Daily Archives: 16 December 2015

Management of Renewable Energy Sources Integrated in a Micro Smart Grid

16 December 2015Fără categoriecburada

Abstract 

 

Future trends in the energy sector are crossing from centralized to distributed electricity production. A national and international organism encourages and informs consumers about the efficient use of energy. Such an approach of an efficient energy consumption lead to use of a certain number of renewable energy sources and a proper management of their. This paper, approach some issues of energy management and the use of unconventional sources of energy under the stochastic conditions. It showed a possibility of interconnection of renewable energy sources in a micro-smart grid. Four energy sources are proposed: the main source – power grid; secondary source 1 – photovoltaic generator; secondary source 2 – wind generator; secondary source backup 3 – diesel generator. The interconnection of these energy sources is achieved by a system of energy management and control based on a microcontroller structure type. Interconnection is based on the availability of energy sources and by energy consumption. The command and control algorithms for energy sources were implemented in Matlab Simulink software using specific functions and blocks. The energy management system ensures directing the flow of energy between sources and consumers. Also it manages the total energy distributed to consumers. The information can be stored and interpreted by a PC.

Lead Acid Battery Pack Charging Optimization

16 December 2015Fără categoriecburada

Abstract 

Still used as a rechargeable power sources, rechargeable batteries pack require attention primarily to ensure higher life operating. One of the factors that influence lifespan is the process of charging and discharging. For batteries is manifested in the so-called memory effect which manifests itself by decreasing the operating voltage, even when was loaded to its maximum capacity. The article presents this issue but also offers a solution direct applicable for lead-acid batteries. The principle has based on reducing the number of charge and discharge processes in a certain time. So the hysteresis characteristic becomes wider and the time between switching from charge mode in the discharge and vice versa is higher. Analysis of three algorithms, step-by-step set of operations, and implementation in an experimental device is the main goals of paper. Optimization technique represents here to maximize battery lifetime. The device developed has a microcontroller and proves useful with minimal changes in any situation, by replacing the existing or interposing circuit between the power source and battery. Designed circuit can have easily adapted to correspond for other types of batteries. It can integrate with minimal changes, additional functions such as current battery measure and temperature.

Aspects Regarding Influences of Voltage and Resistant Torque on Asynchronous Motors Operation

16 December 2015Fără categoriecburada

Abstract 

In this paper there are analyzed a series of dynamic regimes that occur in the case when a phase of an asynchronous motor is accidentally interrupted and in the case when the resistant torque increases by step. For these situations there have been carried out, starting from the motor equations written in the two-axes theory, two Simulink programs (detailed in the paper). With their help, for a motor rated at1,2 kW, there have been obtained relevant simulations together with conclusions emerging from them. Thus, in the case when a phase was interrupted it results that: the interruption of a phase leads to a dynamic regime that is relatively quickly stabilized; this stabilized regime is characterized by high values of currents, slight decrease of the rotor speed, small oscillations of speed, important oscillations of torque. In the case when the resistant torque is modified by step there have been resulted the following conclusions: a reduced torque shock leads to increased values of the currents and to a slight decrease of the speed (after a few oscillations); an increased value of the inertia moment leads to an increased number of current oscillations in dynamic regime but also to the disappearance of the speed and torque oscillations when a torque shock occurs; for very high resistant torques the maximum torque developed by the motor becomes smaller than the resistant one which causes the decrease of the speed towards zero, finally reaching, if the protections do not cut, the shortcircuit regime; the simulation program conceived here can also be used for establishing the value of the motor maximum torque; the simulations have been confirmed, as essential elements, quantitatively and qualitatively, by experiment.

About the Analytical Methods Applying for Fault Diagnosis of the Static Converters from the Electric Locomotive

16 December 2015Fără categoriecburada

Abstract 

 

In this paper, the results of the monitoring and diagnosis system based on the analytical methods of the auxiliary ventilation service of the electric locomotive which is supplied from the static converter are presented. Because of the complexity of the electric locomotive structure and of the big number of components, a large number of the parameters must be monitored and detected the range of variation of their imposed values. Consequently, a large variety of monitoring and diagnosis procedures have been developed. In literature in the field, the many advanced fault diagnosis methods were presented. Using the analytical method, the analytical model of the static converter was developed using the Matlab Simulink. Starting from the model of the static converter, three types of the faults were simulated: losing inverter supply, interrupting of the inverter output phase and biphasic shortcircuit at inverter output. For all three types of mentioned faults, the waveforms of motor speed, electromagnetic torque and electric currents have been registered. These waveforms were compared with those corresponding to the normal operation regime. The impact of the type of fault on the waveforms was pointed out. The results were analyzed based on the evolution of the motor parameters in the normal and abnormal operating regime.

Modern Techniques for Monitoring Circuit Breakers by using Microcontroller System

16 December 2015Fără categoriecburada

Abstract 

The paper deals with experimental monitoring system, developed by the authors, by using a microcontroller within the 8051 family, Dallas DS87C550. This micro-system has two main parts: the acquiring and transfer module and the user interface developed using the facilities specific to Graphic User Interface of Matlab®. The achievement such a way implies designing a hardware structure that meets the proposed functions in a versatile approach and programming of controller using its facilities. The electrical equipments, being characterized by small time constants and high risk, impose major efforts in orderto develop competitive monitoring systems. On the other hand, the costs involved by such systems need to be as low as possible, without cutting the imposed performances. The possible functions of the experimental system are related to the monitoring of IO breaker using modern diagnostic methods: monitoring of the contacts condition, the computation equivalent switching number, the estimation of the insulating oil quality, monitoring the achieved service, the diagnostics of the weaken contact by vibration analysis technique and the dependence of voltage versus temperature on contact. The results are presented as graphical user interfaces developed by using the facilities of the software MATLAB. The interface is versatile and with ease allows the tracking of results after data processing.

Electromagnetic Field Coupling Between Over-Head Power Lines and Nearby Metallic Pipelines in Case of Direct Lightning

16 December 2015Fără categoriecburada

Abstract 

Lightning-induced voltages in power systems are nowadays one of the causes of the main power quality and electromagnetic compatibility issues. In recent years, due to the increasing demand by customers for good quality in the power supply along with the widespread use of sensitive devices connected to distribution lines, the protection against lightning-induced disturbances became of primary importance. Installing pipelines in energy utility corridors containing high-voltage AC transmission lines subjects the pipelines to induced AC voltages which are a real and serious problem which can place both operator safety and pipeline integrity at risk. In case of a lightning strike on power line, the electromagnetic field produce by this pulse induces voltages in the nearby metallic structures. An electromagnetic interference analysis has been performed in case of a metallic gas pipeline that runs nearby a 110 kV/ 50 Hz power line. Different scenarios regarding the lightning strike on HVPL were investigated. Due to high value of the separation distance between HVPL and MP, only the effect of inductive and capacitive coupling is taking into account. Professional software for power system transients (EMTP-RV) is used to create an original transient state equivalent electrical circuit model of the system and to perform simulation of the transient process during lightning strike and compute the induced voltages in the metallic pipeline.

Hybrid Petri Nets in Modeling the Packing Processes: Case Study

16 December 2015Fără categoriecburada

Abstract 

In many cases, the packing processes are considered as hybrid systems, consisting of a set of workstations, where various components must be processed, and at least one flexible transport system used for loading and/or unloading operations. This paper is focused to a Hybrid Petri Nets approach for modeling and simulation the behavior of such systems, considered a hybrid dynamic structure, with both continuous and discrete components interacting. For heuristic representation of the model, several sequences and rules were however followed. For the case study, starting from the structure of the system, in order to achieve a primary topology of the model, a bottomup synthesis technique was used, which allowed us to obtain a basic version, consisting in several sub-models of related physical subsystems of the packing station. Aggregation of these partial models was made in accordance with the interactions of the physical elements of the whole system, laid down in the operation protocol. Hence, into model topology various elements characteristic to generalized Petri Nets were used, with inhibitor arcs and test arcs, mainly aiming to reduce the complexity of the whole model. The validation of the model was done through on-line simulation, in various scenarios, under the Visual Object Net++ tool, which offers multiples facilities for the analysis of behavioral properties in various real operating conditions of the real physical system. Starting on the modular structure of the whole model, consisting in several submodels of the same type, the authors obtained a multilevel architecture, using Object Petri Nets paradigm for representation and exploiting their analysis potential.

Numerical Determination of Inductance of a SMES Device Using the Response Surface Methodology Applied on FEM Modeling

16 December 2015Fără categoriecburada

Abstract 

The paper proposes the determination of the inductance of a Superconducting Magnetic Energy Storage (SMES) device with modular toroid coil based on a new 2-D FEM modeling using the response surface methodology (RSM) applied on 3-D FEM modeling. An earlier 2-D FEM modeling of a SMES device created in FEMM software is based on the assumption of the equality between the inductances of the complete circular cross section toroid and of the rectangular cross section toroid, providing an approximationfor the depth of planar model which does not take into account the leakage magnetic flux. Therefore a 3-D model of real geometry was realized using ANSYS software to improve this approximation. Imposing the equality of the magnetic field energies in 2-D and 3-D simulations, a new value for depth of 2-D FEM planar modeling is derived as polynomial regression of second order of the 3-D results, based on two factors characterizing the geometric torus shape: the coil inner diameter ratio and the coil thickness ratio. The application of analysis of variance (ANOVA) and the computation of some adjusting coefficients prove the descriptive and predictive power of this model. The inductances of different configurations of SMES device derived from the new 2-D FEM modeling are compared to those based on the earlier 2-D FEM modeling and on the 3-D FEM modeling. The results indicate an underestimation of the depth of the earlier 2-D FEM planar modeling and consequently, of the magnetic field energy and of the inductance for SMES devices with large inner diameter, when the leakage magnetic flux increases. The proposed model can improve the results of optimizations of the SMES device performed in previous papers.

The Online Temperature Control

16 December 2015Fără categoriecburada

Abstract 

In this paper is presented the hardware and software design of a remote controlled system which can have multiple destinations. In particularly, this system is used to create an online thermostat using a microcontroller with ARM Cortex M4 architecture and an application designed for Android operating system. The system was designed by authors from the ground with the objective to create a framework for wide range of applications in electromechanical domain with network communication capabilities. The main hardware element is the processing unit for which was chosen the STM32F407VGT6 microcontroller. This is based on a 32-bit architecture working at 168MHz frequency which allow very fast running several tasks: scanning of digital sensors and a touchscreen, achieve SPI communication with an Ethernet driver, run an algorithm for temperature control. All software routines for microcontroller were built to be easy to port in another applications being developed in C language and structured in reusable functions. The application for mobile devices was written in Java language and was compiled with latest Android Studio. The system is functional and can be used in multiple applications offering the advantages provided by network connection. All presented stuff can be used to create a lot of network connected applications.

Performance of an Active DC-Traction Substation with 12-Pulse Parallel Rectifier and Indirect Current Control

16 December 2015Fără categoriecburada

Abstract 

The attention in this paper is directed to the transformation of an existing DC-traction substationsequipped with 12-pulse parallel uncontrolled rectifier into an active substation. In this manner, the traction substation gains the capability of redirecting the braking energy to the power supply and the power quality indicators during the traction regime are greatly improved. The practical solution lies in adding a shunt active power filter, accompanied by appropriate circuits of connection on both the DC and AC sides, between the DC-traction line and the primary of the traction transformer via a dedicated recovery transformer. To control the current provided by the shunt active filter in both traction/active filtering and regeneration regimes, the indirect method of handling the supply current has been adopted. The reference supply current during the operation in traction regime is calculated based on instantaneous powers provided by the concepts of the instantaneous reactive power theory. Two compensation strategies have been implemented for this operation mode, i.e. the total compensationof the current harmonics and reactive power and the partial compensation (only the current harmonics). In regeneration mode, the traction rectifier is blocked and the reference supply current is given by the voltage controller. Based on the conceived Matlab/Simulink models of the whole system, the proper operation is confirmed and the good performance of the system during both traction/filtering and regeneration regimes is shown. Indeed, the total harmonic distortion of the supply current is always below the limits and recommendations of the power quality standards and the operation in regeneration mode is allowed.