Modeling method of small frequency perturbation model of potential in VSC on current time scale

Abstract

The present invention provides a modeling method for a small perturbation model of the electric potential frequency within a VSC under the current time scale, the method comprising: constructing a plurality of rotating coordinate systems and defining the transformation relationship between the rotating coordinate systems; constructing a potential frequency motion model within the VSC based on the transformation relationship between the plurality of rotating coordinate systems and the VSC control equation; and deriving a small perturbation model of the VSC based on the potential frequency motion model within the VSC, the small perturbation model of the VSC being used to assist in understanding the dynamics of grid frequency and the process of new energy participating in frequency modulation. This method derives a small perturbation model based on the potential frequency motion model within the VSC, overcoming the defects of the prior art modeling scheme that does not involve the influence of grid-following power electronic equipment on grid frequency via a phase-locked loop, realizes the modeling and analysis of the influence of grid-following power electronic equipment on grid frequency, and can promote the understanding of the dynamics of grid frequency and the process of new energy participating in frequency modulation.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic equipment control modeling, and in particular to a modeling method for a VSC internal potential frequency small disturbance model on a current time scale. Background Art

[0002] With the development of new energy sources, the degree of power electronics in power systems continues to increase. The large-scale integration of grid-following devices has reduced system inertia, and the frequency distribution characteristics of the power grid will change. The characteristics of new power systems with a high proportion of renewable energy and a high proportion of power electronic equipment mean that their operation and control will be more complex, showing characteristics of model diversity, analysis complexity, and global coupling. Among them, high-proportion power electronic systems face the challenge of low inertia due to the reduction in the number of synchronous machines connected. The power electronic interface will bear more of the responsibilities of frequency regulation and maintaining stability in the system. Renewable energy sources such as wind power and photovoltaics that use conventional control cannot provide inertia and primary frequency regulation support, which will worsen the frequency response of the system under power disturbances. The frequency security issue of dual-high power systems has attracted attention.

[0003] Frequency plays a key role in describing AC power systems and is one of the core indicators of grid operation. In traditional power systems, the rotor magnetic field of a synchronous machine periodically cuts the stator winding to generate an internal potential. Therefore, the rotor speed determines the frequency of the internal potential, which in turn participates in the determination of the frequency of each node in the grid. In recent years, the dynamic characteristics of a large number of power electronic interfaces connected to the grid are completely different from those of traditional synchronous generators. The dynamic characteristics of the dual-high power system are significantly different from those of the power system dominated by traditional synchronous machines. One of them is the frequency dynamics of the system. The access of new energy stations has reduced the inertia of the system, which will cause large fluctuations in frequency during fault disturbances.

[0004] However, in dual-high power systems, frequency changes from a physical quantity describing rotor speed to an electrical quantity describing the speed of voltage phase angle change. Frequency and power are decoupled in the system, requiring a control system to maintain constant power balance. This weakens the system's frequency immunity. Existing technologies have not yet addressed the impact of generator-side frequency on grid-connected power electronic equipment via phase-locked loops (PLLs), and there is also a lack of research on the impact of new energy equipment on system frequency distribution. Summary of the Invention

[0005] The present invention provides a modeling method for a small-disturbance model of the potential frequency within a VSC on a current time scale, which is used to overcome the defects of the existing modeling scheme that does not involve the impact of grid-following power electronic equipment on the grid frequency via a phase-locked loop. It realizes the modeling and analysis of the impact of grid-following power electronic equipment on the grid frequency, and promotes the understanding of grid frequency dynamics and the process of renewable energy participation in frequency modulation.

[0006] On the one hand, the present invention provides a modeling method for a small perturbation model of the internal potential frequency of a VSC under the current time scale, comprising: constructing multiple rotating coordinate systems and defining the transformation relationship between the rotating coordinate systems, the rotating coordinate systems comprising a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system and an internal potential rotating coordinate system; based on the transformation relationship between the multiple rotating coordinate systems and the VSC control equation, constructing a VSC internal potential frequency motion model, the VSC internal potential frequency motion model using the machine-end voltage amplitude and the machine-end voltage phase angle in the synchronous rotating coordinate system as input, and using the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system as output; based on the VSC internal potential frequency motion model, a VSC small perturbation model is derived.

[0007] Furthermore, the transformation relationship of the terminal voltage from the synchronous rotating coordinate system to the phase-locked loop rotating coordinate system is:

[0008]

[0009]

[0010] Among them, U d and U q are the d-axis and q-axis components of the terminal voltage in the phase-locked loop rotating coordinate system, T sp is the coordinate transformation matrix from the synchronous rotating coordinate system to the phase-locked loop rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system.

[0011] Furthermore, the relationship between the potential inside the VSC and the terminal voltage in the steady state is expressed by a circuit equation. The specific expression of the circuit equation is:

[0012]

[0013]

[0014] Among them, E x and E y are the x-axis and y-axis components of the potential inside the VSC in the synchronous rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system, I x and I y are the x-axis and y-axis components of the current in the synchronous rotating coordinate system, Z is the impedance matrix, R f is the resistance, X f The impedance conduction.

[0015] Furthermore, the VSC internal potential frequency motion model includes a current inner loop control equation, and the expression of the current inner loop control equation is:

[0016] E d =G id (s)(I dref -I d )+U d -X f I q

[0017] E q =G iq (s)(I qref -I q )+U q +X f I d

[0018] G id (s) = k p2 +k i2 / s

[0019] G iq (s) = k p4 +k i4 / s

[0020] Among them, E d and E q are the d-axis and q-axis components of the potential inside the VSC in the phase-locked loop rotating coordinate system, G id (s) and G iq (s) is the inner loop PI control equation, I dref and I qref They are the d-axis and q-axis components of the input current reference value, which are constants in the current time scale. d and I q are the d-axis and q-axis components of the current in the phase-locked loop rotating coordinate system, U d and U q are the d-axis and q-axis components of the terminal voltage in the phase-locked loop rotating coordinate system, X f is the reactance, k p2 and k p4 is the proportional gain, k i2 and k i4 is the integral gain, and s is a complex parameter.

[0021] Furthermore, the VSC internal potential frequency motion model includes a phase-locked loop control equation, and the expression of the phase-locked loop control equation is:

[0022]

[0023] G pll (s) = k p5 +k i5 / s

[0024] in, is the phase angle of the terminal voltage in the phase-locked loop coordinate system, G pll (s) is the phase-locked loop PI control equation, U tq is the terminal voltage in the phase-locked loop coordinate system, k p5 is the proportional gain, k i5 is the integral gain, and s is a complex parameter.

[0025] Furthermore, the expressions of the VSC internal potential amplitude, the VSC internal potential phase angle, the generator terminal voltage amplitude, and the generator terminal voltage phase angle are respectively as follows:

[0026]

[0027]

[0028]

[0029]

[0030] Where E is the potential amplitude inside the VSC, θ e is the potential phase angle inside the VSC, U t is the terminal voltage amplitude, θ t Terminal voltage phase angle, E d and E q are the d-axis and q-axis components of the potential inside the VSC in the phase-locked loop rotating coordinate system, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system.

[0031] Furthermore, the VSC small disturbance model is derived based on the VSC internal potential frequency motion model, including: linearizing the transformation relationship between the multiple rotating coordinate systems to obtain a linearized transformation formula; linearizing the circuit equation, the current inner loop control equation, and the phase-locked loop control equation in the VSC internal potential frequency motion model to obtain a linearized circuit equation, a linearized current inner loop control equation, and a linearized phase-locked loop control equation; and obtaining the VSC small disturbance model based on the linearized transformation formula, the linearized circuit equation, the linearized current inner loop control equation, and the linearized phase-locked loop control equation. The VSC small disturbance model is as follows:

[0032]

[0033]

[0034] Where E is the potential amplitude inside the VSC, ω e is the potential frequency in VSC, ω t is the terminal voltage frequency, T pe G is the coordinate transformation matrix from the phase-locked loop rotating coordinate system to the internal potential rotating coordinate system, ω (s) is the PI control equation, U t is the terminal voltage, s is a complex parameter, θ e is the potential phase angle inside the VSC, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system.

[0035] In the second aspect, the present invention also provides a modeling device for a small perturbation model of the internal potential frequency of a VSC under the current time scale, including: a rotating coordinate system construction module, used to construct multiple rotating coordinate systems and define the transformation relationship between each rotating coordinate system, the rotating coordinate system includes a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system and an internal potential rotating coordinate system; a VSC internal potential frequency motion model construction module, used to construct a VSC internal potential frequency motion model based on the transformation relationship between the multiple rotating coordinate systems and the VSC control equation, the VSC internal potential frequency motion model uses the machine-end voltage amplitude and the machine-end voltage phase angle in the synchronous rotating coordinate system as input, and uses the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system as output; a VSC small perturbation model derivation module, used to derive a VSC small perturbation model based on the VSC internal potential frequency motion model.

[0036] In a third aspect, the present invention also provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, a modeling method for a small perturbation model of the potential frequency within a VSC under the current time scale as described in any one of the above is implemented.

[0037] In a fourth aspect, the present invention further provides a non-transient computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a modeling method for a small perturbation model of the potential frequency within a VSC under the current time scale as described in any of the above.

[0038] The present invention provides a method for modeling a small-perturbation model of the internal potential frequency of a VSC on a current time scale. This method constructs multiple rotating coordinate systems and defines transformation relationships between the rotating coordinate systems. Based on the transformation relationships between the multiple rotating coordinate systems and the VSC control equations, a VSC internal potential frequency motion model is constructed. Thus, a VSC small-perturbation model is derived based on the VSC internal potential frequency motion model. This method derives a small-perturbation model based on the VSC internal potential frequency motion model, overcoming the drawbacks of existing modeling schemes that do not address the impact of grid-following power electronic equipment on grid frequency via a phase-locked loop. This method implements modeling and analysis of the impact of grid-following power electronic equipment on grid frequency, and can facilitate understanding of grid frequency dynamics and the process of renewable energy participation in frequency modulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 A schematic diagram of a method for modeling a small-disturbance model of the potential frequency within a VSC on a current time scale provided by the present invention;

[0041] Figure 2 A schematic diagram of the relationship between multiple rotating coordinate systems provided by the present invention;

[0042] Figure 3 Schematic diagram of the potential frequency motion model of the VSC under the inner ring only retained provided by the present invention;

[0043] Figure 4 The block diagram of the current control time scale linearization model provided by the present invention;

[0044] Figure 5 This is a schematic diagram of the overall process of the modeling method of the VSC internal potential frequency small perturbation model under the current time scale provided by the present invention;

[0045] Figure 6 Schematic diagram of the structure of the modeling device of the VSC internal potential frequency small perturbation model under the current time scale provided by the present invention;

[0046] Figure 7 This is a schematic structural diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0048] Figure 1 The schematic diagram of the method for modeling the VSC internal potential frequency small perturbation model under the current time scale provided by the present invention is shown. Figure 1 As shown, the method includes:

[0049] S110 , constructing multiple rotating coordinate systems and defining transformation relationships between the rotating coordinate systems, the rotating coordinate systems including a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system, and an internal potential rotating coordinate system.

[0050] It is understandable that, based on the coordinate characteristics of the VSC (Voltage Source Converter), multiple rotating coordinate systems are established, and the transformation relationships between the multiple rotating coordinate systems are characterized. The multiple rotating coordinate systems include a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system, and an internal potential rotating coordinate system.

[0051] Specifically, Figure 2 FIG. 1 shows a schematic diagram of the relationship between multiple rotating coordinate systems provided by the present invention. Figure 2 As shown, the synchronous rotating coordinate system is based on the grid reference frequency ω s Rotation is used to describe the electrical quantity on the grid side. “x” and “y” are used to represent the components of the electrical quantity in the synchronous rotating coordinate system. The phase-locked loop rotating coordinate system is based on the phase-locked loop frequency ω. pll Rotation is used to describe the internal electrical quantities of the VSC. “d” and “q” are used to represent the components of the electrical quantities in the phase-locked loop rotating coordinate system. For the convenience of derivation, the internal potential rotating coordinate system is also introduced. The internal potential rotating coordinate system is based on the internal potential frequency ω. e Rotation is used to characterize the dynamics of the internal electric potential.

[0052] In addition, Figure 2 Middle,U t is the terminal voltage, E is the potential inside VSC, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system, θ e is the potential phase angle inside the VSC.

[0053] Define the transformation relationship between the rotating coordinate systems. Specifically, for example, the transformation relationship of the terminal voltage from the synchronous rotating coordinate system to the phase-locked loop rotating coordinate system is:

[0054]

[0055]

[0056] Among them, U d and U q are the d-axis and q-axis components of the terminal voltage in the phase-locked loop rotating coordinate system, T sp is the coordinate transformation matrix from the synchronous rotating coordinate system to the phase-locked loop rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system.

[0057] Similarly, the current and internal potential have the same transformation relationship between the synchronous rotating coordinate system and the phase-locked loop rotating coordinate system. Applying the above analytical transformation process of the synchronous rotating coordinate system and the phase-locked loop rotating coordinate system to the mutual transformation of the three rotating coordinate systems, the corresponding transformation relationship can be obtained.

[0058] Among them, the transformation relationship of the terminal voltage from the phase-locked loop rotating coordinate system to the synchronous rotating coordinate system is:

[0059]

[0060] The transformation relationship of the terminal voltage from the synchronous rotating coordinate system to the internal potential rotating coordinate system is:

[0061]

[0062] The transformation relationship of the terminal voltage from the internal potential rotating coordinate system to the synchronous rotating coordinate system is:

[0063]

[0064] The transformation relationship of the terminal voltage from the phase-locked loop rotating coordinate system to the internal potential rotating coordinate system is:

[0065]

[0066] The transformation relationship of the terminal voltage from the internal potential rotating coordinate system to the phase-locked loop rotating coordinate system is:

[0067]

[0068] In the above formulas (1-3) to (1-7), θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system, θ e is the potential phase angle inside the VSC.

[0069] The six transformation relationships (1-2) to (1-7) above can describe the transformation relationship of electrical quantities in the three rotating coordinate systems.

[0070] S120, based on the transformation relationship between multiple rotating coordinate systems and the VSC control equation, construct a VSC internal potential frequency motion model, the VSC internal potential frequency motion model uses the generator terminal voltage amplitude and the generator terminal voltage phase angle in the synchronous rotating coordinate system as input, and uses the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system as output.

[0071] It can be understood that, based on the construction of multiple rotating coordinate systems in step S110 and the definition of the transformation relationship between each rotating coordinate system, the VSC internal potential frequency motion model is constructed according to the transformation relationship between the multiple rotating coordinate systems and the VSC control equation.

[0072] Specifically, while retaining only the AC current control time scale of the inner loop, the VSC controls the feedback current vector by adjusting its internal potential output so that it follows the d- and q-axis current reference values. At this time, the frequency motion model of the VSC internal potential can be defined as the amplitude and frequency dynamic response of the VSC internal potential under the excitation of the generator-end voltage.

[0073] In the process of constructing the frequency motion model of the electric potential in the VSC, it is necessary to utilize the transformation relationship between multiple rotating coordinate systems, especially the mutual transformation relationship between the synchronous rotating coordinate system and the phase-locked loop rotating coordinate system.

[0074] Based on the transformation relationships between multiple rotating coordinate systems, multiple VSC control equations are combined to obtain a VSC internal potential frequency motion model. In this embodiment, the VSC control equations include but are not limited to circuit equations, current inner loop control equations, and phase-locked loop control equations.

[0075] It should also be noted that the constructed VSC internal potential frequency motion model is a two-input and two-output system. Specifically, the machine-end voltage amplitude and the machine-end voltage phase angle in the synchronous rotating coordinate system are used as inputs, and the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system are used as outputs.

[0076] S130: Based on the VSC internal potential frequency motion model, a VSC small disturbance model is derived. The VSC small disturbance model is used to assist in understanding the grid frequency dynamics and the process of renewable energy participating in frequency regulation.

[0077] Based on the VSC internal potential frequency motion model constructed in the above step S120, a VSC small disturbance model can be further derived based on the motion model. The small disturbance model is of great significance for understanding the grid frequency dynamics and the frequency regulation process of new energy parameters.

[0078] The VSC small disturbance model is derived based on the VSC internal potential frequency motion model. Specifically, the transformation relationship between the above-mentioned rotating coordinate systems is first linearized, and the above-mentioned VSC internal potential frequency motion model is linearized near the stable operating point. Then, the VSC small disturbance model is derived based on the linearized transformation relationship and frequency motion model.

[0079] In this embodiment, by constructing multiple rotating coordinate systems and defining transformation relationships between them, a VSC internal potential-frequency motion model is constructed based on these transformation relationships and the VSC control equations. This method, based on the VSC internal potential-frequency motion model, derives a VSC small-disturbance model. This method, which derives the small-disturbance model based on the VSC internal potential-frequency motion model, overcomes the drawback of existing modeling schemes that do not address the impact of grid-following power electronic equipment on grid frequency via a phase-locked loop. This method enables modeling and analysis of the impact of grid-following power electronic equipment on grid frequency, and can facilitate understanding of grid frequency dynamics and the process of renewable energy participation in frequency regulation.

[0080] On the basis of the above embodiment, further, based on the transformation relationship between multiple rotating coordinate systems and the VSC control equation, a VSC internal potential frequency motion model is constructed, wherein the VSC control equation includes a circuit equation, a current inner loop control equation, and a phase-locked loop control equation.

[0081] Specifically, retaining only the inner loop's AC current control timescale, the VSC adjusts its internal potential output to control the feedback current vector in order to follow the commanded current vector. This results in the VSC's internal potential being driven by the imbalanced current vector. In the phase-locked coordinate system, the commanded current value remains approximately constant. Changes in the generator-side voltage cause changes in the current imbalance, which in turn drives changes in the VSC's internal potential. Therefore, the VSC's equation of motion can be defined as the amplitude and frequency dynamic response of the VSC's internal potential under the excitation of the generator-side voltage.

[0082] Within the current control timescale, ignoring the DC voltage control timescale dynamics, this embodiment makes the following reasonable assumptions: the current command value input to the inner loop remains constant, changes in line impedance with frequency fluctuations are ignored, and the switching dynamics of the PWM (Pulse Width Modulation) modulation process are negligible. The amplitude and frequency of the potential within the VSC are directly driven by the unbalanced currents in the d and q axes, while the generator-end voltage is determined by the VSC and other factors in the grid.

[0083] Therefore, the generator terminal voltage can be linked to the internal variables of the VSC through the circuit equation, and the relationship between the generator terminal voltage dynamics and the internal dynamics of the VSC can be obtained. That is, the relationship between the potential inside the VSC and the generator terminal voltage in the steady state can be expressed by the circuit equation. The specific expression of the circuit equation is:

[0084]

[0085]

[0086] Among them, E x and E y are the x-axis and y-axis components of the potential inside the VSC in the synchronous rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system, I x and I y are the x-axis and y-axis components of the current in the synchronous rotating coordinate system, Z is the impedance matrix, R f is the resistance, X f The impedance conduction.

[0087] The VSC internal potential frequency motion model also includes the current inner loop control equation, which is expressed as:

[0088] E d =G id (s)(I dref -I d )+U d -X f I q (2-3)

[0089] E q =G iq (s)(I qref -I q )+U q +X f I d (2-4)

[0090] G id (s) = k p2 +k i2 / s(2-5)

[0091] G iq (s) = k p4 +k i4 / s(2-6)

[0092] Among them, E d and E q are the d-axis and q-axis components of the potential inside the VSC in the phase-locked loop rotating coordinate system, G id(s) and G iq (s) is the inner loop PI control equation, I dref and I qref They are the d-axis and q-axis components of the input current reference value, which are constants in the current time scale. d and I q are the d-axis and q-axis components of the current in the phase-locked loop rotating coordinate system, U d and U q are the d-axis and q-axis components of the terminal voltage in the phase-locked loop rotating coordinate system, X f is the reactance, k p2 and k p4 is the proportional gain, k i2 and k i4 is the integral gain, and s is a complex parameter.

[0093] The VSC internal potential frequency motion model also includes a phase-locked loop control equation, which is expressed as:

[0094]

[0095] G pll (s) = k p5 +k i5 / s(2-8)

[0096] in, is the phase angle of the terminal voltage in the phase-locked loop coordinate system, G pll (s) is the phase-locked loop PI control equation, U tq is the terminal voltage in the phase-locked loop coordinate system, k p5 is the proportional gain, k i5 is the integral gain, and s is a complex parameter.

[0097] Combining the above VSC control equations, the x and y components of the generator-side voltage in the synchronous rotating coordinate system are used as inputs, and the d and q components of the VSC internal potential in the phase-locked loop rotating coordinate system are used as outputs to establish a frequency motion model of the VSC internal potential. The expressions for the VSC internal potential amplitude, VSC internal potential phase angle, generator-side voltage amplitude, and generator-side voltage phase angle are as follows:

[0098]

[0099]

[0100]

[0101]

[0102] Where E is the potential amplitude inside the VSC, θ eis the potential phase angle inside the VSC, U t is the terminal voltage amplitude, θ t Terminal voltage phase angle, E d and E q are the d-axis and q-axis components of the potential inside the VSC in the phase-locked loop rotating coordinate system, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system.

[0103] Based on the generator-end voltage phase angle and the VSC internal potential phase angle, the generator-end voltage frequency can be obtained by differentiating the generator-end voltage phase angle, and the VSC internal potential frequency can be obtained by differentiating the VSC internal potential phase angle.

[0104] Correspondingly, Figure 3 The schematic diagram of the VSC potential frequency motion model provided by the present invention is shown. Figure 3 As shown, the leftmost is the model input of the motion model, that is, the x and y components U of the terminal voltage in the synchronous rotating coordinate system xy , and then through the circuit equations, i.e., equations (2-1)-(2-2), and then, the current inner loop control equations, i.e., equations (2-3)-(2-6), and the phase-locked loop control equations, i.e., equations (2-7)-(2-8), are established in parallel, thus obtaining the model output of the motion model, i.e., the d and q components E of the potential inside the VSC in the phase-locked loop rotating coordinate system. dq .

[0105] In this embodiment, based on the transformation relationship between multiple rotating coordinate systems, circuit equations, current inner loop control equations and phase-locked loop control equations, a VSC internal potential frequency motion model is constructed, and on this basis, a VSC small disturbance model is derived. This overcomes the defects of the existing modeling scheme that does not involve the impact of grid-following power electronic equipment on the grid frequency through a phase-locked loop, realizes the modeling and analysis of the impact of grid-following power electronic equipment on the grid frequency, and can promote the understanding of grid frequency dynamics and the process of new energy participating in frequency regulation.

[0106] On the basis of the above embodiments, further, based on the potential frequency motion model within the VSC, a VSC small disturbance model is derived, including: linearizing the transformation relationship between multiple rotating coordinate systems to obtain a linearized transformation formula; linearizing the circuit equation, the current inner-loop control equation, and the phase-locked loop control equation in the potential frequency motion model within the VSC to obtain a linearized circuit equation, a linearized current inner-loop control equation, and a linearized phase-locked loop control equation; based on the linearized transformation formula, the linearized circuit equation, the linearized current inner-loop control equation, and the linearized phase-locked loop control equation, the VSC small disturbance model is obtained.

[0107] It is understandable that when a small disturbance occurs in the system, the angular velocity corresponding to the phase angle variable in the coordinate transformation will not be constant due to the influence of the phase-locked loop dynamics, and will generally exhibit nonlinear characteristics. Therefore, before performing a small disturbance analysis on the VSC control model, it is necessary to first perform the corresponding linearization processing on the coordinate transformation link.

[0108] For example, by linearizing the transformation formula (1-1) of the terminal voltage, we can get

[0109]

[0110] Simplifying the above formula (3-1), we get:

[0111]

[0112] in,

[0113]

[0114] It can be deduced that the inverse transformation of formula (3-2) can be written as:

[0115]

[0116] The linearization of the conversion relationships of other electrical quantities except the terminal voltage satisfies the above derivation and will not be repeated here.

[0117] For example, according to the above derivation, the current coordinate transformation formula can be obtained:

[0118]

[0119] The circuit equations, current inner loop control equations, and phase-locked loop control equations in the VSC internal potential frequency motion model are linearized to obtain the linearized circuit equations, linearized current inner loop control equations, and linearized phase-locked loop control equations. Specifically:

[0120] The component expressions (2-9) of the potential amplitude within the VSC and the component expressions of the potential frequency within the VSC, i.e., the expressions derived by taking the derivative of equation (2-10), are linearized to obtain:

[0121]

[0122] θ e Use ω e / s instead, and the target equation is obtained:

[0123]

[0124] The same analysis method is used for the terminal voltage. Since the terminal voltage phase angle in steady state is the phase angle of the phase-locked loop, θ t Use θ p Substitution, we get:

[0125]

[0126] Substituting formula (3-7) into formula (3-2), we can simplify and obtain:

[0127]

[0128] According to the time scale assumption, the current command value is a constant value. The above current inner loop control equations (2-3) and (2-4) are linearized to obtain:

[0129]

[0130] Linearizing the above circuit equation (2-1) and considering the line dynamics, we get:

[0131]

[0132] The x and y components of the potential inside the VSC are linearized in the synchronous rotating coordinate system to obtain:

[0133]

[0134] Simplifying (3-11) we get:

[0135]

[0136] Substituting the linearized circuit equation (3-10) into the terminal voltage coordinate transformation equation (3-2), we can obtain:

[0137]

[0138] Combining equations (3-12), (3-13) and current coordinate transformation equation (3-4), we can obtain equation (3-20):

[0139]

[0140] Substituting the target equation (3-6) into equation (3-20), we can obtain equation (3-21):

[0141]

[0142] ΔE d and ΔE q Substituting the linearized current inner loop control equation (3-9) yields equation (3-22):

[0143]

[0144] Arrange the formula (3-23):

[0145]

[0146] So we have:

[0147]

[0148] in,

[0149]

[0150] Wherein, ω0 is the rated frequency of the terminal voltage.

[0151] By combining the linearized current inner loop control equation (3-9) and the target equation (3-6), we obtain:

[0152]

[0153] Substitute equation (3-24) into equation (3-26) to eliminate the current, and substitute equation (3-8) into equation (3-26) to eliminate the small voltage disturbance term, and finally obtain the following equation (3-27):

[0154]

[0155] According to the above formula (3-27), the relationship between the potential amplitude inside the VSC, the potential frequency inside the VSC, the generator terminal voltage amplitude and the generator terminal voltage frequency and the phase-locking angle is obtained.

[0156] The next step is to linearize the phase-locked loop control equations (2-7) and (2-8) to obtain the relationship between the phase-locked loop phase angle and the q-axis component of the generator voltage:

[0157] Δθ p =G pll (s)ΔU q (3-28)

[0158] Substituting formula (3-28) into the above formula (3-8), we can obtain:

[0159]

[0160] Substitute equation (3-28) into equation (3-29) to eliminate Δθ p , we can get the VSC small disturbance model:

[0161]

[0162] Where, E is the potential amplitude inside the VSC, ωe is the potential frequency in VSC, ω t is the terminal voltage frequency, T pe G is the coordinate transformation matrix from the phase-locked loop rotating coordinate system to the internal potential rotating coordinate system, ω (s) is the PI control equation, U t is the terminal voltage, s is a complex parameter, θ e is the potential phase angle inside the VSC, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system.

[0163] Regarding the VSC small disturbance model, specifically, Figure 4 The figure shows a transfer block diagram of the current control time scale linearization model provided by the present invention.

[0164]

[0165] In formula (3-31), the first term T in the brackets is pe (X f AG ie (s))G θi (s) is affected by the inner loop control link and the line dynamic process. It is the constraint brought by the line equation.

[0166] According to the above, the frequency expression of the potential inside the VSC can be obtained:

[0167]

[0168] It can be seen from this that the change in the amplitude of the machine-end voltage affects the change in the internal potential frequency through the internal potential and the machine-end voltage phase angle difference, while the change in the machine-end voltage frequency affects the change in the internal potential frequency through the inner loop control process, the line dynamic process and the delay process of the phase-locked loop.

[0169] In this embodiment, by linearizing the transformation relationship between multiple rotating coordinate systems, and linearizing the circuit equations, current inner loop control equations, and phase-locked loop control equations in the potential frequency motion model within the VSC, a VSC small disturbance model is obtained based on the corresponding linearized equations or expressions obtained. This overcomes the defects of the existing modeling scheme that does not involve the impact of grid-following power electronic equipment on the grid frequency through a phase-locked loop, realizes the modeling and analysis of the impact of grid-following power electronic equipment on the grid frequency, and can promote the understanding of grid frequency dynamics and the process of new energy participating in frequency regulation.

[0170] in addition, Figure 5 The figure shows the overall flow chart of the modeling method of the VSC internal potential frequency small perturbation model under the current time scale provided by the present invention.

[0171] like Figure 5 As shown in the figure, first, a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system and an internal potential rotating coordinate system are established, and the transformation relationship between the three is defined. Then, ignoring the outer loop, the VSC internal potential frequency motion model is established according to the transformation relationship between multiple rotating coordinate systems and the VSC control equation. Furthermore, the transformation relationship between the multiple rotating coordinate systems is linearized, and the established VSC internal potential frequency motion model is linearized. Finally, based on the linearized VSC internal potential frequency motion model and the linearized transformation formula, the VSC small disturbance model is derived.

[0172] That is, ignoring the VSC outer-loop control, a motion model was established with the amplitude and frequency of the VSC terminal voltage as input and the amplitude and frequency of the internal potential as output. Secondly, based on this model, linearization was performed near the stable operating point, a small perturbation model was established, and a transfer function was derived. The system defined the transformations and linearization of three types of rotating coordinate systems and analyzed the impact of each link on the internal potential frequency. This provided a reference for analyzing the impact of VSC on system frequency and offered theoretical guidance for frequency regulation at renewable energy stations.

[0173] Figure 6 The schematic diagram of the structure of the modeling device of the VSC internal potential frequency small perturbation model under the current time scale provided by the present invention is shown. Figure 6 As shown, the device includes: a rotating coordinate system construction module 610, which is used to construct multiple rotating coordinate systems and define the transformation relationship between each rotating coordinate system, wherein the rotating coordinate system includes a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system and an internal potential rotating coordinate system; a VSC internal potential frequency motion model construction module 620, which is used to construct a VSC internal potential frequency motion model based on the transformation relationship between the multiple rotating coordinate systems and the VSC control equation; the VSC internal potential frequency motion model uses the machine-end voltage amplitude and the machine-end voltage phase angle in the synchronous rotating coordinate system as input, and uses the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system as output; a VSC small perturbation model derivation module 630, which is used to derive a VSC small perturbation model based on the VSC internal potential frequency motion model.

[0174] In this embodiment, the rotating coordinate system construction module 610 constructs multiple rotating coordinate systems and defines the transformation relationships between these rotating coordinate systems. The VSC internal potential-frequency motion model construction module 620 constructs the VSC internal potential-frequency motion model based on the transformation relationships between the multiple rotating coordinate systems and the VSC control equations. The VSC small-disturbance model derivation module 630 then derives the VSC small-disturbance model based on this VSC internal potential-frequency motion model. This device derives the small-disturbance model based on the VSC internal potential-frequency motion model, overcoming the drawbacks of existing modeling schemes that do not address the impact of grid-following power electronic equipment on grid frequency via a phase-locked loop. This device implements modeling and analysis of the impact of grid-following power electronic equipment on grid frequency, and can facilitate understanding of grid frequency dynamics and the process of renewable energy participation in frequency regulation.

[0175] The modeling device for the small frequency perturbation model of the potential within the VSC on the current time scale provided in this embodiment can correspond to the modeling method for the small frequency perturbation model of the potential within the VSC on the current time scale described above, and will not be repeated here.

[0176] Figure 7 An example of a physical structure diagram of an electronic device is shown below. Figure 7 As shown, the electronic device may include: a processor 710 , a communication interface 720 , a memory 730 and a communication bus 740 , wherein the processor 710 , the communication interface 720 , and the memory 730 communicate with each other via the communication bus 740 . The processor 710 can call the logic instructions in the memory 730 to execute a modeling method of a small perturbation model of the internal potential frequency of the VSC under the current time scale, the method including: constructing multiple rotating coordinate systems and defining the transformation relationship between each rotating coordinate system, the rotating coordinate system including a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system and an internal potential rotating coordinate system; based on the transformation relationship between the multiple rotating coordinate systems and the VSC control equation, constructing a VSC internal potential frequency motion model, the VSC internal potential frequency motion model uses the machine-end voltage amplitude and the machine-end voltage phase angle in the synchronous rotating coordinate system as input, and uses the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system as output; based on the VSC internal potential frequency motion model, deriving a VSC small perturbation model.

[0177] In addition, the logic instructions in the above-mentioned memory 730 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0178] On the other hand, the present invention also provides a non-transient computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a modeling method for a small-disturbance model of the VSC internal potential frequency under the current time scale provided by the above-mentioned methods, the method comprising: constructing a plurality of rotating coordinate systems and defining a transformation relationship between the rotating coordinate systems, the rotating coordinate systems comprising a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system, and an internal potential rotating coordinate system; constructing a VSC internal potential frequency motion model based on the transformation relationship between the plurality of rotating coordinate systems and the VSC control equation; the VSC internal potential frequency motion model takes the machine-end voltage amplitude and the machine-end voltage phase angle under the synchronous rotating coordinate system as input, and takes the VSC internal potential amplitude and the VSC internal potential phase angle under the phase-locked loop rotating coordinate system as output; and deriving a VSC small-disturbance model based on the VSC internal potential frequency motion model.

[0179] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0180] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiments.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A modeling method for a small-frequency perturbation model of the potential inside a VSC on a current time scale, characterized in that: include: Constructing multiple rotating coordinate systems and defining transformation relationships between the rotating coordinate systems, wherein the rotating coordinate systems include a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system, and an internal potential rotating coordinate system; Based on the transformation relationship between the multiple rotating coordinate systems and the VSC control equation, a VSC internal potential frequency motion model is constructed, wherein the VSC internal potential frequency motion model uses the generator terminal voltage amplitude and the generator terminal voltage phase angle in the synchronous rotating coordinate system as input and uses the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system as output; Based on the VSC internal potential frequency motion model, a VSC small disturbance model is derived, including: Linearizing the transformation relationship between the multiple rotating coordinate systems to obtain a linearized transformation formula; Linearizing the circuit equation, the current inner loop control equation, and the phase-locked loop control equation in the VSC internal potential frequency motion model to obtain a linearized circuit equation, a linearized current inner loop control equation, and a linearized phase-locked loop control equation; The VSC small disturbance model is obtained based on the linearized transformation formula, the linearized circuit equation, the linearized current inner loop control equation, and the linearized phase-locked loop control equation.

2. The modeling method of the VSC internal potential frequency small perturbation model under the current time scale according to claim 1 is characterized in that: The transformation relationship of the terminal voltage from the synchronous rotating coordinate system to the phase-locked loop rotating coordinate system is: Among them, U d and U q are the d-axis and q-axis components of the terminal voltage in the phase-locked loop rotating coordinate system, T sp is the coordinate transformation matrix from the synchronous rotating coordinate system to the phase-locked loop rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system.

3. The modeling method of the VSC internal potential frequency small perturbation model under the current time scale according to claim 1 is characterized in that: The relationship between the potential inside the VSC and the terminal voltage in steady state is expressed by a circuit equation. The specific expression of the circuit equation is: Among them, E x and E y are the x-axis and y-axis components of the potential inside the VSC in the synchronous rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system, I x and I y are the x-axis and y-axis components of the current in the synchronous rotating coordinate system, Z is the impedance matrix, R f is the resistance, X f The impedance conduction.

4. The modeling method of the VSC internal potential frequency small perturbation model under the current time scale according to claim 3 is characterized in that: The VSC internal potential frequency motion model includes a current inner loop control equation, and the expression of the current inner loop control equation is: E d =G id (s)(I dref -I d )+U d -X f I q E q =G iq (s)(I qref -I q )+U q +X f I d G id (s)=k p2 +k i2 / s G iq (s)=k p4 +k i4 / s Among them, E d and E q are the d-axis and q-axis components of the potential inside the VSC in the phase-locked loop rotating coordinate system, G id (s) and G iq (s) is the inner loop PI control equation, I dref and I qref They are the d-axis and q-axis components of the input current reference value, which are constants in the current time scale. d and I q are the d-axis and q-axis components of the current in the phase-locked loop rotating coordinate system, U d and U q are the d-axis and q-axis components of the terminal voltage in the phase-locked loop rotating coordinate system, X f is the reactance, k p2 and k p4 is the proportional gain, k i2 and k i4 is the integral gain, and s is a complex parameter.

5. The modeling method of the VSC internal potential frequency small perturbation model under the current time scale according to claim 4 is characterized in that: The VSC internal potential frequency motion model includes a phase-locked loop control equation, and the expression of the phase-locked loop control equation is: G pll (s)=k p5 +k i5 / s in, is the phase angle of the terminal voltage in the phase-locked loop coordinate system, G pll (s) is the phase-locked loop PI control equation, U tq is the terminal voltage in the phase-locked loop coordinate system, k p5 is the proportional gain, k i5 is the integral gain, and s is a complex parameter.

6. The modeling method of the VSC internal potential frequency small perturbation model under the current time scale according to claim 1 is characterized in that: The expressions for the VSC internal potential amplitude, the VSC internal potential phase angle, the generator terminal voltage amplitude, and the generator terminal voltage phase angle are as follows: Where E is the potential amplitude inside the VSC, θ e is the potential phase angle inside the VSC, U t is the terminal voltage amplitude, θ t Terminal voltage phase angle, E d and E q are the d-axis and q-axis components of the potential inside the VSC in the phase-locked loop rotating coordinate system, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system, U x and U y are the x-axis and y-axis components of the terminal voltage in the synchronous rotating coordinate system.

7. The modeling method of the VSC internal potential frequency small perturbation model under the current time scale according to claim 1 is characterized in that: The VSC small disturbance model is as follows: Where E is the potential amplitude inside the VSC, ω e is the potential frequency in VSC, ω t is the terminal voltage frequency, T pe G is the coordinate transformation matrix from the phase-locked loop rotating coordinate system to the internal potential rotating coordinate system, ω (s) is the PI control equation, U t is the terminal voltage, s is a complex parameter, θ e is the potential phase angle inside the VSC, θ p is the phase angle of the terminal voltage in the phase-locked loop rotating coordinate system.

8. A modeling device for a small perturbation model of the potential frequency in a VSC on a current time scale, characterized in that: include: A rotating coordinate system construction module, used to construct multiple rotating coordinate systems and define the transformation relationship between the rotating coordinate systems, wherein the rotating coordinate systems include a synchronous rotating coordinate system, a phase-locked loop rotating coordinate system, and an internal potential rotating coordinate system; a VSC internal potential frequency motion model construction module, configured to construct a VSC internal potential frequency motion model based on the transformation relationships between the multiple rotating coordinate systems and the VSC control equations, wherein the VSC internal potential frequency motion model takes the generator terminal voltage amplitude and the generator terminal voltage phase angle in the synchronous rotating coordinate system as input, and takes the VSC internal potential amplitude and the VSC internal potential phase angle in the phase-locked loop rotating coordinate system as output; A VSC small disturbance model derivation module is used to derive a VSC small disturbance model based on the VSC internal potential frequency motion model, including: Linearizing the transformation relationship between the multiple rotating coordinate systems to obtain a linearized transformation formula; Linearizing the circuit equation, the current inner loop control equation, and the phase-locked loop control equation in the VSC internal potential frequency motion model to obtain a linearized circuit equation, a linearized current inner loop control equation, and a linearized phase-locked loop control equation; The VSC small disturbance model is obtained based on the linearized transformation formula, the linearized circuit equation, the linearized current inner loop control equation, and the linearized phase-locked loop control equation.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the method for modeling a small-disturbance model of the potential frequency within the VSC on the current time scale are implemented as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for modeling a small-disturbance model of the potential frequency in a VSC on a current time scale are implemented.

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