Showing papers in "IEEE Journal of Emerging and Selected Topics in Power Electronics in 2013"
TL;DR: In this article, the authors review the development of simple factory automation (FA) IPT systems for both today's complex applications and onward to a much more challenging application-IPT roadway.
Abstract: Inductive power transfer (IPT) has progressed to be a power distribution system offering significant benefits in modern automation systems and particularly so in stringent environments. Here, the same technology may be used in very dirty environments and in a clean room manufacture. This paper reviews the development of simple factory automation (FA) IPT systems for both today's complex applications and onward to a much more challenging application-IPT roadway. The underpinning of all IPT technology is two strongly coupled coils operating at resonance to transfer power efficiently. Over time the air-gap, efficiency, coupling factor, and power transfer capability have significantly improved. New magnetic concepts are introduced to allow misalignment, enabling IPT systems to migrate from overhead monorails to the floor. However, the demands of IPT roadway bring about significant challenges. Here, compared with the best FA practice, air-gaps need to be 100 times larger, power levels greater than ten times, system losses ten times lower to meet efficiency requirements, and systems from different manufacturers must be interoperable over the full range of operation. This paper describes how roadway challenges are being met and outlines the problems that still exist and the solutions designers are finding to them.
998 citations
TL;DR: In this article, the authors present a systematical technology review essential for the development and application of SST in the distribution system, including high-voltage power devices, high-power and high-frequency transformers, ac/ac converter topologies, and future research directions.
Abstract: The solid-state transformer (SST), which has been regarded as one of the 10 most emerging technologies by Massachusetts Institute of Technology (MIT) Technology Review in 2010, has gained increasing importance in the future power distribution system. This paper presents a systematical technology review essential for the development and application of SST in the distribution system. The state-of-the-art technologies of four critical areas are reviewed, including high-voltage power devices, high-power and high-frequency transformers, ac/ac converter topologies, and applications of SST in the distribution system. In addition, future research directions are presented. It is concluded that the SST is an emerging technology for the future distribution system.
897 citations
TL;DR: In this paper, the authors give an overview and discuss some development trends in the technologies used for wind power systems, and several state-of-the-art wind turbine concepts, as well as the corresponding power electronic converters and control structures are reviewed, respectively.
Abstract: Wind power is still the most promising renewable energy in the year of 2013. The wind turbine system (WTS) started with a few tens of kilowatt power in the 1980s. Now, multimegawatt wind turbines are widely installed even up to 6-8 MW. There is a widespread use of wind turbines in the distribution networks and more and more wind power stations, acting as power plants, are connected directly to the transmission networks. As the grid penetration and power level of the wind turbines increase steadily, the wind power starts to have significant impacts to the power grid system. Therefore, more advanced generators, power electronic systems, and control solutions have to be introduced to improve the characteristics of the wind power plant and make it more suitable to be integrated into the power grid. Meanwhile, there are also some emerging technology challenges, which need to be further clarified and investigated. This paper gives an overview and discusses some development trends in the technologies used for wind power systems. First, the developments of technology and market are generally discussed. Next, several state-of-the-art wind turbine concepts, as well as the corresponding power electronic converters and control structures, are reviewed, respectively. Furthermore, grid requirements and the technology challenges for the future WTS are also addressed.
736 citations
TL;DR: In this paper, the trends in wind turbine generator systems are discussed and a review of current and possible future generator systems is presented. But the main focus of this paper is on the current state of the art.
Abstract: This paper reviews the trends in wind turbine generator systems. After discussing some important requirements and basic relations, it describes the currently used systems: the constant speed system with squirrel-cage induction generator, and the three variable speed systems with doubly fed induction generator (DFIG), with gearbox and fully rated converter, and direct drive (DD). Then, possible future generator systems are reviewed. Hydraulic transmissions are significantly lighter than gearboxes and enable continuously variable transmission, but their efficiency is lower. A brushless DFIG is a medium speed generator without brushes and with improved low-voltage ride-through characteristics compared with the DFIG. Magnetic pseudo DDs are smaller and lighter than DD generators, but need a sufficiently low and stable magnet price to be successful. In addition, superconducting generators can be smaller and lighter than normal DD generators, but both cost and reliability need experimental demonstration. In power electronics, there is a trend toward reliable modular multilevel topologies.
479 citations
TL;DR: In this paper, the current status and requirements of primary electric propulsion components-the battery, the electric motors, and the power electronics system-were reviewed and future trends in the electric propulsion systems, battery charging, and types of power trains were presented.
Abstract: In this paper, the current status and the requirements of primary electric propulsion components-the battery, the electric motors, and the power electronics system-are reviewed. The future trends in the electric propulsion systems, battery charging, and the types of power trains are presented. Possible future electric vehicle powertrain systems based on lithium air battery and plug-in fuel cell vehicles are also discussed.
344 citations
TL;DR: In this paper, a hierarchical dynamic decoupling of generation, distribution, and consumption by using bidirectional electronic power converters as energy control centers is discussed. But, the authors do not consider the potential for the use of new power electronics technologies in electrical energy generation and consumption.
Abstract: Anticipated widespread usage of new power electronics technologies in electrical energy generation and consumption is expected to provide major efficiency improvements, while the deployment of smart grid technologies should improve the utilization and availability of electricity. This paper explores possible relationships between these two trends. Starting from an analysis of current and expected trends in the generation, transport, and consumption of electrical energy, this paper contemplates possible future ac and dc electronic power distribution system architectures, especially in the presence of renewable energy sources. The proposed nanogrid-microgrid-E-grid structure achieves hierarchical dynamic decoupling of generation, distribution, and consumption by using bidirectional electronic power converters as energy control centers. Several possible directions for modeling, analysis, and system-level design of such systems, including power flow control, protection, stability, and subsystem interactions, are briefly discussed.
232 citations
TL;DR: In this paper, the fundamental functions found in electronic energy processing, the constituent technologies comprising power electronics, and the power electronics technology space in light of the internal driving philosophy of power electronics and its historical development are examined.
Abstract: This paper presents a historical and philosophical perspective on a possible future for power electronics. Technologies have specific life cycles that are driven by internal innovation, subsequently reaching maturity. Power electronics appears to be a much more complex case, functioning as an enabling technology spanning an enormous range of power levels, functions and applications. Power electronics is also divided into many constituent technologies. Till now, the development of power electronics has been driven chiefly by internal semiconductor technology and converter circuit technology, approaching maturity in its internally set metrics, such as efficiency. This paper examines critically the fundamental functions found in electronic energy processing, the constituent technologies comprising power electronics, and the power electronics technology space in light of the internal driving philosophy of power electronics and its historical development. It is finally concluded that, although approaching the limits of its internal metrics indicates internal maturity, the external constituent technologies of packaging, manufacturing, electromagnetic and physical impact, and converter control technology still present remarkable opportunities for development. As power electronics is an enabling technology, its development, together with internal developments, such as wide bandgap semiconductors, will be driven externally by applications in the future.
206 citations
TL;DR: This paper reviews the state-of-the-art and highly applicable mechanical position/speed sensorless control schemes for PMSG-based variable-speed WECSs and proposes new schemes for direct torque and direct power control schemes.
Abstract: Owing to the advantages of higher efficiency, greater reliability, and better grid compatibility, the direct-drive permanent-magnet synchronous generator (PMSG)-based variable-speed wind energy conversion systems (WECSs) have drawn the highest attention from both academia and industry in the last few years. Applying mechanical position/speed sensorless control to direct-drive PMSG-based WECSs will further reduce the cost and complexity, while enhancing the reliability and robustness of the WECSs. This paper reviews the state-of-the-art and highly applicable mechanical position/speed sensorless control schemes for PMSG-based variable-speed WECSs. These include wind speed sensorless control schemes, generator rotor position and speed sensorless vector control schemes, and direct torque and direct power control schemes for a variety of direct-drive PMSG-based WECSs.
206 citations
TL;DR: In this article, the authors describe the growing penetration of power electronics in energy systems is driven by new materials such as SiC and GaN, as well as new packaging technologies which allow the physical integration of electronics with powered and controlled devices such as motors.
Abstract: The continuing trend toward greater electrification and control of functions in consumer, commercial, industrial, transportation, and even medical applications promises a dynamic and increasingly important role for power electronics. The growing penetration of power electronics in energy systems is driven by new materials such as SiC and GaN, as well as new packaging technologies which allow the physical integration of electronics with powered and controlled devices such as motors. Advances in very high-frequency conversion led by the application of SiC and GaN devices promises to make converter-on-a-chip technology possible, but concurrent advances in passive component technology are necessary. The principal challenge to application penetration remains cost reduction.
171 citations
TL;DR: In this article, the details of practical circuit and control implementation of an electric spring for reactive power compensation and voltage regulation of the ac mains are presented, and the proof-of-concept hardware is successfully built and demonstrated in a 10kVA power system fed by wind energy for improving power system stability.
Abstract: In this paper, the details of practical circuit and control implementation of an electric spring for reactive power compensation and voltage regulation of the ac mains are presented. With Hooke's law published three centuries ago, power electronics-based reactive power controllers are turned into electric springs (ESs) for regulating the ac mains of a power grid. The proposed ES has inherent advantages of: 1) ensuring dynamic load demand to follow intermittent power generation; and 2) being able to regulate the voltage in the distribution network of the power grid where numerous small-scale intermittent renewable power sources are connected. Therefore, it offers a solution to solve the voltage fluctuation problems for future power grids with substantial penetration of intermittent renewable energy sources without relying on information and communication technology. The proof-of-concept hardware is successfully built and demonstrated in a 10-kVA power system fed by wind energy for improving power system stability. The ES is found to be effective in supporting the mains voltage, despite the fluctuations caused by the intermittent nature of wind power.
141 citations
TL;DR: In this paper, the double-layer printed spiral coil is used, which could fully take advantage of the limited space and make larger parasitic capacitance for lower resonant frequency, and the circuit model with consideration of parasitic parameters and high-frequency losses is built.
Abstract: As a critical part of the wireless power transfer system via strongly coupled magnetic resonances, the resonant coils must be cautiously designed for the specific resonant frequency and high quality factor. There are some issues needed to be considered and studied in the coil design, such as the coil structure, parasitic parameter extraction, and optimizing. In this paper, the double-layer printed spiral coil is used, which could fully take advantage of the limited space and make larger parasitic capacitance for lower resonant frequency. Using the simplified partial element equivalent circuit method and finite element method, the circuit model with consideration of parasitic parameters and high-frequency losses is built, and the impedance characteristic of coil is simulated, which coincides well with the measurement result. In addition, several elements affecting the high-frequency loss, including the skin effect, proximity effect, and dielectric loss, are discussed for reaching higher quality factor, which is critical for the power transfer system.
TL;DR: In this article, extrapolations of current silicon power device technology into the future are discussed, followed by discussions of wide band gap (WBG) power devices with a focus on silicon carbide and gallium nitride.
Abstract: This paper discusses extrapolations of current silicon power device technology into the future, followed by discussions of wide band gap (WBG) power devices with a focus on silicon carbide and gallium nitride. Other WBG materials are included from carbon, such as diamond and nanotubes, to various nitrides. Far future material development, that may impact power electronic devices decades out, is also discussed.
TL;DR: In this article, a leaky least mean square-based control algorithm for a three-phase distribution static compensator (DSTATCOM) is proposed to mitigate multiple power quality problems such as reactive power, current harmonics, load unbalancing, and so on with self-supporting dc bus voltage of voltage source converter used as a DSTATCOM.
Abstract: This paper describes a leaky least mean square-based control algorithm for a three-phase distribution static compensator (DSTATCOM) to mitigate multiple power quality problems such as reactive power, current harmonics, load unbalancing, and so on with self-supporting dc bus voltage of voltage source converter used as a DSTATCOM. The proposed control algorithm is implemented for the extraction of tuned weighted values of fundamental active and reactive power components of distorted load currents which are major components in reference supply currents. Developed DSTATCOM is operated under various operating conditions and its performance is found satisfactory.
TL;DR: In this paper, the design and implementation of an appliance for operation in a dc-based nanogrid is detailed and an induction heating range is considered as a design example, with some of the design considerations generalizable to any other appliances.
Abstract: Efficiency has become a key design parameter when designing any electrical system In recent years, significant attention has been paid to the design of optimized micro and nanogrids comprising residential area subsystems Among the different proposed approaches, one of the most promising consists of a dc-based nanogrid optimized for the interoperation of electric loads, sources, and storage elements Home appliances are one of the main loads in such dc-based nanogrids In this paper, the design and implementation of an appliance for operation in a dc-based nanogrid is detailed An induction heating range is considered as a design example, with some of the design considerations generalizable to any other appliances The main design aspects, including the inductor system, power converter, and control, are considered Finally, some simulation and experimental results of the expected converter performance are shown
TL;DR: In this paper, a model predictive control strategy for the ac-dc-ac converter of wind system is derived and implemented to capture the maximum wind energy as well as provide desired reactive power.
Abstract: This paper presents the operation and controller design of a microgrid consisting of a direct drive wind generator and a battery storage system A model predictive control strategy for the ac-dc-ac converter of wind system is derived and implemented to capture the maximum wind energy as well as provide desired reactive power A novel supervisory controller is presented and employed to coordinate the operation of wind farm and battery system in the microgrid for grid-connected and islanded operations The proposed coordinated controller can mitigate both active and reactive power disturbances that are caused by the intermittency of wind speed and load change Moreover, the control strategy ensures the maximum power extraction capability of wind turbine while regulating the point of common coupling bus voltage within acceptable range in both grid-connected and islanded operations The designed concept is verified through various simulation studies in EMTDC/PSCAD, and the results are presented and discussed
TL;DR: In this article, a model predictive control (MPC) algorithm for dc-dc boost converters is proposed, which is implemented as a current-mode controller, with two control loops are employed, with the inner loop being designed in the framework of MPC.
Abstract: A model predictive control (MPC) algorithm for dc-dc boost converters is proposed in this paper. The proposed control scheme is implemented as a current-mode controller. Two control loops are employed, with the inner loop being designed in the framework of MPC. Two different objective functions are formulated and investigated. The control objective, i.e., the regulation of the current to its reference, is achieved by directly manipulating the switch, thus a modulator is not required. As a prediction model, a hybrid model of the converter is used, which captures precisely the continuous and the discontinuous conduction modes. The proposed control strategy achieves very fast current regulation, while exhibiting only a modest computational complexity. Simulation and experimental results substantiate the effectiveness of the proposed approach.
TL;DR: In this paper, an optimal efficiency control strategy for wind energy conversion systems (WECSs) with squirrel cage induction generators (SCIGs) is presented, where a minimum electric loss controller is introduced to minimize the generator electric loss and a maximum power point tracking (MPPT) controller is used to maximize the wind turbine output power.
Abstract: This paper presents an optimal efficiency control strategy for wind energy conversion systems (WECSs) with squirrel cage induction generators (SCIGs). The developed control scheme provides an optimal efficiency of the induction generator and maximum power extraction from the wind turbine. Thus, maximum power harvesting from the whole WECS is achieved and additionally expansion of the exploitable wind speed region toward the lower speed range is accomplished. A minimum electric loss (MEL) controller is introduced to minimize the generator electric loss and a maximum power point tracking (MPPT) controller is used to maximize the wind turbine output power. Common input to the two optimal controllers is only the generator speed, while the measurement of the wind speed is not required. The controllers determine the optimal d- and q-axis stator current components of the SCIG through optimal conditions and, therefore, fast dynamic response of the WECS is accomplished. An experimental procedure is proposed to determine the MEL and MPPT controller parameters. Therefore, neither the knowledge of SCIG loss model, nor the characteristic curves of the wind turbine are required. The effectiveness and the operational improvements of the suggested optimal control scheme have been verified experimentally.
TL;DR: In this paper, an evolutionary strategy called covariance matrix adaptation (CMA) is employed to obtain optimal power flows inside the offshore network for integration of wind energy in the North Sea, and the optimal power flow results obtained from the CMA algorithm are tested in a dynamic simulation model to check the control strategy performance in different case studies.
Abstract: Europe is rapidly expanding its wind energy capacity, especially offshore. Hence, the construction of a multiterminal dc (MTdc) network could bring several advantages to accommodate the generated electrical energy, but will also bring many challenges. This paper focuses on one of these challenges, namely the operation and control of an MTdc network. Moreover, a study is carried on how to optimally operate and control an offshore MTdc network for integration of wind energy in the North Sea. An evolutionary strategy called covariance matrix adaptation (CMA) is employed to obtain optimal power flows inside the offshore network. The MTdc grid is composed of 19 nodes, interconnecting nine offshore wind farms to five European countries. The optimal power flow results obtained from the CMA algorithm are tested in a dynamic simulation model to check the control strategy performance in different case studies.
TL;DR: In this article, the trade-off between power-to-weight ratio (W/kg) and efficiency of a 100 kW airborne wind turbine with a power kite flying at high speed perpendicular to the wind is investigated.
Abstract: Airborne wind turbines (AWTs) represent a radically new and fascinating concept for future harnessing of wind power. This concept consists of realizing only the blades of a conventional wind turbine (CWT) in the form of a power kite flying at high speed perpendicular to the wind. On the kite are mounted a turbine, an electrical generator, and a power electronics converter. The electric power generated is transmitted via a medium voltage cable to the ground. Because of the high flight speed of the power kite, several times the actual wind speed, only a very small swept area of the turbine is required according to Betz's Law and/or a turbine of low weight for the generation of a given electric power. Moreover, because of the high turbine rotational speed, no gear transmission is necessary and the size of the generator is also reduced. For takeoff and landing of the power kite, the turbines act as propellers and the generators as motors, i.e., electric power is supplied so that the system can be maneuvered like a helicopter. In the present work, the configuration of power electronics converters for the implementation of a 100 kW AWT is considered. The major aspect here is the trade-off between power-to-weight ratio (W/kg) and efficiency. The dependence of cable weight and cable losses on the voltage level of power transmission is investigated, and a comparison is made between low voltage (LV) and medium voltage (MV) versions of generators. Furthermore, the interdependence of the weight and efficiency of a bidirectional dual active bridge dc-dc converter for coupling the rectified output voltage of a LV generator to the MV cable is discussed. On the basis of this discussion, the concept offering the best possible compromise of weight and efficiency in the power electronics system is selected and a model of the control behavior is derived for both the power flow directions. A control structure is then proposed and dimensioned. Furthermore, questions of electromagnetic compatibility and electrical safety are treated. In conclusion, the essential results of this paper are summarized, and an outlook on future research is given. To enable the reader to make simplified calculations and a comparison of a CWT with an AWT, the aerodynamic fundamentals of both the systems are summarized in highly simplified form in an Appendix, and numerical values are given for the 100 kW system discussed in this paper.
TL;DR: In this paper, the authors proposed a new topology called Halbach-FSPM capable of achieving an electromagnetic torque 20% higher than the C-core FSPM machine, while maintaining machine volume and phase current constant and using no more magnet material than a conventional FFPM machine.
Abstract: Recently, flux-switching permanent magnet (FSPM) machines have been increasingly investigated due to its torque density and fault tolerance. Because of this, they are attractive for aerospace applications where weight, installation spaces, and safety play a critical role. Recent research has investigated a variation of the conventional FSPM machine called the C-core FSPM machine, which offers 40% greater electromagnetic torque, while using half of the magnet mass. This paper proposes a new topology called Halbach-FSPM capable of achieving an electromagnetic torque 20% higher than the C-core FSPM machine, while maintaining machine volume and phase current constant and using no more magnet material than a conventional FSPM machine. First, a physical explanation of the advantages are developed for use in all FSPM machines using Halbach arrays. An analysis and comparison of torque, power and efficiency are made. Further, magnet losses and segmentation applicable to all FSPM topologies are discussed, plus an analysis on magnet usage is given.
TL;DR: In this article, a power-electronics-based controller is proposed to attenuate the drivetrain load in a wind turbine by temporarily shifting the closed-loop eigenfrequency through the addition of virtual inertia.
Abstract: Failure of the drivetrain components is currently listed among the most problematic failures during the operational lifetime of a wind turbine. Guaranteeing robust and reliable drivetrain designs is important to minimize the wind turbine downtime as well as to meet demand in both power quantity and quality. While aeroelastic codes are often used in the design of wind turbine controllers, the drivetrain model in such codes is limited to a few (mostly two) degrees of freedom, resulting in a restricted detail in describing its dynamic behavior and assessing the effectiveness of controllers on attenuating the drivetrain load. In the previous work, the capability of the well-known FAST aeroelastic tool for wind turbine has been enhanced through integration of a dynamic model of a drivetrain. The drivetrain model, built using the Simscape in the MATLAB/Simulink environment, is applied in this paper. The model is used to develop a power-electronics-based controller to prevent excessive drivetrain load. The controller temporarily shifts the closed-loop eigenfrequency of the drivetrain through the addition of virtual inertia, thus avoiding the resonance. Simulation results demonstrating the fidelity of the expanded drivetrain model as well as the effectiveness of the virtual inertia controller are presented.
TL;DR: In this paper, Li-ion capacitors are investigated as a potential solution for filtering power variations at the scale of tens of seconds, and a novel topology and control technique has been introduced to integrate capacitors and power conversion circuitry.
Abstract: Utilization of wind energy in modern power systems creates many technical and economical challenges that need to be addressed for successful large scale wind energy integration. Variations in wind velocity result in variations of output power produced by wind turbines. Variable power output becomes a challenge as the share of wind energy in power systems increases. Large power variations cause voltage and frequency deviations from nominal values that may lead to activation of protective relay equipment, which may result in disconnection of the wind turbines from the grid. Particularly community wind power systems, where only one or few wind turbines supply loads through a weak grid such as distribution network, are sensitive to supply disturbances. Energy storage integrated with wind turbines can address this challenge. In this paper, Li-ion capacitors are investigated as a potential solution for filtering power variations at the scale of tens of seconds. A novel topology and control technique has been introduced to integrate capacitors and power conversion circuitry. Modeling and scaled-down experimental results are provided to verify the theoretical analyses.
TL;DR: In this paper, an adaptive multi-mode power control algorithm for the converter of a direct-drive permanent magnetic wind generation system in a microgrid is presented, which can operate the wind generation either in maximum power point tracking (MPPT) mode or non-MPPT mode with enhanced tracking performance.
Abstract: This paper presents an adaptive multi-mode power control algorithm for the converter of a direct-drive permanent magnetic wind generation system in a microgrid. The strategy is implemented in a field-oriented control machine drive system, with a two-level IGBT full-power rated ac-dc machine-side converter. The objective of this paper control is to operate the wind generation either in maximum power point tracking (MPPT) mode or non-MPPT mode with enhanced tracking performance. The simulation proves that the proposed MPPT algorithm is faster, more robust, and adaptive to changes of the environment than the conventional variable-step hill climbing search algorithm, while the non-MPPT module has a fast dynamic response to the change of the power command and the environment, and an accurate steady-state response as well. Moreover, the result shows that the control strategy can automatically switch between the MPPT and non-MPPT modes.
TL;DR: In this article, a high performance, nonlinear, passivity-based controller that ensures asymptotic convergence to the maximum power extraction point together with regulation of the dc link voltage and grid power factor to their desired values is presented.
Abstract: The problem of controlling small-scale wind turbines providing energy to the grid is addressed in this paper. The overall system consists of a wind turbine plus a permanent magnet synchronous generator connected to a single-phase ac grid through a passive rectifier, a boost converter, and an inverter. The control problem is challenging for two reasons. First, the dynamics of the plant are described by a highly coupled set of nonlinear differential equations. Since the range of operating points of the system is very wide, classical linear controllers may yield below par performance. Second, due to the use of a simple generator and power electronic interface, the control authority is quite restricted. In this paper we present a high performance, nonlinear, passivity-based controller that ensures asymptotic convergence to the maximum power extraction point together with regulation of the dc link voltage and grid power factor to their desired values. The performance of the proposed controller is compared via computer simulations against the industry standard partial linearizing and decoupling plus PI controllers.
TL;DR: In this article, a nonlinear control loop mapping has been designed for mitigating the dead zone of a noninverting buck-boost converter while minimizing state variable perturbation, which enables a converter with fixed switching frequency to achieve reduced switching loss as though operating at an effective switching frequency lower than the actual.
Abstract: A nonlinear control loop mapping has previously been designed for mitigating the dead zone of a noninverting buck-boost converter while minimizing state variable perturbation. This paper derives a new nonlinearity that enables a converter with fixed switching frequency to achieve reduced switching loss as though operating at an effective switching frequency lower than the actual. The new control loop nonlinearity accomplishes this by interleaving a specified fraction of pass-through and nonpass-through switching periods. The derived nonlinearity also reduces the increase in waveform ripple associated with a switching frequency reduction. Through adapting the effective switching frequency across the full range of conversion ratios and loads, reductions in loss up to 58% are realized.
TL;DR: In this article, the electromagnetic torque, stator power, and the grid side converter power outputs of a doubly fed induction generator (DFIG) are differentiated to obtain a feedback linear relationship with the rotor voltage vectors serving as the control inputs.
Abstract: The electromagnetic torque, stator power, and the grid side converter power outputs of a doubly fed induction generator (DFIG) are differentiated to obtain a feedback linear relationship with the rotor voltage vectors serving as the control inputs. The derived model is such that can allow for a transition of DFIG to operate at low wind speed by shorting its stator terminal to one another. The torque and power quantities are the state variables of the system, which are insensitive to coordinate system orientation. Steady-state models are used to obtain optimal operating regimes with respect to minimal electrical losses. Decoupled torque control is developed by field orientation, while decoupled power control is derived from voltage orientation of the DFIG. Transients originating from transitioning into low wind speed operation are investigated. Robustness of each of the decoupled controllers against parameter variations is investigated by locating the poles of its closed-loop transfer function. The results for a 5-Hp machine are presented.
TL;DR: In this article, a method that utilizes synchrophasor measurements to estimate the equivalent inertia of a power source such as synchronous generators or wind turbine generators was proposed to detect angle instability.
Abstract: The alternating current machines in a power system have the ability to remain synchronized following a severe disturbance such as loss of generations, line switching, or fault. This is described as power system transient stability. During system transients, the machines will accelerate or decelerate because of the mismatch between electrical torque and mechanical torque. Their power angles will travel and finally settle down to a new equilibrium, if the system has enough stored energy to absorb the disturbance, and rest the system at another steady state. In case of system instability, some machines will have aperiodic angular separation from the rest of the system and finally lose synchronization. Therefore, the power system transient stability is also called angle stability. The total system inertia is an essential force to rest the system transient. The inertias stored in all rotating masses that are connected to a power system, such as synchronous generators and induction motors, typically respond to disturbances voluntarily, without any control actions; however, several types of renewable generation, particularly those with power electronic interfaces, have an inertial response governed by a control function. To ensure bulk power system stability, there is a need to estimate the equivalent inertia available from a renewable generation plant. An equivalent voluntary inertia constant analogous to that of conventional rotating machines can be used to provide a readily understandable metric, such as the angle instabilities detections, because one of the most difficult obstacles for angle instability detection is the knowledge of the real-time generator inertias. This paper explores a method that utilizes synchrophasor measurements to estimate the equivalent inertia of a power source such as synchronous generators or wind turbine generators. This paper also investigates the angle instability detection method for a system with high wind power penetration using the synchrophasor measurements.
TL;DR: In this article, the authors present a new approach for time-domain analyses using model quadratization quadratized model and subsequent quadratic integration of the quadratised dynamic-models quadrized model-quadratic integration (QMQI) method.
Abstract: This paper presents a new approach for time-domain analyses using model quadratization quadratized model and subsequent quadratic integration of the quadratized dynamic-models quadratized model-quadratic integration (QMQI) method. The modeling methodology is suitable for analysis of power systems with nonlinear components and switching subsystems. The quadratic integration (QI) method has been demonstrated to be more numerically stable, robust, and accurate than trapezoidal integration (TI), one of the most popularly used methods for power transient analyses. The model quadratization enables nonlinearities to be modeled with equations of nonlinearities no higher than second order without approximations or simplifications. Upon QI, the resulting companion form is a model with nonlinearities no higher than second order (quadratic companion form). Newton's method is employed for the solution of the quadratic companion form equations. The numerical convergence of the overall method is robust and fast. The performance of the QMQI method is quantified with a couple of systems of nonlinear components and power electronics. The method can be expanded to cubic integration (CI) as well as higher-order integration methods. This paper compares the QMQI method with the TI and the CI, for the purpose of determining the pros and cons as higher (or lower)-order integration methods are used.
TL;DR: This inaugural Special Issue of JESTPE serves two purposes: to cover the emerging nature of the technology from a relatively longterm view and to celebrate the 25th anniversary of PELS.
Abstract: With this inaugural editorial, we welcome our readers to the brand-new publication - IEEE nal of Emerging and Selected Topics in Power Electronics (IEEE JESTPE). It is jointly sponsored by the IEEE Power Electronics Society (PELS) and the IEEE Industry Applications Society (IAS). By mutual agreement, the JESTPE is currently administered by PELS. It is only fitting for JESTPE to celebrate PELS 25th anniversary by publishing the very first Special Issue focusing on the future of power electronics. This serves two purposes: to cover the emerging nature of the technology from a relatively longterm view and to celebrate the 25th anniversary. We have invited a group of experts to write special surveys or review papers. Because of the review cycle and the need to fulfill our commitment to publish in a timely and regular fashion, this inaugural Special Issue is organized into two parts: Part 1 and Part 2. Part 1 is in this issue and Part 2 will appear in June. The article of Part 1 are briefly summarized.
TL;DR: This paper attempts to address the practical design and simulation of power supplies by designing specifications that give extra relations, considerations based on domain knowledge, iterative methods, and simulation are integrated with circuit analysis to formulate effective power supply design strategies.
Abstract: This paper attempts to address the practical design and simulation of power supplies. Formal circuit analysis provides a set of equations which is usually insufficient for solving all unknowns or calculating the values of all the components in the circuit being designed. Additional relationships or domain knowledge (industry-specific knowledge) is required to make up for the necessary equations to find all the unknown design values; otherwise the solution would need to resort to iterative approaches. In practice, design specifications that give extra relations, considerations based on domain knowledge, iterative methods, and simulation are integrated with circuit analysis to formulate effective power supply design strategies.