Control method and device for stable operation of doubly-fed fan and electronic equipment

Abstract

The invention discloses a control method and device for stable operation of a doubly-fed fan and electronic equipment. The control method comprises the steps that a real-time reactive current reference value is acquired; a corresponding control mode is determined according to the relation between the real-time reactive current reference value and the grid-side reactive current limit value and the relation between the real-time reactive current reference value and the rotor-side reactive current limit value; the reactive current is controlled according to the corresponding control mode, so that the grid-connected voltage meets the requirement, and coordination control of switching of three strategy modes of a rotor side converter and a grid side converter in the low-voltage and high-voltage continuous fault ride-through process of the doubly-fed fan supported by the self-design reactive current is adopted. Different control modes are set according to different judgment conditions of reactive current reference values which can be provided by the rotor side converter and the grid side converter, so that the problem of out-of-limit voltage of a direct current bus when the fan breaks down can be solved, and stable operation of the doubly-fed fan is ensured.

Description

Technical Field

[0001] The present invention belongs to the field of new energy technology, and specifically relates to a control method, device and electronic equipment for the stable operation of a doubly-fed wind turbine. Background Art

[0002] With the rapid development of the global economy, the wind power market has been fully supported, and the global wind turbine installed capacity has expanded rapidly. However, with the continuous increase in wind turbine installed capacity, the operating requirements for wind turbines connected to the grid have become increasingly stringent. Wind farms not only need to provide frequency and voltage regulation similar to traditional power plants, but also need to provide a certain degree of low-voltage operation capability for wind turbines. Doubly fed asynchronous generators have become the mainstream model in the wind energy market because of their many advantages, such as low converter capacity, large speed regulation range, active and reactive decoupling control, and low cost. In order to meet the State Grid's requirements for grid-connected wind turbines to provide reactive support in the event of voltage faults, it is necessary to ensure that they have the ability of low voltage ride-through (LVRT) and high voltage ride-through (HVRT), so that the doubly fed asynchronous wind turbine generator DFIG (Doubly fed Induction Generator) can continuously supply power to the power system to support the recovery of the faulty power grid.

[0003] Although the research on the low-high voltage continuous fault ride-through control strategy of DFIG has received extensive attention. However, most of the existing research is on the reactive power support capability, overcurrent suppression, and overvoltage capability, and does not consider the over-limit problem during the ride-through process. At the same time, the above are all studies on the control strategy of a single voltage drop or rise, which is difficult to apply to continuous fault ride-through. Therefore, it is necessary to further study and improve the low-high voltage continuous fault ride-through control strategy of the doubly fed wind turbine, so that the doubly fed wind turbine can operate safely and stably during the fault. Summary of the invention

[0004] The present application provides a control method and device electronic device for the stable operation of a doubly-fed wind turbine, which are used to implement a low-high voltage continuous fault ride-through control strategy for the doubly-fed wind turbine, so that the doubly-fed wind turbine can operate safely and stably during a fault.

[0005] According to the first aspect of the present application, a control method for stable operation of a doubly fed wind turbine is provided, comprising the steps of: obtaining a real-time reactive current reference value; determining a corresponding control mode according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value; and controlling the reactive current according to the corresponding control mode so that the grid-connected voltage meets the requirements.

[0006] Optionally, the step of obtaining the real-time reactive current reference value comprises the steps of: i rq_ref and stator side reactive current reference valuei sq_ref The relationship between and the requirements of wind farm testing is used to calculate the reactive current reference value. I ref ; Provide a preset assignment rule, and calculate the reactive current reference value according to the calculation I ref The values ​​are assigned according to the assignment rule to determine the reactive current reference values ​​on the rotor side and the grid side.

[0007] Optionally, the preset assignment rule further includes: obtaining the output limit value of the grid-side reactive current during the voltage drop period I gq_lout , the absorption limit value of the reactive current on the grid side during the voltage rise period I gq_hin , the limit value of reactive current on the stator side during voltage drop I sq_lout And the absorption limit of the stator side reactive current during the voltage rise period I sq_hin , and according to I gq_lout , I gq_hin , I sq_lout as well as I sq_hin Get the total reactive current limit value of the wind turbine during the fault period I q_lout and total reactive current absorption limit I q_hin ; The preset assignment rule performs corresponding assignment according to the corresponding voltage ride-through period. During the low voltage ride-through period, if I ref < I gq_lout ,make I gq_ref = I ref .like I ref > I gq_lout , then further judge: like I ref < I q_lout , this season I gq_ref = I gq_lout , I sq_ref = I ref - Igq_lout ; like I ref > I q_lout , then let I gq_ref = I gq_lout , I sq_ref = I sq_lout ; During high voltage ride through, if I ref < I gq_hin ,make I gq_ref = I ref .like I ref > I gq_hin , then further judge, like I ref < I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I ref - I gq_hin ; like I ref > I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I sq_hin. Wherein, the determining of the corresponding control mode according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value comprises the following steps: when the grid-side reactive current limit value is greater than the real-time reactive current reference value, determining the control mode to be the first control mode; when the rotor-side reactive current limit value is greater than the real-time reactive current reference value, determining the control mode to be the second control mode; when the rotor-side reactive current limit value is less than the real-time reactive current reference value, determining the control mode to be the third control mode. The controlling of reactive current according to the corresponding control mode so that the grid-connected voltage meets the requirements includes: when in the first control mode, the grid-side converter controls the absorption and emission of reactive current, and the reactive current of the rotor-side converter operates in the conventional control mode; when in the second control mode, the grid-side converter controls the absorption and emission of reactive current, and at the same time, the reactive current required by the system is greater than the reactive current of the grid side, so the rotor-side converter control mode is also switched to reactive current control to compensate for the lack of reactive current, the grid-side converter and the rotor-side converter emit reactive current together, and the rotor side and the grid side coordinate control to restore the voltage to a normal value; when in the third control mode, the grid-side converter and the rotor-side converter simultaneously provide or absorb reactive current at their own maximum limit values ​​to restore the voltage to a normal value.

[0008] Optionally, define the state variable of the real-time reactive current reference value I ref ( t ), the reactive current emission or absorption limit values ​​of the grid-side converter and the rotor-side converter during low and high voltage ride-through are collectively referred to as I gq_max , I rq_max When the grid-side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)≤ I gq_max When the rotor side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)> I gq_maxWhen the rotor side reactive current limit value is less than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I q_max and I ref ( t +1)> I q_max .

[0009] Before the step of obtaining the real-time reactive current reference value, the step also includes: determining the operating state of the voltage, the operating state of the voltage including: normal operating state, low voltage operating state and high voltage operating state, wherein when the operating state of the voltage is the low voltage operating state and the high voltage operating state, the corresponding control mode is determined according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value.

[0010] According to the second aspect of the present application, a device for stable operation of a doubly fed wind turbine is provided, comprising: an acquisition module for acquiring a real-time reactive current reference value; a determination module for determining a corresponding control mode based on the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value; and a control module for controlling the reactive current according to the corresponding control mode so that the grid-connected voltage meets the requirements.

[0011] According to the rotor side reactive current reference value i rq_ref and stator side reactive current reference value i sq_ref The relationship between and the requirements of wind farm testing is used to calculate the reactive current reference value. I ref ; Provide a preset assignment rule, and calculate the reactive current reference value according to the calculation I ref Assign values ​​according to the assignment rules Optionally, the acquisition module includes: a calculation module for calculating the reactive current reference value of the rotor side i rq_ref and stator side reactive current reference value i sq_ref The relationship between and the requirements of wind farm testing is used to calculate the reactive current reference value. I ref ; Assignment module, used to provide a preset assignment rule, and according to the reactive current reference value obtained by the calculation I refAssign values ​​according to the assignment rules to determine the reference values ​​of reactive current on the rotor side and the grid side; wherein the assignment module includes: a limit value acquisition module for obtaining the limit value of reactive current on the grid side during voltage drop; I gq_lout , the absorption limit value of the reactive current on the grid side during the voltage rise period I gq_hin , the limit value of reactive current on the stator side during voltage drop I sq_lout And the absorption limit of the stator side reactive current during the voltage rise period I sq_hin , and according to I gq_lout , I gq_hin , I sq_lout as well as I sq_hin Get the total reactive current limit value of the wind turbine during the fault period I q_lout and total reactive current absorption limit I q_hin The assignment module also includes a module for performing corresponding assignments according to the corresponding voltage ride-through period, wherein, during the low voltage ride-through period, if I ref < I gq_lout ,make I gq_ref = I ref ;like I ref > I gq_lout , then further judge: if I ref < I q_lout , this season I gq_ref = I gq_lout , I sq_ref = I ref - I gq_lout ;like I ref > I q_lout , then let I gq_ref = I gq_lout , I sq_ref = Isq_lout ; During high voltage ride through, if I ref < I gq_hin ,make I gq_ref = I ref ;like I ref > I gq_hin , then further judge, if I ref < I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I ref - I gq_hin ;like I ref > I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I sq_hin .

[0012] Optionally, the control module also includes: a first control module, which is used to determine that the control mode is the first control mode when the grid-side reactive current limit value is greater than the real-time reactive current reference value; a second control module, which is used to determine that the control mode is the second control mode when the rotor-side reactive current limit value is greater than the real-time reactive current reference value; a third control module, which is used to determine that the control mode is the third control mode when the rotor-side reactive current limit value is less than the real-time reactive current reference value; wherein the first control module is used for the grid-side converter to control the absorption of reactive current The reactive current of the rotor side converter is operated in the normal control mode; the second control module is used for the grid side converter to control the absorption and emission of reactive current. At the same time, the reactive current required by the system is greater than the reactive current of the grid side, so the control mode of the rotor side converter is also switched to reactive current control to compensate for the lack of reactive current. The grid side converter and the rotor side converter emit reactive current together, and the rotor side and the grid side coordinate control to restore the voltage to normal value; the third control module is used for the grid side converter and the rotor side converter to provide or absorb reactive current at their own maximum limit value at the same time to restore the voltage to normal value.

[0013] Optionally, it also includes a condition determination module: the condition determination module is used to define the state variable of the real-time reactive current reference value I ref ( t ), the reactive current emission or absorption limit values ​​of the grid-side converter and the rotor-side converter during low and high voltage ride-through are collectively referred to as I gq_max , I rq_max When the grid-side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)≤ I gq_max When the rotor side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)> I gq_max When the rotor side reactive current limit value is less than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I q_max and I ref ( t +1)> I q_max . It also includes a state determination module: used to determine the operating state of the voltage, the operating state of the voltage includes: normal operating state, low voltage operating state and high voltage operating state, wherein when the operating state of the voltage is a low voltage operating state and a high voltage operating state, the corresponding control mode is determined according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value.

[0014] In order to achieve the above-mentioned objectives, the third aspect of the present application proposes an electronic device for the stable operation of a doubly fed wind turbine, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the control method for the stable operation of the doubly fed wind turbine as described in the first aspect is implemented.

[0015] In order to achieve the above-mentioned objectives, the fourth aspect of the present application proposes a storage medium for stable operation of a doubly fed wind turbine, which is a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute a control method for stable operation of a doubly fed wind turbine as described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 A flow chart of a control method for stable operation of a doubly-fed wind turbine provided in an embodiment of the present application; Figure 2 A schematic diagram of a typical structure of a doubly-fed wind turbine provided in an embodiment of the present application; Figure 3 A reactive current distribution rule diagram provided in an embodiment of the present application; Figure 4 A flow chart of the coordination control strategy provided in the embodiment of the present application; Figure 5 The reactive current reference value mode control strategy provided in the embodiment of the present application; Figure 6 A schematic diagram of the grid connection point voltage of the simulation result of the coordinated control of the doubly-fed wind turbine during the continuous riding process provided by the embodiment of the present application; Figure 7 A schematic diagram of grid-side active and reactive power of simulation results of a double-fed wind turbine using coordinated control during a continuous ride-through process provided by an embodiment of the present application; Figure 8 A schematic diagram of DC bus voltage of a simulation result of a double-fed wind turbine using coordinated control during a continuous ride-through process provided by an embodiment of the present application; Fig. 9 A schematic diagram of grid-side current of a simulation result of a double-fed wind turbine using coordinated control during a continuous ride-through process provided by an embodiment of the present application; Fig.10 A schematic diagram of the stator-side current of the simulation result of the double-fed wind turbine using coordinated control during the continuous riding process provided by the embodiment of the present application; Fig.11 A schematic diagram of reactive power at a point in network of simulation results of a double-fed wind turbine using coordinated control during a continuous ride-through process provided by an embodiment of the present application; Fig.12 A schematic diagram of the structure of a device for stable operation of a doubly-fed wind turbine provided in an embodiment of the present application; Fig.13A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0018] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0019] Ps is the active power output on the stator side of DFIG; Qs is the reactive power output on the stator side of DFIG; Pr is the active power input on the DFIG rotor side; Qr is the reactive power input on the DFIG rotor side; Pg is the active power input of the grid-side converter; Qg is the reactive power input of the grid-side converter; Pt is the total active power output of DFIG; Qt is the total reactive power output of DFIG; Figure 1 A flow chart of a control method for stable operation of a doubly-fed wind turbine provided in an embodiment of the present application.

[0020] like Figure 1 As shown, the control method for stable operation of a doubly-fed wind turbine provided in the present application comprises the following steps: S101. Obtain a real-time reactive current reference value.

[0021] According to the rotor side reactive current reference value i rq_ref and stator side reactive current reference value i sq_ref The relationship between and the requirements of wind farm testing is used to calculate the reactive current reference value. I ref ; Provide a preset assignment rule, and calculate the reactive current reference value according to the calculation The values ​​are assigned according to the assignment rule to determine the rotor side and grid side current reference values.

[0022] Obtain the output limit value of the grid-side reactive current during voltage drop I gq_lout, the absorption limit value of the reactive current on the grid side during the voltage rise period I gq_hin , the limit value of reactive current on the stator side during voltage drop I sq_lout And the absorption limit of the stator side reactive current during the voltage rise period I sq_hin ; according to I gq_lout , I gq_hin , I sq_lout as well as I sq_hin Get the total reactive current limit value of the wind turbine during the fault period I q_lout and total reactive current absorption limit I q_hin ; The preset assignment rule performs corresponding assignment according to the corresponding voltage ride-through period, wherein different judgment criteria are used during the low voltage ride-through period and the high voltage ride-through period, respectively.

[0023] S102: Determine a corresponding control mode according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value.

[0024] When the grid-side reactive current limit value is greater than the real-time reactive current reference value, the control mode is determined to be the first control mode; when the rotor-side reactive current limit value is greater than the real-time reactive current reference value, the control mode is determined to be the second control mode; when the rotor-side reactive current limit value is less than the real-time reactive current reference value, the control mode is determined to be the third control mode.

[0025] S103: Control reactive current according to the corresponding control mode so that the grid-connected voltage meets the requirement.

[0026] When in the first control mode, the grid-side converter controls the absorption and emission of reactive current, and the reactive current of the rotor-side converter operates in the normal control mode; when in the second control mode, the grid-side converter controls the absorption and emission of reactive current, and at the same time, the reactive current required by the system is greater than the reactive current of the grid side, so the rotor-side converter control mode is also switched to reactive current control to compensate for the lack of reactive current, and the grid-side converter and the rotor-side converter emit reactive current together, and the rotor side and the grid side coordinate control to restore the voltage to a normal value; when in the third control mode, the grid-side converter and the rotor-side converter simultaneously provide or absorb reactive current at their maximum limit values ​​to restore the voltage to a normal value.

[0027] In this embodiment, before the step of obtaining the real-time reactive current reference value, the step also includes: determining the operating state of the voltage, the operating state of the voltage including: normal operating state, low voltage operating state and high voltage operating state, wherein when the operating state of the voltage is a low voltage operating state and a high voltage operating state, the corresponding control mode is determined according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value.

[0028] It should be understood that the present invention proposes a coordinated control method for the stable operation of a double-fed wind turbine under continuous faults. The double-fed wind turbine generator is composed of a wind turbine, a transmission system, an induction motor, a group of back-to-back converters and their control systems, such as Figure 2 As shown. P s , Q s They are the active power and reactive power output of DFIG stator side respectively; P r , Q r They are the active power and reactive power input on the DFIG rotor side respectively; P g , Q g They are the active power and reactive power input of the grid-side converter respectively; P t , Q t They are the total active power and reactive power output of DFIG respectively.

[0029] Part 1: Under the constraints of converter overcurrent limitation and grid-connected guidelines, the relationship between the current value and current limit and reactive current limit of the rotor-side converter and the grid-side converter is derived; in order to obtain a reasonable reactive current to support grid voltage recovery, the reactive current reference value distribution rule of the rotor-side converter and the grid-side converter is designed; the specific process is as follows: The current value of the grid-side converter and the current limit of the grid-side converter have the following relationship: (1) The grid voltage-oriented vector control is used as the basic control strategy for the grid-side converter. The active power and reactive power output from the grid side have the following relationship with the grid-side dq axis current: (2) When no fault occurs, the grid-side reactive current is 0 when the operation is under the condition of unit power factor. U s <0.9pu or 1.1pu<U s <1.3pu), combined with equations (1) and (2), in low voltage ride-through, the denominator takes the voltage value at the maximum drop level, and it can also ensure that the reactive power limit is met under other working conditions. The reactive current emission and absorption limits of the grid-side converter in low and high voltage ride-through can be obtained, that is: (3) Where: I gq_lout , I gq_hin They are respectively the limiting values ​​of reactive current emission and absorption on the grid side during voltage drop and rise.

[0030] The current value of the rotor-side converter and the current limit of the rotor-side converter have the following relationship: (4) Stator voltage-oriented vector control is used as the basic control strategy for the rotor-side converter. The active power and reactive power output on the stator side have the following relationship with the stator and rotor currents: (5) Use formula (5) i rd and i rq After expressing it in the form of , substituting it into formula (4), we get: (6) In formula (5), Substituting into equation (6), we can obtain the reactive current emission limit and absorption limit during low and high voltage ride-through on the stator side, namely: (7) Where: I sq_lout , I sq_hin They are respectively the limit values ​​of reactive current emission and absorption on the stator side during voltage drop and rise.

[0031] Combining equations (4) and (7) gives the total reactive current emission and absorption limit of the wind turbine during the fault period, namely: (8) According to formula (5), the RSC reactive current reference value can be derived: i rq_ref and stator side reactive current reference value I sq_ref The relationship between them is: (9) The wind farm test requirements clearly stipulate that during low voltage ride-through and high voltage ride-through, the wind farm should provide dynamic reactive current to support the grid voltage. The reactive current magnitudes (per unit value) are: (10) Where: point K 1. K 2 are the reactive current coefficients during low voltage ride through and high voltage ride through respectively.

[0032] First, the grid connection point voltage is judged. When the grid connection point voltage is less than 0.9pu (normal floating lower limit), it is necessary to provide capacitive reactive current to the grid to raise the voltage; when the grid connection point voltage is greater than 1.1pu (normal floating upper limit), it is necessary to provide inductive reactive current to the grid to reduce the voltage.

[0033] Secondly, the required reactive current reference value is obtained by calculation ( I ref ), and then determine the rotor side and grid side current reference values. The reactive current reference values ​​of the grid side converter and rotor side converter control link are reasonably assigned according to the following rules. The specific rules are as follows: During the low voltage ride-through phase, the wind turbine needs to send reactive power to the grid to support voltage recovery. I ref Compared with the formula (3) I gq_lout For comparison, if I ref < I q_lout , indicating that only the grid-side converter is needed to provide reactive power. I gq_ref = I ref .like I ref > I gq_lout , still need to judge Is it greater than the value in formula (8)? I q_lout ,like I ref < I q_lout , indicating that additional reactive power support is required on the rotor side. I gq_ref = I gq_lout , I sq_ref = I ref - I gq_lout .likeI ref > I q_lout , it exceeds the total limit reactive current generated by the fan, so the reactive current is generated according to the limit, so I gq_ref = I gq_lout , I sq_ref = I sq_lout During the high voltage ride-through period, the wind turbine needs to absorb reactive power from the grid to restore the voltage. I ref Compared with the formula (3) I gq_hin For comparison, if I ref < I gq_hin , indicating that only the grid-side converter is needed to absorb reactive power. I gq_ref = I ref .like I ref > I gq_hin , still need to judge I ref Is it greater than the value in formula (8)? I q_hin ,like I ref < I q_hin , indicating that the rotor side needs to absorb additional reactive power. I gq_ref = I gq_hin , I sq_ref = I ref - I gq_hin. .like I ref > I q_hin , it exceeds the total limit reactive current absorbed by the fan, so according to the limit reactive current absorption, let I gq_ref = I gq_hin , I sq_ref = I sq_hin .

[0034] Finally, according to the above reactive current assignment rules, a new control strategy is designed based on the traditional control strategy to meet the above reactive current switching process during the fault period. The reactive current reference value assignment rules are as follows: Figure 3 shown.

[0035] It can be understood that the new control strategy may be the control method in the above step S102.

[0036] Part II: Determine the switching of the control strategy of the doubly fed wind turbine during a fault; the specific contents are as follows: The fault ride-through process of a doubly fed wind turbine can be divided into three stages: the steady-state stage before the fault, the fault persistence stage, and the post-fault recovery stage. The control strategy switching process of the fault ride-through process is as follows: Figure 4 shown.

[0037] Before the wind turbine fails, it operates in a normal state. The rotor-side converter control system adopts a double closed-loop structure, consisting of an outer power loop and an inner current loop. In the outer power loop control, the active power reference value is calculated based on the MPPT, and the reactive power reference value is set to 0 based on the constant power factor control. The current reference value of the inner current loop is calculated by the active and reactive power control links to obtain the reference values ​​of the d and q axis components of the rotor. I rd_ref , I rq_ref As the input of the current inner loop. The grid-side converter control system consists of two parts: the voltage outer loop and the current inner loop. The rotor-side converter adopts a stator voltage-oriented control strategy, and the grid-side converter adopts a grid voltage-oriented control strategy.

[0038] When the grid voltage drops due to excessive reactive compensation and then the voltage rises continuously during fault crossing, it will cause rotor bus overcurrent or DC bus overvoltage. In order to ensure stable operation, it is necessary to inject reactive current into the grid when the voltage drops and absorb reactive current from the grid when the voltage rises to support the voltage to recover and stabilize. The method adopted by the present invention is to switch the control mode of the rotor-side converter and the grid-side converter to a coordinated control strategy during the continuous fault continuation stage without adding a Crowbar protection circuit, lock the power control links of the rotor-side converter and the grid-side converter, and use current control to inject reactive current into the grid.

[0039] Defining state variables U s ( t ), when U s ( t )as well as U s ( t+1) at all times, the reactive current reference values ​​of the rotor-side converter and the grid-side converter are between 0.9pu and 1.1pu. i rq0 , i gq0 When operating in the conventional control mode, the reactive current expressions of the rotor-side converter and the grid-side converter in the steady state are: (11) Where: K rp , K ri , i load , i c They are respectively the proportional coefficient of the rotor side power outer loop controller, the integral coefficient of the rotor side power outer loop controller, the DC side load current of the converter, and the DC side capacitor current.

[0040] When the state variable U s ( t ) is greater than 0.9pu and U s ( t +1) less than 0.9pu or U s ( t ) is less than 1.1 pu and U s ( t +1) is greater than 1.1pu, the reactive current control strategy of the rotor-side converter and the grid-side converter switches to the coordinated control mode during the fault period, that is, the rotor-side converter and the grid-side converter switch the control strategy between the three modes according to the judgment conditions. The following formulas are all in per-unit form.

[0041] (12) Where: , They are the reactive current reference value of the rotor-side converter and the reactive current reference value of the grid-side converter respectively.

[0042] Defining state variables I ref ( t ), the reactive current limit of the grid-side converter and rotor-side converter during low and high voltage ride-through is I gq_max , I rq_max When satisfied I ref ( t )< Igq_max and I ref ( t +1)< I gq_max When the trigger condition occurs, the control strategy switches to the first control mode, that is, the grid-side converter controls the absorption and emission of reactive current, and the rotor-side converter reactive current operates in the conventional control mode.

[0043] (13) When satisfied I ref ( t )< I gq_max and I ref ( t +1)> I gq_max When the trigger condition occurs, it switches to the second control mode, that is, the grid-side converter controls the absorption and emission of reactive current. At the same time, the reactive current required by the system is greater than the reactive current on the grid side, so the rotor-side converter control mode is also switched to reactive current control to compensate for the missing reactive current. The grid-side converter and the rotor-side converter emit reactive current together, and the rotor side and the grid side coordinate control to restore the voltage to normal. (14) When satisfied I ref ( t )< I q_max and I ref ( t +1)> I q_max When the trigger condition occurs, the system switches to the third control mode, that is, the grid-side converter and the rotor-side converter simultaneously provide or absorb reactive current at their maximum limit values ​​to ensure safe operation of the system.

[0044] (15) Detection status changes to U s ( t ) measure U s ( t ), when U s ( t ) and U s ( t +1) all meet 0.9pu-1.1pu, exit the coordinated control strategy of the three control modes, switch to the conventional control mode, the coordinated control strategy is as follows Figure 5 .

[0045] When it is detected that the grid fault has been cleared, the active power and reactive power of the unit quickly recover to the steady-state values ​​before the fault, and the operation of the rotor-side converter and the grid-side converter switches to the normal control mode.

[0046] The application effect of the present invention is described in detail with the help of simulation examples. The present invention example is built on the Matlab / Simulink simulation platform. Figures 6 to 11 This is the simulation result of the coordinated control strategy proposed in the present invention. The simulation of a three-phase symmetrical fault causes the system to undergo continuous fault ride-through. At 1s, the voltage drops to 0.7pu for 200ms and then rises to 1.2pu for 200ms. The grid-side converter first generates reactive power for support and the rotor side supplements the remaining reactive power. When the voltage drops slightly, the DC bus voltage and the grid-side and stator-side currents of this coordinated control strategy do not exceed the limit, so that the double-fed wind turbine can operate stably during the fault stage.

[0047] In order to implement the above embodiment, this embodiment provides a device for stable operation of a doubly-fed wind turbine. Fig.12 A schematic diagram of the structure of a device 100 for stable operation of a doubly-fed wind turbine provided in an embodiment of the present application. The device 100 for stable operation of a doubly-fed wind turbine comprises: an acquisition module 110, which can acquire a real-time reactive current reference value; a discrimination module 120, which can determine a corresponding control mode according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value; and a control module 130, which can control the reactive current according to the corresponding control mode so that the grid-connected voltage meets the requirements.

[0048] The acquisition module 110 includes: a calculation module for calculating the reactive current reference value of the rotor side i rq_ref and stator side reactive current reference value i sq_ref The relationship between and the requirements of wind farm testing is used to calculate the reactive current reference value. I ref ; Provide a preset assignment rule, and calculate the reactive current reference value according to the calculation The values ​​are assigned according to the assignment rule to determine the rotor side and grid side current reference values.

[0049] The assignment module includes: a limit value acquisition module for obtaining the limit value of the reactive current on the grid side during the voltage drop period; I gq_lout , the absorption limit value of the reactive current on the grid side during the voltage rise period I gq_hin , the limit value of reactive current on the stator side during voltage drop I sq_loutAnd the absorption limit of the stator side reactive current during the voltage rise period I sq_hin , and according to I gq_lout , I gq_hin , I sq_lout as well as I sq_hin Get the total reactive current limit value of the wind turbine during the fault period I q_lout and total reactive current absorption limit I q_hin The assignment module also includes a module for performing corresponding assignments according to the corresponding voltage ride-through period, wherein, during the low voltage ride-through period, if I ref < I gq_lout ,make I gq_ref = I ref ;like I ref > I gq_lout , then further judge: if I ref < I q_lout , this season I gq_ref = I gq_lout , I sq_ref = I ref - I gq_lout ;like I ref > I q_lout , then let I gq_ref = I gq_lout , I sq_ref = I sq_lout ; During high voltage ride through, if I ref < I gq_hin ,make I gq_ref = I ref ;like I ref > I gq_hin , then further judge, ifI ref < I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I ref - I gq_hin ;like I ref > I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I sq_hin The determination module 120 further includes: a first control module, for determining that the control mode is the first control mode when the grid-side reactive current limit value is greater than the real-time reactive current reference value; a second control module, for determining that the control mode is the second control mode when the rotor-side reactive current limit value is greater than the real-time reactive current reference value; and a third control module, for determining that the control mode is the third control mode when the rotor-side reactive current limit value is less than the real-time reactive current reference value.

[0050] The first control module is used for the grid-side converter to control the absorption and emission of reactive current, and the reactive current of the rotor-side converter operates in a conventional control mode; the second control module is used for the grid-side converter to control the absorption and emission of reactive current. At the same time, the reactive current required by the system is greater than the reactive current on the grid side, so the rotor-side converter control mode is also switched to reactive current control to compensate for the lack of reactive current. The grid-side converter and the rotor-side converter emit reactive current together, and the rotor side and the grid side coordinate control to restore the voltage to a normal value; the third control module is used for the grid-side converter and the rotor-side converter to simultaneously provide or absorb reactive current at their own maximum limit values ​​to restore the voltage to a normal value.

[0051] It also includes a condition determination module: the condition determination module is used to define the state variable of the real-time reactive current reference value I ref ( t ), the reactive current emission or absorption limit values ​​of the grid-side converter and the rotor-side converter during low and high voltage ride-through are collectively referred to as I gq_max , I rq_maxWhen the grid-side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)≤ I gq_max When the rotor side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)> I gq_max When the rotor side reactive current limit value is less than the real-time reactive current reference value, the following steps are included: setting the judgment condition to I ref ( t )< I q_max and I ref ( t +1)> I q_max .

[0052] It also includes a state determination module: used to determine the operating state of the voltage, the operating state of the voltage including: normal operating state, low voltage operating state and high voltage operating state, wherein when the operating state of the voltage is a low voltage operating state and a high voltage operating state, the corresponding control mode is determined according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value.

[0053] In order to implement the above embodiment, Fig.13 A schematic diagram of an electronic device is provided for this embodiment. The present application proposes an electronic device 200 for stable operation of a doubly fed wind turbine, comprising: a memory 210, a processor 220, and a computer program stored in the memory 210 and executable on the processor 220. When the processor executes the program, the control method for stable operation of the doubly fed wind turbine as described above is implemented.

[0054] In order to achieve the above-mentioned objectives, the fourth aspect of the present application proposes a storage medium for stable operation of a doubly fed wind turbine, which is a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute a control method for stable operation of a doubly fed wind turbine as described in the first aspect.

[0055] In order to achieve the above-mentioned purpose, the present application also proposes a computer program product, including a computer program, which, when executed by a processor, implements the control method for stable operation of a doubly-fed wind turbine as described in the first aspect.

[0056] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

[0057] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0058] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0059] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0060] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A control method for stable operation of a doubly-fed wind turbine, characterized in that: Includes steps: Get real-time reactive current reference value; Determine a corresponding control mode according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value; The reactive current to be provided by the rotor side and the grid side is controlled according to the corresponding control mode, so that the grid-connected voltage is restored quickly.

2. The control method according to claim 1, characterized in that: The step of obtaining the real-time reactive current reference value comprises the following steps: According to the requirements of dynamic reactive current for low voltage ride-through and high voltage ride-through specified in the wind farm test, the reactive current reference value is calculated. I ref ; Provide a preset assignment rule, and calculate the reactive current reference value according to the calculation I ref and the assignment rules to determine the reactive current reference values ​​of the rotor side and the grid side; The preset assignment rules also include: Obtain the output limit value of the grid-side reactive current during voltage drop I gq_lout , the absorption limit value of the reactive current on the grid side during the voltage rise period I gq_hin , the limit value of reactive current on the stator side during voltage drop I sq_lout And the absorption limit of the stator side reactive current during the voltage rise period I sq_hin ; according to I gq_lout , I gq_hin , I sq_lout as well as I sq_hin Get the total reactive current limit value of the fan during the fault period I q_lout And the total reactive current absorption limit I q_hin ; The preset assignment rules are used to perform corresponding assignments according to the corresponding voltage ride-through period. Among them, during the low voltage ride-through period, if I ref < I gq_lout ,make I gq_ref = I ref ; like I ref > I gq_lout , then further judge: like I ref < I q_lout , this season I gq_ref = I gq_lout , I sq_ref = I ref - I gq_lout ; like I ref > I q_lout , then let I gq_ref = I gq_lout , I sq_ref = I sq_lout ; During high voltage ride through, if I ref < I gq_hin ,make I gq_ref = I ref ; like I ref > I gq_hin , then further judge, like I ref < I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I ref - I gq_hin ; like I ref > I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I sq_hin .

3. The control method according to claim 1, characterized in that: According to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value, determining the corresponding control mode comprises the steps of: When the grid-side reactive current limit value is greater than the real-time reactive current reference value, the control mode is determined to be the first control mode. In the first control mode, the grid-side converter controls the absorption and emission of reactive current, and the rotor-side converter reactive current operates in a conventional control mode. When the reactive current limit value on the rotor side is greater than the real-time reactive current reference value, the control mode is determined to be the second control mode. In the second control mode, the grid-side converter controls the absorption and emission of reactive current. Meanwhile, the reactive current required by the system is greater than the reactive current on the grid side. Therefore, the control mode of the rotor-side converter is also switched to reactive current control to compensate for the lack of reactive current. The grid-side converter and the rotor-side converter emit reactive current together. The rotor side and the grid side coordinate control to restore the voltage to a normal value. When the rotor-side reactive current limit value is less than the real-time reactive current reference value, the control mode is determined to be the third control mode. In the third control mode, the grid-side converter and the rotor-side converter simultaneously provide or absorb reactive current at their own maximum limit values ​​to restore the voltage to a normal value. The step also includes: defining a state variable of a real-time reactive current reference value I ref ( t ), the reactive current emission or absorption limit values ​​of the grid-side converter and the rotor-side converter during low and high voltage ride-through are collectively referred to as I gq_max , I rq_max ; When the grid-side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition as I ref ( t )< I gq_max and I ref ( t +1)≤ I gq_max ; When the rotor side reactive current limit value is greater than the real-time reactive current reference value, the method includes the steps of: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)> I gq_max ; When the rotor side reactive current limit value is less than the real-time reactive current reference value, the method includes the steps of: setting the judgment condition as I ref ( t )< I q_max and I ref ( t +1)> I q_max .

4. The control method according to claim 1, characterized in that: Before the step of obtaining the real-time reactive current reference value, the step also includes: determining the operating state of the voltage, the operating state of the voltage including: normal operating state, low voltage operating state and high voltage operating state, wherein when the operating state of the voltage is the low voltage operating state and the high voltage operating state, the corresponding control mode is determined according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value.

5. A device for stable operation of a doubly-fed wind turbine, characterized in that: include: An acquisition module is used to obtain a real-time reactive current reference value; A determination module, used for determining a corresponding control mode according to a relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value; The control module is used to control the reactive current according to the corresponding control mode so that the grid-connected voltage meets the requirements.

6. The device according to claim 5, characterized in that The acquisition module comprises: Computing module, According to the dynamic reactive current requirements for low voltage ride-through and high voltage ride-through specified in the wind farm test, the reactive current reference value is calculated. I ref ; An assignment module is used to provide a preset assignment rule and calculate the reactive current reference value according to the calculation and the assignment rules to determine the reactive current reference values ​​of the rotor side and the grid side; Wherein, the assignment module includes: The limit value acquisition module is used to obtain the limit value of the reactive current on the grid side during voltage drop. I gq_lout , the absorption limit value of the reactive current on the grid side during the voltage rise period I gq_hin , the limit value of reactive current on the stator side during voltage drop I sq_lout And the absorption limit of the stator side reactive current during the voltage rise period I sq_hin ; And according to I gq_lout , I gq_hin , I sq_lout as well as I sq_hin Get the total reactive current limit value of the wind turbine during the fault period I q_lout and total reactive current absorption limit I q_hin ; The assignment module also includes a module for assigning a corresponding value to the reactive current according to the corresponding voltage ride-through period, Among them, during the low voltage ride-through period, if I ref < I gq_lout ,make I gq_ref = I ref ; like I ref > I gq_lout , then further judge: like I ref < I q_lout , this season I gq_ref = I gq_lout , I sq_ref = I ref - I gq_lout ; like I ref > I q_lout , then let I gq_ref = I gq_lout , I sq_ref = I sq_lout ; During high voltage ride through, if I ref < I gq_hin ,make I gq_ref = I ref ; like I ref > I gq_hin , then further judge, like I ref < I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I ref - I gq_hin ; like I ref > I q_hin , this season I gq_ref = I gq_hin , I sq_ref = I sq_hin .

7. The device according to claim 5, characterized in that The control module also includes: A first control module, configured to determine that the control mode is a first control mode when the grid-side reactive current limit value is greater than the real-time reactive current reference value, and, when in the first control mode, the grid-side converter controls the absorption and emission of reactive current, and the rotor-side converter reactive current operates in a conventional control mode; The second control module is used to determine that the control mode is the second control mode when the reactive current limit value of the rotor side is greater than the real-time reactive current reference value, and when in the second control mode, the grid-side converter controls the absorption and emission of reactive current, and at the same time, the reactive current required by the system is greater than the reactive current of the grid side, so the rotor-side converter control mode is also switched to reactive current control to compensate for the lack of reactive current, the grid-side converter and the rotor-side converter emit reactive current together, and the rotor side and the grid side coordinate control to restore the voltage to a normal value; a third control module, configured to determine that the control mode is a third control mode when the rotor-side reactive current limit value is less than the real-time reactive current reference value, and, in the third control mode, the grid-side converter and the rotor-side converter simultaneously provide or absorb reactive current at their own maximum limit values ​​to restore the voltage to a normal value; It also includes a condition determination module: the condition determination module is used to define the state variable of the real-time reactive current reference value I ref ( t ), the reactive current emission or absorption limit values ​​of the grid-side converter and the rotor-side converter during low and high voltage ride-through are collectively referred to as I gq_max , I rq_max ; When the grid-side reactive current limit value is greater than the real-time reactive current reference value, the following steps are included: setting the judgment condition as I ref ( t )< I gq_max and I ref ( t +1)≤ I gq_max ; When the rotor side reactive current limit value is greater than the real-time reactive current reference value, the method includes the steps of: setting the judgment condition to I ref ( t )< I gq_max and I ref ( t +1)> I gq_max ; When the rotor side reactive current limit value is less than the real-time reactive current reference value, the method includes the steps of: setting the judgment condition as I ref ( t )< I q_max and I ref ( t +1)> I q_max .

8. The device according to claim 5, characterized in that It also includes a state identification module: used to identify the operating state of the voltage, the operating state of the voltage including: normal operating state, low voltage operating state and high voltage operating state, wherein when the operating state of the voltage is a low voltage operating state and a high voltage operating state, the corresponding control mode is determined according to the relationship between the real-time reactive current reference value and the grid-side reactive current limit value and the rotor-side reactive current limit value.

9. An electronic device for stable operation of a double-fed wind turbine, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, a control method for stable operation of a doubly-fed wind turbine as described in any one of claims 1 to 4 is implemented.

10. A storage medium for stable operation of a doubly-fed wind turbine, characterized in that: A non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to cause the computer to execute a control method for stable operation of a doubly-fed wind turbine according to any one of claims 1-4.

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