An improved closed loop hybrid phase shift controller for dual active bridge converter

In this paper, a new closed loop hybrid phase shift control is proposed for dual active bridge (DAB) converter with variable input voltage. The extended phase shift (EPS) control is applied when load gets heavy enough and the secondary side phase shift angle decreases to zero. When this modified DAB converter operates at light loads, the triple phase shift (TPS) modulation method is applied, and the added control freedom is the secondary phase shift angle between the two-secondary side switching legs. The hybrid phase shift control (HPS) scheme is a combination of EPS and TPS modulations, and it provides a very simple closed form implementation for the primary and secondary side phase shift angles. Depending on the application by changing the phase shift angles we can achieve Buck or Boost operation. A characteristic table feedback control method has been used for closed loop operation. By using 1D look up table the proposed DAB converter provides constant 400V for any given input voltage

A simplified controller and detailed dynamics of constant off-time peak current control

A fast and reliable current control is often the base of power electronic converters. The traditional constant frequency peak control is unstable above 50 % duty ratio. In contrast, the constant off-time peak current control (COTCC) is unconditionally stable and fast, so it is worth analyzing it. Another feature of the COTCC is that one can combine a current control together with a current protection. The time dynamics show a zero-transient response, even when the inductor changes in a wide range. It can also be modeled as a special transfer function for all frequencies. The article shows also that it can be implemented in a simple analog circuit using a wide temperature range IC, such as the LM2903, which is compatible with PV conversion and automotive temperature range. Experiments are done using a 3 kW step-up converter. A drawback is still that the principle does not easily fit in usual digital controllers up to now

Integrated DC-DC Charger Powertrain Converter Design for Electric Vehicles Using Wide Bandgap Semiconductors

Electric vehicles (EVs) adoption is growing due to environmental concerns, government subsidies, and cheaper battery packs. The main power electronics design challenges for next-generation EV power converters are power converter weight, volume, cost, and loss reduction. In conventional EVs, the traction boost and the onboard charger (OBC) have separate power modules, passives, and heat sinks. An integrated converter, combining and re-using some charging and powertrain components together, can reduce converter cost, volume, and weight. However, efficiency is often reduced to obtain the advantage of cost, volume, and weight reduction.An integrated converter topology is proposed to combine the functionality of the traction boost converter and isolated DC-DC converter of the OBC using a hybrid transformer where the same core is used for both converters. The reconfiguration between charging and traction operation is performed by the existing Battery Management System (BMS) contactors. The proposed converter is operated in both boost and dual active bridge (DAB) mode during traction operation. The loss mechanisms of the proposed integrated converter are modeled for different operating modes for design optimization. An aggregated drive cycle is considered for optimizing the integrated converter design parameters to reduce energy loss during traction operation, weight, and cost. By operating the integrated converter in DAB mode at light-load and boost mode at high-speed heavy-load, the traction efficiency is improved. An online mode transition algorithm is also developed to ensure stable output voltage and eliminate current oscillation during the mode transition. A high-power prototype is developed to verify the integrated converter functionality, validate the loss model, and demonstrate the online transition algorithm. An automated closed-loop controller is developed to implement the transition algorithm which can automatically make the transition between modes based on embedded efficiency mapping. The closed-loop control system also regulates the integrated converter output voltage to improve the overall traction efficiency of the integrated converter. Using the targeted design approach, the proposed integrated converter performs better in all three aspects including efficiency, weight, and cost than comparable discrete solutions for each converter

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

Impedance Control Network Resonant Step-Down DC-DC Converter Architecture

In this paper, we introduce a step-down resonant dc-dc converter architecture based on the newly-proposed concept of an Impedance Control Network (ICN). The ICN architecture is designed to provide zero-voltage and near-zero-current switching of the power devices, and the proposed approach further uses inverter stacking techniques to reduce the voltages of individual devices. The proposed architecture is suitable for large-step-down, wide-input-range applications such as dc-dc converters for dc distribution in data centers. We demonstrate a first-generation prototype ICN resonant dc-dc converter that can deliver 330 W from a wide input voltage range of 260 V – 410 V to an output voltage of 12 V.MIT Skoltech InitiativeMIT Energy InitiativeNational Science Foundation (U.S.) (Award 1307699)Texas Instruments Incorporated (Graduate Women's Fellowship for Leadership in Microelectronics