Selective Harmonic Compensation (SHC) PWM for grid-interfacing high-power converters

Compensating the pre-existing (background) harmonics from the power system in a grid-interfacing high-power converter system through the Active-Front-End (AFE) converter is a very attractive approach to improve the system harmonic performance. However, this is challenging due to the low switching frequency requirement of the high-power applications, and therefore traditional methods for active power filters cannot be applied. This paper proposes a new PWM technique, Selective Harmonic Compensation (SHC), which actively compensates the pre-existing harmonics from the power system, but still operates at very low switching frequencies. Details of the proposed SHC are presented and an SHC application example with a high-power Current Source Rectifier (CSR) is provided in this paper. The simulations and experiments are carried out on a 1 MVA CSR model in Matlab and a 10 kVA CSR prototype controlled by dSPACE-CPLD system. Results show that the proposed SHC scheme can improve the line current harmonic performance significantly.