Evaluation of two fundamental positive-sequence detectors for highly distorted and unbalanced systems

This paper presents an evaluation of the performance of two different Positive-Sequence Detectors. This evaluation is made by comparing a PLL (Phase-Locked- Loop), combined with Lagrange Multipliers Method, with an Adaptive Filter. Both algorithms aim to detect the positive sequence at the fundamental frequency on a given three-phase system voltages or currents. The purpose of this evaluation is to assess the better Positive-Sequence Detector for custom power devices, such as Active Power Filters. The comparative analysis was based on the evaluation of a series of steady state performance arameters (phase and amplitude errors, THD and unbalance) and on the response time. The tests were made to study the behavior of both approaches when working with highly distorted and unbalanced signals. This work was carried out using the computer simulation tool PSCAD/EMTDC.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/EEA-EEL/104569/2008.FEDER Funds - Operational Programme for Competitiveness Factors – COMPET

Single phase NPC inverter controller with Integrated MPPT for PV grid connection

This paper presents a single-stage three-level Neutral Point Clamped (NPC) inverter for connection to the electrical power grid, with integrated Maximum Power Point Tracking (MPPT) algorithm to extract the maximum power available from solar photovoltaic (PV) panels. This single-stage topology is more compact than the traditional topology, it was chosen because with the proper control strategy. It is suitable to connect the PV panels to the power grid. The paper describes the design of a 5 kW NPC inverter for the interface of PV panels with the power grid, presenting the circuit parameters and the description of the control algorithms. A phase locked loop control is used to connect the inverter into the grid. Then, a proposed DC Link voltage control to regulate the input voltage of the inverter. Although an MPPT algorithm was used to optimize the energy extraction and the system efficiency. Inverter Output Current control to produce an output current (current injected in the power grid) with low Total Harmonic Distortion (THD) implemented in a DSP. Simulation and experimental results verify the correct operation of the proposed system, even with fluctuations in the solar radiation.info:eu-repo/semantics/publishedVersio

Simulations of a Current-Source Shunt Active Power Filter with Carrier-Based PWM and Periodic Sampling modulation techniques

Bruno Exposto, Helder Carneiro, J. G. Pinto, Carlos Couto, João L. Afonso, "Simulations of a current-source Shunt Active Power Filter with Carrier-Based PWM and Periodic Sampling Modulation Techniques" Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011), pp.1-8, 30 Aug. – 1 Sept., 2011.This paper presents a Shunt Active Power Filter that is built using a current-source inverter. The control of the Active Filter relies in the p-q Theory with the “Sinusoidal Currents at Source” algorithm implemented. The Active Power Filter was simulated using two modulation techniques: Periodic Sampling and Carrier-Based Pulse Width Modulation (CBPWM). To assess the performance of the Active Filter, the simulations were made using two different loads. The first load was a RL balanced load. The second was a non-linear load, namely a full bridge rectifier with a RL load in the DC side. These loads allowed determining the performance of the Active Filter when compensating current harmonics and power factor, using the two modulation techniques.This work is financed by FEDER Funds, through the Operational Programme for Competitiveness Factors – COMPETE, and by National Funds through FCT – Foundation for Science and Technology of Portugal, under the project PTDC/EEA-EEL/104569/2008

Improved vehicle-to-home (iV2H) operation mode: experimental analysis of the electric vehicle as off-line UPS

This paper presents experimental results of electric vehicle (EV) operation as an off-line uninterruptible power supply (UPS). Besides the traditional grid-to-vehicle and vehicle-to-grid modes, this paper presents an improved vehicle-to-home operation mode. This new operation mode consists of the detection of a power outage in the power grid and the change of the EV battery charger control to operate as an off-line UPS. When the power grid voltage is restored, the voltage produced by the on-board EV battery charger is slowly synchronized with the power grid voltage before a complete transition to the normal mode. This paper presents results of two algorithms to detect a power outage: the root mean square (rms) calculation method based on half-cycle of the power grid voltage, and the rms estimation based on a Kalman filter. The experimental results were obtained in steady and transient state considering two cases with the EV plugged in at home:when charging the batteries and without charging the batteries. This paper describes the EV battery charger, the power outage detection methods, and the voltage and current control strategies.- This work was supported by the Fundacao para a Ciencia e Tecnologia (FCT) in the scope of the projects under Grant PEst-UID/CEC/00319/2013. The work of V. Monteiro was supported by the Doctoral Scholarship through the Portuguese FCT Agency under Grant SFRH/BD/80155/2011. The work of B. Exposto was supported by the Doctoral Scholarship through the Portuguese FCT Agency under Grant SFRH/BD/87999/2012.info:eu-repo/semantics/publishedVersio

Three phase four wire shunt active power filter from theory to industrial facility tests

Non-linear loads are very common in present industrial facilities, office buildings and even in our homes. This loads present several Power Quality problems to the electrical grid. The conventional solutions do not solve these problems in a suitable way. Therefore, it is necessary to find new solutions such as Active Power Filters. This paper presents and discusses the main steps that are necessary to implement a Three Phase Four Wire Shunt Active Power Filter from theory to field tests. Therefore it is a contribution on several topics. Starting with the main control theories used on this topology, it explains the p-q Theory in a more detailed way. It also gives a brief presentation of some modulation techniques. There are presented computational simulation results and field tests results of the developed filter operating in an industrial facility.Fundação para a Ciência e a Tecnologia (FCT

Single-phase series active conditioner active power flow in a harmonic free electrical system during sag and swell events

This paper presents a Single-Phase Active Conditioner, which primal function is regulate load voltage, thus protecting the most sensitive loads from sags, swells, flicker and voltage harmonics. It is constituted by two back-to-back H-bridge converters. One regulates load voltage, the other DC-link voltage. This paper will focus essentially on the active power flow during sag and swell events, in a harmonic free Electrical System. It is shown that, ideally, during a sag or swell event, the active power consumed from the AC mains, is the same that is delivered to the load. It also shows how this is achieved, by analyzing the working principle of the Single-Phase Series Active Converter, and, particularly, the crucial action of the DC link capacitor. The control strategy of the proposed custom power device is also presented in a brief form, for contextualization with the operating principle for the compensation of voltage variation events. Simulation results are presented, showing transient and steady state waveforms of the Single-phase Series Active Conditioner with a purely resistive load. The controller of Series Active Conditioner was implemented on a TMS320F2812F from Texas Instruments. Experimental results are also presented, and for better understanding of the active power flow in the Single-Phase Series Active Conditioner, the implemented electrical system has only a resistive load.Fundação para a Ciência e a Tecnologia (FCT

Transformerless series active power filter to compensate voltage disturbances

This paper presents a transformerless topology of series active power filter with capability to protect sensitive loads against harmonics, sags, swells and unbalances of the power system voltages. The proposed topology is constituted by three isolated H-bridge with a voltage source at the DC side. The series active power filter has been studied with the help of PSIM (Power Simulation software) and simulation results are presented. A laboratory prototype is under development and experimental results are shown.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/EEA-EEL/104569/200

Renewable energy system for an isolated sustainable social centre

This paper describes the development of the power converters and control algorithms to implement an isolated microgrid based in renewable energy sources used to feed a Sustainable Social Centre in a remote place. The microgrid is designed to work with photovoltaic panels, micro wind and micro-hydro turbines, or even with diesel generators. The control system of the power converters is totally digital and implemented by means of a TMS320f28335 Digital Signal Controller (DSC) from Texas Instruments. One of the most im-portant requirements imposed for the microgrid power system is the capability of providing a sinusoidal supply voltage with low harmonic distortion even in the presence of non linear electrical loads. The hardware topologies and the digital control systems of the power converters are evaluated through experimental results obtained with a developed laboratory prototype. This work is focused in the DC AC converter of the renewable energy system for the isolated Sustainable Centre.(undefined

Comprehensive comparison of a current-source and a voltage-source converter for three-phase EV fast battery chargers

This paper presents a comprehensive comparison of a current-source converter and a voltage-source converter for three-phase electric vehicle (EV) fast battery chargers. Taking into account that the current-source converter (CSC) is a natural buck-type converter, the output voltage can assume a wide range of values, which varies between zero and the maximum instantaneous value of the power grid phase-to-phase voltage. On the other hand, taking into account that the voltage-source converter (VSC) is a natural boost-type converter, the output voltage is always greater than the maximum instantaneous value of the power grid phase-to-phase voltage, and consequently, it is necessary to use a dc-dc buck-type converter for applications as EV fast battery chargers. Along the paper is described in detail the principle of operation of both the CSC and the VSC for EV fast chargers, as well as the main equations of the power theory and current control strategies. The comparison between both converters is mainly established in terms of the total harmonic distortion of the grid current and the estimated efficiency for a range of operation between 10 kW and 50 kW

Experimental and simulation results of a current-source three-phase shunt active power filter using periodic-sampling

In this paper are presented experimental and simulation results of a Current-Source Three-Phase Shunt Active Power Filter, during its operation to compensate the currents a low power factor load and a nonlinear load. The Shunt Active Power Filter controller, described in detail along the paper, relies in the p-q Theory to generate the reference compensation currents and to regulate the DC-link inductor current. The regulation of the DC-link inductor current is done consuming sinusoidal currents in phase with the system voltages. The performance and the dynamic behavior of the Shunt Active Power Filter using Periodic Sampling Modulation Technique was assessed first through several computer simulations, and then through the analysis of experimental results obtained with a developed laboratory prototype. Thereby, in this paper are presented several obtained results that show the correct operation of a Current-Source Three-Phase Shunt Active Power Filter using the Periodic Sampling Modulation Technique.Fundação para a Ciência e a Tecnologia (FCT