IEEE Std 1887-2017 pdf download – IEEE Guide for Wayside Energy Storage Systems for DC Traction Applications.
5.3 Mechanical storage Mechanical storage involves storing energy in mechanical kinetic or potential form. A common method is to store energy in kinetic form using fywheels. A fywheel is a rotating mass with a high moment of inertia. Some fywheels are optimized for energy capacity through the use of larger rotational mass while other systems are optimized for higher rotational speed. An advantage of fywheel systems is that the capacity of the fywheel itself does not degrade over time nor is it afected by the operational duty cycle of the equipment or by environmental factors such as temperature. 5.4 Electrochemical storage Electrochemical storage involves storing energy in chemical form using one or more electrochemical cells or batteries. Electrochemical cells function by relying on chemical reaction within the cell to store and release electrical energy. An advantage of electrochemical storage is the relatively large amount of energy that can be stored relative to other technologies. Many battery chemistries currently exist, and new types are constantly being developed. Common types in- clude, but are not limited to, lead-acid, nickel-metal hydride, and lithium-ion. Each type of battery chemistry has its own characteristic charge and discharge behavior, duty cycle capabilities, and energy capacity ratings, making each optimal for diferent applications.
6.2.2 Passive or limited control Passive energy storage systems typically have limited or no ability to control the fow of energy in and out of the energy storage. In this topology, the fow of power is dictated solely by the traction line voltage conditions and the voltage current characteristics of the storage medium itself. Typically, the energy storage medium is connected directly to the traction supply, without employing the use of a power converter. While hardware can be simpler, this topology may lack some or all of the benefts provided by active control. For either active or passive control, it is essential that the operational behavior is fully understood and correct- ly modeled so that the performance can be simulated and considered in the cost-beneft analysis. 6.3 Connectivity 6.3.1 Traction only In this topology, the energy storage system charges and discharges to the dc traction supply only. There is no connection to a utility supply except for control and auxiliaries (if required). The energy storage system typically charges and discharges in response to prevailing conditions of the dc traction supply only. 6.3.2 Traction and utility In this topology, the energy storage system may charge and discharge to either the dc traction supply or a utility source.