pwm整流器外文翻译.docx

1、pwm整流器外文翻译 AC Voltage and Current Sensorless Control of Three-Phase PWM Rectifiers Dong-Choon Lee, Member, IEEE, and Dae-Sik Lim1 THREE-PHASE PWM RECTIFIERSA System ModelingFig.1 shows the power circuit of the three-phase PWM rectifier. The voltage equations are given by (1)Fig. 1. Three-phase PWM r

2、ectifier without ac-side sensors.where , and are the source voltage, the line current, and the rectifier input 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 bal

3、anced three-phase system, the source phase voltage is expressed as (2)Where (3)A transformation matrix based on the estimated phase angle ,which transforms three-phase variables into a synchronous dq reference frame, is (4)Transforming (1) into the reference frame using (4) (5)where p is a different

4、ial operator and . Expressing (5) in a vector notation (6)where, , (7)Taking a transformation of (2) by using (4) (8)Where (9)Expressing (6) and (8) in a discrete domain, by approximating the derivative term in (6) by a forward difference 9, respectively, (10) (11) Where T is the sampling period. Fi

5、g. 2. Overall control block diagram.B System ControlThe 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 as a disturbance. For

6、 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 following sections.2 PREDI

7、CTIVE CURRENT ESTIMATIONThe currents of and 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 estimated variable.Expressing (5) in a st

8、ate-space form, (12) (13)where, ,And y is the output. Transforming (12) and (13) into a discrete domain, respectively, (14) (15)where,Then, the observer equation adding an error correction term to is given by (16)Where K is the observer gain matrix and “ ” means the estimated quantity, andis the sta

9、te variable estimated ahead one sampling period. Subtracting (15) from (16), the error dynamic equation of the observer is expressed as (17)where . Here, it is assumed that the model parameters match well with the real ones. Fig. 3 shows the block diagram of the closed-loop state observer.The state

10、variable error depends only on the initial error and is independent of the input. For (17) to converge to the zero state, the roots of the characteristic equation of (17) should be located within the unit circle. Fig. 3. Closed-loop state observer. Fig. 4. Short pulse region. 3 EXPERIMENTS AND DISCU

11、SSIONSA. System Hardware ConfigurationFig.5 shows the system hardware configuration.The source voltage is a three-phase,110V.The input resistance and inductance are 0.06 and 3.3 mH, respectively. The dc link capacitance is 2350F and the switching frequency of the PWM rectifier is 3.5 kHz.Fig. 5. Sys

12、tem hardware configuration.Fig. 6. Dc link currents and corresponding phase currents (in sector V ).The TMS320C31 DSP chip operating at 33.3 MHz is used as a main processor and two 12-b A/D converters are used. One of them is dedicated for detecting the dc link current and the other is used for meas

13、uring the dc output voltage and the source voltages and currents, where ac side quantities are just measured for performance comparison.One of two internal timers in the DSP is employed to decide the PWM control period and the other is used to determine the dc link current interrupt. Considering the

14、 rectifier blanking time of 3.5 s, A/D conversion time of 2.6 s, and the other signal delay time, the minimum pulse width is set to 10 s.A.Experimental Results Fig. 6 shows measured dc link currents and phase currents. In case of sector V of the space vector diagram, the dc link current corresponds

15、to for the switching state of and for that of . Fig. 7(a) shows the raw dc link current before filtering. It has a lot of ringing components due to the resonance of the leakage inductance and the snubber capacitor. When the dc current is sampled at the end point of the active voltage vectors as shown in the figure, the measuring error can be reduced. Fig. 7. Sampling of dc link currents. Fig. 8. Estimated source voltage and current at starting. To reduce this error further, the low pass filter should be employed, of which result is s