Doubly-fed wind driven generator black start system and wind driven generator set

Abstract

The invention discloses a black start system of a doubly-fed wind driven generator and a wind driven generator set. Relates to the field of wind power generation, solves the problem of high failure rate of traditional black start, supplies power to a converter through a diesel generator, establishes a direct-current bus voltage, starts to establish a lower stator voltage when the rotating speed of a machine-side converter meets a preset condition, gradually establishes a power grid voltage and avoids impact on a system. The iron core of the step-up transformer is in an unsaturated state in the initial stage, the magnetic flux is increased slowly, the initial inrush current is small, the exciting current of the transformer can gradually reach a steady-state value in the step-by-step voltage increasing process, sudden impact is avoided, and finally self-starting of the doubly-fed wind generator and step-by-step recovery of a power grid are achieved. The power grid is started under the condition of complete power loss, the generator set without self-starting capability is driven, the system recovery range is gradually expanded, the recovery of the whole system is finally realized, the reliability of the power grid is improved, and the economic loss caused by power loss of the power grid is reduced.

Description

Technical Field

[0001] The present application relates to the field of wind power generation, and in particular to a double-fed wind generator black start system and a wind generator set. Background Art

[0002] In the current context of energy transformation and power system development, wind power generation has been widely used as a clean and renewable energy source. Doubly-fed wind turbine generators (DFIGs) have become an important part of the wind power sector due to their excellent active and reactive power control capabilities. As the penetration rate of wind power generation in the power system gradually increases, the grid structure of the power grid where the wind farm is located has become increasingly complex and weak. Therefore, wind farms need to have the ability to independently serve as black start power supplies to ensure that initial power supply can be provided when the total system is shut down. Black start refers to the process of gradually restoring the power supply of the entire system through backup power supplies after the power system suffers a serious fault. This process requires wind turbines to have the ability to respond quickly and operate stably to ensure the reliability and stability of the power grid.

[0003] Traditional control strategies cannot effectively perform adaptive adjustments when faced with a sudden power outage, resulting in a slow system recovery and even instability. In the traditional black start solution, due to the high stator voltage, the box transformer will be excited at the moment the stator contactor is closed, resulting in a large excitation surge current, which is generally 5 to 10 times the rated current and 50 to 100 times the no-load current. The single decay is fast, and this impact current will cause great damage to the generator and converter, resulting in a shortened unit life and increased failure rate.

[0004] It can be seen that how to solve the problem of high failure rate of traditional black start is a technical problem that needs to be solved urgently by people in this field. Summary of the invention

[0005] The purpose of the present application is to provide a doubly-fed wind turbine black start system and a wind turbine generator set to solve the problem of high failure rate of traditional black starts.

[0006] In order to solve the above technical problems, the present application provides a doubly-fed wind generator black start system, which is applied to a doubly-fed wind generator, wherein the stator winding of the doubly-fed wind generator is directly connected to a step-up transformer and then connected to the grid, and the rotor winding is connected to the step-up transformer through a converter and then connected to the grid, comprising: a step-up transformer, a diesel generator, a main controller, and the converter comprises a machine-side converter and a grid-side converter;

[0007] After the power grid loses power, the step-up transformer is disconnected from the grid, and the diesel generator is started to supply power to the auxiliary power system; after the main controller is powered on, it controls the double-fed wind turbine to increase its speed to the synchronous speed, and then sends a black start instruction to the converter to control the diesel generator to supply power to the converter, and establishes a DC bus voltage through uncontrolled rectifier slow start;

[0008] When the machine-side converter detects that the speed meets the preset speed, the excitation constructs a stator voltage of a first preset voltage, until the speed, stator voltage phase and amplitude of the machine-side converter meet the preset conditions, the doubly-fed wind turbine is controlled to magnetize the step-up transformer, and the stator voltage is controlled to continue to rise to a second preset voltage through the voltage outer loop;

[0009] The grid-side converter starts modulation to make the doubly-fed wind turbine generator enter a black-start self-built grid state; the diesel generator is controlled to be disconnected and the stator winding output of the doubly-fed wind turbine generator is controlled to supply power to the auxiliary power system, and enter a black-start self-maintaining state.

[0010] As an optional solution, the above-mentioned doubly-fed wind turbine generator black start system further includes: a diesel generator contactor;

[0011] The output end of the diesel generator is connected to the first end of the diesel generator contactor, and the second end of the diesel generator contactor is connected to the auxiliary power system;

[0012] After the diesel generator is started, the diesel generator contactor is energized to supply power to the auxiliary power system; the main controller controls the diesel generator contactor to be disconnected to control the diesel generator to be disengaged.

[0013] As an optional solution, in the above-mentioned doubly-fed wind turbine generator black start system, the converter further includes: a converter controller, a slow-start contactor;

[0014] The output end of the grid-side converter is connected to the diesel generator contactor through the slow-start contactor;

[0015] After the converter receives the black start instruction sent by the main controller, the converter controller controls the slow-start contactor to close so that the diesel generator supplies power to the converter; and controls the slow-start contactor to open so as to disconnect the diesel generator from supplying power to the converter.

[0016] As an optional solution, the above-mentioned doubly-fed wind turbine generator black start system further includes: a stator contactor; a main circuit breaker;

[0017] The stator of the doubly-fed wind turbine generator is connected to the first end of the stator contactor, the second end of the stator contactor is connected to the first end of the main circuit breaker and the output end of the grid-side converter, and the second end of the main circuit breaker is connected to the low-voltage side switch of the step-up transformer;

[0018] When the phase and amplitude of the stator voltage constructed by the machine-side converter meet the preset conditions, the converter controller controls the slow-start contactor to open, so as to disconnect the diesel generator from supplying power to the converter, and then the converter controller controls the stator contactor to close; when the low-voltage side switch is in the closed state, the converter controller controls the main circuit breaker to close, so that the doubly-fed wind turbine magnetizes the step-up transformer, and controls the stator voltage to continue to rise to a second preset voltage through the voltage outer loop.

[0019] As an optional solution, the above-mentioned doubly-fed wind turbine generator black start system further includes: a power supply contactor;

[0020] The second end of the main circuit breaker is connected to the first end of the power supply contactor, and the second end of the power supply contactor is connected to the input end of the auxiliary power system;

[0021] The converter controller controls the power supply contactor to close so that the stator winding output of the double-fed wind generator supplies power to the auxiliary power system.

[0022] As an optional solution, the above-mentioned doubly-fed wind turbine generator black start system further includes: a slow-start resistor;

[0023] The output end of the grid-side converter is connected to the slow-start contactor through the slow-start resistor.

[0024] As an optional solution, in the above-mentioned doubly-fed wind turbine generator black start system, the auxiliary power system includes a plurality of auxiliary transformers;

[0025] The input ends of the plurality of auxiliary transformers are connected to the second end of the power supply contactor and the second end of the diesel generator contactor, and the output ends of the plurality of auxiliary transformers are connected to each fan device.

[0026] As an optional solution, in the above-mentioned doubly-fed wind turbine black start system, the second end of the diesel generator contactor is connected to the second end of the power supply contactor;

[0027] The diesel generator contactor is hardware interlocked with the power supply contactor.

[0028] As an optional solution, the above-mentioned doubly-fed wind turbine generator black start system further includes: an alarm device;

[0029] The main controller controls the alarm device to send out an alarm signal when the black start is started, and stops sending out the alarm signal after entering the black start self-maintaining state.

[0030] In order to solve the above technical problems, the present application also provides a wind turbine generator set, which includes the above-mentioned doubly-fed wind turbine generator black start system.

[0031] The doubly-fed wind turbine black start system provided by the present application controls the doubly-fed wind turbine to increase its speed to the synchronous speed after the main controller is powered on, and then sends a black start instruction to the converter, controls the diesel generator to power the converter, and establishes a DC bus voltage through uncontrolled rectifier slow start; when the machine-side converter detects that the speed meets the preset speed, excitation builds a stator voltage of a first preset voltage until the speed, stator voltage phase, and amplitude of the machine-side converter meet the preset conditions, controls the doubly-fed wind turbine to magnetize the step-up transformer, and controls the stator voltage to continue to rise to a second preset voltage through the voltage outer loop; wherein the first preset voltage is less than the second preset voltage; the grid-side converter starts modulation to make the doubly-fed wind turbine enter a black start self-built grid state; controls the diesel generator to disengage and controls the stator winding output of the doubly-fed wind turbine to power the auxiliary power system, and enters a black start self-maintaining state. In this application, in order to achieve the purpose of quickly restoring power supply after the power grid loses power, the converter is powered by a diesel generator to establish a DC bus voltage, and when the machine-side converter detects that the speed meets the preset conditions, a lower stator voltage is established, which is to gradually establish the grid voltage and avoid impacting the system. The iron core of the step-up transformer is in an unsaturated state in the initial stage, and the magnetic flux increases slowly, making the initial inrush current smaller. In the process of gradually increasing the voltage, the excitation current of the transformer can gradually reach a steady-state value instead of reaching a peak value instantly, avoiding sudden impacts, and finally realizing the self-starting of the doubly fed wind turbine and the gradual recovery of the power grid. When the power grid is completely powered off, the generator set without self-starting capability is started, and the system recovery range is gradually expanded, and then the recovery of the entire system is finally realized, which not only improves the reliability of the power grid, but also reduces the economic losses caused by power outages in the power grid.

[0032] In addition, the present application also provides a wind turbine generator set corresponding to the above-mentioned double-fed wind turbine generator black start system, and the effect is the same as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1A schematic diagram of a black start system for a doubly-fed wind turbine generator provided in an embodiment of the present application;

[0035] Reference numerals:

[0036] 11-doubly-fed wind turbine generator; 12-boosting transformer; 13-diesel generator; 14-main controller; 15-converter; 16-converter controller. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] The core of the present application is to provide a double-fed wind turbine black start system and a wind turbine generator set.

[0039] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0040] In the context of the current energy transformation and power system development, wind power generation has been widely used as a clean and renewable energy source. Doubly-fed wind turbine generators (DFIGs) have become an important part of the wind power field due to their excellent active power and reactive power control capabilities. As the penetration rate of wind power generation in the power system gradually increases, the grid structure of the power grid where the wind farm is located has become more and more complex and weak. Therefore, wind farms need to have the ability to independently serve as black start power sources to ensure that initial power supply can be provided when the total system is shut down. In addition, since most wind farms are located in remote areas, the reliability requirements of the power grid where they are located are higher, which makes black start technology particularly important.

[0041] Black start refers to the process of gradually restoring the power supply of the entire system through backup power after the power system suffers a serious fault. This process requires wind turbines to have the ability to respond quickly and operate stably to ensure the reliability and stability of the power grid.

[0042] Traditional control strategies may not be able to quickly and effectively perform adaptive adjustments when faced with a sudden power outage in the power grid, resulting in a slow system recovery or even instability. In addition, traditional double-fed wind turbine units must be connected to additional power sources such as diesel generators to power the auxiliary circuits for dynamic debugging, and there is a lack of operation and maintenance power when the power grid is completely out of power, making it impossible to quickly handle problems. In the traditional black start solution, the box transformer will be excited at the moment the stator contactor is closed due to the high stator voltage during the direct excitation process of the box transformer, thereby generating a large excitation surge current, which is generally 5 to 10 times the rated current and 50 to 100 times the no-load current. The single decay is fast, and the impact current will cause great damage to the generator and converter, resulting in a shortened unit life and increased failure rate.

[0043] To solve the above problems, the embodiment of the present application provides a doubly-fed wind turbine black start system, which is applied to the doubly-fed wind turbine. The stator winding of the doubly-fed wind turbine 11 is directly connected to the step-up transformer and then connected to the grid, and the rotor winding is connected to the step-up transformer through the converter and then connected to the grid. Figure 1 A schematic diagram of a black start system for a doubly-fed wind turbine generator provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, it includes: a step-up transformer 12, a diesel generator 13, a main controller 14, and a converter 15 including a machine-side converter and a grid-side converter;

[0044] After the power grid loses power, the step-up transformer 12 is disconnected from the grid, and the diesel generator 13 is started to supply power to the auxiliary power system;

[0045] After receiving power, the main controller 14 controls the double-fed wind turbine generator 11 to increase the speed to the synchronous speed, and then sends a black start instruction to the converter to control the diesel generator 13 to supply power to the converter, and establishes the DC bus voltage through uncontrolled rectifier slow start;

[0046] When the machine-side converter detects that the speed meets the preset speed, the excitation constructs a stator voltage of the first preset voltage until the speed, stator voltage phase and amplitude of the machine-side converter meet the preset conditions, and the double-fed wind turbine generator 11 is controlled to magnetize the step-up transformer 12, and the stator voltage is controlled to continue to rise to the second preset voltage through the voltage outer loop; wherein the first preset voltage is less than the second preset voltage;

[0047] The grid-side converter starts modulation to make the doubly-fed wind generator 11 enter the black start self-built grid state; the diesel generator 13 is controlled to be disconnected and the stator winding output of the doubly-fed wind generator 11 is controlled to supply power to the auxiliary power system, and enter the black start self-maintaining state.

[0048] In this embodiment, the doubly-fed wind turbine 11, also known as a doubly-fed asynchronous wind turbine (DFIG), can convert the mechanical power output by the wind wheel into electrical energy and output it to the grid by controlling the difference in speed between the rotor side and the grid side, thereby achieving stable output power.

[0049] The converter includes a machine-side converter and a grid-side converter, which are used to adjust the current on the rotor side of the doubly-fed wind generator 11 and the DC bus voltage inside the converter 15 to control the current and voltage of the generator.

[0050] Black start means that after the entire system stops operating due to a fault, the entire system is out of power (it does not rule out the possibility that isolated small power grids remain in operation), and is in a completely "black" state. It does not rely on the help of other networks. The self-starting generator sets in the system are started to drive the generator sets without self-starting capabilities, gradually expanding the system recovery range and ultimately achieving the recovery of the entire system.

[0051] The step-up transformer 12 is a power transformer used to increase the output voltage of the doubly-fed wind turbine generator 11 to a voltage level suitable for grid connection.

[0052] The diesel generator 13 is started as a backup power source after the power grid loses power, and supplies power to the auxiliary power system, ensuring that the double-fed wind turbine 11 can perform a black start process. The diesel generator 13 is used to provide auxiliary circuit power to the wind turbine to achieve a black start in the case of a power grid failure. In the case of a complete power grid failure, the wind turbine can be used as a self-starting power source to build voltage for the grid and supply power to other loads in the grid. This enables the wind turbine to resume grid operation in a short time, significantly improving the recovery speed of the grid.

[0053] The main controller 14 is responsible for receiving system status information and sending control instructions to coordinate the startup of the double-fed wind turbine generator 11 and the grid recovery process.

[0054] It should be noted that the transformer's excitation inrush current is caused by a sudden change in the magnetic flux in the core. When the voltage is applied to the transformer instantaneously, the magnetic flux in the core increases rapidly. This rapidly changing magnetic flux will cause a large inrush current. According to Faraday's law of electromagnetic induction, the induced electromotive force (EMF) is proportional to the rate of change of the magnetic flux. At the moment the voltage is applied, if the voltage rises rapidly, the rate of change of the magnetic flux will be large, resulting in a large inrush current. The transformer's core is in an unsaturated state in the initial stage, and the magnetic flux increases slowly, resulting in a small initial inrush current. In the process of gradually increasing the voltage, the transformer's excitation current can gradually reach a steady-state value, rather than reaching a peak value instantly, avoiding sudden shocks.

[0055] In this embodiment, the first preset voltage refers to the lower voltage constructed when the machine-side converter starts to be excited, and the second preset voltage is the higher voltage required for the power grid to resume normal operation. When the speed of the machine-side converter meets the preset conditions, a lower stator voltage begins to be established. This is to gradually establish the grid voltage and avoid impact on the system. The first preset voltage is less than the second preset voltage to ensure that the system safely and stably transitions to the normal operating voltage. During the generator excitation process, the impact of the box transformer excitation surge current on the wind turbine is reduced by building a small voltage and then increasing the stator voltage after grid connection.

[0056] The grid-side converter starts modulation, and the energy produced on the stator side of the generator provides energy for the generator excitation through the converter to maintain the stability of the stator voltage phase and amplitude. At this time, the doubly fed wind generator 11 enters the black start self-built grid state, and the black start is successful; the diesel generator 13 is disconnected and at the same time controls the stator winding output of the doubly fed wind generator 11 to supply power to the auxiliary power system, and enters the black start self-maintaining state.

[0057] The doubly-fed wind turbine black start system provided by the embodiment of the present application is applied to a doubly-fed wind turbine 11. The stator winding of the doubly-fed wind turbine 11 is directly connected to the step-up transformer 12 and then connected to the grid. The rotor winding is connected to the step-up transformer 12 through the converter and then connected to the grid. The system includes: a step-up transformer 12, a diesel generator 13, a main controller 14, and the converter includes a machine-side converter and a grid-side converter. After the power grid loses power, the step-up transformer 12 is disconnected from the grid, and the diesel generator 13 is started to supply power to the auxiliary power system. After the main controller 14 is powered on, it controls the doubly-fed wind turbine 11 to increase its speed to the synchronous speed, and then sends a black start instruction to the converter to control the diesel generator 13 to supply power to the converter. Electricity, establish a DC bus voltage through uncontrolled rectifier slow start; when the machine-side converter detects that the speed meets the preset speed, excitation constructs a stator voltage of the first preset voltage until the speed, stator voltage phase, and amplitude of the machine-side converter meet the preset conditions, control the doubly fed wind generator 11 to magnetize the step-up transformer 12, and control the stator voltage to continue to rise to the second preset voltage through the voltage outer loop; wherein, the first preset voltage is less than the second preset voltage; the grid-side converter starts modulation, so that the doubly fed wind generator 11 enters a black start self-built grid state; the diesel generator 13 is controlled to disengage and the stator winding output of the doubly fed wind generator 11 is controlled to supply power to the auxiliary power system, and enters a black start self-maintaining state. In this application, in order to achieve the purpose of quickly restoring power supply after the power grid loses power, the converter is powered by the diesel generator 13 to establish a DC bus voltage, and when the machine-side converter detects that the speed meets the preset conditions, a lower stator voltage is established, in order to gradually establish the grid voltage and avoid impact on the system. The core of the step-up transformer 12 is in an unsaturated state in the initial stage, and the magnetic flux increases slowly, resulting in a small initial inrush current. In the process of gradually increasing the voltage, the excitation current of the transformer can gradually reach a steady-state value, rather than reaching a peak value instantly, avoiding sudden shocks, and ultimately achieving the self-starting of the doubly fed wind turbine 11 and the gradual recovery of the power grid. When the power grid is completely out of power, the generator set without self-starting capability is started, gradually expanding the system recovery range, and finally achieving the recovery of the entire system, which not only improves the reliability of the power grid, but also reduces the economic losses caused by power outages in the power grid.

[0058] According to the above embodiment, in order to achieve accurate control of the power supply of the diesel generator 13, a specific embodiment is further provided, wherein the above double-fed wind generator black start system further includes: a diesel generator contactor 13;

[0059] The output end of the diesel generator 13 is connected to the first end of the diesel generator contactor, and the second end of the diesel generator contactor is connected to the auxiliary power system;

[0060] After the diesel generator 13 is started, the diesel generator contactor is energized to supply power to the auxiliary power system; the main controller 14 controls the diesel generator contactor KM1 to be disconnected to disengage the diesel generator 13.

[0061] In the above-mentioned doubly-fed wind turbine black start system, in order to further provide a specific embodiment, the system also includes a diesel generator contactor KM1, and its connection relationship and operation mode are as follows:

[0062] The diesel generator contactor KM1 is an electrical switch device used to control the electrical connection between the diesel generator 13 and the auxiliary power system. In the black start system, the diesel generator contactor KM1 is a key control element responsible for connecting or disconnecting the connection between the diesel generator 13 and the auxiliary power system at different stages.

[0063] The output end of the diesel generator 13 is connected to the first end of the diesel generator contactor KM1, and the electric energy generated by the diesel generator 13 is connected to the input end of the diesel generator contactor KM1 through a cable or a busbar. This connection method allows the output power of the diesel generator 13 to flow directly to the diesel generator contactor KM1. The second end of the diesel generator contactor KM1 is connected to the auxiliary power system: it means that the output end of the diesel generator contactor KM1 is connected to the auxiliary power system, so that the diesel generator contactor KM1 can control whether the power of the diesel generator 13 flows to the auxiliary power system.

[0064] After the diesel generator 13 is started, the diesel generator contactor KM1 is energized. After the diesel generator 13 is started and reaches a suitable operating state, the diesel generator contactor KM1 is activated (energized), thereby connecting the power supply of the auxiliary power system and providing power to the auxiliary power system. The main controller 14 controls the diesel generator contactor KM1 to disconnect, which means that during the black start process, when the double-fed wind turbine 11 successfully establishes a power grid and can self-sustaining operation, the main controller 14 sends a signal to disconnect the diesel generator contactor KM1, cut off the connection between the diesel generator 13 and the auxiliary power system, and thus disconnect the diesel generator 13 from the power grid.

[0065] Through the specific implementation method, the black start system can quickly start the diesel generator 13 after the power grid loses power, and supply power to the auxiliary power system through the diesel generator contactor KM1, ensuring that the double-fed wind turbine 11 can smoothly perform a black start. Once the double-fed wind turbine 11 can maintain the operation of the power grid by itself, the system will control the diesel generator contactor KM1 to disconnect through the main controller 14, so that the diesel generator 13 is disengaged, thereby completing the entire black start process. Through the introduction of the diesel generator contactor KM1, precise control of the power supply state of the diesel generator 13 is achieved.

[0066] According to the above embodiment, a specific embodiment is further provided, in the above doubly-fed wind turbine generator black start system, the converter further includes: a converter controller 16, a slow-start contactor KM2;

[0067] The output end of the grid-side converter is connected to the diesel generator contactor KM1 through the slow-start contactor KM2;

[0068] After the converter receives the black start command sent by the main controller 14, the converter controller 16 controls the slow-start contactor KM2 to close, so that the diesel generator 13 supplies power to the converter; and controls the slow-start contactor KM2 to open, so as to disconnect the diesel generator 13 from supplying power to the converter.

[0069] In the black start system of the doubly-fed wind turbine generator, the converter includes not only the machine-side converter and the grid-side converter, but also integrates a converter controller 16 and a slow-start contactor KM2. The converter controller 16 is responsible for managing the operation of the converter to ensure the stable supply of power and the correct response of the system.

[0070] The slow-start contactor KM2 is installed between the output end of the grid-side converter and the diesel generator contactor KM1. The function of this contactor is to control the power supply state of the diesel generator 13 to the converter during the black start process.

[0071] When the main controller 14 detects a power outage in the power grid and decides to start the black start procedure, it sends a black start instruction to the converter. After receiving this instruction, the converter controller 16 will start a series of operations to prepare the system for self-start. The converter controller 16 first controls the slow-start contactor KM2 to be attracted. This operation enables the diesel generator 13 to power the converter, establish the DC bus voltage through uncontrolled rectification slow start, and provide initial power for the start and operation of the converter. Uncontrolled rectification is to use diodes for rectification. Since diodes only allow current to flow in one direction, AC power is converted into DC power, thereby achieving the purpose of charging the DC bus capacitor in the converter.

[0072] After the slow-start contactor KM2 is energized, the power of the diesel generator 13 will flow to the converter through the slow-start contactor KM2, helping to establish the DC bus voltage and providing necessary power support for the subsequent excitation and self-starting processes.

[0073] Once the doubly-fed wind turbine generator 11 reaches synchronous speed, the machine-side converter starts excitation to build up the stator voltage. When the preset conditions (speed, stator voltage phase, amplitude) are met, the converter controller 16 controls the slow-start contactor KM2 to disconnect, thereby disconnecting the power supply from the diesel generator 13 to the converter. This indicates that the converter and the doubly-fed wind turbine generator 11 are ready to operate independently and no longer rely on the diesel generator 13.

[0074] After the slow-start contactor KM2 is disconnected, the converter controller 16 will control the grid-side converter to start modulation, maintain the phase and amplitude of the stator voltage stable, and make the double-fed wind turbine generator 11 enter the black start self-built grid state. Subsequently, the main controller 14 will control the diesel generator 13 to be disconnected, while the double-fed wind turbine generator 11 continues to supply power to the auxiliary power system through its stator winding, and enters the black start self-maintaining state.

[0075] The use of the slow-start contactor KM2 can start the converter smoothly, reduce the current impact during the startup process, and improve the startup efficiency and reliability of the system. Accurately control the power supply and disconnection of the diesel generator 13 to ensure the safety of the system during the black start process and avoid equipment damage caused by sudden power failure or overload.

[0076] According to the above embodiment, a specific embodiment is further provided, the above doubly-fed wind turbine generator black start system further includes: a stator contactor KM3; a main circuit breaker QF1;

[0077] The stator of the doubly-fed wind turbine 11 is connected to the first end of the stator contactor KM3, the second end of the stator contactor KM3 is connected to the first end of the main circuit breaker QF1 and the output end of the grid-side converter, and the second end of the main circuit breaker QF1 is connected to the low-voltage side switch QF3 of the step-up transformer 12;

[0078] When the machine-side converter detects that the phase and amplitude of the stator voltage meet the preset conditions, the converter controller 16 controls the slow-start contactor KM2 to open, so as to disconnect the diesel generator 13 from supplying power to the converter, and then the converter controller 16 controls the stator contactor KM3 to close; when the low-voltage side switch QF3 is in the closed state, the converter controller 16 controls the main circuit breaker QF1 to close, so that the doubly-fed wind turbine 11 magnetizes the step-up transformer 12, and controls the stator voltage to continue to rise to the second preset voltage through the voltage outer loop.

[0079] The double-fed wind turbine black start system in this embodiment includes a stator contactor KM3 and a main circuit breaker QF1, and these components are used to accurately control the energy flow and the conversion of the system state.

[0080] The stator of the doubly-fed wind turbine 11 is connected to the first end of the stator contactor KM3, and the second end of the stator contactor KM3 is connected to the first end of the main circuit breaker QF1 and the output end of the grid-side converter. This connection mode allows the output energy of the grid-side converter to flow to the step-up transformer 12 through the stator contactor KM3 and the main circuit breaker QF1.

[0081] The second end of the main circuit breaker QF1 is connected to the low-voltage side switch QF3 of the step-up transformer 12 , ensuring that energy can smoothly flow from the double-fed wind generator 11 to the step-up transformer 12 during the black start process.

[0082] When the machine-side converter detects that the phase and amplitude of the stator voltage meet the preset conditions, the converter controller 16 controls the slow-start contactor KM2 to open, thereby disconnecting the power supply of the diesel generator 13 to the converter. Subsequently, the converter controller 16 controls the stator contactor KM3 to close, so that the energy of the doubly-fed wind turbine 11 can flow directly to the step-up transformer 12.

[0083] Magnetization of the step-up transformer 12: After the low-voltage side switch QF3 is in the closed state, the converter controller 16 controls the main circuit breaker QF1 to close, so that the double-fed wind turbine 11 magnetizes the step-up transformer 12. Through the voltage outer loop control, the stator voltage continues to rise to the second preset voltage, completing the power supply recovery during the black start process.

[0084] Through precise control of stator contactor KM3 and main circuit breaker QF1, the system can more accurately manage the flow of power and ensure the stability and safety of the black start process. During the black start process, by gradually closing stator contactor KM3 and main circuit breaker QF1, the system can avoid equipment damage or grid instability caused by sudden power changes.

[0085] It should be noted that Figure 1 The high-voltage side switch QF2 of the medium-voltage step-up transformer 12 is a high-voltage side circuit breaker of the step-up transformer and is not disconnected under normal circumstances.

[0086] Further providing a specific embodiment, the above-mentioned doubly-fed wind turbine generator black start system further includes: a power supply contactor KM4;

[0087] The second end of the main circuit breaker QF1 is connected to the first end of the power supply contactor KM4, and the second end of the power supply contactor KM4 is connected to the input end of the auxiliary power system;

[0088] The main controller 14 controls the power supply contactor KM4 to close so that the stator winding output of the double-fed wind generator 11 supplies power to the auxiliary power system.

[0089] The black start system of the doubly-fed wind turbine generator in this embodiment includes a power supply contactor KM4, which is used to control the path for the stator winding of the doubly-fed wind turbine generator 11 to supply power to the auxiliary power system.

[0090] The second end of the main circuit breaker QF1 is connected to the first end of the power supply contactor KM4, and the second end of the power supply contactor KM4 is connected to the input end of the auxiliary power system. This connection method ensures that when the auxiliary power system needs power support, the stator winding of the doubly fed wind generator 11 can directly supply power to it.

[0091] The main controller 14 controls the closing of the power supply contactor KM4 according to the system status and power demand. When the double-fed wind turbine generator 11 successfully enters the black start self-built power grid state, and the low-voltage side switch QF3 of the step-up transformer 12 has been closed, the main controller 14 controls the power supply contactor KM4 to close, so that the stator winding of the double-fed wind turbine generator 11 starts to supply power to the auxiliary power system.

[0092] With the introduction of the power supply contactor KM4, the system can more reliably supply power to the auxiliary power system, especially in the early stage of grid recovery or when the grid is unstable. The power supply contactor KM4 provides an additional control point, allowing the system to flexibly adjust the energy flow according to the actual power demand and grid status.

[0093] Before the doubly-fed wind turbine 11 supplies power to the auxiliary power system, the main controller 14 controls the closing of the power supply contactor KM4 to ensure the safety of power supply and avoid equipment damage caused by voltage surge or instability.

[0094] It should be noted that Figure 1 The switch Q1 in the circuit is an isolating switch that provides 1140V power to the auxiliary power system. It is normally closed. In addition, the contactor KM2 will be shielded in the black start state. The function of this contactor is a slow-start contactor in the normal grid-connected state. KM2 is used as a slow-start contactor in the black start state.

[0095] According to the above embodiment, a specific embodiment is further provided, wherein the above doubly-fed wind turbine generator black start system further includes: a slow-start resistor;

[0096] The output end of the grid-side converter is connected to the slow-start contactor KM2 through a slow-start resistor.

[0097] The double-fed wind turbine black start system in this embodiment includes a slow-start resistor, which is used to limit the initial current when the grid-side converter is started, thereby protecting the converter and the grid from excessive starting current shock.

[0098] The output end of the grid-side converter is connected to the slow-start contactor KM2 through a slow-start resistor. When the converter starts, the current is first limited by the slow-start resistor, and then the resistor is gradually removed after the system stabilizes to smoothly transition to normal operation.

[0099] When the converter receives the black start command sent by the main controller 14, the converter controller 16 controls the slow start contactor KM2 to close, so that the diesel generator 13 supplies power to the converter. At this time, the current first passes through the slow start resistor, which limits the starting current and reduces the impact on the converter and the power grid.

[0100] The use of slow-start resistors can limit the initial current when the converter starts, reduce the impact on the power system, and improve the reliability and stability of the system.

[0101] According to the above embodiment, a specific embodiment is further provided, in the above doubly-fed wind turbine generator black start system, the auxiliary power system includes a plurality of auxiliary transformers;

[0102] The input ends of the multiple auxiliary transformers are connected to the second end of the power supply contactor KM4 and the second end of the diesel generator contactor KM1, and the output ends of the multiple auxiliary transformers are connected to each fan device.

[0103] The power supply capacity and flexibility of the system can be enhanced by equipping the auxiliary power system with multiple auxiliary transformers.

[0104] The auxiliary power system of the double-fed wind turbine black start system in this embodiment includes multiple auxiliary transformers, which are used to provide the required power for various wind turbine components of the wind turbine. The auxiliary transformer obtains power from the stator winding of the double-fed wind turbine 11 or the diesel generator 13, depending on which power source is active.

[0105] The output of the auxiliary transformer is connected to each wind turbine component to provide them with stable power. These wind turbine components may include control systems, sensors, actuators, and other components that have specific requirements for power supply. Specifically, power supplies of 1140V, 380V, 220V, etc. can be provided.

[0106] The auxiliary power system also includes power supply for the main controller 14. The main controller 14 also monitors the operating status of the diesel generator 13, and disconnects the diesel generator contactor KM1 in time after the power grid is restored to switch to a self-sustaining state.

[0107] Multiple auxiliary transformers can be adjusted according to actual power demand to adapt to different loads and operating conditions.

[0108] According to the above embodiment, a specific embodiment is further provided, in the above double-fed wind turbine generator black start system, the second end of the diesel generator contactor KM1 is connected to the second end of the power supply contactor KM4;

[0109] Diesel engine contactor KM1 and power supply contactor KM4 are hardware interlocked.

[0110] The doubly-fed wind turbine black start system of this embodiment ensures that the diesel generator contactor KM1 and the power supply contactor KM4 are not closed at the same time through a hardware interlocking mechanism, thereby avoiding potential circuit short circuit and equipment damage.

[0111] The diesel generator contactor KM1 and the power supply contactor KM4 are connected via a hardware interlocking mechanism. This means that when one contactor is closed, the other contactor will be locked in the open state, and vice versa. This ensures that the auxiliary power system can obtain energy from the stator winding of the diesel generator 13 or the doubly fed wind turbine generator 11, but not from both at the same time.

[0112] Hardware interlocks can be implemented as mechanical interlocks or electronic interlocks. Mechanical interlocks involve the use of physical stops or locking mechanisms to prevent both contactors from closing at the same time. Electronic interlocks use electronic control logic to monitor the state of the contactors and stop operation if a conflict is detected.

[0113] The main controller 14 is responsible for coordinating the operation of the diesel generator contactor KM1 and the power supply contactor KM4 to ensure a smooth transition of the power supply during the black start process. When the double-fed wind turbine generator 11 is ready to switch to the self-sustaining state, the main controller 14 will control the diesel generator contactor KM1 to disconnect, and after the interlocking mechanism ensures that the power supply contactor KM4 is in the disconnected state, close the power supply contactor KM4.

[0114] The hardware interlock mechanism of this embodiment prevents the diesel generator contactor KM1 and the power supply contactor KM4 from being closed at the same time, thereby avoiding the risk of circuit short circuit and equipment damage. The interlock ensures that the auxiliary power system does not receive energy from the stator windings of the diesel generator 13 and the doubly fed wind turbine generator 11 at the same time, which may cause overload or instability.

[0115] A specific embodiment is further provided, further comprising: an alarm device;

[0116] The main controller 14 controls the alarm device to send out an alarm signal when the black start is initiated, and stops sending out the alarm signal after entering the black start self-maintaining state.

[0117] An alarm device is added to provide operator warning and system status indication. The double-fed wind turbine black start system in this embodiment includes an alarm device for sending a visual or audible alarm signal to the operator when the system is black started.

[0118] The function of the alarm device is to alert the operator during critical operation stages and ensure that changes in system status are observed, especially during black start and when entering self-sustaining state.

[0119] The main controller 14 is responsible for controlling the operation of the alarm device. When the system begins to execute the black start procedure, the main controller 14 will activate the alarm device and send out an alarm signal. This can be an audible alarm, a flashing light or any other form of obvious indication. Once the double-fed wind turbine generator 11 successfully completes the black start process and enters the black start self-sustaining state, the main controller 14 will detect the change in the system state and control the alarm device to stop sending out the alarm signal. This indicates that the system has been running stably and no further intervention is required.

[0120] The alarm device ensures that the operator is immediately notified when the system is black-started, and can monitor and respond to the system status in a timely manner.

[0121] Finally, the present application provides a wind turbine generator set, including the above-mentioned doubly-fed wind turbine generator black start system.

[0122] The wind turbine generator set comprises a double-fed wind turbine generator 11 and a black start system thereof. The black start system is designed to enable the wind turbine generator to autonomously resume operation and reconnect to the grid after a power outage event.

[0123] The above is a detailed introduction to the doubly-fed wind turbine black start system and wind turbine generator set provided by the present application. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0124] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A doubly-fed wind turbine black start system, applied to a doubly-fed wind turbine, wherein the stator winding of the doubly-fed wind turbine is directly connected to a step-up transformer and then connected to the grid, and the rotor winding is connected to the step-up transformer through a converter and then connected to the grid, characterized in that: include: Step-up transformer, diesel generator, main controller, the converter includes machine-side converter and grid-side converter; After the power grid loses power, the step-up transformer is disconnected from the grid, and the diesel generator is started to supply power to the auxiliary power system; after the main controller is powered on, it controls the double-fed wind turbine to increase its speed to the synchronous speed, and then sends a black start instruction to the converter to control the diesel generator to supply power to the converter, and establishes a DC bus voltage through uncontrolled rectifier slow start; When the machine-side converter detects that the speed meets the preset speed, the excitation constructs a stator voltage of a first preset voltage, until the speed, stator voltage phase and amplitude of the machine-side converter meet the preset conditions, the doubly-fed wind turbine is controlled to magnetize the step-up transformer, and the stator voltage is controlled to continue to rise to a second preset voltage through the voltage outer loop; The grid-side converter starts modulation to make the doubly-fed wind turbine generator enter a black-start self-built grid state; the diesel generator is controlled to be disconnected and the stator winding output of the doubly-fed wind turbine generator is controlled to supply power to the auxiliary power system, and enter a black-start self-maintaining state.

2. The double-fed wind turbine black start system according to claim 1, characterized in that: Also includes: Diesel engine contactor; The output end of the diesel generator is connected to the first end of the diesel generator contactor, and the second end of the diesel generator contactor is connected to the auxiliary power system; After the diesel generator is started, the diesel generator contactor is energized to supply power to the auxiliary power system; the main controller controls the diesel generator contactor to be disconnected to control the diesel generator to be disengaged.

3. The double-fed wind turbine black start system according to claim 2, characterized in that: The converter also includes: a converter controller and a slow-start contactor; The output end of the grid-side converter is connected to the diesel generator contactor through the slow-start contactor; After the converter receives the black start instruction sent by the main controller, the converter controller controls the slow-start contactor to close so that the diesel generator supplies power to the converter; and controls the slow-start contactor to open so as to disconnect the diesel generator from supplying power to the converter.

4. The double-fed wind turbine black start system according to claim 3, characterized in that: Also includes: Stator contactor; Main circuit breaker; The stator of the doubly-fed wind turbine generator is connected to the first end of the stator contactor, the second end of the stator contactor is connected to the first end of the main circuit breaker and the output end of the grid-side converter, and the second end of the main circuit breaker is connected to the low-voltage side switch of the step-up transformer; When the phase and amplitude of the stator voltage constructed by the generator-side converter meet the preset conditions, the converter controller controls the slow-start contactor to open, so as to disconnect the diesel generator to supply power to the converter, and then the converter controller controls the stator contactor to close; When the low-voltage side switch is in a closed state, the converter controller controls the main circuit breaker to close, so that the double-fed wind turbine generator magnetizes the step-up transformer and controls the stator voltage to continue to rise to a second preset voltage through the voltage outer loop.

5. The double-fed wind turbine black start system according to claim 4, characterized in that: Also includes: Power supply contactor; The second end of the main circuit breaker is connected to the first end of the power supply contactor, and the second end of the power supply contactor is connected to the input end of the auxiliary power system; The converter controller controls the power supply contactor to close so that the stator winding output of the double-fed wind generator supplies power to the auxiliary power system.

6. The double-fed wind turbine black start system according to claim 3, characterized in that: Also includes: Slow-start resistor; The output end of the grid-side converter is connected to the slow-start contactor through the slow-start resistor.

7. The double-fed wind turbine black start system according to claim 5, characterized in that: The auxiliary power system includes a plurality of auxiliary transformers; The input ends of the plurality of auxiliary transformers are connected to the second end of the power supply contactor and the second end of the diesel generator contactor, and the output ends of the plurality of auxiliary transformers are connected to each fan device.

8. The double-fed wind turbine black start system according to claim 5, characterized in that: The second end of the diesel generator contactor is connected to the second end of the power supply contactor; The diesel generator contactor is hardware interlocked with the power supply contactor.

9. The double-fed wind turbine black start system according to claim 1, characterized in that: Also includes: an alarm device; The main controller controls the alarm device to send out an alarm signal when the black start is started, and stops sending out the alarm signal after entering the black start self-maintaining state.

10. A wind turbine generator set, characterized in that: It comprises a black start system for a doubly-fed wind turbine generator as described in any one of claims 1 to 9.

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