Unique solvability of RLC nullor networks

Sufficient conditions for the unique solvability of linear active networks modelled as RLC nullor networks are given. an interpretation of these sufficient conditions in terms of subnetworks of the network being studied is also given. A simple procedure for calculating the matrices involved in these sufficient conditions is described and illustrated by example.     

Sensitivity analysis of RLC nullor networks

Linear active networks can be represented either as RLC-dependent source networks or as RLC nullor networks. The calculation of the sensitivities of the transfer functions of active networks modelled by RLC nullor networks is considered. Three methods for calculating sensitivity are applied to the class of RLC-nullor networks. Some simplifications resulting from the absence of coupled elements in such networks are observed. The resulting algorithms are implemented as FORTRAN programs and the execution times are compared.     

Determination of initial conditions in active RLC networks

A new method is described of determining the initial values of state variables in active RLC networks. This method utilizes neither the conservation principle of charges and fluxes nor the theory of distributions. An RLC active network is assumed to be formed at t = 0 by joining or disconnecting the elements that are contained in it, this operation being performed by the use of a set of switches. The new method is based on the consideration of switches as independent sources, and the state equations are extended to cover this situation, and their solution at t = 0⁺ gives the initial conditions that have been sought. Further, the new method is applicable to any state-space formulation techniques used.     

A novel canonic,bipolynomial analogue filter configuration with a minimum number of common-ground capacitors

We proposed a novel canonic, multiple-loop feedback, bipolynomial analogue filter configuration with a minimum number of common-ground capacitors which contains same-type active functional blocks. A detailed analysis of sensitivity criterion minimization is given and a comparison is made with other filter configurations.     

Short-circuit admittance matrix synthesis with rc common-ground networks and a minimum number of grounded finite-gain phase-inverting voltage-controlled voltage sources

A new procedure for the synthesis of active RC networks when grounded finite-gain phase-inverting voltage-controlled voltage sources serve as active elements is developed. It is proved that an arbitrary n × n matrix of real rational functions of the complex frequency variable can be realized as the short-circuit admittance matrix of a grounded transformerless active RC n-port network containing (n+1) grounded finite-gain phase-inverting voltage-controlled voltage sources (VCVSs). In general all the (n+1) grounded VCVSs are necessary. The structure proposed to prove a general theorem is later simplified for the realization of a restricted but important class of real rational matrices to obtain considerable savings in the computation volume and in the number of passive components used for the realization of the network. Examples are given to illustrate presented synthesis procedures.     

Separability and reducibility criteria of RLC networks over Fz and their applications

The separability condition for the RLC network over the field F^z of rational functions in multi-parameters is derived. Some criteria and technique are proposed to check the reducibility of the characteristic polynomial of the network. The technique is straightforward since it is only necessary to observe its graph. © 1998 John Wiley & Sons, Ltd.     

Controllability and observability criteria of RLC networks over F(z)

RLC networks are a class of important linear systems. This paper discusses the problem of controllability and observability of RLC networks over the field F(z) of rational functions in independently variable parameters. Copyright © 2001 John Wiley & Sons, Ltd.     

On a class of SC resistors and its application to the synthesis of non-linear driving-point and transfer-characteristic plots

The use of switched-capacitor components for designing non-linear networks is discussed in this paper. We first introduce a new type of network component, the BESC resistor, and consider its application to the design of non-linear transfer characteristic and driving point plots. Systematic methods for designing piecewise-linear BESC resistors using switched capacitors are then given. Finally, experimental results showing the performance of the proposed circuits are included.     

A new structure of single-phase two-stage hybrid transformerless multilevel PV inverter

Transformerless inverters are becoming popular for grid-connected photovoltaic applications due to their simplicity, reduced size, weight, cost, and higher efficiency. In this paper, a two-stage hybrid transformerless multilevel inverter (MLI) for single-phase grid-connected photovoltaic power generation system (PVPGS) is presented. The proposed topology comprises a multilevel boost converter (MLBC) and a symmetrical hybrid MLI. MLBC combines the boosting and switched capacitor voltage functions to produce self-balanced multiple voltage levels. The proposed MLI is derived from a combination of bidirectional switches, a half bridge, and a diode-clamped branch, which can produce only two variations in the total common mode voltage and is capable of suppressing leakage current as per DIN VDE 0126-1-1 grid standards. It offers the advantages of scalability, reactive power capability, reduced total harmonic distortion, and filter size. The proposed hybrid transformerless seven-level inverter is simulated in MATLAB, and experimental setup is built to validate the effectiveness of the proposed configuration. Finally, a comprehensive comparison is made with other seven-level inverter topologies.     

On the dynamics of non-linear RLC networks from a geometric point of view

The dynamics of non-linear RLC networks is considered from a geometric point of view. the concept of the Kirchhoff-Maxwell space is presented and next it is explored in the formulation of the equations of motion for a broad class of dynamic non-linear networks. Linearized networks and eventually strictly passive networks are examined. Several new structural stability results are given.     

Some topologico-dynamical properties of linear passive reciprocal networks

The paper considers the complete solvability and the order of complexity of passive RLCT (T = multiwinding ideal transformer) networks. A topological approach based on the determinant polynomial of the matrix of hybrid equations, formed as a set of 1st-order differential and algebraic equations, reveals the structure of the formulation tree and the subnetworks accountable for degeneracies. Topological and algebraic degeneracies are defined. Necessary and sufficient conditions for complete solvability are derived, and two algorithms are given to determine the order of complexity topologically, i.e. without having an explicit state-space representation.     

A new canonic realization of lossless immittance functions using six-element sections

A new canonic realization cycle for lossless driving point immittance functions is given. This is achieved by extracting a six-element section (involving three inductors and three capacitors), which is terminated in a simpler immittance function whose form is the same but of order six lower than that of the original. This method is easily extended to RC and RL cases.     

A new characteristics-variable two-input/output filter in D-module-designs, realizations, and equivalence

This paper proposes a new nth order two-input/output filter in module for two-phase signal processing. The filter can make the distinction between positive and negative frequencies of two-phase signals and can allow for processing of the signals based on frequency polarity. The filter can also change dynamically its filtering characteristics by simply injecting a shift signal to the filter. The filtering effects equivalent to ones by parallel-arranged filters with vector rotators can be obtained, but in a much simpler manner. Unified analyses about attractive general properties of the proposed filter are given for easy designs and realizations as well. Effectiveness of the analyses and usefulness of the filter are examined and confirmed through numerical experiments. The proposed two-input/output filter in the module has potential usefulness in a variety of polyphase signal filtering applications, including three-phase power systems with active filtering function and sensorless vector controls of three-phase AC motors.     

Optimum realizations of single-amplifier networks with zero pole frequency sensitivity and with minimized pole-Q deviation

This paper discusses realizations of second-order open-circuit voltage transfer functions by single-amplifier active RC networks. These realizations are based on the polynomial decompositions having the property that the sensitivity of ω₀ with respect to the amplifier gain is zero. In addition, the gain-sensitivity product of Q is minimized and the element spread is contained to be within acceptable limits. The realizations are suitable for hybrid IC technology.     

On a class of nonlinear networks

Some of the properties of a class of nonlinear networks are discussed. The class of networks under consideration is allowed to have very general branch characteristics including couplings among elements of different kinds and discontinuities in time. Firstly, local existence and uniqueness of solutions to the state equations are discussed. Secondly, several global properties of the class of networks are discussed. Some of the properties of the degree of a function and a differential property of implicit function theorem turn out to be useful.     

MMC型柔性直流输电系统无源网络供电的直接电压控制

介绍了向无源网络供电的模块化多电平换流器(MMC)型电压源换流器型高压直流输电(VSC-HVDC)的系统结构和工作原理,引入了MMC的数学模型。提出了MMC无源逆变的直接电压控制策略,其中电压幅值控制由参考信号的直馈和负反馈PI补偿来实现,频率控制通过给定调制信号频率来实现,保证了良好的供电质量。在PSCAD/EMTDC中搭建了向无源网络供电的MMC型VSC-HVDC仿真系统,对有功和无功负荷变化以及交流电压降低等工况进行了仿真研究。仿真结果表明所设计的无源逆变控制器可以向无源网络提供高质量的电能。     

The future of low voltage networks: Moving from passive to active

The growth of energy consumption, the ever extensive use of conventional fossil fuels from exhaustible resources and concerns about the environment have led to the development of sustainable renewable energy as a necessary global requirement. Today, the trend in the electrical sector is the generation of electrical power at low voltage. Distributed generation at low voltage enables consumers to contribute to the country’s energy mix system without large investments by governments. This means that dwellers are able to produce and inject electrical power into the grid thus enjoying the status of energy producer and also reducing the burden on the national electrical grid system. In order for this system to produce high quality energy in a safe and coordinated manner, stringent health & safety and technical measures must be implemented. Moreover, such systems require strong legal support and well-established contracts. Technical training of personnel, implementation of well established planned/corrective maintenance systems and electrical spare part availability are also crucial to the reliability and long term operation of such systems. The aims of the paper are to present the basis for development of renewable energy for household usage in countries such as Germany, Denmark, Spain and Brazil, in terms of technical requirements for electrical generation and grid connection at low voltage. In Brazil about 70% of the electricity comes from hydropower and around 50% of its automobiles run on renewable biofuel, which results in a low per capita emission. The country however faces some tough barriers to overcome in order to implement household generation from renewable sources. These will be discussed in due course.     

A Step-Up Phenomenon of the Thyristor Control Circuit with Series RLC Elements

A circuit controlled by thyristors and having series RLC elements gives rise to a step-up phenomenon. The term step-up is defined with respect to the capacitance voltage on steady state operation, i.e., the ratio of the maximum peak value when controlled by thyristers to the peak amplitude when thyristors are short-circuited exceeds unity. The domain of possible step-up voltage is determined by the angle of displacement between current and voltage and damping factor. The step-up voltages appear across each element, i.e., not only across the capacitance, inductance, and resistance but also across the thyristors. The control characteristic has a distinctive hump phenomenon. The interrupted current results in waveform distortion, phase lag, and improved power factor. The difference of characteristics between the peak and rms values of voltages, particularly of inductance and thyristors, is large. The response time, which is evaluated by numbers of half cycles, is large when the step-up ratio becomes large. The output voltage when the circuit is used as a voltage source has a drooping characteristic.     

Long transient oscillations in a class of cooperative cellular neural networks

The real‐time processing capabilities of cellular neural networks (CNNs) are inherently related to the fast convergence time of the solutions toward the asymptotically stable equilibrium points. A typical requirement is that the settling time should not exceed a few (or at most 10) cell time constants. This paper introduces a class of completely stable nonsymmetric cooperative CNN rings whose solutions display unexpectedly long transient oscillations for a wide set of initial conditions and for a wide set of interconnection parameters. Numerical simulations show that the oscillations can easily last hundreds of cycles, and thousands of cell time constants, before settling to a steady state, thus possibly impairing their real‐time processing capabilities. Goal of the paper is also to show, by means of laboratory experiments on a discrete component prototype of the CNN ring, that the long oscillation phenomenon is physically robust with respect to the non‐idealities of the circuit implementation. The experiments show some other peculiar features of the long lasting oscillations as the metamorphosis between different periodic behaviors during the transient. Finally, analytic asymptotic estimates on the duration of the transient oscillations are provided. Copyright © 2013 John Wiley & Sons, Ltd.     

On global asymptotic stability for a class of delayed neural networks

This paper deals with the problem of stability analysis for a class of delayed neural networks described by nonlinear delay differential equations of the neutral type. A new and simple sufficient condition guaranteeing the existence, uniqueness and global asymptotic stability of an equilibrium point of such a kind of delayed neural networks is developed by the Lyapunov–Krasovskii method. The condition is expressed in terms of a linear matrix inequality, and thus can be checked easily by recently developed standard algorithms. When the stability condition is applied to the more commonly encountered delayed neural networks, it is shown that our result can be less conservative. Examples are provided to demonstrate the effectiveness of the proposed criteria. Copyright © 2011 John Wiley & Sons, Ltd.