An internal model control for enhanced grid-connection of direct-driven PMSG-based wind generators

This paper aims to develop a coordinated controller to enhance the low voltage ride through (LVRT) performance of a permanent magnet synchronous generator (PMSG) based variable speed wind energy conversion system (WECS). This coordinated control comprises of a pitch angle control, a flux weakening control and a static synchronous compensator (STATCOM) control. The pitch angle control is adjusted to smooth the WECS output power fluctuations or to enhance the LVRT performance. The flux weakening controller is used to reduce the overvoltage of DC-link capacitor, and the STATCOM control is used to ensure continuous operation of WECS during symmetrical and asymmetrical grid faults. The proposed coordinated control method is compared with the conventional LVRT strategy based on the braking chopper (BC) via time series simulation results and effectiveness of the proposed control is verified.

Augmenting effectiveness of control loops of a PMSG (permanent magnet synchronous generator) based wind energy conversion system by a virtually adaptive PI (proportional integral) controller

Recently, the electric power generation by wind energy conversion systems (WECSs) has increased significantly. Therefore, wind power generation systems are required to achieve the grid codes (GCs) requirements stated by the power system operators. In case of grid voltage dips, a mismatch between the generated active power from the generator and the active power delivered to the grid is produced. The traditional solution is using a braking chopper (BC) in the DC-link to dissipate this surplus active power. This paper proposes a low-voltage ride through (LVRT) strategy for variable-speed WECSs based on permanent magnet synchronous generators (PMSGs). The proposed method uses the PMSG-rotor inertia to store the surplus active power during the grid voltage dips. Therefore, no additionally hardware components is required. Moreover, a finite control set-model predictive control (FCS-MPC) system for the PMSG is proposed in order to improve the transient performance of the system. The performance of the proposed LVRT strategy is compared with the traditional BC solution for all the operation conditions via simulation results.

Introduction. The integration of Renewable Energy Sources (RESs), particularly Wind Energy Conversion Systems (WECS), is vital for reducing reliance on fossil fuels and addressing climate change. However, this transition poses challenges, including ensuring grid stability in the face of intermittent RESs. Compliance with grid codes is crucial, with a focus on Low Voltage Ride Through (LVRT) capability. Problem. The intermittent nature of RESs, specifically in Permanent Magnet Synchronous Generator (PMSG) based WECS, presents challenges to grid stability during voltage dips. Goal. To enhance voltage stability and LVRT capability in PMSG-based WECS by integrating a Dynamic Voltage Restorer (DVR) with an energy storage device. This involves regulating the input DC voltage to the DVR using a type 2 fuzzy controller, adapting intelligently to changing conditions. Methodology. DVR, powered by an energy storage device, is strategically integrated with WECS. A type 2 fuzzy controller regulates the DC voltage to DVR. The rectified WECS output undergoes processing through an isolated flyback converter. A 31-level Cascaded H-Bridge Multilevel Inverter (CHBMLI) with PI control ensures high-quality AC output. Results. The validation of developed system is executed using MATLAB/Simulink revealing a reduced Total Harmonic Distortion (THD) value of 1.8 %, ensuring significance in LVRT capability. Originality. The strategic integration of DVR with PMSG-based WECS, addresses the LVRT challenges. The use of type 2 fuzzy controller for intelligent voltage regulation and a sophisticated multilevel inverter contributes to the uniqueness of proposed solution. Practical value. The developed system provides benefits by ensuring reliable LVRT capability in PMSG-based WECS with reduced THD of 1.8 % indicating improved grid compatibility. References 26, tables 5, figures 20.

To enhance the control and stability of the wind energy conversion system (WECS) based on direct drive permanent magnet synchronous generator (PMSG), this artefact presents a modified sliding mode control approach. A detailed time domain dynamic model of PMSG-based WECS integrated to infinite bus is also presented in terms of d-q reference frame. In order to compensate the general limitations with regard to various control strategies, a proportional integral (PI) type sliding surface-based fast sliding mode control is executed for the above. A current control strategy has been suggested for real and reactive power control keeping voltage under the desired limit. To justify the superior performance of the proposed controller in terms of robustness, reliability and accuracy compared to PI controller, the control strategy is validated through MATLAB simulation, when the system is subjected to diverse operating conditions like wind speed and system parameter variations.

This paper presents a novel control strategy employing the artificial neural network-based direct torque control (DTC) strategy and direct power control (DPC) strategy for permanent magnet synchronous generator (PMSG)-based wind energy conversion system (WECS). The Aeolos 3 kW wind system ratings are considered in this paper for real time system validation. The proposed control strategy combines artificial neural network (ANN)-based DTC as machine side control (MSC) strategy and ANN-based DPC as grid side control (GSC) strategy in order to track the maximum power and to regulate the active power, respectively. To generate the switching pulse for the converter in generator side and grid side, a neural network-based technique is employed. Furthermore, the DC link voltage is optimised using the GSC topology. The proposed controller provides a stable voltage and power which is an effective solution for grid integration and constant power flow from the generator system to the grid system. The proposed coordinate control strategy is validated using MATLAB/Simulink software to analysis the working condition. The experimental test bench is implemented using dSPACE to study the real time analysis of the proposed control strategy.

This paper displays an simple method for identification of controller for wind based Quadratic Boost Converter Inverter system. India, being the fourth largest wind power generator has attracted numerous researchers towards the improvement of wind energy conversion system. This paper also presents improved controller techniques for a Permanent Magnet Synchronous Generator (PMSG) coupled with Cascaded Quadratic Boost Converter (QBC) and Space Vector Modulation Inverter (SVMI). The digital simulation and execution of PMSG based wind turbine along with QBC and SVM Inverter is presented in a closed loop system. The performance of closed loop system is realized using Proportional Integral (PI) and Fractional Order Proportional Integral (FOPI) controllers. Initially, the AC power from PMSG wind turbine is rectified to DC using rectifier circuit. The DC power from the bridge rectifier is then boosted to the required level using quadratic boost converter. The output from QBC is then given to the SVM inverter. The closed loop investigations are carried with PI and FOPI controllers. The simulation results of both PI and FOPI controlled QBC are compared. The outcome of FOPI controller represents that the steady state error and settling time are reduced when compared to PI controlled closed loop Quadratic Boost Converter. The overall Matlab/simulink model is applied to undergraduate/postgraduate course as a educational tool and assessed thoroughly.

This manuscript introduces an innovative Maximum Power Point Tracking (MPPT) strategy to improve the efficiency of Wind Energy Conversion Systems (WECS) equipped with Permanent Magnet Synchronous Generators (PMSG) under variable wind conditions. The proposed approach integrates Active Disturbance Rejection Control (ADRC) with the Perturb and Observe (P&O) algorithm, effectively addressing challenges such as external disturbances and fluctuating wind environments. By combining ADRC with P&O control, the system achieves enhanced tracking performance and adaptability.To validate the added value of this approach, we compare it with a traditional P&O strategy combined with Proportional Integral (PI) control. For the PI-based method, controller parameters Kp and Ki are optimized using Genetic Algorithm (GA) and Ant Colony Optimization (ACO) to enhance control precision. The Integrated Time Absolute Error (ITAE) objective function is employed to fine-tune these parameters, further optimizing system performance. Our analysis underscores the superiority of ADRC in disturbance rejection and quick adaptability over the PI approach.The proposed strategy is tested under two distinct wind speed profiles—constant and fluctuating—through time-domain simulations in MATLAB/Simulink. Simulation results confirm the superior performance of the ADRC-P&O method, highlighting its effectiveness in maximizing power extraction from wind energy and proving its potential for real-world applications. This study offers a significant advancement in wind energy technology by providing a robust and efficient solution for MPPT in WECS.

To meet the requirement of grid codes about Low Voltage Ride Through (LVRT) of Wind Turbine Generators (WTGs), a Resistor-type Superconducting Fault Current Limiter (R-SFCL) based scheme for Permanent Magnetic Synchronous Generator (PMSG) based WTGs is proposed in this paper. The basic technical principle of the proposed scheme is analyzed based on the proposed equivalent modelling of PMSG-based WTGs under grid faults. Moreover, the resistance modelling of R-SFCL is introduced in detail. Finally, a PMSG-based WTGs integrated with a R-SFCL model is built in PSCAD/EMTDC to validate the feasibility of the proposed scheme on assisting the LVRT operation and improving transient stability of PMSG. The performance evaluation and comparison are also conducted based on the simulation results with the proposed scheme and traditional Braking-Chopper (BC) scheme respectively, which demonstrates the proposed scheme boasts more advantage than BC-based scheme in improving transient stability of PMSG.

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.

The output power of direct-driven wind energy conversion system (WECS) will be limited during grid voltage sag, but the operation of wind turbine will not be influenced by adding damp load in DC-side, then the capability of low voltage ride through (LVRT) may be enhanced. Full power back-to-back PWM converter is adopted in direct-driven variable-speed constant frequency WECS using permanent magnet synchronous generator (PMSG), which can effectively improve system efficiency; the principles of generator-side, grid-side converters and damp load are analyzed in detail, and the whole system modeling of converters is realized. Then the simulation model of converters is built based on Matlab7.3/simulink6.5, and the characteristic during grid voltage sag is simulated; the validity of the model and analysis is verified by simulation, and the results show that direct-driven WECS have good fault ride through capability.

The integral servomechanism based linear output feedback control for wind energy conversion systems (WECSs) with permanent magnets synchronous generator (PMSG) has been designed for maximum power extraction. The extended state space equation for given system's error dynamics has been formed. The linear quadratic regulator's optimal control laws are designed and calculated offline. The maximum power extraction from wind energy is achieved via accurate tracking variable reference of the generator's angular shaft speed. The wind is acted as an external disturbance and its speed is estimated with high order disturbance observer (HODO) enhancing reliability of the whole system in case of fault of the anemometer. The simulation results are shown effectiveness of the proposed control system under nominal parameters and some parameters uncertainties, noise, and modelling errors than with traditional disturbance compensation scheme.

The grid code for renewable energy is increasingly strict to circumvent issues with grid stability and reliability. One grid code standard that is enforced for most modern variable speed wind turbines (WTs) is the low-voltage ride-through (LVRT) criteria, where WTs are to be grid-connected during voltage dips. Traditionally, for permanent magnet synchronous generator (PMSG) WTs, LVRT is achieved by using a DC crowbar or DC chopper to dissipate the power difference between the grid and the generator. Alternatively, a popular LVRT strategy proposed by the research community for PMSG-based wind energy conversion system (WECS) is the stored energy in rotor inertia (SEIRI) strategy, which is done by altering the control of the machine-side converter (MSC) with potential cost savings. However, there are some concerns regarding additional mechanical stress to the drivetrain that may pertain to this method. A hybrid LVRT method has been suggested to combine the crowbar and the SEIRI methods to incorporate the benefits from both methods. In this article, we are studying and comparing the electrical and mechanical performance of PMSG WTs operating with the traditional crowbar, the SEIRI, and the hybrid LVRT method. To do so, the electrical and mechanical dynamics of these strategies are simulated using a two-mass drive train model, which is necessary for analyzing WTs under mechanical transient. Finally, the performance of wind farms with power reserves while using an inertia based LVRT method will be investigated to show the impact of the power reserve on the WT's LVRT mechanical dynamics.

Wind energy is one of the most available and exploitable forms of renewable energy. Variable speed PMSG based Wind Energy Conversion System (WECS) offers many advantages compared to the fixed speed squirrel cage induction generators such as improved stator output operation at better power factor, no maintenance cost for gear box (as it is direct-driven) reduction in weight and losses, higher efficiency and ability to run at low speeds. The elimination of the gear box and brushes can enhance the efficiency of wind turbine by 10%. In this paper a Permanent Magnet Synchronous Generator (PMSG) is modeled whose stator is connected to the constant single phase load (in place of grid) through AC/DC thyristors based rectifier followed by capacitor (dc-link) and DC/DC converter control. Overall arrangement provides constant output to connected load if applied with proper controlling techniques. Hence this proposed wind generation system design can be extended for grid connection also via DC/AC inverter control. Results are simulated and verified in MATLAB/Simulink platform at constant rated (12m/s) and varying (stepped) wind speed for smooth and constant output voltage. DOI: http://dx.doi.org/10.11591/telkomnika.v13i3.7097

In this paper, a nonlinear power transfer matrix model is presented for power control of Permanent Magnet Synchronous Generator (PMSG) wind turbines, incorporating the DC link dynamics to account for transient stability, thereby clarifying the technical aspect and purpose. The rising penetration of wind turbines (WTs) into the power grid necessitates that they remain connected during and after faults to ensure system reliability. During voltage dips, the stator and grid-side converter (GSC) of a permanent magnet synchronous generator (PMSG) system are directly impacted by the sudden voltage changes. These disturbances can induce large transient voltages and currents in the stator, which in turn may lead to uncontrolled current flow in the rotor circuit and stress the converter components. Moreover, Low Voltage Ride-Through (LVRT) is a critical requirement for grid connection to Wind Energy Conversion Systems (WECS). It ensures that WTs remain connected and operational during short periods of grid voltage dips (faults), instead of disconnecting immediately. This capability is essential for maintaining grid stability. However, in this paper, the authors propose an LVRT scheme for a grid-connected PMSG-based WECS. A sequence of attempts was performed to validate the effectiveness of the proposed control scheme under fault conditions and to improve its overall performance.