Abstract
In this paper, a new topology of multilevel inverter (MLI) is designed with a fewer number of components and low total harmonic distortion (THD) for high-power photovoltaic (PV) systems. The key limitations of conventional MLI topologies are high total harmonic distortion (THD) and the use of a large number of switching components due to which the cost of the overall inverter is high. In conventional MLI, THD can be significantly reduced by the addition of a large value filter element at the input side; however, it will result in increased size and cost. Thus, achieving a pure sinusoidal AC at the output and to maintain a low THD level is a major issue in conventional MLIs. The proposed MLI has the advantage of decreasing the output THD by using a modified form of the cascaded H-Bridge structure and sine pulse width modulation technique. The proposed inverter consists of 6 unidirectional switches and 2 bidirectional switches, and there is no extra requirement for additional voltage balancing capacitors or clinching diodes. The individual switching states and SPWM operation for generating the gate pulses of the proposed MLI are discussed in detail. Relevant waveforms are plotted, equations are derived, and mathematical analysis is carried out. A steady-state analysis of the proposed MLI demonstrates an output voltage with 17 levels while using only four DC sources. Simulation results of the proposed MLI for single-phase and three-phase structures are obtained, and comparison is carried out with existing MLI topologies which shows that the proposed MLI has significantly low THD and better performance. From the results, it is clear that the proposed MLI has a THD of 3.52% in comparison with four conventional MLIs whose THDs are 6.1%, 6.63%, 7.3%, and 9.93%. Moreover, the proposed MLI generates 17 voltage levels by using only 08 switching devices, whereas the conventional MLIs use more than 10 switching devices for the generation of 15 voltage levels.
Highlights
Multilevel inverters are a candidate topology for highvoltage and high-power applications in industries nowadays
The resulting voltage waveform of single-phase multilevel inverter (MLI) is depicted in Figures 25 and 26; it is compared with a clean sinusoidal waveform of the same frequency to get a good visualization of the reduction in total harmonic distortion (THD)
Total harmonic distortion is a helpful procedure to break down any nonlinear conduct of a framework, which is normally done with the help of fast Fourier transform (FFT)
Summary
Multilevel inverters are a candidate topology for highvoltage and high-power applications in industries nowadays. A switch ladder MLI is presented in [6] which is a modified form of cascaded H-Bridge MLI This MLI utilizes few components and provides an output waveform that is almost sine waveform, which has low THD. A simple circuit (Op-Amp) controlled voltage source MLI is presented that utilized PWM strategy for harmonics decrease and demonstrates the best way to produce SPWM distinctive Op-Amp circuits where the passive type of filters is utilized toward the output for the reduction of harmonics; in this way, the components of the inverter are increased [16] Another inverter named cascaded H-Bridge MLI with a phase disposition technique is presented in [17]. Reduced switch count multilevel inverter topologies using the cascaded structure and switched capacitor techniques have been presented to lower the THD level and reduce the number of switching devices [18,19,20]
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