J.I. San Martín

Influence of power quality on the performance of digital protection relays

The performance of protection relays depends on many factors and needs to be carefully evaluated. One of the significant factors impacting protection system behaviour is power quality. Depending on which of the power quality parameters is distorted, the influence on the performance of digital protection relays will be different. This paper analyses the influence of power quality deterioration on digital protection relays. In the first part of the paper, the historical limitations related to electromechanical relays and the signal processing algorithms used in digital relays are outlined. In the second part, the influence of distorted waveforms on the behaviour of digital relays is analyzed. Two aspects of power quality are taken into account: harmonics and frequency variations. Additionally, several simulation examples supported by laboratory measurements are presented in order to illustrate practical implications of poor quality of power.

Co-simulation with DIgSILENT PowerFactory and Matlab: Optimal integration of plug-in electric vehicles in distribution networks

Smart grid concept is gaining more and more importance in electric power systems. In near term, electric grids will be more intelligent, interconnected and decentralised. Dealing with a significant number of distributed resources in a smart way frequently requires the use of optimal control techniques, which find the best solution according to a defined objective function. Taking into account all these aspects, the simulation of these types of problems is characterised by having a great number of controlled resources and the use of advanced control techniques. In this context, DIgSILENT PowerFactory provides useful tools to simulate complex systems. On the one hand, the DIgSILENT Programming Language (DPL) can be used for multiple purposes such as automation of simulations, automatic generation of simulation scenarios, analysis of results. On the other hand, the DIgSILENT Simulation Language (DSL) and the digexfun interface allow the implementation of advanced control techniques. Using the digexfun interface, DIgSILENT PowerFactory can send and receive data from other mathematical software APIs such as MATLAB. This chapter presents a co-simulation framework developed to test optimal control methods for root mean square (RMS) simulations on DIgSILENT PowerFactory. As an example, the implementation of a smart charging control for plug-in electric vehicles in electric distribution networks is explained.

Empirical-Analytical Modelling of the Thermal Performance of a PEMFC-based CHP System

This paper focuses on the thermal modelling of a CHP system based on Proton Exchange Membrane Fuel Cell (PEMFC) by experimental analysis and analytical relationships. To this end, there have been carried out several experimental tests on a PEMFC 600 W of electrical power in order to obtain the necessary data for thermal modelling and its subsequent validation. Once made the experimental analysis, data obtained have been used to develop the thermal model of the stack of the fuel cell as well as the entire temperature management system, by implementing various analytical relationships in the MATLAB/Simulink environment. The model obtained has allowed to characterize the thermal behaviour of the fuel cell to different profiles of electrical and thermal energy demand, with a minimum and maximum relative error in the temperature of the stack of 3.77% and 11.05%, respectively.

New Control Algorithms for Microgrids Based on Microturbines

This paper analyses the performance of a lowvoltage microgrid, based on microturbines, and presents new control algorithms to improve the efficiency and reliability of microgrids. Due to the importance of islanding and focusing on the efficiency and the harness of the heat of the exhaust gasses in islanded operation mode, a new control algorithm has been developed. Additionally, a new control strategy is presented for the seamless transition between islanded and grid connected operation modes based on changing the control algorithms of the microturbines. The new proposed control algorithms are tested by simulation using a low voltage network fed by 5 microturbines. Lasseter model is used to represent the dynamic behaviour of the microturbines. The paper shows the simulation results and the main conclusions of the validation process.

Testing and analysis of a fuel cell based stand-alone power system for residential use

Nowadays, there are residential buildings which cannot be connected to a distribution network, due to the lack of electric infrastructure. Also, there are other electric applications where it is necessary to have a back-up system, i.e. hospitals, hotels, etc. Additionally, there are users who just want to be off-grid. In all these cases, a dedicated stand-alone generation system can provide a valuable service. In this context, this paper is focused on testing and analysis of a real small stand-alone generation system composed by two proton membrane exchange fuel cells (PEMFC) and a micro wind generator (WG). The key feature of this configuration is to be an on-site zero-emission system. Additionally, quality of supply and energy efficiency of this microgrid in islanded mode are analyzed. Furthermore, possible optimization methods and future enlargements of the system are proposed, in order to improve the overall efficiency of the proposed microgrid.

Decentralized controltechniques for plug-in electric vehicles in MV/LV distribution networks

Decentralized control techniques are acquiring more and more importance to efficiently manage a large number of distributed energy resources (DER). It is expected that, in the future, plug-in electric vehicles (PEVs) will act as DERs providing valued services to power grids. In addition, it has been proven that uncontrolled charging of PEVs will have a significant impact on the operation of MV/LV distribution networks. In this context, this paper presents a review on decentralized control approaches to adequately integrate PEVs in MV/LV distribution networks. Among these decentralized control techniques, optimal and droop based controls are the most common. Both have strengths and weaknesses, so, more research about mixing both methods is needed.

Modeling and validation of photovoltaic plants using generic dynamic models

Dynamic simulation models of photovoltaic plants are needed during the design stage of the plant, to show compliance with grid code requirements, as well as after commissioning, to validate the model response with the real plant performance. Due to the large number of PV installations and inverter models, there is a strong need to move from specific manufacturers user models to generic models, as the ones proposed by the Western Electricity Coordinating Council (WECC). This paper discusses the need for generic models, introduces the photovoltaic plant model developed by WECC and presents a case of generic model parameterization and validation of a commercial three-phase inverter, based on factory test. The simulation results show the validity of the generic model to reproduce the Low Voltage Fault Ride Through (LVFRT) capability of the inverter.

A Survey on Innovative Solutions and Projects for the Integration of Renewable Generation in Weak Power Grids

This paper deals with the most relevant issues about the integration of renewable generation in weak power grids. Initially, the main parameters that characterize these types of networks are reviewed, in terms of short circuit power, system inertia and frequency and voltage characteristics. Afterwards, improvement measures in the structure of weak power grids are proposed, analyzing different storage technologies in order to guarantee a high efficiency and reliability of the power system. Finally, the paper reviews the most prominent projects developed worldwide which include the integration of renewable energy in weak grids.