Particle swarm optimisation‐based modified SHE method for cascaded H‐bridge multilevel inverters

Abstract

Low-frequency switching strategies are considered as an effective way of achieving efficient performance in multilevel inverters. Selective harmonic elimination (SHE) is a modulation technique of this category which gives a superior outcome suppressing low-order detrimental harmonics. Limited number of decision variables offered by SHE in the corresponding non-linear equations hinders obtaining high-quality waveforms. Current research is targeted on two distinct objectives for cascaded H-bridge inverters. First objective is to obtain a high-quality output signal. The second one is accomplishing a realistic solution with compromised voltage quality where a broad operating range becomes mathematically challenging. These aims are achievable by deploying additional degree of freedom in the equation set. In other words, the introduction of floating voltage levels contributes to effectively doubling the number of variables. The enhancement of output waveforms is presented through several illustrations and comparisons. Subsequent laboratory implementation validates the proposal and confirms its feasibility.

Selected Harmonic Elimination for Cascaded Multilevel Inverter Based on Photovoltaic with Fuzzy Logic Control Maximum Power Point Tracking Technique

“…Currently SHE technique is being prominently used to synthesize output voltage of multilevel inverters [5,27,33]. By applying Fourier series analysis, the staircase output voltage of cascaded multilevel inverter with non-equal DC sources can be described as [15]:…”

“…Inverter having equal steps was considered in the work of [15]; however, some investigators may try to provide an optimization of voltage levels of unequal magnitude as shown in Figure 8 as per reference [12]. Output waveform pattern with unequal DC source of single phase 9-level CHB-MLI is shown in Figure 8.…”

“…The search ends when a final set of solutions for the problem by consecutive generations from a large population is achieved, based on some terminating criteria. Four switching angles are calculated in the present work to achieve the minimum THD keeping the harmonics within the limits as mentioned in Equation (15). In the GA toolbox, graphical user interface allows using GA at MATLAB platform without working at the command line [5,34].…”

“…For this, researchers have proposed many traditional control schemes such as Newton-Raphson sequential quadratic programming, mathematical theory of resultants, pulse width modulation (sinusoidal/space vector/selective harmonic elimination) and so forth [5,[12][13][14][15]. The conventional iterative method like Newton-Rephson requires an initial guess of switching angles close to the exact solution [5,12,15]. However, optimized selected harmonic elimination based control schemes also have emerged as the feasible alternative to the traditional control schemes.…”

“…The authors of [16,17] have considered the design of single-phase system with the consideration that in the application of interest of three-phase system, the triplen harmonics in each phase need not be canceled as they automatically cancel in the line-to-line voltages. A topology for single phase H-bridge inverter is also reported by [15] and mentioned therein that in three-phase systems the self-suppressing feature of zero-sequence harmonics gives a computational advantage as no additional measure with respect to these harmonic components is necessary. Transcendental equations can be solved subsequently through applying an appropriate optimization algorithm to obtain desired solutions.…”