CN-119401539-B - Land wind power transmission system

CN119401539BCN 119401539 BCN119401539 BCN 119401539BCN-119401539-B

Abstract

The invention discloses a land wind power transmission system which is used for solving the problems of AC collection and delivery of harmonic resonance, reactive power transmission and the like existing in the prior art. The land wind power transmission system comprises a wind power transmitting end unit and a wind power receiving end unit, wherein the wind power transmitting end unit comprises a direct current transformer and more than two wind power units, a machine side converter is arranged in each wind power unit and corresponds to one low-voltage circuit breaker, a direct current circuit breaker is arranged on each direct current transformer in a bipolar mode, electric energy generated by each wind power unit is rectified into first direct current through the machine side converter and is connected into the direct current transformer in parallel through the low-voltage circuit breaker to be boosted into second direct current, the second direct current is sent into the wind power receiving end unit through a bipolar direct current circuit breaker of the direct current transformer, and after the second direct current is converted by the receiving end converter, the second direct current is boosted through the connecting transformer and is connected into an alternating current power grid through the starting circuit.

Inventors

PENG FAXI
LI GUIYUAN
HOU TING
HUANG WEIHUANG
LU YUXIN
ZOU CHANGYUE
XU DIZHEN
LIU TAO
GUO ZHU
CAI DONGXIAO
CAO RUNBIN

Assignees

南方电网科学研究院有限责任公司

Dates

Publication Date: 20260505
Application Date: 20241125

Claims (9)

1. A land wind power transmission system is characterized by comprising a wind power transmitting end unit and a wind power receiving end unit, wherein, The wind power transmission end unit comprises a direct current transformer and more than two wind power units, wherein a machine side converter is arranged in each wind power unit, and each wind power unit corresponds to one low-voltage circuit breaker; For each wind turbine generator, the electric energy generated by the wind turbine generator is rectified into first direct current through the machine side converter, and is connected into the direct current transformer in parallel through the low-voltage circuit breaker; The first direct current is boosted into second direct current through the direct current transformer, and the second direct current is sent into the wind power receiving end unit through a bipolar direct current breaker of the direct current transformer; the wind power receiving end unit comprises a receiving end converter station, a connecting transformer and a starting loop; After the second direct current is subjected to current conversion through the receiving-end converter station, the second direct current is subjected to secondary voltage boosting through the connecting transformer, then passes through the starting loop, and finally is connected into an alternating current power grid; The receiving end converter station adopts a full-bridge half-bridge hybrid MMC converter with direct-current fault clearing capacity, wherein the bipolar direct-current circuit breakers are respectively an anode direct-current circuit breaker and a cathode direct-current circuit breaker; When the plus or minus 30kV direct current overhead line breaks down, the full-bridge half-bridge hybrid MMC converter is matched with the bipolar direct current breaker together to remove the direct current line faults, the method comprises the steps that the line protection of the wind power transmitting end unit and the line protection of the wind power receiving end unit detect faults and execute fault removing actions respectively to achieve the common matching of the transmitting end and the receiving end direct current line faults, the line protection of the wind power transmitting end unit generates tripping instructions, the tripping instructions are sent to the positive direct current breaker and the negative direct current breaker simultaneously to control the positive direct current breaker and the negative direct current breaker to be tripped, the line protection of the wind power receiving end unit generates voltage control instructions, and the voltage control instructions are sent to the full-bridge half-bridge hybrid MMC converter, so that the positive and negative voltage of the receiving end direct current side of the full-bridge half-bridge hybrid MMC converter is controlled to be below 0.
2. The land wind power transmission system of claim 1, wherein a mechanical portion of each of said wind turbines is 690V ac, and electrical energy generated by said wind turbines is rectified to a first dc power of ±550V by said machine side converter.
3. The land wind power transmission system according to claim 2, wherein the first direct current of +/-550V obtained by rectification of the machine side converter is connected in parallel to the input end of the direct current transformer through the low voltage circuit breaker, wherein the input end of the direct current transformer corresponds to a low voltage side, and the output end corresponds to a high voltage side; The low voltage side of the dc transformer boosts a first dc voltage of 550V to a second dc voltage of 30kV and outputs via the high voltage side of the dc transformer.
4. A land wind power transmission system according to claim 3, wherein said dc transformer is constituted by a plurality of dc converter units, said plurality of dc converter units being coupled in series-parallel combination; boosting and rectifying the first direct current of +/-550V through each direct current converter unit, and outputting direct current rectifying power; and carrying out voltage summation according to each direct current rectifying power to obtain a second direct current of +/-30 kV.
5. The land wind power transmission system of claim 4, wherein each of said dc transformer units is comprised of an IGBT module, a high frequency transformer, and a rectifying and filtering output; In each direct current transformer unit, the first direct current of +/-550V is subjected to alternating current inversion through the IGBT module, then is boosted through the high-frequency transformer, and then is subjected to rectification and filtering through the rectification filtering output to output direct current rectification current.
6. An onshore wind power transmission system according to any one of claims 3 to 5 wherein, After the second direct current of +/-30 kV passes through the full-bridge half-bridge hybrid MMC converter for conversion, the second direct current is boosted by the connecting transformer for the second time to obtain boosted alternating current of 35kV, and then the boosted alternating current passes through the starting loop and finally is connected into an alternating current power grid through 35kV power frequency alternating current power transmission.
7. The land wind power transmission system of claim 1, wherein said bipolar dc breaker and said full-bridge half-bridge hybrid MMC converter are both of symmetrical unipolar topology.
8. The land wind power transmission system according to claim 1, wherein when the transmitting end and the receiving end perform fault clearing actions, after a preset recovery time is set free, the full-bridge half-bridge hybrid MMC converter recovers the positive and negative voltages of the direct current side of the receiving end to +/-30 kV, and the positive dc breaker and the negative dc breaker are reclosed at the same time, and the land wind power transmission system resumes operation.
9. The land wind power transmission system according to claim 1, wherein when the system capacity is greater than or equal to a preset capacity threshold, the bipolar dc breaker and the full-bridge half-bridge hybrid MMC converter both adopt a true bipolar topology; When one of the dipoles breaks down, the broken down one pole enters a fault crossing state, and the direct current breaker with the same fault pole and the full-bridge half-bridge hybrid MMC converter cooperate to execute the action of clearing the direct current line fault; the line operation of the one pole that is not faulty is not affected.

Description

Land wind power transmission system Technical Field The invention relates to the technical field of wind power transmission, in particular to a land wind power transmission system. Background The wind power generation base gathers dominant resources, can fully exert scale effect, reduces power generation cost, and is an important direction of large-scale development of wind power generation. Currently, wind power generation systems mainly include two modes of ac collection-ac delivery and ac collection-dc delivery. However, if the ac collection-ac delivery system is adopted, problems such as harmonic resonance and reactive power transmission are prominent. If the alternating current collecting-direct current sending mode is adopted, the problems of more electric energy conversion links and high system cost exist. Disclosure of Invention The invention provides a land wind power transmission system which is used for solving or partially solving the problems of AC collection and sending out such as harmonic resonance, reactive power transmission and the like in the prior art. The invention provides a land wind power transmission system which comprises a wind power transmitting end unit and a wind power receiving end unit, wherein, The wind power transmission end unit comprises a direct current transformer and more than two wind power units, wherein a machine side converter is arranged in each wind power unit, and each wind power unit corresponds to one low-voltage circuit breaker; For each wind turbine generator, the electric energy generated by the wind turbine generator is rectified into first direct current through the machine side converter, and is connected into the direct current transformer in parallel through the low-voltage circuit breaker; The first direct current is boosted into second direct current through the direct current transformer, and the second direct current is sent into the wind power receiving end unit through a bipolar direct current breaker of the direct current transformer; the wind power receiving end unit comprises a receiving end converter station, a connecting transformer and a starting loop; After the second direct current is subjected to current conversion through the receiving-end converter station, the second direct current is subjected to secondary voltage boosting through the connecting transformer, then passes through the starting loop and finally is connected into an alternating current power grid. Optionally, the mechanical part of each wind turbine generator is 690V ac, and the electric energy generated by the wind turbine generator is rectified into a first direct current of ±550v by the machine side converter. Optionally, a first direct current of +/-550V obtained after rectification of the machine side converter is connected in parallel to the input end of the direct current transformer through the low-voltage circuit breaker, wherein the input end of the direct current transformer corresponds to a low-voltage side, and the output end of the direct current transformer corresponds to a high-voltage side; The low voltage side of the dc transformer boosts a first dc voltage of 550V to a second dc voltage of 30kV and outputs via the high voltage side of the dc transformer. Optionally, the dc transformer is composed of a plurality of dc converter units, and the plurality of dc converter units are connected in series-parallel connection; boosting and rectifying the first direct current of +/-550V through each direct current converter unit, and outputting direct current rectifying power; and carrying out voltage summation according to each direct current rectifying power to obtain a second direct current of +/-30 kV. Optionally, each direct current transformer unit is composed of an IGBT module, a high-frequency transformer and a rectifying and filtering output; In each direct current transformer unit, the first direct current of +/-550V is subjected to alternating current inversion through the IGBT module, then is boosted through the high-frequency transformer, and then is subjected to rectification and filtering through the rectification filtering output to output direct current rectification current. Optionally, the receiving end converter station adopts a full-bridge half-bridge hybrid MMC converter with direct-current fault clearing capacity; after the second direct current of +/-30 kV passes through the full-bridge half-bridge hybrid MMC converter for conversion, the second direct current is boosted by the connecting transformer for the second time to obtain boosted alternating current of 35kV, and then the boosted alternating current passes through the starting loop and finally is connected into an alternating current power grid through 35kV power frequency alternating current power transmission. Optionally, the bipolar direct current circuit breaker at the sending end is respectively connected to two ends of the full-bridge half-bridge hybrid MMC converter at the re