Voltage Amplitude-Phase Decoupling Based Grid-side Harmonic Suppression Strategy for Electrolytic Capacitorless PMSM Drives

In electrolytic capacitorless motor drives, the drastic variation of system impedance from the constant torque (CT) region to the flux-weakening (FW) region is the root cause of the degraded performance of harmonic suppression. In this letter, a new voltage amplitude-phase decoupling control method is proposed. By reconstructing the dq-axis current control loops, the modulation index and voltage angle can be controlled in a decoupled manner. Then the loop gains are adaptively adjusted according to operating conditions to ensure the loop bandwidth. No additional control loops are introduced in the FW control, which enables the continuous variation of impedance characteristics. A voltage angle harmonic regulation mechanism based on the DC-link voltage is established. The control parameters are optimized according to the continuous impedance model and steady-state operating point information to realize specific-order harmonic suppression. Experimental results demonstrate that the proposed method can effectively reduce grid-side current harmonics across different operation regions.