Observer based model predictive current control of distorted grid connected single phase rectifier without AC voltage sensor

Abstract

In this research, a grid voltage sensorless control scheme under the distorted grid voltage condition for a single-phase rectifier was proposed. For eliminating the grid voltage sensor, a time-varying state observer was designed, which provided direct, accurate, and fast estimation of the grid voltage without subsequent complex calculations, even for the presence of harmonics, a DC component, and frequency fluctuations, and it was implemented in the digital processor through Forward Euler discretization. In addition, the aforementioned observer would be partially reused in another observer to modify the input of the PI controller and then reduce the total harmonic distortion of the input current. To warrant robustness for the real world, the proposed observers were investigated in detail for load resistance variations and grid voltage fluctuations. Several simulations and experimentation tests were conducted to verify the effectiveness of proposed scheme. The obtained results indicated that the proposed observers had fast dynamic responses and low estimation errors. The proposed scheme decreased the THD of the input current.