Direct-drive Permanent Magnet Synchronous Wind Research Articles

Cooperative Primary Frequency Regulation Strategy of Wind Storage System Based on Variable Inertia Coefficient

Direct-drive permanent magnet synchronous wind turbine-generator (PMSG) is connected to the grid through the rotor side and grid side converter. The rotor speed is decoupled from the grid frequency, so PMSG output power cannot respond to the change in system frequency. However, with the gradual increase of wind power penetration, the static stability of system frequency is weakened, so the new grid-connected wind farm should have the ability of active frequency support. This paper proposes a cooperative primary frequency regulation (PFR) strategy for wind storage systems based on variable inertia coefficient. PMSG provides inertia based on the distribution of rotational kinetic energy and modifies the polarity of the inertia coefficient at the frequency recovery stage to speed up the frequency recovery. Droop control is realized by energy storage and variable power tracking control (VPPT). Energy storage and VPPT respectively suppress the frequency decrease/increase and only participate in the down/up single-side PFR, which can reduce the energy storage configuration capacity. And a safety discharge coefficient considering the state of charge (SOC) is introduced to prevent over-discharge of energy storage devices when outputting energy. Finally, the PFR capability of PMSG under the proposed control strategy is verified by simulation results.

Primary Frequency Regulation Strategy of PMSG-Based Wind Turbines Integrated Inertia Control

Direct-drive permanent magnet synchronous wind turbine-generator (PMSG) generally operates in maximum power point tracking (MPPT) mode. PMSG cannot provide additional active power support when the grid frequency fluctuates.The gradual increase of wind power penetration leads to greater frequency regulation pressure, which brings hidden dangers to the power grid. This paper focuses on the grid connection of direct-drive PMSG, proposing a primary frequency regulation strategy integrated with inertia control. The proposed strategy controls the rotor kinetic energy to simulate inertia of synchronous units by adding the support power of the response frequency variation. It concludes with variable power tracking control and energy storage system control. Compared with the traditional strategy retains active power, this proposed strategy increases wind energy utilization. Adopting variable power tracking control combined with energy storage can overcome secondary frequency drop and reduce energy storage configuration capacity.

Modeling of Direct-Drive Permanent Magnet Synchronous Wind Power Generation System Considering the Power System Analysis in Multi-Timescales

The dynamics of wind power generation cannot be neglected in the modern power system and could have a great impact on the system dynamics, even raising the risk of a blackout. Because of this, power system simulation has to include the model of wind power generation. However, due to the high order of the full model of the wind power generator, it is impossible to model them in detail in the use of the power system dynamic simulation considering the thousands of wind generators in the grid. In this context, a simplified model is normally used with the trade-off in lower accuracy. As a direct-drive permanent magnet synchronous wind power generation system (D-PMSG) would take up a certain occupation in the modern power system, a proper D-PMSG simplified model is needed in the power system simulation. For a different research purpose in a different timescale, a different complexity of the model can be used to maximize the accuracy, in the meantime speeding up the simulation. This paper proposes a set of simplified models of the direct-drive permanent magnet synchronous wind power generation system (D-PMSG) and classifies them according to the timescale of the dynamics and the use cases, i.e., faults (transient stability analysis), system contingencies (voltage and frequency stability analysis) and wind speed variations (energy transformation). The accuracy of the proposed simplified models is verified by comparing them with the detailed D-PMSG electromagnetic transient mode in Matlab/Simulink, and their use case of the power system simulation is validated based on the case study of the IEEE 39-bus system considering the above scenarios.

A Dual Adaptive Inertia and Damping Control Strategy of ANFIS-VSG for Direct-drive Permanent Magnet Synchronous Wind Generator Systems

A Dual Adaptive Inertia and Damping Control Strategy of ANFIS-VSG for Direct-drive Permanent Magnet Synchronous Wind Generator Systems

Ripple Analysis and Suppression Method Research of Direct Drive Permanent Magnet Synchronous Wind Turbine under Wind Shear

Wind shear is among the important sources of torque fluctuation on mechanical side and output power fluctuation on electromagnetic side and grid connection point, which frequency are triple turbine rotation frequency. With the increase in wind turbine single capacity and wind power integration scale, the power fluctuation caused by wind shear cannot be ignored. The paper takes a direct-drive permanent magnet synchronous wind turbine (PMSWT) as the research object. Firstly, the fluctuation transfer mechanism model is established; then, the current ripple is extracted by a notch filter to calculate the voltage control signal to suppress power fluctuation actively by the DC link capacitor which absorbs fluctuation energy. The simulation experiment shows that the suppression strategy is effective and reliable.

Switched model based control of dual-PWM converters in the direct-drive permanent magnet synchronous wind turbine system

Nowadays, permanent magnet synchronous generator (PMSG) based direct drive wind power generation systems are developing rapidly and are attracting more and more attention. Dual-PWM (pulse width modulation) converters, as full power converters of the direct-drive wind power system, have excellent performance and have been widely used in recent years. The effective control of the back-to-back Dual-PWM converters plays an important role in generating the wind power efficiently. As the back-to-back Dual-PWM converters of the direct-drive wind power generation system can be considered as switched systems according to their working characteristics, this study presents one switched model based control strategy for the control of the Dual-PWM converters. First, the switched dynamic models of the converters on the PMSG side and the grid side are established, respectively. In contrast to the traditional averaged or linearized models, the proposed models can be more precise because no approximation will be introduced when the wind speed changes. Then, in order to realize the highest convergent rate, the min-projection strategy based switched control laws are derived. Furthermore, the stability analysis is done to assure the global stability of the proposed control strategy. Finally, detailed simulations and experiments are available to verify the proposed control method. The simulation and experimental results demonstrate that the proposed models and the control strategy are correct and effective. Comparing with the conventional proportional-integral control method, this paper integrates the back-to-back Dual-PWM converters as part of the proposed controller and utilizes the states of the converters as control variables, and thus, faster torque dynamics can be achieved.

Research on Inverter Side Steady Operation of Direct-Drive Permanent Magnet Synchronous Wind Power System

Currently, back-to-back converter is widely used in rectifier and inverter of direct-drive permanent magnet synchronous wind power system. But there are two shortages in the system, not stable of control effect and higher ripple of DC voltage. The dual-channel parallel boost converter can shunt the DC current, reduce the ripple effectively, and improve the quality of inverter side DC current. The paper uses the space vector pulse width modulation control strategy to control the inverter. Simplifying and decoupling the complex control system and control the DC bus voltage to remain stable. The simulation results confirm that dual-channel parallel boost converter have a better control effect than back to back converter, it through control the inverter to make power quality reached the grid connected requirement, verified the correctness of the design of inverter.

Maximum Wind Power Tracking Control Based on PID and Feedback Linearization

Based on the mathematical model of permanent magnet synchronous generator, the paper discussed the effect of the simplifying torque coefficient equation on direct-drive permanent magnet synchronous wind power generator. On the basis of feedback linearization principle, designed a PID and feedback linearization compound controller in this paper, and validated under varying wind speed, power coefficient remains at a constant value, which reached the maximum wind power capture purposes. Using MATLAB/simulink tool to build direct-drive permanent magnet synchronous wind power system simulation model, the paper verify the stability of the system when the external applied load mutate. The result shows that the control strategy of the composite is effective and timely when tacking the maximum power.

Wind Power Development in Power Grid and Study on Dispatching Strategy

Firstly, This paper summarizes the development situation of wind power in China, and analyzes the operation characteristics of all types of generating units one by one according to constant speed constant frequency asynchronous wind turbine, double-fed asynchronous wind turbine and direct-driven permanent magnet synchronous wind turbine. Then various effects of wind power integration on power grid are analyzed based on the actual situation of power grid. Finally, according to these effects, various measures of strengthening wind power integration management are proposed from management and technology levels. These measures are generally instructive and applicable to the same types of power grid with wind power.

Analysis of Low Voltage Ride-Through Capability for Variable Speed Wind Turbines Using Experimental and Measured Data

With an increasing amount of wind energy installed, the behavior of wind turbines during grid disturbances becomes more and more important. This paper introduces the basic structures of doubly-fed wind turbines and direct-drive permanent magnet synchronous wind turbines and analyses the capability of low voltage ride through (LVRT) of the wind turbines. Finally this paper elaborates the principle and the procedures of the LVRT tests. The results of the tests show that: Doubly-fed wind turbines and direct-drive permanent magnet synchronous wind turbines are equipped with LVRT capability. The turbines are able to operate normally without disconnection and provide reactive power to support grid restoration during the dip. The direct-drive permanent magnet synchronous wind turbines are superior to the doubly-fed wind turbines on LVRT since a full-power converter is used.

Dynamic Modeling and Operation Strategy for a Microgrid With Wind and Photovoltaic Resources

This paper presents a dynamic modeling and control strategy for a sustainable microgrid primarily powered by wind and solar energy. A current-source-interface multiple-input dc-dc converter is used to integrate the renewable energy sources to the main dc bus. Potential suitable applications range from a communication site or a residential area. A direct-driven permanent magnet synchronous wind generator is used with a variable speed control method whose strategy is to capture the maximum wind energy below the rated wind speed. This study considers both wind energy and solar irradiance changes in combination with load power variations. As a case study a 30-kW wind/solar hybrid power system dynamic model is explored. The examined dynamics shows that the proposed power system is a feasible option for a sustainable microgrid application.

Unity Power Factor Control of a Direct-Driven Permanent Magnet Synchronous Wind-Power Generator Based on Three-Level Converter

Direct-driven permanent magnet synchronous generator (PMSG) has become an important research subject besides the double-fed induction generator. With the increasing of unit capacity, the study of topology of high power converters based on multi-level converter is attracting more and more attention. The study of vector control of the direct-driven permanent magnet synchronous wind turbines based on three-level converter is carried out in this paper. Based on the maximum wind-energy capture control of the PMSG, the unity power factor operation of PMSG is realized by controlling the d-axis current to zero in the generator-side converter. A detailed comparative study of two-level system and three-level system is conducted. The simulation results verify the validity of this algorithm.

Investigating the overload capacity of a direct-driven synchronous permanent magnet wind turbine generator designed using high-voltage cable technology

Utilization of wind energy to maximum permissible limits for generating electrical power has become necessary to meet the global energy demands. Under such circumstances the present day conventional wind turbine generators pose a limitation regarding the overload capability, specifically significant when they need to operate in high-energy wind conditions. It is proposed that by employing a completely different generator winding concept, based on high-voltage cable technology, to a specific generator, it is possible to increase the generator overload capabilities and thereby making it operationally efficient in high wind speed situations. Therefore, the possibility of extracting more energy is predicted to increase. Simulations, based on finite-element methods combined with external circuit models for the generator, have been performed. The results demonstrate that under given thermal and electrical restrictions, a direct-driven permanent magnet synchronous wind turbine generator, based on high-voltage cable windings, is capable of being overloaded more than twice the rated power, thus making it very suitable for strong wind situations.