Hybrid converter and wind power generating system

• US 9,502,991 B2
• Filed: 02/25/2014
• Issued: 11/22/2016
• Est. Priority Date: 05/22/2013
• Status: Active Grant

• Current Assignee: Huazhong University of Science & Technology
• Original Assignee: Huazhong University of Science & Technology
• Inventors: Lin, Weixing, Wen, Jinyu, Wang, Shaorong, Cheng, Shijie
• Primary Examiner(s): Zhang, Jue
• Application Number:
  US14/411,801
• Publication Number:
  US 20150145252A1
• Time in Patent Office: 1,001 Days
• US Class Current: 1/1
• CPC Class Codes: F03D 9/257 the wind motor being part of a wind farm
• CPC Class Codes: H02J 3/36 Arrangements for transfer of electric power between ac networks via a high-tension dc link
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 1/0095 Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
• CPC Class Codes: H02M 7/145 using devices of a thyratron or thyristor type requiring extinguishing means
• CPC Class Codes: H02M 7/19 arranged for operation in series, e.g. for voltage multiplication
• CPC Class Codes: H02M 7/21 using devices of a triode or transistor type requiring continuous application of a control signal
• CPC Class Codes: H02M 7/25 arranged for operation in series, e.g. for multiplication of voltage
• CPC Class Codes: H02M 7/4835 comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects
• CPC Class Codes: Y02E 60/60 Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The present invention discloses a hybrid converter and a wind power generating system, the hybrid converter including a voltage source converter, a line commutated converter and a line commutated converter, a positive DC terminal of the voltage source converter is connected to a negative DC terminal of the line commutated converter, a positive DC terminal of the line commutated converter is connected to a positive DC transmission line, a negative DC terminal of the voltage source converter is connected to a positive DC terminal of the line commutated converter, and a negative DC terminal of the line commutated converter is connected to a negative DC transmission line. The present invention features a self-commutating capability, can be directly connected to a wind farm to convert wind power to DC power, and is able to improve rated voltage and rated power of the hybrid converter, technology of each component thereof is mature, and system reliability thereof is high.

Claims

1. A hybrid converter, comprising a voltage source converter (2), a first line commutated converter (3a), and a second line commutated converter (3b), wherein:

a positive DC terminal of said voltage source converter (2) is connected to a negative DC terminal of said first line commutated converter (3a), a positive DC terminal of said first line commutated converter is connected to a positive DC transmission line (8), a negative DC terminal of said voltage source converter (2) is connected to a positive DC terminal of said second line commutated converter (3b), and a negative DC terminal of said second line commutated converter (3b) is connected to a negative DC transmission line (9); and

an AC terminal of said voltage source converter (2), an AC terminal of said first line commutated converter (3a), and an AC terminal of said second line commutated converter (3b) are connected to a common AC bus (14).

2. The hybrid converter of claim 1, wherein said voltage source converter (2) operates to control an AC voltage of said common AC bus (14), said AC voltage is applied to said first line commutated converter (3a) and said second line commutated converter (3b) to provide commutating voltage for said first line commutated converter (3a) and said second line commutated converter (3b), so that said hybrid converter is able to operate normally without a conventional synchronous generator maintaining AC voltage of said common AC bus (14).

3. The hybrid converter of claim 1, wherein said first line commutated converter (3a) or said second line commutated converter (3b) comprises one or more six-pulse line commutated converter bridges connected in series, and said six-pulse line commutated converter bridge comprises a three-phase full bridge AC-DC converting circuit based on thyristors.

4. The hybrid converter of claim 1, wherein said voltage source converter (2) comprises a three-phase full-bridge AC-DC converting circuit based on fully-controllable power semiconductors.

5. The hybrid converter of claim 1, wherein said hybrid converter further comprises a first bypass switch connected in parallel with said first line commutated converter, and a second bypass switch connected in parallel with said second line commutated converter;

wherein said first bypass switch operates to bypass said first line commutated converter during black-start and power reversal, and said second bypass switch operates to bypass said second line commutated converter during black-start and power reversal, thereby enabling said hybrid converter to have black-start and power reversal capabilities.

6. The hybrid converter of claim 5, wherein said first bypass switch and said second bypass switch are of the same structure, and said first bypass switch comprises a mechanical switch (4), and an anti-parallel thyristor pair (5a, 5b) serially connected with said mechanical switch.

7. The hybrid converter of claim 6, wherein said anti-parallel thyristor pair is formed by multiple thyristors connected in anti-parallel.

8. A wind power generating system, comprising a common AC bus (14), a first step-up transformer (18), a second step-up transformer (20), a third transformer (12), a fourth transformer (13), a hybrid converter (1), and an AC filter (15), and a reactive power compensator (16) respectively connected to said common AC bus (14);

wherein an input port of said first AC transformer (18) is connected to a wind turbine generator set (17), an output port of said first step-up transformer (18) is connected to an input port of said second step-up transformer (20) via an AC transmission line (19), and an output port of said second step-up transformer (20) is connected to said common AC bus (14) via said AC transmission line (21);

wherein

said hybrid converter (1) comprises a voltage source converter (2), a first line commutated converter (3a), and a second line commutated converter (3b);

a positive DC terminal of said voltage source converter (2) is connected to a negative DC terminal of said first line commutated converter (3a), a positive DC terminal of said first line commutated converter is connected to a positive DC transmission line (8) via a first inductor (10), a negative DC terminal of said voltage source converter (2) is connected to a positive DC terminal of said second line commutated converter (3b), and a negative DC terminal of said second line commutated converter (3b) is connected to a negative DC transmission line (9) via a second inductor (11); and

an AC terminal of said second voltage source converter (2) is connected to said common AC bus (14) via said fourth transformer (13), and an AC terminal of said first line commutated converter (3a) and an AC terminal of said second line commutated converter (3b) are respectively connected to said common AC bus (14) via said third transformer (12).

9. The wind power generating system of claim 8, wherein said hybrid converter further comprises a first bypass switch connected in parallel with said first line commutated converter, and a second bypass switch connected in parallel with said second line commutated converter;

wherein said first bypass switch operates to bypass said first line commutated converter during black-start and power reversal, and said second bypass switch operates to bypass said second line commutated converter during black-start and power reversal.

10. The wind power generating system of claim 9, wherein said first bypass switch and said second bypass switch are of the same structure, and said first bypass switch comprises a mechanical switch (4), and an anti-parallel thyristor pair (5a, 5b) serially connected with said mechanical switch.

11. The wind power generating system of claim 10, wherein said anti-parallel thyristor pair is formed by multiple thyristors connected in anti-parallel.

12. The wind power generating system claim 8, wherein said first line commutated converter (3a) and said second line commutated converter (3b) are of the same structure;

said first line commutated converter (3a) comprises one or more six-pulse line commutated converter bridges connected in series, and said six-pulse line commutated converter bridge comprises a three-phase full bridge AC-DC converting circuit based on thyristors.