This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate hi...This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate high dv/dt and high frequency common mode voltages which are harmful for the drive applications. It reduces the motor bearings life and conducted EMI （electro magnetic interference） deteriorates the insulation. In this paper, a diode clamped multilevel （3-level） inverter is used to perform dual task. It generates HF （high frequency） current to be injected at the input of the three-phase front-end rectifier thereby improving the harmonic spectra and the power factor. It also drives the induction motor. The salient feature of this paper is that it does not require separate converters for improving power factor and to drive induction motor. Furthermore, inverter switches operate with ZVS （zero voltage switching）, thus reducing the switching losses substantially, The voltage stress of the switches also has been reduced to half of the conventional 2-level converter. The inverter is operated with SPWM （sinusoidal pulse width modulation） technique. The simulation results for a prototype of 2.2 kW are presented.展开更多
A new modulation format in optical fiber communication system, the eight differential phase shift keying (8DPSK) of multi-phase modulation technology based on carrier-suppressed return-to-zero (CSRZ) is proposed in th...A new modulation format in optical fiber communication system, the eight differential phase shift keying (8DPSK) of multi-phase modulation technology based on carrier-suppressed return-to-zero (CSRZ) is proposed in this paper. The formulae of CSRZ-8DPSK modem methods are derived theoretically and the methods are demonstrated. Spectra based on CSRZ and CSRZ-8DPSK modulation methods and their eye diagrams by simulation with MATLAB are obtained. The results show that the CSRZ-8DPSK modulation methods have narrower spectra with higher efficiency. The performance of eye diagrams is also much satisfactory after demodulation, suggesting some possible applications of the methods in the next generation of optical fiber communications.展开更多
文摘This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate high dv/dt and high frequency common mode voltages which are harmful for the drive applications. It reduces the motor bearings life and conducted EMI （electro magnetic interference） deteriorates the insulation. In this paper, a diode clamped multilevel （3-level） inverter is used to perform dual task. It generates HF （high frequency） current to be injected at the input of the three-phase front-end rectifier thereby improving the harmonic spectra and the power factor. It also drives the induction motor. The salient feature of this paper is that it does not require separate converters for improving power factor and to drive induction motor. Furthermore, inverter switches operate with ZVS （zero voltage switching）, thus reducing the switching losses substantially, The voltage stress of the switches also has been reduced to half of the conventional 2-level converter. The inverter is operated with SPWM （sinusoidal pulse width modulation） technique. The simulation results for a prototype of 2.2 kW are presented.
文摘A new modulation format in optical fiber communication system, the eight differential phase shift keying (8DPSK) of multi-phase modulation technology based on carrier-suppressed return-to-zero (CSRZ) is proposed in this paper. The formulae of CSRZ-8DPSK modem methods are derived theoretically and the methods are demonstrated. Spectra based on CSRZ and CSRZ-8DPSK modulation methods and their eye diagrams by simulation with MATLAB are obtained. The results show that the CSRZ-8DPSK modulation methods have narrower spectra with higher efficiency. The performance of eye diagrams is also much satisfactory after demodulation, suggesting some possible applications of the methods in the next generation of optical fiber communications.
