A single-phase virtual synchronous machine control method with dynamic characteristic optimization

Abstract

This invention discloses a single-phase virtual synchronous machine (VSG) control method with optimized dynamic characteristics, comprising: constructing two sets of orthogonal signals of voltage and current using the SOGI power measurement loop, and calculating the average active power and reactive power; based on the nonlinear and time-varying characteristics of the SOGI single-phase power calculation loop, using a system identification method based on N4SID and PSO algorithms to fit the optimal linearized transfer function of the SOGI power calculation loop; establishing a state-space model of the single-phase VSG system based on the optimal linearized transfer function, and realizing single-phase virtual synchronous machine control through partial state feedback pole configuration. The SOGI power measurement loop linearization method based on system identification in this invention aims to optimize the active closed-loop response characteristics of the single-phase VSG, eliminate low-frequency oscillations, and maintain fast dynamic response capability, and on this basis, performs a precise pole configuration scheme for the single-phase VSG closed loop.

Description

Technical Field

[0001] This invention relates to the field of synchronous machine control technology, and in particular to a single-phase virtual synchronous machine control method with optimized dynamic characteristics. Background Technology

[0002] With increasing energy consumption and growing energy problems, the development and utilization of new energy sources have attracted much attention, and distributed generation technology using new energy sources has become an important way to solve energy problems. However, traditional grid-connected inverters cannot provide voltage support, inertial support, and primary frequency regulation capabilities to the power grid like synchronous generators. When they are connected to the power system, they may cause power quality and stability problems, thus limiting the proportion of traditional new energy grid-connected inverters in the power grid.

[0003] Figure 1 The Virtual Synchronous Generator (VSG) technology shown is an effective method to solve the above problems. By simulating the oscillation equations and speed governor (droop control) of a synchronous generator in the grid-connected inverter control system, the VSG can provide effective inertial support and primary frequency regulation for the power grid. Current research on VSG technology mainly focuses on three-phase power electronic devices.

[0004] Single-phase power electronic devices are often overlooked due to their small individual unit capacity and limited ability to provide grid frequency support. However, single-phase VSGs with relatively small rated power per unit can provide significant frequency support to the grid if they can achieve clustering effects. Therefore, the application of VSGs in single-phase power electronic devices should be given sufficient attention. However, single-phase devices have some characteristics that three-phase devices do not have, such as ① more complex power calculation units; ② the presence of second harmonic power oscillations. How to comprehensively consider these unique issues of single-phase power electronic devices when designing single-phase VSG systems has become another problem that needs to be solved in promoting VSG control. The second harmonic power ripple in a single-phase system is very large, and theoretically its amplitude is equal to the average power, making it difficult to remove with first-order filtering. However, if the power measurement value containing the second harmonic ripple component is directly used for VSG control, the output frequency command will also contain the second harmonic component, affecting the power quality of the VSG output. A common approach to solving this problem is shown in Figure 2. This approach uses a second-order generalized integrator (SOGI) to filter the voltage and current and generate orthogonal components. These components are then multiplied and summed as shown in the figure to obtain the average value of the instantaneous active power of the single-phase system.

[0005] On the other hand, while simulating the oscillation equation of a synchronous generator, the VSG also inherits the latter's low-frequency oscillation characteristics. To suppress low-frequency oscillations, a damping control loop is generally added, as shown in Figure 3, and the dominant poles of the entire closed-loop system are precisely designed and configured to a position where the damping coefficient can be specified by the designer and is sufficiently large. As can be seen from Figure 3, the equivalent model of the power measurement loop in Figure 2 is equivalent to the feedback path transfer function of the closed loop. Existing technology proposes a three-phase VSG damping design method that ignores the power measurement loop, which can be applied to single-phase VSGs, but ignoring the feedback path transfer function will limit the improvement of the system's dynamic performance. Existing technology also discloses a three-phase damping design method for first-order power measurement filtering, but this scheme is only applicable to first-order filter systems and cannot be used for higher-order filters. Existing technology also proposes a damping control method for three-phase VSGs that can consider a precise closed-loop pole configuration method applicable to higher-order filtering in power measurement loops. However, given that Figure 2 Given the complexity of the single-phase VSG power measurement circuit, the existing method for precise closed-loop pole configuration of three-phase VSGs is no longer applicable. A new scheme based on SOGI filtering is needed for the power measurement circuit of single-phase VSGs.

[0006] Based on the above analysis of existing closed-loop damping design schemes for VSG systems, there is currently no method for single-phase VSG damping design that comprehensively considers the influence of SOGI power measurement. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a single-phase virtual synchronous machine (VSG) control method with optimized dynamic characteristics. This invention is based on a system identification-based SOGI power measurement loop linearization method, aiming to optimize the active power closed-loop response characteristics of the single-phase VSG, eliminate low-frequency oscillations, and maintain rapid dynamic response capability. Furthermore, it employs a precise pole configuration scheme for the single-phase VSG closed loop.

[0008] The objective of this invention is achieved through the following technical solutions:

[0009] A dynamic characteristic optimized single-phase virtual synchronous machine control method includes:

[0010] Two sets of orthogonal signals of voltage and current are constructed using the SOGI power measurement circuit to calculate the average active power and reactive power.

[0011] Based on the nonlinear and time-varying characteristics of the SOGI single-phase power calculation stage, a system identification method based on intelligent optimization algorithm is adopted to fit the optimal linearized transfer function of the SOGI power calculation stage.

[0012] A state-space model of a single-phase VSG system is established based on the optimal linearized transfer function, and single-phase virtual synchronous machine control is realized through state feedback.

[0013] As a further improvement of the present invention, the method of constructing two sets of orthogonal signals of voltage and current using the SOGI power measurement circuit to calculate the average active power and reactive power includes:

[0014] Voltage and current are respectively passed through two second-order generalized integrator quadrature signal generators with identical parameters to obtain two sets of orthogonal signals; the input sinusoidal quantity generates two mutually orthogonal signals, with the transfer functions of the two signals being:

[0015] (1)

[0016] (2)

[0017] in x For input signal, x α , x β The output consists of two orthogonal signals. ω For system frequency, k For SOGI parameters; after obtaining two sets of orthogonal signals of voltage and current, the average active power and reactive power are calculated as follows:

[0018] (3)

[0019] (4)

[0020] In the formula, v outα , v outβ , i outα , i outβ These are two orthogonal signals, one for voltage and one for current.

[0021] As a further improvement of the present invention, the nonlinear and time-varying characteristics of the SOGI-based single-phase power calculation stage are addressed by employing a system identification method based on intelligent optimization algorithms to fit the optimal linearized transfer function of the SOGI power calculation stage, including:

[0022] Different power factor angles were established through simulation. θ and voltage initial phase angle φ Data set of the system step response;

[0023] By averaging all response curves at each time point, an averaged step response curve is obtained.

[0024] The transfer function that is closest to the average step response is obtained through the system identification algorithm, and it is defined as the preliminary identification result.

[0025] Using the initially identified transfer function as the initial value, the intelligent optimization algorithm further optimizes the previously obtained averaged transfer function, thus obtaining the optimal linearized transfer function for the SOGI power measurement stage.

[0026] As a further improvement of the present invention, the step of using the initially identified transfer function as the initial value of the intelligent optimization algorithm includes:

[0027] Choose by D The transfer function coefficients, represented by a dimensional vector, serve as the particle's position vector. Each particle represents a multi-order transfer function, and the cluster size is set to... N ;

[0028] (27)

[0029] (28)

[0030] Calculate the fitness function for each particle, and select the optimal value for each particle based on the fitness function. and the group optimal value Gb Then, update the optimal particle position for each individual. and the optimal particle position of the swarm ;

[0031] Calculate the position update rate for each particle, and update the position of each particle:

[0032] (29)

[0033] (30)

[0034] in r 1 and r 2 is the acceleration constant. c 1 and c 2 represents the iteration coefficient;

[0035] Repeat until the population optimum is reached. Gb The optimal linearized transfer function of the SOGI power measurement stage is obtained by reducing the error to below the predefined allowable error or reaching the maximum number of iterations.

[0036] As a further improvement of the present invention, a state-space model of a single-phase VSG system is established based on the optimal linearized transfer function, including:

[0037] After obtaining the optimal transfer function of the power calculation part based on SOGI, the closed-loop damping of the single-phase VSG system is obtained.

[0038] According to transmission line theory, when the line is essentially inductive, the active power transmitted by the inverter to the bus can be expressed as:

[0039] (5)

[0040] in, E This represents the effective value of the inverter's electromotive force. V bus This is the effective value of the bus voltage. X For line impedance, δ Power angle; synchronous power factor K Defined as:

[0041] (6)

[0042] And the angle of the action δ The differential can be expressed as:

[0043] (7)

[0044] An open-loop model of active power transmission under grid-connected inverter conditions is obtained. For the active-frequency control section of the single-phase VSG, damping power is generated through state feedback control.

[0045] (8)

[0046] (9)

[0047] in, ω m For the virtual rotor angular frequency of the virtual synchronous machine, ω 0 is the standard angular frequency. k p The droop coefficient is... J sf For nominal virtual inertia, P d For damping power, P SOGI The average power obtained from the SOGI power measurement stage. k xω , k xp , k xi For the state feedback control parameters; considering the transfer function of the SOGI power measurement loop, we have:

[0048] (10)

[0049] P out The actual average power; by performing small-signal linearization on equations (5)-(10), the active-frequency grid-connected closed-loop small-signal state-space model of a single-phase VSG under partial state feedback damping is obtained:

[0050] (11)

[0051] in:

[0052] (12)

[0053] (13)

[0054] (14)

[0055] (15)

[0056] Under grid-connected operating conditions, Δ P 0 represents a small active power signal, Δ ω m This is a disturbance of small-signal voltage frequencies in the power grid; x add T Additional multi-order state variables introduced for SOGI power measurement. A Here is the state transition matrix. B For the input matrix, B f For the feedback input matrix, E The perturbation input matrix, K For the feedback matrix, C For the output matrix, C f This is the feedback output matrix.

[0057] As a further improvement to the present invention, the state transition matrix A Input matrix B Feedback input matrix B f Perturbation input matrix E Feedback matrix K Output matrix C Feedback output matrix C f It is calculated using the following method:

[0058] (16)

[0059] (17)

[0060] (18)

[0061] (19)

[0062] (20)

[0063] (twenty one)

[0064] (twenty two)

[0065] (twenty three)

[0066] (twenty four)

[0067] in A s and C s This refers to the controllable standard form state transition matrix and output matrix of the SOGI power measurement stage, while

[0068] (25)

[0069] (26).

[0070] As a further improvement of the present invention, the status feedback includes:

[0071] After obtaining the closed-loop small-signal state-space model of the system, a suitable feedback matrix is ​​set using partial state feedback pole configuration. K The coefficients allow the closed-loop poles of the system to be placed at arbitrary locations.

[0072] As a further improvement of the present invention, the method of using partial state feedback pole configuration to set a suitable feedback matrix is ​​described. K The coefficients include:

[0073] After obtaining the optimal linearized transfer function, the resulting closed-loop small-signal state-space model of the system is used to set a suitable feedback matrix using partial state feedback pole placement. K The coefficient is used to position the closed-loop poles of the system at the locations where inertia provision and active power oscillation attenuation occur, that is, to position the two dominant poles at the damping ratio. ζ =0.9, a high-damping position, while the system's natural angular frequency ω n Maintaining a high constant of inertia J The need:

[0074] (31)

[0075] The third non-dominant pole is located far from the imaginary axis; the other uncontrollable poles are located far from the imaginary axis.

[0076] The actual inertial constant is usually taken as a typical value for a synchronous generator, where... S base Inverter capacity:

[0077] (32)

[0078] The actual inertia of VSG is ultimately equivalent. J Determined by the location of the closed-loop poles, defined J sf Ratio to actual inertia:

[0079] (33)

[0080] Compared with the prior art, the multi-port power router of the present invention has the following advantages:

[0081] This invention addresses the shortcomings of current single-phase VSG technology. Based on the nonlinear and time-varying characteristics of the single-phase power calculation stage of SOGI, it employs a system identification method based on N4SID and PSO algorithms to fit the optimal linearized transfer function of the SOGI power calculation stage. Furthermore, the obtained transfer function is used for the precise closed-loop design of a single-phase virtual synchronous generator-controlled inverter, establishing a state-space model of the single-phase VSG system. Through partial state feedback pole configuration, it achieves both maintaining a large system inertia support capability and good low-frequency active power oscillation attenuation and rapid active power dynamic response. The single-phase VSG damping design method proposed in this invention effectively improves the system's dynamic response capability, especially for rapid response and effective attenuation of low-frequency oscillations when the active power setpoint changes under grid-connected conditions, showing significant advantages over existing VSG damping schemes. Attached Figure Description

[0082] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0083] Figure 1 A conceptual diagram of a new energy virtual synchronous generator system;

[0084] Figure 2 This is a schematic diagram of active power measurement for a single-phase inverter.

[0085] Figure 3This is a schematic diagram of the VSG closed-loop model;

[0086] Figure 4 This is a block diagram of the internal structure of SOGI-QSG;

[0087] Figure 5 This is a block diagram of the active-frequency control of a single-phase VSG.

[0088] Figure 6 A schematic diagram of a power transmission model for an inverter connected to an infinitely large bus.

[0089] Figure 7 Flowchart for identifying the optimal linearized transfer function;

[0090] Figure 8 This is a diagram showing the active power closed-loop pole distribution of the configured system. Detailed Implementation

[0091] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0092] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0093] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of the present invention.

[0094] The purpose of this invention is to propose a method that fully considers the dynamic characteristics of SOGI power measurement and applies it to the precise design of single-phase VSG closed-loop poles, eliminating low-frequency power oscillations while maintaining good dynamic response speed.

[0095] This invention provides a dynamic characteristic optimization control method for a single-phase virtual synchronous machine, comprising:

[0096] Two sets of orthogonal signals of voltage and current are constructed using the SOGI power measurement circuit to calculate the average active power and reactive power.

[0097] Based on the nonlinear and time-varying characteristics of the single-phase power calculation stage of SOGI, a system identification method based on intelligent optimization algorithms such as N4SID and PSO is adopted to fit the optimal linearized transfer function of the SOGI power calculation stage.

[0098] A state-space model of a single-phase VSG system is established based on the optimal linearized transfer function, and single-phase virtual synchronous machine control is realized through state feedback.

[0099] Example

[0100] To achieve the above objectives, the present invention adopts the following detailed technical solution:

[0101] (1) Linearization method for SOGI power measurement stage

[0102] exist Figure 2 In the SOGI-based power calculation method, voltage and current are respectively processed by two second-order generalized integrator quadrature signal generators (SOGI-QSG) with identical parameters to obtain two sets of orthogonal signals. The block diagram of the SOGI-QSG is shown below. Figure 4 As shown. It can generate two mutually orthogonal signals from an input sinusoidal quantity, with the two transfer functions being:

[0103] (1)

[0104] (2)

[0105] in x For input signal, x α , x β The output consists of two orthogonal signals. ω For system frequency, k These are the SOGI parameters; after obtaining two sets of orthogonal signals for voltage and current, the average active power and reactive power can be calculated as follows:

[0106] (3)

[0107] (4)

[0108] In the formula, v outα , v outβ , i outα , i outβ These are two orthogonal signals, one for voltage and one for current.

[0109] As can be seen from equations (3) and (4), the average active power and reactive power are obtained by multiplying and adding two orthogonal signals generated by voltage and current signals through SOGI-QSG. The multiplication in the time domain introduces strong nonlinearity into the system and also has periodic time-varying characteristics.

[0110] To address the nonlinearity and time-varying nature of the SOGI power calculation process, this scheme employs a system identification method to obtain the linearized transfer function of the SOGI power measurement process, including:

[0111] First, simulations were used to establish different power factor angles. θ and voltage initial phase angle φ A dataset of the system's step response. Simulation software can include PLECS, etc.

[0112] Secondly, by averaging all response curves at each time point, an averaged step response curve is obtained. The transfer function that best approximates the average step response is obtained through the Numerical State Subspace Model System Identification (N4SID) algorithm, and this is defined as the preliminary identification result.

[0113] To further optimize the identification results, the Particle Swarm Optimization (PSO) algorithm was used. The initially identified transfer function was used as the initial value for the PSO algorithm to further optimize the previously obtained averaged transfer function.

[0114] Finally, the sixth-order optimal linearized transfer function of the SOGI power measurement stage is obtained. The SOGI power measurement stage is systematically identified based on intelligent optimization algorithms, including but not limited to the aforementioned N4SID plus PSO scheme; other combinations of identification and optimization algorithms can also be used.

[0115] (2) Single-phase VSG closed-loop pole design

[0116] After obtaining the optimal transfer function for the power calculation part based on SOGI, it is possible to utilize Figure 5 The control scheme shown precisely designs the closed-loop damping of a single-phase VSG system.

[0117] According to transmission line theory, for an inverter connected to the infinite bus common connection (PCC) point as shown in Figure 9, the phase difference between the inverter output voltage and the voltage at the PCC point, i.e., the inverter power angle δ, is very small. When the line is essentially inductive, the active power transmitted by the inverter to the bus can be approximately expressed as:

[0118] (5)

[0119] in, E This represents the effective value of the inverter's electromotive force. V bus This is the effective value of the bus voltage. X For line impedance, δ Power angle; synchronous power factor K Defined as:

[0120] (6)

[0121] The differential of the work angle δ can be expressed as:

[0122] (7)

[0123] Combining equations (5) to (7), we obtain the open-loop model of active power transmission under grid-connected inverter conditions. For the single-phase VSG active-frequency control section, through methods including but not limited to... Figure 3 The state feedback method of the structure shown generates damping power:

[0124] (8)

[0125] (9)

[0126] in, ω m For the virtual rotor angular frequency of the virtual synchronous machine, ω 0 is the standard angular frequency. k p The droop coefficient is... J sf For nominal virtual inertia, P d For damping power, P SOGI The average power obtained from the SOGI power measurement stage. k xω , k xp, k xi Let these be the state feedback control parameters; and considering the transfer function of the obtained SOGI power measurement loop, we have:

[0127] (10)

[0128] P out The actual average power; by combining equations (5) to (10) and performing small-signal linearization, we can obtain the active-frequency grid-connected closed-loop small-signal state-space model of a single-phase VSG under partial state feedback damping:

[0129] (11)

[0130] in:

[0131] (12)

[0132] (13)

[0133] (14)

[0134] (15)

[0135] Under grid-connected operating conditions, the active power small signal Δ P 0 is considered as the system input, while the small signal Δ of the grid voltage frequency is... ω m This is then considered a disturbance. x add T This introduces an additional 6th-order state variable for the SOGI power measurement stage. The state transition matrix... A Input matrix B Feedback input matrix B f Perturbation input matrix E Feedback matrix K Output matrix C Feedback output matrix C f All of these can be obtained through calculation:

[0136] (16)

[0137] (17)

[0138] (18)

[0139] (19)

[0140] (20)

[0141] (twenty one)

[0142] (twenty two)

[0143] (twenty three)

[0144] (twenty four)

[0145] Where A s and C s This refers to the controllable standard form state transition matrix and output matrix of the SOGI power measurement stage, while

[0146] (25)

[0147] (26)

[0148] After obtaining the closed-loop small-signal state-space model of the system, a suitable feedback matrix is ​​set using partial state feedback pole configuration. K The coefficients can be used to configure the three closed-loop poles of the system in any position, thereby improving the dynamic characteristics of the system. The above example uses partial state feedback pole configuration. In practical applications, the state feedback variables can be selected differently, and the control design method is the same.

[0149] Figure 7 This is a flowchart of the optimal linearized transfer function identification process for the SOGI power measurement stage proposed in this invention. Assuming the SOGI power measurement stage is a system of order 3 to 10, multiple sets of transfer functions are obtained by sequentially applying the N4SID algorithm.

[0150] At lower system orders, increasing the system order leads to more non-dominant poles farther from the imaginary axis, which helps improve model accuracy. However, for systems of order 6 and above, increasing the identification order splits the dominant poles into a group of neighboring poles, similar to the original dominant poles but increasing system complexity and the difficulty of subsequent closed-loop controller design. Furthermore, for systems of order higher than 5, the system identification accuracy can reach over 99%. Considering identification accuracy and the computational complexity of subsequent controller design, the SOGI power measurement stage is approximated as a 6th-order linear system. The corresponding 6th-order system transfer function is then used as the initial value for the PSO algorithm.

[0151] The optimization steps of the PSO algorithm are as follows:

[0152] 1) Select by D The transfer function coefficients, represented by a dimensional vector, serve as the particle's position vector. This means that each particle represents a 6th-order transfer function, as shown in equations (27) and (28). The purpose of the particle swarm optimization algorithm is to optimize the problem. The swarm size is set to... N .

[0153] (27)

[0154] (28)

[0155] 2) The fitness function is defined as the average spatial distance between the step response of the transfer function and all step responses in the database. The fitness function of each particle is calculated, and the optimal value for each particle is selected based on the fitness function. and the group optimal value Gb Then, update the optimal particle position for each individual. and the optimal particle position of the swarm .

[0156] 3) Calculate the position update rate of each particle using equation (29), and update the position of each particle using equation (30).

[0157] (29)

[0158] (30)

[0159] in r 1 and r 2 is the acceleration constant, a random number between 0 and 1, while c 1 and c 2 represents the iteration coefficient. During the iteration process, c 1 and c The value of 2 decreases from its initial value to 0.

[0160] 4) Repeat steps 1)-3) until the population optimum is reached. Gb Reduce to below the predefined allowable error or reach the maximum number of iterations.

[0161] Finally, the optimal linearized transfer function for the SOGI power measurement stage was obtained.

[0162] After obtaining the optimal linearized transfer function, the system closed-loop small-signal state-space model obtained by equations (11)-(26) is used to set a suitable feedback matrix by utilizing partial state feedback pole configuration. K The coefficient is used to configure the system's three closed-loop poles at positions that simultaneously satisfy both a large inertia supply and the attenuation of active power oscillations, that is, to configure the two dominant poles at the damping ratio. ζ =0.9, a high-damping position, while the system's natural angular frequency ωn Maintaining a high constant of inertia J The need:

[0163] (31)

[0164] The third non-dominant pole is located relatively far from the imaginary axis. The remaining uncontrollable poles are also located far from the imaginary axis, and the specific pole distribution after configuration is as follows: Figure 8 As shown.

[0165] The actual inertial constant is usually taken as a typical value for a synchronous generator, where... S base Inverter capacity:

[0166] (32)

[0167] The actual inertia of VSG is ultimately equivalent. J The location of the closed-loop poles is determined by equation (31), and Figure 5 In J sf It does not necessarily need to be equal to the actual inertia of the system. J ,Change J sf It does not change the closed-loop poles of the system. Definition J sf Ratio to actual inertia:

[0168] (33)

[0169] It can be adjusted ρ The value of is chosen such that, without changing the system poles, the system response speed is changed by adjusting the system zeros, thereby selecting a system with better dynamic performance. Generally, a value is chosen such that the feedback matrix (20) is such that . k xp =1 ρ After the precise pole configuration described above, the characteristics of the entire closed-loop system approximate a low-overshoot, underdamped second-order system, possessing both fast dynamic response and good low-frequency oscillation attenuation.

[0170] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

[0171] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation schemes of the present invention, and these modifications or equivalent substitutions do not depart from the spirit and scope of the present invention, and are all within the protection scope of the claims of the present invention.

Claims

1. A method for controlling a single-phase virtual synchronous machine with optimized dynamic characteristics, characterized in that, include: Two sets of orthogonal signals of voltage and current are constructed using the SOGI power measurement circuit to calculate the average active power and reactive power. Based on the nonlinear and time-varying characteristics of the SOGI single-phase power calculation stage, a system identification method based on intelligent optimization algorithm is adopted to fit the optimal linearized transfer function of the SOGI power calculation stage. A state-space model of a single-phase VSG system is established based on the optimal linearized transfer function, and single-phase virtual synchronous machine control is realized through state feedback. A state-space model of a single-phase VSG system is established based on the optimal linearized transfer function, including: After obtaining the optimal transfer function of the power calculation part based on SOGI, the closed-loop damping of the single-phase VSG system is obtained. According to transmission line theory, when the line is inductive, the active power transmitted by the inverter to the bus can be expressed as: (5) in, E This represents the effective value of the inverter's electromotive force. V bus This is the effective value of the bus voltage. X For line impedance, δ Power angle; synchronous power factor K ′ is defined as: (6) And the angle of the action δ The differential expression is: (7) An open-loop model of active power transmission under grid-connected inverter conditions is obtained. For the active-frequency control section of the single-phase VSG, damping power is generated through state feedback control. (8) (9) in, ω m For the virtual rotor angular frequency of the virtual synchronous machine, ω 0 is the standard angular frequency. k p The droop coefficient is... J sf For nominal virtual inertia, P d For damping power, P SOGI The average power obtained from the SOGI power measurement stage. k xω , k xp , k xi For the state feedback control parameters; considering the transfer function of the SOGI power measurement loop, we have: (10) P out The actual average power; by performing small-signal linearization on equations (5)-(10), the active-frequency grid-connected closed-loop small-signal state-space model of a single-phase VSG under partial state feedback damping is obtained: (11) in: (12) (13) (14) (15) Under grid-connected operating conditions, Δ P 0 represents a small active power signal, Δ ω m This is a disturbance of small-signal voltage frequencies in the power grid; x add T Additional multi-order state variables introduced for SOGI power measurement. A Here is the state transition matrix. B For the input matrix, B f For the feedback input matrix, E The perturbation input matrix, K For the feedback matrix, C For the output matrix, C f For feedback output matrix; State transition matrix A Input matrix B Feedback input matrix B f Perturbation input matrix E Feedback matrix K Output matrix C Feedback output matrix C f It is calculated using the following method: (16) (17) (18) (19) (20) (21) (22) (23) (24) in A s and C s This refers to the controllable standard form state transition matrix and output matrix of the SOGI power measurement stage, while (25) (26)。 2. The single-phase virtual synchronous machine control method with dynamic characteristic optimization according to claim 1, characterized in that, The method of constructing two sets of orthogonal signals of voltage and current using the SOGI power measurement circuit to calculate the average active power and reactive power includes: Voltage and current are respectively passed through two second-order generalized integrator quadrature signal generators with identical parameters to obtain two sets of orthogonal signals; the input sinusoidal quantity generates two mutually orthogonal signals, with the transfer functions of the two signals being: (1) (2) in x For input signal, x α , x β The output consists of two orthogonal signals. ω For system frequency, k For SOGI parameters; after obtaining two sets of orthogonal signals of voltage and current, the average active power and reactive power are calculated as follows: (3) (4) In the formula, v outα , v outβ , i outα , i outβ These are two orthogonal signals, one for voltage and one for current.

3. The single-phase virtual synchronous machine control method with dynamic characteristic optimization according to claim 1, characterized in that, The nonlinear and time-varying characteristics of the SOGI-based single-phase power calculation stage are addressed by employing a system identification method based on intelligent optimization algorithms to fit the optimal linearized transfer function of the SOGI power calculation stage, including: Different power factor angles were established through simulation. θ and voltage initial phase angle φ Data set of the system step response; By averaging all response curves at each time point, an averaged step response curve is obtained. The transfer function that is closest to the average step response is obtained through the system identification algorithm, and it is defined as the preliminary identification result. Using the initially identified transfer function as the initial value, the intelligent optimization algorithm further optimizes the previously obtained averaged transfer function, thus obtaining the optimal linearized transfer function for the SOGI power measurement stage.

4. The single-phase virtual synchronous machine control method with dynamic characteristic optimization according to claim 3, characterized in that, The step of using the initially identified transfer function as the initial value for the intelligent optimization algorithm includes: Choose by D The transfer function coefficients, represented by a dimensional vector, serve as the particle's position vector. Each particle represents a multi-order transfer function, and the cluster size is set to... N ; (27) (28) Calculate the fitness function for each particle, and select the optimal value for each particle based on the fitness function. and the group optimal value Gb Then, update the optimal particle position for each individual. and the optimal particle position of the swarm ; Calculate the position update rate for each particle, and update the position of each particle: (29) (30) in r 1 and r 2 is the acceleration constant. e 1 and e 2 represents the iteration coefficient; Repeat until the population optimum is reached. Gb The optimal linearized transfer function of the SOGI power measurement stage is obtained by reducing the error to below the predefined allowable error or reaching the maximum number of iterations.

5. The single-phase virtual synchronous machine control method with dynamic characteristic optimization according to claim 1, characterized in that, The status feedback includes: After obtaining the closed-loop small-signal state-space model of the system, a suitable feedback matrix is ​​set using partial state feedback pole configuration. K The coefficients allow the closed-loop poles of the system to be placed at arbitrary locations.

6. The single-phase virtual synchronous machine control method with dynamic characteristic optimization according to claim 5, characterized in that, The method of using partial state feedback pole configuration to set a suitable feedback matrix. K The coefficients include: After obtaining the optimal linearized transfer function, the resulting closed-loop small-signal state-space model of the system is used to set a suitable feedback matrix using partial state feedback pole placement. K The coefficient is used to position the closed-loop poles of the system at the locations where inertia provision and active power oscillation attenuation occur, that is, to position the two dominant poles at the damping ratio. ζ =0.9, a high-damping position, while the system's natural angular frequency ω n Maintaining a high constant of inertia J The need: (31) The third non-dominant pole is located far from the imaginary axis; the other uncontrollable poles are located far from the imaginary axis. The actual inertial constant is usually taken as a typical value for a synchronous generator, where... S base Inverter capacity: (32) The actual inertia of VSG is ultimately equivalent. J Determined by the location of the closed-loop poles, defined J sf Ratio to actual inertia: (33)。

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