چكيده به لاتين
Inverter are important a part of power electronic devices. inverter convert DC voltage AC
voltage by desired amplitude and frequency.Output voltage of inverters must be sinusoidal but
these voltages are non-sinusoidal and include harmonics. The harmonics cause to very
problems for power system and electrical devices such as losses in power system and electrical
devices, undesirable heat, high current, noise in control systems, improper performance of
machines and relays and so on. On the other hand application of inverters in high power and
voltage need to high voltage components that limit the use of inverters in these cases ,which
will increase costs.
In this study, two improved structures of symmetrical seven level and asymmetrical fifteen in
order to reduce the costs associated with the number of components used in the inverters have
been proposed , and then these proposed structures compared to the number of parts used with
other existing structures. In the seven levels inverters output voltage Generate the high
harmonics. In order to reduce the this harmonics a switching method are proposed to control
this inverter. In order to obtain the switching angles and the amount of voltage sources
suggested method and to use of this proposed method meets the limitations of power quality
standards, and observe the harmonic limits in power quality standards the total harmonic
distortion relation output voltage is minimized by using the particle swarm optimization
algorithm (APSO). Further on as well methods sinusoidal pulse width modulation(SPWM),
selective harmonic elimination(SHE) and sinusoidal tracing on the single-phase system and
three-phase inverter, seven levels are simulated and the results of these three methods are
compared with the results from the proposed minimization method and based on this
comparison, the proposed method has the lowest amount of total harmonic distortion. Also in
order to switching of inverter fifteen levels methods selective harmonic elimination, sinusoidal
pulse width modulation and sine tracing used. Based on the simulation results obtained from
these methods The selective harmonic elimination method generally has the lowest amount of
total harmonic distortion.
