A double-fed wind turbine black start system and wind turbine generator set

Abstract

The present application discloses a doubly-fed wind turbine black start system and a wind turbine generator set; it relates to the field of wind power generation and solves the problem of high failure rate of traditional black start. The system uses a diesel generator to power the converter, establishes a DC bus voltage, and starts to establish a lower stator voltage when the speed of the machine-side converter meets the preset conditions, gradually establishes the grid voltage and avoids impact on the system. The iron core of the step-up transformer is in an unsaturated state in the initial stage, the magnetic flux increases slowly, and the initial inrush current is small. During the process of gradually increasing the voltage, the excitation current of the transformer can gradually reach a steady-state value, avoiding sudden impact, and ultimately achieving self-starting of the doubly-fed wind turbine and gradual recovery of the grid. When the grid is completely out of power, the system starts up, driving the generator set without self-starting capability, gradually expanding the system recovery range, and ultimately achieving recovery of the entire system, improving the reliability of the grid and reducing the economic losses caused by grid outages.

Description

Technical Field

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

[0002] In the current context of energy transformation and power system development, wind power generation has been widely adopted as a clean, renewable energy source. Doubly-fed wind turbines (DFIGs) have become a crucial component of the wind power sector due to their superior active and reactive power control capabilities. As wind power penetration in the power system gradually increases, the grid structure of the power grid where wind farms are located becomes increasingly complex and fragile. Therefore, wind farms need to be able to independently serve as black start power sources to ensure initial power supply during a system shutdown. A black start is the process of gradually restoring power to the entire power system through backup power sources after a severe power system failure. This process requires wind turbines to have the ability to respond quickly and operate stably to ensure grid reliability and stability.

[0003] Traditional control strategies are unable to effectively adapt to sudden power outages, resulting in slow system recovery and even instability. Traditional black-start schemes directly excite the transformer. Due to the high stator voltage, the stator contactor instantly closes and excites the transformer, generating a large inrush current. This current is typically 5 to 10 times the rated current and 50 to 100 times the no-load current, with rapid decay. This inrush current can significantly damage the generator and converter, shortening the unit's service life and increasing the 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 this 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] To solve the above technical problems, the present application provides a doubly-fed wind turbine black start system, which is applied to a doubly-fed wind turbine. 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. The system comprises: 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 receiving power, the main controller controls the doubly 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 the 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 all 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 and modulates the doubly-fed wind turbine generator to enter a black start self-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, thereby entering 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 closed 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 black start system, the converter further comprises: a converter controller, a soft-start contactor;

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

[0015] After the converter receives the black start instruction sent by the main controller, the converter controller controls the soft-start contactor to be closed, so that the diesel generator supplies power to the converter; and controls the soft-start contactor to be opened, 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 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 stator voltage phase and amplitude constructed by the machine-side converter meet the preset conditions, the converter controller controls the soft-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 doubly-fed wind turbine 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 via the slow-start resistor.

[0024] As an optional solution, in the above-mentioned doubly-fed wind turbine 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 in the present application controls the doubly-fed wind turbine to increase its speed to the synchronous speed after the main controller is energized, 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 soft start; when the machine-side converter detects that the speed meets the preset speed, excitation is used to build 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, and then 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 be disconnected 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 after a power outage in the power grid, a diesel generator is used to power the converter, establish a DC bus voltage, and start to establish a lower stator voltage when the machine-side converter detects that the speed meets the preset conditions. This is to gradually build up the power grid voltage and avoid causing impact on 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. During 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 ultimately achieving self-starting of the doubly fed wind turbine and 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 then 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.

[0032] In addition, the present application also provides a wind turbine generator set corresponding to the above-mentioned doubly-fed wind turbine generator black start system, with the same effect 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 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-step-up transformer; 13-diesel generator; 14-main controller; 15-converter; 16-converter controller. DETAILED DESCRIPTION

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

[0038] The core of this application is to provide a doubly-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 with reference to the accompanying drawings and specific implementation methods.

[0040] In the current context of energy transformation and power system development, wind power generation has been widely adopted as a clean, renewable energy source. Doubly-fed wind turbines (DFIGs) have become a key component of the wind power sector due to their excellent active and reactive power control capabilities. As wind power penetration in the power system gradually increases, the grid structure of the power grid where wind farms are located is becoming increasingly complex and fragile. Therefore, wind farms need to be able to independently serve as black start power sources to ensure initial power supply when the main system is shut down. Furthermore, since wind farms are often located in remote areas, the reliability requirements of the power grids in which they are located are even higher, making black start technology particularly important.

[0041] A black start is the process of gradually restoring power to the entire power system through backup power after a serious power failure. 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 be unable to quickly and effectively adapt to sudden grid power outages, resulting in slow system recovery and even instability. Furthermore, traditional doubly-fed wind turbines must be connected to an additional power source, such as a diesel generator, to power the auxiliary circuits for dynamic commissioning. In the event of a complete grid power outage, they lack an operational power source, making it impossible to quickly address the problem. Traditional black-start schemes directly excite the transformer. Due to the high stator voltage, the transformer is excited at the moment the stator contactor closes, generating a large inrush current, typically 5-10 times the rated current and 50-100 times the no-load current. This current decays rapidly, significantly damaging the generator and converter, shortening the unit's service life and increasing the 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 a 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 a 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 starts to supply power to the auxiliary power system;

[0045] After receiving power, the main controller 14 controls the doubly fed wind turbine generator 11 to increase its speed to the synchronous speed, then sends a black start instruction to the converter, controls 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 builds a stator voltage of a first preset voltage until the speed, stator voltage phase, and amplitude of the machine-side converter all meet the preset conditions. The doubly-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 a 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 and modulates the doubly fed wind turbine 11 to enter a 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 turbine 11 is controlled to supply power to the auxiliary power system, entering a 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 turbine generator 11 and the DC bus voltage inside the converter 15 to control the current and voltage of the generator.

[0050] A 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 may continue to operate), 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, driving 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] After a power outage, diesel generator 13 starts as a backup power source, powering the auxiliary power system and ensuring that doubly-fed wind turbine 11 can complete a black start. Diesel generator 13 provides auxiliary circuit power to the wind turbine, enabling a black start in the event of a power outage. In the event of a complete power outage, the wind turbine can serve as a self-starting power source to build voltage for the grid and power other loads within the grid. This allows the wind turbine to resume grid operation in a short period of time, significantly accelerating grid recovery.

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

[0054] It's important to note that a transformer's magnetizing inrush current is caused by a sudden change in the magnetic flux in the core. When voltage is instantaneously applied to the transformer, the magnetic flux within the core increases rapidly. This rapidly changing magnetic flux results in 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. If the voltage increases rapidly at the moment of application, the rate of change of the magnetic flux can be very large, resulting in a large inrush current. Initially, the transformer's core is unsaturated, and the magnetic flux increases slowly, resulting in a small initial inrush current. As the voltage gradually increases, the transformer's magnetizing current can gradually reach a steady-state value, rather than reaching a peak value instantaneously, thus avoiding a sudden surge.

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

[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 turbine 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 turbine 11 to supply power to the auxiliary power system, entering 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 a 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 energized, 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. The DC bus voltage is established by uncontrolled rectifier slow start; 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 all meet the preset conditions, and the doubly fed wind turbine 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; the grid-side converter starts the modulation, so that the doubly fed wind turbine 11 enters 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 turbine 11 is controlled to supply power to the auxiliary power system, and enters the black start self-maintaining state. In this application, in order to achieve the purpose of quickly restoring power 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 started to be established. This is to gradually establish the grid voltage and avoid causing 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. As the voltage gradually increases, the transformer's excitation current can gradually reach a steady-state value, rather than instantly reaching a peak value. This avoids sudden shocks and ultimately achieves the self-starting of the doubly fed wind turbine 11 and the gradual recovery of the power grid. In the event of a complete power outage, the generator set without self-starting capability can be started, gradually expanding the system recovery range and ultimately achieving the recovery of the entire system. This not only improves the reliability of the power grid, but also reduces the economic losses caused by power outages.

[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 turbine generator black start system further includes: a diesel generator contactor KM1;

[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 closed to supply power to the auxiliary power system; the main controller 14 controls the diesel generator contactor KM1 to be disconnected to disengage the control 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 further includes a diesel-generator contactor KM1, whose connection relationship and operation mode are as follows:

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

[0063] The output of the diesel generator 13 is connected to the first terminal of the diesel generator contactor KM1. The electricity generated by the diesel generator 13 is connected to the input terminal of the diesel generator contactor KM1 via a cable or busbar. This connection allows the output power of the diesel generator 13 to flow directly to the diesel generator contactor KM1. The second terminal of the diesel generator contactor KM1 is connected to the auxiliary power system. This connection allows the diesel generator contactor KM1 to control whether the power from the diesel generator 13 flows to the auxiliary power system.

[0064] After diesel generator 13 starts, diesel generator contactor KM1 closes. Once diesel generator 13 has started and reached a suitable operating state, diesel generator contactor KM1 is activated (closed), connecting the auxiliary power system and providing power to the system. Main controller 14 controls diesel generator contactor KM1 to open. During a black start, when doubly-fed wind turbine 11 successfully establishes a grid connection and is capable of self-sustaining operation, main controller 14 sends a signal to open diesel generator contactor KM1, severing the connection between diesel generator 13 and the auxiliary power system, thereby disconnecting diesel generator 13 from the grid.

[0065] Through its specific implementation, the black-start system rapidly starts the diesel generator 13 after a power outage, supplying power to the auxiliary power system via the diesel-generator contactor KM1, ensuring a smooth black-start of the doubly-fed wind turbine 11. Once the doubly-fed wind turbine 11 is able to maintain grid operation, the system controls the main controller 14 to disconnect the diesel-generator contactor KM1, disengaging the diesel generator 13 and completing the black-start process. The introduction of the diesel-generator contactor KM1 enables precise control of the power supply status of the diesel generator 13.

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

[0067] The output of the grid-side converter is connected to the diesel generator contactor KM1 via 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 be closed, so that the diesel generator 13 supplies power to the converter; and controls the slow-start contactor KM2 to be opened, so as to stop the diesel generator 13 from supplying power to the converter.

[0069] In a doubly-fed wind turbine black-start system, the converter includes not only the generator-side converter and the grid-side converter, but also a converter controller 16 and a soft-start contactor KM2. Converter controller 16 manages converter operation, ensuring a stable power supply and proper system response.

[0070] The soft-start contactor KM2 is installed between the grid-side converter output and the diesel generator contactor KM1. This contactor controls the power supply from the diesel generator 13 to the converter during a black start.

[0071] When the main controller 14 detects a grid power outage and decides to initiate a black start procedure, it sends a black start command to the converter. Upon receiving this command, the converter controller 16 initiates a series of operations to prepare the system for a self-start. First, the converter controller 16 controls the soft-start contactor KM2 to close. This operation enables the diesel generator 13 to power the converter. Uncontrolled rectification, through a soft start, establishes the DC bus voltage, providing initial power for converter startup and operation. Uncontrolled rectification utilizes diodes for rectification. Since diodes only allow current to flow in one direction, they convert AC power to DC power, thereby charging the DC bus capacitors 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 subsequent excitation and self-starting processes.

[0073] Once the doubly-fed wind turbine 11 reaches synchronous speed, the generator-side converter begins excitation to build up the stator voltage. When preset conditions (speed, stator voltage phase, and amplitude) are met, the converter controller 16 controls the soft-start contactor KM2 to open, thereby disconnecting the power supply from the diesel generator 13 to the converter. This indicates that the converter and doubly-fed wind turbine 11 are ready for independent operation, no longer relying on the diesel generator 13.

[0074] After the soft-start contactor KM2 opens, the converter controller 16 controls the grid-side converter to start modulation, maintaining stable stator voltage phase and amplitude, allowing the doubly-fed wind turbine 11 to enter a black-start, self-powered grid state. Subsequently, the main controller 14 controls the diesel generator 13 to disconnect, while the doubly-fed wind turbine 11 continues to power the auxiliary power system through its stator windings, entering a black-start, self-sustaining state.

[0075] The use of the slow-start contactor KM2 allows for smooth inverter startup, reduces current surges during startup, and improves system startup efficiency and reliability. Precisely controlling the power supply and disconnection of the diesel generator 13 ensures system safety during black starts and prevents equipment damage caused by sudden power outages or overloads.

[0076] According to the above embodiment, a specific embodiment is further provided, wherein the above doubly-fed wind turbine 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 soft-start contactor KM2 to disconnect, so as to disconnect the diesel generator 13 from supplying power to the converter. 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 doubly-fed wind turbine black start system in this embodiment includes a stator contactor KM3 and a main circuit breaker QF1 . 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 terminal of the stator contactor KM3. The second terminal of the stator contactor KM3 is connected to the first terminal of the main circuit breaker QF1 and the output terminal of the grid-side converter. This connection 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 flow smoothly from the doubly-fed wind turbine 11 to the step-up transformer 12 during the black start process.

[0082] When the generator-side converter detects that the stator voltage phase and amplitude meet preset conditions, converter controller 16 controls the soft-start contactor KM2 to open, thereby disconnecting the diesel generator 13 from supplying power to the converter. Converter controller 16 then controls the stator contactor KM3 to close, allowing energy from the doubly-fed wind turbine 11 to flow directly to the step-up transformer 12.

[0083] Magnetizing step-up transformer 12: After low-voltage switch QF3 is closed, converter controller 16 controls main circuit breaker QF1 to close, allowing doubly-fed wind turbine 11 to magnetize step-up transformer 12. Through voltage outer loop control, the stator voltage continues to rise to a second preset voltage, completing power restoration during the black start process.

[0084] Through precise control of stator contactor KM3 and main circuit breaker QF1, the system manages power flow more precisely, ensuring stability and safety during black starts. During a black start, by gradually closing stator contactor KM3 and main circuit breaker QF1, the system avoids equipment damage or grid instability caused by sudden power fluctuations.

[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 doubly-fed wind turbine 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 turbine 11 can directly supply power to it.

[0091] The main controller 14 controls the closing of the power contactor KM4 based on the system status and power demand. When the doubly-fed wind turbine 11 successfully enters the black start self-built grid state and the low-voltage side switch QF3 of the step-up transformer 12 is closed, the main controller 14 controls the closing of the power contactor KM4, allowing the stator winding of the doubly-fed wind turbine 11 to begin supplying power to the auxiliary power system.

[0092] The introduction of the KM4 power contactor allows the system to more reliably supply power to the auxiliary power system, especially during the initial phase of grid recovery or during grid instability. The KM4 power contactor provides an additional control point, allowing the system to flexibly adjust energy flow based on actual power demand and grid conditions.

[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 Switch Q1 is the isolating switch that provides 1140V power to the auxiliary power system from the converter and is normally closed. Furthermore, during a black start, contactor KM2 is shielded. This contactor functions as a slow-start contactor during normal grid-connected conditions. During a black start, KM2 serves as a slow-start contactor.

[0095] According to the above embodiment, a specific embodiment is further provided, wherein the black start system of the doubly-fed wind turbine generator 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 doubly-fed wind turbine black start system in this embodiment includes a slow-start resistor for limiting the initial current when the grid-side converter starts, 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. Then, after the system stabilizes, the resistor is gradually removed to smoothly transition to normal operation.

[0099] When the converter receives the black start command from the main controller 14, the converter controller 16 closes the slow-start contactor KM2, allowing the diesel generator 13 to supply power to the converter. At this point, the current first flows through the slow-start resistor, limiting the starting current and reducing the impact on the converter and the 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 which the auxiliary power system of the above doubly-fed wind turbine black start 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 wind turbine component.

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

[0104] The auxiliary power system of the doubly-fed wind turbine black start system in this embodiment includes multiple auxiliary transformers, which are used to provide the required power to the various wind turbine components of the wind turbine. The auxiliary transformers receive power from the stator windings of the doubly-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 various wind turbine components, providing them with stable power. These components may include control systems, sensors, actuators, and other components with specific power supply requirements. Power supplies are available in 1140V, 380V, and 220V configurations.

[0106] The auxiliary power system also provides power to 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 doubly-fed wind turbine 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] The diesel generator contactor KM1 and the power supply contactor KM4 are hardware interlocked.

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

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

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

[0113] Main controller 14 coordinates the operation of diesel-generator contactor KM1 and power supply contactor KM4 to ensure a smooth transition of power supply during a black start. When doubly-fed wind turbine 11 is ready to transition to a self-sustaining state, main controller 14 controls diesel-generator contactor KM1 to open. After an interlock mechanism ensures that power supply contactor KM4 remains open, main controller 14 closes power supply contactor KM4.

[0114] The hardware interlock mechanism in this embodiment prevents the simultaneous closing of diesel generator contactor KM1 and power supply contactor KM4, thereby avoiding the risk of short circuits and equipment damage. This interlock ensures that the auxiliary power system does not simultaneously receive energy from both the diesel generator 13 and the stator windings of the doubly-fed wind turbine 11, which could 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 to stop sending out the alarm signal after entering the black start self-maintaining state.

[0117] An alarm device is added to provide operator warnings and system status indications. 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 the black start procedure, the main controller 14 activates the alarm device and issues an alarm signal. This can be an audible alarm, a flashing light, or any other visible indication. Once the doubly-fed wind turbine 11 successfully completes the black start process and enters the self-sustaining black start state, the main controller 14 detects the change in system status and controls the alarm device to stop emitting the alarm signal. This indicates that the system has stabilized and no further intervention is required.

[0120] The alarm device ensures that the operator is immediately notified when the system undergoes a black start, 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 includes a doubly-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.

[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 referred 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 this 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 this application.

[0124] It should also be noted that, in this specification, relational terms such as first and second, etc., are used only 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 "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising 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 receiving power, the main controller controls the doubly 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 the 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 all 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 and modulates the doubly-fed wind turbine generator to enter a black start self-grid state; controls the diesel generator to be disconnected and controls the stator winding output of the doubly-fed wind turbine generator to supply power to the auxiliary power system, thereby entering a black start self-sustaining state; Also includes: diesel generator 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 closed 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; The converter further comprises: a converter controller and a soft-start contactor; The output end of the grid-side converter is connected to the diesel generator contactor via the slow-start contactor; After the converter receives the black start instruction sent by the main controller, the converter controller controls the soft-start contactor to be closed, so that the diesel generator supplies power to the converter; and controls the soft-start contactor to be opened, so as to disconnect the diesel generator from supplying power to the converter; Also includes: stator contactor; main circuit breaker; The stator of the doubly-fed wind turbine 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 stator voltage phase and amplitude constructed by the machine-side converter meet the preset conditions, the converter controller controls the soft-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.

2. The doubly-fed wind turbine black start system according to claim 1, 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 doubly-fed wind turbine generator supplies power to the auxiliary power system.

3. The doubly-fed wind turbine black start system according to claim 1, characterized in that: Also includes: Soft-start resistor; The output end of the grid-side converter is connected to the slow-start contactor via the slow-start resistor.

4. The doubly-fed wind turbine black start system according to claim 2, 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.

5. The doubly-fed wind turbine black start system according to claim 2, 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.

6. The doubly-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 to stop sending out the alarm signal after entering the black start self-maintaining state.

7. A wind turbine generator set, characterized in that: It comprises the black start system of the doubly-fed wind turbine generator as described in any one of claims 1 to 6.

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