Power supply circuit of doubly-fed air-cooled converter and control method

Abstract

The invention relates to the technical field of converters, in particular to a power supply circuit of a doubly-fed air-cooled converter and a control method, and the power supply circuit comprises a power supply loop which comprises a generator stator end, a generator rotor end, a first line connected with the generator stator end, and a second line connected with the generator rotor end, the network side line is connected with the first line and the second line; the connecting unit comprises a main circuit breaker connected in series with a network side line and a plurality of grid-connected contactors connected in series with the first line; and the plurality of grid-connected contactors are connected in parallel. According to the power supply circuit of the doubly-fed air-cooled converter and the control method, the current generated by the operation of the generator can be connected with the power grid through the power supply loop so as to supply power to the power grid, and the plurality of parallel grid-connected contactors are arranged on the first line connected with the stator end of the generator, so that the effect of dispersing the current of the stator end of the generator can be achieved; power supply operation of the first line is protected.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and particularly to a power supply circuit and a control method for a doubly-fed air-cooled converter. Background Art

[0002] The doubly-fed air-cooled converter is a key component in a wind power generation system. In a doubly-fed wind power generation system, the wind drives the wind turbine blades to rotate, driving the rotation of the generator rotor. The stator winding is directly connected to the power grid, and the rotor winding is connected to the power grid through a doubly-fed air-cooled converter. When the rotor speed changes, the converter controls the amplitude, phase, frequency, etc. of the rotor excitation so that the stator side can input constant-frequency electricity to the power grid.

[0003] In a power generation system, circuit safety cannot be ignored. Especially when the stator side of the converter can input high-voltage current to the power grid, it is easy to cause overcurrent damage to other electrical components in the power supply circuit. Therefore, it is necessary to add a protection device in the power supply line to protect the circuit from being disconnected in time after a fault occurs. Summary of the Invention

[0004] In view of the problems existing in the power supply circuit and control method of the existing doubly-fed air-cooled converter, the present invention is proposed.

[0005] Therefore, the object of the present invention is to provide a power supply circuit for a doubly-fed air-cooled converter, and its purpose is to provide a power supply circuit for a doubly-fed air-cooled converter with a high degree of operating safety.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A power supply circuit for a doubly-fed air-cooled converter, including,

[0007] A power supply loop, which includes a generator stator end and a generator rotor end, a first line connected to the generator stator end, a second line connected to the generator rotor end, and a grid-side line connected to the first line and the second line;

[0008] A connection unit, which includes a main circuit breaker connected in series with the grid-side line, and a plurality of grid-connected contactors connected in series with the first line;

[0009] The grid-connected contactors connect the generator stator end and the grid-side line for power generation, and the plurality of grid-connected contactors are connected in parallel to distribute the current passing through.

[0010] As a preferred solution of the power supply circuit for the doubly-fed air-cooled converter of the present invention, wherein: there are two grid-connected contactors;

[0011] The grid-connected contactor includes a wiring package, a contactor body connected in parallel with the wiring package, and a control switch connected in series with the contactor body.

[0012] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter according to the present invention, wherein: the main circuit breaker includes an energy storage coil, a closing coil and a tripping coil;

[0013] The energy storage coil stores electric energy capable of controlling the operation of the closing coil and the tripping coil;

[0014] The closing coil controls the main circuit breaker to connect to the grid-side line;

[0015] The tripping coil controls the main circuit breaker to disconnect the grid-side line.

[0016] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter according to the present invention, wherein: on the second line, in the direction from the grid-side line to the generator rotor end, a grid-side converter, a DC bus and a machine-side converter are connected in series in sequence;

[0017] A pre-charge unit is provided between the grid-side line and the second line;

[0018] The pre-charge unit is connected in parallel with the main circuit breaker and charges the DC bus before the main circuit breaker is closed.

[0019] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter according to the present invention, wherein: the pre-charge unit includes a fuse, a third contactor and a charging resistor connected in series;

[0020] The third contactor controls the connection of the circuit;

[0021] The fuse protects the operation of the circuit.

[0022] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter according to the present invention, wherein: a first reactor and a second reactor are connected in series on the second line;

[0023] The first reactor is located between the grid-side line and the grid-side converter;

[0024] The second reactor is located between the generator stator end and the machine-side converter.

[0025] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter according to the present invention, wherein: a filtering unit is provided on the first line, which includes a first branch connected to the first line, a filtering capacitor provided at the end of the first branch, and a current transformer provided on the first branch.

[0026] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter according to the present invention, wherein: the filtering capacitor includes three copper bars, namely a first copper bar, a second copper bar, a third copper bar and a fourth copper bar connected to the first copper bar;

[0027] Four capacitors and one resistor are connected in parallel between every two adjacent copper bars separately.

[0028] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter described in the present invention, further comprising: a control unit, which includes a main controller, a first sub-controller disposed between the grid-side converter and the main controller, and a second sub-controller disposed between the machine-side converter and the main controller.

[0029] As a preferred embodiment of the power supply circuit of the doubly-fed air-cooled converter described in the present invention, an energy dissipation circuit is connected to the DC bus, which can absorb the energy at the stator end of the generator when the voltage of the grid-side line drops, protecting the power supply circuit from malfunctioning and shutting down.

[0030] The beneficial effects of this power supply line are as follows: The current generated by the generator during operation can be connected to the power grid through the power supply loop, thereby supplying power to the power grid. The stator end and the rotor end of the generator can generate electricity bidirectionally. At the same time, the current at the stator end is greater than that at the rotor end. A plurality of parallel grid-connection contactors are provided on the first line connected to the stator end of the generator, which can disperse the stator-end current of the generator and protect the power supply operation of the first line.

[0031] Another object of the present invention is to provide a control method for a doubly-fed air-cooled converter, aiming to provide a doubly-fed air-cooled converter with a high operating safety level.

[0032] To solve the above technical problems, the present invention provides the following technical solution: A control method for a doubly-fed air-cooled converter, applied to the power supply circuit of the doubly-fed air-cooled converter, includes the following steps;

[0033] When the doubly-fed air-cooled converter is in operation, close the main circuit breaker;

[0034] After the grid-side line is connected to the first line and the second line, close a plurality of grid-connection contactors;

[0035] A plurality of grid-connection contactors are arranged in parallel, which can disperse the current passing through the grid-connection contactors on the first line;

[0036] In case of a fault, the grid-connection contactor can disconnect to protect the grid-side circuit.

[0037] As a preferred embodiment of the control method for the doubly-fed air-cooled converter described in the present invention, before the main circuit breaker is closed, the grid-side line first pre-charges the DC bus to avoid the DC bus being directly impacted by the grid-side line voltage when the main circuit breaker is closed;

[0038] After the grid-connected contactor is closed, the stator terminal and the rotor terminal of the generator supply power to the grid, and the filter capacitor filters out the AC components in the pulsating DC voltage at the stator terminal of the motor.

[0039] The beneficial effects of the control method of this doubly-fed air-cooled converter: When the doubly-fed air-cooled converter is working, the main circuit breaker is first closed to provide a stable power supply basis for the entire system. Subsequently, the closing of the grid-connected contactor further stabilizes the connection between the grid side line and other lines. Multiple parallel grid-connected contactors can play a role in dispersing the current at the stator terminal of the generator and protecting the power supply of the equipment on the first line. Brief Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0041] Figure 1 Shows the single-line diagram of the system in Embodiment 1;

[0042] Figure 2 Shows the circuit diagram of the parallel contactor in Embodiment 1;

[0043] Figure 3 Shows the circuit diagram of the main circuit breaker in Embodiment 1;

[0044] Figure 4 Shows the single-line diagram of the system in Embodiment 2;

[0045] Figure 5 Shows the single-line diagram of the system in Embodiment 3;

[0046] Figure 6 Shows the filter circuit diagram in Embodiment 3;

[0047] Figure 7 Shows the filter capacitor circuit diagram in Embodiment 3;

[0048] Figure 8 Shows the single-line diagram of the system in Embodiment 4. Detailed Embodiments

[0049] In order to enable those skilled in the art to better understand the present invention, the following further details the present invention in conjunction with the specific embodiments and the drawings.

[0050] The terms used in the present invention are those general terms that are currently widely used in the art in consideration of the functions of the present invention. However, these terms may vary according to the intentions of those of ordinary skill in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the present invention. Therefore, the terms used in the specification should not be construed as simple names, but rather based on the meanings of the terms and the overall description of the present invention.

[0051] Example 1, referring to Figure 1 and Figure 3 , which is the first embodiment of the present invention, provides a power supply circuit for a doubly-fed air-cooled converter. This circuit includes a power supply loop 100 and a connection unit 200.

[0052] Among them, the power supply loop 100 includes a generator stator terminal 101 and a generator rotor terminal 102. In a doubly-fed wind power generation system, the wind pushes the wind turbine blades to rotate, driving the rotation of the generator rotor. The stator winding is directly connected to the power grid, and the rotor winding is connected to the power grid through a doubly-fed air-cooled converter. That is, the generator stator terminal 101 and the generator rotor terminal 102 can generate electricity bidirectionally. A first line 103 connected to the generator stator terminal 101, a second line 104 connected to the generator rotor terminal 102, and a grid-side line 105 connected to the first line 103 and the second line 104. The grid-side line 105 is connected to the power grid. The currents generated by the generator stator terminal 101 and the generator rotor terminal 102 are sent into the grid-side line 105 through the first line 103 and the second line 104, and finally incorporated into the power grid to achieve the power supply function.

[0053] The connection unit 200 includes a main circuit breaker 201 connected in series with the grid-side line 105, and a plurality of grid-connected contactors 202 connected in series with the first line 103. Among them, the main circuit breaker 201 can control the opening and closing of the grid-side line 105. When the main circuit breaker 201 is disconnected, the grid-side line 105 is disconnected, and the generator stator terminal 101 and the generator rotor terminal 102 cannot supply power to the power grid. When the main circuit breaker 201 is closed, the grid-side line 105 is connected, and the currents generated by the generator stator terminal 101 and the generator rotor terminal 102 can be sent into the power grid.

[0054] Furthermore, a plurality of grid-connected contactors 202 are connected in series with the first line 103. The grid-connected contactors 202 can control the opening and closing of the first line 103. When the grid-connected contactors 202 are disconnected, the first line 103 is disconnected, and at this time, the generator stator terminal 101 cannot supply power to the grid-side line 105. When the grid-connected contactors 202 are closed, the first line 103 is connected, and at this time, the generator stator terminal 101 can supply power to the grid-side line 105.

[0055] Among them, the grid-connected contactor 202 can adjust the power output from the generator stator terminal 101 according to the wind force and the operating state of the generator. The grid-connected contactor 202 can ensure that the output electric power is stable and meets the requirements of the power grid, improve the power quality. At the same time, the grid-connected contactor 202 has a monitoring function and can monitor the parameters of current and voltage in the first line 103 in real time, including voltage amplitude, frequency, phase, etc., as well as power quality indicators such as the harmonic content of electric energy, so as to detect power quality problems in time; when abnormal conditions such as overcurrent and overvoltage occur in the first line 103, the grid-connected contactor 202 can quickly detect them and disconnect the circuit in time to protect equipment such as the generator stator winding and the converter from damage.

[0056] Furthermore, multiple grid-connected contactors 202 are connected in parallel to each other in the first line 103. Preferably, there are two grid-connected contactors 202. The two grid-connected contactors 202 can shunt the current passing through the first line 103, thereby protecting the grid-connected contactor 202 and preventing damage to it due to excessive current passing through the grid-connected contactor 202. The parallel arrangement of multiple grid-connected contactors 202 can also improve the reliability of the power supply circuit 100. When one grid-connected contactor 202 fails, the other grid-connected contactor 202 can continue to work, ensuring the normal on-off control and power transmission functions of the first line 103, so that the generator stator terminal 101 can still be connected to the grid-side line 105 and supply power to the power grid.

[0057] Moreover, the two parallel grid-connected contactors 202 can monitor and diagnose each other. When it is detected that a certain grid-connected contactor 202 is abnormal, the system can automatically switch to the working mode of the normal grid-connected contactor 202, and at the same time send an alarm signal to notify the operation and maintenance personnel to carry out repairs, which improves the fault tolerance of the system to a certain extent and reduces the power outage time caused by faults.

[0058] Furthermore, the grid-connected contactor 202 includes a wiring package 202a, a contactor body 202b connected in parallel with the wiring package 202a, and a control switch 202c connected in series with the contactor body 202b. When the wiring package 202a receives a closing electrical signal, it will cause the control switch 202c to close, and then the line where the contactor body 202b is installed will be connected to the first line 103, so that the grid-connected contactor 202 is connected to the first line 103 and monitors the first line 103. When the wiring package 202a receives a fault signal, it will also cause the control switch 202c to disconnect immediately to protect the safety of the equipment in the first line 103.

[0059] When the power supply circuit 100 is operating, first, the main circuit breaker 201 is closed, and then the grid-connected contactor 202 is closed to complete the connection of the entire power supply circuit 100, enabling the generator stator terminal 101 and the generator rotor terminal 102 to supply power to the power grid.

[0060] Furthermore, the main circuit breaker 201 includes an energy storage coil 201a, a closing coil 201b, and a tripping coil 201c; the energy storage coil 201a stores electrical energy that can control the operation of the closing coil 201b and the tripping coil 201c; the closing coil 201b controls the main circuit breaker 201 to connect to the grid-side line 105; the tripping coil 201c controls the main circuit breaker 201 to disconnect from the grid-side line 105.

[0061] The energy storage coil 201a usually obtains electrical energy through an external power supply (such as a DC power supply). When the power supply supplies power to the energy storage coil 201a, a magnetic field is generated inside the coil, converting the electrical energy into magnetic field energy and storing it. The energy stored in the energy storage coil 201a is the energy source for the closing and tripping operations of the main circuit breaker 201. It provides the necessary power support for the actions of the closing coil 201b and the tripping coil 201c, ensuring that the main circuit breaker 201 can perform reliable closing and opening operations.

[0062] When it is necessary to close the main circuit breaker 201 to connect the grid-side line 105, the energy storage coil 201a supplies current to the closing coil 201b. After the closing coil 201b is supplied with current, a strong magnetic field is generated. This magnetic field generates an electromagnetic force that attracts the connected mechanical mechanism (such as the closing iron core) to move. Through a series of mechanical transmission devices, the moving contact and the static contact of the main circuit breaker 201 are closed, thereby realizing the connection of the grid-side line 105;

[0063] When a fault occurs in the system or it is necessary to disconnect the main circuit breaker 201, the tripping coil 201c receives a control signal and is supplied with current. The magnetic field generated after the tripping coil 201c is energized causes the related mechanical mechanism to act, usually by releasing the locking device or pushing the tripping rod, etc., to separate the moving contact and the static contact of the main circuit breaker 201, thereby disconnecting the grid-side line 105.

[0064] During use, when the power supply circuit 100 is operating, the main circuit breaker 201 and the grid-connected contactor 202 are closed in sequence, enabling the generator stator terminal 101 and the generator rotor terminal 102 to supply power to the power grid. The grid-connected contactor 202 can be disconnected during a line fault to protect the generator stator terminal from damage, and the main circuit breaker 201 can also be powered off when a fault occurs in the power supply circuit 100 to protect the equipment in the power supply circuit from damage.

[0065] Example 2, refer to Figure 4, which is the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that: on the second line 104, in the direction from the grid side line 105 to the generator rotor end 102, a grid side converter 106, a DC bus 107, and a machine side converter 108 are connected in series in sequence; among them, the DC bus 107 transmits the direct current output by the grid side converter 106 to the machine side converter 108, providing a stable DC power supply for the machine side converter 108, realizing the power transmission from the grid side to the generator rotor side, and ensuring the smooth flow of electric energy in the entire power generation system; during the operation of the system, due to the volatility of wind power and the dynamic changes in the power exchange between the generator and the grid, the generation and consumption of electric energy will be unbalanced instantaneously. The DC bus 107 can act as an energy buffer, temporarily storing or releasing energy to balance this power difference, alleviating the impact of power fluctuations on the system, and enabling the system to operate more smoothly.

[0066] Among them, the grid side converter 106 converts the three-phase alternating current on the grid side into direct current, preparing for the stable DC power supply of the subsequent DC bus 107, enabling electric energy to be transmitted and processed in the system in the form of direct current, and facilitating the matching and collaborative work with the equipment of other DC links; the machine side converter 108 converts the direct current input by the DC bus 107 into three-phase alternating current suitable for the generator rotor winding, providing the required excitation current for the generator rotor, enabling the generator to generate a stable induced electromotive force under different wind speeds and load conditions, and realizing the power generation function.

[0067] In a doubly-fed wind power generation system, the rotor speed of the generator will change with the change of wind speed. The machine side converter 108 controls the frequency of the rotor current, so that the frequency of the alternating current output by the generator stator end 101 always remains consistent with the grid frequency, realizing variable speed constant frequency power generation, ensuring that the electric energy output by the generator can be smoothly connected to the grid, and meeting the strict requirements of the grid for the electric energy frequency.

[0068] A pre-charge unit 300 is provided between the grid side line 105 and the second line 104; the pre-charge unit 300 is connected in parallel with the main circuit breaker 201, charges the DC bus 107 before the main circuit breaker 201 is closed, and the pre-charge unit 300 bypasses the main circuit breaker 201 and is connected to the second line 104. Through the pre-charge unit 300, the grid side line 105 can be directly connected to the second line 104;

[0069] The grid-side converter 106 and the machine-side converter 108 require the DC bus 107 to provide a stable voltage when starting. Before the main circuit breaker 201 is closed, the DC bus 107 is charged by the pre-charging unit 300. The pre-charging can enable the DC bus 107 to reach a suitable voltage level before the converter is started, thereby providing a stable power supply condition for the normal startup and initialization of the converter. This can avoid problems such as startup failure and control logic confusion caused by abnormal voltage of the DC bus 107, thereby ensuring that the converter can be put into operation smoothly, thereby ensuring the stable startup and operation of the entire wind power generation system.

[0070] Furthermore, the pre-charging unit 300 includes a fuse 301, a third contactor 302 and a charging resistor 303 connected in series; the third contactor 302 controls the connection of the circuit; and the fuse 301 protects the operation of the circuit.

[0071] When the third contactor 302 is closed, the grid-side line 105 can pre-charge the DC bus 107 through the charging resistor 303. The resistance of the charging resistor 303 can control the length of charging of the DC bus 107. The fuse 301 is disconnected when the line current is too large, thereby protecting the equipment on the circuit from damage.

[0072] Furthermore, a first reactor 109 and a second reactor 1010 are connected in series on the second line 104 ; the first reactor 109 is located between the grid-side line 105 and the grid-side converter 106 ; and the second reactor 1010 is located between the generator stator terminal 101 and the generator-side converter 108 .

[0073] The first reactor 109 and the second reactor 1010 can limit the short-circuit current. When a short-circuit fault occurs in the system, the short-circuit current may increase to a very high level instantly, which will cause a great impact on the electrical equipment in the system and even cause damage to the equipment. The first reactor 109 and the second reactor 1010 can effectively limit the magnitude and rising speed of the short-circuit current at the moment of short-circuit, so that the short-circuit current is within the range that the equipment can withstand, and buy time for the protection device to operate and the fault to be removed, thereby protecting the grid-side converter 106, the machine-side converter 108, the generator and other equipment from damage by the short-circuit current;

[0074] At the same time, in the wind power generation system, the grid-side converter 106 and the machine-side converter 108 will generate certain harmonic currents during the power conversion process. If these harmonic currents are injected into the power grid and the generator side, the power quality will be reduced, affecting the normal operation of other electrical equipment. The first reactor 109 and the second reactor 1010 can form a filter circuit with components such as capacitors in the system, presenting a higher impedance to harmonic currents of a specific frequency, thereby effectively suppressing the propagation of harmonic currents, making the current waveforms on the grid side and the generator side closer to sine waves, and improving the power quality.

[0075] Further, an energy dissipation circuit 1011 is connected to the DC bus 107. When the voltage of the grid-side line 105 drops, it can absorb the energy at the generator stator end 101 to protect the power supply circuit from malfunctioning and shutting down. The energy dissipation circuit 1011 has a discharge resistor. When the voltage of the grid-side line 105 drops, the energy at the generator stator end 101 may not be able to be normally transmitted to the power grid, which may cause the voltage of the DC bus 107 to rise. At this time, to protect the circuit, the excess electrical energy accumulated on the DC bus 107 due to the inability of the generator stator end 101 to normally transmit energy to the power grid needs to be dissipated in the form of heat through the resistor, thereby reducing the voltage of the DC bus 107 and protecting other devices in the power supply circuit from malfunctioning and shutting down due to overvoltage.

[0076] The remaining structure is the same as that of Embodiment 1.

[0077] Embodiment 3, refer to Figure 5 - Figure 7 This is the third embodiment of the present invention. The difference between this embodiment and the second embodiment is that a filtering unit 400 is provided on the first line 103, which includes a first branch 401 connected to the first line 103, a filtering capacitor 402 provided at the end of the first branch 401, and a current transformer 403 provided on the first branch 401.

[0078] Among them, the first line 103 connects the generator stator end 101 and the grid-side line 105. When the generator is running, affected by factors such as unstable wind force, the output voltage at the stator end will fluctuate. The filtering capacitor 402 can store electrical energy when the voltage rises and release electrical energy when the voltage drops, keeping the voltage on the first line 103 relatively stable, providing a stable voltage input for subsequent devices, and avoiding affecting the normal operation of the devices due to large voltage fluctuations. At the same time, a large amount of high-frequency harmonics will be generated during the operation of the generator and power electronic devices. These harmonics will increase the line loss and interfere with the normal operation of the devices. The filtering capacitor 402 and the inductor in the line form a filtering circuit, presenting a low impedance to high-frequency harmonics, enabling the high-frequency harmonic current to flow through the capacitor branch, reducing the harmonic content in the first line 103, and improving the power quality.

[0079] Among them, the current transformer 403 can convert the large current in the first line 103 into a small current in proportion, facilitating the accurate measurement of the current value by the measuring instrument. By monitoring the magnitude of the current in the first line 103, the operation and maintenance personnel can understand the output power situation of the generator stator end 101, judge whether the operation state of the generator is normal, and timely discover potential problems.

[0080] Further, the filtering capacitor 402 includes three copper bars, namely a first copper bar 402a, a second copper bar 402b, a third copper bar 402c, and a fourth copper bar 402d connected to the first copper bar 402a;

[0081] Four capacitors and one resistor are separately connected in parallel between every two connected copper bars. A first branch 401 is branched out from the stator end of the generator. Three wires are led out from the first branch 401 and are respectively connected to the second copper bar 402b, the third copper bar 402c, and the fourth copper bar 402d, thereby connecting the filtering capacitor 402 in the first line 103, reducing the harmonic content in the first line 103, and improving the power quality.

[0082] The remaining structure is the same as that of Embodiment 1.

[0083] Embodiment 4, referring to Figure 8 This is the fourth embodiment of the present invention. The difference between this embodiment and the third embodiment is that it further includes a control unit 500, which includes a main controller 501, a first sub-controller 502 disposed between the grid-side converter 106 and the main controller 501, and a second sub-controller 503 disposed between the machine-side converter 108 and the main controller 501.

[0084] The main controller 501 is the core component of the entire control unit 500. Usually, it is an electronic device with powerful computing power and logical processing ability, such as an industrial computer, a digital signal processor (DSP), or a programmable logic controller (PLC), etc. The first sub-controller 502 and the second sub-controller 503 are extensions of the main controller 501. They separately monitor the data of the grid-side converter 106 and the machine-side converter 108, and are responsible for coordinating the operation of the grid-side converter 106, the machine-side converter 108, and other related devices to ensure their mutual cooperation and realize the overall function of the system. For example, during the grid connection process, the main controller 501 will simultaneously control the grid-side converter 106 and the machine-side converter 108 to enable the electric energy output by the generator to be smoothly connected to the grid, and ensure that parameters such as voltage, frequency, and phase during the grid connection process meet the requirements.

[0085] Further, the main controller 501 is electrically connected to the current transformer 403, can receive the monitoring information of the current transformer 403, and will perform a series of processing on the signal to convert the analog current signal into a digital signal. Then, the main controller 501 will perform processing such as filtering, calculation, and analysis on the digital signal according to specific application requirements.

[0086] The remaining structure is the same as that of Embodiment 2.

[0087] Embodiment 5 is the fifth embodiment of the present invention, which provides a control method for a doubly-fed air-cooled converter. This method includes;

[0088] When the doubly-fed air-cooled converter is in operation, the main circuit breaker 201 is closed; the entire converter system is powered on, enabling the grid-side line 105 to establish an electrical connection with other parts of the converter, providing conditions for subsequent power transmission and conversion operations;

[0089] After the grid-side line 105 is connected to the first line 103 and the second line 104, multiple grid-connected contactors 202 are closed; at this time, the converter is ready to integrate the electric energy generated by the generator into the grid; the function of the grid-connected contactor 202 is to control the power exchange between the converter and the grid, ensuring the stable transmission of electric energy and the smooth progress of the grid-connection process.

[0090] Multiple grid-connected contactors 202 are arranged in parallel to be able to disperse the current of the first line 103 passing through the grid-connected contactor 202, which can improve the reliability and flexibility of the system, and avoid problems such as overload caused by a single controller bearing excessive current. At the same time, by reasonably distributing the current, the operating efficiency of the system can be optimized, enabling each grid-connected contactor 202 to operate in a relatively ideal working state; when faults such as overcurrent, overvoltage, and short circuit occur in the grid-side line 105, the grid-connected contactor 202 will quickly respond and cut off its connection with the circuit, thereby isolating the faulty part from other normal parts for protection that can be disconnected.

[0091] Furthermore, before the main circuit breaker 201 is closed, the grid-side line 105 first pre-charges the DC bus 107 to avoid the DC bus 107 being directly impacted by the voltage of the grid-side line 105 when the main circuit breaker 201 is closed; enabling the DC bus 107 to reach an appropriate voltage level before the converter starts, providing stable power supply conditions for the normal start and initialization of the converter.

[0092] After the grid-connected contactor 202 is closed, the generator stator terminal 101 and the generator rotor terminal 102 work to supply power to the grid, and the filter capacitor filters out the AC components in the pulsating DC voltage at the motor stator terminal, reducing the harmonic content in the first line 103 and improving the power quality.

[0093] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A power supply circuit for a double-fed air-cooled converter, characterized in that: include, A power supply circuit (100), comprising a generator stator end (101) and a generator rotor end (102), a first line (103) connected to the generator stator end (101), a second line (104) connected to the generator rotor end (102), and a grid-side line (105) connected to the first line (103) and the second line (104); A connection unit (200), comprising a main circuit breaker (201) connected in series with a grid-side line (105), and a plurality of grid-connected contactors (202) connected in series with the first line (103); The grid-connected contactor (202) connects the generator stator end (101) with the grid-side line (105) to generate electricity, and a plurality of the grid-connected contactors (202) are connected in parallel to disperse the current flow.

2. The power supply circuit of the doubly-fed air-cooled converter according to claim 1, characterized in that: The grid-connected contactors (202) are provided with two; The grid-connected contactor (202) comprises a wiring package (202a), a contactor body (202b) connected in parallel with the wiring package (202a), and a control switch (202c) connected in series with the contactor body (202b).

3. The power supply circuit of the doubly-fed air-cooled converter according to claim 1 or 2, characterized in that: The main circuit breaker (201) comprises an energy storage coil (201a), a closing coil (201b) and a tripping coil (201c); The energy storage coil (201a) stores electric energy capable of controlling the operation of the closing coil (201b) and the tripping coil (201c); The closing coil (201b) controls the main circuit breaker (201) to connect to the grid-side line (105); The tripping coil (201c) controls the main circuit breaker (201) to disconnect the grid-side line (105).

4. The power supply circuit of the doubly-fed air-cooled converter according to claim 1 or 2, characterized in that: A grid-side converter (106), a DC bus (107) and a generator-side converter (108) are sequentially connected in series on the second line (104) in a direction from the grid-side line (105) to the generator rotor end (102); A pre-charging unit (300) is provided between the grid-side line (105) and the second line (104); The pre-charging unit (300) is connected in parallel with the main circuit breaker (201) and charges the DC bus (107) before the main circuit breaker (201) is closed.

5. The power supply circuit of the doubly-fed air-cooled converter according to claim 4, characterized in that: The pre-charging unit (300) comprises a fuse (301), a third contactor (302) and a charging resistor (303) connected in series; The third contactor (302) controls the connection of the circuit; The fuse (301) protects the operation of the circuit.

6. The power supply circuit of the doubly-fed air-cooled converter according to claim 5, characterized in that: The second line (104) is connected in series with a first reactor (109) and a second reactor (1010); The first reactor (109) is located between the grid-side line (105) and the grid-side converter (106); The second reactor (1010) is located between the generator stator terminal (101) and the machine-side converter (108).

7. The power supply circuit of the doubly-fed air-cooled converter according to any one of claims 1, 2, 5 and 6, characterized in that: A filtering unit (400) is provided on the first line (103), comprising a first branch (401) connected to the first line (103), a filtering capacitor (402) arranged at the end of the first branch (401), and a current transformer (403) arranged on the first branch (401).

8. The power supply circuit of the doubly-fed air-cooled converter according to claim 7, characterized in that: The filter capacitor (402) comprises three copper bars, namely a first copper bar (402a), a second copper bar (402b) connected to the first copper bar (402a), a third copper bar (402c) and a fourth copper bar (402d); Four capacitors and one resistor are connected in parallel between every two connected copper bars.

9. The power supply circuit of the doubly-fed air-cooled converter according to claim 5, characterized in that: It also includes a control unit (500), which includes a main controller (501), a first sub-controller (502) arranged between the grid-side converter (106) and the main controller (501), and a second sub-controller (503) arranged between the machine-side converter (108) and the main controller (501).

10. The power supply circuit of the doubly-fed air-cooled converter according to claim 5 or 6, characterized in that: The DC bus (107) is connected to an energy discharge circuit (1011), which can absorb the energy of the generator stator terminal (101) when the voltage of the grid-side line (105) drops, thereby protecting the power supply circuit from failure and shutdown.

11. A control method for a doubly-fed air-cooled converter, applied to a power supply circuit of the doubly-fed air-cooled converter, characterized in that: The steps include: When the double-fed air-cooled converter is in operation, the main circuit breaker (201) is closed; After the grid-side line (105) is connected to the first line (103) and the second line (104), the plurality of grid-connected contactors (202) are closed; The grid-connected contactor (202) is provided with a plurality of parallel connections capable of dispersing the current of the first line (103) passing through the grid-connected contactor (202); In case of a fault, the grid-connected contactor (202) can disconnect the protection grid-side circuit.

12. The control method of the doubly-fed air-cooled converter according to claim 11, characterized in that: Before the main circuit breaker (201) is closed, the grid-side line (105) first pre-charges the DC bus (107) to prevent the DC bus (107) from being directly impacted by the voltage of the grid-side line (105) when the main circuit breaker (201) is closed; After the grid-connected contactor (202) is closed, the generator stator end (101) and the generator rotor end (102) work to supply power to the grid, and the filter capacitor (402) filters out the AC component in the pulsating DC voltage at the motor stator end.

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