Abstract
Multilevel converters (MLCs) are extensively used in medium- and high-power applications. Currently, MLCs are also used in grid integration of renewable sources of energy. In this paper a three-phase 11-level MLC topology is investigated which requires a smaller number of active switches compared to similar existing topologies for the same number of levels. In order to eliminate lower order harmonics, selective harmonic elimination (SHE) pulse width modulation technique is used. A projectile target search (PTS) algorithm is used to solve nonlinear SHE equations to determine the optimum values of switching angles to eliminate 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> , 7 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> , 11 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> and 13 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> harmonics from the converter output voltage. The PTS algorithm finds the best value of switching angles for different modulation indices (M) and these values are used in simulating the converter for eliminating lower order harmonics. Total harmonic distortion (THD) analysis is conducted for PTS optimization techniques at different modulation index. Simulation results are verified by hardware-in-the-loop test of the proposed three-phase converter using a Typhoon HIL-402 emulator.
Highlights
Multilevel converters (MLCs) were introduced over 40 years ago and have become the preferred choice for grid-connected and off-grid solar photovoltaic systems
The results show that genetic algorithm (GA) yields better performance in %Total harmonic distortion (THD) minimization and takes less computational time than particle swarm optimisation (PSO)
PROJECTILE TARGET SEARCH ALGORITHM BASED selective harmonic elimination (SHE) RESULTS In this subsection the results related to the projectile target search (PTS) algorithm are presented
Summary
Multilevel converters (MLCs) were introduced over 40 years ago and have become the preferred choice for grid-connected and off-grid solar photovoltaic systems. The converter presented in this paper produces an 11-level output voltage and there are 5 degrees of freedom for eliminating lower-order harmonics. Among these controllable switching angles, one is used to control the fundamental component of the voltage waveform and the remaining four can be assigned to eliminate 5th, 7th, 11th and 13th order harmonics as per the following equations [28]: cos α1 + cos α2 + cos α3 + cos α4 + cos α5 = M (1). In this paper we have chosen the PTS optimization technique to solve the SHE equations for different values of M
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