An over view of damping methods for three-phase PWM rectifier

In this paper, an over view of damping method for three-phase voltage-source PWM rectifier with LCL filter is given. The traditional rectifier connected to supply network with an L filter. Increasing the L value can attenuate the ripple current around switch frequency which fulfills standards but it will decrease the response speed and stability of the system. An LCL filter is more effective and reduce harmonic distortion at lower switch frequency than an L filter. However an LCL filter will bring stability problem. One solution is to use a damping resistor which is in series or parallel with the filter capacitor and this is called "passive damping". This method will increase the losses and decrease the efficiency of the system. Other solution is to modify control algorithm to stabilize the system which is called "active damping (AD)". This method avoid lose problem through adding complexity of control strategy. This paper analyze damping principle of each method include passive damping and active damping, show the advantages and disadvantages of these methods. In this paper, the ripple current attenuation function of passive damping is given to analyze the filter effort for the first time. At the end of this paper, a prospect on this subject is given.