Lucian Mihet-Popa

Simulation model developed for a small-scale PV system in distribution networks

This paper presents a PV panel simulation model using the single-diode four-parameter model based on data sheet values. The model was implemented first in MATLAB/Simulink, and the results have been compared with the data sheet values and characteristics of the PV panels in standard test conditions. Moreover to point out the strong dependency on ambient conditions and its influence on array operation and to validate simulation results with measured data a complex model has also been developed. A PV inverter model, using the same equations and parameters as in MATLAB/Simulink has also been developed and implemented in PowerFactory to study load flow, steady-state voltage stability and dynamic behavior of a distributed power system.

Electrical Vehicle Batteries Testing in a Distribution Network Using Sustainable Energy

EV technologies are still relatively new and under strong development. Many different designs and choices of technologies have been pursued by the automotive OEMs, battery industry and EV research centers. Although some standardized solutions are being promoted and becoming a new trend, there is an outstanding need for common platforms and sharing of knowledge and core technologies. This paper presents the development of a test platform, including three Li-ion batteries designed for EV applications and three associated bi-directional power converters, for testing impacts on different advanced loadings of EV batteries. The aim of the tests has been to study the impact of smart charging and fast charging on the power system, on the battery state of health and degradation, and to find out the limitations of the batteries for a Smart Grid. The paper outlines the advantages and disadvantages of both tests in terms of regulation of the aggregated local power, power capacity and the power exchange with the grid.

Variable Speed Wind Turbines Using Cage Rotor Induction Generators Connected to the Grid

In this paper, the performance of variable speed wind turbine concept with cage rotor induction generator connected to the grid is investigated. Variable-speed wind turbine generator system has been modeled and simulated to study their steady state and dynamic behavior. A cage rotor induction machine of 11 kW rating with a vector controlled back-to-back PWM-VSI inverter on the stator side have been tested and the results compared with digital simulations. The cage rotor induction machine allows good speed range and it should be used in low-power variable-speed systems, replacing the classical direct grid connected fixed speed wind generator systems. Its capacity to deliver reactive power is remarkable.

Charging and discharging tests for obtaining an accurate dynamic electro-thermal model of high power lithium-ion pack system for hybrid and EV applications

This paper presents a battery test platform including two Li-ion battery designed for hybrid and EV applications, and charging/discharging tests under different operating conditions carried out for developing an accurate dynamic electro-thermal model of a high power Li-ion battery pack system. The aim of the tests has been to study the impact of the battery degradation and to find out the dynamic characteristics of the cells including nonlinear open circuit voltage, series resistance and parallel transient circuit at different charge/discharge currents and cell temperature. An equivalent circuit model, based on the runtime battery model and the Thevenin circuit model, with parameters obtained from the tests and depending on SOC, current and temperature has been implemented in MATLAB/Simulink and Power Factory. A good alignment between simulations and measurements has been found.

Development of tools for simulation systems in a distribution network and validated by measurements

The increasing amount of DER components into distribution networks involves the development of accurate simulation models that take into account an increasing number of factors that influence the output power from the DG systems. This paper presents two simulation models: a PV panel model using the single-diode four-parameter model based on data sheet values and a VRB system model based on the efficiency of different components and the power losses. The models were implemented first in MATLAB/Simulink and the results have been compared with the data sheet values and with the characteristics of the units. Moreover to point out the strong dependency on ambient conditions and its influence on array operation and to validate simulation results with measured data a complex model has also been developed. A PV inverter model and a VRB inverter model, using the same equations and parameters as in MATLAB/Simulink, has also been developed and implemented in Power Factory to study load flow, steady-state voltage stability and dynamic behavior of a distribution power system.

Modeling and Design of a Grid Connection Control Mode for a Small Variable-Speed Wind Turbine System

In this paper, a variable-speed wind turbine generator system with a vector controlled back-to-back PWM- VSI on the stator side has been modeled, designed and simulated to study its steady state and dynamic behavior. The grid connection control mode of a wind turbine based on a flexible dSPACE digital signal processor system that allows user-friendly code development, monitoring and online tuning is used. The design of an LCL-filter, current controller and DC-link voltage controller are described in detail. The PI- controllers are designed using pole-zero placement technique and the gain of the regulators are found using root locus method.

Simulation models developed for voltage control in a distribution network using energy storage systems for PV penetration

This paper presents the development of simulation models for DER components in a distribution network, with focus on voltage controllers using energy storage systems for PV penetration. The Vanadium Redox Battery (VRB) system model, used as an energy storage system, was implemented in MATLAB/Simulink and DIgSILENT PowerFactory, based on the efficiency of different components-such as: cell stacks, electrolytes, pumps and power converters, whilst power losses were also taken into account. The simulation results have been validated against measurements using experimental facility of a distributed power system laboratory. To study the variability and the interaction between feeders including VRB, PV system and active units an overvoltage controller has also been developed, implemented and tested successfully.

Annual wind and energy loss distribution for two variable speed wind turbine concepts of 3 MW

In this paper, the performance of two variable speed wind turbine concepts regarding efficiency of generated power are investigated. A method to calculate annual energy loss distribution of a wind generator system is presented. The losses of different components of two variable-speed wind generator topologies of 3 MW using Doubly-Fed Induction Generators are evaluated with regards to their annual energy production.

Modeling and Simulation of a 12 MW Active-Stall Constant-Speed Wind Farm

The conventional energy sources such as oil, natural gas, or nuclear are finite and generate pollution. Alternatively, the renewable energy sources like wind, solar, tidal, fuel cell, etc are clean and abundantly available in nature. Among those the wind energy has the huge potential of becoming a major source of renewable energy for this modern world. In 2008, 27 GW wind power has been installed all over the world, bringing world-wide install capacity to 120.8 GW (GWEC publication, 2009). The wind energy industry has developed rapidly through the last 20-30 years. The development has been concentrated on grid connected wind turbines (wind farms) and their control strategies. Conventional stall wind turbines are equipped with cage rotor induction generators, in which the speed is almost constant, while the variable speed and variable pitch wind turbines use doubly-fed induction generators or synchronous generators in connection with a power converter (partial rate or full rate). The variable speed wind turbine has a more complicated electrical system than the fixed-speed wind turbine, but it is able to achieve maximum power coefficient over a wide range of wind speeds and about (510) % gain in the energy capture can be obtained (Hansen, A.D. et.al, 2001). In this paper a complete simulation model of a 6 x 2 MW constant-speed wind turbines (wind farm) using cage-rotor induction generators is presented using data from a wind farm installed in Denmark. The purpose of the model is to simulate the dynamical behaviour and the electrical properties of a wind turbine existing in a wind farm. The wind farm model has also been built to simulate the influence on the transient stability of power systems. The model of each wind turbine includes the wind fluctuation model, which will make the model useful also to simulate the power quality and to study control strategies of a wind turbine.

Heat dissipation improvement for ZnO based varistors

ZnO based varistors are today frequently used for making state of the art surge arresters for all voltage levels, due to some advantages like a high non-linearity coefficient and a high energy absorption capacity. Due to their thermal activated conduction, the heat dissipation inside that semiconductor device is crucial for its service. Heat dissipation study could be done only by modelling the thermal and electrical status of the varistor in case of some special and original configurations. The new configuration proposed in this paper consists in a disc varistor with an additional brass mass used for heat extraction and dissipation. The structure is suitable for medium and high voltage metal oxide based surge arresters. This paper presents the finite-element model used for the direct control of heat dissipation, some predictions concerning temperature in different points of the device in steady and shock regime, as well as some experimental results.