oa A High-Power Photovoltaic Power System based on Quasi-Z-Source Cascade Multilevel Inverter

I. INTRODUCTION The utility-scale Photovoltaic (PV) system experienced a tremendous growth to satisfy the fast increase of world's power demand. Nowadays, focus has been placed on innovative and cheap inverter solutions and system configurations. Among them, The Cascaded Multi-level Inverter (CMI) structure is more preferable to reach utility-scale power ratings and medium-voltage levels due to transformer-less, small size, high efficiency, high power density, and low cost. However, due to lack of boost function, the traditional CMI will lead to overrating the inverter by a factor of two to cope with wide (1:2) PV voltage variations. The recently proposed quasi-Z-source CMI (qZS-CMI) structure provides attracting improvement by combing the quasi-Z-source network into the traditional CMI. In addition to the advantages of traditional CMI, the qZS-CMI provides buck/boost function in a single-stage inverter topology, the independent dc-link voltage balance, and the one-third module reduction. All of those will bring positive effects on the system volume, efficiency, and cost. Contributions of this paper are proposing a high-power PV system based on qZS-CMI, which is 1-MW power and 11-kV voltage with 16 cascaded quasi-Z-source H-Bridge inverter (qZS-HBI) modules per phase. In this way, the high-power system can be fulfilled by low-power-low-frequency devices, aiming at the proposed PV system of low cost, high efficiency and reliability, and high performance-cost ratio, thus to improve the scientific and economic developments of Qatar. II. METHODS AND RESULTS The proposed system was simulated in MATLAB / Simulink by: 1) Sixteen cascaded quasi-Z-source H-Bridge inverter modules per phase. 2) Each qZS-HBI is fed by separate PV panels. 3) The phase-shifted sinewave pulsewidth modulation is applied to synthesize the multilevel voltage waveform. 4) Next step is to design the control scheme of the system with maximum power point tracking, grid-tie injection, novel modulation, etc.. ACKNOWLEDGEMENT This work was supported by NPRP-EP No. X - 033 - 2 - 007 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.