Control method of offshore wind power uncontrolled rectification direct current power transmission system

Abstract

The invention relates to a control method of an offshore wind power uncontrolled rectification direct-current power transmission system, which comprises the following steps of: setting an offshore wind power uncontrolled rectification direct-current power transmission system which comprises an offshore wind power plant, an offshore converter station, a seabed direct-current submarine cable, an onshore converter station and an onshore power grid which are connected in sequence; the offshore converter station comprises a full-bridge MMC unit and a diode uncontrolled rectification unit. The land converter station comprises a thyristor rectification unit; in the black start process, the land converter station is controlled to pre-charge the full-bridge MMC unit in the offshore converter station, and black start is carried out on the offshore wind plant through the full-bridge MMC unit; during normal operation, according to whether a wind driven generator in the offshore wind power plant has the network construction capability or not, a network construction type control strategy or a network following type control strategy is selected, and energy emitted by the offshore wind power plant is output to a direct current side and sent to an onshore converter station and an onshore power grid through positive and negative pole seabed direct current submarine cables. The method can be widely applied to the technical field of flexible direct current transmission.

Description

technical field [0001] The invention relates to a control method of an offshore wind power uncontrolled rectification direct current transmission system, belonging to the technical field of flexible direct current transmission. Background technique [0002] Offshore wind power development is an important way to build a new type of power system in the future and achieve "carbon peaking and carbon neutrality". At present, the direct current transmission scheme is the only engineering implementation scheme to realize offshore wind power grid connection. However, the current direct current transmission scheme has the following problems: 1) The offshore converter station platform is bulky and expensive; 2) The converter valve generally adopts flexible direct current The inverter has a large number of sub-modules and expensive capacitors. Therefore, reducing the weight of offshore converter valves and offshore converter station platforms and improving the overall economics of HVD...

AI Technical Summary

Problems solved by technology

At present, the direct current transmission scheme is the only engineering implementation scheme to realize offshore wind power grid connection. However, the current direct current transmission scheme has the following problems: 1) The offshore converter station platform is bulky and expensive; 2) The converter valve generally adopts flexible direct current Inverter, a large number of sub-modules, expensive capacitors

However, this DC transmission scheme is generally only applicable to offshore wind power. When offshore wind power is connected to the grid, submarine AC cables cannot achieve long-distance AC connections due to capacitive currents. In addition, modular multilevel converters in onshore converter stations are still There is an expensive problem

[0004]Aiming at the problem of difficult black start of the offshore wind farm connected to the diode uncontrolled rectifier unit, the existing public literature proposes to connect a diode valve in parallel to the DC side of the offshore converter station Auxiliary converter scheme, the auxiliary converter provides grid-connected voltage and black start power supply for offshore wind farms, but because the auxiliary converter needs to be directly connected in series with the DC side of the diode valve, its sub-module selection must be consistent with the DC side voltage match, so the number of sub-modules is large

In order to reduce the cost, some literature proposes to upgrade the topology of the auxiliary converter. The auxiliary converter adopts the combination of high and low arms, and the topology is complex. In order to maintain the voltage balance of the high-voltage arm sub-module capacitors, high-frequency harmonic injection is required. modulation, complex control strategies

In addition, there are also literatures that propose to use large-capacity diesel engines in offshore wind farms to solve the black start problem of offshore wind farms, but offshore wind farms need to transform the wind turbines to have network-type control

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