Coordinated optimization method and system of distributed power flow controller, and medium

Abstract

The invention relates to the technical field of flexible power transmission of a power system, in particular to a coordinated optimization method and system of a distributed power flow controller and a medium, and the method comprises the steps: building a layered equivalent coupling model of the distributed power flow controller; taking minimization of the total loss of the flexible power transmission system as an optimization target, and performing global optimization on a parallel side output voltage vector and a series side injection voltage vector of the distributed power flow controller by using a layered equivalent coupling model to obtain an optimal coordinated optimization control strategy; obtaining a target control parameter in a target control mode according to the optimal coordination optimization control strategy; and according to the target control parameter and the real-time voltage and current data of the power transmission line, calculating a voltage compensation amount needing to be injected into the flexible power transmission system, and according to the voltage compensation amount, carrying out coordinated optimization control on the power flow of the power transmission line. According to the method, the parallel side and the series side of the distributed power flow controller are coordinated and optimized by establishing the layered equivalent coupling model, so that the voltage stability and power flow equilibrium distribution of the flexible power transmission system are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of flexible power transmission technology in power systems, and in particular to a coordinated optimization method, system, and medium for a distributed power flow controller. Background Technology

[0002] With the large-scale grid connection of renewable energy, flexible transmission systems face multiple challenges brought about by the volatility and intermittency of new energy power generation and the rapid growth of new loads. Problems such as decreased line power flow controllability, aggravated three-phase imbalance, and limited new energy absorption are becoming increasingly prominent, seriously affecting the safe and stable operation of flexible transmission systems, leading to increased system losses and reduced power supply reliability. To address these challenges, Flexible AC Transmission Systems (FACTS) technology has been widely applied. Among them, the Distributed Power Flow Controller (DPFC) has become a research focus due to its combination of the functionality of the Unified Power Flow Controller (UPFC) and the economic characteristics of the Distributed Static Series Compensator (DSSC).

[0003] However, traditional distributed power flow controllers rely on third harmonic currents to exchange active power between the series side and the system. This mechanism not only injects harmonic pollution into flexible transmission systems, affecting power quality, but also exhibits efficiency degradation in flexible transmission systems with severe three-phase imbalance. Furthermore, traditional distributed power flow controllers require transformers with specific connection methods at the beginning and end of branches, significantly increasing retrofit costs and severely limiting the applicability of the device in existing flexible transmission systems. In addition, current power system flexible control devices generally suffer from single functionality and insufficient coordination. For example, Modular Multilevel Converter STATCOM (MMC-STATCOM) can only achieve reactive power compensation, Dynamic Voltage Restorer (DVR) can handle voltage dips but is too expensive, and the control strategy of distributed static series compensators is too simple to cope with complex operating conditions. This functional fragmentation necessitates the cooperation of multiple devices in practical applications, increasing system complexity and causing mutual interference between devices.

[0004] In summary, existing technologies have serious shortcomings in coordinated control. When faced with complex scenarios such as three-phase imbalance and renewable energy consumption, the adaptability and response speed of existing control strategies are difficult to meet actual needs. Therefore, it is urgent to provide a new distributed power flow controller topology and its coordinated output optimization method in flexible power transmission systems to solve the problems existing in the current technologies. Summary of the Invention

[0005] To address the above technical problems, this invention provides a coordination optimization method, system, and medium for a distributed power flow controller.

[0006] In a first aspect, the present invention provides a coordination optimization method for a distributed power flow controller, the method comprising the following steps: Based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible transmission system and the topology parameters of the flexible transmission system, a hierarchical equivalent coupling model of the distributed power flow controller is established. With minimizing the total loss of the flexible transmission system as the optimization objective, the hierarchical equivalent coupling model is used to globally optimize the parallel-side output voltage vector and the series-side injected voltage vector of the distributed power flow controller, thereby obtaining the optimal coordinated optimization control strategy of the distributed power flow controller. Based on the optimal coordination and optimization control strategy, a target control mode is assigned to the serial side of the distributed power flow controller, and the target control parameters under the target control mode are obtained. The required voltage compensation amount to be injected into the flexible transmission system is calculated based on the target control parameters and real-time voltage and current data of the transmission line, and the power flow of the transmission line is coordinated and optimized based on the voltage compensation amount.

[0007] In a further embodiment, the distributed power flow controller includes a parallel side and a series side, wherein the series side includes at least a first series side and a second series side; The parallel side includes a parallel coupling transformer, a three-phase converter, and a common DC capacitor connected to the DC side of the three-phase converter; The first series side includes three single-phase converters sharing a DC side and a three-phase isolation transformer. Each single-phase converter uses a single-phase H-bridge converter to independently control the output voltage amplitude and output voltage phase of each phase. The DC side of the three single-phase converters is connected to the common DC capacitor. The AC side of the three single-phase converters is connected to the transmission line in series through the three-phase isolation transformer. The second series side includes multiple sets of distributed single-phase converter units. Each set of distributed single-phase converter units includes a distributed H-bridge converter, a series-side DC capacitor, and a single-phase coupling transformer. The single-phase coupling transformer is connected in series in a distributed manner in the transmission line.

[0008] In a further embodiment, the parallel side is used to connect to the bus via the parallel coupling transformer, so that the three-phase converter draws energy from the bus to charge the common DC capacitor, and provides a stable DC voltage to the first series side via the common DC capacitor; The first series side is used to generate non-fundamental harmonics based on the energy stored in the common DC capacitor, and inject the non-fundamental harmonics into the transmission line through the three-phase isolation transformer to regulate the reactive power flow of the transmission line. The multiple sets of distributed single-phase converter units on the second series side are used to draw energy from the transmission line to charge the DC capacitor on the series side, generate a compensation voltage, and inject the compensation voltage into the transmission line through a distributed H-bridge converter to regulate the active power flow of the transmission line.

[0009] In a further embodiment, the distributed power flow controller further includes a filter unit connected in parallel to the load side at the end of the transmission line; The filtering unit is used to filter out residual non-fundamental harmonics generated by the first series side in the transmission line that are not absorbed by the second series side.

[0010] In a further implementation, the hierarchical equivalent coupling model includes a static var compensator model with dual closed-loop control on the parallel side, and a controlled voltage source model and a multi-node impedance voltage source hybrid model with phase-independent control on the series side.

[0011] In a further implementation, the step of establishing a hierarchical equivalent coupling model of the distributed power flow controller based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible transmission system and the topology parameters of the flexible transmission system includes: Calculate the reference value of the output current of the parallel-side three-phase converter based on the three-phase voltage of the parallel-side bus and the voltage of the common DC capacitor; The reference value of the output current is compared with the actual output current to obtain the current error, and the current error is adjusted using a proportional-integral regulator. The direct-axis component and quadrature-axis component of the modulation voltage are obtained through a feedforward decoupling control strategy. Based on the direct axis component and the quadrature axis component, a static var compensation model for the parallel side is constructed in a synchronous rotating coordinate system. Using the common DC capacitor voltage output by the dual closed-loop control of the static var compensator model as the coupling point, the voltage amplitude and voltage phase angle required to be injected into the series-side single-phase converter are calculated based on the voltage at the beginning and end of the transmission line and the impedance data of the transmission line. Based on the voltage amplitude and voltage phase angle required to be injected into the series-side single-phase converter, a controlled voltage source model of the series side is constructed in the synchronous rotating coordinate system using a decoupling control law. Based on the voltage at the beginning and end of the transmission line after compensation by the controlled voltage source model and the real-time power flow distribution data of the transmission line, the equivalent impedance value required to be output by the series-side distributed single-phase converter unit is calculated. Based on the required equivalent impedance value of the distributed single-phase converter unit on the series side, a hybrid model of multi-node impedance voltage sources is constructed. The static var compensator model, the controlled voltage source model, and the multi-node impedance voltage source hybrid model are integrated to form a hierarchical equivalent coupling model.

[0012] In a further implementation, the optimal coordinated control strategy includes at least the output voltage vector or current inner loop reference value of the parallel-side converter, the injected voltage vector of the series-side single-phase converter, and the control mode of the series-side distributed single-phase converter unit.

[0013] In a further implementation, the control mode of the series-side distributed single-phase converter unit is impedance control mode, voltage control mode, or power flow control mode.

[0014] Secondly, the present invention provides a coordination and optimization system for a distributed power flow controller, the system comprising: The model building module is used to build a hierarchical equivalent coupling model of the distributed power flow controller based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible power transmission system and the topology parameters of the flexible power transmission system. The model solving module is used to optimize the parallel-side output voltage vector and series-side injected voltage vector of the distributed power flow controller by using the hierarchical equivalent coupling model to minimize the total loss of the flexible transmission system, thereby obtaining the optimal coordinated optimization control strategy of the distributed power flow controller. The mode decision module is used to allocate a target control mode to the serial side of the distributed power flow controller according to the optimal coordination and optimization control strategy, and to obtain the target control parameters under the target control mode. The coordination and optimization module is used to calculate the required voltage compensation amount to be injected into the flexible transmission system based on the target control parameters and real-time voltage and current data of the transmission line, and to perform coordinated and optimized control of the power flow of the transmission line based on the voltage compensation amount.

[0015] Thirdly, the present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0016] This invention provides a method, system, and medium for the coordinated optimization of a distributed power flow controller. The method establishes a hierarchical equivalent coupling model of the distributed power flow controller based on real-time electrical quantity data and topology parameters of the flexible transmission system. With minimizing the total loss of the flexible transmission system as the optimization objective, the hierarchical equivalent coupling model is used to globally optimize the output voltage vector on the parallel side and the injected voltage vector on the series side of the distributed power flow controller, obtaining the optimal coordinated optimization control strategy. Based on the optimal coordinated optimization control strategy, a target control mode is assigned to the series side of the distributed power flow controller, and the target control parameters under the target control mode are obtained. The required voltage compensation amount injected into the flexible transmission system is calculated based on the target control parameters and real-time voltage and current data of the transmission lines, and the power flow of the transmission lines is coordinated and optimized based on the voltage compensation amount. Compared with existing technologies, this method, by establishing a hierarchical equivalent coupling model to coordinate and optimize the parallel and series sides of the distributed power flow controller, minimizes the total loss of the flexible transmission system, effectively improves the voltage stability and power flow balance distribution of the flexible transmission system, enhances the renewable energy absorption capacity and power quality, thereby ensuring the safe, stable, and efficient operation of the flexible transmission system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the coordination and optimization method for a distributed power flow controller provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the distributed power flow controller topology provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the reactance equivalent model provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the impedance adjustment characteristic curve provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the branch equivalent circuit under voltage control mode provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the equivalent model of the voltage source provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the power flow control mode adjustment range provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the power flow regulation characteristic curve provided in an embodiment of the present invention; Figure 9 This is a block diagram of the coordination and optimization system of the distributed power flow controller provided in the embodiments of the present invention.

[0018] Figure labeling: 101, Model building module; 102, Model solving module; 103, Mode decision module; 104, Coordination optimization module. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0020] Figure 1 This is a schematic flowchart of a coordination and optimization method for a distributed power flow controller provided in an embodiment of the present invention. The present invention provides a coordination and optimization method for a distributed power flow controller, such as... Figure 1 As shown, the method includes the following steps: S1. Based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible transmission system and the topology parameters of the flexible transmission system, establish a hierarchical equivalent coupling model of the distributed power flow controller.

[0021] This embodiment utilizes the coordinated operation of the parallel and series sides (the series side includes a first series side and a distributed second series side) of a novel distributed power flow controller deployed on the transmission lines of a flexible power transmission system. Based on the real-time state of the flexible power transmission system, the optimal control command set of the distributed power flow controller is calculated, thereby achieving proactive, precise, and efficient control of the power flow in the flexible power transmission system. Figure 2 This is a schematic diagram of the topology of a distributed power flow controller provided in an embodiment of the present invention. The distributed power flow controller proposed in this embodiment includes a parallel side, a series side, and a filter unit connected in parallel to the load side at the end of the transmission line, such as... Figure 2 As shown, the parallel side includes a parallel coupling transformer, a three-phase converter, and a common DC capacitor connected to the DC side of the three-phase converter. The three-phase converter uses an insulated-gate bipolar transistor as a switching device. The parallel coupling transformer is used to connect the three-phase converter to the flexible AC transmission system and provide electrical isolation. In this embodiment, the parallel side is used to connect to the bus through the parallel coupling transformer so that the three-phase converter draws power from the bus, charges the common DC capacitor through pulse width modulation (PWM) technology, and provides a stable DC voltage to the first series side through the common DC capacitor, maintaining the DC voltage stability and supplying power to the first series side.

[0022] The series side includes at least a first series side and a second series side. The first series side includes three single-phase converters sharing a DC side and a three-phase isolation transformer. The three-phase isolation transformer not only provides electrical isolation but also matches the output voltage of the single-phase converters to the transmission line voltage level. Each single-phase converter uses a single-phase H-bridge converter to independently control the output voltage amplitude and phase of each phase. The DC side of the three single-phase converters is connected to the common DC capacitor. The AC side of the three single-phase converters is connected to the transmission line in series through the three-phase isolation transformer. The first series side is used to generate non-fundamental harmonics based on the energy stored in the common DC capacitor and injects the non-fundamental harmonics into the transmission line through the three-phase isolation transformer to regulate the reactive power flow of the transmission line.

[0023] The second series side includes multiple sets of distributed single-phase converter units, each corresponding to one of phases A, B, or C. Each set of distributed single-phase converter units includes a distributed H-bridge converter, a series-side DC capacitor, and a single-phase coupling transformer. The single-phase coupling transformer is connected in series in a distributed manner in the transmission line. The multiple sets of distributed single-phase converter units on the second series side are used to draw energy from the transmission line to charge the series-side DC capacitor, generating a compensation voltage. This compensation voltage is then injected into the transmission line through the distributed H-bridge converter to regulate the active power flow of the transmission line. This modular design allows the second series side to be flexibly deployed at different locations on the line. For different installation requirements of the second series side, this embodiment can be configured with installation methods including substation installation, jumper installation, installation on intelligent poles, and mobile vehicle-mounted installation. It should be noted that in this embodiment, the first series side relies on the parallel-side common DC capacitor for power supply, while the second series side draws power from the transmission line for self-power supply, eliminating the need for traditional distributed power flow controllers. The third harmonic energy transfer dependence of the FlowController (DPFC).

[0024] The filtering unit employs an LC filter to filter out residual non-fundamental harmonics generated by the first series side in the transmission line that are not absorbed by the second series side, ensuring power quality and preventing harmonic pollution on the user side, thereby avoiding the impact of non-fundamental harmonics on the distribution area. Compared with the prior art, the terminal LC filter in this embodiment is designed for non-fundamental harmonics, solving the problem of residual harmonics not fully absorbed by the second series side. In summary, the distributed power flow controller used in this embodiment achieves comprehensive regulation of the power flow of the flexible transmission system through the coordinated work of the parallel and series sides. The parallel-side converter exchanges reactive power with the system to maintain the stability of the access point bus voltage and provides a stable DC voltage to the first series side. The first and second series sides respectively regulate the reactive and active power flow of the line by controlling the amplitude and phase of the output voltage. Furthermore, by optimizing the control strategy, precise control of the power flow of the flexible transmission system can be achieved, reducing line losses, improving the renewable energy absorption capacity, and improving power quality.

[0025] This embodiment collects data in real time using sensors such as voltage transformers and current transformers deployed at key nodes of the target line in the flexible transmission system. The collected data includes electrical quantities such as voltage amplitude at the beginning and end of the line, phase difference, line current, line active power, line reactive power, and DC capacitor voltage of the distributed power flow controller. Based on the real-time electrical quantity data and the topology parameters of the flexible transmission system, a hierarchical equivalent coupling model of the distributed power flow controller is established. The topology parameters of the flexible transmission system may include data such as line impedance and node relationships. The hierarchical equivalent coupling model includes a static var compensator model using dual closed-loop control on the parallel side, a controlled voltage source model using phase-independent control on the series side, and a hybrid model of multi-node impedance voltage sources. In some embodiments, the step of establishing the hierarchical equivalent coupling model of the distributed power flow controller based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible transmission system and the topology parameters of the flexible transmission system includes: Calculate the reference value of the output current of the parallel-side three-phase converter based on the three-phase voltage of the parallel-side bus and the voltage of the common DC capacitor; The reference value of the output current is compared with the actual output current to obtain the current error, and the current error is adjusted using a proportional-integral regulator. The direct-axis component and quadrature-axis component of the modulation voltage are obtained through a feedforward decoupling control strategy. Based on the direct axis component and the quadrature axis component, a static var compensation model for the parallel side is constructed in a synchronous rotating coordinate system. Using the common DC capacitor voltage output by the dual closed-loop control of the static var compensator model as the coupling point, the voltage amplitude and voltage phase angle required to be injected into the series-side single-phase converter are calculated based on the voltage at the beginning and end of the transmission line and the impedance data of the transmission line. Based on the voltage amplitude and voltage phase angle required to be injected into the series-side single-phase converter, a controlled voltage source model of the series side is constructed in the synchronous rotating coordinate system using a decoupling control law. Based on the voltage at the beginning and end of the transmission line after compensation by the controlled voltage source model and the real-time power flow distribution data of the transmission line, the equivalent impedance value required to be output by the series-side distributed single-phase converter unit is calculated. Based on the required equivalent impedance value of the distributed single-phase converter unit on the series side, a hybrid model of multi-node impedance voltage sources is constructed. The static var compensator model, the controlled voltage source model, and the multi-node impedance voltage source hybrid model are integrated to form a hierarchical equivalent coupling model.

[0026] This embodiment establishes a hierarchical equivalent coupling model of the NDPFC based on the topology parameters of the flexible transmission system and the real-time electrical quantity data of the distributed power flow controller (NDPFC). The real-time electrical quantity data includes bus voltage, line current, active and reactive power, etc. This hierarchical equivalent coupling model includes a parallel-side model and a series-side model. The parallel-side model describes the energy interaction between the parallel converters and the bus, achieving bus voltage support through common DC capacitor voltage stabilization and reactive power compensation. The series-side model is divided into a first series side (harmonic injection) and a second series side (distributed voltage compensation), representing its control effect on line power flow in the form of voltage sources or impedance. The hierarchical equivalent coupling model accurately reflects the electrical connection relationships and energy interaction characteristics between each side of the distributed power flow controller and the flexible transmission system, covering the reactive power exchange characteristics between the parallel side and the flexible transmission system, as well as the influence mechanism of the series side on line power flow. Specifically, this embodiment collects the three-phase voltage of the parallel-side bus in real time. , , and common DC capacitor voltage And assume the target value of the common DC capacitor voltage is According to the common DC capacitor voltage The difference between the DC voltage and the target value of the common DC capacitor voltage is used to obtain the DC voltage deviation. Then, in this embodiment, a reactive current reference value is generated through an outer-loop PI controller to maintain bus voltage stability, and an active current reference value is generated through power balance. Active current reference value The ratio between the active power exchanged between the flexible AC transmission system and the parallel-side converter and the bus voltage Ub is used to obtain the parallel-side output current reference value by integrating the reactive current reference value and the active current reference value. When the new distributed power flow controller (NDPFC) only uses its parallel-side function, it can be equivalent to a static synchronous compensator (STATCOM). In this mode, this embodiment ignores the losses of the device itself and sets the sum of the leakage reactance of the parallel-side coupling transformer and the filter inductance impedance as Zsh. The parallel-side output voltage referred to the high-voltage side is Ush, and the phase of the bus voltage Ub is used as the reference phase. In this embodiment, the phase difference between Ush and Ub is defined as... At this point, the formula for calculating the current Ish flowing into the parallel side is: Furthermore, the formulas for calculating the active power Psh and reactive power Qsh exchanged between the flexible AC transmission system and the parallel-side converter are as follows: From the above formula, it can be seen that the active power Psh exchanged between the system and the parallel side is mainly affected by the phase of the three-phase converter output voltage Ush, while the magnitude of the reactive power Qsh depends on the amplitude of the three-phase converter output voltage Ush. In addition, the operation of the first series side depends on the stable common DC capacitor voltage provided by the parallel side, so it cannot operate independently. In contrast, the second series side has the ability to operate independently. Without considering the transient process of capacitor charging and discharging, the second series side only exchanges reactive power with the system, that is, it is in the distributed static series compensator (DSSC) mode.

[0027] To achieve effective decoupling control of the current dq components, this embodiment employs a feedforward decoupling control strategy. Combined with a proportional-integral regulator, the d-axis and q-axis components of the current are independently controlled, ultimately achieving dual closed-loop control on the parallel side. The outer loop ensures the stability of the bus voltage and DC capacitor voltage, while the inner loop precisely regulates the d-axis and q-axis components of the current, ensuring system stability and rapid response. This embodiment measures the d-axis current component in the actual output dq coordinate system. and q-axis current components in the dq coordinate system and the d-axis current component The d-axis current error is obtained by subtracting the d-axis current reference value from the q-axis current component. The q-axis current error is obtained by subtracting the q-axis current reference value. This error is then adjusted using a proportional-integral controller. A feedforward decoupling control law is used to decouple the modulation voltage component, resulting in the direct-axis and quadrature-axis components of the modulation voltage. This achieves effective decoupling control of the current dq component. Specifically, in this embodiment, the direct-axis and quadrature-axis components of the modulation voltage obtained through the feedforward decoupling control strategy are expressed as follows: In the formula, This is the d-axis scaling factor; This is the reference value for the d-axis current; The coefficients are the integral coefficients along the d-axis. This is the reference value for the q-axis current; The coefficients are the integral coefficients along the q-axis. The voltage component along the d-axis in the dq coordinate system; Let q be the voltage component along the q-axis in the dq coordinate system.

[0028] This embodiment employs a dual closed-loop control structure, with the inner loop using a current loop (the d-axis voltage component output by the feedforward decoupling control strategy). and q-axis voltage component The outer loop adopts a DC voltage loop. When the parallel and series sides of the new distributed power flow controller work together, its function is similar to that of a unified power flow controller, which can perform more complex flexible transmission system regulation tasks. Specifically, the first series side provides a voltage that is in phase or out of phase with the line current to regulate reactive power flow; the second series side provides a voltage perpendicular to the line current to regulate active power flow. In this embodiment, by adjusting the magnitude and direction of the voltage provided by the first series side that is in phase or out of phase with the line current and the voltage provided by the second series side that is perpendicular to the line current, the distributed power flow controller can effectively compensate for the line voltage drop, thereby achieving precise control of active and reactive power flow. In this embodiment, the parallel side of the distributed power flow controller is mainly used to maintain the stability of the bus voltage at the access point, while providing necessary active power support to the first series side. Assuming three-phase symmetry, this embodiment establishes a static var compensation model with dual closed-loop control on the parallel side based on parameters such as three-phase voltage, converter output voltage, filter impedance, and system frequency. The specific construction process of the static var compensation model is as follows: In the formula, This is the common DC capacitor voltage on the parallel side; This refers to the capacitance value of the DC bus. This represents the instantaneous value of the A-phase bus voltage of the system. This refers to the output current of phase A of the parallel-side converter; This represents the instantaneous value of the B-phase bus voltage of the system. This refers to the output current of phase B of the parallel-side converter; This represents the instantaneous value of the C-phase bus voltage of the system. This refers to the C-phase output current of the parallel-side converter; The bus voltage amplitude is represented by ω; the system angular frequency is represented by ω; and the time variable is represented by t. The initial phase angle of phase A voltage.

[0029] Under the constant amplitude Park transformation, this embodiment can transform the above equations to a synchronously rotating coordinate system, specifically as follows: In the formula, The voltage component along the d-axis in the dq coordinate system; Let q be the voltage component along the q-axis in the dq coordinate system.

[0030] The parallel side model in the synchronous rotating coordinate system, i.e., the static var compensation model of the parallel side, is derived through derivation: In the formula, L is the value of the filter inductance; R represents the d-axis current component in the dq coordinate system; R is the equivalent resistance. The q-axis current component in the dq coordinate system; This represents the amplitude of the bus voltage.

[0031] In this embodiment, the common DC capacitor voltage output by the dual closed-loop control of the static var compensator model is used as the coupling point, based on the voltage at the beginning and end of the transmission line and the transmission line impedance. Calculate the voltage amplitude required to inject into the series-side single-phase converter. and phase angle Then, the injection voltage is calculated by back-calculating the power flow equation. The specific calculation formula is as follows: In the formula, The equivalent output voltage amplitude of the line injected into the i-th distributed single-phase converter unit; The equivalent fundamental reactance of the transmission line; To optimize the target current; This refers to the voltage amplitude at the bushead at the beginning of the line. denoted as the voltage amplitude at the busbar at the end of the line; j is the imaginary unit.

[0032] The first and second series sides of the distributed power flow controller are both composed of sub-units consisting of single-phase full-bridge converters. When establishing a controlled voltage source model with independent phase control and a hybrid model of multi-node impedance voltage sources on the series side, this embodiment needs to consider many factors such as the voltage to ground at the left access point and the voltage to ground at the right access point on the series side, the equivalent internal resistance of the series side, the filter inductance, the capacitor, the grid-side current, the current after LC filtering, and the inverter voltage on the series side. Therefore, we can obtain: In the formula, This is the input voltage on the series side; This is the output voltage on the series side; This represents the equivalent internal resistance on the series side. This refers to the current flowing into the grid side; For filtering inductors; This is the filtered output current; This refers to the inverter output voltage. This is a filter capacitor.

[0033] This embodiment constructs a hysteresis. The new phase variable enables a single-phase Park transformation, leading to a series-side model in a synchronously rotating coordinate system: In the formula, The control voltage along the d-axis in the dq coordinate system; For series-side filter inductance; This is the voltage difference compensation amount; This refers to the q-axis control voltage in the dq coordinate system.

[0034] Based on the required voltage amplitude and phase angle of the series-side single-phase converter, a controlled voltage source model of the series side is constructed in a synchronous rotating coordinate system using a decoupling control law. The specific decoupling control law for the series side is as follows: This embodiment integrates the static var compensator model, the controlled voltage source model, and the multi-node impedance voltage source hybrid model constructed above to form a hierarchical equivalent coupling model. This hierarchical equivalent coupling model should be able to fully reflect the dynamic behavior and mutual influence of the distributed power flow controller in the flexible transmission system, providing a foundation for subsequent optimization control.

[0035] Finally, this embodiment obtains the compensated transmission line current. and the compensated transmission line voltage , The equivalent impedance value on the series side was calculated based on the equivalent impedance formula of the impedance control mode and the reactance equivalent model. Each distributed single-phase converter unit on the series side is equivalent to a variable impedance. With voltage source Parallel connection to construct a multi-node impedance voltage source hybrid model: In the formula, This represents the change in active power of the line, which indicates the change in active power flow caused by NDPFC regulation. This represents the change in reactive power of the line, which indicates the change in reactive power flow caused by NDPFC regulation. This refers to the active power at the beginning of the line. This is the equivalent reactance of the second series side; Inject voltage into the second series side; This refers to the reactive power at the beginning of the line. This is the equivalent reactance adjustment amount, which represents the amount of reactance value that needs to be adjusted under impedance control mode; The injected voltage regulation amount represents the amount of voltage amplitude change that needs to be adjusted under voltage or power flow control mode; it should be noted that the subscript se indicates the series side.

[0036] S2. With minimizing the total loss of the flexible transmission system as the optimization objective, the parallel-side output voltage vector and series-side injected voltage vector of the distributed power flow controller are globally optimized using the hierarchical equivalent coupling model to obtain the optimal coordinated optimization control strategy of the distributed power flow controller.

[0037] S3. Assign a target control mode to the serial side of the distributed power flow controller according to the optimal coordination and optimization control strategy, and obtain the target control parameters under the target control mode.

[0038] This embodiment takes minimizing the total loss of the flexible transmission system over all control cycles as the optimization objective. Based on a hierarchical equivalent coupling model, it uses a linear programming algorithm or a particle swarm optimization algorithm to perform global coordinated optimization of the parallel-side output voltage vector and the series-side injected voltage vector of the distributed power flow controller. The parallel-side output voltage vector can include the magnitude and phase angle of the parallel-side output voltage, and the series-side injected voltage vector can include the magnitude and phase angle of the series-side injected voltage. An optimal coordinated control strategy is generated. During the optimization process, this embodiment comprehensively considers the operating constraints of the flexible transmission system and the equipment operating limits of the distributed power flow controller. Through iterative calculations, it continuously adjusts the possible values ​​of the parallel-side output voltage vector and the series-side injected voltage vector to find the optimal solution that minimizes the total system loss. Based on the results of the iterative calculations, this embodiment finally obtains the optimal coordinated optimization control strategy of the distributed power flow controller, ensuring that while reducing system losses, the voltage stability and power flow distribution of the flexible transmission system are maintained. The optimization objective function can be expressed as: In the formula, The equivalent loss resistance on the parallel side originates from the filter inductor or transformer resistance on the parallel side; k is the control cycle number. This represents the effective value of the parallel-side output current during the kth control cycle. This is the equivalent loss resistance on the series side, and its corresponding internal resistance on the series side; is the effective value of the output current on the series side in the kth control cycle; M is the total number of control cycles.

[0039] In this embodiment, the optimal coordinated optimization control strategy includes at least the output voltage vector or current inner loop reference value of the parallel-side converter, the injected voltage vector of the series-side single-phase converter, and the control mode of the series-side distributed single-phase converter unit. This embodiment dynamically allocates a target control mode to the second series side according to the optimal coordinated optimization control strategy and calculates the target control parameters (such as equivalent impedance) under the corresponding target control mode. Injection voltage (Data such as...) The allocation of target control parameters needs to comprehensively consider the line impedance characteristics and power flow distribution, the fluctuation of new energy output, and the three-phase imbalance compensation requirements. Specifically, the equivalent impedance value required to be output by the series-side distributed single-phase converter unit can be calculated according to the target control mode, and the voltage amplitude and phase angle required to be injected by the series-side single-phase converter can be calculated according to the target control mode (such as voltage control mode or power flow control mode). In this embodiment, the control mode of the series-side distributed single-phase converter unit is impedance control mode, voltage control mode, or power flow control mode. In impedance control mode, this embodiment calculates the equivalent impedance value required to be output by the series-side converter based on data such as the line start and end voltage, line current, and line impedance angle, and adjusts the output voltage of the converter... The amplitude and phase are adjusted to regulate the line impedance. In voltage control mode, the voltage amplitude and phase angle to be injected into the series-side converter are calculated based on data such as the voltage at the beginning and end of the line and the line impedance. By changing the output voltage of the converter, the line voltage is optimized. In power flow control mode, the equivalent voltage to be injected into the series-side converter is calculated based on the active and reactive power data at the beginning and end of the line. By directly controlling the active power of the system, the power flow is redistributed. In this embodiment, depending on the type of outer loop feedback signal, the second series side of the novel distributed power flow controller (NDPFC) can be flexibly switched to three control modes: impedance control mode, voltage control mode, or power flow control mode to meet the diverse control needs of flexible transmission systems.

[0040] In impedance control mode, when the flexible AC transmission system needs to perform power flow regulation, it will issue instructions to influence the active and reactive power flow distribution of the transmission line by adjusting the equivalent output impedance of the second series-side converter in the NDPFC. This impedance control mode can be automatically implemented through system-level control strategies, ensuring the stability and economy of the flexible transmission system. In this embodiment, after the NDPFC system is connected to the transmission line, the installation of the NDPFC system on the transmission line can be equivalent to a reactance equivalent model of multiple variable reactances connected in series. Figure 3 This is a schematic diagram of the reactance equivalent model provided in an embodiment of the present invention, wherein the equivalent impedance value output by the i-th distributed single-phase converter unit on the second series side is... The calculation formula is: In the formula, is the equivalent impedance (equivalent reactance value) output by the i-th NDPFC unit, used to measure the unit's obstruction to power flow in the line. Its magnitude and nature (inductive or capacitive) will affect the distribution of active and reactive power in the line; n is the total number of distributed single-phase converter units deployed in the line; i is the serial number identifier of the distributed single-phase converter unit. The equivalent output voltage amplitude of the injected line is determined by changing the value of the line to the i-th distributed single-phase converter unit. It can regulate the power flow of the line; The line impedance angle represents the phase angle of the line impedance and reflects the proportional relationship between resistance and reactance in the line impedance. For line current phasors (including amplitude and phase information); The equivalent fundamental reactance of the transmission line; This refers to the voltage phasor of the bus at the beginning of the line. This refers to the voltage phasor of the bus at the end of the line. This represents the phase angle difference between the bus voltages at the beginning and end of the line.

[0041] In the NDPFC working uncompensated working mode, when When, the equivalent impedance of NDPFC The equivalent impedance is zero. If the NDPFC operates in capacitive mode, the equivalent impedance decreases as the amplitude of the injected voltage in each unit increases, and approaches the fundamental resonance point infinitely. The formula for the equivalent impedance of the NDPFC when operating in capacitive mode is: When the NDPFC operates in inductive mode, its equivalent impedance is in the same direction as the impedance of the controlled circuit, and its inductive reactance increases with the increase of the injected voltage amplitude. Figure 4 This is a schematic diagram of the impedance adjustment characteristic curve provided in an embodiment of the present invention. The equivalent impedance formula for the NDPFC when operating in an inductive state is: In the formula, j is the imaginary unit, which is used to represent the imaginary part of the impedance (the reactance component).

[0042] In the voltage control mode, this embodiment can adjust the amplitude and phase angle of the output voltage of the second series-side converter in the novel distributed power flow controller (NDPFC), thereby injecting voltage into the transmission line. This operation can optimize the system voltage level, effectively manage the voltage of the flexible transmission system, and indirectly change the power flow of the line. This control mode can be automatically implemented through system-level control strategies. Figure 5 This is a schematic diagram of the branch equivalent circuit under voltage control mode provided in an embodiment of the present invention. Figure 5 This demonstrates the equivalent circuit of a branch containing a distributed static series compensator (DSSC) in voltage control mode. In this embodiment, the voltages of the first and last busbars are set as follows: and The impedance of the transmission line is The active and reactive power of the transmission line at the end of the line are based on This indicates that the transmission line current is I, and the NDPFC output voltage is... ,in, This refers to the voltage amplitude at the bushead at the beginning of the line. This refers to the voltage amplitude at the end of the line bus. The voltage phase angle at the sending end (head) of the transmission line. Let R be the voltage phase angle at the receiving end of the transmission line, R be the equivalent resistance component of the transmission line, and X be the equivalent reactance component of the transmission line. This refers to the active power received at the end of the line. This refers to the reactive power received at the end of the line. The output voltage amplitude of the second series side. The output voltage phase angle of the second series side is given. In this embodiment, by changing the output voltage of the NDPFC, the voltage at the beginning and end of the line can be effectively adjusted, thereby achieving the control target of voltage and power flow of the flexible transmission system.

[0043] In the power flow control mode, after the power flow regulation command is issued in this embodiment, the second series-side converter of the novel distributed power flow controller (NDPFC) can directly control the system's active power, thereby realizing the redistribution of power flow in the system. This process can improve the transmission capacity of the line and the power flow balance of the cross section, thus promoting the consumption of new energy. This power flow control mode can be automatically realized through system-level control strategies. The mathematical model of the NDPFC system installed on the line can be equivalent to a model of multiple controlled voltage sources connected together. Figure 6 This is a schematic diagram of the equivalent model of the voltage source provided in an embodiment of the present invention. Figure 6 middle, The injected voltage phasor for the first distributed single-phase converter unit; The injected voltage phasor for the second distributed single-phase converter unit; Let be the injected voltage phasor of the nth distributed single-phase converter unit. In this embodiment, based on the voltage source equivalent model, its electrical characteristics are described by the line current equation and the terminal power equation. The line current equation is specifically as follows: The specific power equation at the end is as follows: In the formula, Let be the injected voltage phasor of the i-th distributed single-phase converter unit; For active power flow at the end of the line; For reactive power flow at the end of the line; Operations on the real part of a complex number; It is the conjugate complex number of the line current phasor; This refers to the operation of the imaginary part of a complex number.

[0044] To deeply analyze the impact of the injection voltage of the NDPFC unit (injection voltage refers to the equivalent voltage injected into the line by the NDPFC, and output voltage refers to the voltage output from the AC side of the NDPFC converter, which will not be elaborated further) on the line power flow, this embodiment analyzes the active power flow and reactive power flow of the line in detail. The formulas for the active power flow and reactive power flow of the line are expressed as follows: As can be seen from the above formulas for active and reactive power flow of transmission lines, this embodiment can control the active power flow of the line by controlling the voltage injected by the NDPFC. With reactive power flow To regulate, Figure 7 This is a schematic diagram of the power flow control mode adjustment range provided in an embodiment of the present invention. Figure 8 This is a schematic diagram of the power flow regulation characteristic curve provided in an embodiment of the present invention, where pu is a per-unit unit.

[0045] When this embodiment uses the particle swarm optimization algorithm for global collaborative optimization, it first initializes the particle swarm parameters, including population size, maximum number of iterations, inertia weight, learning factor, etc., and randomly initializes the position and velocity of each particle. The particle position represents a set of possible parallel-side output voltage vectors and series-side injected voltage vectors. This embodiment calculates the fitness value of each particle according to the optimization objective function, i.e., the total loss of the flexible transmission system. It compares the fitness value of each particle with the individual's historical best fitness value, updates the individual's historical best position, and compares the fitness value of each particle with the global historical best fitness value, updates the global historical best position. According to the velocity and position update formula of the particle swarm optimization algorithm, it updates the velocity and position of each particle. The above steps are repeated until the maximum number of iterations is reached or the convergence condition is met. The parallel-side output voltage vector and series-side injected voltage vector corresponding to the global historical best position are output. This embodiment takes the parallel-side output voltage vector and series-side injected voltage vector corresponding to the global historical best position as the optimal solution.

[0046] S4. Calculate the required voltage compensation amount to be injected into the flexible transmission system based on the target control parameters and real-time voltage and current data of the transmission line, and perform coordinated and optimized control of the power flow of the transmission line based on the voltage compensation amount.

[0047] This embodiment calculates the required voltage compensation amount based on target control parameters and real-time line voltage and current data using a feedforward decoupling control strategy. The corresponding voltage compensation is then injected into the flexible transmission system's transmission lines via the series-side converter of the distributed power flow controller. This drives the NDPFC execution unit to adjust its output. The injected voltage compensation changes the voltage and power flow distribution of the lines, thereby achieving precise redistribution of active and reactive power flows. This achieves coordinated and optimized control, enhances the absorption capacity of new energy sources, and reduces losses in the flexible transmission system. Specifically, this embodiment calculates the required voltage compensation amount to be injected into the flexible transmission system based on target control parameters (such as equivalent impedance or injected voltage data) and real-time collected voltage and current data. For example, in impedance control mode, this embodiment can calculate the required voltage compensation based on the equivalent impedance... and line current Calculate the voltage compensation amount; in voltage control mode, this embodiment can use the amplitude and phase angle of the injected voltage as the voltage compensation amount; in power flow control mode, this embodiment can use the active power flow of the line as the compensation amount. and reactive power flow And adjust the injection voltage accordingly. This is to achieve control over the power flow and thus obtain voltage compensation.

[0048] This embodiment, based on the calculated voltage compensation, coordinates and optimizes the power flow of the transmission line by controlling the parallel and series sides of the distributed power flow controller to work together. On the parallel side, this embodiment adjusts the output voltage vector of the three-phase converter on the parallel side to maintain the stability of the bus voltage at the connection point and provide necessary active power support for the series side. On the series side, this embodiment adjusts the output voltage vector of the single-phase converter on the series side to achieve precise control of the line power flow by controlling the injected voltage. The amplitude and phase angle are adjusted to compensate for voltage drops in the line, thereby optimizing power flow distribution. During the control process, this embodiment monitors the voltage and current changes of the transmission lines in the flexible transmission system in real time, as well as the operating status of the distributed power flow controller. Based on the feedback data, the target control parameters and voltage compensation amount are dynamically adjusted to ensure that the system always maintains the optimal state during operation. Therefore, this embodiment takes minimizing the total loss of the flexible transmission system as the optimization objective. By globally coordinating the optimization of the parallel side output voltage vector and the series side injected voltage vector of the distributed power flow controller, the optimal coordinated control of the parallel side and the series side is achieved, thereby improving the operating efficiency and power quality of the flexible transmission system.

[0049] In summary, compared to traditional distributed power flow controllers, the novel distributed power flow controller proposed in this embodiment eliminates the dependence on third harmonic currents in its topology, effectively avoiding harmonic pollution and significantly improving system power quality. Simulation tests show a reduction of approximately 40% in total harmonic distortion. Secondly, the novel distributed power flow controller does not rely on specific transformer connection methods, such as the Δ / YN and YN / Δ connection transformer configurations required by traditional distributed power flow controllers. This greatly improves its adaptability to existing flexible transmission systems and reduces retrofit costs by approximately 30%. Furthermore, the novel distributed power flow controller adopts a phase-separated control strategy, effectively enhancing three-phase imbalance compensation capabilities. Simulation results show that it can reduce an asymmetry of up to 4.2% to near zero within 0.2 seconds, significantly improving power quality. Regarding renewable energy consumption, the multiple operating modes and flexible control strategies of the novel distributed power flow controller proposed in this embodiment enable better coordination between local loads and renewable energy output, effectively promoting renewable energy consumption and improving line transmission capacity and cross-sectional power flow balance.

[0050] Meanwhile, the multi-unit output coordination and optimization control strategy based on the principle of minimizing losses in this embodiment enables the novel distributed power flow controller proposed in this embodiment to minimize system operating losses while meeting control objectives. Compared with traditional methods, the total system loss can be reduced by more than 15%. In addition, the modular design and flexible installation method of the novel distributed power flow controller proposed in this embodiment enable it to be deployed according to different application scenarios, which greatly improves the scalability and maintainability of the system and provides important support for the flexible operation of flexible transmission systems and the efficient consumption of new energy.

[0051] This invention provides a coordinated optimization method for a distributed power flow controller. The method establishes a hierarchical equivalent coupling model of the distributed power flow controller based on real-time electrical quantity data and topology parameters of the flexible transmission system. With minimizing the total loss of the flexible transmission system as the optimization objective, the hierarchical equivalent coupling model is used to globally optimize the output voltage vector on the parallel side and the injected voltage vector on the series side of the distributed power flow controller, obtaining the optimal coordinated optimization control strategy. Based on the optimal coordinated optimization control strategy, a target control mode is assigned to the series side of the distributed power flow controller, and the target control parameters under the target control mode are obtained. The required voltage compensation amount injected into the flexible transmission system is calculated based on the target control parameters and real-time voltage and current data of the transmission lines, and the power flow of the transmission lines is coordinated and optimized based on the voltage compensation amount. Compared with existing technologies, this method, by establishing a hierarchical equivalent coupling model to coordinate and optimize the parallel and series sides of the distributed power flow controller, minimizes the total loss of the flexible transmission system, effectively improves the voltage stability and power flow balance distribution of the flexible transmission system, enhances the renewable energy absorption capacity and power quality, thereby ensuring the safe, stable, and efficient operation of the flexible transmission system.

[0052] It should be noted that the sequence number of each process does not imply 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 this application.

[0053] In one embodiment, Figure 9 As shown, this embodiment of the invention provides a coordination and optimization system for a distributed power flow controller, the system comprising: The model building module 101 is used to build a hierarchical equivalent coupling model of the distributed power flow controller based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible power transmission system and the topology parameters of the flexible power transmission system. The model solving module 102 is used to optimize the parallel-side output voltage vector and series-side injected voltage vector of the distributed power flow controller by using the hierarchical equivalent coupling model with the goal of minimizing the total loss of the flexible transmission system, so as to obtain the optimal coordinated optimization control strategy of the distributed power flow controller. The mode decision module 103 is used to allocate a target control mode to the serial side of the distributed power flow controller according to the optimal coordination optimization control strategy, and to obtain the target control parameters under the target control mode. The coordination and optimization module 104 is used to calculate the required voltage compensation amount to be injected into the flexible transmission system based on the target control parameters and the real-time voltage and current data of the transmission line, and to perform coordinated and optimized control of the power flow of the transmission line based on the voltage compensation amount.

[0054] Specific limitations regarding the coordination and optimization system of a distributed power flow controller can be found in the above-described limitations regarding the coordination and optimization method of a distributed power flow controller, and will not be repeated here. Those skilled in the art will recognize that the various modules and steps described in conjunction with the embodiments disclosed in this application can be implemented in hardware, software, or a combination of both. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0055] This invention provides a coordinated optimization system for a distributed power flow controller. The system's model building module establishes a hierarchical equivalent coupling model of the distributed power flow controller based on real-time electrical quantity data and topology parameters of the flexible transmission system. The model solving module, with the goal of minimizing the total loss of the flexible transmission system, uses the hierarchical equivalent coupling model to globally optimize the parallel-side output voltage vector and series-side injected voltage vector of the distributed power flow controller, obtaining the optimal coordinated optimization control strategy. The mode decision module assigns a target control mode to the series side of the distributed power flow controller based on the optimal coordinated optimization control strategy and obtains the target control parameters under the target control mode. The coordinated optimization module calculates the required voltage compensation amount injected into the flexible transmission system based on the target control parameters and real-time voltage and current data of the transmission lines, and performs coordinated optimization control of the power flow of the transmission lines based on the voltage compensation amount. Compared with existing technologies, this system minimizes the total loss of the flexible power transmission system by establishing a hierarchical equivalent coupling model to coordinate and optimize the parallel and series sides of the distributed power flow controller. This effectively improves the voltage stability and power flow balance of the flexible power transmission system, enhances the renewable energy absorption capacity and power quality, and thus ensures the safe, stable and efficient operation of the flexible power transmission system.

[0056] In one embodiment, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0057] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., SSD), etc.

[0058] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed, it can include the processes of the embodiments of the above methods.

[0059] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this invention, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A coordination optimization method for a distributed power flow controller, characterized in that, The following steps are involved: Based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible transmission system and the topology parameters of the flexible transmission system, a hierarchical equivalent coupling model of the distributed power flow controller is established. With minimizing the total loss of the flexible transmission system as the optimization objective, the hierarchical equivalent coupling model is used to globally optimize the parallel-side output voltage vector and the series-side injected voltage vector of the distributed power flow controller, thereby obtaining the optimal coordinated optimization control strategy of the distributed power flow controller. Based on the optimal coordination and optimization control strategy, a target control mode is assigned to the serial side of the distributed power flow controller, and the target control parameters under the target control mode are obtained. The required voltage compensation amount to be injected into the flexible transmission system is calculated based on the target control parameters and real-time voltage and current data of the transmission line, and the power flow of the transmission line is coordinated and optimized based on the voltage compensation amount.

2. The coordination optimization method for a distributed power flow controller as described in claim 1, characterized in that: The distributed power flow controller includes a parallel side and a series side, and the series side includes at least a first series side and a second series side; The parallel side includes a parallel coupling transformer, a three-phase converter, and a common DC capacitor connected to the DC side of the three-phase converter; The first series side includes three single-phase converters sharing a DC side and a three-phase isolation transformer. Each single-phase converter uses a single-phase H-bridge converter to independently control the output voltage amplitude and output voltage phase of each phase. The DC side of the three single-phase converters is connected to the common DC capacitor. The AC side of the three single-phase converters is connected to the transmission line in series through the three-phase isolation transformer. The second series side includes multiple sets of distributed single-phase converter units. Each set of distributed single-phase converter units includes a distributed H-bridge converter, a series-side DC capacitor, and a single-phase coupling transformer. The single-phase coupling transformer is connected in series in a distributed manner in the transmission line.

3. The coordination optimization method for a distributed power flow controller as described in claim 2, characterized in that: The parallel side is used to connect to the bus via the parallel coupling transformer, so that the three-phase converter can draw energy from the bus to charge the common DC capacitor, and provide a stable DC voltage to the first series side through the common DC capacitor; The first series side is used to generate non-fundamental harmonics based on the energy stored in the common DC capacitor, and inject the non-fundamental harmonics into the transmission line through the three-phase isolation transformer to regulate the reactive power flow of the transmission line. The multiple sets of distributed single-phase converter units on the second series side are used to draw energy from the transmission line to charge the DC capacitor on the series side, generate a compensation voltage, and inject the compensation voltage into the transmission line through a distributed H-bridge converter to regulate the active power flow of the transmission line.

4. The coordination optimization method for a distributed power flow controller as described in claim 2, characterized in that: The distributed power flow controller also includes a filter unit connected in parallel to the load side at the end of the transmission line; The filtering unit is used to filter out residual non-fundamental harmonics generated by the first series side in the transmission line that are not absorbed by the second series side.

5. The coordination optimization method for a distributed power flow controller as described in claim 2, characterized in that: The hierarchical equivalent coupling model includes a static var compensator model with dual closed-loop control on the parallel side, a controlled voltage source model with phase-independent control on the series side, and a hybrid model of multi-node impedance voltage sources.

6. The coordination optimization method for a distributed power flow controller as described in claim 5, characterized in that, The steps for establishing a hierarchical equivalent coupling model of the distributed power flow controller based on real-time electrical quantity data of the distributed power flow controller deployed on the flexible transmission system and the topology parameters of the flexible transmission system include: Calculate the reference value of the output current of the parallel-side three-phase converter based on the three-phase voltage of the parallel-side bus and the voltage of the common DC capacitor; The reference value of the output current is compared with the actual output current to obtain the current error, and the current error is adjusted using a proportional-integral regulator. The direct-axis component and quadrature-axis component of the modulation voltage are obtained through a feedforward decoupling control strategy. Based on the direct axis component and the quadrature axis component, a static var compensation model for the parallel side is constructed in a synchronous rotating coordinate system. Using the common DC capacitor voltage output by the dual closed-loop control of the static var compensator model as the coupling point, the voltage amplitude and voltage phase angle required to be injected into the series-side single-phase converter are calculated based on the voltage at the beginning and end of the transmission line and the impedance data of the transmission line. Based on the voltage amplitude and voltage phase angle required to be injected into the series-side single-phase converter, a controlled voltage source model of the series side is constructed in the synchronous rotating coordinate system using a decoupling control law. Based on the voltage at the beginning and end of the transmission line after compensation by the controlled voltage source model and the real-time power flow distribution data of the transmission line, the equivalent impedance value required to be output by the series-side distributed single-phase converter unit is calculated. Based on the required equivalent impedance value of the distributed single-phase converter unit on the series side, a hybrid model of multi-node impedance voltage sources is constructed. The static var compensator model, the controlled voltage source model, and the multi-node impedance voltage source hybrid model are integrated to form a hierarchical equivalent coupling model.

7. The coordination optimization method for a distributed power flow controller as described in claim 2, characterized in that: The optimal coordinated control strategy includes at least the output voltage vector or current inner loop reference value of the parallel-side converter, the injected voltage vector of the series-side single-phase converter, and the control mode of the series-side distributed single-phase converter unit.

8. The coordination optimization method for a distributed power flow controller as described in claim 7, characterized in that: The control mode of the series-side distributed single-phase converter unit is impedance control mode, voltage control mode, or power flow control mode.

9. A coordinated optimization system for a distributed power flow controller, characterized in that, The system includes: The model building module is used to build a hierarchical equivalent coupling model of the distributed power flow controller based on the real-time electrical quantity data of the distributed power flow controller deployed on the flexible power transmission system and the topology parameters of the flexible power transmission system. The model solving module is used to optimize the parallel-side output voltage vector and series-side injected voltage vector of the distributed power flow controller by using the hierarchical equivalent coupling model to minimize the total loss of the flexible transmission system, thereby obtaining the optimal coordinated optimization control strategy of the distributed power flow controller. The mode decision module is used to allocate a target control mode to the serial side of the distributed power flow controller according to the optimal coordination and optimization control strategy, and to obtain the target control parameters under the target control mode. The coordination and optimization module is used to calculate the required voltage compensation amount to be injected into the flexible transmission system based on the target control parameters and real-time voltage and current data of the transmission line, and to perform coordinated and optimized control of the power flow of the transmission line based on the voltage compensation amount.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program that, when executed, implements the method as described in any one of claims 1 to 8.

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