Investigation on active method for stabilization of LC input filter and DC/DC buck converter under voltage mode control

The switching mode power electronic converter with feedback loop control functions as a constant power load (CPL). CPLs have negative input impedance which may cause system instability. Both passive and active stabilization methods can solve this problem. However, active stabilization methods are more power efficient. Several active stabilization methods have been proposed for DC/AC inverter based CPLs. However, active stabilization methods for DC/DC converter based CPLs under voltage mode control have received little attention. In this paper, an active method is proposed for stabilization of DC/DC converter in voltage mode control. A systematic investigation on this active method is carried out. In the active method, a feedforward loop is designed and fed to the voltage control loop of the DC/DC converter. This feedforward loop is a combination of a bandpass filter and a proportional gain. This feedforward loop can create a virtual resistor and a virtual capacitor in parallel with the CPL. And this virtual circuit can modify the negative input impedance of the CPL to satisfy the impedance criterion. Experimental results are reported to verify the analysis and the effectiveness of the active method.