Institute of Electrical and Electronics Engineers, IEEE Journal of Emerging and Selected Topics in Power Electronics, 1(2), p. 3-13, 2014
DOI: 10.1109/jestpe.2013.2294920
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A new power conversion system is explored in this paper aiming wind turbines rated at the megawatt level. The proposed configuration consists of a medium-voltage, permanent magnet synchronous generator connected to a low-cost three-phase diode bridge rectifier, a dc–dc four-level boost converter as the intermediate stage, and a four-level diode-clamped inverter on the grid-side. The dc-link capacitor voltages are balanced by the boost converter, and thus the control complexity for the grid-tied inverter is greatly simplified. To control the boost converter and grid-tied inverter, a simple method based on a two-step model predictive strategy is presented. In the first part of this paper, the continuous- and discrete-time modeling of the proposed power conversion system is analyzed. The control objectives such as maximum power point tracking, dc-link capacitor voltages balancing, regulation of net dc-bus voltage, reactive power generation, lower switching frequency operation, and common-mode voltage minimization are considered in the design of controller.