Power Electronics Applications in Renewable Energy Systems

The renewable generation system is currently experiencing rapid growth in various power grids. The stability and dynamic response issues of power grids are receiving attention due to the increase in power electronics-based renewable energy. The main focus of this Special Issue is to provide solutions for power system planning and operation. Power electronics-based devices can offer new ancillary services to several industrial sectors. In order to fully include the capability of power conversion systems in the network integration of renewable generators, several studies should be carried out, including detailed studies of switching circuits, and comprehensive operating strategies for numerous devices, consisting of large-scale renewable generation clusters

Modeling and Optimal Operation of Hydraulic, Wind and Photovoltaic Power Generation Systems

The transition to 100% renewable energy in the future is one of the most important ways of achieving "carbon peaking and carbon neutrality" and of reducing the adverse effects of climate change. In this process, the safe, stable and economical operation of renewable energy generation systems, represented by hydro-, wind and solar power, is particularly important, and has naturally become a key concern for researchers and engineers. Therefore, this book focuses on the fundamental and applied research on the modeling, control, monitoring and diagnosis of renewable energy generation systems, especially hydropower energy systems, and aims to provide some theoretical reference for researchers, power generation departments or government agencies

Low-Cost Inventions and Patents

Inventions have led to the technological advances of mankind. There are inventions of all kinds, some of which have lasted hundreds of years or even longer. Low-cost technologies are expected to be easy to build, have little or no energy consumption, and be easy to maintain and operate. The use of sustainable technologies is essential in order to move towards a greater global coverage of technology, and therefore to improve human quality of life. Low-cost products always respond to a specific need, even if no in-depth analysis of the situation or possible solutions has been carried out. It is a consensus in all industrialized countries that patents have a decisive influence on the organization of the economy, as they are a key element in promoting technological innovation. Patents must aim to promote the technological development of countries, starting from their industrial situations

Stability Analysis of Converter Control Strategies for Power Electronics-Dominated Power Systems

The electric power system, whose well-established structure consolidated over decades of studies is composed of large centralized generating units, transmission systems, and distributed loads, is currently experiencing a significant transformation, posing new challenges for its safe operation in the near future. The increasing amount of grid-connected power electronics-based converters associated with renewable energy sources, is reducing the amount of energy produced by means of conventional generating units, generally represented by large synchronous machines (SMs) directly connected to the grid. As a consequence, declining system inertia, as well as reduced fault currents affecting short-circuit level and retained voltage under fault conditions, are expected. This has caused concerns among system operators (SOs) worldwide about the stability of the future power system, triggering discussions in different countries about the need for new converter control strategies, which would allow safe system operation under the expected grid configuration. In this scenario, the concept of ”grid-forming (GFM) converters” has been recently proposed as a possible solution allowing high-penetration of power electronics-based generation. Initially introduced in the context of microgrids, the concept of GFM converters needs to be reviewed for applications in wide interconnected systems. Indeed, at the present time, a well-established formulation is still missing in the literature, and several committees worldwide are currently working on a definition for identifying the characteristics of such converters. Due to the initial concern of SOs related to declining system inertia, the concept of GFM converters has been often associated with the idea of virtual inertia, and namely the emulation of a synthetic inertial response by means of a power electronics-based converter. Yet, this is only one aspect related to the increase of power electronics-based generation, and the concept of a GFM converter includes other features, which, however, need to be properly specified in order to provide clear guidelines for manufacturers aiming to the development of suitable converter control strategies. This thesis addresses the topic of GFM converters from a control perspective, and aims to characterize potential features, as well as the relevant issues related to this technology. First, the characteristics of a GFM converter are identified according to an extensive literature overview, so that by reviewing international practice on this technology, a general formulation for a GFM converter control structure is identified. Particular emphasis is given to the synchronization principle adopted by the converter which, contrary to state-of-the-art grid-connected converters adopting a dedicated unit for grid synchronization purposes, is generally achieved in a GFM converter by reproducing the power-synchronization mechanism of a SM. An extensive small-signal stability analysis is performed in order to identify the implications of the identified converter behaviour on converter stability, as well as the effects due to the interactions between converters operating nearby. Finally, potential issues related to the implementation of a GFM converter are highlighted, and possible solutions are proposed, whose effectiveness is validated by means of hardware-in-the-loop (HIL) simulations, as well as experimental tests in a laboratory environment, by adopting power-HIL (PHIL) test benches

Benelux meeting on systems and control, 23rd, March 17-19, 2004, Helvoirt, The Netherlands

Book of abstract

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

Control of AC/DC microgrids with renewables in the context of smart grids including ancillary services and electric mobility

Microgrids are a very good solution for current problems raised by the constant growth of load demand and high penetration of renewable energy sources, that results in grid modernization through “Smart-Grids” concept. The impact of distributed energy sources based on power electronics is an important concern for power systems, where natural frequency regulation for the system is hindered because of inertia reduction. In this context, Direct Current (DC) grids are considered a relevant solution, since the DC nature of power electronic devices bring technological and economical advantages compared to Alternative Current (AC). The thesis proposes the design and control of a hybrid AC/DC Microgrid to integrate different renewable sources, including solar power and braking energy recovery from trains, to energy storage systems as batteries and supercapacitors and to loads like electric vehicles or another grids (either AC or DC), for reliable operation and stability. The stabilization of the Microgrid buses’ voltages and the provision of ancillary services is assured by the proposed control strategy, where a rigorous stability study is made. A low-level distributed nonlinear controller, based on “System-of-Systems” approach is developed for proper operation of the whole Microgrid. A supercapacitor is applied to deal with transients, balancing the DC bus of the Microgrid and absorbing the energy injected by intermittent and possibly strong energy sources as energy recovery from the braking of trains and subways, while the battery realizes the power flow in long term. Dynamical feedback control based on singular perturbation analysis is developed for supercapacitor and train. A Lyapunov function is built considering the interconnected devices of the Microgrid to ensure the stability of the whole system. Simulations highlight the performance of the proposed control with parametric robustness tests and a comparison with traditional linear controller. The Virtual Synchronous Machine (VSM) approach is implemented in the Microgrid for power sharing and frequency stability improvement. An adaptive virtual inertia is proposed, then the inertia constant becomes a system’s state variable that can be designed to improve frequency stability and inertial support, where stability analysis is carried out. Therefore, the VSM is the link between DC and AC side of the Microgrid, regarding the available power in DC grid, applied for ancillary services in the AC Microgrid. Simulation results show the effectiveness of the proposed adaptive inertia, where a comparison with droop and standard control techniques is conducted.As Microrredes são uma ótima solução para os problemas atuais gerados pelo constante crescimento da demanda de carga e alta penetração de fontes de energia renováveis, que resulta na modernização da rede através do conceito “Smart-Grids”. O impacto das fontes de energia distribuídas baseados em eletrônica de potência é uma preocupação importante para o sistemas de potência, onde a regulação natural da frequência do sistema é prejudicada devido à redução da inércia. Nesse contexto, as redes de corrente contínua (CC) são consideradas um progresso, já que a natureza CC dos dispositivos eletrônicos traz vantagens tecnológicas e econômicas em comparação com a corrente alternada (CA). A tese propõe o controle de uma Microrrede híbrida CA/CC para integrar diferentes fontes renováveis, incluindo geração solar e frenagem regenerativa de trens, sistemas de armazenamento de energia como baterias e supercapacitores e cargas como veículos elétricos ou outras (CA ou CC) para confiabilidade da operação e estabilidade. A regulação das tensões dos barramentos da Microrrede e a prestação de serviços anciliares são garantidas pela estratégia de controle proposta, onde é realizado um rigoroso estudo de estabilidade. Um controlador não linear distribuído de baixo nível, baseado na abordagem “System-of-Systems”, é desenvolvido para a operação adequada de toda a rede elétrica. Um supercapacitor é aplicado para lidar com os transitórios, equilibrando o barramento CC da Microrrede, absorvendo a energia injetada por fontes de energia intermitentes e possivelmente fortes como recuperação de energia da frenagem de trens e metrôs, enquanto a bateria realiza o fluxo de potência a longo prazo. O controle por dynamical feedback baseado numa análise de singular perturbation é desenvolvido para o supercapacitor e o trem. Funções de Lyapunov são construídas considerando os dispositivos interconectados da Microrrede para garantir a estabilidade de todo o sistema. As simulações destacam o desempenho do controle proposto com testes de robustez paramétricos e uma comparação com o controlador linear tradicional. O esquema de máquina síncrona virtual (VSM) é implementado na Microrrede para compartilhamento de potência e melhoria da estabilidade de frequência. Então é proposto o uso de inércia virtual adaptativa, no qual a constante de inércia se torna variável de estado do sistema, projetada para melhorar a estabilidade da frequência e prover suporte inercial. Portanto, o VSM realiza a conexão entre lado CC e CA da Microrrede, onde a energia disponível na rede CC é usada para prestar serviços anciliares no lado CA da Microrrede. Os resultados da simulação mostram a eficácia da inércia adaptativa proposta, sendo realizada uma comparação entre o controle droop e outras técnicas de controle convencionais