J. Software Engineering & Applications, 2010, 3, 723-727

doi:10.4236/jsea.2010.37083 Published Online July 2010 (http://www.SciRP.org/journal/jsea)

Copyright © 2010 SciRes. JSEA

723

Modeling and Analysis of Submerged Arc Weld

Power Supply Based on Double Closed-Loop Control

Baoshan Shi1, Kuanfang He2, Xuejun Li2, Dongmin Xiao3

1School of Mechanical and Vehicle Engineering, Beijing Institute of Technology, Zhuhai, China; 2Hunan Provincial Key Laboratory of

Health Maintenance for Mechanical Equipment, Xiantan, China; 3College of Electromechanical Engineering, Xiantan, China.

Email: hkf791113@163.com

Received January 6th, 2010; revised May 9th, 2010; accepted May 11th, 2010.

ABSTRACT

According to the soft-switching pulsed SAW (Submerged arc weld) weld power supply based on the double closed-loop

constant current control mode, a small signal mathematic model of main circuit of soft-switching SAW inverter was

established by applying the method of three-terminal switching device modeling method, and the mathematic model of

double closed-loop phase-shift control system circuit was established by applying the method of state-space averaging

method. Dynamic performance of the inverter was analyzed on base of the established mathematic model, and the tested

wave of dynamic performance was shown by experimentation. Research and experimentation show that relation be-

tween structure of the power source circuit and dynamic performance of the controlling system can be announced by

the established mathematic model, which provides development of power supply and optimized design of controlling

parameter with theoretical guidance.

Keywords: SAW, Double Loop Control, Soft-Switching, Inverter, Mathematic Model

1. Introduction

The full-bridge phase-shift zero-voltage soft-switching

PWM inverter now is widely used in the weld field for its

many excellent performances. Through establishing ma-

thematic model and transfer function of soft-switching

pulsed metal active gas welding power supply, the rela-

tion between structural parameters of circuit and dynamic

performance of system is obtained, which is an effective

method of designing and development of that power sup-

ply [1,2]. In the field of power electronics, problem of

linear PWM DC-DC converter modeling was solved, there

are many methods of modeling such as three-terminal

switching device modeling method, data-sampling, symbol

analysis and so on [3-6], and method of space state aver-

age applied to inverter modeling [7-10], which provide

mathematic model of soft-switching pulsed metal active

gas welding power supply with theoretical guidance.

This paper proposes a soft-switching SAW weld pow-

er supply based on the double closed-loop constant cur-

rent control mode, which adopts structure of soft-

switching full-bridge circuit and combines the conven-

tional negative feedback of current or voltage and the

peak current control mode. A small signal mathematic

model of main circuit of soft-switching SAW inverter

and the mathematic model of double loop control circuit

are established by applying the method of three-terminal

switching device modeling method and the method of

space state average. According to mathematic model,

dynamic performance of the inverter is analyzed, and

tested wave of dynamic performance is shown to prove

the rationality of the inverter by experimentation.

2. Principles

The sketch map of the double closed-loop feedback con-

trol system is shown in figure1. It uses hall sensor to

sample current signal from primary transformer, and

pouring into control loop after sophisticated high-speed

rectifying. The control loop needs a reasonable slope

compensation circuit to ensure the system to be stable

and get appropriate open-loop frequency.

In the course of operation, the peak current signal

)(tis is sampled from the peak current of the VT, then

plus a peak current slope compensation signal1

)( fa Rti ,

which is a signal substituted traditional triangular wave

signal in voltage mode control. The saw tooth sig-

nal 1

)( fa Rti is synchronized with the signal of inverter

cycle, which is mainly used to improve waveform of the