Survey on Photo-Voltaic Powered Interleaved Converter System

Renewable energy is the best solution to meet the growing demand for energy in the country. The solar energy is considered as the most promising energy by the researchers due to its abundant availability, eco-friendly nature, long lasting nature, wide range of application and above all it is a maintenance free system. The energy absorbed by the earth can satisfy 15000 times of today’s total energy demand and its hundred times more than that our conventional energy like coal and other fossil fuels. Though, there are overwhelming advantages in solar energy, It has few drawbacks as well such as its low conversion ratio, inconsistent supply of energy due to variation in the sun light, less efficiency due to ripples in the converter, time dependent and, above all, high capitation cost. These aforementioned flaws have been addressed by the researchers in order to extract maximum energy and attain hundred percentage benefits of this heavenly resource. So, this chapter presents a comprehensive investigation based on photo voltaic (PV) system requirements with the following constraints such as system efficiency, system gain, dynamic response, switching losses are investigated. The overview exhibits and identifies the requirements of a best PV power generation system

Design and Implementation of Control Techniques of Power Electronic Interfaces for Photovoltaic Power Systems

The aim of this thesis is to scrutinize and develop four state-of-the-art power electronics converter control techniques utilized in various photovoltaic (PV) power conversion schemes accounting for maximum power extraction and efficiency. First, Cascade Proportional and Integral (PI) Controller-Based Robust Model Reference Adaptive Control (MRAC) of a DC-DC boost converter has been designed and investigated. Non-minimum phase behaviour of the boost converter due to right half plane zero constitutes a challenge and its non-linear dynamics complicate the control process while operating in continuous conduction mode (CCM). The proposed control scheme efficiently resolved complications and challenges by using features of cascade PI control loop in combination with properties of MRAC. The accuracy of the proposed control system’s ability to track the desired signals and regulate the plant process variables in the most beneficial and optimised way without delay and overshoot is verified. The experimental results and analysis reveal that the proposed control strategy enhanced the tracking speed two times with considerably improved disturbance rejection. Second, (P)roportional Gain (R)esonant and Gain Scheduled (P)roportional (PR-P) Controller has been designed and investigated. The aim of this controller is to create a variable perturbation size real-time adaptive perturb and observe (P&O) maximum power point tracking (MPPT) algorithm. The proposed control scheme resolved the drawbacks of conventional P&O MPPT method associated with the use of constant perturbation size that leads to a poor transient response and high continuous steady-state oscillations. The prime objective of using the PR-P controller is to utilize inherited properties of the signal produced by the controller’s resonant path and integrate it to update best estimated perturbation that represents the working principle of extremum seeking control (ESC) to use in a P&O algorithm that characterizes the overall system learning-based real time adaptive (RTA). Additionally, utilization of internal dynamics of the PR-P controller overcome the challenges namely, complexity, computational burden, implantation cost and slow tracking performance in association with commonly used soft computing intelligent systems and adaptive control strategies. The experimental results and analysis reveal that the proposed control strategy enhanced the tracking speed five times with reduced steady-state oscillations around maximum power point (MPP) and more than 99% energy extracting efficiency.Third, the interleaved buck converter based photovoltaic (PV) emulator current control has been investigated. A proportional-resonant-proportional (PR-P) controller is designed to resolve the drawbacks of conventional PI controllers in terms of phase management which means balancing currents evenly between active phases to avoid thermally stressing and provide optimal ripple cancellation in the presence of parameter uncertainties. The proposed controller shows superior performance in terms of 10 times faster-converging transient response, zero steady-state error with significant reduction in current ripple. Equal load sharing that constitutes the primary concern in multi-phase converters has been achieved with the proposed controller. Implementing of robust control theory involving comprehensive time and frequency domain analysis reveals 13% improvement in the robust stability margin and 12-degree bigger phase toleration with the PR-P controller. Fourth, a symmetrical pole placement Method-based Unity Proportional Gain Resonant and Gain Scheduled Proportional (PR-P) Controller has been designed and investigated. The proposed PR-P controller resolved the issues associated with the use of the PI controller which are tracking repeating control input signal with zero steady-state and mitigating the 3rd order harmonic component injected into the grid for single-phase PV systems. Additionally, the PR-P controller has overcome the drawbacks of frequency detuning in the grid and increase in the magnitude of odd number harmonics in the system that constitute the common concerns in the implementation of conventional PR controller. Moreover, the unprecedented design process based on changing notch filter dynamics with symmetrical pole placement around resonant frequency overcomes the limitations that are essentially complexity and dependency on the precisely modelled system. The verification and validation process of the proposed control schemes has been conducted using MATLAB/Simulink and implementing MATLAB/Simulink/State flow on dSPACE Real-time-interface (RTI) 1007 processor, DS2004 High-Speed A/D and CP4002 Timing and Digital I/O boards

Contributions to the efficiency and safety of stand-alone DC microgrids

Currently, the distributed generation based on renewable energy sources is mainly DC. Those DC systems are used diverse applications such as airplanes, automobiles, ships, spaceships, computers, servers, telecommunications stations, among others. This thesis considers an isolated DC microgrid architecture composed of a renewable source, an energy storage system, and a DC load. The thesis is aimed at identifying and solving efficiency and safety problems at the source, the DC bus, and the load. During the development of this Thesis, six contributions to the state-of-the-art of DC microgrids were obtained. The first contribution is the mathematical model of a distributed maximum power point platform formed by multiple module-converter sets connected in series, which can be implemented in different programming languages and deployed on multiple platforms to evaluate optimization strategies. The second contribution is a vectorial MPPT algorithm for a distributed photovoltaic system, based in the perturb and observe algorithm. This algorithm provides a satisfactory trade-off between implementation cost and energy production since it uses a single I/V sensor. The third contribution is a reconfiguration algorithm that optimizes the electrical connections of a commercial photovoltaic array, which enables to maximize the energy extraction under arbitrary shading conditions. The fourth and fifth contributions are two control strategies, based on sliding-modes, designed for a charger/discharger DC/DC converter. Those solutions enable to regulate the voltage on the DC-bus of the microgrid to improve the microgrid safety. One of the strategies considers the current of the DC-bus into the sliding surface, which gives a better performance in terms of overshoot and settling time of the DC bus voltage. The final contribution concerns a control strategy, also based on sliding modes, to regulate a point-of-load DC/DC converter. Such a contribution enables to improve the conversion efficiency, and at the same time, to improve the load safety by reducing the current and voltage ripples delivered by the converter. Finally, those contributions improve the electrical efficiency and operational safety of DC microgrids based on renewable sources. The results obtained in this thesis were published in five journals articles and three communications to conferences. From those, three articles were published in Q1 journals, one article was published in Q3 journal, and another one was published in a Colombian journalResumen: Actualmente, la generación distribuida basada en fuentes de energía renovable es principalmente DC. Estos sistemas DC son utilizados en aviones, automóviles, barcos, naves espaciales, computadores, servidores, estaciones de telecomunicaciones, etc. Esta Tesis considera una arquitectura de microrred DC aislada compuesta por una fuente renovable, un sistema de almacenamiento de energía y una carga DC. La tesis tiene como objetivo identificar y solucionar problemas de eficiencia y seguridad de operación en la fuente, en el bus DC y en la carga. Durante el desarrollo de esta Tesis se obtuvieron seis aportes al estado del arte en microrredes DC. La primera contribución es el modelo matemático de una plataforma de seguimiento del punto de máxima potencia formada por múltiples conjuntos panel-convertidor conectados en serie, el cual se puede implementar en diferentes lenguajes de programación y desplegar en múltiples plataformas para evaluar estrategias de optimización. La segunda contribución es un algoritmo MPPT vectorial para un sistema fotovoltaico distribuido, basado en el algoritmo de perturbar y observar. Este algoritmo proporciona una compensación satisfactoria entre el costo de implementación y la producción de energía, ya que utiliza un solo sensor de I/V. La tercera contribución es un algoritmo de reconfiguración que optimiza las conexiones eléctricas de un arreglo de paneles fotovoltaicos comercial, el cual permite maximizar la extracción de energía bajo condiciones arbitrarias de sombreado. La cuarta y quinta contribución son dos estrategias de control, basadas en modos deslizantes, diseñadas para un convertidor DC/DC cargador/descargador. Estas soluciones permiten regular el voltaje del bus DC de la microrred para mejorar la seguridad de su operación. Una de las estrategias considera la corriente del bus DC en la superficie deslizante, lo cual da un mejor desempeño en cuanto al sobreimpulso y el tiempo de establecimiento del voltaje del bus DC. La contribución final es una estrategia de control, también basada en modos deslizantes, para regular un convertidor DC/DC point-of-load. Esta contribución permite mejorar la eficiencia de la conversión y al mismo tiempo mejorar la seguridad operativa de la carga reduciendo el rizado de voltaje y corriente entregado por el convertidor. Finalmente, estas contribuciones mejoran la eficiencia eléctrica y la seguridad operativa de microrredes DC basadas en fuentes de energía renovable. Los resultados obtenidos en esta Tesis fueron publicados en cinco artículo de revista y tres ponencias en conferencias. De estos, tres artículos fueron publicados en revistas clasificadas en Q1, un artículo fue publicado en una revista con clasificación Q3 y otro en una revista colombianaDoctorad

Design and Control of Power Converters 2019

In this book, 20 papers focused on different fields of power electronics are gathered. Approximately half of the papers are focused on different control issues and techniques, ranging from the computer-aided design of digital compensators to more specific approaches such as fuzzy or sliding control techniques. The rest of the papers are focused on the design of novel topologies. The fields in which these controls and topologies are applied are varied: MMCs, photovoltaic systems, supercapacitors and traction systems, LEDs, wireless power transfer, etc

Advanced Statistical Modeling, Forecasting, and Fault Detection in Renewable Energy Systems

Fault detection, control, and forecasting have a vital role in renewable energy systems (Photovoltaics (PV) and wind turbines (WTs)) to improve their productivity, ef?ciency, and safety, and to avoid expensive maintenance. For instance, the main crucial and challenging issue in solar and wind energy production is the volatility of intermittent power generation due mainly to weather conditions. This fact usually limits the integration of PV systems and WTs into the power grid. Hence, accurately forecasting power generation in PV and WTs is of great importance for daily/hourly efficient management of power grid production, delivery, and storage, as well as for decision-making on the energy market. Also, accurate and prompt fault detection and diagnosis strategies are required to improve efficiencies of renewable energy systems, avoid the high cost of maintenance, and reduce risks of fire hazards, which could affect both personnel and installed equipment. This book intends to provide the reader with advanced statistical modeling, forecasting, and fault detection techniques in renewable energy systems

Power quality improvement utilizing photovoltaic generation connected to a weak grid

Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids and may have been considered as the culprit of poor power quality affecting other loads in particular sensitive loads connected to the same point of common coupling (PCC). This paper is intended to demystify the renewable generation, and turns the negative perception into positive revelation of the superiority of PV generation to the power quality improvement in a microgrid system. The main objective of this work is to develop a control method for the PV inverter so that the power quality at the PCC will be improved under various disturbances. The method is to control the reactive current based on utilizing the grid current to counteract the negative impact of the disturbances. The proposed control method is verified in PSIM platform. Promising results have been obtaine

Design and Development of FPGA based Controllers for Photovoltaic Power System

In the recent years owing to increased energy consumption and consequent rise in crude oil price and global climatic change have motivated researchers to focus towards harnessing power from renewable energy resources such as photovoltaic (PV), fuel cell, biomass and wind energy systems. Among the different renewable resources, PV technology is one of the fastest growing technologies, because of abundance availability of solar irradiance and it has no adverse environmental impacts. But, the cost of PV energy is higher than the other conventional sources owing to its low PV conversion efficiency. Therefore, research opportunities lie in applying power electronics and control techniques for harvesting PV power at higher efficiencies for appropriate utilization. For simulation, analysis and control design of a PV power system, an accurate model of the PV cell is essential because PV cell is the basic bulding block of a PV power system. To maximise the power generation of a PV system it is necessary that the PV array should be operated at the maximum power point. A maximum power point tracker (MPPT) is required in the PV system to enable it to operate at the MPP. The output current-voltage (I-V) and power-voltage (P-V) characteristics of a PV vell are non-linear and hence its power fluctuates in accordance with the variation in solar irradiance and temperature. During the last decade, a lot of research has been directed to develop efficient MPPT schemes. But, research opportunities are still promising for designing new MPPT algorithms and to address their digital implementation issues. Further, there lies challenge to design MPPTs that can handle partial shading conditions. The thesis first proposes development of new MPPT algorithms and different pulse width modulated-voltage source inverter control strategies for a PV system. Firstly an integral sliding mode MPPT controller (ISMC) has been proposed for achieving an effective MPPT scheme, and then a modified P&O MPPT controller is developed which is implemented using a real-time digital simulator called Opal-RT. The performance of the modified ISMC is compared with that of the conventional proportional integral (PI) MPPT controller using both MATLAB simulation and real-time experimentation. The performance of the modified P&O MPPT controller with fixed step size is compared with that of the conventional incremental conductance (Inc Cond) and P&O MPPT controllers, and these are validated by using Opal-RT and subsequently through FPGA implementation. A modified incremental conductance MPPT controller with variable step size is then proposed for handling partial shading conditions. The tracking performance of the proposed modified Inc Cond MPPT controller is also compared with that of the conventional Inc Cond MPPT controller, from the obtained results by using Opal-RT. Further, an experimental prototype PV set-up is developed in the laboratory to implement the proposed MPPT algorithms on the physical hardware. After having developed efficient parameter extraction algorithms for a PV panel, the thesis subsequently proposes five new MPPT algorithms such as Integral sliding mode MPPT, modified P&O MPPT, modified Inc Cond MPPT, Model predictive MPPT, and modified Inc Cond variable step size MPPT controllers. All these developed MPPT algorithms have been implemented on a Solar array simulator (SAS) PV system, in MATLAB/SIMULINK, OPAL-RT and on a prototype hardware PV set-up. From the obtained results, it is found that these MPPTs adjust the power of a PV system effectively to its maximum power value smoothly with fast response and accuracy whilst reducing the fluctuations in its power. Tracking performance of all these proposed MPPT algorithms are found to be superior to some of the existing MPPTs such as perturb and observe (P&O), incremental conductance (INC), HCC and adaptive HCC. Further more, a PV system is observed to be stable with all these proposed MPPTs. From the results obtained it is also confirmed that the proposed modified P&O MPPT exhibits better MPP tracking performance in terms of quick settling time and least steady state error. Further, less voltage fluctuation and less maximum overshoot are observed in the case of the proposed modified Inc Cond MPPT among all the proposed MPPT algorithms. The proposed controllers are also well suited to all weather conditions. A grid connected PV system involves a power conversion from DC power into AC power. Due to high switching frequencies of this conversion by inverter, there is a power loss. An efficient control scheme needs to be developed for integrating the PV system to the grid. The thesis then proposes a Model Predictive Control (MPC) for integrating a PV system to the grid. The performance of the MPC is compared with conventional hysteresis current controller (HCC) and also with that of an adaptive HCC (AHCC) through a real-time simulatin using the Opal-RT then through FPGA implementations. FPGA implementation of the controllers such as HCC, AHCC and MPC were also performed by using LABVIEW configured with NI-cRIO-9014 platform. For elimination of current harmonic and reactive power of the grid connected PV system, there is a need of designing a filter. The PV system based shunt active power filter (SAPF) with modified incremental conductance MPPT controller with variable step size is then designed. From the MATLAB simulation and real-time digital simulation studies it is envisaged that the proposed PV based SAPF exhibits good harmonics compensation

Pem fuel cell modeling and converters design for a 48 v dc power bus

Fuel cells (FC) are electrochemical devices that directly convert the chemical energy of a fuel into electricity. Power systems based on proton exchange membrane fuel cell (PEMFC) technology have been the object of increasing attention in recent years as they appear very promising in both stationary and mobile applications due to their high efficiency, low operating temperature allowing fast startup, high power density, solid electrolyte, long cell and stack life, low corrosion, excellent dynamic response with respect to the other FCs, and nonpolluting emissions to the environment if the hydrogen is obtained from renewable sources. The output-voltage characteristic in a PEMFC is limited by the mechanical devices which are used for regulating the air flow in its cathode, the hydrogen flow in its anode, its inner temperature, and the humidity of the air supplied to it. Usually, the FC time constants are dominated by the fuel delivery system, in particular by the slow dynamics of the compressor responsible for supplying the oxygen. As a consequence, a fast load transient demand could cause a high voltage drop in a short time known as oxygen starvation phenomenon that is harmful for the FC. Thus, FCs are considered as a slow dynamic response equipment with respect to the load transient requirements. Therefore, batteries, ultracapacitors or other auxiliary power sources are needed to support the operation of the FC in order to ensure a fast response to any load power transient. The resulting systems, known as FC hybrid systems, can limit the slope of the current or the power generated by the FC with the use of current-controlled dc-dc converters. In this way, the reactant gas starvation phenomena can be avoided and the system can operate with higher efficiency. The purpose of this thesis is the design of a DC-DC converter suitable to interconnect all the different elements in a PEMFC-hybrid 48-V DC bus. Since the converter could be placed between elements with very different voltage levels, a buck-boost structure has been selected. Especially to fulfill the low ripple requirements of the PEMFCs, but also those of the auxiliary storage elements and loads, our structure has inductors in series at both its input and its output. Magnetically coupling these inductors and adding a damping network to its intermediate capacitor we have designed an easily controllable converter with second-order-buck-like dominant dynamics. This new proposed topology has high efficiency and wide bandwidth acting either as a voltage or as a current regulator. The magnetic coupling allows to control with similar performances the input or the output inductor currents. This characteristic is very useful because the designed current-controlled converter is able to withstand shortcircuits at its output and, when connected to the FC, it facilitates to regulate the current extracted from the FC to avoid the oxygen starvation phenomenon. Testing in a safe way the converter connected to the FC required to build an FC simulator that was subsequently improved by developing an emulator that offered real-time processing and oxygen-starvation indication. To study the developed converters and emulators with different brands of PEMFCs it was necessary to reactivate long-time inactive Palcan FCs. Since the results provided by the manual reactivation procedure were unsatisfactory, an automatic reactivation system has been developed as a complementary study of the thesis.En esta tesis se avanzo en el diseño de un bus DC de 48 V que utiliza como elemento principal de generación de energía eléctrica una pila de combustible. Debido a que la dinámica de las pilas de combustible están limitadas por sus elementos mecánicos auxiliares de control una variación rápida de una carga conectada a ella puede ocasionar daños. Es por esto que es necesario utilizar elementos almacenadores de energía que puedan suministrar estas rápidas variaciones de carga y convertidores para que gestionen de una forma controlada la potencia del bus DC. Durante la realización de pruebas de los convertidores es de gran importancia utilizar emuladores o simuladores de pilas de combustibles, esto nos permite de una forma económica y segura realizar pruebas criticas antes de conectar los convertidores a la pila. Adicionalmente una nueva topologia de convertidor fue presentada y ésta gestionará la potencia en el bu