Analysis Of Power Electronic Converters Research Articles

A Novel Three-Pulse Equivalent Power Loss Profile for Simplified Thermal Estimation

One of the key challenges for long-term reliability analysis of power electronic converters is to quickly estimate extensive junction temperature cycles of power semiconductor devices while fulfilling an accepted accuracy. To address this challenge, this article proposes a novel three-pulse equivalent power loss profile. By contrast to the conventional methods of dividing the power loss equally, this article discretizes the power loss profile based on the identified occurrences of maximum and minimum junction temperatures (i.e., thermal characteristics). This proposed model decouples the conventional conflict between the thermal estimation accuracy and computational burdens. And it has the advantages of improving accuracy in terms of the maximum and minimum junction temperatures, and power-on time of thermal profiles, which are majorly concerned by today’s lifetime models of power semiconductors. Moreover, the proposed method also helps to reduce computational burdens. The relevant variables of the thermal modeling methods are investigated. Finally, the effectiveness of the proposed method is verified through simulation and experiments, and the impact of its thermal estimation advantages on lifetime evaluation is analyzed further.

Control Design and Stability Analysis of Power Converters: The Discrete Generalized Bode Criterion

For the controller design and stability analysis of power electronic converters, the Bode stability criterion and its subsequent revisions are the most practical tools. However, even though the control of the power converter is usually implemented in a microprocessor, none of these methods is infallible when applied to a discrete system. This article therefore proposes a new stability criterion, named the Discrete Generalized Bode Criterion (DGBC). This method is based on the Nyquist criterion but developed from the open-loop Bode diagram, evaluated also at 0 Hz and at the Nyquist frequency. The proposed criterion combines the advantages of the Nyquist and Bode criteria, since it is always applicable and provides an interesting and useful tool for the controller design process. The method is applied to design an active damping control of an inverter with LCL filter, showing how the proposed criterion accurately predicts stability, in contrast to the existing Bode criteria. The theoretical analysis is validated through experimental results performed with a three-phase inverter and an LCL filter.

Controller-Embeddable Probabilistic Real-Time Digital Twins for Power Electronic Converter Diagnostics

In this article, an approach is proposed for the online diagnostic analysis of power electronic converters utilizing real-time, probabilistic digital twinning. Under this approach, a digital twin (DT) of a power converter is defined as a real-time, probabilistic simulation model with stochastic (random) variables, developed using generalized polynomial chaos expansion. The DT models are partitioned in perspective of control layers for power converter subsystems in the approach, with emphasis on the application and converter control layers. Real-time executed solvers of these divided probabilistic DT models are embedded into power converter controllers running on field programmable gate array (FPGA) computing devices. Using a monitoring system, the real-time probabilistic DTs at each control layer and the corresponding physical twins of the power converter are compared by the controllers to determine if the power converter is operating within probable behavior. Knowing the large computational cost of probabilistic modeling, the resource usage and timing of real-time DT solvers on modern FPGAs is reported for common power electronic converter topologies, showing the approach is feasible and able to perform probabilistic real-time simulation of smaller power converters in perspective of application and converter control layers using $\leq 2\; \mu s$ time steps, with as low as $\text{70}\;{\rm ns}$ steps; while staying embeddable within FPGA-based controllers. To highlight the capabilities of the proposed approach, a case study is presented using a probabilistic DT in the application layer controller of a pair of converters to comparatively monitor their behavior and corresponding controller action under hardware-in-the-loop testing.

Analysis of Power Electronic Converters for Electric Vehicle Applications

this work presents a performance analysis of various power electronic converters with RL load to reduce the total harmonic distortion. The power converters inspected are: ZETA converter, single-ended primary inductance converter, often written SEPIC converter and Z SOURCE converter. The objective is to analyze which power electronic converter exhibits less total harmonic distortion (THD) and more efficiency in order to select the suitable converter for electric vehicle propulsion system. Three above mentioned converters are designed, modeled, and simulated. The zeta converter is advantageous over other converters inspected and have reduced total harmonic distortion, higher output power and hence improved efficiency. The simulations are done with MATLAB/SIMULINK and the results are presented.

Some New Results on the Averaging Theory Approach for the Analysis of Power Electronic Converters

The paper deals with some new results on the averaging theory approach for the analysis of feedback controlled pulsewidth modulation power electronic converters. It develops some considerations regarding the averaging approximation of time-variant differential systems proving an analytical relationship between the accuracy with which the solution of the averaged model converges to the solution of the original time-variant model (i.e., the switched model) and the switching frequency of the converters. This relation is valid both for stable and unstable systems. Moreover, this paper confirms, as corollary, that under suitable conditions (verified during the standard operations of the power electronic converters) the averaged model uniformly converges to the switched model.

On the Practical Stability of Hybrid Control Algorithm With Minimum Dwell Time for a DC–AC Converter

This brief presents a control law based on a hybrid dynamical systems theory for a dc–ac converter. This theory is very suited for an analysis of power electronic converters, since it combines continuous (voltages and currents) and discrete (ON–OFF state of switches) signals avoiding, in this way, the use of averaged models. Here, practical stability results are induced for this tracking problem, ensuring a minimum dwell time associated with an Linear–Quadratic Regulator (LQR) performance level during the transient response and an admissible chattering around the operating point. The effectiveness of the resultant control law is validated by means of experiments.

On the Equivalence and Impact on Stability of Impedance Modeling of Power Electronic Converters in Different Domains

Small-signal analysis of power electronic converters and systems is often carried out by impedance-based methods. At the core of these methods lies the impedance modeling, which can either be obtained through analytical calculations, simulations, or measurements. The impedance models can be obtained into two main domains: the dq -domain and the sequence domain. In the dq -domain, the impedance model is a $2\times 2$ matrix, while in the sequence domain, it is composed by the positive and negative sequence impedance. Recently, a third domain called the modified sequence domain was defined as an extension to the sequence domain, but also with clear similarities to the dq -domain. The objective of this paper is to unambiguously relate to each other the impedances in these three domains, and to show how this equivalence translates into their respective stability assessments. It is also proven that the sequence domain impedance has the same marginal stability condition as the dq -domain impedance matrix. The three-phase voltage source converter is used as an example converter in this paper, as its impedance model in all three domains is well established and reported by previous research. The results in this paper show that the modified sequence domain model can be derived from the dq -domain model (and vice versa), and that the stability analysis will be identical in these two domains. It is also shown how the original sequence domain model can be derived from the two other models through a model reduction. However, a small discrepancy between the two Nyquist plots is observed in the presence of components such as phase-locked loop or dc-link control.

Quadratic state-space modeling technique for analysis and simulation of power electronic converters

This paper presents a quadratic state-space modeling technique for analysis of power electronic converters. The methodology is based on using a least-square-error fitting to derive a quadratic state-space representation for each topology, together with automatic determination of switching topology. The algorithm integrates the advantages of calculating topology responses at the circuit level and determining switching instants at the device level. Several key features of the new model that lead to significant improvements in computational efficiency include: (1) its simple quadratic polynomial representation for the state-transition matrix in solving the differential equations describing each topology; (2) its direct and single-step calculation of the switching instants; and (3) its generality in determining valid topology without a prior understanding of the switching relationships. Several examples illustrating the generality and simulation speed of the proposed approach are presented. The computational efficiency of the new approach is demonstrated by comparing its simulation time with commercial software using the stepwise integration algorithm. The accuracy is verified with the exact method and available literature.

Analysis of power electronic converters using the generalized state-space averaging approach

Power electronic converters are periodic time-variant systems, because of their switching operation. The generalized state-space averaging method is a way to model them as time independent systems, defined by a unified set of differential equations, capable of representing circuit waveforms. Therefore, it can be a convenient approach for designing controllers to he applied to switched converters. This brief shows that the generalized state-space averaging method works well only within specific converter topologies and parametric limits, where the model approximation order is not defined by the topology number of components. This point is illustrated with detailed examples from several basic dc/dc converter topologies.

Simulateur digital des convertisseurs de puissance à thyristors

This paper deals with a digital simulator for the analysis of any thyristor converter. The analysis is based upon a topological method of formulation of state equations and power thyristors and diodes are modelled as inductances. The value of each thyristor inductance changes from a finite value equal to the di/dt limiting series inductance, while conducting, to an infinite value when blocked. The simulator takes into consideration the presence of the snubber circuits associated with each thyristor element. The simulator library which has been named ATOSEC I has been developed having in mind the creation of a tool for the design by computer aided analysis of power electronic converters. It has been presently implemented on a CDC CYBER and will be available to prospective users from the authors.