Signal flow graph modeling of two-cell cascade buck converters

This paper presents signal flow graph nonlinear modeling of two-cell cascade buck converters. A systematic procedure for developing the unified flow graph model of the cascade converter is discussed. A simplified procedure is described that can be used to deduce large, small-signal and steady-state models from the unified signal flow graph of the converter. Converter performance expressions, and small-signal and steady-state transfer functions are derived. The large-signal model is developed and programmed into a TUTSIM simulator. Converter large-signal responses are obtained against supply and load disturbances. The validity of the proposed signal flow graph modeling of cascade converters is verified and comparisons are made via PSIM simulator results. A few experimental results are provided to verify the proposed method.     

Small‐signal analysis of interleaved dual boost converter

This paper presents a systematic development of steady‐state, small‐signal models of interleaved dual boost converter operating in a continuous current mode. These models are derived by employing the well‐known signal flow graph method. This signal flow graph approach provides a means to directly translate the switching converter into its equivalent graphic model, from which a complete behaviour of the converter can easily be studied. Steady‐state performance, small‐signal characteristic transfer functions are derived using Mason's gain formula. The bode plots of audiosusceptibility, input impedance, output impedance, and control‐to‐output transfer functions are determined and illustrated using MATLAB for different values of load resistances, duty ratios. Small‐signal frequency responses obtained from the signal flow graph method are validated with PSPICE simulator results. To validate the signal flow graph modelling equations, sample steady‐state experimental results are provided. Copyright © 2001 John Wiley & Sons, Ltd.     

Design and implementation of an interleaved soft‐switching converter with output voltage doubler

An interleaved pulse‐width modulation (PWM) converter with less power switches is presented in this paper. The buck type of active clamp circuit is used to recycle the energy stored in the leakage inductor of a transformer. The zero voltage switching (ZVS) turn‐on of power switches is realized by the resonance during the transition interval of power switches. At the secondary side of transformers, two full‐wave rectifiers with dual‐output configuration are connected in parallel to reduce the current stresses of the secondary windings of transformers. In the proposed converter, power switches can accomplish two functions of the interleaved PWM modulation and active clamp feature at the same time. Therefore, the circuit components in the proposed converter are less than that of the conventional interleaved ZVS forward converter. The operation principle and system analysis of the proposed converter are provided in detail. Experimental results for a 280 W prototype operated at 100 kHz are provided to demonstrate the effectiveness of the proposed converter. Copyright © 2008 John Wiley & Sons, Ltd.     

BUCK型开关变换器最优PID控制器设计

针对开关电源的复杂性和时变性,传统PID控制器整定方法无法很好满足其控制性能要求的问题,提出一种面向性能指标的最优PID控制器参数整定方法。基于DP算法,计算保证闭环系统稳定的PID控制器参数范围;利用具有全局寻优能力的遗传算法,按照ITAE性能指标在该范围内进行参数寻优。以BUCK变换器为利的仿真研究表明,该方法在指定的性能指标上取得了满意的控制效果,在负载发生摄动时,较传统PID控制器,具有较好的鲁棒性,且计算相对简单、实用性强,可推广到非线性PID控制器的参数整定和相关工程实践中。     

后缘调制Buck变换器的周期借用数字电流控制

为了解决数字电流控制环路的硬件处理速度与带宽之间的矛盾,提出了基于后缘调制Buck变换器的周期借用数字电流控制方法,实现了传统延迟电流控制的硬件速度要求和无拍差电流控制的环路带宽.针对谷值、平均值和峰值电流控制目标,建立了电流控制律,研究了次谐振荡现象及其消除方法,分析了周期借用数字电流控制的Buck变换器鲁棒性.仿真结果表明,周期借用数字电流控制和无拍差电流控制的Buck变换器具有相同的瞬态性能,并且优于延迟电流控制.     

Foldings and grazings of tori in current controlled interleaved boost converters

Interleaved boost converters (IBCs) are used when energy conversion is required at high current levels. Such converter systems may undergo various nonlinear phenomena which can affect their performance adversely. In this paper, we study an IBC and demonstrate the first instability through a Neimark–Sacker bifurcation, resulting in a torus. An analysis based on the calculation of the monodromy matrix reveals that the torus has a rather strange form as the complex Floquet multipliers that became unstable have a real value close to ?1. We show that further variation in a parameter can result in novel nonlinear phenomena where the torus itself folds and grazes a switching manifold, resulting in a ‘wobbling’ of the closed loop that represents the torus in discrete time. Numerical and analytical results validate our work. Copyright © 2013 John Wiley & Sons, Ltd.     

多相并联同步Buck变换器控制技术进展

多相并联控制技术适用于高频、低压大电流场合,能满足开关电源日益提高的可靠性、效率和功率密度的要求,已成为开关电源研究领域的重要内容之一,并取得许多成果。对现有的多相并联同步Buck变换器的控制技术进行归纳和分类,分析了各种控制技术的工作原理、特点、实现方法和适用场合,为进一步应用提供了参考。     

Higher‐order differentiation of network functions using signal flow graphs

This paper presents the application of signal flow graphs (SFG) in the calculation of higher‐order derivatives (sensitivities) of the linear circuit functions. The idea of exact differentiation of the circuit functions is based on the adjoint networks, translated into SFG language. Thanks to its application, it is possible to calculate the exact value of any order derivative of circuit function without knowing this function in explicit form. Moreover, these derivatives can be determined on the basis of analysis of only two graphs (circuits): the original and adjoint one. We show that the SFG approach to the sensitivity calculation allows to reduce greatly the complexity of calculations. Copyright © 2011 John Wiley & Sons, Ltd.     

交错并联开关电感Boost变换器的失稳分析与控制

为提高输出电压增益,减小开关管电压应力,将开关电感结构代替传统电感嵌入到交错并联Boost变换器中。利用频闪映射法得到交错并联开关电感Boost变换器在峰值电流控制下的离散数学模型,并通过分岔图、相轨图、Jacobian矩阵特征值研究其失稳机理,结合参数共振微扰与电荷控制的优点,设计了补偿方案对失稳系统进行混沌控制。研究结果表明,开关电感的嵌入有效拓宽了交错并联Boost变换器的稳定范围,并通过补偿方案使得混沌系统重回周期-1稳态,提高了变换器的工作性能和稳定性。     

Unified power flow controller based on two shunt converters and a series capacitor

In this paper a novel configuration of unified power flow controller (UPFC) which consists of two shunt converters and a series capacitor is proposed. In this configuration, a series capacitor is used between two shunt converters to inject desired series voltage. As a result, it is possible to control the active and reactive power flow as same as the conventional configuration of UPFC. The main advantage of the proposed UPFC in comparison with the conventional configuration is injection of a series voltage waveform with a very low total harmonic distortion (THD). Also, using two shunt converters instead of a series and a shunt converters, results in reduction of design efforts and simplification of control, measuring and protection strategies. An optimal control strategy based on the discrete model of converters is applied to shunt converters. The proposed UPFC is simulated using PSCAD/EMTDC and MATLAB software and simulation results are presented to validate the effectiveness of the novel configuration of UPFC. Also, the experimental results which are obtained from an experimental set-up are presented.     

一种交错并联零电流软开关双向DC/DC变换器设计*

针对传统交错并联式双向DC/DC变换器在高频大功率工作时,开关管损耗大的问题,设计了一种零电流软开关交错并联式双向DC/DC变换器;通过在开关过程前后引入谐振,实现零电流开通和零电流关断,降低开关损耗;进一步分时段模态分析了Boost/Buck模式下的电路工作机理,并在其基础上提出了一种适用于特定占空比的改进型零电流软开关双向DC/DC变换器。最后,通过仿真对比,验证了所设计零电流软开关变换器能量转换效率得到了提高。     

Effects of the input filter on the stability of a voltage‐mode controlled buck converter

This letter presents a favorable effect of the input filter on the stability of a filter‐converter system, which employs a cascade configuration of a voltage‐mode controlled buck converter and a third‐order input filter. Such an effect can enlarge the stable region of the stand‐alone buck converter when appropriately selecting the damping resistor of the input filter. Effectively, the frequency‐domain model based on the extra element theory is used to analyze and illustrate the input filter interaction regarding this favorable effect. Our work provides a supplementary view for engineers to deal with input filter interaction. Copyright © 2007 John Wiley & Sons, Ltd.     

A new single‐phase high‐power‐factor converter with buck and buck–boost hybrid operation

In recent years, a wide variety of high‐power‐factor converter schemes have been proposed to solve the harmonic problem. The schemes are based on conventional boost, buck, or buck–boost topology, and their performance, such as output voltage control range in the boost and buck topology or efficiency in the buck–boost topology, is limited. To solve this, the authors propose a single‐phase high‐power‐factor converter with a new topology obtained from a combination of buck and buck–boost topology. The power stage performs the buck and buck–boost operations by a compact single‐stage converter circuit while the simple controller/modulator appropriately controls the alternation of the buck and buck–boost operation and maintains a high‐quality input current during both the buck and buck–boost operations. The proposed scheme results in a high‐performance rectifier with no limitation of output voltage control range and a high efficiency. In this paper, the principle and operation of the proposed converter scheme are described in detail and the theory is confirmed through experimental results obtained from 2‐kW prototype converter. © 2000 Scripta Technica, Electr Eng Jpn, 131(3): 91–100, 2000     

信号流图在配电网潮流计算中的应用

为了解决采用传统方法进行配电网潮流计算所面临的实际困难,提出了基于流图理论求解线性方程的配电网潮流计算新方法,避免了繁琐的矩阵运算,提高了计算精度,克服了传统算法不适用的配电网特殊环境带来的影响,且该方法不存在计算的收敛性问题及其多解问题,避免了传统的潮流方法的纯“数值计算”所带来的各种误差。     

A new interleaved bidirectional dc/dc converter with zero voltage switching and high voltage gain: analyses,design and simulation

In this paper, a new interleaved non‐isolated bidirectional dc–dc converter with capability of zero voltage switching and high voltage gain is proposed. In the proposed converter by using two coupled inductors and one capacitor, the voltage gain is extended. Moreover, by using only an auxiliary circuit that includes an inductor and two capacitors, the zero voltage switching (ZVS) of two used switches in the first phase of converter can be achieved. The ZVS operation of two used switches in the second phase is always obtained without using any extra auxiliary circuit. This converter similar to other interleaved converters has low input current ripple and low current stress on switches. In this paper, the proposed converter is analyzed in all operating modes, and also the voltage gain, required conditions for ZVS operation of switches, voltage and current stresses of all switches, and the value of input current ripple in both boost and buck operations are obtained. Finally, the accuracy performance of the proposed converter is verified through simulation results in EMTDC/PSCAD software. Copyright © 2017 John Wiley & Sons, Ltd.     

Exact and explicit expressions for the small‐signal dynamics and frequency response of switching converters

In this paper, exact and explicit expressions for the dynamics and small‐signal responses of piecewise linear switching converters are derived. The results are very useful for the exact simulation and analysis of converter circuits. These expressions can also be used to develop simplified (approximate) models of converters for practical design purposes. An example is given to show that the well‐known state‐space averaging model is in fact the first‐order approximation of our exact model. Copyright © 2004 John Wiley & Sons, Ltd.     

Investigation of multiple output operation for switched‐capacitor resonant converters

A family of switched‐capacitor circuits using two transistors is presented. This family only requires very small inductor for resonance and therefore is suitable for hybridization. It has variable topologies which provide different voltage conversion ratios. Each of the topologies can be merged to produce multiple outputs. This paper investigates the feasibility of this circuit merger technique. Experimental and theoretical analyses are presented. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance of a Zero Average Dynamics‐controlled buck converter using different pulse‐width modulation schemes

The response of a digital Zero Average Dynamics (ZAD)‐controlled buck converter under the variation of its intrinsic parameters as well as the pulse‐width modulation signal is studied in detail. The multiparameter analysis presented here leads to a complete knowledge of the different dynamical scenarios exhibited by the system. Numerical results indicate that the success of the ZAD‐strategy is highly dependent on the parameter and pulse‐width modulation (PWM) combinations. Experiments are included to validate the performance inside the so‐called optimum region. Copyright © 2013 John Wiley & Sons, Ltd.     

改进的Boost变换器小信号模型及其应用

Boost变换器足一个非线性时变系统,用解析方法进行动态分析较为复杂.针对日前无法建立开关电源精确数学模型情况,提出利用状态空间平均法建立Boost变换器的小信号模型,目的在于改进Boost变换器的仿真模型.应用Matlab软件对其进行了仿真.同时设计了40 V/120 V的Boost变换器.以该变换器为对象,对电路的动态响应特性和稳定性进行了实际应用研究.仿真和实验结果证明了该模型的有效性.     

The piecewise‐affine model of buck converter suitable for practical stability analysis

A generalized geometrical piecewise‐affine continuous‐time model (GMD) of buck converter under pulse‐width modulated (PWM) voltage‐mode control is presented in this paper. In general, such a model can be applied to any DC‐DC power electronic converter (PEC) in which the valves are modelled as ideal switches. The GMD is suitable and convenient to analyse PEC practical stability which is a completely different concept in relation to the notion of its stability in the classical Lyapunov sense. The PEC GMD is based on its commutation structure which is a general geometrical model of its commutation. The general idea of this model consists in determining the local dynamic behaviour of PEC trajectories on the faces of its commutation structure and/or their sections. These faces and sections are treated as geometrical objects with generalized local dynamics. The analysis of buck converter practical stability is carried out using a new method based directly on the definition of this term but not Lyapunov‐like functions as in the direct method. It has been shown that PEC Lyapunov stability does not imply its practical stability. These two concepts are complementary to each other. Copyright © 2013 John Wiley & Sons, Ltd.