Technical Services/Products

Metro train braking kinetic energy can be converted into electrical energy, can provide electrical energy to the traction network, this part of the braking energy is about 40-50% of the traction energy of the train, the earlier lines using braking resistor will be converted to braking energy dissipation of heat in the air in the rail area, so it will increase the energy consumption of the ring control system. In Guangzhou Metro Line 9 was the first to propose medium-voltage feedback braking energy feedback program, the use of inverter-type regenerative braking device, through the traction to the medium-voltage network inverter channel, the train electric braking generated by the traction network of the surplus power back to the 35kV (33kV) medium-voltage power supply network.

With the development of power electronic technology and the topology optimization design of traction system in recent years, our institute has successively proposed the integrated bidirectional converter technology based on axial double-split four-winding transformer and the bidirectional converter scheme based on high-power four-quadrant converter in different DC traction system lines. Both technologies have the ability to realize traction and rectifier functions at the same time, without the need to set up additional diode rectifier units, which can be flexibly set up in accordance with the actual situation of different lines, and both of them can play a good effect of efficiency and loss reduction, and have already been granted with one authorized invention patent.

Technical features and advantages/innovation points

(1) Highly intensive: integrating traction power supply, regenerative energy feedback and reactive power compensation, it can realize distributed reactive power compensation. It can not only reduce the SVG capacity of the main substation/open closure, but also effectively reduce the number of traction substation equipments and floor space;

(2) Green and high-efficiency: the active voltage control function reduces network voltage fluctuation, reduces traction current, restricts over-zone power supply, reduces traction network loss, and improves energy saving by about 5% on the basis of energy saving of regenerative energy feeding device. The application of bi-directional converter unit can save more than 20% energy compared with traditional rectifier unit.

Application/Scenario

Starting from Line 9, Guangzhou Metro takes the lead in adopting the medium-voltage feed-back braking energy feedback program, which has gradually become the industry standard program; in the case of the Knowledge City Line where all four sets of energy-feeding devices are put into use, without considering the transformer no-load loss and line loss, the average daily feed-back power is 4,687 kW-h, which generates an economic benefit of more than 855,000 yuan per year. The payback period is about 4~5 years; in Guangzhou Line 12, the pilot application of integrated bidirectional converter technology based on axial double-split four-winding transformers is carried out; the bidirectional converter technology program based on high-power four-quadrant converter is being promoted for the subsequent lines.