Tree-shaped dual-side power supply system compensation device based on three-port power flow controller and control method thereof

Abstract

The application discloses a tree-shaped double-side power supply system compensation device based on a three-port power flow controller and a control method thereof. The compensation device comprises a three-port power flow controller, three step-down transformers and a measurement and control unit. The primary sides of the three step-down transformers are connected to three-phase of a main transformer substation respectively, and the secondary sides of the three step-down transformers are connected to three ports of the three-port power flow controller respectively. The measurement and control unit is used for collecting feeder current of a traction transformer substation and bus voltage of the main transformer substation, and outputs a control signal after processing, so as to control the three-port power flow controller and compensate the tree-shaped double-side power supply system. The application realizes decoupling of the traction transformer and the compensation device, directly carries out negative sequence treatment and reactive power compensation on the system at the PCC point of the high-voltage side of the tree-shaped double-side power supply system, is not limited by the wiring form of the traction transformer in each traction transformer substation in the tree-shaped double-side power supply system, and is more widely applicable.

Description

Technical Field

[0001] This invention relates to the field of electrified railway traction power supply system technology, and in particular to a tree-shaped bilateral power supply system compensation device and its control method based on a three-port power flow controller. Background Technology

[0002] To address the operational safety issues caused by phase separation, a tree-shaped bilateral power supply system was proposed. In this system, all traction substations are connected to the same busbar of the same main substation. These traction substations connected to the same main substation are grouped together as a single traction substation group (referred to as a "substation group"). No phase separation is required between adjacent substations within the substation group. Because the high-voltage sides of each traction substation are connected to the same main substation, the voltage amplitude and phase are identical, effectively avoiding circulating current problems. The elimination of phase separation between adjacent substations allows the power supply arm to be supplied simultaneously by substations on both sides, effectively improving the stability of the traction network voltage and significantly enhancing the regenerative braking energy utilization rate. The tree-shaped bilateral power supply system demonstrates clear economic and technical advantages. If the traction substations within the substation group use single-phase traction transformers, phase separation at the substation outlet can be further eliminated, achieving full-through power supply within the substation group and further improving the regenerative braking energy utilization rate. However, the negative sequence problem will also become more severe. Regardless of the wiring configuration of the traction transformers within the power grid, the overall negative sequence situation caused by the entire power grid must be examined at the point of common coupling (PCC) of the external power grid. This can easily lead to excessive negative sequence. Therefore, resolving the negative sequence problem is one of the key technologies for tree-shaped bilateral power supply systems. Summary of the Invention

[0003] The purpose of this invention is to provide a compensation device and control method for a tree-shaped bilateral power supply system based on a three-port power flow controller, which solves the problem of severe negative sequence in the tree-shaped bilateral power supply system, and at the same time can improve the power factor of the tree-shaped bilateral power supply system.

[0004] The technical solution for achieving the objective of this invention is as follows:

[0005] A compensation device for a tree-shaped bilateral power supply system based on a three-port power flow controller is provided. The tree-shaped bilateral power supply system includes a main substation and multiple traction substations, with the multiple traction substations drawing power from the main substation bus via feeders. The device includes a three-port power flow controller, three step-down transformers, and a measurement and control unit. The primary sides of the three step-down transformers are connected to the three phases of the main substation, and the secondary sides are connected to the three ports of the three-port power flow controller. The measurement and control unit collects the feeder current drawn from the traction substations and the bus voltage of the main substation, processes the data, and outputs a control signal to control the three-port power flow controller to compensate the tree-shaped bilateral power supply system.

[0006] Preferably, the compensation device is set at the minimum distance from the main substation.

[0007] The control method for the above-mentioned compensation device is as follows:

[0008] The maximum three-phase voltage imbalance caused by the tree-shaped bilateral power supply system at the point of common coupling of the external power grid is ε. 0,max The 95% statistical value of three-phase voltage imbalance is ε. 0,95％ The daily average power factor is PF0;

[0009] Step 1: Collect the feeder current drawn from the traction substation at time t. and the bus voltage of the main substation Where i = 1, 2, ..., n is the serial number of the traction substation; A, B and C represent three phases; CT refers to current transformer and VT refers to voltage transformer;

[0010] Step 2: Calculate the three-phase voltage imbalance ε0(t) caused by the tree-shaped bilateral power supply system at time t.

[0011]

[0012] Among them, S n Indicates the short-circuit capacity of the external power grid, where U is the rated value of the three-phase voltage, and I... - (t) represents the negative sequence current at time t.

[0013]

[0014] In the formula, a = e j120° , These are the total currents for phases A, B, and C, respectively.

[0015]

[0016] Step 3, determine the satisfactory compensation target: compensate the power factor to the expected daily average power factor value PF1, and compensate the maximum three-phase voltage imbalance to ε. 1,max The statistical value of the three-phase voltage imbalance is compensated to ε. 1,95％ ;

[0017] 3.1 Determine the reactive power compensation degree C at time t q (t),

[0018]

[0019] Where PF(t) is the power factor of the tree-shaped two-sided power supply system at time t.

[0020]

[0021] In the formula, P L (t), Q L (t) represents the total active power and total reactive power of the tree-shaped bilateral power supply system at time t, respectively. The power flowing into the tree-shaped bilateral power supply system from the external power grid is positive, and the power flowing back from the tree-shaped bilateral power supply system to the external power grid is negative.

[0022] 3.2 Determine the negative order compensation degree C at time t n (t),

[0023]

[0024] Step 4: Perform satisfactory compensation for the tree-shaped two-sided power supply system:

[0025] 4.1 Solving for the three-phase complex power of the external power grid

[0026] in, The three-phase voltages at time t are respectively The vector representation of , They are time t respectively The conjugate vector representation of ;

[0027] 4.2 Extraction The active component P in A (t), P B (t), P C (t) and reactive component Q A (t), Q B (t), Q C (t), calculate the average value P of the active component. ave (t) and the average value of the reactive component Q ave (t):

[0028]

[0029] 4.3 Calculate the expected complex power of the converter in the three-port power flow controller.

[0030]

[0031] In the formula, Let represent the expected complex power values ​​of the converters connected to phases A, B, and C in the three-port power flow controller at time t;

[0032] 4.4 Calculate the expected value of the compensation current of the converter in the three-port power flow controller.

[0033]

[0034] In the formula, i1,ref (t), i 2,ref (t), i 3,ref (t) represents the expected compensation current of the converters connected to phases A, B, and C in the three-port power flow controller at time t, respectively, and k y The turns ratio of a step-down transformer; These are vector representations of the voltages in phases A, B, and C, respectively. * " indicates conjugate;

[0035] 4.5 A voltage and current dual closed-loop control method is adopted to control the converters connected to phases A, B, and C in the three-port power flow controller to achieve satisfactory compensation.

[0036] Another control method for the above-mentioned compensation device is as follows:

[0037] Step 1: Collect the feeder current drawn from the traction substation at time t. and the bus voltage of the main substation Where i = 1, 2, ..., n is the serial number of the traction substation; A, B and C represent three phases; CT refers to current transformer and VT refers to voltage transformer;

[0038] Step 2, Determine the target for complete compensation: reactive power compensation degree C at time t. q (t) = 1, negative order compensation degree C at time t n (t) = 1;

[0039] Step 3: Perform full compensation for the tree-shaped bilateral power supply system:

[0040] 3.1 Solving for the three-phase complex power of the external power grid

[0041] in, The three-phase voltages at time t are respectively The vector representation of , They are time t respectively The conjugate vector representation of ;

[0042] 3.2 Extraction The active component P in A (t), P B (t), P C (t) and reactive component Q A (t), Q B (t), Q C (t), calculate the average value P of the active component. ave (t) and the average value of the reactive component Q ave (t):

[0043]

[0044] 3.3 Calculate the expected complex power of the converter in the three-port power flow controller.

[0045]

[0046] In the formula, Let represent the expected complex power values ​​of the converters connected to phases A, B, and C in the three-port power flow controller at time t;

[0047] 3.4 Calculate the expected value of the compensation current of the converter in the three-port power flow controller.

[0048]

[0049] In the formula, i 1,ref (t), i 2,ref (t), i 3,ref (t) represents the expected compensation current of the converters connected to phases A, B, and C in the three-port power flow controller at time t, respectively, and k y The turns ratio of a step-down transformer; These are vector representations of the voltages in phases A, B, and C, respectively. * " indicates conjugate;

[0050] 3.5 A voltage and current dual closed-loop control method is adopted to control the converters connected to phases A, B, and C in the three-port power flow controller for complete compensation.

[0051] The beneficial effects of this invention are: it decouples the traction transformer from the compensation device, and directly performs negative sequence management and reactive power compensation on the PCC point on the high-voltage side of the tree-shaped bilateral power supply system; it is not limited by the wiring form of the traction transformer in each traction substation of the tree-shaped bilateral power supply system, and its application scope is wider. Attached Figure Description

[0052] Figure 1 This is the electrical structure diagram of the present invention. Detailed Implementation

[0053] This invention proposes a centralized negative sequence management scheme based on a Three-Port Power Flow Controller (TPFC) to address the severe negative sequence problem in tree-shaped bilateral power supply systems. First, feeder current and bus voltage information from the main substation are collected and transmitted via a fiber optic network to the controller CD in the main traction substation. The controller CD calculates a compensation current reference value and sends it to the TPFC. The TPFC then issues a compensation current to achieve negative sequence management and reactive power compensation. This invention features fast dynamic response and high compensation accuracy, demonstrating excellent compensation effects for both negative sequence and reactive power.

[0054] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0055] Figure 1 This is a schematic diagram of the topology of a tree-shaped bilateral power supply system. The tree-shaped bilateral power supply system contains n traction substations, forming a traction substation group. These n traction substations are named TTS. i (i = 1, 2, ..., n). Figure 1 The traction transformers in the n traction substations can have any wiring configuration. Each traction substation draws power from different sections of the same busbar in the same main substation. The negative sequence voltage is centrally examined at the PCC point. Given: The maximum three-phase voltage imbalance caused by the tree-shaped bilateral power supply system at the point of common coupling (PCC) of the external power grid is ε. 0,max The 95% statistical value of three-phase voltage imbalance is ε. 0,95％ The daily average power factor is PF0. The compensation effect of the compensation device can be flexibly determined according to the actual line requirements. The expected values ​​of the three-phase voltage imbalance and the daily average power factor are set: Let the expected value of the maximum three-phase voltage imbalance of the compensated tree-shaped bilateral power supply system be ε. 1,max The expected value of the 95% statistical value of the three-phase voltage imbalance of the compensated tree-shaped bilateral power supply system is ε. 1,95％ The expected value of the daily average power factor after compensation is PF1. To reduce the required fiber optic cable length and further lower costs, a separate negative sequence compensation station (the closer to the main substation the better) will be constructed and equipped with compensation devices. The compensation station will be powered by three phases and connected to the same three-phase sectional busbar of the main substation as the tree-shaped bilateral power supply system.

[0056] The compensation device consists of a step-down transformer (ST), a three-port power flow controller (TPFC), and a measurement and control unit (MC). The TPFC connects to the external power grid's three phases (A, B, and C) via the step-down transformer. The converter connected to phase A is designated VSC1, the converter connected to phase B is designated VSC2, and the converter connected to phase C is designated VSC3. The measurement and control unit mainly consists of voltage transformers (TA), current transformers (TV), and a controller (CD). Voltage transformers (TV) and current transformers (TA) are installed in the feeders of each traction substation in the tree-shaped double-sided power supply system. The input terminal of the controller (CD) receives voltage and current information, and its output terminal is connected to the TPFC control terminal.

[0057] Achieving comprehensive compensation for negative sequence and reactive power in a tree-shaped two-sided power supply system includes the following steps:

[0058] Step 1: Collect feeder current information of the main substation at time t Voltage information of three phases and busbar Electrical information is transmitted to the controller of the compensation device via a fiber optic network laid along the route.

[0059] Step 2: The current information transmitted in Step 1 is processed centrally to calculate the three-phase voltage imbalance ε0(t) caused by the tree-shaped bilateral power supply system at time t.

[0060] 2.1 Calculate the magnitude of the negative sequence current of phases A, B, and C at point PCC at time t using the transmitted current information: Total current of phase A for: Total current in phase B for: The total current of phase C for: Negative sequence current I - The calculation formula is:

[0061]

[0062] Where a = e j120° .

[0063] 2.2 The three-phase voltage imbalance ε0(t) caused by the tree-shaped bilateral power supply system at point PCC at time t is calculated as follows: Where S n This indicates the short-circuit capacity of the external power grid, where U is the rated value of the three-phase power grid line voltage.

[0064] Step 3: Determine the compensation mode based on the actual line requirements. Different compensation modes will have different compensation effects. Introduce the negative sequence compensation degree C. n With reactive power compensation degree C q This controls the compensation degree of the compensation device. The negative sequence compensation degree at time t is C. n (t), reactive power compensation degree is C q (t) can be divided into two types of compensation modes: full compensation and satisfactory compensation. The operation steps of the two compensation modes are explained respectively:

[0065] (1) Full Compensation Mode: The three-phase voltage imbalance caused by the tree-shaped bilateral power supply system is compensated to 0%, and the power factor is compensated to 1. The specific steps are as follows:

[0066] 3.1 Determine the value of reactive power compensation: Let the reactive power compensation at time t be 1, that is: C q (t) = 1.

[0067] 3.2 Determining the value of the negative order compensation degree: Let the negative order compensation degree at time t be 1, that is: C n(t) = 1.

[0068] (2) Satisfactory compensation mode: The power factor is compensated to the expected daily average power factor value PF1, and the maximum value of the three-phase voltage imbalance is compensated to ε. 1,max The following calculations compensate for 95% of the statistical value of the three-phase voltage imbalance to ε. 1,95％ the following.

[0069] The steps for satisfactory compensation of a tree-shaped two-sided power supply system are as follows:

[0070] 3.1 Determining the value of reactive power compensation: The selection of reactive power compensation needs to refer to the expected power factor PF1 and the power factor PF(t) of the tree-shaped two-sided power supply system at time t: Where P L With Q L These represent the total active power and total reactive power measured using voltage and current information, respectively. The positive direction is defined as the power flowing from the external grid into the tree-shaped bilateral power supply system, and the power returning to the external grid as negative. When the daily average power factor PF0 of the tree-shaped bilateral power supply system is less than the specified expected daily average power factor PF1 and PF(t) is less than PF1, the compensation device performs reactive power compensation; otherwise, the compensation device does not perform reactive power compensation. The reactive power compensation degree C at time t is... q (t) is:

[0071]

[0072] 3.2 Determining the value of the negative sequence compensation degree: This invention adopts a dual-limitation control strategy, that is, compensating the maximum value of the three-phase voltage imbalance to ε. 1,max The statistical value of the three-phase voltage imbalance is compensated to ε. 1,95％ Specifically, when the three-phase voltage imbalance caused by the tree-shaped bilateral power supply system exceeds ε at time t. 1,max At time t, the compensation device performs negative sequence compensation, compensating the three-phase voltage imbalance at time t to ε. 1,max When the three-phase voltage imbalance caused by the tree-shaped bilateral power supply system exceeds ε at time t. 1,95％ And less than ε 1,max With ε 0,95％ When the value is at its minimum, the compensation device performs negative sequence compensation, compensating the three-phase voltage imbalance at time t to ε. 1,95％ In other cases, negative order compensation is not performed. The specific formula for calculating the negative order compensation degree is:

[0073]

[0074] Step 4: Based on the information obtained in Steps 2 and 3 at time t, calculate the expected value of the TPFC compensation current, and use voltage and current dual closed-loop control to achieve DC-side voltage stabilization and rapid response and output of AC compensation current.

[0075] 4.1 The voltage and current information of each substation feeder obtained at time t is centrally processed to calculate the three-phase power of the external power grid: Let A, B, and C represent the complex power of the three phases A, B, and C at time t, with the power direction defined as: positive for power flowing from the external power grid into the substation, and negative for power flowing back into the power grid. The calculation formula is: in Let represent the phase voltage vector representation of the three-phase power system at time t. The vector representation of the conjugate of the phase currents on the three-phase power system side at time t.

[0076] 4.2 The calculated power of each phase on the external power grid side is processed to calculate the expected value of the compensation current of the converter in the three-port power flow controller of the compensation device at time t:

[0077] 4.2.1 Extracting the active component P from the three-phase complex power at time t r (t)(r=A,B,C) and reactive component Q r (t)(r=A,B,C), calculate the average value of the active component: The average value of the reactive component is:

[0078]

[0079] 4.2.2 Write the expression for the expected value of the complex power that the three converters should emit / absorb at time t:

[0080]

[0081] In the formula, Representing the port complex power of converter i (i = 1, 2, 3), to facilitate the distinction between the parameters in the expression for the expected value of the compensation current and the relevant quantities in the preceding steps, C′ n (t), C′ q (t) represents the negative sequence compensation degree and the reactive power compensation degree, respectively.

[0082] Calculate the complex power that the three converters should output / absorb at time t in both full compensation and satisfactory compensation modes:

[0083] (1) The negative order compensation degree C obtained in step 3 n (t) and reactive power compensation degree C qSubstituting (t) into the above formula, the expected value of the complex power of the converter in the three-port power flow controller under satisfactory compensation mode can be calculated:

[0084]

[0085] (2) The negative sequence compensation degree value at time t determined in step 3 is 1, and the reactive power compensation degree value is 1. Substituting these values ​​into the above formula, we can obtain the expected value of the complex power of the converter in the three-port power flow controller under full compensation mode:

[0086]

[0087] 4.2.3 From the calculation formula of the complex power of the three-port converter at time t obtained in 4.2.2 and the three-phase voltage, the expected value of the compensation current of the three-port converter can be obtained as follows:

[0088]

[0089] In the formula, i 1,ref (t), i 2,ref (t), i 3,ref (t) represents the expected compensation current values ​​of VSC1, VSC2, and VSC3 at time t, respectively, and k y For ST's ratio, These are the vector representations of the voltages of the three-phase buses A, B, and C, respectively. An asterisk indicates the conjugate form of the result of dividing the two.

[0090] 4.3 A voltage and current dual closed-loop control strategy is adopted to stabilize the DC side voltage of the back-to-back converter and control the output current of the three-port converter to make it equal to the expected value of the compensation current, thereby completing the comprehensive compensation of negative sequence and reactive power for the tree-shaped bilateral power supply system.

[0091] The present invention also provides a method for obtaining the calculated capacity of back-to-back converters in a compensation device:

[0092] The voltage and current information of the main substation connected to the tree-shaped bilateral power supply system can be obtained through methods such as power flow calculation of the electrified railway traction power supply system (but not limited to these methods). The compensation current reference value i of VSC1 of the compensation device can be calculated according to the above steps. 1,ref (t), VSC2 compensation current reference value i 2,ref (t), VSC3 compensation current reference value i 3,ref (t), the port voltage u1(t) of VSC1, the port voltage u2(t) of VSC2, and the port voltage u3(t) of VSC3 can be easily obtained through power flow calculation. The calculation formula for the calculated capacity S1(t) of VSC1 is: The formula for calculating the computational capacity S2(t) of VSC2 is: The formula for calculating the computational capacity S3(t) of VSC3 is: in, Let u1(t), u2(t), and u3(t) be the vector representations of the voltages, respectively. The compensation current i are respectively 1,ref (t), i 2,ref (t), i 3,ref The vector representation of the conjugate value of (t).

[0093] The expressions for calculating the capacity of the compensation device differ under different compensation modes. The expressions for calculating the capacity of the compensation device under both full compensation and satisfactory compensation modes are listed below:

[0094] (1) Satisfaction compensation mode:

[0095]

[0096] (2) Fully compensated mode:

[0097]

[0098] Considering the diurnal periodicity of traction loads, a single day is taken as the entire load cycle. The capacity at different times within the entire load cycle under either satisfactory or full compensation modes is calculated. Then, the maximum calculated capacity S of converters VSC1, VSC2, and VSC3 within the entire load cycle is selected. 1,max S 2,max S 3,max As the capacity of the converter, the total capacity S of the compensation device m For: S m =S 1,max +S 2,max +S 3,max .

[0099] This invention utilizes a three-port power flow controller to draw upon three-phase power from the external power grid, achieving three-phase power balance and mitigating negative sequence power. It decouples the compensation device from the traction transformer, directly addressing negative sequence power and reactive power compensation at the PCC point on the high-voltage side of the tree-shaped bilateral power supply system, reducing the investment costs associated with building fiber optic networks. Furthermore, this invention is not limited to traction transformers with single-phase wiring in each traction substation within a power grid; it also provides good compensation for traction transformers with other wiring configurations, broadening its applicability. Finally, this invention enables centralized compensation for negative sequence and reactive power in tree-shaped bilateral power supply systems, achieving excellent compensation results, wider applicability, and lower investment costs.

Claims

1. A control method for a compensation device for a tree-shaped bilateral power supply system based on a three-port power flow controller, wherein the tree-shaped bilateral power supply system includes a main substation and multiple traction substations, and the multiple traction substations draw power from the bus of the main substation through feeders; Its features are, It includes a three-port power flow controller, three step-down transformers, and a measurement and control unit; the primary sides of the three step-down transformers are respectively connected to the three phases of the main substation, and the secondary sides of the three step-down transformers are respectively connected to the three ports of the three-port power flow controller; the measurement and control unit is used to collect the feeder current from the traction substation and the bus voltage of the main substation, process them, and output control signals to control the three-port power flow controller to compensate the tree-shaped bilateral power supply system; This includes providing satisfactory compensation, specifically: The maximum three-phase voltage imbalance caused by the tree-shaped bilateral power supply system at the point of common coupling of the external power grid is: The 95% statistical value of three-phase voltage imbalance is The daily average power factor is PF0; Step 1: Collect the feeder current drawn from the traction substation at time t. , , and the bus voltage of the main substation , , ;in, , is the serial number of the traction substation; A, B and C represent three phases; CT refers to current transformer and VT refers to voltage transformer; Step 2: Calculate the three-phase voltage imbalance caused by the tree-shaped bilateral power supply system at time t. , ； in, This indicates the short-circuit capacity of the external power grid, where U is the rated value of the three-phase voltage. Let be the negative sequence current at time t. ， In the formula, , These are the total currents for phases A, B, and C, respectively. 、 、 ； Step 3, Determine the satisfactory compensation target: Compensate the power factor to the expected daily average power factor value PF1, and compensate the maximum value of the three-phase voltage imbalance to... The statistical value of the three-phase voltage imbalance is compensated to 95%. ; 3.1 Determine the reactive power compensation degree at time t , ； Where PF(t) is the power factor of the tree-shaped two-sided power supply system at time t. ； In the formula, , Let t represent the total active power and total reactive power of the tree-shaped bilateral power supply system at time t, respectively. The power flowing into the tree-shaped bilateral power supply system from the external grid is positive, and the power flowing back from the tree-shaped bilateral power supply system to the external grid is negative. 3.2 Determine the negative order compensation degree at time t , ； Step 4: Perform satisfactory compensation for the tree-shaped two-sided power supply system: 4.1 Solving for the three-phase complex power of the external power grid : , , ;in, , , The three-phase voltages at time t are respectively , , The vector representation of , , , They are time t respectively , , The conjugate vector representation of ; 4.2 Extraction active component and reactive components Calculate the average value of the active components. and the average value of reactive components : ， ； 4.3 Calculate the expected complex power of the converter in the three-port power flow controller. ； In the formula, , , Let represent the expected complex power values ​​of the converters connected to phases A, B, and C in the three-port power flow controller at time t; 4.4 Calculate the expected value of the compensation current of the converter in the three-port power flow controller. ； In the formula, , , Let represent the expected compensation current values ​​of the converters connected to phases A, B, and C in the three-port power flow controller at time t. The turns ratio of a step-down transformer; , , These are vector representations of the voltages in phases A, B, and C, respectively. " indicates conjugate; 4.5 A voltage and current dual closed-loop control method is adopted to control the converters connected to phases A, B, and C in the three-port power flow controller to achieve satisfactory compensation.

2. The control method for the tree-shaped bilateral power supply system compensation device based on a three-port power flow controller as described in claim 1, characterized in that, The compensation device is set at the minimum distance from the main substation.

3. The control method for the tree-shaped bilateral power supply system compensation device based on a three-port power flow controller as described in claim 1, characterized in that, This also includes providing full compensation, specifically: Step 1: Collect the feeder current drawn from the traction substation at time t. , , and the bus voltage of the main substation , , ;in, , is the serial number of the traction substation; A, B and C represent three phases; CT refers to current transformer and VT refers to voltage transformer; Step 2, Determine the target for complete compensation: reactive power compensation degree at time t. Negative order compensation degree at time t ; Step 3: Perform full compensation for the tree-shaped bilateral power supply system: 3.1 Solving for the three-phase complex power of the external power grid : , , ;in, , , The three-phase voltages at time t are respectively , , The vector representation of , , , They are time t respectively , , The conjugate vector representation of ; 3.2 Extraction active component and reactive components Calculate the average value of the active components. and the average value of reactive components : ， ； 3.3 Calculate the expected complex power of the converter in the three-port power flow controller. ； In the formula, , , Let represent the expected complex power values ​​of the converters connected to phases A, B, and C in the three-port power flow controller at time t; 3.4 Calculate the expected value of the compensation current of the converter in the three-port power flow controller. ； In the formula, , , Let represent the expected compensation current values ​​of the converters connected to phases A, B, and C in the three-port power flow controller at time t. The turns ratio of a step-down transformer; , , These are vector representations of the voltages in phases A, B, and C, respectively. " indicates conjugate; 3.5 A voltage and current dual closed-loop control method is adopted to control the converters connected to phases A, B, and C in the three-port power flow controller for complete compensation.

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