Dynamic modeling of a dual active bridge DC to DC converter with average current control and load-current feed-forward

Bidirectional power flow is needed in many power conversion systems like energy storage systems, regeneration systems, power converters for improvement of the power quality and some DC-DC applications where bidirectional high power conversion and galvanic isolation are required. The dual active bridge (DAB) is an isolated, high voltage ratio DC-DC converter suitable for high power density and high power applications, being a key interface between renewable energy sources and energy storage devices. This paper is focused on the modeling and control design of a DC-DC system with battery storage based on a DAB converter with average current mode control of the output current and output voltage control. The dynamic response of the output voltage to load steps is improved by means of an additional load-current feed-forward control loop. An analytical study of the load-current feed-forward is presented and validated by means of both simulations and experimental results.This work was supported by the Spanish Ministry of Economy and Competitiveness under grant ENE2012-37667-C02-01.Guacaneme Moreno, JA.; Gabriel Garcerá; Figueres Amorós, E.; Patrao Herrero, I.; González Medina, R. (2015). Dynamic modeling of a dual active bridge DC to DC converter with average current control and load-current feed-forward. International Journal of Circuit Theory and Applications. 43(10):1311-1332. https://doi.org/10.1002/cta.2012S131113324310Vazquez, S., Lukic, S. M., Galvan, E., Franquelo, L. G., & Carrasco, J. M. (2010). Energy Storage Systems for Transport and Grid Applications. IEEE Transactions on Industrial Electronics, 57(12), 3881-3895. doi:10.1109/tie.2010.2076414De Doncker, R. W. A. A., Divan, D. M., & Kheraluwala, M. H. (1991). A three-phase soft-switched high-power-density DC/DC converter for high-power applications. IEEE Transactions on Industry Applications, 27(1), 63-73. doi:10.1109/28.67533Kheraluwala, M. N., Gascoigne, R. W., Divan, D. M., & Baumann, E. D. (1992). Performance characterization of a high-power dual active bridge DC-to-DC converter. IEEE Transactions on Industry Applications, 28(6), 1294-1301. doi:10.1109/28.175280Chang, Y.-H., & Wu, K.-W. (2012). A gain/efficiency-enhanced bidirectional switched-capacitor DC-DC converter. International Journal of Circuit Theory and Applications, 42(5), 468-493. doi:10.1002/cta.1863Li H Liu D Peng FZ Gui-Jia S Small Signal Analysis of A Dual Half Bridge Isolated ZVS Bi-directional DC-DC converter for Electrical Vehicle Applicat 36th IEEE Power Electronics Specialists Conference 2005 2777 2782Chiu, H.-J., Yao, C.-J., & Lo, Y.-K. (2009). A DC/DC converter topology for renewable energy systems. International Journal of Circuit Theory and Applications, 37(3), 485-495. doi:10.1002/cta.475Doishita K Hashiwaki M Aoki T Kawagoe Y Murakami N Highly reliable uninterruptible power supply using a bi-directional converter The 21st International Telecommunication Energy Conference (INTELEC '99), Copenhagen 1999 10.1109/INTLEC.1999.794066Krismer F Biela J Kolar JW A comparative evaluation of isolated bi-directional DC/DC converters with wide input and output voltage range 40th IAS Annual Meeting Industry Applications Conference 2005 1 599 606Aggeler D Biela J Inoue S Akagi H Kolar JW Bi-Directional Isolated DC-DC Converter for Next-Generation Power Distribution - Comparison of Converters using Si and SiC Devices Power Conversion Conference-Nago 2007 510 517Krishnamurthy HK Ayyanar R Building Block Converter Module for Universal (AC-DC, DC-AC, DC-DC) Fully Modular Power Conversion Architecture IEEE Power Electronics Specialists Conference 2007 483 489Romero-Cadaval, E., Spagnuolo, G., Franquelo, L. G., Ramos-Paja, C. A., Suntio, T., & Xiao, W. M. (2013). Grid-Connected Photovoltaic Generation Plants: Components and Operation. IEEE Industrial Electronics Magazine, 7(3), 6-20. doi:10.1109/mie.2013.2264540Yu, X., She, X., Ni, X., & Huang, A. Q. (2014). System Integration and Hierarchical Power Management Strategy for a Solid-State Transformer Interfaced Microgrid System. IEEE Transactions on Power Electronics, 29(8), 4414-4425. doi:10.1109/tpel.2013.2289374Liserre, M., Sauter, T., & Hung, J. (2010). Future Energy Systems: Integrating Renewable Energy Sources into the Smart Power Grid Through Industrial Electronics. IEEE Industrial Electronics Magazine, 4(1), 18-37. doi:10.1109/mie.2010.935861Mi, C., Bai, H., Wang, C., & Gargies, S. (2008). Operation, design and control of dual H-bridge-based isolated bidirectional DC–DC converter. IET Power Electronics, 1(4), 507. doi:10.1049/iet-pel:20080004Friedemann A Krismer F Kolar JW Design of a Minimum Weight Dual Active Bridge Converter for an Airborne Wind Turbine System Proceedings of the 27th Applied Power Electronics Conference and Exposition (APEC) 2012Krismer, F., & Kolar, J. W. (2010). Accurate Power Loss Model Derivation of a High-Current Dual Active Bridge Converter for an Automotive Application. IEEE Transactions on Industrial Electronics, 57(3), 881-891. doi:10.1109/tie.2009.2025284Hengsi Qin, & Kimball, J. W. (2012). Generalized Average Modeling of Dual Active Bridge DC–DC Converter. IEEE Transactions on Power Electronics, 27(4), 2078-2084. doi:10.1109/tpel.2011.2165734Segaran D McGrath B Holmes DG Adaptive dynamic control of a Bidirectional DC-DC converter IEEE Proceedings Energy Conversion Congress 2010 1442 1449Bai H Mi C Wang C Gargies S The dynamic model and hybrid phase-shift control of a dual-active-bridge converter Proceedings IECON 2008 2840 2845Segaran, D., Holmes, D. G., & McGrath, B. P. (2013). Enhanced Load Step Response for a Bidirectional DC–DC Converter. IEEE Transactions on Power Electronics, 28(1), 371-379. doi:10.1109/tpel.2012.2200505Tang W Lee FC Ridley RB Small-signal modeling of average current-mode control APEC'92. Seventh Annual Conference Proceedings 1992 747 755Kheraluwala MH High-Power High frequency DC-DC converters PhD thesis 1991Fang, C.-C. (2011). Sampled-data poles, zeros, and modeling for current-mode control. International Journal of Circuit Theory and Applications, 41(2), 111-127. doi:10.1002/cta.790Redl, R., & Sokal, N. O. (1986). Near-Optimum Dynamic Regulation of DC-DC Converters Using Feed-Forward of Output Current and Input Voltage with Current-Mode Control. IEEE Transactions on Power Electronics, PE-1(3), 181-192. doi:10.1109/tpel.1986.4766303Qin H Kimball JW Closed-loop control of DC-DC dual active bridge converters driving single-phase inverters IEEE Energy Conversion Congress and Exposition (ECCE) 2012 173 17

Active Power and DC Voltage Coordinative Control for Cascaded DC–AC Converter With Bidirectional Power Application

("(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, 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 components of this work in other worksTwo stage-cascaded converters are widely used in dc–ac hybrid systems to achieve the bidirectional power transmission. The topology of dual active bridge cascaded with inverter DABCI) is commonly used in this application. This paper proposes a coordinative control method for DABCI and it is able to reduce the dc-link voltage fluctuation between the DAB and inverter, then reduce the stress on the switching devices, as well as improve the system dynamic performance. In the proposed control method, the DAB and inverter are coordinated to control the dc-link voltage and the power, and this responsibility sharing control can effectively suppress the impact of the power variation on the dc-link voltage, without sacrificing stability. The proposed control method is also effective for DABCI in unidirectional power transmission. The effectiveness of the propose control has been validated by both simulations and experiments

Solid state transformer technologies and applications: a bibliographical survey

This paper presents a bibliographical survey of the work carried out to date on the solid state transformer (SST). The paper provides a list of references that cover most work related to this device and a short discussion about several aspects. The sections of the paper are respectively dedicated to summarize configurations and control strategies for each SST stage, the work carried out for optimizing the design of high-frequency transformers that could adequately work in the isolation stage of a SST, the efficiency of this device, the various modelling approaches and simulation tools used to analyze the performance of a SST (working a component of a microgrid, a distribution system or just in a standalone scenario), and the potential applications that this device is offering as a component of a power grid, a smart house, or a traction system.Peer ReviewedPostprint (published version

EMTP model of a bidirectional cascaded multilevel solid state transformer for distribution system studies

This paper presents a time-domain model of a MV/LV bidirectional solid state transformer (SST). A multilevel converter configuration of the SST MV side is obtained by cascading a single-phase cell made of the series connection of an H bridge and a dual active bridge (dc-dc converter); the aim is to configure a realistic SST design suitable for MV levels. A three-phase four-wire converter has been used for the LV side, allowing the connection of both load/generation. The SST model, including the corresponding controllers, has been built and encapsulated as a custom-made model in the ATP version of the EMTP for application in distribution system studies. Several case studies have been carried out in order to evaluate the behavior of the proposed SST design under different operating conditions and check its impact on power qualityPostprint (published version

Power Interface Design and System Stability Analysis for 400 V DC-Powered Data Centers

The demands of high performance cloud computation and internet services have increased in recent decades. These demands have driven the expansion of existing data centers and the construction of new data centers. The high costs of data center downtime are pushing designers to provide high reliability power supplies. Thus, there are significant research questions and challenges to design efficient and environmentally friendly data centers with address increasing energy prices and distributed energy developments. This dissertation work aims to study and investigate the suitable technologies of power interface and system level configuration for high efficiency and reliable data centers. A 400 V DC-powered data center integrated with solar power and hybrid energy storage is proposed to reduce the power loss and cable cost in data centers. A cascaded totem-pole bridgeless PFC converter to convert grid ac voltage to the 400 V dc voltage is proposed in this work. Three main control strategies are developed for the power converters. First, a model predictive control is developed for the cascaded totem-pole bridgeless PFC converter. This control provides stable transient performance and high power efficiency. Second, a power loss model based dual-phase-shift control is applied for the efficiency improvement of dual-active bridge converter. Third, an optimized maximum power point tracking (MPPT) control for solar power and a hybrid energy storage unit (HESU) control are given in this research work. The HESU consists of battery and ultracapacitor packs. The ultracapacitor can improve the battery lifetime and reduce any transients affecting grid side operation. The large signal model of a typical solar power integrated datacenter is built to analyze the system stability with various conditions. The MATLAB/Simulink™-based simulations are used to identify the stable region of the data center power supply. This can help to analyze the sensitivity of the circuit parameters, which include the cable inductance, resistance, and dc bus capacitance. This work analyzes the system dynamic response under different operating conditions to determine the stability of the dc bus voltage. The system stability under different percentages of solar power and hybrid energy storage integrated in the data center are also investigated

Power Interface Design and System Stability Analysis for 400 V DC-Powered Data Centers

The demands of high performance cloud computation and internet services have increased in recent decades. These demands have driven the expansion of existing data centers and the construction of new data centers. The high costs of data center downtime are pushing designers to provide high reliability power supplies. Thus, there are significant research questions and challenges to design efficient and environmentally friendly data centers with address increasing energy prices and distributed energy developments. This dissertation work aims to study and investigate the suitable technologies of power interface and system level configuration for high efficiency and reliable data centers. A 400 V DC-powered data center integrated with solar power and hybrid energy storage is proposed to reduce the power loss and cable cost in data centers. A cascaded totem-pole bridgeless PFC converter to convert grid ac voltage to the 400 V dc voltage is proposed in this work. Three main control strategies are developed for the power converters. First, a model predictive control is developed for the cascaded totem-pole bridgeless PFC converter. This control provides stable transient performance and high power efficiency. Second, a power loss model based dual-phase-shift control is applied for the efficiency improvement of dual-active bridge converter. Third, an optimized maximum power point tracking (MPPT) control for solar power and a hybrid energy storage unit (HESU) control are given in this research work. The HESU consists of battery and ultracapacitor packs. The ultracapacitor can improve the battery lifetime and reduce any transients affecting grid side operation. The large signal model of a typical solar power integrated datacenter is built to analyze the system stability with various conditions. The MATLAB/Simulink™-based simulations are used to identify the stable region of the data center power supply. This can help to analyze the sensitivity of the circuit parameters, which include the cable inductance, resistance, and dc bus capacitance. This work analyzes the system dynamic response under different operating conditions to determine the stability of the dc bus voltage. The system stability under different percentages of solar power and hybrid energy storage integrated in the data center are also investigated

DC-Link Voltage Coordinated-Proportional Control for Cascaded Converter with Zero Steady-State Error and Reduced System Type

copyright 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, 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 components of this work in other works.Cascaded converter is formed by connecting two sub-converters together, sharing a common intermediate DC-link voltage. Regulation of this DC-link voltage is frequently realized with a Proportional-Integral (PI) controller, whose high gain at DC helps to force a zero steady-state tracking error. Such precise tracking is however at the expense of increasing the system type, caused by the extra pole at the origin introduced by the PI controller. The overall system may hence be tougher to control. To reduce the system type while preserving precise DC-link voltage tracking, this paper proposes a coordinated control scheme for the cascaded converter, which uses only a proportional DC-link voltage regulator. The resulting converter is thus dynamically faster, and when compared with the conventional PI-controlled converter, it is less affected by impedance interaction between its two sub-converters. The proposed scheme can be used with either unidirectional or bidirectional power flow, and has been verified by simulation and experimental results presented in the paper

Digital Multi-Loop Control of an LLC Resonant Converter for Electric Vehicle DC Fast Charging

This paper proposes a digital control strategy for LLC resonant converters, specifically intended for EV battery charging applications. Two cascaded control loops, i.e. an external battery voltage loop and an internal battery current loop, are designed and tuned according to analytically derived expressions. Particular attention is reserved to the output current control analysis, due to its extremely non-linear behaviour. The well known seventh-order LLC small-signal model, derived with the extended describing function (EDF) method, is simplified to an equivalent first-order model at the resonance frequency. In theseconditions,whichareproventobethemostunderdamped, the current control loop is tuned taking into account the delays introduced by the digital control implementation. Moreover, the adoption of a look-up table (LUT) in the feed-forward path is proposed to counteract the system non-linearities, ensuring high dynamical performance over the full frequency operating range. Finally, the proposed control strategy and controller design procedure are verified both in simulation and experimentally on a 15 kW LLC converter prototype

Analysis of a new family of DC-DC converters with input-parallel output-series structure

There is an increasing trend of development and installation of switching power supplies due to their highly efficient power conversion, fast power control and high quality power conditioning for applications such as renewable energy integration and energy storage management systems. In most of these applications, high voltage conversion ratio is required. However, basic switching converters have limited voltage conversion ratio. There has been much research into development of high gain power converters. While most of the reported topologies focus on high gain and high efficiency, in this thesis, the input and output ripple currents and reliability are also considered to derive a new converter structure suitable for high step-up voltage conversion applications. High ripple currents and voltages at the input and output of dc-dc converters are not desirable because they may affect the operation of the dc source or the load. A number of converters operating in an interleaved manner can reduce these ripples. This thesis proposes a dc/dc switching converter structure which is capable of reducing the ripple problem through interleaved action, in addition to high gain and high efficiency voltage conversion. The thesis analyses the proposed converter structure through a dual buck-boost converter topology. The structure allows different converter topologies and combinations of them for different applications to be configured. The study begins with a motivation and a literature review of dc/dc converters. The new family of high step-up converters is introduced with an interleaved buck-boost as an example, followed by small-signal analysis. Experimental verifications, conclusions and future work are discussed