Network construction converter control method, system and device based on network side information feedback and medium

Abstract

The present application belongs to the technical field of networked converter control, and discloses a networked converter control method, system, device and medium based on network side information feedback to solve the problem of subsynchronous oscillation. The method comprises: collecting voltage signals of a grid side point of common connection and voltage signals and current signals of a converter side; calculating steady-state active power and steady-state reactive power based on the voltage signals of the grid side point of common connection and line impedance parameters; calculating transient active power and transient reactive power based on the voltage signals and current signals of the converter side; introducing a composite factor to fuse the steady-state active power and the transient active power to obtain composite active and reactive power; and inputting the composite active and reactive power to a power outer loop controller of the networked converter to generate a reference signal for inner loop control. The present application improves system damping and the ability to suppress subsynchronous oscillation.

Description

Technical Field

[0001] This invention belongs to the field of grid-connected converter control technology, specifically relating to grid-connected converter control methods, systems, equipment, and media based on grid-side information feedback. Background Technology

[0002] With the increasing penetration of renewable energy sources such as wind power and photovoltaics in the power system, the control strategies and operational stability of new energy grid-connected interfaces, with power electronic converters at their core, are having an increasingly prominent impact on the safe and reliable operation of the power grid. As an emerging grid-connected control technology, grid-connected converters, by simulating the operating mechanism of synchronous generators, can autonomously construct and support the voltage and frequency of the power grid, providing the necessary inertia and damping for the system, and significantly improving the operational reliability of weak grids or islanded systems.

[0003] Virtual synchronous machines (VSMs) are a typical control strategy for grid-connected converters. However, research and engineering practice show that under conditions of high short-circuit ratio and strong grid strength, VSMs and other grid-connected control strategies may generate unfavorable dynamic interactions with the grid impedance, leading to subsynchronous oscillations at frequencies lower than the power frequency. These oscillations can cause distortion of the converter's output current, abnormal heating of equipment, and in severe cases, trigger protection actions that could disconnect the equipment from the grid or even damage power equipment, threatening the stable operation of the system.

[0004] Currently, most methods for suppressing subsynchronous oscillations in grid-connected converters still involve introducing local voltage and current state variables of the converter into the existing control framework to add an auxiliary damping controller. For example, the virtual impedance method simulates additional impedance characteristics through control algorithms, thereby changing the output external characteristics of the converter to improve oscillation damping. However, such methods have inherent drawbacks: First, they rely excessively on local state variables on the converter side, resulting in insufficient "global observability" of system-level oscillation modes, which limits the effectiveness of oscillation detection and suppression. Second, and more importantly, strategies such as the virtual impedance method, while introducing additional control, change the original power balance equation of the system, causing a shift in the steady-state operating point of the converter. This not only affects the static performance of the system but also reduces the stability margin, leading to poor compatibility in engineering applications.

[0005] In addition, there are other oscillation suppression strategies such as modulated signal feedback active damping control and virtual admittance control. However, modulated signal feedback active damping control is mainly used for subsynchronous oscillation problems caused by series-compensated power grids, and its application scenario is different from the strong power grid conditions targeted in this application; while the virtual admittance control strategy, while changing the control structure, also changes the steady-state operating point of the system, similar to the virtual impedance method, and has the problem of poor static compatibility.

[0006] In summary, existing subsynchronous oscillation suppression methods have two main drawbacks: first, control strategies based on local variables lack the ability to perceive system-level oscillations globally, thus limiting the suppression effect; second, typical methods, such as the virtual impedance method, change the steady-state operating point of the system, sacrificing static performance and stability margin, resulting in poor engineering compatibility. Summary of the Invention

[0007] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a grid-connected converter control method, system, device, and medium based on grid-side information feedback that meets one or more of the aforementioned requirements, aiming to effectively suppress subsynchronous oscillations by enhancing system damping through changes in the dynamic characteristics of the power control loop.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a grid-connected converter control method based on grid-side information feedback, comprising the following steps:

[0010] S1. Acquire the voltage signal at the power grid side common coupling point. Voltage signal on the converter side and current signal ;

[0011] S2, Based on the voltage signal of the power grid side common connection point Calculate the steady-state active power using the preset line impedance parameters. and steady-state reactive power ;

[0012] S3, Based on the voltage signal on the converter side and current signal Calculate transient active power and transient reactive power ;

[0013] S4. Introducing composite factors The steady-state active power With the transient active power The composite active power is obtained by fusion. The steady-state reactive power With the transient reactive power The composite reactive power is obtained by fusion. ;

[0014] S5, the composite active power and the composite reactive power The input is fed to the outer power loop controller of the grid converter to generate a reference signal for the inner loop control, thereby suppressing subsynchronous oscillations.

[0015] As a preferred embodiment, the steady-state active power is calculated in step S2. and steady-state reactive power include:

[0016] The voltage signal of the common coupling point on the power grid side Transform to a rotating coordinate system to obtain the d-axis and q-axis components of the voltage. , ;

[0017] Based on the voltage d and q axis components , The steady-state current d-axis and q-axis components are obtained by calculating the line impedance parameters. ;

[0018] Based on the steady-state current d-axis and q-axis components With respect to the voltage d-axis and q-axis components , The steady-state active power was calculated. and steady-state reactive power .

[0019] As a preferred embodiment, the transient active power is calculated in step S3. and transient reactive power include:

[0020] The voltage signal on the converter side and current signal By transforming to a rotating coordinate system, the d-axis and q-axis components are obtained, thereby calculating the transient active power. and transient reactive power .

[0021] As a preferred embodiment, the composite active power and the composite reactive power The calculation formula is:

[0022] ,

[0023] In the formula, the composite factor The value range is between 0 and 1.

[0024] As a preferred embodiment, the composite factor The value of is tuned to enhance the damping characteristics of the system in the subsynchronous frequency band.

[0025] As a preferred embodiment, the composite factor The tuning method includes the following steps:

[0026] Acquisition system in different The value corresponds to the modal information of the subsynchronous oscillation;

[0027] Based on the modal information, an optimal composite factor is calculated. ;

[0028] The composite factor The value of should not be less than the optimal composite factor. The value.

[0029] As a preferred embodiment, the modal information includes system eigenvalues ​​and their pairs. The sensitivity of the value; the optimal composite factor It is calculated based on the real part of the eigenvalue and its sensitivity.

[0030] Secondly, the present invention provides a grid-connected converter control system based on grid-side information feedback, for implementing the grid-connected converter control method as described in the first aspect.

[0031] Thirdly, the present invention provides an electronic device, the computer device including a memory, a processor and a computer program, wherein when the computer program is executed by the processor, it implements the grid converter control method as described in the first aspect.

[0032] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the grid converter control method as described in the first aspect.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Significantly improves the suppression capability of subsynchronous oscillations and system damping: By incorporating grid-side voltage information to calculate steady-state power and combining it with local transient power, this invention reshapes the dynamic characteristics of the power control loop. This is equivalent to adding a forward-looking damping channel to the system, which can effectively counteract the negative dynamic processes that trigger subsynchronous oscillations, causing the oscillations to decay rapidly, thereby significantly improving the system's stability and transient performance.

[0035] 2. Maintains the steady-state performance and static compatibility of the system: Unlike existing suppression strategies such as the virtual impedance method, the composite power control strategy introduced in this invention does not mathematically change the power balance equation of the system. Therefore, the steady-state operating point of the converter remains consistent with that of traditional control strategies, fundamentally solving the problem of changing the steady-state operating point and sacrificing static performance due to the introduction of additional control, and exhibiting excellent engineering compatibility.

[0036] 3. Achieved global perception and precise intervention of system-level oscillation modes: By collecting and utilizing voltage information from the grid-side point of common coupling, this invention overcomes the limitations of traditional methods that rely solely on local variables on the converter side, enhancing the "global observability" of system-level oscillation modes. This enables control strategies to more accurately perceive the dynamics of the entire system, thereby allowing for more precise and effective intervention.

[0037] 4. Provides a clear and reliable method for tuning key parameters: This invention not only proposes the concept of a composite factor, but also provides a quantitative tuning method based on the sensitivity of system eigenvalues. This method provides a clear and reliable theoretical basis and operational path for guiding engineering practice and ensuring the optimization of control effects, avoiding the blindness of parameter tuning.

[0038] Further or more detailed beneficial effects will be described in conjunction with specific embodiments in the detailed implementation. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram illustrating the principle of the grid converter control method described in Embodiment 1 of the present invention.

[0041] Figure 2 The composite factor described in Embodiment 1 of this invention A schematic diagram of the trajectory of changing characteristic values.

[0042] Figure 3 It is the composite factor described in Embodiment 1 of the present invention. Schematic diagram of the tuning method.

[0043] Figure 4 This is a structural diagram of the electronic device described in Embodiment 3 of the present invention.

[0044] Figure 5 This is a schematic diagram of the traditional grid converter and its control structure used in Comparative Group 1 of Embodiment 5 of the present invention.

[0045] Figure 6 This is a schematic diagram of the virtual impedance grid converter and its control structure used in Comparative Group 2 of Embodiment 5 of the present invention.

[0046] Figure 7This is a schematic diagram showing the comparison results of the power angle waveforms of the three methods under strong power grid conditions in the comparative experiment of Embodiment 5 of the present invention.

[0047] Figure 8 This is a schematic diagram of the voltage waveform of the traditional method in the comparison group 1 under strong power grid conditions in the comparative experiment of Embodiment 5 of the present invention.

[0048] Figure 9 This is a schematic diagram of the voltage waveform of the method proposed by the experimental group under strong power grid conditions in the comparative experiment of Embodiment 5 of the present invention.

[0049] Figure 10 This is a schematic diagram showing the comparison results of active and reactive power of three methods under weak power grid conditions in the comparative experiment of Embodiment 5 of the present invention.

[0050] Icon labels:

[0051] 400. Electronic devices;

[0052] 401. Processor; 402. Communication bus; 403. User interface; 404. Network interface; 405. Memory. Detailed Implementation

[0053] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0054] In the following description, several embodiments of the present invention are provided. Different embodiments can be substituted or combined. Therefore, the present invention can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present invention should also be considered to include embodiments containing one or more other possible combinations of A, B, C, and D, even if such embodiments are not explicitly described in the following text.

[0055] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of the invention. Various processes or components may be appropriately omitted, substituted, or added to the various examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0056] To facilitate a better understanding of the embodiments of the present invention, its application scenarios will be explained before providing a detailed explanation of the specific implementation methods.

[0057] The grid-connected converter control method described in this specification is applied to power system grid-connected scenarios that include a high proportion of renewable energy generation, particularly under conditions of high short-circuit ratio and high grid intensity. In these scenarios, the application of the grid-connected converter control method aims to solve the subsynchronous oscillation problem caused by the interaction between the grid-connected converter and the grid impedance, thereby improving system stability and power quality, while ensuring that the steady-state operating performance of the converter itself is not degraded by additional control.

[0058] The following is a brief explanation of the grid-connected converter, subsynchronous oscillation, grid-side information, power control loop, system damping, steady-state power, transient power, and composite power involved in several embodiments of this specification:

[0059] A grid-connected converter is a power electronic converter that can autonomously establish and maintain grid voltage and frequency. Its control mode simulates the operating characteristics of a synchronous generator and is used in fields such as grid connection of new energy power generation, microgrids and energy storage systems.

[0060] Subsynchronous oscillation refers to an electromagnetic oscillation phenomenon in a power system with a frequency lower than the power frequency (50Hz / 60Hz). It is caused by an unfavorable interaction (resonance) between the dynamic characteristics of the converter control system and the grid impedance at a specific subsynchronous frequency, which may lead to equipment damage or system instability.

[0061] In this invention, grid-side information specifically refers to the three-phase voltage signal at the grid-side point of common coupling. This information reflects the overall operating status of the power grid and is a key input for achieving global observation and forward-looking control in this invention.

[0062] The power control loop is the core outer loop of the grid-connected converter control system. It typically calculates the reference commands for the inner loop control based on the active power-frequency and reactive power-voltage droop characteristics or a virtual synchronous machine algorithm. This invention primarily focuses on reshaping the dynamic characteristics of this loop.

[0063] System damping is a physical concept characterizing the ability of a power system to suppress power or electromagnetic oscillations. The greater the damping, the faster the oscillations decay, and the higher the system stability. One of the core objectives of this invention is to enhance the system's damping in the subsynchronous frequency band.

[0064] In this invention, steady-state power refers to the power value that the system should transmit under ideal, stable operating conditions, calculated based on grid-side voltage and line parameters. It serves as a feedforward signal to guide the system's dynamic processes.

[0065] Transient power refers to the real-time power value directly calculated from the instantaneous voltage and current on the converter side. It contains all the dynamic response information of the system, but may also contain oscillatory components that need to be suppressed.

[0066] Composite power refers to the new power signal obtained by weighting and fusing the steady-state power and transient power through a composite factor. As the command for the final input power outer loop controller, it combines the guidance of steady-state and the speed of transient, and is the core variable for achieving damping reshaping.

[0067] Example 1:

[0068] This embodiment provides a grid-connected converter control method based on grid-side information feedback, such as... Figure 1 As shown, the core idea of ​​the proposed method is to introduce grid-side information into the power control loop to calculate the steady-state power value, and combine it with the transient power calculated from instantaneous voltage and current in the traditional control structure to generate composite power that is connected to the GFM outer loop control, thereby reducing the adverse effects of current transient components on the control system.

[0069] The specific implementation method is as follows: Collect the voltage at the point of common coupling on the power grid side. Transform to a rotating coordinate system to obtain its d-axis and q-axis components. , If the system is in a steady state at this time, then it satisfies equation (1):

[0070] (1),

[0071] In equation (1), Let be the d-axis component of the capacitor voltage. This represents the q-axis component of the capacitor voltage. For the grid converter angular velocity, for, These are the d-axis and q-axis components of the steady-state current, respectively. Combined with the line parameters, they can be calculated according to (13):

[0072] (2),

[0073] In equation (2), This represents the line resistance.

[0074] Based on the steady-state current d-axis and q-axis components With respect to the voltage d-axis and q-axis components , Calculate the steady-state active power sent to the power control loop. and steady-state reactive power As shown in equation (3):

[0075] (3).

[0076] Introducing composite factors ， The steady-state active power With the transient active power The composite active power is obtained by fusion. The steady-state reactive power With the transient reactive power The composite reactive power is obtained by fusion. As shown in equation (4):

[0077] (4),

[0078] In equation (4), the composite factor The value range is between 0 and 1, composite factor The larger the value, the greater the proportion of steady-state power in the composite power. When the composite factor is 1, the higher the proportion of steady-state power in the composite power. The composite power is equal to the transient power; when the composite factor is This indicates that the composite power is entirely composed of steady-state power.

[0079] By replacing the transient power of the outer power loop with the composite power, a new outer power loop control equation is obtained, as shown in equation (5):

[0080] (5),

[0081] In equation (5), For virtual synchronous machine inertia, For the angular acceleration of the grid converter, This is the active power droop coefficient. Set the angular velocity value. This is the active power setpoint. The d-axis time constant, This is the reactive power droop factor. Set the d-axis voltage value. This is the reactive power setpoint. The derivative of the work angle, Let be the system angular velocity.

[0082] Unlike traditional grid-connected converter control strategies that rely solely on locally measured voltage and current, the grid-connected converter control method described in this embodiment introduces grid-side voltage information. This approach is feasible in practical systems and is particularly suitable for applications with high grid connection strength and short electrical distance, such as short-line connection conditions or cluster systems with multiple grid-connected converters operating in parallel. Grid-side voltage information can be obtained through communication or additional sensing methods.

[0083] From a mathematical modeling perspective, unlike methods such as the virtual impedance method, the grid-connected converter control method described in this embodiment, although introducing an additional control loop, does not change the system's equilibrium equations. Therefore, the steady-state operating point remains consistent with traditional methods, exhibiting good static performance compatibility. During dynamic processes, due to the use of pre-calculated steady-state power as a feedforward signal, the dynamic response of the power loop is reshaped, and the damping characteristics of the system's oscillation modes are significantly enhanced, thereby effectively suppressing subsynchronous oscillations caused by current dynamics.

[0084] Using the grid converter control method described in this embodiment, while maintaining the system short-circuit ratio (SCR) at 12, the composite factor is adjusted. The system's eigenvalue distribution is calculated based on the given values, and the results are plotted on [the graph]. Figure 2 The system parameters are shown in Table 1. Figure 2 It can be seen that, with As the value gradually increases (from 0 to 1), a pair of conjugate eigenvalues, originally located in the right half of the complex plane and corresponding to the subsynchronous oscillation (mode 1), gradually shift to the left half of the plane, eventually entering the stable region. This phenomenon indicates that the proposed control strategy can effectively enhance the damping characteristics of the system in subsynchronous oscillations, thereby suppressing subsynchronous oscillations and improving the stability of the system.

[0085] Table 1:

[0086] .

[0087] In addition, by Figure 2 It can be seen that the composite factor The changes in [the eigenvalue] have a relatively limited impact on other eigenvalues ​​in the system. In particular, another pair of eigenvalues ​​(mode 2) that might trigger subsynchronous oscillations [are affected]. The performance remains almost unchanged during changes. This demonstrates that the grid converter control method described in this embodiment, while suppressing subsynchronous oscillations (mode 1), exhibits good robustness to other dynamic modes of the system and does not cause unnecessary coupling effects.

[0088] For composite factors For the tuning, this embodiment proposes the following method. First, assume that when At this time, the system is in an unstable state, and there exists a pair of characteristic roots in the right half-plane that cause subsynchronous oscillations (mode 1). The pair of eigenvalues ​​closest to the imaginary axis in the left half-plane are the ones that cause subsynchronous oscillations (mode 2). Let these two pairs of eigenvalues ​​be composite factors. The sensitivities are respectively and As we can see from the analysis in the previous section, increasing... This will shift the eigenvalues ​​corresponding to the subsynchronous oscillation to the left half-plane, and shift the other pair of eigenvalues ​​to the right half-plane. Therefore, there must exist a... Values ​​such that the real parts of the two pairs of eigenvalues ​​mentioned above are equal, such as Figure 3 As shown. Record this moment. for The real parts of both pairs of characteristic roots are At this point, if it continues to increase... The value indicates that the dominant eigenvalue of the system changes from mode 1 to mode 2.

[0089] For estimation This embodiment assumes that in The sensitivity of the characteristic roots to the parameters does not change significantly during the process, and the following relationship can be established:

[0090] (6),

[0091] In equation (6), for and The difference, Characteristic roots The real part, for right k The partial derivatives, for and The difference, Characteristic roots The real part, for right k The partial derivatives of .

[0092] Furthermore, we can obtain The possible values ​​of:

[0093] (7),

[0094] Depend on Figure 2 ,have ,make It can be further simplified The expression for is shown in equation (8):

[0095] (8).

[0096] Actual selection of composite factors During the value process, the following should be satisfied: Not less than The principle. If If the value is too small, the real part of the eigenvalue of the subsynchronous oscillation (mode 1) cannot be effectively reduced, and the system is in an unstable state or has a low stability margin.

[0097] It should be noted that although the eigenvalues ​​of the subsynchronous oscillation (mode 2) are... The sensitivity of the value is low, but The increase in the factor still causes it to shift to the right half-plane. If the system's dominant oscillation mode becomes a subsynchronous oscillation (mode 2) due to changes in the actual system parameter configuration or operating conditions, the control effect of the grid converter control method described in this embodiment will be limited, and may even exacerbate the instability risk of low-frequency modes. Therefore, before applying the grid converter control method described in this embodiment, the system oscillation modes must be fully identified, and the applicability of the method must be judged accordingly. When mode mismatch occurs, the composite factor should be reduced. This avoids potentially adverse control effects.

[0098] Example 2:

[0099] This embodiment provides a grid-connected converter control system based on grid-side information feedback, used to implement the grid-connected converter control method as described in Embodiment 1.

[0100] Example 3:

[0101] like Figure 4 As shown, this embodiment provides an electronic device, which may include: at least one processor, at least one network interface, a user interface, a memory, and at least one communication bus.

[0102] The communication bus can be used to enable communication between the various components mentioned above.

[0103] The user interface may include buttons, and optional user interfaces may also include standard wired interfaces and wireless interfaces.

[0104] The network interface may include, but is not limited to, Bluetooth modules, NFC modules, Wi-Fi modules, etc.

[0105] The processor may include one or more processing cores. It connects various parts of the electronic device via various interfaces and lines, executing instructions, programs, code sets, or instruction sets stored in memory, and accessing data stored in memory to perform various functions and process data. Optionally, the processor can be implemented using at least one hardware form of DSP, FPGA, or PLA. The processor may integrate one or more of the following: CPU, GPU, and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content required for display; and the modem handles wireless communication. It is understood that the modem may also be implemented as a separate chip without being integrated into the processor.

[0106] The memory may include RAM or ROM. Optionally, the memory may include a non-transitory computer-readable medium. The memory can be used to store instructions, programs, code, code sets, or instruction sets. The memory may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the above-described method embodiments, etc.; the data storage area may store data involved in the above-described method embodiments, etc. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor. The memory, as a computer storage medium, may include an operating system, a network communication module, a user interface module, and a control application program. The processor can be used to call the control application program stored in the memory and execute the steps of the grid converter control method mentioned in the foregoing embodiments.

[0107] Example 4:

[0108] This embodiment provides a computer-readable storage medium storing instructions that, when executed on a computer or processor, cause the computer or processor to perform the above-described instructions. Figure 1 One or more steps in the illustrated embodiment. If the constituent modules of the above-described electronic device are implemented as software functional units and sold or used as independent products, they can be stored in the computer-readable storage medium.

[0109] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this specification are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in or transmitted through a computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., Digital Versatile Discs (DVDs)), or semiconductor media (e.g., Solid State Disks (SSDs)).

[0110] Those skilled in the art will understand that all or part of the processes in the method of Embodiment 1 described above can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks. Unless otherwise specified, the technical features of this embodiment and the implementation scheme can be combined arbitrarily.

[0111] Example 5:

[0112] To verify the effectiveness of the grid-side information feedback-based grid converter control method described in this specification, a comparative experiment was conducted in this embodiment. Control group 1 used the traditional grid converter control method, control group 2 used the virtual impedance method, and the experimental group used the grid converter control method described in this invention.

[0113] like Figure 5The diagram shows a traditional grid-connected converter and its control structure. After acquiring the voltage and inductor current across the filter capacitors at the converter ports, these data are fed into the inner loop via an abc / dg conversion, and simultaneously input into the grid-connected control outer loop via a power calculation stage. This generates the amplitude and phase of the external reference voltage for the filter, which are then fed into the inner loop. The inner loop includes voltage and current feedback loops, outputting the dq component of the converter reference voltage, which is then converted into a three-phase reference voltage via a dq / abc conversion. e abc The signal is modulated into a gate signal by a PWM stage to drive the converter. Note the phase angle used in the dq transform and inverse transform. θ It is generated autonomously by a network-type control system, without the need for a traditional phase-locked loop.

[0114] In traditional grid-connected converter control loops, the outer loop can take the form of a Virtual Synchronous Generator (VSG) or droop control. The full-order mathematical model of a grid-connected converter using a VSG is shown below:

[0115] Outer loop power control:

[0116] (9),

[0117] In equation (9), For virtual synchronous machine inertia, These are the active and reactive power droop coefficients, respectively. These are the setpoints for angular velocity, active power, reactive power, and d-axis voltage. The d-axis voltage regulation time constant is... These are the reference values ​​for the voltage dq axis, respectively. For the system power angle, The angular frequency of GFM. The angular frequency of the power grid. The transient active and reactive power are respectively, as shown in equation (10):

[0118] (10)

[0119] In equation (10), These are the voltages of the filter capacitors. u tabc The dq axis components, Line current i tabc The dq axis components.

[0120] Outer loop voltage control:

[0121] The voltage loop is controlled by a PI controller, and the mathematical model is shown in equation (11):

[0122] (11),

[0123] In equation (11), This is an intermediate variable in the voltage loop. These are the integral and proportional parameters for the voltage loop PI control, respectively. These are the reference values ​​for the dq axis currents, respectively.

[0124] Inner loop current control:

[0125] The current loop is controlled by a PI controller, and the mathematical model is shown in equation (12):

[0126] (12)

[0127] In equation (12), These are the filter inductor currents. i labc The dq axis components, This is an intermediate variable in the current loop. These are the integral and proportional parameters for current PI control, respectively. These are the reference values ​​for the dq-axis components of the inverter port voltage, respectively. This is the filter inductor.

[0128] Inverter:

[0129] Assuming that the higher harmonics are filtered by the filter, the inverter can be represented by a first-order hysteresis element, as shown in Equation (13).

[0130] (13)

[0131] In equation (13), These represent the dq-axis components of the inverter port voltage, respectively. This is the proportionality coefficient. is the time constant.

[0132] Filter inductor:

[0133] (14)

[0134] In equation (14), These are the filter resistors.

[0135] Filter capacitors:

[0136] (15)

[0137] In equation (15), This is the filter capacitor.

[0138] Line resistance:

[0139] (16)

[0140] In equation (16), These are the line inductance and resistance, respectively. For grid voltage u sabc The dq axis components.

[0141] As can be seen from the above, the full-order model of the network-type VSG is 15th order.

[0142] Virtual impedance is a key control strategy in grid-connected converters. Its core is to "simulate" an impedance characteristic similar to a real inductor or resistor at the converter output through a control algorithm. This method monitors the output current in real time and multiplies it by a preset virtual impedance value to calculate the virtual voltage drop, which is then used to correct the reference voltage signal. Its control structure is as follows: Figure 6 As shown.

[0143] Compared to the mathematical model of traditional grid-connected converters, there are some differences in its mathematical model. First, equation (11) is changed to equation (17):

[0144] (17)

[0145] In equation (17), These are the new voltage dq-axis reference values. They are derived from the original voltage dq-axis reference values. The voltage drop calculated using the virtual impedance is shown in equation (18):

[0146] (18)

[0147] In equation (18), Rvi , Xvi These represent the resistance and reactance values ​​of the virtual impedance, respectively.

[0148] Combining equations (17) and (18), the outer-loop voltage control model using virtual impedance control can be obtained as shown in equation (19):

[0149] (19).

[0150] The rest of the control method is consistent with that of traditional grid-connected converters. The introduction of virtual impedance enables the converter to actively shape its external characteristics and effectively suppress subsynchronous oscillations. However, by comparing equation (17) and equation (11), it can be seen that the system's equilibrium equation has changed, indicating that the stable operating point of the system has changed after the introduction of virtual impedance, thus resulting in poor static compatibility in engineering.

[0151] The comparative experimental results show that the grid converter control method of the present invention has a significant suppression effect on high-frequency synchronous oscillations, can effectively enhance system damping, promote the rapid decay of oscillation modes, thereby improving system stability and ensuring good power quality. Figure 7 The diagram shows a comparison curve of the power angle using the traditional method, the virtual impedance method, and the grid-connected converter control method described in this invention under strong grid conditions. Figure 7 As shown, when the SCR undergoes a step change at 1.5s, the traditional control method exhibits significant instability, with the power angle response curve showing continuous constant-amplitude oscillations with a period of approximately 35ms. After adopting the proposed control method, the system's dynamic performance is improved. The system quickly converges to a stable value of approximately 2° after a brief adjustment, without oscillation. The virtual impedance method also improves the system's stability, preventing oscillations and leading to stability. However, because it alters the system's equilibrium point, its steady-state power angle converges to a stable value of approximately 4.5°. Figure 8 and Figure 9 The voltage waveforms of the conventional method and the grid converter control method described in this invention are shown respectively. Figure 8 The voltage waveform is distorted, and the amplitude exhibits obvious periodic fluctuations. Figure 9 The voltage waveform shown exhibits good sinusoidal characteristics, with stable amplitude and no obvious distortion, indicating that the grid converter control method described in this invention can effectively maintain stable system operation while ensuring good power quality.

[0152] This invention improves the system's ability to suppress subsynchronous oscillations without altering the system's equilibrium equations, maintaining the same equilibrium relationship as traditional control strategies. Therefore, this method does not affect the system's static operating point and steady-state performance, exhibiting good compatibility in engineering applications. Figure 10 The active and reactive power outputs under three control strategies were compared under weak power grid conditions. Figure 10 This indicates that, for active power, the steady-state value of the output active power remains consistent under all three control strategies. This is consistent with expectations, as the system input active power reference command is consistent. However, for reactive power, the proposed method maintains the same steady-state value as the traditional method. The virtual impedance method, by altering the system's operating point, causes a shift in the steady-state value of reactive power.

[0153] Based on the above, this embodiment verifies the effectiveness of the grid-connected converter control method based on grid-side information feedback described in this specification.

[0154] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0155] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0156] The above description is merely an exemplary embodiment of the present invention and should not be construed as limiting the scope of the invention. Any equivalent changes and modifications made in accordance with the teachings of this invention are still within the scope of this invention. Those skilled in the art will readily conceive of embodiments of the invention upon considering the specification and practicing the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of the invention are defined by the claims.

Claims

1. A grid-connected converter control method based on grid-side information feedback, characterized in that, Including the following steps: S1. Acquire voltage signals at the connection points between power grid lines and the power system. Voltage signal at the connection point between the filter capacitor and the power grid line and current signal ; S2. Voltage signal based on the connection point between the power grid line and the power system Calculate the steady-state active power using the preset line impedance parameters. and steady-state reactive power ; S3. Based on the voltage signal at the connection point between the filter capacitor and the power grid line. and current signal Calculate transient active power and transient reactive power ; S4. Introducing composite factors The steady-state active power With the transient active power The composite active power is obtained by fusion. The steady-state reactive power With the transient reactive power The composite reactive power is obtained by fusion. ; S5, the composite active power and the composite reactive power The input is fed to the outer power loop controller of the grid converter to generate a reference signal for the inner loop control, thereby suppressing subsynchronous oscillations.

2. The grid-connected converter control method based on grid-side information feedback according to claim 1, characterized in that, In step S2, the steady-state active power is calculated. and steady-state reactive power include: The voltage signal at the connection point between the power grid line and the power system Transform to a rotating coordinate system to obtain the d-axis and q-axis components of the voltage. , ; Based on the voltage d and q axis components , The steady-state current d-axis and q-axis components are obtained by calculating the line impedance parameters. ; Based on the steady-state current d-axis and q-axis components With respect to the voltage d-axis and q-axis components , The steady-state active power was calculated. and steady-state reactive power .

3. The grid-connected converter control method based on grid-side information feedback according to claim 2, characterized in that, In step S3, the transient active power is calculated. and transient reactive power include: The voltage signal at the connection point between the filter capacitor and the power line and current signal By transforming to a rotating coordinate system, the d-axis and q-axis components are obtained, thereby calculating the transient active power. and transient reactive power .

4. The grid-connected converter control method based on grid-side information feedback according to claim 3, characterized in that, The composite active power and the composite reactive power The calculation formula is: ， In the formula, the composite factor The value range is between 0 and 1.

5. The grid-connected converter control method based on grid-side information feedback according to claim 4, characterized in that: The composite factor The value of is tuned to enhance the damping characteristics of the system in the subsynchronous frequency band.

6. The grid-connected converter control method based on grid-side information feedback according to claim 5, characterized in that, The composite factor The tuning method includes the following steps: Acquisition system in different The value corresponds to the modal information of the subsynchronous oscillation; Based on the modal information, an optimal composite factor is calculated. ; The composite factor The value of should not be less than the optimal composite factor. The value.

7. The grid-connected converter control method based on grid-side information feedback according to claim 6, characterized in that: The modal information includes system eigenvalues ​​and their pairs. Sensitivity to the value; The optimal composite factor It is calculated based on the real part of the eigenvalue and its sensitivity.

8. A grid-connected converter control system based on grid-side information feedback, characterized in that, Used to implement the grid converter control method as described in any one of claims 1 to 7.

9. A computer device, the computer device comprising a memory, a processor, and a computer program, characterized in that, When the computer program is executed by the processor, it implements the grid converter control method as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the grid converter control method as described in any one of claims 1 to 7.

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