Showing papers by "V. Fernao Pires published in 2016"

Quasi-Z-Source Inverter With a T-Type Converter in Normal and Failure Mode

Abstract: This paper presents a three-phase multilevel quasi-Z-source inverter (qZSI) topology operating in normal and fault-tolerant operation mode. This structure is composed by two symmetrical quasi-Z-source networks and a three-phase T-type inverter. Besides the intrinsic advantages of multilevel voltage source inverters, the proposed structure is also characterized by their semiconductor fault tolerance capability. This feature is only obtained through changes on the modulation scheme after the semiconductor fault and does not require additional extra-phase legs or collective switching states. In certain fault types, the reduction of the output power capacity will be compensated by the boost characteristic of the qZSI. The fault-tolerant behavior of the proposed topology is demonstrated by several simulation results of the converter in normal and fault condition. To validate the characteristics of this multilevel qZSI, an experimental prototype was also built to experimentally confirm the results.

Bidirectional boost/buck quadratic converter for distributed generation systems with electrochemical storage systems

Abstract: The increasing number of distributed generation systems using renewable and non-conventional energy sources show the trend of future generation systems. Most of these systems require power electronic converters as an interface between the DC voltage buses and electrochemical storage systems. Such storage systems, like batteries or supercapacitors, usually need bidirectional DC-DC converters to allow their charge or discharge according with necessary operation conditions. In this paper, a non-isolated bidirectional Buck-Boost converter with high voltage gain for electrochemical storage devices used in distributed generation systems is presented. To achieve high voltage gain ratios, the proposed topology presents quadratic characteristics in both step-down (Buck) and step-up (Boost) operation modes. In addition to the wide conversion range, it presents continuous input and output current, reduced charging/discharging ripple and simple control circuitry. All these features allow the energy exchange smoothly and continuously resulting in a longer durability of storage devices. The principle of the operation of the proposed converter in both operation modes, as well as their theoretical analysis will be discussed. The performance of this bidirectional power converter is confirmed through simulation and experimental results.

Induction motor broken bar fault detection based on MCSA, MSCSA and PCA: A comparative study

Abstract: The early failure detection of induction motors is considered very important in order to ensure their stability and high performance. Thus, condition monitoring of these motors are essential to ensure that. However, the effectiveness of the fault diagnosis depends on the quality of the fault features selection that is used in the adopted method. In this way, this paper will present a comparative study of three methods based on the electrical signal analysis. The first one is the most known method, motor current signature analysis (MCSA). Another method based on the analysis of spectral current, is the motor square current signature analysis (MSCSA), will also be used. Finally a third method based on principal component analysis (PCA) is also used. The performance of the methods is tested under different fault and load conditions. Experimental results are presented in order to compare the performance between the three methods.

Study on electromagnetic emissions from wireless energy transfer

Abstract: In recent years the interest in Wireless Energy Transfer (WET) technology especially for electric vehicles batteries charging is rapidly growing. As a result of the increasing use of this technology in industrial and consumer electronic products, more concerns are raised about the electromagnetic compatibility since the WET systems produce electromagnetic emissions in the surrounding environment. Thus, the impact of the WET technology on other electrical and electronic equipment and in humans is the issue of high relevance. This paper presents a study related with the measurements of the electromagnetic emissions generated by a magnetic resonance wireless energy transfer (WET) system operating at kHz range of frequency.

Wireless power transfer impact on data channel

Abstract: This paper presents measurement results and analysis of the interference produced by the high-power electromagnetic field in a wireless energy transfer system. Through this analysis it is expected to be possible to evaluate the influence of the strong electromagnetic field on the data transmission channel. The wireless power transfer aimed at electric vehicles battery charging receives a great deal of attention in the recent years. However, the performance of those systems depends on the exchange of information between the transmitter and the receiver, e.g. vehicle identification, frequency, required power, payment information. Thus, it is essential to ensure that the electromagnetic interference, generated by the wireless power transfer system will not influence or disrupt the communication between the transmitter and the receiver.

Hybrid PV-UPS system with multilevel structure of power converters and reliability improvment

Abstract: This paper presents a new configuration for an uninterruptible power system (UPS) with the integration of a photovoltaic system (PV. Currently, the safest way to supply energy to critical equipment or data processing system is still the use of an online UPS. On other hand, normally it is not required to use the same security for a PV system. This work proposes the integration of these two systems resulting not only in the improvement of the PV system reliability but also of the UPS system. This integration will also result in a multilevel structure for the electronic power converter systems with the inherent advantages of this structure. A control system for the proposed structure will also be presented. Several simulation results will be presented to verify the operation of this hybrid system.

Study of the HVDC dual transmission system under faults in the power converters

Abstract: HVDC transmission systems based on voltage source converters have lately emerged as a good alternative to conventional AC transmission. In these transmission systems multilevel converters have become a promising energy conversion technology. The reliability of the power converters are extremely important since a fault in these equipments may lead to an unavailability for a long period of the transmission system. Thus, this paper will focuses in HVDC dual transmission system under semiconductor failure conditions. As presented in this paper this structure presents interesting characteristics under the point of view the reliability considering a power semiconductor failure. It will present the consequences for the transmission system when there is a semiconductor fault. A study for the change of the modulation system in order to ensure DC link capacitors voltage balance under a fault condition is also presented. Simulation studies are shown in order to confirm the characteristics of the proposed methodology in normal and fault condition mode.

Impact of photovoltaic systems with ancillary services in low voltage grids

Abstract: Photovoltaic systems (PV) are now playing an important role in low voltage (LV) grids. Due to this there are impacts in these grids that previously were not expected. Usually these systems are connected to the grid with the goal of transferring the maximum power generated by the solar panel to the grid. However, the power inverter can be controlled in order to also provide ancillary services (AS). In this context this paper presents a study of the impact of PV with AS in LV grids. In this study it will be proposed the injection of the active power in an unbalanced way, taking into consideration the characteristics of the grid. It will also be considered the PV plants providing a reactive power AS. The impact of these AS in a LV grid will be analyzed.

A grid-connected PV system based on a four wire dual-buck inverter with ancillary services support

Abstract: This paper presents a four wire dual-buck inverter integrated in a photovoltaic system with grid support capabilities. In the context of smart-grids this kind of systems can play an important role. In this particular case the system will supply the ancillary services for unbalanced loads and reactive power compensation. A dual-buck inverter is adopted in order to ensure a higher reliability. This kind of inverter is characterized by the non-existence of shoot-through problems and by the possibility of the using power MOSFETs as active switches. The control system for the dual-buck inverter with the ancillary service functions is also presented. In order to verify the performance of this system several simulation results are presented and discussed.

Bidirectional DC-DC converter with high voltage gain for the charge/discharge control of storage systems

Abstract: This paper presents a study of a bidirectional dc-dc converter with high voltage gain to regulate the charge and discharge of electrochemical storage systems. The converter is characterized by quadratic voltage gain characteristics in both directions. In this context it can be used to regulate a dc interface between the storage system and a dc/ac converter connected to the electrical grid. It will be analysed the converter in ideal and non-ideal conditions. A control system to regulate the output voltages and currents are also proposed. Simulation results are presented in order to validate the control system associated to the converter for the charge/discharge of the storage system.

Impact of Self-consumption and Storage in Low Voltage Distribution Networks: An Economic Outlook

Abstract: A paradigm shift is taking place in Low Voltage (LV) distribution networks, motivated by progressive implementation of renewable micro-generation (µG), mainly Photovoltaic (PV), near household consumers. The concept of self-consumption linked to battery storage is emerging as a way to enhance the quality of electrical network. Smart-Grid (SG) environment comes close to this approach and may have a crucial relevance on management of intelligent power distribution networks, in the framework of a Smart Environment. This paper proposes an additional contribution on the subject by investigating the economic profitability of PV battery systems being analyzed with respect to its impact and economic feasibility, taking into consideration their initial investment and operation costs. The purpose is to verify if prosumer’s investment is financially more interesting than purchasing all electricity needed for consumption from the LV grid. The results of the performed economic analysis show that self-consumption with storage is a potential solution.

A computer based system for the teaching of fault diagnosis in power electronic inverters

Abstract: Voltage source inverters are essential systems in many applications. Thus, the diagnosis of the faults that could appear in these systems allows detecting, isolating, and identifying the faults. In this context the teaching of this subject is becoming very important. However, laboratory experience is fundamental in order to provide a real understanding of this subject. This paper presents a computer based system to provide practical experience in diagnosis of voltage source inverters. This system is composed by a computer that is connected to a voltage source inverter. A Matlab program was developed to impose several types of faults in the inverter. Through the analysis of the current and/or voltage waveforms students must identify the different fault types.