A relay protection method for fault escalation detection in wind power systems

Abstract

A relay protection method for fault escalation detection in wind power systems, belonging to the field of relay protection technology, includes: real-time acquisition of three-phase current and voltage signals of the wind power system by current and voltage acquisition branches; decomposition of the positive-sequence, negative-sequence, and zero-sequence current components in the current signal by a core processor, and calculation of the voltage change rate; comparison of each current component with its corresponding current component threshold, comparison of the voltage change rate with the voltage change threshold, and determination of system fault status based on the comparison results; when a fault is detected in the wind power system but has not escalated, the core processor outputs a control signal to the conventional delay circuit to control the circuit breaker to trip; when a fault is detected in the wind power system and has escalated, the core processor outputs an accelerated trip signal to the accelerated delay circuit to control the circuit breaker to trip faster and disconnect the faulty circuit. The effect is improved: the sensitivity, response speed, and reliability of relay protection for wind power systems are enhanced.

Description

Technical Field

[0001] This invention relates to the field of relay protection technology, and in particular to a relay protection method for fault escalation identification in wind power systems. Background Technology

[0002] Wind power generation is the energy conversion process that ultimately transforms wind energy into electrical energy, and its core principles follow aerodynamics and the laws of electromagnetic induction. It includes stages such as wind energy capture, speed-up transmission, energy conversion, and grid connection. Throughout the process, an intelligent control system adjusts the yaw and pitch systems in real time to ensure the wind turbine precisely faces the wind and operates safely and efficiently at different wind speeds.

[0003] With technological advancements, the single-unit capacity and efficiency of wind turbines have continuously improved, and the application of large-capacity wind turbine units has become a new trend in wind power development. However, the intermittency and volatility of wind power, coupled with its grid connection via power electronic converters, leads to complex power flow, making traditional relay protection devices based on unidirectional power flow design inadequate and posing a significant challenge to traditional relay protection systems.

[0004] Traditional protection devices rely on power frequency characteristics, but the rapid adjustments and topology changes of power electronic equipment after wind power integration can cause transient electrical distortions, leading to maloperation or failure of protection systems. Wind power is intermittent and fluctuating, making the distribution network unstable. Traditional relay protection devices are designed based on steady-state fault currents, but the characteristics of these fault currents change after wind power integration, such as potentially reduced amplitude and altered phase, leading to decreased sensitivity and reliability of traditional protection devices. Furthermore, wind power systems have short transient response times and contain numerous harmonics and high-frequency components, placing higher demands on the speed and anti-interference capabilities of protection devices.

[0005] Disadvantages of existing technologies: Existing relay protection methods for wind power systems often suffer from disadvantages such as low sensitivity, low reliability, and slow response speed. Summary of the Invention

[0006] The present invention provides a relay protection method for fault escalation identification in wind power systems, which can improve the sensitivity, response speed and reliability of relay protection in wind power systems.

[0007] To achieve the above objectives, the present invention provides a relay protection method for fault escalation identification in wind power systems, which, as a key feature, includes the following steps:

[0008] Step 1: Construct a relay protection system for fault escalation identification in wind power systems. This relay protection system includes a current acquisition branch, a voltage acquisition branch, and a core processor. The current acquisition branch is connected to the current input terminal of the core processor via a current signal processing circuit. The voltage acquisition branch is connected to the voltage input terminal of the core processor via a voltage signal processing circuit. The output terminal of the core processor is connected to the input terminal of a delay selection switch. The first output terminal of the delay selection switch is connected to a circuit breaker via a conventional delay circuit, and the second output terminal of the delay selection switch is connected to the circuit breaker via an accelerated delay circuit.

[0009] Step 2: The current acquisition branch acquires the three-phase current signal of the wind power system in real time, and transmits it to the core processor after processing by the current signal processing circuit;

[0010] The voltage acquisition branch synchronously acquires the three-phase voltage signal of the wind power system, and transmits it to the core processor after processing by the voltage signal processing circuit.

[0011] Step 3: The core processor acquires the processed current signal and voltage signal, then uses the symmetrical component method to decompose the positive sequence, negative sequence and zero sequence current components in the current current signal, and calculates the voltage change rate based on the current voltage signal;

[0012] Step 4: The core processor compares the positive-sequence, negative-sequence, and zero-sequence current components with their corresponding current component thresholds, and simultaneously compares the voltage change rate with the voltage change threshold to obtain the comparison results.

[0013] When the positive sequence current component Positive sequence current component threshold When this occurs, it indicates the presence of a positive-sequence current component. ;

[0014] When the negative sequence current component Negative sequence current component threshold When this occurs, it indicates the presence of a negative sequence current component. ;

[0015] When zero-sequence current component Zero-sequence current component threshold When this occurs, it indicates the presence of a zero-sequence current component. ;

[0016] When the voltage change rate of phase A Phase A voltage change rate threshold When this occurs, it indicates that the voltage of phase A exceeds the voltage change rate threshold;

[0017] When the voltage change rate of phase B B-phase voltage change rate threshold When this occurs, it indicates that the voltage of phase B exceeds the voltage change rate threshold.

[0018] When the voltage change rate of phase C C-phase voltage change rate threshold When this occurs, it indicates that the voltage of phase C exceeds the voltage change rate threshold.

[0019] Step 5: The core processor determines the system fault condition based on the current and voltage comparison results, specifically including the following situations:

[0020] When positive-sequence, negative-sequence, and zero-sequence current components are present simultaneously, and any single-phase voltage exceeds the voltage change threshold, it indicates that a single-phase ground fault has occurred.

[0021] When positive-sequence, negative-sequence, and zero-sequence current components are present simultaneously, and the voltage of any two phases exceeds the voltage change threshold, it indicates that a two-phase ground fault has occurred.

[0022] When positive-sequence and negative-sequence current components exist simultaneously, and the voltage of any two phases exceeds the voltage change threshold, it indicates that a two-phase short-circuit fault has occurred.

[0023] When only a positive sequence current component exists and all three phase voltages exceed the voltage change threshold, it indicates that a three-phase short circuit fault has occurred.

[0024] Step 6: When the core processor detects a fault in the wind power system, it outputs a control signal to the conventional delay circuit through a delay selection switch to control the circuit breaker to trip and disconnect the faulty circuit.

[0025] When the core processor detects a fault in the wind power system and there is a decrease in the current sequence component or an increase in the voltage over-threshold signal for 60ms, it indicates that the fault has escalated. The core processor detects this and outputs an accelerated trip signal to the accelerated delay circuit through a delay selection switch to control the circuit breaker to trip faster and disconnect the faulty circuit.

[0026] Through the above design, this invention synchronously acquires three-phase voltage and current signals from the power grid. After signal conditioning and analog-to-digital conversion, it decomposes the current into positive-sequence, negative-sequence, and zero-sequence components using the symmetrical component method and calculates the voltage change rate to capture the core characteristics of the fault. Based on quantitative criteria such as the amplitude threshold of each sequence component and the voltage change rate threshold, it accurately identifies fault types such as single-phase grounding, two-phase short circuit, two-phase grounding short circuit, and three-phase short circuit. At the same time, it tracks the status of the current sequence component signal and escalation signals such as the voltage change rate exceeding the threshold in real time. Combined with a 60ms duration to verify and filter transient interference, after confirming the fault escalation, it accelerates the action strategy, quickly triggers the circuit breaker to trip, and disconnects the fault circuit, preventing the fault from evolving from a minor type, such as a single-phase grounding, to a more serious phase-to-phase short circuit or three-phase short circuit, thereby preventing greater losses such as equipment damage and system voltage collapse.

[0027] Preferably, in step 3, the core processor uses the symmetric component method to decompose the positive-sequence, negative-sequence, and zero-sequence current components in the current signal, as expressed in the following expression:

[0028] Zero order: ;

[0029] Ascending order: ;

[0030] Negative order: ;

[0031] in, It is the zero-sequence current component. This is the positive sequence current component. It is the negative sequence current component; , , It is a three-phase current; For complex number operators, , is the base of the natural logarithm. It is the imaginary unit.

[0032] This invention sets corresponding current component thresholds and compares them with calculated positive-sequence, negative-sequence, and zero-sequence current components. If the positive, negative, or zero-sequence current components exceed their respective thresholds, then their sequence components are considered to exist. This method effectively eliminates interference factors and improves the accuracy and reliability of subsequent fault identification.

[0033] Preferably, in step 3, the core processor calculates the voltage change rate based on the current voltage signal, expressed as:

[0034] ;

[0035] in, The rate of change of voltage. The initial fault voltage is set. This is the current voltage signal. The system's rated voltage is used, and the calculation method for the three-phase voltages A, B, and C is the same.

[0036] Preferably, the current signal processing circuit is provided with a current limiting protection circuit, a level conversion circuit, a first low-pass filter, a first operational amplifier, a first time module, and a first AD converter connected in sequence.

[0037] The first low-pass filter and the first operational amplifier together form the first signal conditioning circuit, and the first timing module and the first AD converter together form the first fast conversion circuit.

[0038] Preferably, the voltage signal processing circuit includes a voltage divider resistor circuit, a second low-pass filter, a second operational amplifier, a second timing module, and a second AD converter connected in sequence.

[0039] The second low-pass filter and the second operational amplifier together form the second signal conditioning circuit, and the second timing module and the second AD converter together form the second fast conversion circuit.

[0040] Preferably, the current acquisition branch obtains the three-phase current through a current transformer.

[0041] Preferably, the current transformer is provided with a primary winding, a first secondary winding, and a second secondary winding. The two ends of the primary winding are connected to the current sampling line of the wind power system. A first ammeter is connected in parallel to the two ends of the first secondary winding, and a second ammeter is connected in parallel to the two ends of the second secondary winding. The first secondary winding and the second secondary winding are grounded.

[0042] The above design, by setting two secondary windings on the current transformer and having the two secondary windings synchronously acquire current signals, effectively improves the sensitivity of the current transformer, shortens the current acquisition time, and thus improves the overall response speed of the system.

[0043] Preferably, the relay protection system is further provided with a phase-to-phase distance protection module and a ground distance protection module. The input terminals of the phase-to-phase distance protection module and the ground distance protection module are connected to the output terminals of the measuring devices, and the output terminals of the phase-to-phase distance protection module and the ground distance protection module are connected to the control input terminals of the circuit breaker.

[0044] Preferably, the phase-to-phase distance protection module and the ground distance protection module are used to compare the calculated impedance with the preset set impedance of each segment, and select whether to output a trip signal to the circuit breaker.

[0045] The grounding distance protection module is wired using a zero-sequence compensation grounding distance zero-degree connection. The expression for calculating the measured impedance is:

[0046] ; ; ;

[0047] in, To measure impedance, To measure voltage, For measuring current; The zero-order compensation coefficient is... ; Zero-sequence impedance, It is a positive sequence impedance; for Mutually, for Mutually, for Mutually; For zero-sequence current measurement;

[0048] The phase-to-phase distance protection module is wired using a zero-degree phase-to-phase connection. The expression for calculating the measured impedance is:

[0049] ; ; ;

[0050] The equation for comparing the amplitude of the offset characteristic is:

[0051] ;

[0052] in, To measure impedance, This is the offset coefficient. For setting impedance;

[0053] when At that time, the amplitude motion equation for the direction circle is: ;

[0054] when When the amplitude of the full impedance circle is used, the equation of action is: .

[0055] The beneficial effects of this invention are as follows: This invention synchronously acquires three-phase voltage and current signals from the power grid. After signal conditioning and analog-to-digital conversion, it uses the symmetrical component method to decompose positive-sequence, negative-sequence, and zero-sequence current components and calculates the voltage change rate to capture the core characteristics of the fault. Based on quantitative criteria such as the amplitude threshold of each sequence component and the voltage change rate threshold, it accurately identifies fault types such as single-phase grounding, two-phase short circuit, two-phase grounding short circuit, and three-phase short circuit. At the same time, it tracks the status of the current sequence component signal and the escalation signal such as the voltage change rate exceeding the threshold in real time. Combined with a 60ms duration to verify and filter transient interference, after confirming the escalation of the fault, it accelerates the action strategy, quickly triggers the circuit breaker to trip, and disconnects the fault circuit, preventing the fault from evolving from a minor type, such as a single-phase grounding, to a more serious phase-to-phase short circuit or three-phase short circuit, thereby preventing greater losses such as equipment damage and system voltage collapse.

[0056] This method effectively improves the sensitivity, response speed, and reliability of relay protection in wind power systems. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0058] Figure 2 This is the system circuit block diagram;

[0059] Figure 3 This is a fault identification logic diagram;

[0060] Figure 4 For fault escalation logic diagram;

[0061] Figure 5 To protect the flowchart of the scheme;

[0062] Figure 6 The image shows the Matlab simulation model in the example.

[0063] Figure 7 This is a schematic diagram of the delay switching device in the embodiment;

[0064] Figure 8 This is a simulation model diagram of the embodiment without the acceleration device installed;

[0065] Figure 9 The current and voltage waveforms in the embodiment are without the acceleration device installed.

[0066] Figure 10 This is a simulation model diagram of an acceleration device added to the embodiment;

[0067] Figure 11 This is a current and voltage waveform diagram of the embodiment with an acceleration device added;

[0068] Figure 12(a) is a simulation diagram of the Hongqing South Line without the acceleration device installed in the embodiment;

[0069] Figure 12(b) shows the actual operation signal diagram of the Hongqing South Line in the embodiment;

[0070] Figure 13 This is a simulation diagram of the Hongqing South Line without the acceleration device installed in the embodiment;

[0071] Figure 14 This is a structural diagram of the current transformer in the embodiment;

[0072] Figure 15 This is a comparison chart of the current acquisition curves of the improved current transformer and the traditional current transformer in the embodiment. Detailed Implementation

[0073] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples. The following embodiments or drawings are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0074] like Figure 1 As shown, a relay protection method for fault escalation detection in wind power systems includes the following steps:

[0075] Step 1: Construct a relay protection system for fault escalation detection in wind power systems, such as... Figure 2As shown, the relay protection system is equipped with a current acquisition branch, a voltage acquisition branch, and a core processor. The current acquisition branch is connected to the current input terminal of the core processor via a current signal processing circuit. The voltage acquisition branch is connected to the voltage input terminal of the core processor via a voltage signal processing circuit. The output terminal of the core processor is connected to the input terminal of a delay selection switch. The first output terminal of the delay selection switch is connected to a circuit breaker via a conventional delay circuit. The second output terminal of the delay selection switch is connected to the circuit breaker via an accelerated delay circuit.

[0076] The current signal processing circuit is provided with a current limiting protection circuit, a level conversion circuit, a first low-pass filter, a first operational amplifier, a first time module, and a first AD converter connected in sequence.

[0077] The first low-pass filter and the first operational amplifier together form the first signal conditioning circuit, and the first timing module and the first AD converter together form the first fast conversion circuit.

[0078] The voltage signal processing circuit is provided with a voltage divider resistor circuit, a second low-pass filter, a second operational amplifier, a second time module, and a second AD converter connected in sequence.

[0079] The second low-pass filter and the second operational amplifier together form the second signal conditioning circuit, and the second timing module and the second AD converter together form the second fast conversion circuit.

[0080] Step 2: The current acquisition branch acquires the three-phase current signal of the wind power system in real time, and transmits it to the core processor after processing by the current signal processing circuit;

[0081] The voltage acquisition branch synchronously acquires the three-phase voltage signal of the wind power system, and transmits it to the core processor after processing by the voltage signal processing circuit.

[0082] Step 3: The core processor acquires the processed current signal and voltage signal, then uses the symmetrical component method to decompose the positive sequence, negative sequence and zero sequence current components in the current current signal, and calculates the voltage change rate based on the current voltage signal;

[0083] Step 4: The core processor compares the positive-sequence, negative-sequence, and zero-sequence current components with their corresponding current component thresholds, and simultaneously compares the voltage change rate with the voltage change threshold to obtain the comparison results.

[0084] When the positive sequence current component Positive sequence current component threshold When this occurs, it indicates the presence of a positive-sequence current component. ;

[0085] When the negative sequence current component Negative sequence current component threshold When this occurs, it indicates the presence of a negative sequence current component. ;

[0086] When zero-sequence current component Zero-sequence current component threshold When this occurs, it indicates the presence of a zero-sequence current component. ;

[0087] When the voltage change rate of phase A Phase A voltage change rate threshold When this occurs, it indicates that the voltage of phase A exceeds the voltage change rate threshold;

[0088] When the voltage change rate of phase B B-phase voltage change rate threshold When this occurs, it indicates that the voltage of phase B exceeds the voltage change rate threshold.

[0089] When the voltage change rate of phase C C-phase voltage change rate threshold When this occurs, it indicates that the voltage of phase C exceeds the voltage change rate threshold.

[0090] Step 5: The core processor determines the system fault condition based on the current and voltage comparison results, specifically including the following situations: Figure 3 As shown:

[0091] When positive-sequence, negative-sequence, and zero-sequence current components are present simultaneously, and any single-phase voltage exceeds the voltage change threshold, it indicates that a single-phase ground fault has occurred.

[0092] When positive-sequence, negative-sequence, and zero-sequence current components are present simultaneously, and the voltage of any two phases exceeds the voltage change threshold, it indicates that a two-phase ground fault has occurred.

[0093] When positive-sequence and negative-sequence current components exist simultaneously, and the voltage of any two phases exceeds the voltage change threshold, it indicates that a two-phase short-circuit fault has occurred.

[0094] When only a positive sequence current component exists and all three phase voltages exceed the voltage change threshold, it indicates that a three-phase short circuit fault has occurred.

[0095] Step 6: When the core processor detects a fault in the wind power system, it outputs a control signal to the conventional delay circuit through a delay selection switch to control the circuit breaker to trip and disconnect the faulty circuit.

[0096] like Figure 4As shown, when the core processor detects a fault in the wind power system and there is a decrease in the current sequence component or an increase in the voltage over-threshold signal for 60ms, it indicates that the fault has escalated. The core processor detects this and outputs an accelerated trip signal to the accelerated delay circuit through a delay selection switch, controlling the circuit breaker to trip faster and disconnect the faulty circuit.

[0097] like Figure 5 As shown, the entire process of the protection device is to detect the fault within the zone and detect the escalation of the fault. When the escalation of the fault is detected, the protection action is accelerated, thereby effectively shortening the protection time, reducing the response speed, and improving the protection efficiency.

[0098] This invention synchronously acquires three-phase voltage and current signals from the power grid. After signal conditioning and analog-to-digital conversion, it uses the symmetrical component method to decompose positive-sequence, negative-sequence, and zero-sequence current components and calculates the voltage change rate to capture the core characteristics of the fault. Based on quantitative criteria such as amplitude thresholds for each sequence component and voltage change rate thresholds, it accurately identifies fault types such as single-phase grounding, two-phase short circuit, two-phase grounding short circuit, and three-phase short circuit. Simultaneously, it tracks the status of the current sequence component signal and escalation signals such as the voltage change rate exceeding the threshold in real time. Combined with a 60ms duration verification to filter transient interference, after confirming the fault escalation, it accelerates the action strategy to quickly trigger the circuit breaker to trip, disconnect the fault circuit, and prevent the fault from evolving from a minor type, such as a single-phase grounding, to a more serious phase-to-phase short circuit or three-phase short circuit, thereby preventing greater losses such as equipment damage and system voltage collapse.

[0099] The current acquisition branch obtains the three-phase current through a current transformer. The core processor uses the symmetrical component method to decompose the positive-sequence, negative-sequence, and zero-sequence current components in the current signal, as expressed in:

[0100] Zero order: ;

[0101] Ascending order: ;

[0102] Negative order: ;

[0103] in, It is the zero-sequence current component. This is the positive sequence current component. It is the negative sequence current component; , , It is a three-phase current; For complex number operators, , is the base of the natural logarithm. It is the imaginary unit.

[0104] The core processor calculates the voltage change rate based on the current voltage signal, expressed as:

[0105] ;

[0106] in, The rate of change of voltage. The initial fault voltage is set. This is the current voltage signal. The system's rated voltage is used, and the calculation method for the three-phase voltages A, B, and C is the same.

[0107] like Figure 14 As shown, the current transformer is provided with a primary winding, a first secondary winding, and a second secondary winding. The two ends of the primary winding are connected to the current sampling line of the wind power system. A first ammeter is connected in parallel to the two ends of the first secondary winding, and a second ammeter is connected in parallel to the two ends of the second secondary winding. The first secondary winding and the second secondary winding are grounded.

[0108] Figure 15 This is a graph showing the current signal curves acquired by the improved current transformer of this invention and the traditional current transformer. Figure 15 It can be seen that the improved current transformer has a faster response speed to current signals, higher sensitivity, and higher current signal detection accuracy, and can quickly and accurately detect subtle changes in current signals.

[0109] The invention will then be verified through MATLAB simulation experiments.

[0110] like Figure 6 As shown, the grounding distance protection and phase-to-phase distance protection in the Matlab simulation model select whether to output a trip signal to the circuit breaker by comparing the calculated impedance with the preset setting impedance of each section. Figure 6 The circuit breaker in the circuit is selected to open and close via an external signal; Figure 6 The protection acceleration device in the system monitors the zero-sequence, positive-sequence, and negative-sequence current components, as well as the three-phase voltage change rate information, to identify the fault escalation characteristics and output an acceleration action output signal to the ground distance protection and phase-to-phase distance protection. Figure 6 The fault escalation device consists of two faults: a single-phase ground fault and a three-phase fault, with durations of 0.1s-1.5s and 0.5s-5s respectively, used to simulate fault escalation conditions. Figure 6 The three-phase power supply on both the left and right sides is 110kV.

[0111] The grounding distance protection module is wired using a zero-sequence compensation grounding distance zero-degree connection. The expression for calculating the measured impedance is:

[0112] ; ; ;

[0113] in, To measure impedance, To measure voltage, For measuring current; The zero-order compensation coefficient is... ; Zero-sequence impedance, It is a positive sequence impedance; for Mutually, for Mutually, for Mutually; For zero-sequence current measurement;

[0114] The phase-to-phase distance protection module is wired using a zero-degree phase-to-phase connection. The expression for calculating the measured impedance is:

[0115] ; ; ;

[0116] The equation for comparing the amplitude of the offset characteristic is:

[0117] ;

[0118] in, To measure impedance, This is the offset coefficient. For setting impedance;

[0119] when At that time, the amplitude motion equation for the direction circle is: ;

[0120] when When the amplitude of the full impedance circle is used, the equation of action is: .

[0121] like Figure 7 As shown, the acceleration action signal emitted by the acceleration action device switches the delay, thereby achieving the acceleration action.

[0122] Figure 8 The simulation model is without an acceleration device installed. A single-phase ground fault occurs at the end of the line, and the fault escalates to a three-phase fault 0.5 seconds after it occurs.

[0123] As Figure 9As shown, when a single-phase fault occurs in phase A, the phase A voltage decreases significantly, the phase BC voltage increases slightly, and the phase A current increases significantly, while the phase BC current remains essentially unchanged. After the fault escalates to a three-phase fault, the three-phase voltage and current stabilize to a certain amplitude after a certain period of time. At 1.5 seconds, the relay protection trips the circuit breaker, and the three-phase voltage recovers to a steady state after a certain period of time. Because the three-phase current is zero after the circuit breaker trips, the time from the fault occurrence to the relay protection action is 1.5 seconds. If the tripping time is too long, it will cause damage such as equipment insulation burnout, system transient instability, and large-scale power outages.

[0124] Figure 10 The simulation model is equipped with an acceleration device. The model experiences a single-phase ground fault at the end of the line, which escalates to a three-phase fault 0.5 seconds after the fault occurs.

[0125] Since the single-phase fault escalated into a three-phase fault, monitoring of characteristic quantities revealed that the voltage change rate exceeded the set value at the fault escalation point, and the negative sequence current component disappeared, thus confirming the fault escalation and issuing an acceleration action signal. The fault escalation occurred at 0.5s, and the tripping action occurred at 0.538s. In this case, compared with the system without the acceleration action device, the acceleration was (1.4-0.438) / 1.4*100%=68.71%.

[0126] Without the device, it takes 1.5 seconds for the relay protection to activate after a fault occurs; after the device is installed, the trip is triggered after only 0.038 seconds, with an acceleration rate of 68.71%, which solves the problem of equipment burnout and system instability that may be caused by excessive delay of traditional protection.

[0127] Next, an acceleration device was installed on the power line of a wind power system to simulate the fault conditions of the line: a single-phase fault would escalate to a three-phase fault after 64ms. In reality, after a fault occurs, the circuit breaker trips after a 0.9s delay. In the simulation, a single-phase fault occurred at 0.1s, and the fault escalated to a three-phase fault at 0.164s, with the delay also set to 0.9s.

[0128] As shown in Figure 12(a), the time from the start of the fault to the fault clearing is 0.982s, which is similar to the time of 0.92s shown in the upper right corner of Figure 12(b).

[0129] Figure 13 The data shows that after the acceleration device was installed, the time from the start of the fault to the fault clearing was 0.102 seconds. Compared with the time without the acceleration device, the acceleration was accelerated by (0.982-0.102) / 0.982*100%=89.61%.

[0130] Without the device, the total fault clearing time was 0.982s, which is highly consistent with the actual line action time of 0.92s, indicating that the simulation has realistic reference value. After the device was installed, the fault clearing time was only 0.102s, and the acceleration rate soared to 89.61%, almost achieving "rapid disconnection upon fault escalation", which greatly reduced the impact window of the fault on the system.

[0131] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A relay protection method for fault escalation judgment in wind power systems, characterized in that, Includes the following steps: Step 1: Construct a relay protection system for fault escalation identification in wind power systems. This relay protection system includes a current acquisition branch, a voltage acquisition branch, and a core processor. The current acquisition branch is connected to the current input terminal of the core processor via a current signal processing circuit. The voltage acquisition branch is connected to the voltage input terminal of the core processor via a voltage signal processing circuit. The output terminal of the core processor is connected to the input terminal of a delay selection switch. The first output terminal of the delay selection switch is connected to a circuit breaker via a conventional delay circuit, and the second output terminal of the delay selection switch is connected to the circuit breaker via an accelerated delay circuit. Step 2: The current acquisition branch acquires the three-phase current signal of the wind power system in real time, and transmits it to the core processor after processing by the current signal processing circuit; The voltage acquisition branch synchronously acquires the three-phase voltage signal of the wind power system, and transmits it to the core processor after processing by the voltage signal processing circuit. Step 3: The core processor acquires the processed current signal and voltage signal, then uses the symmetrical component method to decompose the positive sequence, negative sequence and zero sequence current components in the current current signal, and calculates the voltage change rate based on the current voltage signal; Step 4: The core processor compares the positive-sequence, negative-sequence, and zero-sequence current components with their corresponding current component thresholds, and simultaneously compares the voltage change rate with the voltage change threshold to obtain the comparison results. When the positive sequence current component Positive sequence current component threshold When this occurs, it indicates the presence of a positive-sequence current component. ; When the negative sequence current component Negative sequence current component threshold When this occurs, it indicates the presence of a negative sequence current component. ; When zero-sequence current component Zero-sequence current component threshold When this occurs, it indicates the presence of a zero-sequence current component. ; When the voltage change rate of phase A Phase A voltage change rate threshold When this occurs, it indicates that the voltage of phase A exceeds the voltage change rate threshold; When the voltage change rate of phase B B-phase voltage change rate threshold When this occurs, it indicates that the voltage of phase B exceeds the voltage change rate threshold. When the voltage change rate of phase C C-phase voltage change rate threshold When this occurs, it indicates that the voltage of phase C exceeds the voltage change rate threshold. Step 5: The core processor determines the system fault condition based on the current and voltage comparison results, specifically including the following situations: When positive-sequence, negative-sequence, and zero-sequence current components are present simultaneously, and any single-phase voltage exceeds the voltage change threshold, it indicates that a single-phase ground fault has occurred. When positive-sequence, negative-sequence, and zero-sequence current components are present simultaneously, and the voltage of any two phases exceeds the voltage change threshold, it indicates that a two-phase ground fault has occurred. When positive-sequence and negative-sequence current components exist simultaneously, and the voltage of any two phases exceeds the voltage change threshold, it indicates that a two-phase short-circuit fault has occurred. When only a positive sequence current component exists and all three phase voltages exceed the voltage change threshold, it indicates that a three-phase short circuit fault has occurred. Step 6: When the core processor detects a fault in the wind power system, it outputs a control signal to the conventional delay circuit through a delay selection switch to control the circuit breaker to trip and disconnect the faulty circuit. When the core processor detects a fault in the wind power system and there is a decrease in the current sequence component or an increase in the voltage over-threshold signal for 60ms, it indicates that the fault has escalated. The core processor detects this and outputs an accelerated trip signal to the accelerated delay circuit through a delay selection switch to control the circuit breaker to trip faster and disconnect the faulty circuit.

2. The relay protection method for fault escalation judgment in wind power systems according to claim 1, characterized in that: In step 3, the core processor uses the symmetric component method to decompose the positive-sequence, negative-sequence, and zero-sequence current components in the current signal, as expressed in the following expression: Zero order: ; Ascending order: ; Negative order: ; in, It is the zero-sequence current component. This is the positive sequence current component. It is the negative sequence current component; , , It is a three-phase current; For complex number operators, , is the base of the natural logarithm. It is the imaginary unit.

3. The relay protection method for fault escalation judgment in wind power systems according to claim 1, characterized in that: In step 3, the core processor calculates the voltage change rate based on the current voltage signal, expressed as: ； in, The rate of change of voltage. The initial fault voltage is set. This is the current voltage signal. This is the system's rated voltage.

4. The relay protection method for fault escalation judgment in wind power systems according to claim 1, characterized in that: The current signal processing circuit is provided with a current limiting protection circuit, a level conversion circuit, a first low-pass filter, a first operational amplifier, a first time module, and a first AD converter connected in sequence. The first low-pass filter and the first operational amplifier together form the first signal conditioning circuit, and the first timing module and the first AD converter together form the first fast conversion circuit.

5. A relay protection method for fault escalation judgment in wind power systems according to claim 1, characterized in that: The voltage signal processing circuit is provided with a voltage divider resistor circuit, a second low-pass filter, a second operational amplifier, a second time module, and a second AD converter connected in sequence. The second low-pass filter and the second operational amplifier together form the second signal conditioning circuit, and the second timing module and the second AD converter together form the second fast conversion circuit.

6. The relay protection method for fault escalation judgment in wind power systems according to claim 1, characterized in that: The current acquisition branch obtains the three-phase current through a current transformer.

7. A relay protection method for fault escalation judgment in wind power systems according to claim 6, characterized in that: The current transformer is provided with a primary winding, a first secondary winding, and a second secondary winding. The two ends of the primary winding are connected to the current sampling line of the wind power system. A first ammeter is connected in parallel to the two ends of the first secondary winding, and a second ammeter is connected in parallel to the two ends of the second secondary winding. The first secondary winding and the second secondary winding are grounded.

8. A relay protection method for fault escalation judgment in wind power systems according to claim 1, characterized in that: The relay protection system is also equipped with a phase-to-phase distance protection module and a ground distance protection module. The input terminals of the phase-to-phase distance protection module and the ground distance protection module are connected to the output terminals of the measuring devices, and the output terminals of the phase-to-phase distance protection module and the ground distance protection module are connected to the control input terminals of the circuit breaker.

9. A relay protection method for fault escalation judgment in wind power systems according to claim 8, characterized in that: The phase-to-phase distance protection module and the ground distance protection module are used to compare the calculated impedance with the preset set impedance of each segment and select whether to output a trip signal to the circuit breaker. The grounding distance protection module is wired using a zero-sequence compensation grounding distance zero-degree connection. The expression for calculating the measured impedance is: ； ； ； in, To measure impedance, To measure voltage, For measuring current; The zero-order compensation coefficient is... ; Zero-sequence impedance, It is a positive sequence impedance; for Mutually, for Mutually, for Mutually; For zero-sequence current measurement; The phase-to-phase distance protection module is wired using a zero-degree phase-to-phase connection. The expression for calculating the measured impedance is: ； ； ； The equation for comparing the amplitude of the offset characteristic is: ； in, To measure impedance, This is the offset coefficient. For setting impedance; when At that time, the amplitude motion equation for the direction circle is: ; when When the amplitude of the full impedance circle is used, the equation of action is: .

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