Flexible power control method and device of hybrid power flow controller

Abstract

The invention provides a flexible power control method and device of a hybrid power flow controller, and relates to the technical field of power system control. The method comprises the steps that an initial difference value is calculated, the gear number of the phase-shifting transformer needing to be adjusted at the current moment is calculated through the initial difference value, and the initial difference value is the difference value between the current line power and the target power of the electric power system; according to the current line power and the target power, the current d-axis voltage of the cascaded H bridge is adjusted; when the current d-axis voltage of the cascaded H bridge reaches a preset threshold value, the current gear of the phase-shifting transformer is updated, meanwhile, the output power, needing to be compensated, of the cascaded H bridge at the current moment is calculated, and the current d-axis voltage of the cascaded H bridge is updated through the output power. The stability in the power flow control process of the power system can be enhanced, and the system oscillation or fault risk caused by power flow adjustment is reduced.

Description

Technical Field

[0001] This application relates to the field of power system control technology, and in particular to a flexible power control method and device for a hybrid power flow controller. Background Technology

[0002] In power systems, power flow control is a crucial means of ensuring stable grid operation. Traditional mechanical and electromagnetic devices, such as phase-shifting transformers (PSTs), offer large regulation capacity but low accuracy and cannot be continuously adjusted. Each adjustment causes a significant power jump, negatively impacting grid stability. Flexible Alternating Current Transmission Systems (FACTS), such as Unified Power Flow Controllers (UPFCs), offer high regulation accuracy but are complex and costly, hindering widespread engineering applications. Hybrid Unified Power Flow Controllers (HUPFCs), combining discrete-time PSTs with cascaded H-bridges (CHBs), can achieve both high-power and high-precision power regulation.

[0003] However, while a simple combination of PST and CHB can achieve continuous power flow regulation through certain strategies, there will still be short-term power surges during PST shifting. Summary of the Invention

[0004] This application provides a flexible power control method and apparatus for a hybrid power flow controller to solve the problem of the impact on the power system caused by the hybrid power flow controller during power regulation.

[0005] In a first aspect, this application provides a flexible power control method for a hybrid power flow controller, comprising:

[0006] Calculate the initial difference and use the initial difference to calculate the number of taps that the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system.

[0007] Adjust the current d-axis voltage of the cascaded H-bridge based on the current line power and the target power;

[0008] When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap position of the phase-shifting transformer is updated, the output power that the cascaded H-bridge needs to compensate at the current moment is calculated, and the current d-axis voltage of the cascaded H-bridge is updated using the output power.

[0009] Secondly, this application provides a flexible power control device for a hybrid power flow controller, comprising:

[0010] The calculation module is used to calculate the initial difference and use the initial difference to calculate the number of taps that the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system.

[0011] A voltage adjustment module is used to adjust the current d-axis voltage of the cascaded H-bridge based on the current line power and the target power.

[0012] The adjustment module is used to update the current tap position of the phase-shifting transformer when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, while calculating the output power that the cascaded H-bridge needs to compensate at the current moment, and using the output power to update the current d-axis voltage of the cascaded H-bridge.

[0013] This application provides a flexible power control method and apparatus for a hybrid power flow controller. It calculates an initial difference and uses this initial difference to determine the number of taps the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system. Based on the current line power and the target power, the current d-axis voltage of the cascaded H-bridge is adjusted. When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap position of the phase-shifting transformer is updated, and the output power that the cascaded H-bridge needs to compensate at the current moment is calculated. The output power is then used to update the current d-axis voltage of the cascaded H-bridge. When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, this application simultaneously updates the current tap position of the phase-shifting transformer and calculates the output power that the cascaded H-bridge needs to compensate at the current moment. Then, it uses this output power to update the current d-axis voltage of the cascaded H-bridge. This coordinated control strategy enables the phase-shifting transformer and the cascaded H-bridge to cooperate and work together. When the system power changes, the coordinated actions of the two can quickly and smoothly adjust the system power, effectively suppress power fluctuations, enhance the stability of the power flow control process, and reduce the risk of system oscillations or faults caused by power flow regulation. At the same time, this application comprehensively considers the power control effects of the phase-shifting transformer and the cascaded H-bridge. Through the organic combination of the two, it achieves comprehensive control of the system's active and reactive power. It can not only regulate the active power transmission of the line to meet the load's demand for electricity, but also flexibly compensate for reactive power, optimize the voltage distribution of the system, improve power quality, and provide users with a more stable and high-quality power supply. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the hybrid power flow controller provided in an embodiment of this application;

[0016] Figure 2 This is a flowchart illustrating the flexible power control method of the hybrid power flow controller provided in the embodiments of this application;

[0017] Figure 3 This is a timing diagram for power flexible control provided in an embodiment of this application;

[0018] Figure 4 This is a schematic diagram of the flexible power control device of the hybrid power flow controller provided in the embodiments of this application. Detailed Implementation

[0019] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0021] To address the issue of power system impact caused by hybrid power flow controllers during power regulation, specifically considering that traditional phase-shifting transformer tap-off methods lead to sudden power fluctuations, and existing hybrid power flow control still cannot completely avoid power fluctuations during phase-shifting transformer tap-off, this application achieves flexible power regulation by optimizing the dynamic regulation strategy of cascaded H-bridges and combining it with the tap-off operation of phase-shifting transformers, thereby reducing the impact of sudden power fluctuations on the power grid.

[0022] Among them, reference Figure 1The hybrid power flow controller consists of a phase-shifting transformer (including a series transformer and an excitation transformer) and a cascaded H-bridge. The output side of the cascaded H-bridge is connected in series with the excitation transformer of the phase-shifting transformer, and then connected to the series transformer of the phase-shifting transformer. Specifically, the excitation transformer of the phase-shifting transformer has an adjustable range function. After being connected in series with the cascaded H-bridge, it can achieve continuous voltage regulation. Finally, it is connected to the line through the series transformer to achieve phase regulation of the voltage, thereby achieving line power regulation.

[0023] In flexible power control, the phase-shifting transformer in the hybrid power flow controller is used for coarse power adjustment, while the cascaded H-bridge is used for fine power adjustment. The tap position of the phase-shifting transformer and the d-axis voltage of the cascaded H-bridge are adjusted according to the target power issued by the power system. The cascaded H-bridge can cover the power change value of one tap position of the phase-shifting transformer. The power that the phase-shifting transformer cannot achieve through tap adjustment is achieved by adjusting the d-axis voltage through the cascaded H-bridge.

[0024] The hybrid power flow controller's control system is based on a DSP-based real-time control platform. It integrates a dynamic step-size algorithm and mode-switching logic by setting the computation cycle. The computation cycle can be 10ms, but the specific setting depends on the actual CPU performance.

[0025] Specifically, the control system has a dual-core DSP and CPU, which has both computing and control functions. The DSP accurately calculates the acquired secondary side voltage and current and performs power calculations. The CPU communicates in real time with the phase-shifting transformer and the cascaded H-bridge to read the status of the hybrid power flow controller and telemetry information. Then, it performs dynamic strategy allocation to control the phase-shifting transformer tap adjustment and the voltage output of the cascaded H-bridge, thereby changing the line power flow.

[0026] This application's embodiment effectively smooths power changes during phase-shifting transformer tap-changing by employing a dynamic adjustment strategy using a cascaded H-bridge, reducing the impact of sudden power surges on the power grid. Simultaneously, by optimizing the coordinated operation of the cascaded H-bridge and the phase-shifting transformer, equipment losses are reduced, and equipment lifespan is extended, resulting in high economic efficiency.

[0027] Figure 2 The implementation flowchart of the flexible power control method of the hybrid power flow controller provided in the embodiments of this application is described in detail below:

[0028] In step 101, the initial difference is calculated, and the number of taps that the phase-shifting transformer needs to adjust at the current moment is calculated using the initial difference. The initial difference is the difference between the current line power and the target power of the power system.

[0029] In this embodiment of the application, the target power P is issued by the power system. ref Then, calculate the current line power P. t With target power P refThe difference is taken as the initial difference ΔP, i.e., ΔP = P t -P ref Then, using the initial difference ΔP, the theoretical number of taps required for the phase-shifting transformer at the current moment is calculated.

[0030] This embodiment calculates the initial difference between the current line power and the target power of the power system, and based on this, calculates the number of taps the phase-shifting transformer needs to be adjusted at the current moment. This allows for precise adjustment of the phase-shifting transformer taps according to the actual power deviation. This tap adjustment method based on precise calculation avoids blind adjustments, enabling the phase-shifting transformer to more accurately change the power transmission characteristics of the line, thereby achieving fine-tuning of power and improving the accuracy of power regulation throughout the power system.

[0031] In one possible implementation, calculating the number of taps required for the phase-shifting transformer at the current moment using the initial difference can include:

[0032] The ratio of the initial difference to the single-step size of the phase-shifting transformer is used as the number of taps that the phase-shifting transformer needs to adjust at the current moment.

[0033] Optionally, the formula for calculating the number of taps required for the phase-shifting transformer at the current moment is:

[0034]

[0035] Among them, DW tar P represents the number of taps that the phase-shifting transformer needs to adjust at the current moment, where ΔP is the initial difference. step This refers to the single-step size of the phase-shifting transformer.

[0036] In one possible implementation, after calculating the initial difference, the method may further include:

[0037] Determine whether the absolute value of the initial difference is less than the preset dead zone power;

[0038] If the absolute value of the initial difference is less than the preset dead zone power, then the hybrid power flow controller is determined to be in place.

[0039] If the absolute value of the initial difference is not less than the preset dead zone power, then it is determined that the hybrid power flow controller adjustment is not in place.

[0040] Optionally, after calculating the initial difference, this embodiment of the application needs to determine the absolute value of the initial difference |ΔP| and the preset dead zone power P. dead If the absolute value of the initial difference is less than the preset dead zone power, i.e., |ΔP| <P deadIf the initial power flow controller is adjusted to the desired level at the current moment, the outputs of the phase-shifting transformer and the cascaded H-bridge remain unchanged, and the hybrid power flow controller exits the flexible power control process; if the absolute value of the initial difference is not less than the preset dead zone power, i.e., |ΔP|≥P dead If the mixed power flow control is not properly adjusted at the current moment, it is necessary to use the initial difference to calculate the number of taps that the phase-shifting transformer needs to be adjusted at the current moment and perform subsequent operations.

[0041] In this embodiment, frequent adjustments to the hybrid power flow controller increase mechanical wear and electrical losses, shortening the equipment's lifespan. For example, frequent tap changes in phase-shifting transformers and frequent switching of power devices in cascaded H-bridges accelerate equipment aging. By determining the relationship between the initial difference and the preset dead-zone power, adjustments are not made when power fluctuations are small, effectively reducing the number of adjustments, decreasing wear and losses, extending equipment lifespan, and lowering maintenance and replacement costs.

[0042] In step 102, the current d-axis voltage of the cascaded H-bridge is adjusted according to the current line power and the target power.

[0043] In this embodiment, the current d-axis voltage of the cascaded H-bridge is updated in real time by using the line power and the target power issued by the power system detected periodically by the control system of the hybrid power flow controller.

[0044] It should be noted that in this embodiment, the current d-axis voltage of the cascaded H-bridge is updated periodically, with a timing interval of 10ms, which can be set according to the CPU performance.

[0045] This embodiment of the application obtains the current d-axis voltage of the cascaded H-bridge based on the current line power and the target power, enabling the output voltage of the cascaded H-bridge to dynamically match the line power demand. As the line power changes, the d-axis voltage is adjusted accordingly, ensuring that the cascaded H-bridge can output a suitable voltage under different operating conditions. This further improves the accuracy and flexibility of power regulation and helps meet the power system's requirements for precise power control.

[0046] In one possible implementation, adjusting the current d-axis voltage of the cascaded H-bridge based on the current line power and the target power may include:

[0047] Determine if the current line power is less than the target power;

[0048] If the current line power is less than the target power, the current d-axis voltage is updated by using the sum of the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size.

[0049] If the current line power is not less than the target power, the current d-axis voltage is updated using the difference between the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size.

[0050] Optionally, determine the current line power P. t and target power P ref The magnitude of P is such that if the current line power is less than the target power, i.e., P... t <P ref Then, the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size V are used. step The sum updates the current d-axis voltage, i.e., V. d =V d +V step If the current line power is not less than the target power, i.e., P t ≥P ref Then, the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size V are used. step The difference updates the current d-axis voltage, i.e., V. d =V d -V step The adjustable range of the d-axis voltage of the cascaded H-bridge is V. ddown ~V dup V ddown V represents the lower limit of the d-axis voltage of the cascaded H-bridge. dup This represents the upper limit of the d-axis voltage of the cascaded H-bridge.

[0051] This application embodiment utilizes the timing adjustment of a cascaded H-bridge to inject compensating power into the power grid.

[0052] In step 103, when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap position of the phase-shifting transformer is updated, the output power required to compensate for the cascaded H-bridge at the current moment is calculated, and the current d-axis voltage of the cascaded H-bridge is updated using the output power.

[0053] In this embodiment, when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the pre-compensation stage for line power by the cascaded H-bridge is triggered, and the current tap position of the phase-shifting transformer is recorded, sending a tap adjustment command to the phase-shifting transformer. At this time, the timeout counter in the hybrid power flow control is started. Then, the timeout counter is used to set time intervals, and while updating the current tap position of the phase-shifting transformer, the output power that the cascaded H-bridge needs to compensate at the current moment is calculated in each time interval, and the current d-axis voltage of the cascaded H-bridge is updated using this output power.

[0054] In this embodiment, when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap position of the phase-shifting transformer is simultaneously updated, and the output power required for compensation by the cascaded H-bridge at the current moment is calculated. Then, this output power is used to update the current d-axis voltage of the cascaded H-bridge. This coordinated control strategy enables the phase-shifting transformer and the cascaded H-bridge to cooperate and work together. When system power changes, the coordinated actions of both can quickly and smoothly adjust the system power, effectively suppressing power fluctuations, enhancing the stability of power flow control, and reducing the risk of system oscillations or faults caused by power flow regulation.

[0055] In one possible implementation, when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, while updating the current tap position of the phase-shifting transformer, the output power required to compensate for the cascaded H-bridge at the current moment is calculated, and the current d-axis voltage of the cascaded H-bridge is updated using the output power, including:

[0056] The current d-axis voltage of the cascaded H-bridge within a preset time interval is updated using the number of taps required to be adjusted by the phase-shifting transformer at the current moment, the current tap position of the phase-shifting transformer, the progress of the adjustment of the current tap position of the phase-shifting transformer, the current line power, and the target power.

[0057] After the preset time interval is completed, determine whether the progress of the current tap of the phase-shifting transformer has been adjusted to 1.

[0058] If the current tap position of the phase-shifting transformer has been adjusted to a progress of 1, then update the current tap position of the phase-shifting transformer using the sum of the current tap position of the phase-shifting transformer and the preset step size, set the current d-axis voltage of the cascaded H-bridge to 0, update the current line power using the line power after the preset time interval, return to calculate the initial difference, and continue to execute the step of calculating the number of tap positions that the phase-shifting transformer needs to be adjusted at the current moment using the initial difference.

[0059] If the current tap adjustment progress of the phase-shifting transformer is not 1, then update the current tap adjustment progress of the phase-shifting transformer using the current tap adjustment progress of the phase-shifting transformer in the next preset time interval, and return to the step of updating the current d-axis voltage of the cascaded H-bridge within the preset time interval using the number of taps required to be adjusted by the phase-shifting transformer at the current moment, the current tap of the phase-shifting transformer, the current tap adjustment progress of the phase-shifting transformer, the current line power and the target power to continue execution.

[0060] Optionally, when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the system enters the pre-compensation stage for line power by the cascaded H-bridge and the tap adjustment stage of the phase-shifting transformer. There is a mechanical delay before the phase-shifting transformer tap adjustment command is executed; during this mechanical delay stage, the current d-axis voltage of the cascaded H-bridge remains unchanged. The specific process is as follows:

[0061] Step 1: When the phase-shifting transformer enters the tap-switching state, use the number of taps (DW) that the phase-shifting transformer needs to adjust to at the current moment. tar The current tap position (DW) of the phase-shifting transformer. cur The progress of adjusting the current tap position of the phase-shifting transformer. Current line power P t and target power P ref Update the current d-axis voltage V of the cascaded H-bridge within a preset time interval. d .

[0062] Step 2: After the preset time interval is completed, determine whether the current tap position of the phase-shifting transformer has been adjusted to 1. If it is 1, proceed to Step 3; otherwise, proceed to Step 4.

[0063] Step 3: Update the current tap position of the phase-shifting transformer using the sum of the current tap position and the preset step size. Set the current d-axis voltage of the cascaded H-bridge to 0. Update the current line power using the line power after the preset time interval. Return to step 101 to continue execution. For example, after the phase-shifting transformer has completed adjusting one tap position, exit pre-compensation and re-enter step 101 to continue execution.

[0064] Step 4: Update the current tap adjustment progress of the phase-shifting transformer using the current tap adjustment progress of the phase-shifting transformer at the next preset time interval, and return to Step 1 to continue execution.

[0065] The preset time interval can be set to 10ms, 15ms, or 20ms, depending on the actual needs.

[0066] Finally, the current d-axis voltage of the cascaded H-bridge is used to dynamically compensate the line power.

[0067] In one possible implementation, the preset thresholds include a first threshold and a second threshold, where the first threshold is less than the second threshold, and the preset step sizes are 1 and -1. Updating the current tap position of the phase-shifting transformer using the sum of the current tap position and the preset step size can include:

[0068] When the current d-axis voltage of the cascaded H-bridge reaches the first threshold, the current tap of the phase-shifting transformer is updated using the sum of the current tap of the phase-shifting transformer and -1.

[0069] When the current d-axis voltage of the cascaded H-bridge reaches the second threshold, the current tap of the phase-shifting transformer is updated by the sum of the current tap of the phase-shifting transformer and 1.

[0070] In this embodiment, the preset threshold includes a first threshold and a second threshold. The first threshold is the product of the pre-compensation coefficient and the lower limit of the d-axis voltage of the phase-shifting transformer, i.e., βV. ddownThe second threshold is the product of the preset compensation coefficient and the upper limit of the d-axis voltage of the phase-shifting transformer, i.e., βV. dup And βV dup >βV ddown .

[0071] Then, when the current d-axis voltage of the cascaded H-bridge decreases to the first threshold, i.e., V d →βV ddown If the value is 0, it indicates that the gear shifting command of the phase-shifting transformer is a downshifting command, that is, the current gear of the phase-shifting transformer is updated by using the sum of the current gear of the phase-shifting transformer and -1.

[0072] When the current d-axis voltage of the cascaded H-bridge increases to the second threshold, i.e., V d →βV dup If , it indicates that the gear shifting command of the phase-shifting transformer is an upshift command, that is, the current gear of the phase-shifting transformer is updated by using the sum of the current gear of the phase-shifting transformer and 1.

[0073] In one possible implementation, updating the current d-axis voltage of the cascaded H-bridge within a preset time interval using the number of taps the phase-shifting transformer needs to adjust at the current moment, the current tap position of the phase-shifting transformer, the progress of the adjustment of the current tap position of the phase-shifting transformer, the current line power, and the target power can include:

[0074] Calculate the remaining adjustable power of the phase-shifting transformer by using the number of taps required to be adjusted at the current moment, the current tap position of the phase-shifting transformer, and the progress of the adjustment of the current tap position.

[0075] The adaptive proportional coefficient of the cascaded H-bridge is calculated using the progress of the current tap position adjustment of the phase-shifting transformer.

[0076] Using the current line power, target power, remaining adjustable power of the phase-shifting transformer, and adaptive proportional coefficient of the cascaded H-bridge, calculate the output power required to compensate for the preset time interval of the cascaded H-bridge;

[0077] The output power required to compensate for the cascaded H-bridge within the preset time interval is used to update the current d-axis voltage of the cascaded H-bridge within the preset time interval.

[0078] Optionally, the calculation process for updating the current d-axis voltage of the cascaded H-bridge within a preset time interval is as follows:

[0079] First, utilize the number of taps (DW) that the phase-shifting transformer needs to be adjusted at the current moment. tar The current tap position (DW) of the phase-shifting transformer. cur And the progress of adjusting the current tap position of the phase-shifting transformer. The formula for calculating the remaining adjustable power of a phase-shifting transformer is as follows:

[0080]

[0081] Among them, P remain For the remaining adjustable power of the phase-shifting transformer, DW tar DW represents the number of taps that the phase-shifting transformer needs to adjust at the current moment. cur This refers to the current tap position of the phase-shifting transformer. This represents the progress of the current tap adjustment of the phase-shifting transformer. This value can be provided by the phase-shifting transformer itself, or it can be simulated in the hybrid power flow controller based on the tap adjustment characteristics of the phase-shifting transformer. For example, if the phase-shifting transformer requires 1 second to complete the tap adjustment, the hybrid power flow controller reads the current power every 10 ms for calculation; P step This refers to the single-step size of the phase-shifting transformer.

[0082] Secondly, dynamic pre-compensation calculations are performed on the cascaded H-bridge. The adaptive proportional coefficient of the cascaded H-bridge is calculated using the adjustment progress of the current tap position of the phase-shifting transformer, i.e.:

[0083]

[0084] Where δ is the adaptive proportional coefficient of the cascaded H-bridge, ratio is the preset pre-compensation coefficient, such as 0.7; a is the attenuation factor, used to control the decreasing rate of the compensation amount, such as 0.3; This indicates the progress of adjusting the current tap position of the phase-shifting transformer.

[0085] Then, using the current line power P t Target power P ref And the remaining adjustable power P of the phase-shifting transformer calculated above. remain Given the adaptive scaling factor δ of the cascaded H-bridge, calculate the output power P required to compensate for the preset time interval of the cascaded H-bridge. CHB .

[0086] Finally, the output power P required for compensation is utilized using the preset time interval of the cascaded H-bridge. CHB Update the current d-axis voltage V of the cascaded H-bridge within a preset time interval. d .

[0087] In one possible implementation, the output power to be compensated for by the cascaded H-bridge at a preset time interval is calculated using the current line power, the target power, the remaining adjustable power of the phase-shifting transformer, and the adaptive proportional coefficient of the cascaded H-bridge. This may include:

[0088] The sum of the current line power and the remaining adjustable power of the phase-shifting transformer is used as the first value;

[0089] The difference between the target power and the first value is used as the second value;

[0090] The product of the adaptive scaling factor of the cascaded H-bridge and the second value is used as the output power that needs to be compensated for during the preset time interval of the cascaded H-bridge.

[0091] Optionally, the formula for calculating the output power compensation required for the preset time interval of the cascaded H-bridge is as follows:

[0092] P CHB =δ×(P ref -(P t +P remain ))

[0093] Among them, P CHB The output power required for compensation at the preset time interval of the cascaded H-bridge, where δ is the adaptive proportional coefficient of the cascaded H-bridge, and P... ref For the target power, P t P represents the current line power. remain P represents the remaining adjustable power of the phase-shifting transformer. t +P remain As the first value, P ref -(P t +P remain ) is the second value.

[0094] In one possible implementation, updating the current d-axis voltage of the cascaded H-bridge within a preset time interval using the output power required for compensation during the preset time interval can include:

[0095] The ratio of the output power required to be compensated for the preset time interval of the cascaded H-bridge to the maximum value of the output power required to be compensated for the preset time interval of the cascaded H-bridge is taken as the first ratio.

[0096] If the first ratio is greater than the upper limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the upper limit of the d-axis voltage.

[0097] If the first ratio is greater than the lower limit of the d-axis voltage and less than the upper limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the first ratio.

[0098] If the first ratio is less than the lower limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the lower limit of the d-axis voltage.

[0099] Optionally, the current d-axis voltage of the cascaded H-bridge within a preset time interval is updated using per-unit limiting processing, i.e.:

[0100]

[0101] Among them, V d V is the d-axis voltage of the phase-shifting transformer. dup V represents the upper limit of the d-axis voltage of the phase-shifting transformer. ddownP is the lower limit of the d-axis voltage of the phase-shifting transformer. CHB The output power required to compensate for the preset time interval of the cascaded H-bridge. The ratio of the maximum output power that needs to be compensated for the preset time interval of the cascaded H-bridge. This is the first ratio.

[0102] This application provides a flexible power control method for a hybrid power flow controller. It calculates an initial difference and uses this initial difference to determine the number of taps the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system. Based on the current line power and the target power, the current d-axis voltage of the cascaded H-bridge is obtained. When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap position of the phase-shifting transformer is updated, and the output power that the cascaded H-bridge needs to compensate at the current moment is calculated. The current d-axis voltage of the cascaded H-bridge is then updated using the output power. When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, this application simultaneously updates the current tap position of the phase-shifting transformer and calculates the output power that the cascaded H-bridge needs to compensate at the current moment. Then, it uses this output power to update the current d-axis voltage of the cascaded H-bridge. This coordinated control strategy enables the phase-shifting transformer and the cascaded H-bridge to cooperate and work together. When the system power changes, the coordinated actions of the two can quickly and smoothly adjust the system power, effectively suppress power fluctuations, enhance the stability of the power flow control process, and reduce the risk of system oscillations or faults caused by power flow regulation. At the same time, this application comprehensively considers the power control effects of the phase-shifting transformer and the cascaded H-bridge. Through the organic combination of the two, it achieves comprehensive control of the system's active and reactive power. It can not only regulate the active power transmission of the line to meet the load's demand for electricity, but also flexibly compensate for reactive power, optimize the voltage distribution of the system, improve power quality, and provide users with a more stable and high-quality power supply.

[0103] The flexible power control method of the hybrid power flow controller described above is illustrated below through an implementation example.

[0104] The flexible power control timing of the hybrid power flow controller control system is as follows: Figure 3 As shown, specifically:

[0105] (1) Design a phase-shifting transformer with adjustable PST range from -8 to 8 levels, and a single-step size p for each power level. step =30MW, d-axis voltage V of cascaded H-bridge CHB d It is continuously adjustable within the range of -0.9 to 0.9, corresponding to a maximum power range of -30MW to 30MW.

[0106] (2) When the initial gear is 0 and the initial system power is 50MW, the target power p issued by the power system to the hybrid power flow control is...ref =120MW, calculate the initial difference Δp = 70MW, calculate the number of taps DW required to adjust the phase-shifting transformer according to PST theory. tar =70 / 30≈2.33, cascaded H-bridge CHB power electronic components, fast response, cascaded H-bridge CHB prioritizes power regulation response, 10ms timing to determine the current line power P t and target power P ref The size relationship, at this time, P t <P ref Each time the d-axis voltage V of the cascaded H-bridge CHB is applied... d Increase V step =0.01, with the d-axis voltage V of the cascaded H-bridge CHB. d Increase the power supply to the power system by cascading H-bridge positions CHB.

[0107] (3) Until V d Reaching βV dup =0.63, where the pre-compensation coefficient β = 0.7, triggering the pre-compensation stage, the current tap position of the phase-shifting transformer PST is recorded as 0. At this time, P t <P ref The hybrid power flow control sends an upshift command to the phase-shifting transformer PST and starts the timeout counter to count.

[0108] (4) The phase-shifting transformer PST is a mechanical structure, and there is a delay after receiving the tap change command. During this time, the cascaded H-bridge CHB maintains V. d =0.63 output; After the phase-shifting transformer PST enters the tap adjustment process, the remaining adjustable power P of the phase-shifting transformer PST is dynamically calculated in real time. rmain :

[0109] P remain =(2-0-1)×30+(1-0.4)×30=48MW

[0110] Among them, the number of gears that need to be adjusted at the current moment, DW tar =2, current gear DW cur It is currently between 0 and 1, and is considered to be in the current gear DW. cur =0, the progress of the current tap position adjustment of the phase-shifting transformer PST.

[0111] Then, dynamic pre-compensation calculations are performed for the cascaded H-bridge CHB:

[0112] First, calculate the adaptive scaling factor of the cascaded H-bridge CHB:

[0113] δ=0.7×(1-0.3×0.4)=0.616

[0114] Then, calculate the output power P to be compensated during the current adjustment period (10ms) of the cascaded H-bridge. CHB :

[0115] P CHB =0.616×(120-(62+48))=6.16MW

[0116] Finally, per-unit value limiting is performed:

[0117] V d =6.16 / 30 = 0.205

[0118] Finally, the cascaded H-bridge CHB achieves dynamic compensation, with this process cycling once every 10ms. According to P... remain Real-time value dynamic adjustment of the V of the cascaded H-bridge CHB d This allows the power contributed to the system by the phase-shifting transformer PST and the cascaded H-bridge CHB to increase linearly.

[0119] In addition, if the response time of the phase-shifting transformer PST exceeds the set timeout counter time, such as 150ms (set according to the characteristics of the phase-shifting transformer), the pre-compensation will be terminated and an emergency stop command will be sent to the phase-shifting transformer PST.

[0120] (5) After the hybrid power flow controller detects that the phase-shifting transformer PST has successfully switched, it returns to the pre-compensation stage. At this time, the V of the cascaded H-bridge CHB... d Near 0, directly let V d =0, at this time it will not have a significant impact on the power system, and the cascaded H-bridge CHB priority response mode will be restored.

[0121] (6) Repeat the above process until the phase-shifting transformer PST tap DW is reached. cur =2, V of cascaded H-bridge CHB d When P = 0.3, then P t ≈118MW, entering the dead zone |ΔP|<5MW, exiting the flexible control process, the phase-shifting transformer PST maintains the current tap position, and the cascaded H-bridge CHB maintains the current V. d Output.

[0122] It should be understood that the sequence number of each step in the above embodiments 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.

[0123] The following are device embodiments of this application. For details not described in detail, please refer to the corresponding method embodiments described above.

[0124] Figure 4A schematic diagram of the flexible power control device of the hybrid power flow controller provided in this application embodiment is shown. For ease of explanation, only the parts related to the embodiments of this application are shown, and are described in detail below:

[0125] like Figure 4 As shown, the flexible power control device 4 of the hybrid power flow controller includes:

[0126] The calculation module 41 is used to calculate the initial difference and use the initial difference to calculate the number of taps that the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system.

[0127] Voltage adjustment module 42 is used to adjust the current d-axis voltage of the cascaded H-bridge according to the current line power and the target power;

[0128] The adjustment module 43 is used to update the current tap position of the phase-shifting transformer when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, while calculating the output power that the cascaded H-bridge needs to compensate at the current moment, and using the output power to update the current d-axis voltage of the cascaded H-bridge.

[0129] This application provides a flexible power control device for a hybrid power flow controller. It calculates an initial difference and uses this initial difference to calculate the number of taps that the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system. Based on the current line power and the target power, the current d-axis voltage of the cascaded H-bridge is adjusted. When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap of the phase-shifting transformer is updated, and the output power that the cascaded H-bridge needs to compensate at the current moment is calculated. The current d-axis voltage of the cascaded H-bridge is then updated using the output power. When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, this application simultaneously updates the current tap position of the phase-shifting transformer and calculates the output power that the cascaded H-bridge needs to compensate at the current moment. Then, it uses this output power to update the current d-axis voltage of the cascaded H-bridge. This coordinated control strategy enables the phase-shifting transformer and the cascaded H-bridge to cooperate and work together. When the system power changes, the coordinated actions of the two can quickly and smoothly adjust the system power, effectively suppress power fluctuations, enhance the stability of the power flow control process, and reduce the risk of system oscillations or faults caused by power flow regulation. At the same time, this application comprehensively considers the power control effects of the phase-shifting transformer and the cascaded H-bridge. Through the organic combination of the two, it achieves comprehensive control of the system's active and reactive power. It can not only regulate the active power transmission of the line to meet the load's demand for electricity, but also flexibly compensate for reactive power, optimize the voltage distribution of the system, improve power quality, and provide users with a more stable and high-quality power supply.

[0130] In one possible implementation, the computation module can be used for:

[0131] The ratio of the initial difference to the single-step size of the phase-shifting transformer is used as the number of taps that the phase-shifting transformer needs to adjust at the current moment.

[0132] In one possible implementation, the voltage regulation module can be used for:

[0133] Determine if the current line power is less than the target power;

[0134] If the current line power is less than the target power, the current d-axis voltage is updated by using the sum of the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size.

[0135] If the current line power is not less than the target power, the current d-axis voltage is updated using the difference between the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size.

[0136] In one possible implementation, the adjustment module can be used to:

[0137] The current d-axis voltage of the cascaded H-bridge within a preset time interval is updated using the number of taps required to be adjusted by the phase-shifting transformer at the current moment, the current tap position of the phase-shifting transformer, the progress of the adjustment of the current tap position of the phase-shifting transformer, the current line power, and the target power.

[0138] After the preset time interval is completed, determine whether the progress of the current tap of the phase-shifting transformer has been adjusted to 1.

[0139] If the current tap position of the phase-shifting transformer has been adjusted to a progress of 1, then update the current tap position of the phase-shifting transformer using the sum of the current tap position of the phase-shifting transformer and the preset step size, set the current d-axis voltage of the cascaded H-bridge to 0, update the current line power using the line power after the preset time interval, return to calculate the initial difference, and continue to execute the step of calculating the number of tap positions that the phase-shifting transformer needs to be adjusted at the current moment using the initial difference.

[0140] If the current tap adjustment progress of the phase-shifting transformer is not 1, then update the current tap adjustment progress of the phase-shifting transformer using the current tap adjustment progress of the phase-shifting transformer in the next preset time interval, and return to the step of updating the current d-axis voltage of the cascaded H-bridge within the preset time interval using the number of taps required to be adjusted by the phase-shifting transformer at the current moment, the current tap of the phase-shifting transformer, the current tap adjustment progress of the phase-shifting transformer, the current line power and the target power to continue execution.

[0141] In one possible implementation, the adjustment module can also be used for:

[0142] Calculate the remaining adjustable power of the phase-shifting transformer by using the number of taps required to be adjusted at the current moment, the current tap position of the phase-shifting transformer, and the progress of the adjustment of the current tap position.

[0143] The adaptive proportional coefficient of the cascaded H-bridge is calculated using the progress of the current tap position adjustment of the phase-shifting transformer.

[0144] Using the current line power, target power, remaining adjustable power of the phase-shifting transformer, and adaptive proportional coefficient of the cascaded H-bridge, calculate the output power required to compensate for the preset time interval of the cascaded H-bridge;

[0145] The output power required to compensate for the cascaded H-bridge within the preset time interval is used to update the current d-axis voltage of the cascaded H-bridge within the preset time interval.

[0146] In one possible implementation, the adjustment module can be used to:

[0147] The ratio of the output power required to be compensated for the preset time interval of the cascaded H-bridge to the maximum value of the output power required to be compensated for the preset time interval of the cascaded H-bridge is taken as the first ratio.

[0148] If the first ratio is greater than the upper limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the upper limit of the d-axis voltage.

[0149] If the first ratio is greater than the lower limit of the d-axis voltage and less than the upper limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the first ratio.

[0150] If the first ratio is less than the lower limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the lower limit of the d-axis voltage.

[0151] In one possible implementation, the adjustment module can be used to:

[0152] The sum of the current line power and the remaining adjustable power of the phase-shifting transformer is used as the first value;

[0153] The difference between the target power and the first value is used as the second value;

[0154] The product of the adaptive scaling factor of the cascaded H-bridge and the second value is used as the output power that needs to be compensated for during the preset time interval of the cascaded H-bridge.

[0155] In one possible implementation, the preset threshold includes a first threshold and a second threshold, where the first threshold is less than the second threshold, and the preset step size is 1 and -1; the adjustment module can be used to:

[0156] When the current d-axis voltage of the cascaded H-bridge reaches the first threshold, the current tap of the phase-shifting transformer is updated using the sum of the current tap of the phase-shifting transformer and -1.

[0157] When the current d-axis voltage of the cascaded H-bridge reaches the second threshold, the current tap of the phase-shifting transformer is updated by the sum of the current tap of the phase-shifting transformer and 1.

[0158] In one possible implementation, the device may further include a determination module, which can be used to:

[0159] Determine whether the absolute value of the initial difference is less than the preset dead zone power;

[0160] If the absolute value of the initial difference is less than the preset dead zone power, then the hybrid power flow controller is determined to be in place.

[0161] If the absolute value of the initial difference is not less than the preset dead zone power, then it is determined that the hybrid power flow controller adjustment is not in place.

[0162] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0163] Those skilled in the art will recognize that the templates, units, and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. 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 implementations should not be considered beyond the scope of this invention.

[0164] If the module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the flexible power control method embodiments of the various hybrid power flow controllers described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0165] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A flexible power control method for a hybrid power flow controller, characterized in that, include: Calculate the initial difference and use the initial difference to calculate the number of taps that the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system. Adjust the current d-axis voltage of the cascaded H-bridge based on the current line power and the target power; When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap position of the phase-shifting transformer is updated, the output power that the cascaded H-bridge needs to compensate at the current moment is calculated, and the current d-axis voltage of the cascaded H-bridge is updated using the output power.

2. The flexible power control method for a hybrid power flow controller according to claim 1, characterized in that, The calculation of the number of taps required for the phase-shifting transformer at the current moment using the initial difference includes: The ratio of the initial difference to the single-step size of the phase-shifting transformer is used as the number of taps that the phase-shifting transformer needs to adjust at the current moment.

3. The flexible power control method for a hybrid power flow controller according to claim 1, characterized in that, The step of adjusting the current d-axis voltage of the cascaded H-bridge based on the current line power and the target power includes: Determine whether the current line power is less than the target power; If the current line power is less than the target power, the current d-axis voltage is updated using the sum of the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size. If the current line power is not less than the target power, the current d-axis voltage is updated using the difference between the current d-axis voltage of the cascaded H-bridge and the preset adjustment step size.

4. The flexible power control method for a hybrid power flow controller according to claim 1, characterized in that, When the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, the current tap position of the phase-shifting transformer is updated, and the output power required for compensation by the cascaded H-bridge at the current moment is calculated. The current d-axis voltage of the cascaded H-bridge is then updated using the output power. This includes: The current d-axis voltage of the cascaded H-bridge within a preset time interval is updated using the number of taps required to be adjusted by the phase-shifting transformer at the current moment, the current tap position of the phase-shifting transformer, the progress of the adjustment of the current tap position of the phase-shifting transformer, the current line power, and the target power. After the preset time interval is completed, it is determined whether the progress of the current tap of the phase-shifting transformer has been adjusted is 1. If the current tap position of the phase-shifting transformer has been adjusted to a progress of 1, then the current tap position of the phase-shifting transformer is updated using the sum of the current tap position of the phase-shifting transformer and the preset step size, the current d-axis voltage of the cascaded H-bridge is set to 0, and the current line power is updated using the line power after the preset time interval. Then, the calculation of the initial difference value is returned, and the step of calculating the number of tap positions that the phase-shifting transformer needs to be adjusted to at the current moment is continued. If the adjustment progress of the current tap position of the phase-shifting transformer is not 1, then the adjustment progress of the current tap position of the phase-shifting transformer is updated using the adjustment progress of the current tap position of the phase-shifting transformer in the next preset time interval, and the step of updating the current d-axis voltage of the cascaded H-bridge in the preset time interval using the number of tap positions required to be adjusted by the phase-shifting transformer at the current moment, the current tap position of the phase-shifting transformer, the adjustment progress of the current tap position of the phase-shifting transformer, the current line power and the target power continues to be executed.

5. The flexible power control method for a hybrid power flow controller according to claim 4, characterized in that, The step of updating the current d-axis voltage of the cascaded H-bridge within a preset time interval using the number of taps required to be adjusted by the phase-shifting transformer at the current moment, the current tap position of the phase-shifting transformer, the progress of the adjustment of the current tap position of the phase-shifting transformer, the current line power, and the target power includes: The remaining adjustable power of the phase-shifting transformer is calculated using the number of taps required to be adjusted at the current moment, the current tap position of the phase-shifting transformer, and the progress of the adjustment of the current tap position. The adaptive proportional coefficient of the cascaded H-bridge is calculated using the progress of the current tap position adjustment of the phase-shifting transformer. Using the current line power, the target power, the remaining adjustable power of the phase-shifting transformer, and the adaptive proportional coefficient of the cascaded H-bridge, calculate the output power that the cascaded H-bridge needs to compensate for at the preset time interval; The current d-axis voltage of the cascaded H-bridge within the preset time interval is updated using the output power required to compensate for the preset time interval.

6. The flexible power control method for a hybrid power flow controller according to claim 5, characterized in that, The step of updating the current d-axis voltage of the cascaded H-bridge within the preset time interval using the output power required for compensation during the preset time interval includes: The ratio of the output power that needs to be compensated for during the preset time interval of the cascaded H-bridge to the maximum value of the output power that needs to be compensated for during the preset time interval of the cascaded H-bridge is taken as the first ratio. If the first ratio is greater than the upper limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the upper limit of the d-axis voltage; If the first ratio is greater than the lower limit of the d-axis voltage and less than the upper limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the first ratio. If the first ratio is less than the lower limit of the d-axis voltage, then the current d-axis voltage of the cascaded H-bridge is updated using the lower limit of the d-axis voltage.

7. The flexible power control method for a hybrid power flow controller according to claim 5, characterized in that, The step of calculating the output power to be compensated for by the cascaded H-bridge at the preset time interval using the current line power, the target power, the remaining adjustable power of the phase-shifting transformer, and the adaptive proportional coefficient of the cascaded H-bridge includes: The sum of the current line power and the remaining adjustable power of the phase-shifting transformer is taken as the first value; The difference between the target power and the first value is taken as the second value; The product of the adaptive scaling factor of the cascaded H-bridge and the second value is used as the output power that the cascaded H-bridge needs to compensate for during the preset time interval.

8. The flexible power control method for a hybrid power flow controller according to claim 4, characterized in that, The preset threshold includes a first threshold and a second threshold, wherein the first threshold is less than the second threshold, and the preset step size is 1 and -1; The step of updating the current tap position of the phase-shifting transformer using the sum of the current tap position and a preset step size includes: When the current d-axis voltage of the cascaded H-bridge reaches the first threshold, the current tap of the phase-shifting transformer is updated using the sum of the current tap of the phase-shifting transformer and -1. When the current d-axis voltage of the cascaded H-bridge reaches the second threshold, the current tap of the phase-shifting transformer is updated using the sum of the current tap of the phase-shifting transformer and 1.

9. The flexible power control method for a hybrid power flow controller according to claim 1, characterized in that, After calculating the initial difference, the method further includes: Determine whether the absolute value of the initial difference is less than the preset dead zone power; If the absolute value of the initial difference is less than the preset dead zone power, then the hybrid power flow controller is determined to be adjusted in place. If the absolute value of the initial difference is not less than the preset dead zone power, then it is determined that the hybrid power flow controller adjustment is not in place.

10. A flexible power control device based on a hybrid power flow controller, characterized in that, include: The calculation module is used to calculate the initial difference and use the initial difference to calculate the number of taps that the phase-shifting transformer needs to adjust at the current moment. The initial difference is the difference between the current line power and the target power of the power system. A voltage adjustment module is used to adjust the current d-axis voltage of the cascaded H-bridge based on the current line power and the target power. The adjustment module is used to update the current tap position of the phase-shifting transformer when the current d-axis voltage of the cascaded H-bridge reaches a preset threshold, while calculating the output power that the cascaded H-bridge needs to compensate at the current moment, and using the output power to update the current d-axis voltage of the cascaded H-bridge.

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