Duwang Li

Extended ripple analysis of PWM DC-to-DC converters

By employing a Taylor series expansion of the state, simplified expressions are derived for the first- and second-order terms of the state ripple of any pulse-width-modulated (PWM) DC-to-DC power converter operating in continuous conduction mode. Under the assumption that the ripple is dominated by its lowest-order nonzero component, along with the ripple order relationships between state variables, these expressions may be used on any PWM power converter to derive design guidelines for optimum ripple performance. An example is given of a fourth-order boost-type power converter in which, after determining conditions by which the first two lowest-order components in the output voltage ripple are nulled, further conditions are derived that minimize the third-order component, resulting in enhanced ripple performance. The results are verified by simulation. >

PECS-an efficient solution for simulating switched networks with nonlinear elements

PECS (Power Electronics Circuit Simulator) enables the time-domain simulation of switched networks that may contain nonlinear elements. Focus has been placed not only on obtaining high speed, but also on achieving a very high degree of accuracy. A set of optimized computer algorithms that have been incorporated into PECS to achieve these objectives are explained. Examples run, which include a power-factor correction circuit containing a multiplier/divider element, have shown over an order of magnitude speed advantage over other leading approaches.

Time-domain simulation of switched networks using the Chebyshev series

An efficient integration routine based on the Chebyshev series expansion is given. Adoption of a Chebyshev expansion minimizes the order of the polynomial approximation which together with a number of basic properties of the expansion results in an efficient integration method. Furthermore, integration error control may conveniently be approached by monitoring the coefficients of the expansion. The proposed error control scheme varies the expansion order while keeping the step size fixed. A software program for the simulation of networks with ideal switches was written which incorporates the above features. Two examples, one of a nonswitched network and the other a switched network, are given to illustrate the speed and accuracy of the program and effectiveness of the error control scheme. To quantify the advantages of the proposed scheme, a comparison is made with a previously developed simulator (viz. LAPS) and also a commercially available SPICE program.<<ETX>>

Object oriented design of a power electronics circuit simulator

The features of object oriented programming (OOP) are explained and contrasted with the traditional procedural programming paradigm. Incorporating any or all of the OOP features of encapsulation, polymorphism and inheritance results in faster, less error prone, code implementation which promotes code reuse with the further benefit of ease of maintainability. The basic functions of a power electronics circuit simulator are described. A class structure for the simulator is outlined. This class structure has been successfully implemented using the C++ language which supports OOP. Experience with this project has indicated that C++ shines in numerical applications in comparison with FORTRAN and C.<<ETX>>

Chebyshev series integration method for transient simulation of switched networks

An efficient integration routine based on the Chebyshev series expansion is given. Adoption of a Chebyshev expansion minimizes the order of the polynomial approximation which together with a number of basic properties of the expansion results in an efficient integration method. Furthermore, integration error control may conveniently be approached by monitoring the coefficients of the expansion. The proposed error control scheme varies the expansion order while keeping the step size fixed. A software program for the simulation of networks with ideal switches was written which incorporates the above features. Two examples, one of a nonswitched network and the other of a switched network, are given to illustrate the speed and accuracy of the program and effectiveness of the error control scheme. To quantify the advantages of the proposed scheme, a comparison is made with a previously developed simulator (viz., LAPS) and also a commercially available SPICE program.

Simulation of networks with ideal switches

Recently developed simulation techniques that may be used for switched networks, as typified by switching power converters, are reviewed. The use of the numerical inverse Laplace transform is useful in performing equation integration and resolution of inconsistent initial conditions. Step-size control algorithms used for error control are examined and it is seen that an algorithm which does not change the step size at each step may be exploited to optimize simulation speed by reusing the previously determined factorization of the system matrix. Two examples are given which illustrate the relative gains of this optimization as well as illustrating the need for sparse matrix techniques in solving equations. The problem of simulating networks containing unsolvable intermediate topologies is also highlighted.

PECS. An efficacious solution for simulating switched networks with nonlinear elements

PECS (Power Electronics Circuit Simulator) enables the time-domain simulation of switched networks that may contain nonlinear elements. Focus has been placed not only in obtaining high speed but also in achieving a very high degree of accuracy. A set of optimized computer algorithms that have been incorporated into PECS to achieve these objectives are explained. Examples run, which include a PFC (power factor converter) containing a multiplier/divider element, have shown over an order of magnitude speed advantage over other leading approaches.

PECS-Power Electronics Circuit Simulator

PECS (Power Electronics Circuit Simulator) enables the time-domain simulation of switched networks that may contain nonlinear elements. In the design of PECS focus has been placed not only in obtaining high speed but also in achieving a very high degree of accuracy. A set of optimized computer algorithms that have been incorporated into the software to achieve these objectives are explained. A closed-loop buck DC-to-DC regulator and a boost power factor correction circuit are simulated with PECS and a number of other simulators highlighting the speed and accuracy advantages of PECS.

Computer aided design tool for PWM converters

A user friendly program which integrates schematic capture, simulation, analysis and measurement of PWM DC-to-DC power converters in one package is described. It provides several alternatives to obtaining the frequency response of PWM and current programmed power converters, which include a model that accounts for the effect of sampling in current programmed converters, and models that provide exact small-signal responses for both PWM and current programmed converters. Design aspects of the package are also discussed. The analysis part of the program is designed using the Model-View-Controller framework for which it is well suited. The program is written in C++ which supports object-oriented programming. A multiple models approach is used to identify and define the appropriate objects for data management, user interface and program control.<<ETX>>