Dynamic control of a 20kW interleaved boost converter for traction applications

Auxiliary power supplies for traction rolling stock are used to power the carriage service facilities and control systems that are essential to keep a train operational. The design of converters for such applications is quite challenging, since the traction environment requires high performance systems that can manage a range of harsh environmental and electrical requirements without compromising performance, reliability and robustness. This paper presents the controller design for a 20 kW traction auxiliary converter that boosts a nominal 110 V DC battery supply to a regulated 600 V DC bus, to supply an associated 3-phase AC output inverter. The converter is required to operate over a wide DC input voltage range, produce a regulated high voltage DC output voltage, operate from no load to full power over the full input voltage range, support full output load rejection, and meet all usual traction converter robustness and reliability requirements. A further challenge for the system was to achieve good dynamic response under both continuous and discontinuous conduction modes despite the converter's high boost ratio and low switching frequency. The final controller was implemented as a fully digital DSP based system with an inner PI current regulator and an outer PI voltage regulator. Second order design issues that were also considered included the effect of DC source resistance and PWM transport delay. Modelling analysis, simulation results and experimental results are presented to demonstrate the controller's success in meeting its performance objectives.