Modeling of a new ZVS bi-directional dc-dc converter

A dual half-bridge (DHB) bidirectional dc-dc converter is a new proposed topology that has the advantages of decreased number of devices, soft-switching implementation, low cost, and high efficiency. Typical applications of this converter are the auxiliary power supply in fuel cell vehicles and battery charging and discharging systems where the power density, cost, weight, and reliability are critical factors. A switching-frequency-dependent state-space averaged model of the converter is developed here for either direction of power flow. This averaged model can be used to derive the steady-state characteristics and small signal dynamics of the proposed topology. It also provides a fast simulation tool to investigate the transient response of the converter. The simulated waveforms of the mathematical model are compared with the detailed circuit simulation to verify the accuracy of the modeling.     

Tapped-inductor filter assisted soft-switching PWM DC-DC power converter

A novel high-frequency transformer linked full-bridge type soft-switching phase-shift pulsewidth modulated (PWM) controlled dc-dc power converter is presented, which can be used as a power conditioner for small-scale photovoltaic and fuel cell power generation systems as well as isolated boost dc-dc power converter for automotive ac power supply. In these applications with low-voltage large-current sources, the full-bridge circuit is the most attractive topology due to the possibility of using low-voltage high-performance metal-oxide-semiconductor field-effect transistor (MOSFET) and achieving high efficiency of the dc-dc power converter. A tapped-inductor filter including the freewheeling diode is newly implemented in the output stage of the full-bridge phase-shift PWM dc-dc converter to achieve soft-switching operation for the wide load variation range. Moreover, in the proposed converter circuit, the circulating current is effectively minimized without using additional resonant circuit and auxiliary power switching devices. The practical effectiveness of the proposed soft-switching dc-dc power converter was verified in laboratory level experiment with 1 kW 100 kHz breadboard setup using power MOSFETs. Actual efficiency of 94-97% was obtained for the wide duty cycle and load variation ranges.     

A Large-Signal Dynamic Simulation for the Series Resonant Converter

A simple nonlinear discrete-time dynamic model for the series resonant dc-dc converter is derived using approximations appropriate to most power converters. This model is useful for the dynamic simulation of a series resonant converter using only a desktop calculator. The model is compared with a laboratory converter for a large transient event.     

Current Injected Equivalent Circuit Approach to Modeling Switching DC-DC Converters

A new current injected equivalent circuit approach (CIECA) to modeling switching dc-dc converter power stages is developed, which starts with the current injected approach and results in either a set of equations which completely describe input and out-put properties or an equivalent linear circuit model valid at small signal, low frequency levels. This approach to modeling switching dc-dc converter power stages has the merits but not the demerits of both the electronic equivalent circuit state space average approach and the current injected control type approach, namely, 1) the modeling is very clear and is simple whether the converter operates in continuous or discontinuous inductor conduction modes, 2) the modeling results in an equivalent circuit which is very close to the actual converter, and 3) the equivalent circuit can be used directly in the computer for theoretical predictions like SPICE, etc.     

Small signal analysis of the LCC-type parallel resonant converter

In this paper, the small signal analysis of the LCC-type parallel resonant converter (LCC-PRC) operating in the continuous conduction mode is given. This analysis is based on both the state-plane diagram, which has been successfully used to obtain the steady state response for resonant converters, and the Taylor series expansion. Applying perturbation directly to the steady state trajectory, a discrete small signal model for the converter can be derived in terns of the input voltage, switching frequency, and the converter state variables. Based on this analysis, closed-loop form solutions for the input-to-output and control-to-output transfer functions are derived. It is shown that the theoretical and computer simulation results are in full agreement     

应用于超级电容储能系统的双向DC/DC变换器混沌控制方法研究

超级电容储能系统(SCESS)主要通过对双向DC/DC变换器进行控制来快速平抑直流母线电压的波动。为了抑制控制过程中所产生的一些分岔和混沌现象,提出了一种应用于SCESS的混沌控制方法。分析了该方法的控制原理,并根据非线性动力学理论建立了双向DC/DC变换器的离散迭代模型；然后设计了一种能够自动调节补偿斜率的混沌控制信号；最后对该信号作用下的异步切换函数和同步切换映射式进行了数值求解,从而绘出系统分叉图。通过仿真和试验证明,该方法能够有效抑制SCESS的分岔和混沌现象,提高了系统的稳定工作范围和动态响应速度。     

Design Optimization for a Half-Bridge DC-DC Converter

A nonlinear programming technique using the penalty function method is employed for the minimum weight design of a halfbridge dc-dc buck power converter. The cost-effective computeraided approach provides a minimum weight design down to the details of the component level which concurrently meets all power circuit performance requirements. Important design insights and guidelines are obtained to readily assess 1) the tradeoffs between weight and loss as the switching frequency is increased, 2) the optimum operating frequency range over which the total weight/loss is minimized, 3) the impact of device characteristics on the total weight and loss profile.     

New ZVT-PWM DC/DC converters using active snubber

A novel active snubber soft switching method is proposed. The unique location of the resonant inductor and capacitor ensures low current and voltage stresses in the converter. An analytical study of a boost dc-dc converter with the proposed active snubber method is presented in detail to illustrate its operation principles and design considerations. By simple modification, this soft switching method is also suitable for ac-dc boost topology, especially for high power-factor-correction (PFC) universal interface applications. A 500 W prototype system has been made to simulatively and experimentally verify the performance of the soft switching.     

Improved Switching Converter Model Using Discrete and Averaging Techniques

The nonlinear modeling and analysis of dc-dc converters has been done by averaging and discrete-sampling techniques. The averaging technique is simple, but inaccurate, as the modulation frequencies approach the theoretical limit of one-half the switching frequency. The discrete technique is accurate even at high frequencies, but is very complex and cumbersome. An improved model is developed by combining the aforementioned techniques. This new model is easy to implement in circuit and state variable forms and is accurate to the theoretical limit.     

几何非线性机翼本征梁元素模型的高效化改进

 采用Hodges等提出的时间-空间离散化的几何精确非线性本征梁通用模型处理柔性机翼结构动力学问题时,当离散化的节点数增大时,该方法的未知数数量成倍地增长,而且方程组是严重病态的,因此数值模拟计算的速度非常缓慢。针对机翼中最常见的悬臂梁结构,根据空间离散化的边界条件,提出了空间缩聚法把空间离散差分方程缩聚为常系数矩阵格式,得到了只与时间相关的微分方程组,进一步推导得到了该方程组的雅可比矩阵,因而大大减少了方程组的数量以及求解过程的循环和迭代步数。采用Gear方法分别求解了原始的本征梁元素模型和本文提出的缩聚模型,结果表明空间缩聚模型在相同条件下可提高运算速度约5.1倍,而且对不同类型的外载荷都具有较好的通用性、稳定性和高效性。     

General rules for signal flow graph modeling and analysis of dc-dc converters

Signal flow graph (SFG) nonlinear modeling approach is well known for modeling dc-dc converters. However, all possible SFGs of a given dc-dc converter system will not yield the generalized graph. A systematic procedure and guidelines for developing unified flow graph models of the dc-dc boost converters, from which complete behavior can be determined is presented. Usefulness of the proposed method is demonstrated through examples. As an illustration a 2-cell cascade boost and interleaved boost converter systems are taken as examples. Derivation of large, small-signal and steady-state models from generalized flow graph is also demonstrated. Large-signal model is developed and programmed in TUTSIM simulator. Large-signal, responses against supply and load disturbances are obtained. Experimental observations are provided to validate the proposed algorithm.     

Suitability of pulse train control technique for BIFRED converter

Pulse Train/spl trade/ control scheme is presented and applied to a boost integrated flyback rectifier/energy storage dc-dc (BIFRED) converter operating in discontinuous conduction mode (DCM), which avoids the light-load high-voltage stress problem. In contrast to the conventional control techniques, the principal idea of Pulse Train technique is to regulate the output voltage using a series of high and low energy pulses generated by the current of the inductor. The applicability of the proposed technique to both the input and magnetizing inductances of BIFRED converter is investigated. Analysis of BIFRED converter operating in DCM as well as the output voltage ripple estimation is given. Experimental results on a prototype converter are also presented.     

An efficient active ripple filter for use in DC-DC conversion

When low ripple is required from a switched mode dc-dc converter, dissipative active filters offer an alternative to passive LC and coupled inductor filters. Analytical and experimental results are presented for a simple active ripple filter. The filter employs a pair of current transformers as sensors for feedforward and feedback control and two metal-oxide-semiconductor field-effect transistors (MOSFETs) as cancellation current drivers. Measurements demonstrate good ripple attenuation up to 5 MHz, more than 70 dB being obtained at 100 kHz, the switching frequency of a test converter. The overall efficiency was measured as 95%, with room for further improvement. The filter is suitable for input and output smoothing in dc-dc converters for aerospace and other critical applications     

Alternate forms of the PWM switch models

Vorperian's pulsewidth modulation (PWM) switch model consists of a PWM transformer and a nonlinear resistor. The recognition that any of the three transformer terminals can serve as the common terminal leads to two alternate PWM transformer models and the corresponding two alternate PWM switch models. For a given PWM dc-dc converter, one of the three PWM switch models is more “natural” for graphic-oriented analysis/design, e.g., it allows the idealized converter to be analyzed by inspection. Furthermore, all three PWM transformers may be used to graphically manipulate the converter circuit to a form that can be analyzed by inspection. The alternate forms of the PWM transformers and the PWM switch models are effective as graphic-oriented teaching and learning tools for PWM converters. This is demonstrated using examples based on the boost converter and the Cuk converter     

Design and Application of Discrete Sliding Mode Control with RBF Network-based Switching Law

This article proposes a novel approach combining exponential-reaching-law-based equivalent control law with radial basis function (RBF) network-based switching law to strengthen the sliding mode control (SMC) tracking capacity for systems with uncertainties and disturbances. First, SMC discrete equivalent control law is designed on the basis of the nominal model of the system and the adaptive exponential reaching law, and subsequently, stability of the algorithm is analyzed. Second, RBF network is used to form the switching law in a direct and online manner with sliding-mode-related inputs and by approximating evaluation function; and the method to adjust its parameters is devised. Finally, comparable experiments are carried out to verify the application of the proposed approach to an inner-axis driven by a direct current (DC) torque motor through extra-low speed servo for a high precision flight simulator, and the axis works under deteriorating conditions such as periodically fluctuating torques of motor, nonlinear friction, and time-varying model parameters. The results show that the combined SMC can effectively improve the servo performance, for instance, to a stable 0.000 08 (°)/s speed response, the tracking error would be within 0.000 08° in 98% of operating times. Moreover, the hybrid nature of the approach imparts the RBF network the features of removing offline training and ease to set initial parameters.     

Analysis of parallel resonant converter operating above resonance

A high-frequency DC-DC converter using a parallel resonant inverter operating above resonance is analyzed using a state-space approach and a constant current model. Closed-form solutions are obtained under steady-state conditions. The analysis shows that with some changes most equations are of the same form as those corresponding to operations below resonance. The analysis is also used to obtain the design curves and to provide a simple design procedure, which is illustrated by a design example. Experimental results obtained with a prototype MOSFET unit (using metal-oxide-semiconductor field-effect transistors as switches and operating above 90 kHz) are presented to support the theory     

并联H桥DC/DC变换器软开关技术研究

与传统的Buck电路相比,基于H桥并联的DC/DC变换器可以实现电压的双极性输出和故障时的冗余控制,非常适合用于大功率电动机正反转控制的场合。分析了并联H桥型DC/DC变换器的结构组成和双脉宽调制(PWM)模式。为了降低双脉宽调制下H桥型DC/DC变换器的开通和关断损耗,对无源软开关技术进行了分析,重点探讨了RCD缓冲电路和最小应力缓冲电路之间的性能差异,指出最小应力软开关技术可以获得更好的软开关性能,并就将其用于双脉宽调制下的并联H桥DC/DC变换器进行了仿真研究。仿真结果表明:最小应力软开关技术用于双脉宽调制下并联H桥DC/DC变换器时,可以实现开关管的零电压开通和零电流关断。     

Improved ZCS-PWM commutation cell for IGBTs application

An improved zero-current-switching pulsewidth-modulated (ZCS-PWM) commutation cell is presented, which is suitable for high-power applications using insulated gate bipolar transistors (IGBTs) as the power switches. It provides ZCS operation for active switches and zero-voltage-switching (ZVS) operation for passive switches. Besides operating at constant frequency and reducing commutation losses, the proposed ZCS-PWM switch cell has no additional current stress and conduction loss in the main switch. To demonstrate the feasibility of the proposed ZCS-PWM commutation cell, it was applied to a boost converter. Operating principle, theoretical analysis, design guidelines, and a design example are described and verified by experiment results obtained from a prototype rated 1 kW and operating at 40 kHz. The PWM switch model and state-space averaging approach is also used to estimate and examine the steady-state and dynamic character of ZCS-PWM boost converter system. Finally, the application of the proposed soft-switching technique in the dc-dc nonisolated converters is presented.     

Robust controller design for a series resonant converter

Because of their reduced switching losses, allowing a higher operating frequency, dc-to-dc resonant converters have been used extensively in the design of smaller size and lighter weight power supplies. The steady state and dynamic behavior of both the conventional series and parallel resonant converters have been thoroughly analyzed and small-signal models around given nominal operating points have been obtained. These models have been used in the past to design controllers that attempted to keep the output voltage constant in the presence of input perturbations. However, these controllers did not take into account either load or components variations, and this could lead to instability in the face of component or load changes. Moreover, prediction of the frequency range for stability was done a posteriori, either experimentally or by a trial and error approach In this paper we use μ-synthesis to design a robust controller for a series resonant converter (SRC). In addition to robust stability the design objectives include rejection of disturbances at the converter input while keeping the control input and the settling time within values compatible with a practical implementation     

Analysis of series-parallel resonant converter

A frequency-domain steady-state analysis is given for a series-parallel resonant converter (SPRC) operating in the continuous conduction mode (CCM) using Fourier series techniques. Equations for performance parameters are derived under steady-state conditions to provide simple design tools. The topology of the SPRC combines the advantageous properties of both the series resonant converter (SRC) and the parallel resonant converter (PRC). The key results of the work are: a novel half-wave rectifier SPRC, conditions for obtaining high part-load efficiency; and several boundary frequencies and limiting conditions such as the capacitive/inductive load boundary and open-circuit and short-circuit cases. Experimental results measured for an 80-W converter above the resonance at different load resistances and input voltages show excellent agreement with the theoretical performance predicted by the equations