Series-parallel hybrid power flow control method and system

Abstract

This invention discloses a series-parallel hybrid power flow control method and system, applied in the field of power grid power flow control. The method includes: determining power grid demand information based on key operating data of the transmission network; determining the equivalent active power control quantity of UPFC, the equivalent power flow regulation quantity of SSSC, and the equivalent reactive power control quantity of STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network; and injecting equivalent voltage and equivalent current into the transmission network through the series-parallel connection of UPFC, SSSC, and STATCOM to regulate the key operating data of the transmission network. When power flow control is required in the transmission network, this invention injects controllable voltage and current into the transmission network through UPFC, SSSC, and STATCOM to achieve adaptive control of power flow on transmission network lines.

Description

Technical Field

[0001] This invention relates to the field of power flow control in power grids, and in particular to a hybrid series-parallel power flow control method and system. Background Technology

[0002] With the development of power transmission networks, their structures have become increasingly complex, often leading to uneven power flow distribution. Therefore, installing Flexible AC Transmission Systems (FACTS) in existing power transmission network structures has become a primary means of improving power flow control capabilities. However, existing FACTS devices, when dealing with complex power transmission networks, have relatively limited functionality and are difficult to flexibly adapt to the power flow control needs of power transmission networks under different operating scenarios. Summary of the Invention

[0003] This invention provides a hybrid series-parallel power flow control method and system to solve the technical problem that existing power flow control methods for power transmission networks cannot flexibly adapt to power flow control requirements.

[0004] To address the aforementioned technical problems, this invention provides a hybrid series-parallel power flow control method for a power transmission network equipped with a hybrid series-parallel power flow control device. The hybrid series-parallel power flow control device includes a Unified Power Flow Controller (UPFC), a Static Synchronous Series Compensator (SSSC), and a Static Synchronous Compensator (STATCOM). The UPFC is connected to the power transmission network via both parallel and series connections; the SSSC is connected to the power transmission network via series connection; and the STATCOM is connected to the power transmission network via parallel connection. The method includes: Based on the key operational data of the power transmission network, the demand information of the power transmission network is determined; Based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM are determined. The first voltage corresponding to the equivalent active power control quantity is injected into the transmission network through the series connection of the UPFCs; the first current corresponding to the equivalent active power control quantity is injected into the transmission network through the parallel connection of the UPFCs; the second voltage corresponding to the equivalent power flow regulation quantity is injected into the transmission network through the series connection of the SSSCs; and the second current corresponding to the equivalent reactive power control quantity is injected into the transmission network through the parallel connection of the STATCOMs. The key operating data of the power transmission network are adjusted based on the first voltage, the first current, the second voltage, and the second current.

[0005] By coordinating the control of UPFC, SSSC and STATCOM in the series-parallel hybrid power flow control device, when the power flow regulation of the transmission network is required, the joint operation of UPFC and SSSC can achieve precise control of the power flow of the transmission network lines; when the power flow regulation and voltage support of the transmission network are required, the STATCOM can perform dynamic reactive power regulation of the transmission network to achieve stable control of the voltage of the transmission network bus.

[0006] As one preferred embodiment, the key operational data includes system frequency deviation, bus voltage deviation, and line power flow deviation; after determining the demand information of the transmission network based on the key operational data of the transmission network, the process includes: If the system frequency deviation is greater than a preset frequency threshold, the power transmission network is determined to be in an active power support demand state; if the bus voltage deviation is greater than a preset voltage threshold, the power transmission network is determined to be in a voltage regulation demand state. If the system frequency deviation is less than or equal to a preset frequency threshold, the bus voltage deviation is less than or equal to a preset voltage threshold, and the line power flow deviation is greater than a preset power flow threshold, then the power transmission network is determined to be in a power flow optimization operation state. When the transmission network is in any of the active power support demand state, the voltage regulation demand state, and the power flow optimization operation state, the quantitative result of the demand information is determined based on the system active power deviation, the bus voltage deviation, and the line power flow deviation; the system active power deviation is determined based on the system frequency deviation.

[0007] By analyzing the key operational data of the power transmission network, the demand information of the power transmission network is quantified, and the results of the demand quantification can be used to guide the injection of power flow control quantities in the power transmission network.

[0008] As one preferred embodiment, after determining the demand information of the transmission network based on the key operational data of the transmission network, the method further includes: Obtain the quantization result of the maximum output capability of any one of the UPFC, SSSC, and STATCOM; Obtain the DC-side capacitor voltage inside any of the UPFC, SSSC, and STATCOM; Based on the quantization results of the maximum output capability and the DC-side capacitor voltage, the first constraint data of the series-parallel hybrid power flow control device is constructed.

[0009] The physical feasibility of power flow control is ensured by constructing hardware constraints for UPFC, SSSC, and STATCOM.

[0010] As one preferred embodiment, after determining the demand information of the transmission network based on the key operational data of the transmission network, the method further includes: Obtain the injection voltage threshold and injection current threshold of the power transmission network; Based on the injection voltage threshold and the injection current threshold, the second constraint data of the power transmission network is constructed.

[0011] By constructing safety constraints for the power transmission network, it is ensured that the series-parallel hybrid power flow control device will not damage the power transmission network when regulating the power flow.

[0012] As one preferred embodiment, determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network includes: Based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the first weight of the UPFC, the second weight of the SSSC, and the third weight of the STATCOM are determined. A comprehensive control objective is determined based on the first control objective of the UPFC, the second control objective of the SSSC, and the third control objective of the STATCOM; the first control objective is determined based on the first weight and the first demand deviation of the SSSC; the second control objective is determined based on the second weight and the second demand deviation of the UPFC; and the third control objective is determined based on the third weight and the third demand deviation of the UPFC. The integrated control objective is optimized to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM.

[0013] Under the constraints, a multi-objective optimization problem is solved to achieve coordinated control based on the real-time needs of the power transmission network.

[0014] As one preferred embodiment, optimizing the integrated control objective to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM includes: Based on the first constraint data of the series-parallel hybrid power flow control device, the comprehensive control objective is optimized to obtain the first optimization objective; Based on the second constraint data of the transmission network, the first optimization objective is optimized to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM.

[0015] Under multi-level constraints and multi-objective optimization, flexible adaptation to power flow control of the transmission network is achieved.

[0016] As one preferred embodiment, after determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the process includes: The amplitude and phase of the first voltage corresponding to the equivalent active power control quantity are determined to be adjustable; The first voltage is injected into the transmission network through the series connection of the UPFC, thereby regulating the voltage phasor and equivalent impedance of the transmission network to achieve the regulation of active power flow and reactive power flow.

[0017] By injecting controllable voltage into the transmission network through series connection of UPFCs, the voltage phasor and equivalent impedance of the transmission network lines are changed, thereby achieving regulation of the active and reactive power flow of the transmission network lines.

[0018] As one preferred embodiment, after determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the process further includes: The phase of the second voltage corresponding to the equivalent power flow regulation is determined to be adjustable; The second voltage is injected into the transmission network through the series connection of the SSSCs to regulate the equivalent impedance of the transmission network, thereby achieving the regulation of reactive power flow in the transmission network.

[0019] By injecting controllable current into the transmission network through the series connection of SSSCs, the equivalent reactance of the transmission network lines is changed, thereby achieving the regulation of reactive power flow in the transmission network lines.

[0020] As one preferred embodiment, after determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the process further includes: It is determined that the first current corresponding to the equivalent active power control quantity is adjustable; The first current is injected into the bus of the transmission network through the parallel connection of the UPFC, and the reactive power of the UPFC and the connection point of the transmission network is regulated to support the bus voltage of the transmission network.

[0021] By using UPFC in parallel, controllable reactive current is injected into the power grid to compensate for the reactive power of the power grid and stabilize the bus voltage of the power grid.

[0022] Another embodiment of the present invention provides a series-parallel hybrid power flow control system, comprising: The demand information determination module is used to determine the demand information of the power transmission network based on key operational data of the power transmission network. The power flow control quantity determination module is used to determine the equivalent active power control quantity of the unified power flow controller UPFC, the equivalent power flow regulation quantity of the static synchronous series compensator SSSC, and the equivalent reactive power control quantity of the static synchronous compensator based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the power grid. The power flow control injection module is used to inject a first voltage corresponding to the equivalent active power control quantity into the transmission network through the series connection of the UPFCs, inject a first current corresponding to the equivalent active power control quantity into the transmission network through the parallel connection of the UPFCs, inject a second voltage corresponding to the equivalent power flow regulation quantity into the transmission network through the series connection of the SSSCs, and inject a second current corresponding to the equivalent reactive power control quantity into the transmission network through the parallel connection of the STATCOMs. The power flow control module is used to regulate key operating data of the power transmission network based on the first voltage, the first current, the second voltage, and the second current. Attached Figure Description

[0023] Figure 1 This is one of the flowcharts of the series-parallel hybrid power flow control method provided by the present invention; Figure 2 This is the second flowchart of the series-parallel hybrid power flow control method provided by the present invention; Figure 3 This is a schematic diagram of the series-parallel hybrid power flow control system provided by the present invention.

[0024] Figure label: Among them, 301 is the demand information determination module; 302 is the power flow control quantity determination module; 303 is the power flow control quantity injection module; and 304 is the power flow control module. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0028] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0029] See Figure 1 , Figure 1This is a flowchart illustrating an embodiment of the hybrid series-parallel power flow control method provided by the present invention. The hybrid series-parallel power flow control method provided by the present invention is used in power transmission networks equipped with a hybrid series-parallel power flow control device. The hybrid series-parallel power flow control device includes a unified power flow controller (UPFC), a static synchronous series compensator (SSSC), and a static synchronous compensator (STATCOM). The UPFC is connected to the power transmission network via parallel and series connections; the SSSC is connected to the power transmission network via series connection; and the STATCOM is connected to the power transmission network via parallel connection. Figure 1 As shown, this embodiment includes steps 100 to 400, and the specific steps are as follows: Step 100: Based on the key operational data of the power transmission network, determine the demand information of the power transmission network; Key operational data for power transmission networks refer to operational data related to power flow control, such as system frequency deviation, bus voltage deviation, and line power flow deviation. This key operational data is used to determine whether the power transmission network requires power flow control. For example, if the system frequency deviation exceeds a corresponding threshold, it indicates that the power transmission network has a need for active power support; if the bus voltage deviation exceeds a corresponding threshold, it indicates that the power transmission network has a need for voltage regulation. The demand information of the power transmission network includes the power flow information that the power transmission network needs to regulate.

[0030] Step 200: Based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, determine the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM. The demand information of the transmission network is quantified to obtain the active power deviation, bus voltage deviation, and line power flow deviation of the transmission network demand, i.e., the quantified results of the transmission network demand information. Based on the quantified results of the transmission network demand information, the first constraint of the series-parallel hybrid power flow control device and the second constraint of the transmission network are introduced to globally optimize and adjust the equivalent control quantities output by UPFC (Unified Power Flow Controller), SSSC (Static Synchronous Series Compensator), and STATCOM (Static Synchronous Compensator), thereby obtaining the equivalent active power control quantity of UPFC, the equivalent power flow regulation quantity of SSSC, and the equivalent reactive power control quantity of STATCOM.

[0031] Step 300: Inject the first voltage corresponding to the equivalent active power control quantity into the transmission network through the series connection of the UPFCs; inject the first current corresponding to the equivalent active power control quantity into the transmission network through the parallel connection of the UPFCs; inject the second voltage corresponding to the equivalent power flow regulation quantity into the transmission network through the series connection of the SSSCs; inject the second current corresponding to the equivalent reactive power control quantity into the transmission network through the parallel connection of the STATCOMs. After obtaining a set of optimal equivalent control outputs through optimization, these outputs are injected into the transmission network via the series and parallel connection of the UPFC, SSSC, and STATCOM modules to control the power flow. Taking the parallel connection of the STATCOM as an example, the STATCOM is connected in parallel to the transmission network bus via its internal parallel converter. The STATCOM dynamically adjusts the reactive power at the parallel connection point by injecting or absorbing controllable reactive current (i.e., the second current in this embodiment) into or from the bus, thereby quickly supporting and stabilizing the transmission network bus voltage. The STATCOM provides stable support to the transmission network by improving its voltage quality.

[0032] Step 400: Adjust the key operating data of the power transmission network according to the first voltage, the first current, the second voltage, and the second current.

[0033] For UPFC, after determining the equivalent active power control quantity, the series section of the UPFC converts the equivalent active power control quantity into a specific voltage (i.e., the first voltage in this embodiment) and injects it into the transmission network line. Simultaneously, the parallel section of the UPFC outputs a corresponding reactive current (i.e., the first current in this embodiment) as needed to participate in voltage regulation and handle active power exchange, supporting the independent operation of the series section of the UPFC. Based on this unique series-parallel combination access method, the UPFC can simultaneously control the power flow of the transmission network line and the voltage of the transmission network bus. For SSSC, after determining the equivalent power flow regulation quantity, the series converter of the SSSC converts the equivalent power flow regulation quantity into a voltage orthogonal to the transmission network line current (i.e., the second voltage in this embodiment) and injects it into the transmission network line, effectively changing the transmission network line parameters. For STATCOM, after determining the equivalent reactive power control quantity, the parallel converter of the STATCOM converts the equivalent reactive power control quantity into a reactive current with a specific amplitude and direction (i.e., the second current in this embodiment) and injects it into the transmission network bus.

[0034] See Figure 2 , Figure 2 This is a flowchart illustrating another embodiment of the hybrid series-parallel power flow control method provided by the present invention, as shown below. Figure 2As shown, this embodiment includes steps 500 to 700, and the specific steps are as follows: Step 500: If the system frequency deviation is greater than a preset frequency threshold, the power transmission network is determined to be in an active power support demand state; if the bus voltage deviation is greater than a preset voltage threshold, the power transmission network is determined to be in a voltage regulation demand state. Step 600: If the system frequency deviation is less than or equal to a preset frequency threshold, the bus voltage deviation is less than or equal to a preset voltage threshold, and the line power flow deviation is greater than a preset power flow threshold, then the power transmission network is determined to be in a power flow optimization operation state. Step 700: When the transmission network is in any of the active power support demand state, the voltage regulation demand state, and the power flow optimization operation state, determine the quantification result of the demand information based on the system active power deviation, the bus voltage deviation, and the line power flow deviation; the system active power deviation is determined based on the system frequency deviation.

[0035] Before controlling the power flow of the transmission network, key operational data of the transmission network should be collected, including system frequency deviation. Bus voltage deviation and line power flow deviation Wait. If If the frequency exceeds a preset threshold, the power transmission network is determined to be in a state of active power support demand; if If the voltage deviation is greater than the preset voltage threshold, the transmission network is determined to be in a voltage regulation demand state; if the system frequency deviation is less than or equal to the preset frequency threshold, the bus voltage deviation is less than or equal to the preset voltage threshold, and the line power flow deviation is greater than the preset power flow threshold, the transmission network is determined to be in a power flow optimization operation state.

[0036] Under active power support demand conditions, the UPFC is determined as the main control unit; under voltage regulation demand conditions, the SSSC is determined as the main control unit; and under power flow optimization operation conditions, the STATCOM is determined as the main control unit. Based on the determination of the transmission network state and the main control unit, the degree of participation of UPFC, SSSC, and STATCOM in controlling the transmission network power flow is quantitatively allocated to obtain the quantitative results of transmission network demand information.

[0037] In this embodiment, the system active power deviation is... It is determined based on the system frequency deviation. For example, the system active power deviation is proportional to the system frequency deviation, as shown in the formula. , where k is the proportionality coefficient.

[0038] In another embodiment of the series-parallel hybrid power flow control method provided by the present invention, step 200 specifically includes: Step 210: Obtain the quantization result of the maximum output capability of any one of the UPFC, SSSC, and STATCOM; Step 220: Obtain the DC-side capacitor voltage inside any of the UPFC, SSSC, and STATCOM; Step 230: Based on the quantization result of the maximum output capability and the DC-side capacitor voltage, construct the first constraint data of the series-parallel hybrid power flow control device.

[0039] To ensure the safe operation of the hybrid series-parallel power flow control device, the equivalent active power control quantity of the UPFC needs to be determined. Equivalent power flow regulation of SSSC and the equivalent reactive power control quantity of STATCOM Previously, it was necessary to construct the first constraint condition for the series-parallel hybrid power flow control device. The first constraint condition includes the capacity constraint, as shown in Equation 1, where, , and These are the quantified results of the maximum controllability corresponding to UPFC, SSSC, and STATCOM, respectively; for example, for UPFC, This corresponds to the maximum amplitude of the series injection voltage that the converter inside the UPFC can generate; for STATCOM, This corresponds to the maximum reactive current that the STATCOM can output or absorb. The constraints in Equation 1 ensure that the power flow control commands (acting on the hybrid series-parallel power flow control device) are physically executable, preventing power flow control failure due to commands exceeding the hardware limits of the UPFC, SSSC, and STATCOM. These are necessary boundary conditions to follow when optimizing the equivalent control quantities of the UPFC, SSSC, and STATCOM.

[0040] (1) (2) The first constraint also includes a DC-side energy constraint, as shown in Equation 2, where i is any module among UPFC, SSSC, and STATCOM. The DC-side energy constraint limits the voltage stability of the DC-side capacitors within each module of UPFC, SSSC, and STATCOM. The normal operation of the converters within each module of UPFC, SSSC, and STATCOM is based on maintaining the voltage of the internal DC bus capacitors. At a stable reference value Nearby, when each module exchanges active power with the transmission network, the DC capacitors inside the modules will charge or discharge, causing fluctuations in capacitor voltage. This can be mitigated by limiting the range of capacitor voltage fluctuations (not exceeding...). This ensures that each module maintains dynamic energy balance when performing power flow regulation tasks in the power grid, preventing excessively high or low DC voltage from causing module lockout or damage.

[0041] In another embodiment of the series-parallel hybrid power flow control method provided by the present invention, step 200 specifically further includes: Step 240: Obtain the injection voltage threshold and injection current threshold of the power transmission network; Step 250: Based on the injected voltage threshold and the injected current threshold, construct the second constraint data of the power transmission network.

[0042] To ensure the safe operation of the power transmission network, the equivalent active power control quantity of UPFC needs to be determined. Equivalent power flow regulation of SSSC and the equivalent reactive power control quantity of STATCOM Previously, it was necessary to construct the second constraint condition for the transmission network, which included injection voltage constraint and injection current constraint, as shown in Equation 3. Among them, Inject the voltage of the power grid into any of the modules in UPFC, SSSC, and STATCOM; Inject power grid current into any of the modules in UPFC, SSSC, and STATCOM; The upper limit of the injection voltage that the power transmission network can safely withstand; This refers to the upper limit of the injection current that the power transmission network can safely withstand.

[0043] (3) By constructing constraints on the power transmission network, the control of the series-parallel hybrid power flow control device is prevented from impacting the power transmission network itself, avoiding safety issues such as overvoltage and overcurrent, and ensuring that the series-parallel hybrid power flow control device does not damage the power transmission network when regulating the power flow.

[0044] In another embodiment of the series-parallel hybrid power flow control method provided by the present invention, step 200 specifically further includes: Step 260: Based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, determine the first weight of the UPFC, the second weight of the SSSC, and the third weight of the STATCOM; Step 270: Determine the integrated control objective based on the first control objective of the UPFC, the second control objective of the SSSC, and the third control objective of the STATCOM; the first control objective is determined based on the first weight and the first demand deviation of the SSSC; the second control objective is determined based on the second weight and the second demand deviation of the UPFC; the third control objective is determined based on the third weight and the third demand deviation of the UPFC. Step 280: Optimize the integrated control objective to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM.

[0045] Define the equivalent control outputs of UPFC, SSSC, and STATCOM. As shown in Formula 4, where, This is the equivalent active control quantity of UPFC, corresponding to the active component of the series injection voltage of UPFC. This is the equivalent power flow regulation of the SSSC, corresponding to the magnitude or phase angle of the series injection voltage; This represents the equivalent reactive power control quantity of STATCOM, corresponding to the amplitude of the injected reactive current. Formula 4 is used to quantify the deviation between the control effects of each module of UPFC, SSSC, and STATCOM and the actual needs of the transmission network. For example, The active power control output of the UPFC plan was measured. Active power regulation in relation to total demand of the power grid Minimize the square of the difference between them. This means that the output of the UPFC must match the active power support requirements of the power grid as accurately as possible.

[0046] (4) (5) (6) For UPFC, SSSC, and STATCOM, the local control objective functions are defined as shown in Equation 5, where, This is the first requirement deviation for UPFC; This is the second demand deviation for SSSC; This represents the third demand deviation of STATCOM. The integrated coordination objective function, as shown in Equation 6, is constructed using Equation 5, where... The first weight of UPFC; This is the second weight of the SSSC; This is the third weight of STATCOM; The primary control objective of UPFC; The second control objective of SSSC; The third control objective of STATCOM; The overall control objective is for a hybrid series-parallel power flow control device.

[0047] Under the condition that the first and second constraints mentioned above are satisfied, solve for a set of optimal equivalent control outputs. , making Minimize. This approach balances multi-objective optimization with coordinated control based on the real-time needs of the power transmission network.

[0048] In another embodiment of the series-parallel hybrid power flow control method provided by the present invention, step 280 specifically includes: Step 281: Optimize the integrated control objective based on the first constraint data of the series-parallel hybrid power flow control device to obtain the first optimization objective; Step 282: Optimize the first optimization objective based on the second constraint data of the transmission network to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM.

[0049] The first and second constraints mentioned above are executed in parallel, meaning that the series-parallel hybrid power flow control method provided by this invention needs to simultaneously satisfy both constraints. Based on these two constraints, a set of optimal equivalent control output quantities is solved according to Equation 6 above. Each weight coefficient is dynamically determined based on the current power grid operating status. In global optimization, the weight coefficient determines which module's tracking deviation (in UPFC, SSSC, and STATCOM) is more important to reduce.

[0050] For example, when the power transmission network is in a state of active power support demand, Setting it to maximum means that the optimization algorithm shown in Equation 6 will prioritize minimizing it. (That is, to ensure that UPFC accurately meets the active power demand), while for and Optimization is of relatively minor importance.

[0051] In another embodiment of the series-parallel hybrid power flow control method provided by the present invention, step 300 specifically includes: Step 310: Determine that the amplitude and phase of the first voltage corresponding to the equivalent active power control quantity are adjustable; Step 320: Inject the first voltage into the transmission network through the series connection of the UPFC, and regulate the voltage phasor and equivalent impedance of the transmission network to achieve the regulation of active power flow and reactive power flow of the transmission network.

[0052] After optimizing and solving Formula 6 to obtain a set of optimal equivalent control outputs, these outputs are injected into the transmission network through the series and parallel connection of the UPFC, SSSC, and STATCOM modules to control the power flow. Taking the series connection of the UPFC as an example, the series connection section of the UPFC (its internal series converter) is connected to the transmission network in series. This series connection method is a key means of injecting the first voltage corresponding to the equivalent active power control quantity into the transmission network. By injecting a controllable first voltage (amplitude and phase) into the transmission network, the voltage phasor and equivalent impedance of the transmission network lines are directly changed, thereby regulating the active and reactive power flow of the transmission network lines.

[0053] The parallel section of the UPFC can also provide an active power exchange channel for the series section, which is the physical basis for the UPFC to achieve independent active power regulation. When the series section of the UPFC injects voltage into the transmission line for power flow control, it exchanges active power with the transmission line. The parallel section of the UPFC provides or absorbs this active power difference to its series section through the DC bus (within the UPFC), thereby maintaining the stability of the UPFC's own DC capacitor voltage. It does not need to obtain active power from the transmission line itself, thus achieving independent control of the power flow of the transmission line.

[0054] In another embodiment of the series-parallel hybrid power flow control method provided by the present invention, step 300 further includes: Step 330: Determine that the phase of the second voltage corresponding to the equivalent power flow regulation is adjustable; Step 340: Inject the second voltage into the power transmission network through the series connection of the SSSCs to regulate the equivalent impedance of the power transmission network, thereby achieving the regulation of the reactive power flow of the power transmission network.

[0055] Taking the series connection of the SSSC as an example, the SSSC is connected to the transmission network in series through its internal series converter. This series connection method injects a series voltage (i.e., the second voltage in this embodiment, equivalent to a controllable virtual reactance) that is 90 degrees phase with the transmission network line current into the transmission network, thereby changing the equivalent reactance of the transmission network line and indirectly affecting the power flow of the transmission network line. It mainly affects the reactive power of the transmission network line, and its ability to regulate the active power of the transmission network line is limited and not independent. The active power required for the operation of the SSSC needs to be obtained from the transmission network line or compensated through other means (e.g., absorbing the third harmonic generated by the STATCOM).

[0056] In another embodiment of the series-parallel hybrid power flow control method provided by the present invention, step 300 further includes: Step 350: Determine that the first current corresponding to the equivalent active power control quantity is adjustable; Step 360: Inject the first current into the bus of the power transmission network through the parallel connection of the UPFC, and regulate the reactive power of the UPFC and the connection point of the power transmission network to support the bus voltage of the power transmission network.

[0057] The parallel connection method of STATCOM is similar to that of UPFC. Taking the parallel connection method of UPFC as an example, the parallel access part of UPFC (its internal parallel converter) is connected to the transmission network bus in parallel. Through this parallel access part, a controllable reactive current (i.e. the first current in this embodiment) is injected into the transmission network to compensate for the reactive power of the transmission network and stabilize the voltage of the transmission network bus.

[0058] The series-parallel hybrid power flow control system provided by the present invention is described below. The series-parallel hybrid power flow control system described below can be referred to in correspondence with the series-parallel hybrid power flow control method described above.

[0059] Please refer to Figure 3 The present invention also provides a series-parallel hybrid power flow control system, comprising: Demand information determination module 301 is used to determine the demand information of the power transmission network based on key operational data of the power transmission network. The power flow control quantity determination module 302 is used to determine the equivalent active power control quantity of the unified power flow controller UPFC, the equivalent power flow regulation quantity of the static synchronous series compensator SSSC, and the equivalent reactive power control quantity of the static synchronous compensator based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the power grid. The power flow control injection module 303 is used to inject a first voltage corresponding to the equivalent active power control quantity into the transmission network through the series connection of the UPFCs, inject a first current corresponding to the equivalent active power control quantity into the transmission network through the parallel connection of the UPFCs, inject a second voltage corresponding to the equivalent power flow regulation quantity into the transmission network through the series connection of the SSSCs, and inject a second current corresponding to the equivalent reactive power control quantity into the transmission network through the parallel connection of the STATCOMs. The power flow control module 304 is used to regulate key operating data of the power transmission network based on the first voltage, the first current, the second voltage, and the second current.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A hybrid series-parallel power flow control method, characterized in that, A power transmission network equipped with a hybrid series-parallel power flow control device; the hybrid series-parallel power flow control device includes a unified power flow controller (UPFC), a static synchronous series compensator (SSSC), and a static synchronous compensator (STATCOM); wherein, the UPFC is connected to the power transmission network in both parallel and series configurations; the SSSC is connected to the power transmission network in series configuration; and the STATCOM is connected to the power transmission network in parallel configuration; the method includes: Based on the key operational data of the power transmission network, the demand information of the power transmission network is determined; Based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM are determined. The first voltage corresponding to the equivalent active power control quantity is injected into the transmission network through the series connection of the UPFCs; the first current corresponding to the equivalent active power control quantity is injected into the transmission network through the parallel connection of the UPFCs; the second voltage corresponding to the equivalent power flow regulation quantity is injected into the transmission network through the series connection of the SSSCs; and the second current corresponding to the equivalent reactive power control quantity is injected into the transmission network through the parallel connection of the STATCOMs. The key operating data of the power transmission network are adjusted based on the first voltage, the first current, the second voltage, and the second current.

2. The series-parallel hybrid power flow control method as described in claim 1, characterized in that, The key operational data includes system frequency deviation, bus voltage deviation, and line power flow deviation; after determining the demand information of the transmission network based on the key operational data of the transmission network, the process includes: If the system frequency deviation is greater than a preset frequency threshold, the power transmission network is determined to be in an active power support demand state; if the bus voltage deviation is greater than a preset voltage threshold, the power transmission network is determined to be in a voltage regulation demand state. If the system frequency deviation is less than or equal to a preset frequency threshold, the bus voltage deviation is less than or equal to a preset voltage threshold, and the line power flow deviation is greater than a preset power flow threshold, then the power transmission network is determined to be in a power flow optimization operation state. When the transmission network is in any of the active power support demand state, the voltage regulation demand state, and the power flow optimization operation state, the quantitative result of the demand information is determined based on the system active power deviation, the bus voltage deviation, and the line power flow deviation; the system active power deviation is determined based on the system frequency deviation.

3. The hybrid series-parallel power flow control method as described in claim 1, characterized in that, After determining the demand information of the transmission network based on its key operational data, the process also includes: Obtain the quantization result of the maximum output capability of any one of the UPFC, SSSC, and STATCOM; Obtain the DC-side capacitor voltage inside any of the UPFC, SSSC, and STATCOM; Based on the quantization results of the maximum output capability and the DC-side capacitor voltage, the first constraint data of the series-parallel hybrid power flow control device is constructed.

4. The series-parallel hybrid power flow control method as described in claim 1, characterized in that, After determining the demand information of the transmission network based on its key operational data, the process also includes: Obtain the injection voltage threshold and injection current threshold of the power transmission network; Based on the injection voltage threshold and the injection current threshold, the second constraint data of the power transmission network is constructed.

5. The series-parallel hybrid power flow control method as described in claim 1, characterized in that, The step of determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network includes: Based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the first weight of the UPFC, the second weight of the SSSC, and the third weight of the STATCOM are determined. A comprehensive control objective is determined based on the first control objective of the UPFC, the second control objective of the SSSC, and the third control objective of the STATCOM; the first control objective is determined based on the first weight and the first demand deviation of the SSSC; the second control objective is determined based on the second weight and the second demand deviation of the UPFC; and the third control objective is determined based on the third weight and the third demand deviation of the UPFC. The integrated control objective is optimized to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM.

6. The series-parallel hybrid power flow control method as described in claim 5, characterized in that, The optimization of the integrated control objective to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM includes: Based on the first constraint data of the series-parallel hybrid power flow control device, the comprehensive control objective is optimized to obtain the first optimization objective; Based on the second constraint data of the transmission network, the first optimization objective is optimized to obtain the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM.

7. The series-parallel hybrid power flow control method as described in claim 1, characterized in that, After determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the process includes: The amplitude and phase of the first voltage corresponding to the equivalent active power control quantity are determined to be adjustable; The first voltage is injected into the transmission network through the series connection of the UPFC, thereby regulating the voltage phasor and equivalent impedance of the transmission network to achieve the regulation of active power flow and reactive power flow.

8. The series-parallel hybrid power flow control method as described in claim 1, characterized in that, After determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the process further includes: The phase of the second voltage corresponding to the equivalent power flow regulation is determined to be adjustable; The second voltage is injected into the transmission network through the series connection of the SSSCs to regulate the equivalent impedance of the transmission network, thereby achieving the regulation of reactive power flow in the transmission network.

9. The series-parallel hybrid power flow control method as described in claim 1, characterized in that, After determining the equivalent active power control quantity of the UPFC, the equivalent power flow regulation quantity of the SSSC, and the equivalent reactive power control quantity of the STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network, the process further includes: It is determined that the first current corresponding to the equivalent active power control quantity is adjustable; The first current is injected into the bus of the transmission network through the parallel connection of the UPFC, and the reactive power of the UPFC and the connection point of the transmission network is regulated to support the bus voltage of the transmission network.

10. A series-parallel hybrid power flow control system, characterized in that, include: The demand information determination module is used to determine the demand information of the power transmission network based on key operational data of the power transmission network. The power flow control quantity determination module is used to determine the equivalent active power control quantity of the unified power flow controller UPFC, the equivalent power flow regulation quantity of the static synchronous series compensator SSSC, and the equivalent reactive power control quantity of the static synchronous compensator based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the power grid. The power flow control injection module is used to inject a first voltage corresponding to the equivalent active power control quantity into the transmission network through the series connection of the UPFCs, inject a first current corresponding to the equivalent active power control quantity into the transmission network through the parallel connection of the UPFCs, inject a second voltage corresponding to the equivalent power flow regulation quantity into the transmission network through the series connection of the SSSCs, and inject a second current corresponding to the equivalent reactive power control quantity into the transmission network through the parallel connection of the STATCOMs. The power flow control module is used to regulate key operating data of the power transmission network based on the first voltage, the first current, the second voltage, and the second current.

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