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In this paper, a model predictive scheme is proposed to control the grid-connected high-power four-level diode-clamped inverter. To predict the future behavior of active and reactive grid power values and dc link capacitor voltages, a discrete-time model of the inverter is developed in synchronous reference frame. The controller uses all the possible switching states of the inverter for the prediction and evaluates them using a cost function. The switching state, which minimizes the cost function, is then chosen and applied at the next sampling interval. The switching frequency minimization is also achieved by including an extra constraint in the cost function. A simplified extrapolation method with reduced computational burden is proposed to safeguard the semiconductor devices during the dynamic changes in reference power values. The performance of the proposed method is investigated with the perturbations in the grid filter and dc link parameters. The feasibility of the proposed method is verified through simulation and experimental results, showing good dynamic and steady-state performance. [ABSTRACT FROM PUBLISHER]

Grid-connected power conversion systems for renewable energy sources must fulfill several requirements, e.g., the high efficiency, the reduced cost and complexity, and, quite often, the boost capabilities that is usually achieved using a front-end dc–dc boost converter before the inversion stage, leading to a two-stage architecture. Meanwhile, single-stage power conversion systems, which perform the boosting operation within the inversion one, offer some potential advantages, in terms of reducing the complexity and the volume of the whole system. Among several proposed options, the split-source inverter (SSI) has been recently proposed by Abdelhakim et al. as an alternative option with some interesting features to the commonly used Z-source inverter. Taking into account that the SSI is controlled by a single parameter, i.e., its dc and ac sides are controlled by the modulation index, it is of paramount importance to investigate its control scheme in grid-connected mode, which has never been studied yet. Hence, this paper models the SSI dc side and proposes a modified modulation scheme combined with the commonly used synchronous reference frame control technique to achieve a decoupled control scheme of the SSI in grid-connected mode, i.e., the dc and the ac sides of the SSI can be controlled independently, which is convenient for many applications. The introduced control scheme is analyzed and simulated using a MATLAB/Simulink model, where a reduced scale 1-kVA grid-connected SSI is designed and simulated for the sake of experimental validation. Finally, the designed system is implemented experimentally to validate and verify the reported analysis and simulations. [ABSTRACT FROM PUBLISHER]

This paper presents a novel double uneven power converter-based dc–dc converter and its design and control methods. The main objectives are to reduce the power losses in the power semiconductor devices and to reduce the output filter inductance in a high-power (megawatt-level) dc–dc converter. The proposed converter utilizes two full-bridge converters in a special way to realize zero-current switching and to reduce the output filter inductance. The advantages of the proposed converter become more significant for high-power applications. A comparative simulation for a dc-grid wind farm application has been performed to verify the effectiveness of the proposed converter in high-power applications. It has been shown that the proposed converter not only requires less filter inductance but also has less power losses in the semiconductor devices. A small-scale prototype has been built to verify the operational principle of the proposed converter. [ABSTRACT FROM PUBLISHER]

Unbalanced grids introduce performance deterioration for Vienna rectifier topology by producing twice fundamental frequency ripples in dc-link voltage and input active/reactive power. A common current reference generation for the purpose of eliminating the input power ripple, such as dual-frame hybrid vector control, can maintain constant input power and eliminate ripples in dc-link voltage under light voltage unbalanced grids. Under severe unbalanced grids, this type of a control method will fail to work. This paper first analyzes the theoretical operation area of a constant power control method under unbalanced grids, and then a novel control method is proposed. The proposed control method can work under severe unbalanced grids by injecting a small amount of input power ripple and balance the performance of working area and output dc voltage ripples. Finally, the experiment results using the constant power control method are given and validate the performance of the proposed control method. [ABSTRACT FROM PUBLISHER]