Topologies And Control Strategies Of Multiple-input Dc-dc Converters

Renewable energy has been receiving more and more attentions for solving the energy crisis and environmental pollution. Most renewable energy are intermittent and random not possible at all times because they are strongly dependent on the climates and weather. But they are mutually complementary in the sense that they can be utilized simultaneously to maintain continuous delivery of power to the load, which can be named as hybrid renewable power system. In such 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 topologies and control strategies of MICs.Recently, several types of MIC topologies have been proposed and the approaches for synthesizing MIC topologies have been reported in some papers, but they are imperfect in a sense. In this paper, by decomposing converters into basic cells, namely, the pulsating source cell and the output filter, a set of the pulsating source cells and the basic rules for connecting cells are proposed. Based on which, a systematic method for synthesizing of MICs is proposed, and all of the existing MIC topologies and numerous new ones can be generated systematically, which include non-isolated and isolated ones. Furthermore, the isolated MIC topologies are simplified. Since the configuration of a double-input Buck dc/dc converter is very simple and all of the power sources can deliver power to the load either individually or simultaneously through this converter, it is chosen as an example in this paper to illustrate the operating principle and characteristics of the non-isolated MICs. In addition, this paper discusses the relationship between the inductor current ripple and the phase difference among the drive signals of the two switches, and an interleaved dual-edge modulation (IDEM) is proposed in order to minimize the inductor current ripple. As a result, the filter inductor can be reduced significantly, leading to a fast dynamic response and a high power density. The IDEM can be applied to other double-input converters. A 400 W prototype is fabricated to verify the theoretical analysis and the effectiveness of the IDEM.A specific dual-input full-bridge dc/dc converter is chosen as an example to illustrate the operating principle and characteristics of the isolated MICs. The dual phase-shift control strategy are proposed so that the converter can operate in two operation modes, in which the power sources can deliver power o the load either simultaneously or individually, and the switches realize zero-voltage-switching (ZVS). The parameters design procedure is also shown and an 800 W prototype is built to verify the theoretical analysis and the effectiveness of the control strategy.In order to utilize the renewable energy as much as possible, power management is necessary for the hybrid renewable power system. In this paper, an effective power management strategy is proposed, by which this system can operate in several operation modes and the demanded power of the load is provided by renewable power source as much as possible and the rest is provided by the other power source. Moreover, when only one source powers the load, the system operates with a dual-loop, where the voltage loop is the outer loop and the current loop is the inner one, leading to a fast dynamic response. Due to the existence of the several operation modes, the current and voltage regulators will operate in the different situations. In this paper, the small-signal model of the hybrid power system with a dual-input Buck dc/dc converter is derived, and an effective design approach of the closed-loop system is proposed. The current and voltage regulators are designed firstly when one source powers the load individually; and then they are checked when two sources power the load simultaneously. A 400 W prototype was built and experimentally evaluated. The experimental results show that the system with the designed regulators can operate stably at various operating modes and can transit smoothly among the multiple operation modes.