A Survey on Topologies and Controls of Z-Source Matrix Converter

This paper describes the Z-source matrix converter (ZS-MC) topology which specifically discusses topology and control on the ZS-MC. There are two topologies on the ZS-MC, namely Z-source direct-MC (ZS-DMC) and indirect-MC (ZS-IMC). The difference of each of these topologies is in the number of switching mosfets, where ZS-DMC put on nine switches, while ZS-IMC eighteen switches. ZS-IMC topology overcomes the limitations of traditional MC voltage reinforcement and accommodates the operation of buck and boost converter by reducing the number of switches and providing high efficiency

Machine Learning and Data Mining Applications in Power Systems

This Special Issue was intended as a forum to advance research and apply machine-learning and data-mining methods to facilitate the development of modern electric power systems, grids and devices, and smart grids and protection devices, as well as to develop tools for more accurate and efficient power system analysis. Conventional signal processing is no longer adequate to extract all the relevant information from distorted signals through filtering, estimation, and detection to facilitate decision-making and control actions. Machine learning algorithms, optimization techniques and efficient numerical algorithms, distributed signal processing, machine learning, data-mining statistical signal detection, and estimation may help to solve contemporary challenges in modern power systems. The increased use of digital information and control technology can improve the grid’s reliability, security, and efficiency; the dynamic optimization of grid operations; demand response; the incorporation of demand-side resources and integration of energy-efficient resources; distribution automation; and the integration of smart appliances and consumer devices. Signal processing offers the tools needed to convert measurement data to information, and to transform information into actionable intelligence. This Special Issue includes fifteen articles, authored by international research teams from several countries

PMSG-based wind power integration-modelling and analysis of impacts on the dynamic performances of a power system and mitigation under stochastic wind disturbances.

Doctor of Philosophy in Electrical Engineering. University of KwaZulu-Natal, Durban 2017.Because of the ever-growing demand for electrical energy and environmental challenges of fossil fuel consumption, a priority has been given to the development of wind energy systems, among which, currently, permanent magnet synchronous generator (PMSG)-based wind power is receiving much attention from researchers, engineers, and turbine manufacturers. However, high PMSG-based wind power integration into a power system brings several challenges to transmission system operators. One of the challenges is its impacts on the dynamic performances of a power system due to the presence of stochastic wind disturbances. Thus, for a thorough investigation of the influences of stochastic wind speed disturbances, a proper wind speed model should be adopted. Therefore, this thesis proposes the use of Markov chain model for modelling wind speed series in dynamic simulations of wind turbines. In this regard, comparison of statistical quantities of measured wind speed data from Durban and Markov model generated ones confirms the accuracy of the model adopted. The results have shown that the dynamic performances of a power system deteriorate with the presence of stochastic wind speed disturbances, and thus the need for improving poor dynamic performances. Wind gusts cause stress, over currents, over voltages and instability in a power system. This thesis, therefore, introduces novel mitigation techniques based on virtual controls stemming from real resistors, compensators, and damper windings, and supplementary controllers to enhance the dynamic performances of a wind turbine directdriven PMSG, the main component of a PMSG-based wind farm. In the proposed schemes, the virtual controllers adjust the terminal d- and q-axis reference voltages in the generator side converter controller and their influences on the dynamic performances of the wind turbine are investigated. MATLAB/Simulink simulations on a wind turbine connected to an infinite bus show that virtual controls are effective in enhancing the dynamic performances of the PMSG. Local oscillations caused by wind disturbances are efficiently suppressed. Overall, the proposed mitigation techniques smooth the rotor speed and power of a PMSG, and hence reducing the influences of the stochastic wind speed disturbances. Furthermore, the results have demonstrated that stochastic wind speed disturbances affect the dynamic performances of a power system containing a PMSG-based wind farm as the dynamics of synchronous machines within the system depend on power balance, which is influenced by the power response of the wind farm. Finally, investigations in this thesis have confirmed that virtual controls and FACTS devices such as STATCOM and SVC are efficient in improving the dynamic performances of a power system containing PMSG-based wind farms under stochastic wind disturbances

Intelligent voltage dip mitigation in power networks with distributed generation

Includes bibliographical references.The need for ensuring good power quality (PQ) cannot be over-emphasized in electrical power system operation and management. PQ problem is associated with any electrical distribution and utilization system that experiences any voltage, current or frequency deviation from normal operation. In the current power and energy scenario, voltage-related PQ disturbances like voltage dips are a fact which cannot be eliminated from electrical power systems since electrical faults, and disturbances are stochastic in nature. Voltage dip tends to lead to malfunction or shut down of costly and mandatory equipment and appliances in consumers’ systems causing significant financial losses for domestic, commercial and industrial consumers. It accounts for the disruption of both the performance and operation of sensitive electrical and electronic equipment, which reduces the efficiency and the productivity of power utilities and consumers across the globe. Voltage dips are usually experienced as a result of short duration reduction in the r.m.s. (r.m.s.- root mean square) value of the declared or nominal voltage at the power frequency and is usually followed by recovery of the voltage dip after few seconds. The IEEE recommended practice for monitoring electric power quality (IEEE Std. 1159-2009, revised version of June 2009), provides definitions to label an r.m.s. voltage disturbance based upon its duration and voltage magnitude. These disturbances can be classified into transient events such as voltage dips, swells and spikes. Other long duration r.m.s. voltage variations are mains failures, interruption, harmonic voltage distortion and steady-state overvoltages and undervoltages. This PhD research work deals with voltage dip phenomena only. Initially, the present power network was not designed to accommodate renewable distributed generation (RDG) units. The advent and deployment of RDG over recent years and high penetration of RDG has made the power network more complex and vulnerable to PQ disturbances. It is a well-known fact that the degree of newly introduced RDG has increased rapidly and growing further because of several reasons, which include the need to reduce environmental pollution and global warming caused by emission of carbon particles and greenhouse gases, alleviating transmission congestion and loss reduction. RDG ancillary services support especially voltage and reactive power support in electricity networks are currently being recognized, researched and found to be quite useful in voltage dip mitigation

Use, Operation and Maintenance of Renewable Energy Systems:Experiences and Future Approaches

The aim of this book is to put the reader in contact with real experiences, current and future trends in the context of the use, exploitation and maintenance of renewable energy systems around the world. Today the constant increase of production plants of renewable energy is guided by important social, economical, environmental and technical considerations. The substitution of traditional methods of energy production is a challenge in the current context. New strategies of exploitation, new uses of energy and new maintenance procedures are emerging naturally as isolated actions for solving the integration of these new aspects in the current systems of energy production. This book puts together different experiences in order to be a valuable instrument of reference to take into account when a system of renewable energy production is in operation

Entropy and Exergy in Renewable Energy

Lovelock identified Newcomen’s atmospheric steam engine as the start of Anthropocene with these words: “…there have been two previous decisive events in the history of our planet. The first was … when photosynthetic bacteria first appeared [conversing sunlight to usable energy]. The second was in 1712 when Newcomen created an efficient machine that converted the sunlight locked in coal directly into work.” This book is about the necessity of energy transition toward renewables that convert sunlight diurnally, thus a sustainable Anthropocene. Such an energy transition is equally momentous as that of the kick start of the second Industrial Revolution in 1712. Such an energy transition requires “it takes a village” collective effort of mankind; the book is a small part of the collective endeavor