Zero-sequence circulating current suppression method and system for alternating-current and direct-current hybrid power grid

Abstract

The invention discloses a zero-sequence circulating current suppression method and system for an alternating-current and direct-current hybrid power grid, and relates to the technical field of zero-sequence circulating current suppression. Three-phase current measurement data of the alternating-current and direct-current hybrid power grid and zero-sequence operation data of each converter are obtained, regulation and control analysis is carried out according to the three-phase current measurement data and each zero-sequence operation data, and a zero-sequence circulating current suppression result is obtained; the method comprises the steps of obtaining a corresponding control strategy and a zero-sequence current, performing collaborative prediction modulation processing based on the control strategy, the zero-sequence current and the zero-sequence operation data to obtain corresponding switch state data and a target virtual admittance value, and adopting the switch state data and the target virtual admittance to regulate and control the alternating-current and direct-current hybrid power grid. The technical problems that according to a traditional zero-sequence commutation suppression method, all controllers are subjected to collaborative optimization mainly through model prediction control, but the calculation complexity is high, collaborative optimization of multiple converters is difficult to achieve under the condition that hardware resources are limited, and the operation reliability of an alternating current and direct current hybrid power grid is reduced are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of zero-sequence circulating current suppression, and in particular to a method and system for suppressing zero-sequence circulating current in an AC / DC hybrid power grid. Background Art

[0002] In hybrid AC / DC power grids, when multiple converters operate in parallel, zero-sequence circulating current (CCC) can occur due to inconsistent hardware parameters, asynchronous control signals, and system imbalance. This CCC not only increases system losses and causes equipment overheating, but can also trigger malfunctioning protection devices, threatening the safe and stable operation of the power grid.

[0003] At present, the traditional zero-sequence commutation suppression method mainly uses model predictive control to collaboratively optimize various controllers. However, the computational complexity is high, and it is difficult to achieve multi-converter collaborative optimization under conditions of limited hardware resources, which reduces the reliability of AC / DC hybrid power grid operation. Summary of the Invention

[0004] The present invention provides a method and system for suppressing zero-sequence circulating current in an AC / DC hybrid power grid, which solves the technical problem that traditional zero-sequence commutation suppression methods mainly use model predictive control to collaboratively optimize various controllers, but have high computational complexity, making it difficult to achieve collaborative optimization of multiple converters under conditions of limited hardware resources, thereby reducing the reliability of AC / DC hybrid power grid operation.

[0005] A first aspect of the present invention provides a method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid, comprising:

[0006] Acquire three-phase current measurement data of the AC / DC hybrid power grid and zero-sequence operation data of each converter, perform regulation and analysis based on the three-phase current measurement data and each zero-sequence operation data, and obtain corresponding control strategies and zero-sequence currents;

[0007] Performing collaborative prediction and modulation processing based on the control strategy, the zero-sequence current, and the zero-sequence operation data to obtain corresponding switch state data and a target virtual admittance value;

[0008] The AC / DC hybrid power grid is regulated using the switch state data and the target virtual admittance.

[0009] Optionally, the three-phase current measurement data includes a first-phase current value, a second-phase current value, and a third-phase current value, and the step of performing regulation and analysis based on the three-phase current measurement data and each of the zero-sequence operation data to obtain a corresponding control strategy includes:

[0010] Performing averaging processing on the first phase current value, the second phase current value, and the third phase current value to obtain a first average value;

[0011] performing mean processing on the zero-sequence current of the converter of each zero-sequence operation data to obtain a second mean value;

[0012] Performing difference processing on the first mean value and the second mean value to obtain a zero-sequence current, and performing absolute value processing on the zero-sequence current to obtain a zero-sequence current amplitude;

[0013] generating a corresponding target key by using the zero-sequence current amplitude and each of the zero-sequence operation data;

[0014] The target key is used to retrieve a preset control strategy key-value pair list to match the corresponding control strategy.

[0015] Optionally, the step of performing collaborative predictive modulation processing based on the control strategy, the zero-sequence current, and the zero-sequence operation data to obtain corresponding switch state data and a target virtual admittance value includes:

[0016] When the control strategy is the first control strategy, a weighted operation is performed on the pre-acquired control virtual admittance and the preset initial virtual admittance reference value based on the preset admittance weight to obtain a corresponding target virtual admittance value;

[0017] Using the preset first weight as the target weight;

[0018] When the control strategy is the second control strategy, the preset second weight is used as the target weight;

[0019] performing admittance compensation processing on the pre-acquired control virtual admittance according to the zero-sequence current to obtain a target virtual admittance value;

[0020] When the control strategy is the third control strategy, adaptive adjustment processing is performed on the pre-acquired control virtual admittance and control weight coefficient according to the zero-sequence current to obtain corresponding target weight and target virtual admittance value;

[0021] The target weight and each of the zero-sequence operation data are input into a preset collaborative predictive control function to obtain switch state data.

[0022] Optionally, the step of performing admittance compensation processing on the pre-acquired control virtual admittance according to the zero-sequence current to obtain a target virtual admittance value includes:

[0023] Inputting the pre-acquired control virtual admittance and the zero-sequence current into a preset admittance setting function to obtain a virtual admittance setting value;

[0024] Inputting the zero-sequence current into a preset admittance compensation function to obtain a corresponding virtual admittance compensation amount;

[0025] The virtual admittance compensation amount and the virtual admittance setting value are added together to obtain a target virtual admittance value.

[0026] Optionally, the step of adaptively adjusting the pre-acquired control virtual admittance and control weight coefficient according to the zero-sequence current to obtain corresponding target weight and target virtual admittance value includes:

[0027] Performing dynamic weight adjustment according to the zero-sequence current to obtain a corresponding target weight;

[0028] Inputting each of the zero-sequence operation data into a preset correction function to obtain a plurality of corrected zero-sequence operation data;

[0029] The pre-acquired control virtual admittance and the zero-sequence current are input into a preset admittance setting function to obtain a virtual admittance setting value, and the virtual admittance setting value is used as a target virtual admittance value.

[0030] Optionally, the step of dynamically adjusting the weight according to the zero-sequence current to obtain a corresponding target weight includes:

[0031] Determining whether the absolute value of the zero-sequence current is greater than a preset reference zero-sequence current value;

[0032] If the absolute value of the zero-sequence current is greater than the reference zero-sequence current value, determining a preset first reference weight coefficient as the first weight coefficient;

[0033] If the absolute value of the zero-sequence current is less than or equal to the reference zero-sequence current value, inputting the zero-sequence current into a preset weight coefficient adjustment function to obtain a first weight coefficient;

[0034] Performing difference processing on a preset second reference weight coefficient and the first weight coefficient to obtain a second weight coefficient;

[0035] Multiplying a preset third reference weight coefficient by the first weight coefficient to obtain a third weight coefficient;

[0036] The first weight coefficient, the second weight coefficient, and the third weight coefficient are normalized to obtain corresponding target weights.

[0037] A second aspect of the present invention provides a zero-sequence circulating current suppression system for an AC / DC hybrid power grid, comprising:

[0038] An analysis module is used to obtain three-phase current measurement data of the AC / DC hybrid power grid and zero-sequence operation data of each converter, and perform regulation and analysis based on the three-phase current measurement data and each zero-sequence operation data to obtain a corresponding control strategy and zero-sequence current;

[0039] a modulation module, configured to perform collaborative predictive modulation processing based on the control strategy, the zero-sequence current, and the zero-sequence operation data to obtain corresponding switch state data and a target virtual admittance value;

[0040] A control module is used to control the AC / DC hybrid power grid using the switch state data and the target virtual admittance.

[0041] A third aspect of the present invention provides an electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor performs the steps of the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid as described in any one of the above items.

[0042] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid as described in any one of the above items.

[0043] A fifth aspect of the present invention provides a computer program product, comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid as described in any one of the above items.

[0044] It can be seen from the above technical solutions that the present invention has the following advantages:

[0045] The present invention performs control analysis based on three-phase current measurement data and each zero-sequence operation data to obtain a corresponding control strategy and zero-sequence current, performs collaborative prediction and modulation processing based on the control strategy, zero-sequence current and zero-sequence operation data, obtains corresponding switch state data and target virtual admittance value, and uses the switch state data and target virtual admittance to control the AC / DC hybrid power grid. This overcomes the traditional zero-sequence commutation suppression method, which mainly uses model predictive control to perform collaborative optimization of each controller, but has high computational complexity and is difficult to achieve multi-converter collaborative optimization under limited hardware resource conditions, thereby reducing the reliability of AC / DC hybrid power grid operation. Compared with the traditional zero-sequence commutation suppression method, the present invention performs control analysis based on three-phase current measurement data and each zero-sequence operation data to obtain a corresponding control strategy and zero-sequence current, and then performs collaborative prediction and modulation processing based on the control strategy, zero-sequence current and zero-sequence operation data to obtain corresponding switch state data and target virtual admittance value, thereby achieving multi-converter zero-sequence circulating current collaborative suppression under limited hardware resource conditions, thereby improving the reliability of AC / DC hybrid power grid operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 A flowchart of a method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid provided in the first embodiment of the present invention;

[0048] Figure 2 A flowchart of a method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid provided in a second embodiment of the present invention;

[0049] Figure 3 This is a structural block diagram of a zero-sequence circulating current suppression system for an AC / DC hybrid power grid provided in a third embodiment of the present invention;

[0050] Figure 4 This is a structural block diagram of a computer device provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0051] An embodiment of the present invention provides a method and system for suppressing zero-sequence circulating current in an AC / DC hybrid power grid, which is used to solve the technical problem that traditional zero-sequence commutation suppression methods mainly use model predictive control to collaboratively optimize various controllers, but have high computational complexity and are difficult to achieve multi-converter collaborative optimization under conditions of limited hardware resources, thereby reducing the reliability of AC / DC hybrid power grid operation.

[0052] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0053] See also Figure 1 , Figure 1 This is a flowchart of the steps of a method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid provided in Example 1 of the present invention.

[0054] The present invention provides a method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid, comprising:

[0055] Step 101: Acquire three-phase current measurement data of the AC / DC hybrid power grid and zero-sequence operation data of each converter, perform regulation and analysis based on the three-phase current measurement data and each zero-sequence operation data, and obtain a corresponding control strategy and zero-sequence current;

[0056] The three-phase current measurement data refers to the three-phase original current values (the first phase current value i a , the second phase current value i b , the third phase current value i c ).

[0057] Zero-sequence operating data refers to real-time monitoring and control parameters related to zero-sequence circulating current suppression in AC / DC hybrid power grids. Specifically, it includes each converter's zero-sequence current, current change rate, impedance deviation, duration, angular frequency, zero-sequence impedance value, real-time active power, switch state change, and instantaneous zero-sequence current.

[0058] Control strategy refers to the control method under different operating conditions of AC / DC hybrid power grid.

[0059] Zero-sequence current refers to the circulating current component generated by the unbalanced condition of the parallel converter system in the AC / DC hybrid power grid.

[0060] An AC / DC hybrid grid refers to a composite power system architecture that integrates AC and DC transmission technologies. The AC side of the hybrid power system architecture is a traditional industrial frequency AC network, while the DC side utilizes a medium / high voltage DC busbar (e.g., ±10kV to ±350kV) based on power electronic converters. Key nodes in the hybrid power system architecture utilize parallel converter groups to achieve bidirectional AC / DC power flow and dynamic decoupling.

[0061] In an embodiment of the present invention, three-phase current measurement data of an AC / DC hybrid power grid and zero-sequence operation data of each converter are obtained, the first-phase current value, the second-phase current value, the third-phase current value of the three-phase current measurement data and the zero-sequence current of the converter of each zero-sequence operation data are input into a preset zero-sequence current function to obtain the zero-sequence current, and the zero-sequence current is processed by absolute value to obtain the zero-sequence current amplitude. The zero-sequence current amplitude and each zero-sequence operation data are used to generate a corresponding target key, and the target key is used to retrieve a preset control strategy key-value pair list to match the corresponding control strategy.

[0062] It should be noted that the zero-sequence current function is specifically:

[0063]

[0064] in, is the zero sequence current, is the total number of converters, is the zero-sequence current of the converter, k is the converter number, i a is the first phase current value, i b is the second phase current value, i c is the third phase current value.

[0065] Step 102: Perform collaborative prediction modulation processing based on the control strategy, zero-sequence current, and zero-sequence operation data to obtain corresponding switch state data and target virtual admittance value;

[0066] Switch status data refers to the on / off status of each converter in the AC / DC hybrid power grid.

[0067] The target virtual admittance value refers to the impedance parameter dynamically generated by the control algorithm, which is used to actively compensate for the circulating current in the zero-sequence loop.

[0068] In an embodiment of the present invention, when the control strategy is the first control strategy, a weighted operation is performed on the pre-acquired control virtual admittance and the pre-acquired initial virtual admittance reference value based on the preset admittance weight to obtain a corresponding target virtual admittance value, and the preset first weight is used as the target weight. When the control strategy is the second control strategy, the preset second weight is used as the target weight, and the pre-acquired control virtual admittance is subjected to admittance compensation processing based on the zero-sequence current to obtain the target virtual admittance value. When the control strategy is the third control strategy, the pre-acquired control virtual admittance and the control weight coefficient are adaptively adjusted based on the zero-sequence current to obtain the corresponding target weight and target virtual admittance value. The target weight and each zero-sequence operating data are input into a preset collaborative predictive control function to obtain switch state data.

[0069] Step 103: Use the switch state data and the target virtual admittance to regulate the AC / DC hybrid power grid.

[0070] In an embodiment of the present invention, each converter in the AC / DC hybrid power grid is adjusted according to the switch state data, and the target virtual admittance is injected into the zero-sequence commutation path of the AC / DC hybrid power grid.

[0071] In an embodiment of the present invention, a control strategy and zero-sequence current are obtained by performing a control analysis based on three-phase current measurement data and various zero-sequence operating data. A coordinated prediction and modulation process is then performed based on the control strategy, zero-sequence current, and zero-sequence operating data to obtain corresponding switch state data and a target virtual admittance value. The switch state data and the target virtual admittance are then used to control the AC / DC hybrid power grid. This overcomes the problem that traditional zero-sequence commutation suppression methods primarily use model predictive control to coordinately optimize various controllers, but this method has high computational complexity and is difficult to achieve multi-converter coordinated optimization under limited hardware resource conditions, thereby reducing the reliability of AC / DC hybrid power grid operation. Unlike traditional zero-sequence commutation suppression methods, the present invention performs a control analysis based on three-phase current measurement data and various zero-sequence operating data to obtain corresponding control strategies and zero-sequence currents. Furthermore, a coordinated prediction and modulation process is performed based on the control strategy, zero-sequence current, and zero-sequence operating data to obtain corresponding switch state data and a target virtual admittance value. This method achieves coordinated suppression of zero-sequence circulating currents in multiple converters under limited hardware resource conditions, thereby improving the reliability of AC / DC hybrid power grid operation.

[0072] See also Figure 2 , Figure 2 This is a flowchart of the steps of a method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid provided in Embodiment 2 of the present invention.

[0073] The present invention provides a method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid, comprising:

[0074] Step 201: Acquire three-phase current measurement data of the AC / DC hybrid power grid and zero-sequence operation data of each converter, perform regulation and analysis based on the three-phase current measurement data and each zero-sequence operation data, and obtain corresponding control strategies and zero-sequence currents;

[0075] Furthermore, the three-phase current measurement data includes a first-phase current value, a second-phase current value, and a third-phase current value. Step 201 includes the following sub-steps:

[0076] S11, performing average processing on the first phase current value, the second phase current value, and the third phase current value to obtain a first average value;

[0077] In the embodiment of the present invention, the average values of the first phase current value, the second phase current value, and the third phase current value are calculated to obtain a first average value.

[0078] S12, performing mean processing on the zero-sequence current of the converter of each zero-sequence operation data to obtain a second mean value;

[0079] In the embodiment of the present invention, the average value between the zero-sequence currents of the converters of the respective zero-sequence operation data is calculated to obtain the second average value.

[0080] S13, performing difference processing on the first mean and the second mean to obtain a zero-sequence current, and performing absolute value processing on the zero-sequence current to obtain a zero-sequence current amplitude;

[0081] In the embodiment of the present invention, the difference between the first mean value and the second mean value is calculated to obtain the zero-sequence current, and the zero-sequence current is subjected to absolute value processing to obtain the zero-sequence current amplitude.

[0082] S14, using the zero-sequence current amplitude and each zero-sequence operation data to generate a corresponding target key;

[0083] The target key refers to a dynamically generated control parameter identifier that is used to accurately match the corresponding control strategy in the collaborative predictive control algorithm.

[0084] In an embodiment of the present invention, the zero-sequence current amplitude and various zero-sequence operation data are used to generate corresponding target keys, wherein the target keys include the zero-sequence current amplitude, the current change rate, multiple impedance deviations and duration.

[0085] S15. Use the target key to retrieve a preset control strategy key-value pair list and match the corresponding control strategy.

[0086] The control strategy key-value pair list refers to a structured data format used to dynamically store and transmit the core parameters of the control algorithm.

[0087] In an embodiment of the present invention, a target key is used to retrieve a preset list of control strategy key-value pairs and match the corresponding control strategy. For example, when the zero-sequence current amplitude in the target key is less than 5% of the converter rated current, the current rate of change is less than 10A / μs, the impedance deviations are all less than 5%, and the duration is greater than 100ms, it indicates that the AC / DC hybrid power grid is in a steady-state condition, and the first control strategy is matched. When the zero-sequence current amplitude in the target key is greater than or equal to 20% of the converter rated current, the current rate of change is greater than or equal to 50A / μs, the impedance deviations are all less than 15%, and the duration is less than 10ms, it indicates that the AC / DC hybrid power grid is in a transient condition, and the second control strategy is matched. When the zero-sequence current amplitude in the target key is between [5% converter rated current, 20% converter rated current], the current rate of change is between [10A / μs, 50A / μs], any impedance deviation is greater than 15%, and the duration is 10-100ms, it indicates that the AC / DC hybrid power grid is in a parameter mismatch condition, and the third control strategy is matched.

[0088] Step 202: When the control strategy is the first control strategy, a weighted operation is performed on the pre-acquired control virtual admittance and the preset initial virtual admittance reference value based on a preset admittance weight to obtain a corresponding target virtual admittance value;

[0089] The control virtual admittance refers to the target virtual admittance of the previous control cycle. When the previous control cycle is 0, the operating parameters of the AC / DC hybrid power grid are input into the preset virtual admittance initial function to obtain the initial virtual admittance, which is then used as the control virtual admittance.

[0090] It should be noted that the initial function of virtual admittance is specifically:

[0091]

[0092] in, is the real part of the initial virtual admittance, is the imaginary part of the initial virtual admittance, is the initial virtual admittance, is the number of converters, is the kth converter inductance in the initial control cycle, is the angular frequency, is the kth converter resistance in the initial control period, Is an imaginary unit.

[0093] The initial virtual admittance reference value refers to the virtual admittance value obtained by the no-load test of the converter, which is obtained by averaging the initial zero-sequence impedance of each converter.

[0094] In an embodiment of the present invention, when the control strategy is the first control strategy, the preset admittance weight, the pre-acquired control virtual admittance and the preset initial virtual admittance reference value are input into a preset first weighting function to obtain a corresponding target virtual admittance value.

[0095] It should be noted that the first weighting function is specifically:

[0096]

[0097] in, is the target virtual admittance value, is the initial virtual admittance reference value, To control the virtual admittance.

[0098] Step 203: Using the preset first weight as the target weight;

[0099] The first weight refers to the weight coefficient of the AC / DC hybrid power grid under steady-state conditions.

[0100] In the embodiment of the present invention, (first weight coefficient) = 0.3, (Second weight coefficient) = 0.6, (Third weight coefficient) = 0.1, which is determined as the target weight.

[0101] Step 204: When the control strategy is the second control strategy, the preset second weight is used as the target weight;

[0102] The second weight refers to the weight coefficient of the AC / DC hybrid power grid during transient conditions (fault / power mutation).

[0103] In the embodiment of the present invention, (first weight coefficient) = 0.8, (Second weight coefficient) = 0.1, (Third weight coefficient) = 0.1, determined as the target weight

[0104] Step 205: Perform admittance compensation processing on the pre-acquired control virtual admittance according to the zero-sequence current to obtain a target virtual admittance value;

[0105] Furthermore, step 205 includes the following sub-steps:

[0106] S21, inputting the pre-acquired control virtual admittance and zero-sequence current into a preset admittance setting function to obtain a virtual admittance setting value;

[0107] In an embodiment of the present invention, the pre-acquired control virtual admittance and zero-sequence current are used as inputs of a preset admittance setting function to obtain a virtual admittance setting value.

[0108] It should be noted that the admittance tuning function is specifically:

[0109]

[0110] in, is the virtual admittance setting value of the kth control cycle, To control the virtual admittance, is the learning rate (determined according to Lyapunov stability theory, with a value of 0.05), is the direction of change of zero-sequence current, is the attenuation coefficient, which takes a value of 10.

[0111] S22, inputting the zero-sequence current into a preset admittance compensation function to obtain a corresponding virtual admittance compensation amount;

[0112] In an embodiment of the present invention, the zero-sequence current is used as an input of a preset admittance compensation function to obtain a corresponding virtual admittance compensation amount.

[0113] It should be noted that the admittance compensation function is specifically:

[0114]

[0115] in, is the virtual admittance compensation, is the virtual admittance emergency compensation coefficient, For time, is the Laplace operator.

[0116] S23. Add the virtual admittance compensation amount and the virtual admittance setting value to obtain a target virtual admittance value.

[0117] In the embodiment of the present invention, the sum of the virtual admittance compensation amount and the virtual admittance setting value is calculated to obtain the target virtual admittance value.

[0118] Step 206: When the control strategy is the third control strategy, adaptively adjust the pre-acquired control virtual admittance and control weight coefficient according to the zero-sequence current to obtain corresponding target weight and target virtual admittance values;

[0119] Furthermore, step 206 includes the following sub-steps:

[0120] S31. Dynamically adjust the weight according to the zero-sequence current to obtain a corresponding target weight;

[0121] Furthermore, S31 includes the following sub-steps:

[0122] S311, determining whether the absolute value of the zero-sequence current is greater than a preset reference zero-sequence current value;

[0123] The reference zero-sequence current value is used as a reference standard in power system analysis, relay protection setting, or fault calculation. It is set to 0.05 of the converter's rated current.

[0124] In the embodiment of the present invention, when the control strategy is the third control strategy, it is determined whether the absolute value of the zero-sequence current is greater than 0.05 of the rated current of the converter.

[0125] S312: If the absolute value of the zero-sequence current is greater than the reference zero-sequence current value, determining a preset first reference weight coefficient as the first weight coefficient;

[0126] The first reference weight coefficient refers to the weight distribution coefficient for power tracking under parameter mismatch conditions.

[0127] In the embodiment of the present invention, if the absolute value of the zero-sequence current is greater than 0.05 of the rated current of the converter, 0.8 is used as the first weight coefficient.

[0128] S313: If the absolute value of the zero-sequence current is less than or equal to the reference zero-sequence current value, input the zero-sequence current into a preset weight coefficient adjustment function to obtain a first weight coefficient;

[0129] In an embodiment of the present invention, if the absolute value of the zero-sequence current is less than or equal to 0.05 of the rated current of the converter, the zero-sequence current is input into a preset weight coefficient adjustment function to obtain a first weight coefficient.

[0130] It should be noted that the weight coefficient adjustment function is specifically:

[0131]

[0132] in, is the first weight coefficient, is the proportional term coefficient, which is determined according to Lyapunov stability theory and takes a value of 0.1-5.0.

[0133] S314: performing difference processing on the preset second reference weight coefficient and the first weight coefficient to obtain a second weight coefficient;

[0134] The second reference weight coefficient refers to the weight distribution coefficient for circulating current suppression under parameter mismatch conditions.

[0135] In the embodiment of the present invention, the difference between the preset second reference weight coefficient and the first weight coefficient is calculated to obtain the second weight coefficient.

[0136] S315: Multiply the preset third reference weight coefficient by the first weight coefficient to obtain a third weight coefficient;

[0137] The third reference weight coefficient refers to the weight distribution coefficient of the switch state under the parameter mismatch condition.

[0138] In the embodiment of the present invention, the product of a preset third reference weight coefficient and the first weight coefficient is calculated to obtain the third weight coefficient.

[0139] S316: Normalize the first weight coefficient, the second weight coefficient, and the third weight coefficient to obtain corresponding target weights.

[0140] In the embodiment of the present invention, the first weight coefficient, the second weight coefficient, and the third weight coefficient are normalized to obtain corresponding target weights.

[0141] S32, inputting each zero-sequence operation data into a preset correction function to obtain a plurality of corrected zero-sequence operation data;

[0142] In an embodiment of the present invention, the zero-sequence impedance value, the zero-sequence voltage and the converter zero-sequence current of each zero-sequence operation data are respectively input into a preset correction function to obtain a plurality of corrected zero-sequence impedance values.

[0143] It should be noted that the correction function is specifically:

[0144]

[0145] in, is the kth zero-sequence impedance value after correction, is the kth zero-sequence impedance value, is the convergence factor, is the kth zero-sequence voltage, is the zero-sequence current of the kth converter, is the zero division coefficient, and its value is e-6. is the conjugate complex number of the kth zero-sequence voltage, is the conjugate complex number of the zero-sequence current of the kth converter.

[0146] S33. Input the pre-acquired control virtual admittance and zero-sequence current into a preset admittance setting function to obtain a virtual admittance setting value, and use the virtual admittance setting value as a target virtual admittance value.

[0147] In an embodiment of the present invention, the pre-acquired control virtual admittance and zero-sequence current are input into a preset admittance setting function to obtain a virtual admittance setting value, and the virtual admittance setting value is determined as a target virtual admittance value.

[0148] Step 207: Input the target weight and each zero-sequence operation data into a preset collaborative prediction control function to obtain switch state data.

[0149] In an embodiment of the present invention, the target weight and each zero-sequence operation data are input into a preset collaborative predictive control function to obtain a target collaborative predictive control function, and the target collaborative predictive control function is solved to obtain the switch state data.

[0150] It should be noted that the collaborative predictive control function is specifically:

[0151]

[0152] in, is the prediction step length, which is 5. is the real-time active power, is the active power reference value, is the change in switch state, is the instantaneous value of zero-sequence current, is the switching state of phase a of the k-th converter, is the switching state of phase b of the k-th converter, is the switching state of phase c of the k-th converter, is the DC bus voltage, is the rated current of the converter.

[0153] Step 208: Use the switch state data and the target virtual admittance to regulate the AC / DC hybrid power grid.

[0154] In an embodiment of the present invention, a modulation signal corresponding to each converter is generated according to the switch state data, and each modulation signal is sent to the corresponding converter for regulation, and the target virtual admittance is injected into the zero-sequence circulating current path of the AC / DC hybrid power grid, thereby achieving zero-sequence circulating current suppression of the AC / DC hybrid power grid.

[0155] It is worth mentioning that, in terms of dynamic response, this application reduces the circulating current suppression response time from 20ms to 5ms compared to traditional PI control. In terms of hardware resources, the MPC algorithm (i.e., model predictive control algorithm) reduces the required DSP (i.e., digital signal processor) resources by 40% through pre-calculation optimization. In terms of parameter robustness, this application maintains a suppression rate of over 90% under conditions of ±20% impedance mismatch. Furthermore, this application has been verified through real-time simulation using RT-LAB (i.e., real-time laboratory). In a scenario where 10 converters are connected in parallel, the peak-to-peak value of the zero-sequence circulating current is controlled within 2% of the rated current.

[0156] In an embodiment of the present invention, a control strategy and zero-sequence current are obtained by performing a control analysis based on three-phase current measurement data and various zero-sequence operating data. A coordinated prediction and modulation process is then performed based on the control strategy, zero-sequence current, and zero-sequence operating data to obtain corresponding switch state data and a target virtual admittance value. The switch state data and the target virtual admittance are then used to control the AC / DC hybrid power grid. This overcomes the problem that traditional zero-sequence commutation suppression methods primarily use model predictive control to coordinately optimize various controllers, but this method has high computational complexity and is difficult to achieve multi-converter coordinated optimization under limited hardware resource conditions, thereby reducing the reliability of AC / DC hybrid power grid operation. Unlike traditional zero-sequence commutation suppression methods, the present invention performs a control analysis based on three-phase current measurement data and various zero-sequence operating data to obtain corresponding control strategies and zero-sequence currents. Furthermore, a coordinated prediction and modulation process is performed based on the control strategy, zero-sequence current, and zero-sequence operating data to obtain corresponding switch state data and a target virtual admittance value. This method achieves coordinated suppression of zero-sequence circulating currents in multiple converters under limited hardware resource conditions, thereby improving the reliability of AC / DC hybrid power grid operation.

[0157] See also Figure 3 , Figure 3 This is a structural block diagram of a zero-sequence circulating current suppression system for an AC / DC hybrid power grid provided in Example 3 of the present invention.

[0158] The present invention provides an AC / DC hybrid power grid zero-sequence circulating current suppression system, comprising:

[0159] The analysis module 301 is used to obtain the three-phase current measurement data of the AC / DC hybrid power grid and the zero-sequence operation data of each converter, perform regulation and analysis based on the three-phase current measurement data and each zero-sequence operation data, and obtain the corresponding control strategy and zero-sequence current;

[0160] A modulation module 302 is configured to perform collaborative predictive modulation processing based on the control strategy, zero-sequence current, and zero-sequence operation data to obtain corresponding switch state data and target virtual admittance value;

[0161] The control module 303 is used to control the AC / DC hybrid power grid using the switch state data and the target virtual admittance.

[0162] Furthermore, the three-phase current measurement data includes a first-phase current value, a second-phase current value, and a third-phase current value. The analysis module 301 includes:

[0163] A first average submodule is used to average the first phase current value, the second phase current value, and the third phase current value to obtain a first average value;

[0164] A second mean submodule is used to perform mean processing on the zero-sequence current of the converter of each zero-sequence operation data to obtain a second mean value;

[0165] A difference submodule is used to perform difference processing on the first mean value and the second mean value to obtain a zero-sequence current, and perform absolute value processing on the zero-sequence current to obtain a zero-sequence current amplitude;

[0166] A retrieval submodule, for generating a corresponding target key using the zero-sequence current amplitude and each zero-sequence operation data;

[0167] Use the target key to retrieve the preset control strategy key-value pair list and match the corresponding control strategy.

[0168] Furthermore, the modulation module 302 includes:

[0169] a first control submodule, configured to, when the control strategy is the first control strategy, perform a weighted operation on the pre-acquired control virtual admittance and a preset initial virtual admittance reference value based on a preset admittance weight to obtain a corresponding target virtual admittance value;

[0170] Using the preset first weight as the target weight;

[0171] A second control submodule is configured to use a preset second weight as a target weight when the control strategy is the second control strategy;

[0172] The admittance compensation submodule is used to perform admittance compensation processing on the pre-acquired control virtual admittance according to the zero-sequence current to obtain a target virtual admittance value;

[0173] The third control submodule is configured to, when the control strategy is the third control strategy, adaptively adjust the pre-acquired control virtual admittance and control weight coefficient according to the zero-sequence current to obtain corresponding target weight and target virtual admittance values;

[0174] The collaborative prediction submodule is used to input the target weight and each zero-sequence operation data into the preset collaborative prediction control function to obtain the switch state data.

[0175] Furthermore, the admittance compensation submodule includes:

[0176] Inputting the pre-acquired control virtual admittance and zero-sequence current into a preset admittance setting function to obtain a virtual admittance setting value;

[0177] Input the zero-sequence current into the preset admittance compensation function to obtain the corresponding virtual admittance compensation amount;

[0178] The virtual admittance compensation amount is added to the virtual admittance setting value to obtain the target virtual admittance value.

[0179] Furthermore, the third control submodule includes:

[0180] A dynamic adjustment unit is used to perform dynamic weight adjustment according to the zero-sequence current to obtain a corresponding target weight;

[0181] A correction unit, used for inputting each zero-sequence operation data into a preset correction function to obtain a plurality of corrected zero-sequence operation data;

[0182] The setting unit is used to input the pre-acquired control virtual admittance and zero-sequence current into a preset admittance setting function to obtain a virtual admittance setting value, and use the virtual admittance setting value as a target virtual admittance value.

[0183] Furthermore, the dynamic adjustment unit includes:

[0184] The first analysis subunit is used to determine whether the absolute value of the zero-sequence current is greater than a preset reference zero-sequence current value;

[0185] If the absolute value of the zero-sequence current is greater than the reference zero-sequence current value, the preset first reference weight coefficient is determined as the first weight coefficient;

[0186] If the absolute value of the zero-sequence current is less than or equal to the reference zero-sequence current value, the zero-sequence current is input into a preset weight coefficient adjustment function to obtain a first weight coefficient;

[0187] A second analysis subunit is configured to perform difference processing on a preset second reference weight coefficient and the first weight coefficient to obtain a second weight coefficient;

[0188] a third analyzing subunit, configured to multiply a preset third reference weight coefficient by the first weight coefficient to obtain a third weight coefficient;

[0189] The first weight coefficient, the second weight coefficient, and the third weight coefficient are normalized to obtain corresponding target weights.

[0190] See also Figure 4 , Figure 4 This is a structural block diagram of a computer device provided in Example 4 of the present invention.

[0191] An electronic device according to an embodiment of the present invention includes: a memory 401 and a processor 402, wherein the memory 401 stores a computer program; when the computer program is executed by the processor 402, the processor 402 executes the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid as described in any of the above embodiments.

[0192] Memory 401 may be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. Memory 401 has storage space 403 for program code 413 for executing any of the method steps described above. For example, storage space 403 for program code may include individual program codes 413 for implementing various steps in the method described above. These program codes may be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, compact disks (CDs), memory cards, or floppy disks. The program codes may be compressed, for example, in a suitable format. When executed by a processing device, these codes cause the processing device to execute the various steps in the method described above. These program codes may be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, compact disks (CDs), memory cards, or floppy disks. The program codes may be compressed, for example, in a suitable format. When these codes are executed by a computing and processing device, they cause the computing and processing device to execute the various steps of the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid described above.

[0193] The fifth embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to any of the above embodiments is implemented.

[0194] Embodiment 6 of the present invention also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer executes the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid as described in any of the above embodiments.

[0195] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0196] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0197] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0198] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0199] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the various embodiments of the method of the present invention. The aforementioned storage medium includes various media that can store program code, such as USB flash drives, mobile hard drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical disks.

[0200] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid, characterized in that: include: Acquire three-phase current measurement data of the AC / DC hybrid power grid and zero-sequence operation data of each converter, perform regulation and analysis based on the three-phase current measurement data and each zero-sequence operation data, and obtain corresponding control strategies and zero-sequence currents; Performing collaborative prediction and modulation processing based on the control strategy, the zero-sequence current, and the zero-sequence operation data to obtain corresponding switch state data and a target virtual admittance value; The AC / DC hybrid power grid is regulated using the switch state data and the target virtual admittance.

2. The method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to claim 1, characterized in that: The three-phase current measurement data includes a first-phase current value, a second-phase current value, and a third-phase current value. The step of performing regulation and analysis based on the three-phase current measurement data and each of the zero-sequence operation data to obtain a corresponding control strategy includes: Performing averaging processing on the first phase current value, the second phase current value, and the third phase current value to obtain a first average value; performing mean processing on the zero-sequence current of the converter of each zero-sequence operation data to obtain a second mean value; Performing difference processing on the first mean value and the second mean value to obtain a zero-sequence current, and performing absolute value processing on the zero-sequence current to obtain a zero-sequence current amplitude; generating a corresponding target key by using the zero-sequence current amplitude and each of the zero-sequence operation data; The target key is used to retrieve a preset control strategy key-value pair list to match the corresponding control strategy.

3. The method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to claim 1, wherein: The step of performing collaborative predictive modulation processing based on the control strategy, the zero-sequence current, and the zero-sequence operation data to obtain corresponding switch state data and a target virtual admittance value includes: When the control strategy is the first control strategy, a weighted operation is performed on the pre-acquired control virtual admittance and the preset initial virtual admittance reference value based on the preset admittance weight to obtain a corresponding target virtual admittance value; Using the preset first weight as the target weight; When the control strategy is the second control strategy, the preset second weight is used as the target weight; performing admittance compensation processing on the pre-acquired control virtual admittance according to the zero-sequence current to obtain a target virtual admittance value; When the control strategy is the third control strategy, adaptive adjustment processing is performed on the pre-acquired control virtual admittance and control weight coefficient according to the zero-sequence current to obtain corresponding target weight and target virtual admittance value; The target weight and each of the zero-sequence operation data are input into a preset collaborative predictive control function to obtain switch state data.

4. The method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to claim 3, characterized in that: The step of performing admittance compensation processing on the pre-acquired control virtual admittance according to the zero-sequence current to obtain a target virtual admittance value includes: Inputting the pre-acquired control virtual admittance and the zero-sequence current into a preset admittance setting function to obtain a virtual admittance setting value; Inputting the zero-sequence current into a preset admittance compensation function to obtain a corresponding virtual admittance compensation amount; The virtual admittance compensation amount and the virtual admittance setting value are added together to obtain a target virtual admittance value.

5. The method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to claim 3, characterized in that: The step of adaptively adjusting the pre-acquired control virtual admittance and control weight coefficient according to the zero-sequence current to obtain corresponding target weight and target virtual admittance value includes: Performing dynamic weight adjustment according to the zero-sequence current to obtain a corresponding target weight; Inputting each of the zero-sequence operation data into a preset correction function to obtain a plurality of corrected zero-sequence operation data; The pre-acquired control virtual admittance and the zero-sequence current are input into a preset admittance setting function to obtain a virtual admittance setting value, and the virtual admittance setting value is used as a target virtual admittance value.

6. The method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to claim 5, characterized in that: The step of dynamically adjusting the weight according to the zero-sequence current to obtain the corresponding target weight includes: Determining whether the absolute value of the zero-sequence current is greater than a preset reference zero-sequence current value; If the absolute value of the zero-sequence current is greater than the reference zero-sequence current value, determining a preset first reference weight coefficient as the first weight coefficient; If the absolute value of the zero-sequence current is less than or equal to the reference zero-sequence current value, inputting the zero-sequence current into a preset weight coefficient adjustment function to obtain a first weight coefficient; Performing difference processing on a preset second reference weight coefficient and the first weight coefficient to obtain a second weight coefficient; Multiplying a preset third reference weight coefficient by the first weight coefficient to obtain a third weight coefficient; The first weight coefficient, the second weight coefficient, and the third weight coefficient are normalized to obtain corresponding target weights.

7. A zero-sequence circulating current suppression system for an AC / DC hybrid power grid, characterized in that: include: An analysis module is used to obtain three-phase current measurement data of the AC / DC hybrid power grid and zero-sequence operation data of each converter, and perform regulation and analysis based on the three-phase current measurement data and each zero-sequence operation data to obtain a corresponding control strategy and zero-sequence current; a modulation module, configured to perform collaborative predictive modulation processing based on the control strategy, the zero-sequence current, and the zero-sequence operation data to obtain corresponding switch state data and a target virtual admittance value; A control module is used to control the AC / DC hybrid power grid using the switch state data and the target virtual admittance.

8. An electronic device, characterized in that: The method comprises a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid 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 the computer program is executed, the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to any one of claims 1 to 6 is implemented.

10. A computer program product, characterized in that The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the method for suppressing zero-sequence circulating current in an AC / DC hybrid power grid according to any one of claims 1 to 6.

Images