A Bidirectional Soft-Switched DAB-Based Single-Stage Three-Phase AC–DC Converter for V2G Application

In vehicle-to-grid applications, the battery charger of the electric vehicle (EV) needs to have a bidirectional power flow capability. Galvanic isolation is necessary for safety. An ac-dc bidirectional power converter with high-frequency isolation results in high power density, a key requirement for an on-board charger of an EV. Dual-active-bridge (DAB) converters are preferred in medium power and high voltage isolated dc-dc converters due to high power density and better efficiency. This paper presents a DAB-based three-phase ac-dc isolated converter with a novel modulation strategy that results in: 1) single-stage power conversion with no electrolytic capacitor, improving the reliability and power density; 2) open-loop power factor correction; 3) soft-switching of all semiconductor devices; and 4) a simple linear relationship between the control variable and the transferred active power. This paper presents a detailed analysis of the proposed operation, along with simulation results and experimental verification

Generic closed loop controller for power regulation in dual active bridge DC-DC converter with current stress minimization

This paper presents a comprehensive and generalized analysis of the bidirectional dual active bridge (DAB) DC/DC converter using triple phase shift (TPS) control to enable closed loop power regulation while minimizing current stress. The key new achievements are: a generic analysis in terms of possible conversion ratios/converter voltage gains (i.e. Buck/Boost/Unity), per unit based equations regardless of DAB ratings, and a new simple closed loop controller implementable in real time to meet desired power transfer regulation at minimum current stress. Per unit based analytical expressions are derived for converter AC RMS current as well as power transferred. An offline particle swarm optimization (PSO) method is used to obtain an extensive set of TPS ratios for minimizing the RMS current in the entire bidirectional power range of - 1 to 1 per unit. The extensive set of results achieved from PSO presents a generic data pool which is carefully analyzed to derive simple useful relations. Such relations enabled a generic closed loop controller design that can be implemented in real time avoiding the extensive computational capacity that iterative optimization techniques require. A detailed Simulink DAB switching model is used to validate precision of the proposed closed loop controller under various operating conditions. An experimental prototype also substantiates the results achieved

Comprehensive steady state analysis of bidirectional dual active bridge DC/DC converter using triple phase shift control

Several papers have been published recently on TPS control of dual active bridge (DAB) converter, however, no complete study of the converter operation behaviour exists, that takes into account all switching modes in both charging and discharging (bidirectional) power transfer. In this paper, six switching modes and their complements with opposite power transfer direction are defined with their operational constraints. Exact expressions for power transferred are derived with no fundamental frequency assumptions and range of power transfer for each mode is also defined to characterize mode limitations. Detailed constraints for zero voltage switching (ZVS) are also obtained. A new definition for converter reactive power consumption is introduced. This is based on calculation of inductor apparent power which avoids fundamental frequency approximations as well as the vague negative (back flowing) power definitions in recent papers. All known DAB phase shift modulation techniques including conventional, dual and extended phase shift, represent special cases from triple phase shift, therefore the presented analysis provides a generalised theory for all phase shift based modulation techniques

Operation and control of a current source converter series tapping of an LCC-HVDC link for integration of offshore wind power plants

This work presents a series tapping station for integrating Offshore Wind Power Plants (OWPP) into a (Line Commutated Converter High Voltage Direct Current) LCC-HVDC transmission system. The tapping station allows to integrate wind power resources without building a new HVDC link and it is based on a Current Source Converter (CSC). However, the CSC requires a minimum DC current to extract the power coming from the OWPP which may not be guaranteed depending on the power conditions of the HVDC corridor. For this reason, this paper proposes a coordinated operation and control of the CSC and the OWPP. A steady-state analysis is performed to determine the appropriate AC voltage level of the CSC. A power reduction algorithm is presented to limit power extraction during a reduction in the current of the HVDC transmission system and under loss of communications between the CSC and the OWPP. The proposed algorithm and the performance of the system are validated through simulation results.Peer ReviewedPostprint (author's final draft

Switching-Cell Arrays - An Alternative Design Approach in Power Conversion

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThe conventional design of voltage-source power converters is based on a two-level half-bridge configuration and the selection of power devices designed to meet the full application specifications (voltage, current, etc.). This leads to the need to design and optimize a large number of different devices and their ancillary circuitry and prevents taking advantage from scale economies. This paper proposes a paradigm shift in the design of power converters through the use of a novel configurable device consisting on a matrix arrangement of highly-optimized switching cells at a single voltage class. Each switching cell consists of a controlled switch with antiparallel diode together with a self-powered gate driver. By properly interconnecting the switching cells, the switching cell array (SCA) can be configured as a multilevel active-clamped leg with different number of levels. Thus, the SCA presents adjustable voltage and current ratings, according to the selected configuration. For maximum compactness, the SCA can be conceived to be only configurable by the device manufacturer upon the customer needs. For minimum cost, it can also be conceived to be configurable by the customer, leading to field-configurable SCAs. Experimental results of a 6x3 field-configurable SCA are provided to illustrate and validate this design approach.Peer ReviewedPostprint (author's final draft

Comparison of single-phase matrix converter and H-bridge converter for radio frequency induction heating

This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order to maintain the comparable performance to the H-bridge converter. Simulation and experimental results for both converters are presented. Comparisons between two converters have confirmed the excellent performance of the proposed matrix converter

System configuration, fault detection, location, isolation and restoration: a review on LVDC Microgrid protections

Low voltage direct current (LVDC) distribution has gained the significant interest of research due to the advancements in power conversion technologies. However, the use of converters has given rise to several technical issues regarding their protections and controls of such devices under faulty conditions. Post-fault behaviour of converter-fed LVDC system involves both active converter control and passive circuit transient of similar time scale, which makes the protection for LVDC distribution significantly different and more challenging than low voltage AC. These protection and operational issues have handicapped the practical applications of DC distribution. This paper presents state-of-the-art protection schemes developed for DC Microgrids. With a close look at practical limitations such as the dependency on modelling accuracy, requirement on communications and so forth, a comprehensive evaluation is carried out on those system approaches in terms of system configurations， fault detection, location, isolation and restoration

A solid state Marx generator with a novel configuration

The new configuration proposed in this paper for Marx Generator (MG.) aims to generate high voltage for pulsed power applications through reduced number of semiconductor components with a more efficient load supplying process. The main idea is to charge two groups of capacitors in parallel through an inductor and take the advantage of resonant phenomenon in charging each capacitor up to a double input voltage level. In each resonant half a cycle, one of those capacitor groups are charged, and eventually the charged capacitors will be connected in series and the summation of the capacitor voltages can be appeared at the output of the topology. This topology can be considered as a modified Marx generator which works based on the resonant concept. Simulated models of this converter have been investigated in Matlab/SIMULINK platform and the acquired results fully satisfy the anticipations in proper operation of the converter

Investigation of Fault-Tolerant Capabilities in an Advanced Three-Level Active T-Type Converter

A novel fault-tolerant three-level power converter topology, named advanced three-level active T-Type (A3L-ATT) converter, is introduced to increase the reliability of multilevel power converters used in safety-critical applications. This new fault-tolerant multilevel power converter is derived from the conventional T-Type converter topology. The topology has significantly improved the fault-tolerant capability under any open circuit or certain short-circuit faults in the semiconductor devices. In addition, under healthy condition, the redundant phase leg can be utilized to share overload current with other main legs, which enhances the overload capability of the converter. The conduction losses in the original outer devices can be reduced by sharing the load current with the redundant leg. Moreover, unlike other existing fault-tolerant power converters in the literature, full output voltages can be always obtained in this proposed A3L-ATT converter during fault-tolerant operation. A 13.5-kW ATT-A3L converter prototype was developed and constructed using silicon carbide MOSFETs. Simulation and experimental results were obtained to substantiate the theoretical claims of this new fault-tolerant power converter