چكيده به لاتين
Progressive use of power-electronic equipment, distributed power generation units, etc. results in higher harmonic distortion level of the grid voltage. Thus, calculating steady-state harmonic voltages has been becoming more and more important. Harmonic power flow algorithms play an important role at analysis and design of power systems because they contribute to calculate harmonic distortion levels. Most current standards consider an upper limit for the amplitude of customer’s harmonic emissions, whereas the phase angle of customer’s harmonic emissions can affect the harmonic distortion in the grid voltage as well. Therefore, this thesis focuses on investigating the influence of harmonic phase angle on the harmonic distortion level. In this thesis, at the first algorithm of three-phase harmonic power flow by direct Z_Bus method is simulated in MATLAB software for three cases in the absence of shunt capacitors and passive filters, in the presence of capacitors and in the presence of passive filters, and its results are validated. According to the results, both capacitors and filters can improve the fundamental voltage. At the same time, the capacitor may cause the phenomenon of resonance and increase the level of total harmonic distortion. While the filter can also improve total harmonic distortion. In the following, using the harmonic power flow algorithm, the effect of the phase angle of fundamental voltage on the determination of the harmonic phase angles and the harmonic power flow results is investigated ,and it is shown that with increasing harmonic order the effect will be increased. Then, the sensitivity of the level of harmonics distortion against the harmonic source phase angle is investigated ,and it is shown that harmonic sources under different phase angles can amplify or weaken each other's effects. In the next step, the Z_Bus direct harmonic power flow algorithm is modified using the Monte Carlo simulation method. Accordingly, an algorithm is proposed to consider the random nature of the phase angle of the harmonic sources. Then, using the proposed algorithm, the random nature of the phase angle of the harmonic sources is simulated for different prevailing ratios, that determine the randomness of the angle. According to the results, the random nature of the phase angle of the harmonic sources has a significant effect on the distortion level of the network harmonics, and the more stochastic nature of harmonic source phase angles result in the lower voltage total harmonic distortion in power network.
Keywords: Harmonic power flow, Harmonic phase angle, Monte-Carlo Simulations, Non-linear loads
