A method for fault isolation of distributed regional protection and flexible interconnection device coordinated control

Abstract

This invention discloses a fault isolation method for distributed area protection and coordinated control of flexible interconnected devices. After a fault is triggered, the method first disconnects the outer loop control on the fault side of the flexible interconnected device. Considering fault support and phase angle compensation requirements, a positive-sequence current inner loop reference value is calculated using the high-inductance fault characteristic impedance angle as the target. Then, it performs real-time verification based on fault limiting requirements. If the fault limiting requirements are met, the value is input into the positive-sequence current inner loop; otherwise, the negative-sequence current inner loop reference value is calculated using the remaining short-circuit capacity to ensure that the negative-sequence fault characteristic impedance exhibits high inductance. Finally, combining the fault component direction element area protection criteria and through communication between adjacent protection devices, the fault location is determined, achieving fault isolation. This invention considers fault support and current limiting control requirements, reshapes the fault characteristic impedance of the flexible interconnected device, effectively identifies faults in the flexible interconnected system, and achieves precise fault isolation.

Description

Technical Field

[0001] This invention belongs to the field of protection and control technology for flexible interconnected systems, and particularly relates to a fault isolation method for distributed area protection and collaborative control of flexible interconnected devices in flexible interconnected systems. Background Technology

[0002] In recent years, the application of power electronics technology in power systems has become an important development trend. Against this backdrop, flexible interconnection devices (FIDs), represented by intelligent soft switches, are gradually replacing traditional tie switches, forming flexible interconnection systems and enabling flexible closed-loop operation of the power system. Flexible interconnection devices can significantly improve the stability and resilience of the power system through flexible active control methods. On the one hand, they enhance system operational stability by dynamically balancing feeder loads and suppressing voltage fluctuations and three-phase imbalances; on the other hand, they provide support during faults, promote power restoration, and provide flexible access and power support for distributed generation, thereby comprehensively improving the resilience and reliability of the power system.

[0003] However, while flexible interconnection devices improve system stability, they also pose significant challenges to relay protection, primarily in two aspects: First, flexible interconnection devices enable bidirectional controllable power flow, rendering traditional fault current-based location methods ineffective, and compromising the selectivity and speed of protection. Existing protection methods that add directional elements have adaptability issues in practical applications, while injection-based protection schemes require additional injection equipment, resulting in complex configurations and high costs. Second, the low-voltage ride-through and fault current limiting control strategies employed by flexible interconnection devices during faults actively alter the amplitude and phase of their output fault current, significantly changing the system fault characteristics. This affects the sensitivity and reliability of protection principles relying on fixed fault characteristics, such as traditional impedance protection, under controlled changes in system impedance characteristics, potentially leading to failure to operate or false operation. Therefore, there is an urgent need to deeply research fault isolation methods that coordinate flexible interconnection device control with distributed area protection. By integrating control strategies and protection criteria, accurate and rapid fault isolation can be achieved without modifying the hardware architecture, thereby ensuring the safe operation of the system. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention discloses a fault isolation method for distributed area protection and flexible interconnection device collaborative control.

[0005] The specific technical solution adopted in this invention is as follows:

[0006] A fault isolation method for distributed area protection and flexible interconnection device collaborative control includes the following steps:

[0007] 1. Construction of Distributed Data Transmission Architecture

[0008] In a flexible interconnected power distribution system, a data interaction architecture based on peer-to-peer communication is constructed. Relying on this architecture, adjacent protection devices can quickly and reliably exchange key information, including fault electrical quantities and fault direction determination results, to achieve information sharing.

[0009] 2. Flexible interconnected device control system

[0010] The flexible interconnection equipment control system is configured on each AC port of the flexible interconnection equipment. When the flexible interconnection system is operating normally, the outer loop of the flexible interconnection equipment based on the back-to-back converter adopts a constant DC voltage control strategy to maintain DC voltage stability, while the outer loop on the opposite side adopts a constant power control strategy to accurately control power. The inner current loop adopts a positive and negative sequence separation control method.

[0011] 3. Data Acquisition and Fault Trigger Judgment

[0012] The voltage transformers and current transformers in the flexible interconnection system are used to collect the three-phase voltage and three-phase current before and after the fault at each port of the flexible interconnection equipment and on both sides of the protected line in real time.

[0013] The protection devices installed on each AC port of the flexible interconnection equipment and on both sides of the protected line use the voltage and current before and after the fault to calculate the fault components of voltage and current. Then, the sequence component extraction algorithm is used to extract the sequence components of the fault components voltage and current. Based on the degree of voltage drop and sudden change before and after the fault, the activation element is used to determine whether the flexible interconnection system has failed. If the flexible interconnection system is determined to have failed, the following fault handling process is initiated.

[0014] 4. Shaping the characteristic impedance angle of high-inductance positive-sequence faults

[0015] When a system fault is detected in step 3, the flexible interconnect device control system disconnects the outer loop control on the fault side. Based on the low voltage ride-through control requirements, voltage drop degree, and phase angle compensation, the positive sequence q-axis current reference value of the inner current loop is directly given. The d-axis current reference value of the inner current loop is calculated and directly given with the goal of the positive sequence fault characteristic impedance of the flexible interconnect device on the fault side exhibiting high inductance. The switching trigger signal of the flexible interconnect device is generated through PWM modulation to achieve the shaping of the high inductance positive sequence fault characteristic impedance angle.

[0016] 5. Real-time monitoring of fault limiting

[0017] The flexible interconnected device control system monitors in real time whether the positive sequence d-axis current reference value and positive sequence q-axis current reference value calculated in step 4 meet the fault limiting control requirements. If the fault limiting requirements are met, the calculated reference values ​​are directly input into the positive sequence current inner loop, and the negative sequence current d-axis and q-axis reference values ​​are directly given to 0 to suppress negative sequence. If the fault limiting requirements are not met, the system proceeds to the following high-inductance negative sequence fault characteristic impedance angle shaping process.

[0018] 6. Shaping the characteristic impedance angle of highly inductive negative-sequence faults

[0019] After determining in step 5 that the positive sequence current reference value does not meet the fault limiting requirements, the process proceeds to shaping the high-inductance negative sequence impedance angle. Based on the low-voltage ride-through control requirements and the degree of voltage drop after the fault, a positive sequence q-axis current reference value is directly assigned to provide fault support. Utilizing the remaining short-circuit capacity and aiming for high inductance in the negative sequence fault characteristic impedance on the fault side of the flexible interconnect device, the positive sequence d-axis current reference value and the negative sequence current d-axis and q-axis reference values ​​are rationally allocated. Similarly, the switching trigger signal for the flexible interconnect device is generated through PWM modulation to achieve the shaping of the high-inductance negative sequence fault characteristic impedance angle.

[0020] 7. Fault detection and isolation

[0021] The protection devices at each port of the flexible interconnection equipment and on both sides of the protected line determine the fault direction in real time based on the characteristic impedance angle of positive-sequence and negative-sequence faults and the protection criteria for the direction of positive-sequence and negative-sequence fault components. Utilizing the data transmission architecture described in step 1, the fault location is determined through communication between adjacent protection devices. Only when the local protection device determines that the fault occurs in the positive direction and receives the positive-direction fault determination result from the opposite protection device will the local protection device send a trip signal to the local circuit breaker to achieve fault isolation.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) Current research on flexible interconnection equipment mainly focuses on its control strategies during system steady state or fault recovery, with less consideration given to the impact of its control strategies on system fault characteristics and relay protection performance while ensuring stable system operation. Compared with existing methods that passively adapt to the fault characteristics of flexible interconnection systems and modify protection criteria, such as longitudinal protection based on voltage or impedance characteristics, this technology considers the requirements for fault support and current limiting control. By shaping the high-inductive fault characteristic impedance angle, it actively changes the fault characteristics, ensuring that the fault characteristic impedance of the flexible interconnection equipment exhibits high inductiveness, adapting to the fault component direction element area protection criteria, and improving the fault direction discrimination sensitivity without changing the original protection device, thereby achieving accurate fault isolation.

[0024] (2) Compared with the method of controlling the fault impedance angle of flexible equipment by only using positive sequence current, this technology introduces fault limiting judgment and negative sequence fault characteristic impedance angle shaping, which solves the problem that when the voltage drop is severe, i.e., more than 80%, due to the low voltage ride-through requirement and fault current limiting safety constraint, the method of shaping the characteristic impedance angle of positive sequence fault cannot control the impedance angle and leads to protection misjudgment, thus expanding the protection range. Attached Figure Description

[0025] Figure 1 This is a typical structure diagram of a flexible interconnected system;

[0026] Figure 2 shows the control block diagram of the flexible interconnect device, (a) DC voltage side control block diagram, (b) constant power side control block diagram;

[0027] Figure 3 Flowchart for fault direction determination in distributed area protection and flexible unit collaborative control;

[0028] Figure 4 A waveform diagram showing the degree of voltage drop on the DC voltage control side when a fault occurs on the DC voltage control side of a flexible interconnect device;

[0029] Figure 5 To protect the positive sequence fault characteristic impedance angles measured at P1 and M3. Detailed Implementation

[0030] The technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples, but this is not intended to limit the scope of protection of the present invention. All technical solutions obtained by equivalent substitution or equivalent transformation are within the scope of protection of the present invention.

[0031] Figure 1 As a typical flexible interconnection system, distribution networks 1 to 3 are interconnected by flexible interconnection devices FID1-FID3. Lines L1-L5 have lengths of 10km, 8km, 10km, 5km, and 8km respectively. f1 represents the fault point within the protected line L3, and f2 represents the fault point within the protected line L1, corresponding to positions 50% and 40% of the distance from bus M3, respectively. The DC voltage side and constant power control block diagrams of FID2 are shown in Figures 2(a) and (b), respectively. The control block diagrams of FID1 and FID3 are similar to those of FID2. The fault direction determination flowchart of the AC port control and protection device of the flexible interconnection equipment is shown in Figure 2(a). Figure 3 As shown.

[0032] Example:

[0033] Assumption Figure 1 A phase AB short-circuit fault occurred at point f1 of the flexible interconnection system shown, which is a fault in the output line of the constant DC voltage control side of FID2. The fault time is The fault duration is 0.15s, which is a positive fault for protection device P1.

[0034] 1. Construction of Distributed Data Transmission Architecture

[0035] In a flexible interconnected power distribution system, a peer-to-peer communication-based data interaction architecture is constructed. Adjacent protection devices utilize fiber optic Ethernet for real-time data transmission, adhering to the IEC 61850 GOOSE protocol. Based on this architecture, redundant and reliable bidirectional communication links can be established between adjacent protection devices, enabling rapid exchange and sharing of various key data, including fault characteristic impedance, fault direction determination results, and trip signals. This communication architecture supports millisecond-level information transmission and high-precision time synchronization, enhancing the collaborative judgment capabilities of regional protection and providing a stable, low-latency data communication foundation for rapid fault location and isolation.

[0036] 2. Flexible interconnected device control system

[0037] The flexible interconnection equipment control system is configured at each AC port of the flexible interconnection equipment. During normal operation of the flexible interconnection system, one port of the flexible interconnection equipment based on back-to-back converters adopts a constant DC voltage control strategy. By adjusting the power output of the converter on that side, the DC bus voltage is maintained stable, providing reliable DC support for the system. The opposite port adopts a constant power control strategy, precisely adjusting the transmitted active and reactive power according to dispatch instructions or local power demand, achieving flexible power flow management. The inner current loops of both ports employ a positive and negative sequence separation control method. By designing controllers in the positive and negative sequence synchronous rotating coordinate systems respectively, independent and accurate tracking of current components under unbalanced operating conditions is achieved, effectively suppressing the effects of harmonics and asymmetrical operation, thereby ensuring stable system operation under various operating conditions.

[0038] 3. Data Acquisition and Fault Trigger Judgment

[0039] The voltage and current transformers in the flexible interconnection system are used to collect real-time three-phase voltages and three-phase currents at each AC port of the flexible interconnection equipment and on both sides of the protected line before and after a fault. In this embodiment, the protection device P1 uses the voltage transformer at bus N3 to collect the three-phase voltage at the FID2 constant DC voltage control side outlet. The three-phase current at the FID2 constant DC voltage control side outlet is collected using the current transformer on the protected line L3. Similarly, the three-phase voltage at point M3 on busbar 1 of the distribution network is collected. and three-phase current ;in For phase differentiation, it represents the three phases A, B, and C.

[0040] The protection devices installed at each AC port and bus M3 of the flexible interconnection equipment use the voltage and current collected before and after the fault to calculate the fault component voltage and current at the constant power control port and bus M3 of the flexible interconnection equipment. , , and Then, the positive and negative sequence components of the fault components voltage and current are extracted using Fourier transform and the symmetric component method shown in equation (1).

[0041] (1)

[0043] In the formula, and These represent the zero-sequence, positive-sequence, and negative-sequence components of the fault voltage, respectively. , and These are phasors representing the fault component voltages, respectively. Indicates the measurement location, including PQ, Udc, and M3; .

[0044] The fault status of the flexible interconnection system is determined by the voltage drop before and after the fault and the sudden change in the starting element. That is, when the relationship shown in equation (2) is satisfied, the flexible interconnection system is determined to have a fault, and the following fault handling process is initiated. Compared with the existing single criterion of starting element or voltage drop, which only uses sudden change to ensure the speed of the starting element and the sensitivity to high-resistance faults, this technology uses sudden change to ensure the accuracy and anti-interference of the starting element. By taking the logical "AND" of the two, the high reliability and anti-interference of the protection starting link of the flexible interconnection system are achieved, and the problem of false starting caused by load switching and control mode switching in complex flexible interconnection systems due to single criteria is solved.

[0045] (2)

[0047] In the formula, This indicates the degree of voltage drop. and These are the positive sequence voltages of the AC ports of the flexible interconnect device before and after the fault, respectively. This is the voltage start-up threshold value, which is set to 95% in this embodiment; , representing the abrupt change in phase current at the h-th instant. The number of sampling points per wave is taken in this embodiment. ; The phase current start-up threshold value is taken as in this embodiment. .

[0048] 4. Shaping the characteristic impedance angle of high-inductance positive-sequence faults

[0049] In step 3, a system fault is determined. The flexible interconnect device control system disconnects the outer loop control on the faulty side and directly provides the positive sequence current inner loop reference value. and Specifically, considering the deviation between the PCC voltage phase angle and the phase-locked loop phase angle, phase angle compensation is calculated according to equation (3); secondly, based on the voltage drop degree in step 3... The positive-sequence q-axis current reference value of the inner current loop is directly given to meet the low-voltage ride-through control requirements, and the goal is to achieve high inductance based on the positive-sequence fault characteristic impedance on the fault side of the flexible interconnect device. The d-axis current reference value of the inner current loop is calculated and directly given. Finally, the switching trigger signal of the flexible interconnect device is generated through PWM modulation to achieve the shaping of the characteristic impedance angle of the high-inductive positive-sequence fault. The positive-sequence current inner loop reference value after phase angle compensation is considered. and The calculation formula is shown in equation (6). Compared with existing impedance angle control methods, this step considers the deviation between the PCC voltage phase angle and the phase-locked loop phase angle, and provides an accurate reference value for the inner current loop through phase angle compensation. and This reduces the deviation between the fault characteristic impedance angle and the shaped target, thereby improving the accuracy of the shaped method.

[0050] (3)

[0052] In the formula, Indicates phase angle compensation. This represents the q-axis positive sequence voltage amplitude extracted using a phase-locked loop. This represents the positive sequence voltage amplitude.

[0053] (4)

[0055] (5)

[0057] In the formula,

[0058] ; , In this embodiment, m=1.5; The phase angle of the positive-sequence fault component voltage at the AC port of the flexible interconnection device; This indicates the phase angle at which the positive sequence voltage of the AC port of the flexible interconnect device lags behind the voltage before the fault.

[0059] (6)

[0061] Voltage drop level in this embodiment like Figure 4 As shown.

[0062] 5. Real-time monitoring of fault limiting

[0063] The positive sequence d-axis current reference value calculated in step 4 of the real-time detection process of the flexible interconnected device control system. and positive sequence q-axis current reference value Does it meet the fault limiting control requirements shown in equation (7)?

[0064] (7)

[0066] If the fault limiting requirement shown in equation (7) is met, then the reference value calculated in step 5 can be directly applied. and The positive sequence current inner loop is input, and the negative sequence current d-axis and q-axis reference values ​​are directly set to 0 to suppress the negative sequence. If the fault limiting requirement shown in equation (7) is not met, the following high-inductance negative sequence fault characteristic impedance angle shaping process is entered. Compared with the prior art, this step calculates the positive sequence current amplitude in real time based on the obtained positive sequence current reference value and judges whether it exceeds the limit. It considers the fault limiting safety constraint and also takes corresponding measures based on the exceeding the limit judgment result to prioritize the safety of flexible equipment.

[0067] 6. Shaping the characteristic impedance angle of highly inductive negative-sequence faults

[0068] After determining in step 5 that the positive sequence current reference value does not meet the fault limiting requirement shown in equation (7), the high-inductance negative sequence impedance angle shaping process begins. Specifically, this is based on the degree of voltage drop after the fault. Equation (4) directly provides a positive-sequence q-axis current reference value to provide fault support, utilizes the remaining short-circuit capacity, and aims to exhibit high inductance with the negative-sequence fault characteristic impedance on the fault side of the flexible interconnection device. By rationally allocating positive-sequence d-axis current reference values ​​and negative-sequence d-axis and q-axis current reference values, and generating switching trigger signals for flexible interconnected devices through PWM modulation, a high-inductive negative-sequence fault characteristic impedance angle is shaped. Compared to existing methods that only use positive-sequence impedance angle shaping, this step introduces a negative-sequence fault characteristic impedance angle shaping method. When the positive-sequence impedance angle shaping method cannot guarantee the shaping effect of the high-inductive impedance angle due to low-voltage ride-through requirements and fault current limiting safety constraints, the high-inductive negative-sequence impedance angle is shaped instead to ensure the provision of fault characteristics with a high-inductive impedance angle, thereby expanding the effective protection range.

[0069] Specifically, the inner loop reference value of the negative sequence current is calculated using equation (8). and .

[0070] (8)

[0072] In the formula, the negative sequence current amplitude It is obtained by iterative calculation using equations (9) and (10).

[0073] (9)

[0075] (10)

[0077] In the formula, , and For the three-phase current of the AC port of the flexible interconnection device;

[0078] Positive sequence current amplitude And the magnitudes of the positive and negative sequence currents satisfy the relationship , In this embodiment, n is taken as 0.3; Equation (10) is the convergence condition, and in this embodiment, n is taken as 0.3. It is 0.01MW.

[0079] In this example, the result calculated in step 4... and Substituting into equation (7) satisfies the fault limiting control requirements, the inner loop reference value of the fault negative sequence current is set to 0 to suppress the negative sequence.

[0080] 7. Fault detection and isolation

[0081] The protection devices at each port of the flexible interconnection equipment and on both sides of the protected line use formula (11) to calculate the characteristic impedance angle of positive sequence and negative sequence faults in real time, and select the corresponding fault component direction element protection criterion according to the high inductive impedance type to determine the fault direction.

[0082] (11)

[0084] In the formula, and These represent the characteristic impedance angles of positive-sequence and negative-sequence faults measured at the protection installation location, respectively. and These represent the phase angles of the positive-sequence fault component voltage and current, respectively. and These represent the phase angles of the negative sequence voltage and current, respectively.

[0085] In this embodiment, the positive sequence current reference value calculated in step 4 meets the fault limiting requirement. Therefore, the high-inductance negative sequence fault characteristic impedance angle shaping method is adopted. The positive sequence fault characteristic impedance angles measured at P1 and M3 of the constant DC voltage control side port protection of the flexible interconnection equipment are as follows: Figure 5 As shown, after a fault occurs in 1.0s, the temperature stabilizes at -90.01° and -99.92° respectively. According to the positive sequence fault component direction element protection criterion shown in Equation (12), the protection devices at protection P1 and M3 both determine that the fault is in the positive direction. The data transmission architecture in step 1 is used to complete the communication of fault direction information, determine that the fault occurs on line L3, and send trip signals to the circuit breakers on this side to disconnect the switches on both sides of L3 and realize fault isolation.

[0086] (12)

[0088] The above description represents only preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A fault isolation method for distributed area protection and flexible interconnection device collaborative control, characterized in that, Includes the following steps: S1, Distributed data transmission architecture construction: In the flexible interconnection system, a distributed data interaction architecture based on peer-to-peer communication is constructed. Adjacent protection devices rely on this architecture to establish bidirectional communication links to achieve real-time data interaction. S2, Flexible interconnection equipment is configured with a control system. A control system is configured on each AC port of the flexible interconnection equipment. When the flexible interconnection system is running normally, the AC port on one side of the flexible interconnection equipment adopts a constant DC voltage control strategy to maintain DC voltage stability, and the AC port on the other side adopts a constant power control strategy to accurately control the power. The positive and negative sequence separation control method is used for the inner current loop. S3, Data Acquisition and Fault Trigger Judgment: Real-time acquisition of voltage and current at each AC port of the flexible interconnection equipment and on both sides of the protected line; calculation of fault components and extraction of their sequence components using protection devices installed at each AC port of the flexible interconnection equipment and on both sides of the protected line; and determination of whether a fault has occurred in the flexible interconnection system based on the degree of voltage drop and the amount of sudden change. If a fault is determined to have occurred, the following fault handling process is triggered. S4, shaping the characteristic impedance angle of high-inductance positive-sequence fault: After determining that a system fault has occurred in step S3, the flexible interconnect device control system disconnects the outer loop control on the fault side. Based on the low voltage ride-through control requirements, voltage drop degree and phase angle compensation, and with the goal of presenting high inductance in the characteristic impedance of the positive-sequence fault on the fault side of the flexible interconnect device, the reference values ​​of the positive-sequence q and d-axis currents in the inner loop are directly given. Then, the switching trigger signal of the flexible interconnect device is generated through PWM modulation to realize the shaping of the characteristic impedance angle of high-inductance positive-sequence fault. S5, Real-time monitoring of fault limiting: The flexible interconnected equipment control system monitors in real time whether the positive sequence d and q axis current reference values ​​calculated in step S4 meet the fault limiting control requirements. If the fault limiting requirements are met, the calculated reference values ​​are directly input into the positive sequence current inner loop, and the negative sequence current d axis and q axis reference values ​​are directly given to 0. Otherwise, the following high-inductance negative sequence fault characteristic impedance angle shaping process is triggered. S6, shaping the characteristic impedance angle of high-inductive negative-sequence fault: After determining in step S5 that the positive-sequence current reference value does not meet the fault limiting requirement, considering the low voltage ride-through control requirement and the degree of voltage drop after the fault, and aiming at the high inductiveity of the negative-sequence fault characteristic impedance on the fault side of the flexible interconnection device, the positive-sequence and negative-sequence d and q-axis current reference values ​​are reasonably allocated, and then the switching trigger signal of the flexible interconnection device is generated by PWM modulation to realize the shaping of the characteristic impedance angle of high-inductive negative-sequence fault. S7. Fault detection and isolation: The protection devices determine the fault direction in real time based on the characteristic impedance angle of positive and negative sequence faults and the protection criteria for the direction of positive and negative sequence fault components. They also use the data transmission architecture in step S1 to determine the fault location and isolate the fault through communication between adjacent protection devices.

2. The fault isolation method for distributed area protection and flexible interconnection device collaborative control according to claim 1, characterized in that, The specific method for determining fault triggering in step S3 is as follows: the protection device determines fault triggering only when the voltage drop and the sudden change in the starting element satisfy equation (1). (1) In the formula, Indicates the degree of voltage drop. This is the voltage-based start-up threshold value. This represents the abrupt change in phase current at the h-th instant. This is the phase current start-up threshold value.

3. The fault isolation method for distributed area protection and flexible interconnection device collaborative control according to claim 1, characterized in that, The specific steps for calculating the positive sequence current inner loop reference value in step S4 are as follows: Calculate the phase angle compensation amount according to formula (2). : (2) In the formula, This represents the q-axis positive sequence voltage amplitude extracted using a phase-locked loop. Indicates the positive sequence voltage amplitude; Based on the voltage drop at the AC port of the flexible interconnection device and the low-voltage ride-through control requirements, the positive sequence current reference value is calculated using equations (3) and (4). and : (3) (4) In the formula, ; ； This is the fault current limiting value. The phase angle of the positive-sequence fault component voltage at the AC port of the flexible interconnection device; The phase angle indicating that the positive sequence voltage at the AC port of the flexible interconnect device lags behind the voltage before the fault; The positive sequence current reference value after considering phase angle compensation is calculated using equation (5). and , (5)。 4. The fault isolation method for distributed area protection and flexible interconnection device collaborative control according to claim 1, characterized in that, The specific steps for calculating the inner loop reference value of the negative sequence current in step S6 are as follows: The inner loop reference value of the negative sequence current is calculated using equation (6). and : (6) In the formula, the negative sequence current amplitude It is obtained by iterative calculation using equations (7) and (8). (7) (8) In the formula, , and The three-phase current amplitudes at the AC ports of the flexible interconnection device; the phase angle difference between the positive and negative sequence currents of phase A. Positive sequence current amplitude And the magnitudes of the positive and negative sequence currents satisfy the relationship Equation (8) is the convergence condition. Maximum phase current and fault current limiting values The difference between them; This indicates the convergence tolerance.

5. The fault isolation method for distributed area protection and flexible interconnection device collaborative control according to claim 1, characterized in that, The specific method for fault isolation in step S8 is as follows: when the positive sequence current reference value in step S5 meets the fault limiting requirement, the protection device uses the positive sequence fault component direction element protection criterion to determine the fault direction; otherwise, it uses the negative sequence fault component direction element protection criterion to determine the fault direction. Adjacent protection devices communicate using the data transmission architecture in step S1. Only when the local protection device determines that the fault occurs in the positive direction and receives the positive direction fault determination result transmitted by the other protection device, will the local protection device send a trip signal to the local circuit breaker to achieve fault isolation.

6. A control and protection system for implementing the method of any one of claims 1 to 5, characterized in that, include: The data acquisition module is used to collect the voltage and current of each AC port of the flexible interconnection device and both sides of the protected line in real time; The data processing module is used to calculate the fault component voltage and current, extract its sequence component, and then calculate the fault characteristic impedance angle. The fault triggering module is used to calculate the voltage drop and current surge, and to determine whether a fault has occurred. The control parameter calculation module is used to calculate the reference values ​​of the positive sequence and negative sequence inner loop currents; The control execution module is used to update the positive and negative sequence current reference values ​​of the inner loop of the input current and generate a modulation signal. The isolation decision module is used to determine the fault location based on the fault characteristic impedance angle and directional element protection criteria, and to complete the switching decision.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 6.

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