Analysis and comparison of peak to-peak current ripple in two-level and multilevel pwm inverters
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This document analyzes and compares the peak-to-peak current ripple in two-level (2L) and three-level (3L) PWM inverters. It shows that the current ripple amplitude in 3L inverters can be determined based on the ripple in 2L inverters. The analysis is verified through numerical simulations and experimental tests. Three-phase multilevel inverters are commonly used in medium- and high-power applications like motor drives and grid-connected systems. While various PWM techniques have been developed for multilevel inverters, this paper addresses their impact on output current ripple.
Analysis and comparison of peak to-peak current ripple in two-level and multilevel pwm inverters
- 1. Head office: 3nd floor, Krishna Reddy Buildings, OPP: ICICI ATM, Ramalingapuram, Nellore www.pvrtechnology.com, E-Mail: pvrieeeprojects@gmail.com, Ph: 81432 71457 ANALYSIS AND COMPARISON OF PEAK-TO-PEAK CURRENT RIPPLE IN TWO-LEVEL AND MULTILEVEL PWM INVERTERS ABSTRACT Three-phase multilevel (ML) inverters are used in many medium- and high-power applications such as motor drives and grid-connected systems. Despite the fact that numerous pulse width modulation (PWM) techniques for ML inverters have been developed, the impact of these modulation schemes on the peak-to-peak output current ripple amplitude has not been addressed yet. In this paper, analysis and comparison of current ripple for two-level (2L) and three-level (3L) voltage source inverters are given. Reference is made to optimal and popular modulation, so called centered PWM, easily obtained by both carrier-based modulation (phase disposition, with proper common-mode voltage injection) and space vector modulation (nearest three vectors). It is shown that the peak-to-peak current ripple amplitude in 3L inverters can be determined on the basis of the ripple in 2L inverters, obtaining the same results as by directly analyzing the output voltage waveforms of the 3L inverters. This procedure can be readily extended to higher level numbers. The proposed analytical developments are verified by both numerical simulations and experimental tests. Three phase two-level (2L) inverters are widely utilized in ac motor drives and, in general, for grid-connected applications. In the last decades, multilevel (ML) inverters have become more and more popular, due to improved output voltage waveforms and increased power ratings. In particular, the ML structure is capable of reaching high output voltage amplitudes by using standard power switches with limited voltage ratings. Simple and reliable implementations
- 2. Head office: 3nd floor, Krishna Reddy Buildings, OPP: ICICI ATM, Ramalingapuram, Nellore www.pvrtechnology.com, E-Mail: pvrieeeprojects@gmail.com, Ph: 81432 71457 of ML inverters are the cascaded connection of single-phase inverters (H-bridge) and the neutral point clamped (NPC) configuration. Among ML inverters, the three-level (3L) inverters are a viable solution for many high-power applications, both grid connected and motor load. Block diagram for proposed system: SV diagrams of inverter output voltage. (a) 2L inverter. (b) 3L inverter DESIGNING TOOLS AND SOFTWARE: MATLAB/SIMULATION Software and Sim power system tools are used. Mainly power electronics tools and electrical elements tools are used.
- 3. Head office: 3nd floor, Krishna Reddy Buildings, OPP: ICICI ATM, Ramalingapuram, Nellore www.pvrtechnology.com, E-Mail: pvrieeeprojects@gmail.com, Ph: 81432 71457 CONCLUSION This paper has given the analysis and comparison of instantaneous output current ripple in three-phase 2L and 3L inverters. The peak-to-peak ripple evaluation in the 2L inverter is performed by analyzing the output voltage waveforms. It is shown that ripple evaluation in the 3L inverter can be carried out either as an extension of the analysis of the 2L inverter or by directly analyzing the 3L inverter output voltage waveform. The same procedure can be extended to the case of more than three levels. Normalized peak-to-peak current ripple is introduced, and different ripple diagrams are given for 2L and 3L inverters, making possible a comparison considering the same output voltage range or the same dc voltage supply. In particular, reference is made to centered SVM for both 2L and 3L inverters inverters. Readable and effective ripple maps are introduced to emphasize the ripple distribution in the fundamental period for the whole voltage modulation range of 2L and 3L inverters. As expected, the comparison shows that the ripple in the 3L inverter is generally lower than the ripple in the 2L inverter in case of the same output voltage range. The analytical developments have been verified with numerical simulations and corresponding experimental tests for various modulation indexes, showing a good matching.