To enhance the gain of conventional boost converters in applications such as fuel cells and photovoltaic systems, cascade boost converters are normally applied. In this study, a new cascade boost converter topology with reduced conduction losses is proposed. This converter shows reduced root-mean-square currents of the circuit elements and reduced conduction losses. The proposed converter is analysed and compared with the conventional circuit topology. The proposed converter has all the advantages of cascade boost converter with the advantage of reduced conduction losses. Finally, simulation and experimental results of a 200 W laboratory prototype are presented.

This study considers the hierarchical control of microgrid and harmonic compensation of non-linear load specially in transition from grid-connected to unplanned islanding. The proposed controllers are based on the stationary reference frame with hierarchical control levels (inner, primary, and secondary). In the inner control loop, proportional and multi-resonant voltage and current controllers for three-phase voltage source inverters are proposed. Moreover, a droop control is used to share active and reactive power in the primary control loop. To achieve decoupled active and reactive power sharing, virtual impedance loop is implemented, too. The mentioned procedure increases the total impedance and consequently reduces the initial current and subsequently facilitates the continuous connection of DGs to the MG. To attain smoother transition, selective harmonic virtual impedance is applied by multiple second-order generalised integrator module to extract the fundamental positive sequence and harmonic components of the output current of the DGs. In secondary control level, synchronisation procedure is considered to make connection and restoration by the advanced three-phase synchronous reference frame PLL with in-loop moving average filter which significantly enhances its disturbance rejection capability. The results are shown smoother transition, robustness, and high performance of the proposed hierarchical control VSIs during variation of system configuration.

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This study focuses on considering battery one time constant model in the design of controllers of a two-stage AC/DC and DC/DC battery charger using the small-signal approach. For this aim, small-signal models of DC/DC and AC/DC converters and also the battery model are obtained. Moreover, the effect of disturbance terms are analysed to be omitted in controller loops. Simulation and experimental results of a 1 kW laboratory prototype show appropriate performance of designed controllers in tracking reference signals. Also, tuned controllers using this approach have guaranteed unity power factor and low total harmonic distortion. Furthermore, a complete charge cycle of a lithium-ion battery evaluates the performance of the converter in different constant current/voltage controlling modes. In comparison with restive model consideration, results show a more accurate model with grater damping ration and better stability characteristics.

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