The Theory of Matrices. By F R. Gantmacher. Two volumes, pp. 374 and 276. 1959. (Translated from the Russian by K. A. Hirsch; Chelsea Publishing Company, New York)

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

DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

This paper proposes a novel dual-phase-shift (DPS) control strategy for a dual-active-bridge isolated bidirectional DC-DC converter. The proposed DPS control consists of a phase shift between the primary and secondary voltages of the isolation transformer, and a phase shift between the gate signals of the diagonal switches of each H-bridge. Simulation on a 600-V/5-kW prototype shows that the DPS control has excellent dynamic and static performance compared to the traditional phase-shift control (single phase shift). In this paper, the concept of ldquoreactive powerrdquo is defined, and the corresponding equations are derived for isolated bidirectional DC-DC converters. It is shown that the reactive power in traditional phase-shift control is inherent, and is the main factor contributing to large peak current and large system loss. The DPS control can eliminate reactive power in isolated bidirectional DC-DC converters. In addition, the DPS control can decrease the peak inrush current and steady-state current, improve system efficiency, increase system power capability (by 33%), and minimize the output capacitance as compared to the traditional phase-shift control. The soft-switching range and the influence of short-time-scale factors, such as deadband and system-level safe operation area, are also discussed in detail. Under certain operation conditions, deadband compensation can be implemented easily in the DPS control without a current sensor.

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Eliminate Reactive Power and Increase System Efficiency of Isolated Bidirectional Dual-Active-Bridge DC–DC Converters Using Novel Dual-Phase-Shift Control

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

This paper presents a new zero-voltage-switching (ZVS) bidirectional dc-dc converter. Compared to the traditional full and half bridge bidirectional dc-dc converters for the similar applications, the new topology has the advantages of simple circuit topology with no total device rating (TDR) penalty, soft-switching implementation without additional devices, high efficiency and simple control. These advantages make the new converter promising for medium and high power applications especially for auxiliary power supply in fuel cell vehicles and power generation where the high power density, low cost, lightweight and high reliability power converters are required. The operating principle, theoretical analysis, and design guidelines are provided in this paper. The simulation and the experimental verifications are also presented.

A new ZVS bidirectional DC-DC converter for fuel cell and battery application

An inverter topology and control scheme has been developed and tested to demonstrate that it can drive low-inductance, surface mounted permanent magnet motors over the wide constant power speed range (CPSR) required in electric vehicle applications. This new controller, called the dual-mode inverter controller (DMIC) , can drive both the Permanent Magnet Synchronous Machine with sinusoidal back emf, and the brushless dc machine (BDCM) with trapezoidal emf as a motor or generator. Here we concentrate on the application of the DMIC to the operation of the BDCM in the motoring mode. Simulation results, supported by closed form analytical expressions, show that the CPSR of the DMIC driven BDCM is infinite when all of the motor and inverter loss mechanisms are neglected. The expressions further show that the ratio of high-to-low motor inductances accommodated by the DMIC is 11 making the DMIC compatible with both low- and high-inductance BDCMs. Classical hysteresis-band motor current control used below base speed is integrated with DMICs phase advance above base speed. The power performance of the DMIC is then simulated across the entire speed range. Laboratory testing of a low-inductance, 7.5-hp BDCM driven by the DMIC demonstrated a CPSR above 6:1. Current peak and rms values remained controlled below rated values at all speeds. A computer simulation accurately reproduced the results of lab testing showing that the limiting CPSR of the test motor is 8:1.

Extending the constant power speed range of the brushless DC motor through dual-mode inverter control

The brushless DC motor (BDCM) has high-power density and efficiency relative to other motor types. These properties make the BDCM well suited for applications in electric vehicles provided a method can be developed for driving the motor over the 4 to 6:1 constant power speed range (CPSR) required by such applications. The present state of the art for constant power operation of the BDCM is conventional phase advance (CPA). In this paper, we identify key limitations of CPA. It is shown that the CPA has effective control over the developed power but that the current magnitude is relatively insensitive to power output and is inversely proportional to motor inductance. If the motor inductance is low, then the RMS current at rated power and high speed may be several times larger than the current rating. The inductance required to maintain RMS current within rating is derived analytically and is found to be largely relative to that of BDCM designs using high-strength rare earth magnets. Thus, the CPA requires a BDCM with a large equivalent inductance.

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Limitations of the conventional phase advance method for constant power operation of the brushless DC motor

It is shown that in the absence of speed sensitive losses the constant power speed range (CPSR) of the switched reluctance motor (SRM) is infinite when continuous conduction is allowed during high speed operation. Therefore, the SRM is a candidate motor for all traction applications including those involving heavy vehicles which may require a CPSR of 10:1 or greater. Analytic expressions are derived relating average and rms motor current and average motor power to the design parameters of the motor. The analysis is based on a linear magnetics model that neglects saturation. Generally, magnetic saturation has a pronounced impact on the performance characteristics of an SRM and linear analysis yields inaccurate results; however, it is shown that a linear model is highly accurate in predicting high speed performance when the SRM operates in continuous conduction. The analytic results may provide useful guidance for tailoring the design of SRMs for high CPSR applications

Impact of continuous conduction on the constant power speed range of the switched reluctance motor

The dual-mode inverter control (DMIC) was initially developed to provide broad constant power speed range (CPSR) operation for a surface mounted permanent magnet machine (PMSM) having low inductance. The DMIC interfaces the output of a common voltage source inverter (VSI) to the PMSM through an ac voltage controller. The ac voltage controller consists of three pairs of anti-parallel silicon controlled rectifiers (SCRs), one anti-parallel SCR pair in series with each winding of the motor. In a recent paper a fundamental frequency model of DMIC type controllers was developed using an equivalent reactance interpretation of the in-line SCRs. In this work, the same fundamental frequency model is used to show that the DMIC may have considerable loss reduction benefits even if the motor winding inductance is large. Specifically, it is shown that the SCRs enable maximum watts per rms amp control during constant power operation. The rms motor current can be minimized for any given power level and sufficiently large speed with DMIC. A fixed winding inductance and a conventional inverter can only be optimized for a single speed and power level. The performance predicted by the fundamental frequency model of the DMIC is compared to that of a conventional PMSM drive where the motor has sufficiently large inductance to achieve an infinite CPSR. It is shown that the SCRs can reduce motor current by a factor of 0.7071 at high speed and rated power. This would reduce the motor copper losses by 50% and reduce the conduction losses in the VSI by 29.3%. At less than rated power the percentage of motor/VSI loss reduction enabled by the SCRs is seen to be even larger.

J.S. Lawler

Papers

A new ZVS bidirectional DC-DC converter for fuel cell and battery application

Extending the constant power speed range of the brushless DC motor through dual-mode inverter control

Limitations of the conventional phase advance method for constant power operation of the brushless DC motor

Impact of continuous conduction on the constant power speed range of the switched reluctance motor

Minimum current magnitude control of surface PM synchronous machines during constant power operation