Contact-free two-quadrant converter and a method for regulating its output voltage

摘要

Two-quadrant converters are used for operating vehicle AC/three-phase machines (M) with an invertor (26) and a DC intermediate circuit (24) connected upstream, it being possible to supply braking energy back into the power supply network when the vehicle is braking. Using known two-quadrant converters, the acceleration of the vehicle and the transition from driving to braking operation cannot be carried out without a jerk, since a so-called "dead voltage zone" exists in the voltage range from approximately -60V to +60V, in which zone the output voltage of the two-quadrant converter cannot be controlled continuously. Disadvantageous and costly circuits are known for controlling in the region of this "dead voltage zone". In order to avoid these disadvantages, a two-quadrant converter (23) is specified which manages with few semiconductor components and in which the braking path (12-10) is used a) to convert the braking energy into heat in the event of a reduction in the absorption capability of the power network, b) to control the two-quadrant converter output voltage in the region of the previous "dead voltage zone" and c) to eliminate the controllable regrouping valve (14) by taking over the intermediate-circuit current (I15). In order to achieve this, a freewheeling thyristor (13) is used instead of a conventionally used freewheeling diode. A method for regulating the output voltage of the two-quadrant converter (U23) is also ... Original abstract incomplete. <IMAGE>