1,724,804 research outputs found
Operating and Loading Conditions of a Three-Level Neutral-Point-Clamped Wind Power Converter Under Various Grid Faults
No full textIn order to fulfill the growing demands from the grid side, full-scale power converters are becoming popular in the wind turbine system. The low-voltage ride-through (LVRT) requirements may not only cause control problems but also result in overstressed components for the power converter. However, the thermal loading of the wind power converter under various grid faults is still not yet clarified, particularly at megawatt power level. In this paper, the impacts by three types of grid faults to a three-level neutral-point-clamped (3L-NPC) wind power converter in terms of operating and loading conditions are analytically solved and simulated. It has been found that the operating and loading conditions of the converter under LVRT strongly depend on the types/severity values of grid voltage dips and also the chosen control algorithms. The thermal distribution among the three phases of the converter may be quite uneven, and some devices are much more stressed than the normal operating condition
Virtual inertia operation of renewables
No full textThe synchronous rotating inertia is the key parameter of power system stability. Increasing the penetration of nonsynchronous generators, e.g., wind turbine, photovoltaics, and energy storage system, in the power grids leads to some stability challenges due to the lack of rotating mass and kinetic inertia in the system. In this chapter, the effect of high penetration of renewables on power system stability is shown. Moreover, the recent low-inertia grid challenges in Europe and South Australia are presented. Technically, in order to achieve 100% renewables, providing virtual inertia is a demand. The virtual synchronous machine (VSM) is a promising solution to emulate the behavior of a synchronous machine and provide inertia virtually. In this chapter, the theoretical concept of VSM, as well as the control structure, is also presented. Furthermore, the VSM implementation in the power system is explained, and some RMS simulation results are provided in a fault situation. Since in a controller based on the swing equation, the current is not controlled in the short time frame directly, a current limitation controller is also implemented in VSM and scrutinized in this chapter.</p
Multisampled current control of grid-following voltage source converters
No full textPulse width modulation (PWM)–based current control is widely used in grid-following voltage source converters (VSCs). However, a large control delay is induced in the regular PWM process, which limits the current control bandwidth and deteriorates VSC-grid interactive stability. Multisampling PWM is a potential candidate to reduce the control delay, and state variables are sampled multiple times within one switching period. In this chapter, the internal mechanism of multisampling PWM is revealed, and two low phase–lag digital filters are introduced to suppress low-order aliasing. Based on that, passivity-based multisampling damping strategies controlling converter-side current and grid-side current are presented with high stability robustness.</p
Overview of Maximum Power Point Tracking Techniques for Photovoltaic Energy Production Systems
No full textA substantial growth of the installed photovoltaic (PV) systems capacity has occurred around the world during the last decade, thus enhancing the availability of electric energy in an environmentally friendly way. The maximum power point tracking (MPPT) technique enables to maximize the energy production of PV sources, despite the stochastically varying solar irradiation and ambient temperature conditions. Thereby, the overall efficiency of the PV energy production system is increased. Numerous techniques have been presented during the last decades for implementing the MPPT process in a PV system. This chapter provides an overview of the operating principles of these techniques, which are suited for either uniform or nonuniform solar irradiation conditions. The operational characteristics and implementation requirements of these MPPT methods are alsoanalyzed in order to demonstrate their performance features
Dual active bridge converter and its control
No full textIsolated bidirectional DC–DC (IBDC) converters are needed in a wide range of applications including DC microgrids, electric vehicles, and energy storage devices. Among various IBDC topologies, the dual active bridge (DAB) converter is one of the most promising solutions owing to its simple and symmetric structure, the capability of zero-voltage switching (ZVS) for all switches, and the wide voltage conversion range. This chapter presents the working principle and performance characterization of the DAB converter as well as its modeling and control. Four typical modulation schemes are introduced. Based on the single-phase shift modulation, active and reactive power flows are derived. Trade-offs among ZVS operation range, component current stress, and output power rating are analyzed, providing guidance for optimizing the inductance. In terms of control, large- and small-signal circuits of the reduced-order model are developed. The small-signal model is further improved by capturing the impacts of power losses. Two typical closed loop control strategies, output voltage feedback and output voltage feedback plus output current feedforward, are introduced and designed for an example DAB converter. Both the modeling methods and control strategies are verified by piecewise linear electrical circuit simulation (PLECS). The presented performance characterizations, large- and small-signal models, and control strategies offer practical design insights for DAB converters.</p
High switching frequency three-phase current-source converters and their control
No full textHigh switching frequency (current source converters) CSCs are increasingly concerned for improving the power efficiency and power density in many new applications. This chapter discusses the stability and control of high switching frequency CSCs. By involving the DC-link dynamics, stability of single-loop DC-link current control and design of three active damping methods are presented.</p
Artificial intelligence–assisted data-driven control of power electronics systems
No full textData-driven solutions enabled by artificial intelligence (AI) have shown great potential in power electronics. Compared with conventional control methods, data-driven control methods are flexible and efficient and have fewer requirements regarding system physical knowledge. As for control-related applications, this chapter presents AI-based control approaches to power electronics applications, covering control fundamentals, data-driven principles, practical examples, and outlooks. It starts by discussing the control fundamentals from a data-driven perspective. Then, relevant AI tools, including metaheuristic methods, fuzzy logic, and machine learning methods, are presented. Specific examples are analyzed in control optimization, a fuzzy logic–based controller, a neural network-based controller, and a reinforcement learning controller. Finally, future outlooks on the state of the art in this synergistic topic are summarized.</p
Surrogate models for power electronic systems applying machine learning techniques
No full textAs society advances toward a green transformation, digitalization, and Industry 4.0, power electronics have an important role in controlling and converting electric energy in a flexible, efficient, and reliable way. The increasing use of power electronics and the shortening of product development cycles are promoting design automation in the field of power electronics, which can reduce the complexity of the design process and provide excellent insight into optimization. A key element of implementing design automation is establishing efficient models. Surrogate models, which replace expensive numerical simulations and experiments by mathematical functions such as polynomial chaos expansions, Kriging, and neural networks, have become a promising method for engineering design and optimization. This chapter introduces the concept and workflow of surrogate modeling for power electronics. Based on typical applications of power electronics, surrogate modeling approaches in terms of active components, passive components, power electronics converters, and systems are demonstrated. Finally, an example of applying a surrogate model in the thermal modeling of power semiconductors considering cross-coupling effects is presented in detail. Through a surrogate model, quantities of interest can be quickly explored within sufficient accuracy while consuming less time and effort.</p
Single-Phase Induction Motor and AC Drives
No full textThis chapter presents the working principle and modeling of the single-phase induction motor (SPIM), as well as the control strategies of the SPIM with several different power electronics device-based variable frequency AC drives. The SPIM has been widely used for the water pumps, compressors, and fans with no tough demand for high performance and they are especially used at small-rated power below 1 kW. Besides the conventional single-phase main power supply, the SPIM can also be supplied by a single-phase or three-phase voltage source inverter. This chapter will first introduce the working principle of the SPIM, and then establish the modeling of the motor. Thereafter, this chapter will present theoretical analysis on how the SPIM performance is influenced by different supply methods, i.e., including the supply methods using a single-phase inverter with a running capacitor, or using a three-phase inverter with/without a running capacitor. Further comparisons will be made in terms of starting torque, starting current, pulsation torque, efficiency, etc. Simulation results are provided to compare and demonstrate the similarities and differences between these power electronics device-based variable frequency AC drives for SPIM
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