A new robust control scheme: Application for MPP tracking of a PMSG-based variable-speed wind turbine

With the advance of power electronics, direct-driven permanent magnet synchronous generators have drawn increased interest to wind turbine manufacturers due to its advantages over other variable-speed wind turbines. This article studies permanent magnet synchronous generator characteristics under the general d-q control strategy in the rotor-flux-oriented frame so as to benefit the development of advanced permanent magnet synchronous generator control technology. Compared to traditional approaches, the specific features of the article are (1) a steady-state permanent magnet synchronous generator model in a d-q reference frame, (2) a simulation mechanism that reflects the general permanent magnet synchronous generator d-q control strategy, (3) an integrative study that combines generator-converted power with extracted wind power characteristics, and (4) a joint investigation incorporating both steady-state and transient evaluations. Extensive simulation-based analysis is conducted to study how permanent magnet synchronous generator characteristics are affected by different d-q control conditions and are interacted with wind power drive characteristics in power generation and speed regulation of a permanent magnet synchronous generator wind turbine.

Wind Turbines with Permanent Magnet Synchronous Generator and Full-Power Converters: Modelling, Control and Simulation

This paper presents power quality issues of a grid connected wind generation system with a MW-class direct-driven permanent magnet synchronous generator (PMSG). A variable speed wind turbine model was simulated and developed with the simulation tool of PSCAD/EMTDC. The model includes a wind turbine with one mass-model drive train model, a PMSG model and a full-scale voltage source back to back PWM converter. The converter controller model is employed in the dq-synchronous rotating reference frame and applied to both generator and grid sides. To achieve maximum power point tracking, a tip speed ratio method is applied in machine side, whereas DC voltage control is applied in grid side to achieve constant DC voltage. Due to wind fluctuation and power oscillation as a result of wind shear and tower shadow effects (3p), there will be a fluctuation in the output power and voltage. The concerned power quality issues in this work are Harmonics, power fluctuation and flicker emission. The measurements will be carried out under different wind speed and circumstances.

The present paper aims to design shunt active power filter (APF) for harmonic cancelation of grid-connected wind turbine (WT). The wind energy conversion system (WECS) consists of permanent magnet synchronous generator (PMSG) driven by a variable-speed WT. The output of the PMSG is connected to a direct three phase AC/AC matrix converter (MC) to interface the system with the distribution grid. The MC controls the wind maximum power point tracking (MPPT) via perturbation and observation (P&O) technique. The MC output current harmonics and harmonics of non-linear load are canceled by the proposed shunt APF based on d-q theory. The system under study is simulated using MATLAB/SIMULINK platform. The digital results prove that, the suggested system can submit the generated wind power to the grid without currents/voltages harmonic distortion at grid side, it can also satisfactory eliminate the non-linear load harmonic currents. The system dynamic performance is investigated under different wind speed and loading conditions. The system responses prove that the system works significantly irrespective of wind speed values and demanded load.

A new practical way of modelling direct-driven permanent magnet synchronous generator (PMSG) wind turbines is proposed. The model emphasizes on the wind-rotor-to-PMSG-to-converter-to-grid system, which is the main energy flow system of the direct-driven wind turbine. In this article, a new wind-rotor back propagation neural network is proposed, which consists of a four-layer network and is used to describe the wind-rotor aerodynamic characteristics. According to the orthogonal experimental method, 1200 sets of wind-rotor aerodynamic data, which are calculated based on combining blade element momentum-modified theory with a dynamic stall model, are adopted as the sample data; and the wind-rotor neural network is trained using the Levenberg–Marquardt algorithm. Then, the coupling dynamic models of the wind-rotor and PMSG, and AC–DC–AC converter model are established, respectively; the control strategies for the generator-side and grid-side converters are constructed, too. The mechanical model, electric model, and control model are integrated into the whole simulation model, and the numerical simulation are carried out. The research results show that all the wind-rotor aerodynamic characteristics, electrical characteristics, and control characteristics can be obtained quickly and efficiently from the constructed model, and are helpful for optimization design and control for large-scale direct-direct PMSG wind turbines.

With the advance of power electronic technology, direct-driven permanent magnet synchronous generators (PMSG) have increasingly drawn interests to wind turbine manufacturers. Unlike a fixed-speed wind turbine, the maximum power extraction of a PMSG wind turbine is affected by (1) electrical characteristics of the generator, (2) aerodynamic characteristics of the turbine blades, and (3) maximum power extraction strategies. In an environment integrating all the three characteristics, it is found in this paper that the existing commercial lookup-table maximum power extraction mechanism suitable to a DFIG wind turbine is not suitable to a PMSG wind turbine. Through the integrative study of all the three characteristics, this paper proposes a novel PMSG maximum power extraction design. The special features of the proposed strategy include (i) an adaptive virtual lookup-table approach for PMSG maximum power extraction and (ii) an implementation of the peak power-tracking scheme based on a novel direct-current vector control configuration. The proposed maximum power extraction mechanism with a nested speed- and current-loop control structure is built by using MatLab SimPowerSystems. Simulation studies demonstrate that the proposed PMSG peak power-tracking strategy has superior performance in various aspects under both stable and gust wind conditions. Copyright © 2010 John Wiley & Sons, Ltd.

Conventional wind energy conversion systems (WECS) typically employ rotor side synchronous frame current control strategies to regulate the active/reactive power supplied by the WECS generator. Such strategies require accurate information regarding the rotor position and speed in order to set the dq frame reference currents and to perform the necessary frame transformations. This information can be obtained using a rotor speed sensor (i.e. a shaft encoder) or via a sensor-less strategy in which a dynamic machine model and stator current measurements are used to estimate the true rotor position. This paper now presents an alternative approach to control the active/reactive power supplied by the WECS permanent magnet synchronous generator (PMSG). The proposed strategy uses the three phase converter modulation commands to identify the phase and frequency of the PMSG stator terminal voltages. This enables the direct regulation of the real and reactive power extracted at the PMSG terminal voltages using a stationary frame Proportional + Resonant (PR) stator current regulation strategy, without requiring precise knowledge of the rotor position. Maximum power point tracking (MPPT) functions are realized using the measured PMSG terminal voltage frequency to form an estimate of the rotor speed. The result is a simple robust WECS control strategy that rapidly and accurately tracks rotor speed changes caused by wind speed variations. Detailed simulation and experimental results obtained for a scaled laboratory prototype system are presented to validate the proposed strategy.

This paper presents a new wind speed sensorless maximum power point tracking (MPPT) controller for variable speed wind energy conversion systems (WECS). The MPPT control of the WECS, in this work, is achieved using optimum speed - power curve of the WECS after taking into account the changes in system efficiency while operating at different operating points due to the change in wind speed. The method proposed is based on the fact that the optimum output power of a WECS at a certain wind speed depends upon the total mechanical power developed by the turbine and efficiency of the WECS at the corresponding optimum speed (OS) of rotation of the turbine. Implementation of this control algorithm requires the knowledge of output power and air density as its inputs in addition to requiring the knowledge of turbine parameters. The proposed method is analyzed experimentally in a variable speed direct drive permanent magnet synchronous generator (PMSG) WECS using a wind turbine emulator.

Low voltage ride through enhancement of a permanent magnet synchronous generator based wind energy conversion system in an islanded microgrid: A dynamic matrix controlled virtual DC machine

This paper proposes a simple technique to extract maximum power at a particular wind speed of a wind energy conversion system (WECS). This system uses permanent magnet synchronous generator (PMSG), uncontrolled rectifier, DC-DC boost converter and a resistive load. It utilizes the DC current and DC voltage obtained after rectification to calculate DC power and to control the duty cycle of the DC-DC boost converter to obtain maximum power point tracking (MPPT). From the measurement of DC current and voltage, maximum DC power can be tracked and optimum value of power coefficient of wind turbine (Cp) can be reached. The advantage of proposed system is that no prior knowledge of wind speed characteristics as well as wind generator optimal power characteristics is required. This system uses fixed pitch angle.

Recently, as wind energy has increased considerably in the electric power generation system, the wind turbines must maintain connected to the grid and improve the system stability during and after the grid faults. The enhancement of fault-ride through (FRT) capability of permanent magnet synchronous generator (PMSG) based on wind energy conversion system (WECS) is a vital issue. An active crowbar protection system in this paper is proposed to the improvement of FRT capability and the enhancement of the power quality of PMSG based on WECS system during and after the grid faults. The active crowbar in this paper is designed from a series resistor with an insulated gate bipolar transistor (IGBT) switch, unlike the passive crowbar, which has only one resistor. The active crowbar protects the power converters from the damaging effects of overcurrent during grid fault. The main aims of the active crowbar system are reduction of the amplitude of stator fault voltages, remains constant DC link voltage, general enhancement in all response of the PMSG, minimizing in the trigger time of the active crowbar. These aims are achieved with the introduction of the active crowbar between the machine side converter (MSC) and PMSG. The proposed protection system implemented a 1.5MVA PMSG based on WECS during different grid faults conditions using MATLAB/Simulation. The proposed protection system is compared with without protection system during different faults conditions and the validity of the proposed protection system is verified by simulation results.DOI: http://dx.doi.org/10.5755/j01.eie.24.2.20637

Wind energy has established as fastest growing renewable energy technology. During last few decades world has witnessed multidimensional development in this area and made this technology acceptable for efficient production of bulk power. Recent research articles and renewable energy market trends have demonstrated the popularity of permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS) for such requirements. Objective of present work is to examine the performance of the cylindrical pole PMSG based wind turbine (WT) interfaced to the grid via back-to-back voltage source converter. Present work focuses on generator performance with zero d-axis current control (ZDC) and maximum torque per ampere control (MTPA), it has been observed that cylindrical rotor PMSG displays identical performance with ZDC and MTPA control. In order to analyze the WECS performance, simulation is done in MATLAB/Simulink platform. Excellent performance is observed and is validated with the obtained performance parameters for the system at steady state. The WECS performance is studied in maximum power point tracking (MPPT) range only.

The direct-drive Permanent Magnet Synchronous Generator (PMSG) wind power imitation platform is an essential requirement for its research, development and product test. It's more efficient and flexible to demonstrate control strategies including the wind turbine's Maximum Power Point Tracking (MPPT). Conventionally, many control strategies of the motor's speed or torque are used to implement the turbine MPPT imitation, which, however, much depend on the motor parameters and are only for the Double Feed Induction Generator (DFIG) system, but rarely for direct-drive PMSG one. Thus, a novel control strategy for the wind turbine MPPT implementation is proposed, which provides a direct power control method of DC motor together with decoupled vector control of PMSG without the speed sensor. Using this control strategy, the system less depends on either parameters of the DC motor or the PMSG, and has excellent dynamic performance and high steady-state precision. The analysis, simulation and experimental results have verified its feasibility and validity.

This paper explains a control strategy for variable speed wind turbine coupled to a permanent magnet synchronous generator (PMSG) in stand-alone mode. The control structure for a variable speed wind turbine is explained with a maximum power extraction. The wind generating system consists of variable speed wind turbine (VSWT) with three types of wind speed data (i) Step wind speed (ii) Staircase wind speed and (iii) random wind speed, Permanent magnet synchronous generator, uncontrolled rectifier, voltage source inverter and Bidirectional DC-DC converter along with a Battery storage system has been presented. The control strategy is so adapted to supply the load with a constant voltage and frequency under load change and wind speed change. The control strategy involves control of the bi-directional DC-DC converter of a battery system in order to maintain the constant DC-link voltage due to the variation in wind speed to the constant DC-link voltage. The control strategy used for Inverter control consists of a DC-link control, voltage and current control which is used to control the load voltage and frequency under load variation. The wind energy system is modelled in MATLAB/ SIMULINK.

In this paper, the implementation of the Maximum Power Point Tracking (MPPT) technique is developed using buck-boost converter. Perturb and observe (P&O) MPPT algorithm is used to searching maximum power from the wind power plant for charging of the battery. The model used in this study is the Variable Speed Wind Turbine (VSWT) with a Permanent Magnet Synchronous Generator (PMSG). Analysis, design, and modeling of wind energy conversion system has done using MATLAB/simulink. The simulation results show that the proposed MPPT produce a higher output power than the system without MPPT. The average efficiency that can be achieved by the proposed system to transfer the maximum power into battery is 90.56%.