Method and system for analyzing low-frequency passivity of multiple parallel virtual synchronous generators

Abstract

The invention discloses a method and a system for analyzing low-frequency passivity of multiple parallel virtual synchronous generators, and relates to the technical field of power systems. According to the method, a closed-loop control model of active power and reactive power of a single VSG in consideration of reactive coupling influence is constructed in a grid-connected mode, an equivalent P / omega admittance model of grid connection of the single VSG is constructed on the basis of the relationship between power and frequency represented by the model, and then a P / omega admittance model of grid connection of multiple parallel VSGs is constructed on the basis of the equivalent P / omega admittance model. Therefore, the low-frequency passivity of the multiple parallel VSGs can be analyzed. Therefore, the problem that the power frequency response of the VSG cannot be described accurately when the output active power and frequency response of the VSG are analyzed through an existing P / omega admittance model is solved, the coupling influence brought by reactive power control is equivalent to an active control ring under the condition that the power coupling influence is considered, the influence of reactive power coupling on the active power response is described, and the VSG output active power response can be accurately described. Therefore, the low-frequency passivity analysis of the multiple parallel virtual synchronous generators is more visual and accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and more specifically to a method and system for analyzing low-frequency passivity of multiple parallel virtual synchronous generators. Background Art

[0002] As the penetration rate of new energy sources such as photovoltaics and wind power continues to increase, the proportion of traditional synchronous generators has decreased, resulting in a decrease in the inertia and damping of the power system, which is not conducive to the safe and stable operation of the power grid. By making the grid-connected inverter simulate the operating characteristics of the synchronous generator, that is, using virtual synchronous generator (VSG) control, inertia and damping support can be provided for the power grid. However, VSG also has inherent low-frequency oscillation modes similar to synchronous generators. When multiple VSGs are connected in parallel, the low-frequency oscillation characteristics of the multi-parallel VSG system are far more complicated than those of a single VSG.

[0003] At present, the output active power and frequency response of VSG are analyzed by establishing a power loop equivalent P / ω admittance model by equating the active power loop to a two-port network. However, this model establishment process ignores the influence of power coupling on the power-frequency characteristics and cannot accurately characterize the power-frequency response of VSG. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators, so as to solve the problem that the output active power and frequency response of VSG cannot be accurately characterized by analyzing the existing P / ω admittance model. By considering the influence of power coupling, the coupling influence brought by reactive power control is equivalent to the active control loop, so as to describe the influence of reactive coupling on the active power response, making the analysis of the low-frequency passivity of multiple parallel virtual synchronous generators more intuitive and accurate.

[0005] In a first aspect, the present invention provides a method for analyzing low-frequency passivity of multiple parallel virtual synchronous generators, comprising:

[0006] In the grid-connected mode, a closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling;

[0007] Based on the relationship between power and frequency represented by the closed-loop control model, an equivalent P / ω admittance model of a single VSG connected to the grid is constructed;

[0008] Based on the equivalent P / ω admittance model of a single VSG grid-connected, a P / ω admittance model of multiple parallel VSG grid-connected is constructed;

[0009] Based on the P / ω admittance model of multiple parallel VSGs connected to the grid, the low-frequency passivity of multiple parallel VSGs is analyzed.

[0010] In a preferred solution, in the grid-connected mode, constructing a closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling includes:

[0011] In grid-connected mode, an initial closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling.

[0012] The reactive power reference variation in the initial closed-loop control model is taken as zero as a simplification condition, the initial closed-loop control model is simplified to obtain the closed-loop control model.

[0013] In a preferred solution, in the grid-connected mode, constructing an initial closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling includes:

[0014] In the grid-connected mode, based on the relationship between the system control parameters and the active power and the reactive power, an initial closed-loop control model of the active power and the reactive power of a single VSG is constructed when the reactive coupling effect is taken into account;

[0015] The system control parameters include: active power reference P0, reactive power reference Q0, virtual inertia J, angular frequency ω of VSG, frequency ω of public grid connection point pcc , Active power droop coefficient D p , power angle δ, reactive power droop coefficient K p , reactive power integral coefficient K i , VSG output voltage amplitude E, and the power angle coefficient and voltage amplitude coefficient of the active power and the reactive power.

[0016] In a preferred solution, the power angle coefficient and voltage amplitude coefficient of the active power and the reactive power include:

[0017]

[0018] Among them, H Pδ and H Qδ are the power angle coefficients of the active power and the reactive power respectively; H PE and H QE are the voltage amplitude coefficients of the active power and the reactive power respectively; R l and L l are the resistance and inductance of the circuit respectively; V ppc0 is the amplitude of the voltage at the common connection point when the system is running in steady state; E0 is the rated amplitude of the VSG output voltage; δ0 is the VSG steady-state operating power angle; ω0 is the rated angular frequency of the VSG.

[0019] In a preferred solution, the equivalent P / ω admittance model of a single VSG grid-connected is constructed based on the relationship between power and frequency represented by the closed-loop control model, including:

[0020] Based on the relationship between power and frequency represented by the closed-loop control model, the first admittance Y is determined respectively. a and the second admittance Y b ;

[0021] Based on the relationship between the first admittance and the second admittance and the active power reference, the angular frequency of the VSG and the frequency of the common grid connection point, an equivalent P / ω admittance model of a single VSG grid connection is constructed;

[0022] Wherein, the first admittance and the second admittance are respectively:

[0023] Y a =Jω0s+D p

[0024]

[0025] Among them, G RPC is the reactive power controller, equal to K p +K i / s; s is the Laplace operator.

[0026] In a preferred solution, the equivalent P / ω admittance model of a single VSG grid-connected is used to construct a P / ω admittance model of multiple parallel VSG grid-connected, including:

[0027] Based on the equivalent P / ω admittance model of a single VSG connected to the grid, the active power output ΔP is determined;

[0028] Based on active power output and grid P / ω admittance and ω g The relationship between them is used to construct the P / ω admittance model of multi-parallel VSG grid-connected.

[0029] In a second aspect, the present invention provides a system for analyzing low-frequency passivity of multiple parallel virtual synchronous generators, comprising:

[0030] The first model building unit is used to build a closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling in the grid-connected mode;

[0031] A second model building unit is used to build an equivalent P / ω admittance model of a single VSG grid-connected based on the relationship between power and frequency represented by the closed-loop control model;

[0032] A third model building unit is used to build a P / ω admittance model of multiple parallel VSGs connected to the grid based on an equivalent P / ω admittance model of a single VSG connected to the grid;

[0033] The passivity analysis unit is used to analyze the low-frequency passivity of multiple parallel VSGs based on the P / ω admittance model of multiple parallel VSGs connected to the grid.

[0034] In a preferred embodiment, the first model building unit is specifically used for:

[0035] In grid-connected mode, an initial closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling.

[0036] The reactive power reference variation in the initial closed-loop control model is taken as zero as a simplification condition, the initial closed-loop control model is simplified to obtain the closed-loop control model.

[0037] In a preferred embodiment, the first model building unit is more specifically used for:

[0038] In the grid-connected mode, based on the relationship between the system control parameters and the active power and the reactive power, an initial closed-loop control model of the active power and the reactive power of a single VSG is constructed when the reactive coupling effect is taken into account;

[0039] The system control parameters include: active power reference P0, reactive power reference Q0, virtual inertia J, angular frequency ω of VSG, frequency ω of public grid connection point pcc , Active power droop coefficient D p , power angle δ, reactive power droop coefficient K p , reactive power integral coefficient K i , VSG output voltage amplitude E, and the power angle coefficient and voltage amplitude coefficient of the active power and the reactive power.

[0040] In a third aspect, the present invention provides an electronic device, the electronic device comprising:

[0041] processor;

[0042] a memory for storing instructions executable by the processor;

[0043] The processor is used to execute the method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators described in the first aspect of the present invention.

[0044] In order to achieve the above-mentioned purpose, the present invention provides a method and system for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators. In the grid-connected mode, a closed-loop control model of the active power and reactive power of a single VSG is constructed when the reactive coupling effect is taken into account. Then, based on the relationship between power and frequency characterized by the closed-loop control model, an equivalent P / ω admittance model of a single VSG grid-connected is constructed. Then, based on the equivalent P / ω admittance model of a single VSG grid-connected, a P / ω admittance model of multiple parallel VSG grid-connected is constructed. The constructed equivalent P / ω admittance model is a model that integrates the coupling effect brought by reactive power control into the active control loop while considering the power coupling effect, and can describe the effect of reactive coupling on the active power response. Therefore, when analyzing the low-frequency passivity of multiple parallel VSGs based on the P / ω admittance model of multiple parallel VSGs connected to the grid, the influence of line resistance-inductance ratio, VSG output power and reactive control loop parameters on the P / ω admittance low-frequency passivity can be determined, making the analysis of the low-frequency passivity of multiple parallel virtual synchronous generators more intuitive and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A flow chart of a method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators provided for the implementation of the present invention.

[0046] Figure 2 An initial closed-loop control model of active power and reactive power of a single VSG is constructed in a grid-connected mode and takes reactive coupling effects into account, provided in an embodiment of the present invention.

[0047] Figure 3 A closed-loop control model of active power and reactive power of a single VSG is provided in a grid-connected mode and takes reactive coupling effects into account.

[0048] Figure 4 An equivalent P / ω admittance model of a single VSG grid-connected is provided in an embodiment of the present invention.

[0049] Figure 5 A P / ω admittance model of a multi-parallel VSG grid-connected system is provided in an embodiment of the present invention.

[0050] Figure 6 The reactive power droop coefficient K provided in the embodiment of the present invention is p When the admittance Y changes from 0 to 0.1, p The real part characteristics of vary with frequency.

[0051] Figure 7 The reactive power control integral coefficient K provided in the embodiment of the present invention i When the admittance Y changes from 0 to 10, p The real part characteristics of vary with frequency.

[0052] Figure 8 When the line resistance-inductance ratio R / X provided in the embodiment of the present invention changes from 0.01 to 10, the admittance Y p The real part characteristics of vary with frequency.

[0053] Fig. 9 When the power angle δ provided in the embodiment of the present invention increases from 0 to 1.5 rad, the admittance Y p The real part characteristics of vary with frequency.

[0054] Fig.10 A structural diagram of a system for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators provided in an embodiment of the present invention.

[0055] Fig.11 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0056] The present invention is further described in detail below through the accompanying drawings and specific embodiments.

[0057] As the penetration rate of new energy sources such as photovoltaics and wind power continues to increase, the proportion of traditional synchronous generators has decreased, resulting in a decrease in the inertia and damping of the power system, which is not conducive to the safe and stable operation of the power grid. By making the grid-connected inverter simulate the operating characteristics of the synchronous generator, that is, using VSG control, inertia and damping support can be provided for the power grid. However, VSG also has an inherent low-frequency oscillation mode similar to that of a synchronous generator. When multiple VSGs are connected in parallel, the low-frequency oscillation characteristics of the multi-parallel VSG system are far more complicated than those of a single VSG.

[0058] However, the current time-domain analysis method based on the state-space model is prone to large state-space matrix size and large amount of calculation when applied to multi-machine scenarios. The impedance / admittance model can be obtained through port measurement and does not require detailed system parameters. Therefore, the frequency-domain analysis method has good applicability in the modeling and analysis of multi-machine systems. However, although the impedance / admittance method in the frequency domain is more effective in reducing the computational burden, the system needs to be remodeled and the stability evaluated every time the number of multi-parallel VSGs changes, such as when VSGs are connected or disconnected. Therefore, the impedance method is not applicable to the analysis of multi-parallel VSG systems with time-varying structures.

[0059] In recent years, frequency domain passivity theory has been used for the analysis and design of multi-parallel inverter systems, such as high-frequency resonance analysis of parallel grid-following or parallel grid-building types. The salient feature of these methods is that if each inverter in the system is passive, then the entire parallel system is passive and stable, regardless of the number of parallel inverters. However, the use of frequency domain passivity methods for low-frequency oscillation analysis of parallel VSGs is not well studied.

[0060] Furthermore, by equating the active power loop to a two-port network, a P / ω admittance model equivalent to the power loop is established, which can be used to analyze the output active power and frequency response of the VSG. However, in the process of establishing the P / ω admittance model, the influence of power coupling on the power-frequency characteristics is ignored, and the power-frequency response of the VSG cannot be accurately characterized. Taking power coupling into account in the P / ω admittance model improves the accuracy, so that the influence of line impedance ratio and reactive power control on the power-frequency response can be analyzed.

[0061] However, there is no literature that systematically analyzes the low-frequency passivity of P / ω admittance under power coupling, which restricts the further application of P / ω admittance model in multi-VSG grid-connected systems. In a multi-machine system, the port characteristics of VSG are closely related to the stability of the system.

[0062] Based on this, it is necessary to consider the influence of the reactive control loop on the passivity of P / ω admittance and propose a corresponding P / ω admittance passivity analysis method.

[0063] Specifically, the present invention provides a method for analyzing the low-frequency passivity of a multi-parallel virtual synchronous generator. Under the condition of considering the influence of power coupling, the coupling influence brought by reactive power control is equivalent to the active control loop, so as to describe the influence of reactive coupling on the active power response. Through the P / ω admittance model of a multi-parallel VSG established on this basis, the influence of line resistance-inductance ratio, VSG output power and reactive control loop parameters on the low-frequency passivity of P / ω admittance can be analyzed. Thus, the analysis of the low-frequency passivity of the multi-parallel virtual synchronous generator is more accurate and intuitive.

[0064] The method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators provided by the present invention is executed on an electronic device, which can be a controller connected to the power grid, or an intelligent terminal device such as a laptop, a personal computer, and a tablet computer that can be connected to the power grid. Of course, in some cases, it can also be a server on the network side.

[0065] like Figure 1 As shown, the method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators provided by the embodiment of the present invention mainly includes the following steps:

[0066] 110. In the grid-connected mode, a closed-loop control model of the active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling.

[0067] Specifically, when connected to the grid, each VSG is connected to the common grid connection point via its own line impedance, and then connected to the grid through the grid impedance. The control strategy adopted by each VSG is usually: the active power is controlled by a virtual synchronous generator, the reactive power is controlled by proportional-integral control, and the inner loop adopts a voltage and current double closed-loop control in the dq coordinate system. Since the dynamic response of the inner loop is much faster than the power outer loop, the response of the system in the low-frequency band is mainly dominated by the power outer loop, so the influence of the inner loop can be ignored when analyzing low-frequency passivity.

[0068] More specifically, in an optional embodiment, in the grid-connected mode, an initial closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling is constructed, specifically including:

[0069] In the grid-connected mode, based on the relationship between system control parameters and active power and reactive power, an initial closed-loop control model of active power and reactive power of a single VSG is constructed when considering the influence of reactive coupling.

[0070] Among them, the system control parameters include: active power reference P0, reactive power reference Q0, virtual inertia J, VSG angular frequency ω, public grid connection point frequency ω pcc , Active power droop coefficient D p , power angle δ, reactive power droop coefficient K p , reactive power integral coefficient K i , VSG output voltage amplitude E, and the power angle coefficient and voltage amplitude coefficient of the active power and the reactive power.

[0071] In this embodiment, in the grid-connected mode, when considering the influence of reactive coupling, the active power loop and the reactive power loop can be determined, and then the closed-loop control model of active power and reactive power can be established as follows: Figure 2 shown.

[0072] in, Figure 2 The ω and ω0 shown in the figure are the angular frequency of VSG and its reference value, respectively. RPC is the reactive power controller, G RPC =K p +K i / s, where s is the Laplace operator; H Pδ and H Qδ are the power angle coefficients of active power and reactive power respectively; H PE and H QE are the voltage amplitude coefficients of active power and reactive power respectively.

[0073] In an alternative embodiment, H Pδ , H Qδ , H PE and H QE They are:

[0074]

[0075]

[0076] Among them, R l and L l are the resistance and inductance of the circuit respectively; V ppc0 is the amplitude of the voltage at the common connection point when the system is running in steady state; E0 is the rated amplitude of the VSG output voltage; δ0 is the steady-state operating power angle; ω0 is the rated angular frequency of the VSG.

[0077] In this embodiment, the line specifically refers to the line connecting the VSG output terminal to the public grid connection point.

[0078] It should be noted that by assuming that the reactive power reference change is zero, that is, ΔQ0 = 0, the constructed Figure 2 The model shown is simplified, that is, the complexity of the model is reduced and the analysis efficiency is improved while ensuring the accuracy of the P / ω admittance model based on the grid-connected multiple VSGs and analyzing the low-frequency passivity of the multiple parallel VSGs.

[0079] Based on this, in an optional embodiment, in the grid-connected mode, a closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling is constructed, including:

[0080] In grid-connected mode, an initial closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling.

[0081] The reactive power reference variation in the initial closed-loop control model is taken as zero as a simplification condition, and the initial closed-loop control model is simplified to obtain a closed-loop control model.

[0082] In this embodiment, by assuming that ΔQ0=0, Figure 2 The multi-input multi-output model shown can be equivalent to Figure 3 The single-input single-output model shown in Figure 1 is equivalent to the reactive power coupling in Figure 1. Figure 3 The additional forward path is shown in the dashed box.

[0083] Based on the relationship between power and frequency represented by the closed-loop control model, an equivalent P / ω admittance model of a single VSG grid-connected is constructed.

[0084] Specifically, based on Figure 3The power-frequency relationship shown can be constructed as Figure 4 The equivalent P / ω admittance model of a single VSG grid-connected is shown.

[0085] That is, in an optional embodiment, based on the relationship between power and frequency represented by the closed-loop control model, an equivalent P / ω admittance model of a single VSG grid-connected is constructed, specifically including:

[0086] Based on the relationship between power and frequency represented by the closed-loop control model, the first admittance Y is determined respectively. a and the second admittance Y b ;

[0087] Based on the relationship between the first admittance and the second admittance and the active power reference, the angular frequency of the VSG and the frequency of the common grid connection point, an equivalent P / ω admittance model of a single VSG grid connection is constructed;

[0088] Among them, the first admittance and the second admittance are:

[0089] Y a =Jω0s+D p (5)

[0090]

[0091] In this embodiment, it can be seen from formula (5) and formula (6) that the admittance Y a It is only related to the control parameters such as the virtual inertia and angular frequency reference of VSG, while Y a It is passive in itself; the admittance Y b The system operating point (line impedance, VSG output power, system voltage level) and reactive power droop controller G RPC Therefore, by Figure 4 The equivalent P / ω admittance model of a single VSG connected to the grid can respectively characterize the influence of the active loop, system operating point and reactive loop on the P / ω admittance characteristics.

[0092] 130. Based on the equivalent P / ω admittance model of a single VSG grid-connected system, a P / ω admittance model of multiple parallel VSG grid-connected systems is constructed.

[0093] Specifically, after the equivalent P / ω admittance model based on a single VSG grid connection is determined, the P / ω admittance model of multiple parallel VSG grid connection can be constructed based on the equivalent P / ω admittance model of a single VSG grid connection.

[0094] In an optional embodiment, based on the equivalent P / ω admittance model of a single VSG grid-connected, a P / ω admittance model of multiple parallel VSG grid-connected is constructed, including:

[0095] Based on the equivalent P / ω admittance model of a single VSG connected to the grid, the active power output ΔP is determined;

[0096] Based on active power output and grid P / ω admittance and ω g The relationship between them is used to construct the P / ω admittance model of multi-parallel VSG grid-connected.

[0097] Specifically, based on Figure 4 The equivalent P / ω admittance model of a single VSG grid-connected is shown, and the expression of active power output can be determined as:

[0098]

[0099] Where Φ is defined as the transfer function of the VSG active power closed-loop control as shown in the following formula (8), Y p The port output P / ω admittance of the VSG is shown in the following formula (9), and the expression of the active power output shown in formula (7) is shown in formula (10):

[0100]

[0101]

[0102] ΔP=ΦΔP0+Y p Δω pcc (10)

[0103] Furthermore, based on the active power output and the P / ω admittance and ω g The relationship between them can be constructed as follows Figure 5 The P / ω admittance model of multiple parallel VSG grid-connected is shown.

[0104] in, Figure 5 The Y shown in g is the P / ω admittance of the power grid, Y g =K g / s, Kg is the synchronization coefficient.

[0105] Furthermore, since there is usually a step-up transformer on the grid side, considering that the grid impedance is inductive, K g =(3V pcc V g cosδ g0 ) / (2X g ), where δ g0 is the PCC voltage V at the initial steady-state operating point pcc Phase θ pcc and the grid voltage amplitude V g Phase θ g The grid admittance is usually passive.

[0106] 140. Based on the P / ω admittance model of multiple parallel VSG grid-connected, the low-frequency passivity of multiple parallel VSG is analyzed.

[0107] Specifically, after obtaining Figure 5 After the P / ω admittance model of multiple parallel VSGs connected to the grid is shown, Figure 5 It can be seen that the admittance Y a It is passive in itself, and the port output of VSG is P / ω admittance Y p The passivity of b The influence of Y b It is related to the line R / X ratio, power angle and reactive power control. Therefore, it is possible to determine the low-frequency passivity of multiple parallel VSGs and analyze the effects of line R / X ratio, power angle and reactive power on admittance Y. p Passive influence.

[0108] The following is a specific example to illustrate the P / ω admittance model based on multiple parallel VSG grid connection, and analyze the effect of line R / X ratio, power angle and reactive power on admittance Y. p Passive influence.

[0109] Specifically, based on the coefficients in Table 1, the control variable method is used to change the line R / X ratio, power angle and different reactive control parameters to draw the admittance Y p The real part characteristics of .

[0110] Table 1 System parameters

[0111]

[0112]

[0113] 1. Analysis of the effect of reactive power control on admittance Y p Passive influence

[0114] 1. Analysis of reactive power droop coefficient K p Admittance Y p Passive influence

[0115] Assume K p From 0 to 0.1, K i Set it to 0, and get the admittance Y p The real part characteristics of the frequency change law as shown in Figure 6 As shown. Figure 6 (a) It can be seen that no matter K p No matter how it changes, Re[Y p (jω)]<0, which shows that when only proportional reactive droop control is used, reactive coupling will not affect the output admittance Y pIntroduce non-passive regions. And from Figure 6 (b) It can be seen that Re[Y p (jω)]>0 is mainly concentrated in the low frequency band, and with the increase of frequency, Re[Y p (jω)] first increases and then decreases. In the high frequency band, Re[Y p (jω)] is zero, while in the low frequency band, K p The larger the Re[Y p (jω)] is larger, the corresponding maximum Re[Y p (jω)] is larger, the admittance Y p The stronger the passivity.

[0116] 2. Analysis of reactive power control integral coefficient K i Admittance Y p Passive influence

[0117] Assume K i From 0 to 10, we get the admittance Y p The real part of changes with frequency as Figure 7 As shown. The reactive power droop coefficient K in the figure p The values ​​of are shown in Table 1. Figure 7 (a) It can be seen that Re[Y p (jω)]<0 mainly appears in the low frequency band, and in the high frequency band Re[Y p (jω)] is zero. At the same time, when K i When the value is large, Re[Y p (jω)] is zero. Figure 7 (b) is K i When taking different values, Re[Y p (jω)] curve, it can be seen that Re[Y p The lowest point of (jω)] first follows K i decreases with the increase of K i Increase with the increase of. Figure 6 Only proportional reactive droop control is known, and the admittance Y p The non-passivity is mainly due to K i Introduction.

[0118] 2. Analysis of line resistance-inductance ratio R / X on admittance Y p Passive influence

[0119] First, in order to ensure the accuracy of the analysis, the control parameters of the reactive loop are fixed to eliminate the effect of reactive control on the admittance Y. p The influence of passivity, for example, the values ​​of reactive control parameters are fixed according to Table 1 so that reactive control will not be introduced into the non-passive area.

[0120] Furthermore, the grid impedance magnitude |Z is maintained while changing the line R / X ratio. g | unchanged, to exclude the influence of power grid strength on admittance Y p Passive influence.

[0121] Specifically, assuming that R / X changes from 0.01 to 10, the admittance Y is obtained p The variation law of the real part characteristics is as follows Figure 8 As shown. Figure 8 (a) It can be seen that Re[Y p (jω)]<0 mainly occurs in the case of high resistance-to-inductance ratio, which means that high resistance-to-inductance ratio will reduce the admittance Y p The passivity of the resistor is large, and the larger the resistance-to-inductance ratio is, the larger the amplitude of the negative real part is, and the maximum amplitude appears in the low frequency band. In the high frequency band, the amplitude of the negative real part decreases with the increase of frequency.

[0122] 3. Analysis of the effect of power angle δ on admittance Y p Passive influence

[0123] First, in order to eliminate the reactive loop effect on the admittance Y p The influence of passivity, the reactive loop control parameters are fixed, for example, the values ​​are taken according to Table 1.

[0124] Furthermore, by fixing the control parameters of the reactive loop and the line R / X ratio and changing the power angle δ, the effect of the power angle δ on the admittance Y is analyzed. p Passive influence.

[0125] Specifically, assuming that the power angle increases from 0 to 1.5 rad, the admittance Y is obtained p The real part characteristics of the frequency change law as shown in Fig. 9 As shown. Fig. 9 It can be seen that, unlike Figure 8 The change of R / X in the middle line and the change of the power angle will not significantly affect the admittance Y p The passivity.

[0126] More specifically, by Fig. 9 (a) It can be seen that the admittance Y p The magnitude of the negative real part is much smaller than Figure 8 In addition, from Fig. 9 (b) It can be seen that as the power angle increases, the admittance Y p The amplitude of the negative real part increases first and then decreases, and as the power angle increases further, Y p The real part of becomes positive, and the amplitude becomes larger and larger, indicating that the passivity is gradually enhanced.

[0127] However, it should be noted that in actual operation, if the steady-state power angle is too large, it will easily cause the power angle to cross the unstable equilibrium point when disturbed, thereby causing system instability, so the actual power angle will not be too large.

[0128] In summary, the method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators provided in the above embodiments of the present invention improves the accuracy of the P / ω admittance modeling method by equating the coupling effect brought by VSG reactive power control into P / ω admittance, so that it can intuitively describe the influence of reactive power coupling on the active power and angular frequency response of VSG from the perspective of circuit, and can also characterize the port output characteristics of each VSG in the multi-machine grid-connected system from the perspective of passivity.

[0129] Furthermore, the method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators provided in the above embodiment of the present invention is also applicable to VSGs that adopt other reactive power control schemes, has good versatility, and can conveniently analyze the impact of reactive power coupling on the low-frequency passivity of VSGs. Compared with the traditional admittance model based on current / voltage response, it can be intuitively used to analyze the low-frequency passive characteristics of VSG power / frequency response, and is suitable for large-scale promotion and application.

[0130] The following is an introduction to the analysis system of the low-frequency passivity of multiple parallel virtual synchronous generators provided in an embodiment of the present invention. The analysis system of the low-frequency passivity of multiple parallel virtual synchronous generators described below can be considered as a module architecture for implementing the analysis method of the low-frequency passivity of multiple parallel virtual synchronous generators provided in an embodiment of the present invention; the content described below can be cross-referenced with the above.

[0131] Optional, see Fig.10 , Fig.10 : is a structural block diagram of a system for analyzing low-frequency passivity of multiple parallel virtual synchronous generators provided by an embodiment of the present invention. The system may include:

[0132] A first model building unit 10 is used to build a closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling in the grid-connected mode;

[0133] The second model building unit 20 is used to build an equivalent P / ω admittance model of a single VSG grid-connected based on the relationship between power and frequency represented by the closed-loop control model;

[0134] The third model building unit 30 is used to build a P / ω admittance model of multiple parallel VSGs connected to the grid based on an equivalent P / ω admittance model of a single VSG connected to the grid;

[0135] The passivity analysis unit 40 is used to analyze the low-frequency passivity of the multiple parallel VSGs based on the P / ω admittance model of the multiple parallel VSGs connected to the grid.

[0136] Optionally, the first model building unit 10 is specifically used for:

[0137] In grid-connected mode, an initial closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling.

[0138] The reactive power reference variation in the initial closed-loop control model is taken as zero as a simplification condition, and the initial closed-loop control model is simplified to obtain a closed-loop control model.

[0139] Optionally, the first model building unit 10 is more specifically configured to:

[0140] In the grid-connected mode, based on the relationship between system control parameters and active power and reactive power, an initial closed-loop control model of active power and reactive power of a single VSG is constructed when considering the influence of reactive coupling.

[0141] Among them, the system control parameters include: active power reference P0, reactive power reference Q0, virtual inertia J, VSG angular frequency ω, public grid connection point frequency ω pcc , Active power droop coefficient D p , power angle δ, reactive power droop coefficient K p , reactive power integral coefficient K i , VSG output voltage amplitude E, as well as the power angle coefficient and voltage amplitude coefficient of active power and reactive power.

[0142] Optionally, the power angle coefficient and voltage amplitude coefficient of active power and reactive power are as shown in the above formulas (1) to (4).

[0143] Optionally, the second model building unit 20 is specifically used for:

[0144] Based on the relationship between power and frequency represented by the closed-loop control model, the first admittance Y is determined respectively. a and the second admittance Y b ;

[0145] Based on the relationship between the first admittance and the second admittance and the active power reference, the angular frequency of the VSG and the frequency of the common grid connection point, an equivalent P / ω admittance model of a single VSG grid connection is constructed;

[0146] The first admittance and the second admittance are respectively shown in formula (5) and formula (6).

[0147] Optionally, the third model building unit 30 is specifically used for:

[0148] Based on the equivalent P / ω admittance model of a single VSG connected to the grid, the active power output ΔP is determined;

[0149] Based on active power output and grid P / ω admittance and ωg The relationship between them is used to construct the P / ω admittance model of multi-parallel VSG grid-connected.

[0150] Below, reference Fig.11 To describe the electronic device provided by the embodiment of the present application, the electronic device provided by the embodiment may include: at least one processor 100, at least one communication interface 200, at least one memory 300 and at least one communication bus 400;

[0151] In the embodiment of the present invention, the number of the processor 100, the communication interface 200, the memory 300, and the communication bus 400 is at least one, and the processor 100, the communication interface 200, and the memory 300 communicate with each other through the communication bus 400; obviously, Fig.11 The communication connections shown for the processor 100, the communication interface 200, the memory 300, and the communication bus 400 are merely optional;

[0152] Optionally, the communication interface 200 may be an interface of a communication module, such as an interface of a GSM module; the processor 100 may be a central processing unit CPU, or an application specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0153] The memory 300 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0154] The processor 100 is specifically used to execute the application program in the memory to implement the steps of the above-mentioned crane hoisting wire rope installation control method.

[0155] The above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators, characterized in that: include: In the grid-connected mode, a closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling; Based on the relationship between power and frequency represented by the closed-loop control model, an equivalent P / ω admittance model of a single VSG connected to the grid is constructed; Based on the equivalent P / ω admittance model of a single VSG grid-connected, a P / ω admittance model of multiple parallel VSG grid-connected is constructed; based on the P / ω admittance model of multiple parallel VSG grid-connected, the low-frequency passivity of multiple parallel VSGs is analyzed.

2. The method for analyzing low-frequency passivity of multiple parallel virtual synchronous generators according to claim 1 is characterized in that: The closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling in the grid-connected mode is constructed, including: In grid-connected mode, an initial closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling. The reactive power reference variation in the initial closed-loop control model is taken as zero as a simplification condition, the initial closed-loop control model is simplified to obtain the closed-loop control model.

3. The method for analyzing low-frequency passivity of multiple parallel virtual synchronous generators according to claim 2 is characterized in that: The initial closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling is constructed in the grid-connected mode, including: In the grid-connected mode, based on the relationship between the system control parameters and the active power and the reactive power, an initial closed-loop control model of the active power and the reactive power of a single VSG is constructed when the reactive coupling effect is taken into account; The system control parameters include: active power reference P0, reactive power reference Q0, virtual inertia J, angular frequency ω of VSG, frequency ω of public grid connection point pcc , Active power droop coefficient D p , power angle δ, reactive power droop coefficient K p , reactive power integral coefficient K i , VSG output voltage amplitude E, and the power angle coefficient and voltage amplitude coefficient of the active power and the reactive power.

4. The method for analyzing low-frequency passivity of multiple parallel virtual synchronous generators according to claim 3 is characterized in that: The power angle coefficient and voltage amplitude coefficient of the active power and the reactive power include: Among them, H Pδ and H Qδ are the power angle coefficients of the active power and the reactive power respectively; H PE and H QE are the voltage amplitude coefficients of the active power and the reactive power respectively; R l and L l are the resistance and inductance of the circuit respectively; V ppc0 is the amplitude of the voltage at the common connection point when the system is running in steady state; E0 is the rated amplitude of the VSG output voltage; δ0 is the VSG steady-state operating power angle; ω0 is the rated angular frequency of the VSG.

5. The method for analyzing low-frequency passivity of multiple parallel virtual synchronous generators according to claim 4 is characterized in that: The equivalent P / ω admittance model of a single VSG grid-connected is constructed based on the relationship between power and frequency represented by the closed-loop control model, including: Based on the relationship between power and frequency represented by the closed-loop control model, the first admittance Y is determined respectively. a and the second admittance Y b ; Based on the relationship between the first admittance and the second admittance and the active power reference, the angular frequency of the VSG and the frequency of the common grid connection point, an equivalent P / ω admittance model of a single VSG grid connection is constructed; Wherein, the first admittance and the second admittance are respectively: Y a =Jω0s+D p Among them, G RPC is the reactive power controller, equal to K p +K i / s; s is the Laplace operator.

6. The method for analyzing low-frequency passivity of multiple parallel virtual synchronous generators according to claim 5 is characterized in that: The equivalent P / ω admittance model based on a single VSG grid-connected is used to construct a P / ω admittance model for multiple parallel VSG grid-connected, including: Based on the equivalent P / ω admittance model of a single VSG connected to the grid, the active power output ΔP is determined; Based on active power output and grid P / ω admittance and ω g The relationship between them is used to construct the P / ω admittance model of multi-parallel VSG grid-connected.

7. A system for analyzing low-frequency passivity of multiple parallel virtual synchronous generators, characterized in that: include: The first model building unit is used to build a closed-loop control model of active power and reactive power of a single VSG taking into account the influence of reactive coupling in the grid-connected mode; A second model building unit is used to build an equivalent P / ω admittance model of a single VSG grid-connected based on the relationship between power and frequency represented by the closed-loop control model; A third model building unit is used to build a P / ω admittance model of multiple parallel VSGs connected to the grid based on an equivalent P / ω admittance model of a single VSG connected to the grid; The passivity analysis unit is used to analyze the low-frequency passivity of multiple parallel VSGs based on the P / ω admittance model of multiple parallel VSGs connected to the grid.

8. The low-frequency passivity analysis system for multiple parallel virtual synchronous generators according to claim 7, characterized in that: The first model building unit is specifically used for: In grid-connected mode, an initial closed-loop control model of active power and reactive power of a single VSG is constructed taking into account the influence of reactive coupling. The reactive power reference variation in the initial closed-loop control model is taken as zero as a simplification condition, the initial closed-loop control model is simplified to obtain the closed-loop control model.

9. The low-frequency passivity analysis system of multiple parallel virtual synchronous generators according to claim 8, characterized in that: The first model building unit is more specifically used for: In the grid-connected mode, based on the relationship between the system control parameters and the active power and the reactive power, an initial closed-loop control model of the active power and the reactive power of a single VSG is constructed when the reactive coupling effect is taken into account; The system control parameters include: active power reference P0, reactive power reference Q0, virtual inertia J, angular frequency ω of VSG, frequency ω of public grid connection point pcc , Active power droop coefficient D p , power angle δ, reactive power droop coefficient K p , reactive power integral coefficient K i , VSG output voltage amplitude E, and the power angle coefficient and voltage amplitude coefficient of the active power and the reactive power.

10. An electronic device, characterized in that: The electronic device comprises: processor; a memory for storing instructions executable by the processor; The processor is used to execute the method for analyzing the low-frequency passivity of multiple parallel virtual synchronous generators as described in any one of claims 1 to 6.

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