Modelling, control, and stability analysis of quasi-Z-source matrix converter as the grid interface of a PMSG-WECS

This work aims to carry out a comprehensive analytical evaluation of a quasi-Z-source matrix converter (qZSMC), which is comprised of a three-phase quasi-Z-source network (TPQZSN) followed by an MC, as the grid interface of a permanent magnet synchonous generator (PMSG)-based wind energy conversion system (PMSG-WECS). First, the small-signal model of the TPQZSN in space domain is obtained by the state-space averaging method, while the parasitic elements are also considered. The TPQZSN's transfer functions are further calculated and analysed. The results together with a frequency-domain analysis are used to render a comprehensive guide for the selection of proper passive components of the TPQZSN. The qZSMC is then employed as the grid interface of a PMSG-WECS. A control system is designed for the grid-connected operation. The small-signal model of the whole system is developed. The qZSMC is compared with conventional MC (CMC) from stability point of view, indicating that, unlike the CMC, the qZSMC has no trouble working stable for all ranges of output power. Furthermore, it is shown that the proposed WECS can operate stably without using digital filter. The system performance is compared with CMC-based WECS.