Implementation of solar photovoltaic array and battery powered enhanced DC-DC converter using B4-inverter fed brushless DC motor drive system for agricultural water pumping applications

The proposed research involves, an implementation of solar photovoltaic array and battery powered enhanced dc-dc converter using B4-inverter fed brushless dc motor drive system for agricultural water pumping applications. It consists of step up and step-down converter, DC-link module. DC-link switching is achieved by reduced ripple voltage which results in improved quality of obtained output power. The Three Port Converter has been proposed and operated in unidirectional and/or bidirectional way simultaneously, for achieving an inherent dual voltage and power flow control. Switch count makes the system more cost effective. An excellent tracking performance under dynamic condition with negligible oscillations around optimum operating point is achieved. Optimally selecting the initial value of duty ratio and its perturbation size offer soft starting of BLDC motor by slowly increasing the DC-link voltage of VSI. A simulation model of solar photovoltaic array and battery powered enhanced DC-DC converter is developed and its performance is analysed for various operating conditions

Experimental evaluation of Kalman filter based MPPT in grid-connected PV system

Mestrado de dupla diplomação com a Ecóle Supérieur en Sciences ApliquéesPhotovoltaic (PV) energy is becoming an important alternative energy source, since it is abundant in nature, non-polluting and requires low maintenance. However, it suffers from low energy conversion efficiency, which can be even lower if the photovoltaic generator does not operate around a so-called Maximum Power Point (MPP). Tracking this point, which changes its location depending on weather conditions, is a very important step in the design of a photovoltaic system. Several techniques have been investigated in the literature in the MPP context. However, some techniques such as the Kalman filter are steel unknown with a lack of information in real test conditions, since their evaluation is limited only in simulation and literature review. This work presents an experimental evaluation of the Kalman filter based on a comparison with two well-known maximum power point tracking (MPPT) algorithms, which are the Perturbation and observation (among the simplest techniques) and the Particle Swarm Optimization (among the most complex techniques). The experimental tests were carried out under real atmospheric conditions, using Matlab/Simulink and the 1103 dSPACE real-time controller board. The results show that the Kalman filter has a higher aptitude to operate closer to the MPP, with a low oscillation in steady-state compared to the other MPPT evaluated in this work. However, the technique’s flaw lies in the shadow situation where it can not differentiate between the local and global optimums, unlike the particle swarm optimization.A energia fotovoltaica (PV) está a tornar-se uma importante fonte de energia alternativa, uma vez que é abundante na natureza, não poluente, e requer pouca manutenção. No entanto, sofre de uma baixa eficiência de conversão energética, que pode ser ainda mais baixa se o gerador PV não operar em torno do chamado Ponto de Potência Máxima (MPP). O rastreio deste ponto, que muda a sua localização dependendo das condições meteorológicas, é um passo muito importante na concepção de um sistema PV. Várias técnicas têm sido investigadas na literatura no contexto do MPP. No entanto, o desempenho de algumas técnicas, como o filtro Kalman, em condições reais de teste, ainda desconhecido, ou existe pouca informação, uma vez que a sua avaliação é limitada apenas na simulação e revisão da literatura. Este trabalho apresenta uma avaliação experimental do filtro de Kalman com base numa comparação com dois seguidores de ponto de potência máxima (MPPT) bem conhecidos, que são a Perturbação e observação e a Optimização do Enxame de Partículas. Os testes experimentais foram realizados em condições atmosféricas reais, utilizando o Matlab/Simulink e a carta de controlo em tempo real dSPACE. Os resultados mostram que o filtro de Kalman tem uma maior aptidão para operar mais perto do MPP, com uma baixa oscilação em regime permenente, comparativemente com os outros algoritmos MPPT avaliados neste trabalho. No entanto, a desvantagem ocorre aquando da ocorãncia de sombra, onde a técnica não consegue diferenciar entre os óptimos locais e global, ao contrário da optimização do enxame de partículas. Palavras-chave: Fotovoltaico (PV), Seguimento do Ponto de Potência Máxima (MPPT), Perturbação e Observação (PO), Optimização de enxame de partículas (PSO), Filtro de Kalman (KF), Sistema PV ligado à Rede, dSPACE 1103

CONTROL STRATEGIES OF DC MICROGRID TO ENABLE A MORE WIDE-SCALE ADOPTION

Microgrids are gaining popularity in part for their ability to support increased penetration of distributed renewable energy sources, aiming to meet energy demand and overcome global warming concerns. DC microgrid, though appears promising, introduces many challenges in the design of control systems in order to ensure a reliable, secure and economical operation. To enable a wider adoption of DC microgrid, this dissertation examines to combine the characteristics and advantages of model predictive control (MPC) and distributed droop control into a hierarchy and fully autonomous control of the DC microgrid. In addition, new maximum power point tracking technique (MPPT) for solar power and active power decoupling technique for the inverter are presented to improve the efficiency and reliability of the DC microgrid. With the purpose of eliminating the oscillation around the maximum power point (MPP), an improved MPPT technique was proposed by adding a steady state MPP determination algorithm after the adaptive perturb and observe method. This control method is proved independent with the environmental conditions and has much smaller oscillations around the MPP compared to existing ones. Therefore, it helps increase the energy harvest efficiency of the DC microgrid with less continuous DC power ripple. A novel hierarchy strategy consisting of two control loops is proposed to the DC microgrid in study, which is composed of two PV boost converters, two battery bi-directional converters and one multi-level packed-u-cell inverter with grid connected. The primary loop task is the control of each energy unit in the DC microgrid based on model predictive current control. Compared with traditional PI controllers, MPC speeds up the control loop since it predicts error before the switching signal is applied to the converter. It is also free of tuning through the minimization of a flexible user-defined cost function. Thus, the proposed primary loop enables the system to be expandable by adding additional energy generation units without affecting the existing ones. Moreover, the maximum power point tracking and battery energy management of each energy unit are included in this loop. The proposed MPC also achieves unity power factor, low grid current total harmonics distortion. The secondary loop based on the proposed autonomous droop control identifies the operation modes for each converter: current source converter (CSC) or voltage source converter (VSC). To reduce the dependence on the high bandwidth communication line, the DC bus voltage is utilized as the trigger signal to the change of operation modes. With the sacrifice of small variations of bus voltage, a fully autonomous control can be realized. The proposed distributed droop control of different unit converters also eliminates the potential conflicts when more than two converters compete for the VSC mode. Single-phase inverter systems in the DC microgrid have low frequency power ripple, which adversely affects the system reliability and performance. A power decoupling circuit based on the proposed dual buck converters are proposed to address the challenges. The topology is free of shoot-through and deadtime concern and the control is independent with that of the main power stage circuit, which makes the design simpler and more reliable. Moreover, the design of both PI and MPC controllers are discussed and compared. While, both methods present satisfied decoupling performances on the system, the proposed MPC is simpler to be implemented. In conclusion, the DC microgrid may be more widely adopted in the future with the proposed control strategies to address the current challenges that hinder its further development

Three-port DC-DC converter for stand-alone photovoltaic systems

System efficiency and cost effectiveness are of critical importance for photovoltaic (PV) systems. This paper addresses the two issues by developing a novel three-port dc-dc converter for stand-alone PV systems, based on an improved Flyback-Forward topology. It provides a compact single-unit solution with a combined feature of optimized maximum power point tracking (MPPT), high step-up ratio, galvanic isolation, and multiple operating modes for domestic and aerospace applications. A theoretical analysis is conducted to analyze the operating modes followed by simulation and experimental work. This paper is focused on a comprehensive modulation strategy utilizing both PWM and phase-shifted control that satisfies the requirement of PV power systems to achieve MPPT and output voltage regulation. A 250-W converter was designed and prototyped to provide experimental verification in term of system integration and high conversion efficiency

Investigations on performance enhancement measures of the bidirectional converter in PV–wind interconnected microgrid system

This is the final version. Available from MDPI via the DOI in this record. In this work, a hybrid microgrid framework was created with the assistance of a photovoltaic (PV) and wind turbine (WT) generator. Additionally, bidirectional control mechanisms were implemented where an AC system was integrated with permanent magnet synchronous generator (PMSG)-based WT and a DC system was integrated with a sliding mode algorithm controlled maximum power point tracker (MPPT)-integrated PV system. The wind and PV interconnected microgrid system was mathematically modeled for steady-state conditions. This hybrid microgrid model was simulated using the MATLAB/SIMULINK platform. Optimal load management strategy was performed on a chosen hybrid microgrid system. Various case studies pertaining to connection and disconnection of sources and loads were performed on the test system. The outcomes establish that the system can be kept up in a steady-state condition under the recommended control plans when the network is changed, starting with one working condition then onto the next

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

Bidirectional Electric Vehicles Service Integration in Smart Power Grid with Renewable Energy Resources

As electric vehicles (EVs) become more popular, the utility companies are forced to increase power generations in the grid. However, these EVs are capable of providing power to the grid to deliver different grid ancillary services in a concept known as vehicle-to-grid (V2G) and grid-to-vehicle (G2V), in which the EV can serve as a load or source at the same time. These services can provide more benefits when they are integrated with Photovoltaic (PV) generation. The proper modeling, design and control for the power conversion systems that provide the optimum integration among the EVs, PV generations and grid are investigated in this thesis. The coupling between the PV generation and integration bus is accomplished through a unidirectional converter. Precise dynamic and small-signal models for the grid-connected PV power system are developed and utilized to predict the system’s performance during the different operating conditions. An advanced intelligent maximum power point tracker based on fuzzy logic control is developed and designed using a mix between the analytical model and genetic algorithm optimization. The EV is connected to the integration bus through a bidirectional inductive wireless power transfer system (BIWPTS), which allows the EV to be charged and discharged wirelessly during the long-term parking, transient stops and movement. Accurate analytical and physics-based models for the BIWPTS are developed and utilized to forecast its performance, and novel practical limitations for the active and reactive power-flow during G2V and V2G operations are stated. A comparative and assessment analysis for the different compensation topologies in the symmetrical BIWPTS was performed based on analytical, simulation and experimental data. Also, a magnetic design optimization for the double-D power pad based on finite-element analysis is achieved. The nonlinearities in the BIWPTS due to the magnetic material and the high-frequency components are investigated rely on a physics-based co-simulation platform. Also, a novel two-layer predictive power-flow controller that manages the bidirectional power-flow between the EV and grid is developed, implemented and tested. In addition, the feasibility of deploying the quasi-dynamic wireless power transfer technology on the road to charge the EV during the transient stops at the traffic signals is proven