Component connection model for the automated steady state analysis of power electronic systems

In this paper a novel Voter Based Markov model will be presented for evaluation of the reliability in a multi-port power electronic interface. In the new Markov model, a new technique called Voter Based State Reduction (VBSR) technique will be introduced for reducing the number of states in Failure Mode and Effect Analysis (FMEA). The VBSR technique will simplify the reliability analysis of power electronic systems. It will also make the results of the reliability assessment more meaningful. In order to show the effectiveness of the proposed model, reliability of a Multi-port Power Electronics Interface (MPEI) will be evaluated using both conventional and Voter based Markov model. Comparison of FMEA and reliability evaluation results between conventional Markov model and the new Voter Based Markov model confirms the effectiveness of the proposed method.

A novel formulation of induction machines with modified nodal analysis is proposed for simulations of power electronics systems. The size of formulated matrix of a three-phase induction machine becomes 15/spl times/15, which includes the voltage and torque equations. The simulation written in C++ programming language and experiment of the generator system, which consists of a cascaded induction generator and a six-pulse rectifier, were carried out. These results prove the effectiveness of the proposed formulation.

Power electronics based power distribution systems (PEDSs) are becoming increasingly common, particularly in marine and aerospace applications. Stability analysis of this class of systems is crucial due to the potential for negative impedance instability. Existing techniques of stability analysis introduce artificial conservativeness, are sensitive to component grouping, and at the same time do not explicitly address uncertainties and variations in operating point. A new stability criterion, which reduces artificial conservativeness and is also insensitive to component grouping is described. In addition, a means of readily establishing design specifications from an arbitrary stability criterion which specifically includes a provision to incorporate uncertainty, parameter variation, and nonlinearities is set forth. The method is presented in the context of a hardware test system and is experimentally validated.

Power electronic systems have become a key component in the efficient generation, distribution, storage, and use of energy. This increasingly places power electronic systems in harsh environments under elevated stress conditions where, in many cases, their reliable operation is now mission critical. The semiconductor material conventionally used, silicon, possesses limited capability for high temperature applications due to its small bandgap. Power electronic components based on wide bandgap (WBG) semiconductors, such as SiC and GaN, can be operated reliably at higher temperatures. Furthermore, WBG devices have higher breakdown voltages and switching frequencies, rendering them more ideal switches and rectifiers for highefficiency as well as low-volume and low-weight systems. Yet, new packaging concepts are required to make use of the high temperature capability of power electronic systems based on WBG semiconductor devices. In this paper, a summary of the progress in the development and commercialization of wide bandgap power components and power electronic systems is given. The properties of SiC and GaN components are compared to those based on silicon. The shortcomings of conventional power electronic packaging technologies are analyzed, and alternatives introduced and compared. An overview of research is given on Transient Liquid Phase Sintering (TLPS), a promising interconnect technology for the manufacturing of WBG and high temperature power electronic systems. TLPS is a liquid-assisted sintering process during which a low melting temperature constituent melts, surrounds, and diffuses in a high melting temperature constituent. Intermetallic compounds with high melting temperatures are formed by liquid-solid diffusion. Interconnect systems can be processed at low temperatures but are capable of operating at the high melting temperatures of the intermetallic compound. Different process approaches are contrasted and material systems compared. Latest results of research on paste-based low temperature TLPS are presented. The pastes assessed are based on the Cu-Sn and Ni-Sn material systems. It is shown that joints formed by TLPS remain strong up to 600°C and exhibit softening temperatures far higher than conventional interconnect technologies. They show minimum creep and possess very limited voiding. The process does not require an inert or reducing atmosphere or vacuum and is compatible with standard reflow soldering equipment. It shows good wettability to common metallizations such as Cu, Ni, Ag, and ENIG. This attach technology shows the potential to enable reliable operation of wide bandgap power electronic systems under high stress conditions.

We consider nonnegative steady-state solutions of the evolution equationformula hereOur class of coefficients f, g allows degeneracies at h = 0, such as f(0) = 0, as well as divergences like g(0) = ±∞. We first construct steady states and study their regularity. For f, g > 0 we construct positive periodic steady states, and non-negative steady states with either zero or nonzero contact angles. For f > 0 and g < 0, we prove there are no non-constant positive periodic steady states or steady states with zero contact angle, but we do construct non-negative steady states with nonzero contact angle. In considering the volume, length (or period) and contact angle of the steady states, we find a rescaling identity that enables us to answer questions such as whether a steady state is uniquely determined by its volume and contact angle. Our tools include an improved monotonicity result for the period function of the nonlinear oscillator. We also relate the steady states and their scaling properties to a recent blow-up conjecture of Bertozzi and Pugh.

The Nyquist stability criterion is a graphical technique for determining the stability of a dynamical system. It relates the stability of a closed‐loop system to the open‐loop frequency response and open‐loop pole location. The Nyquist technique is limited to linear, time‐invariant (LTI) systems and has been widely used for designing and analyzing systems with feedback. A practical advantage of the technique is that it can be applied directly to measured frequency response data, due to which the technique is widely used in power electronics systems, where the complexity of a mathematical model would make its widespread use unfeasible. In its first part, this article guides through the fundamentals of the Nyquist stability criterion applied to feedback systems with SISO and MIMO representations. The generalized Nyquist criterion for MIMO systems is then discussed to illustrate its application to the stability assessment of three‐phase power electronics systems. In the second part, four representative cases are introduced to illustrate the applicability of Nyquist criterion–based stability analysis for power electronics systems: a dc‐dc converter, an HVDC system, a three‐phase converter, and a wind farm–HVDC grid integrated system. In the last section of this article, some advanced topics related to large‐scale power electronics systems are introduced. Inherent aspects that are essential for the proper use of these stability techniques are elaborated and discussed in detail, for instance, impedance transformation and modified sequence impedance or the system‐level analysis.

We present flow-based results from the early stage design cycle, based on computational modeling, of a prototype flow-diverter device, known as the ‘Sphere’, intended to treat bifurcation aneurysms of the cerebral vasculature. The device is available in a range of diameters and geometries and is constructed from a single loop of NITINOL® wire. The ‘Sphere’ reduces aneurysm inflow by means of a high-density, patterned, elliptical surface that partially occludes the aneurysm neck. The device is secured in the healthy parent vessel by two armatures in the shape of open loops, resulting in negligible disruption of parent or daughter vessel flow. The device is virtually deployed in six anatomically accurate bifurcation aneurysms: three located at the Basilar tip and three located at the terminus bifurcation of the Internal Carotid artery (at the meeting of the middle cerebral and anterior cerebral arteries). Both steady state and transient flow simulations reveal that the device presents with a range of aneurysm inflow reductions, with mean flow reductions falling in the range of 30.6–71.8% across the different geometries. A significant difference is noted between steady state and transient simulations in one geometry, where a zone of flow recirculation is not captured in the steady state simulation. Across all six aneurysms, the device reduces the WSS magnitude within the aneurysm sac, resulting in a hemodynamic environment closer to that of a healthy vessel. We conclude from extensive CFD analysis that the ‘Sphere’ device offers very significant levels of flow reduction in a number of anatomically accurate aneurysm sizes and locations, with many advantages compared to current clinical cylindrical flow-diverter designs. Analysis of the device’s mechanical properties and deployability will follow in future publications.

The basic principles of an efficient new methodology for the calculation of the nonsinusoidal periodic steady state in power systems with nonlinear and time-varying components are described. All linear parts, including the network and part of the loads, are represented in the frequency domain, while nonlinear and time-varying components, mainly loads, are represented in the time domain. This hybrid process is iterative, with periodic, nonsinusoidal, bus voltages as inputs for both frequency domain solutions and time domain simulations: a current mismatch is calculated at each bus and used to update the voltages until convergence is reached. Thus the process, but not the solution, is decoupled for the individual harmonics. Its efficiency is enhanced by the use of Newton type algorithms for fast convergence to the periodic steady state in the time domain simulations. Potential applications of this methodology are in the computation of harmonic power flow and in the steady state initialization needed in the calculation of electromagnetic transients.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The electronic power system can be viewed as a system composed of a set of concurrently interacting subsystems to generate, transmit, and distribute electric power. The complex interaction among sub-systems makes the design of electronic power system complicated. Furthermore, in order to guarantee the safe generation and distribution of electronic power, the fault tolerant mechanisms are incorporated in the system design to satisfy high reliability requirements. As a result, the incorporation makes the design of such system more complicated. We propose a dependable electronic power system architecture, which can provide a generic framework to guide the development of electronic power system to ease the development complexity. In order to provide common idioms and patterns to the system *designers, we formally model the electronic power system architecture by using the PVS formal language. Based on the PVS model of this system architecture, we formally verify the fault tolerant properties of the system architecture by using the PVS theorem prover, which can guarantee that the system architecture can satisfy high reliability requirements. KeywordsSystem Architecture; PVS System; Fault Tolerance; Formal Modeling; Formal Verification.

We consider chemical reactions occurring in a compartment separated by semipermeable membranes from reservoirs of reactant and product, both held at constant pressure. In earlier work, we have developed a nonequilibrium thermodynamic theory applicable to systems with a single reactive intermediate, and we have established a link between the thermodynamic and stochastic analyses of such systems. Here we show that our results generalize directly to cases with two or more reactive intermediates, if the reaction mechanism is nonautocatalytic, or if the system is evolving toward an equilibrium steady state in the reaction compartment without first exhausting the reactant or product reservoir. Starting with nonautocatalytic mechanisms, we identify effective driving forces for each intermediate; we then obtain the driving force for an arbitrary system by mapping to an instantaneously equivalent nonautocatalytic system. The driving force can be cast thermodynamically in terms of the difference between the actual chemical potential of the intermediate and its chemical potential at a reference state (the steady state of the instantaneously equivalent nonautocatalytic system); it can also be cast kinetically in terms of reactive fluxes in the instantaneously equivalent system. Taking the product of the driving force and the net flux of each intermediate and then summing over the species gives a term in the dissipation that is specific to the intermediates. This term is minimized at nonequilibrium steady states, unlike the total dissipation (or entropy production). For the nonautocatalytic or equilibrating systems, an integral of the driving forces yields a Liapunov function for the evolution of the reaction chamber toward the steady state. The same integral also determines the stationary solution of the birth–death master equation for the species numbers of intermediates in the reaction compartment; this generalizes the Einstein relation for the probability of equilibrium fluctuations to far-from-equilibrium conditions.

Gas Turbine Simulation (GTS) is an integrated general purpose simulation package developed for steady state (matching) and transient simulation of gas turbine-based propulsion systems such as turbofans. Steady state simulation is based on matching engine components with given performance maps. Matching is achieved by zeroing the difference in mass flow rate of adjacent components, and work of compressor/fanturbine pairs. Steady state (matched condition) serves as initial condition for transient simulation of the engine. Transient simulation of the engine is based on the method of intercomponent volumes, and considers the mass and rotor dynamics of the components as well as the dynamics of engine control system. The program is capable of simulating an open loop engine (i.e. an engine without the consideration of the control system) as well as an engine and its control system (closed loop control) as one dynamic unit. The program is equipped with a graphic user interface (GUI) for configuring the engine as well as its control system, accepting inputs, commanding the run-time routines and providing outputs in graph and output file forms. The program can run for a variety of options and has produced reasonable results for several engine configurations.

Computer algorithms of the Newton-Raphson type are derived for the harmonic analysis of systems containing nonlinear dynamic components in periodic steady state. The problem is formulated in the complex conjugate multiharmonic space that inherently represents the harmonic coupling between the different harmonic frequencies. The theory is applied to single-phase systems, including magnetic nonlinearities. >

Abstract. This paper presents an electrical, fully integrated, high quality (Q) factor GmC bandpass filter (BPF) stage for a wireless 27 MHz direct conversion receiver for a bendable sensor system-in-foil (Briem et al., 2016). The core of the BPF with a Q factor of more than 200 is an operational transconductance amplifier (OTA) with a high linearity at an input range of up to 300 mVpp, diff. The OTA's signal-to-noise-and-distortion-ratio (SNDR) of more than 80 dB in the mentioned range is achieved by stabilizing its transconductance Gm with a respective feedback loop and a source degeneration resistors RDG. The filter stage can be tuned and is tolerant to global and local process variations due to offset and common-mode feedback (CMFB) control circuits. The results are determined by periodic steady state (PSS) simulations at more than 200 global and local process variation parameter and temperature points and corner simulations. It is expected, that the parasitic elements of the layout have no significant influence on the filter behaviour. The current consumption of the whole filter stage is less than 600 µA.

The vast majority of the occurrences of condition numbers in the study of linear systems of equations involve the normwise condition number κ(A). Almost invariably, the use of κ(A) is enough to provide a satisfying explanation of the phenomena observed in practice.The case of triangular systems of linear equations provides, in contrast, an example in which κ(A) turns out to be inadequate. Practitioners long observed that triangular systems of equations are generally solved to high accuracy in spite of being, in general, ill-conditioned. Thus, for instance, J.H. Wilkinson wrote: “In practice one almost invariably finds that if L is ill-conditioned, so that ∥L∥∥L −1∥≫1, then the computed solution of Lx=b (or the computed inverse) is far more accurate than [what forward stability analysis] would suggest.”A first goal in this chapter is to give a precise meaning to the feeling that triangular matrices are, in general, ill-conditioned. We prove that if \(L\in \mathbb {R}^{n\times n}\) is a lower-triangular matrix whose entries are independent standard Gaussian random variables, then \(\mathbb {E}(\log \kappa(L))=\varOmega(n)\). This yields an expected loss of precision satisfying $$\mathbb {E}\bigl(\mathsf {LoP}\bigl(L^{-1}b\bigr)\bigr)= \mathcal {O}(n). $$ Were the loss of precision in the solution of triangular systems to conform to this bound, we would not be able to accurately find these solutions. The reason we actually do find them can be briefly stated. The error analysis of triangular systems reveals that we may use a componentwise condition number Cw(L,b) instead of the normwise condition number. The second goal of this chapter is to prove that when L and \(b\in \mathbb {R}^{n}\) are drawn from standard Gaussian distributions, then we have \(\mathbb {E}(\log \mathsf {Cw}(L,b))=\mathcal {O}(\log n)\). This bound, together with some backward error analysis, yields bounds for \(\mathbb {E}(\mathsf {LoP}(L^{-1}b))\) that are much smaller than the one above, as well as closer to the loss of precision observed in practice.KeywordsTriangular Linear SystemNormwise Condition NumberComponentwise ConditionIndependent Standard Gaussian Random VariablesBackward Error AnalysisThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

It has long been known that roots of an equation (or a system of equations), can be obtained by first writing the system in the form xn+1 = F(xn), then deriving the recurrence system xn+1 — F(xn) ; these roots are the fixed points of the iteration, i.e. the values x0 such that x0 = F(x0). However, an iterative process may converge to or diverge from a fixed point x0, depending on the slope of F(x) at this point. Many efficient methods have been derived to promote (or accelerate) the convergence of this type of iterative process. The method described here as "directed iteration" aims to render attractive any chosen type of fixed point from a large domain of initial points. The present paper describes one-variable systems ; a subsequent paper will deal with n-variable systems. In short, we substitute for the original recurrence : [FORMULA] in which A is a positive or a negative number depending on whether the slope of F(x) at the fixed point chosen is itself positive or negative. Convergence is fastest when the value of A equals this slope ; for higher absolute values of A, convergence persists, although it is increasingly slow. More generally, one can write : [FORMULA] in which A is a caricature of the Jacobian matrix of F(x0) and I is the unitary matrix. For n-variable systems, however, it is more convenient to adopt a form closer to the Newton-Raphson recurrence : [FORMULA] in which H(xn) = F(xn) — xn and J is a caricature of the Jacobian matrix of H(x0). Our algorithm is included (as well as the Newton-Raphson and the Whit-taker algorithms) in a more general formulation given by Isaacson and Keller (1966) ; however, its usefulness in the context described here does not seem to have been considered before. As pointed out to us by C. Mira, a method developped by Giraud (1969) for two variable systems also uses ad hoc matrices which modify the attractiveness of fixed points. In the search for steady state values of systems of non-linear ordinary differential equations, directed iteration often permits convergence to a chosen steady state (or type of steady state) from a wide range of initial guesses where classical iterations fail to converge or converge from a small interval around the steady state.