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A very simple geometric structure whose branches can be filled by inductors, capacitors, diodes, short-circuits, or open-circuits is proposed. It serves for generating large dc gain-purposed switching cells by making different choices of the type of component on each branch. The switching cells are integrated in basic converters. It is shown that almost all the high dc gain nonisolated converters based on switched-capacitor-inductor cells proposed in the last years, regardless of their complexity, can be derived through this method. From the same geometric structure, new high dc gain boosting converters can be derived in a systematic manner. The available and the new converters in each class as defined by the number of reactive components are compared in terms of their performance: dc gain, semiconductor elements count, voltage and current stress on transistors and diodes, character of the input current, easiness of the transistor driving, and easiness of the control as determined by common/uncommon line-load ground, power stage efficiency. This comparison allows us to choose the optimal solution for each specific application in conjunction with the green sources of energy, multisource microgrids, electric vehicles, data and communications systems, and so on. The geometric structure is generalized in different ways, allowing for the development of ultrahigh dc gain converters. One of the proposed generalized ultrahigh dc gain converters is fully analyzed and built in the laboratory, with the experimental results verifying the theoretical analysis. [ABSTRACT FROM AUTHOR]

The energy-efficiency issue of switched-capacitor converters is still a controversial topic that requires a more in-depth discussion. In this paper, we address the issue by dividing the analysis of the entire efficiency problem into two parts. In the first part, the efficiency of a capacitor-charging RC circuit under different aspects (partial charging, full charging, at zero capacitor voltage, at nonzero capacitor voltage, etc.) will be conducted. The efficiency analysis of a capacitor-discharging RC circuit with a resistor, capacitor, and paralleled resistor–capacitor loads will be covered. A complete evaluation of the overall efficiency is then performed in terms of both the charging and discharging efficiencies. Based on the analysis, some design rules useful for developing high-efficiency switched-capacitor converters is suggested. Additionally, it is shown that the belief that quasi-switched-capacitor converters are more lossy than switched-capacitor converters is a common misconception. [ABSTRACT FROM AUTHOR]

Power conversion from an input voltage of several kilovolts to a low load voltage is of great significance in various applications, but poses serious challenges. In this paper, a new converter, which is able to realize such a large step-down conversion in a single step, is proposed by introducing a novel concept of dc–dc multiphase conversion and n-phase interleaving rectification. The proposed structure is formed by n switch pairs in the primary side, an n-phase isolation transformer with the primary windings connected to dc blocking capacitors, and an n-phase current multiplier in the output side. The switching patterns applied to the switch pairs have a phase difference of 360^\circ \mathord\left/ \vphantom 360^\circ n \right. \kern-\nulldelimiterspace n, and the output inductor currents are interleaved correspondingly, making necessary a smaller output filter. For a V_i input voltage and I_o load current, the converter features V_i/n voltage stress on the primary-side switches, and I_o/n current stress on the secondary-side inductors and diodes. Thus, the magnetic size of the inductors is considerable reduced. The primary-side switches are commutated with zero-voltage-switching (ZVS). Therefore, rather than using insulated-gate bipolar transistors (IGBTs) or MOSFETs with higher voltage ratings, the most available, notable performing 500/600 V MOSFETs can be used in the proposed converter with several kilovolts supply voltage, allowing for a higher operation frequency and lower conduction losses. Compared with an input-series–output-parallel (ISOP) connection of full-bridge (FB) isolated converters, for the same voltage stress on the switches, the proposed converter requires half of the number of transistors and inherently balances the input voltage among the switch pairs. The switching mechanism of a typical switch pair in the kth interval T_s/n of a switching cycle is analyzed. A dc analysis was carried out to determine the dc conversion ratio and the ZVS conditions in an analytical form. It allows for a tradeoff design of the converter, such that to minimize the duty-cycle loss and maximize the ZVS load range. A 1500/48-V, 2-kW prototype with four switch pairs was designed, implemented, and evaluated. The experimental results prove the soft switching of the switches, the low voltage stress across the primary-side switches, and the low current flowing through the rectifier's diodes and inductors. The efficiency measured at nominal power rating was 90.75%. [ABSTRACT FROM AUTHOR]

A state-space averaging description of a non-linear boost converter, operating in the discontinuous conduction mode, is used to obtain the ‘equivalent’ duty ratio to output voltage, respectively line voltage to output voltage transfer functions. The coefficients of both of them may vary within some intervals due to the variation of the converter parameter values. Feedback compensators of a switching regulator in which the converter is incorporated are designed such as (a) the start-up transient response lies within imposed specifications despite parameter values and load variation, and (b) the output voltage is kept constant regardless of any variation of input voltage. [ABSTRACT FROM AUTHOR]

A feedback system for controlling the speed of a separately excited DC motor supplied from a 3-phase semi-converter circuit is presented. The electronic feedback structure is designed to assure that, in the starting transient state, the motor speed climbs from zero to its steady-state value within specified ‘customer’ bounds. This has to be achieved despite random variations in the characteristics of the supply voltage, of the motor and of the converter, and despite uncertain values of the load, keeping at the same time the starting current peak below a dangerous level. When feedback is applied, the system becomes highly non-linear; but owing to its quantitative approach, the design algorithm uses no small-signal linearizations. [ABSTRACT FROM AUTHOR]

The article focuses on power electronics. Today high-demanding requests on the switching supplies have to be addressed by researchers: the need of high power density supplies for miniaturization purpose, fast transient response to rapidly changing loads like computers, absorption of clean sinusoidal currents from the electrical network for avoiding its harmonic pollution, supply of low voltages at high currents and steep voltage step-up, as required by telecommunication consumers. Neimark Sacker bifurcation is influenced by interleaving parallel-connected converters.

The development of microgrids is an advantageous option for integrating rapidly growing renewable energies. However, the stochastic nature of renewable energies and variable power demand have created many challenges like unstable voltage/frequency and complicated power management and interaction with the utility grid. Recently, predictive control with its fast transient response and flexibility to accommodate different constraints has presented huge potentials in microgrid applications. This paper provides a comprehensive review of model predictive control (MPC) in individual and interconnected microgrids, including both converter-level and grid-level control strategies applied to three layers of the hierarchical control architecture. This survey shows that MPC is at the beginning of the application in microgrids and that it emerges as a competitive alternative to conventional methods in voltage regulation, frequency control, power flow management and economic operation optimization. Also, some of the most important trends in MPC development have been highlighted and discussed as future perspectives. • A comprehensive review of model predictive control (MPC) in microgrids, including both converter-level and grid-level control strategies applied to three layers of microgrid hierarchical architecture. • Illustrating MPC is at the beginning of the application to microgrids and it emerges as a competitive alternative to conventional methods. • Some of the most important trends in MPC development have been highlighted and discussed as future perspectives. [ABSTRACT FROM AUTHOR]