmonic distortion at the terminals of the PMG, along with negligible impacts on the operation and control of the grid-side PEC.