1、 PDF外文：http:/ AC Voltage and Current Sensorless Control of Three-Phase PWM Rectifiers Dong-Choon Lee, Member, IEEE, and Dae-Sik Lim 1 THREE-PHASE PWM RECTIFIERS A System Modeling Fig. 1 shows the power circuit of the three-phase PWM rectifier. The voltage equations are gi
2、ven by 000000a a ab b bc c cR p LR p LR p Le i ve i ve i v (1) Fig. 1. Three-phase PWM rectifier without ac-side sensors. where , and are the source voltage, the line current, and the rectifier in
3、put voltage, respectively and are the input resistance and the input inductance, respectively. When the peak line voltage , angular frequency , and initial phase angle are given, assuming a balanced three-phase system, the source phase voltage is expressed as
4、; c o s2c o s ( )32c o s ( )3abcEeee (2) Where 0t &
5、nbsp; (3) A transformation matrix based on the estimated phase angle ,which transforms three-phase variables into a synchronous dq reference frame, is 2 2322332c o s c o s ( ) c o s ( )323 s i n s i n ( )
6、s i n ( )M M MM M MC (4) Transforming (1) into the reference frame using (4) q c q c q cMMd c d c d ce i vR p L LL R p Le i v
7、 (5) where p is a differential operator and . MM Expressing (5) in a vector notation Me R i L J i p L i v
8、 (6) where, qcdceee,qcdciii,qcdcvvv,0110J (7) Taking a transformation of (2) by using (4) &
9、nbsp; cossinEe E (8) Where M
10、 (9) Expressing (6) and (8) in a discrete domain, by approximating the derivative term in (6) by a forward difference 9, respectively, ( 1 ) ( 1 ) ( 1 )( ) ( 1 ) ( 1 )Me k R i k L J i
11、 kL i k i k v kT (10) c o s ( 1 )( 1 ) s i n ( 1 )Ekek (11) Where T is the sampling period.
12、; 3 Fig. 2. Overall control block diagram. B System Control The PI controllers are used to regulate the dc output voltage and the ac input current. For decoupling current control, the cross-coupling terms are compensated in a feed forward-type and the source voltage is also compensated a
13、s a disturbance. For transient responses without overshoot, the anti-windup technique is employed 10. The overall control block diagram eliminating the source voltage and line current sensors is shown in Fig. 2. The estimation algorithm of source voltages and line currents is described in the follow
14、ing sections. 2 PREDICTIVE CURRENT ESTIMATION The currents of ()aIk and ()cIk can not be calculated instantly since the calculation time of the DSP is required. To eliminate the delay effect, a state observer can be used. In addition, the state observer provides the filtering effects for the estimat
15、ed variable. Expressing (5) in a state-space form, x Ax Bu (12) y Cx (13) where, RLARL,1 010LBL, 1001C
