Method and apparatus for determining positive-sequence active current during fault ride-through in three-phase grid-connected power systems

Abstract

This application relates to a method and apparatus for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system. The method includes acquiring parameter data of a fault occurring in the three-phase grid-connected power system; performing Clark transformation and phase-locked loop processing on the three-phase voltages to obtain positive-sequence and negative-sequence voltage components; calculating the positive-sequence and negative-sequence reactive currents based on the reactive power gain coefficient, the three-phase rated current, and the positive-sequence and negative-sequence voltage components; calculating the feedforward estimated current based on the three-phase rated current, positive-sequence reactive current, and negative-sequence reactive current; obtaining the constraint type; and calculating the positive-sequence active current based on the constraint type, the feedforward estimated current, and the parameter data. This method calculates the positive-sequence active current by combining the feedforward estimated current with the constraint type, and controls the operation of the three-phase grid-connected power system using the positive-sequence active current to ensure that the output current during fault ride-through meets the safety regulations' constraints on current or power.

Description

Technical Field

[0001] This application belongs to the field of power grid fault ride-through technology, and in particular relates to a method and apparatus for determining the positive sequence active current for fault ride-through in a three-phase grid-connected power system. Background Technology

[0002] A three-phase grid-connected power system is a power supply system consisting of three AC power sources with the same frequency and a phase difference of 120 degrees. It is connected to the load through transmission lines to form a complete power transmission network.

[0003] In current three-phase grid-connected power systems, different safety standards all have fixed calculation formulas for generating positive-sequence and negative-sequence reactive current commands during the power system fault ride-through process. Negative-sequence active current is assumed to be 0. However, some safety regulations impose constraints on the total three-phase current / maximum single-phase current or the total three-phase apparent power / maximum single-phase apparent power during the ride-through process, thus creating constraints on the positive-sequence active current. Based on these constraints, accurately obtaining the positive-sequence active current has become a key challenge that needs to be addressed. Summary of the Invention

[0004] One embodiment of this application provides a method and apparatus for determining the positive sequence active current for fault ride-through in a three-phase grid-connected power system, in order to solve the problem that it is difficult to determine the positive sequence active current data required for fault ride-through in existing three-phase grid-connected power systems.

[0005] In a first aspect, one embodiment of this application provides a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, comprising the following steps: Acquire parameter data of a fault in a three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, three-phase current RMS value, three-phase apparent power, apparent power rated value, reactive power gain coefficient, and controller control parameters, including integral coefficient and proportional coefficient. The three-phase voltages are subjected to Clark transformation and phase-locked loop processing to obtain positive-sequence voltage components and negative-sequence voltage components; The positive-sequence reactive current and the negative-sequence reactive current are calculated based on the reactive power gain coefficient, the three-phase rated current, the positive-sequence voltage component, and the negative-sequence voltage component; the feedforward estimated current is calculated based on the three-phase rated current, the positive-sequence reactive current, and the negative-sequence reactive current. Obtain the constraint type, and calculate the positive sequence active current based on the constraint type, the feedforward estimated current, and the parameter data.

[0006] Optionally, the positive sequence active current is calculated based on the constraint type, the feedforward estimated current, and the parameter data, including: if the constraint type is that the maximum phase current is not greater than the maximum rated current of a single phase, then the largest value is selected from the three-phase current RMS values ​​as the maximum current RMS value, and the positive sequence active current is calculated based on the feedforward estimated current, the three-phase rated current, the maximum current RMS value, the integral coefficient, and the proportional coefficient.

[0007] Optionally, calculating the positive-sequence active current based on the constraint type, the feedforward estimated current, and the parameter data includes: if the constraint type is that the average of the sum of the three-phase currents is equal to the three-phase rated current, then the average current is calculated based on the effective values ​​of the three-phase currents to obtain the average current; the positive-sequence active current is calculated based on the feedforward estimated current, the average current, the three-phase rated current, the integral coefficient, and the proportional coefficient.

[0008] Optionally, the positive sequence active current is calculated based on the constraint type, the feedforward estimated current, and the parameter data, including: if the constraint type is that the apparent power of any phase is not greater than the maximum power of a single phase, then the largest value of the apparent power of the three phases is selected as the maximum apparent power value, and the positive sequence active current is calculated based on the feedforward estimated current, the maximum apparent power value, the rated apparent power value, the integral coefficient, and the proportional coefficient.

[0009] Optionally, calculating the positive-sequence active current based on the constraint type, the feedforward estimated current, and the parameter data includes: if the constraint type is that the sum of the three-phase apparent power equals the rated apparent power of the three phases, then the average value of the power is calculated based on the apparent power of the three phases; and the positive-sequence active current is calculated based on the feedforward estimated current, the average power, the rated apparent power, the integral coefficient, and the proportional coefficient.

[0010] Secondly, one embodiment of this application provides a positive sequence active current determination device for fault ride-through in a three-phase grid-connected power system, comprising: a data acquisition module, a phase-locked loop separation module, a reactive current determination module, and an active current determination module; The data acquisition module is used to acquire parameter data of a fault in a three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, three-phase current RMS value, three-phase apparent power, apparent power rated value, reactive power gain coefficient, and controller control parameters, including integral coefficient and proportional coefficient. The phase-locked module is used to perform Clark transformation and phase-locked processing on the three-phase voltages to obtain positive-sequence voltage components and negative-sequence voltage components. The reactive current determination module is used to calculate the positive-sequence reactive current and the negative-sequence reactive current based on the reactive power gain coefficient, the three-phase rated current, the positive-sequence voltage component, and the negative-sequence voltage component; and to calculate the feedforward estimated current based on the three-phase rated current, the positive-sequence reactive current, and the negative-sequence reactive current. The active current determination module is used to obtain the constraint type, and calculate the positive sequence active current based on the constraint type, the feedforward estimated current and the parameter data.

[0011] Optionally, the active current determination module is further configured to, based on the constraint condition that the maximum phase current is not greater than the maximum rated current of a single phase, select the largest value from the three phase current effective values ​​as the maximum current effective value, and calculate the positive sequence active current based on the feedforward estimated current, the three phase rated current, the maximum current effective value, the integral coefficient, and the proportional coefficient.

[0012] Optionally, the active current determination module is further configured to calculate the mean value of the three-phase currents based on the effective values ​​of the three-phase currents if the mean value of the sum of the three-phase currents is equal to the three-phase rated current, and obtain the mean value of the current; and to calculate the positive sequence active current based on the feedforward estimated current, the mean value of the current, the three-phase rated current, the integral coefficient, and the proportional coefficient.

[0013] Optionally, the active current determination module is further configured to, based on the constraint condition that the apparent power of any phase is not greater than the maximum power of a single phase, select the largest value from the apparent power of the three phases as the maximum apparent power, and calculate the positive sequence active current based on the feedforward estimated current, the maximum apparent power, the rated apparent power, the integral coefficient, and the proportional coefficient.

[0014] Optionally, the active current determination module is further configured to calculate the average value of the apparent power of the three phases based on the constraint condition that the sum of the apparent power of the three phases is equal to the rated apparent power of the three phases, and obtain the power average value; and to calculate the positive sequence active current based on the feedforward estimated current, the power average value, the rated apparent power value, the integral coefficient and the proportional coefficient.

[0015] One embodiment of this application provides a method and apparatus for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system. The method includes acquiring parameter data of a fault occurring in the three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, three-phase RMS current, three-phase apparent power, apparent power rating, reactive power gain coefficient, and controller parameters, including integral and proportional coefficients. The three-phase voltage is then subjected to Clark transformation and phase-locked loop processing to obtain positive-sequence and negative-sequence voltage components. Positive-sequence and negative-sequence reactive currents are calculated based on the reactive power gain coefficient, three-phase rated current, positive-sequence voltage components, and negative-sequence voltage components. A feedforward estimated current is calculated based on the three-phase rated current, positive-sequence reactive current, and negative-sequence reactive current. The constraint type is obtained, and the positive-sequence active current is calculated based on the constraint type, feedforward estimated current, and parameter data. This method for determining the positive-sequence active current during fault ride in a three-phase grid-connected power system first calculates the feedforward estimated current by acquiring parameter data of the fault in the three-phase grid-connected power system, and then calculates the positive-sequence active current based on the feedforward estimated current and the type of constraint conditions. The operation of the three-phase grid-connected power system is controlled by the positive-sequence active current, so that the current output by the three-phase grid-connected power system during fault ride meets the safety regulations' constraints on current or power, thus solving the problem that it is difficult to determine the positive-sequence active current data required for fault ride in existing three-phase grid-connected power systems.

[0016] The device for determining the positive-sequence active current during fault ride in a three-phase grid-connected power system uses a data acquisition module, a phase-locked loop module, a reactive current determination module, and an active current determination module to determine the positive-sequence active current during fault ride in a three-phase grid-connected power system. Attached Figure Description

[0017] To more clearly illustrate the technical solution in one embodiment of this application, the accompanying drawings used in the description of the embodiment will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0018] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0019] Figure 1 A flowchart illustrating the steps of a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application.

[0020] Figure 2This is a schematic diagram illustrating the framework for calculating and estimating the current in a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application.

[0021] Figure 3 This is a schematic diagram of the framework for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application.

[0022] Figure 4 A schematic diagram of the framework of a device for determining the positive sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application. Detailed Implementation

[0023] The technical solution of one embodiment of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0024] Patent terminology used in this application: The Clark transformation is a mathematical tool that converts variables (such as current and voltage) in a three-phase AC system into a two-phase stationary coordinate system (αβ coordinate system). It is widely used in fields such as motor control. Its core is to achieve system decoupling and simplified analysis through coordinate transformation.

[0025] A second-order generalized integrator (SOGI) can generate a 90° phase shift on an input AC sinusoidal signal, resulting in two orthogonal signals. In power electronics or grid-connected control systems, the phase-locked loop (PLL) of the SOGI accurately extracts the phase and frequency from the grid voltage signal.

[0026] One embodiment of this application provides a method and apparatus for determining the positive sequence active current for fault ride-through in a three-phase grid-connected power system, in order to solve the problem that it is difficult to determine the positive sequence active current data required for fault ride-through in existing three-phase grid-connected power systems.

[0027] Example 1: One embodiment of this application provides a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system. For an example, please refer to [link to relevant documentation]. Figure 1 , Figure 1 A flowchart illustrating the steps of a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application. Figure 2 This is a schematic diagram illustrating the framework for calculating and estimating the current in a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application. Figure 3This is a schematic diagram of the framework for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application.

[0028] like Figures 1 to 3 As shown, this application provides a method for determining the positive sequence active current during fault ride-through in a three-phase grid-connected power system, comprising the following steps: S10. Obtain parameter data of a fault in a three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, three-phase RMS current, three-phase apparent power, apparent power rating, reactive power gain coefficient, and controller control parameters, including integral coefficient and proportional coefficient.

[0029] Further explanation is needed: step S10 involves acquiring parameter data for the three-phase four-wire system experiencing a fault in the three-phase grid-connected power system, providing data for calculating the positive-sequence voltage component Udpos and the negative-sequence voltage component Udneg. The parameter data includes the three-phase voltages, three-phase rated currents In, three-phase RMS current values, three-phase apparent power, apparent power rating Pn, reactive power gain coefficient k, and controller parameters, including integral coefficient kp and proportional coefficient ki. The three-phase voltages are denoted as phase a voltage Vgrid_a, phase b voltage Vgrid_b, and phase c voltage Vgrid_c, respectively. The three-phase RMS current values ​​are denoted as phase a current RMS IaRMS, phase b current RMS IbRMS, and phase c current RMS IcRMS, respectively. The three-phase apparent power is denoted as phase a apparent power Sa, phase b apparent power Sb, and phase c apparent power Sc, respectively.

[0030] S20. Perform Clark transformation and phase-locked loop processing on the three-phase voltage to obtain the positive-sequence voltage component and the negative-sequence voltage component.

[0031] To further explain, such as Figure 2 As shown, in step S20, the voltages Vgrid_a (phase a), Vgrid_b (phase b), and Vgrid_c (phase c) are first processed using the Clark transform to obtain voltage α and voltage β. Then, a second-order generalized integrator SOGI is used to perform phase-locked processing on the voltages α and β to obtain the positive-sequence voltage component Udpos and the negative-sequence voltage component Udneg, providing data for calculating the positive-sequence reactive current Iqpos and the negative-sequence reactive current Iqneg. In this embodiment, the technology of using the Clark transform and the second-order generalized integrator SOGI to process the voltages is a relatively mature technology in the field, and will not be described in detail in this embodiment.

[0032] S30. Based on the reactive power gain coefficient, three-phase rated current, positive sequence voltage component and negative sequence voltage component, calculate the positive sequence reactive current and negative sequence reactive current; based on the three-phase rated current, positive sequence reactive current and negative sequence reactive current, calculate the feedforward estimated current.

[0033] To further clarify, step S30 first uses the reactive current formula to calculate the positive-sequence reactive current Iqpos and the negative-sequence reactive current Iqneg based on the reactive gain coefficient K obtained in step S10, the three-phase rated current In, and the positive-sequence voltage component Udpos and negative-sequence voltage component Udneg calculated in step S2. Then, the feedforward estimated current Idpos_cal is calculated using the current estimation formula based on the three-phase rated current In, the positive-sequence reactive current Iqpos, and the negative-sequence reactive current Iqneg.

[0034] In the embodiments of this invention, the reactive current formula is: Iqpos=K*(1-Udpos)*In, Iqneg=-K*Udneg*In.

[0035] In the embodiments of this invention, the current estimation formula is: Idpos_cal=sqrt(In^2-Iqpos^2-Iqneg^2).

[0036] S40. Obtain the constraint type, and calculate the positive sequence active current based on the constraint type, feedforward estimated current, and parameter data.

[0037] To further clarify, step S40 first determines the constraint type. Then, based on the constraint type and the feedforward estimated current Idpos_cal calculated in step S30, the positive-sequence active current command Idpos is obtained through the PI controller by the parameter data and the positive-sequence active current value. The negative-sequence active current command Idneg is defaulted to 0. In the PI controller, the target value of the constraint (such as the three-phase rated current In or the apparent power rated value Sn) is used as the reference value of the PI loop, and the current or power is used as the feedback value. The output PI_out of the PI loop is assigned to IdPos. Considering the adjustment time requirement, a feedforward estimated current Idpos_cal can be initially estimated based on the constraint adjustment as the feedforward, reducing the adjustment time. By solving the positive-sequence active current Idpos through this method for determining the positive-sequence active current during fault ride in a three-phase grid-connected power system, the existing method for accurately solving the positive-sequence active current is bypassed, thus achieving the same purpose. The types of constraints include different safety regulations on the total three-phase current, maximum single-phase current, total three-phase apparent power, or single-phase apparent power.

[0038] In an embodiment of this invention, the method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system is described. One embodiment of this application provides a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system. The method includes acquiring parameter data of a fault occurring in the three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, effective current value of the three phases, apparent power of the three phases, rated apparent power value, reactive power gain coefficient, and controller parameters, including integral coefficients and proportional coefficients. The method performs Clark transformation and phase-locked loop processing on the three-phase voltage to obtain positive-sequence and negative-sequence voltage components. Based on the reactive power gain coefficient, three-phase rated current, positive-sequence voltage components, and negative-sequence voltage components, the method calculates the positive-sequence reactive current and negative-sequence reactive current. Based on the three-phase rated current, positive-sequence reactive current, and negative-sequence reactive current, the method calculates the feedforward estimated current. Finally, the method acquires the constraint type and calculates the positive-sequence active current based on the constraint type, the feedforward estimated current, and the parameter data. This method for determining the positive-sequence active current during fault ride in a three-phase grid-connected power system first calculates the feedforward estimated current by acquiring parameter data of the fault in the three-phase grid-connected power system, and then calculates the positive-sequence active current based on the feedforward estimated current and the type of constraint conditions. The operation of the three-phase grid-connected power system is controlled by the positive-sequence active current, so that the current output by the three-phase grid-connected power system during fault ride meets the safety regulations' constraints on current or power, thus solving the problem that it is difficult to determine the positive-sequence active current data required for fault ride in existing three-phase grid-connected power systems.

[0039] In one embodiment of the present invention, the positive sequence active current is calculated based on the constraint type, feedforward estimated current, and parameter data. If the constraint type is that the maximum phase current is not greater than the maximum rated current of a single phase, the maximum value of the three-phase current is selected as the maximum effective value of the current. The positive sequence active current is then calculated based on the feedforward estimated current, the three-phase rated current, the maximum effective value of the current, the integral coefficient, and the proportional coefficient.

[0040] To further clarify, the constraint type refers to generating active current as much as possible under asymmetrical voltage drop conditions while satisfying reactive power requirements, but ensuring that the maximum phase current does not exceed the maximum rated current of a single phase. Therefore, based on the constraint type, feedforward estimated current, and parameter data, the first positive sequence active current formula is used to calculate the positive sequence active current Idpos. The first positive sequence active current formula is: Idpos = Idpos_cal + (In - max(IaRMS, IbRMS, IcRMS)) * (Kp + Ki / s), where s is the Laplace operator.

[0041] In one embodiment of the present invention, the positive sequence active current is calculated based on the constraint type, the feedforward estimated current, and the parameter data, including: if the constraint type is that the average of the sum of the three-phase currents is equal to the three-phase rated current, then the average value is calculated based on the effective value of the three-phase current to obtain the average current; and the positive sequence active current is calculated based on the feedforward estimated current, the average current, the three-phase rated current, the integral coefficient, and the proportional coefficient.

[0042] To further clarify, the constraint type refers to generating active current as much as possible under asymmetrical voltage drop conditions while satisfying reactive power requirements, but ensuring that the average value of the sum of the three-phase currents equals the three-phase rated current In. Therefore, based on the constraint type, feedforward estimated current, and parameter data, the second positive sequence active current formula is used to calculate the positive sequence active current Idpos. The second positive sequence active current formula is: Idpos = Idpos_cal + (In - sum(IaRMS, IbRMS, IcRMS) / 3) * (Kp + Ki / s), where s is the Laplace operator.

[0043] In one embodiment of the present invention, the positive sequence active current is calculated based on the constraint type, feedforward estimated current, and parameter data. This includes: if the constraint type is that the apparent power of any phase is not greater than the maximum power of a single phase, then the largest value among the three phases' apparent power is selected as the maximum apparent power value. The positive sequence active current is then calculated based on the feedforward estimated current, the maximum apparent power value, the rated apparent power value, the integral coefficient, and the proportional coefficient.

[0044] To further clarify, the constraint type refers to maximizing active current output under asymmetrical voltage drop conditions while satisfying reactive power requirements, but ensuring that the apparent power of any phase does not exceed the maximum power of a single phase. Therefore, based on the constraint type, feedforward estimated current, and parameter data, the third positive sequence active current formula is used to calculate the positive sequence active current Idpos. The third positive sequence active current formula is: Idpos = Idpos_cal + (Sn / 3 - max(Sa, Sb, Sc)) * (Kp + Ki / s), where s is the Laplace operator.

[0045] In one embodiment of the present invention, the calculation of positive sequence active current based on constraint type, feedforward estimated current and parameter data includes: if the constraint type is that the sum of the apparent power of the three phases is equal to the rated apparent power of the three phases, then the average value is calculated based on the apparent power of the three phases to obtain the power average; and the positive sequence active current is calculated based on the feedforward estimated current, the power average, the rated apparent power, the integral coefficient and the proportional coefficient.

[0046] To further clarify, the constraint type refers to maximizing active current output under asymmetrical voltage drop conditions while satisfying reactive power requirements, but ensuring that the sum of the apparent power of any three phases equals the rated apparent power Pn. Based on the constraint type, feedforward estimated current, and parameter data, the fourth positive sequence active current formula is used to calculate the positive sequence active current Idpos. The fourth positive sequence active current formula is: Idpos = Idpos_cal + (Sn - sum(Sa, Sb, Sc) / 3)) * (Kp + Ki / s), where s is the Laplace operator.

[0047] Example 2: Figure 4 A schematic diagram of the framework of a device for determining the positive sequence active current during fault ride-through in a three-phase grid-connected power system, provided as an embodiment of this application.

[0048] like Figure 4 As shown, this application invention provides a positive sequence active current determination device for fault ride-through in a three-phase grid-connected power system, including a data acquisition module 100, a phase-locked loop module 200, a reactive current determination module 300, and an active current determination module 400. The data acquisition module 100 is used to acquire parameter data of a fault in a three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, three-phase current RMS value, three-phase apparent power, apparent power rated value, reactive power gain coefficient, and controller control parameters, including integral coefficient and proportional coefficient. The phase-locked module 200 is used to perform Clark transformation and phase-locked processing on the three-phase voltages to obtain positive-sequence voltage components and negative-sequence voltage components. The reactive current determination module 300 is used to calculate the positive-sequence reactive current and the negative-sequence reactive current based on the reactive gain coefficient, the three-phase rated current, the positive-sequence voltage component, and the negative-sequence voltage component; and to calculate the feedforward estimated current based on the three-phase rated current, the positive-sequence reactive current, and the negative-sequence reactive current. The active current determination module 400 is used to obtain the constraint type, calculate the positive sequence active current based on the constraint type, feedforward estimated current and parameter data.

[0049] It should be noted that the module content in this embodiment corresponds to the steps of the method in Embodiment 1. The method for determining the positive sequence active current during fault ride-through of a three-phase grid-connected power system has already been described in Embodiment 1, and will not be repeated in this embodiment. This device for determining the positive sequence active current during fault ride-through of a three-phase grid-connected power system determines the positive sequence active current during fault ride-through of the three-phase grid-connected power system through a data acquisition module, a phase-locked loop (PLL) module, a reactive current determination module, and an active current determination module.

[0050] In the embodiments of the present invention, the active current determination module 400 is further configured to, based on the constraint condition that the maximum phase current is not greater than the maximum rated current of a single phase, select the largest value from the three-phase current effective values ​​as the maximum current effective value, and calculate the positive sequence active current based on the feedforward estimated current, the three-phase rated current, the maximum current effective value, the integral coefficient, and the proportional coefficient.

[0051] In the embodiments of the present invention, the active current determination module 400 is further configured to calculate the mean value of the three-phase current based on the effective value of the three-phase current according to the constraint condition type of the sum of the three-phase currents being equal to the three-phase rated current, and obtain the mean value of the current; and to calculate the positive sequence active current based on the feedforward estimated current, the mean value of the current, the three-phase rated current, the integral coefficient and the proportional coefficient.

[0052] In the embodiments of the present invention, the active current determination module 400 is further configured to select the largest value from the apparent power of the three phases as the maximum apparent power based on the constraint condition that the apparent power of any phase is not greater than the maximum power of a single phase, and calculate the positive sequence active current based on the feedforward estimated current, the maximum apparent power, the rated apparent power, the integral coefficient, and the proportional coefficient.

[0053] In the embodiments of the present invention, the active current determination module 400 is further configured to calculate the average value of the apparent power of the three phases based on the constraint condition that the sum of the apparent power of the three phases is equal to the rated apparent power of the three phases, and obtain the power average value; and to calculate the positive sequence active current based on the feedforward estimated current, the power average value, the rated apparent power value, the integral coefficient and the proportional coefficient.

[0054] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0055] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features.

[0056] The above provides a detailed description of a method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, based on an embodiment of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, characterized in that, Includes the following steps: Acquire parameter data of a fault in a three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, three-phase current RMS value, three-phase apparent power, apparent power rated value, reactive power gain coefficient, and controller control parameters, including integral coefficient and proportional coefficient. The three-phase voltages are subjected to Clark transformation and phase-locked loop processing to obtain positive-sequence voltage components and negative-sequence voltage components; The positive-sequence reactive current and the negative-sequence reactive current are calculated based on the reactive power gain coefficient, the three-phase rated current, the positive-sequence voltage component, and the negative-sequence voltage component; the feedforward estimated current is calculated based on the three-phase rated current, the positive-sequence reactive current, and the negative-sequence reactive current. Obtain the constraint type, and calculate the positive sequence active current based on the constraint type, the feedforward estimated current, and the parameter data; In the PI controller, the target value of the constraint condition is used as the reference value of the PI loop. The target value of the constraint condition includes the three-phase rated current In or the apparent power rated value Sn. The current or power is used as the feedback value, and the output of the PI loop PI_out is assigned to IdPos. Based on the constraint adjustment, a feedforward estimation current Idpos_cal is initially estimated as the feedforward. The positive sequence active current Idpos is solved by the method for determining the positive sequence active current during fault ride in the three-phase grid-connected power system.

2. The method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 1, characterized in that, The positive sequence active current is calculated based on the constraint type, the feedforward estimated current, and the parameter data, including: if the constraint type is that the maximum phase current is not greater than the maximum rated current of a single phase, then the largest value among the three phase current RMS values ​​is selected as the maximum RMS current value, and the positive sequence active current is calculated based on the feedforward estimated current, the three phase rated current, the maximum RMS current value, the integral coefficient, and the proportional coefficient.

3. The method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 1, characterized in that, The positive sequence active current is calculated based on the constraint type, the feedforward estimated current, and the parameter data, including: if the constraint type is that the average sum of the three-phase currents equals the three-phase rated current, then the average current is calculated based on the effective values ​​of the three-phase currents to obtain the average current; the positive sequence active current is calculated based on the feedforward estimated current, the average current, the three-phase rated current, the integral coefficient, and the proportional coefficient.

4. The method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 1, characterized in that, The positive sequence active current is calculated based on the constraint type, the feedforward estimated current, and the parameter data, including: if the constraint type is that the apparent power of any phase is not greater than the maximum power of a single phase, then the largest value of the apparent power of the three phases is selected as the maximum apparent power value, and the positive sequence active current is calculated based on the feedforward estimated current, the maximum apparent power value, the rated apparent power value, the integral coefficient, and the proportional coefficient.

5. The method for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 1, characterized in that, The positive sequence active current is calculated based on the constraint type, the feedforward estimated current, and the parameter data, including: if the constraint type is that the sum of the apparent power of the three phases is equal to the rated apparent power of the three phases, then the average value of the apparent power of the three phases is calculated to obtain the power average; the positive sequence active current is calculated based on the feedforward estimated current, the power average, the rated apparent power, the integral coefficient, and the proportional coefficient.

6. A device for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system, characterized in that, It includes a data acquisition module, a phase-locked loop (PLL) separation module, a reactive current determination module, and an active current determination module; The data acquisition module is used to acquire parameter data of a fault in a three-phase grid-connected power system. The parameter data includes the three-phase voltage, three-phase rated current, three-phase current RMS value, three-phase apparent power, apparent power rated value, reactive power gain coefficient, and controller control parameters, including integral coefficient and proportional coefficient. The phase-locked module is used to perform Clark transformation and phase-locked processing on the three-phase voltages to obtain positive-sequence voltage components and negative-sequence voltage components. The reactive current determination module is used to calculate the positive-sequence reactive current and the negative-sequence reactive current based on the reactive power gain coefficient, the three-phase rated current, the positive-sequence voltage component, and the negative-sequence voltage component; and to calculate the feedforward estimated current based on the three-phase rated current, the positive-sequence reactive current, and the negative-sequence reactive current. The active current determination module is used to obtain the constraint condition type, and calculate the positive sequence active current based on the constraint condition type, the feedforward estimated current and the parameter data. In the PI controller, the target value of the constraint condition is used as the reference value of the PI loop. The target value of the constraint condition includes the three-phase rated current In or the apparent power rated value Sn. The current or power is used as the feedback value, and the output of the PI loop PI_out is assigned to IdPos. Based on the constraint adjustment, a feedforward estimation current Idpos_cal is initially estimated as the feedforward. The positive sequence active current Idpos is solved by the method for determining the positive sequence active current during fault ride in the three-phase grid-connected power system.

7. The device for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 6, characterized in that, The active current determination module is further configured to, based on the constraint condition that the maximum phase current is not greater than the maximum rated current of a single phase, select the largest value from the three phase current effective values ​​as the maximum current effective value, and calculate the positive sequence active current based on the feedforward estimated current, the three phase rated current, the maximum current effective value, the integral coefficient, and the proportional coefficient.

8. The device for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 6, characterized in that, The active current determination module is also used to calculate the average value of the three-phase currents based on the effective values ​​of the three-phase currents, and obtain the average current value, according to the constraint condition that the average value of the sum of the three-phase currents is equal to the three-phase rated current. The positive sequence active current is calculated based on the feedforward estimated current, the average current, the three-phase rated current, the integral coefficient, and the proportional coefficient.

9. The device for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 6, characterized in that, The active current determination module is further configured to, based on the constraint condition that the apparent power of any phase is not greater than the maximum power of a single phase, select the largest value from the apparent power of the three phases as the maximum apparent power, and calculate the positive sequence active current based on the feedforward estimated current, the maximum apparent power, the rated apparent power, the integral coefficient, and the proportional coefficient.

10. The device for determining the positive-sequence active current during fault ride-through in a three-phase grid-connected power system according to claim 6, characterized in that, The active current determination module is further configured to calculate the average value of the apparent power of the three phases based on the constraint condition that the sum of the apparent power of the three phases is equal to the rated apparent power of the three phases, and obtain the power average value; and to calculate the positive sequence active current based on the feedforward estimated current, the power average value, the rated apparent power value, the integral coefficient and the proportional coefficient.

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