Properties and Structures of Three-phase PWM AC Power Controllers Ryszard Strzelecki, Zbigniew Fedyczak Industrial Electrotechnic Institute, HigherEngineer’s School, Zielona Gora, Poland zyxw Abstract zyxwvutsrqpo - In this paper, structures of PWM AC power controller circuits with the “dead time” control are presented. Theoretical anlysis results of basic electrical propekes of simplified circuit models, essential especially taking in account the quality conversion are presented, and some testing results obtained during laboratory model investigations of selected three-phase PWM AC power controller circuits are proposed in this paper. I. INTRODUCTION The most essential advantages of PWh4 AC power controllers with Ts << T, where: T- period of supplying voltage, comparing to conventional thyristor systems are [l-51: - substantially smaller deformations of loading current waveforms (influencing on the life-time of the load) and supply source currents what decrease the power loss in the source and the overall dimensions of the input filter; - a constant value of the phase displacement angle between the fundamental current harmonic and supply source voltage and smaller loading of the source with reactive power, practically independent from the control signal value. In case of application of PWM AC power controllers the change of delivered power to the load proceed with a linear change of the amplitude value of load fundamental harmonic voltages and currents in function to the control signal duty-factor. Such a PWM AC power controller fulfills then the part of a semiconductor transformer with a regulated ratio [ 1-51, Despite a considerate number of publications discussing the practical realisation of PWM AC power controller [I-61 we state a lack of industrial solutions taking into consideration the real impedance (inductance) of the supply network in a sufficient degree and useful to a large practical application. Optimal solutions of the main circuit structure are constantly being in search in consideration of the efficiency and component costs, and effectiveness of the by-pass suppressor circuit considering the overvoltage safeguard for the “dead time” and accumulated energy in the network inductance. The goal of the hereby paper is the property analysis of three-phase PWM AC power controller main circuits with the “dead time” control and by- pass suppressors circuit in consideration of their optimal solutions. The content of this paper has been elaborated on the base of so far work results related with the elaboration of the industrial series of types of PWM zyxwvutsrq AC power controllers, from 20 kVA to 150 kVA. 11. STRUCTURES OF zyxwvut I” AC POWER CONTROLLERS The block diagram of an industrial three-phase AC line conditioner with a PWh4 AC power controller with the “dead time” control is shown on the Fig. 1 [4]. Simplified structures of three-phase PWM AC power controllers main circuit, without by-pass suppressor circuit are shown on the F i g 2 zyx a) I i ’ LOAD , PWM AC POWER CONTROLLER - - - - - - - b) forward witches freewheellng swltcher S4, zyxwv S5, zyxwvu S6 on off I zyxwvu ’2’ TI AT T2 AT T1+ AT f = . 6= E T1+ T2 + 2AT ’ T1 +T2 +2AT Figure 1 : AC line conditioner with three-phase PWM AC power controllers, a) the block diagram, b) switch gating signals fs-switching frequency, &pulse duty-factor, AT-“dead time” On the base of carried out setting-up of the quantity of needed elements to realize these controllers and estimated analysis of maximal power loss values [6] it appears that the most effective (among circuits without a separating transformer) is the circuit No. 11[1,2,4,5]. Among circuits with a transformer unabling the three-phase supply source poles switching off from the common point, the circuit No. 13 v.1 [5,6] is highly efficient. The application of this power controller is most advisable in AC conditioner with load requiring a supply voltage different from the one that is used in the industrial network. These power controllers were the subject of experimental researches, the selected results of which are presented in the last chapter of the hereby paper. 0-7803-3500-7/96/$ 5.00 0 1996 IEEE 740