Additional current limiting method and device for network construction type equipment

Abstract

The invention provides an additional current limiting method and device for network construction type equipment, and relates to the field of power system control, and the method comprises the steps: determining a current real-time effective value of the network construction type equipment and a voltage difference value between the voltage of a grid-connected point and the internal potential of the network construction type equipment through detecting a current instantaneous value of the network construction type equipment and the voltage of the grid-connected point; if it is determined that the network construction type equipment is over-current according to a preset over-current criterion, the current real-time effective value and the voltage difference value, a modulation voltage increment of the network construction type equipment based on a virtual resistor is calculated; superposing the modulation voltage increment to the modulation voltage output by the potential plastic current limiting in the network construction type equipment to obtain an updated modulation voltage; and controlling the network-forming equipment to limit the current based on the updated modulation voltage. On the basis of an internal potential vector remodeling virtual impedance transient over-current suppression method, a virtual resistance additional control strategy can be provided and is used for suppressing a current direct-current component borne by equipment when a system fault occurs.

Description

Technical Field

[0001] This application relates to the field of power system control, specifically to a method and device for additional current limiting of grid-type equipment. Background Technology

[0002] With the rapid increase in the proportion of renewable energy, power systems face problems such as reduced synchronous machines, decreased inertia, and insufficient short-circuit capacity, leading to weakened system strength and deteriorated voltage stability. Traditional grid-forming inverters rely on grid voltage support, which can easily cause instability and oscillations under weak grid conditions. In contrast, grid-forming equipment, by autonomously establishing voltage and frequency references and simulating the external characteristics of synchronous machines, can independently provide virtual inertia and dynamic reactive power support, significantly enhancing the system's disturbance rejection capability. Grid-forming equipment can effectively provide voltage support and inertia in weak grids and high-proportion renewable energy transmission channels. In new power systems dominated by renewable energy, configuring grid-forming equipment has become an important trend to ensure the safe and stable operation of the power grid.

[0003] Networked SVG devices exhibit voltage source characteristics, which dictate that they should maintain a constant voltage when the system voltage suddenly changes. However, this can easily lead to overcurrent in the devices. Furthermore, due to the inherent physical characteristics of IGBTs, their overcurrent tolerance is very limited. Therefore, current limiting control is crucial for the safe operation and system reliability of networked SVG devices.

[0004] Currently, commonly used current limiting methods mainly fall into two categories: current saturation algorithms and virtual impedance. The former can achieve the purpose of current limiting simply and directly through current reference limiting, but it violates the original design intention of grid-type active voltage support. The latter achieves the effect of current limiting by equivalently increasing the output impedance of the grid-type device when the risk of current overcurrent is detected. However, this method only considers steady-state overcurrent when setting parameters, which means that the grid-type device still has the risk of DC component current overcurrent during voltage disturbances.

[0005] This section is intended to provide background or context for the embodiments of the invention set forth in the claims. The description herein is not an admission that it is prior art simply because it is included in this section. Summary of the Invention

[0006] To address the problems in the prior art, this application provides a method and apparatus for additional current limiting in network-type equipment. Based on the method for suppressing transient overcurrent caused by reshaping the virtual impedance of the internal potential vector, it proposes a virtual resistance additional control strategy to suppress the DC component of the current borne by the equipment during system faults.

[0007] To solve the above-mentioned technical problems, this application provides the following technical solution: In a first aspect, this application provides an additional current limiting method for network-type devices, including: The real-time effective value of the current of the grid-connected equipment and the voltage difference between the grid connection point voltage and the internal potential of the grid-connected equipment are determined by detecting the instantaneous current value of the grid-connected equipment and the grid connection point voltage. If the overcurrent of the network-type device is determined based on the preset overcurrent criterion, the real-time effective value of the current, and the voltage difference, the modulation voltage increment of the network-type device based on the virtual resistance is calculated. The modulation voltage increment is superimposed on the modulation voltage of the potential-plastic current-limited output in the network-type device to obtain the updated modulation voltage; The current limiting of the network-type equipment is controlled based on the updated modulation voltage.

[0008] Further, the step of determining the real-time effective value of the current of the grid-connected device and the voltage difference between the grid-connected point voltage and the internal potential of the grid-connected device by detecting the instantaneous current value of the grid-connected device and the grid connection point voltage includes: The real-time effective value of the current is obtained by performing a sliding window root mean square operation on the instantaneous current value within the sliding window; The voltage difference is obtained by subtracting the voltage at the grid connection point from the potential inside the grid-connected equipment.

[0009] Further, determining the overcurrent of the network-type equipment based on the preset overcurrent criterion, the real-time effective value of the current, and the voltage difference includes: Determine whether the real-time effective value of the current exceeds the current limit in the overcurrent criterion; if so, determine that the network-type device is overcurrent. Alternatively, determine whether the voltage difference exceeds the voltage difference generated on the connected reactor by the current limit; if so, determine that the network-type equipment is overcurrent.

[0010] Further, calculating the modulation voltage increment of the network-type device based on virtual resistance includes: Calculate the ratio of the real-time effective value of the current to the current limit to obtain the current ratio value; The product of the current ratio and the virtual resistance coefficient is determined as the virtual resistance of the network-type device; The product of the instantaneous current value and the virtual resistance is determined as the modulation voltage increment; wherein, the instantaneous current value includes the three-phase current instantaneous value; and the modulation voltage increment includes the three-phase modulation voltage increment.

[0011] Further, the step of superimposing the modulation voltage increment onto the modulation voltage of the potential-plastic current-limited output within the network-type device to obtain the updated modulation voltage includes: The internal potential of the network-type equipment is determined based on the internal potential relationship expression in the control model of the network-type equipment. dq Quantity; According to the above dq The components determine the three-phase coordinate components of the potential within the network-type equipment; The three-phase modulation voltage increment is superimposed onto the three-phase coordinate components to obtain the updated modulation voltage.

[0012] Furthermore, the current limiting of the network-type device based on the updated modulation voltage includes: Generate a corresponding pulse width modulation waveform based on the updated modulation voltage; The instantaneous voltage value of the grid-connected device is adjusted using the pulse width modulation waveform, and the voltage difference between the instantaneous voltage value and the grid connection point voltage is reduced to achieve smooth current limiting.

[0013] Secondly, this application provides an additional current limiting device for network-type equipment, comprising: The voltage difference determination unit is used to determine the real-time effective value of the current of the grid-type equipment and the voltage difference between the grid-connection point voltage and the internal potential of the grid-type equipment by detecting the instantaneous current value of the grid-type equipment and the grid connection point voltage. The voltage increment determination unit is used to calculate the modulation voltage increment of the network-type device based on the virtual resistance if the overcurrent of the network-type device is determined according to the preset overcurrent criterion, the real-time effective value of the current and the voltage difference. A modulation voltage update unit is used to superimpose the modulation voltage increment onto the modulation voltage of the potential plastic current-limited output in the network-type device to obtain an updated modulation voltage. A network device current limiting unit is used to control the current limiting of the network device based on the updated modulation voltage.

[0014] Thirdly, this application provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the network-type device additional current limiting method.

[0015] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the network-type device additional current limiting method.

[0016] Fifthly, this application provides a computer program product, including a computer program / instructions that, when executed by a processor, implement the steps of the network-type device additional current limiting method.

[0017] To address the problems in the prior art, the current limiting method and apparatus for grid-type equipment provided in this application can calculate the modulation voltage increment of the grid-type equipment through a virtual resistance additional control strategy after determining that the grid-type equipment is overcurrent. The modulation voltage increment is then superimposed on the modulation voltage of the internal potential plastic current limiting output to obtain a new modulation voltage. This allows the DC component that appears in the electromagnetic induction process caused by the sudden change in power system voltage to decay as quickly as possible, preventing the converter from breaking down due to overcurrent and ensuring the safety of the grid-type equipment. This enables it to continue to provide maximum support to the entire power system during power system faults. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the network-type device circuit in an embodiment of this application; Figure 2 This is a schematic diagram illustrating the relationship between the network-type device and the system voltage in an embodiment of this application; Figure 3 This is a schematic diagram of the overcurrent of the network-type device in the embodiments of this application; Figure 4 This is a schematic diagram of the overcurrent criterion for a network-type device in an embodiment of this application; Figure 5 This is a schematic diagram of the frequency response characteristics of the low-pass filter in the embodiments of this application; Figure 6 This is a schematic diagram illustrating the virtual resistance calculation process for a network-type device in an embodiment of this application. Figure 7 This refers to the per-unit voltage value at the grid connection point of the grid-connected device in the embodiments of this application; Figure 8 This refers to the effective value of the output current of the network-type device in the embodiments of this application; Figure 9 This is a flowchart of the method for adding current limiting to network-type devices in the embodiments of this application; Figure 10 This is a flowchart illustrating the determination of the real-time effective value of the current and the voltage difference in the embodiments of this application; Figure 11 This is a flowchart for determining the overcurrent of the network-type device in the embodiments of this application; Figure 12 This is a flowchart illustrating the calculation of the modulation voltage increment in an embodiment of this application; Figure 13This is a flowchart illustrating the process of obtaining the updated modulation voltage in an embodiment of this application; Figure 14 This is a flowchart illustrating the current limiting control of network-type devices in the embodiments of this application; Figure 15 This is a structural diagram of the additional current limiting device for the network-type equipment in the embodiments of this application; Figure 16 This is a schematic diagram of the structure of the electronic device in the embodiments of this application; Figure 17 This is a schematic diagram illustrating the expression of the short-circuit current when a three-phase short-circuit fault occurs in the system, as described in this application embodiment. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0021] The information collected in the technical solution of this application is information and data authorized by the user or fully authorized by all parties. The collection, storage, use, processing, transmission, provision, disclosure and application of the relevant data all comply with the relevant laws, regulations and standards of the relevant countries and regions, necessary confidentiality measures have been taken, and they do not violate public order and good morals. Corresponding operation portals are provided for users to choose to authorize or refuse.

[0022] Provide users with corresponding operation entry points, allowing them to choose to agree to or reject the automated decision results; if the user chooses to reject, the process will proceed to the expert decision-making process.

[0023] In one embodiment, see Figure 1 To address the transient overcurrent suppression method based on the virtual impedance reshaping internal potential vector, this application proposes a virtual resistance-added control strategy to suppress the DC component of the current borne by the equipment during system faults. This method includes an additional current limiting method for network-type equipment, comprising: S101: Determine the real-time effective value of the current of the grid-connected equipment and the voltage difference between the grid connection point voltage and the internal potential of the grid-connected equipment by detecting the instantaneous current value of the grid-connected equipment and the grid connection point voltage; S102: If the overcurrent of the network-type device is determined according to the preset overcurrent criterion, the real-time effective value of the current and the voltage difference, calculate the modulation voltage increment of the network-type device based on the virtual resistance; S103: The modulation voltage increment is superimposed on the modulation voltage of the potential-plastic current-limited output in the network-type device to obtain the updated modulation voltage; S104: Control the current limiting of the network-type device based on the updated modulation voltage.

[0024] Understandably, see Figure 1 , Figure 9 This application proposes a virtual resistance-added control strategy for grid-type equipment based on internal potential plasticity virtual resistance current limiting. It determines whether the grid-type equipment is overcurrent by jointly judging voltage and current, and maximizes the utilization rate of its overcurrent capacity during the overcurrent instant through the virtual resistance-added control strategy, thereby maximizing system voltage support and improving the renewable energy transmission capacity of the renewable energy aggregation area.

[0025] A virtual resistance-based control strategy for networked devices, based on current limiting by internal potential-plastic virtual resistance, includes: The first step is to set the overcurrent criteria for network-type devices; The second step is to detect the current of the grid-connected equipment and the voltage at the grid connection point, and to calculate the effective value of the current and the voltage difference in real time. The third step is to determine whether the network-type device is overcurrent based on the set criteria and to calculate the virtual resistance; The fourth step is to calculate the modulation voltage increment of the network-type equipment using a virtual resistor-added control strategy. The fifth step is to add the calculated modulation voltage increment to the modulation voltage of the internal potential plastic current-limited output to obtain a new modulation voltage.

[0026] As can be seen, in the current limiting control process of network-type equipment, when the effective value of the current is detected to exceed the safety threshold, the system first uses the virtual resistance value calculated by the open-loop control of the current as a dynamic compensation quantity. This virtual resistance value is then vector-synthesized with the internal electromotive force (i.e., the original voltage reference signal) generated inside the equipment, thereby adjusting the amplitude and phase angle of the PWM modulation waveform in real time. This adjustment reduces the instantaneous DC current component caused by voltage fluctuations. Especially in systems with weak resistance, the introduction of virtual resistance enhances the adaptability of network-type equipment to the system, avoids overcurrent blocking during large voltage disturbances, and improves the voltage support capability of network-type equipment for the system.

[0027] As can be seen from the above description, the current limiting method for grid-type equipment provided in this application can calculate the modulation voltage increment of the grid-type equipment through a virtual resistance additional control strategy after determining that the grid-type equipment is overcurrent, and then superimpose the modulation voltage increment onto the modulation voltage of the internal potential plastic current limiting output to obtain a new modulation voltage. This allows the DC component that appears in the electromagnetic induction process caused by the sudden change in power system voltage to decay as quickly as possible, avoids the converter from breaking down due to overcurrent, ensures the safety of the grid-type equipment, and enables it to still provide maximum support to the entire power system during power system faults.

[0028] In one embodiment, see Figure 10The step of determining the real-time effective value of the current of the grid-connected equipment and the voltage difference between the grid-connected point voltage and the internal potential of the grid-connected equipment by detecting the instantaneous current value of the grid-connected equipment and the grid connection point voltage includes: S201: Perform root mean square calculation on the instantaneous current value within the sliding window to obtain the real-time effective value of the current; S202: Subtract the voltage at the grid connection point from the potential inside the grid-connected equipment to obtain the voltage difference.

[0029] Understandable, Figure 1 The diagram shown is a typical circuit diagram of a network-type device. The converter is connected to a reactor. Grid connection, It is the internal electromotive force of the network-type equipment. It is the grid connection point voltage of grid-connected equipment. It is the output current of the network-type equipment. It is the equivalent impedance on the system side. It is the system-side voltage.

[0030] If the connection resistance of the grid-connected equipment is ignored, the relationship between the grid connection point voltage, output current, and output voltage of the grid-connected equipment is as follows: Figure 2 As shown. Under normal operating conditions, the internal potential of the grid-type equipment. Almost the same as the grid connection point voltage When in phase, the interaction between grid-connected equipment and the system consists only of reactive power. However, when a system fault occurs, in addition to the grid connection point voltage... In addition to the amplitude drop, internal potential With grid connection point voltage The phase angle between them is also very likely to widen, at which point the internal potential of the grid-type equipment will increase. The sudden and unpredictable nature of these changes can cause the current in network-connected equipment to exceed its tolerance range, resulting in overcurrent. When a three-phase short-circuit fault occurs in the system, the short-circuit current can be expressed as follows: Figure 17 The formula shown illustrates that the current components include a periodic component and a DC decay component. For existing methods using internal potential-based plastic virtual impedance, overcurrent suppression targeting the periodic component refers to... Figure 3 shown E The amplitude and phase angle of the zero phasor change instantaneously; that is, while keeping the starting point of the phasor unchanged, its ending point is made to fall into any position within the pink circle, thereby achieving the purpose of current limiting for the periodic component. The pink circle represents the voltage at the grid connection point after the disturbance. U pccA circle is drawn with the endpoint of the phasor as the center and the product of the device-limited current value and the connection reactance value as the radius. However, the DC attenuation component is not specifically suppressed, which may still cause overcurrent. The embodiments of this application propose a method for suppressing shunt components with virtual resistance based on the existing internal potential plastic virtual impedance method, which can effectively solve the above-mentioned technical problems.

[0031] in, Figure 17 In the formula shown, This represents the instantaneous value of the short-circuit current; This represents the effective value of the steady-state short-circuit current; This represents the effective value of the subtransient short-circuit current; Indicates the system's rated angular frequency; Indicates the initial phase angle of the system voltage; It represents the steady-state impedance angle, that is, the phase angle by which the steady-state short-circuit current lags behind the power supply voltage; Indicates the subtransient impedance angle; This represents the decay time constant.

[0032] In the current monitoring stage, the system first performs a root mean square (RMS) calculation on the instantaneous current value within the sliding window. Through square, average, and square root operations, it calculates the real-time effective current value in real time, ensuring the accuracy and response speed of current detection. Then, in the voltage difference calculation, the system subtracts the grid connection point voltage (actual grid voltage) from the potential within the grid-connected equipment (internal voltage reference signal) to obtain the voltage difference. This voltage difference directly reflects the voltage difference between the output voltage and the grid voltage and is a key parameter for controlling the current output. These two steps together ensure the real-time performance and accuracy of current monitoring and voltage control, providing a reliable data foundation for subsequent current limiting control.

[0033] As can be seen from the above description, the current limiting method for grid-type equipment provided in this application can determine the real-time effective value of the current of the grid-type equipment and the voltage difference between the grid-connection point voltage and the internal potential of the grid-type equipment by detecting the instantaneous current value of the grid-type equipment and the grid connection point voltage.

[0034] In one embodiment, see Figure 11 The step of determining the overcurrent of the network-type equipment based on the preset overcurrent criterion, the real-time effective value of the current, and the voltage difference includes: S301: Determine whether the real-time effective value of the current exceeds the current limit in the overcurrent criterion; if so, determine that the network-type device is overcurrent. S302: Alternatively, determine whether the voltage difference exceeds the voltage difference generated on the connected reactor by the current limit; if so, determine that the network-type equipment is overcurrent.

[0035] Understandably, it's necessary to determine whether current limiting is required at the moment a system fault occurs. One criterion is to directly detect the instantaneous current value to obtain the real-time effective current value, and then determine whether the network-type equipment is experiencing overcurrent based on the current limit in the overcurrent criterion. However, because the harmonics of the three-phase current are relatively large at the moment of a system fault, the accuracy of the measurement is affected, and errors may occur in the calculation.

[0036] In addition, the voltage at the grid connection point can also be used. With the internal potential of the network-type equipment The voltage difference between them is used to determine whether it exceeds the voltage difference generated across the connected reactor due to the current limit. Figure 3 The vector shown Is it greater than .

[0037] The two criteria mentioned above can be used together to determine whether current limiting is required for network-type devices, thus improving the reliability of overcurrent detection. If current limiting is required for network-type devices, the virtual resistor-added control method provided in this application can be used for subsequent processing.

[0038] In other words, if the voltage difference across the connected reactor exceeds the preset maximum value, or if the current output of the grid-type equipment exceeds the maximum current it can withstand, the "current limiting control and virtual resistance additional control strategy" provided in this application can be enabled. Figure 4 The logic block diagram for determining whether to enable the virtual resistor additional control strategy.

[0039] As can be seen from the above description, the network-type device additional current limiting method provided in this application can determine the overcurrent of the network-type device based on the preset overcurrent criterion, the real-time effective value of the current, and the voltage difference.

[0040] In one embodiment, see Figure 12 The calculation of the modulation voltage increment of the network-type device based on virtual resistance includes: S401: Calculate the ratio of the real-time effective value of the current to the current limit to obtain the current ratio value; S402: The product of the current ratio and the virtual resistance coefficient is determined as the virtual resistance of the network-type device; S403: The product of the instantaneous current value and the virtual resistance is determined as the modulation voltage increment; wherein, the instantaneous current value includes the three-phase current instantaneous value; the modulation voltage increment includes the three-phase modulation voltage increment.

[0041] Understandably, in the current limiting control process of grid-connected equipment, the system first calculates the real-time effective value of the current using a sliding window root mean square algorithm, and then compares (divides) this value with a preset current limit to obtain the current ratio. This ratio directly reflects the degree to which the current exceeds the safe threshold. Next, the current ratio is multiplied by a virtual resistance coefficient to determine the virtual resistance value of the grid-connected equipment. This coefficient is typically set to 1-2 to dynamically adjust the system impedance, ensuring that the current limiting response matches the degree of current overshoot. Finally, the instantaneous values ​​of the three-phase currents are multiplied by the virtual resistance to calculate the three-phase modulation voltage increments. These increments are then used by the voltage outer loop controller to adjust the amplitude and phase of the PWM modulation waveform in real time, reducing the voltage difference between the output voltage and the grid voltage, thereby naturally suppressing current growth. The entire process achieves smooth and continuous current limiting control, avoiding sudden current changes and system oscillations, while maintaining grid voltage stability, providing a reliable guarantee for high-proportion renewable energy integration.

[0042] Prior to this, the grid connection point voltage and output current of the grid-connected equipment are monitored in real time. The difference between the grid connection point voltage and the internal potential is calculated according to formula (1), and the real-time effective value of the output current is calculated according to formula (2).

[0043] (1) (2) In the formula, Indicates the grid connection point voltage of grid-connected equipment d Axial components; Indicates the internal potential and voltage of network-type equipment d Axial components; Indicates the grid connection point voltage of grid-connected equipment q Axial components; Indicates the internal potential and voltage of network-type equipment q Axial components; It represents the difference between the grid connection point voltage and the internal potential voltage, that is, the voltage difference generated on the connected reactor; This indicates the effective value of the grid-connected current for grid-connected equipment. , and These represent the instantaneous values ​​of the currents in phases A, B, and C, respectively.

[0044] The kHz harmonics are filtered out by a first-order low-pass filter. The filter can use the transfer function shown in equation (3). G ( s ).

[0045] (3)

[0046] In the formula, TLet represent the time constant of the first-order low-pass filter, and s be the Laplace transform operator. T The selection of the frequency response characteristic takes into account that it does not affect the input of the mains frequency, while filtering out harmonics of the kHz switching frequency. T=0.001s is set, and its frequency response characteristic is described in [reference needed]. Figure 5 As shown, the cutoff frequency is approximately 158Hz, which meets the setting requirements.

[0047] After obtaining the real-time effective value of the current, according to Figure 6 The virtual resistance calculation process shown calculates the virtual resistance. VR The virtual resistance coefficient is... Next, multiply by the network-type equipment. abc The three-phase currents are given by equation (4). abc Three-phase modulation voltage increment.

[0048] (4)

[0049] In the formula, VR Indicates virtual resistance; , and These represent the instantaneous values ​​of the currents in phases A, B, and C, respectively. , and These represent the modulated voltage with added A-phase, B-phase, and C-phase components obtained through current open-loop control, respectively.

[0050] As can be seen from the above description, the current limiting method for network-type devices provided in this application can calculate the modulation voltage increment of the network-type device based on virtual resistance.

[0051] In one embodiment, see Figure 13 The step of superimposing the modulation voltage increment onto the modulation voltage of the potential-plastic current-limited output within the network-type device to obtain the updated modulation voltage includes: S501: Determine the internal potential of the network-type equipment based on the internal potential relationship expression in the network-type equipment control model. dq Quantity; S502: According to the above dq The components determine the three-phase coordinate components of the potential within the network-type equipment; S503: The three-phase modulation voltage increment is superimposed on the three-phase coordinate components to obtain the updated modulation voltage.

[0052] It is understandable that the modulation voltage increment obtained by virtual resistor additional control has been determined in the previous steps, and it is superimposed on the original modulation voltage in this step.

[0053] The mathematical model for the control of network-type devices is shown in equation (5).

[0054] (5)

[0055] In the formula, The phase angle for outputting the internal potential of network-type equipment; For grid-connected equipment; This represents the target active power value for network-type equipment; This represents the measured active power output value of the network-type equipment; Indicates the damping of the network-type equipment; Indicates the reference angular frequency of the network-type equipment; This indicates the actual angular frequency of the network-type equipment; This indicates the amplitude of the output internal potential of a network-type device; This indicates the target value of the grid-connected voltage for grid-connected equipment; This indicates the actual value of the grid-connected voltage of the grid-connected equipment; This indicates the target reactive power value for network-type equipment; This represents the measured reactive power output value of the network-type equipment; This represents the proportional coefficient for voltage loop control in network-type equipment; This represents the proportional coefficient for reactive power loop control of network-type equipment.

[0056] Based on the mathematical model of equation (5), Direction allows the internal potential to be converted from amplitude to phase. dq Axial components and ,Right now , , .

[0057] Then the internal potential in the dq coordinates is inversely transformed by the transformation matrix shown in equation (6) to... abc In coordinate system, we obtain , and .

[0058] (6)

[0059] After inverse transformation, we obtain abc coordinate system , and The modulation voltage increment in equation (4) is superimposed on the original modulation voltage, and the final modulation voltage is as shown in equation (7).

[0060] (7)

[0061] In the formula, , and These represent the A-phase, B-phase, and C-phase components of the original modulation voltage of the network-type equipment, respectively. , and These represent the modulated voltage with added A-phase, B-phase, and C-phase components obtained through current open-loop control, respectively. , and These represent the A-phase, B-phase, and C-phase components of the new modulation voltage for network-type equipment, respectively.

[0062] Taking a grid-connected device with a capacity of 20Mvar and a connection point voltage of 16kV as an example, its rated current is 0.72kA, and the device has a three-fold overcurrent capacity. When a system fault occurs, the voltage drop is as follows: Figure 7 As shown, the output current of the network-type device before and after adopting the aforementioned virtual resistor-added control strategy is as follows: Figure 8 As shown, without the virtual resistance control strategy, the instantaneous output current during a fault reaches 5.78kA, while with the virtual resistance control strategy, the instantaneous output current during a fault is only 3.90kA, effectively reducing the risk of equipment breakdown and proving the effectiveness of this patent.

[0063] As can be seen from the above description, the current limiting method for network-type devices provided in this application can superimpose the modulation voltage increment onto the modulation voltage of the potential plastic current limiting output in the network-type device to obtain an updated modulation voltage.

[0064] In one embodiment, see Figure 14 The current limiting of the network-type device based on the updated modulation voltage includes: S601: Generate a corresponding pulse width modulation waveform based on the updated modulation voltage; S602: The instantaneous voltage value of the grid-connected device is adjusted using the pulse width modulation waveform, and the voltage difference between the instantaneous voltage value and the grid connection point voltage is reduced to achieve smooth current limiting.

[0065] Understandably, in the current limiting control process of grid-connected equipment, the system first generates a corresponding pulse width modulation (PWM) waveform based on the updated modulation voltage. This waveform precisely controls the on / off timing of power devices by adjusting the duty cycle and frequency of the pulses, thereby generating a voltage output signal that meets the requirements. Then, the instantaneous voltage value of the grid-connected equipment is dynamically adjusted using the PWM waveform. By adjusting the amplitude and phase of the output voltage in real time, the voltage difference between the output voltage and the grid connection point voltage is gradually reduced. This process is based on Ohm's law; when the voltage difference between the output voltage and the grid voltage decreases, the output current naturally decreases, achieving a smooth and continuous current limiting effect. Through the precise control of the PWM waveform, the system avoids current surges and system oscillations in traditional current limiting methods, while maintaining the stability of the grid voltage, providing reliable dynamic support for high-proportion renewable energy integration.

[0066] As can be seen from the above description, the current limiting method for network-type devices provided in this application can control the current limiting of the network-type devices based on the updated modulation voltage.

[0067] Based on the same inventive concept, this application also provides a current limiting device for network-type devices, which can be used to implement the method described in the above embodiments, as shown in the following embodiments. Since the principle of the current limiting device for network-type devices in solving the problem is similar to that of the current limiting method for network-type devices, the implementation of the current limiting device for network-type devices can refer to the implementation of the method based on software performance benchmarks, and will not be repeated. As used below, the terms "unit" or "module" can refer to a combination of software and / or hardware that implements a predetermined function. Although the system described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0068] In one embodiment, see Figure 15 To address the transient overcurrent suppression method based on the virtual impedance reshaping internal potential vector, this application proposes a virtual resistance-added control strategy to suppress the DC component of the current borne by the equipment during system faults. This strategy includes an additional current-limiting device for network-type equipment, comprising: The voltage difference determination unit 701 is used to determine the real-time effective value of the current of the grid-type equipment and the voltage difference between the grid-connection point voltage and the internal potential of the grid-type equipment by detecting the instantaneous current value of the grid-type equipment and the grid connection point voltage. The voltage increment determination unit 702 is used to calculate the modulation voltage increment of the network-type device based on the virtual resistance if the overcurrent of the network-type device is determined according to the preset overcurrent criterion, the real-time effective value of the current and the voltage difference. The modulation voltage update unit 703 is used to superimpose the modulation voltage increment onto the modulation voltage of the potential plastic current-limited output in the network-type device to obtain the updated modulation voltage. The network device current limiting unit 704 is used to control the current limiting of the network device based on the updated modulation voltage.

[0069] From a hardware perspective, in order to propose a virtual resistance-added control strategy based on the internal potential vector reshaping virtual impedance transient overcurrent suppression method to suppress the DC component of the current borne by the device during system faults, this application provides an embodiment of an electronic device for implementing all or part of the above-mentioned network-type device additional current limiting method. The electronic device specifically includes the following: The system comprises a processor, a memory, a communications interface, and a bus; wherein the processor, memory, and communications interface communicate with each other via the bus; the communications interface is used to realize information transmission between the network-type device's additional rate limiting device and core business systems, user terminals, and related databases; the logic controller can be a desktop computer, tablet computer, or mobile terminal, etc., and this embodiment is not limited to these. In this embodiment, the logic controller can be implemented with reference to the embodiments of the network-type device's additional rate limiting method and the network-type device's additional rate limiting device, the content of which is incorporated herein, and repeated details will not be described again.

[0070] It is understood that the user terminal may include smartphones, tablet computers, network set-top boxes, portable computers, desktop computers, personal digital assistants (PDAs), in-vehicle devices, smart wearable devices, etc. Among these, the smart wearable devices may include smart glasses, smartwatches, smart bracelets, etc.

[0071] In practical applications, the additional rate limiting method for network-based devices can be executed on the electronic device side as described above, or all operations can be completed in the client device. The choice can be made based on the processing power of the client device and the limitations of the user's usage scenario. This application does not impose any limitations on this. If all operations are completed in the client device, the client device may further include a processor.

[0072] The aforementioned client device may have a communication module (i.e., a communication unit) that can communicate with a remote server to achieve data transmission. The server may include a server on the task scheduling center side; in other implementation scenarios, it may also include a server on an intermediate platform, such as a server on a third-party server platform that has a communication link with the task scheduling center server. The server may include a single computer device, a server cluster consisting of multiple servers, or a distributed server structure.

[0073] Figure 16 This is a schematic block diagram illustrating the system configuration of the electronic device 9600 according to an embodiment of this application. Figure 16 As shown, the electronic device 9600 may include a central processing unit 9100 and a memory 9140; the memory 9140 is coupled to the central processing unit 9100. It is worth noting that... Figure 16 This is an example; other types of structures can also be used to supplement or replace this structure to achieve telecommunications functions or other functions.

[0074] In one embodiment, the additional current limiting method functionality for network-connected devices can be integrated into the central processing unit 9100. The central processing unit 9100 can be configured to perform the following control: S101: Determine the real-time effective value of the current of the grid-connected equipment and the voltage difference between the grid connection point voltage and the internal potential of the grid-connected equipment by detecting the instantaneous current value of the grid-connected equipment and the grid connection point voltage; S102: If the overcurrent of the network-type device is determined according to the preset overcurrent criterion, the real-time effective value of the current and the voltage difference, calculate the modulation voltage increment of the network-type device based on the virtual resistance; S103: The modulation voltage increment is superimposed on the modulation voltage of the potential-plastic current-limited output in the network-type device to obtain the updated modulation voltage; S104: Control the current limiting of the network-type device based on the updated modulation voltage.

[0075] As can be seen from the above description, the current limiting method for grid-type equipment provided in this application can calculate the modulation voltage increment of the grid-type equipment through a virtual resistance additional control strategy after determining that the grid-type equipment is overcurrent, and then superimpose the modulation voltage increment onto the modulation voltage of the internal potential plastic current limiting output to obtain a new modulation voltage. This allows the DC component that appears in the electromagnetic induction process caused by the sudden change in power system voltage to decay as quickly as possible, avoids the converter from breaking down due to overcurrent, ensures the safety of the grid-type equipment, and enables it to still provide maximum support to the entire power system during power system faults.

[0076] In another embodiment, the network-type device additional current limiting device can be configured separately from the central processing unit 9100. For example, the data composite transmission device network-type device additional current limiting device can be configured as a chip connected to the central processing unit 9100, and the function of the network-type device additional current limiting method can be realized through the control of the central processing unit.

[0077] like Figure 16 As shown, the electronic device 9600 may further include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It is worth noting that the electronic device 9600 does not necessarily need to include these components. Figure 16 All components shown; in addition, the electronic device 9600 may also include Figure 16 For components not shown, please refer to existing technology.

[0078] like Figure 16 As shown, the central processing unit 9100, sometimes also referred to as a controller or operating control, may include a microprocessor or other processor device and / or logic device, which receives inputs and controls the operation of various components of the electronic device 9600.

[0079] The memory 9140 may be, for example, one or more of a cache, flash memory, hard drive, removable media, volatile memory, non-volatile memory, or other suitable devices. It may store the aforementioned failure-related information, and also store a program for executing that information. The central processing unit 9100 may execute the program stored in the memory 9140 to perform information storage or processing, etc.

[0080] Input unit 9120 provides input to central processing unit 9100. Input unit 9120 may be, for example, a keypad or touch input device. Power supply 9170 provides power to electronic device 9600. Display 9160 displays images and text. Display may be, for example, an LCD display, but is not limited thereto.

[0081] The memory 9140 can be a solid-state memory, such as a read-only memory (ROM), random access memory (RAM), a SIM card, etc. It can also be a memory that retains information even when power is off, can be selectively erased, and contains more data; examples of this type of memory are sometimes referred to as EPROMs. The memory 9140 can also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 may include an application / function storage unit 9142 for storing application programs and function programs or processes for executing the operation of the electronic device 9600 via the central processing unit 9100.

[0082] The memory 9140 may also include a data storage unit 9143 for storing data, such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 may include various drivers for the electronic device's communication functions and / or for performing other functions of the electronic device (such as messaging applications, address book applications, etc.).

[0083] The communication module 9110 is a transmitter / receiver that sends and receives signals via the antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processing unit 9100 to provide input signals and receive output signals, which is the same as in a conventional mobile communication terminal.

[0084] Based on different communication technologies, multiple communication modules 9110 can be configured in the same electronic device, such as cellular network modules, Bluetooth modules, and / or wireless LAN modules. The communication module (transmitter / receiver) 9110 is also coupled to a speaker 9131 and a microphone 9132 via an audio processor 9130 to provide audio output via the speaker 9131 and receive audio input from the microphone 9132, thereby realizing typical telecommunications functions. The audio processor 9130 may include any suitable buffer, decoder, amplifier, etc. Additionally, the audio processor 9130 is also coupled to a central processing unit 9100, enabling on-device recording via the microphone 9132 and on-device playback of stored sound via the speaker 9131.

[0085] Embodiments of this application also provide a computer-readable storage medium capable of implementing all steps of the rate limiting method for network-based devices with server or client execution subjects in the above embodiments. The computer-readable storage medium stores a computer program that, when executed by a processor, implements all steps of the rate limiting method for network-based devices with server or client execution subjects in the above embodiments. For example, when the processor executes the computer program, it implements the following steps: S101: Determine the real-time effective value of the current of the grid-connected equipment and the voltage difference between the grid connection point voltage and the internal potential of the grid-connected equipment by detecting the instantaneous current value of the grid-connected equipment and the grid connection point voltage; S102: If the overcurrent of the network-type device is determined according to the preset overcurrent criterion, the real-time effective value of the current and the voltage difference, calculate the modulation voltage increment of the network-type device based on the virtual resistance; S103: The modulation voltage increment is superimposed on the modulation voltage of the potential-plastic current-limited output in the network-type device to obtain the updated modulation voltage; S104: Control the current limiting of the network-type device based on the updated modulation voltage.

[0086] As can be seen from the above description, the current limiting method for grid-type equipment provided in this application can calculate the modulation voltage increment of the grid-type equipment through a virtual resistance additional control strategy after determining that the grid-type equipment is overcurrent, and then superimpose the modulation voltage increment onto the modulation voltage of the internal potential plastic current limiting output to obtain a new modulation voltage. This allows the DC component that appears in the electromagnetic induction process caused by the sudden change in power system voltage to decay as quickly as possible, avoids the converter from breaking down due to overcurrent, ensures the safety of the grid-type equipment, and enables it to still provide maximum support to the entire power system during power system faults.

[0087] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0088] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (devices), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0089] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0090] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0091] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for additional current limiting in a network-type device, characterized in that, include: The real-time effective value of the current of the grid-connected equipment and the voltage difference between the grid connection point voltage and the internal potential of the grid-connected equipment are determined by detecting the instantaneous current value of the grid-connected equipment and the grid connection point voltage. If the overcurrent of the network-type device is determined based on the preset overcurrent criterion, the real-time effective value of the current, and the voltage difference, the modulation voltage increment of the network-type device based on the virtual resistance is calculated. The modulation voltage increment is superimposed on the modulation voltage of the potential-plastic current-limited output in the network-type device to obtain the updated modulation voltage; The current limiting of the network-type equipment is controlled based on the updated modulation voltage.

2. The method for additional current limiting in network-type equipment according to claim 1, characterized in that, The method of determining the real-time effective value of the current of the grid-connected equipment and the voltage difference between the grid connection point voltage and the internal potential of the grid-connected equipment by detecting the instantaneous current value of the grid-connected equipment and the grid connection point voltage includes: The real-time effective value of the current is obtained by performing a sliding window root mean square operation on the instantaneous current value within the sliding window; The voltage difference is obtained by subtracting the voltage at the grid connection point from the potential inside the grid-connected equipment.

3. The method for additional current limiting in network-type equipment according to claim 1, characterized in that, The step of determining the overcurrent of the network-type equipment based on the preset overcurrent criterion, the real-time effective value of the current, and the voltage difference includes: Determine whether the real-time effective value of the current exceeds the current limit in the overcurrent criterion; if so, determine that the network-type device is overcurrent. Alternatively, determine whether the voltage difference exceeds the voltage difference generated on the connected reactor by the current limit; if so, determine that the network-type equipment is overcurrent.

4. The method for additional current limiting in network-type equipment according to claim 3, characterized in that, The calculation of the modulation voltage increment of the network-type device based on virtual resistance includes: Calculate the ratio of the real-time effective value of the current to the current limit to obtain the current ratio value; The product of the current ratio and the virtual resistance coefficient is determined as the virtual resistance of the network-type device; The product of the instantaneous current value and the virtual resistance is determined as the modulation voltage increment; wherein, the instantaneous current value includes the three-phase current instantaneous value; and the modulation voltage increment includes the three-phase modulation voltage increment.

5. The method for additional current limiting in a network-type device according to claim 4, characterized in that, The step of superimposing the modulation voltage increment onto the modulation voltage of the potential-limited current output within the network-type device to obtain the updated modulation voltage includes: The internal potential of the network-type equipment is determined based on the internal potential relationship expression in the control model of the network-type equipment. dq Quantity; According to the above dq The components determine the three-phase coordinate components of the potential within the network-type equipment; The three-phase modulation voltage increment is superimposed onto the three-phase coordinate components to obtain the updated modulation voltage.

6. The method for additional current limiting in network-type equipment according to claim 1, characterized in that, The current limiting of the network-type device based on the updated modulation voltage includes: Generate a corresponding pulse width modulation waveform based on the updated modulation voltage; The instantaneous voltage value of the grid-connected device is adjusted using the pulse width modulation waveform, and the voltage difference between the instantaneous voltage value and the grid connection point voltage is reduced to achieve smooth current limiting.

7. A current limiting device for a network-type equipment, characterized in that, include: The voltage difference determination unit is used to determine the real-time effective value of the current of the grid-type equipment and the voltage difference between the grid-connection point voltage and the internal potential of the grid-type equipment by detecting the instantaneous current value of the grid-type equipment and the grid connection point voltage. The voltage increment determination unit is used to calculate the modulation voltage increment of the network-type device based on the virtual resistance if the overcurrent of the network-type device is determined according to the preset overcurrent criterion, the real-time effective value of the current and the voltage difference. A modulation voltage update unit is used to superimpose the modulation voltage increment onto the modulation voltage of the potential plastic current-limited output in the network-type device to obtain an updated modulation voltage. A network device current limiting unit is used to control the current limiting of the network device based on the updated modulation voltage.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the network-type device additional current limiting method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the additional current limiting method for network-type devices as described in any one of claims 1 to 6.

10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps of the additional current limiting method for network-type devices as described in any one of claims 1 to 6.

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