In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.

Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

In the first part of this paper, three-phase power factor correction (PFC) rectifier topologies with sinusoidal input currents and controlled output voltage are derived from known single-phase PFC rectifier systems and/or passive three-phase diode rectifiers. The systems are classified into hybrid and fully active pulsewidth modulation boost-type or buck-type rectifiers, and their functionality and basic control concepts are briefly described. This facilitates the understanding of the operating principle of three-phase PFC rectifiers starting from single-phase systems, and organizes and completes the knowledge base with a new hybrid three-phase buck-type PFC rectifier topology denominated as Swiss Rectifier. Finally, core topics of future research on three-phase PFC rectifier systems are discussed, such as the analysis of novel hybrid buck-type PFC rectifier topologies, the direct input current control of buck-type systems, and the multi-objective optimization of PFC rectifier systems. The second part of this paper is dedicated to a comparative evaluation of four rectifier systems offering a high potential for industrial applications based on simple and demonstrative performance metrics concerning the semiconductor stresses, the loading and volume of the main passive components, the differential mode and common mode electromagnetic interference noise level, and ultimately the achievable converter efficiency and power density. The results are substantiated with selected examples of hardware prototypes that are optimized for efficiency and/or power density.

The Essence of Three-Phase PFC Rectifier Systems—Part II

1. Control Methodology 2. Dynamical Systems 3. Applications to Social and Environmental Problems

Dynamics and Control

This paper provides a comprehensive review and analyses on the state-of-the-art and future trends for high-power conductive on-board chargers (OBCs) for electric vehicles. To provide a global context, a summary of global charging standards and electric vehicle (EV) related trends are presented, which demonstrates momentum toward the OBCs with higher power rating. High-power OBCs are either unidirectional or bidirectional, and they have either an integrated or non-integrated system architecture. Non-integrated high-power OBCs are studied both from industry and academia, and the former are used to illustrate the current state of the art. The latter are classified on the basis of the converter design approach, studied for their principle of operation, and compared over power density, weight, efficiency, and other metrics. In addition to non-integrated OBCs, recent advancements in propulsion-machine integrated OBC solutions are also presented. Other integrated OBC techniques, such as system integration with the EV's auxiliary power module and wireless charging systems, are also discussed. Finally, future charging strategies and functionalities in charging infrastructures are addressed, and global OBC trends are summarized.

Global Trends in High-Power On-Board Chargers for Electric Vehicles

Modern development of semiconductor power-switching devices has promoted the use of power electronic converters as power transformers at the distribution level. This paper presents an ac–ac dual-active-bridge (DAB) converter for a solid-state transformer. The proposed converter topology consists of two active H-bridges and one high-frequency transformer. Four-quadrant switch cells are used to allow bidirectional power flow. Because power is controlled by the phase shift between two bridges, output voltage can be regulated when input voltage changes. This paper analyzes the steady-state operation and the range of zero-voltage switching. It develops a switch commutation scheme for the ac–ac DAB converters. Experimental results from a scaled-down prototype are provided to verify the theoretical analysis.

Solid-State Transformer Architecture Using AC–AC Dual-Active-Bridge Converter

Recent developments in the electricity sector encourage a high penetration of Renewable Energy Sources (RES). In addition, European policies are pushing for mass deployment of Electric Vehicles (EVs). Due to their non-controllable characteristics, these loads have brought new challenges in distribution networks, resulting in increased difficulty for Distribution System Operators (DSOs) to guarantee a safe and reliable operation of the grid. Battery Energy Storage Systems (BESSs) are promising solutions for mitigating the impact of the new loads and RES. In this paper, different aspects of the BESS's integration in distribution grids are reviewed. At first, the physical layer will be considered, focusing on the main battery technologies commercially available and on the power electronics converter. Secondly, the different functionalities that a grid-connected BESS can provide will be investigated, and then its sizing, location and control in distribution network will be discussed. In addition, an overview of actual BESSs installations is given. All in all, this paper aims at providing a comprehensive view of BESSs integration in distribution grids, highlighting the main focus, challenges, and research gaps for each one of these aspects.

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A Comprehensive Review of the Integration of Battery Energy Storage Systems Into Distribution Networks

This paper presents highly efficient three-phase high-power-factor hybrid rectifiers assembled by the parallel connection of a three-phase diode-bridge rectifier and series dc–dc boost converter with a two- or three-level unidirectional pulse width modulation (PWM) rectifier. The idea is to obtain a rectifier that is robust, highly efficient, and simple as a diode-based rectifier and also able to benefit from the PWM rectifier capability to reduce the line current harmonic content. Exemplary three-phase unidirectional hybrid systems built with a two-level delta-switch rectifier and three-level T-type or VIENNA six-switch rectifiers are suggested. Additionally, control schemes, which are appropriate for safeguarding the high-power-factor operation while improving the power sharing rating of the hybrid paralleled rectifier units and able to handle a phase loss without changing the controller structure, are proposed. In order to evaluate the studied hybrid rectifiers, first, an efficiency comparison between two- and three-level hybrid systems with conventional PWM rectifiers is performed. After that, the loss calculations are extended to a variable chip area to allow a fair comparison between these rectifiers. Interestingly, it is shown that the presented hybrid systems not only can achieve a higher efficiency but also require less silicon area than the single PWM rectifiers they are based on. Finally, experimental results obtained with an assembled unidirectional hybrid delta-switch rectifier prototype are presented in order to demonstrate the performance and advantages of this solution.

Analysis of High-Efficiency Three-Phase Two- and Three-Level Unidirectional Hybrid Rectifiers

This work presents an automated design procedure for series parallel resonant converters (LCC) employed in electrostatic precipitator (ESP) power supplies, which reduces the designer effort significantly. The requirements for the power supplies in ESP applications and means to derive an accurate mathematical model of the LCC converter, such as the power loss from commercial insulated-gate bipolar transistors, are described in detail in this paper. The converter parameters, such as resonant tank elements, are selected in order to improve the overall efficiency of the system, when a typical ESP energization operation range is considered. The analysis comprises two different control strategies: the conventional variable frequency control and the dual control. Both control strategies are analyzed by comparing semiconductor losses of five commercial modules. Finally, the circuit operation and design are verified with a 60 kW LCC resonant converter test setup.

Automated Design of a High-Power High-Frequency LCC Resonant Converter for Electrostatic Precipitators

This paper introduces a novel three-phase buck-type unity power factor rectifier appropriate for high power Electric Vehicle battery charging mains interfaces. The characteristics of the converter, named the Swiss Rectifier, including the principle of operation, modulation strategy, suitable control structure, and dimensioning equations are described in detail. Additionally, the proposed rectifier is compared to a conventional 6-switch buck-type ac-dc power conversion. According to the results, the Swiss Rectifier is the topology of choice for a buck-type PFC. Finally, the feasibility of the Swiss Rectifier concept for buck-type rectifier applications is demonstrated by means of a hardware prototype.

Swiss rectifier — A novel three-phase buck-type PFC topology for Electric Vehicle battery charging

This paper introduces a novel three-level voltage-source converter (VSC) as an alternative to known three-level topologies, including the conventional neutral-point-clamped converter (NPCC), many T-type VSCs, and active NPCC. It is shown that, operating in the low converter dc-link voltage range, this new solution not only can achieve higher efficiency than many typical three-level structures but also can overcome their drawback of asymmetrical semiconductor loss distribution for some operating conditions. Therefore, a remarkable increase of the converter output power capability and/or system reliability can be accomplished. The switching states and commutations of the converter, named here as hybrid NPCC (H-NPCC), are analyzed, and a loss-balancing scheme is introduced. Five- and seven-level H-NPCC topologies with loss-balancing features are also presented. Finally, a semiconductor-area-based comparison is used to further evaluate many three-level VSC systems. Interestingly, the total chip area of the proposed H-NPCC is already the lowest for low switching frequencies.

Thiago Batista Soeiro

Papers

A Comprehensive Review of the Integration of Battery Energy Storage Systems Into Distribution Networks

Analysis of High-Efficiency Three-Phase Two- and Three-Level Unidirectional Hybrid Rectifiers

Automated Design of a High-Power High-Frequency LCC Resonant Converter for Electrostatic Precipitators

Swiss rectifier — A novel three-phase buck-type PFC topology for Electric Vehicle battery charging

The New High-Efficiency Hybrid Neutral-Point-Clamped Converter