P. Pejovic

A method for fast time-domain simulation of networks with switches

A method for fast time-domain simulation of piecewise-linear networks with switches is described in this paper. The method is based on a discrete-time switch model that consists of a constant conductance in parallel with a current source. In each simulation step, the value of the current source is updated as a function of known network signals. The function takes one of two forms, depending on the state (on or off) of the switch. Since the system matrix is constant, regardless of the states of the switches, simulation time is essentially the same as for a linear, time-invariant network of the same complexity. The paper discusses selection of the model and simulation parameters. The simulation algorithm is described and an example is included. It is shown that the method is not only efficient but also quite general and void of convergence problems. Its primary application is for long-term transient simulation of power electronic systems such as switching power converters. >

An analysis of three-phase low-harmonic rectifiers applying the third-harmonic current injection

An analysis of the three-phase low-harmonic rectifiers applying passive third-harmonic current injection networks is presented in this paper. Optimal amplitude of the injected current to minimize the input current total-harmonic distortion (THD) is derived as a function of the injected current phase displacement. Power aspects of the third-harmonic current injection are analyzed, and it is shown that improvement in the input current THD could be obtained at the expense of the power taken by the current injection network. In the case of optimal current injection, the power taken by the current injection network is shown to be equal to 8.571% of the input power, resulting in the input current THD of 5.125%. Effects of unwanted higher order harmonics in the injected currents are studied for two previously proposed passive current injection networks. The current injection networks are compared under the constraint that volt-ampere ratings of applied components are the same. Analytically obtained results are experimentally verified.

Optimal current programming in three-phase high-power-factor rectifier based on two boost converters

Current programming in a three-phase high-power-factor rectifier based on two boost converters is discussed in this paper. It is shown that the converter currents can be expressed in terms of two mutually related auxiliary functions. The auxiliary functions are related to the input current spectrum. Optimal auxiliary functions that eliminate harmonics of the input currents are derived. A method to generate reference signals for the optimal current programming is proposed. Experimental results confirming the proposed concepts are presented.

A new algorithm for simulation of power electronic systems using piecewise-linear device models

This paper describes a new algorithm for simulation of power electronic systems. Piecewise-linear (PWL) approximation is used to model nonlinear components, including switching devices, nonlinear reactive components, and nonlinear control circuitry. A representation of PWL elements is constructed such that a constant system matrix is obtained, regardless of the states of PWL elements. An efficient method for state determination is proposed, which is capable of resolving difficulties caused by discontinuous characteristics of PWL elements. The resulting simulation algorithm is quite general, requires no prior knowledge of the circuit operation, is void of convergence problems, and yields relatively short simulation times on desktop PC machines. >

Two three-phase high power factor rectifiers that apply the third harmonic current injection and passive resistance emulation

Two high power factor rectifiers that apply the third harmonic current injection principle and passive resistance emulation are presented in this paper. Two methods of current injection, simultaneous current injection in all three of the phases, and current injection to only one of the phases, are discussed. Conditions for the optimal third harmonic current injection are derived, structures of the rectifiers that apply passive resistance emulation, enabling recovery of the power taken by the current injection network, are presented. The proposed resistance emulator consists of a transformer, two diodes and a capacitor. Choice of the passive components is discussed, and their values are proposed, volt-ampere ratings of the magnetic components are derived. Influence of the higher order harmonics is discussed. Dependence of the input current total harmonic distortion on the load level is presented for both of the current injection methods. Analytically obtained results are verified on 1.5 kW experimental rectifiers.

An improved current injection network for three-phase high-power-factor rectifiers that apply the third harmonic current injection

A novel current injection network for low-harmonic rectifiers that apply the third harmonic current injection is proposed in this paper. The current injection network requires one inductor, two capacitors, and one 1:1 transformer with a voltampere rating of only 0.16% of the input power. The transformer is introduced to provide complete rejection of harmonic components of the injected currents at even triples of the line frequency, resulting in significant reduction of the input current total harmonic distortion (THD). Dependence of the input current THD on the current injection network Q factor is computed. The THD is shown to be in the range 4%<THD<5.125%. Analytically obtained results are experimentally verified on a 1.5 kW rectifier.

PETS-a simulation tool for power electronics

This paper describes PETS (Power Electronics Transient Simulator), a computer program for the time-domain analysis of power electronic circuits. Methods implemented in PETS include standard techniques such as the modified nodal approach to forming system equations and numerical integration with automatic time-step control, together with new techniques including a state determination algorithm and representation of elements to maintain a constant system matrix. The simulator supports arbitrarily complex piecewise-linear models and smooth nonlinear models using a delay approximation. The methods implemented in PETS are illustrated using two examples: a quadratic buck power converter, and a closed-loop power factor corrector.

Exact Analysis of Three-Phase Rectifiers With Constant Voltage Loads

In this paper, an exact solution of a circuit model for a three-phase rectifier with constant-voltage load and AC-side reactance that operates in the continuous conduction mode is presented. Obtained results are compared to the results provided applying sinusoidal approximation, published previously. It is shown that the sinusoidal approximation provides acceptable results at low output voltages, with the accuracy being decreased for the output voltages approaching to the discontinuous conduction mode boundary. Computational complexity of the exact solution is about the same as for the solution obtained applying sinusoidal approximation.

An Algorithm for Determining Mobile Station Location Based on Space Segmentation

An algorithm to determine mobile station location using segmentation of space, taking the set of nearest base stations as the segmentation criterion, is proposed. According to the set of nearest base stations observed by the mobile station, the algorithm selects a precalculated segment where the mobile station is located. By assuming uniform probability density for the mobile station location within the segment, the expectation for the mobile station coordinates is computed. Application of the algorithm is illustrated by simulation of a real GSM network. The algorithm is characterized by low computational cost and traffic burden.

Corona Discharge Surface Treater Without High Voltage Transformer

A corona discharge generator for surface treatment without the use of a step-up transformer with a high-voltage secondary is presented. The oil bath for high-voltage components is eliminated and still a reasonable volume, efficiency, and reliability of the generator are obtained. The voltage multiplication is achieved by an LC series resonant circuit. The resonant circuit is driven by a bridge type voltage-source resonant inverter. First, feasibility of the proposed method is proved by calculations. Closed form design expressions for key components of the electronic generator are provided. Second, a prototype of the electronic generator is built and efficiency measurements are performed. For power measurement, Lissajous figures and direct averaging of the instantaneous voltage-current product are used. The overall efficiency achieved is in the range between 80% and 90%.