This paper proposes a novel nonisolated single-input dual-output three-level dc-dc converter (SIDO-TLC) appropriate for medium- and high-voltage applications. The SIDO-TLC is an integration of the ...three-level buck and boost converters, whose output voltages are regulated simultaneously. Reducing voltage stress across semiconductor devices, improving efficiency, and reducing inductors size are among the main merits of the new topology. Moreover, due to the considerably reduced volume of the step-down filter capacitor, a small film capacitor can be used instead, whose advantages are lower equivalent series resistance and a longer lifespan. A closed-loop control system has been designed based on a small-signal model derivation in order to regulate the output voltages along with the capacitors' voltage balancing. In order to verify the theoretical and simulation results, a 300-W prototype was built and experimented. The results prove the aforementioned advantages of the SIDO-TLC, and the high effectiveness of the balancing control strategy. Furthermore, the converter shows very good stability, even under simultaneous step changes of the loads and input voltage.
This article aims to propose a new nonisolated step-up multiport dc-dc converter. The proposed topology is a dual-input dual-output dc-dc converter with different output voltages levels. This makes ...it possible to be used in hybrid energy systems with different input sources as well as in electric vehicles to supply the traction motor and auxiliary loads. The proposed converter is capable of providing high voltage gains with small values of duty cycles and low normalized peak voltage stress across the semiconductor devices. Therefore, the switches with small turn- on resistance and the diodes with a reduced nominal voltage can be used, which in turn reduces the switching and conduction losses. The operation principles of the proposed converter are explained and steady-state analysis is carried out. Then, the circuit performance is compared with other related step-up multiport dc-dc converters in the literature. Eventually, the performance of the proposed converter is validated with experimental results.
In this article, a resonant push-pull dc-dc converter suitable for switching frequencies in the MHz-range is investigated. Despite a simple design procedure with no need of multiresonant tuning, the ...converter topology is capable of providing a constant output current over a wide output voltage range in unregulated operation. Based on an analytical solution of steady-state operation, normalized dependencies of converter behavior are determined and used to formulate generalized design considerations. In order to verify the theoretical analysis, the design procedure of a 300-W prototype operating at a switching frequency of 6.78 MHz is described considering the impact of circuit parasitics on converter operation. The prototype provides a stable operation within the full output voltage range of 0-150 V and reaches a peak efficiency of 93% at the nominal output voltage. A rapid transient response of the converter is demonstrated by applying a closed-loop on / off -control to the prototype.
A modular dc-dc converter (MDCC) has been proposed for high-step-ratio interconnection in dc grid applications. To further optimize the performance of the MDCC, this article presents a trapezoidal ...current modulation with bidirectional power flow ability. By giving all the submodule (SM) capacitors an equal duty to withstand the stack dc voltage, their voltages are balanced without additional feedback control. Moreover, based on soft-switching performance and circulating current analysis, three-level and two-level operation modes featured with high efficiency conversion and large power transmission, respectively, are introduced. The control schemes of both modes are designed to minimize the conduction losses. Besides, the SM capacitor voltage ripples with different switching patterns are compared, and the option for ripple minimization is presented. A full-scale case study is provided to introduce the design process and device selection of the MDCC. The experimental tests based on a downscaled prototype are finally presented to validate the theoretical analysis.
Nonisolated dc-dc converterswith multi-inputfeatures are very popular in the area of hybrid energy integration since they are compact and cost efficient compared to the isolated topologies. A ...dual-input hybrid step-up dc-dc converter (DIHDC) with a compact structure is introduced in this article. DIHDC operates based on the switched inductor technique. DIHDC has two inductors with equal values that are parallelly energized in the initial working modes (i.e., switch on condition) and dissipates the stored energy in series in the final working mode (switch off condition). Also, the proposed converter can be extended up to multiple inputs with slight modifications in the structure. Simple and compact structure, relatively higher efficiency, and good voltage conversion ratio are the potential merits of the new converter. Analysis of DIHDC in steady-state condition is explained elaborately and the simulation results are presented. Detailed dynamic analysis of the converter has been performed based on the small signal model of the converter and the necessary transfer functions are derived. A laboratory scale converter model is developed to confirm the efficient operation of DIHDC in realistic environments.
Summary
In this paper, a new nonisolated bidirectional dc‐dc converter is proposed. In this converter, a 4‐winding coupled inductor is used. The second winding of coupled inductor, which is connected ...in series with a capacitor, is applied to eliminate input current ripple at low‐voltage side for whole range of duty cycles in both boost and buck operations. Working of this converter is in such a way that increasing or decreasing turns ratio of third and fourth windings of coupled inductor increases the voltage conversion ratio. This paper has analyzed the value of current and voltage stresses of all switches, required condition for canceling input current ripple at low‐voltage side and the voltage conversion ratio for boost and buck operations. Finally, the accuracy and precision of analytic results are justified through experimental results for both boost and buck operations.
In this paper, a bidirectional push-pull converter is investigated with new add-on feature of three-level PWM plus phase-shift (PPS) control scheme, and a control map is proposed to assist converter ...operation and design in the optimized region. The PPS control strategy is adopted to reduce peak current of the transistors, to increase the input-voltage-variation range and to expand the soft-switching region. A comprehensive analysis of operation principle, transmission capability, and soft-switching operation in 12 different operation modes is presented. Based on the complete analysis, a control map is proposed to assist converter operation that can effectively avoid high-circulating-current regions, low-power-transmission-capability regions, and hard-switched regions. In the control map, a circuit parameter k is signified and its range is found, beyond which the PPS converter no longer operates normally. The proposed control map and the circuit parameter k are general to all PPS converters, providing a meaningful analyzing method to design and operate all PPS converters. A 30~48 V/380 V prototype rated at 100-1000 W was built under the guideline. The analysis is verified by both simulation and experimental results.
DC-DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts ...to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc-dc converters, this paper aims to comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc-dc converters are presented and summarized with comparative study of different voltage-boosting techniques.
This paper presents the design and control of an advanced unidirectional dc-dc modular multilevel converter (MMC), which enables the integration of off-shore windfarms with the high-voltage direct ...current (HVdc) transmission system. The proposed converter consists of a single-phase MMC inverter, coupled with series-connected rectifier modules through a medium frequency transformer of multiple secondary windings. The modularity feature of the proposed converter enables scalability for different voltage levels. In addition to the galvanic isolation, the transformer also provides stepping gain to the output voltage. The proposed converter shows superior performance in terms of efficiency, losses, and devices utilization, when compared with the most competitive unidirectional cascaded dc-dc converters such as input series output series and input parallel output series. Furthermore, unlike the conventional d-q control method, which involves multiple transformations, this paper employs a simple proportional resonant control strategy that directly acts on the ac output of the MMC, under the stationary reference frame. The analytical design along with the simulation and experimentally validated results, confirmed the excellent performance of the proposed converter.
This paper proposes a family of soft-switching bidirectional converters. In many applications, the bidirectional converters operate over a wide range of duty cycle and load variations. In the ...proposed converters, in order to extend the zero-voltage switching operation range, two supplemental voltage sources utilizing passive components are implemented in the auxiliary circuit. By using this method, the soft-switching features are ensured for an extensive range of the converter duty cycles. This is achieved independent of the output power value or the converter operation mode, and so, soft switching is ensured within the entire converter operating region. In these converters, all semiconductors components are soft switched, and the auxiliary circuit does not contribute to the complexity of the control circuit. Also, no extra voltage stress exists on the main switches and the voltage stress on the auxiliary switches is lower than the main switches voltage stress. In this paper, the proposed bidirectional buck/boost converter is analyzed and to confirm the feasibility of the proposed method, experimental results of a 150-W prototype converter are presented.
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