Wind turbine pitch system and control method

Abstract

The present invention relates to the technical field of wind power generation, and provides a wind turbine pitch system and a control method. The wind turbine pitch system comprises a charging / discharging unit and a control unit; the charging / discharging unit comprises an energy storage device, a bidirectional direct-current switching circuit, and a switch assembly; the energy storage device is connected to a direct-current bus by means of the switch assembly; the direct-current bus is connected to the energy storage device by means of the bidirectional direct-current switching circuit; the bidirectional direct-current switching circuit comprises a plurality of different working modes; the control unit is configured to acquire states of a direct-current bus voltage and a power grid voltage, and send different control instructions to the bidirectional direct-current switching circuit on the basis of the states of the direct-current bus voltage and the power grid voltage, so as to switch the working mode of the bidirectional direct-current switching circuit, thereby adjusting different charging / discharging states of the energy storage device. On the basis of low cost and high integration, the present invention can avoid the risk of open flame caused by a large amount of heat generated by frequent operation of a braking resistor, and improves the energy utilization rate.

Description

Wind turbine pitch control system and control method Technical Field

[0001] This invention relates to the field of wind power generation technology, and more specifically, to a wind power pitch control system and control method. Background Technology

[0002] The pitch control system is a crucial component of a wind turbine generator set. Its main function is to adjust the blades to a specified angle according to master control commands. During blade adjustment, the pitch motor operates in both acceleration and deceleration modes. As the blades gradually increase in size, the energy fed back to the DC bus capacitor in the wind turbine generator set increases during deceleration. This necessitates the connection of a larger-power braking resistor to the DC bus to ensure the DC bus voltage remains within its normal operating range.

[0003] However, the above-mentioned solution of using a higher-power external braking resistor is not conducive to the integration of the wind turbine pitch system and may even lead to energy waste. At the same time, the frequent operation of the braking resistor generates a lot of heat, which poses a risk of open flame and improves energy utilization.

[0004] Therefore, there is an urgent need for a wind power pitch control solution that can ensure the normal operation of the DC bus while maintaining low cost and high integration. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a wind power pitch control system and control method that can avoid the risk of open flame caused by the frequent operation of the braking resistor generating a large amount of heat, ensure the normal operation of the DC bus, and improve energy utilization efficiency, based on low cost and high integration.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0007] In a first aspect, the present invention provides a wind power pitch system, which includes a DC bus, a rectifier unit, and an inverter unit. The rectifier unit is connected to the inverter unit via the DC bus. The wind power pitch system also includes a charging / discharging unit and a control unit. The charging / discharging unit includes an energy storage device, a bidirectional DC-DC switching circuit, and a switching assembly. The energy storage device is connected to the DC bus via the switching assembly. The DC bus is connected to the energy storage device via the bidirectional DC-DC switching circuit. The control unit is connected to the control terminal of the bidirectional DC-DC switching circuit.

[0008] The bidirectional DC-DC switching circuit includes several different operating modes;

[0009] The control unit is used to obtain the status of the DC bus voltage and the grid voltage; and according to the status of the DC bus voltage and the grid voltage, it sends different control commands to the bidirectional DC switching circuit to switch the operating mode of the bidirectional DC switching circuit.

[0010] A bidirectional DC-DC switching circuit is used to adjust the charging / discharging state of the energy storage device according to different operating modes.

[0011] Secondly, the present invention also provides a control method for a wind power pitch system, wherein the wind power pitch system further includes a charging / discharging unit and a control unit, the charging / discharging unit including an energy storage device, a bidirectional DC-DC switching circuit, and a switching assembly; the energy storage device is connected to a DC bus through the switching assembly; the DC bus is connected to the energy storage device through the bidirectional DC-DC switching circuit; the bidirectional DC-DC switching circuit includes multiple different operating modes; the control method includes:

[0012] The control unit acquires the status of the DC bus voltage and the grid voltage;

[0013] The control unit sends different control commands to the bidirectional DC switching circuit according to the state of the DC bus voltage and the grid voltage, so as to switch the working mode of the bidirectional DC switching circuit.

[0014] The bidirectional DC switching circuit adjusts the charging / discharging state of the energy storage device according to different operating modes.

[0015] The wind power pitch control system and control method provided by this invention have the following beneficial effects:

[0016] This invention relates to a wind power pitch system, specifically a wind power generation technology system. It includes a DC bus, a rectifier unit, and an inverter unit. The rectifier unit is connected to the inverter unit via the DC bus. The wind power pitch system also includes a charging / discharging unit, a control unit, and a switching assembly. An energy storage device is connected to the DC bus via the switching assembly. The DC bus is connected to the energy storage device via a bidirectional DC-DC switching circuit. The bidirectional DC-DC switching circuit includes multiple operating modes. The control unit acquires the DC bus voltage and grid voltage status and sends different control commands to the bidirectional DC-DC switching circuit based on these statuses to switch its operating modes. The bidirectional DC-DC switching circuit then adjusts the energy storage device's charging / discharging state according to the different operating modes. Based on this, this invention can adjust the energy storage device's operating state in real time based on the DC bus voltage and grid voltage status, achieving low cost and high integration. This avoids the risk of open flame caused by excessive heat generated by frequent operation of the braking resistor, ensuring the normal operation of the DC bus and improving energy utilization.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 shows one of the module schematic diagrams of the wind power pitch system in this invention;

[0020] Figure 2 shows one of the circuit diagrams of the wind power pitch system in this invention;

[0021] Figure 3 shows a second schematic diagram of the wind power pitch system in this invention;

[0022] Figure 4 shows the second circuit schematic of the wind power pitch system in this invention;

[0023] Figure 5 shows the third circuit diagram of the wind power pitch system in this invention;

[0024] Figure 6 shows a schematic diagram of the steps of the control method in this invention;

[0025] Figure 7 shows one of the step-by-step schematic diagrams of step 200 in this invention;

[0026] Figure 8 shows a second step-by-step schematic diagram of step 200 in this invention.

[0027] Icons: 10-Wind power pitch system; 11-DC bus; 12-Rectifier unit; 13-Inverter unit; 14-Motor; 21-Charging / discharging unit; 22-Control unit; 31-Energy storage device; 32-Bidirectional DC switching circuit; 33-Braking unit; 34-Switching assembly; WB1-Positive bus; WB2-Negative bus; C1-Bus capacitor; Q1-First switch; Q2-Second switch; Q3-Third switch; C2-First capacitor; L1-First inductor; R1-First resistor; Q4-Fourth switch; SC1-Supercapacitor; F1-Fuse; D1-First diode; D2-Second diode. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] As wind turbine blades gradually increase in size, existing solutions can convert all the energy fed back from motor deceleration on the DC bus into heat energy to ensure the normal operation of the DC bus. However, this approach increases the difficulty of device integration, increases the frequency of use of the braking resistor, and increases the risk of open flame.

[0032] Alternatively, the on / off state of the preceding rectifier bridge can be adjusted to simultaneously supply power to the DC bus via the energy storage device while the preceding rectifier bridge is disconnected, until the voltage of the energy storage device drops to normal, at which point the preceding rectifier bridge is closed. This control method requires frequent adjustments to the on / off state of the preceding rectifier bridge. When closing the preceding rectifier bridge, a large inrush current may be generated due to the mismatch between the grid voltage and the energy storage device voltage, causing the preceding circuit breaker to trip or the rectifier bridge to be damaged, thereby damaging the wind turbine pitch control system.

[0033] Based on this, the present invention provides a wind power pitch control solution that can avoid the risk of open flame caused by the frequent operation of the braking resistor generating a large amount of heat, while ensuring the normal operation of the DC bus, based on low cost and high integration.

[0034] The following will provide a detailed description of the wind power pitch control scheme provided by this invention.

[0035] Firstly, please refer to Figure 1, which shows a schematic diagram of the modules of a wind power pitch system. The wind power pitch system 10 includes a DC bus 11, a rectifier unit 12, and an inverter unit 13. The rectifier unit 12 is connected to the inverter unit 13 through the DC bus 11. In this embodiment, the inverter unit 13 is also connected to the motor 14.

[0036] The wind power pitch system 10 also includes a charging / discharging unit 21 and a control unit 22. The charging / discharging unit 21 includes an energy storage device 31, a bidirectional DC-DC switching circuit 32, and a switching assembly 34. The energy storage device 31 is connected to the DC bus 11 via the switching assembly 34; the DC bus 11 is also connected to the energy storage device 31 via the bidirectional DC-DC switching circuit 32. The control unit 22 is connected to the control terminal of the bidirectional DC-DC switching circuit 32.

[0037] The bidirectional DC-DC switching circuit includes several different operating modes. Each operating state corresponds to a different charging or discharging state, and the charging state can also correspond to different charging currents.

[0038] The control unit is used to obtain the status of the DC bus voltage and the grid voltage; and according to the status of the DC bus voltage and the grid voltage, it sends different control commands to the bidirectional DC switching circuit to switch the operating mode of the bidirectional DC switching circuit.

[0039] The bidirectional DC-DC switching circuit is used to adjust the charging / discharging state of the energy storage device according to different operating modes.

[0040] This embodiment obtains the state of the DC bus voltage and the grid voltage, eliminating the need for frequent switching of the front-end rectifier bridge. Instead, it directly adjusts the operating mode of the bidirectional DC switching circuit based on the state of the DC bus voltage and the grid voltage to drive the energy storage device for charging / discharging. This reduces device costs, improves device integration, and allows for real-time adjustment of the energy storage device's operating state based on the DC bus voltage and the grid voltage. This avoids the risk of open flame caused by the frequent operation of the braking resistor generating a large amount of heat, ensuring the normal operation of the DC bus.

[0041] It should be noted that this embodiment does not limit the structure of the bidirectional DC-DC switching circuit, as long as it can include multiple operating modes and adjust the charging / discharging state of the energy storage device under different operating modes. To reduce the cost of the wind power pitch system, in one possible implementation, the bidirectional DC-DC switching circuit is implemented by a bidirectional DC-DC (Direct Current) circuit.

[0042] Please refer to Figure 2, which shows a schematic diagram of the bidirectional DC-DC switching circuit 32 in this embodiment. The DC bus 11 includes a positive bus WB1 and a negative bus WB2. The bidirectional DC-DC switching circuit 32 includes a first switch Q1, a second switch Q2, a third switch Q3, a first capacitor C2, and a first inductor L1. The first terminal (collector) of the first switch Q1 is connected to the positive bus WB1. The second terminal (emitter) of the first switch Q1 is connected to the first terminal (collector) of the second switch Q2 and the first terminal of the first inductor L1, respectively. The second terminal of the first inductor L1 is connected to the first terminal (emitter) of the third switch Q3. The second terminal (collector) of the third switch Q3 is connected to the first terminal (positive) of the first capacitor C2, the first terminal of the energy storage device 31, and the first terminal of the switching assembly 34, respectively. The second terminal of the switching assembly 34 is connected to the positive bus WB1. The second terminal (emitter) of the second switch Q2, the second terminal (negative) of the first capacitor C2, and the second terminal of the energy storage device 31 are all connected to the negative bus WB2. The third terminal (base) of the first switch Q1, the third terminal (base) of the second switch Q2, and the third terminal (base) of the third switch Q3 are connected to the control unit 22.

[0043] Please continue to refer to Figure 2. The wind power pitch system 10 also includes a bus capacitor C1. The second end of the bus capacitor C1 is connected to the negative bus WB2. The first end of the first switch Q1 is connected to the first end (positive pole) of the bus capacitor C1 and the positive bus WB1, respectively.

[0044] The bidirectional DC-DC switching circuit includes multiple operating modes. Each operating mode corresponds to a different on / off state of the switching transistor. The transistor in the on state is used to output a pulse-width modulation signal to adjust the charging current of the energy storage device. In one possible implementation, the energy storage device can be a supercapacitor.

[0045] For the same operating mode, the bidirectional DC-DC switching circuit can also include different output modes. For example, in the same operating mode, the pulse width modulation (PWM) signals output by the switching transistors are different in different output modes. Taking PWM signals as an example, the duty cycles corresponding to each PWM signal are different.

[0046] First Embodiment

[0047] When the acquired DC bus voltage is less than the operating voltage, such as the second preset threshold in the following text, the operating mode of the bidirectional DC switching circuit 32 can be further determined according to the state of the grid voltage.

[0048] The grid voltage is in an abnormal state.

[0049] When it is determined that the current grid voltage state is in an abnormal state, and at the same time the DC bus voltage is less than the first preset value. For example, taking the DC bus voltage as U1 and the first preset value as A, that is, satisfying: U1 < A, the control unit 22 can send a first control instruction to the bidirectional DC switching circuit 32 to make the bidirectional DC switching circuit 32 be in the first working mode, the bidirectional DC switching circuit 32 does not work, and the energy storage device 31 discharges to the DC bus 11 through the switch component 34.

[0050] In a possible implementation manner, the first preset value A is the rated voltage of the energy storage device (or the charging target voltage of the energy storage device). That is, when it is determined that the DC bus voltage is less than the rated voltage, the bidirectional DC switching circuit 32 is in the first working mode, and each switching tube in the bidirectional DC switching circuit 32 does not perform any action.

[0051] Please continue to refer to FIG. 2. When the bidirectional DC switching circuit 32 is in the first working mode, the first switching tube Q1, the second switching tube Q2, and the third switching tube Q3 are all turned off.

[0052] When it is determined that the current grid voltage state is in an abnormal state, and at the same time the DC bus voltage is greater than the first preset value and less than the second preset value. For example, taking the DC bus voltage as U1, the first preset value as A, and the second preset value as B, that is, satisfying: A < U1 < B, the control unit 22 will send a second control instruction to the bidirectional DC switching circuit 32 to make the bidirectional DC switching circuit 32 be in the second working mode, and the bidirectional DC switching circuit 32 drives the DC bus 11 to supply power to the energy storage device 31.

[0053] Please continue to refer to FIG. 2. At this time, in the bidirectional DC switching circuit 32 when the bidirectional DC switching circuit 32 is in the second working mode, for example, the DC - DC Buck mode (step - down conversion mode), at this time the second switching tube Q2 and the third switching tube Q3 are both turned off; the first switching tube Q1 is in the first working state to drive the DC bus 11 to supply power to the energy storage device 31. At this time, the energy storage device 31 works in a small - current floating - charge charging mode, and the corresponding charging current is I1 to ensure that the voltage of the energy storage device 31 is stable near the charging target voltage.

[0054] In a possible implementation manner, the first preset value A can be the rated voltage of the energy storage device (or the charging target voltage of the energy storage device), and the second preset value B can be set as the first preset action voltage. That is, when the DC bus voltage U1 is greater than the rated voltage and less than the first preset action voltage, the bidirectional DC - DC circuit works in the Buck mode (step - down conversion mode) and is in the first working state.

[0055] In this embodiment, the first working state represents an output state of a pulse - width modulation signal.

[0056] It should be noted that in this embodiment, when the grid voltage is abnormal, the supercapacitor provides the large amount of energy required for motor operation to the DC bus through the switching components, rather than through the bidirectional DC switching circuit. This can significantly reduce the power of the bidirectional DC switching circuit, thereby reducing its size and facilitating the integration of the pitch system and reducing costs.

[0057] The grid voltage is in a normal state.

[0058] If it is determined that the current grid voltage is in a normal state, and the DC bus voltage U1 is less than the second preset value B and the voltage U2 of the energy storage device 31 is less than or equal to the first preset value A, that is: U1≤B and U2≤A, the control unit 22 sends a second control command to the bidirectional DC switching circuit 32, so that the bidirectional DC switching circuit 32 is in the second working mode; the bidirectional DC switching circuit 32 then drives the DC bus 11 to supply power to the energy storage device 31.

[0059] Please continue to refer to Figure 2. At this time, the bidirectional DC switching circuit 32 is in the second working mode. At this time, the second switch Q2 and the third switch Q3 are both turned off. The first switch Q1 is in the first working state to drive the DC bus 11 to supply power to the energy storage device 31. At this time, the energy storage device 31 is in the low current float charging mode. At this time, the charging current of the energy storage device 31 is I1 to ensure that the voltage of the energy storage device 31 is stable near the charging target voltage.

[0060] In one possible implementation, the first preset value is the rated voltage of the energy storage device 31, and the second preset value is the first preset operating voltage. At this time, the DC bus voltage is less than the first preset operating voltage, the voltage of the energy storage device 31 is less than or equal to the rated voltage of the energy storage device, and the bidirectional DC-DC circuit operates in Buck mode (step-down conversion mode).

[0061] If the current grid voltage is determined to be in a normal state, and the DC bus voltage is less than the second preset value and the voltage of the energy storage device 31 is greater than or equal to the third preset value, the control unit 22 sends a third control command to the bidirectional DC switching circuit 32, so that the bidirectional DC switching circuit 32 is in the third working mode; the bidirectional DC switching circuit 32 then drives the energy storage device 31 to discharge to the DC bus 11.

[0062] Please continue to refer to Figure 2. At this time, the bidirectional DC switching circuit 32 is in the third working mode. At this time, the first switch Q1 is off; the second switch Q2 is in the second working state; and the third switch Q3 is on to drive the energy storage device 31 to discharge to the DC bus 11. At this time, the energy storage device 31 is in the discharge mode until the energy storage device 31 discharges to the charging target voltage.

[0063] In this embodiment, the second operating state represents the output state of the second pulse width modulation signal. The output state of the second pulse width modulation signal differs from that of the first pulse width modulation signal; for example, the duty cycle of the second pulse width modulation signal is different from that of the first pulse width modulation signal.

[0064] In one possible implementation, the first preset value is assumed to be the rated voltage of the energy storage device 31. If the rated voltage of the energy storage device 31 is represented as Un, then the third preset value C can satisfy Un±ΔU, where ΔU is a constant value. At this time, the DC bus voltage is less than the first preset operating voltage. When the voltage of the energy storage device 31 is greater than or equal to Un±ΔU, the bidirectional DC-DC circuit operates in Boost mode (boost conversion mode), and the energy storage device 31 is in discharge mode. Its discharge current can be represented as Idn, so as to discharge the voltage of the energy storage device 31 to the rated voltage Un.

[0065] It should be noted that this embodiment does not limit the method of determining whether the grid voltage is abnormal or normal. To increase the integration of the wind power pitch system, in one possible implementation, the control unit can integrate a grid voltage detection component and a DC bus voltage detection component to acquire the grid voltage and DC bus voltage respectively. Then, the real-time acquired grid voltage can be used to determine whether the grid voltage is abnormal or normal. For example, the control unit can determine whether the currently detected grid voltage is lower than a preset voltage value. If it is lower, the current grid voltage is determined to be in an abnormal state; otherwise, the current grid voltage is determined to be in a normal state.

[0066] Second Embodiment

[0067] When the acquired DC bus voltage is greater than or equal to the operating voltage, such as the second preset threshold, the operating mode of the bidirectional DC switching circuit 32 can be further determined directly based on the DC bus voltage.

[0068] When the DC bus voltage is determined to be greater than or equal to the second preset value (i.e., U1≥B), the control unit 22 sends a fourth control command to the bidirectional DC switching circuit 32, causing the bidirectional DC switching circuit 32 to enter the fourth operating mode. The bidirectional DC switching circuit 32 can then drive the DC bus 11 to supply power to the energy storage device 31. At this time, the charging current in the fourth operating mode is I2. In one possible implementation, the charging current I2 in the fourth operating mode can be the rated charging current.

[0069] Please continue to refer to FIG. 2. At this time, in the bidirectional DC switching circuit 32, the bidirectional DC switching circuit 32 is in the fourth operating mode. For example, in the DC-DC Buck mode (step-down conversion mode), at this time, the first switching transistor Q1 is in the third operating state; the second switching transistor Q2 and the third switching transistor Q3 are both turned off to drive the DC bus 11 to supply power to the energy storage device 31. At this time, the energy storage device 31 is in the large current charging mode, and the energy of the DC bus 11 can be quickly discharged to the energy storage device 31, thereby causing the DC bus voltage to drop.

[0070] To suppress the instantaneous large feedback energy, in this embodiment, the fourth control instruction includes a first control command and a second control command. Each control command corresponds to a first output state and a second output state in the fourth operating mode respectively; among them, each output state corresponds to a different modulation signal to generate different charging currents.

[0071] Under the condition that the DC bus voltage is greater than the second preset value B and less than or equal to the fourth preset value D, that is: B≤U1≤D, the control unit 22 sends a second control command to the bidirectional DC switching circuit 32 to make the bidirectional DC switching circuit 32 in the second output state; the bidirectional DC switching circuit 32 then drives the DC bus 11 to supply power to the energy storage device 31; at this time, it is assumed that the charging current of the energy storage device 31 is Icn.

[0072] When it is determined that the DC bus voltage is greater than the fourth preset value D and less than or equal to the fifth preset value E, that is: D<U1≤E, the control unit 22 sends a second control command to the bidirectional DC switching circuit 32 to make the bidirectional DC switching circuit 32 in the second output state; the bidirectional DC switching circuit 32 then drives the DC bus 11 to supply power to the energy storage device 31; at this time, it is assumed that the charging current of the energy storage device 31 is Icn.

[0073] When it is determined that the DC bus voltage is greater than the fifth preset value E, that is: E<U1, the control unit 22 sends a first control command to the bidirectional DC switching circuit 32 to make the bidirectional DC switching circuit 32 in the first output state; the bidirectional DC switching circuit 32 then drives the DC bus 11 to supply power to the energy storage device 31; at this time, it is assumed that the charging current of the energy storage device 31 is I3.

[0074] Among them, the charging current in the first output state is greater than the charging current in the second output state, that is, the ratio between the charging current in the first output state and the charging current in the second output state is greater than 1. The corresponding ratio formula is expressed as: I3 = K*Icn, where K is a constant greater than 1.

[0075] It should be noted that, to avoid overheating and damage of the bidirectional DC / DC circuit, the time for the DC bus to supply power to the energy storage device in the first output state can be limited. For example, it can be set to return to the normal current Icn within a short time of this current charging. Based on this, the short-term overload characteristic of the bidirectional DC-DC circuit can be utilized to discharge the instantaneous large feedback energy on the DC bus caused by the motor-side deceleration.

[0076] To ensure that the DC bus voltage operates within the normal operating voltage range, please refer to Figure 3 based on Figure 1. Figure 3 shows another schematic diagram of a module of the wind power pitch system. Among them, the wind power pitch system 10 further includes a braking unit 33. The first end of the braking unit 33 is connected to the positive bus WB1, and the second end of the braking unit 33 is connected to the negative bus WB2; the control end of the braking unit 33 is also connected to the control unit 22.

[0077] In this embodiment, the operating state of the braking unit can be adjusted according to the DC bus voltage.

[0078] In a possible implementation manner, the control unit 22 sends different control signals to the braking unit 33 according to the DC bus voltage to switch the on / off state of the braking unit 33, so that the DC bus voltage is within the normal operating voltage range.

[0079] Among them, under the condition that the DC bus voltage U1 is greater than the fourth preset value D, that is, D < U1, the control unit 22 sends a first control signal to the braking unit 33 to make the braking unit 33 in the on state.

[0080] The control unit 22 is also used to send a second control signal to the braking unit 33 under the condition that the DC bus voltage U1 is less than or equal to the fourth preset value D, that is, U1 ≤ D, to make the braking unit 33 in the off state.

[0081] In a possible implementation manner, please refer to Figure 4 based on Figure 3. Figure 4 shows the circuit schematic diagram of the braking unit. The braking unit 33 includes a first resistor R1, a fourth switching tube Q4, and a first diode D1; among them, the first end of the first resistor R1 and the first end of the first diode D1 are both connected to the positive bus WB1, and the second end of the first resistor R1 is respectively connected to the second end of the first diode D1 and the first end (collector) of the fourth switching tube Q4; the second end (base) of the fourth switching tube Q4 is connected to the control unit 22; the third end (emitter) of the fourth switching tube Q4 is connected to the negative bus WB2.

[0082] When the DC bus voltage is less than or equal to the fourth preset value D, the braking unit 33 is in the off state, that is, the fourth switch Q4 is open, and the first resistor R1, i.e., the braking resistor, is not used. When the DC bus voltage is greater than the fourth preset value D, the braking unit 33 is in the open state, that is, the fourth switch Q4 is closed, and the first resistor R1 is used.

[0083] When the fourth switch Q4 switches from the closed state to the open state, the first diode D1 provides a freewheeling circuit for the parasitic inductance in the first resistor R1 circuit, thereby ensuring that the voltage spike caused by the turn-off of the fourth switch Q4 will not break down the fourth switch Q4.

[0084] In summary, please continue to refer to Figure 4. In this embodiment, when the bidirectional DC switching circuit 32 is in the first working mode, the braking unit 33 is in the off state, the first switch Q1, the second switch Q2, and the third switch Q3 are all off, and the fourth switch Q4 is off.

[0085] When the bidirectional DC switching circuit 32 is in the second operating mode, the braking unit 33 is in the off state, and the second switch Q2 and the third switch Q3 are both off; the first switch Q1 is in the first operating state, and the fourth switch Q4 is off.

[0086] When the bidirectional DC switching circuit 32 is in the third operating mode, the braking unit 33 is in the off state, the first switch Q1 is off; the second switch Q2 is in the second operating state; the third switch Q3 is on; and the fourth switch Q4 is off.

[0087] When the bidirectional DC switching circuit 32 is in the fourth operating mode, the first switch Q1 is in the third operating state; the second switch Q2 and the third switch Q3 are both off. Except when the DC bus voltage is greater than the second preset value and less than or equal to the fourth preset value, the fourth switch Q4 is closed.

[0088] In one possible implementation, based on Figure 1, refer to Figure 5, which shows another circuit diagram of the wind power pitch system. The energy storage device 31 includes a supercapacitor SC1. To implement simple control logic, it uses its own switching properties to achieve on / off operation. The switching component 34 can be a second diode D2. The first terminal of the supercapacitor SC1 is connected to the first terminal of the second diode D2 and the first terminal of the bidirectional DC-DC switching circuit 32 (the collector of the third switch Q3). The second terminal of the second diode D2 is connected to the positive bus WB1. The second terminal of the supercapacitor SC1 and the second terminal of the bidirectional DC-DC switching circuit 32 (the emitter of the second switch Q2 and / or the negative terminal of the first capacitor C2) are both connected to the negative bus WB2.

[0089] In this embodiment, the second diode D2 is a power diode.

[0090] Referring to Figure 5, the switching assembly 34 also includes a fuse F1. The supercapacitor SC1 is connected to the second diode D2 via fuse F1. Specifically, the first end of fuse F1 is connected to the first end of the second diode D2, and the second end of fuse F1 is connected to both the first end of the supercapacitor SC1 and the first end of the bidirectional DC-DC switching circuit 32. The third end of the bidirectional DC-DC switching circuit 32 (the collector of the first switching transistor Q1) is connected to the positive bus WB1.

[0091] In summary, the wind power pitch system in this embodiment includes a DC bus, a rectifier unit, and an inverter unit. The rectifier unit is connected to the inverter unit via the DC bus. The wind power pitch system also includes a charge / discharge unit, a control unit, and a switching assembly. The energy storage device is connected to the DC bus via the switching assembly. The DC bus is connected to the energy storage device via a bidirectional DC-DC switching circuit. The bidirectional DC-DC switching circuit includes multiple operating modes. The control unit acquires the states of the DC bus voltage and the grid voltage and sends different control commands to the bidirectional DC-DC switching circuit based on these states to switch the operating modes of the circuit. The bidirectional DC-DC switching circuit then adjusts the charging / discharging states of the energy storage device according to the different operating modes.

[0092] Based on this, the present invention can adjust the working state of the energy storage device in real time based on the DC bus voltage and grid voltage, while maintaining low cost and high integration. This avoids the risk of open flame caused by the frequent operation of the braking resistor generating a large amount of heat, ensuring the normal operation of the DC bus, and improving energy utilization.

[0093] Similar to the previous embodiment, this embodiment of the invention also provides a control method for a wind power pitch system. The wind power pitch system includes a charging / discharging unit and a control unit. The charging / discharging unit includes an energy storage device, a bidirectional DC-DC switching circuit, and a switching assembly. The energy storage device is connected to a DC bus via the switching assembly. The DC bus is connected to the energy storage device via the bidirectional DC-DC switching circuit. The bidirectional DC-DC switching circuit includes several different operating modes. Referring to Figure 6, Figure 6 shows a flowchart of the control method, which includes steps 100 to 300.

[0094] Step 100: The control unit obtains the status of the DC bus voltage and the grid voltage.

[0095] Step 200: The control unit sends different control commands to the bidirectional DC switching circuit according to the state of the DC bus voltage and the grid voltage, so as to switch the working mode of the bidirectional DC switching circuit.

[0096] Step 300: The bidirectional DC switching circuit adjusts the charging / discharging state of the energy storage device according to different operating modes.

[0097] Through steps 100 to 300 above, the states of the DC bus voltage and the grid voltage are obtained. Instead of frequently cutting off and closing the front-end rectifier bridge, the working mode of the bidirectional DC switching circuit is directly adjusted based on the states of the DC bus voltage and the grid voltage to drive the energy storage device to charge / discharge. This reduces device costs, improves device integration, and allows for real-time adjustment of the energy storage device's working state based on the states of the DC bus voltage and the grid voltage. This avoids the risk of open flame caused by the frequent operation of the braking resistor generating a large amount of heat, ensuring the normal operation of the DC bus, and improving energy utilization.

[0098] Furthermore, under the condition that the grid voltage is in an abnormal state, please refer to Figure 7 based on Figure 6. Figure 7 shows the step-by-step flowchart of step 200, including steps 201A to 202A.

[0099] Step 201A: When the DC bus voltage is less than the first preset value, the control unit sends a first control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into the first working mode, and the energy storage device discharges to the DC bus through the switching assembly.

[0100] Step 202A: When the DC bus voltage is between the first preset value and the second preset value, the control unit sends a second control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into the second working mode so as to drive the DC bus to supply power to the energy storage device.

[0101] The second preset value is greater than the first preset value.

[0102] Furthermore, when the grid voltage is in a normal state, referring to Figure 8 based on Figure 7, Figure 8 shows another sub-step flowchart of step 200, including steps 201B to 202B.

[0103] Step 201B: When the DC bus voltage is less than the second preset value and the voltage of the energy storage device is less than or equal to the first preset value, the control unit sends a second control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into the second working mode so as to drive the DC bus to supply power to the energy storage device.

[0104] Step 202B: When the DC bus voltage is less than the second preset value and the voltage of the energy storage device is greater than or equal to the third preset value, the control unit sends a third control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into the third working mode so as to drive the energy storage device to discharge to the DC bus.

[0105] The third preset value is greater than the first preset value.

[0106] Through steps 201A to 202A and steps 201B to 202B, under the conditions of normal or abnormal grid voltage, the operating mode of the bidirectional DC switching circuit is adjusted by the control unit to drive the energy storage device to charge / discharge, ensuring that the DC bus voltage is within the normal operating range.

[0107] Each step in the above control method can be implemented in whole or in part through software, hardware, or a combination thereof.

[0108] Following the same approach as the previous embodiment, this embodiment of the invention also provides a wind turbine generator set, including the wind power pitch system described in the above embodiment.

[0109] Similar to the previous embodiment, this embodiment of the invention also provides an electronic device, including a processor and a memory. The memory stores machine-executable instructions that can be executed by the processor. The processor can execute the machine-executable instructions to use the control method described in any of the above-mentioned embodiments, i.e., the control unit obtains the state of the DC bus voltage and the grid voltage, and sends different control instructions to the bidirectional DC switching circuit based on the state of the DC bus voltage and the grid voltage, so as to switch the operating mode of the bidirectional DC switching circuit.

[0110] The memory is used to store programs or data. The memory may be, but is not limited to, Random Access Memory (RAM), Read Only Memory (ROM), Programmable Read-Only Memory (PROM), Erasable Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), etc.

[0111] The processor is used to read / write data or programs stored in the memory, such as the programs and data implemented by the LVDS, TDC and processing unit described above, and to execute the methods provided in any embodiment of this application.

[0112] This application provides a computer program product, which includes a computer program (also referred to as code or instructions) that, when run, causes a computer to execute the control method described in any possible implementation of the method embodiments of this application.

[0113] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0114] In addition, the functional modules in the various embodiments of the present invention can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0115] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wind power pitch control system, comprising a DC bus, a rectifier unit, and an inverter unit, wherein the rectifier unit is connected to the inverter unit via the DC bus; characterized in that, The wind power pitch system further includes a charging / discharging unit and a control unit. The charging / discharging unit includes an energy storage device, a bidirectional DC-DC switching circuit, and a switching assembly. The energy storage device is connected to the DC bus through the switching assembly. The DC bus is connected to the energy storage device through the bidirectional DC-DC switching circuit. The control unit is connected to the control terminal of the bidirectional DC-DC switching circuit. The bidirectional DC-DC switching circuit includes a variety of different operating modes; The control unit is used to acquire the status of the DC bus voltage and the grid voltage; and according to the status of the DC bus voltage and the grid voltage, send different control commands to the bidirectional DC switching circuit to switch the operating mode of the bidirectional DC switching circuit. The bidirectional DC switching circuit is used to adjust the charging / discharging state of the energy storage device according to different operating modes.

2. The wind power pitch control system according to claim 1, characterized in that, Under the condition that the power grid voltage is in an abnormal state, The control unit is also used to send a first control command to the bidirectional DC switching circuit when the DC bus voltage is less than a first preset value, so that the bidirectional DC switching circuit is in a first working mode. The bidirectional DC switching circuit is used in the first operating mode for the energy storage device to discharge to the DC bus through the switching assembly; The control unit is also configured to send a second control command to the bidirectional DC switching circuit under the condition that the DC bus voltage is greater than the first preset value and less than the second preset value, so that the bidirectional DC switching circuit is in a second working mode. In the second operating mode, the bidirectional DC switching circuit drives the DC bus to supply power to the energy storage device.

3. The wind power pitch control system according to claim 1, characterized in that, Under the condition that the power grid voltage is in a normal state, The control unit is also configured to send a second control command to the bidirectional DC switching circuit under the condition that the DC bus voltage is less than a second preset value and the voltage of the energy storage device is less than or equal to a first preset value, so that the bidirectional DC switching circuit is in a second working mode. The bidirectional DC switching circuit is also used to drive the DC bus to supply power to the energy storage device in the second operating mode; The control unit is also configured to send a third control command to the bidirectional DC switching circuit under the condition that the DC bus voltage is less than a second preset value and the voltage of the energy storage device is greater than or equal to a third preset value, so that the bidirectional DC switching circuit is in a third working mode. The bidirectional DC switching circuit is also used in the third operating mode to drive the energy storage device to discharge to the DC bus; The third preset value is greater than the first preset value.

4. The wind power pitch control system according to claim 2 or 3, characterized in that, The control unit is also configured to send a fourth control command to the bidirectional DC switching circuit when the DC bus voltage is greater than or equal to the second preset value, so that the bidirectional DC switching circuit is in a fourth working mode. The bidirectional DC switching circuit is used in the fourth operating mode to drive the DC bus to supply power to the energy storage device.

5. The wind power pitch control system according to claim 4, characterized in that, Under the condition that the fourth control command includes a first control command and a second control command, and the fourth working mode includes a first output state and a second output state; The control unit is further configured to send a first control command to the bidirectional DC switching circuit when the DC bus voltage is greater than a fifth preset value, so that the bidirectional DC switching circuit is in the first output state. The control unit is further configured to send a second control command to the bidirectional DC switching circuit under the condition that the DC bus voltage is greater than a fourth preset value and less than or equal to a fifth preset value, so that the bidirectional DC switching circuit is in the second output state. The control unit is further configured to send a second control command to the bidirectional DC switching circuit under the condition that the DC bus voltage is greater than a second preset value and less than or equal to a fourth preset value, so that the bidirectional DC switching circuit is in the second output state. The bidirectional DC switching circuit is used to drive the DC bus to supply power to the energy storage device in the first output state or the second output state. The charging current in the first output state is greater than the charging current in the second output state.

6. The wind power pitch control system according to claim 5, characterized in that, The DC bus includes a positive bus and a negative bus; the wind power pitch system also includes a braking unit, the first end of which is connected to the positive bus and the second end of which is connected to the negative bus; the control end of the braking unit is also connected to the control unit. The control unit is used to send different control signals to the braking unit according to the DC bus voltage, and switch the on / off state of the braking unit so that the DC bus voltage is within the normal operating voltage range.

7. The wind power pitch control system according to claim 6, characterized in that, The control unit is also used to send a first control signal to the braking unit when the DC bus voltage is greater than a fourth preset value, so that the braking unit is in a conducting state. The control unit is also used to send a second control signal to the braking unit when the DC bus voltage is less than or equal to the fourth preset value, so that the braking unit is in a closed state.

8. The wind power pitch control system according to claim 1, characterized in that, The DC bus includes a positive bus and a negative bus; the bidirectional DC switching circuit includes a first switch, a second switch, a third switch, a first capacitor, and a first inductor. The first terminal of the first switch is connected to the positive bus, and the second terminal of the first switch is connected to the first terminal of the second switch and the first terminal of the first inductor, respectively. The second terminal of the first inductor is connected to the first terminal of the third switch, and the second terminal of the third switch is connected to the first terminal of the first capacitor, the first terminal of the energy storage device, and the first terminal of the switching assembly, respectively. The second terminal of the switching assembly is connected to the positive bus; the second terminals of the second switch, the first capacitor, and the energy storage device are all connected to the negative bus. When the bidirectional DC switching circuit is in the first operating mode, the first switch, the second switch, and the third switch are all turned off. When the bidirectional DC-DC switching circuit is in the second operating mode, both the second and third switching transistors are turned off; the first switching transistor is in the first operating state. When the bidirectional DC-DC switching circuit is in the third operating mode, the first switch is off; the second switch is in the second operating state; and the third switch is on. When the bidirectional DC-DC switching circuit is in the fourth operating mode, the first switch is in the third operating state; the second switch and the third switch are both off. The first operating state, the second operating state, and the third operating state are used to characterize the output states of different pulse width modulation signals.

9. The wind power pitch system according to claim 1 or 8, characterized in that, The DC bus includes a positive bus and a negative bus; the switching assembly also includes a second diode; the first end of the energy storage device is connected to the first end of the second diode and the first end of the bidirectional DC switching circuit; the second end of the second diode is connected to the positive bus; the second end of the energy storage device and the second end of the bidirectional DC switching circuit are both connected to the negative bus.

10. A control method for a wind power pitch control system, characterized in that, The wind power pitch system further includes a charging / discharging unit and a control unit. The charging / discharging unit includes an energy storage device, a bidirectional DC-DC switching circuit, and a switching assembly. The energy storage device is connected to the DC bus via the switching assembly. The DC bus is connected to the energy storage device via the bidirectional DC-DC switching circuit. The bidirectional DC-DC switching circuit includes multiple different operating modes. The control method includes: The control unit acquires the status of the DC bus voltage and the grid voltage; The control unit sends different control commands to the bidirectional DC switching circuit according to the state of the DC bus voltage and the grid voltage, so as to switch the working mode of the bidirectional DC switching circuit. The bidirectional DC switching circuit adjusts the charging / discharging state of the energy storage device according to different operating modes.

11. The control method according to claim 10, characterized in that, The steps of sending different control commands to the bidirectional DC switching circuit according to the states of the DC bus voltage and the grid voltage include: Under the condition that the power grid voltage is in an abnormal state, When the DC bus voltage is less than a first preset value, the control unit sends a first control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into a first working mode, and the energy storage device discharges to the DC bus through the switching assembly. When the DC bus voltage is between the first preset value and the second preset value, the control unit sends a second control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into a second working mode so as to drive the DC bus to supply power to the energy storage device. Wherein, the second preset value is greater than the first preset value.

12. The control method according to claim 11, characterized in that, The step of sending different control commands to the bidirectional DC switching circuit according to the states of the DC bus voltage and the grid voltage further includes: Under the condition that the power grid voltage is in a normal state, When the DC bus voltage is less than a second preset value and the voltage of the energy storage device is less than or equal to a first preset value, the control unit sends a second control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into a second working mode so as to drive the DC bus to supply power to the energy storage device. When the DC bus voltage is less than a second preset value and the voltage of the energy storage device is greater than or equal to a third preset value, the control unit sends a third control command to the bidirectional DC switching circuit to put the bidirectional DC switching circuit into a third working mode so as to drive the energy storage device to discharge to the DC bus. The third preset value is greater than the first preset value.

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