Three-to-five-phase matrix converter using carrier-based PWM technique

<p><strong>Abstract</strong> - This paper proposes a simple Carrier-Based PWM (CBPWM) technique to control the three- to five-phase Direct Matrix Converter (3×5 DMC). The proposed technique uses the indirect modulation approach to control the 3×5 DMC such as a three-phase bidirectional rectifier followed by five-phase voltage source inverter (VSI). Based on this approach, it is possible to synthesize the desired five-phase output voltages with sinusoidal three-phase input currents and unity input power factor. A CBPWM method is suggested for each stage independently including both linear and overmodulation operating modes. By the proposed technique, in both operating modes, the maximum possible overall Voltage Transfer Ratio (VTR) are achieved. Moreover, this technique allows the input power factor to be controlled by controlling the input current displacement angle. The feasibility of the proposed technique has been verified by a series of simulation and experimental results based on Matlab/Simulink and dSPACE-DS1104 platform. The results show that, a sinusoidal output and input waveforms can be achieved with a maximum possible VTR in the linear region. However, in the overmodulation region, a maximum possible VTR is achieved at the cost of some distortion of output and input waveforms. Therefore, this technique can be used for the application where a higher VTR is essential.</p

SPACE VECTOR PWM TECHNIQUE FOR THREE- TO SEVEN-PHASE AC-TO-AC POWER CONVERTERS: ANALYSIS AND EXPERIMENTAL VERIFICATIONS

This paper presents Pulse Width Modulation (PWM) control technique for three to seven-phase ac-to-ac power converters. These proposed PWM techniques are based on Indirect Space Vector Modulation (ISVM), which model the converter as two independent stages perform rectification and inversion stages. Two schemes of ISVM are proposed. The first scheme maximizes the voltage transfer ratio (VTR) of the converter but it produces unwanted low order harmonics. The second scheme generates sinusoidal output voltage waveforms; the cost is a reduction in the VTR of this configuration in linear mode. The viability of the proposed technique is proved using experimental results

A family of discontinuous PWM strategies for quasi Z-source nine-switch inverters

This paper proposes a new family of discontinuous PWM strategies to control the quasi-Z-source nine-switch inverters (qZS-NSI). The presented strategies provide buck and boost inversion capabilities, and suitable for common-frequency and different-frequency modes of operation. Accordingly, two different shoot-through (ST) approaches are introduced and compared. The first approach uses three-leg ST, while the second uses single-leg ST to reduce the number of switching commutations, therefore minimizing switching losses. Both approaches can be implemented using simple-boost (SB) and maximum boost (MB) control methods. The operating principles, performance criteria, and PWM modulator of each scheme are introduced. Compared to the conventional PWM technique for the same output voltage gains, the proposed schemes ensure continuous input current with minimum ripples, and the voltage stresses on the switching devices and capacitors could be reduced in the proposed MB control schemes. Moreover, the effective switching frequency of upper and lower switches of all schemes is fixed and could be reduced by 1/3 from the switching frequency of the conventional technique of the qZS-NSI, while only the single-leg ST schemes ensure minimum effective switching frequency of the middle switches. The proposed modulation strategies are digitally implemented and tested on the LAUNCHXL-F28379D DSP. The feasibility of the proposed modulation schemes is confirmed via simulation and experimental results, which show good agreement with the theoretical analysis. Moreover, the presented strategies can be applied to other types of Z-source NSIs.Scopu

Comparison between Intravitreal Injection of Ranibizumab and Bevacizumab as Preoperative Measure for Diabetic Vitrectomy

Purpose: In order to examine the parameters of surgical operation between intravitreal bevacizumab and ranibizumab as adjuvant therapy before pars plana vitrectomy in proliferative diabetic retinopathy. Patients &amp; methods:A randomized clinical study on 68 eyes, the patients are classified into two groups, group A (n = 34), and group B (n =34), both groups injected by anti-vascular endothelial growth factor before vitrectomy operation, group A injected by Bevacizumab and group B injected by Ranibizumab, the duration between injection and the operation was 3-6 days, the basic data of each patient include vision, type of DM, duration of DM, level of HbA1c, during the operation we record the following parameters diathermy application number, breaks, bleeding, bottle height, and type of tamponade. Results: The mean BCVA was improved from base line to post- operative in both groups without statistically difference between the groups p value =0.231, diathermy application was one application in 30.3% in group A and 32.4% in group B, and two applications in 15.2% in group A and 2.9% in group B. break was one break in 23.5% in group A and 20.6% in group B. two breaks in 2.9% in each group. Bleeding was in 16 cases in group A and 17 cases in group B. tamponade was silicon in 58.8% in group A and 52.9% in group B, fluid tamponade was 38.3% in group A and 44.2% in group B, air tamponade was one case in each group. without statistical difference between groups. Conclusion: When administered preoperatively during a diabetic vitrectomy procedure, there is no difference between bevacizumab and ranibizumab