Harmonic Elimination Method of SCR Firing Angle Linear Distribution of Three-phase Multi- drive System

Adjustable speed drives (ASD) are widely used in three-phase multi-drives in the industry. For simplicity, in practice, the front-end rectifier still uses a low-cost, simple control structure diode rectifier (DR) or silicon-controlled rectifier (SCR). However, the non-linearity and time-varying nature of the rectifier will bring a lot of harmonic currents to the power grid, causing serious harmonic pollution. The harmonic problem in the multi-drive system must be solved. The existing harmonic elimination strategy is difficult to apply to the multi-drive system because of the high total cost and complexity. Therefore, this paper proposes a harmonic elimination strategy for the three-phase multi-drive system, so that the firing angle of the SCR drive unit is linear Distribute, control the phase shift of the SCR input current, and at the same time use DC modulation on the DC side to improve the controllability of the harmonic current, thereby reducing the harmonics appearing in the power grid. Simulation and experimental results prove the effectiveness of this scheme in harmonic elimination in a three-phase multi-drive system.