Effect of Angles of Harmonic Components of Back to Back Converter of Distributed Generation Resources on Current Behavior of Distribution Networks

The total current and voltage wave changes in the harmonic distribution networks is one of the major problems in distribution networks. By increasing the power electronic devices in the structure of electrical equipment such as laptop and mobile chargers, LED lights, etc., today, different components of the harmonics in the network can be seen. One of the major factors affecting the study of harmonic disturbances is the phase difference of harmonic components with the current angle in the main frequency. This can cause the phenomenon of peak and valley in waveform. Although, the presence of peaks or valleys in the waveform does not increase the effective amount of waveform, but the peaks result in the sharper waveform and increase the peak of domain. The peaks of waveform cannot be seen in the main equations, but practically can pass through electrical equipment including transformers, protective switches, relays, cables, and so on. The amount of peak points is sometimes from the nominal value of the above equipment current and will result in inappropriate performance and decreased lifetime. In this paper, using the Matlab software capabilities, the size and angle of the harmonic components of back to back converter, and extraction diode bridge rectifier AC-DC-AC, and effect of angles of each one to cause peaks and valleys in waveform will be analyzed and examined. The results of the study show that the converters used in the structure of distributed generation resources cause changes in angle of main component of current. The results also show that changes in the angles of diode bridge rectifier AC-DC-AC converter increased the peak of waveform by 26% compared to the main component of current, while in the back to back converter, there is a 9% deviation compared to the current in main component. The other simulation studies show that the angle change of 180 degrees reduces the waveform peak by 40%.