A maximum power output control method suitable for centralized variable current control of variable speed wind turbines

Abstract

The invention discloses a maximum power output control method suitable for controlling a variable speed wind turbine group through concentrated variable flow. According to n wind turbines which are controlled by the same converter in a concentrated mode and are constant in rotating speed and different in input air speeds, the concentrated converter and overall wind turbine propeller pitch variation mechanisms are controlled in a coordinated mode, and therefore maximum power output of the wind turbine group is achieved. A control objective of the concentrated converter is that the speed of the wind turbine with the higher wind speed approaches to the optimal rotating speed as much as possible and a control objective of the propeller pitch variation mechanisms is that the highest wind energy utilization rate of the wind turbine with the lower wind speed is obtained at the unified rotating speed of the wind turbine group. The optimal calculation method is adopted and the frequency conversion alternating current bus frequency and the overall wind turbine propeller pitch angle which correspond to the maximized output power of the wind turbine group are worked out. The maximum power output control method is suitable for the variable speed wind turbine group controlled by an AC-DC converter in a high-voltage direct current power transmission system and an AC-AC frequency converter in a frequency division power transmission system.

Description

technical field [0001] The invention belongs to the field of wind power generation, and relates to a variable-speed wind generator group under centralized variable-flow control, in particular to a maximum power output control method suitable for centralized variable-flow control and variable-speed wind turbine group. Background technique [0002] Compared with onshore wind power generation, offshore wind power generation has the advantages of high wind speed, low turbulent intensity, and stable wind speed and direction, and is the main trend of the development of the wind power industry. [0003] It is the mainstream solution for onshore wind farms to configure individual converters for each wind turbine to achieve maximum wind energy capture. However, for offshore wind farms, offshore maintenance costs are high, and maintenance after failure may be difficult to carry out in time due to weather and marine environment, resulting in long-term downtime. If the wind turbine clu...

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Problems solved by technology

However, both solutions face the same problem: the speed of all wind turbines on the variable frequency AC bus is basically the same, and the uneven distribution of wind speed in the wind farm will lead to wind energy loss.

[0005] 1. Assuming that the wind speed in the wind farm is basically the same, and the wind turbine group is controlled to operate at the average optimal speed, the loss of wind energy in this way is relatively large;

[0006] 2. Carry out centralized control of wind turbine groups in groups. By weighing wind energy loss and system investment, the number of wind turbines controlled by each converter unit is selected as a compromise. However, the control method still follows the idea of ​​single-machine maximum wind energy capture, and does not address uneven wind speed. The distribution is specially optimized;

[0007] 3. Apply disturbance to the frequency of the variable frequency AC bus and observe the power change trend of the wind farm to dynamically search for the optimal frequency. This method is easy to fall into a local maximum and does not involve pitch angle optimization;

[0008] 4. The output power function of the wind farm is derived from the variable frequency AC bus frequency, and the frequency when the derivative is zero is the optimal frequency. This method is only optimized for frequency and does not involve pitch angle optimization

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