High-frequency-link (HFL) power conversion systems (PCSs) are attracting more and more attentions in academia and industry for high power density, reduced weight, and low noise without compromising efficiency, cost, and reliability. In HFL PCSs, dual-active-bridge (DAB) isolated bidirectional dc-dc converter (IBDC) serves as the core circuit. This paper gives an overview of DAB-IBDC for HFL PCSs. First, the research necessity and development history are introduced. Second, the research subjects about basic characterization, control strategy, soft-switching solution and variant, as well as hardware design and optimization are reviewed and analyzed. On this basis, several typical application schemes of DAB-IBDC for HPL PCSs are presented in a worldwide scope. Finally, design recommendations and future trends are presented. As the core circuit of HFL PCSs, DAB-IBDC has wide prospects. The large-scale practical application of DAB-IBDC for HFL PCSs is expected with the recent advances in solid-state semiconductors, magnetic and capacitive materials, and microelectronic technologies.

Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System

An isolated three-port bidirectional dc-dc converter composed of three full-bridge cells and a high-frequency transformer is proposed in this paper. Besides the phase shift control managing the power flow between the ports, utilization of the duty cycle control for optimizing the system behavior is discussed and the control laws ensuring the minimum overall system losses are studied. Furthermore, the dynamic analysis and associated control design are presented. A control-oriented converter model is developed and the Bode plots of the control-output transfer functions are given. A control strategy with the decoupled power flow management is implemented to obtain fast dynamic response. Finally, a 1.5 kW prototype has been built to verify all theoretical considerations. The proposed topology and control is particularly relevant to multiple voltage electrical systems in hybrid electric vehicles and renewable energy generation systems.

An Isolated Three-Port Bidirectional DC-DC Converter With Decoupled Power Flow Management

Advances and trends of energy storage technology in Microgrid

Multiport DC-DC converters are of potential interest in applications such as generation systems utilising multiple sustainable energy sources. A family of multiport bidirectional DC-DC converters derived from a general topology is presented. The topology shows a combination of DC-link and magnetic coupling. This structure makes use of both methods to interconnect multiple sources without the penalty of extra conversion or additional switches. The resulting converters have the advantage of being simple in topology and have a minimum number of power devices. The proposed general topology and basic cells show several possibilities to construct a multiport converter for particular applications and provide a solution to integrate diverse sources owing to their flexibility in structure. The system features a minimal number of conversion steps, low cost and compact packaging. In addition, the control and power management of the converter by a single digital processor is possible. The centralised control eliminates complicated communication structures that would be necessary in the conventional structure based on separate conversion stages. A control strategy based on classical control theory is proposed, showing a multiple PID-loop structure. The general topology and a set of three-port embodiments are detailed.

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Family of multiport bidirectional DC¿DC converters

The reliability of the microinverter is a very important feature that will determine the reliability of the ac-module photovoltaic (PV) system. Recently, many topologies and techniques have been proposed to improve its reliability. This paper presents a thorough study for different power decoupling techniques in single-phase microinverters for grid-tie PV applications. These power decoupling techniques are categorized into three groups in terms of the decoupling capacitor locations: 1) PV-side decoupling; 2) dc-link decoupling; and 3) ac-side decoupling. Various techniques and topologies are presented, compared, and scrutinized in scope of the size of decoupling capacitor, efficiency, and control complexity. Also, a systematic performance comparison is presented for potential power decoupling topologies and techniques.

A Review of Power Decoupling Techniques for Microinverters With Three Different Decoupling Capacitor Locations in PV Systems

This paper presents a new multi-input bidirectional dc-dc converter which connects a fuel cell, storage and load by a combination of a dc-link and magnetic-coupling. A boost-dual-half-bridge and a bidirectional direct-connected switching cell are used. The topology is simple and only needs six power switches. The load and the sources are galvanically isolated. Furthermore, the proposed converter draws/injects smooth current from the fuel cell and the supercapacitor. The system is suitable for medium-power applications where simple topology, autonomous operation, compact packaging, and low cost are required. Different control schemes to manage power flow are proposed and compared. Simulation and experimental results that verify the effectiveness of the topology and its control scheme are presented. Moreover, it is shown that the idea of combining the dc-link and magnetic-coupling can be further developed to a general topology for multi-port bidirectional dc-dc converters.

Multi-input bidirectional DC-DC converter combining DC-link and magnetic-coupling for fuel cell systems

The implementation of a fuel cell/battery hybrid system is proposed to improve the slow transient response of a PEM fuel cell stack. This system can be used for an autonomous device with quick load variations. A suitable three-port, galvanic isolated, bi-directional power converter is proposed to control the power flow. An energy management method for the proposed three-port circuit is analyzed and implemented. Measurements from a 500 W laboratory prototype are presented to demonstrate the validity of the approach.

A three-port bi-directional converter for hybrid fuel cell systems

This paper proposes a novel control method for DC voltage in single-phase voltage-source inverters fed by constant-current or constant-power sources. The technique predicts the inverter power require to correct a DC voltage error within one fundamental AC cycle. This is based on the power balance between DC input and AC output, and the energy stored in the DC link capacitor. The fast response means a smaller capacitor can be used, and operation with a large double-line-frequency ripple on the DC bus is possible without causing distortion of the AC output current. This scheme is suitable for applications where substantial DC link buffer energy is unnecessary, e.g.: grid-connected photovoltaic generators. The reliability and lifetime of the inverter can be significantly improved if a non-electrolytic type capacitor is used. Experimental results are presented that verify the inverter operation.

Predictive DC voltage control of single-phase PV inverters with small DC link capacitance

This paper presents a zero-voltage-switching (ZVS) three-port bidirectional converter for fuel cell and supercapacitor applications. A simple and effective method to extend the soft-switching range is proposed, especially for the three-port active-bridge topology. By continuously adjusting the duty cycle on the supercapacitor side H-bridge according to the supercapacitor voltage level, soft-switching conditions are achieved over the full operating range due to the equivalent volt-second products applied to the transformer over half the switching period. Detailed analysis is provided for both the two-port and the three-port converters. Furthermore, a dual PI-loop based control strategy is proposed to achieve constant output voltage and precise power flow management, as well as soft-switching. The converter is implemented and tested

Mam Marcel Hendrix

Papers

Family of multiport bidirectional DC¿DC converters

Multi-input bidirectional DC-DC converter combining DC-link and magnetic-coupling for fuel cell systems

A three-port bi-directional converter for hybrid fuel cell systems

Predictive DC voltage control of single-phase PV inverters with small DC link capacitance

A Soft-Switched Three-Port Bidirectional Converter for Fuel Cell and Supercapacitor Applications