A Bilateral Impedance-Emulating Control of PWM Rectifier under Unbalanced Grids

The dc-link voltage oscillation is a direct reflection of the performance degradation caused by the unbalanced power grid in a three-phase voltage-source rectifier. A bilateral impedance-emulating control method is presented in this paper to solve this issue. The equivalent circuit model elucidates that VSR is characterized by emulated impedance on both sides under the proposed control scheme, providing a lucid and insightful physical interpretation. The bilateral impedanceemulating control provides the following features: 1) The elimination of grid voltage sensor; 2) Robustness to circuit parameters; 3) Easy to implement, as it only requires the design of a proportional-integral controller and two emulated RLC resonant circuits. In conclusion, the proposed control approach is straightforward, robust, and economical. Experimental results demonstrate its effectiveness and strong performance.