A system and method for protecting a double-fed wind turbine generator and outgoing cables using electrical quantities

Abstract

The invention discloses a system and method for protecting a doubly-fed wind turbine generator and an outlet cable for electrical quantity, comprising a doubly-fed generator, an outlet cable of the generator, a rotor converter, a phase current transformer on the neutral point side of the generator, a zero-sequence current transformer on the neutral point of the generator, a phase current transformer on the grid side of the converter, a current transformer on the low-voltage side of the step-up transformer of the unit, a differential protection and a zero-sequence grounding protection device, a dry-type current transformer for power supply of the unit and a circuit breaker on the low-voltage side of the transformer. The system and method can identify the fault type, remove the fault and perform emergency shutdown when an electrical fault occurs in the generator and the outlet cable of the generator.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection of new energy wind turbine sets, and relates to a system and method for electrical quantity protection of a double-fed wind turbine generator and an outgoing cable. Background Art

[0002] At present, variable speed and variable pitch wind turbines use variable pitch technology and variable speed constant frequency technology. The speed of the wind wheel can be adjusted according to the change of wind speed to maximize the absorption of wind energy and improve conversion efficiency. The structure of the doubly fed asynchronous generator is similar to that of a wound asynchronous motor. The stator and rotor are three-phase symmetrical, and the rotor current is connected by a slip ring. The change in wind speed is transmitted to the generator through the speed increase gearbox. The frequency and phase of the rotor current can be controlled by the rotor converter to keep the stator current frequency constant. When the generator rotor is higher (lower) than the synchronous speed, the inverter energy is controlled to flow into (out of) the power grid, and the motor stator supplies the power grid with a stable frequency.

[0003] In GB / T19960.1 "Wind Turbine Generator Set Part 1: General Technical Conditions", the protection of the generator and the generator output cable of the wind turbine generator set is based on the control system of the unit, mainly including generator over-temperature protection, cable over-winding protection, over-current protection, over-voltage protection, over-power protection, and instantaneous over-power protection. When an electrical fault occurs in the generator and the generator output cable, the over-current protection (converter grid side, machine side) cannot be accurately judged, and the generator over-temperature (bearing, winding) protection, over-voltage protection, over-power protection, and instantaneous over-power protection cannot be timely and effectively judged. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a system and method for electrical quantity protection of a doubly-fed wind turbine generator and its outgoing cables. The system and method can identify the fault type, eliminate the fault and perform emergency shutdown when an electrical fault occurs in the generator and its outgoing cables.

[0005] To achieve the above-mentioned object, the system of electrical quantity protection for a doubly-fed wind turbine generator and an outlet cable of the present invention comprises a doubly-fed generator, an outlet cable of a generator, a rotor converter, a phase current transformer on the neutral point side of the generator, a zero-sequence current transformer on the neutral point of the generator, a phase current transformer on the grid side of the converter, a current transformer on the low-voltage side of the step-up transformer of the unit, a differential protection and a zero-sequence grounding protection device, a dry-type current transformer for the unit power supply, and a circuit breaker on the low-voltage side of the transformer;

[0006] The phase current transformer on the neutral point side of the generator is installed on the phase branch outgoing line on the neutral side of the doubly fed generator. After the phase branch outgoing lines on the neutral side of the doubly fed generator are connected, they are connected to the neutral point through the generator neutral point zero-sequence current transformer. The output end of the doubly fed generator is connected to the transformer low-voltage side circuit breaker through the generator outgoing cable and the unit power dry-type transformer current transformer. The grid side of the rotor converter is connected to the generator outgoing cable through the converter grid side phase current transformer. The unit step-up low-voltage side of the rotor converter is connected to the generator outgoing cable through the unit step-up low-voltage side current transformer.

[0007] The differential protection and zero-sequence grounding protection device is connected to the transformer low-voltage side circuit breaker, the generator neutral point side phase current transformer, the generator neutral point zero-sequence current transformer, the converter grid side phase current transformer, the unit step-up transformer low-voltage side current transformer and the unit power dry-type transformer current transformer.

[0008] The electrical fault occurring within the protection range between the phase current transformer on the neutral point side of the generator, the phase current transformer on the grid side of the converter, the current transformer on the low voltage side of the unit step-up transformer and the dry-type current transformer for unit power supply is one or a combination of the following: a three-phase short circuit fault of the stator winding of the doubly fed generator, a two-phase short circuit fault of the stator winding of the doubly fed generator, a three-phase short circuit fault of the generator output cable, and a two-phase short circuit fault of the generator output cable.

[0009] The electrical faults occurring in the doubly-fed generator and the generator outgoing cable within the protection range of the generator neutral point zero-sequence current transformer are one or a combination of two-phase short-circuit grounding fault of the doubly-fed generator stator winding, single-phase grounding fault of the doubly-fed generator stator winding, two-phase short-circuit grounding fault of the generator outgoing cable and single-phase grounding fault of the generator outgoing cable.

[0010] The electrical analog quantities collected by the differential protection and zero-sequence grounding protection devices include the phase current on the neutral point side of the generator, the phase current on the converter side, the current on the dry high-voltage side of the unit, the zero-sequence current on the neutral point of the generator, the generator terminal voltage and the generator frequency.

[0011] The switching quantities collected by the differential protection and zero-sequence grounding protection devices include the zero-position signal of the variable pitch device and the converter operation signal.

[0012] The tripping outputs of the differential protection and zero-sequence grounding protection devices include the output to the safety chain device, the output to the circuit breaker on the low-voltage side of the transformer and the output to the converter.

[0013] A method for protecting a double-fed wind turbine generator and an outgoing cable by electrical quantity comprises the following steps:

[0014] During the operation of the doubly fed generator, the differential protection and zero-sequence grounding protection devices determine whether there is a three-phase short circuit fault in the stator winding of the doubly fed generator, a two-phase short circuit fault in the stator winding of the doubly fed generator, a three-phase short circuit fault in the generator output cable, a two-phase short circuit fault in the generator output cable, a two-phase short circuit fault in the stator winding of the doubly fed generator, a single-phase grounding fault in the stator winding of the doubly fed generator, a two-phase short circuit grounding fault in the generator output cable, and a single-phase grounding fault in the generator output cable according to the collected electrical analog quantity and switch quantity. When there is a three-phase short circuit fault in the stator winding of the doubly fed generator, a two-phase short circuit fault in the stator winding of the doubly fed generator, a three-phase short circuit fault in the generator output cable, a two-phase short circuit fault in the generator output cable, a two-phase short circuit grounding fault in the stator winding of the doubly fed generator, a single-phase grounding fault in the stator winding of the doubly fed generator, a two-phase short circuit grounding fault in the generator output cable, or a single-phase grounding fault in the generator output cable, the tripping outlet is activated, the safety chain is triggered, and the transformer low-voltage side circuit breaker is tripped.

[0015] The present invention has the following beneficial effects:

[0016] In the specific operation of the system and method for protecting the doubly-fed wind turbine generator and outgoing cables of the present invention, the differential protection and zero-sequence grounding protection devices determine whether a fault occurs based on the collected electrical analog quantities and switch quantities. When a fault occurs, the tripping outlet is activated, the safety chain is triggered, and the low-voltage side circuit breaker of the transformer is tripped. That is, when a fault occurs in the generator and its outgoing cables, the differential protection and zero-sequence grounding protection devices operate the low-voltage side circuit breaker of the transformer connected to the safety chain system, the converter and the power grid through the protection device outlet, the wind turbine generator set is shut down urgently, the generator terminal voltage drops with the speed, and the short-circuit current provided by the generator is quickly cut off; the rectification and inversion functions of the converter are prohibited; and the low-voltage side circuit breaker of the transformer is disconnected to achieve the purpose of cutting off the fault and reduce the loss of electrical equipment during the fault process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of a double-fed wind turbine generator and an outgoing cable in the prior art;

[0018] Figure 2 is a system diagram of the present invention;

[0019] Figure 3 It is the differential protection (fast trip) logic diagram in the present invention;

[0020] Figure 4 It is a differential protection (ratio differential) logic diagram in the present invention;

[0021] Figure 5 This is the ground protection logic diagram of the present invention.

[0022] Among them, 1 is a doubly-fed generator, 2 is the generator outgoing cable, 3 is the rotor converter, 4 is the generator neutral point side phase current transformer, 5 is the generator neutral point zero-sequence current transformer, 6 is the converter grid side phase current transformer, 7 is the unit step-up transformer low-voltage side current transformer, 8 is the differential protection and zero-sequence grounding protection device, 9 is the transformer low-voltage side circuit breaker, and 10 is the unit power dry-type transformer current transformer. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0024] The accompanying drawings show schematic diagrams of structures according to embodiments disclosed in the present invention. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0025] refer to Figure 1 and Figure 2 The system for protecting a doubly-fed wind turbine generator and an outlet cable of an electrical quantity of the present invention comprises a doubly-fed generator 1, an outlet cable of a generator 2, a rotor converter 3, a phase current transformer on the neutral point side of the generator 4, a zero-sequence current transformer on the neutral point of the generator 5, a phase current transformer on the grid side of the converter 6, a current transformer on the low-voltage side of the unit step-up transformer 7, a differential protection and zero-sequence grounding protection device 8, a dry-type current transformer for unit power supply 10 and a circuit breaker on the low-voltage side of the transformer 9;

[0026] The phase current transformer 4 on the neutral point side of the generator is installed on the phase branch outgoing line of the neutral point of the doubly fed generator 1. After the phase branch outgoing lines on the neutral side of the doubly fed generator 1 are connected, they are connected to the neutral point through the generator neutral point zero-sequence current transformer 5. The output end of the doubly fed generator 1 is connected to the transformer low-voltage side circuit breaker 9 through the generator outgoing cable 2 and the unit power dry-type current transformer 10. The grid side of the rotor converter 3 is connected to the generator outgoing cable 2 through the converter grid side phase current transformer 6. The unit step-up and low-voltage side of the rotor converter 3 is connected to the generator outgoing cable 2 through the unit step-up and low-voltage side current transformer 7.

[0027] The differential protection and zero-sequence grounding protection device 8 is connected to the transformer low-voltage side circuit breaker 9, the generator neutral point side phase current transformer 4, the generator neutral point zero-sequence current transformer 5, the converter grid side phase current transformer 6, the unit step-up transformer low-voltage side current transformer 7 and the unit power dry-type transformer current transformer 10.

[0028] The electrical fault occurring within the protection range between the phase current transformer 4 on the neutral point side of the generator, the phase current transformer 6 on the grid side of the converter, the current transformer 7 on the low voltage side of the unit step-up transformer, and the dry-type current transformer 10 for unit power supply is one or a combination of the following: a three-phase short circuit fault of the stator winding of the doubly fed generator 1, a two-phase short circuit fault of the stator winding of the doubly fed generator 1, a three-phase short circuit fault of the generator output cable 2, and a two-phase short circuit fault of the generator output cable 2.

[0029] The electrical fault occurring in the doubly-fed generator 1 and the generator outgoing cable 2 within the protection range of the generator neutral point zero-sequence current transformer 5 is one or a combination of a two-phase short-circuit grounding fault of the stator winding of the doubly-fed generator 1, a single-phase grounding fault of the stator winding of the doubly-fed generator 1, a two-phase short-circuit grounding fault of the generator outgoing cable 2 and a single-phase grounding fault of the generator outgoing cable 2.

[0030] The electrical analog quantities collected by the differential protection and zero-sequence grounding protection device 8 include the generator neutral point side phase current, the converter side phase current, the unit power dry high-voltage side current, the generator neutral point zero-sequence current, the generator terminal voltage and the generator frequency;

[0031] The switch quantities collected by the differential protection and zero-sequence grounding protection device 8 include the zero position signal of the pitch device and the converter operation signal;

[0032] The tripping outlets of the differential protection and zero-sequence grounding protection device 8 include an outlet to the safety chain device, an outlet to the transformer low-voltage side circuit breaker, and an outlet to the converter.

[0033] During the operation of the doubly fed generator 1, the differential protection and zero sequence grounding protection device 8 determines whether there is a three-phase short circuit fault of the stator winding of the doubly fed generator 1, a two-phase short circuit fault of the stator winding of the doubly fed generator 1, a three-phase short circuit fault of the generator output cable 2, a two-phase short circuit fault of the generator output cable 2, a two-phase short circuit grounding fault of the stator winding of the doubly fed generator 1, a single-phase grounding fault of the stator winding of the doubly fed generator 1, a two-phase short circuit grounding fault of the generator output cable 2, and a three-phase short circuit fault of the generator output cable 2. Cable 2 single-phase grounding fault. When there is a three-phase short circuit fault in the stator winding of the doubly fed generator, a two-phase short circuit fault in the stator winding of the doubly fed generator 1, a three-phase short circuit fault in the generator output cable 2, a two-phase short circuit fault in the generator output cable 2, a two-phase short circuit fault in the stator winding of the doubly fed generator 1, a two-phase short circuit grounding fault in the generator output cable 2 or a single-phase grounding fault in the generator output cable 2, the tripping output is activated, the safety chain is triggered, and the transformer low-voltage side circuit breaker 9 is tripped.

[0034] like Figure 3 As shown, when a short-circuit fault with a large short-circuit current occurs in the phase current transformer 4 on the neutral point side of the generator, the phase current transformer 6 on the grid side of the converter, the current transformer 7 on the low-voltage side of the unit step-up transformer, and the dry-type current transformer 10 for the unit power supply, the currents on the four sides are unbalanced, the differential protection is activated, the protection is started without delay, the safety chain is activated, the emergency stop is performed, the slurry is quickly smoothed and the brake is applied, the short-circuit current provided by the generator is quickly cut off, the converter is locked, and the circuit breaker 9 on the low-voltage side of the transformer is disconnected.

[0035] like Figure 4 As shown, when a short-circuit current with a large magnitude occurs in the phase current transformer 4 on the neutral point side of the generator, the phase current transformer 6 on the grid side of the converter, the current transformer 7 on the low voltage side of the unit step-up transformer, and the dry-type current transformer 10 for the unit power supply, the ratio differential protection is activated, and the protection exit time is delayed by more than ten milliseconds compared to the differential break, and the exit mode is the same as the differential break protection action.

[0036] like Figure 5 As shown, when the doubly-fed wind turbine generator is operating normally, the zero-sequence current at the neutral point of the generator is detected. If the zero-sequence current is less than or equal to the set value, the protection will not operate; when a grounding fault occurs inside the generator, the generator and its outgoing cables, and the grounding current is greater than the set value, the protection will start the safety chain after a time delay of seconds, the rotor converter 3 will stop running, and the transformer low-voltage side circuit breaker 9 will be tripped.

Claims

1. A system for protecting a double-fed wind turbine generator and outgoing cables, characterized in that: It comprises a doubly-fed generator (1), a generator outlet cable (2), a rotor converter (3), a generator neutral point side phase current transformer (4), a generator neutral point zero-sequence current transformer (5), a converter grid side phase current transformer (6), a unit step-up transformer low-voltage side current transformer (7), a differential protection and zero-sequence grounding protection device (8), a unit electric dry-type transformer current transformer (10) and a transformer low-voltage side circuit breaker (9); The generator neutral point side phase current transformer (4) is installed on the neutral side middle phase branch line of the doubly fed generator (1); each phase branch line on the neutral side of the doubly fed generator (1) is connected and then connected to the neutral point via the generator neutral point zero sequence current transformer (5); the output end of the doubly fed generator (1) is connected to the transformer low voltage side circuit breaker (9) via the generator output cable (2) and the unit electric dry type transformer current transformer (10); the grid side of the rotor converter (3) is connected to the generator output cable (2) via the converter grid side phase current transformer (6); the unit step-up to low voltage side of the rotor converter (3) is connected to the generator output cable (2) via the unit step-up to low voltage side current transformer (7); The differential protection and zero-sequence grounding protection device (8) is connected to the transformer low-voltage side circuit breaker (9), the generator neutral point side phase current transformer (4), the generator neutral point zero-sequence current transformer (5), the converter grid side phase current transformer (6), the unit step-up transformer low-voltage side current transformer (7) and the unit power dry-type transformer current transformer (10); The electrical fault occurring within the protection range between the generator neutral point side phase current transformer (4), the converter grid side phase current transformer (6), the unit step-up transformer low voltage side current transformer (7) and the unit power dry type transformer current transformer (10) is one of the following: a three-phase short circuit fault of the stator winding of the doubly fed generator (1), a two-phase short circuit fault of the stator winding of the doubly fed generator (1), a three-phase short circuit fault of the generator output cable (2), a two-phase short circuit fault of the generator output cable (2), or a combination of the above; The electrical fault occurring in the doubly-fed generator (1) and the generator output cable (2) within the protection range of the generator neutral point zero-sequence current transformer (5) is one of a two-phase short-circuit grounding fault of the stator winding of the doubly-fed generator (1), a single-phase grounding fault of the stator winding of the doubly-fed generator (1), a two-phase short-circuit grounding fault of the generator output cable (2) and a single-phase grounding fault of the generator output cable (2), or a combination of the two or more thereof; The electrical analog quantities collected by the differential protection and zero-sequence grounding protection device (8) include the phase current on the neutral point side of the generator, the phase current on the converter side, the current on the high-voltage side of the unit power supply, the zero-sequence current on the neutral point of the generator, the terminal voltage of the generator and the frequency of the generator; The switch quantities collected by the differential protection and zero-sequence grounding protection device (8) include the zero position signal of the variable pitch device and the operation signal of the converter; The tripping outlet of the differential protection and zero-sequence grounding protection device (8) includes an outlet to the safety chain device, an outlet to the transformer low-voltage side circuit breaker and an outlet to the converter.

2. A method for protecting a doubly-fed wind turbine generator and an outgoing cable by electrical quantity, characterized in that: The system for protecting a doubly-fed wind turbine generator and outgoing cables based on the electrical quantity of claim 1 comprises the following steps: During the operation of the doubly-fed generator (1), the differential protection and zero-sequence grounding protection device (8) determines whether a three-phase short circuit fault of the stator winding of the doubly-fed generator (1), a two-phase short circuit fault of the stator winding of the doubly-fed generator (1), a three-phase short circuit fault of the generator output cable (2), a two-phase short circuit fault of the generator output cable (2), a two-phase short circuit grounding fault of the stator winding of the doubly-fed generator (1), a single-phase grounding fault of the stator winding of the doubly-fed generator (1), a two-phase short circuit grounding fault of the generator output cable (2), or a three-phase short circuit fault of the generator output cable (2) occurs. When there is a three-phase short circuit fault in the stator winding of the doubly fed generator (1), a two-phase short circuit fault in the stator winding of the doubly fed generator (1), a three-phase short circuit fault in the generator output cable (2), a two-phase short circuit fault in the generator output cable (2), a two-phase short circuit fault in the stator winding of the doubly fed generator (1), a single-phase grounding fault in the stator winding of the doubly fed generator (1), a two-phase short circuit grounding fault in the generator output cable (2), or a single-phase grounding fault in the generator output cable (2), the tripping output is activated, the safety chain is triggered, and the transformer low-voltage side circuit breaker (9) is tripped.

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