Abstract
Regenerative braking systems are an efficient way to increase the energy efficiency of electric rail vehicles. During the development phase, testing of a regenerative braking system in an electric vehicle is costly and potentially dangerous. For this reason, Hardware-In-the-Loop (HIL) simulation is a useful technique to conduct the system’s testing in real time where the physical parts of the system are replaced by simulation models. This paper presents a HIL simulation of a tram regenerative braking system performed on a scaled model. First, offline simulations are performed using a measured speed profile in order to validate the tram, supercapacitor, and power grid model, as well as the energy control algorithm. The results are then verified in the real-time HIL simulation in which the tram and power grid are emulated using a three-phase converter and LiFePO4 batteries. The energy flow control algorithm controls a three-phase converter which enables the control of energy flow within the regenerative braking system. The results validate the simulated regenerative braking system, making it applicable for implementation in a tram vehicle.
Highlights
Regenerative braking systems for rail vehicles enable energy savings and a stabilizing effect on the supply network
In order to develop a suitable energy flow control algorithm within the regenerative braking system, a system model is first used in the MATLAB/Simulink environment to test the basic principles of the algorithm through an offline simulation
The error signal values indicate that noticeable differences occur at different times, mainly due to two reasons: (i) time delays between similar waveform shapes caused by the PI controllers in the HIL simulation, (ii) measurement and modeling uncertainties caused by the scaled supercapacitor voltage range which results in charge/discharge state changes in the HIL simulation that do not occur during the offline simulation
Summary
Regenerative braking systems for rail vehicles enable energy savings and a stabilizing effect on the supply network. Using the developed models and conducting offline simulations and HIL experiments, the supercapacitor energy storage system is dimensioned and an appropriate control algorithm for energy flow is designed, which further increases the efficiency of the tram vehicle. In order to develop a suitable energy flow control algorithm within the regenerative braking system, a system model is first used in the MATLAB/Simulink environment to test the basic principles of the algorithm through an offline simulation In this case, the model of the whole system should describe the voltage-current relationships on the power grid as a function of the tram vehicle speed and acceleration with sufficient accuracy to determine the minimum energy storage capacity and the energy flow control algorithm. The mathematical models of the regenerative braking system components are determined according to the fundamental physical laws of vehicle motion and electrical phenomena in the power grid to provide the power required to accelerate and decelerate the vehicle
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