Design method of virtual additional stability controller for phase-locked synchronous grid-connected vsc

Abstract

The application discloses a design method of a virtual additional stability controller of a phase-locked synchronization type grid-connected VSC and belongs to the technical field of phase-locked synchronization, comprising the following steps: designing a stability controller composed of a direct-current isolation link, a lead-lag and a proportional coefficient, defining an angle of operation as an included angle of an output current and an equivalent current of a power grid, taking the angle of operation as an input of the stability controller and taking an additional q-axis voltage of a grid-connected point as an output, establishing a Heffron-Philips model based on the defined angle of operation to obtain a feedback branch transfer function from the angle of operation to power, calculating a lag angle caused by the feedback branch transfer function from the angle of operation to power according to a sub-synchronous oscillation frequency of the phase-locked synchronization type grid-connected VSC, realizing compensation of negative damping caused by the lag angle of the negative feedback branch, thereby improving damping of the phase-locked synchronization type grid-connected VSC and enhancing synchronization stability of the phase-locked synchronization type grid-connected VSC, and thus solving the technical problem that the existing phase-locked synchronization type grid-connected VSC has low synchronization stability and is prone to sub-synchronous oscillation.

Description

Technical Field

[0001] This invention belongs to the field of phase-locked loop (PLL) synchronization technology, and more specifically, relates to a design method for a virtual additional stability controller for a PLL-synchronous grid-connected VSC. Background Technology

[0002] In recent years, with the continuous increase in installed capacity of new energy sources, more and more new energy converters are replacing traditional synchronous machines as the interface between the generation side and the grid. Phase-locked synchronous grid-connected voltage-source converters (VSCs), as the most widely used new energy converters, are prone to subsynchronous oscillations when connected to weak grids due to insufficient system damping, and may even face the risk of synchronous instability. Simultaneously, since the converter acts as the interface device for the grid, a single unit losing synchronization may cause grid oscillations through the network, leading to large-scale instability and power outages. Improving the stability of phase-locked synchronous grid-connected VSCs is beneficial to enhancing the safety and reliability of the power grid.

[0003] The phase-locked loop circuit of the existing typical phase-locked synchronous grid-connected VSC will generate negative damping on the system, which will reduce the synchronization stability of the phase-locked synchronous grid-connected VSC and make it prone to subsynchronous oscillation. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a design method for a virtual additional stability controller in a phase-locked synchronous grid-connected VSC. The purpose is to add a virtual additional stability controller to the phase-locked synchronous grid-connected VSC, using a preset power angle as input and the q-axis component of the terminal voltage as output. This compensates for the negative damping caused by the lag angle of the negative feedback branch, thereby improving the damping of the phase-locked synchronous grid-connected VSC and enhancing its synchronization stability. This solves the technical problem of low synchronization stability and susceptibility to subsynchronous oscillations in existing phase-locked synchronous grid-connected VSCs.

[0005] To achieve the above objectives, according to one aspect of the present invention, a design method for a virtual additional stability controller of a phase-locked synchronous grid-connected VSC is provided, comprising:

[0006] The structure of the virtual additional stability controller includes the following components connected in sequence: a proportional element, a lead-lag element, and a DC blocking element.

[0007] The angle between the output current of the phase-locked synchronous grid-connected VSC and the equivalent current of the grid is defined as the power angle; the power angle is used as the input of the virtual additional stability controller, and the output of the virtual additional stability controller is added to the q-axis component of the common coupling voltage in the phase-locked synchronous grid-connected VSC.

[0008] Obtain the mapping relationship between the unbalanced power and the power angle corresponding to the Heffron-Philips model equivalent to the phase-locked synchronous grid-connected VSC; calculate the lag angle using the mapping relationship; the Heffron-Philips model includes: the motion equation with DC voltage loop as the main body and the additional feedback branch with phase-locked loop as the main body;

[0009] The lag angle is used to adjust the lead-lag element, and the DC blocking element and the proportional element are adjusted respectively.

[0010] In this embodiment, calculating the lag angle using the mapping relationship includes:

[0011] The transfer function between the additional output power and the power angle is determined based on the mapping relationship between the unbalanced power and the power angle.

[0012] The hysteresis angle is calculated using the transfer function and the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC.

[0013] In this embodiment, obtaining the mapping relationship between the unbalanced power and the power angle corresponding to the Heffron-Philips model equivalent to the phase-locked synchronous grid-connected VSC includes:

[0014] Using the formula ΔP in =T J s 2 Δδ i +DsΔδ i +KΔδ i +G(s)G1(s)Δδ i This represents the unbalanced power ΔP corresponding to the Heffron-Philips model. in With the aforementioned work angle Δδ i The mapping relationship between them;

[0015] Where s represents the complex variable of the Laplace transform, and T J Where is the equivalent inertia constant, D is the equivalent damping coefficient, K is the equivalent synchronization coefficient, G(s) is the transfer function of the influence of the phase-locked loop output angle on the output power, and G1(s) is the transfer function from the power angle to the phase-locked loop output angle.

[0016] In this embodiment, determining the transfer function between the additional output power and the power angle based on the mapping relationship between the unbalanced power and the power angle includes:

[0017] The mapping relationship ΔP between the unbalanced power and the power angle. in =T J s 2 Δδi +DsΔδ i +KΔδ i +G(s)G1(s)Δδ i The fourth part, G(s)G1(s), represents the additional output power ΔP. f With the aforementioned work angle Δδ i Transfer function G between f (s), G f (s)=G(s)G1(s);

[0018] in, K pdvc K is the proportional coefficient of the DC loop PI controller. idvc U is the integral coefficient of the DC loop PI controller. g K represents the grid voltage. I δ is the proportionality coefficient between the power angle and the output current after linearization. i0 δ is the steady-state value of the output power angle. p0 K is the steady-state value of the phase-locked loop output angle. id X is the proportionality coefficient between the linearized power angle and the d-axis component of the output current. g K is the equivalent reactance of the power grid. ppll K is the proportional coefficient of the phase-locked loop PI controller. ipll This represents the integral coefficient of the phase-locked loop PI controller.

[0019] In this embodiment, calculating the hysteresis angle using the transfer function and the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC includes:

[0020] Substituting s = jωd into the transfer function G f (s) = G(s)G1(s), to transform the transfer function into G f (jω d ) = D f jω d +K f Where j is a complex unit, ωd is the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC; D f For the additional damping coefficient, K f An additional synchronization coefficient is added;

[0021] Using formula Calculate the hysteresis angle γ.

[0022] In this embodiment, adjusting the lead-lag element using the lag angle includes:

[0023] Using formula The tuning parameters α, lead-lag time constant T1, and lead-lag time constant T2 of the lead-lag element are calculated, thereby achieving the tuning of the lead-lag element.

[0024] In this embodiment, the tuning of the proportional element includes:

[0025] K of the proportional element PSS Tuning to -K id X g K id X g The proportional coefficient is the same as that from the power angle to the output signal access point of the virtual additional stabilization controller, so that the increased damping of the virtual additional stabilization controller can offset the negative damping effect added by the phase-locked loop branch.

[0026] Among them, K id =K I sin(δ i0 -δ p0 )-I0 cos(δ i0 -δ p0 ), I0 is the steady-state value of the output current, I d0 δ is the steady-state value of the d-axis component of the output current. i0 δ is the steady-state value of the output power angle. p0 This is the steady-state value of the phase-locked loop output angle.

[0027] According to another aspect of the present invention, a design apparatus for a virtual additional stability controller of a phase-locked synchronous grid-connected VSC is provided, comprising:

[0028] The structural design module is used to design the structure of the virtual additional stability controller, which includes the following components connected in sequence: proportional element, lead-lag element, and DC blocking element.

[0029] The parameter design module is used to define the angle between the output current of the phase-locked synchronous grid-connected VSC and the equivalent current of the grid as the power angle; the power angle is used as the input of the virtual additional stability controller, and the output of the virtual additional stability controller is added to the q-axis component of the common coupling voltage in the phase-locked synchronous grid-connected VSC.

[0030] An angle calculation module is used to obtain the mapping relationship between the unbalanced power and the power angle corresponding to the Heffron-Philips model equivalent to the phase-locked synchronous grid-connected VSC; and to calculate the lag angle using the mapping relationship; the Heffron-Philips model includes: the motion equation with DC voltage loop as the main body and the additional feedback branch with phase-locked loop as the main body;

[0031] The link tuning module uses the lag angle to tune the lead-lag link, and tunes the blocking link and the proportional link respectively.

[0032] According to another aspect of the present invention, a control system for a phase-locked synchronous grid-connected VSC is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0033] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0034] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0035] (1) This invention proposes a design method for a virtual additional stability controller to suppress subsynchronous oscillations of a phase-locked synchronous grid-connected VSC. The virtual additional stability controller takes the power angle as input and the q-axis additional component of the terminal voltage as output. The phase-locked synchronous grid-connected VSC is equivalent to the Heffron-Philips model. The lag angle is calculated by using the mapping relationship between the unbalanced power and the power angle corresponding to the model. The lag angle is used to compensate for the negative damping caused by the lag angle of the negative feedback branch, thereby improving the damping of the phase-locked synchronous grid-connected converter and enhancing its synchronous stability.

[0036] (2) Based on the mapping relationship between unbalanced power and power angle in the Heffron-Philips model, this scheme determines the transfer function between additional output power and power angle; by using the transfer function and the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC to calculate the lag angle, the expressions for the damping power coefficient and synchronous power coefficient of the phase-locked synchronous grid-connected VSC can be obtained, which has guiding significance for the parameter design of the phase-locked synchronous grid-connected VSC.

[0037] (3) This scheme utilizes the formula ΔP in =T J s 2 Δδ i +DsΔδ i +KΔδ i +G(s)G1(s)Δδ i This represents the unbalanced power ΔP corresponding to the Heffron-Philips model. in With the work angle Δδ iThe mapping relationship between them can be used to divide the output power of the phase-locked synchronous grid-connected VSC into three parts: synchronous power, damping power and additional power, so as to analyze the stability of the grid-connected VSC from the perspective of dynamics and determine the cause of oscillation or instability of the phase-locked synchronous grid-connected VSC and the dominant loop.

[0038] (4) This scheme maps the unbalanced power to the power angle ΔP in =T J s 2 Δδ i +DsΔδ i +KΔδ i +G(s)G1(s)Δδ i The fourth part, G(s)G1(s), represents the additional output power ΔP. f With the work angle Δδ i Transfer function G between f (s), G f (s)=G(s)G1(s); The additional power dominated by the phase-locked loop can be decomposed into additional synchronization power and additional damping power, so as to realize the influence of the phase-locked loop on the stability of the phase-locked synchronous grid-connected VSC from the physical level.

[0039] (5) This scheme utilizes the formula Calculating the hysteresis angle γ yields the phase relationship between the power angle and the dominant additional power of the phase-locked loop, providing guidance for the subsequent design of the virtual additional stability controller.

[0040] (6) This scheme utilizes the formula The calculated settings of the lead and lag elements can compensate for the angle of the lag angle of the additional power, thus achieving the goal of only increasing the damping power of the phase-locked synchronous grid-connected VSC.

[0041] (7) This scheme will reduce the K value of the proportional element. PSS Tuning to -K id X g K id X g The proportional coefficient from the power angle to the output signal access point of the virtual additional stabilizer controller is the same, which allows the increased damping power of the virtual additional stabilizer controller to just offset the negative damping power provided by the phase-locked loop branch. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a design method for a virtual additional stability controller of a phase-locked synchronous grid-connected VSC according to Embodiment 1 of this application.

[0043] Figure 2a This is a control block diagram of the virtual additional stabilization controller in Embodiment 1 of this application.

[0044] Figure 2b This is the installation location of the virtual additional stability controller in Embodiment 1 of this application in the actual control block diagram of the phase-locked synchronous grid-connected VSC.

[0045] Figure 3 This is the phase-locked synchronous grid-connected VSC based on the power angle δ in Embodiment 2 of this application. i The Heffron-Philips model.

[0046] Figure 4a This is the installation location of the additional stability controller in the Heffron-Philips model in Embodiment 2 of this application.

[0047] Figure 4b This refers to the phase relationship between the power angle disturbance and the power disturbance in Embodiment 2 of this application.

[0048] Figure 5a This is the response curve of the power angle without the addition of a virtual auxiliary stabilizing controller in Embodiment 7 of this application when subjected to a small disturbance.

[0049] Figure 5b This is the response curve of the DC capacitor voltage without the virtual additional stabilizing controller in Embodiment 7 of this application when subjected to a small disturbance.

[0050] Figure 6a This is the response curve of the power angle after adding a virtual additional stabilizing controller in Embodiment 7 of this application when subjected to a small disturbance.

[0051] Figure 6b This is the response curve of the DC capacitor voltage after adding a virtual additional stabilizing controller in Embodiment 7 of this application when subjected to a small disturbance. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0053] The steps in the embodiments below are not necessarily performed in numerical order. Unless otherwise expressly stated herein, there is no strict order in which these steps are performed, and they may be performed in other orders.

[0054] Example 1

[0055] like Figure 1 As shown, this invention provides a design method for a virtual additional stability controller of a phase-locked synchronous grid-connected VSC, comprising:

[0056] S1: The structure of the virtual additional stability controller includes the following components connected in sequence: proportional element, lead-lag element, and DC blocking element;

[0057] S2: Define the angle between the output current of the phase-locked synchronous grid-connected VSC and the equivalent current of the grid as the power angle; use the power angle as the input of the virtual additional stability controller, and use the q-axis component of the common coupling voltage in the phase-locked synchronous grid-connected VSC as the output of the virtual additional stability controller.

[0058] S3: Obtain the mapping relationship between unbalanced power and power angle corresponding to the Heffron-Philips model, which is equivalent to the phase-locked synchronous grid-connected VSC; calculate the lag angle using the mapping relationship; the Heffron-Philips model includes: the motion equation with DC voltage loop as the main body and the additional feedback branch with phase-locked loop as the main body.

[0059] S4: Use the lag angle to adjust the lead and lag components, and adjust the blocking component and the proportional component respectively.

[0060] The process of step S1 is as follows: Based on the traditional power system stabilizer, using the grid-connected VSC power angle as the input signal and the q-axis component of the additional terminal voltage Ut as the output signal, the structure of the additional virtual stability controller is obtained, as follows: Figure 2a As shown. The virtual attached stability controller mainly consists of three parts:

[0061] ① The formula for a DC blocking circuit used to isolate DC quantities is as follows:

[0062] ② The lead-lag element used to compensate for the lag angle is formulated as follows:

[0063] ③ The proportional element K used to adjust the magnitude of the additional damping PSS ;

[0064] In the formula, s represents the complex variable used in the Laplace transform, and G HPF (s) represents the DC blocking element, which can be a high-pass filter. T W G is the time constant of the DC blocking element; PSS (s) is the angle correction transfer function of the virtual additional stabilizing controller, and T1 and T2 are the time constants of the lead and lag elements; K PSS The gain coefficient for the virtual additional stabilizing controller.

[0065] Step S2 is as follows: The power angle is defined as the angle between the output current and the equivalent current of the grid. The power angle is used as the input of the stability controller, and the q-axis additional voltage at the grid connection point is used as the output. The relationship between the input and output of the virtual additional stability controller is as follows: ΔU′ tq =K PSS G LPF (s)G PSS (s)Δδ i In the formula, s represents the complex variable of the Laplace transform, and the input signal Δδ i The output power angle deviation of a phase-locked synchronous grid-connected VSC is ΔU. tq Add a q-axis component to the grid-connected voltage. Based on the input and output signals, design the installation position of the stability controller in the control block diagram of a phase-locked synchronous grid-connected VSC. The method of adding the virtual auxiliary stability controller to the control block diagram of a phase-locked synchronous grid-connected VSC is as follows. Figure 2b As shown.

[0066] Step S3 is as follows: Based on the defined power angle of the phase-locked synchronous grid-connected VSC, a Heffron-Philips model including the equation of motion and the additional feedback branch is established. This allows us to further understand the relationship between the unbalanced power and the power angle corresponding to the Heffron-Philips model. The impact of the additional feedback branch on the negative damping of the phase-locked synchronous grid-connected VSC is analyzed based on the lag angle of the transfer function of the feedback branch.

[0067] The process of step S4 is as follows: the lead-lag link is tuned using the lag angle, and the blocking link and the proportional link are tuned respectively.

[0068] Example 2

[0069] In this embodiment, S3 includes:

[0070] S31: Obtain the mapping relationship between unbalanced power and power angle corresponding to the Heffron-Philips model of the phase-locked synchronous grid-connected VSC; the Heffron-Philips model of the phase-locked synchronous grid-connected VSC is as follows: Figure 3 As shown. The Heffron-Philips model includes: the equations of motion based on the DC voltage loop and the additional feedback branch based on the phase-locked loop; the location of the virtual additional stabilizer controller based on the Heffron-Philips model is as follows. Figure 4a As shown, the phase relationship between the power affected by the feedback branch and the power angle is as follows: Figure 4b As shown.

[0071] S32: Determine the transfer function between the additional output power and the power angle based on the mapping relationship between unbalanced power and power angle;

[0072] S33: Calculate the lag angle using the transfer function and the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC.

[0073] Example 3

[0074] In this embodiment, S31 includes:

[0075] The phase-locked synchronous grid-connected VSC is equivalent to the Heffron-Philips model;

[0076] Using the formula ΔP in =T J s 2 Δδ i +DsΔδ i +KΔδ i +G(s)G1(s)Δδ i This represents the unbalanced power ΔP corresponding to the Heffron-Philips model. in With the work angle Δδ i The mapping relationship between them; where s represents the complex variable of the Laplace transform, T J Where is the equivalent inertia constant, D is the equivalent damping coefficient, K is the equivalent synchronization coefficient, G(s) is the transfer function of the effect of the phase-locked loop output angle on the output power, and G1(s) is the transfer function from the power angle to the phase-locked loop output angle.

[0077] The expressions for each equivalent quantity and the transfer function in the above formula are shown below:

[0078]

[0079] In the formula, s represents the complex variable of the Laplace transform, I0 is the steady-state value of the output current, and I d0 δ is the steady-state value of the d-axis component of the output current. i0 δ is the steady-state value of the output power angle. p0 U is the steady-state value of the phase-locked loop output angle, C is the DC capacitor, and U is the output angle. g K represents the grid voltage. pdvc K is the proportional coefficient of the DC loop PI controller. idvc K is the integral coefficient of the DC loop PI controller. ppll K is the proportional coefficient of the phase-locked loop PI controller. ipll This represents the integral coefficient of the phase-locked loop PI controller.

[0080] Example 4

[0081] In this embodiment, S32 includes:

[0082] The mapping relationship between unbalanced power and power angle ΔP in =T J s2 Δδ i +DsΔδ i +KΔδ i +G(s)G1(s)Δδ i The fourth part, G(s)G1(s), represents the additional output power ΔP. f With the work angle Δδ i Transfer function G between f (s), G f (s)=G(s)G1(s);

[0083] in, K pdvc K is the proportional coefficient of the DC loop PI controller. idvc U is the integral coefficient of the DC loop PI controller. g K represents the grid voltage. I δ is the proportionality coefficient between the power angle and the output current after linearization. i0 K is the steady-state value of the output power angle. id X is the proportionality coefficient between the linearized power angle and the d-axis component of the output current. g K is the equivalent reactance of the power grid. ppll K is the proportional coefficient of the phase-locked loop PI controller. ipll This represents the integral coefficient of the phase-locked loop PI controller.

[0084] Example 5

[0085] In this embodiment, S33 includes:

[0086] Substituting s = jωd into the transfer function G f (s)=G(s)G1(s) transforms the transfer function into G f (jω d ) = D f jω d +K f Where ωd is the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC; D f For the additional damping coefficient, K f An additional synchronization coefficient is added;

[0087] Using formula Calculate the hysteresis angle γ.

[0088] Example 6

[0089] In this embodiment, adjusting the lag angle for the lead-lag element in S4 includes:

[0090] S41: Utilize the formula The tuning parameters α, lead-lag time constant T1, and lead-lag time constant T2 of the lead-lag element are calculated, thereby achieving the tuning of the lead-lag element.

[0091] Example 7

[0092] In this embodiment, the tuning of the proportional element in S4 includes:

[0093] K in the proportional element PSS Tuning to -K id X g The proportional coefficient from the power angle to the output signal access point of the virtual additional stabilizer controller is the same, which allows the added damping of the virtual additional stabilizer controller to just offset the negative damping effect of the phase-locked loop branch. K id =K I sin(δ i0 -δ p0 )-I0cos(δ i0 -δ p0 ), K I This is the proportionality coefficient between the power angle and the output current after linearization. I0 is the steady-state value of the output current, I d0 δ is the steady-state value of the d-axis component of the output current. i0 δ is the steady-state value of the output power angle. p0 This is the steady-state value of the phase-locked loop output angle.

[0094] In the above implementation examples, the effect of the virtual additional stability controller on suppressing the subsynchronous oscillation of the phase-locked synchronous grid-connected VSC is as follows: Figure 5a , Figure 5b , Figure 6a and Figure 6b As shown. Figure 5a , Figure 5b For phase-locked synchronous grid-connected VSCs without the addition of a virtual auxiliary stability controller, the power angle δ i and DC capacitor voltage U dc The response curve to a small external disturbance at t=2s. Figure 6a and Figure 6b The power angle δ of a phase-locked synchronous grid-connected VSC after adding a virtual auxiliary stability controller i and DC capacitor voltage U dc The response curve of a small external disturbance at t=2s. Figure 5a , Figure 5b , Figure 6a and Figure 6b All of them were designed based on the MATLAB / Simulink simulation platform.

[0095] Depend on Figure 5a , Figure 5bIt can be seen that the system is operating stably before t=2s, and the power angle δ i and DC capacitor voltage U dc The system is initially in a stable state, but at t = 2s, it is affected by a small disturbance and begins to oscillate subsynchronously. The amplitude of the oscillations continues to increase, leading to instability. This indicates that the total damping of the system is negative at this point, and the oscillations cannot be calmed.

[0096] Depend on Figure 6a and Figure 6b It can be seen that after adding the virtual auxiliary stabilizer, at t=2s, although affected by a small disturbance, the system quickly returns to a stable state, and the amplitude and duration of the system oscillation are very small. This indicates that adding the virtual auxiliary stabilizer greatly enhances the damping of the phase-locked synchronous grid-connected VSC, suppressing the generation of subsynchronous oscillations. Furthermore, the steady-state value remains unchanged before and after the addition, indicating that the virtual auxiliary stabilizer does not affect the normal operation of the system.

[0097] The simulation experiment verifies that the virtual additional stability controller of the present invention can effectively suppress the subsynchronous oscillation of the phase-locked synchronous grid-connected VSC, increase its damping to enhance the stability of the new energy power generation grid-connected system, and provide certain theoretical support and technical guarantee for the grid-connected stability control of new energy power generation systems using phase-locked synchronous VSC.

[0098] Example 8

[0099] According to another aspect of the present invention, a design apparatus for a virtual additional stability controller of a phase-locked synchronous grid-connected VSC is provided, comprising:

[0100] The structural design module is used to design the structure of the virtual additional stability controller, which includes the following components connected in sequence: proportional element, lead-lag element, and DC blocking element.

[0101] The parameter design module is used to define the angle between the output current of the phase-locked synchronous grid-connected VSC and the equivalent current of the grid as the power angle; the power angle is used as the input of the virtual additional stability controller, and the output of the virtual additional stability controller is added to the q-axis component of the common coupling voltage in the phase-locked synchronous grid-connected VSC.

[0102] The angle calculation module is used to obtain the mapping relationship between unbalanced power and power angle corresponding to the Heffron-Philips model, which is equivalent to the phase-locked synchronous grid-connected VSC; and to calculate the lag angle using the mapping relationship; the Heffron-Philips model includes: the motion equation with DC voltage loop as the main body and the additional feedback branch with phase-locked loop as the main body.

[0103] The link tuning module uses the lag angle to tune the lead and lag links, and tunes the blocking link and the proportional link respectively.

[0104] Example 9

[0105] According to another aspect of the present invention, a control system for a phase-locked synchronous grid-connected VSC is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0106] Example 10

[0107] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0108] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A design method for a virtual supplementary stability controller of a phase-locked synchronous grid-connected VSC, characterized in that, include: The structure of the virtual additional stability controller includes the following components connected in sequence: a proportional element, a lead-lag element, and a DC blocking element. The angle between the output current of the phase-locked synchronous grid-connected VSC and the equivalent current of the grid is defined as the power angle; the power angle is used as the input of the virtual additional stability controller, and the output of the virtual additional stability controller is added to the q-axis component of the common coupling voltage in the phase-locked synchronous grid-connected VSC. Obtain the mapping relationship between the unbalanced power and the power angle corresponding to the Heffron-Philips model equivalent to the phase-locked synchronous grid-connected VSC; calculate the lag angle using the mapping relationship; the Heffron-Philips model includes: the motion equation with DC voltage loop as the main body and the additional feedback branch with phase-locked loop as the main body; The lag angle is used to adjust the lead-lag element, and the DC blocking element and the proportional element are adjusted respectively. The step of calculating the lag angle using the mapping relationship includes: determining the transfer function between the additional output power and the power angle based on the mapping relationship between the unbalanced power and the power angle; and calculating the lag angle using the transfer function and the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC. The step of obtaining the mapping relationship between the unbalanced power and the power angle corresponding to the Heffron-Philips model equivalent to the phase-locked synchronous grid-connected VSC includes: using the formula The unbalanced power Δ corresponding to the Heffron-Philips model is represented by... P in With the aforementioned work angle Δ δ i The mapping relationship between them; s represents the complex variable of the Laplace transform, It is the equivalent inertia constant. D This is the equivalent damping coefficient. K The equivalent synchronization coefficient, G(s) Let be the transfer function of the effect of the phase-locked loop output angle on the output power. G 1 (s) The transfer function from the power angle to the phase-locked loop output angle; Determining the transfer function between the additional output power and the power angle based on the mapping relationship between the unbalanced power and the power angle includes: mapping the unbalanced power and the power angle... Part 4 Indicates additional output power With the stated work angle Transfer function between , ; ; K pdvc This refers to the proportional coefficient of the DC loop PI controller. K idvc The integral coefficient of the DC loop PI controller. This is the grid voltage. This is the proportionality coefficient between the power angle and the output current after linearization. To output the steady-state value of the power angle, δ p0 This represents the steady-state value of the phase-locked loop output angle. K id This is the proportionality coefficient between the power angle and the d-axis component of the output current after linearization. For the equivalent reactance of the power grid, K ppll This refers to the proportional coefficient of the phase-locked loop PI controller. K ipll This represents the integral coefficient of the phase-locked loop PI controller.

2. The design method of the virtual additional stability controller for a phase-locked synchronous grid-connected VSC as described in claim 1, characterized in that, The calculation of the hysteresis angle using the transfer function and the subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC includes: Will s=jω d Substitute the transfer function To transform the transfer function into Where j is the complex unit, ω d The subsynchronous oscillation frequency of the phase-locked synchronous grid-connected VSC; D f For the additional damping coefficient, K f An additional synchronization coefficient is added; Using formula Calculate the hysteresis angle .

3. The design method of the virtual additional stability controller for a phase-locked synchronous grid-connected VSC as described in claim 1, characterized in that, The step of adjusting the lead-lag element using the lag angle includes: Using formula The calculated tuning parameters of the lead-lag element α Lead and lag time constants T 1 and lead-lag time constant T Two constants are used to achieve tuning of the lead-lag element.

4. The design method of the virtual additional stability controller for a phase-locked synchronous grid-connected VSC as described in claim 3, characterized in that, Tuning the proportional element includes: The proportional element K PSS Adjusted to -K id X g , K id X g The proportional coefficient is the same as that from the power angle to the output signal access point of the virtual additional stabilization controller, so that the increased damping of the virtual additional stabilization controller can offset the negative damping effect added by the phase-locked loop branch. in, , , I 0 represents the steady-state value of the output current. I d0 This represents the steady-state value of the d-axis component of the output current. δ i0 To output the steady-state value of the power angle, δ p0 This is the steady-state value of the phase-locked loop output angle.

5. A design device for a virtual auxiliary stability controller of a phase-locked synchronous grid-connected VSC, characterized in that, A design method for implementing a virtual supplementary stability controller for a phase-locked synchronous grid-connected VSC as described in any one of claims 1-4 includes: The structural design module is used to design the structure of the virtual additional stability controller, which includes the following components connected in sequence: proportional element, lead-lag element, and DC blocking element. The parameter design module is used to define the angle between the output current of the phase-locked synchronous grid-connected VSC and the equivalent current of the grid as the power angle; the power angle is used as the input of the virtual additional stability controller, and the output of the virtual additional stability controller is added to the q-axis component of the common coupling voltage in the phase-locked synchronous grid-connected VSC. An angle calculation module is used to obtain the mapping relationship between the unbalanced power and the power angle corresponding to the Heffron-Philips model equivalent to the phase-locked synchronous grid-connected VSC; and to calculate the lag angle using the mapping relationship; the Heffron-Philips model includes: the motion equation with DC voltage loop as the main body and the additional feedback branch with phase-locked loop as the main body; The link tuning module uses the lag angle to tune the lead-lag link, and tunes the blocking link and the proportional link respectively.

6. A control system for a phase-locked synchronous grid-connected VSC, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 4.

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