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An important feature of an inductive power transfer (IPT) system is its power transfer efficiency and capability can be significantly affected by the load and the magnetic coupling variations. Therefore, identifying the load and the mutual inductance is essential to improve the system performance. This paper proposes a load and mutual inductance identification method for IPT systems with parallel-compensated power pickups based only on the information detected from the primary side. The proposed method can be implemented for primary resonant circuits whether they are series or parallel tuned, or with a hybrid compensation, such as an LCL configuration. An identification model is established according to the steady-state characteristics of the system. Identification results are obtained based on mathematical derivations and analyses. The proposed identification method is realized without any extra communication or control, and both the simulation and experimental results have verified its feasibility. [ABSTRACT FROM AUTHOR]

Switched-capacitor (SC) converters have drawn more and more attention in recent years due to their unique advantages. The accurate analysis methods will fully determine an SC converter's steady-state and dynamical performance. Proper design of SC converters requires full understanding of all impacts on circuit operation including steady-state and dynamical performance. Some previous modeling methods for SC converters have established a popular static model for SC converters which is composed of an ideal transformer and equivalent output resistance. This paper presents a dynamic capacitor ampere-second balance transient calculation modeling method. The instantaneous state of input voltage, instantaneous state of output voltage, instantaneous state of voltage of flying capacitor, “on time” and “off time,” as well as switching period are all included in the proposed model. The proposed modeling method was applied in both the dual-phase SC converters and the two-switch boosting SC converters. This modeling method was validated by the simulation and experimental results. The proposed model can be used to accurately predict and optimize the performance in the design phase for the low and high power SC converters. Based on the proposed modeling method, the SC converters could be controlled by a variable frequency control method. [ABSTRACT FROM AUTHOR]

Resonant power conversion leads to advantages such as soft switching and high-frequency operation; however, analysis and design of a resonant converter require an efficient methodology. In general, conventional methodologies use a design-oriented architecture, which requires previously specifications and iterative circuit-level simulations. This procedure is the simplest; notwithstanding, it can be time consuming and inaccurate for more complex systems, as resonant converters. This paper proposes a result-oriented architecture that is independent of specifications; in other words, real circuit parameters are waived in exchange for generalized results. A normalization procedure is proposed by using an equivalence transformation to modeling the system with a state vector composed of terms as the square roots of the stored energy in the reactive components. The system is represented in a dimensionless state-space model, in which the terms of the state-space matrices are composed of resonant parameters, such as normalized resonant frequencies and quality factor; thereby, the system is independent of circuit parameters, such as inductances, capacitances, and resistances. The sixth-order hybrid Ćuk converter is used to derivate the equations. Simulation results and an implementation of a 500-kHz hybrid buck converter are shown to compare theoretical, simulation, and experimental results. [ABSTRACT FROM AUTHOR]

Switched-capacitor (SC) converter is a type of variable structure systems. SC converters are typically equipped with open-loop control or some linear feedback control methods. However, these approaches provide slow dynamic response speed, small operation region, and large voltage ripple. Some new nonlinear control methods have been proposed in the literature to overcome these barriers. However, such control methods are usually proposed for applications involving low-power SC converters due to the limitations of them. This paper presents a nonlinear constant on-time variable frequency one-cycle control (CVFOCC) strategy based on dynamic capacitor ampere-second balance transient calculation (CASBTC) modeling method and one-cycle control (OCC) technique for high-power SC converters. This method successfully addresses the regulation issue of high-power SC converters. A high-power 3X Two-switch Boosting Switched-Capacitor converter (TBSC) is employed as an example topology. Simulation and experimental results both demonstrate that CVFOCC method could significantly improve the dynamic response speed and achieve excellent line and load regulation for the high-power SC converter in wide operation range. [ABSTRACT FROM AUTHOR]

Switched capacitor converters with ideal switches exhibit discontinuities in the electrical variables, i.e., state jumps at the switching time instants. This feature introduces some difficulties for the determination of compact dynamic models for these power converters. In this paper, we tackle the issue by considering a switched model where the dynamics of the modes are represented through differential algebraic equations. For this class of systems the classical averaged model fails. By including a suitable jump mode that approximates the state discontinuities, a generalized frequency-dependent averaged model is proposed. The effectiveness of the switched and averaged models is numerically and experimentally verified by analyzing the ladder, series–parallel, Fibonacci, and Dickson topologies, and by considering different switching frequencies, voltage sources, and circuits parameters. [ABSTRACT FROM PUBLISHER]

LLC resonant converter is a nonlinear system, limiting the use of typical linear control methods. This paper proposed a new nonlinear control strategy, using load feedback linearization for an LLC resonant converter. Compared with the conventional PI controllers, the proposed feedback linearized control strategy can achieve better performance with elimination of the nonlinear characteristics. The LLC resonant converter's dynamic model is built based on fundamental harmonic approximation using extended describing function. By assuming the dynamics of resonant network is much faster than the output voltage and controller, the LLC resonant converter's model is simplified from seven-order state equations to two-order ones. Then, the feedback linearized control strategy is presented. A double loop PI controller is designed to regulate the modulation voltage. The switching frequency can be calculated as a function of the load, input voltage, and modulation voltage. Finally, a 200 W laboratory prototype is built to verify the proposed control scheme. The settling time of the LLC resonant converter is reduced from 38.8 to 20.4 ms under the positive load step using the proposed controller. Experimental results prove the superiority of the proposed feedback linearized controller over the conventional PI controller. [ABSTRACT FROM PUBLISHER]

Diode–capacitor-based dc–dc converters provide a simple and low cost solution for high step-up voltage regulation in solar and fuel cell generation. Transient modeling analysis reveals their worse influence of nonlinear and nonminimum-phase system characteristic due to right-half-plane (RHP) zero, especially in high voltage gain application. However, the process of energy transfer for diode–capacitor-based dc–dc converter is different from basic dc–dc converter. Based on the unique feature, this paper proposes an improved main circuit structure with parallel connection of resistive–capacitive damping network across the intermediate capacitor to achieve good dynamic performance. By optimal parameter design according to Routh–Hurtwitz criterion, all the RHP zeros in the transfer function of control-to-output voltage are eliminated completely. Then, by the case of diode–capacitor-based boost converter, the adaptive PI controller is designed to deal with nonlinear characteristic of voltage gain. It gets good dynamic performance under wide range output voltage. All the theoretical findings and design approaches are verified by simulation and experiment results. The existing diode–capacitor-based high step-up dc–dc converters with slight main circuit modification are more promising in renewable energy application. [ABSTRACT FROM AUTHOR]

A recently reported modeling methods for a switched capacitor converter either assume output as “firm” voltage or a resistor to facilitate calculation. When the size of output filter capacitor is moderate, accompanied by noticeable output ripple, previous modeling results may not provide accurate prediction and design guidelines. In this paper, a new modeling technique taking into account the output capacitor effect is proposed for simple dual-phase switched capacitor converters without complex coupling loops. The proposed model employs transient calculation, takes charge redistribution phase into account, and includes the duty cycle, switching frequency as well as output capacitor simultaneously in the final output impedance formula, which enhances accuracy of the model. It is suitable for interleaved and noninterleaved switched capacitor converters. The simulation and experimental results for the unity gain SC converter are provided to verify the proposed theory. [ABSTRACT FROM PUBLISHER]

Many analytical methods of establishing accurate models of the switched-capacitor (SC) converters have been developed. These methods are applicable to simple low-order SC converters and can permit only a general efficiency calculation of SC converters. They do not provide analytical solutions that describe how individual electrical component in the circuit practically affects the SC converter at different frequencies. Such an analysis is important for the optimal design and realization of a complex (high-order) SC converter. This is particularly true for those SC converters which have more than two operating states. For complex SC converters, a constituent capacitor may have a profound effect on the converter's efficiency and is dependent on the configuration of the switches and the arrangement of the energy flow paths. In this paper, the relationship of the value of capacitors and the efficiency of complex SC converters is derived and investigated using an energy-flow-path analysis. Optimal design of SC converters can be achieved through a systematic component value selection by: 1) increasing the proportion of energy flow through the most efficient paths; and 2) increasing the efficiency of the paths that have a higher energy flow. The design of complex SC converters in terms of optimizing their power efficiency is discussed using an exponential SC converter as an illustration. The results of both calculation and experimental measurement show that the approach is effective. [ABSTRACT FROM AUTHOR]

The operation and efficiency of on-chip switched-capacitor (SC) converters are highly affected by the parasitic bottom plate capacitor present in on-chip capacitor technologies. Existing modeling frameworks do not in a comprehensive manner take the effect of the bottom plate capacitor on converter operation and efficiency into account. This paper extends an existing SC state space modeling framework to include the bottom plate capacitor. The developed model is used in a Pareto optimization procedure to optimally select the component values of a 2:1 on-chip SC converter. Implemented in a 32 nm SOI CMOS technology that features the high-density deep trench capacitor, the on-chip converter achieves $86\%$ maximum efficiency at 4.6\,\text{W}/\text{m}\text{m}^2 power density while converting from a 1.8 V input voltage to 830 mV output voltage. [ABSTRACT FROM AUTHOR]

This paper proposes a four-plate compact capacitive coupler and its circuit model for large air-gap distance capacitive power transfer (CPT). The four plates are arranged vertically, instead of horizontally, to save space in the electric vehicle charging application. The two plates that are on the same side are placed close to each other to maintain a large coupling capacitance, and they are of different sizes to maintain the coupling between the primary and secondary sides. The circuit model of the coupler is presented, considering all six coupling capacitors. The LCL compensation topology is used to resonate with the coupler and provide high voltage on the plates to transfer high power. The circuit model of the coupler is simplified to design the parameters of the compensation circuit. Finite-element analysis is employed to simulate the coupling capacitance and design the dimensions of the coupler. The circuit performance is simulated in LTspice to design the specific parameter values. A prototype of the CPT system was designed and constructed with the proposed vertical plate structure. The prototype achieved an efficiency of 85.87% at 1.88-kW output power with a 150-mm air-gap distance. [ABSTRACT FROM AUTHOR]

Switched-capacitor (SC) converters were initially introduced for low-power applications and monolithic integration. In recent years, SC converter has found high-power applications. However, voltage regulation remains an issue. This paper addresses regulation challenges for high-power SC converters, based on charge-balance transient-calculation (CT) modeling method and peak current stress estimation. With the help of CT model, due to its accuracy and comprehensive relationship, circuit and control parameters’ impacts on regulation become straightforward and concerns on components stresses can be addressed quantitatively. The suitability of CT method for regulation analysis is confirmed by comparison with traditional modeling methods. The CT method is used in a 1-kW 3X two-switch boosting switched-capacitor converter (TBSC) circuit for steady-state analysis and current stress estimation. The soft rising input current and nature interleaving properties of 3X TBSC make it well suited for high-power application. Finally, the small-signal model of the 3X TBSC is developed and a closed-loop operation is achieved under 1 kW power rating. [ABSTRACT FROM AUTHOR]

Modular multilevel converters have several attractive features such as a modular structure, high voltage capability and scalability, excellent quality of the output voltage waveforms, as well as, low expense for redundancy. However, the main drawback of this converter is the complexity of the control system due to the multiple control objectives which include the input, output, circulating current and the capacitor voltages. Several control schemes for the capacitor voltages have been proposed, being usually divided into the control of the average voltage and the balancing of the capacitor voltages among the submodules and among the arms. These control schemes can effectively control the capacitor voltage when the reference is the same for all arms, but they cannot manage arbitrary voltage references when each arm capacitor voltage must be controlled independently as required, for example, to achieve maximum power point tracking in photovoltaic applications. This paper proposes a control strategy for a modular multilevel converter capable to manage the average capacitor voltage of each arm independently. The proposed scheme is based on a decomposition of the energy of the arms in different components, according to theirs symmetries. Results validating the performance of the proposed control scheme are shown and the impact on the output current is also discussed. [ABSTRACT FROM PUBLISHER]

The high-intensity laser power beaming (HILPB) system is one of the most promising system in the field of long-range wireless power transfer. In HILPB system, the high-power laser diode (LD) is employed for its excellent character of high efficiency, high reliability, and small size. Normally, LD can operate in two different driving modes: the continuous mode and the pulse mode. The injected current has a direct effect on the electro-optical conversion efficiency of LD. This paper centers around LD model and its current source driver. The conversion efficiencies of the two driving modes are evaluated by means of simulations and experiments. The experimental results are shown to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents modeling and triple-loop control for a high-efficiency three-phase balanced inverter for using in grid-connected two-stage microinverter applications. An average signal model based on a synchronous rotation frame for a three-phase four-wire inverter has been developed. The inner current loop consists of a variable frequency bidirectional current mode (VFBCM) controller which regulates output filter inductor current thereby achieving ZVS, improved system response, and reduced grid current THD. Active damping of the LCL output filter using filter inductor current feedback is discussed along with small signal modeling of the proposed control method. Since the dc-link capacitor plays a critical role in two-stage microinverter applications, a dc-link controller is implemented outside of the two current control loops to keep the bus voltage constant. Finally, based on a two-stage 400-W prototype, simulation and experimental results are presented to verify the validity of the theoretical analysis, the effectiveness and feasibility of the proposed VFBCM control strategy. [ABSTRACT FROM AUTHOR]

Nonlinear, voltage-dependent capacitances of power semiconductor devices are capable of having significant impact on the operation of switched-mode power converters. Particularly at high switching frequency, these nonlinearities play a significant role in determining switching times, losses, and converter dynamics during switching transitions. In order to accommodate the well-established design and analysis techniques commonly used for linear circuits, this paper examines the nonlinear voltage-dependence of switching device capacitances and proposes a circuit-oriented analysis technique that allows the parasitic capacitances to be replaced with linear equivalents. The multitude of developed equivalents are verified through full nonlinear simulation in both MATLAB/Simulink and SPICE, as well as through experimental results. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) structures are composed of several hundreds to thousands of half-bridge converters. Such large numbers of power switches and electrical nodes introduce important numerical challenges for the computation of electromagnetic transients. The problem becomes particularly more complex for the real-time simulations. This paper presents a feasibility study on the real-time simulation of the MMC models. CPU-based and field-programmable gate array-based implementations are proposed and evaluated for the MMCs having up to 401 levels. The study also provides guidelines for the real-time simulation platform requirements to simulate these MMC models. [ABSTRACT FROM AUTHOR]

Fuel cells are one of the most promising energy sources, especially for onboard applications. However, fuel cells present several drawbacks, such as slow dynamic response, load-dependent voltage, and unidirectional power flow, which cause an inappropriate vehicle operation. So, secondary energy sources and power converters must be implemented in order to satisfy fast changes in the current load and to store the energy delivered by the load if regenerative braking is intended. Taking into account the number and nature of the power converters, loads, secondary energy sources, and the possibilities for the control strategies, the design of a power distribution architecture based on fuel cells for transport applications is a complex task. In order to address these architectures, modeling and simulation design tools at system level are essential. This paper proposes a complete fuel cell black-box model which reproduces the behavior of a commercial fuel cell with overshooted transient response. The identification technique applied to parameterize the model components, based on manufacturer's datasheets and a test based on load steps, is explained thoroughly. In addition, if only the fuel cell frequency response and manufacturer's datasheet are available, an alternative parameterization methodology based on the fuel cell frequency response is presented. The fuel cell black-box model is validated experimentally using a commercial proton exchange membrane fuel cell. Two different parameterizations are carried out with the aim of verifying the robustness of both the fuel cell model and the proposed identification methodology. [ABSTRACT FROM AUTHOR]

This paper addresses on-chip solar energy harvesting and proposes a circuit that can be employed to generate high voltages from integrated photodiodes. The proposed circuit uses a switched-inductor approach to avoid stacking photodiodes to generate high voltages. The effect of parasitic photodiodes present in integrated circuits (ICs) is addressed and a solution to minimize their impact is presented. The proposed circuit employs two switch transistors and two off-chip components: an inductor and a capacitor. A theoretical analysis of a switched-inductor dc-dc converter is carried out and a mathematical model of the energy harvester is developed. Measurements taken from a fabricated IC are presented and shown to be in good agreement with hardware measurements. Measurement results show that voltages of up to 2.81 V (depending on illumination and loading conditions) can be generated from a single integrated photodiode. The energy harvester circuit achieves a maximum conversion efficiency of 59%. [ABSTRACT FROM AUTHOR]