DESIGN AND IMPLEMENTATION OF A PULSE WIDTH MODULATED RECTIFIER FOR INDUSTRIAL APPLICATIONS Ali PASHAEI M.Timur AYDEMIR Gazi University Faculty of Engineering Dept. of Electrical and Electronic Eng. 06570 Maltepe Ankara -TURKEY Gazi University Faculty of Engineering Dept. of Electrical and Electronic Eng. 06570 Maltepe Ankara -TURKEY ali.pashaei@gazi.edu.tr aydemirmt@gazi.edu.tr Abstract –Three phase pulse width modulated voltage source rectifiers are widely used in uninterruptible power supplyand motor drive applications due to their low input current THD, adjustable input power factor,and bi- directional power transfer characteristics.In this paper utilization of this type of rectifier at the front end unit of an industrial type uninterrupted power supply is discussed. DC bus voltage is controlled through two high gain PI controllers. Sinusoidal Pulse Width Adjustable Triangle Wave Comparison for switching (SPWM) was selected as the control method. Unity power factor has been attained at the input along with very low THD values. Keywords: PWM rectifier, uninterrupted power supplies (UPS). Unity power factor I. INTRODUCTION Several industrial systems utilize a rectifier at the front end and typical choice for rectifiers is traditional six-pulse thyristor converters. However, this type of rectifiers suffer from high current THD values, low power factors and create pollution at the grid they are connected to [1-3]. Three phase PWM rectifiers have been suggested as the alternative of thyristor converters due to their advantages such as sinusoidal input currents, ability of bi-directional power transfer and fast control of DC output voltage. While it is difficult to comply with the limitations of IEEE standards for harmonics with traditional rectifiers, Pulse Width Modulated(PWM) rectifiers can easily match these standards. There are several control strategies proposed for PWM rectifiers in the literature [4]-[12].In direct current control techniques dc bus voltage is regulated along with improvement in ac current harmonics [13]. Two control loops are used for this purpose. The outer loop regulates the bus voltage while the faster inner loop regulates the input current. A 110-V, 1.1 kW PWM rectifier for the front-end of an industrial type UPS is presented in this paper. Design and implementation of the rectifier power circuit and control system are given. Small signal model defined in [14] for three phase voltage source PWM rectifiers in a synchronous rotating frame or (d-q) coordinates has been used for simulation and design of the controller. 2. Three-phase voltage source PWM rectifier model Figure 1 shows the circuit of three phase PWM rectifier. There is a reactor on each input line for filtering and boosting functions. Fig. 1 Three-phase PWM VSR topology The following equations define the dynamic behavior of three phase PWM rectifier in synchronously rotating d-q frame:      L di d dt =v d − Ri d + ωLi q − v rd L di q dt =v q − Ri q −ωLi d − v rq C dV dc dt = − V dc R L + 3 2 S d i d +S q i q  (1) In these equations, S d and S q are d- and q- components of the switching functions. v rd and v rq are the d- and q- components of the rectifier input voltage and are defined as follows: v rd =S d V dc v rq =S q V dc ω is the angularfrequency of the rotating frame. In order to express the complex phasors in the synchronously rotating reference frame transformation matrix given in (2) is used. T=  2 3      cos ωt cosωt − 2π 3  cosωt+ 2π 3  − sin ωt − sinωt − 2π 3  − sinωt+ 2π 3   1 2  1 2  1 2      (2)