The paper presents an innovative concept of applying a combination of well-known selective harmonic elimination (SHE) and selective harmonics mitigation (SHM) methods to shape a spectrum of catenary current harmonics, generated by a traction drive system equipped with a voltage source inverter. Application of this method allows for reducing distorting influence of a modern rolling stock supplied by a 3 kV dc catenary on the railway signaling, command, and control systems. The efficiency of the proposed method is independent of synchronization of a vehicle's inverters and of load balance of traction motors, which makes it more reliable than as it is proposed in the literature. Results of computer simulations were presented and compared with laboratory measurements. The obtained dc-link current spectrum using the proposed SHE/SHM method was compared with spectra received using synchronized and unsynchronized sinusoidal pulse-width modulations (SPWMs). Based on the conducted tests, it was shown that the proposed method of control, which was implemented in a laboratory drive system, is effective in reducing dc side current harmonics in a frequency range of 1300-3100 Hz, which is used by track circuits on railway lines, e.g., in Poland. The technique proposed by the authors allows taking into account any restrictions arising from the technical nature of low-frequency traction drives.

This paper presents an analysis on using an on-board energy storage device (ESD) for enhancing braking energy re-use in electrified railway transportation. A simulation model was developed in the programming language C++ to help with the sizing of the ESD. The simulation model based on the mathematical description has been proposed for a train equipped with on-board ESD for analysis of effectiveness of its application. A case study was carried out for a metro line taking into consideration train characteristics, track alignment, line velocity limits and a running time table. This case study was used to assess the energy savings and perform a cost-benefit analysis for different sizes of the on-board ESD by applying the proposed approach. It was shown that when additional environmental benefits (reduction of CO₂ emissions) are considered, this may significantly improve effectiveness of the investments due to CO₂ European Emission allowances.

In this paper, an application of the recently developed Grasshopper Optimization Algorithm (GOA) for calculation of switching angles for Selective Harmonic Elimination (SHE) PWM in low-frequency voltage source inverter is proposed. The algorithm is based on insect behavior in the food foraging swarm of grasshoppers. The characteristic feature of GOA is the movement of agents is based on the position of all agents in the swarm. This method represents a higher probability of convergence than Particle Swarm Optimization (PSO) Modifications of GOA have been examined regarding their effect on the algorithm’s convergence. The proposed modifications were based on the following techniques: Grey Wolf Optimizer (GWO), Natural Selection (NS), Adaptive Grasshopper Optimization Algorithm (AGOA), and Opposite Based Learning (OBL). The performance of GOA and its modifications were compared with well-known PSO. Areas, where GOA is superior to PSO in terms of probability of convergence, have been shown. The efficiency of the GOA algorithm applied for solving the SHE problem was confirmed by measurements in the laboratory.

The traction substation in conventional power supply systems for trams is a bottleneck of the system. It requires the connection with medium-voltage grid, demands high values of instant power and its centralized topology generates additional energy losses. Since the availability of low-power photovoltaic (PV) generation is increasing in the utility system, we propose to replace conventional substations with a distributed system of low-power devices cooperating with low-voltage grid and PV installations owned by individual households. The proposed in this article distributed power supply system for trams (DPSS-T) consists of multiple traction aggregators (TAs) equipped with energy storage devices (ESDs) which are distributed along the tram line. In order to evaluate the benefits of applying DPSS-T this proposed system was compared with the conventional topology regarding the energy losses in terms of annual operation. Moreover, the following aspects have been studied for the wide range EDS sizes and PV generation: PV energy injection into the power utility system, the utilization of installed ESD, and the contribution of PV generation in energy consumed by traction vehicles. At the same time, the energy management for this new topology has been proposed. The ESDs are charged with relatively low power, between tram runs and discharged with full power during the runs. The suggested energy management eliminates peaks in substation power demand. The obtained results show that despite the fact that the proposed DPSS-T is supplied from low-voltage grid the energy losses are reduced by 58%–69%.