Dynamic voltage restorer voltage sag compensation method and system

Abstract

The embodiment of the application provides a dynamic voltage restorer voltage sag compensation method, comprising: collecting three-phase voltage signals of a power grid side in real time and performing transformation processing to obtain corresponding real-time amplitude and phase information; calculating a voltage sag depth according to the real-time amplitude and a set rated voltage threshold, and calculating a phase jump angle according to the real-time phase and a set rated phase; calculating a compensation voltage amplitude and a compensation phase according to the voltage sag depth and the phase jump angle, and simultaneously determining a current compensation mode; calculating compensation active power and compensation reactive power according to the compensation voltage amplitude, the compensation phase and the compensation mode, and generating corresponding energy release instructions; transforming the direct-current electric energy into alternating-current compensation voltage consistent with the compensation voltage amplitude and the compensation phase, and injecting the alternating-current compensation voltage into a line between the power grid and a load in series through a series injection transformer to complete voltage sag compensation.

Description

Technical Field

[0001] This application relates to the field of voltage sag technology, and in particular to a method and system for voltage sag compensation in a dynamic voltage restorer. Background Technology

[0002] With the rapid development of modern industry, the number of sensitive loads in power systems is constantly increasing, such as precision manufacturing equipment, data centers, and automated production lines. These loads have extremely high requirements for the stability of the power supply voltage. Voltage sag, as one of the most common power quality problems in power systems, refers to the phenomenon where the effective value of the supply voltage drops to 10% to 90% of the rated voltage within a short period of time before returning to the normal level. The duration of voltage sag is usually 0.5 cycles to 1 minute, which can lead to the shutdown of sensitive equipment, production interruptions, and huge economic losses.

[0003] A Dynamic Voltage Restorer (DVR) is one of the most effective power electronic devices for addressing voltage sags. Connected in series between the power grid and the sensitive load, the DVR quickly outputs a compensation voltage via an inverter when a voltage sag is detected on the grid side. This compensation voltage is then injected into the power supply line through a series transformer, maintaining the load-side voltage at its rated level and ensuring the normal operation of the sensitive load. Existing DVRs typically employ a fixed compensation strategy, directly outputting a compensation voltage of the corresponding amplitude based on the detected voltage sag depth.

[0004] However, existing technologies have at least the following problems: on the one hand, the compensation mode is singular and cannot be adaptively adjusted according to the characteristics of the protected load, failing to achieve differentiated compensation for different types of sensitive loads; on the other hand, the energy utilization efficiency during the compensation process is not high, and in some scenarios, the energy released by the energy storage system far exceeds the actual demand, shortening the continuous compensation time of the energy storage system; in addition, there is still room for improvement in the generation accuracy and response speed of the compensation voltage, making it difficult to simultaneously meet the differentiated requirements of different loads for voltage amplitude and phase. Summary of the Invention

[0005] In a first aspect, embodiments of this application provide a method for compensating voltage sags in a dynamic voltage restorer, including: The three-phase voltage signals from the power grid side are acquired in real time and transformed to obtain the corresponding real-time amplitude and phase information. When a voltage sag is determined to occur based on the real-time amplitude, the voltage sag depth is calculated based on the real-time amplitude and the set rated voltage threshold, and the phase jump angle is calculated based on the real-time phase and the set rated phase. The compensation voltage amplitude and compensation phase are calculated based on the voltage sag depth and the phase jump angle, and the current compensation mode is determined at the same time. The compensated active power and compensated reactive power are calculated based on the compensated voltage amplitude, the compensated phase and the compensated mode, and corresponding energy release commands are generated to control the energy storage system to output DC power of the corresponding magnitude according to the energy release commands. The DC power is converted into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase. The AC compensation voltage is then injected into the line between the power grid and the load via a series injection transformer to complete the voltage sag compensation.

[0006] Secondly, embodiments of this application also provide a dynamic voltage restorer voltage sag compensation system, comprising: The first calculation module is used to collect the three-phase voltage signal from the power grid side in real time and perform transformation processing to obtain the corresponding real-time amplitude and phase information; The second calculation module is used to calculate the voltage sag depth based on the real-time amplitude and the set rated voltage threshold when a voltage sag is determined to occur based on the real-time amplitude, and to calculate the phase jump angle based on the real-time phase and the set rated phase. The third calculation module is used to calculate the compensation voltage amplitude and compensation phase based on the voltage sag depth and the phase jump angle. The mode determination module is used to determine the current compensation mode; The instruction generation module is used to calculate the compensation active power and compensation reactive power according to the compensation voltage amplitude, the compensation phase and the compensation mode, and generate corresponding energy release instructions to control the energy storage system to output DC power of the corresponding amount according to the energy release instructions; The injection module is used to convert the DC power into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase. The AC compensation voltage is then injected into the line between the power grid and the load via a series injection transformer to complete the voltage sag compensation.

[0007] Thirdly, embodiments of this application also provide a dynamic voltage restorer voltage sag compensation device, the device comprising: One or more processors; Storage device, configured to store one or more programs, When the one or more programs are executed by the one or more processors, the one or more processors implement the dynamic voltage restorer voltage sag compensation method described in the embodiments of this application.

[0008] Fourthly, embodiments of this application also provide a non-volatile storage medium for storing computer-executable instructions, which, when executed by a computer processor, are configured to perform the dynamic voltage restorer voltage sag compensation method described in embodiments of this application.

[0009] Fifthly, embodiments of this application also provide a computer program product, which includes a computer program stored in a computer-readable storage medium. At least one processor of the device reads from the computer-readable storage medium and executes the computer program, causing the device to perform the dynamic voltage restorer voltage sag compensation method described in embodiments of this application. Attached Figure Description

[0010] Figure 1 A flowchart of a dynamic voltage restorer voltage sag compensation method provided in this application embodiment; Figure 2 A flowchart illustrating a method for determining voltage sag and calculating compensation voltage, provided in an embodiment of this application; Figure 3 A flowchart illustrating a method for determining a compensation mode provided in an embodiment of this application; Figure 4 A flowchart illustrating a method for power calculation and instruction generation under different compensation modes provided in this application embodiment; Figure 5 A flowchart illustrating a method for converting DC power into AC compensated voltage, provided in an embodiment of this application; Figure 6 A structural block diagram of another dynamic voltage restorer voltage sag compensation system provided in this application embodiment; Figure 7 This is a schematic diagram of a dynamic voltage restorer voltage sag compensation device provided in an embodiment of this application. Detailed Implementation

[0011] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of this application and are not intended to limit the scope of the embodiments. Furthermore, it should be noted that, for ease of description, only the parts relevant to the embodiments of this application are shown in the accompanying drawings, not the entire structure.

[0012] Figure 1 This is a flowchart illustrating a voltage sag compensation method for a dynamic voltage restorer provided in an embodiment of this application. Figure 1 As shown, it includes the following steps: Step S101: Real-time acquisition of three-phase voltage signals from the power grid side and transformation processing to obtain the corresponding real-time amplitude and phase information.

[0013] The three-phase voltage signal refers to the instantaneous AC voltage values ​​of phases A, B, and C on the grid side, which can be acquired from the grid bus via voltage transformers or voltage sensors. Transformation processing involves converting the acquired three-phase AC voltage signal into a DC quantity that is easier to calculate and control using mathematical methods such as coordinate transformation, from which voltage amplitude and phase information are extracted. Real-time amplitude refers to the effective value of the grid voltage at the current moment, and phase information refers to the phase angle of the grid voltage relative to the reference coordinate system at the current moment.

[0014] In one embodiment, the Park transform method based on instantaneous reactive power theory is used for transformation processing. The specific process is as follows: First, the acquired instantaneous three-phase voltage values ​​u_a, u_b, and u_c are converted into u_α and u_β components in a two-phase stationary coordinate system using the Clark transform. The transformation formulas are u_α = (2 / 3)×u_a - (1 / 3)×u_b - (1 / 3)×u_c and u_β = (√3 / 3)×u_b - (√3 / 3)×u_c. Then, u_α and u_β are converted into d-axis components u_d and q-axis components in a two-phase rotating coordinate system using the Park transform. The d-axis is in phase with the fundamental positive-sequence component of the grid voltage. Finally, the voltage amplitude U = √(u_d² + u_q²) and the phase θ = arctan(u_q / u_d) are calculated based on u_d and u_q. The sampling frequency is set to 10kHz, which means that voltage data is collected every 0.1 milliseconds to ensure that voltage sag events can be captured quickly.

[0015] For example, assuming the rated phase voltage is 220V, the instantaneous three-phase voltage values ​​collected during normal operation are u_a = 311×sin(ωt)V, u_b = 311×sin(ωt-120°)V, and u_c = 311×sin(ωt+120°)V. After Clark and Park transformations, we calculate u_d = 311V and u_q = 0V. Therefore, the real-time amplitude U = 311V (peak value), i.e., the effective value is 220V, and the phase θ = 0°. When a voltage sag occurs, the grid voltage amplitude decreases. For example, u_a becomes 156×sin(ωt)V. After transformation, u_d = 156V, and the effective real-time amplitude becomes 110V, a decrease of 50%.

[0016] Therefore, by acquiring and transforming the three-phase voltage signals in real time, the real-time amplitude and phase information of the grid voltage can be obtained quickly and accurately, providing a reliable data foundation for subsequent voltage sag detection and compensation control.

[0017] Step S102: If a voltage sag is determined to occur based on the real-time amplitude, calculate the voltage sag depth according to the real-time amplitude and the set rated voltage threshold, and calculate the phase jump angle according to the real-time phase and the set rated phase.

[0018] Voltage sag refers to the phenomenon where the effective value of the grid voltage drops below 90% of the rated voltage and lasts for more than half a cycle. The rated voltage threshold is a pre-set reference voltage value used to determine whether a voltage sag has occurred, typically 90% of the rated voltage. The depth of voltage sag refers to the extent of voltage drop during the sag, usually expressed as a percentage of the rated voltage. The calculation formula is: Depth of voltage sag = (Rated voltage - Real-time amplitude) / Rated voltage × 100%. The phase jump angle refers to the change in voltage phase before and after a voltage sag, i.e., the difference between the phase after the sag and the rated phase.

[0019] In one embodiment, the real-time calculated voltage amplitude is compared with a rated voltage threshold. A voltage sag is determined to have occurred when the real-time amplitude is lower than the rated voltage threshold for multiple consecutive sampling periods. A preset time of 2 milliseconds is set; that is, a voltage sag event is confirmed when the voltage amplitude is lower than the threshold for a duration of 2 milliseconds. When calculating the voltage sag depth, the rated voltage U_N is used as a reference: sag depth ΔU = (U_N - U_real) / U_N, where U_real is the real-time amplitude. When calculating the phase transition angle, the rated phase θ_N during normal operation is used as a reference: phase transition angle Δθ = θ_real - θ_N, where θ_real is the current real-time phase.

[0020] For example, the rated voltage is 220V, and the rated voltage threshold is set to 90% of the rated voltage, i.e., 198V. When a real-time amplitude drop from 220V to 154V is detected and lasts for more than 2 milliseconds, a voltage sag is determined to have occurred. In this case, the voltage sag depth ΔU = (220 - 154) / 220 = 0.3, which is 30% of the rated voltage sag depth. If the rated phase is 0° during normal operation, and the real-time phase changes to 10° after the sag occurs, then the phase jump angle Δθ = 10° - 0° = 10°.

[0021] Therefore, by accurately calculating the voltage sag depth and phase jump angle, the severity of the voltage sag and the phase change can be quantitatively described, providing accurate input parameters for subsequent compensation voltage calculations.

[0022] Step S103: Calculate the compensation voltage amplitude and compensation phase based on the voltage sag depth and the phase jump angle, and determine the current compensation mode.

[0023] Here, the compensation voltage amplitude refers to the effective value of the compensation voltage that the dynamic voltage restorer needs to output, and the compensation phase refers to the phase angle of the compensation voltage relative to the grid voltage. The compensation mode refers to the control strategy and operating mode adopted by the dynamic voltage restorer when performing voltage compensation; different compensation modes correspond to different compensation targets and energy consumption characteristics.

[0024] In one embodiment, the compensation voltage amplitude is calculated based on the voltage sag depth, where the compensation voltage amplitude U_c = U_N × ΔU, meaning the compensation voltage amplitude equals the rated voltage multiplied by the voltage sag depth. The compensation phase is calculated based on the phase transition angle, requiring the phase relationship between the compensation voltage and the grid voltage to be determined according to the compensation mode. The compensation mode is determined based on the voltage withstand characteristics and phase withstand characteristics of the protected load, using a pre-stored load characteristic database for matching and selection to choose the most suitable compensation mode for the current load type.

[0025] For example, when the voltage sag depth is 30% and the rated voltage is 220V, the target amplitude of the compensation voltage is 220V × 0.3 = 66V. If the phase jump angle is 10°, the compensation phase needs to be determined according to the compensation mode: in the in-phase compensation mode, the compensation phase is the same as the grid voltage phase, that is, the compensation voltage phase follows the change of the grid voltage phase; in the minimum energy compensation mode, the compensation phase needs to be optimized to minimize the active power required for compensation.

[0026] Therefore, by calculating the compensation voltage amplitude and compensation phase, and adaptively determining the compensation mode, the optimal compensation strategy can be selected based on the actual voltage sag and load characteristics, laying the foundation for subsequent power calculation and energy control.

[0027] Step S104: Calculate the compensated active power and compensated reactive power according to the compensated voltage amplitude, the compensated phase and the compensated mode, and generate corresponding energy release commands to control the energy storage system to output DC power of the corresponding magnitude according to the energy release commands.

[0028] Here, compensated active power refers to the amount of active power that the dynamic voltage restorer needs to provide to the grid during the compensation process, while compensated reactive power refers to the amount of reactive power that needs to be provided. Energy release command refers to the control command sent to the energy storage system to control the power and duration of the energy storage system's discharge. Energy storage system refers to the energy storage device that provides DC power to the dynamic voltage restorer; it can be a battery bank, supercapacitor, or other form of energy storage device.

[0029] In one embodiment, the compensated active power P = U_c × I_L × cosφ and the compensated reactive power Q = U_c × I_L × sinφ are calculated based on the compensation voltage amplitude U_c, the load current I_L, and the phase difference φ between the compensation voltage and the load current. Under different compensation modes, the phase relationship between the compensation voltage and the load current differs, thus the allocation ratio of active and reactive power also differs. Based on the calculated active power demand, a corresponding energy release command is generated to control the DC / DC converter of the energy storage system to output the corresponding power of DC power, maintaining the stability of the DC bus voltage.

[0030] For example, assuming a load current of 100A, in in-phase compensation mode, the compensation voltage amplitude is 66V, and the compensation voltage is in phase with the load current. Therefore, the compensated active power P = 66V × 100A × cos0° = 6600W = 6.6kW, and the compensated reactive power Q = 66V × 100A × sin0° = 0var. The generated active power release command is 6.6kW, controlling the energy storage system to discharge at 6.6kW. In minimum energy compensation mode, the compensation voltage phase is optimized to minimize active power, for example, reducing it to 4.5kW and reactive power to 4.8kvar. In this mode, the energy storage system only needs to release 4.5kW of active power.

[0031] Therefore, by accurately calculating the compensated active and reactive power according to the compensation mode and generating corresponding energy release commands to control the output of the energy storage system, the optimal utilization of energy storage can be achieved, minimizing active power consumption and extending the continuous compensation time of the energy storage system while ensuring the compensation effect.

[0032] Step S105: Convert the DC power into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase, and inject the AC compensation voltage into the line between the power grid and the load through a series injection transformer to complete the voltage sag compensation.

[0033] The conversion of DC power to AC compensation voltage is achieved through a voltage-source inverter. The inverter converts the DC power on the DC side into a three-phase AC voltage, the amplitude of which and its phase can be adjusted through control strategies. A series injection transformer is a transformer connected in series between the power grid and the load. Its primary side is connected to the compensation voltage output from the inverter, and its secondary side is connected in series in the power supply line. The compensation voltage is injected into the power supply line through the transformer's electromagnetic induction. Voltage sag compensation refers to restoring the voltage on the load side to its rated level by injecting compensation voltage, ensuring the normal operation of sensitive loads.

[0034] In one embodiment, a three-phase full-bridge voltage-source inverter is used as the main circuit. Pulse width modulation (PWM) technology is used to control the switching of each device in the inverter, converting DC power into a three-phase AC voltage with adjustable amplitude and phase. The AC voltage output by the inverter is filtered by an LC filter to remove high-frequency harmonics, resulting in a smooth sinusoidal voltage, which is then connected to the primary side of a series injection transformer. The turns ratio of the series injection transformer is designed according to the compensation voltage level and the inverter output voltage level to ensure sufficient compensation voltage output. Ultimately, the load-side voltage equals the grid-side voltage plus the series-injected compensation voltage, i.e., U_load = U_grid + U_compensation, thus maintaining the load-side voltage at its rated value.

[0035] For example, if a 30% voltage dip occurs on the grid side, dropping from 220V to 154V, the dynamic voltage restorer outputs a 66V compensation voltage, which is injected into the power supply line via a series injection transformer. The load-side voltage then equals 154V + 66V = 220V, restoring it to the rated voltage level. The entire compensation process has a response time of less than 5 milliseconds, ensuring that sensitive loads do not shut down due to voltage dips.

[0036] Therefore, by inverting DC power into a precisely controlled AC compensation voltage and injecting it into the power supply line through a series injection transformer, voltage sags can be quickly and effectively compensated, ensuring the stability of the load-side voltage and achieving effective protection for sensitive loads.

[0037] The technical solution of this embodiment obtains real-time amplitude and phase information by acquiring and transforming the three-phase voltage signal from the grid side. When a voltage sag is detected, the voltage sag depth and phase jump angle are calculated. Then, the compensation voltage parameters are calculated and the compensation mode is adaptively determined. Based on the compensation mode, the corresponding active power and reactive power are calculated to control the output DC power of the energy storage system. Finally, the DC power is converted into AC compensation voltage and injected into the line in series to complete the compensation. It can adaptively select the optimal compensation mode according to the characteristics of the protected load, which improves the energy utilization efficiency of energy storage, extends the continuous compensation time, and improves the accuracy and flexibility of voltage sag compensation.

[0038] Figure 2 This is a flowchart illustrating a method for determining voltage sag and calculating compensation voltage, provided in an embodiment of this application. Based on the above embodiments, this embodiment further refines the process for determining voltage sag and calculating compensation voltage. Figure 2 As shown, it includes the following steps: Step S201: Compare the real-time amplitude with the set rated voltage threshold. When the real-time amplitude is lower than the rated voltage threshold and continues for a preset time, it is determined that a voltage dip has occurred.

[0039] The rated voltage threshold is a benchmark value used to determine whether a voltage sag has occurred. It is usually set as a certain percentage of the rated voltage, such as 90% of the rated voltage, according to national standards or user requirements. The preset time refers to the shortest time that the voltage amplitude needs to remain below the threshold. It is used to avoid misjudging instantaneous voltage fluctuations or interference as voltage sags, and is usually set to half a cycle to one cycle.

[0040] In one embodiment, a sliding window approach is used to determine voltage sags: a sliding window of length N sampling points is maintained, with each sampling point recording the current voltage amplitude; a voltage sag is determined to have occurred when the voltage amplitudes of all sampling points within the window are lower than the rated voltage threshold. The number of sampling points N corresponding to the preset time is N = preset time × sampling frequency. For example, if the sampling frequency is 10kHz and the preset time is 2 milliseconds, then N = 20 sampling points. A voltage sag recovery criterion is also set; when the voltage amplitude recovers to above the rated voltage threshold and remains above it for the preset time, the voltage sag is determined to have ended.

[0041] For example, the rated voltage is 220V, the rated voltage threshold is set to 198V (90% of the rated voltage), and the preset time is 2 milliseconds. When the voltage amplitude is detected to start decreasing from 220V, drop to 190V (below the threshold) in the first millisecond, and remain at around 190V for the next 2 milliseconds, a voltage sag is determined to have occurred in the third millisecond. If the voltage only momentarily drops to 190V but recovers to above 200V within 1 millisecond, it is not considered a voltage sag.

[0042] Therefore, by setting the rated voltage threshold and duration criteria, voltage sag events can be detected accurately and reliably, avoiding false alarms and missed alarms, and ensuring that the compensation device is put into operation only when it is truly needed.

[0043] Step S202: Calculate the target amplitude of the compensation voltage based on the voltage sag depth, and calculate the target phase of the compensation voltage based on the phase jump angle.

[0044] The target amplitude of the compensation voltage refers to the theoretically required voltage amplitude to be compensated, i.e., the portion of the grid voltage that is missing. The target phase of the compensation voltage refers to the theoretically required phase angle of the compensation voltage. The target amplitude and target phase are calculated based on ideal compensation conditions and form the basis for subsequent corrections.

[0045] In one embodiment, the formula for calculating the target amplitude of the compensation voltage is U_c_target = U_N - U_real = U_N × ΔU, where U_N is the rated voltage, U_real is the real-time amplitude of the grid voltage, and ΔU is the voltage sag depth. The calculation of the target phase of the compensation voltage needs to consider the direction and magnitude of the phase jump. In in-phase compensation mode, the target phase of the compensation voltage is consistent with the phase of the grid voltage, i.e., θ_c_target = θ_real; in other compensation modes, the target phase needs to be determined according to the specific compensation strategy.

[0046] For example, if the rated voltage is 220V and the voltage sag depth is 30%, then the target amplitude of the compensation voltage is 220V × 0.3 = 66V. If the grid voltage phase jumps from 0° to 10°, then in in-phase compensation mode, the target phase of the compensation voltage is also 10°, meaning the compensation voltage follows the phase change of the grid voltage and remains in phase with the grid voltage.

[0047] Therefore, by calculating the target amplitude and target phase of the compensation voltage, the compensation voltage parameters under ideal conditions can be determined, providing a reference value for subsequent correction and optimization.

[0048] Step S203: Correct the target amplitude of the compensation voltage and the phase jump angle according to the voltage deviation range set on the load side to obtain the compensation voltage amplitude and compensation phase.

[0049] The voltage deviation range refers to the maximum allowable deviation of the load-side voltage from the rated voltage, typically set based on the load's voltage tolerance, for example, ±5% of the rated voltage. Correction refers to appropriately adjusting the target compensation voltage value while ensuring the load voltage remains within the allowable deviation range, in order to reduce energy consumption and optimize the compensation effect.

[0050] In one embodiment, the permissible voltage deviation range on the load side is first determined, for example, the voltage is allowed to fluctuate between 95% and 105% of the rated voltage. Then, the minimum and maximum amplitudes of the compensation voltage are calculated based on the voltage deviation range: minimum compensation amplitude U_c_min = U_real - 0.95 × U_N, maximum compensation amplitude U_c_max = U_real - 1.05 × U_N (absolute values). In minimum energy compensation mode, the minimum compensation amplitude is selected as the final compensation voltage amplitude to reduce active power consumption. Similarly, a similar correction is made to the phase, adjusting the compensation phase within the permissible phase deviation range of the load to optimize the power factor.

[0051] For example, with a rated voltage of 220V and a permissible voltage deviation range of ±5% for the load (meaning the load voltage can be between 209V and 231V), when the mains voltage drops to 154V (30% sag), the target compensation voltage amplitude is 66V. At this point, the load voltage is 154V + 66V = 220V. If the minimum permissible load voltage is 209V, then the minimum compensation voltage can be 209V - 154V = 55V. Choosing 55V as the final compensation voltage amplitude is 11V less than the target amplitude, correspondingly reducing active power consumption while keeping the load voltage within the permissible range.

[0052] Therefore, by correcting the target value of the compensation voltage according to the voltage deviation range on the load side, the compensation voltage parameters can be optimized while ensuring the normal operation of the load, thereby reducing the energy consumption of the energy storage system and improving energy utilization efficiency.

[0053] The technical solution of this embodiment ensures the accuracy of detection by setting the threshold and duration conditions for voltage sag determination, determines the ideal compensation parameters by calculating the target amplitude and target phase of the compensation voltage, and then corrects them according to the load voltage deviation range to obtain the final compensation parameters. Under the premise of ensuring the compensation effect, the compensation parameters are optimized and the energy utilization efficiency is improved.

[0054] Figure 3 This is a flowchart illustrating a method for determining a compensation mode according to an embodiment of this application. This embodiment further refines the process of determining the compensation mode based on the above embodiments. For example... Figure 3 As shown, it includes the following steps: Step S301: Obtain the voltage withstand curve and phase transition withstand information of the protected load.

[0055] The Voltage Tolerance Curve (VTC) describes the relationship between the depth and duration of a voltage sag that a load can withstand. The area above the curve represents the normal operating range of the load, while the area below represents the load shutdown or fault range. Phase transition tolerance information refers to the maximum angle of a voltage phase transition that the load can withstand. When the phase transition exceeds this value, the load will not function properly. This information is typically obtained through experimental testing or manufacturer technical manuals and is pre-stored in the system's database.

[0056] In one embodiment, the voltage withstand curve uses the CBEMA or ITIC curve as a reference standard. The horizontal axis of the curve represents the duration of voltage sag (in milliseconds or cycles), and the vertical axis represents the voltage amplitude (per unit or percentage). Phase transition withstand information includes the maximum phase transition angle that the load can withstand. For example, some precision electronic equipment can only withstand phase transitions within 5°, while some motor loads can withstand phase transitions greater than 30°. The system stores withstand characteristic data for various typical loads. Users can select the corresponding characteristic parameters according to the type of load being protected, or they can customize the input.

[0057] For example, if the protected load is a precision CNC machine tool, its voltage withstand curve indicates that the load can withstand 200 milliseconds when the voltage sag depth is 30%, and only 50 milliseconds when the sag depth is 50%. Phase jump withstand information shows that the equipment can only withstand phase jumps within 10°; jumps exceeding 10° will lead to decreased machining accuracy or machine shutdown. The system reads the withstand curve and phase withstand parameters of this CNC machine tool model from the database as the basis for selecting the compensation mode.

[0058] Therefore, by obtaining the voltage withstand curve and phase transition withstand information of the protected load, we can accurately understand the voltage sag withstand capability of the load, providing a scientific basis for the selection of subsequent compensation modes.

[0059] Step S302: If the protected load is determined to be of the voltage amplitude sensitive type based on the voltage withstand curve, the current compensation mode is determined to be the minimum energy compensation mode.

[0060] Among them, voltage amplitude sensitive type refers to loads that are highly sensitive to drops in voltage amplitude, and will shut down or malfunction if the voltage amplitude falls below a certain level, but have relatively strong tolerance to phase jumps. Minimum energy compensation mode refers to a compensation mode that minimizes the active power required for compensation by optimizing the phase angle of the compensation voltage while ensuring that the load voltage amplitude meets the requirements, thereby minimizing the energy consumption of the energy storage system.

[0061] In one embodiment, the load type is determined by comparing the load's voltage amplitude tolerance threshold and phase jump tolerance threshold. If the voltage amplitude tolerance threshold is low (i.e., sensitive to amplitude) while the phase jump tolerance threshold is high (i.e., insensitive to phase), the load is classified as voltage amplitude sensitive. In minimum energy compensation mode, the phase angle of the compensation voltage is adjusted to maximize reactive power and minimize active power when the angle between the compensation voltage and the load current is 90°, while ensuring the load voltage amplitude remains within allowable limits. The optimal phase angle is determined using mathematical optimization methods, with the objective function being to minimize active power P, and the constraint being that the load voltage amplitude U_load ≥ U_min.

[0062] For example, if the protected load is a motor-type load, which is sensitive to voltage amplitude (it will shut down if the voltage drops below 80% of the rated voltage), but can withstand large phase jumps (up to 30°), it is determined to be a voltage amplitude sensitive type, and the minimum energy compensation mode is selected. In this mode, the phase of the compensation voltage is optimized, reducing the active power required for compensation from 6.6kW in in-phase compensation to 4.2kW, reducing active power consumption by 36%, while the load voltage amplitude is still maintained at more than 95% of the rated value, meeting the load's operating requirements.

[0063] Therefore, for loads sensitive to voltage amplitude, adopting the minimum energy compensation mode can significantly reduce active power consumption and extend the continuous compensation time of the energy storage system while ensuring that the load voltage amplitude meets the requirements.

[0064] Step S303: If the protected load is determined to be phase-sensitive based on the phase jump tolerance information, the current compensation mode is determined to be the in-phase compensation mode.

[0065] Among them, phase-sensitive type refers to loads that are highly sensitive to changes in voltage phase; even small phase jumps can cause the load to malfunction, but they have a certain tolerance for small drops in voltage amplitude. In-phase compensation mode refers to a compensation voltage that is in phase with the grid voltage, that is, it fully compensates for voltage amplitude drops, and also compensates for phase jumps, so that the amplitude and phase of the load-side voltage are restored to the rated state.

[0066] In one embodiment, the load is determined to be phase-sensitive based on its low phase jump tolerance threshold (e.g., less than 10°) and relatively high voltage amplitude tolerance threshold (e.g., able to withstand a 10% to 15% voltage drop). In in-phase compensation mode, the phase of the compensation voltage is consistent with the phase of the grid voltage; that is, the compensation voltage completely follows the phase changes of the grid voltage, ensuring that the phase of the load-side voltage is the same as the rated phase during normal operation. In this mode, the waveform and phase of the load-side voltage are consistent with those during normal power supply, making it most suitable for phase-sensitive loads.

[0067] For example, the protected load is a data center server power supply, which is highly sensitive to phase transitions (a phase transition exceeding 5° can cause power supply malfunctions), but has a certain tolerance for small voltage amplitude drops (it can withstand a 10% voltage drop). Therefore, it is determined to be a phase-sensitive type, and the in-phase compensation mode is selected. In this mode, the compensation voltage is in phase with the grid voltage, the phase of the load-side voltage returns to the rated phase, and the amplitude also returns to the rated value, ensuring stable operation of the server power supply. Although this mode consumes more active power, it guarantees the reliable operation of the phase-sensitive load.

[0068] Therefore, for phase-sensitive loads, adopting the in-phase compensation mode can ensure that the phase and amplitude of the load-side voltage are restored to the rated state, thus protecting the phase-sensitive load from the effects of voltage sags to the greatest extent.

[0069] The technical solution of this embodiment obtains the voltage withstand curve and phase jump withstand information of the protected load, and classifies the load into voltage amplitude sensitive type and phase sensitive type according to the load characteristics. The minimum energy compensation mode and in-phase compensation mode are selected respectively, realizing the adaptive selection of compensation mode. It can adopt the most suitable compensation strategy for different types of loads, taking into account both compensation effect and energy utilization efficiency.

[0070] Figure 4 This is a flowchart illustrating a method for power calculation and instruction generation under different compensation modes, provided as an embodiment of this application. Based on the above embodiments, this embodiment further refines the power calculation and instruction generation process under different compensation modes. For example... Figure 4 As shown, it includes the following steps: Step S401: In the case of the minimum energy compensation mode, calculate the minimum active power and corresponding reactive power required to maintain the load voltage amplitude based on the compensation voltage amplitude and the compensation phase, and generate an active power release command and a reactive power support command according to the minimum active power and the reactive power.

[0071] Minimum active power refers to the minimum active power value that the dynamic voltage restorer needs to provide while ensuring that the load voltage amplitude meets the requirements. Correspondingly, reactive power refers to the reactive power value that the dynamic voltage restorer needs to provide under the minimum active power condition. The active power release command is the command that controls the energy storage system to release active power, while the reactive power support command is the command that controls the inverter to output reactive power.

[0072] In one embodiment, power calculation under the minimum energy compensation mode is based on phasor analysis: Let the grid voltage phasor be U_s, the compensation voltage phasor be U_c, and the load voltage phasor be U_L = U_s + U_c. The load current phasor is I_L, and the load power factor angle is φ_L. The magnitude of the compensation voltage is |U_c|, and the phase angle is δ (the phase difference relative to the grid voltage). The objective is to minimize the active power P = Re(U_c × I_L*) under the constraint that |U_L| ≥ U_L_min. The optimal value of δ can be obtained by differentiation or geometric methods to minimize the active power. The specific calculation formula is: when the load power factor is cosφ_L, the optimal compensation phase angle minimizes the projection of the compensation voltage in the load current direction. At this time, the minimum active power P_min = U_c × I_L × cos(δ_opt + φ_L), and the corresponding reactive power Q = U_c × I_L × sin(δ_opt + φ_L).

[0073] For example, the grid voltage amplitude is 154V (after sag), the load voltage requirement is no less than 209V (95% of the rated voltage), the load current is 100A, and the load power factor is 0.9 (φ_L = 25.8°). After optimization calculation, the optimal compensation phase angle δ_opt = 35°, and the compensation voltage amplitude is 62V. At this time, the minimum active power P_min = 62V × 100A ×cos(35° + 25.8°) = 6200 × cos(60.8°) = 6200 × 0.487 ≈ 3020W = 3.02kW. The corresponding reactive power Q = 6200 × sin(60.8°) = 6200 × 0.873 ≈ 5413var = 5.41kvar. The generated active power release command is 3.02kW, and the reactive power support command is 5.41kvar, controlling the energy storage system to discharge at a power of 3.02kW.

[0074] Therefore, in the minimum energy compensation mode, by optimizing the compensation voltage phase to minimize active power, the energy consumption of the energy storage system can be significantly reduced, the continuous compensation time can be extended, and the load voltage amplitude can be guaranteed to meet the requirements.

[0075] Step S402: In the in-phase compensation mode, calculate the full active power and full reactive power required for complete compensation based on the compensation voltage amplitude and the compensation phase, and generate an active power release command and a full reactive power support command according to the full active power and the full reactive power.

[0076] Full active power refers to all active power required to fully compensate for voltage sags, i.e., the active power when the compensation voltage and load current are in phase. Full reactive power refers to all reactive power required for full compensation. The full reactive power support command is the command that controls the inverter to output full reactive power.

[0077] In one embodiment, under in-phase compensation mode, the compensation voltage is in phase with the grid voltage, meaning the phase of the compensation voltage is completely consistent with the phase of the grid voltage. At this time, the load voltage fully recovers to the amplitude and phase of the rated voltage, exactly the same as during normal power supply. The compensated active power P = U_c × I_L × cosφ_L, where φ_L is the load power factor angle, i.e., the phase difference between the compensation voltage and the load current is equal to the load power factor angle. The compensated reactive power Q = U_c × I_L × sinφ_L.

[0078] For example, the compensation voltage amplitude is 66V, the load current is 100A, and the load power factor is 0.9 (φ_L = 25.8°). In in-phase compensation mode, the total active power P = 66V × 100A × cos(25.8°) = 6600 × 0.9 = 5940W = 5.94kW. The total reactive power Q = 6600 × sin(25.8°) = 6600 × 0.435 ≈ 2871var = 2.87kvar. The generated active power release command is 5.94kW, and the total reactive power support command is 2.87kvar, controlling the energy storage system to discharge at a power of 5.94kW.

[0079] Therefore, in the in-phase compensation mode, by fully compensating for the voltage amplitude and phase, the load-side voltage can be completely restored to the rated state, providing the most comprehensive protection for phase-sensitive loads.

[0080] The technical solution of this embodiment adopts different power calculation methods for the minimum energy compensation mode and the in-phase compensation mode, respectively, to generate corresponding energy release commands and reactive power support commands, thereby realizing precise power control under different compensation modes and ensuring that the compensation effect is consistent with the mode design goal.

[0081] Figure 5This is a flowchart illustrating a method for converting DC power into AC compensated voltage, provided as an embodiment of this application. Based on the above embodiments, this embodiment further refines the specific process of converting DC power into AC compensated voltage. For example... Figure 5 As shown, it includes the following steps: Step S501: Synthesize a corresponding three-phase sinusoidal modulation wave based on the compensation voltage amplitude and the compensation phase, and compare the three-phase sinusoidal modulation wave with a high-frequency triangular carrier wave to generate a PWM pulse signal that controls the switching devices of the inverter to turn on and off.

[0082] Among them, the three-phase sinusoidal modulation wave refers to a three-phase sinusoidal wave signal whose amplitude and phase are set according to compensation requirements, serving as the reference signal for PWM modulation. The high-frequency triangular carrier wave refers to a triangular wave signal with a frequency much higher than the power frequency, serving as the carrier signal for PWM modulation. The PWM pulse signal refers to a pulse signal whose pulse width varies according to a sinusoidal law, used to control the on / off time ratio of the switching devices in the inverter, thereby achieving output voltage regulation.

[0083] In one embodiment, a sinusoidal pulse width modulation (SPWM) method is used to generate the PWM signal. First, a three-phase sinusoidal modulation wave is synthesized based on the compensation voltage amplitude U_c and the compensation phase θ: u_ma = U_m × sin(ωt + θ), u_mb = U_m × sin(ωt + θ - 120°), u_mc = U_m × sin(ωt + θ + 120°), where U_m is the modulation wave amplitude, proportional to the compensation voltage amplitude. A 10kHz isosceles triangular wave is used as the carrier wave. The sinusoidal modulation wave of each phase is compared with the triangular carrier wave: when the modulation wave is greater than the carrier wave, a high level is output; when the modulation wave is less than the carrier wave, a low level is output. The resulting pulse signal is the SPWM wave, whose pulse width varies sinusoidally, and the fundamental component is a sine wave.

[0084] For example, the compensation voltage amplitude is 66V (RMS), and the compensation phase is 0°. The modulation wave amplitude U_m = 66 × √2 = 93.3V (peak value). The three-phase modulation waves are u_ma = 93.3 × sin(314t)V, u_mb = 93.3 × sin(314t - 120°)V, and u_mc = 93.3 × sin(314t + 120°)V. These three modulation waves are compared with a 10kHz triangular carrier wave (peak value 100V) to generate three SPWM pulse signals. When the instantaneous value of the modulation wave is 50V, the duty cycle of the pulse generated after comparison with the triangular carrier wave is 50%.

[0085] Therefore, by generating PWM pulse signals through SPWM modulation, the amplitude and phase of the inverter output voltage can be precisely controlled, providing a control basis for generating high-quality compensation voltage.

[0086] Step S502: After the generated PWM pulse signal is amplified by the driver, the switching on and off of each IGBT in the three-phase full-bridge inverter circuit is controlled to chop and transform the DC power into a high-frequency pulse voltage sequence with constant amplitude and a width that varies according to a sine law.

[0087] In this context, drive amplification refers to amplifying the logic-level PWM pulse signal into a power signal capable of driving the IGBT gate, typically achieved using a dedicated IGBT drive circuit. A three-phase full-bridge inverter circuit is a three-phase bridge circuit composed of six IGBTs (Insulated Gate Bipolar Transistors), and it forms the main circuit structure of a voltage-source inverter. Chopper conversion refers to cutting the DC voltage into a series of pulse voltages through high-frequency switching of switching devices, and controlling the output voltage by adjusting the pulse width.

[0088] In one embodiment, the three-phase full-bridge inverter circuit adopts a two-level topology, with each bridge arm consisting of one IGBT and one anti-parallel diode. The DC-side input voltage is U_dc. The six IGBTs are S_a1, S_a2 (upper and lower bridge arms of phase A), S_b1, S_b2 (upper and lower bridge arms of phase B), and S_c1, S_c2 (upper and lower bridge arms of phase C). The upper and lower bridge arms of each phase conduct complementaryly, that is, when the upper bridge arm is on, the lower bridge arm is off, and when the lower bridge arm is on, the upper bridge arm is off. When the upper bridge arm S_a1 of phase A is on and the lower bridge arm S_a2 is off, the output voltage of phase A is +U_dc / 2; when S_a1 is off and S_a2 is on, the output voltage of phase A is -U_dc / 2. By controlling the on / off time ratio of each bridge arm, the fundamental component of the output pulse voltage sequence is the required sinusoidal AC voltage.

[0089] For example, the DC bus voltage is 400V, and the output voltage of each phase switches between +200V and -200V. Within one power frequency cycle (20 milliseconds), the IGBT switching frequency is 10kHz via SPWM control, meaning it switches 200 times per cycle. The output pulse voltage amplitude is constant at ±200V, but the pulse width varies according to a sine wave: at the peak of the sine wave, the positive pulse is the widest and the negative pulse is the narrowest; at the zero-crossing point of the sine wave, the positive and negative pulse widths are equal. The fundamental component of this pulse voltage sequence is a sine wave with controllable amplitude and phase.

[0090] Thus, through the high-frequency chopping action of the IGBT, DC power is converted into a high-frequency pulse voltage sequence with a pulse width varying according to a sinusoidal law. Its fundamental component is the required compensation voltage, thereby realizing the conversion of DC to AC power.

[0091] Step S503: The output high-frequency pulse voltage sequence is sent to a filter to filter out high-frequency harmonics and obtain a smooth sinusoidal AC voltage; at the same time, the actual output voltage is dynamically compared and corrected with the set target command value to ensure that the final output AC voltage is completely consistent with the command value in amplitude and phase, and then sent to a series injection transformer to complete the compensation injection.

[0092] The filter refers to an LC low-pass filter composed of inductors and capacitors, used to filter out high-frequency harmonic components in the inverter output voltage, making the output voltage a smooth sine wave. Dynamic comparison correction refers to using a closed-loop control method to compare the actual output voltage with the target command value, adjusting the control signal according to the error, so that the output voltage tracks the changes in the command value.

[0093] In one embodiment, an LC filter is connected to the inverter output, with a filter inductor L = 2mH and a filter capacitor C = 50μF. The cutoff frequency is approximately 500Hz, effectively filtering out high-frequency switching harmonics of 10kHz and above. Simultaneously, a voltage instantaneous value closed-loop control strategy is employed: the actual compensation voltage at the filter output is sampled in real time and compared with the target command value to obtain a voltage error signal; this error signal is then processed by a PI regulator (proportional-integral regulator) to adjust the amplitude and phase of the PWM modulation wave, ensuring that the actual output voltage tracks the target command value. The PI regulator has a proportional coefficient Kp = 5 and an integral coefficient Ki = 100, ensuring the system has a fast dynamic response and zero steady-state error.

[0094] For example, the target compensation voltage command is a three-phase sinusoidal voltage with an amplitude of 66V and a phase of 0°. Due to factors such as load variations, the actual output voltage has an amplitude of only 64V and a phase offset of 1°. The voltage detection circuit samples the actual output voltage and compares it with the command value, obtaining an amplitude error of 2V and a phase error of 1°. The PI regulator adjusts the amplitude and phase of the modulation wave based on the error signal, gradually bringing the output voltage closer to the command value. After several switching cycles, the actual output voltage amplitude stabilizes at 66V, and the phase error is less than 0.5°, meeting the accuracy requirements before being fed into the series injection transformer.

[0095] Therefore, a smooth sinusoidal voltage is obtained by filtering out high-frequency harmonics through an LC filter, and the output voltage is precisely regulated through voltage closed-loop control, ensuring that the amplitude and phase of the compensation voltage can accurately track the command value, thus guaranteeing the accuracy and effectiveness of voltage sag compensation.

[0096] The technical solution of this embodiment generates a PWM pulse signal through SPWM modulation, controls the three-phase full-bridge inverter circuit to chop and transform DC power into a high-frequency pulse voltage sequence, and then obtains a precise sinusoidal compensation voltage through LC filtering and closed-loop control. Finally, the compensation is injected through a series injection transformer, realizing the generation of high-quality and high-precision AC compensation voltage and ensuring the effect of voltage sag compensation.

[0097] Figure 6 This is a structural block diagram of a dynamic voltage restorer voltage sag compensation system provided in an embodiment of this application. The system is configured to execute the dynamic voltage restorer voltage sag compensation method provided in the above embodiment, and possesses the corresponding functional modules and beneficial effects of the method. Figure 6 As shown, the system includes: The first calculation module 101 is used to acquire the three-phase voltage signal from the power grid side in real time and perform transformation processing to obtain the corresponding real-time amplitude and phase information.

[0098] The first calculation module 101 includes a voltage sampling unit and a coordinate transformation unit. The voltage sampling unit collects the instantaneous values ​​of the three-phase voltage on the grid side through a voltage transformer, and the coordinate transformation unit converts the three-phase voltage into DC values ​​in the dq coordinate system through Clarke transformation and Park transformation, from which voltage amplitude and phase information are extracted.

[0099] The second calculation module 102 is used to calculate the voltage sag depth based on the real-time amplitude and the set rated voltage threshold when a voltage sag is determined to occur based on the real-time amplitude, and to calculate the phase jump angle based on the real-time phase and the set rated phase.

[0100] The second calculation module 102 includes a sag detection unit and a parameter calculation unit. The sag detection unit compares the real-time amplitude with the rated voltage threshold and determines whether a voltage sag has occurred based on the duration criterion. The parameter calculation unit calculates the sag depth and phase jump angle based on the changes in voltage amplitude and phase.

[0101] The third calculation module 103 is used to calculate the compensation voltage amplitude and compensation phase based on the voltage sag depth and the phase jump angle.

[0102] The third calculation module 103 includes a target value calculation unit and a correction unit. The target value calculation unit calculates the target amplitude and target phase of the compensation voltage based on the sag depth and phase jump angle. The correction unit corrects the target value based on the load voltage deviation range to obtain the final compensation voltage amplitude and phase.

[0103] The mode determination module 104 is used to determine the current compensation mode.

[0104] The mode determination module 104 includes a load characteristic storage unit and a mode selection unit. The load characteristic storage unit stores voltage withstand curves and phase withstand information for various typical loads. The mode selection unit determines the load type based on the characteristics of the protected load and selects the corresponding compensation mode (minimum energy compensation mode or in-phase compensation mode).

[0105] The instruction generation module 105 is used to calculate the compensated active power and compensated reactive power according to the compensated voltage amplitude, the compensated phase and the compensated mode, and generate corresponding energy release instructions to control the energy storage system to output DC power of the corresponding amount according to the energy release instructions.

[0106] The instruction generation module 105 includes a power calculation unit and an instruction output unit. The power calculation unit calculates the corresponding active and reactive power according to the compensation mode. The instruction output unit generates an energy release instruction to control the DC / DC converter of the energy storage system to output DC power of the corresponding power.

[0107] The injection module 106 is used to convert the DC power into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase, and inject the AC compensation voltage into the line between the power grid and the load through a series injection transformer to complete the voltage sag compensation.

[0108] The injection module 106 includes an inverter unit, a filter unit, and a series injection transformer. The inverter unit uses a three-phase full-bridge inverter to convert DC power into AC pulse voltage through SPWM modulation. The filter unit filters out high-frequency harmonics to obtain a smooth sinusoidal voltage. The series injection transformer injects the compensation voltage into the power supply line in series.

[0109] The technical solution of this embodiment, by setting up a first calculation module, a second calculation module, a third calculation module, a mode determination module, an instruction generation module, and an injection module, enables the detection of voltage sag, calculation of compensation parameters, selection of compensation mode, energy control, and injection of compensation voltage through the collaborative work of each module. It can adaptively select the optimal compensation mode according to the characteristics of the protected load, thereby improving the energy utilization efficiency and compensation accuracy of energy storage.

[0110] Figure 7 This is a schematic diagram of the structure of a dynamic voltage restorer voltage sag compensation device provided in an embodiment of this application, as shown below. Figure 7 As shown, the device includes a processor 201, a memory 202, an input device 203, and an output device 204; the number of processors 201 in the device can be one or more. Figure 7 Taking a processor 201 as an example; the processor 201, memory 202, input device 203, and output device 204 in the device can be connected via a bus or other means. Figure 7Taking the example of a connection between China and Israel via a bus.

[0111] The memory 202, as a computer-readable storage medium, can be used to store software programs, computer-executable programs, and modules, such as the program instructions / modules corresponding to the dynamic voltage restorer voltage sag compensation method in this embodiment (e.g., the first calculation module 101, the second calculation module 102, the third calculation module 103, the mode determination module 104, the instruction generation module 105, and the injection module 106). The processor 201 executes various functional applications and data processing of the device by running the software programs, instructions, and modules stored in the memory 202, thereby implementing the aforementioned dynamic voltage restorer voltage sag compensation method.

[0112] The memory 202 may primarily include a program storage area and a data storage area. The program storage area may store the operating system and at least one application program required for a given function; the data storage area may store data created based on terminal usage. Furthermore, the memory 202 may include high-speed random access memory and non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some instances, the memory 202 may further include memory remotely located relative to the processor 201, which can be connected to the device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0113] Input device 203 can be used to receive input digital or character information, and to generate key signal inputs related to user settings and function control of the device, such as receiving voltage sampling signals and load parameter settings. Output device 204 can be used to output PWM control signals, status indication signals, etc., and can be used to connect to IGBT drive circuits, display devices, etc.

[0114] The dynamic voltage restorer voltage sag compensation device provided in this application embodiment can execute the dynamic voltage restorer voltage sag compensation method provided in any embodiment of this application, and has the corresponding functional modules and beneficial effects of executing the method.

[0115] This application embodiment also provides a storage medium storing computer-executable instructions, which, when executed by a computer processor, are used to perform a dynamic voltage restorer voltage sag compensation method, the method comprising: The three-phase voltage signals from the power grid side are acquired in real time and transformed to obtain the corresponding real-time amplitude and phase information. When a voltage sag is determined to occur based on the real-time amplitude, the voltage sag depth is calculated based on the real-time amplitude and the set rated voltage threshold, and the phase jump angle is calculated based on the real-time phase and the set rated phase. The compensation voltage amplitude and compensation phase are calculated based on the voltage sag depth and the phase jump angle, and the current compensation mode is determined at the same time. The compensated active power and compensated reactive power are calculated based on the compensated voltage amplitude, the compensated phase and the compensated mode, and corresponding energy release commands are generated to control the energy storage system to output DC power of the corresponding magnitude according to the energy release commands. The DC power is converted into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase. The AC compensation voltage is then injected into the line between the power grid and the load via a series injection transformer to complete the voltage sag compensation.

[0116] Of course, the storage medium for storing computer-executable instructions provided in the embodiments of this application is not limited to the method operation described above, but can also perform related operations in the dynamic voltage restorer voltage sag compensation method provided in any embodiment of this application.

[0117] Based on the above description of the implementation methods, those skilled in the art can clearly understand that this application can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0118] It is worth noting that the various units and modules included in the above system embodiments are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of each functional unit are only for easy differentiation and are not used to limit the scope of protection of this application.

[0119] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for compensating voltage sag in a dynamic voltage restorer, characterized in that, include: The three-phase voltage signals from the power grid side are acquired in real time and transformed to obtain the corresponding real-time amplitude and phase information. When a voltage sag is determined to occur based on the real-time amplitude, the voltage sag depth is calculated based on the real-time amplitude and the set rated voltage threshold, and the phase jump angle is calculated based on the real-time phase and the set rated phase. The compensation voltage amplitude and compensation phase are calculated based on the voltage sag depth and the phase jump angle, and the current compensation mode is determined at the same time. The compensated active power and compensated reactive power are calculated based on the compensated voltage amplitude, the compensated phase and the compensated mode, and corresponding energy release commands are generated to control the energy storage system to output DC power of the corresponding magnitude according to the energy release commands. The DC power is converted into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase. The AC compensation voltage is then injected into the line between the power grid and the load via a series injection transformer to complete the voltage sag compensation.

2. The voltage sag compensation method for a dynamic voltage restorer according to claim 1, characterized in that, The determination of voltage sag based on the real-time amplitude includes: The real-time amplitude is compared with the set rated voltage threshold. When the real-time amplitude is lower than the rated voltage threshold and continues for a preset time, it is determined that a voltage sag has occurred. The calculation of the compensation voltage amplitude and compensation phase based on the voltage sag depth and the phase jump angle includes: The target amplitude of the compensation voltage is calculated based on the voltage sag depth, and the target phase of the compensation voltage is calculated based on the phase jump angle. The compensation voltage amplitude and compensation phase are obtained by correcting the target amplitude of the compensation voltage and the phase jump angle according to the voltage deviation range set on the load side.

3. The voltage sag compensation method for a dynamic voltage restorer according to claim 1, characterized in that, Determining the current compensation mode includes: Obtain the voltage withstand curve and phase transition withstand information of the protected load; If the protected load is determined to be voltage amplitude sensitive based on the voltage withstand curve, the current compensation mode is determined to be the minimum energy compensation mode. If the protected load is determined to be phase-sensitive based on the phase jump tolerance information, the current compensation mode is determined to be the in-phase compensation mode.

4. The voltage sag compensation method for a dynamic voltage restorer according to claim 3, characterized in that, The step of calculating the compensated active power and compensated reactive power based on the compensated voltage amplitude, the compensated phase, and the compensated mode, and generating corresponding energy release commands, includes: In the minimum energy compensation mode, the minimum active power and corresponding reactive power required to maintain the load voltage amplitude are calculated based on the compensation voltage amplitude and the compensation phase, and an active power release command and a reactive power support command are generated according to the minimum active power and the reactive power. In the in-phase compensation mode, the full active power and full reactive power required for complete compensation are calculated based on the compensation voltage amplitude and the compensation phase. An active power release command and a full reactive power support command are generated according to the full active power and the full reactive power.

5. The method for compensating voltage sag in a dynamic voltage restorer according to any one of claims 1-4, characterized in that, The step of converting the DC power into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase includes: The three-phase sinusoidal modulation wave is synthesized based on the compensation voltage amplitude and the compensation phase, and the three-phase sinusoidal modulation wave is compared with a high-frequency triangular carrier wave to generate a PWM pulse signal that controls the switching devices of the inverter. The generated PWM pulse signal is amplified and then used to control the on / off state of each IGBT in the three-phase full-bridge inverter circuit, thereby chopping and transforming the DC power into a high-frequency pulse voltage sequence with constant amplitude and a sinusoidal width. The output high-frequency pulse voltage sequence is fed into a filter to filter out high-frequency harmonics and obtain a smooth sinusoidal AC voltage. At the same time, the actual output voltage is dynamically compared and corrected with the set target command value to ensure that the final output AC voltage is completely consistent with the command value in amplitude and phase. Then, it is fed into a series injection transformer to complete the compensation injection.

6. A dynamic voltage restorer voltage sag compensation system, characterized in that, include: The first calculation module is used to collect the three-phase voltage signal from the power grid side in real time and perform transformation processing to obtain the corresponding real-time amplitude and phase information; The second calculation module is used to calculate the voltage sag depth based on the real-time amplitude and the set rated voltage threshold when a voltage sag is determined to occur based on the real-time amplitude, and to calculate the phase jump angle based on the real-time phase and the set rated phase. The third calculation module is used to calculate the compensation voltage amplitude and compensation phase based on the voltage sag depth and the phase jump angle. The mode determination module is used to determine the current compensation mode; The instruction generation module is used to calculate the compensation active power and compensation reactive power according to the compensation voltage amplitude, the compensation phase and the compensation mode, and generate corresponding energy release instructions to control the energy storage system to output DC power of the corresponding amount according to the energy release instructions; The injection module is used to convert the DC power into an AC compensation voltage that matches the compensation voltage amplitude and the compensation phase. The AC compensation voltage is then injected into the line between the power grid and the load via a series injection transformer to complete the voltage sag compensation.

7. The dynamic voltage restorer voltage sag compensation system according to claim 6, characterized in that, The second calculation module is specifically used to: compare the real-time amplitude with the set rated voltage threshold, and determine that a voltage sag occurs when the real-time amplitude is lower than the rated voltage threshold and continues for a preset time; The third calculation module is specifically used for: calculating the target amplitude of the compensation voltage based on the voltage sag depth, calculating the target phase of the compensation voltage based on the phase jump angle; and correcting the target amplitude of the compensation voltage and the phase jump angle based on the voltage deviation range set on the load side to obtain the compensation voltage amplitude and the compensation phase.

8. The dynamic voltage restorer voltage sag compensation system according to claim 6, characterized in that, The pattern determination module is specifically used for: Obtain the voltage withstand curve and phase jump withstand information of the protected load; if the protected load is determined to be voltage amplitude sensitive based on the voltage withstand curve, determine the current compensation mode as minimum energy compensation mode; if the protected load is determined to be phase sensitive based on the phase jump withstand information, determine the current compensation mode as in-phase compensation mode.

9. A dynamic voltage restorer voltage sag compensation device, the device comprising: One or more processors; A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the dynamic voltage restorer voltage sag compensation method as described in any one of claims 1-5.

10. A storage medium storing computer-executable instructions, which, when executed by a computer processor, are used to perform the dynamic voltage restorer voltage sag compensation method as described in any one of claims 1-5.

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