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This work presents a comprehensive set of steady state models to be included in power flow simulation studies of DC railway networks. This simulation framework covers all important aspects and features of each element of modern DC railways. The proposed models are simplified to achieve the maximum simulation speed while keeping the required accuracy. Not only non-reversible, controlled and uncontrolled reversible substations are considered, but also on-board and off-board accumulation systems. The train model can consider the low network receptivity (overvoltage protection for trains equipped with regenerative braking) and overcurrent protection. It is also possible to include in the simulation DC/DC links between nodes of the railway network at the same or different voltage. To date, there is no other work able to conjugate all the mentioned models in a complex multi-train scenario.

Cumulative plastic production worldwide skyrocketed from about 2 million tonnes in 1950 to 8.3 billion tonnes in 2015, with 6.3 billion tonnes (76%) ending up as waste. Of that waste, 79% is either in landfills or the environment. The purpose of the review is to establish the current global status quo in the plastics industry and assess the sustainability of some bio-based biodegradable plastics. This integrative and consolidated review thus builds on previous studies that have focused either on one or a few of the aspects considered in this paper. Three broad items to strongly consider are: Biodegradable plastics and other alternatives are not always environmentally superior to fossil-based plastics; less investment has been made in plastic waste management than in plastics production; and there is no single solution to plastic waste management. Some strategies to push for include: increasing recycling rates, reclaiming plastic waste from the environment, and bans or using alternatives, which can lessen the negative impacts of fossil-based plastics. However, each one has its own challenges, and country-specific scientific evidence is necessary to justify any suggested solutions. In conclusion, governments from all countries and stakeholders should work to strengthen waste management infrastructure in low- and middle-income countries while extended producer responsibility (EPR) and deposit refund schemes (DPRs) are important add-ons to consider in plastic waste management, as they have been found to be effective in Australia, France, Germany, and Ecuador.

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Abstract-This paper proposes a combined distributed/centralized architecture for the control and monitoring of a hybrid DC/AC microgrid with energy storage capabilities. The monitoring system is based on an own developed C++ framework for the measurement and real-time state estimation of the microgrid. Calculations running at sampled values (SV) frequency (10kHz) are implemented into a set of distributed measurement and processing units which have a TCP/IP communication link with a central server running the powerflow (PF) algorithm. The architecture is fully scalable, with the only restrictions of the signal processing capabilities of the distributed units, LAN bandwidth and central server calculation capabilities. The proposed system includes the hardware and software architecture for the monitoring of the microgrid, the communications scheme, the implementation of real-time algorithms for grid state estimation, a graphical user interface including different visualization alternatives and data storing/retrieving capabilities.

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Abstract-In this paper a new procedure based on a Backward/forward sweep (BFS) algorithm for solving power flows in weakly meshed DC traction networks is presented. The proposed technique is able to consider the trains as non-linear and nonsmooth (non-differentiable) voltage dependent loads or generators. This feature permits the inclusion of the trains overcurrent protection and the squeeze control. With the use of the mentioned controls, the conventional power flow problem becomes a voltage constrained power flow problem, and the interaction between the trains and the network can be accurately modeled. However, the train control induces a highly non-smooth voltage dependent load characteristics, causing convergence problems in most of the derivative based algorithms. The proposed algorithm is faster, more robust and stable than the derivative based ones. In addition, the authors present all the formulation in a compact matrix based form by means of the graph theory application and the node incident matrix.

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