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This paper proposes a current sensorless control strategy for the dual active bridge (DAB) converter with nonlinear disturbance observer (NDO)-based load current feedforward. The proposed method can regulate both the dc-bus voltage and the current of the DAB converter without current sensors. Several performance indexes are established for the parameter design and a detailed design method is presented in this paper. When a single-phase H-bridge inverter is connected, the double-frequency oscillation from the feedback path is suppressed by proper parameter design, while the transient response of dc-bus voltage can be further improved by the NDO-based load current feedforward with a notch filter in the feedforward path. The performance of the proposed control method and the effectiveness of the parameter design are verified in a prototype by experimental results. [ABSTRACT FROM PUBLISHER]

A recently reported modeling methods for a switched capacitor converter either assume output as “firm” voltage or a resistor to facilitate calculation. When the size of output filter capacitor is moderate, accompanied by noticeable output ripple, previous modeling results may not provide accurate prediction and design guidelines. In this paper, a new modeling technique taking into account the output capacitor effect is proposed for simple dual-phase switched capacitor converters without complex coupling loops. The proposed model employs transient calculation, takes charge redistribution phase into account, and includes the duty cycle, switching frequency as well as output capacitor simultaneously in the final output impedance formula, which enhances accuracy of the model. It is suitable for interleaved and noninterleaved switched capacitor converters. The simulation and experimental results for the unity gain SC converter are provided to verify the proposed theory. [ABSTRACT FROM PUBLISHER]

At a certain level of abstraction, power converters can be represented as linear circuits connected to diodes and controlled electronic switches. The evolutions of the electrical variables are determined by the state-dependent switchings, which complicate the mathematical modeling of controlled power converters. Differently from the complementarity models previously presented in the literature, the model proposed in this paper allows to represent as a linear complementarity system also closed-loop power converters, without requiring the a priori knowledge of the converter modes. A model construction procedure, not dependent on the specific converter topology, is presented. The discretization of the continuous-time model allows to formulate mixed linear complementarity problems for the computation of the control-to-output frequency response and the evolutions of both transient and steady-state currents and voltages. As illustrative examples, Z-source, boost, and buck dc-dc power converters under voltage-mode control and current-mode control operating both in continuous and discontinuous conduction modes are considered. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMC) are considered a top converter alternative for voltage-source converter (VSC) high-voltage, direct current (HVDC) applications. Main circuit design and converter performance evaluation are always important issues to consider before installing a VSC-HVDC system. Investigation into a steady-state analysis method for an MMC-based VSC-HVDC system is necessary. This paper finds a circular interaction among the electrical quantities in an MMC. Through this circular interaction, a key equation can be established to solve the unknown circulating current. A new steady-state model is developed to simply and accurately describe the explicit analytical expressions for various voltage and current quantities in an MMC. The accuracy of the expressions is improved by the consideration of the circulating current when deriving all the analytical expressions. The model's simplicity is demonstrated by having only one key equation to solve. Based on the analytical expressions for the arm voltages, the equivalent circuits for MMC are proposed to improve the current understanding of the operation of MMC. The feasibility and accuracy of the proposed method are verified by comparing its results with the simulation and experimental results. [ABSTRACT FROM AUTHOR]

Microgrid is widely accepted as an effective mean of integrating various distributed energy resources (DERs) through their interface converters to provide electric power of high quality and reliability. These distributed resources interface converters can operate in an autonomous fashion without any communication for enhanced system reliability and reduced complexity. Conventionally, the real power-frequency droop control and the reactive power-voltage magnitude droop are adopted as the decentralized control strategies in these DERs interface converters for the autonomous power sharing operations. However, the reactive power sharing of Q\--V droop control often deteriorates due to its dependence on the line impedances. In this paper, a Q\--\dotV droop control method with \dotV restoration mechanism is proposed to improve reactive power sharing. Its operation principle and control method are explained and analyzed. Simulation and experimental results are presented to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In paper (IEEE Trans. Power Electron., vol. 22, no. 1, pp. 69-79, Jan. 2007), large signal and small signal transfer function models of dc-dc power converters are obtained using concept of energy factor (EF) and its associated parameters. In sections II-D and II-E of the original paper, authors describe that the two key parameters of the transfer function are independent of conduction duty cycle k. This is not true and the correct small signal analysis is also reported. [ABSTRACT FROM AUTHOR]