Variable speed wind-power system based on variable frequency transformer and control method of variable speed wind-power system

Abstract

The invention discloses a variable speed wind-power system based on a variable frequency transformer and a control method of the variable speed wind-power system. The variable speed wind-power system comprises a cage type wind-power unit group, a variable frequency AC bus, a booster transformer, a high voltage transmission line, a step down transformer, a variable frequency transformer and a power frequency power grid, wherein a variable frequency AC sent by the cage type wind-power unit group is collected to the variable frequency AC bus, the variable frequency AC subjected to voltage reduction of the step down transformer enters the variable frequency transformer, the variable frequency transformer converts the variable frequency AC into power frequency AC, and the power frequency AC is injected into the power frequency power grid. According to the variable speed wind-power system based on the variable frequency transformer, the single-machine capacity of the wind-power unit group can be increased, the failure rate of the wind-power unit group is reduced, the maintenance work is reduced, the effective power generation time is increased, the wind energy utilization rate can be increased, and mechanical stress and output power fluctuation are decreased. The control method is simple in control and is convenient for operation.

Description

technical field [0001] The invention belongs to the field of wind power generation, relates to the development of offshore wind farms and the renovation of existing constant-speed wind farms, and in particular to a variable-speed wind power system based on a variable-frequency transformer and a control method thereof. Background technique [0002] Wind power generation is currently one of the fastest-growing renewable energy power generation methods with the most large-scale development conditions and commercial development prospects. Offshore wind power has the advantages of high wind speed, low turbulence intensity, and stable wind speed and direction, and is an inevitable trend in the future development of the wind power industry. my country's offshore wind energy resources are abundant and close to the eastern power load center, which is conducive to grid consumption and avoiding long-distance power transmission. Therefore, vigorously developing offshore wind power resou...

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Problems solved by technology

The existing low-voltage ride-through schemes of cage-type wind turbines have the following problems: ① STATCOM or SVC output reactive power to restore the wind farm terminal voltage, because the reactive power output capabilities of STATCOM and SVC are proportional to the voltage and the square of the voltage, respectively , the reactive power output capacity is greatly reduced during the voltage drop, so a large-capacity reactive power compensation device is required, resulting in high cost; ②The series dynamic voltage regulator is used to maintain the terminal voltage of the wind turbine at the rated value during the grid fault, Since the series dynamic voltage regulator must absorb and consume most of the active power generated by the wind turbine, it also requires a large-capacity power electronic device; The dynamic resistance does not produce reactive power, and it cannot solve the problem of transient instability when the load power factor is low

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