Research On The Suppression And Oscillation In DC Bus For Multi-Drive System

In the field of industrial electric drive,a common DC bus system consists of rectifiers and inverters is used to save costs and increase energy efficiency.The rectifiers and the inverters working in energy feedback state shall supply energy to the inverters working in motor state.However,there is a risk of DC bus oscillation in this system and the paper studies the conditions of system oscillation and the feasible solution of the oscillation.This paper first analyzes the harmonic components caused by the rectifier and inverter on the DC bus.By the analysis of the topology of single drive system,the paper gives the condition must be met when oscillation occurs.The analytic procedure used in single drive system can be applied in multi-drive common DC bus system.At the same time,according to the analysis of the single transmission system,the conditions for the oscillation of the single transmission system are obtained,and the research method is applied to the more complex multi-transmission system.At the same time,the simulation results verified the conclusion of single drive system and multi-drives system about system oscillation analyzed in this paper.The paper presents a calculation method of the maximum DC bus length in the multi-drive common DC bus system according to the analysis in the former.And by the simulation of layout of converters in the multi-drive system of shared DC bus,the optimal layout of the units can be found to make the bus ripple voltage and current the minimum.The conclusions in this paper can provide a theoretical basis for the design of a common DC bus system of converters.The oscillation of the system can be solved by the feasible layout of the units in the system or an active filter.The design of the system can make the natural oscillation frequency do not correspond to the harmonic frequencies.The adopt of the active filter can reduce the amplitude of the harmonic frequencies in DC bus.Both way can resolve the oscillation effectively.Finally,this paper introduces the case of the common DC bus system in the steelworks,analyzes the reason of the oscillation of the system.The case can verify the correctness of this study of the paper.