Design method of low loss and fast response LC filters based on locomotive battery testing system

The locomotive battery is sensitive to the fluctuation of its charge/discharge current, so the battery test system is proposed to offer high quality current, such as low ripples (<= 0.5 %), fast response and wide adjustable extent. Because the battery test system is a non-matched network to the filter, there is a flat decay for the DC current which can't be avoided. Besides, the locomotive battery has a very tiny inner resistance which is capacitive and with opposing voltage, it makes the filter design more difficult. This paper introduces a method for bidirectional DC/DC filter design. The synthesis method for single-end system is introduced to minimize the flat decay to the DC current. The influence to the characteristic of the filter caused by component dissipation is demonstrated. The dissipation factor of the lossy filter made a left shift to the normalized pole and zero of its transfer-function, this feature is imposed to enhance the response speed of the filter Simulations and tests proved that the filter possesses low transient peak value, fast converse ability and good filtering result.