SIMULATION AND ANALYSIS OF CURRENT CONTROLLED PWM INVERTER

Abstract

Most of the high performance AC drives utilize current controllers for inner loop current control. The current controller should be able to track its, current command. The selection of current controller depend on its fast response, ease in • control and simple in implementation. The current controller follow sinusoidal current command in order to produce torque with minimum ripples. The PWM current regulated inverter follows a set of reference current waveforms to control the drive speed/torque. Among the various current controllers generally hysteresis band current controllers are widely used because of its simplicity and ease implementation. The present work describes 'theory of hysteresis current -control in detail. Four types of current controllers (fixed band, sinusoidal band, fixed frequency and space vector based HCC) are described and simulated. Their performances are compared at variable amplitude and frequency at R-L load. The switching frequency of fixed band and sinusoidal band is very high. To reduce the number of switching space vector based hysteresis current controller (SVBHCC) is proposed. The SVBHCC determines a set of space vectors from region detector and applies a space voltage vector selected according to main HCC. The performance of is also compared with their reduced switch count. A simple hardware for fixed band is also implemented.