Analysis And Design Optimization Of Multiphase Converter

Future microprocessors pose many challenges to the power conversion techniques. Multiphase synchronous buck converters have been widely used in high current low voltage microprocessor application. Design optimization needs to be carefully carried out with pushing the envelope specification and ever increasing concentration towards power saving features. In this work, attention has been focused on dynamic aspects of multiphase synchronous buck design. The power related issues and optimizations have been comprehensively investigated in this paper. In the first chapter, multiphase DC-DC conversion is presented with background application. Adaptive voltage positioning and various nonlinear control schemes are evaluated. Design optimization are presented to achieve best static efficiency over the entire load range. Power loss analysis from various operation modes and driver IC definition are studied thoroughly to better understand the loss terms and minimize the power loss. Load adaptive control is then proposed together with parametric optimization to achieve optimum efficiency figure. New nonlinear control schemes are proposed to improve the transient response, i.e. load engage and load release responses, of the multiphase VR in low frequency repetitive transient. Drop phase optimization and PWM transition from long tri-state phase are presented to improve the smoothness and robustness of the VR in mode transition. During high frequency repetitive transient, the control loop should be optimized and nonlinear loop should be turned off. Dynamic current sharing are thoroughly studied in chapter 4. The output impedance of the multiphase v synchronous buck are derived to assist the analysis. Beat frequency is studied and mitigated by proposing load frequency detection scheme by turning OFF the nonlinear loop and introducing current protection in the control loop. Dynamic voltage scaling (DVS) is now used in modern Multi-Core processor (MCP) and multiprocessor System-on-Chip (MPSoC) to reduce operational voltage under light load condition. With the aggressive motivation to boost dynamic power efficiency, the design specification of voltage transition (dv/dt) for the DVS is pushing the physical limitation of the multiphase converter design and the component stress as well. In this paper, the operation modes and modes transition during dynamic voltage transition are illustrated. Critical dead-times of driver IC design and system dynamics are first studied and then optimized. The excessive stress on the control MOSFET which increases the reliability concern is captured in boost mode operation. Feasible solutions are also proposed and verified by both simulation and experiment results. CdV/dt compensation for removing the AVP effect and novel nonlinear control scheme for smooth transition are proposed for dealing with fast voltage positioning. Optimum phase number control during dynamic voltage transition is also proposed and triggered by voltage identification (VID) delta to further reduce the dynamic loss. The proposed schemes are experimentally verified in a 200 W six phase synchronous buck converter. Finally, the work is concluded. The references are listed

The Period adding and incrementing bifurcations: from rotation theory to applications

International audienceThis survey article is concerned with the study of bifurcations of discontinuous piecewise-smooth maps, with a special focus on the one-dimensional case. We review the literature on circle maps and quasi-contractions and provide paths through this literature to prove sufficient conditions for the occurrence of two types of bifurcation scenarios involving rich dynamics. The first scenario consists of the appearance of periodic orbits whose symbolic sequences and “rotation” numbers follow a Farey tree structure; the periods of the periodic orbits are given by consecutive addition. This is called the period adding bifurcation, and the proof of its existence relies on results for maps on the circle. In the second scenario, symbolic sequences are obtained by consecutive attachment of a given symbolic block, and the periods of periodic orbits are incremented by a constant term. This is called the period incrementing bifurcation, and its proof relies on results for maps on the interval. We also discuss the expanding cases, as some of the partial results found in the literature also hold when these maps lose contractiveness. The higher-dimensional case is also discussed by means of quasi-contractions. We provide applied examples in control theory, power electronics, and neuroscience, where these results can be used to obtain precise descriptions of their dynamics

Model-based powertrain design and control system development for the ideal all-wheel drive electric vehicle

The transfer case based all-wheel drive electric vehicle (TCAWDEV) and dual-axle AWDEV have been investigated to balance concerns about energy consumption, drivability and stability of vehicles. However, the mentioned powertrain architectures have the torque windup issue or the wheel skidding issue. The torque windup is an inherent issue of mechanical linked all-wheel drive systems. The hydraulic motor-based or the electric motor-based ideal all-wheel drive powertrain can provide feasible solutions to the mentioned issues. An ideal AWDEV (IAWDEV) powertrain architecture and its control schemes were proposed by this research; the architecture has four independent driving motors in powertrain. The IAWDEV gives more control freedoms to implement active torque controls and traction mode controls. In essence, this research came up with the distributed powertrain concept, and developed control schemes of the distributed powertrain to replace the transfer case and differential devices. The study investigated the dual-loop motor control, the hybrid sliding mode control (HSMC) and the neural network predictive control to reduce energy consumption and achieve better drivability and stability by optimizing the torque allocation of each dependent wheel. The mentioned control schemes were respectively developed for the anti-slip, differential and yaw stability functionalities of the IAWDEV powertrain. This study also investigated the sizing method that the battery capacity was estimated by using cruise performance at 3% road grade. In addition, the model-based verification was employed to evaluate the proposed powertrain design and control schemes. The verification shows that the design and controls can fulfill drivability requirements and minimize the existing issues, including torque windup and chattering of the slipping wheel. In addition, the verification shows that the IAWDEV can harvest around two times more energy while the vehicle is running on slippery roads than the TCAWDEV and the dual-axle AWDEV; the traction control can achieve better drivability and lower energy consumption than mentioned powertrains; the mode control can reduce 3% of battery charge depleting during the highway driving test. It also provides compelling evidences that the functionalities achieved by complicated and costly mechanical devices can be carried out by control schemes of the IAWDEV; the active torque controls can solve the inherent issues of mechanical linked powertrains; the sizing method is credible to estimate the operation envelop of powertrain components, even though there is some controllable over-sizing

Hybrid and Thin Power Electronics for Electrical Power Networks

A new hybrid diverter design for an On-Load Tap Changer (OLTC) is presented and experimentally validated. The design differs from existing semiconductor-assisted OLTC systems in that the part of the system containing semiconductor devices is connected in a purely shunt con guration to the main current path, resulting in a system that is electrically robust and very low loss. The new design provides zero-current, zero-voltage operation of both diverter switches at all times, eff ectively eliminating arc-induced contact wear. Contact lifetime of over twenty-five million operations is demonstrated. Contact wear rates under the new design are compared experimentally with those under alternative contact protection schemes and are shown to be dramatically reduced. A fast electromechanical switch intended for use under the new hybrid diverter is presented. The low-wear conditions created by the new diverter allows a dramatic reduction in the switch moving mass when compared to that of the standard OLTC, allowing sub-half-cycle actuation times to be achieved. A study of switch topology is made in order to guide the design process. An analysis of a magnetic actuator providing both high actuation and static contact forces is also presented. In a second strand of this thesis, a general method of formulating optimal modulation problems for thin power electronic systems incorporating a buck converter is presented. The method is employs a frequency domain representation of the buck converter where the describing equations are formed into a square matrix relating a set of input harmonics to sets of output harmonics. This allows the interaction between the buck converter and a set of linear filters to be modelled in a systematic way. Two example circuits, the Inverter-Less Active Filter and the Controllable Network Transformer, are used as example problems. The use of general-purpose optimisation software for finding optimal modulation waveforms for these circuits is demonstrated