Application of memetic algorithm for selective harmonic elimination in multi‐level inverters

Abstract

Multi-level inverter (MLI) is a promising technology, able to generate high-quality power with lower switching frequency. Therefore it leads to high conversion efficiency and low switching losses. Selective harmonic elimination is a fundamental frequency switching strategy that theoretically provides desirable output waveform for MLIs by elimination of low order harmonics. Unfortunately, complexity, non-linearity and solvability features attached to this method have limited its industrial application. In this study, a particle swarm optimisation (PSO)-based memetic algorithm (MA) guided by mesh adaptive direct search is introduced as a suitable choice for the harmonic optimisation problem. This algorithm is precise and applicable to any MLI. The results show that MA converges to the exact solution for feasible modulation index. When the problem has no exact solution, the algorithm finds a relatively proper solution to regulate the fundamental component of the voltage. Furthermore, the comparison between MA and other methods shows that the probability of convergence of MA is higher than others. For 48% of the analysed data MA reaches to a fitness value lower than 10 −30 whereas this probability is 5% for PSO and almost zero for genetic algorithm and bee algorithm. The proposed method has been implemented on a cascade seven-level inverter.

An improved SHM‐PWM scheme for three‐phase seven‐level CHB inverter to improve power quality by fulfilling CIGRE WG 36‐05 and EN 50160 and sharing equal power between the H‐bridge cells

“…In literature, several modulation schemes have been proposed for controlling the output voltage waveform quality of multilevel inverters. These can be listed as sinusoidal pulse width modulation (SPWM), space vector modulation, selective harmonic elimination (SHE)‐pulse width modulation (PWM), optimal minimization of THD (OMTHD), optimal PWM (OPWM), and selective harmonic mitigation‐(SHM) PWM . Out of these PWM schemes, SHE‐PWM scheme works on the low‐switching frequency, and it is used to completely eliminate (E‐1) number of specific low‐order harmonics of the output voltage using “E” number of switching instances in each quarter cycle of the output waveform.…”

“…Out of these PWM schemes, SHE‐PWM scheme works on the low‐switching frequency, and it is used to completely eliminate (E‐1) number of specific low‐order harmonics of the output voltage using “E” number of switching instances in each quarter cycle of the output waveform. The major drawback of this scheme is that it only eliminates a limited number of low‐order harmonics while other harmonics (which are not incorporated into the problem) are totally uncontrolled and can attain high magnitudes . Hence, for a specific number of output voltage levels, this scheme requires more number of switching instances to fulfill some power quality standards and to remove more number of low‐order harmonics.…”

“…But it requires more number of switching instances in a quarter period to fulfill some specific power quality standards. Besides that, uneven power distribution between the H‐bridge cells of CHB inverter can occur in the aforesaid SHE‐PWM and SHM‐PWM schemes . This will affect the rating and size of both semiconductor devices and input side isolation transformers.…”

“…The major drawback of this scheme is that it only eliminates a limited number of low-order harmonics while other harmonics (which are not incorporated into the problem) are totally uncontrolled and can attain high magnitudes. [16][17][18][19][20][21][22][23] Hence, for a specific number of output voltage levels, this scheme requires more number of switching instances to fulfill some power quality standards and to remove more number of low-order harmonics. Thus, it results in higher switching losses in power switching devices and reduces the conversion efficiency.…”

Hybrid Control Strategy for BCD Topology Based Modular Multilevel Inverter

“…Various modulation techniques have been introduced to improve the performance of the MLIs [2] [11] [22]- [27]. The commonly used modulation techniques are selective harmonic elimination (SHE) [22]- [24] carrier-based PWM (CBPWM) [25] and space vector PWM (SVPWM) [26] [27]. In [28], the MLI performances of a SVPWM and a carrier based PWM are compared, and a carrier based PWM method is proposed to obtain an optimal output voltage in the MLI.…”