This paper presents a comprehensive study on the state-of-the-art and emerging wind energy technologies from the electrical engineering perspective. In an attempt to decrease cost of energy, increase the wind energy conversion efficiency, reliability, power density, and comply with the stringent grid codes, the electric generators and power electronic converters have emerged in a rigorous manner. From the market based survey, the most successful generator-converter configurations are addressed along with few promising topologies available in the literature. The back-to-back connected converters, passive generator-side converters, converters for multiphase generators, and converters without intermediate dc-link are investigated for high-power wind energy conversion systems (WECS), and presented in low and medium voltage category. The onshore and offshore wind farm configurations are analyzed with respect to the series/parallel connection of wind turbine ac/dc output terminals, and high voltage ac/dc transmission. The fault-ride through compliance methods used in the induction and synchronous generator based WECS are also discussed. The past, present and future trends in megawatt WECS are reviewed in terms of mechanical and electrical technologies, integration to power systems, and control theory. The important survey results, and technical merits and demerits of various WECS electrical systems are summarized by tables. The list of current and future wind turbines are also provided along with technical details.

High-Power Wind Energy Conversion Systems: State-of-the-Art and Emerging Technologies

Wind energy is rapidly growing in recent years. Among different types of wind turbines, due to several advantages, permanent magnet synchronous generator (PMSG) is attractive concept. Since the penetration level of wind power in the grid is increased, therefore, wind power can influence to the grid and vice versa. Some of the important problems in the grid are fault condition and voltage sags. These conditions may affect the operation of wind turbine. In order to enhance low voltage ride through (LVRT) capability in PMSG-based wind turbines, various approaches have been proposed in the last years. In this paper, the review and comparison of several LVRT capability enhancement methods is performed. The two foremost types of LVRT capability enhancement methods are external devices based methods and modified controller based methods. The main objectives of this paper are to introduce performances of different LVRT capability enhancement methods and use of some LVRT capability enhancement methods in PMSG based wind turbine which are applied in other kind of wind power generators. The external devices based methods can be effective but some of these methods are of significant cost. According to the literatures, modified controller based methods can reduce the LVRT capability enhancement cost. Several modified controller based methods have been proposed for LVRT capability enhancement. To compare the mentioned methods, several simulations are performed in MATLAB software. From the review of simulation results, series connection of FACTS devices and modification of back-to-back converter controllers are the highly efficient LVRT capability enhancement approaches.

A review of low-voltage ride-through enhancement methods for permanent magnet synchronous generator based wind turbines

The permanent magnet synchronous generator (PMSG) is dominantly used in the present wind energy market. Reflecting the latest wind energy market trends and research articles, this study presents a survey on important electrical engineering aspects for PMSG-based megawatt-level wind energy conversion systems (WECSs). A comprehensive analysis on power converter topologies for wind turbines (WTs), grid integration of wind farms, digital control schemes, fault-ride-through compliance methods, and future trends is presented. The updated market share, technology trends, WT products information, in-depth technical analysis, and promising research works highlighted in this study will help the reader to understand the state-of-the-art and emerging technologies for PMSG-based WECS.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-epa.2016.0799

PMSG-based wind energy conversion systems: survey on power converters and controls

In this paper, a predictive control scheme is proposed for the low-voltage ride-through (LVRT) enhancement of direct-driven permanent-magnet-synchronous-generator-based megawatt-level wind turbines. The proposed method uses the turbine-generator rotor inertia to store the surplus energy during the grid voltage dips. The power conversion system is realized using a three-phase diode-bridge rectifier, a three-level-boost converter, and a neutral-point-clamped (NPC) inverter. The wind turbine requirements, such as maximum power point tracking, net dc-bus voltage control, balancing of the dc capacitor voltages, and reactive power generation, are modeled as the reference control variables. The generator- and grid-side cost functions are defined to deal with these control objectives. During each sampling interval, the control goals are achieved based on the minimization of cost functions. The coordination of boost and NPC converters and the exchange of reference control variables during normal and LVRT operation are formulated such that the power converters operate in a safe mode while meeting the grid code requirements. Simulation and experimental results are presented to validate the proposed strategy.

Predictive Control for Low-Voltage Ride-Through Enhancement of Three-Level-Boost and NPC-Converter-Based PMSG Wind Turbine

The deep penetration of renewable energy sources is on the cutting edge of smart grid vision. However, the variability and limited predictability of these sources have brought many technical challenges to grids. Many regulatory communities and system operators in the power sector have established grid codes to ensure proper connection of these renewable sources. This paper investigates the up-to-date methods used to enhance power system performance in the presence of a large share of renewable energy generation. In particular, two areas are addressed; the first is the techniques used for improving the wind and photovoltaic low-voltage ride-through capabilities to meet the required grid codes. The second is the contribution of these sources to the small signal stability of the power system in terms of inter-area oscillation damping.

Challenges of integrating renewable energy sources to smart grids: A review

Research of grid connected wind turbines has gained great interest in the recent years. This led to introduce guidelines and regulations regarding the connection of large wind farms to the electrical network. One of such guidelines is low voltage ride-through capability (LVRT). In this paper, a survey on recent LVRT solutions for permanent magnet synchronous generators (PMSG) is carried out along with a brief explanation of grid codes. Among those solutions is the control of fully rated converters, blade pitch angle control and capacitor sizing. Other solutions such as active crowbar rotor circuit and the DC bus energy storage circuit are illustrated. The survey extends to provide possibilities for the development of further LVRT research at the wind farm level using high power FACT devices.

A review on recent low voltage ride-through solutions for PMSG wind turbine

This paper introduces a detailed comparison between possible connections of AC voltage controllers. For each configuration, the experimental setup is implemented and the corresponding simulation program is presented using Simulink under Matlab. The simulated and experimental instantaneous voltage and current waveforms in case of resistive and inductive loads are matched well, validating the simulation comparison for analysis. The comparison analysis includes the required number of devices and isolated gate signals, which determines the complexity and the size, hence the overall cost. Also harmonic spectrum, total harmonic distortion, effective rms value, dc offset and the control range are compared to specify the performance. The implementation of a fixed-capacitor thyristor controlled reactor (FC-TCR) and three phase induction motor starters (SOFT STARTER) as two application case studies of AC voltage regulators has been discussed. Experimental and simulation results have been obtained and well correlated, showing the effectiveness of such configurations in the fields of control of reactive power flow and in the field of controlling the starting performance of three phase induction motor.

Comparison Analysis of AC Voltage Controllers Based on Experimental and Simulated Application Studies

This paper introduces two different microcontroller based three phase induction motor starters, the first using electromechanical star-delta with reactor starting and the second utilizes electronic AC voltage controllers starting technique For each of the proposed methods, the experimental setup is implemented and the output voltage, current and speed waveforms were demonstrated and analyzed for different selection options and operating conditions A dynamic model of three phase induction motor has been developed to validate a model of six terminals connection motor for star and delta performance analysis The model has been utilized for the simulation analysis and comparison of various electromechanical and electronic induction motor starters techniques Comparison between commercial analog controller based soft starter LH4-N2 and the proposed starter has been introduced as well Experimental and simulation waveforms obtained are matched validating the proposed starters for practical applications

Implementation and Analysis of Microcontroller Based Soft Starters for Three Phase Induction Motors

Direct-drive wind turbines based on permanent magnet synchronous generator with full scale back to back converters are becoming very promising due to their high power density, gearless structure and flexible control. With the remarkable growth of wind energy capacity connected to the utility grids, strict grid interconnection requirements of power plants comprising permanent magnet synchronous generators technology are essential to improve the control of electrical power system, both in steady-state and transient operation. Low voltage ride through capability enhancement is one of the grid requirements which ensures the safe operation of the wind farm during the network disturbances and avoids its shutdown. This paper proposes an improved topology based on magnetic amplifier in the boost converter circuit to enhance the ride through capability of permanent magnet synchronous generators based wind energy systems.

/pdf/improved-ride-through-of-pmsg-wind-turbine-during-3yohpee0l2.pdf

Improved ride-through of PMSG wind turbine during symmetrical voltage dip using a magnetic amplifier

Energy shortage and environmental pollution have led to the increasing demand of using renewable sources for electricity production. Currently, power generation from wind energy systems (WES) is of global significance and will continue to grow during the coming years leading to concerns about power system stability where wind farms replace conventional generating technologies that use fossil fuels as the primary energy source. One of these concerns is Low-Voltage Ride-Through (LVRT). In this paper, a novel topology based on the use of magnetic amplifier for enhancing the LVRT capability for grid connected permanent magnet synchronous generators (PMSG) is presented. The system performance is investigated using Matlab.

/pdf/a-novel-topology-for-enhancing-the-low-voltage-ride-through-zxscfpu5uj.pdf

R. A. Ibrahim

Papers

A review on recent low voltage ride-through solutions for PMSG wind turbine

Comparison Analysis of AC Voltage Controllers Based on Experimental and Simulated Application Studies

Implementation and Analysis of Microcontroller Based Soft Starters for Three Phase Induction Motors

Improved ride-through of PMSG wind turbine during symmetrical voltage dip using a magnetic amplifier

A novel topology for enhancing the Low Voltage Ride through capability for grid connected wind turbine generators