Self-adaptive virtual synchronous generator impedance setting method and device and medium

Abstract

The invention discloses a self-adaptive virtual synchronous generator impedance setting method and device and a medium, and the method comprises the steps: obtaining a first voltage reference value and a second voltage reference value through building an open-loop voltage control model; when the current flowing through the grid-forming converter is smaller than the current limiting amplitude, the voltage of the grid-forming converter is adjusted to be a first voltage reference value, and otherwise, the voltage is adjusted to be a second voltage reference value; and the resistance and inductance of the virtual impedance are controlled in a conservative feasible region. According to the self-adaptive virtual synchronous generator impedance setting method and device and the medium, the voltage is correspondingly adjusted according to the numerical value of the current flowing through a grid-forming type current converter, and the impedance of the grid-forming type current converter is adjusted by limiting the change of the parameter of the virtual impedance in a conservative feasible region considering the time delay. According to the method, the converter can be ensured to operate stably under various power grid conditions, and the problem that current limiting is difficult to carry out on the network-forming type converter under the condition that time delay is considered so as to improve the overall performance of the converter can be solved.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to an adaptive virtual synchronous generator impedance setting method, device and medium. Background Art

[0002] The massive access to new energy sources has led to a continuous increase in the proportion of power electronic converter-type power sources; at the same time, grid-type converters are more popular than grid-type converters because they can spontaneously provide inertia or frequency support when the power system needs it. However, the grid-type converter has limited current tolerance and requires additional current limiting measures to ensure the safe operation of the converter. Among the traditional current limiting measures, the virtual impedance method and the saturation current method are the two main methods for current limiting grid-type converters. Among them, the virtual impedance method mainly introduces virtual impedance in the control loop to achieve certain control goals of the power grid, such as power decoupling, reactive power distribution, etc.; the response speed of the control loop is crucial to achieving these goals.

[0003] Since the time delay of voltage measurement will increase the overall response time of the control loop and reduce the dynamic response performance of the system, this time delay is often not specifically considered and compensated in the traditional virtual impedance control strategy. However, the time delay of voltage measurement will cause a deviation between the voltage signal received by the control strategy and the actual grid voltage. This deviation will directly affect the calculation results and decision-making process of the control strategy, resulting in a decrease in control accuracy. In addition, the traditional virtual impedance control mode is relatively complex, and its set virtual impedance can easily cause the converter fault current to be over-restricted under shallow faults, thereby affecting the power delivery of the converter under faults, causing it to fail to meet the low voltage ride-through requirements. Summary of the invention

[0004] The present invention provides an adaptive virtual synchronous generator impedance setting method, device and medium to solve the problem that it is difficult to limit the current of a grid-type converter in consideration of time delay to improve the overall performance of the converter.

[0005] Obtaining control data of a grid-type converter;

[0006] According to the control data, a first voltage reference value is obtained by establishing an open-loop voltage control model;

[0007] Based on the open-loop voltage control model, a second voltage reference value is established by adding resistance and inductance of a virtual impedance;

[0008] When a fault occurs and causes the current flowing through the grid-type converter to be less than the current limit, the voltage of the grid-type converter is adjusted to the first voltage reference value; otherwise, the voltage is adjusted to the second voltage reference value;

[0009] Controlling the resistance and inductance of the virtual impedance to be within a conservative feasible domain; wherein the conservative feasible domain is established based on the initial feasible domain and according to the time-delay measurement voltage of the common coupling point;

[0010] Among them, the initial feasible domain is:

[0011]

[0012] Among them, R v is the virtual impedance resistor, L v is the virtual impedance inductor, ω min is the minimum frequency of the grid-type converter, u pf is the time-delay measurement voltage value that needs to be substituted into the parameter, U p is the voltage modulus, I max is the preset maximum current threshold.

[0013] The present invention can obtain a first voltage reference value by establishing an open-loop voltage control model. The first voltage reference value mainly reflects the influence of the internal parameters of the converter on the voltage reference value. Therefore, when it is detected that the current flowing through the grid-type converter is less than the current limit, it means that the system may be experiencing a certain fault or abnormal situation, but has not yet reached a serious overload state; at this time, by quickly adjusting the voltage to the first voltage reference value, it can be ensured that the fluctuation of the output voltage is within an acceptable range. By adding the resistance and inductance of the virtual impedance, the second voltage reference value more comprehensively considers the influence of the resistance and inductance of the entire system on the voltage reference value, which can better adapt to the characteristics of the power grid and reduce the mismatch and conflict with the power grid; therefore, when it is detected that the current flowing through the grid-type converter is greater than or equal to the current limit, it means that the system may be experiencing a certain fault or abnormal situation and has reached a serious overload state, so it is necessary to consider the influence of the entire system on the converter voltage control. At this time, by quickly adjusting the voltage to the second voltage reference value, customized control of the converter voltage output can be achieved, improving the overall performance and efficiency of the system. In addition, by considering the time delay of voltage measurement to establish a conservative feasible domain, it can be ensured that the parameters of the virtual impedance can still be kept within a reasonable range when the voltage measurement is inaccurate or there is a delay, which helps prevent system instability or failure caused by improper parameter setting, thereby improving the stability and reliability of the entire system.

[0014] Compared with the prior art, the present invention adjusts the voltage of the mesh converter according to the value of the current flowing through the mesh converter. This flexible and simple fault response mechanism ensures the stability and reliability of the system under different working conditions. By limiting the parameters of the virtual impedance to change within the conservative feasible domain considering the time delay, it can ensure that the converter can operate stably under various power grid conditions and achieve effective current limiting. Therefore, it can solve the problem of difficulty in current limiting the mesh converter while considering the time delay to improve the overall performance of the converter.

[0015] As a preferred solution, according to the control data, an open-loop voltage control model is established to obtain a first voltage reference value, specifically:

[0016] In the grid-type converter, based on the control data, a system model is established by equating the right circuit of the common coupling point to an equivalent circuit consisting of an infinite voltage source and a series reactance; wherein the system model represents the difference between the output voltage of the grid-type converter and the voltage at the common coupling point;

[0017] Based on the system model, the open-loop voltage control model is established by controlling the voltage of the common coupling point to be parallel to the d-axis, and the first voltage reference value is obtained according to the open-loop voltage control model.

[0018] This preferred solution can greatly reduce the complexity of the system model by simplifying the complex power system network into an equivalent voltage source and series reactance. This simplification not only reduces the amount of calculation, but also improves the understandability and controllability of the system. In the control of the grid-type converter, by setting the voltage control target to be parallel to the d-axis, that is, the direct axis component in the synchronous rotating coordinate system, the stability of the common coupling point voltage can be more effectively maintained.

[0019] As a preferred solution, the conservative feasible region is established based on the initial feasible region and according to the time-delay measurement voltage of the common coupling point, specifically:

[0020] When the grid-side voltage drops, establishing a voltage equation at the common coupling point;

[0021] In combination with the second voltage reference value and the voltage equation, a current equation is established by replacing the voltage and current in the second voltage reference value with the voltage and current when the fault occurs;

[0022] By limiting the current in the current equation to not exceed a preset maximum threshold, a feasible domain of virtual impedance resistance and virtual impedance inductance that can meet the current limiting condition is established;

[0023] The initial feasible region is established based on the virtual impedance resistor and the virtual impedance inductor feasible region, and the conservative feasible region is obtained by combining the time-delay measurement voltage of the common coupling point.

[0024] In this preferred solution, when the voltage on the grid side drops, by establishing voltage equations and current equations, the grid fault can be evaluated and responded to in real time. By substituting the voltage and current at the time of the fault into the current equation, and combining the condition that the current is limited to not exceed the preset maximum threshold, the feasible range of virtual impedance resistance and inductance values ​​that meet the current limiting conditions can be accurately calculated. In addition, the establishment of the conservative feasible domain not only takes into account the current limiting conditions, but also combines the voltage conditions of the common coupling point when the grid side voltage drops. This comprehensive consideration helps to optimize the operating efficiency and performance of the system while ensuring the safe and stable operation of the system.

[0025] As a preferred solution, the initial feasible region is established based on the feasible regions of the virtual impedance resistor and the virtual impedance inductor, and the conservative feasible region is obtained by combining the time-delay measurement voltage of the common coupling point, which is specifically:

[0026] Replacing the frequency of the feasible domain of the virtual impedance resistor and the virtual impedance inductor with the minimum frequency of the grid-type converter, and performing parameter transformation on the feasible domain of the virtual impedance resistor and the virtual impedance inductor to obtain the initial feasible domain of the virtual impedance resistor and the virtual impedance inductor;

[0027] In the case of voltage drop and recovery, the conservative feasible region including two types of threshold values ​​is obtained by substituting the time-delay measured voltage including the common coupling point into the initial feasible region for calculation.

[0028] This preferred solution can reduce system oscillation and improve system stability in the face of complex and changeable power grid environments through frequency replacement. During voltage drop and recovery, reasonable setting of virtual impedance parameters can reduce protection actions triggered by voltage fluctuations and reduce the risk of power grid failure.

[0029] As a preferred solution, in the case of voltage drop and recovery, the conservative feasible region including two types of threshold values ​​is obtained by substituting the time-delay measurement voltage including the common coupling point into the initial feasible region for calculation, specifically:

[0030] When the grid-side voltage drops, the time-delayed measured voltage after the change of the common coupling point is substituted into the initial feasible region for calculation to obtain a first conservative feasible region;

[0031] When the grid-side voltage is restored, the voltage modulus value of the common coupling point in a steady state is substituted into the initial feasible region for calculation to obtain a second conservative feasible region;

[0032] The conservative feasible region is composed of the first conservative feasible region and the second conservative feasible region.

[0033] In this preferred solution, the construction of the conservative feasible domain takes into account the extreme changes in voltage. By calculating the first conservative feasible domain and the second conservative feasible domain respectively, the virtual impedance parameters can be adjusted more finely to adapt to the different needs during voltage drop and recovery. This adaptive response method enhances the adaptability of the power grid to various operating conditions and improves the robustness of the system.

[0034] The present invention also provides an adaptive virtual synchronous generator impedance setting device, comprising a data module, a model module, a parameter module, an adjustment module and a control module;

[0035] Wherein, the data module is used to obtain control data of the grid-type converter;

[0036] The model module is used to obtain a first voltage reference value by establishing an open-loop voltage control model according to the control data;

[0037] The parameter module is used to establish a second voltage reference value by adding resistance and inductance of a virtual impedance based on the open-loop voltage control model;

[0038] The adjustment module is used to adjust the voltage of the meshed converter to the first voltage reference value when a fault occurs and causes the current flowing through the meshed converter to be less than the current limit, otherwise, adjust the voltage to the second voltage reference value;

[0039] The control module is used to control the resistance and inductance of the virtual impedance within a conservative feasible domain; wherein the conservative feasible domain is established based on the initial feasible domain and according to the time-delay measurement voltage of the common coupling point;

[0040] Among them, the initial feasible domain is:

[0041]

[0042] Among them, R v is the virtual impedance resistor, L v is the virtual impedance inductor, ω min is the minimum frequency of the grid-type converter, u pf is the time-delay measurement voltage value that needs to be substituted into the parameter, U p is the voltage modulus, I max is the preset maximum current threshold.

[0043] As a preferred solution, the model module includes a model unit and a numerical unit;

[0044] The model unit is used to establish a system model in the grid-type converter based on the control data by equating the right circuit of the common coupling point to an equivalent circuit consisting of an infinite voltage source and a series reactance; wherein the system model represents the difference between the output voltage of the grid-type converter and the voltage at the common coupling point;

[0045] The numerical unit is used to establish the open-loop voltage control model based on the system model by controlling the voltage of the common coupling point to be parallel to the d-axis, and obtain the first voltage reference value according to the open-loop voltage control model.

[0046] As a preferred solution, the control module includes a voltage unit, a current unit, a construction unit and a threshold unit;

[0047] Wherein, the voltage unit is used to establish a voltage equation at the common coupling point when the grid-side voltage drops;

[0048] The current unit is used to combine the second voltage reference value and the voltage equation to establish a current equation by replacing the voltage and current in the second voltage reference value with the voltage and current when a fault occurs;

[0049] The construction unit is used to establish a feasible domain of virtual impedance resistance and virtual impedance inductance that can meet the current limiting condition by limiting the current in the current equation to not exceed a preset maximum threshold;

[0050] The threshold unit is used to establish the initial feasible domain based on the virtual impedance resistor and the virtual impedance inductor feasible domain, and obtain the conservative feasible domain in combination with the time-delay measurement voltage of the common coupling point.

[0051] As a preferred solution, the threshold unit includes a transformation subunit and a parameter subunit;

[0052] The transformation subunit is used to replace the frequency of the feasible domain of the virtual impedance resistor and the virtual impedance inductor with the minimum frequency of the grid-type converter, and to perform parameter transformation on the feasible domain of the virtual impedance resistor and the virtual impedance inductor to obtain the initial feasible domain of the virtual impedance resistor and the virtual impedance inductor;

[0053] The parameter subunit is used for obtaining the conservative feasible region including two types of threshold values ​​by substituting the time-delay measurement voltage including the common coupling point into the initial feasible region for calculation in the case of voltage drop and recovery.

[0054] As a preferred solution, the parameter subunit is specifically:

[0055] When the grid-side voltage drops, the time-delayed measured voltage after the change of the common coupling point is substituted into the initial feasible region for calculation to obtain a first conservative feasible region;

[0056] When the grid-side voltage is restored, the voltage modulus value of the common coupling point in a steady state is substituted into the initial feasible region for calculation to obtain a second conservative feasible region;

[0057] The conservative feasible region is composed of the first conservative feasible region and the second conservative feasible region.

[0058] The present application also provides a storage medium, on which a computer program is stored. The computer program is called and executed by a computer to implement the above-mentioned adaptive virtual synchronous generator impedance setting method. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a flow chart of an adaptive virtual synchronous generator impedance setting method provided in an embodiment of the present application;

[0060] Figure 2 is a topological diagram of a test system provided in an embodiment of the present application;

[0061] Figure 3 is a power control block diagram of a test system considering current limitation provided in an embodiment of the present application;

[0062] Figure 4 is a dynamic response diagram of the test system provided in the embodiment of the present application under severe fault;

[0063] Figure 5 It is a structural schematic diagram of an adaptive virtual synchronous generator impedance setting device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0064] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0065] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "several" means two or more.

[0066] An adaptive virtual synchronous generator impedance setting method provided in an embodiment of the present application is mainly used in situations where it is necessary to provide a suitable virtual impedance setting solution while considering time delay to improve the overall performance of the converter.

[0067] Embodiment 1:

[0068] See also Figure 1 The embodiment of the present application provides an adaptive virtual synchronous generator impedance setting method, including S1 to S5, and the specific implementation steps are as follows:

[0069] S1. Obtain control data of the grid-connected converter.

[0070] Step S1 of the embodiment of the present application is specifically as follows:

[0071] The control data of a VSC is obtained; wherein the VSC is connected to an infinite bus system via a transmission line, and the VSC adopts a virtual synchronous control strategy.

[0072] S2. Obtain a first voltage reference value by establishing an open-loop voltage control model according to the control data.

[0073] Step S2 of the embodiment of the present application is specifically as follows:

[0074] In a grid-type converter, based on control data, when the shunt capacitor at the point of common coupling (PCC) is less than a preset value, the shunt capacitor is ignored by using the Thevenin theorem to equate the right circuit of the PCC to an equivalent circuit consisting of an infinite voltage source and a series reactance. C f The influence of isotropic converter is considered, and a system model is established; wherein the system model represents the difference between the output voltage of the grid-type converter and the voltage at the common coupling point;

[0075] Based on the system model, an open-loop voltage control model (a virtual synchronous generator open-loop voltage control model) is established by controlling the voltage of the common coupling point to be parallel to the d-axis, and a first voltage reference value is obtained according to the open-loop voltage control model, and the first voltage reference value is defined as a steady-state control strategy;

[0076] Among them, the equation for the grid-type converter connected to the infinite bus system via a transmission line can be written as follows:

[0077]

[0078] Expanding the above formula, we can get the system model, that is, the circuit equation:

[0079]

[0080] The voltage at the control common coupling point is parallel to the d-axis and can be expressed as:

[0081]

[0082] The open-loop voltage control model is:

[0083]

[0084] Among them, R c and L c is the resistance and inductance of the phase reactor, U p is the voltage modulus of the common coupling point in steady state, and are the voltage reference values ​​of the grid-type converter on the d-axis and q-axis respectively, and are the voltage reference values ​​of the common coupling point on the d-axis and q-axis respectively, and are the current reference values ​​of the grid-type converter on the d-axis and q-axis respectively, and are voltage reference values ​​of the first voltage reference value on the d-axis and on the q-axis respectively, j is an imaginary unit, and ω is an angular frequency.

[0085] This embodiment S2 can greatly reduce the complexity of the system model by simplifying the complex power system network into an equivalent voltage source and series reactance. This simplification not only reduces the amount of calculation, but also improves the understandability and controllability of the system. In the control of the grid-type converter, by setting the voltage control target to be parallel to the d-axis, that is, the direct axis component in the synchronous rotating coordinate system, the stability of the common coupling point voltage can be more effectively maintained;

[0086] Moreover, the steady-state control strategy can control the voltage at the common coupling point without introducing a voltage outer loop; at the same time, the control strategy does not need to control the voltage u on the grid side. s and angular frequency ω s The measurement is carried out regardless of the strength of the receiving power grid.

[0087] S3. Based on the open-loop voltage control model, a second voltage reference value is established by adding resistance and inductance of the virtual impedance.

[0088] Step S3 of the embodiment of the present application is specifically as follows:

[0089] Based on the open-loop voltage control model, a second voltage reference value is established by adding the resistance and inductance of the virtual impedance, and the second voltage reference value is defined as a virtual impedance control strategy;

[0090] Among them, the second voltage reference value is:

[0091]

[0092] Among them, R c and L c are the resistance and inductance of the phase reactor, U p is the voltage magnitude at the common coupling point in the steady state, and are the current reference values of the network-forming converter on the d-axis and the q-axis respectively, and are the voltage reference values of the second voltage reference value on the d-axis and the q-axis respectively, ω is the angular frequency, R ν and L ν are the resistance and inductance of the virtual impedance respectively.

[0093] S4. When a fault occurs and the current flowing through the network-forming converter is less than the current limit, adjust the voltage of the network-forming converter to the first voltage reference value; otherwise, adjust the voltage to the second voltage reference value.

[0094] Specifically, step S4 of the embodiment of the present application is as follows:

[0095] According to the relationship between the current i c flowing through the network-forming converter and the preset current limit I cmax when a fault occurs, establish an algebraic variable criterion and a state variable criterion respectively;

[0096] Based on the algebraic variable criterion and the state variable criterion, when a fault occurs and the absolute value of the current flowing through the network-forming converter is less than the current limit, that is, when |i c | < I cmax or -arccos(d) < θ c < arccos(d), adjust the voltage of the network-forming converter to the first voltage reference value, so that the network-forming converter still operates under the steady-state control strategy of the first voltage reference value;

[0097] Based on the algebraic variable criterion and the state variable criterion, when a fault occurs and the absolute value of the current flowing through the network-forming converter is greater than or equal to the current limit, that is, when |i c | ≥ I cmax or "θ c ≤ -arccos(d) or θ c (d)", adjust the voltage of the network-forming converter to the second voltage reference value, so that the network-forming converter operates under the virtual impedance control strategy of the second voltage reference value;

[0098] Among them, the algebraic variable criterion is:

[0099]

[0100] The state variable criterion is:

[0101]

[0102] θ c =arccos(d)

[0103] Among them, U p is the voltage modulus of the common coupling point in steady state, U s is the voltage amplitude on the grid side, I cmax is the maximum current flowing through the grid-type converter, θ c is the power factor angle of the grid-type converter, d is the cosine value of the power factor, R l and L l are the resistance and inductance of the transmission line, j is the imaginary unit, ω is the angular frequency, i c is the current flowing through the grid-type converter.

[0104] In this embodiment S4, when a fault occurs, the current flowing through the grid-type converter can be controlled by voltage switching, thereby limiting the voltage u s Overcurrent caused by falling.

[0105] S5. Control the resistance and inductance of the virtual impedance within the conservative feasible domain; wherein the conservative feasible domain is established based on the initial feasible domain and the time-delay measured voltage at the common coupling point;

[0106] Among them, the initial feasible domain is:

[0107]

[0108] Among them, R v is the virtual impedance resistor, L v is the virtual impedance inductor, ω min is the minimum frequency of the grid-type converter, u pf is the time-delay measurement voltage value that needs to be substituted into the parameter, U p is the voltage modulus, I max is the preset maximum current threshold.

[0109] Step S5 of the embodiment of the present application includes S5.1 to S5.4; specifically, it is:

[0110] S5.1, on the grid side voltage u s When the voltage drops, the voltage at the common coupling point becomes u pf , thereby establishing the voltage equation (circuit equation) at the common coupling point;

[0111] The open-loop control speed of the converter is very fast, so it can be considered Combining the second voltage reference value and the voltage equation, the voltage u at the time of the fault is calculated by cf and current i cf Substitute u in the second voltage reference value c and i c , establish the transition voltage equation;

[0112] Solve the transition voltage equation to obtain the current equation;

[0113] By limiting the current in the current equation to not exceed the preset maximum threshold I max , establish the feasible domain of virtual impedance resistance and virtual impedance inductance that can meet the current limiting conditions;

[0114] The voltage equation is:

[0115]

[0116] The transition voltage equation is:

[0117]

[0118] The current equation is:

[0119]

[0120] The control current does not exceed the preset maximum threshold, which can be expressed as:

[0121]

[0122] The feasible domain of virtual impedance resistance and virtual impedance inductance is:

[0123]

[0124] Among them, R c and L c is the resistance and inductance of the phase reactor, U p is the voltage modulus of the common coupling point in steady state, and is the grid side voltage u s The voltages of the grid-type converter on the d-axis and q-axis during the drop, and is the grid side voltage u s The voltage of the common coupling point on the d-axis and q-axis respectively during the drop, and is the grid side voltage u s The current of the grid-type converter on the d-axis and q-axis respectively during the drop, R ν and Lν are the resistance and inductance of the virtual impedance, ω is the angular frequency, I max is the preset maximum threshold value for current.

[0125] In this embodiment S5.1, when the grid voltage drops, the grid fault can be evaluated and responded to in real time by establishing the voltage equation and the current equation. By substituting the voltage and current at the time of the fault into the current equation, and combining the condition that the current is limited to not exceed the preset maximum threshold, the feasible range of virtual impedance resistance and inductance values ​​that meet the current limiting condition can be accurately calculated.

[0126] S5.2, based on the feasible domain of virtual impedance resistance and virtual impedance inductance, record the ellipse This formula represents the virtual impedance resistance R in the parameter space ν and virtual impedance inductor L ν The constraint is an ellipse;

[0127] remember Then the feasible domain of virtual impedance resistance and virtual impedance inductance shows that R ν and L ν The feasible region is about R ν and L ν The area outside the ellipse Γ;

[0128] Assume that the voltage u on the grid side is s The actual voltage of the common coupling point on the d-axis during the drop and the actual voltage on the q-axis can be accurately measured, then an adaptive R that satisfies current limiting and frequency limiting can be obtained. v and L v The first feasible domain of is:

[0129]

[0130] When a fault occurs, the voltage amplitude at the common coupling point is smaller than that in steady-state operation, as shown in the voltage formula:

[0131]

[0132] Based on voltage type, By estimating, we can get the estimated formula, namely:

[0133]

[0134] It can be seen that the estimation formula shows that under the adaptive setting strategy, any situation The upper bounds are all less than Therefore, the first feasible region gives a wider feasible region, so Rv and L v The value of can be smaller, and the current of the system will not be limited too low under shallow faults;

[0135] Among them, R ν and L ν are the resistance and inductance of the virtual impedance, R c and L c is the resistance and inductance of the phase reactor, ω min is the minimum frequency of the grid-type converter, U p is the voltage modulus of the common coupling point in steady state, and is the grid side voltage u s The actual measured voltage on the d-axis and the actual measured voltage on the q-axis at the common coupling point during the drop, is the grid side voltage u s The actual measured voltage at the common coupling point during the drop, I max is the preset maximum current threshold.

[0136] S5.3, Yes Make an initial estimate and obtain an estimated value;

[0137] Based on the estimated value, the frequency of the feasible domain of the virtual impedance resistor and the virtual impedance inductor is replaced with the minimum frequency of the grid-type converter, and the parameters of the feasible domain of the virtual impedance resistor and the virtual impedance inductor are transformed to obtain the initial feasible domain of the virtual impedance resistor and the virtual impedance inductor;

[0138] When the voltage on the grid side drops, the changed voltage at the common coupling point is substituted into the initial feasible region for calculation to obtain the first conservative feasible region;

[0139] When the grid voltage is restored, the voltage modulus U p , substitute into the initial feasible region for calculation, and obtain the second conservative feasible region;

[0140] The first conservative feasible domain and the second conservative feasible domain constitute a conservative feasible domain;

[0141] Among them, the estimated value is:

[0142]

[0143] The initial feasible domain is:

[0144]

[0145] Among them, U p is the voltage modulus of the common coupling point in steady state, and is the grid side voltage u s The voltage of the common coupling point on the d-axis and q-axis respectively during the drop, u pf is the grid side voltage u s Voltage at the common coupling point during the drop, I max is the preset maximum current threshold, R ν is the virtual impedance resistor, L ν is the virtual impedance inductor, ω min It is the minimum frequency of the grid-type converter.

[0146] In this embodiment S5.3, frequency replacement can reduce system oscillation and improve system stability in the face of complex and changeable power grid environments. During voltage drop and recovery, reasonable setting of virtual impedance parameters can reduce protection actions triggered by voltage fluctuations and reduce the risk of power grid failures;

[0147] In addition, the construction of the conservative feasible domain takes into account the extreme changes in voltage. By calculating the first conservative feasible domain and the second conservative feasible domain respectively, the virtual impedance parameters can be adjusted more finely to adapt to the different needs during voltage drop and recovery. This adaptive response method enhances the grid's adaptability to various operating conditions and improves the robustness of the system.

[0148] S5.4, record For the voltage drop process on the grid side, there is Δu pf > 0, for the grid side voltage recovery process, there is Δu pf <0;

[0149] When Δu pf >0, the resistance and inductance of the virtual impedance are in the first conservative feasible region of the conservative feasible region;

[0150] When Δu pf When <0, the resistance and inductance of the virtual impedance are within the second conservative feasible region of the conservative feasible region.

[0151] It should be noted that when Δu pf >0, it is the voltage drop process, use Substituting into the initial feasible region, it is obvious that: Therefore, the use of Determining the feasible domain is relative to adopting It is more conservative, and the solution of this embodiment can support the current under shallow faults as much as possible;

[0152] When Δu pf When <0, it is the voltage recovery process, and g(U p ) is substituted into the initial feasible region to determine the feasible region. The specific reasons are: on the one hand, when the voltage is restored Right now Compared to is not more conservative, so the delayed As a reference for setting. On the other hand, g(U p ) compared to is always more conservative, and during voltage recovery, since the grid voltage is u s In order to ensure the smooth progress of the voltage recovery process, the current i flowing through the converter c Always do not exceed the limit, so use g(U p ) to conservatively determine the virtual impedance R v and L v feasible domain.

[0153] Please refer to Table 1, which is a table of test system parameters provided in an embodiment of the present application, indicating system parameters used to verify the proposed adaptive virtual synchronous generator impedance setting method.

[0154] Table 1 Test system parameters

[0155]

[0156] To apply the embodiments of this application, please refer to Figure 2 , Figure 2 It is a topological diagram of the test system provided in an embodiment of the present application, showing a main circuit in which a meshed converter is connected to an infinite AC bus through a transmission line.

[0157] To apply the embodiments of this application, please refer to Figure 3 , Figure 3 It is a power control block diagram of the test system provided in an embodiment of the present application taking current limitation into consideration, representing a power control method of a grid-type converter taking current limitation into consideration.

[0158] To apply the embodiments of this application, please refer to Figure 4 , Figure 4 It is a dynamic response diagram of the test system provided in the embodiment of the present application under a serious fault, which indicates the global stability of the system under a serious fault. As shown in part (a), after the fault at point B is cleared, the deceleration area of ​​the first cycle in the CLC mode is not enough to reduce the system angular velocity to the synchronous angular velocity, and the system enters the second cycle and switches to the CVC mode. After that, the trajectory runs along DEF, enters the CLC control mode in the second cycle, and finally at point G in the second cycle, the system angular velocity is reduced to the synchronous angular velocity. After that, the system swings back and reaches point H as far as possible. Finally, after a series of oscillations, the system stabilizes at a stable equilibrium point. The phase plane diagram shown in part (c) also shows that the system continuously switches at the switching line of the two cycles, and finally maintains the stability of the system. It is worth noting that even under such a serious fault, the system of this embodiment still maintains stability.

[0159] Overall, the embodiments of the present application have the following beneficial effects:

[0160] The present invention can obtain a first voltage reference value by establishing an open-loop voltage control model. The first voltage reference value mainly reflects the influence of the internal parameters of the converter on the voltage reference value. Therefore, when it is detected that the current flowing through the grid-type converter is less than the current limit, it means that the system may be experiencing a certain fault or abnormal situation, but has not yet reached a serious overload state; at this time, by quickly adjusting the voltage to the first voltage reference value, it can be ensured that the fluctuation of the output voltage is within an acceptable range. By adding the resistance and inductance of the virtual impedance, the second voltage reference value more comprehensively considers the influence of the resistance and inductance of the entire system on the voltage reference value, which can better adapt to the characteristics of the power grid and reduce the mismatch and conflict with the power grid; therefore, when it is detected that the current flowing through the grid-type converter is greater than or equal to the current limit, it means that the system may be experiencing a certain fault or abnormal situation and has reached a serious overload state, so it is necessary to consider the influence of the entire system on the converter voltage control. At this time, by quickly adjusting the voltage to the second voltage reference value, customized control of the converter voltage output can be achieved, improving the overall performance and efficiency of the system. In addition, by considering the time delay of voltage measurement to establish a conservative feasible region, it can be ensured that the parameters of the virtual impedance can still be kept within a reasonable range when the voltage measurement is inaccurate or there is a delay, which helps to prevent system instability or failure caused by improper parameter setting, thereby improving the stability and reliability of the entire system;

[0161] Therefore, the embodiment of the present application first establishes an open-loop voltage control model of a virtual synchronous generator, and then proposes a virtual impedance control strategy based on the proposed open-loop voltage control model. Finally, considering the time delay problem in actual working conditions, an adaptive virtual impedance setting scheme that takes time delay into consideration is proposed, which is beneficial to improving the safe and stable operation capability of the converter.

[0162] Embodiment 2:

[0163] See also Figure 5 , an embodiment of the present application provides an adaptive virtual synchronous generator impedance setting device, including a data module 10, a model module 20, a parameter module 30, an adjustment module 40 and a control module 50;

[0164] Wherein, the data module 10 is used to obtain the control data of the grid-type converter;

[0165] A model module 20, configured to obtain a first voltage reference value by establishing an open-loop voltage control model according to the control data;

[0166] A parameter module 30, for establishing a second voltage reference value by adding resistance and inductance of a virtual impedance based on the open-loop voltage control model;

[0167] an adjustment module 40, configured to adjust the voltage of the grid-type converter to the first voltage reference value when a fault occurs and causes the current flowing through the grid-type converter to be less than the current limit, and otherwise, adjust the voltage to the second voltage reference value;

[0168] A control module 50, for controlling the resistance and inductance of the virtual impedance within a conservative feasible domain; wherein the conservative feasible domain is established based on the initial feasible domain and according to the time-delayed measured voltage of the common coupling point;

[0169] Among them, the initial feasible domain is:

[0170]

[0171] Among them, R v is the virtual impedance resistor, L v is the virtual impedance inductor, ω min is the minimum frequency of the grid-type converter, u pf is the time-delay measurement voltage value that needs to be substituted into the parameter, U p is the voltage modulus, I max is the preset maximum current threshold.

[0172] In one embodiment, the data module 10 is specifically:

[0173] The control data of a VSC is obtained; wherein the VSC is connected to an infinite bus system via a transmission line, and the VSC adopts a virtual synchronous control strategy.

[0174] In one embodiment, the model module 20 includes a model unit and a value unit;

[0175] The model unit is used to, in the grid-type converter, based on the control data, when the parallel capacitor at the point of common coupling (PCC) is less than a preset value, by using the Thevenin theorem to equate the right circuit of the common coupling point to an equivalent circuit consisting of an infinite voltage source and a series reactance, thereby ignoring the parallel capacitor C f The influence of isotropic converter is considered, and a system model is established; wherein the system model represents the difference between the output voltage of the grid-type converter and the voltage at the common coupling point;

[0176] A numerical unit is used to establish an open-loop voltage control model (a virtual synchronous generator open-loop voltage control model) based on a system model by controlling the voltage of the common coupling point to be parallel to the d-axis, obtain a first voltage reference value according to the open-loop voltage control model, and define the first voltage reference value as a steady-state control strategy;

[0177] Among them, the equation for the grid-type converter connected to the infinite bus system via a transmission line can be written as follows:

[0178]

[0179] Expanding the above formula, we can get the system model, that is, the circuit equation:

[0180]

[0181] The voltage at the control common coupling point is parallel to the d-axis and can be expressed as:

[0182]

[0183] The open-loop voltage control model is:

[0184]

[0185] Among them, R c and L c is the resistance and inductance of the phase reactor, U p is the voltage modulus of the common coupling point in steady state, and are the voltage reference values ​​of the grid-type converter on the d-axis and q-axis respectively, and are the voltage reference values ​​of the common coupling point on the d-axis and q-axis respectively, and are the current reference values ​​of the grid-type converter on the d-axis and q-axis respectively, and are voltage reference values ​​of the first voltage reference value on the d-axis and on the q-axis respectively, j is an imaginary unit, and ω is an angular frequency.

[0186] The model module 20 of this embodiment can greatly reduce the complexity of the system model by simplifying the complex power system network into an equivalent voltage source and series reactance. This simplification not only reduces the amount of calculation, but also improves the understandability and controllability of the system. In the control of the grid-type converter, by setting the voltage control target to be parallel to the d-axis, that is, the direct axis component in the synchronous rotating coordinate system, the stability of the common coupling point voltage can be more effectively maintained;

[0187] Moreover, the steady-state control strategy can control the voltage at the point of common coupling without introducing an outer voltage loop; meanwhile, this control strategy does not require the measurement of the grid-side voltage u s and the angular frequency ω s and is independent of the strength of the receiving-end grid.

[0188] In one embodiment, the parameter module 30 is specifically:

[0189] Based on the open-loop voltage control model, by adding the resistance and inductance of the virtual impedance, a second voltage reference value is established, and the second voltage reference value is defined as the virtual impedance control strategy;

[0190] wherein, the second voltage reference value is:

[0191]

[0192] wherein, R c and L c are the resistance and inductance of the phase reactor, U p is the voltage magnitude at the point of common coupling in the steady state, and are the current reference values of the grid-forming converter on the d-axis and on the q-axis respectively, and are the voltage reference values of the second voltage reference value on the d-axis and on the q-axis respectively, ω is the angular frequency, R ν and L ν are the resistance and inductance of the virtual impedance respectively.

[0193] In one embodiment, the adjustment module 40 is specifically:

[0194] According to the relationship between the current i c flowing through the grid-forming converter and the preset current limit I cmax when a fault occurs, an algebraic variable criterion and a state variable criterion are established respectively;

[0195] Based on the algebraic variable criterion and the state variable criterion, when a fault causes the absolute value of the current flowing through the grid-forming converter to be less than the current limit, that is, when |i c |<I cmax or -arccos(d) < θ c < arccos(d), the voltage of the grid-forming converter is adjusted to the first voltage reference value, so that the grid-forming converter still operates under the steady-state control strategy of the first voltage reference value;

[0196] Based on the algebraic variable criterion and the state variable criterion, when a fault causes the absolute value of the current flowing through the grid-forming converter to be greater than or equal to the current limit, that is, when |i c |≥Icmax When, or "θ c ≤-arccos(d) or θ c (d)”, adjusting the voltage of the grid-type converter to a second voltage reference value, so that the grid-type converter operates under a virtual impedance control strategy of the second voltage reference value;

[0197] Among them, the algebraic variable criterion is:

[0198]

[0199] The state variable criterion is:

[0200]

[0201] θ c =arccos(d)

[0202] Among them, U p is the voltage modulus of the common coupling point in steady state, U s is the voltage amplitude on the grid side, I cmax is the maximum current flowing through the grid-type converter, θ c is the power factor angle of the grid-type converter, d is the cosine value of the power factor, R l and L l are the resistance and inductance of the transmission line, j is the imaginary unit, ω is the angular frequency, i c is the current flowing through the grid-type converter.

[0203] In the present embodiment, the adjustment module 40 can control the current flowing through the grid-type converter by means of voltage switching when a fault occurs, thereby limiting the current caused by the grid-side voltage u s Overcurrent caused by falling.

[0204] In one embodiment, the control module 50 includes a voltage unit, a current unit, a construction unit, a certification unit, a transformation subunit, a parameter subunit and a control unit; specifically:

[0205] Voltage unit, used for grid-side voltage u s When the voltage drops, the voltage at the common coupling point becomes u pf , thereby establishing the voltage equation (circuit equation) at the common coupling point;

[0206] The current unit is used for the open-loop control of the converter at a very fast speed. Combining the second voltage reference value and the voltage equation, the voltage u at the time of the fault is calculated by cf and current i cf Substitute u in the second voltage reference value c and i c, establish the transition voltage equation;

[0207] The current unit is also used to solve the transition voltage equation to obtain the current equation;

[0208] A building block is used to limit the current in the current equation to not exceed a preset maximum threshold value I max , establish the feasible domain of virtual impedance resistance and virtual impedance inductance that can meet the current limiting conditions;

[0209] The voltage equation is:

[0210]

[0211] The transition voltage equation is:

[0212]

[0213] The current equation is:

[0214]

[0215] The control current does not exceed the preset maximum threshold, which can be expressed as:

[0216]

[0217] The feasible domain of virtual impedance resistance and virtual impedance inductance is:

[0218]

[0219] Among them, R c and L c is the resistance and inductance of the phase reactor, U p is the voltage modulus of the common coupling point in steady state, and is the grid side voltage u s The voltages of the grid-type converter on the d-axis and q-axis during the drop, and is the grid side voltage u s The voltage of the common coupling point on the d-axis and q-axis respectively during the drop, and is the grid side voltage u s The current of the grid-type converter on the d-axis and q-axis respectively during the drop, R ν and L ν are the resistance and inductance of the virtual impedance, ω is the angular frequency, I max is the preset maximum threshold value for current.

[0220] In the voltage unit, current unit and construction unit of this embodiment, when the voltage on the grid side drops, by establishing the voltage equation and the current equation, the grid fault can be evaluated and responded to in real time. By substituting the voltage and current at the time of the fault into the current equation, and combining the condition that the current is limited to not exceed the preset maximum threshold, the feasible range of virtual impedance resistance and inductance values ​​that meet the current limiting condition can be accurately calculated.

[0221] Proof unit for feasible domain based on virtual impedance resistor and virtual impedance inductor, note ellipse This formula represents the virtual impedance resistance R in the parameter space ν and virtual impedance inductor L ν The constraint is an ellipse;

[0222] Proof unit, also used to record Then the feasible domain of virtual impedance resistance and virtual impedance inductance shows that R ν and L ν The feasible region is about R ν and L ν The area outside the ellipse Γ;

[0223] The proof unit is also used to assume that the grid voltage u s The actual voltage of the common coupling point on the d-axis during the drop and the actual voltage on the q-axis can be accurately measured, then an adaptive R that satisfies current limiting and frequency limiting can be obtained. ν and L ν The first feasible domain of is:

[0224]

[0225] The proof unit is also used to prove that when a fault occurs, the voltage amplitude at the common coupling point is smaller than the amplitude during steady-state operation, as shown in the voltage formula:

[0226]

[0227] Proof unit, also used for voltage-based, By estimating, we can get the estimated formula, namely:

[0228]

[0229] It can be seen that the estimation formula shows that under the adaptive setting strategy, any situation The upper bounds are all less than Therefore, the first feasible region gives a wider feasible region, so R ν and L vThe value of can be smaller, and the current of the system will not be limited too low under shallow faults;

[0230] Among them, R ν and L ν are the resistance and inductance of the virtual impedance, R c and L c is the resistance and inductance of the phase reactor, ω min is the minimum frequency of the grid-type converter, U p is the voltage modulus of the common coupling point in steady state, and is the grid side voltage u s The actual measured voltage on the d-axis and the actual measured voltage on the q-axis at the common coupling point during the drop, is the grid side voltage u s The actual measured voltage at the common coupling point during the drop, I max is the preset maximum current threshold.

[0231] Transformation subunit, used to Make an initial estimate and obtain an estimated value;

[0232] The transformation subunit is further used to replace the frequency of the feasible domain of the virtual impedance resistor and the virtual impedance inductor with the minimum frequency of the grid-forming converter based on the estimated value, and to perform parameter transformation on the feasible domain of the virtual impedance resistor and the virtual impedance inductor to obtain the initial feasible domain of the virtual impedance resistor and the virtual impedance inductor;

[0233] The parameter subunit is used to substitute the changed voltage of the common coupling point into the initial feasible domain for calculation when the voltage on the grid side drops, so as to obtain the first conservative feasible domain;

[0234] The parameter subunit is also used to convert the voltage modulus U of the common coupling point at steady state into the value when the grid voltage is restored. p , substitute into the initial feasible region for calculation, and obtain the second conservative feasible region;

[0235] The parameter subunit is further used to form a conservative feasible domain from the first conservative feasible domain and the second conservative feasible domain;

[0236] Among them, the estimated value is:

[0237]

[0238] The initial feasible domain is:

[0239]

[0240] Among them, U p is the voltage modulus of the common coupling point in steady state, and is the grid side voltage u s The voltage of the common coupling point on the d-axis and q-axis respectively during the drop, u pf is the grid side voltage u s Voltage at the common coupling point during the drop, I max is the preset maximum current threshold, R ν is the virtual impedance resistor, L ν is the virtual impedance inductor, ω min It is the minimum frequency of the grid-type converter.

[0241] The conversion subunit and parameter subunit of this embodiment can reduce system oscillation and improve system stability in the face of complex and changeable power grid environments through frequency replacement. During voltage drop and recovery, reasonable setting of virtual impedance parameters can reduce protection actions triggered by voltage fluctuations and reduce the risk of power grid failures;

[0242] In addition, the construction of the conservative feasible domain takes into account the extreme changes in voltage. By calculating the first conservative feasible domain and the second conservative feasible domain respectively, the virtual impedance parameters can be adjusted more finely to adapt to the different needs during voltage drop and recovery. This adaptive response method enhances the grid's adaptability to various operating conditions and improves the robustness of the system.

[0243] Control unit for recording For the voltage drop process on the grid side, there is Δu pf > 0, for the grid side voltage recovery process, there is Δu pf <0;

[0244] The control unit is also used when Δu pf >0, the resistance and inductance of the virtual impedance are in the first conservative feasible region of the conservative feasible region;

[0245] The control unit is also used when Δu pf When <0, the resistance and inductance of the virtual impedance are within the second conservative feasible region of the conservative feasible region.

[0246] It should be noted that when Δu pf >0, it is the voltage drop process, use Substituting into the initial feasible region, it is obvious that: Therefore, the use of Determining the feasible domain is relative to adopting It is more conservative, and the solution of this embodiment can support the current under shallow faults as much as possible;

[0247] When Δu pf When <0, it is the voltage recovery process, and g(U p) is substituted into the initial feasible region to determine the feasible region. The specific reasons are: on the one hand, when the voltage is restored Right now Compared to is not more conservative, so the delayed As a reference for setting. On the other hand, g(U p ) compared to is always more conservative, and during voltage recovery, since the grid voltage is u s In order to ensure the smooth progress of the voltage recovery process, the current i flowing through the converter c Always do not exceed the limit, so use g(U p ) to conservatively determine the virtual impedance R v and L ν feasible domain.

[0248] Please refer to Table 1, which is a test system parameter table provided in an embodiment of the present application, indicating system parameters used to verify the proposed adaptive virtual synchronous generator impedance setting device.

[0249] Table 1 Test system parameters

[0250]

[0251] To apply the embodiments of this application, please refer to Figure 2 , Figure 2 It is a topological diagram of the test system provided in an embodiment of the present application, showing a main circuit in which a meshed converter is connected to an infinite AC bus through a transmission line.

[0252] To apply the embodiments of this application, please refer to Figure 3 , Figure 3 It is a power control block diagram of the test system provided in an embodiment of the present application taking current limitation into consideration, representing a power control method of a grid-type converter taking current limitation into consideration.

[0253] To apply the embodiments of this application, please refer to Figure 4 , Figure 4It is a dynamic response diagram of the test system provided in the embodiment of the present application under a serious fault, which indicates the global stability of the system under a serious fault. As shown in part (a), after the fault at point B is cleared, the deceleration area of ​​the first cycle in the CLC mode is not enough to reduce the system angular velocity to the synchronous angular velocity, and the system enters the second cycle and switches to the CVC mode. After that, the trajectory runs along DEF, enters the CLC control mode in the second cycle, and finally at point G in the second cycle, the system angular velocity is reduced to the synchronous angular velocity. After that, the system swings back and reaches point H as far as possible. Finally, after a series of oscillations, the system stabilizes at a stable equilibrium point. The phase plane diagram shown in part (c) also shows that the system continuously switches at the switching line of the two cycles, and finally maintains the stability of the system. It is worth noting that even under such a serious fault, the system of this embodiment still maintains stability.

[0254] Overall, the embodiments of the present application have the following beneficial effects:

[0255] The present invention can obtain a first voltage reference value by establishing an open-loop voltage control model. The first voltage reference value mainly reflects the influence of the internal parameters of the converter on the voltage reference value. Therefore, when it is detected that the current flowing through the grid-type converter is less than the current limit, it means that the system may be experiencing a certain fault or abnormal situation, but has not yet reached a serious overload state; at this time, by quickly adjusting the voltage to the first voltage reference value, it can be ensured that the fluctuation of the output voltage is within an acceptable range. By adding the resistance and inductance of the virtual impedance, the second voltage reference value more comprehensively considers the influence of the resistance and inductance of the entire system on the voltage reference value, which can better adapt to the characteristics of the power grid and reduce the mismatch and conflict with the power grid; therefore, when it is detected that the current flowing through the grid-type converter is greater than or equal to the current limit, it means that the system may be experiencing a certain fault or abnormal situation and has reached a serious overload state, so it is necessary to consider the influence of the entire system on the converter voltage control. At this time, by quickly adjusting the voltage to the second voltage reference value, customized control of the converter voltage output can be achieved, improving the overall performance and efficiency of the system. In addition, by considering the time delay of voltage measurement to establish a conservative feasible region, it can be ensured that the parameters of the virtual impedance can still be kept within a reasonable range when the voltage measurement is inaccurate or there is a delay, which helps to prevent system instability or failure caused by improper parameter setting, thereby improving the stability and reliability of the entire system;

[0256] Therefore, the embodiment of the present application first establishes an open-loop voltage control model of a virtual synchronous generator, and then proposes a virtual impedance control strategy based on the proposed open-loop voltage control model. Finally, considering the time delay problem in actual working conditions, an adaptive virtual impedance setting scheme that takes time delay into consideration is proposed, which is beneficial to improving the safe and stable operation capability of the converter.

[0257] Embodiment three:

[0258] An embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the adaptive virtual synchronous generator impedance setting method;

[0259] Wherein, the adaptive virtual synchronous generator impedance setting method, if implemented in the form of a software functional unit and used as an independent product, can be stored in a computer-readable storage medium. Based on such an understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0260] The above are preferred embodiments of the present invention. It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An adaptive virtual synchronous generator impedance setting method, It is characterized in that include: Obtaining control data of a grid-type converter; According to the control data, a first voltage reference value is obtained by establishing an open-loop voltage control model; Based on the open-loop voltage control model, a second voltage reference value is established by adding resistance and inductance of a virtual impedance; When a fault occurs and causes the current flowing through the grid-type converter to be less than the current limit, the voltage of the grid-type converter is adjusted to the first voltage reference value; otherwise, the voltage is adjusted to the second voltage reference value; Controlling the resistance and inductance of the virtual impedance to be within a conservative feasible domain; wherein the conservative feasible domain is established based on the initial feasible domain and according to the time-delay measurement voltage of the common coupling point; Among them, the initial feasible domain is: Among them, R v is the virtual impedance resistor, L v is the virtual impedance inductor, ω min is the minimum frequency of the grid-type converter, u pf is the time-delay measurement voltage value that needs to be substituted into the parameter, U p is the voltage modulus, I max is the preset maximum current threshold.

2. An adaptive virtual synchronous generator impedance setting method as claimed in claim 1, It is characterized in that According to the control data, an open-loop voltage control model is established to obtain a first voltage reference value, specifically: In the grid-type converter, based on the control data, a system model is established by equating the right circuit of the common coupling point to an equivalent circuit consisting of an infinite voltage source and a series reactance; wherein the system model represents the difference between the output voltage of the grid-type converter and the voltage at the common coupling point; Based on the system model, the open-loop voltage control model is established by controlling the voltage of the common coupling point to be parallel to the d-axis, and the first voltage reference value is obtained according to the open-loop voltage control model.

3. The adaptive virtual synchronous generator impedance setting method according to claim 1, It is characterized in that The conservative feasible region is established based on the initial feasible region and according to the time-delayed measured voltage at the common coupling point, specifically: When the grid-side voltage drops, establishing a voltage equation at the common coupling point; In combination with the second voltage reference value and the voltage equation, a current equation is established by replacing the voltage and current in the second voltage reference value with the voltage and current when the fault occurs; By limiting the current in the current equation to not exceed a preset maximum threshold, a feasible domain of virtual impedance resistance and virtual impedance inductance that can meet the current limiting condition is established; The initial feasible region is established based on the virtual impedance resistor and the virtual impedance inductor feasible region, and the conservative feasible region is obtained by combining the time-delay measurement voltage of the common coupling point.

4. An adaptive virtual synchronous generator impedance setting method as claimed in claim 3, It is characterized in that The initial feasible region is established based on the virtual impedance resistor and the virtual impedance inductor feasible region, and the conservative feasible region is obtained by combining the time-delay measurement voltage of the common coupling point, which is specifically: Replacing the frequency of the feasible domain of the virtual impedance resistor and the virtual impedance inductor with the minimum frequency of the grid-type converter, and performing parameter transformation on the feasible domain of the virtual impedance resistor and the virtual impedance inductor to obtain the initial feasible domain of the virtual impedance resistor and the virtual impedance inductor; In the case of voltage drop and recovery, the conservative feasible region including two types of threshold values ​​is obtained by substituting the time-delay measured voltage including the common coupling point into the initial feasible region for calculation.

5. An adaptive virtual synchronous generator impedance setting method as claimed in claim 4, It is characterized in that In the case of voltage drop and recovery, the conservative feasible region including two types of threshold values ​​is obtained by substituting the time-delay measurement voltage including the common coupling point into the initial feasible region for calculation, specifically: When the grid-side voltage drops, the time-delayed measured voltage after the change of the common coupling point is substituted into the initial feasible region for calculation to obtain a first conservative feasible region; When the grid-side voltage is restored, the voltage modulus value of the common coupling point in a steady state is substituted into the initial feasible region for calculation to obtain a second conservative feasible region; The conservative feasible region is composed of the first conservative feasible region and the second conservative feasible region.

6. An adaptive virtual synchronous generator impedance setting device, It is characterized in that It includes data module, model module, parameter module, adjustment module and control module; Wherein, the data module is used to obtain control data of the grid-type converter; The model module is used to obtain a first voltage reference value by establishing an open-loop voltage control model according to the control data; The parameter module is used to establish a second voltage reference value by adding resistance and inductance of a virtual impedance based on the open-loop voltage control model; The adjustment module is used to adjust the voltage of the meshed converter to the first voltage reference value when a fault occurs and causes the current flowing through the meshed converter to be less than the current limit, otherwise, adjust the voltage to the second voltage reference value; The control module is used to control the resistance and inductance of the virtual impedance within a conservative feasible domain; wherein the conservative feasible domain is established based on the initial feasible domain and according to the time-delay measurement voltage of the common coupling point; Among them, the initial feasible domain is: Among them, R v is the virtual impedance resistor, L v is the virtual impedance inductor, ω min is the minimum frequency of the grid-type converter, u pf is the time-delay measurement voltage value that needs to be substituted into the parameter, U p is the voltage modulus, I max is the preset maximum current threshold.

7. An adaptive virtual synchronous generator impedance setting device as claimed in claim 6, It is characterized in that The model module includes a model unit and a numerical unit; The model unit is used to establish a system model in the grid-type converter based on the control data by equating the right circuit of the common coupling point to an equivalent circuit consisting of an infinite voltage source and a series reactance; wherein the system model represents the difference between the output voltage of the grid-type converter and the voltage at the common coupling point; The numerical unit is used to establish the open-loop voltage control model based on the system model by controlling the voltage of the common coupling point to be parallel to the d-axis, and obtain the first voltage reference value according to the open-loop voltage control model.

8. An adaptive virtual synchronous generator impedance setting device as claimed in claim 6, It is characterized in that The control module includes a voltage unit, a current unit, a construction unit and a threshold unit; Wherein, the voltage unit is used to establish a voltage equation at the common coupling point when the grid-side voltage drops; The current unit is used to combine the second voltage reference value and the voltage equation to establish a current equation by replacing the voltage and current in the second voltage reference value with the voltage and current when a fault occurs; The construction unit is used to establish a feasible domain of virtual impedance resistance and virtual impedance inductance that can meet the current limiting condition by limiting the current in the current equation to not exceed a preset maximum threshold; The threshold unit is used to establish the initial feasible domain based on the virtual impedance resistor and the virtual impedance inductor feasible domain, and obtain the conservative feasible domain in combination with the time-delay measurement voltage of the common coupling point.

9. An adaptive virtual synchronous generator impedance setting device as claimed in claim 8, It is characterized in that The threshold unit includes a transformation subunit and a parameter subunit; The transformation subunit is used to replace the frequency of the feasible domain of the virtual impedance resistor and the virtual impedance inductor with the minimum frequency of the grid-type converter, and to perform parameter transformation on the feasible domain of the virtual impedance resistor and the virtual impedance inductor to obtain the initial feasible domain of the virtual impedance resistor and the virtual impedance inductor; The parameter subunit is used for obtaining the conservative feasible region including two types of threshold values ​​by substituting the time-delay measurement voltage including the common coupling point into the initial feasible region for calculation in the case of voltage drop and recovery.

10. An adaptive virtual synchronous generator impedance setting device as claimed in claim 9, It is characterized in that The parameter subunit is specifically: When the grid-side voltage drops, the time-delayed measured voltage after the change of the common coupling point is substituted into the initial feasible region for calculation to obtain a first conservative feasible region; When the grid-side voltage is restored, the voltage modulus value of the common coupling point in a steady state is substituted into the initial feasible region for calculation to obtain a second conservative feasible region; The conservative feasible region is composed of the first conservative feasible region and the second conservative feasible region.

11. A storage medium, It is characterized in that The storage medium stores a computer program, which is called and executed by a computer to implement any one of the adaptive virtual synchronous generator impedance setting methods according to claims 1 to 5.

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