Cross-regional flexible interconnection power distribution network reliability evaluation method

Abstract

The invention is suitable for the technical field of improving the reliability of a flexible interconnected power distribution network, and provides a cross-regional flexible interconnected power distribution network reliability evaluation method, which comprises the following steps: establishing a mathematical model of a rotation power flow controller composed of two rotation phase-shifting transformers; proposing a power distribution network power supply reliability evaluation index obtained by the load point index and the system reliability index; a basic framework of a power distribution network reliability evaluation algorithm is established based on a sequential Monte Carlo simulation method in a novel power distribution network in which a rotating power flow controller is accessed in a cross-regional manner; and analyzing and calculating the influence of the regional interconnection access condition of the rotary power flow controller of the flexible interconnection device on the reliability index of the system based on the algorithm. According to the invention, the reliability of the cross-regional flexible interconnection power distribution network can be obviously improved.

Description

Technical Field

[0001] The present application is applicable to the technical field of improving the reliability of flexible interconnected distribution networks, and specifically relates to a reliability assessment method for cross-regional flexible interconnected distribution networks. Background Art

[0002] Under the requirements of the "dual carbon" goal, a large number of distributed power sources are connected and the load level of the power grid continues to grow. Low-voltage distribution networks face huge challenges: some lines are overloaded, node voltages exceed the limit, and line currents flow in both directions; distributed resources such as user-side flexible loads participate in power grid dispatching, making it difficult for traditional distribution network topology structures to meet flexibility requirements. As the final link in power transmission, the requirements for power quality and power supply reliability of distribution networks are increasing.

[0003] In order to optimize the dispatching means, flexible AC transmission system devices can be used to transfer power from heavy-load lines to light-load lines, and improve the line transmission capacity through power flow control. Flexible interconnection devices based on power electronic equipment are represented by intelligent soft switches and energy routers. Intelligent soft switches can make the distribution network operate in a closed loop by applying appropriate control to the converters on both sides, balance the power between feeders, and realize power flow control and power mutual assistance between distribution sub-grids. However, intelligent soft switches are mainly based on fully controlled power electronic conversion devices, which occupy a large area and have high investment and maintenance costs. The unified power flow controller also uses power electronic devices to achieve rapid control of power between lines, but has shortcomings such as weak impact resistance and high cost.

[0004] In the 1990s, General Electric Company of the United States proposed the rotating power flow controller, a flexible AC transmission device based on a rotating phase-shifting transformer, which can flexibly adjust the line power flow at a low cost. However, there are few studies on the application of rotating power flow controllers in distribution networks, and the reliability of the new power system distribution network connected to the rotating power flow controller needs to be solved urgently. Summary of the invention

[0005] In order to overcome the problems existing in the related art, an embodiment of the present application provides a reliability assessment method for a cross-regional flexible interconnected distribution network, so as to improve the reliability of the cross-regional flexible interconnected distribution network.

[0006] This application is implemented through the following technical solutions, including:

[0007] A mathematical model of a rotating power flow controller consisting of two rotating phase-shifting transformers was established; a distribution network power supply reliability evaluation index obtained from load point indicators and system reliability indicators was proposed; the basic framework of the distribution network reliability evaluation algorithm was established based on the sequential Monte Carlo simulation method in a new distribution network with cross-regional access of rotating power flow controllers; and the impact of regional interconnection access of rotating power flow controllers of flexible interconnected devices on system reliability indicators was analyzed and calculated based on the proposed algorithm.

[0008] In the method for improving the new energy carrying capacity of the distribution network by using a rotating power flow controller, the working principle of the rotating power flow controller includes:

[0009] The rotating power flow controller is mainly composed of two rotating phase-shifting transformers. The rotor winding is wound with a large number of coils. In actual production, the rotor winding is connected to the line in parallel as the primary winding, and the stator side is connected to the line in series as the secondary winding. Driven by the servo motor, the RPST stator winding with p pairs of poles rotates a certain mechanical angle, and β is generated between the stator and rotor windings. mech The mechanical angle of the axis, then the electrical angle between the windings α = p·β mech The voltage at the output of the two RPSTs is also changed; based on the principle of electromagnetic induction, the rotor angles of the two RPSTs rotate to synthesize a stator voltage with a certain amplitude and a 360° adjustable phase angle, which is injected into the line, enabling the rotating power flow controller to continuously adjust the voltage and smoothly and continuously realize the function of line power control.

[0010] RPST1 and RPST2 are two rotating phase-shifting transformers. and are the voltages at both ends of the line to which the rotary power flow controller is connected, namely the sending end voltage and the receiving end voltage. is the output voltage of the rotating power flow controller, α1 and α2 are the rotation angles of the two RPSTs respectively. The voltage vector size of the line connected in series with the rotating power flow controller can be changed by simply changing the size of the rotor angle, thereby achieving smooth voltage regulation.

[0011] Sending voltage Generated by the rotor winding The rotor winding parallel voltage is generated on the stator winding side through the principle of electromagnetic induction. and The stator side voltage is adjusted by adjusting the rotation angles α1 and α2 to obtain a series output voltage with a constant amplitude and a 360° adjustable phase angle. Assuming that the stator impedance of the two rotating phase-shifting transformers is equal to the stator-rotor winding ratio, we can obtain k = k1 = k2; Z st =Z st1 =Z st2 .

[0012] Furthermore, ignoring the influence of transformer excitation current, the rotating power flow controller can be analyzed as follows:

[0013]

[0014]

[0015]

[0016] Furthermore, the voltage relationship between the stator side of the two rotating phase-shifting transformers can be obtained:

[0017]

[0018] Furthermore, the series output voltage of the rotating power flow controller can be obtained Voltage in parallel with the rotor winding Relational formula:

[0019]

[0020] Furthermore, the series and parallel line currents can be obtained and Relational formula:

[0021]

[0022] Furthermore, the single-phase equivalent circuit diagram of the rotating power flow controller can be obtained, and the output voltage of the rotating power flow controller can be obtained. Current in series with the line The relationship between series and parallel current Relational formula:

[0023]

[0024]

[0025] Where: k RPFC is the equivalent winding ratio of the rotating power flow controller, Z RPFC is the internal impedance of the rotating power flow controller, the sum of the impedances caused by the stator and rotor windings. The impedance value changes with the rotation angle α1 and α2. Among them, the parameter Z RPFC , k RPFC Respectively represented by Z RPFC =4k 2 cos 2 ρZ rt +2Z rt ;k RPFC =2kcosρ.

[0026] Furthermore, the total current of the connected line can be obtained With series line current The relationship is:

[0027]

[0028] In the method for improving the new energy carrying capacity of the distribution network by using a rotating power flow controller, the mathematical model of the rotating power flow controller includes:

[0029] When a large disturbance occurs in the interconnected system, a mathematical model can be derived from the working principle of the rotating power flow controller, and the series output voltage can be obtained. The voltage at the line sending end and line current The relationship is:

[0030]

[0031] The rotating power flow controller is equivalent to an ideal controlled voltage source The mathematical model of the equivalent impedance Z in series, where the parameters The expressions of and Z are:

[0032]

[0033] The rotary power flow controller is put into use, and the output voltage of the rotary power flow controller is Get the line receiving end for:

[0034]

[0035] The servo motor rotates to adjust the rotation angles α1 and α2, and the line transmits active and reactive powers P1 and Q1 respectively:

[0036]

[0037] Where: k eq k is the equivalent transformation ratio of the voltage amplitude at both ends of the line after the rotating power flow controller is put into operation, eq is the equivalent transformation ratio of the voltage phase at both ends of the line, the specific expression is:

[0038]

[0039] In the method for improving the new energy carrying capacity of the distribution network by using a rotating power flow controller, the component state simulation includes:

[0040] In the component state model, the component state changes between normal and shutdown states, and the state of each component is independent of each other; when using Monte Carlo simulation, the time of normal and shutdown states is random.

[0041] In the method for improving the new energy carrying capacity of the distribution network by using a rotating power flow controller, the Monte Carlo simulation method includes:

[0042] The reliability of the distribution network is evaluated by using the digital numbering method and the Monte Carlo simulation method. During the simulation, the Monte Carlo method determines the order and time of component failures as a whole, and simulates each component of the system to randomly generate TTF. Assuming that the system has n components that need to be simulated for faults, the failure rate of the initial failure of the component, and the component repair rate, the system is simulated for N years; the digital numbering method determines the location of the component and the impact of the failure on the load point for a certain fault, and obtains the reliability index of the load point and the system through comprehensive analysis. The specific evaluation process is as follows:

[0043] Step 1: Randomly generate n random numbers between [0,1] and obtain their corresponding TTF;

[0044] Step 2: Find the component j (j=1, 2, ..., n) corresponding to the minimum TTF value, then TTF min =TTF j , component j is the faulty component, generate a random number for j, and find its corresponding TTR j ;

[0045] Step 3: Mark all load points affected by the component j failure, record the power outage situation of each load point, and the first simulation process ends;

[0046] Step 4: Regenerate a random number and obtain the TTF corresponding to the new random number j ', repeat steps 1 and 2 to obtain a new TTF m ' in ;

[0047] Step 5: Determine whether the simulation duration is 1 year. If it is less than one year, continue to accumulate. If it is more than one year, calculate the reliability index of that year and start accumulating the load point index of the new year.

[0048] Step 6: Determine whether the simulation duration has reached the simulation period. If not, return to step 2 to continue the simulation. If exceeded, stop the simulation.

[0049] Step 7: After the simulation is completed, calculate the reliability index of the system for N years, and then take the average to obtain the final reliability result of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a Monte Carlo method evaluation flow chart based on a reliability evaluation method for a cross-regional flexible interconnected distribution network in this application.

[0051] Figure 2The present invention is a topological diagram of a 10kV distribution line in a certain area, which is the basis for a reliability assessment method of a cross-regional flexible interconnected distribution network in this application.

[0052] Figure 3 This is the traditional topology diagram of the 10kV distribution network on which the reliability assessment method of a cross-regional flexible interconnected distribution network is based in this application.

[0053] Figure 4 This is a topological diagram of a 10kV distribution network equipped with a rotating power flow controller, which is the basis for a reliability assessment method for a cross-regional flexible interconnected distribution network in this application.

[0054] Figure 5 The present invention discloses a load power outage index diagram based on which a reliability assessment method for a cross-regional flexible interconnected distribution network is applied.

[0055] Figure 6 The present invention discloses an annual average power outage time index diagram of loads based on a reliability assessment method for a cross-regional flexible interconnected distribution network.

[0056] Figure 7 This is a load average power outage time index diagram based on a reliability assessment method for a cross-regional flexible interconnected distribution network in this application. DETAILED DESCRIPTION

[0057] In the following description of the present invention, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0058] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0059] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0060] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0061] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0062] The present application is described in detail below with reference to the accompanying drawings and specific implementation methods.

[0063] Figure 1 This is a Monte Carlo method evaluation flow chart provided in an embodiment of the present application, referring to Figure 1 , the method is described in detail as follows:

[0064] A mathematical model of a rotating power flow controller consisting of two rotating phase-shifting transformers was established; a distribution network power supply reliability evaluation index obtained from load point indicators and system reliability indicators was proposed; the basic framework of the distribution network reliability evaluation algorithm was established based on the sequential Monte Carlo simulation method in a new distribution network with cross-regional access of rotating power flow controllers; and the impact of regional interconnection access of rotating power flow controllers of flexible interconnected devices on system reliability indicators was analyzed and calculated based on the proposed algorithm.

[0065] Exemplarily, in the method for improving the new energy carrying capacity of the distribution network by using a rotating power flow controller, the working principle of the rotating power flow controller includes:

[0066] The rotating power flow controller is mainly composed of two rotating phase-shifting transformers. The rotor winding is wound with a large number of coils. In actual production, the rotor winding is connected to the line in parallel as the primary winding, and the stator side is connected to the line in series as the secondary winding. Driven by the servo motor, the RPST stator winding with p pairs of poles rotates a certain mechanical angle, and β is generated between the stator and rotor windings. mech The mechanical angle of the axis, then the electrical angle between the windings α = p·β mech The voltage at the output terminal of the two RPSTs is also changed; based on the principle of electromagnetic induction, the rotor angles of the two RPSTs rotate to synthesize a stator voltage with a certain amplitude and a 360° adjustable phase angle, which is injected into the line, enabling the rotating power flow controller to continuously adjust the voltage and smoothly and continuously realize the function of line power control.

[0067] RPST1 and RPST2 are two rotating phase-shifting transformers. and are the voltages at both ends of the line to which the rotary power flow controller is connected, namely the sending end voltage and the receiving end voltage. is the output voltage of the rotating power flow controller, α1 and α2 are the rotation angles of the two RPSTs respectively. The voltage vector size of the line connected in series with the rotating power flow controller can be changed by simply changing the size of the rotor angle, thereby achieving smooth voltage regulation.

[0068] Sending voltage Generated by the rotor winding The rotor winding parallel voltage is generated on the stator winding side through the principle of electromagnetic induction. and The stator side voltage is adjusted by adjusting the rotation angles α1 and α2 to obtain a series output voltage with a constant amplitude and a 360° adjustable phase angle. Assuming that the stator impedance of the two rotating phase-shifting transformers is equal to the stator-rotor winding ratio, we can obtain k = k1 = k2; Z st =Z st1 =Z st2 .

[0069] Optionally, ignoring the effect of transformer excitation current, the rotating power flow controller can be analyzed as follows:

[0070]

[0071]

[0072]

[0073] For example, the relationship between the stator-side voltages of two rotating phase-shifting transformers can be obtained:

[0074]

[0075] For example, the rotating power flow controller series output voltage can be obtained Voltage in parallel with the rotor winding Relational formula:

[0076]

[0077] For example, the series and parallel line currents can be obtained and Relational formula:

[0078]

[0079] Optionally, the single-phase equivalent circuit diagram of the rotating power flow controller can be obtained, and the output voltage of the rotating power flow controller can be obtained. Current in series with the line The relationship between series and parallel current Relational formula:

[0080]

[0081]

[0082] Where: k RPFC is the equivalent winding ratio of the rotating power flow controller, Z RPFC is the internal impedance of the rotating power flow controller, the sum of the impedances caused by the stator and rotor windings. The impedance value changes with the rotation angle α1 and α2. Among them, the parameter Z RPFC , k RPFC Respectively represented by Z RPFC =4k 2 cos 2 ρZ rt +2Z rt ;k RPFC =2kcosρ.

[0083] For example, the total current of the connected line can be obtained With series line current The relationship is:

[0084]

[0085] Optionally, in the method for improving the new energy carrying capacity of a distribution network by using a rotating power flow controller, the mathematical model of the rotating power flow controller includes:

[0086] When a large disturbance occurs in the interconnected system, a mathematical model can be derived from the working principle of the rotating power flow controller, and the series output voltage can be obtained. The voltage at the line sending end and line current The relationship is:

[0087]

[0088] The rotating power flow controller is equivalent to an ideal controlled voltage source The mathematical model of the equivalent impedance Z in series, where the parameters The expressions of and Z are:

[0089]

[0090] Optionally, a rotating power flow controller is put into use, and the output voltage of the rotating power flow controller is Get the line receiving end for:

[0091]

[0092] The servo motor rotates to adjust the rotation angles α1 and α2, and the line transmits active and reactive powers P1 and Q1 respectively:

[0093]

[0094] Where: k eq k is the equivalent transformation ratio of the voltage amplitude at both ends of the line after the rotating power flow controller is put into operation, eq is the equivalent transformation ratio of the voltage phase at both ends of the line, the specific expression is:

[0095]

[0096] In the method for improving the new energy carrying capacity of the distribution network by using a rotating power flow controller, the component state simulation includes:

[0097] In the component state model, the component state changes between normal and shutdown states, and the state of each component is independent of each other; when using Monte Carlo simulation, the time of normal and shutdown states is random.

[0098] Exemplarily, in the method for improving the new energy carrying capacity of the distribution network by using a rotating power flow controller, the Monte Carlo simulation method includes:

[0099] The reliability of the distribution network is evaluated by using the digital numbering method and the Monte Carlo simulation method. During the simulation, the Monte Carlo method determines the order and time of component failures as a whole, and simulates each component of the system to randomly generate TTF. Assuming that the system has n components that need to be simulated for faults, the failure rate of the initial failure of the component, and the component repair rate, the system is simulated for N years; the digital numbering method determines the location of the component and the impact of the failure on the load point for a certain fault, and obtains the reliability index of the load point and the system through comprehensive analysis. The specific evaluation process is as follows:

[0100] Step 1: Randomly generate n random numbers between [0,1] and obtain their corresponding TTF;

[0101] Step 2: Find the component j (j=1, 2, ..., n) corresponding to the minimum TTF value, then TTF min =TTF j , component j is the faulty component, generate a random number for j, and find its corresponding TTR j ;

[0102] Step 3: Mark all load points affected by the component j failure, record the power outage situation of each load point, and the first simulation process ends;

[0103] Step 4: Regenerate a random number and obtain the TTF corresponding to the new random number j ', repeat steps 1 and 2 to obtain a new TTF'min ;

[0104] Step 5: Determine whether the simulation duration is 1 year. If it is less than one year, continue to accumulate. If it is more than one year, calculate the reliability index of that year and start accumulating the load point index of the new year.

[0105] Step 6: Determine whether the simulation duration has reached the simulation period. If not, return to step 2 to continue the simulation. If exceeded, stop the simulation.

[0106] Step 7: After the simulation is completed, calculate the reliability index of the system for N years, and then take the average to obtain the final reliability result of the system.

[0107] Example

[0108] Take the actual distribution network in a certain area as an example to carry out reliability assessment. The network topology is as follows: Figure 2 As shown, load numbers 1 to 12 correspond to node numbers 12 to 23, among which load numbers 1 to 4 are for area A, load numbers 5 to 8 are for area C, load numbers 9 to 12 are for area B, K1 is a flexible interconnection device, areas A and C are urban loads, and area B is a suburban load; the assumptions in the calculation are: all components in the system are repairable; the refusal and malfunction of the switch equipment are not considered; only permanent failures of components are considered and the failed components can only be operated again after repair; the failure rate of each component is shown in Table 1:

[0109] Table 1 shows the parameter point selection of the variable parameter model

[0110]

[0111] In order to explore the impact of the access of the rotating power flow controller on the reliability of the distribution network, a 100-year simulation calculation of the example system is carried out according to the above algorithm; the reliability calculation and analysis of the traditional distribution network and the flexible interconnected distribution network are carried out based on the following two scenarios.

[0112] Scenario 1: No rotating power flow controller is configured, and the traditional radial distribution network is used. That is, the K1 closing function is not disconnected, and the ABC substations operate independently.

[0113] Scenario 2: Configure a rotating power flow controller, close K1 to close the loop, and realize the interconnection of AB substations.

[0114] The numbering method is used to traverse the topological diagram of the distribution network in City A in Case 1 and Case 2, and the structural diagrams before and after the installation of the rotary power flow controller are obtained as shown in the figure. Figure 3 , Figure 4As shown; for substation A, its internal load power demand is provided by the upper-level power grid and the distributed power sources in the region. When the power generation of the distributed power sources exceeds the load demand, the excess power is transmitted to substation B through the rotating power flow controller interconnection line; if the transmitted power reaches the capacity upper limit of the rotating power flow controller device, the output of the distributed power sources in substation A will be reduced; if the power generation in substation A cannot meet the power demand in the region, the insufficient power difference can be supplemented by the upper-level power grid and the rotating power flow controller interconnection device and substation B.

[0115] The Monte Carlo method is used to calculate and analyze the average failure rate, annual average power outage time and average power outage time of each load point with and without the rotation power flow controller. The results are as follows: Figures 5 to 7 As shown. When a distribution feeder in front of the load point in area B fails, the load power can be transmitted through the rotating power flow controller to isolate the fault and transfer the load power demand of area B to the upper power grid via area A. Therefore, the system reliability of the cross-regional interconnected flexible distribution network invested by the rotating power flow controller is significantly improved.

[0116] This application is applicable to the technical field of improving the reliability of flexible interconnected distribution networks, and provides a reliability assessment method for cross-regional flexible interconnected distribution networks, which includes: establishing a mathematical model of a rotating power flow controller composed of two rotating phase-shifting transformers; proposing a distribution network power supply reliability assessment index obtained from load point index and system reliability index; establishing the basic framework of the distribution network reliability assessment algorithm based on the sequential Monte Carlo simulation method in a new distribution network with cross-regional access of the rotating power flow controller; and analyzing and calculating the impact of the regional interconnection access of the rotating power flow controller of the flexible interconnected device on the system reliability index based on the proposed algorithm. This application can significantly improve the reliability of cross-regional flexible interconnected distribution networks.

[0117] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0118] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A reliability assessment method for a cross-regional flexible interconnected distribution network, characterized in that: include: The mathematical model of the rotating power flow controller consisting of two rotating phase-shifting transformers was established. Propose a distribution network power supply reliability evaluation index obtained from load point index and system reliability index; The basic framework of the distribution network reliability assessment algorithm is established based on the sequential Monte Carlo simulation method in a new distribution network with cross-regional access of rotating power flow controllers. Based on the proposed algorithm, the influence of regional interconnection access of rotating power flow controller of flexible interconnected device on system reliability index is analyzed and calculated.

2. The reliability assessment method of a cross-regional flexible interconnected distribution network according to claim 1 is characterized in that: Mathematical modeling of the rotating power flow controller is carried out and a distribution network reliability assessment algorithm is established based on the sequential Monte Carlo simulation method.

3. The reliability assessment method of the cross-regional flexible interconnected distribution network according to claim 2 is characterized in that: The working principle of the rotating power flow controller includes: The rotating power flow controller is mainly composed of two rotating phase-shifting transformers. The rotor winding is wound with a large number of coils. In actual production, the rotor winding is connected to the line in parallel as the primary winding, and the stator side is connected to the line in series as the secondary winding. Driven by the servo motor, the RPST stator winding with p pairs of poles rotates a certain mechanical angle, and β is generated between the stator and rotor windings. mech The mechanical angle of the axis, then the electrical angle between the windings α = p·β mech The voltage of the power line is also changed; based on the principle of electromagnetic induction, the rotor angles of the two RPSTs rotate to synthesize a stator voltage with a certain amplitude and a 360° adjustable phase angle, which is injected into the line, so that the rotating power flow controller can continuously adjust the voltage and smoothly and continuously realize the function of line power control; RPST1 and RPST2 are two rotating phase-shifting transformers. and are the voltages at both ends of the line to which the rotary power flow controller is connected, namely the sending end voltage and the receiving end voltage, is the output voltage of the rotating power flow controller, α1 and α2 are the rotation angles of the two RPSTs, and the voltage vector of the line connected in series with the rotating power flow controller can be changed by simply changing the rotor angle, thereby achieving smooth voltage regulation; Sending voltage Generated by the rotor winding The rotor winding parallel voltage is generated on the stator winding side through the principle of electromagnetic induction. and The stator side voltage is adjusted by adjusting the rotation angles α1 and α2 to obtain a series output voltage with a constant amplitude and a 360° adjustable phase angle. Assuming that the stator impedance of the two rotating phase-shifting transformers is equal to the stator-rotor winding ratio, we can obtain k = k1 = k2; Z st =Z st1 =Z st2 ; Ignoring the influence of transformer excitation current, the rotating power flow controller can be analyzed as follows: The voltage relationship between the stator side of the two rotating phase-shifting transformers can be obtained: The output voltage of the rotating power flow controller in series is Voltage in parallel with the rotor winding Relational formula: The current of series and parallel lines can be obtained and Relational formula: The single-phase equivalent circuit diagram of the rotating power flow controller can be obtained. The output voltage of the rotating power flow controller can be obtained. Current in series with the line The relationship between series and parallel current Relational formula: Where: k RPFC is the equivalent winding ratio of the rotating power flow controller, Z RPFC is the internal impedance of the rotating power flow controller, the sum of the impedances caused by the stator and rotor windings. The impedance value changes with the rotation angle α1 and α2. Among them, the parameter Z RPFC , k RPFC Respectively represented by Z RPFC =4k 2 cos 2 ρZ rt +2Z rt ;k RPFC =2kcosρ.

4. The reliability assessment method of a cross-regional flexible interconnected distribution network according to claim 1 is characterized in that: The mathematical model of the rotating power flow controller includes: When a large disturbance occurs in the interconnected system, a mathematical model can be derived from the working principle of the rotating power flow controller, and the series output voltage can be obtained. The voltage at the line sending end and line current The relationship is: The rotating power flow controller is equivalent to an ideal controlled voltage source The mathematical model of the equivalent impedance Z in series, where the parameters The expressions of and Z are: The rotary power flow controller is put into use, and the output voltage of the rotary power flow controller Get the line receiving end for: The servo motor rotates to adjust the rotation angles α1 and α2, and the line transmits active and reactive powers P1 and Q1 respectively: Where: k eq k is the equivalent transformation ratio of the voltage amplitude at both ends of the line after the rotating power flow controller is put into operation, eq is the equivalent transformation ratio of the voltage phase at both ends of the line.

5. The reliability assessment method of a cross-regional flexible interconnected distribution network according to claim 1 is characterized in that: The component state simulation includes: In the component state model, the component state changes between normal and shutdown states, and the state of each component is independent of each other; when using Monte Carlo simulation, the time of normal and shutdown states is random.

6. The reliability assessment method of the cross-regional flexible interconnected distribution network according to claim 2 is characterized in that: The Monte Carlo simulation method comprises: The reliability of the distribution network is evaluated by using the digital numbering method and the Monte Carlo simulation method. During the simulation, the Monte Carlo method determines the order and time of component failures as a whole, and simulates each component of the system to randomly generate TTF. Assuming that the system has n components that need to be simulated for faults, the failure rate of the initial failure of the component, and the component repair rate, the system is simulated for N years; the digital numbering method determines the location of the component and the impact of the failure on the load point for a certain fault, and obtains the reliability index of the load point and the system through comprehensive analysis. The specific evaluation process is as follows: Step 1: Randomly generate n random numbers between [0,1] and obtain their corresponding TTF; Step 2: Find the component j (j=1, 2, ..., n) corresponding to the minimum TTF value, then TTF min =TTF j , component j is the faulty component, generate a random number for j, and find its corresponding TTR j ; Step 3: Mark all load points affected by the component j failure, record the power outage situation of each load point, and the first simulation process ends; Step 4: Regenerate a random number and obtain the TTF' corresponding to the new random number j Repeat steps 1 and 2 to obtain a new TTF' min ; Step 5: Determine whether the simulation duration is 1 year. If it is less than one year, continue to accumulate. If it is more than one year, calculate the reliability index of that year and start accumulating the load point index of the new year. Step 6: Determine whether the simulation duration has reached the simulation period. If not, return to step 2 to continue the simulation. If exceeded, stop the simulation. Step 7: After the simulation is completed, calculate the reliability index of the system for N years, and then take the average to obtain the final reliability result of the system.

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