外文翻譯--z源逆變器的驅(qū)動(dòng)性能分析 （英文）

1、International Journal of Scientific those are a) Voltage-source inverter and b) Current-source inverter. The gain of the inverter can be controlled by using pulse width modulation. Different PWM techniques are devised t

2、o control these inverters. PWM control technique also reduces harmonic distortion in the output signal and improves the performance of the inverter. PWM with third harmonic injection method eliminates third harmonic comp

3、onent from output waveform and also provides higher range of modulation index than regular PWM modulation technique. These PWM waveforms can be generated using analog circuits using active and passive components or it ca

4、n be generated digitally using microprocessor and microcontroller [4]. Fig. 1 Traditional voltage source inverter Figure.1 shows the traditional three-phase voltage-source inverter. The dc voltage source connected at the

5、 input side across a large capacitor. DC link voltage produced across this capacitor feeds the main three-phase bridge. The input dc supply can be a battery or fuel cell stack or diode rectifier, and/or capacitor. Three

6、phase bridge inverter circuit consists of six switches; each is composed of a power transistor and an anti-parallel diode to provide bidirectional current flow and reverse voltage blocking capability. Figure 2 shows the

7、traditional current-source inverter (CSI). The DC current source is formed by a large dc Inductor fed by a voltage source such as a battery or fuel-cell stack or diode rectifier or converter etc. Like VSI three phase bri

8、dge inverter circuit consists of six switches; each is composed of a switching device with reverse block capability such as a gate-turn-off thyristor and SCR or a power transistor with a series diode to provide unidirect

9、ional current flow and bidirectional voltage blocking. For voltage source inverter and current source inverter the on/off time the switching devices is controlled by applying control voltage (PWM) to the control terminal

10、 i.e. gate of the device. Fig. 2 Traditional current source inverter Traditionally in most of industries these voltage-source inverter and current-source inverter are used in adjustable speed drives. But these tradit

11、ional inverters have many limitations as summarized below: 1) They are either a buck or a boost converter and cannot be a buck–boost converter [1]. That is, the output voltage is either greater or smaller than the input

12、voltage. The output International Journal of Scientific B = T / (T1 – T0) = 1 / (1 – 2T0/T) ≥ 1 (3) is the boost factor resulting from the shoot-through zero state. Fig. 4 Equivalent circuit of Z-Sourc

13、e inverter with inverter in active state The peak dc-link voltage is the equivalent dc-link voltage of the inverter. On the other side, the output peak phase voltage from the inverter can be expressed as; Vacp = M Vip /

14、2 (4) In above equation M is the modulation index of PWM waveform, Vacp is output peak phase voltage and Vip is peak dc link voltage across bridge inverter. Using (2) and (4)

15、 peak phase voltage can be expressed as Vacp = M B Vdc / 2 (5) For the traditional V-source PWM inverter, the output peak phase voltage is given by Vacp = M Vdc / 2. Where Modula

16、tion index M is always less than unity hence in traditional inverter the output voltage is always less than input dc voltage. Equation (5) shows that in Z-Source inverter the output voltage can be stepped up and down by

17、choosing an appropriate buck–boost factor BB. The buck–boost factor is determined by the modulation index M and boost factor B. For Z-source inverter the boost factor is always greater than or equal to unity. When boost

18、factor is equal to unity the Z-source inverter acts like traditional inverter. The boost factor B as expressed in (3) can be controlled by varying shoot-through duty cycle T0/Tof the inverter PWM input. 3 MAXIMUM CONSTAN

19、T BOOST PWM WITH THIRD HARMONIC INJECTION CONTROL METHOD In order to reduce the volume and cost, the shoot-through duty ratio must be kept constant [2]. At the same time, a greater voltage boost for any given modulation

20、 index is desired to reduce the voltage stress across the switches. The maximum constant boost control achieves the maximum voltage gain while always keeping the shoot-through duty ratio constant. Maximum Constant boost

21、control with third harmonic injection method is devised to produce the maximum constant boost while minimizing the voltage stress. Shoot-through pulses are generated as shown in fig.7. These shoot-through pulses can be

22、generated by using triangular waveform generator and comparator. Shoot-through time is decided by the two reference levels called shoot-through level. When triangular carrier wave exceeds above upper shoot-through level

23、or below lower shoot-through level a shoot-through pulse is generated. Shoot-through time remains almost constant from switching cycle to switching cycle. These shoot-through pulses are evenly spread in traditional PWM w

24、aveform to obtain PWM waveform with shoot-through. Figure 8 shows third harmonic injected PWM with shoot-through and the control method is referred as maximum constant boost control with third harmonic injection. The th

25、ird and higher harmonic component can be injected into fundamental to reduce harmonic distortion in the output waveform [8]. The third harmonic component with 16.6% of the fundamental component is injected into the modul

26、ating signals. From the figure 8, it can be seen that the upper shoot-through level is always equal to or higher than the maximum value of the reference signals, and the lower shoot-through level is always equal to or lo

27、wer than the minimum value of the reference signals. Therefore, the shoot-though states only occur during the traditional zero states. As a result, this control method maintains the output voltage waveform. As shown in F

28、ig.8, at an angle of π/3 of modulating signal the third harmonic component crosses zero and then increases towards negative peak. Therefore at π/3 Va reaches its peak value (√3/2)M while Vb is at its minimum value -(√3/2

29、)M. In this method only two straight lines are needed to control the shoot-through time with the third harmonic injection. The boost factor depends up on the shoot-though duty cycle. If the shoot-through duty cycle is ke