Current-limiting energy consumption and reactive compensation integrated crowbar circuit and control method thereof

Abstract

The invention discloses a crowbar circuit integrating current-limiting energy consumption and reactive compensation and a control method thereof, and belongs to the technical field of wind power generation grid-connected protection and low voltage ride through (LVRT). The circuit comprises a current-limiting branch which is formed by connecting a magnetically controlled reactor and a current-limiting resistor in parallel and is used for realizing a current-limiting function; the energy dissipation branch consists of a main energy dissipation resistor, is connected behind the current limiting branch and is used for absorbing excess energy on the rotor side; the capacitor reactive power compensation branch is connected with a capacitor behind the main energy consumption resistor and is used for providing short-time reactive power compensation during a fault period; the trigger control device comprises a fault detection module, a voltage / current sampling unit and a switch tube IGBT (Insulated Gate Bipolar Translator) trigger unit; the LCL filter is used for suppressing high-frequency harmonic waves, current impact and peak interference generated by switching operation so as to improve the electric energy quality of the system, protect equipment safety and ensure smooth operation of the system in the fault ride-through period; and the controller is used for realizing multi-stage response strategy control based on rotor current and stator voltage change.

Description

Technical Field

[0001] This invention relates to the field of wind power grid-connected protection and low voltage ride-through (LVRT) technology, specifically to a crowbar circuit and its control method that integrates current limiting, energy consumption and reactive power compensation. Background Technology

[0002] With the rapid growth of new energy installed capacity, the large-scale grid connection of wind turbines has placed higher demands on the safe and stable operation of the power grid. Doubly-Fed Induction Generators (DFIGs) are widely used in modern wind farms due to their variable speed, constant frequency, and high energy conversion efficiency. However, because the stator of a DFIG is directly connected to the grid, when the grid experiences voltage drops, surges, or short circuits, voltage disturbances are rapidly transmitted to the rotor side via electromagnetic coupling, causing sudden changes in rotor voltage and a surge in current. This can easily cause overcurrent surges or even damage to the rotor-side converter (RSC).

[0003] Therefore, wind power systems commonly incorporate Crowbar protection circuits to forcibly bypass the RSC (Reverse Current Conversion) from the rotor circuit during a fault. This involves using an external high-power resistor to redirect the rotor current into an energy dissipation branch, thus protecting the RSC. Traditional Crowbar circuits are relatively simple in structure, typically using a silicon controlled rectifier (SCR) or IGBT as a trigger switch, connected in series with a set of high-power resistors of fixed resistance. When the voltage drops above a set threshold, the circuit quickly conducts, disconnecting the rotor windings from the converter and forming a closed loop to dissipate the fault current. This structure is widely used in 1.5MW to 2.5MW wind turbine units due to its fast response and low cost.

[0004] In recent years, some research has attempted to improve the Crowbar structure, such as by employing multi-stage resistance switching and improving control strategies to enhance its dynamic performance. However, substantial structural innovation remains relatively limited, and the needs of the Crowbar in areas such as flexible current limiting, reactive power compensation, and system coordination have not yet been fully addressed. Therefore, there is an urgent need for a new type of Crowbar module with structural adjustability and intelligent control response capabilities. This module should not only effectively protect the RSC from fault impacts but also provide basic reactive power compensation capabilities during fault periods to meet the operation and ride-through requirements of wind turbines under complex grid conditions. Summary of the Invention

[0005] 1. The technical problem to be solved by the present invention

[0006] The purpose of this invention is to propose a crowbar circuit and its control method that integrates current limiting, energy dissipation, and reactive power compensation to solve the following problems existing in the prior art:

[0007] 1. Fixed current limiting capacity, lacking flexible adjustment function.

[0008] Traditional crowbar circuits typically use fixed-value resistors as current-limiting and energy-dissipating components, which cannot flexibly adjust the response strategy according to the fault intensity or the level of power grid disturbance, and there is a risk of insufficient or excessive protection.

[0009] 2. Lacks grid-connected reactive power compensation capability.

[0010] During crowbar circuit operation, the rotor-side converter (RSC) is short-circuited, the DFIG system loses its ability to control reactive power output, cannot help maintain grid voltage stability, and affects the system's low-voltage ride-through performance.

[0011] 3. Energy dissipation is concentrated in the resistance, resulting in high thermal stress and poor reliability.

[0012] All rotor feedback energy is concentrated and absorbed by resistors, which can easily cause instantaneous high temperature, thermal shock and resistor aging. Especially when multiple faults occur frequently, the devices are easily damaged and the maintenance cost is high.

[0013] 4. The control method is rigid and lacks a dynamic coordination mechanism.

[0014] Traditional Crowbar circuits mostly use threshold triggering and fixed delay exit, and the response process is rigid switching, which cannot achieve soft start, soft exit and coordinated adjustment with system control strategy, and is prone to voltage fluctuation or power jump.

[0015] 2. Technical Solution

[0016] To achieve the above objectives, the present invention provides the following technical solution:

[0017] This invention proposes a crowbar circuit integrating current limiting, energy dissipation, and reactive power compensation, applied to a doubly-fed induction generator (DFIG) system. When grid voltage dips occur, it provides triple functions of current limiting, energy dissipation, and reactive power compensation to ensure stable system operation; specifically including:

[0018] Current limiting branch: It consists of a magnetically controlled reactor (MCR) connected in parallel with a current limiting resistor R1, and is used to achieve the current limiting function;

[0019] Energy dissipation branch: Composed of the main energy dissipation resistor R2, connected after the current limiting branch, used to absorb excess energy on the rotor side;

[0020] Capacitor reactive power compensation branch: Capacitor C1 is connected after the main energy-consuming resistor R2 to provide short-term reactive power compensation during faults.

[0021] Trigger control device: including fault detection module, voltage / current sampling unit, and IGBT triggering unit;

[0022] LCL filters are used to suppress high-frequency harmonics, current surges, and spike interference generated by switching operations, thereby improving system power quality, protecting equipment safety, and ensuring smooth system operation during fault ride-through.

[0023] Controller: Used to implement multi-level response strategy control based on changes in rotor current and stator voltage.

[0024] Preferably, the crowbar circuit is connected in parallel with the rotor winding of the doubly fed induction generator (DFIG). When the grid voltage drops, the controller triggers the action to quickly introduce the rotor current into the crowbar circuit. The crowbar circuit first consists of a parallel branch formed by a magnetically controlled reactor and a current-limiting resistor to flexibly adjust the impedance according to the fault level. Then, the current releases energy through the main energy-consuming resistor. Finally, the capacitor provides short-term reactive power output to support the system voltage.

[0025] A control method for a crowbar circuit integrating current limiting, energy dissipation, and reactive power compensation includes the following:

[0026] Initialize the monitoring module, sample the grid voltage, and determine if a fault has occurred;

[0027] During normal operation, the crowbar circuit is in a non-conducting state, and the rotor windings transmit power normally through the rotor side converter (RSC). The crowbar circuit is short-circuited.

[0028] When a fault occurs (such as a sudden voltage drop), the fault detection module determines that the stator voltage drop exceeds the set threshold and immediately triggers the crowbar circuit to conduct.

[0029] Current limiting stage: The magnetically controlled reactor (MCR) is initially set to a large reactance value, which, together with the current limiting resistor R1, limits the peak value of the incoming rotor current;

[0030] Energy consumption stage: Current enters the main energy consumption resistor R2, releasing the excess energy fed back by the rotor in the form of heat;

[0031] Support phase: Capacitor C1 after the main energy-consuming resistor R2 provides reactive current injection for a short time to maintain system voltage support and slow down further voltage drop;

[0032] Exit Phase: Once the voltage returns to normal, the controller smoothly shuts down the crowbar circuit and resumes rotor-side converter (RSC) control to avoid system oscillations caused by hard switching.

[0033] Preferably, the current-limiting branch achieves flexible current limiting through a magnetically controlled reactor (MCR). The reactance value of the MCR is controlled by the magnetic excitation winding. By adjusting the magnetic excitation current, the magnetic saturation state of the iron core is affected, thereby achieving dynamic adjustment of the equivalent reactance of the main winding.

[0034] Preferably, the current-limiting branch achieves rotor-side instantaneous overcurrent suppression by shunting the current through a magnetically controlled reactor and a current-limiting resistor R1; assuming the total rotor current is I... rsc Then, when the current flows through the magnetically controlled reactor (MCR) and the current-limiting resistor R1, the current shunt formula is:

[0035] I rsc =I MCR +I R1

[0036] According to the impedance shunting law, we can obtain:

[0037]

[0038] Among them, Z MCR Z represents the impedance of the magnetically controlled reactor (MCR); R1 The impedance of the current-limiting resistor R1 is given.

[0039] Preferably, when the current-limiting branch is operating under current-limiting conditions, the controller sets the excitation current of the magnetically controlled reactor (MCR) to "minimum value → maximum reactance → most of the current flows to the current-limiting resistor R1 → rapid peak shaving and current limiting" to prevent surges. After the fault enters the stable phase, the excitation current is increased, the reactance of the magnetically controlled reactor (MCR) is reduced, and more current is gradually guided into the magnetically controlled reactor (MCR) branch to reduce the thermal load on the current-limiting resistor R1.

[0040] Preferably, the main energy-consuming resistor R2 is a segmented high-power resistor that absorbs rotor feedback energy in a time-sharing / stage-based manner.

[0041] Preferably, the control process of the magnetically controlled reactor (MCR) includes the following:

[0042] The magnitude of the rotor current is detected, and the fault level is determined based on the sampled rotor current.

[0043] The thyristor conduction angle of the magnetically controlled reactor (MCR) is determined according to the fault level, and the initial excitation current is set to put the MCR in the maximum reactance state to achieve strong current limiting.

[0044] The controller dynamically adjusts the excitation current according to the fault level:

[0045] If the fault is minor, gradually increase the excitation current to reduce the reactance, guide more current to flow through the magnetically controlled reactor (MCR) branch, and reduce the burden on the current-limiting resistor R1; if the fault is severe, maintain low excitation to maintain high reactance and enhance the current-limiting effect; the above process can be achieved through graded control or continuous adjustment.

[0046] After the fault is cleared, the controller gradually reduces the excitation current and smoothly increases the reactance value, causing the current in the crowbar circuit to decrease naturally. Eventually, the crowbar circuit is disengaged, and the system returns to normal RSC control.

[0047] 3. Beneficial effects

[0048] (1) This invention introduces a magnetically controlled reactor (MCR) connected in parallel with a current-limiting resistor to form a flexible current-limiting branch, so that the reactance value can be adjusted as needed to meet the current-limiting requirements under different levels of grid faults; a capacitor is connected in series in the main energy-consuming branch of the crowbar circuit to provide short-term reactive power compensation during faults, so as to make up for the problem of system power loss after the rotor-side converter (RSC) leaves the control.

[0049] The multi-branch collaborative structure and soft access / exit control logic design, including a dynamic collaborative operation mechanism of current limiting, energy consumption, and reactive power compensation, improves power quality and system recovery capability.

[0050] (2) Compared with existing technologies, traditional crowbar circuits typically use a fixed resistor series structure as the only energy dissipation path. The current limiting capability is determined by the fixed resistor value, which cannot adapt to current changes under different fault levels, nor can it provide voltage support capability. Moreover, the control method is mostly hard switching, which can easily cause system voltage flicker during the exit process. In contrast, the present invention uses a combined design of "MCR∥R1→R2→C1" to physically decouple the current limiting, energy dissipation and support functions and coordinate the control. In particular, the introduction of the magnetically controlled reactor gives the crowbar circuit a flexible response capability, overcoming the disadvantages of fixed reactor and rigid current limiting in traditional circuits. The addition of the capacitor gives the crowbar circuit a certain degree of reactive power compensation capability, which is a substantial expansion of the functional boundaries of traditional crowbar circuits.

[0051] (3) This invention organically integrates the three functions of current limiting, energy consumption, and support into a collaborative structure, and combines soft-start and soft-exit control strategies to significantly improve the smoothness of fault response and system power quality, avoiding voltage fluctuations and power surges caused by hard switching in traditional Crowbars. These improvements are all based on the composite optimization of structural design and control logic, and have good practicality and engineering promotion value.

[0052] In summary, the technological innovation of this invention is not only reflected in the structural improvement, but also in the breakthrough of the traditional "rigid-passive-single-function" mode of Crowbar response. It constructs an intelligent Crowbar protection module that combines "flexibility-active-multi-function", which has strong novelty and practicality and is suitable for the low voltage ride-through protection requirements of modern wind power systems. Attached Figure Description

[0053] Figure 1 This is a circuit diagram of the crowbar circuit that integrates current limiting, energy dissipation, and reactive power compensation proposed in this invention.

[0054] Figure 2 This is a structural diagram of the LCL filter proposed in Embodiment 1 of the present invention;

[0055] Figure 3 The circuit diagram of the MCR proposed in Embodiment 1 of the present invention is shown below;

[0056] Figure 4 This is the control block diagram of the Crowbar circuit proposed in Embodiment 1 of the present invention;

[0057] Figure 5 This is a control flowchart of the magnetically controlled reactor (MCR) proposed in Embodiment 1 of the present invention;

[0058] Figure 6 The structural device diagram and corresponding circuit diagram proposed in embodiment 1 of the present invention are shown. Detailed Implementation

[0059] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0060] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0061] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0062] Example 1:

[0063] This invention proposes a crowbar circuit and its control method that integrates current limiting energy consumption and reactive power compensation. The core technology lies in introducing an adjustable reactance and capacitor reactive power compensation mechanism, reconstructing the response logic and structure of the traditional crowbar circuit to improve the ride-through capability and system stability of the DFIG under grid fault conditions. Specifically, it includes the following:

[0064] 1. System structure composition (e.g.) Figure 1 (As shown)

[0065] (1) Current-limiting branch: Consists of a magnetically controlled reactor (MCR) connected in parallel with a current-limiting resistor R1, used to achieve flexible current-limiting function; the circuit diagram of the magnetically controlled reactor (MCR) is shown below. Figure 2 As shown;

[0066] (2) Energy dissipation branch: It is composed of the main energy dissipation resistor R2 and is connected after the current limiting branch to absorb excess energy on the rotor side.

[0067] (3) Capacitor reactive power compensation branch: A capacitor C1 is connected after the main energy-consuming resistor R2 to provide short-term reactive power compensation during faults.

[0068] (4) Trigger control device: including fault detection module, voltage / current sampling unit, and IGBT triggering unit;

[0069] (5) LCL filter (e.g.) Figure 3 (As shown): Used to suppress high-frequency harmonics, current surges and spike interference generated by switching operations, thereby improving system power quality, protecting equipment safety and ensuring smooth system operation during fault ride-through;

[0070] (6) Controller: Implements multi-level response strategy control based on changes in rotor current and stator voltage.

[0071] 2. Circuit Topology Description

[0072] Structurally, the flexible Crowbar module is connected in parallel with the rotor winding of the DFIG. When the grid voltage drops, the controller triggers an action to quickly redirect the rotor current into the Crowbar module. Internally, the module first consists of a parallel branch formed by a magnetically controlled reactor and a current-limiting resistor, which flexibly adjusts the impedance according to the fault level. Then, the current releases energy through the main energy-dissipating resistor. Finally, the capacitor provides short-term reactive power output to support the system voltage.

[0073] This structure enables the division of labor and coordination between current limiting, energy consumption and reactive power compensation, which greatly improves the flexibility of Crowbar response and system compatibility.

[0074] 3. Work Process Description

[0075] The following explains the working principle of this module under different operating conditions:

[0076] (1) During normal operation, the Crowbar is in a non-conducting state, the rotor winding transmits power normally through the converter RSC, and the Crowbar module is short-circuited.

[0077] (2) When a fault occurs (such as a sudden voltage drop), the fault detection module determines that the stator voltage drop exceeds the set threshold and immediately triggers the Crowbar to turn on.

[0078] (3) Current limiting stage: The magnetically controlled reactor (MCR) is initially set to a large reactance value, which together with the current limiting resistor R1 limits the peak value of the incoming rotor current;

[0079] (4) Energy consumption stage: Current enters the main energy consumption resistor R2, releasing the excess energy fed back by the rotor in the form of heat;

[0080] (5) Support stage: Capacitor C1 after the main energy-consuming resistor R2 provides reactive current injection for a short time to maintain system voltage support and slow down further voltage drop;

[0081] (6) Exit phase: When the voltage returns to normal, the controller smoothly shuts down the Crowbar circuit and resumes RSC control to avoid system oscillation caused by hard switching.

[0082] 4. Technical Function Implementation Methods

[0083] (1) Flexible current limiting - The reactance value of the magnetically controlled reactor (MCR) is controlled by the excitation winding. By adjusting the excitation current, the magnetic saturation state of the iron core is affected, thereby realizing the dynamic adjustment of the equivalent reactance of the main winding. This reactance determines the current limiting capability of the main branch. Therefore, the magnetically controlled reactor (MCR) indirectly realizes the precise control of the Crowbar current by adjusting the excitation current, and is the core device of flexible current limiting.

[0084] (2) Instantaneous overcurrent suppression – Using a current-limiting resistor R1 connected in parallel with a magnetically controlled reactor (MCR) to shunt the current and control the instantaneous rotor current. Let the total rotor current be: I rsc Then, when the current flows through the current-limiting resistor R1 and the magnetically controlled reactor (MCR), the current shunting formula can be obtained:

[0085] I rsc =I MCR +I R1

[0086] According to the impedance shunting law:

[0087]

[0088] Among them, ZMCR Z represents the impedance of the magnetically controlled reactor (MCR); R1 The impedance of the current-limiting resistor R1 is given.

[0089] Initially, to prevent surges, the controller sets the excitation current of the magnetically controlled reactor (MCR) to "minimum value → maximum reactance → most current flows to the current-limiting resistor R1 → rapid peak shaving and current limiting." After the fault stabilizes, the excitation current is increased, reducing the reactance of the MCR and gradually guiding more current into the MCR branch, thereby reducing the thermal load on the current-limiting resistor R1. This achieves dynamic sharing and transition of current limiting.

[0090] For minor grid voltage dips caused by faults, the magnetically controlled reactor (MCR) provides partial current limiting. For severe grid voltage dips, the MCR reaches full flux saturation, resulting in extremely high reactance, and the main current limiting is provided by the current-limiting resistor R1. Furthermore, the controller dynamically adjusts the excitation current of the MCR based on real-time sampled stator voltage, rotor current, RSC status, and other signals. This changes the reactance value of the MCR accordingly, giving the overall current limiting response "dynamic flexibility."

[0091] (3) Multi-stage energy dissipation - The main energy dissipation resistor R2 is a segmented high-power resistor, which absorbs rotor feedback energy in a time-sharing / stage-based manner.

[0092] (4) Reactive power compensation - Capacitor C1 provides reactive power compensation to make up for the reactive power when RSC fails.

[0093] (5) Anti-interference and filtering: The LCL filter filters out high-frequency spikes when the Crowbar is put into operation, thereby improving grid connection stability.

[0094] (6) The coordinated control controller for entry and exit determines system state changes and realizes soft entry and soft exit.

[0095] 5. Control Strategy Flowchart Explanation

[0096] (1) Crowbar circuit control process as follows Figure 4 As shown:

[0097] 1) Initialize the monitoring module, sample the grid voltage in real time, and determine whether a fault has occurred;

[0098] 2) If the voltage drop exceeds the set threshold, the Crowbar circuit is activated (controlling the magnetically controlled reactor (MCR) to set the initial reactance value to achieve current limiting; turning on the main energy-consuming resistor R2 to release fault energy; and simultaneously connecting the capacitor to provide short-term reactive power compensation).

[0099] 3) If the voltage recovers, the fault is considered resolved, and the Crowbar is disconnected in stages.

[0100] (2) Control flow of a magnetically controlled reactor (MCR) is as follows: Figure 5 As shown, where I ex Z is the excitation current. MCR The impedance of the magnetically controlled reactor (MCR):

[0101] 1) First, the rotor current is detected, and the fault level is determined based on the sampled rotor current. Then, the thyristor conduction angle of the magnetically controlled reactor (MCR) is determined according to the fault level, and the initial excitation current is set to put the MCR in maximum reactance state to achieve strong current limiting. Subsequently, the controller dynamically adjusts the excitation current according to the fault level: if the fault is minor, the excitation current is gradually increased to reduce reactance, guiding more current to flow through the MCR branch and reducing the burden on the current-limiting resistor R1; if the fault is severe, low excitation is maintained to preserve high reactance, thereby enhancing the current-limiting effect. The entire process can be achieved through graded control or continuous adjustment.

[0102] 2) After the fault is cleared, the controller gradually reduces the excitation current and smoothly increases the reactance value, causing the Crowbar branch current to decrease naturally. Finally, the Crowbar branch is deactivated, and the system returns to normal RSC control. This strategy achieves flexible current limiting and smooth transition, significantly improving the system's fault response capability and operational stability.

[0103] 6. System Device Description

[0104] Please see Figure 6 The hardware modules of this system can be integrated into existing wind turbine control cabinets, and its main components are as follows:

[0105] Electromagnetic parameter reconstruction module: Magnetic control reactor (MCR) + excitation control power supply;

[0106] Energy consumption module: current-limiting resistor R1, main energy-consuming resistor R2 and its heat dissipation unit;

[0107] Reactive power compensation module: capacitor C1 array, supporting rapid connection;

[0108] Fault detection and control module: used to monitor voltage / current changes and output switching control commands in real time;

[0109] Filter module: LCL structure filter unit, connected to the main current path;

[0110] Communication and protection interfaces: work in conjunction with the wind turbine main control system to ensure operational safety.

[0111] Example 2:

[0112] Based on Embodiment 1, but differing in that the present invention has the following advantages:

[0113] 1. Feasibility Description: The flexible Crowbar hardware module proposed in this invention has a solid engineering foundation. All components (magnetically controlled reactor, resistor, capacitor, switching device, controller, etc.) are currently common and mature components used in the wind power field, with a clear industrialization implementation path, and can be deployed compatiblely with existing DFIG systems.

[0114] 2. No limitation on specific implementation forms: The structures, connections and functional implementation methods described in this specification are only preferred embodiments. Those skilled in the art can make equivalent substitutions or adjustments to the structural details without departing from the core concept of this invention. The scope of protection of this invention shall be determined by the claims.

[0115] 3. Scalability and compatibility: This invention is applicable to doubly fed wind turbines of various capacity levels, and can also be extended to other types of variable speed constant frequency power generation systems that require current limiting protection and reactive power compensation functions.

[0116] In summary, compared to traditional Crowbar circuits, this invention offers greater structural flexibility, control flexibility, and grid adaptability. Regarding current limiting strategies, by introducing a magnetically controlled reactor (MCR) in parallel with the current-limiting resistor to form a current-limiting branch, dynamic adjustment of fault current can be achieved. This overcomes the shortcomings of traditional Crowbars, such as fixed current limiting capacity and rigid response, and allows for flexible responses to different levels of grid disturbances. The capacitor connected after the main energy-consuming resistor can also provide short-term reactive power compensation during the rotor-side converter (RSC) out-of-control period, helping to stabilize system voltage and improve the unit's low-voltage ride-through (LVRT) capability—a function that traditional Crowbars cannot provide.

[0117] Furthermore, this invention organically integrates current limiting, energy dissipation, and support functions into a synergistic structure, and combines soft-start and soft-stop control strategies to significantly improve the smoothness of fault response and system power quality, avoiding voltage fluctuations and power surges caused by hard switching in traditional Crowbars. These improvements are all based on the composite optimization of structural design and control logic, possessing good practicality and engineering application value.

[0118] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A crowbar circuit integrating current limiting, energy dissipation, and reactive power compensation, characterized in that: include: Current limiting branch: It consists of a magnetically controlled reactor and a current-limiting resistor connected in parallel, and is used to achieve the current limiting function; Energy dissipation branch: Composed of the main energy dissipation resistor, connected after the current limiting branch, used to absorb excess energy on the rotor side; Capacitor reactive power compensation branch: A capacitor is connected after the main energy-consuming resistor to provide short-term reactive power compensation during faults. Trigger control device: including fault detection module, voltage / current sampling unit, and IGBT triggering unit; LCL filters are used to suppress high-frequency harmonics, current surges, and spike interference generated by switching operations, thereby improving system power quality, protecting equipment safety, and ensuring smooth system operation during fault ride-through. Controller: Used to implement multi-level response strategy control based on changes in rotor current and stator voltage.

2. The crowbar circuit according to claim 1, characterized in that, The crowbar circuit is connected in parallel with the rotor winding of the doubly fed induction generator. When the grid voltage drops, the controller triggers the action to quickly introduce the rotor current into the crowbar circuit. The crowbar circuit first consists of a parallel branch composed of a magnetically controlled reactor and a current-limiting resistor to achieve flexible impedance adjustment according to the fault level. Then, the current releases energy through the main energy-consuming resistor. Finally, the capacitor provides short-term reactive power output to support the system voltage.

3. The control method for the crowbar circuit integrating current limiting, energy consumption reduction, and reactive power compensation as described in any one of claims 1-2, characterized in that, Includes the following: Initialize the monitoring module, sample the grid voltage, and determine if a fault has occurred; During normal operation, the crowbar circuit is in a non-conducting state, the rotor winding transmits power normally through the rotor-side converter, and the crowbar circuit is short-circuited. When a fault occurs, the fault detection module determines that the stator voltage drop exceeds the set threshold and immediately triggers the crowbar circuit to conduct. Current limiting phase: The magnetically controlled reactor is initially set to a large reactance value, which, together with the current limiting resistor, limits the peak value of the incoming rotor current; Energy consumption stage: Current enters the main energy consumption resistor, releasing the excess energy fed back by the rotor in the form of heat; Support phase: The capacitor after the main energy-consuming resistor provides reactive current injection for a short time to maintain system voltage support and slow down further voltage drop; Exit Phase: Once the voltage returns to normal, the controller smoothly shuts down the crowbar circuit and resumes rotor-side converter control to avoid system oscillations caused by hard switching.

4. The control method according to claim 3, characterized in that, The current-limiting branch achieves flexible current limiting through a magnetically controlled reactor. The reactance value of the magnetically controlled reactor is controlled by the magnetic excitation winding. By adjusting the magnetic excitation current, the magnetic saturation state of the iron core is affected, thereby achieving dynamic adjustment of the equivalent reactance of the main winding.

5. The control method according to claim 4, characterized in that, The current-limiting branch achieves instantaneous overcurrent suppression on the rotor side by shunting the current through a magnetically controlled reactor and a current-limiting resistor connected in parallel; assuming the total rotor current is I... rsc Then, when the current flows through the magnetically controlled reactor and the current-limiting resistor, the current shunt formula is: I rsc =I MCR +I R1 According to the impedance shunting law, we can obtain: Where MCR represents a magnetically controlled reactor; Z MCR R1 represents the impedance of the magnetically controlled reactor; Z represents the current-limiting resistor. R1 The impedance of the current-limiting resistor.

6. The control method according to claim 5, characterized in that, When the current-limiting branch is in current-limiting operation, the controller sets the excitation current of the magnetically controlled reactor to "minimum value → maximum reactance → most of the current flows to the current-limiting resistor R1 → rapid peak shaving and current limiting" to prevent surges; after the fault enters the stable stage, the excitation current is increased, the reactance of the magnetically controlled reactor is reduced, and more current is gradually guided into the magnetically controlled reactor branch to reduce the thermal load of the current-limiting resistor R1.

7. The control method according to claim 3, characterized in that, The main energy-consuming resistor is a segmented high-power resistor, which absorbs rotor feedback energy in a time-sharing / stage-based manner.

8. The control method according to claim 3, characterized in that, The control process of the magnetically controlled reactor includes the following: The magnitude of the rotor current is detected, and the fault level is determined based on the sampled rotor current. The conduction angle of the thyristor of the magnetically controlled reactor is determined according to the fault level, and the initial excitation current is set to put the magnetically controlled reactor in the maximum reactance state to achieve strong current limiting. The controller dynamically adjusts the excitation current according to the fault level: If the fault is minor, gradually increase the excitation current to reduce the reactance, guide more current to flow through the magnetically controlled reactor branch, and reduce the burden on the current limiting resistor; If the fault is severe, maintain low excitation to preserve high reactance and enhance the current limiting effect; the above process can be achieved through graded control or continuous adjustment. After the fault is cleared, the controller gradually reduces the excitation current and smoothly increases the reactance value, causing the current in the crowbar circuit to decrease naturally. Finally, the crowbar circuit is disengaged, and the system returns to normal RSC control.

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