Single-input Converters Research Articles

Extendable Multiport High Step-Up DC–DC Converter for Photovoltaic-Battery Systems With Reduced Voltage Stress on Switches/Diodes

In the standalone photovoltaic (PV)-battery power system, a multiport converter is more desirable than several single-input converters as it has advantages of the simpler circuit, higher efficiency, and lower cost. In this paper, a novel structure based on a non-isolated high step-up multi-port converter (MPC) is proposed. The proposed MPC has the capability of providing high voltage gain and low normalized peak inverse voltage (NPIV) across semiconductor devices. Maximum power point tracking (MPPT) algorithm can be applied for each PV input source, which is an effective method to prevent mismatches among PV modules. Different from the existing extendable MPCs, the proposed MPC can extend both unidirectional input ports and bidirectional ports to involve more types of renewable energy sources and energy storage devices. Continuous input currents and modularity are the other profits of the proposed MPC. Various operating modes, steady-state analysis, and design considerations have been discussed. Comparison results verify the above advantage of the proposed MPC. Finally, a 240W laboratory prototype is designed to validate the performance of the proposed MPC.

Topology Synthesis of a Family of Integrated Three-Port Converters for Renewable Energy System Applications

In the standalone renewable energy system, a multiport converter is more desirable than several single-input converters as it has advantages of a simpler circuit, higher efficiency, and lower cost. This article proposes a novel topology synthesis method to derive integrated three-port converters with low cost and compact structure. With the proposed topology synthesis method, integrated three-port converters can be easily developed from conventional single-input single-output (SISO) converters by replacing a switch and a diode with a basic cell, including bidirectional power flow. Compared with the SISO converter, the derived integrated three-port converters only need to add the extra switch and diode, which makes them have low cost and compact structure. As an example, topology synthesis based on buck, boost, buck-boost, Cuk, SEPIC, and zeta converters is performed in this article. The proposed topology synthesis method can also be extended to deduce a series of n-port converters. In order to achieve a better understanding of the proposed converters, the integrated three-port SEPIC converter is specifically analyzed, including its operation principle, steady-state performance, small-signal modeling, and control system. Finally, experimental verifications have been carried out to illustrate the feasibility and effectiveness of the proposed topology synthesis method.

Modeling and Regulator Design for Three-Input Power Systems with Decoupling Control

In hybrid renewable power systems, the use of a multiple-input dc/dc converter (MIC) leads to simpler circuit and lower cost, when compared to the conventional use of several single-input converters. This paper proposed a novel three-input buck/boost/buck-boost converter, which can be used in applications with various values of input voltage. The energy sources in this converter can deliver power to the load either simultaneously or individually in one switching period. The steady relationship, the power management strategy and the small-signal circuit model of this converter have been derived. With decoupling technology, modeling and regulator design can be obtained under multi-loop control modes. Finally, three generating methods of a multiple-input buck/boost/buck-boost converter is given, and this method can be extended to the other multiple-input dc/dc converters.

One-Cycle Control for a Double-Input DC/DC Converter

In hybrid power systems, the use of a multiple-input converter (MIC) instead of several single-input converters leads to a simpler circuit and lower cost. Energy management is always required for the MICs in order to ensure the highest utilization of renewable energy. The MIC-based hybrid power system is a typical multiple-input multiple-output coupling system, and it has multiple operating modes. As a result, the design of the controllers is very complicated. This paper proposes one-cycle control (OCC) for double-input buck converter (DIBC) to eliminate the interactions of the control loops and, thus, to simplify the design of the controllers. The mode transition circuit is further proposed to realize seamless mode transition, according to the available renewable energy and the output power. Small signal models of DIBC in different operating modes are derived. It can be seen that with OCC, the two control loops are independent of each other, and no current regulator is required. Moreover, the design conditions of the output voltage regulator in different operating modes are the same. As a result, the controller design is greatly simplified. An 800-W prototype has been built and tested in the lab and the experimental results validate the proposed OCC.

Optimizing Design of Dual-Input Buck DC/DC Converter

In hybrid renewable power systems, the use of a multiple-input dc/dc converter (MIC) leads to simpler circuit and lower cost, compared to the conventional use of several single-input converters. This paper focuses on the optimizing design of MIC. Different from a single–input DC/DC converter, the parameters design of a MIC is very complicated. This is because the converter will operate in multiple operation modes, in which the power sources can deliver power o the load either simultaneously or individually. In this paper, an optimizing design method is proposed with the considerations of the multiple operation modes. A dual-input Buck converter is taken as an example to show the design method and a prototype is built to verify the theoretical analysis.

DESIGN OF A DUAL-INPUT SERIAL DC–DC CONVERTER REALIZING INDIVIDUAL SWITCHING MODES

To drive a white light-emitting diode (LED) in portable devices, a dual-input serial DC–DC converter realizing individual switching modes is proposed in this paper. Unlike conventional single-input converters, the proposed converter provides output voltage by converting not only battery energy but also solar energy. Therefore, the proposed converter can suppress energy consumption of a battery. Furthermore, in the proposed converter, the -1/m× stepped-down voltage (m = 1,2,…,N) is generated to drive LED's cathode only when the voltage of solar-cells is insufficient to drive 1 × transfer mode. In other words, when the voltage of solar-cells is sufficient to drive LEDs, the proposed converter is in standby mode. For this reason, the proposed converter can realize high power efficiency, because energy loss caused by the power conversion is suppressed. The properties of the proposed converter are clarified by theoretical analyses. Furthermore, SPICE simulations and experiments show the validity of circuit design, where theoretical results correspond well with SPICE simulated results. For this reason, derived theoretical formulas can provide basic information to design negative switched capacitors (SC) DC–DC converters. The proposed converter will be useful as a driver circuit of white LEDs for display backlighting.

Quantitative Evaluation of DC Microgrids Availability: Effects of System Architecture and Converter Topology Design Choices

This paper presents a quantitative method to evaluate dc microgrids availability by identifying and calculating minimum cut sets occurrence probability for different microgrid architectures and converter topologies. Hence, it provides planners with an essential tool to evaluate downtime costs and decide technology deployments based on quantitative risk assessments by allowing to compare the effect that converter topologies and microgrid architecture choices have on availability. Conventional architectures with single-input converters and alternative configurations with multiple-input converters (MICs) are considered. Calculations yield that all microgrid configurations except those utilizing center converters achieve similar availability of 6-nines. Three converter topologies are used as representatives of many other circuits. These three benchmark circuits are the boost, the isolated SEPIC (ISEPIC), and the current-source half-bridge. Marginal availability differences are observed for different circuit topology choices, although architectures with MICs are more sensitive to this choice. MICs and, in particular, the ISEPIC, are identified as good compromise options for dc microgrids source interfaces. The analysis also models availability influence of local energy storage, both in batteries and generators' fuel. These models provide a quantitative way of comparing dc microgrids with conventional backup energy systems. Calculations based on widely accepted data in industry supports the analysis.

Synthesis of Multiple-Input DC/DC Converters

Hybrid power systems continuously deliver power to the load from several renewable energy sources. For such systems, the use of a multiple-input converter (MIC) has the advantage of simpler circuit structure and lower cost, compared to the use of several single-input converters. By decomposing converters into basic cells, namely, pulsating source cells and output filters, a set of basic rules for generating multiple-input converter topologies is proposed. Specifically, two families of multiple-input converters are systematically generated. In the first family of MICs, all the input sources can power the load simultaneously or individually. In the second family, only one power source is allowed to transfer energy to the load at a time. Furthermore, some isolated MICs are simplified for reducing the complexity of the circuit configuration.