CONSTANT FREQUENCY DIGITAL HYSTERESIS-BAND CURRENT CONTROLLER FOR A THREE-PHASE VOLTAGE INVERTER

Walid Emar, Rami A. Maher, and Amjad Jalil

Keywords

Constant frequency hysteresis technique, deadbeat current control,hysteresis current technique, voltage fed inverter, phase locked loop

Abstract

In order to reduce the harmonic content normally generated at the input of AC motor drives as a result of using three-phase voltage-fed inverters (VFI) for supplying electric drives with AC motors, and thus, to improve the input power factor of such machines, hysteresis current control technique is usually used to control the amplitude of three-phase motor currents and to decrease the phase shift between these currents and their corresponding voltages. Hysteresis current technique is considered to have a very simple implementation and an instantaneous current control, resulting in a fast response. However, the switching frequency is not constant and varies over a wide range during each half-cycle of the AC input source, and consequently the load current harmonic ripple is not optimal [J. Salmon & H. Zhang, Power and Energy Systems, 2004; Buso et al., IEEE Transactions on Industrial Applications, 2000]. In this paper, an improved implementation of hysteresis cur- rent control of three-phase voltage-source inverter with constant frequency is presented. In order to do that, before developing any inverter prototype, it is very convenient to use one of the several dynamic system software simulators available such as the phase-locked-loop (PLL) with the dead beat current control, even at a high rate of output voltage change, such as required in fast drive systems, and other highly demanding applications. Stability analysis and performance are conīŦrmed through simulation results using Matlab/Simulink and Simplorer 6.

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