Arklow Offshore Wind Farm is located in Wicklow County, Ireland. It is planned to have 200 wind turbine units with a total installed capacity of 500MW from a distance of 7~12km on the east coast of Ireland. The current site selection and demonstration work has been completed and the project will be carried out in phases to 200 It will be put into production in 7 years and will become the largest offshore wind power project in the world. The first phase of the project, commissioned in 2003, will provide approximately 25 MW of electricity to the Irish power system. 7 CE 3.6MW wind turbines will be installed in this phase of the project. It is the wind turbine with the largest single capacity currently in commercial operation. It adopts inverters such as double-fed induction generators and 丨CBT control, variable pitch control and dynamic voltage. And a series of new and practical technologies such as reactive power compensation. At the same time, the wind farm has reached an access grid agreement with the Irish Power Supply Commission (ESB). The wind farm will be connected to ESB's existing 38kV substation through submarine cables. 1. Because Ireland has a short history of wind power development and lacks relevant experience, especially the experience of grid-connected operation of large-scale wind farms, research is urgently needed. Analyze the interaction between similar large-scale wind farms and the Irish national grid, especially the dynamic stability of the system and the ability of wind farms to resist system disturbances.
1 Doubly-fed asynchronous generator model Doubly-fed asynchronous generator has a wound rotor, which is connected to the grid through a voltage source inverter controlled by ICBT. The IGBT operates in four quadrants. The module uses pulse width modulation to output a sine wave voltage. This feature ensures that the voltage and frequency of the generator will remain constant and will not be affected by the speed of the rotor, so that effective use of slip power can be achieved and heat loss can be reduced. If the traditional induction generator is regarded as a special case of the rotor short circuit, then the double-fed induction generator model can be written as: Transformer doubly-fed motor working principle of the rectifier circuit, false iS inverter is the ideal inverter . In order to prevent the model from being distorted, the stability of the DC link in the inverter circuit needs to be considered. Therefore, an anti-time-action low-voltage protection mechanism is added to the model. When the system voltage drops for a period of time, such as 90% normal voltage, delays 1~2nhn cut off the wind turbine. The lower the voltage, the shorter the delay. If the voltage drop is very low and reaches the critical value, instantaneously remove the wind turbine: where: fang = 5 +, transient voltage, rotor voltage; terminal voltage, 80 L, stator current t', mechanical power, rE = - Rs, on the stator. The electromagnetic power; A =, f is the system frequency; rotor slip; rotor speed; X = equivalent reactance; transient reactance, 2 redundancy A rotor loop time constant.
This model has been appropriately simplified on the basis of the asynchronous motor model, ignoring the stator transient process, and is suitable for general transient stability analysis. This kind of generator only uses the pulse width modulation voltage source frequency changer in the rotor circuit, the power that needs to deal with only occupies 20% of the total generated power, so the efficiency is quite high. In order to save the simulation time, the speed and offset are simplified in the model; they are the wind energy captured by the fan and the power delivered by the fan to the generator; the fan shaft angle and the generator rotor angle; ZCS is the torque coefficient; P is the air density. r is the fan swept area radius; V is the wind speed; cp is the fan efficiency coefficient, is the blade tip speed ratio 5V = and the blade angle of the Deng Yuexing function 8. Through the variable speed drive, can achieve the fan speed Precise adjustments to track the optimum tip speed ratio over a wide range to ensure that the fan runs at optimum efficiency. In accordance with this operating strategy, the wind turbine can be switched freely in the three operating states of sub-synchronous speed, synchronous speed and super-synchronous speed through the combination of the pitch angle adjustment of the blade and the control of the frequency converter. As shown, the adjustment of the pitch angle of the blade can be achieved by a proportional-integral controller with the rotor speed of the generator as a feedback signal.
I Asia: Interaction between Arklow Offshore Wind Farm and Jurang Grid Gearbox mines Asia: Interaction between Arklow Offshore Wind Farm and Jurland Power Grid Speed ​​feedback propeller moment control mechanism Wind farm connection to grid 3 Connection to grid as shown In order to efficiently transport the electric energy of the wind farm to the Irish national electric grid, a 38kV booster station on the Arklow Shoal needs to be connected to the ESK38kV Arklow substation through a 12km submarine cable. Because the charging capacity of the submarine cable is quite large, it will bring harmful high voltage to the wind farm during low load period. Therefore, a static var compensator (SVC) is installed near the substation, and the reactive power absorbed during normal operation is , Provide dynamic reactive support to the system (and wind farm) in an emergency.
However, the compensation capacity of the SVC is closely related to the voltage level of the system. When the terminal voltage decreases, the output reactive power decreases in a square relationship. Therefore, during the system failure, the support for the wind turbine is limited.
4 Example Analysis The variable speed, double-fed asynchronous wind turbine model developed on the PSS/E dynamic simulation platform can realize seamless connection with the PSS/E transient simulation module.
Wind turbine rotation speed and the angle of the blade pitch curve. It is the curve of fan angular velocity, generator angular velocity and blade angle. Because the wind farm 3 pong fault location is relatively far, so the wind turbine terminal voltage is not much, to be able to smoothly return to normal operation from the fault, without off the net.
As a comparison, a 220kV substation bus is selected as the fault point in the west, south of the power grid and QWin area of ​​the load center. The simulation results are shown in Table 1. Although the timely removal of the fault (150ms) can avoid the loss of the synchronous generator set, in the case of a single fault in three locations, the voltage of the wind generator terminal may be too low to be disconnected. All three faults are near the Dublin area. Therefore, when analyzing the impact of the system on Arklow wind farms, detailed consideration must be given to the conditions in Dublin and nearby power grids.
The installed capacity of the 4.25 MW wind farm Arklow-period wind power plant is 25 MW. After interconnection of 7 GE 3.6 MW wind turbines, the 38 kV step-up transformers are connected to the ESB main system through submarine cables. It is a 220kV substation in the main grid of a 220kV substation that accounts for the instantaneous three-phase short-circuit fault (about 150 ra). The wind turbine generator's terminal voltage and its output (or absorption) watt-hour table 125MW wind farm transient stability analysis area failure Bus Synchronous Wind Turbine Synchronous Generator Restoring Stability Detachment Stability Restoring Stability Decoupling Net Stability Decoupling Stability
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