Non-isolated Three-port Converter Research Articles

A Two-Switch SEPIC-Based Nonisolated Three-Port Converter Featuring High Step-Up Gain for Solar PV Applications

A two-switch nonisolated DC–DC three-port converter (TPC) based on a modified SEPIC circuit with a high voltage gain is introduced and a unified power control strategy is proposed in this article. The proposed TPC is integrated with one low-voltage input and one high-voltage port and is suitable for photovoltaic (PV) applications. The operating principle of this TPC is analyzed in detail and then its static voltage gain is determined. In addition, the advantage of using a modified SEPIC circuit is that fewer components are employed compared to a similar topology. Furthermore, the state space method is adopted to analyze this multiple-input multiple-output (MIMO) system and then a small signal model is built to design an appropriate control strategy. Finally, the proposed 100 W TPC connects a solar PV energy storage system to a load demonstrating efficiency ranging from 85% to 94%. Moreover, the steady- and dynamic-state performances of this TPC are verified in the SimStar MT3200 HIL platform, which illustrates the feasibility of the proposed TPC and its power control strategy for solar PV applications.

Three-Port Bi-Directional DC–DC Converter with Solar PV System Fed BLDC Motor Drive Using FPGA

The increased need for renewable energy systems to generate power, store energy, and connect energy storage devices with applications has become a major challenge. Energy storage using batteries is most appropriate for energy sources like solar, wind, etc. A non-isolated three-port DC–DC-converter energy conversion unit is implemented feeding the brushless DCmotor drive. In this paper, a non-isolated three-port converter is designed and simulated for battery energy storage, interfaced with an output drive. Based on the requirements, the power extracted from the solar panel during the daytime is used to charge the batteries through the three-port converter. The proposed three-port converter is analyzed in terms of operating principles and power flow. An FPGA-based NI LabView PXI with SbRio interface is used to develop the suggested approach’s control hardware, and prototype model results are obtained to test the proposed three-port converter control system’s effectiveness and practicality. The overall efficiency of the converter’s output improves as a result. The success rate is 96.5 percent while charging an ESS, 98.1 percent when discharging an ESS, and 95.7 percent overall.

High Step-Up Three-Port Converter for Renewable Energy Systems

In this paper, a high voltage gain non-isolated three-port converter with a three-winding coupled inductor is proposed for renewable energy system. By implementing a cascoded structure where a photovoltaic (PV) source is stacked on top of a battery voltage source, the high output voltage can be achieved with a reasonable duty cycle, resulting in higher efficiency when both sources provide energy to the load. Furthermore, only three power switches are needed to regulate the energy flows among the three ports. When the low-voltage PV source provides energy to the load, the primary winding and the secondary winding of this coupled inductor are connected in series with opposite polarities to increase the voltage gain of the proposed converter.The use of a clamp circuit allows for the recycling of leakage inductance energy, which helps to reduce voltage spikes on the power switches. This results in the selection of low on-resistance switches and leads to higher converter efficiency. The proposed topology’s operations, steady-state analyses, and key parameter designs are then discussed. To validate the performance of the proposed converter, a 300 W laboratory prototype is implemented.

Wide input range non-isolated three-port converters for stand-alone PV storage power systems

Wide input range non-isolated three-port converters for stand-alone PV storage power systems

An autonomous solar PV system using boost TPC for energy harvesting with mode-based power flow management control

Energy harvesting from environment provides a compelling alternative to battery-powered standalone systems. The rising use of green energy resources in energy sector has a substantial impact on the low voltage DC (LVDC) systems. Multiport converters make it easier to convert renewable energy for use in everyday situations. To ensure uninterruptible power supply, a non-isolated Three-Port Converter (TPC) acts as a gateway for renewable sources, energy storage, and loads. The paper describes a modified power flow management control for a standalone solar PV system using boost TPC with time sharing control and an added mode-based controller for voltage regulation. To operate the TPC effectively in Dual Output (DO), Dual Input (DI) and Single Input and Single Output (SISO) modes, localized controllers are used. The converter small signal model is developed for all operating modes and based on this, sampled data control theory is applied to design the digital controller for load regulation. When the TPC switches from one operating mode to another, the voltage regulation control sets the controller parameters for the appropriate mode. Also, to extend battery lifespan, the control algorithm includes a battery overcharge prevention mechanism. The proposed algorithm is realized in a System on a Programmable Chip (SoPC) using the Field Programmable Gate Array (FPGA) Cyclone-III and Nios-II as processor. The system is tested in real time with solar PV as the source of energy and a lead-acid battery as the storage.

Three-Port Converter With Single Coupled Inductor for High Step-Up Applications

The output voltages of renewable energy resources are relatively low for practical applications. Hence, a converter with high voltage gain is needed. This article proposes a high voltage gain nonisolated three-port converter for a renewable energy source with energy storage applications. A coupled inductor with three windings is used for transferring energies among photovoltaic (PV), battery, and the load. When the battery provides energy to the load, two primary windings with opposite polarities are connected in series. Thus, the effective primary turns is reduced for improving the voltage gain. In addition, the energy stored in the leakage inductor is recycled to the output so as to suppress voltage stress on the power switches and improve system efficiency for energy transference from either PV or battery to the load. Both PV and the battery can provide power to the load independently, thus sharing the load power coordinately. The operation principles, steady-state analyses and key parameter design of the proposed topology are then described in detail. Finally, an experimental prototype is implemented to verify the theoretical analyses with PV, battery, and load voltages of 48 V, 24 V, and 200 V, respectively.

A Nonisolated Three-Port DC–DC Converter With Two Bidirectional Ports and Fewer Components

This article presents a new nonisolated three-port converter with reduced component count compared with existing reported topologies. This is achieved by developing different power flow graphs and selecting the most appropriate converters arrangement. In addition, as compared to only one bidirectional port in most reported studies, this article considers two bidirectional ports to accommodate applications requiring bidirectional power flow, such as dc microgrid and regenerative braking. The proposed converter is able to work in seven different modes of operation, which cover all possible combinations of power flow among the three ports. Furthermore, seamless and smooth transition, maximum power point tracking, battery protection and output voltage regulation are achieved. Experimental waveforms, particularly for transient responses during mode transition, are reported to verify the proposed TPC.

A High-Gain Non-Isolated Three-Port Converter for Building-Integrated PV Systems

Using a hybrid renewable energy source with an energy storage system, this paper proposed a novel multi-stage non-isolated three-port converter with a 5H inverter to feed a residential load varying from 50 Watts to 3500 Watts. The proposed three-port converter operates in grid-tied and standalone power modes. A novel demand-side management algorithm, which covers eight operation modes, is described. Additionally, a complete control system is discussed. The proposed control system controls the PV maximum power point and battery charging/discharging, and regulates the 400 V DC bus voltage, the load voltage in standalone mode, and the grid-tied injected current. The proposed converter and the control system are validated through simulation for all power modes. The simulation results reveal that the proposed system is viable for Building-Integrated PV Systems.

Synthesis and Analysis of Three-Port DC/DC Converters with Two Bidirectional Ports Based on Power Flow Graph Technique

This paper presents a systematic topological study to derive all possible basic and non-isolated three-port converters (TPCs) using power flow diagrams. Unlike most reported TPCs with one bidirectional port, this paper considers up to two bidirectional ports and provides a comprehensive analytical tool. This tool acts as a framework for all power flow combinations, selection, and design. Some viable converter configurations have been identified and selected for further analysis.

A fuel-cell/battery hybrid DC backup power system via a new high step-up three port converter

In this paper, a fuel-cell (FC)/battery hybrid direct-current (DC) backup power system is proposed for high step-up applications. This system is composed of a newly developed non-isolated three-port converter, which achieves a high voltage gain by taking the advantage of a quasi Z-source network and an energy transfer capacitor. After analyzing the converter, a comprehensive comparison study and a design procedure are provided. Moreover, the controllers regulating the source power levels while smoothing the FC power profile according to the proposed energy management strategy (EMS) are designed based on the developed small-signal model of the proposed converter. Both hardware and controller design procedures are validated through the PSIM model of the whole system. As a result, it is shown that the proposed system can effectively couple FC and battery while transferring their energies to a high voltage DC bus according to the offered EMS.

Implementation of non-isolated three-port converter through augmented time response

<p><span lang="EN-US">The work is concerning a multi-port dc-dc converter with improved time response and steady state output. Here the converter carries bare amount of switches for managing the power with mono inductance. The inductance and along with that the switched capacitance are pre owned to bring large voltage gain. This paper put forwarded an appropriate controller for the closed loop monitored high-gain converter with three ports. Higher is that the conversion rate. This converter is also a good interface between DC-source and load that aims to progressing time response with FLC and PI controller in the closed loop system. The converter with the PI controller and FLC is look over and the fast responses are compared with time domain specifications. The simulation outcome indicates that the FLC based converter brings most excellent time domain response.</span></p>

Analysis and Design of a New Non-Isolated Three-Port Converter With High Voltage Gain for Renewable Energy Applications

This paper proposes a non-isolated three-port converter which integrates the input port, battery port, and load port into one converter for renewable energy applications. The coupled inductor and switched capacitor are used to achieve high voltage gain and three power switches can be utilized to realize the power flows between the sources, the battery, and the load. The energy stored in the leakage inductance is recycled to reduce the voltage stress of the power switch. In addition, various operating stages are analyzed and design considerations are presented. Compared to the relevant converters, the proposed converter can realize power flows and achieve high voltage gain by using few components. Finally, a laboratory prototype of the proposed converter with input port voltage 24 V, battery port voltage 48 V, and output voltage 400 V with 200 W rated power is implemented to validate the feasibility and effectiveness of the theoretical analyses.

Soft-Switched Three-Port DC-DC Converter With Simple Auxiliary Circuit

In this paper, a new high efficiency soft-switching non-isolated three-port converter (TPC) is proposed. In the conventional TPC, three switches are required to process power in different directions between inputs and output. Providing soft-switching condition for all switches using a low number of auxiliary components is a challenging task. In this paper, the conventional TPC topology is modified by changing its structure and adding a simple auxiliary circuit such that all switches operate under soft-switching condition in all operating modes. To reduce the volume of the converter, the magnetic components are integrated using a coupled inductor in the auxiliary soft-switching cell. In this paper, various converter operating modes are presented, and design considerations are discussed. Finally, a prototype 200 W, 100 V converter is implemented in the laboratory, and the theoretical analysis is validated by the experimental results.

Nonisolated PWM Three-Port Converter Realizing Reduced Circuit Volume for Satellite Electrical Power Systems

Three-port converters (TPCs) combining two dc–dc converters into a single unit is a promising solution that can simplify and miniaturize satellite electrical power systems. Conventional nonisolated TPCs, however, face a variety of challenges, such as the necessity of a transformer, low effective duty cycle operation, and unshared ground issues. This article proposes a novel nonisolated TPC integrating a unidirectional and bidirectional pulsewidth modulation converters. The two converters can be integrated into a single unit with reducing total switch count without employing a transformer, thus achieving the simplified circuit. In addition, thanks to the capacitor added in series with switches, not only the voltage stress of semiconductor devices is reduced, but also miniaturized inductor design is feasible. The quantitative analysis revealed that the volume of passive components in the proposed TPC could be reduced by approximately 19% compared with a conventional nonisolated TPC. A 240-W prototype was built for the experimental verification, and the results agreed well with those of the analysis, demonstrating its efficacy.

A family of non-isolated three-port converters based on H-bridge

In order to satisfy the charging and discharging circuits of energy storage element (ESE), a family of non-isolated three-port converter (TPC) by embedding a ESE-centric H-bridge cell into the classic buck, boost and buck/boost converters are proposed. There are two types of embedding method: (1) Without connecting with component of the classic converter, H-bridge is inserted into the classic converter directly. (2) Connected with component of the classic converter in a specific way, the H-bridge is connected with the rest part of the classic converter. The operating mode and port voltage restriction of the obtained TPCs are analyzed and summarized, which features high integration and compact size. Experimental results of one of the proposed TPCs, named LP-3-buck/boost, have been presented to verify the analysis results.

Non-Isolated Single-Inductor DC/DC Converter With Fully Reconfigurable Structure for Renewable Energy Applications

A novel non-isolated three-port converter (NITPC) is introduced in this brief. The purpose of this topology is to integrate a regenerative load such as DC bus and motor with dynamic braking, instead of the widely reported consuming load, with a photovoltaic (PV)-battery system. Conventional methods require either a separate DC–DC converter to process the reversible power flow or employing an isolated three-port converter (TPC), which allows bi-directional power flow between any two ports. However, these methods require many switches, which increases the converter size and control complexity. This brief hence presents a compact but fully functional design by combining and integrating basic converters to form a simplified single-inductor converter structure while keeping a minimum amount of switches. The resultant converter is fully reconfigurable that all possible power flow combinations among the sources and load are achieved through different switching patterns, while preserving the single power processing feature of TPC. This brief presents a design example of the proposed NITPC for a PV-battery powered DC microgrid. Detailed circuitry analysis, operation principles of both DC grid-connected and islanded modes, and experimental results of different modes in steady state and mode transitions are presented.

Nonisolated Wide Operation Range Three-Port Converters With Variable Structures

In the standalone renewable power system, three-port converters (TPCs) are widely used to interface a renewable source, a storage battery, and a load, simultaneously. In nonisolated applications, TPCs without transformers usually suffer from ports’ voltage restrictions. Such a drawback limits TPCs’ operation range because of changeable renewable source voltage and storage battery voltage. In this paper, the TPCs with variable structures are proposed. Compared with the existing available nonisolated TPCs, the proposed TPCs have the loose ports voltage restrictions because of variable structures among ports, and thus feature the wide operation range. These variable structure TPCs can also realize the needed power management requirements. What is more, these variable structure TPCs can be compact size since only one inductor is applied. In this paper, one of the variable structure TPCs is taken as an example for detail analysis. Operational modes of this TPC are designed and optimized for different power management requirements in different ports’ voltage restrictions, and control scheme is also designed. The experimental results are also given to validate the analysis.

Topology Derivation of Nonisolated Three-Port DC–DC Converters From DIC and DOC

A systematic approach is proposed for the derivation of nonisolated three-port converter (TPC) topologies based on dual-input converters (DIC) and dual-output converters (DOC), which serves as an interface for a renewable source, a storage battery, and a load simultaneously. The power flow in a TPC is analyzed and compared with that in a DIC or a DOC, respectively. Beginning with building the power flow paths of a TPC from a DIC or a DOC, the general principles and detailed procedures for the generation and optimization of TPC topologies are presented. Based on these works, a family of nonisolated TPC topologies is developed. The derived TPCs feature single-stage power conversion between any two of the three ports, and result in high integration and high efficiency. One of the proposed TPCs, named Boost-TPC, is taken as an example for verifying the performance of its circuit topology with related operational methods. Pulsewidth modulation and power management methods, used in this circuit, are analyzed in detail. Experiments have been carried out on a 1-kW prototype of the Boost-TPC, which demonstrate the feasibility and effectiveness of the proposed topology derivation method.