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.     

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.     

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.     

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.     

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.     

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.     

A systematic approach to the design of stray-insensitive sc circuits from active-RL or RLC prototypes

A systematic approach to the design of stray-insensitive switched-capacitor (SC) circuits from active-RC or RLC prototypes employing a parasitic insensitive SC differential voltage-controlled current-source as a basic building block is attempted. Procedures for transforming active-RC and RLC circuits into stray-insensitive SC circuits are formulated and illustrated with typical examples. Restrictions on the pole-frequency and pole-Q of the SC biquad are derived so that it closely emulates the frequency response of the original active-RC biquad. the SC biquad and the ladder filter derived by the proposed procedures were simulated with discrete components and tested in the laboratory. Test results agree closely with the theoretical predictions.     

A spreadsheet simulation of logic networks

The authors present a method for simulating logic networks using spreadsheets. This method may be used to simulate combinational, sequential, synchronous and asynchronous networks. The characteristics of the method make it significant as an important tool in the analysis, design and test logic networks in education environments     

A comparison of industrial communications networks

The fundamental characteristics of industrial local area networks are introduced, and how these characteristics effect each application is reviewed. The author identifies which type of network is best suited for different control applications     

A new class of oscillators

The Colpitts is perhaps the best known class of oscillators and is realized in many forms using a variety of sustaining stage active devices. This article describes a new class of oscillator that uses a resonator with three transmission zeros at dc formed by a series capacitor, a shunt inductor and a series capacitor. This structure is suitable for sustaining stages with either equal or dissimilar input and output impedance. The new oscillator class is economic and offers alternative features to complement the classic Colpitts.     

A 6.6‐kV transformerless cascade PWM STATCOM. Experimental verification by a three‐phase 200‐V, 10‐kVa laboratory system

This paper deals with a 6.6‐kV transformerless STATCOM cascading multiple single‐phase H‐bridge PWM converters in each phase. The AC voltage of the STATCOM is almost sinusoidal, so that it requires no harmonic filter. Each converter is equipped with a capacitor and a voltage sensor on the DC side, which are electrically isolated from each other. The STATCOM has the capability of self‐starting and voltage‐balancing without any external power supply or equipment. Experiments using a three‐phase 200‐V, 10‐kVA laboratory system, along with computer simulations, are carried out to confirm the viability and effectiveness of the STATCOM. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 55–64, 2010; Published online in Wiley InterScience ( www.interscience.wiley. com ). DOI 10.1002/eej.20822     

A proposal of a 3.3‐kV/6.6‐kV transformerless hybrid filter,and experimental verification based on a 200‐V laboratory system

This paper proposes a transformerless shunt hybrid filter for harmonic compensation of a three‐phase six‐pulse diode rectifier, where the AC line‐to‐line voltage is 3.3 or 6.6 kV. The hybrid filter consists of a single tuned LC filter per phase and an active filter with a DC capacitor voltage as low as 300 or 600 V. The two filters are directly connected in series with each other without a transformer. The passive filter absorbs harmonic currents produced by the rectifier, whereas the active filter improves the filtering characteristics of the passive filter. The required rating of the active filter is much smaller than that of a conventional shunt active filter used alone. Another advantage is that no additional switching‐ripple filter is required for the active filter because the LC filter acts not only as a tuned LC filter around the seventh‐harmonic frequency but also as a switching‐ripple filter around 10 kHz. A feedforward control scheme is also proposed to improve the active filter performance. Experimental results obtained from a 200‐V, 5‐kW laboratory system and simulation results of a 3.3‐kV, 300‐kW system confirm the validity and effectiveness of the system. The hybrid filter gives satisfactory compensation performance, thus allowing us to put it into practical use. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 54–65, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10236