Capacitor Clamped Dc-dc Converter Research Articles

High-Efficient High-Voltage-Gain Capacitor Clamped DC–DC Converters and Their Construction Method

Due to the low output voltage of photovoltaic cells and fuel cells, a high-voltage-gain dc-dc converter is indispensable in the renewable energy power generation systems. In this article, a series of high-voltage-gain capacitor clamped dc-dc converters is constructed based on interleaved boost structures by considering the requirement of low input current ripple in fuel cell application. Furthermore, the construction method of capacitor clamped dc-dc converters is summarized according to the construction processes of these converters. Finally, the capacitor clamped dc-dc converter with the voltage gain of 3/(1-D) is analyzed in detail. Then, a 250-W prototype is built to validate the theoretical analysis and the construction method.

A grid-connected PV system based on multilevel modular capacitor clamped dc-dc converter

A grid-connected PV system based on multilevel modular capacitor clamped dc-dc converter

Efficiency Characterization and Impedance Modeling of a Multilevel Switched-Capacitor Converter Using Pulse Dropping Switching Scheme

A pulse dropping switching technique (PDT) has been presented in this paper to accomplish variable conversion ratio (CR) in a multilevel modular capacitor-clamped dc-dc converter in the step-up conversion mode. The switching pattern is generated by comparing a triangular wave with a rectangular wave, and a proper output voltage regulation can be obtained by controlling the relative frequency and amplitude of these two waveforms. A state-space modeling technique has been applied here to estimate the variation in equivalent output resistance (EOR) for different operating conditions of the PDT. The EOR can be varied in a wide range without changing the operating frequency of the converter, and thereby the PDT enhances the degrees of freedom to accomplish voltage regulation in a two-phase switched-capacitor converter. Slow-switching limit of the converter has been derived to define the boundary of the EOR. Different challenges and limitations of the proposed modulation scheme has been discussed in detail, and the proposed analysis has been verified by comparing the analytical expressions with the simulation and experimental results for different switching frequencies, modulation indices, and number of active modules. In addition, variations in the CR, efficiency and ripple voltage for different number of active modules and switching conditions have been described in detail.

Optimal Design of a Multilevel Modular Capacitor-Clamped DC–DC Converter

Magnetic-less multilevel dc-dc converters attract much attention in automotive industry due to their small size, high efficiency, and high temperature operation features. A multilevel-modular capacitor-clamped dc-dc converter (MMCCC) is one of the most promising topologies among them with simple control and reduced switch current stress. This paper presents the optimal design considerations for an MMCCC to achieve the highest efficiency and the smallest size. In order to design the converter with the highest efficiency, the analytical power loss equation of an MMCCC should be derived. By considering the stray inductance in the circuit, the optimal design approach should be divided into two cases, overdamped case and underdamped case. The converter can be designed to achieve high efficiency in both cases by varying circuit parameters. If the circuit is designed in overdamped case, huge electrolytic capacitor bank has to be used to achieve high efficiency, which will increase the total converter size. If the circuit is designed in underdamped case, small-size multilayer ceramic capacitor can be utilized due to the low capacitance requirement. Although relatively high switching frequency is required in underdamped case due to practical considerations, zero-current switching (ZCS) can be achieved for all the switching devices which minimize the converter switching loss. Therefore, the optimal design point of an MMCCC with the smallest size and the highest efficiency should be selected at the underdamped case with ZCS for all the switches. Simulation results are provided to validate the design. A prototype of an MMCCC by using the proposed optimal design procedure is built. Experimental results of this optimal designed MMCCC prototype are provided to demonstrate the validity of the proposed method.

Multiple-Load–Source Integration in a Multilevel Modular Capacitor-Clamped DC–DC Converter Featuring Fault Tolerant Capability

A multilevel modular capacitor-clamped DC-DC converter (MMCCC) will be presented in this paper with some of its advantageous features. By virtue of the modular nature of the converter, it is possible to integrate multiple loads and sources with the converter at the same time. The modular construction of the MMCCC topology provides autotransformer-like taps in the circuit, and depending on the conversion ratio of the converter, it becomes possible to connect several dc sources and loads at these taps. The modularity of the new converter is not limited to only this dc transformer (auto) like operation, but also provides redundancy and fault bypass capability in the circuit. Using the modularity feature, some redundant modules can be operated in bypass state, and during some faults, these redundant modules can be used to replace a faulty module to maintain an uninterrupted operation. Moreover, by obtaining a flexible conversion ratio, the MMCCC converter can transfer power in both directions. Thus, this MMCCC topology could be a solution to establish a power management system among multiple sources and loads having different operating voltages.

A Multilevel Modular Capacitor-Clamped DC–DC Converter

A novel topology of a multilevel modular capacitor-clamped dc-dc converter will be presented in this paper. In contrast to the conventional flying capacitor multilevel dc-dc converter, this new topology is completely modular and requires a simpler gate drive circuit. Moreover, the new topology has many advantageous features such as high frequency operation capability, low input/output current ripple, low on-state voltage drop, and bidirectional power flow management. This paper discusses the construction and operation of the new converter along with a comparison to a conventional converter. Finally, simulation and experimental results are used to validate the concept of this new topology.