Study of a varied hysteretic-band current control technology

Abstract

ABSTRACT The inverters and control methods are applied in more and more fields with power electronics development. The technology of current hysteretic band PWM is a kind of easy and reliable control method. But the harmonic distortion of load current is big amplitude around switching frequency side band. The paper introduce a Varied Hysteretic-band Current control technique(VHBCC), this method can spreads the spectrum contents of load current around switching frequency side band, reduces the harmonic distortion of load current . At last, The results of simulation prove the method feasible and effective. Keywords: Varied Hysteretic-band; Computer Simulation ; Expand harmonic spectrum 1. INTRODUCTION In the last twenty years, the inverter was applied widely in field of AC drives. Methods of voltage source inverter pulse width modulation (PWM) control have usually four kinds: Sinusoidal pulse width modulation (SPWM), selected harmonic elimination pulse wi dth modulation (SHEPWM), voltage space vect or pulse width modulation (SVPWM) and Current Hysteretic Band pulse width modulation (CHBPWM).These methods have some advantages and disadvantages[1]:The SPWM is a simple modulation scheme, but its control effect is not well. Its output voltage harmonics is comparatively high. The SHE is an off-line modulation scheme. It can effectively eliminate a number of harmonics with a minimum switching frequency, and therefore is considered an optimal scheme. However, it may be impossible to eliminate more than four low-order harmonics simultaneously since the transcendental equations for the harmonic elimination may not have numerical solutions. The SVPWM is Low switching frequencies for high power applications modulation scheme, but it is difficult to com pound voltage space vectors. The CHBPWM is current close-loop modulation scheme, its advantages are that output current close to sinusoid and electromagnetism torque close to invariables. However, in terms of the traditional hysteretic current control technique, the load current total harmonics distortion (THD) around switching frequency side bands is relatively large. In this paper we adopt a VHBCC technology spreads the spectrum contents of load current. Further more this method also can reduce THD of load current. In this paper, the