VSS control of unity power factor

Three-phase pulsewidth modulation (PWM) converters, specifically, voltage-s ource inverters (VSI's), are possibly the most frequently used power conver ters for applications such as industrial motor control, robotics, air condi tioning and ventilation, uninterruptible power supplies, electric vehicles, etc With the introduction of recent standards on limiting harmonic polluti on of electrical power distribution systems, three-phase PWM converters are being considered as prime candidates for interfacing high-power electronic equipment to power supply lines. In these applications, converters can pro vide input currents without distortion and with unity power factor. In this paper, the idea of using variable-structure system (VSS) control strategy of a boost rectifier in sliding mode will be described. A new discrete-time control algorithm has been developed by combining VSS and Lyapunov design. It possesses all the good properties of the sliding mode and avoids the un necessary discontinuity of the control input, thus eliminating chattering, which has been considered a serious obstacle to applications of VSS. A unif ied control approach for output de voltage and input ac currents based on d iscrete-time sliding mode is developed. The reference tracking performance is demonstrated in terms of transient and steady-state characteristics by s imulation and experimental results. The invariance and the robustness featu res of the proposed control method are verified by experiment in the presen ce of large uncertainty in parameters and external perturbations.