New Reactive Power Compensation Strategies for Railway Infrastructure Capacity Increasing

Abstract

In AC railway electrification systems, the impact of reactive power flow in the feeding voltage magnitude is one aspect contributing to the quality of supply degradation. Specifically, this issue results in limitations in the infrastructure capacity, either in the maximum number of trains and in maximum train power. In this paper, two reactive power compensation strategies are presented and compared, in terms of the theoretical railway infrastructure capacity. The first strategy considers a static VAR compensator, located in the neutral zone and compensating the substation reactive power, achieving a maximum capacity increase up to 50% without depending on each train active power. The second strategy adapts each train reactive power, achieving also a capacity increase around 50%, only with an increase of the train apparent power below 10%. With a smart metering infrastructure, the implementation of such compensation strategy is viable, satisfying the requirements of real-time knowledge of the railway electrification system state. Specifically, the usage of droop curves to adapt in real time the compensation scheme can bring the operation closer to optimality. Thus, the quality of supply and the infrastructure capacity can be increased with a mobile reactive power compensation scheme, based on a smart metering framework.

Towards Smart Railways: A Charging Strategy for Railway Energy Storage Systems

“…This cloud-based strategy has been explored in [43], where the knowledge of the electrification power flow is required for the necessary setpoints and a fast communication link provides better actuation.…”

A Review on Power Electronics Technologies for Electric Mobility

“…However, these passive compensators are not able to follow the fast-dynamic changes of non-linear loads, which is the case of the traction load (electric locomotive). Therefore, there is a need for dynamic compensators that follow the non-linear dynamic changes, and power electronics compensators serve this purpose [256][257][258][259]. In this context, a possible solution is the use of a static synchronous compensator (STATCOM), which consists of a three-phase voltage source converter, coupling power transformer and filter inductors installed on the three-phase ac power grid.…”

“…In that regard, this item presents two relevant power electronics solutions. The first is an interface converter between the three-phase ac power grid and the single-phase TPS, as shown in Figure 30 [256]. This interface is useful to perform frequency conversion when the single-phase TPS frequency is different from the three-phase ac power grid frequency.…”

“…The main disadvantage of this converter is that it should be rated to endure the full load power. In some references, this solution is called a static frequency converter [256,258]. Another interface converter between two traction substations is presented in Figure 31.…”

Experimental Validation of a Reduced-Scale Rail Power Conditioner Based on Modular Multilevel Converter for AC Railway Power Grids

“…Some of the problems related to power quality deterioration are the harmonic distortion produced by the electric locomotives and the negative sequence components (NSC) of currents created by the three-phase current imbalance of the power grid [4]. Numerous approaches to improve power quality have been developed and investigated in recent decades to overcome the deterioration of power quality in electrified railway systems [5,6]. In this regard, active power compensator-based power electronics converters are still in development for consistency with the latest evolution of high-speed electrified railway systems that broadly use 25 kV, 50 Hz power supplies [7].…”