Two Selective Harmonic Control Techniques Applied in 10kV Grid with Three-Level NPC Inverter

Abstract

In high-power applications, bulky and expensive filtering elements or systems are commonly used, since the commutation of high-voltage and high-current rated semiconductors will impact the thermal losses of power systems, which will further lead to distorted output waveforms. In the meantime, due to the non-uniform regulations in the area of power quality and more new and strict grid codes, the harmonic control of power converters' output signal is becoming greatly important. By taking this situation into account, comparisons between selective harmonic elimination pulse width modulation (SHEPWM) and selective harmonic mitigation pulse width modulation (SHMPWM) techniques are proposed in this paper, based on the requirements of two well-known grid codes EN 50160 and CIGRE WG 36-05. In the presented simulation model, a switching frequency that is equal to 750 Hz is considered, and the harmonics up to the 49 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> are considered and the total harmonic distortion (THD) obtained considering up to the 40 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> and 50 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> . The obtained results show that, under the same switching frequency condition, only the SHMPWM technique can satisfy the requirements of the above-mentioned two grid codes, compared with the SHEPWM technique. This fact implies that the SHMPWM technique is more suitable for high-power applications, especially for reducing or removing the additional filtering elements or systems.