Method, device and equipment for protecting converter in doubly-fed motor system and medium

Abstract

The invention discloses a protection method, device and equipment for a converter in a doubly-fed motor system and a medium, and the method comprises the steps: obtaining the three-phase output current instantaneous value of the converter if the voltage drop of the grid-connected side of the doubly-fed motor system is detected; marking the phase with the maximum output current instantaneous value in the three phases of the converter, and recording the bridge arm midpoint potential of the marked phase in the power topological structure of the converter; controlling all switching tubes of the other two-phase bridge arms except the marked phase in the converter power topological structure to be turned off; and controlling a part of switch tubes of the bridge arms of the other two phases except the marked phase in the converter power topological structure to be switched on and the other part of switch tubes to be switched off, so that the midpoint potentials of the bridge arms of the other two phases except the marked phase in the converter power topological structure are equal to the midpoint potential of the bridge arm of the marked phase. According to the method provided by the invention, when the voltage drop fault occurs in the power grid of the doubly-fed motor system, the safety of the converter can be protected without Crowbar equipment, and the cost of the system is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of doubly-fed motor systems, and in particular to a method, device, equipment and medium for protecting a converter in a doubly-fed motor system. Background Art

[0002] Doubly-fed generators (DFGs) are widely used in wind, hydro, and tidal power generation due to their high efficiency, variable-speed operation capability, low power electronics cost, and excellent grid-connection characteristics. In practical applications, when the grid voltage temporarily dips, either symmetrically or asymmetrically, a large induced voltage will appear on the rotor side of the generator set, threatening equipment safety. The deeper the dip, the greater the amplitude of the induced rotor electromotive force, which can cause a machine failure in severe cases. To address this issue, AC excitation converters connected to DFGs are typically equipped with choppers and crowbars. The chopper dissipates excess energy in the bus voltage, while the crowbar dissipates rotor-side overvoltage or overcurrent through a power resistor, thereby protecting the equipment. While the crowbar effectively protects the excitation converter, its addition complicates the system architecture and increases the cost of the excitation converter. Summary of the Invention

[0003] Embodiments of the present invention provide a method, device, equipment, and medium for protecting a converter in a doubly-fed motor system, which solve the problems of complex structure and high cost of an excitation converter in the doubly-fed motor system.

[0004] In a first aspect, an embodiment of the present invention provides a method for protecting a converter in a doubly-fed motor system, the method comprising: if a voltage drop is detected on the grid-connected side of the doubly-fed motor system, obtaining the instantaneous value of the output current of the three phases of the converter; marking the phase with the largest instantaneous value of the output current among the three phases of the converter, and recording the midpoint potential of the bridge arm of the marked phase in the power topology structure of the converter; controlling all switching tubes of the bridge arms of the remaining two phases except the marked phase in the power topology structure of the converter to be turned off; controlling a part of the switching tubes of the bridge arms of the remaining two phases except the marked phase in the power topology structure of the converter to be turned on and another part of the switching tubes to be turned off, so that the midpoint potential of the bridge arms of the remaining two phases except the marked phase of the converter power topology structure is equal to the midpoint potential of the bridge arm of the marked phase.

[0005] In a second aspect, an embodiment of the present invention provides a method and apparatus for protecting a converter in a doubly-fed motor system, which includes a unit for executing the method described in the first aspect.

[0006] In a third aspect, an embodiment of the present invention further provides a computer device, comprising a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the method described in the first aspect is implemented.

[0007] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, wherein the storage medium stores a computer program, and when the computer program is executed by a processor, the method described in the first aspect can be implemented.

[0008] Embodiments of the present invention provide a method, device, equipment, and medium for protecting a converter in a doubly-fed motor system. The method detects a voltage drop on the grid-connected side of the doubly-fed motor system, obtains instantaneous output current values of the three phases of the converter, marks the phase with the largest instantaneous output current value among the three phases of the converter, and records the midpoint potential of the bridge arm of the marked phase in the converter power topology. The method then controls a portion of the switching tubes in the bridge arms of the remaining two phases in the converter power topology, excluding the marked phase, to turn on and another portion of the switching tubes to turn off, so that the midpoint potentials of the bridge arms of the remaining two phases in the converter power topology, excluding the marked phase, are equal to the midpoint potential of the bridge arm of the marked phase. This method replaces the Crowbar function by short-circuiting the rotor of the doubly-fed motor, protects the excitation converter without the need for additional Crowbar equipment, and effectively reduces system costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0010] Figure 1 A schematic flow chart of a method provided in an embodiment of the present invention;

[0011] Figure 2 A schematic flow chart of a method provided in an embodiment of the present invention;

[0012] Figure 3 A schematic diagram of a sub-process of the method provided in an embodiment of the present invention;

[0013] Figure 4 A schematic diagram of a sub-process of the method provided in an embodiment of the present invention;

[0014] Figure 5 A schematic diagram of a sub-process of the method provided in an embodiment of the present invention;

[0015] Figure 6 A schematic diagram of a sub-process of the method provided in an embodiment of the present invention;

[0016] Figure 7 A schematic flow chart of a method provided in an embodiment of the present invention;

[0017] Figure 8 A schematic structural diagram of a doubly-fed generator system according to an embodiment of the present invention;

[0018] Figure 9 The equivalent circuit diagram of the doubly-fed generator rotor with the excitation converter short-circuited;

[0019] Figure 10 A circuit diagram of a two-level topology structure provided by an embodiment of the present invention;

[0020] Figure 11 A circuit diagram of a three-level NPC topology structure provided by an embodiment of the present invention;

[0021] Figure 12 A circuit diagram of a three-level ANPC topology structure provided by an embodiment of the present invention;

[0022] Figure 13 A circuit diagram of a three-level T-type topology structure provided by an embodiment of the present invention;

[0023] Figure 14 A schematic block diagram of an apparatus according to an embodiment of the present invention;

[0024] Figure 15 A schematic block diagram of a computer device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0027] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0029] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0030] In order to facilitate the understanding of the present invention, the doubly-fed motor system is first described. Figure 8 As shown, the DFIG system primarily consists of a main transformer, an excitation transformer, an excitation converter, and a DFIG. The excitation converter includes a grid-side excitation converter (GSC) and a motor-side excitation converter (MSC), which are interconnected. The high-voltage side of the main transformer is connected to the grid, while the low-voltage side is connected to the primary side of the excitation transformer via circuit breaker QF1. The secondary side of the excitation transformer is connected to the input side of the grid-side excitation converter (GSC), and the output side of the motor-side excitation converter (MSC) is connected to the rotor of the DFIG unit. The low-voltage side of the main transformer is connected to the stator of the DFIG unit via circuit breaker QF2. In practical applications, when a symmetrical or asymmetrical voltage drop occurs on the grid-connected side of the DFIG system, a large induced voltage will appear on the rotor side of the DFIG within the unit, threatening equipment safety. The deeper the grid voltage drop, the greater the amplitude of the induced rotor electromotive force, which can cause a machine failure in severe cases.

[0031] Traditional protection methods deploy choppers and crowbars on the AC excitation converter side of a doubly-fed generator. The chopper releases excess energy in the bus voltage, while the crowbar dissipates overvoltage or overcurrent on the rotor side through power resistors, thereby protecting the excitation converter system. However, the addition of a crowbar complicates the overall system structure and increases excitation converter maintenance costs.

[0032] In order to solve the above problems, an embodiment of the present invention provides a method for protecting a converter in a doubly-fed motor system, which is mainly applied to the doubly-fed motor system described in the above embodiment, and mainly controls the machine-side excitation converter MSC in the system to ensure the safety of system equipment. The protection method for the converter in the doubly-fed motor system provided by an embodiment of the present invention is described below.

[0033] like Figure 1 As shown, the method includes the following steps: S110-S140.

[0034] S110: If a voltage drop is detected on the grid-connected side of the doubly-fed generator system, instantaneous output current values of the three phases of the converter are obtained.

[0035] In practice, grid voltage sag faults can be categorized as symmetrical or asymmetrical. A symmetrical sag means the three phases remain symmetrical after the sag, while an asymmetrical sag means the three phases are asymmetrical after the sag. A sag fault can cause oscillations in the stator flux of the doubly-fed generator, leading to overcurrent or overvoltage in the rotor. The doubly-fed generator system is equipped with a voltage detection circuit specifically for detecting the grid-connected voltage and a current detection circuit for detecting the converter output current. The system monitors the grid-connected voltage of the doubly-fed generator system through the voltage detection circuit, thereby detecting voltage sag conditions on the grid-connected side. Simultaneously, the current detection circuit monitors the converter's three-phase output current to obtain current conditions on the converter output side. In this embodiment, when the system detects that the voltage on the grid-connected side drops, that is, when the system detects that the voltage of the power grid drops symmetrically or asymmetrically, the system obtains the instantaneous value of the output current of the three-phase converter through the current detection circuit. The instantaneous value of the output current of the three-phase converter refers to the current value of the three-phase output of the converter when the voltage on the grid-connected side drops. The system can obtain the instantaneous value of the output current of each phase of the converter through the current detection circuit.

[0036] S120 , marking a phase with the largest instantaneous output current value among the three phases of the converter, and recording the midpoint potential of the bridge arm of the marked phase in the power topology structure of the converter.

[0037] In specific implementation, after the system obtains the instantaneous value of the output current of the three phases of the converter through the current detection circuit, it will compare the magnitude of the instantaneous value of the output current of the three phases of the converter, mark the phase with the largest instantaneous value of the three-phase output current of the converter, and record the midpoint potential of the bridge arm of the marked phase in the converter power topology structure. For example, when the system detects that the voltage on the grid-connected side drops symmetrically or asymmetrically, the system obtains the instantaneous value of the output current of converter phase A is 500A, the instantaneous value of the output current of converter phase B is 450A, and the instantaneous value of the output current of converter phase C is 460A. The instantaneous value of the output current of converter phase A is the largest. The system marks phase A as the marked phase and records the bridge arm midpoint potential of phase A in the converter power topology. The converter power topology may include a two-level topology, a three-level NPC topology, a three-level ANPC topology, a three-level T-type topology, etc. For a two-level topology, the bridge arm midpoint potential may include a positive potential and a negative potential. For a three-level topology, the bridge arm midpoint potential may include a positive potential, a negative potential, and a zero potential.

[0038] S130: Control all the switch tubes in the bridge arms of the two phases other than the marked phase in the power topology structure of the converter to turn off.

[0039] In specific implementations, after recording the midpoint potential of the bridge arm of the marked phase in the converter's power topology, the system controls the shutdown of all switches in the bridge arms of the two phases other than the marked phase. Specifically, the switches in the marked phase are not controlled, and only the switches in the bridge arms of the two phases other than the marked phase are controlled to shut down, so that only the marked phase has output. For example, if phase A of the converter is the marked phase, the system controls the shutdown of all switches in the bridge arms of phases B and C in the converter's power topology, so that only phase A has output.

[0040] In one embodiment, if Figure 2 As shown, after step S130, step S131 is also included.

[0041] S131 . Delaying for a first time, where the first time is greater than a switching dead time of the switch tube.

[0042] In a specific implementation, the system controls the power topology of the converter to shut down all the switches in the two-phase bridge arms except the marked phase, and then delays the shutdown time by the first time. That is, the system uses the first time as the shutdown duration of the switch. The first time must be greater than the switch dead time of the switch. The dead time of the switch refers to the time interval required to wait between turning off the switch and turning on the switch during the switching process of the switch on the bridge arm. The system controls the power topology of the converter to ensure that the shutdown time of all the switches in the two-phase bridge arms except the marked phase is greater than the dead time of the switch to prevent the bridge arm from being directly connected. After the delay is completed, the system will execute the corresponding control strategy for all the switches in the two-phase bridge arms except the marked phase.

[0043] S140. Control a part of the switch tubes in the bridge arms of the two phases other than the marked phase in the converter power topology structure to be turned on and another part of the switch tubes to be turned off, so that the midpoint potential of the bridge arms of the two phases other than the marked phase in the converter power topology structure is equal to the midpoint potential of the bridge arm of the marked phase.

[0044] In a specific implementation, after the system controls all the switch tubes in the bridge arms of the two phases other than the marked phase in the converter power topology structure to turn off, and after completing the first time delay, the system controls a portion of the switch tubes in the bridge arms of the two phases other than the marked phase in the converter power topology structure to turn on and another portion of the switch tubes to turn off, so that the midpoint potential of the bridge arms of the two phases other than the marked phase in the converter power topology structure is equal to the midpoint potential of the bridge arm of the marked phase. For example, if the system records that the midpoint potential of the bridge arm of the marked phase in the converter power topology structure is 600V, the system controls a portion of the switch tubes in the bridge arms of the two phases other than the marked phase in the converter power topology structure to turn on and another portion of the switch tubes to turn off, so that the midpoint potential of the bridge arms of the two phases other than the marked phase in the converter power topology structure is consistent with the midpoint potential of the bridge arm of the marked phase, which is 600V. Specifically, the control strategy for making the midpoint potential of the bridge arm of the two phases other than the marked phase of the converter power topology structure consistent with the midpoint potential of the bridge arm of the marked phase is determined according to the type of converter power topology structure. For example, when the converter power topology structure is a two-level topology structure, the two-level topology structure has two switches in the upper and lower bridge arms. The lower bridge arm switch tube can be controlled to be turned on and the upper bridge arm switch tube can be turned off, or the lower bridge arm switch tube can be controlled to be turned on and the upper bridge arm switch tube can be turned off, so as to achieve the same potential as the midpoint of the bridge arm of the marked phase. By controlling the midpoint potential of the bridge arm of the two phases other than the marked phase of the converter power topology structure to be equal to the midpoint potential of the bridge arm of the marked phase, the two-phase rotors of the doubly fed generator other than the marked phase are short-circuited together through the switch tubes in the on state, and the switch tubes in the on state have on-state resistance, and all the switch tubes in the on state of the two-phase bridge arms of the converter power topology structure other than the marked phase form an equivalent resistance. Specifically, if Figure 9As shown in the figure, if the marked phase is phase A, the equivalent resistances are Reqb and Reqc; if the marked phase is phase B, the equivalent resistances are Reqa and Reqc; and if the marked phase is phase C, the equivalent resistances are Reqa and Reqb. In practical applications, when the system detects a symmetrical or asymmetrical voltage drop on the grid side, the system controls the switching tubes of the two-phase bridge arms other than the marked phase in the converter power topology according to the control strategy. The rotors of the two-phase DFIG motor other than the marked phase are short-circuited together through the switching tubes of the two-phase bridge arms in the converter power topology. The on-state resistance of the switching tubes acts as a power resistor to replace the Crowbar, releasing the overvoltage or overcurrent on the rotor side of the DFIG motor, thereby protecting the safety of system equipment.

[0045] In one embodiment, if Figure 3 As shown, the converter power topology is a two-level topology, and step S140 includes S1401 - S1402 .

[0046] S1401, controlling the switch tubes of the upper bridge arms of the two phases except the marked phase in the two-level topology structure to be continuously turned on and the switch tubes of the lower bridge arms to be continuously turned off;

[0047] S1402 , or controlling the switch tubes of the lower bridge arms of the other two phases except the marked phase in the two-level topology structure to be continuously turned on, and the switch tubes of the upper bridge arms to be continuously turned off.

[0048] In the specific implementation, the power topology design of the converter in the doubly fed generator system adopts a two-level topology, such as Figure 10 As shown in the figure, the two-level topology has a total of six switches, two switches per phase. Each phase is composed of two switches forming the upper and lower bridge arms. Each phase has one switch in both the upper and lower bridge arms. The rotor of the doubly-fed generator is connected to the midpoint of the three-phase bridge arm of the two-level topology, that is, connected between the upper and lower bridge arms. In practical applications, when the power topology of the converter in the doubly-fed generator system adopts a two-level topology, the system has the following control strategy:

[0049] (1) Control the switch tubes of the upper bridge arms of the other two phases except the marked phase in the two-level topology structure to be continuously turned on and the switch tubes of the lower bridge arms to be continuously turned off. Figure 10 As shown, Tij represents the jth switch tube of the i-th phase, for example, Ta1 represents the first switch tube of the bridge arm of phase A. The system controls the switch tubes Ti1 (i=a, b, c) of the upper bridge arms of the three phases A, B, and C of the two-level topology structure except the marked phase to be continuously turned on, and the switch tubes Ti2 (i=a, b, c) of the lower bridge arms to be continuously turned off.

[0050] (2) Control the switch tubes of the lower bridge arms of the other two phases except the marked phase in the two-level topology structure to be continuously turned on and the switch tubes of the upper bridge arm to be continuously turned off. Figure 10 As shown, the system controls the switch tubes Ti2 (i=a, b, c) of the lower bridge arms of the two phases A, B, and C of the two-level topology structure except the marked phase to be continuously turned on, and the switch tubes Ti1 (i=a, b, c) of the upper bridge arm to be continuously turned off.

[0051] In summary, the system adopts a two-level topology with two control strategies for the power topology of the converter. Through these two control strategies, the rotor of the doubly fed generator can be short-circuited in two ways, each of which can release the energy of overvoltage or overcurrent on the rotor side of the doubly fed generator, thereby achieving the purpose of protecting the converter equipment in the system.

[0052] In one embodiment, if Figure 4 As shown, the converter power topology is a three-level NPC topology, and step S140 includes S1403-S1405.

[0053] S1403, controlling the switch tubes of the upper bridge arms of the other two phases except the marked phase in the three-level NPC topology structure to be continuously turned on and the switch tubes of the lower bridge arms to be continuously turned off;

[0054] S1404, or controlling the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level NPC topology structure to be continuously turned on and the switch tubes of the upper bridge arms to be continuously turned off;

[0055] S1405 , or controlling the adjacent switch tubes of the upper bridge arms and the lower bridge arms of the other two phases except the marked phase in the three-level NPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off.

[0056] In the specific implementation, the power topology design of the converter in the doubly fed generator system adopts a three-level NPC topology, such as Figure 11 As shown in the figure, the three-level NPC topology has a total of 12 switches. Each phase consists of four switches forming the upper and lower bridge arms. Each phase has two switches in the upper and lower bridge arms. The rotor of the doubly-fed generator is connected to the midpoint of the three-phase bridge arm of the two-level NPC topology, that is, connected between the upper and lower bridge arms. In practical applications, when the power topology of the converter in the doubly-fed generator system adopts the three-level NPC topology, the system has the following control strategy:

[0057] (1) Control the switch tubes of the upper bridge arms of the other two phases except the marked phase in the three-level NPC topology structure to be continuously turned on and the switch tubes of the lower bridge arms to be continuously turned off. Figure 11As shown, Tij represents the jth switch tube of the i-th phase, such as Ta1 represents the first switch tube of the bridge arm of phase A. The system controls the switch tubes Tij (i=a, b, c; j=1, 2) of the upper bridge arms of the three-level NPC topology structure A, B, and C phases except the marked phase to be continuously turned on, and the switch tubes Tij (i=a, b, c; j=3, 4) of the lower bridge arm to be continuously turned off.

[0058] (2) Control the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level NPC topology structure to be continuously turned on and the switch tubes of the upper bridge arm to be continuously turned off. Figure 11 As shown, the system controls the switch tubes Tij (i=a, b, c; j=3, 4) of the lower bridge arms of the three-phase A, B, and C of the three-level NPC topology structure except the marked phase to be continuously turned on, and the switch tubes Tij (i=a, b, c; j=1, 2) of the upper bridge arm to be continuously turned off.

[0059] (3) Control the adjacent switches of the upper bridge arm and the lower bridge arm of the other two phases in the three-level NPC topology structure except the marked phase to be continuously turned on, and all other switches are continuously turned off. Figure 11 As shown, the system controls the three-level NPC topology structure A, B, C three phases except the marked phase to keep the other two adjacent switch tubes Tij (i=a, b, c; j=2, 3) turned on continuously, and all other switch tubes are kept off.

[0060] In summary, the system adopts a three-level NPC topology with a total of three control strategies for the converter's power topology. Through these three control strategies, the rotor of the doubly fed generator can be short-circuited in three ways. Each of these short-circuit methods can release the overvoltage or overcurrent on the rotor side of the doubly fed generator, thereby protecting the converter equipment in the system.

[0061] In one embodiment, if Figure 5 As shown, the converter power topology is a three-level ANPC topology, and step S140 includes S1406 - S1412 .

[0062] S1406, controlling only one of the non-middle switch tubes of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off;

[0063] S1407, or controlling the non-middle switch tubes adjacent to the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off;

[0064] S1408, or controlling the switch tubes of the upper bridge arms adjacent to the lower bridge arms of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off;

[0065] S1409, or controlling the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off;

[0066] S1410, or controlling the middle switch tubes of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off;

[0067] S1411, or controlling the non-middle switch tubes adjacent to the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure and the middle switch tube of either the upper bridge arm or the lower bridge arm to be continuously turned on, and all other switch tubes to be continuously turned off;

[0068] S1412, or controlling the middle switch tubes of the upper bridge arm and the lower bridge arm of the remaining two phases except the marked phase in the three-level ANPC topology structure and at least one non-middle switch tube adjacent to the upper bridge arm and the lower bridge arm to be continuously turned on, and all other switch tubes to be continuously turned off.

[0069] In the specific implementation, the power topology design of the converter in the doubly fed generator system adopts a three-level ANPC topology, such as Figure 12 As shown in Figure 1, the three-level ANPC topology has a total of 18 switches. Each phase consists of 6 switches forming the upper and lower bridge arms. Each phase has 3 switches in both the upper and lower bridge arms, with one switch serving as the middle switch. The rotor of the doubly-fed generator is connected to the midpoint of the three-phase bridge arms of the three-level ANPC topology, that is, connected between the upper and lower bridge arms. In practical applications, when the power topology of the converter in the doubly-fed generator system adopts the three-level ANPC topology, the system has the following control strategy:

[0070] (1) Control the non-middle switch tube of only one of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes are continuously turned off. Figure 12 As shown, Tij represents the jth switch tube of the i-th phase, such as Ta1 represents the first switch tube of the A-phase bridge arm. The system controls the three-level ANPC topology structure A, B, and C phases, except the marked phase, so that only the non-middle switch tube Tij (i=a, b, c; j=1, 2 or j=3, 4) of the upper bridge arm and the lower bridge arm of the other two phases is continuously turned on, and all other switch tubes are continuously turned off.

[0071] (2) Control the non-middle switch tubes adjacent to the upper bridge arm and the lower bridge arm of the other two phases of the three-level ANPC topology structure except the marked phase to be continuously turned on, and all other switch tubes to be continuously turned off. Figure 2 As shown, Figure 12 As shown, the system controls the non-middle switch tubes Tij (i=a, b, c; j=2, 3) adjacent to the upper bridge arm and lower bridge arm of the other two phases of the three-level ANPC topology structure A, B, and C to be continuously turned on except for the marked phase, and all other switch tubes are continuously turned off.

[0072] (3) Control the switch tubes of the upper bridge arms of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off. Figure 12 As shown, the system controls the switch tubes Tij (i=a, b, c; j=2, 5) of the upper bridge arms adjacent to the lower bridge arms of the three-phase ANPC topology structure A, B, and C except the marked phase to be continuously turned on, and all other switch tubes are continuously turned off.

[0073] (4) Control the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off. Figure 12 As shown, the system controls the switch tubes Tij (i=a, b, c; j=3, 6) of the lower bridge arms adjacent to the upper bridge arms of the three-phase ANPC topology structure A, B, and C except the marked phase to be continuously turned on, and all other switch tubes are continuously turned off.

[0074] (5) Control the middle switches of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switches are continuously turned off. Figure 12 As shown, the system controls the middle switch tubes Tij (i=a, b, c; j=5, 6) of the upper bridge arm and the lower bridge arm of the three-phase ANPC topology structure A, B, and C except the marked phase to be continuously turned on, and all other switch tubes are continuously turned off.

[0075] (6) Control the non-middle switch tubes adjacent to the upper bridge arm and the lower bridge arm of the other two phases of the three-level ANPC topology structure except the marked phase and the middle switch tube of either the upper bridge arm or the lower bridge arm to be continuously turned on, and all other switch tubes to be continuously turned off. Figure 12As shown, the system controls the non-middle switch tubes Tij (i=a, b, c; j=2, 3) adjacent to the upper bridge arm and the lower bridge arm of the other two phases of the three-level ANPC topology structure A, B, and C except the marked phase, and the middle switch tube Tij (i=a, b, c; j=5 or j=6) in either the upper bridge arm or the lower bridge arm to be continuously turned on, and all other switch tubes are continuously turned off.

[0076] (7) Control the middle switch tubes of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure and at least one non-middle switch tube adjacent to the upper bridge arm and the lower bridge arm to be continuously turned on, and all other switch tubes to be continuously turned off. Figure 12 As shown, the system controls the middle switch tubes Tij (i=a, b, c; j=5, 6) of the upper bridge arm and the lower bridge arm of the other two phases of the three-level ANPC topology structure A, B, and C except the marked phase, and at least one non-middle switch tube Tij (i=a, b, c; j=2 or j=3 or j=2, 3) adjacent to the upper bridge arm and the lower bridge arm to be continuously turned on, and all other switch tubes are continuously turned off.

[0077] In summary, the system adopts a three-level ANPC topology with a total of 11 control strategies for the converter's power topology. Through these 11 control strategies, the rotor of the doubly-fed generator can have 11 short-circuit modes, each of which can release the energy of overvoltage or overcurrent on the rotor side of the doubly-fed generator, thereby achieving the purpose of protecting the converter equipment in the system.

[0078] In one embodiment, if Figure 6 As shown, the converter power topology is a three-level T-type topology, and step S140 includes S1413 - S1415 .

[0079] S1413, controlling the switch tubes of the upper bridge arms of the other two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and the switch tubes of the lower bridge arms to be continuously turned off;

[0080] S1414, or the switch tube of the lower bridge arm is continuously turned on, and the switch tube of the upper bridge arm is continuously turned off;

[0081] S1415, or the middle switch tube between the upper bridge arm and the lower bridge arm is continuously turned on, and all other switch tubes are continuously turned off.

[0082] In the specific implementation, the power topology design of the converter in the doubly fed generator system adopts a three-level T-type topology, such as Figure 13As shown in the figure, the three-level T-type topology has a total of 12 switches. Each phase is composed of two switches forming the upper and lower bridge arms. Each phase has one switch in the upper and lower bridge arms. Each phase has two intermediate switches connected in series. The rotor of the doubly-fed generator is connected to the midpoint of the three-phase bridge arms of the three-level T-type topology, that is, it is connected between the upper and lower bridge arms. In practical applications, when the power topology of the converter in the doubly-fed generator system adopts the three-level T-type topology, the system has the following control strategy:

[0083] (1) Control the switch tubes of the upper bridge arms of the other two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and the switch tubes of the lower bridge arms to be continuously turned off. Figure 13 As shown, Tij represents the jth switch tube of the i-th phase, such as Ta1 represents the first switch tube of the A-phase bridge arm. The system controls the switch tubes Tij (i=a, b, c; j=1) of the upper bridge arms of the other two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and the switch tubes Tij (i=a, b, c; j=2) of the lower bridge arm to be continuously turned off.

[0084] (2) Control the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and the switch tubes of the upper bridge arm to be continuously turned off. Figure 13 As shown, the system controls the switch tubes Tij (i=a, b, c; j=2) of the lower bridge arms of the other two phases in the three-level T-type topology structure except the marked phase to be continuously turned on, and the switch tubes Tij (i=a, b, c; j=1) of the upper bridge arm to be continuously turned off.

[0085] (3) Control the middle switches of the two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and all other switches to be continuously turned off. Figure 13 As shown, the system controls the intermediate switches Tij (i=a, b, c; j=3, 4) of the other two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and all other switches are continuously turned off.

[0086] In summary, the system adopts a three-level T-type topology with a total of three control strategies for the converter's power topology. Through these three control strategies, the three-phase rotor of the doubly-fed generator has three short-circuit modes. Each of these short-circuit modes can release the overvoltage or overcurrent on the rotor side of the doubly-fed generator, thereby achieving the purpose of protecting the converter equipment in the system.

[0087] In one embodiment, if Figure 14 As shown, after step S140, step S150 is also included.

[0088] S150 , obtaining the output current of the converter and releasing control of the switch tube of the power topology structure of the converter when the modulus of the output current of the converter is less than a first preset threshold.

[0089] In a specific implementation, after the system controls the on / off states of the switches of the two-phase bridge arms other than the marked phase in the converter power topology structure according to the control strategy, the rotor of the doubly-fed generator is short-circuited, and the energy of overvoltage or overcurrent on the rotor side is released by the corresponding switches of the two-phase bridge arms other than the marked phase in the converter power topology structure. After the fault of the grid-connected voltage drop is eliminated, the system needs to determine whether the energy on the rotor side of the doubly-fed generator has gradually returned to normal. Specifically, the system obtains the output current of the converter through a current detection circuit, compares the output current modulus of the converter with a first preset threshold set by the system, and releases control of the switches of the converter power topology structure when it is determined that the output current modulus of the converter is less than the first preset threshold, so that the converter system takes over control of the switches of the converter power topology structure normally, thereby achieving normal function.

[0090] In summary, the method of the present application detects the voltage drop on the grid-connected side of the doubly-fed generator system, obtains the instantaneous output current value of the three phases of the converter, marks the phase with the largest instantaneous output current value among the three phases of the converter, and records the mid-point potential of the bridge arm of the marked phase in the converter power topology structure. Then, part of the switch tubes of the bridge arms of the other two phases except the marked phase in the converter power topology structure are controlled to be turned on and the other part of the switch tubes are turned off, so that the mid-point potential of the bridge arms of the other two phases except the marked phase in the converter power topology structure is equal to the mid-point potential of the bridge arm of the marked phase, thereby realizing the short-circuiting of the doubly-fed generator rotor to replace the Crowbar function. When a voltage drop fault occurs in the power grid, the doubly-fed generator system can protect the converter without additional Crowbar equipment, making the overall structure of the system simpler and the system cost lower.

[0091] Figure 14 FIG. 2 is a schematic block diagram of a protection device 200 for a converter in a doubly-fed generator system according to an embodiment of the present invention. Figure 14 As shown, the present invention provides a protection device 200 for a converter in a doubly-fed generator system. The protection device 200 for a converter in a doubly-fed generator system includes a unit for executing the protection method for a converter in a doubly-fed generator system, and the device can be configured in a computer device.

[0092] Specifically, see Figure 14 The protection device 200 for the converter in the doubly-fed generator system includes: an acquisition unit 201, a marking unit 202, a first control unit 203 and a second control unit 204;

[0093] Among them, the acquisition unit 201 is used to obtain the instantaneous value of the output current of the three phases of the converter if a voltage drop is detected on the grid-connected side of the doubly fed generator system; the marking unit 202 is used to mark the phase with the largest instantaneous output current among the three phases of the converter, and record the mid-point potential of the bridge arm of the marked phase in the power topology structure of the converter; the first control unit 203 controls all the switch tubes of the bridge arms of the other two phases except the marked phase in the power topology structure of the converter to be turned off; the second control unit 204 controls a part of the switch tubes of the bridge arms of the other two phases except the marked phase in the power topology structure of the converter to be turned on and another part of the switch tubes to be turned off, so that the mid-point potential of the bridge arms of the other two phases except the marked phase of the converter power topology structure is equal to the mid-point potential of the bridge arm of the marked phase.

[0094] The protection device 200 for the converter in the doubly-fed generator system can be implemented in the form of a computer program. The computer program can be used in Figure 15 Runs on the computer device shown.

[0095] See also Figure 15 , Figure 15 5 is a schematic block diagram of a computer device provided in an embodiment of the present application. The computer device 500 may be a terminal.

[0096] See Figure 15 The computer device 500 includes a processor 502 , a memory, and a network interface 505 connected via a system bus 501 , wherein the memory may include a non-volatile storage medium 503 and an internal memory 504 .

[0097] The non-volatile storage medium 503 can store an operating system 5031 and a computer program 5032. The computer program 5032 includes program instructions, which, when executed, can enable the processor 502 to execute a method for protecting a converter in a doubly-fed electric machine system.

[0098] The processor 502 is used to provide computing and control capabilities to support the operation of the entire computer device 500.

[0099] The internal memory 504 provides an environment for the operation of the computer program 5032 in the non-volatile storage medium 503. When the computer program 5032 is executed by the processor 502, the processor 502 can execute a method for protecting a converter in a doubly-fed generator system.

[0100] The network interface 505 is used to communicate with other devices through the network. Figure 15The structure shown in the figure is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device 500 to which the solution of the present application is applied. The specific computer device 500 may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0101] The processor 502 is configured to run a computer program 5032 stored in the memory to implement the steps of the above method.

[0102] It should be understood that in the embodiment of the present application, the processor 502 may be a central processing unit (CPU), and the processor 502 may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0103] Those skilled in the art will appreciate that all or part of the steps in the method of the above-described embodiment can be implemented by instructing the relevant hardware through a computer program. The computer program includes program instructions, which can be stored in a storage medium that is computer-readable. The program instructions are executed by at least one processor in the computer system to implement the steps in the method of the above-described embodiment.

[0104] Therefore, the present invention also provides a storage medium. The storage medium may be a computer-readable storage medium. The storage medium stores a computer program, wherein the computer program includes program instructions. When the program instructions are executed by a processor, the processor performs the steps of the above method.

[0105] The storage medium may be any computer-readable storage medium that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a magnetic disk, or an optical disk.

[0106] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the composition and steps of each example according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0107] In the several embodiments provided herein, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the various units is merely a logical functional division, and actual implementation may employ other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be omitted or not implemented.

[0108] The steps in the methods of the embodiments of the present invention may be adjusted in order, combined, or deleted as needed. The units in the devices of the embodiments of the present invention may be combined, divided, or deleted as needed. Furthermore, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit.

[0109] If this integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes a number of instructions for causing a computer device to execute all or part of the steps of the method described in various embodiments of the present invention.

[0110] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0111] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, to the extent such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to encompass such changes and modifications.

[0112] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for protecting a converter in a doubly-fed motor system, characterized in that: The method comprises: If a voltage drop is detected on the grid-connected side of the doubly-fed generator system, the instantaneous output current values of the three phases of the converter are obtained; Marking the phase with the largest instantaneous output current value among the three phases of the converter, and recording the midpoint potential of the bridge arm of the marked phase in the power topology structure of the converter; Controlling all the switch tubes of the bridge arms of the two phases other than the marked phase in the power topology structure of the converter to turn off; Control a part of the switch tubes in the bridge arms of the two phases other than the marked phase in the converter power topology structure to be turned on and another part of the switch tubes to be turned off, so that the midpoint potential of the bridge arms of the two phases other than the marked phase in the converter power topology structure is equal to the midpoint potential of the bridge arm of the marked phase.

2. The method according to claim 1, characterized in that The converter power topology is a two-level topology, and controlling a portion of the switch tubes in the bridge arms of the two phases other than the marked phase in the converter power topology to be turned on and another portion of the switch tubes to be turned off includes: Controlling the switch tubes of the upper bridge arms of the other two phases except the marked phase in the two-level topology structure to be continuously turned on and the switch tubes of the lower bridge arms to be continuously turned off; Or the switch tubes of the lower bridge arms of the other two phases except the marked phase in the two-level topology structure are controlled to be continuously turned on, and the switch tubes of the upper bridge arms are controlled to be continuously turned off.

3. The method according to claim 1, characterized in that The converter power topology is a three-level NPC topology, and controlling a portion of the switch tubes in the bridge arms of two phases other than the marked phase in the converter power topology to be turned on and another portion of the switch tubes to be turned off includes: Controlling the switch tubes of the upper bridge arms of the other two phases except the marked phase in the three-level NPC topology structure to be continuously turned on and the switch tubes of the lower bridge arms to be continuously turned off; Or controlling the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level NPC topology structure to be continuously turned on and the switch tubes of the upper bridge arms to be continuously turned off; Or, in the three-level NPC topology structure, the adjacent switch tubes of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase are controlled to be continuously turned on, and all other switch tubes are continuously turned off.

4. The method according to claim 1, wherein The converter power topology is a three-level ANPC topology, and controlling a portion of the switch tubes in the bridge arms of two phases other than the marked phase in the converter power topology to be turned on and another portion of the switch tubes to be turned off includes: Controlling the non-middle switch tube of only one of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off; or controlling the non-middle switch tubes adjacent to the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off; or controlling the switch tubes of the upper bridge arms adjacent to the lower bridge arms of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off; or controlling the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off; or controlling the middle switches of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure to be continuously turned on, and all other switch tubes to be continuously turned off; or controlling the non-middle switch tubes adjacent to the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure and the middle switch tube of either the upper bridge arm or the lower bridge arm to be continuously turned on, and all other switch tubes to be continuously turned off; Or the middle switch tubes of the upper bridge arm and the lower bridge arm of the other two phases except the marked phase in the three-level ANPC topology structure and at least one non-middle switch tube adjacent to the upper bridge arm and the lower bridge arm are controlled to be continuously turned on, and all other switch tubes are continuously turned off.

5. The method according to claim 1, wherein The converter power topology is a three-level T-type topology, and controlling a portion of the switch tubes in the bridge arms of two phases other than the marked phase in the converter power topology to be turned on and another portion of the switch tubes to be turned off includes: Controlling the switch tubes of the upper bridge arms of the other two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and the switch tubes of the lower bridge arms to be continuously turned off; or controlling the switch tubes of the lower bridge arms of the other two phases except the marked phase in the three-level T-type topology structure to be continuously turned on, and the switch tubes of the upper bridge arms to be continuously turned off; Or the middle switch tubes of the other two phases except the marked phase in the three-level T-type topology structure are controlled to be continuously turned on, and all other switch tubes are controlled to be continuously turned off.

6. The method according to any one of claims 1 to 5, characterized in that After controlling all the switch tubes of the bridge arms of the two phases other than the marked phase in the converter power topology structure to turn off, the method further includes: The delay is performed with a first time, where the first time is greater than the switch dead time of the switch tube.

7. The method according to any one of claims 1 to 5, characterized in that After controlling a portion of the switch tubes in the bridge arms of the two phases other than the marked phase in the converter power topology structure to be turned on and another portion of the switch tubes to be turned off so that the midpoint potentials of the bridge arms of the two phases other than the marked phase in the converter power topology structure are equal to the midpoint potential of the bridge arm of the marked phase, the method further includes: The output current of the converter is obtained and, when a modulus of the output current of the converter is less than a first preset threshold, control of the switch tube of the power topology structure of the converter is released.

8. A protection device for a converter in a doubly-fed generator system, characterized in that: The apparatus comprises means for executing the method according to any one of claims 1 to 7.

9. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and the processor implements the method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the computer program can implement the method according to any one of claims 1 to 7.

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