Model-Based Closed-Loop Control for High-Power Current Source Rectifiers Under Selective Harmonic Elimination/Compensation PWM With Fast Dynamics

Abstract

Selective harmonic elimination/compensation PWM (SHE/SHC-PWM) is widely used in current source rectifiers (CSRs) under normal/distorted grid conditions due to its best line current harmonic performance with reduced switching losses. However, due to the off-line nature of SHE/SHC-PWM that operates over fundamental frequency, its dynamic performance under closed-loop control is usually not satisfactory compared with the space-vector modulation or carrier-based PWM (CB-PWM) for CSR. To improve the closed-loop dynamics of CSR under SHE/SHC-PWM, a model-based closed-loop control scheme is proposed in this article. In case of transient when the dc current reference of CSR changes, the new input references of the SHE/SHC-PWM module, i.e., the modulation index and delay angle, are directly calculated and updated in real-time based on the mathematical model of CSR derived in this article. As a result, the dynamic performance for dc current tracking under closed-loop SHE/SHC-PWM operations can be improved greatly due to this added model-based feedforward path, while the conventional feedback controller is still adopted but only for steady-state error corrections. The application of the proposed method on back-to-back current source converter (CSC) motor drives is also introduced. Simulation and experimental results validate this proposed control for CSR with fast dynamics.