Совершенствование системы авторегулирования тормозных режимов электропоезда с импульсным преобразователем

Abstract

The article discusses the features of automatic regulation of the process of electric braking of a DC electric train. The peculiarity of this process is that traction engines switch to generator mode of operation to reduce the travelling speed. Industrial generators operate at a constant rotational speed and constant voltage. On an electric rolling stock in braking mode, electric machines operate at a continuously changing rotational speed. At the same time, the objective is to maintain a constant level of the set value of the braking force to ensure comfortable conditions for passengers. At the theoretical level, to accomplish this task, it is sufficient to keep the specified braking current constant at a changing rotational speed, which can be done by regulating the excitation current. In real conditions, the traction engine passes through four high-speed control zones, each of them is characterized by its own control algorithm. As braking progresses, it is possible to distinguish - a zone of high speeds, a zone below the running speed, where the process of pulse regulation of the armature current occurs (by pulse shorting of the circuit) and a zone of short-circuit of the armature circuit. The running speed is the speed at which the armature voltage is equal to the mains voltage at the rated excitation current. Within a high-speed zone, the excitation current is regulated, below this speed, the excitation current is maintained at a constant (nominal) value. The regulation of the excitation current is carried out by the control unit of the armature and excitation currents. Transitions from one zone to another are made using nonlinear elements. If the ratio of the armature current increment to the excitation current increment is considered as a transfer function, then in the high-speed zone this function is not constant. If a control system is adjusted in relation to the highest speed of movement, then in the zone of reduced speeds, performance of the system in response to voltage changes in the contact network will be insufficient. When the speed decreases, the magnitude of the transfer function decreases, and this dependence leads either to undesirable self-oscillations, or to a slowdown in the control process. In order to eliminate self-oscillations and improve the quality of regulation, it is proposed to provide in the control unit the possibility of changing the gain of the armature current regulator depending on the speed of movement and the operating mode of the traction electric drive.