A method and device for controlling AC / DC dual-port networking of flexible DC converters

Abstract

The present invention belongs to the field of electric power and discloses a method and device for controlling a flexible DC converter with two AC and DC ports. The method comprises: constructing a large-signal hybrid control model for the converter, including DC bus dynamics and reactive power droop control, based on the AC and DC dual-terminal power fluctuation characteristics, and analyzing the power angle instability mechanism under power fluctuations; constructing a hybrid control power angle swing equation and system differential equation for the dual-terminal grid-connected converter based on the large-signal hybrid control model; generating a power angle command based on the hybrid control power angle swing equation, and adjusting the power angle change rate according to the power angle command; wherein the AC power control branch rapidly responds to power fluctuations based on the power droop coefficient, and the DC voltage control branch regulates the DC bus voltage inertia based on PI control. By establishing the large-signal hybrid control model for the converter, the system stability is analyzed under different power fluctuation conditions, and the coordination effect between the AC power control and the DC voltage control is determined.

Description

Technical Field

[0001] The present invention belongs to the field of electric power, and in particular relates to a method and device for controlling AC / DC dual-port networking of a flexible DC converter. Background Art

[0002] With the advancement of the "dual carbon" goals, renewable energy, primarily wind and photovoltaic power, is being connected to the grid on a large scale, leading to a high proportion of power electronics in the power system. High Voltage Direct Current (HVDC) transmission, due to its flexibility and controllability, has become a core carrier for renewable energy grid integration. However, its operating environment faces two major structural contradictions. The strength of the AC grid continues to weaken: the replacement of synchronous generators by renewable energy has reduced system inertia, and the grid's short-circuit capacity (SCR) is generally below 2, even approaching the critical value of 1.5. In weak grids, the impedance coupling between the converter and the AC system increases, significantly reducing voltage and frequency support capabilities. Traditional grid-based voltage-oriented vector control (VOC) is prone to power angle oscillation due to phase mismatch. DC-side power disturbances are becoming randomized: the intermittent output of wind and solar power combined with the sudden power fluctuations of DC loads (such as electrolytic aluminum and data centers) creates a strong uncertainty. For example, at a photovoltaic site, cloud cover can cause a DC power drop of more than 50% within 100 milliseconds. Existing droop control systems struggle to balance DC voltage dynamics with AC power, leading to energy shocks across timescales. Therefore, the control method for the flexible DC converter needs to have the ability to form a double-end network.

[0003] Traditional control strategies have the following limitations: The inherent correlation between inertia and response speed: Vector control relies on a phase-locked loop (PLL) to track the grid phase, but its bandwidth limitations lead to dynamic response delays (typically 50-100ms). Rapid adjustments, however, exacerbate power angle overshoot due to insufficient virtual inertia, creating a dilemma: "Fast adjustment leads to instability, slow adjustment leads to loss of control." Multi-timescale dynamic mismatch: The coupling effects of AC-side electromagnetic transients (microseconds) and DC-side electromechanical dynamics (milliseconds) are not fully decoupled. For example, when an AC fault causes DC capacitor energy accumulation, existing control strategies struggle to synchronize active and reactive power commands within 10ms, preventing rapid dissipation of transient energy. Lack of nonlinear dynamic modeling: Traditional small-signal models are only suitable for analysis near the equilibrium point. However, in new energy scenarios, systems often operate under wide excursions (e.g., voltage drops to 0.3 pu when the SCR is <1.5). Linearized models cannot capture nonlinear behaviors such as converter saturation and limiting, resulting in control parameter settings that deviate from actual operating conditions.

[0004] Therefore, in actual practice, the flexible DC converter may experience transient power angle instability under power fluctuation conditions, that is, the converter control power angle is difficult to meet the stable transmission of AC and DC dual-end power, and the system DC bus voltage is at risk of collapse. Summary of the Invention

[0005] In view of this, the present invention discloses a method and device for controlling AC / DC dual-port networking of a flexible DC converter, which can solve the deficiencies in the related art.

[0006] To achieve the above purpose, the present invention discloses the following technical solutions:

[0007] According to a first aspect of the present invention, a method for controlling a flexible DC converter AC / DC dual-port network is proposed, wherein the dual-port network includes a DC bus and an AC grid. The method includes:

[0008] Based on the AC / DC dual-terminal power fluctuation characteristics, a large-signal hybrid control model for the converter is constructed, which includes DC bus dynamics and reactive power droop control. The mechanism of power angle instability under power fluctuation is analyzed.

[0009] Based on the converter hybrid control large signal model, a converter hybrid control power angle swing equation and a system differential equation of a double-ended grid-connected converter are constructed;

[0010] Based on the converter hybrid control power angle swing equation, a power angle command for the coordinated action of AC power control and DC voltage control is generated, and the power angle change rate is adjusted according to the power angle command; wherein, the AC power control branch quickly responds to power fluctuations based on the power droop coefficient, and the DC voltage control branch adjusts the DC bus voltage inertia based on PI control.

[0011] According to the second aspect of the present invention, a first construction unit is proposed: based on the AC / DC double-terminal power fluctuation characteristics, a large-signal converter hybrid control model including DC bus dynamics and reactive power droop control is constructed, and the mechanism of power angle instability under power fluctuation is analyzed;

[0012] The second construction unit is: constructing a converter hybrid control power angle swing equation and a system differential equation of a double-ended grid-connected converter based on the converter hybrid control large signal model;

[0013] An adjustment unit generates a power angle command for the coordinated action of AC power control and DC voltage control based on the converter hybrid control power angle swing equation, and adjusts the power angle change rate according to the power angle command; wherein the AC power control branch quickly responds to power fluctuations based on the power droop coefficient, and the DC voltage control branch adjusts the DC bus voltage inertia based on PI control.

[0014] According to a third aspect of the present invention, an electronic device is provided, comprising:

[0015] processor;

[0016] a memory for storing processor-executable instructions;

[0017] The processor implements the steps of the method described in the first aspect by running the executable instructions.

[0018] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, on which computer instructions are stored. When the instructions are executed by a processor, the steps of the method described in the first aspect are implemented.

[0019] As can be seen from the above technical solutions, the AC / DC dual-port networking control method for a flexible DC converter disclosed in the present invention establishes an AC / DC dual-terminal networking hybrid control large-signal model for the converter of the flexible DC transmission system, analyzes the system stability under different power fluctuations, determines the coordination effect between AC power control and DC voltage control, and generates power angle commands based on these two control methods, thereby accelerating the convergence of the transient process and suppressing power angle overshoot, improving the transient stability of the converter, and ultimately achieving a balance between rapid response and stable control of the flexible DC transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a method for controlling AC / DC dual-port networking of a flexible DC converter provided by an exemplary embodiment;

[0021] Figure 2 is a schematic diagram of a hybrid control that takes into account both APC and DVC, provided by an exemplary embodiment;

[0022] Figure 3 This is a schematic diagram of a large signal model for transient stability analysis of a hybrid control converter provided by an exemplary embodiment;

[0023] Figure 4 is a schematic diagram of δ-Pt changes under an AC voltage drop fault condition provided by an exemplary embodiment;

[0024] Figure 5 This is a schematic diagram of a δ-Pt change under a sudden change in DC power provided by an exemplary embodiment;

[0025] Figure 6 This is a schematic diagram of a converter power angle curve during power fluctuation provided by an exemplary embodiment;

[0026] Figure 7 is a schematic structural diagram of a device provided by an exemplary embodiment;

[0027] Figure 8 This is a block diagram of a flexible DC converter AC / DC dual-port networking control device provided by an exemplary embodiment. DETAILED DESCRIPTION

[0028] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent like or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible implementations consistent with one or more embodiments of the present invention. Rather, they are merely examples of apparatuses and methods consistent with certain aspects of one or more embodiments of the present invention, as detailed in the appended claims.

[0029] It should be noted that in other embodiments, the steps of the corresponding method are not necessarily performed in the order shown and described in the present invention. In some other embodiments, the method may include more or fewer steps than those described in the present invention. In addition, a single step described in the present invention may be broken down into multiple steps for description in other embodiments, and multiple steps described in the present invention may be combined into a single step for description in other embodiments.

[0030] To further illustrate the present invention, the following examples are provided:

[0031] In related technologies, the control of double-end power fluctuations in AC / DC distribution networks is not perfect, and several key issues still exist: 1) Existing converter control lacks an analytical model that takes into account both APC and DVC, making it difficult to reveal the interactive influence mechanism of the two on power control; 2) The hybrid control power angle of the converter that takes into account both APC and DVC is affected by the two control branches, and the power angle changes nonlinearly with time. The traditional equal-area rule method for analyzing power angle stability will no longer be applicable.

[0032] In order to solve the deficiencies in the related art, the present invention proposes a method for controlling AC / DC dual-port networking of a flexible DC converter.

[0033] Figure 1 This is a flow chart of a method for controlling a flexible DC converter AC / DC dual-port network. The dual-port includes a DC bus and an AC grid, such as Figure 1 As shown, the method may include the following steps:

[0034] Step 101: construct a large-signal converter hybrid control model including DC bus dynamic and reactive power droop control based on AC / DC dual-terminal power fluctuation characteristics, and analyze the power angle instability mechanism under power fluctuation;

[0035] Step 102: constructing a converter hybrid control power angle swing equation and a system differential equation for a double-ended grid-connected converter based on the converter hybrid control large signal model;

[0036] Step 103: Generate a power angle command for the coordinated action of AC power control and DC voltage control based on the converter hybrid control power angle swing equation, and adjust the power angle change rate according to the power angle command; wherein the AC power control branch quickly responds to power fluctuations based on the power droop coefficient, and the DC voltage control branch adjusts the DC bus voltage inertia based on PI control.

[0037] In this embodiment, an AC / DC two-terminal hybrid control large-signal model of the flexible DC transmission system converter is established to analyze the system stability under different power fluctuations, determine the coordination effect between AC power control and DC voltage control, and generate power angle commands based on these two control methods. This accelerates the convergence of the transient process, suppresses power angle overshoot, improves the transient stability of the converter, and ultimately achieves a balance between rapid response and stable control of the flexible DC transmission system.

[0038] In one embodiment, the converter hybrid control large signal model including DC bus dynamics and reactive power droop control is constructed based on the AC / DC two-terminal power fluctuation characteristics, and the power angle instability mechanism under power fluctuation is analyzed, including: constructing a converter power angle control formula that takes into account both AC power control and DC voltage control based on the control mode of the converter hybrid control; constructing the converter hybrid control large signal model based on the reactive power droop control loop and the active power transmission formula.

[0039] Specifically, such as Figure 2 As shown, the control mode based on the converter hybrid control constructs the converter power angle control formula that takes into account both AC power control and DC voltage control, including: generating the system phase angle θ through AC power control and DC voltage control vsc ; Wherein, the DC voltage control generates a control instruction Δω1 by PI control of the deviation between the DC bus voltage and the reference value, and the control instruction Δω1 is expressed as:

[0040] ;

[0041] Among them, k vp With k vi are the proportional and integral control coefficients of the DC voltage control loop, V dc_ref With V dc Respectively represent the voltage reference value and actual value of the DC bus;

[0042] The control command Δω2 generated by AC power control is expressed as:

[0043] ;

[0044] Among them, k p is the active power droop control coefficient, P e,ref is the reference value of the converter output power, Ppcc is the active power output by the public grid connection point PCC; in order to ensure that the dynamic change of the output power matches the dynamic stability of the AC / DC hybrid distribution network system, the converter output power reference value is consistent with the DC bus input power P dc Equal, that is, the output power setting value of the converter is consistent with the input power of the DC bus, P dc Equal to the DC bus voltage V dc and DC bus input current I dc The product of

[0045] Converter angular velocity ω e Expressed as:

[0046] ;

[0047] Among them, ω ref is the reference value of the converter angular velocity, and ω ref =ω g ;

[0048] The converter hybrid control large signal model is constructed based on the reactive power droop control loop and the active power transmission formula, including:

[0049] The reactive power droop control loop is expressed as:

[0050] ;

[0051] Among them, k q is the reactive power droop control coefficient, Q ref is the reactive power reference value, E0 is the converter control voltage reference value, in control, E0=U g ;

[0052] During the power transmission process, the active power P output by the public grid connection point PCC is pcc and reactive power Q pcc Expressed as:

[0053] ;

[0054] Among them, U g with U pcc They represent the grid voltage and the common coupling point voltage respectively, and δ represents the power angle of the system, which is equal to the common coupling point voltage U pcc With grid voltage U g The angle between them, X g Represents the grid impedance, which is equal to ω g L g ;

[0055] In the dual-loop control of the AC power control and DC voltage control generation system, the converter filter inductance is compensated by using the dq axis decoupling method; wherein, U pcc The output control instruction E is equal to the reactive droop, and the expression of voltage E is:

[0056] ;

[0057] Among them, the simplified expression A(δ) is expressed as:

[0058] ;

[0059] When analyzing transient stability, assuming that the system has unity gain with ideal reference tracking, the converter hybrid control large signal model is expressed as:

[0060] .

[0061] In one embodiment, if Figure 3 As shown, the converter hybrid control power angle swing equation and system differential equation of the double-ended grid-connected converter based on the converter hybrid control large signal model are constructed, including: deriving the relationship between the output power and the power angle under the converter hybrid control to obtain the power angle swing equation and the system differential equation; wherein the power angle swing equation is used to analyze the power oscillation between the converter and the grid, and the relationship between the output power and the power angle under the converter hybrid control is expressed as:

[0062] ;

[0063] The power angle swing equation of the converter hybrid control obtained by derivation is expressed as:

[0064] ;

[0065] Public grid connection point output power P pcc The derivative of the power angle is expressed as:

[0066] ;

[0067] is the voltage U at the public grid connection point PCC pcc The derivative of is expressed as:

[0068] ;

[0069] The system differential equation is:

[0070] ;

[0071] Among them, C dc is the capacitance of the DC bus.

[0072] In one embodiment, the method further comprises:

[0073] The composition of the power angle swing equation is analyzed, and the output power P pcc Derivation of the derivative of the power angle yields:

[0074] ;

[0075] Among them, the DC bus voltage V dc It is regulated by DC bus voltage control, and the control instruction is Δω1; the AC side output power Ppcc is controlled by the system power angle δ.

[0076] Furthermore, the power angle instruction for the coordinated action of AC power control and DC voltage control is generated based on the converter hybrid control power angle swing equation, including: determining the control instruction generated by the DC voltage control as the first control instruction, and determining the control instruction generated by the AC power control as the second control instruction; generating the power angle instruction according to the first control instruction, the second control instruction and the converter angular velocity reference value.

[0077] In one embodiment, the method further includes: analyzing the converter power angle stability under AC voltage drop fault or DC power sudden change conditions, and analyzing the different effects of AC power control and DC voltage control in the transient process based on the power angle stability.

[0078] By analyzing the expression of the power angle swing equation of the flow device mixing control, the composition of the power angle swing equation is expressed as follows:

[0079] Based on the converter hybrid control power angle swing equation, the power angle stability of the converter is determined by the output power P dc and DC bus voltage V dc Jointly decided:

[0080] ;

[0081] Among them, the public grid output power P pcc The derivative of the power angle can be further written as

[0082] ;

[0083] S32: Analysis shows that the hybrid control of the flexible DC converter AC / DC dual-terminal grid generates an angle command through the synergy of AC power control (APC) and DC voltage control (DVC), which is expressed as follows:

[0084] It can be seen that in the power angle swing equation, the system variables are δ, V dcThe DC bus voltage Vdc can be adjusted through DC bus voltage control, with the control command being Δω1. The AC side output power Ppcc is controlled by the system power angle δ. Therefore, based on the converter hybrid control power angle swing equation, the power angle is generated through the synergistic effect of AC power control (APC) and DC voltage control (DVC).

[0085] In one embodiment, based on the complementary characteristics of APC and DVC, when the AC voltage drops or the DC power suddenly changes, the power angle change rate is dynamically adjusted to accelerate the convergence of the transient process and suppress the power angle overshoot. This step may include the following sub-steps: analyzing the converter power angle stability under the AC voltage drop fault condition, and analyzing the converter power angle stability under the DC power sudden change condition.

[0086] Figure 4 This is a diagram showing the power angle-power-time variation under AC side voltage drop fault conditions, showing the δ-Pt curve of the system when the grid voltage drops from 1 pu to 0.9 pu.

[0087] Figure 4 The two black slash lines in the figure represent the VSC output power angle curves under different grid voltages. When a grid voltage sag occurs, its operating state transitions from the steady-state operating point δs1 to the steady-state operating point δs2. During this transition, the VSC's transition curve can be divided into Region I, the rapid power angle augmentation (AFA), and Region II, the slow power angle recovery (ASA). The AFA spans the power angle range from δs1 to δs2, while the ASA spans the power angle range from δs2 to δm. However, as can be seen in the power angle-time diagram below, the time consumed by AFA, Δt1, is much smaller than the time consumed by ASA, Δt2. Therefore, the absolute value of the VSC power angle change rate, |ω-ω0|, is not a constant; it is larger in AFA and smaller in ASA.

[0088] Figure 5 This is the δ-Pt change diagram under DC power mutation, which shows the δ-Pt curve of the system when the DC power suddenly changes from 0.5pu to 1pu.

[0089] Figure 5 When the DC bus feed-in power suddenly changes, its operating state transitions from the steady-state operating point δs1 to the steady-state operating point δs2. The situations of AFA and ASA are the same as those of AC voltage faults, that is, the power angle increases rapidly in AFA and decreases slowly in ASA.

[0090] The different effects of APC and DVC in transient processes are analyzed using power angle stability.

[0091] Figure 6 The converter power angle curve during power fluctuation is given. Figure 4 and Figure 5The relationship between AFA and ASA shows that under the condition of power fluctuation, the power angle difference from δs1 to δs2 is much larger than the power angle difference from δs2 to δm, that is, the increase in the power angle transition process is much larger than the increase in the power angle overshoot process. Figure 6 The AFA region, plotted in Figure 1, is also significantly larger than the ASA region. When analyzing VSC power angle stability, the equal-area method is often used to determine system stability. When using this method, the equal areas of the acceleration and deceleration regions are crucial for determining system stability. However, with the integration of APC and DVC, the synergistic effect of the two controllers results in different rates of change in the system power angle for AFA and ASA. Even when the AFA area is larger than the ASA area, the system can still remain stable.

[0092] Although the equal area law is no longer valid, when the system stabilizes again, the system still obeys the energy conservation law that the input power equals the output power. Figure 4 In the figure, S corresponding to region I XT The area of ​​the region and S corresponding to region II ZH The areas of the regions are the same, which respectively represent the energy increased by the DC bus and the energy reduced by the DC bus.

[0093] In summary, the interaction between APC and DVC at different stages of the transient process is a key factor in improving VSC control performance. The combination of the two allows the system power angle to rapidly increase before approaching the steady-state equilibrium point and slowly adjust back after reaching the steady-state equilibrium point, balancing rapid response and minimal overshoot during transients. The different roles of APC and DVC during transients are key factors in hybrid control improving converter control stability. During VSC transients, the interaction between APC and DVC balances rapid system response with minimal overshoot in power angle swings, thereby optimizing transient characteristics.

[0094] Figure 7 This is a schematic structural diagram of a device provided by an exemplary embodiment. Figure 7 At the hardware level, the device includes a processor 702, an internal bus 704, a network interface 706, a memory 708, and a non-volatile memory 710. Of course, it may also include hardware required for other functions. One or more embodiments of the present invention can be implemented based on software, such as the processor 702 reading the corresponding computer program from the non-volatile memory 710 into the memory 708 and then running it. Of course, in addition to software implementation, one or more embodiments of the present invention do not exclude other implementation methods, such as logic devices or a combination of software and hardware, etc., that is, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0095] Please refer to Figure 8A flexible DC converter AC / DC dual-port network control device can be used in Figure 8 In the device shown, to implement the technical solution of the present invention, the device includes:

[0096] The first construction unit 801 is used to construct a large-signal converter hybrid control model including DC bus dynamic and reactive power droop control based on the AC / DC double-terminal power fluctuation characteristics, and analyze the power angle instability mechanism under power fluctuation;

[0097] A second construction unit 802 is configured to construct a converter hybrid control power angle swing equation and a system differential equation for a double-ended grid-connected converter based on the converter hybrid control large signal model;

[0098] The adjustment unit 803 is used to generate a power angle instruction for the coordinated action of AC power control and DC voltage control based on the converter hybrid control power angle swing equation, and adjust the power angle change rate according to the power angle instruction; wherein, the AC power control branch quickly responds to power fluctuations based on the power droop coefficient, and the DC voltage control branch adjusts the DC bus voltage inertia based on PI control.

[0099] Optionally, the first construction unit 801 is specifically configured to:

[0100] Based on the control mode of the converter hybrid control, the converter power angle control formula that takes into account both AC power control and DC voltage control is constructed;

[0101] The converter hybrid control large signal model is constructed based on the reactive power droop control loop and the active power transmission formula.

[0102] Optional,

[0103] The first construction unit 801 is specifically used to:

[0104] Generate system phase angle θ through AC power control and DC voltage control vsc ; Wherein, the DC voltage control generates a control instruction Δω1 by PI control of the deviation between the DC bus voltage and the reference value, and the control instruction Δω1 is expressed as:

[0105] ;

[0106] Among them, k vp With k vi are the proportional and integral control coefficients of the DC voltage control loop, V dc_ref With V dc Respectively represent the voltage reference value and actual value of the DC bus;

[0107] The control command Δω2 generated by AC power control is expressed as:

[0108] ;

[0109] Among them, k p is the active power droop control coefficient, P e,ref is the reference value of the converter output power, P pcc is the active power output by the public grid connection point PCC; in order to ensure that the dynamic change of the output power matches the dynamic stability of the AC / DC hybrid distribution network system, the converter output power reference value is consistent with the DC bus input power P dc Equal, that is, the output power setting value of the converter is consistent with the input power of the DC bus, P dc Equal to the DC bus voltage V dc and DC bus input current I dc The product of

[0110] Converter angular velocity ω e Expressed as:

[0111] ;

[0112] Among them, ω ref is the reference value of the converter angular velocity, and ω ref =ω g ;

[0113] The converter hybrid control large signal model is constructed based on the reactive power droop control loop and the active power transmission formula, including:

[0114] The reactive power droop control loop is expressed as:

[0115] ;

[0116] Among them, k q is the reactive power droop control coefficient, Q ref is the reactive power reference value, E0 is the converter control voltage reference value, in control, E0=U g ;

[0117] During the power transmission process, the active power P output by the public grid connection point PCC is pcc and reactive power Q pcc Expressed as:

[0118] ;

[0119] Among them, U g with U pcc They represent the grid voltage and the common coupling point voltage respectively, and δ represents the power angle of the system, which is equal to the common coupling point voltage U pcc With grid voltage U g The angle between them, X g Represents the grid impedance, which is equal to ωg L g ;

[0120] In the dual-loop control of the AC power control and DC voltage control generation system, the converter filter inductance is compensated by using the dq axis decoupling method; wherein, U pcc The output control instruction E is equal to the reactive droop, and the expression of voltage E is:

[0121] ;

[0122] Among them, the simplified expression A(δ) is expressed as:

[0123] ;

[0124] When analyzing transient stability, assuming that the system has unity gain with ideal reference tracking, the converter hybrid control large signal model is expressed as:

[0125] .

[0126] Optionally, the second constructing unit 802 is specifically configured to:

[0127] The power angle swing equation and the system differential equation are derived by deriving the relationship between the output power and the power angle under hybrid control of the converter. The power angle swing equation is used to analyze the power oscillation between the converter and the power grid. The relationship between the output power and the power angle under hybrid control of the converter is expressed as:

[0128] ;

[0129] The power angle swing equation of the converter hybrid control obtained by derivation is expressed as:

[0130] ;

[0131] Public grid connection point output power P pcc The derivative of the power angle is expressed as:

[0132] ;

[0133] Voltage U at the public grid connection point PCC pcc The derivative of is expressed as:

[0134] ;

[0135] The system differential equation is:

[0136] ;

[0137] Among them, C dc is the capacitance of the DC bus.

[0138] Optionally, the device further includes:

[0139] The first analysis unit 804 is used to analyze the composition of the power angle swing equation and calculate the output power P pcc Derivation of the derivative of the power angle yields:

[0140] ;

[0141] Among them, the DC bus voltage V dc It is regulated by DC bus voltage control, and the control instruction is Δω1; the AC side output power Ppcc is controlled by the system power angle δ.

[0142] Optionally, the adjusting unit 803 is specifically configured to:

[0143] Determine the control instruction generated by the DC voltage control as a first control instruction, and determine the control instruction generated by the AC power control as a second control instruction;

[0144] An angular speed command is generated according to the first control command, the second control command and the inverter angular speed reference value.

[0145] Optionally, the device further includes:

[0146] The second analysis unit 805 is used to analyze the converter power angle stability under the conditions of AC voltage drop fault or DC power sudden change, and analyze the different effects of AC power control and DC voltage control in the transient process based on the power angle stability.

[0147] The systems, devices, modules, or units described in the above embodiments may be implemented by computer chips or entities, or by products having certain functions. A typical implementation device is a computer, which may be in the form of a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email transceiver, game console, tablet computer, wearable device, or any combination of these devices.

[0148] In a typical configuration, a computer includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0149] Memory may include non-permanent storage in a computer-readable medium, in the form of random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

[0150] Computer-readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic disk storage, quantum memory, graphene-based storage media or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media such as modulated data signals and carrier waves.

[0151] For the computer-readable medium (or computer-readable storage medium) as described above or in any other form, computer instructions may be stored thereon, which, when executed by a processor, implement one or more of the above-mentioned embodiments, thereby realizing the technical solution of the present invention.

[0152] The present invention further provides a computer program that, when executed by a processor, implements one or more of the aforementioned embodiments, thereby realizing the technical solution of the present invention. The computer program may be recorded on the aforementioned or any other form of computer-readable medium, and the present invention is not limited thereto.

[0153] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0154] The foregoing description describes specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different from that described in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order shown or the sequential order to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0155] The terms used in one or more embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit one or more embodiments of the present invention. The singular forms "a", "an", "the" and "the" used in one or more embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0156] It should be understood that although the terms first, second, third, etc. may be used to describe various information in one or more embodiments of the present invention, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of one or more embodiments of the present invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining."

[0157] The above description is merely a preferred embodiment of one or more embodiments of the present invention and is not intended to limit one or more embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present invention shall be included in the scope of protection of one or more embodiments of the present invention.

Claims

1. A method for controlling AC / DC dual-port networking of flexible DC converters, characterized in that: The two ends include a DC bus and an AC grid, and the method includes: Based on the control mode of the converter hybrid control, a converter power angle control formula that takes into account both AC power control and DC voltage control is constructed. Based on the reactive power droop control loop and the active power transfer formula, a large signal model of the converter hybrid control is constructed, and the mechanism of power angle instability under power fluctuations is analyzed. The control mode based on the converter hybrid control constructs a converter power angle control formula that takes into account both AC power control and DC voltage control, including: Generate system phase angle θ through AC power control and DC voltage control vsc ; Wherein, the DC voltage control generates a control instruction Δω1 by PI control of the deviation between the DC bus voltage and the reference value, and the control instruction Δω1 is expressed as: ； Among them, k vp With k vi are the proportional and integral control coefficients of the DC voltage control loop, V dc_ref With V dc Respectively represent the voltage reference value and actual value of the DC bus; The control command Δω2 generated by AC power control is expressed as: ； Among them, k p is the active power droop control coefficient, P e,ref is the reference value of the converter output power, P pcc is the active power output by the public grid connection point PCC; in order to ensure that the dynamic change of the output power matches the dynamic stability of the AC / DC hybrid distribution network system, the converter output power reference value is consistent with the DC bus input power P dc Equal, that is, the output power setting value of the converter is consistent with the input power of the DC bus, P dc Equal to the DC bus voltage V dc and DC bus input current I dc The product of Converter angular velocity ω e Expressed as: ； Among them, ω ref is the reference value of the converter angular velocity, and ω ref =ω g ; The converter hybrid control large signal model is constructed based on the reactive power droop control loop and the active power transmission formula, including: The reactive power droop control loop is expressed as: ； Among them, k q is the reactive power droop control coefficient, Q ref is the reactive power reference value, E0 is the converter control voltage reference value, in the control, E0=U g ; Based on the converter hybrid control large signal model, a converter hybrid control power angle swing equation and a system differential equation of a double-ended grid-connected converter are constructed; Based on the converter hybrid control power angle swing equation, a power angle instruction for the coordinated action of AC power control and DC voltage control is generated, and the power angle change rate is adjusted according to the power angle instruction; wherein, the AC power control branch quickly responds to power fluctuations based on the power droop coefficient, and the DC voltage control branch adjusts the DC bus voltage inertia based on PI control; the power angle instruction for the coordinated action of AC power control and DC voltage control based on the converter hybrid control power angle swing equation is generated, including: determining the control instruction generated by the DC voltage control as the first control instruction, and determining the control instruction generated by the AC power control as the second control instruction; generating the power angle instruction according to the first control instruction, the second control instruction and the converter angular velocity reference value.

2. The method according to claim 1, characterized in that During the power transmission process, the active power P output by the public grid connection point PCC is pcc and reactive power Q pcc Expressed as: ； Among them, U g with U pcc They represent the grid voltage and the common coupling point voltage respectively, and δ represents the power angle of the system, which is equal to the common coupling point voltage U pcc With grid voltage U g The angle between them, X g Represents the grid impedance, which is equal to ω g L g ; In the dual-loop control of the AC power control and DC voltage control generation system, the converter filter inductance is compensated by using the dq axis decoupling method; wherein, U pcc The output control instruction E is equal to the reactive droop, and the expression of voltage E is: ； Among them, the simplified expression A(δ) is expressed as: ； When analyzing transient stability, assuming that the system has unity gain with ideal reference tracking, the converter hybrid control large signal model is expressed as: 。 3. The method according to claim 2, characterized in that The converter hybrid control power angle swing equation and system differential equation of the double-ended grid-connected converter are constructed based on the converter hybrid control large signal model, including: The power angle swing equation and the system differential equation are derived by deriving the relationship between the output power and the power angle under hybrid control of the converter. The power angle swing equation is used to analyze the power oscillation between the converter and the power grid. The relationship between the output power and the power angle under hybrid control of the converter is expressed as: ； The power angle swing equation of the converter hybrid control obtained by derivation is expressed as: ； Public grid connection point output power P pcc The derivative of the power angle is expressed as: ； Voltage U at the public grid connection point PCC pcc The derivative of is expressed as: ； The differential equation of the system is: ； Among them, C dc is the capacitance of the DC bus.

4. The method according to claim 3, characterized in that The method further comprises: The composition of the power angle swing equation is analyzed, and the output power P pcc Derivation of the derivative of the power angle yields: ； Among them, the DC bus voltage V dc It is regulated by DC bus voltage control, and the control instruction is Δω1; the AC side output power Ppcc is controlled by the system power angle δ.

5. The method according to claim 1, characterized in that The method further comprises: The power angle stability of the converter under AC voltage drop fault or DC power sudden change conditions is analyzed, and the different effects of AC power control and DC voltage control in transient processes are analyzed based on the power angle stability.

6. A flexible DC converter AC / DC dual-port network control device, characterized in that: The device comprises: The first construction unit: Based on the control mode of the converter hybrid control, the converter power angle control formula that takes into account both AC power control and DC voltage control is constructed. Based on the reactive power droop control loop and the active power transmission formula, the converter hybrid control large signal model is constructed, and the mechanism of power angle instability under power fluctuations is analyzed. The control mode based on the converter hybrid control constructs a converter power angle control formula that takes into account both AC power control and DC voltage control, including: Generate system phase angle θ through AC power control and DC voltage control vsc ; Wherein, the DC voltage control generates a control instruction Δω1 by PI control of the deviation between the DC bus voltage and the reference value, and the control instruction Δω1 is expressed as: ； Among them, k vp With k vi are the proportional and integral control coefficients of the DC voltage control loop, V dc_ref With V dc Respectively represent the voltage reference value and actual value of the DC bus; The control command Δω2 generated by AC power control is expressed as: ； Among them, k p is the active power droop control coefficient, P e,ref is the reference value of the converter output power, P pcc is the active power output by the public grid connection point PCC; in order to ensure that the dynamic change of the output power matches the dynamic stability of the AC / DC hybrid distribution network system, the converter output power reference value is consistent with the DC bus input power P dc Equal, that is, the output power setting value of the converter is consistent with the input power of the DC bus, P dc Equal to the DC bus voltage V dc and DC bus input current I dc The product of Converter angular velocity ω e Expressed as: ； Among them, ω ref is the reference value of the converter angular velocity, and ω ref =ω g ; The converter hybrid control large signal model is constructed based on the reactive power droop control loop and the active power transmission formula, including: The reactive power droop control loop is expressed as: ； Among them, k q is the reactive power droop control coefficient, Q ref is the reactive power reference value, E0 is the converter control voltage reference value, in the control, E0=U g ; The second construction unit is: constructing a converter hybrid control power angle swing equation and a system differential equation of a double-ended grid-connected converter based on the converter hybrid control large signal model; Adjustment unit: Generates a power angle instruction for the coordinated action of AC power control and DC voltage control based on the converter hybrid control power angle swing equation, and adjusts the power angle change rate according to the power angle instruction; wherein, the AC power control branch quickly responds to power fluctuations based on the power droop coefficient, and the DC voltage control branch adjusts the DC bus voltage inertia based on PI control; the power angle instruction for the coordinated action of AC power control and DC voltage control based on the converter hybrid control power angle swing equation is generated, including: determining the control instruction generated by the DC voltage control as the first control instruction, and determining the control instruction generated by the AC power control as the second control instruction; generating the power angle instruction according to the first control instruction, the second control instruction and the converter angular velocity reference value.

7. An electronic device, characterized in that: include: processor; a memory for storing processor-executable instructions; The processor implements the steps of the method according to any one of claims 1 to 5 by running the executable instructions.

8. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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