۱- Introduction

۲- Generalized (3n+3) converter topology and operation

۳- Generalized sinusoidal and non-sinusoidal PWM method

۴- Particle swarm optimization for the optimal selection of sorting and offsetting

۵- Simulation

۶- Experimental results

۷- Conclusion

References

Abstract

This paper presents a method to improve the power quality of a class of shared inverter topologies utilizing optimal sorting and the offsetting pulsewidth modulation (PWM) method. For the (3n+3)-switch converter topologies, a PWM procedure with two degrees of freedom is proposed to enhance the quality at the power side of the shared loads without adding more passive elements. Moreover, the two degrees of freedom are analyzed and optimized to improve the power quality of the output current of the shared loads. The optimization is achieved using particle swarm optimization (PSO) method in which three objective functions are formulated, each of which impacts the power quality at the shared load sides. The objective functions are: the total harmonic distortion (THD), the scaled total harmonic distortion (STHD), and the summation of the eleventh order of harmonics (SFEH) of the current of the shared loads. A case study that compares the PSO results with the conventional results is investigated to highlight the effectiveness of the proposed procedure. Furthermore, a test bed is built and the proposed procedure is experimentally investigated, verified, and compared to the simulation.

Introduction

Increasing the utilization of nonlinear loads in industry tools and household appliances that are driven by power electronics, and which produce harmonic currents, affects the power quality. Therefore, from a practical and industrial point of view, it is preferable to improve the quality of the power of the electrical load without increasing the cost, size, or complexity of the power electronics devices [1–۳]. Harmonic mitigation can contribute in improving the power quality. Thus, many harmonic mitigation strategies have been proposed and implemented in the literature [4–۷]. The main target of these studies was to maintain the total harmonic distortion (THD) of the phase current below a recommended level to avoid harmonic related problems. Although power quality improvement equipment such as passive filters [8], active filters [9], and hybrid filters [10,11] are commonly used to eliminate the harmonics, the use of such equipment may increase the size or cost of the system. On the other hand, different modulation techniques can be used to mitigate the harmonics [4–۶]. To meet the power quality standards for cascaded H-bridge converter with variable DC-link, the authors in [12] employed an optimal selective harmonic reduction pulsewidth modulation (PWM) technique. Moreover, to improve the performance of a cascaded H-bridge multilevel active rectifier, the authors in [13] proposed a current reference based selective harmonic reduction PWM technique to satisfy current harmonic limits by analyzing and designing switching frequency and coupling inductance. A non-selective harmonic compensation method is introduced in [14] for a grid connected voltage source inverter (VSI), adopting a slide mode current harmonic controller. Due to the utilization of the sliding mode control theory, a fast-dynamic response with good disturbance rejection was achieved.