Wind power converter rectification side overvoltage suppression method and system

Abstract

The invention discloses a wind power converter rectification side overvoltage suppression method and system, and the method comprises the steps: obtaining a power grid state and unit operation parameters in real time, and predicting surplus power and network side maximum output active power at a fault starting moment; on the basis of the rotating speed margin and the direct-current voltage state, surplus power is dynamically distributed to a rotor kinetic energy storage channel (through electromagnetic torque adjustment) and a chopping energy consumption channel; and finally, a collaborative reference instruction of the machine side torque and the grid side current is generated. Through the mode, the overvoltage suppression bottleneck of the wind power converter during low voltage ride through is broken through, accurate and stable DC bus voltage during a fault period is realized through multi-subsystem millisecond-level cooperative control, meanwhile, the reactive support requirement of a power grid guide rule is met, and finally, the high ride through success rate and the equipment safety margin of a wind turbine generator are improved.

Description

Technical Field

[0001] This application relates to the field of intelligent control, and more specifically, to a method and system for suppressing overvoltage on the rectifier side of a wind power converter. Background Technology

[0002] With the increasing proportion of wind power generation in the power grid, the operational stability of wind turbine generators under grid faults, especially their low-voltage ride-through (LVRT) capability, has become a core requirement for ensuring power system security. Wind turbine generators are generally connected to the grid via back-to-back converters, with their rectifier side (generator side) and inverter side (grid side) connected by a DC bus. When a voltage dip fault occurs in the grid, the active power transmission capacity of the grid-side converter is severely limited in order to support the grid. However, due to mechanical inertia, the input power captured by the wind turbine cannot decrease instantaneously, resulting in a huge and instantaneous imbalance between the generator-side input power and the grid-side output power. This unbalanced power will all flow into the DC bus, causing a sharp rise in DC voltage, forming rectifier-side overvoltage, seriously threatening the safety of the converter's power devices, and even causing the generator to disconnect from the grid, disrupting grid stability. Therefore, developing efficient rectifier-side overvoltage suppression methods is crucial.

[0003] Currently, the technical solutions to this problem mainly rely on a combination of DC choppers, generator-side converter control, and pitch control systems. Traditional strategies typically involve a passive response: when the DC bus voltage exceeds a preset threshold, the DC chopper is triggered to dissipate energy, or the generator-side converter control system uses increased generator speed to absorb some kinetic energy. However, these existing solutions generally suffer from core defects such as mismatched response speeds among subsystems and a lack of forward-looking coordinated control. Power imbalances caused by grid faults occur instantaneously, while traditional suppression measures are all delayed responses, passively triggering only after the DC voltage rises. This lag in response, coupled with the lack of unified coordination among control units (such as fast converters, millisecond-level choppers, and second-level pitch control systems), makes it impossible to quickly and effectively allocate and manage surplus energy in the early stages of a fault. This not only causes severe voltage surges but may also lead to unnecessary energy waste, failing to fully utilize the unit's potential capacity to smoothly overcome the fault, thus limiting the overall performance and reliability of the wind turbine.

[0004] Therefore, an optimized method for suppressing overvoltage on the rectifier side of wind power converters is needed. Summary of the Invention

[0005] To address the aforementioned technical problems, this application is proposed. Embodiments of this application provide a method and system for suppressing overvoltage on the rectifier side of a wind turbine converter. This method acquires real-time grid status and generator operating parameters, predicting surplus power and the maximum active power output from the grid side at the onset of a fault. Based on speed margin and DC voltage status, it dynamically allocates surplus power to rotor kinetic energy storage (through electromagnetic torque adjustment) and chopper energy dissipation channels. Finally, it generates a coordinated reference command for generator-side torque and grid-side current. In this way, it overcomes the overvoltage suppression bottleneck of wind turbine converters during low-voltage ride-through, achieving precise stabilization of the DC bus voltage during faults through millisecond-level coordinated control of multiple subsystems, while simultaneously meeting the reactive power support requirements of grid guidelines, ultimately improving the high-voltage ride-through success rate and equipment safety margin of wind turbine units.

[0006] According to one aspect of this application, a method for suppressing overvoltage on the rectifier side of a wind power converter is provided, comprising:

[0007] In response to the detection of a voltage drop fault flag, the grid voltage amplitude, aerodynamic power estimate, generator speed, and DC bus voltage are acquired.

[0008] Based on the grid voltage amplitude and aerodynamic power estimation, and combined with the converter maximum current rating and reactive power reference for low voltage ride-through requirements, surplus power is predicted to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions.

[0009] Based on the predicted surplus power, generator speed and DC bus voltage, dynamic power allocation is performed to obtain dynamic energy storage reference power and chopper reference power.

[0010] Based on the dynamic energy storage reference power, a machine-side electromagnetic torque reference and a grid-side dq-axis current reference are generated. The machine-side electromagnetic torque reference is fed into the machine-side converter, and the grid-side dq-axis current reference is fed into the grid-side converter.

[0011] The PWM drive signal for the chopper IGBT is generated based on the chopper reference power.

[0012] According to another aspect of this application, a wind power converter rectifier-side overvoltage suppression system is provided, comprising:

[0013] The global state awareness module is used to obtain grid voltage amplitude, aerodynamic power estimate, generator speed and DC bus voltage in response to the detection of voltage drop fault flag;

[0014] The surplus power prediction module is used to predict surplus power based on grid voltage amplitude and aerodynamic power estimation, combined with the reactive power reference of converter maximum current rating and low voltage ride-through requirements, so as to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions.

[0015] The dynamic power allocation module is used to perform dynamic power allocation based on the predicted surplus power, generator speed and DC bus voltage to obtain dynamic energy storage reference power and chopper reference power.

[0016] The coordination control module is used to generate a machine-side electromagnetic torque reference and a grid-side dq-axis current reference based on the dynamic energy storage reference power. The machine-side electromagnetic torque reference is sent to the machine-side converter, and the grid-side dq-axis current reference is sent to the grid-side converter.

[0017] The PWM drive signal generation module is used to generate the PWM drive signal for the chopper IGBT based on the chopper reference power.

[0018] Compared with existing technologies, this application provides a method and system for suppressing overvoltage on the rectifier side of a wind power converter. By acquiring real-time grid status and unit operating parameters, it predicts surplus power and the maximum active power output from the grid side at the moment of fault onset. Based on speed margin and DC voltage status, it dynamically allocates surplus power to rotor kinetic energy storage (through electromagnetic torque regulation) and chopper energy dissipation channels. Finally, it generates a coordinated reference command for the turbine-side torque and grid-side current. In this way, it overcomes the overvoltage suppression bottleneck of wind power converters during low-voltage ride-through, achieving precise stabilization of the DC bus voltage during faults through millisecond-level coordinated control of multiple subsystems, while simultaneously meeting the reactive power support requirements of grid guidelines, ultimately improving the high-voltage ride-through success rate and equipment safety margin of wind turbines. Attached Figure Description

[0019] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0020] Figure 1 This is a flowchart of a wind power converter rectifier side overvoltage suppression method according to an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of data flow in the overvoltage suppression method on the rectifier side of a wind power converter according to an embodiment of this application;

[0022] Figure 3This is a block diagram of a wind power converter rectifier side overvoltage suppression system according to an embodiment of this application. Detailed Implementation

[0023] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0024] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0025] While this application makes various references to certain modules of the systems according to embodiments of this application, any number of different modules can be used and run on user terminals and / or servers. The modules described are merely illustrative, and different aspects of the systems and methods may use different modules.

[0026] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously as needed. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0027] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0028] The technical solution of this application proposes a method for suppressing overvoltage on the rectifier side of a wind power converter. Figure 1 This is a flowchart of a wind power converter rectifier side overvoltage suppression method according to an embodiment of this application. Figure 2 This is a system architecture diagram of a wind power converter rectifier side overvoltage suppression method according to an embodiment of this application. Figure 1 and Figure 2As shown, the wind power converter rectifier-side overvoltage suppression method according to an embodiment of this application includes the following steps: S1, in response to detecting a voltage drop fault flag, acquiring the grid voltage amplitude, aerodynamic power estimate, generator speed, and DC bus voltage; S2, based on the grid voltage amplitude and aerodynamic power estimate, and combined with the converter maximum current rating and reactive power reference for low voltage ride-through requirements, performing surplus power prediction to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions; S3, based on the predicted surplus power, generator speed, and DC bus voltage, performing dynamic power allocation to obtain dynamic energy storage reference power and chopper reference power; S4, based on the dynamic energy storage reference power, generating a machine-side electromagnetic torque reference and a grid-side dq-axis current reference, wherein the machine-side electromagnetic torque reference is sent to the machine-side converter, and the grid-side dq-axis current reference is sent to the grid-side converter; S5, based on the chopper reference power, generating a PWM drive signal for the chopper IGBT.

[0029] Specifically, S1, in response to detecting a voltage drop fault flag, acquires the grid voltage amplitude, aerodynamic power estimate, generator speed, and DC bus voltage. It should be understood that power imbalances caused by grid faults occur instantaneously. When a sudden voltage drop occurs in the grid, the grid-side converter (GSC) must prioritize injecting reactive current to support the grid, causing a sharp reduction in its active power transmission capacity (e.g., a 2MW unit drops to 0.3MW). However, due to mechanical inertia, the wind turbine cannot quickly attenuate its input power, resulting in an instantaneous power imbalance (ΔP = 1.7MW) between the generator-side input power (2MW) and the grid-side output power (0.3MW). This power will surge into the DC bus, triggering an overvoltage crisis on the rectifier side. Therefore, in the technical solution of this application, the grid status and unit operating parameters are acquired in real time to provide a data foundation for subsequent power prediction and dynamic allocation.

[0030] In the technical solution of this application, the grid voltage amplitude, aerodynamic power estimate, generator speed, and DC bus voltage can be obtained through the following steps: First, the three-phase grid voltage, three-phase grid current, DC bus voltage, and generator speed are acquired; these are the most primitive analog or digital signals from the physical world, measured in real time by hardware devices such as voltage sensors, current sensors, and speed encoders installed in the wind power converter system. Next, the grid voltage amplitude is extracted from the three-phase grid voltage through a phase-locked loop (PLL); specifically, the system extracts the grid voltage amplitude from the three-phase grid voltage through a PLL. The PLL module can track the frequency and phase of the grid voltage in real time and accurately output its amplitude. Then, based on the comparison between the grid voltage amplitude and a preset threshold, a fault detection result is generated; this preset threshold is usually set according to the requirements of relevant grid guidelines, for example, set to 0.9 times the nominal voltage. The control system continuously compares the real-time voltage amplitude output by the PLL with this threshold. Furthermore, in response to the fault detection result that the grid voltage amplitude is lower than the preset threshold, a voltage drop fault flag is generated. In other words, once the voltage amplitude is detected to be below the threshold, the system immediately sets an internal "voltage drop fault flag" to an active state (e.g., from 0 to 1), thereby officially starting the entire overvoltage suppression process.

[0031] Among them, the grid voltage amplitude refers to the instantaneous value of the peak or effective value of the three-phase AC voltage of the grid after being normalized to a per-unit value. It is the most direct indicator for judging the health status of the grid. The aerodynamic power estimate refers to the mechanical power captured by the wind turbine blades from the wind and transferred to the transmission chain. It represents the original energy input of the system and is usually estimated in real time based on the aerodynamic characteristic curve of the wind turbine or a lookup table using parameters such as wind speed, pitch angle, and generator speed. It is the source of power imbalance in calculation. The generator speed and DC bus voltage are physical quantities that are directly measured by sensors and reflect the dynamics of the generator and the energy state of the DC side of the converter. The voltage drop fault flag is an internal logic signal, usually a Boolean value or a binary status bit, which is generated by the control system after judging that the grid voltage has dropped. It is used to trigger a specific control mode switch.

[0032] More specifically, simultaneously with or after generating the fault flag, to provide a more direct input for subsequent power calculations, the acquired signal undergoes further processing. During this process, the system performs Clark and Park transformations on the three-phase grid voltage and current to obtain the voltage and current components in the dq coordinate system. This is a standard mathematical transformation for realizing AC motor vector control, converting the time-varying voltage and current quantities in the ABC three-phase coordinate system to the synchronously rotating dq coordinate system, obtaining the DC components for easier control and calculation. Furthermore, the system calculates the actual input electromagnetic power based on the generator speed and electromagnetic torque command, and calculates the actual output grid power based on the voltage and current components in the dq coordinate system. The actual input electromagnetic power and actual output grid power serve as the initial state of the system at the time of the fault, used for subsequent surplus power prediction.

[0033] Taking the scheme of this application as an example, assuming the nominal voltage at the grid connection point of the wind turbine is 690V, the preset threshold for judging voltage drop is set to 90% of the nominal voltage, i.e., 621V. During normal operation, the control system acquires the three-phase voltage signal of the power grid through sensors and inputs it into a three-phase phase-locked loop (PLL) module. The voltage amplitude output by the PLL is stable at around 690V. At this time, since the voltage amplitude is higher than 621V, the fault detection result is normal, and the voltage drop fault flag remains at 0. When a remote short-circuit fault suddenly occurs in the power grid, the power grid voltage drops sharply. The PLL module detects the voltage change within microseconds, and its output voltage amplitude quickly drops to, for example, 400V. The comparator in the control system detects that 400V is lower than the preset threshold of 621V, immediately sets the fault detection result to a fault state, and triggers the generation of the voltage drop fault flag, setting its value from 0 to 1. In response to the setting of this flag, the control system immediately latches (or acquires) other key state variables for the current moment: the power estimate obtained from the aerodynamic model (e.g., 2.0 MW), the generator speed read from the speed sensor (e.g., 1200 rpm), and the DC bus voltage read from the voltage sensor (e.g., 1100 V). These four acquired key parameters (grid voltage amplitude 400 V, aerodynamic power estimate 2.0 MW, generator speed 1200 rpm, DC bus voltage 1100 V) will be immediately sent as a complete set of initial state data to the subsequent surplus power prediction module, thereby initiating active cooperative suppression control.

[0034] Specifically, S2, based on the grid voltage amplitude and aerodynamic power estimation, and combined with the converter's maximum current rating and reactive power reference for low-voltage ride-through (LVRT) requirements, predicts surplus power to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions. It should be understood that during grid faults, the grid-side converter (GSC) must prioritize meeting the reactive power support requirements for LVRT. This results in a severe compression of its active power transmission capacity (e.g., a 2MW unit reduced to 0.3MW), while the aerodynamic power captured by wind turbines cannot decay synchronously due to mechanical inertia. If the degree of power imbalance is not predicted in advance, energy distribution cannot be coordinated in the early stages of the fault, ultimately leading to DC bus overvoltage. Therefore, in the technical solution of this application, the maximum output active power and surplus power of the converter are calculated in real time to provide a decision-making basis for dynamic control.

[0035] Among them, the maximum current rating of the converter is an inherent parameter of the converter hardware, specifically referring to the maximum effective current value that its power semiconductor devices (such as IGBTs) can safely carry in the design. It is a fundamental physical constraint that determines the upper limit of the converter's power output. The reactive power reference for low voltage ride-through is a control target dynamically generated according to external grid guidelines. It specifies the amount of reactive power that the converter must inject into the grid to support grid voltage recovery under different levels of voltage dips. The maximum active power that the converter can output under fault conditions is the theoretical upper limit of the active power that the converter can actually transmit to the grid under the dual constraints of reactive power support and hardware current limit. The predicted surplus power is the difference between the system input power (aerodynamic power) and this maximum output active power. It accurately quantifies the unbalanced power that will remain in the system during a fault and cause the DC bus voltage to rise.

[0036] In the technical solution of this application, surplus power prediction can be performed through the following steps to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions: First, based on the grid guidelines and grid voltage amplitude, the reactive power reference required for low voltage ride-through is calculated; the grid guidelines usually specify the relationship between the amount of reactive current or reactive power injection and the grid voltage drop depth in the form of curves or piecewise functions. The control system, based on the real-time grid voltage amplitude obtained in the previous step, obtains the reactive power reference value that must be prioritized under the current fault condition by looking up tables or calculating functions.

[0037] Next, based on the converter's maximum current rating and the grid voltage amplitude, the converter's total apparent power limit is calculated, where the converter's total apparent power limit S max Limited by its maximum current rating I max The specific calculation process for the current grid voltage amplitude U is expressed by the formula:

[0038]

[0039] Among them, S max For the total apparent power limit of the converter, I max U is the maximum current rating of the converter, and U is the grid voltage amplitude. It can be seen that when the voltage drops, the current grid voltage amplitude decreases, so the apparent power transmission capacity of the converter will decrease significantly.

[0040] Subsequently, based on the reactive power reference of the converter's total apparent power limit and low voltage ride-through requirement, the maximum active power that the converter can output under fault conditions is calculated. Specifically, based on the reactive power reference of the converter's total apparent power limit and low voltage ride-through requirement, the maximum active power that the converter can output under fault conditions is calculated using the following formula:

[0041]

[0042] Among them, S limit For the total apparent power limit of the converter, O g-ref-LVRT P serves as the reactive power reference for low voltage ride-through requirements. out-Pmax This represents the maximum active power that the converter can output under fault conditions.

[0043] Finally, based on the maximum active power the converter can output under fault conditions and the aerodynamic power estimate, the predicted surplus power is calculated. In a specific example of this application, the predicted surplus power is the aerodynamic power estimate minus the maximum active power the converter can output under fault conditions.

[0044] Taking the scheme of this application as an example, assume a 2MW wind turbine is operating at full power, with an estimated aerodynamic power of 2.0MW. The maximum current rating of the converter is 1800A. After detecting a drop in grid voltage from 690V to 400V, the system calculates the surplus power and the maximum active power that the converter can output under fault conditions. First, the control system calculates, according to grid guidelines, the reactive power reference required for low-voltage ride-through at 400V is 1.0Mvar. Then, based on the converter's maximum current rating of 1800A and the current grid voltage of 400V, the system calculates the converter's total apparent power limit S. max Approximately 1.25 MVA. Then, the maximum active power that the converter can output under fault conditions is calculated using the following formula:

[0045]

[0046] The calculated maximum active power output of the converter under fault conditions is 0.75MW. Finally, the system subtracts the calculated maximum active power of 0.75MW from the aerodynamic power estimate of 2.0MW to obtain the predicted surplus power P. s-ptr for:

[0047] P s-ptr =2.0 - 0.75 = 1.25

[0048] The predicted surplus power output is 1.25MW.

[0049] Specifically, S3, based on the predicted surplus power, generator speed, and DC bus voltage, performs dynamic power allocation to obtain dynamic energy storage reference power and chopper reference power. It should be understood that traditional solutions often utilize only one method or passively, such as indiscriminately consuming all surplus power through the chopper, which not only results in significant energy waste but also puts immense pressure on the chopper's thermal management; or they rely solely on the unit's inertia without considering the physical limits of its absorption capacity. In the technical solution of this application, by comprehensively evaluating the current state of the system, an optimal allocation decision is made between the two main energy dissipation paths—namely, kinetic energy storage using the generator's rotating components and heat dissipation through the chopper. This proactive, dynamic allocation strategy maximizes the utilization of the wind turbine's own power-free kinetic energy storage potential while minimizing the power consumption of the chopper, thereby achieving optimal energy management while ensuring system safety and improving overall efficiency and system reliability during fault ride-through.

[0050] Among them, dynamic power allocation is a real-time decision-making process based on the multivariable state of the system. It determines the proportion of the predicted surplus power allocated among different execution units. During the allocation process, it adaptively adjusts according to real-time parameters such as generator speed and DC voltage. Dynamic energy storage reference power is a control target value allocated to the machine-side converter. It instructs the machine-side converter to convert this part of the power into the kinetic energy of the generator rotor and transmission chain by controlling the electromagnetic torque, which is manifested as an increase in generator speed. Chopper reference power is a power command allocated to the chopper control unit. It instructs the chopper to dissipate the amount of power. This part of the energy will be consumed as heat through the braking resistor.

[0051] In the technical solution of this application, dynamic power allocation can be performed through the following steps to obtain dynamic energy storage reference power and chopper reference power:

[0052] First, the difference between the generator's maximum safe speed and its current speed is calculated to obtain the speed margin. The generator's maximum safe speed is a fixed upper limit determined by factors such as mechanical structural strength and electrical insulation, while the speed margin directly reflects how much room there is for the generator to increase its speed. Specifically, the calculation process is expressed by the formula:

[0053] Δω=ω max -ω rot

[0054] Where, ω max ω is the maximum safe speed of the generator. rot Where ω is the generator speed, and Δω is the speed margin;

[0055] Next, based on the speed margin, the maximum kinetic energy power that can be safely absorbed at the current speed is calculated. This maximum kinetic energy power is calculated based on the rotational inertia of the generator and wind turbine, the current speed, and the upper limit of the safe speed. It represents the maximum power that can be absorbed per unit time without exceeding the safe range, and signifies the upper limit of the instantaneous absorption rate of the kinetic energy storage pool. Specifically, the calculation process is expressed by the formula:

[0056]

[0057] Among them, P k-max Where J is the maximum kinetic power, and J is the generator's moment of inertia. Preset safe acceleration limits;

[0058] Subsequently, based on the predicted surplus power and DC bus voltage, an allocation weighting factor is specified. This weighting factor k is a key adjustment parameter that determines the proportion of surplus power to be allocated to kinetic energy storage within the allowable range of kinetic energy storage potential. This factor can be a fixed value to prioritize the use of kinetic energy storage, or it can be a function related to the DC bus voltage. For example, when the DC bus voltage is rising rapidly, the value of k can be appropriately reduced to advance and increase the chopper's activation, thereby enhancing the suppression strength. Specifically, the weighting factor k can be specified based on the predicted surplus power and real-time DC bus voltage through table lookup or interpolation algorithms.

[0059] Then, based on the above calculation results, the system generates the final power allocation command. First, the system calculates the dynamic energy storage reference power using the following formula:

[0060] P k-ref =min(P s-ptr *k,P k-max )

[0061] Where k is the allocation weight factor, P s-ptr For the predicted surplus power and Pk-max P is the maximum kinetic energy power that can be safely absorbed at the current rotational speed. k-ref This serves as a reference power for dynamic energy storage.

[0062] Furthermore, the chopper reference power is calculated using the following formula:

[0063] P c-ref =P s-ptr -P k-ref

[0064] Among them, P s-ptr For the predicted surplus power, P k-ref For dynamic energy storage reference power, P c-ref This is the reference power for the chopper.

[0065] Taking the scheme of this application as an example, following the aforementioned steps, the system predicts a surplus power of 1.25MW. At this time, the system obtains the current generator speed as 1200rpm, while the known maximum safe generator speed is 1500rpm. Based on this speed margin and the known system moment of inertia, the control system calculates that the maximum kinetic energy power that can be safely absorbed at the current speed is 1.0MW. In this embodiment, to prioritize the use of energy storage without power consumption, the weighting factor k is set to 1. Subsequently, the system calculates the dynamic energy storage reference power:

[0066] P k-ref =min(1.25*1,1.0)=1.0

[0067] In other words, although there is a surplus power of 1.25MW, for safety reasons, only a maximum of 1.0MW can be absorbed by the generator. The remaining power is allocated to the chopper, and the calculation process for the chopper's reference power is expressed by the following formula;

[0068] P c-ref =1.25 - 1.0 = 0.25

[0069] Finally, this step outputs two precise control commands: a dynamic energy storage reference power of 1.0MW and a chopper reference power of 0.25MW. These two commands will be sent to the control modules of the generator-side converter and the chopper, respectively, to perform coordinated overvoltage suppression.

[0070] Specifically, in step S4, based on the dynamic energy storage reference power, a machine-side electromagnetic torque reference and a grid-side dq-axis current reference are generated. The machine-side electromagnetic torque reference is fed into the machine-side converter, and the grid-side dq-axis current reference is fed into the grid-side converter. It should be understood that millisecond-level coordination between the machine-side and grid-side is required during grid faults. Relying solely on chopper energy dissipation would waste the temporary energy storage potential of the rotor kinetic energy; adjusting only the machine-side torque would fail to meet the reactive power support requirements of the grid LVRT. Therefore, in the technical solution of this application, the dynamic energy storage command is synchronously converted into electromagnetic torque adjustment and grid-side current constraints to maintain DC voltage stability while meeting grid connection guidelines.

[0071] The generator-side electromagnetic torque reference is a target value sent to the generator-side converter controller, directly instructing the generator to produce the required electromagnetic torque. By adjusting this torque, the mechanical power extracted from the wind turbine rotor and drivetrain can be controlled, thereby achieving the absorption or release of kinetic energy. The grid-side dq-axis current reference is a set of target values ​​sent to the grid-side converter controller. In the grid voltage synchronous rotating coordinate system (dq coordinate system), the d-axis current reference directly controls the active power exchanged between the converter and the grid, while the q-axis current reference directly controls the reactive power exchanged. This set of current references is a direct means of achieving grid-friendly grid connection (such as reactive power support during LVRT) and precise active power control.

[0072] In the technical solution of this application, the machine-side electromagnetic torque reference and the grid-side dq-axis current reference can be generated through the following steps: First, the computer-side power reference, the process of which is expressed by the formula:

[0073] P msc-ref =P in-act -P k-ref

[0074] Among them, P in-act For the actual input electromagnetic power, P k-ref For dynamic energy storage reference power, P msc-ref For reference power on the generator side;

[0075] Next, the electromagnetic torque reference on the computer side is used, and the process is expressed by the formula:

[0076] T em-ref =P msc-ref / O rot

[0077] Among them, O rot T is the generator speed. em-ref This serves as a reference for the electromagnetic torque on the machine side.

[0078] Furthermore, the grid-side d-axis current reference is calculated, and the process is expressed by the formula:

[0079] I dg-ref =P out-Pmax / (1.5*V dg )

[0080] Among them, P out-Pmax V represents the maximum active power that the converter can output under fault conditions. dg Let I be the voltage d-component in the voltage components in the dq coordinate system. dg-ref Used as a reference for the d-axis current on the grid side;

[0081] Subsequently, the reference q-axis current on the grid side is calculated, and the process is expressed by the following formula:

[0082] I qq-ref =O g-ref-LVRT / (1.5*V dg )

[0083] Among them, O g-ref-LVRT For reactive power reference, I qg-ref This serves as the reference for the q-axis current on the grid side.

[0084] Finally, the machine-side electromagnetic torque reference is sent to the machine-side converter (MSC), and the grid-side dq-axis current reference is sent to the grid-side converter (GSC).

[0085] Taking the scheme of this application as an example, based on the calculation results of the aforementioned steps, the system has obtained a dynamic energy storage reference power of 1.0MW, a maximum active power output by the converter under fault conditions of 0.75MW, and a reactive power reference of 1.0Mvar required by the LVRT. Assuming the system obtains an actual input electromagnetic power of 2.0MW at the moment of fault, a generator speed of 125.6rad / s (approximately 1200rpm), and a grid voltage d-axis component of 400V, this application performs the following calculations:

[0086] Computer-side power reference:

[0087] P msc-ref =2.0 - 1.0 = 1.0

[0088] Computer-side electromagnetic torque reference:

[0089] T em-ref =1.0 / 125.6≈7962

[0090] This torque reference of 7962 Nm will then be fed into the machine-side converter;

[0091] Reference for calculating d-axis current:

[0092] I dg-ref = (2*0.75*10) 6 ) / (3*400)=1250

[0093] Reference for calculating q-axis current:

[0094] I qg-ref =(-2*1.0*10 6 ) / (3*400)≈-1667

[0095] The dq-axis current reference (1250A, -1667A) will then be fed into the grid-side converter. In this way, the power allocation strategy of the higher layers is precisely translated into instructions that can be executed by the lower-level converter.

[0096] Specifically, S5 generates a PWM drive signal for the chopper's IGBT based on the chopper's reference power. That is, it transforms the energy dissipation task defined by the upper-level dynamic power allocation module into a low-level switching command that the chopper hardware can directly execute, thereby ensuring that the surplus power allocated to the chopper is consumed accurately and in a timely manner. In the entire collaborative control framework, the chopper is the final execution unit for handling the surplus power that kinetic energy storage cannot absorb or exceeds its absorption capacity. Unlike traditional chopper control methods that rely on passive triggering based on a fixed voltage threshold, the control in this application is proactive and based on power commands. This feedforward control method can achieve precise timing coordination with the actions of the generator-side and grid-side converters, intervening in advance before the DC bus voltage experiences a significant surge, and consuming energy according to the preset power target. This not only more effectively suppresses voltage spikes but also avoids voltage oscillations that may be caused by traditional lag control, thus ensuring the closed-loop realization of the entire suppression strategy.

[0097] Among them, the IGBT is the core power semiconductor switching device in the chopper circuit. By frequently turning it on and off, it controls the current flowing through the braking resistor, thereby controlling energy dissipation. The PWM drive signal (pulse width modulation signal) is a digital signal that controls the average conduction time of the IGBT by adjusting the duty cycle of the square wave signal (i.e., the proportion of the high-level time in one cycle), thereby precisely controlling the average power consumed by the chopper.

[0098] In the technical solution of this application, the PWM drive signal for the chopper IGBT can be generated through the following steps: First, in response to the chopper reference power being greater than zero, the chopper controller is started. This is a conditional triggering mechanism, ensuring that the chopper control logic is activated only when the dynamic power allocation module explicitly instructs that energy needs to be dissipated by the chopper. If the reference power is zero or negative, the chopper will remain off to avoid unnecessary energy loss.

[0099] Next, based on the DC bus voltage and the target power dissipation, the PWM idle ratio of the chopper controller is calculated. Here, the relationship between the instantaneous power dissipated by the chopper, the DC bus voltage, and the braking resistor is expressed by the following formula:

[0100]

[0101] Among them, R chopper U is the resistance value of the braking resistor. dc denoted as DC bus voltage, and D as PWM idle ratio; where PWM idle ratio is a key parameter of the PWM signal, its value varies between 0 and 1, and directly determines the working strength of the chopper.

[0102] Subsequently, based on the PWM duty cycle of the chopper controller, a PWM drive signal for the chopper IGBT is generated. This is typically accomplished by a PWM generator module in a microcontroller or FPGA. This module generates a square wave signal with alternating high and low levels at a preset switching frequency (e.g., 10kHz) according to the calculated duty cycle D. This signal is amplified by the drive circuit and directly applied to the gate of the chopper IGBT, controlling it to switch precisely according to the calculated duty cycle.

[0103] Taking the scheme of this application as an example, based on the calculation results of the aforementioned steps, the chopper reference power output by the dynamic power distribution module is 0.25MW. Assume the braking resistor in the chopper circuit is 0.5Ω. At this point, firstly, the system determines that 0.25MW is greater than zero, therefore the chopper controller is activated. Next, the system obtains the current DC bus voltage of 1150V from the sensor. Subsequently, the system begins to calculate the PWM duty cycle:

[0104]

[0105] The calculated PWM duty cycle is 9.45%. Finally, the PWM generator in the control system uses this duty cycle value as input to generate a square wave signal with a high-level time of 9.45% of the entire cycle (100 microseconds) at a switching frequency of, for example, 10kHz. This PWM drive signal is sent to the drive circuit of the chopper IGBT, causing it to begin high-frequency switching with a 9.45% duty cycle, thereby precisely dissipating approximately 0.25MW of power. This perfectly coordinates with the kinetic energy storage operation of the generator-side converter, jointly suppressing the rise of the DC bus voltage.

[0106] In summary, the overvoltage suppression method for the rectifier side of the wind turbine converter according to the embodiments of this application is explained. It acquires the grid status and unit operating parameters in real time, predicting the surplus power and the maximum output active power on the grid side at the moment of fault onset. Based on the speed margin and DC voltage status, the surplus power is dynamically allocated to the rotor kinetic energy storage (through electromagnetic torque adjustment) and the chopper energy dissipation channel. Finally, a coordinated reference command for the turbine-side torque and grid-side current is generated. In this way, the overvoltage suppression bottleneck of the wind turbine converter during low-voltage ride-through is overcome. Through millisecond-level coordinated control of multiple subsystems, precise stabilization of the DC bus voltage during faults is achieved, while simultaneously meeting the reactive power support requirements of the grid guidelines, ultimately improving the high-voltage ride-through success rate and equipment safety margin of the wind turbine.

[0107] Furthermore, an overvoltage suppression system for the rectifier side of a wind power converter is also provided.

[0108] Figure 3 This is a block diagram of a wind power converter rectifier-side overvoltage suppression system according to an embodiment of this application. Figure 3 As shown, the wind power converter rectifier-side overvoltage suppression system 300 according to an embodiment of this application includes: a global state perception module 310, used to acquire grid voltage amplitude, aerodynamic power estimation value, generator speed, and DC bus voltage in response to the detection of a voltage drop fault flag; and a surplus power prediction module 320, used to predict surplus power based on grid voltage amplitude and aerodynamic power estimation value, combined with the reactive power reference of the converter's maximum current rating and low voltage ride-through requirements, to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions. The dynamic power allocation module 330 is used to perform dynamic power allocation based on the predicted surplus power, generator speed, and DC bus voltage to obtain dynamic energy storage reference power and chopper reference power; the coordination control module 340 is used to generate machine-side electromagnetic torque reference and grid-side dq-axis current reference based on the dynamic energy storage reference power, wherein the machine-side electromagnetic torque reference is sent to the machine-side converter and the grid-side dq-axis current reference is sent to the grid-side converter; and the PWM drive signal generation module 350 is used to generate PWM drive signals for the chopper IGBT based on the chopper reference power.

[0109] As described above, the wind power converter rectifier-side overvoltage suppression system 300 according to the embodiments of this application can be implemented in various wireless terminals, such as servers with wind power converter rectifier-side overvoltage suppression algorithms. In one possible implementation, the wind power converter rectifier-side overvoltage suppression system 300 according to the embodiments of this application can be integrated into the wireless terminal as a software module and / or hardware module. For example, the wind power converter rectifier-side overvoltage suppression system 300 can be a software module in the operating system of the wireless terminal, or it can be an application developed for the wireless terminal; of course, the wind power converter rectifier-side overvoltage suppression system 300 can also be one of many hardware modules of the wireless terminal.

[0110] Alternatively, in another example, the wind power converter rectifier side overvoltage suppression system 300 and the wireless terminal can also be separate devices, and the wind power converter rectifier side overvoltage suppression system 300 can be connected to the wireless terminal via wired and / or wireless networks, and transmit interactive information in accordance with an agreed data format.

[0111] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for suppressing overvoltage on the rectifier side of a wind power converter, characterized in that, include: In response to the detection of a voltage drop fault flag, the grid voltage amplitude, aerodynamic power estimate, generator speed, and DC bus voltage are acquired. Based on the grid voltage amplitude and aerodynamic power estimation, and combined with the converter maximum current rating and reactive power reference for low voltage ride-through requirements, surplus power is predicted to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions. Based on the predicted surplus power, generator speed and DC bus voltage, dynamic power allocation is performed to obtain dynamic energy storage reference power and chopper reference power. Based on the dynamic energy storage reference power, a machine-side electromagnetic torque reference and a grid-side dq-axis current reference are generated. The machine-side electromagnetic torque reference is fed into the machine-side converter, and the grid-side dq-axis current reference is fed into the grid-side converter. The PWM drive signal for the chopper IGBT is generated based on the chopper reference power.

2. The overvoltage suppression method on the rectifier side of a wind power converter according to claim 1, characterized in that, In response to the detection of a voltage dip fault flag, the system acquires the grid voltage amplitude, aerodynamic power estimate, generator speed, and DC bus voltage, including: Obtain the three-phase voltage of the power grid, the three-phase current of the power grid, the DC bus voltage, and the generator speed; The grid voltage amplitude is extracted from the three-phase grid voltage using a phase-locked loop. Fault detection results are generated based on a comparison between the grid voltage amplitude and a preset threshold. In response to a fault detection result indicating that the grid voltage amplitude is lower than a preset threshold, a voltage drop fault flag is generated.

3. The overvoltage suppression method on the rectifier side of a wind power converter according to claim 2, characterized in that, In response to the detection of a voltage sag fault flag, the system acquires the grid voltage amplitude, aerodynamic power estimate, generator speed, and DC bus voltage, and also includes: Calculate the actual input electromagnetic power based on the generator speed and electromagnetic torque command; Clark and Park transformations were performed on the three-phase voltage and three-phase current of the power grid to obtain the voltage components and current components in the dq coordinate system. The actual output grid power is calculated based on the voltage and current components in the dq coordinate system.

4. The overvoltage suppression method on the rectifier side of a wind power converter according to claim 3, characterized in that, Based on the grid voltage amplitude and aerodynamic power estimates, and combined with the converter's maximum current rating and reactive power reference for low-voltage ride-through requirements, surplus power is predicted to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions, including: Based on grid guidelines and grid voltage amplitude, the reactive power reference for low voltage ride-through is calculated. Calculate the total apparent power limit of the converter based on the maximum current rating of the converter and the grid voltage amplitude. Based on the reactive power reference of the converter's total apparent power limit and low voltage ride-through requirements, the maximum active power that the converter can output under fault conditions is calculated. Based on the maximum active power output of the converter under fault conditions and the estimated aerodynamic power, the predicted surplus power is calculated.

5. The overvoltage suppression method on the rectifier side of a wind power converter according to claim 4, characterized in that, Based on the reactive power reference of the converter's total apparent power limit and low voltage ride-through requirements, the maximum active power that the converter can output under fault conditions is calculated, including: Based on the reactive power reference of the converter's total apparent power limit and low voltage ride-through requirements, the maximum active power that the converter can output under fault conditions is calculated using the following formula: Among them, S limit For the total apparent power limit of the converter, O g-ref-LVRT P serves as the reactive power reference for low voltage ride-through requirements. out-Pmax This represents the maximum active power that the converter can output under fault conditions.

6. The overvoltage suppression method on the rectifier side of a wind power converter according to claim 5, characterized in that, Based on the predicted surplus power, generator speed, and DC bus voltage, dynamic power allocation is performed to obtain the dynamic energy storage reference power and chopper reference power, including: Calculate the difference between the generator's maximum safe speed and the generator speed to obtain the speed margin; Based on the speed margin, calculate the maximum kinetic energy power that can be safely absorbed at the current speed; Based on the predicted surplus power and DC bus voltage, specify the allocation weighting factor; The dynamic energy storage reference power is calculated using the following formula: P k-ref =min(P s-ptr *k,P k-max ) Where k is the allocation weight factor, P s-ptr For the predicted surplus power and P k-max P is the maximum kinetic energy power that can be safely absorbed at the current rotational speed. k-ref This serves as a reference power for dynamic energy storage. The chopper reference power is calculated using the following formula: P c-ref =P s-ptr -P k-ref Among them, P s-ptr For the predicted surplus power, P k-ref For dynamic energy storage reference power, P c-ref This is the reference power for the chopper.

7. The overvoltage suppression method on the rectifier side of a wind power converter according to claim 6, characterized in that, Based on the dynamic energy storage reference power, a machine-side electromagnetic torque reference and a grid-side dq-axis current reference are generated. The machine-side electromagnetic torque reference is fed into the machine-side converter, and the grid-side dq-axis current reference is fed into the grid-side converter. This includes: Based on the dynamic energy storage reference power, the machine-side electromagnetic torque reference and the grid-side dq-axis current reference are generated using the following formula, wherein the formula is: P msc-ref =P in-act -P k-ref T em-ref =P msc-ref / O rot I dg-ref =P out-Pmax / (1.5*V dg ) I qg-ref =O g-ref-LVRT / (1.5*V dg ) Among them, P msc-ref For machine-side power reference, P = in-act For the actual input electromagnetic power, O rot For generator speed, P out-Pmax V represents the maximum active power that the converter can output under fault conditions. dg Let d be the voltage d component in the voltage components in the dq coordinate system.

8. The overvoltage suppression method on the rectifier side of a wind power converter according to claim 7, characterized in that, Based on the chopper reference power, the PWM drive signal for the chopper IGBT is generated, including: The chopper controller is activated in response to the chopper reference power being greater than zero. Calculate the PWM idle ratio of the chopper controller based on the DC bus voltage and the target dissipation power; The PWM drive signal for the chopper IGBT is generated based on the PWM idle ratio of the chopper controller.

9. A rectifier-side overvoltage suppression system for a wind power converter, characterized in that, include: The global state awareness module is used to obtain grid voltage amplitude, aerodynamic power estimate, generator speed and DC bus voltage in response to the detection of voltage drop fault flag; The surplus power prediction module is used to predict surplus power based on grid voltage amplitude and aerodynamic power estimation, combined with the reactive power reference of converter maximum current rating and low voltage ride-through requirements, so as to obtain the predicted surplus power and the maximum active power that the converter can output under fault conditions. The dynamic power allocation module is used to perform dynamic power allocation based on the predicted surplus power, generator speed and DC bus voltage to obtain dynamic energy storage reference power and chopper reference power. The coordination control module is used to generate a machine-side electromagnetic torque reference and a grid-side dq-axis current reference based on the dynamic energy storage reference power. The machine-side electromagnetic torque reference is sent to the machine-side converter, and the grid-side dq-axis current reference is sent to the grid-side converter. The PWM drive signal generation module is used to generate the PWM drive signal for the chopper IGBT based on the chopper reference power.

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