Method for establishing small signal analysis model of hybrid synchronous new energy networking converter

Abstract

The invention discloses a method for establishing a small signal analysis model of a hybrid synchronous new energy networking converter. The method comprises the following steps: determining a control strategy of the hybrid synchronous networking converter; establishing an s-domain mathematical model under a dq rotating coordinate system, and based on the hybrid synchronous network construction type converter control strategy, when power synchronization control is subjected to small disturbance, linearizing an active control loop to obtain a small signal model of active power and a small signal model of a synchronization loop in the hybrid synchronous control strategy; when the synchronous loop small signal mode control system is subjected to small disturbance, determining a small signal model of each variable and a small signal matrix model of voltage and current double-closed-loop control, establishing a relation between the internal potential and the output power, and performing linearization; determining a small signal model of the hybrid synchronous networking converter; and constructing a transfer function between the small interference signal of the output phase of the active power loop and the small interference signal of the potential phase in the converter.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and more specifically, to a method for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter. Background Art

[0002] At present, the stable operation of mainstream grid-following control of new energy sources under weak grid conditions is severely challenged. Therefore, the grid-building control technology with the ability to build grid synchronous voltage has received widespread attention. However, studies have shown that in actual system grid-connected scenarios, new energy sources using grid-building control face problems such as adaptability to strong and weak grids under steady-state operation, power output efficiency, and synchronization stability under transient conditions. Therefore, it is urgent to propose a new synchronization control strategy that can maximize the dynamic and transient stability characteristics and improve the utilization efficiency of new energy while enabling the new energy grid-connected converter to operate stably under weak grids. Summary of the invention

[0003] According to the present invention, a method and system for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter are provided to solve the technical problem of how to make the new energy grid-connected converter operate stably under a weak power grid while maximizing the dynamic and transient stability characteristics and improving the utilization efficiency of new energy.

[0004] According to a first aspect of the present invention, there is provided a method for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter, comprising:

[0005] Determine the control strategy of the hybrid synchronous grid-connected converter according to the q-axis voltage amplitude at the grid connection point, the proportional control coefficient, and the proportional-integral control coefficient;

[0006] Establishing an s-domain mathematical model in a dq rotating coordinate system, based on the hybrid synchronous grid-type converter control strategy, when the power synchronization control is subject to a small disturbance, linearizing the active control loop to obtain a small signal model of the active power, and obtaining a small signal model of the synchronization loop in the hybrid synchronous control strategy;

[0007] When the synchronous loop small signal model control system is subject to a small disturbance, the small signal model of each variable and the small signal matrix model of the voltage and current double closed loop control are determined, and the relationship between the internal potential and the output power is established and linearized.

[0008] Based on the hybrid synchronous grid-type converter control strategy and the linear relationship between the potential and the output power, a small signal model of the hybrid synchronous grid-type converter is determined;

[0009] Based on the small signal model of the hybrid synchronous grid-type converter, a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter is constructed.

[0010] Optionally, according to the q-axis voltage amplitude at the grid connection point and the proportional control coefficient and the proportional integral control coefficient, a control strategy of the hybrid synchronous grid-connected converter is determined, including:

[0011] The mathematical model of the hybrid synchronous control converter grid-connected system is determined as:

[0012]

[0013] Among them, U q is the q-axis voltage amplitude at the grid connection point, K p and K i are the proportional control coefficient and integral control coefficient of the newly added q-axis voltage controller, P ref is the reference value of the converter output active power, P e is the actual value of the converter output active power, m p is the active power droop coefficient, w ref is the reference value of the rotation angular frequency, w hyb is the angular frequency of the hybrid synchronous control strategy;

[0014] In the dq axis rotating coordinate system, the q axis voltage U q The output phase of the hybrid synchronous control module is θ t , grid phase angle θ g The mathematical expression between and is:

[0015] U q =U t sinθ t θ g (2)

[0016] Among them, U t is the voltage amplitude of the converter terminal, θ g is the grid phase angle, θ t It is the output phase angle of the voltage at the terminal of the hybrid synchronous control converter.

[0017] Optionally, an S-domain mathematical model is established in a dq rotating coordinate system. When the power synchronization control is subjected to a small disturbance, the active control loop is linearized to obtain a small signal model of the active power. According to the S-domain mathematical model, a small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained, including:

[0018] Establishing the s-domain mathematical model in the dq rotating coordinate system

[0019]

[0020] Among them, e dq is the dq-axis component of the potential phasor in the converter, u tdqis the dq-axis component of the voltage phasor at the grid connection point, i dq is the dq axis component of the grid-connected point current phasor, and the filter impedance, line impedance and filter capacitance are expressed in matrix form as C L (s) = diag[sL f +R f ], C g (s) = diag[sL g +R g ], C C (s) = diag[sC];

[0021] e dq ,u tdq ,i dq This is achieved by transforming the abc stationary coordinate system into the dq rotating coordinate system. The coordinate transformation rules of each variable are as follows:

[0022]

[0023] Among them, the specific expressions of each component are: abc =[i a i b i c ] T ,u tabc =[u ta u tb u tc] T ,i dq =[i d i q ] T ,u tdq =[u td u tq ] T ,i abc =[i a i b i c ] T , e refabc =[e refa e refb e refc ] T , e refdq =[e refd e refq ] T .

[0024] When the power synchronization control is subject to a small disturbance, Δδ=Δθt-Δθg, the active control loop is linearized, and the small signal model of active power is obtained as follows:

[0025]

[0026] According to equations (3) and (4), the small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained:

[0027]

[0028] Optionally, when the synchronous loop small signal model control system is subjected to a small disturbance, the small signal model of each variable and the small signal matrix model of the voltage and current dual closed-loop control are determined, and the relationship between the internal potential and the output power is established and linearized, including:

[0029] When the above control system is subject to a small disturbance, the small signal model of each variable is expressed as:

[0030]

[0031] Among them, the matrix form of each variable in the dq coordinate system and the αβ coordinate system is expressed as:

[0032]

[0033] In addition, the small signal matrix model of voltage and current dual closed-loop control is expressed as:

[0034]

[0035] Combining the above formula, the relationship between the electromotive force in the converter and the given value of the grid-type control output is obtained:

[0036]

[0037] Among them, the expressions of each component are:

[0038]

[0039] According to the dq coordinate system, the following dynamic relationship exists among the variables:

[0040]

[0041] Establish the relationship between internal potential and output power:

[0042]

[0043] Linearize the above equation and get:

[0044]

[0045] Optionally, based on the hybrid synchronous grid-connected converter control strategy and the linear relationship between the potential and the output power, determining a small signal model of the hybrid synchronous grid-connected converter includes:

[0046] Based on the hybrid synchronous grid-type converter control strategy and the linear relationship between potential and output power, the small signal model of the grid-type control converter using hybrid synchronous control is expressed as

[0047]

[0048] According to equations (1) to (6), the linearized model of the hybrid synchronous control converter with voltage and current dual closed-loop control is obtained. The input signals of the model are small disturbance signals of active power and reactive power, and the output signals are small disturbance signals of the grid-connected point voltage phase and amplitude.

[0049] Optionally, based on the small signal model of the hybrid synchronous grid-connected converter, a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter is constructed, including:

[0050] Construct the transfer function X between the small interference signal of the active power loop output phase and the small interference signal of the potential phase in the converter θ (s) is:

[0051]

[0052] in,

[0053]

[0054] describes the dynamic interaction channel of the d-axis, G E (s)M q (s) The dynamic interaction channel of the q-axis is described, the reactive power small disturbance signal is ignored, and the linearized model of the hybrid synchronous control converter is organized into a mathematical model of the hybrid synchronous control converter based on the motion equation;

[0055] In the mathematical model of the hybrid synchronous control converter based on the motion equation, the input signal is a small disturbance signal ΔP of the active power reference value. ref , small disturbance signal of internal potential phase angle is the output signal, where X P1 (s) means to ΔP e1 The power feedback channel, X P2 (s) means To ΔE, then to ΔP e2 The coupled power feedback channel, due to the relationship between power and torque: P = Tω, then X P1 (s) and X P2 (s) and the torque component ΔT e1 and ΔT e2There is a proportional relationship. Further, X P1 (s), X P2 (s) and G h The mathematical expression of (s) is written as:

[0056]

[0057] Among them, the transfer function G h2 The expression of (s) can be written as:

[0058]

[0059] According to the mathematical model of the hybrid synchronous control converter based on the equation of motion, the inner loop control can be used to produce an effect on the grid-type control converter through the forward channel, the power channel and the uncoupled power channel. P1 (s), X P2 The torque component corresponding to (s) can be decomposed into two components: damping torque and synchronizing torque.

[0060] According to another aspect of the present invention, there is also provided a system for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter, comprising:

[0061] A hybrid synchronous grid-connected converter control strategy determination module is used to determine the hybrid synchronous grid-connected converter control strategy according to the q-axis voltage amplitude of the grid-connected point and the proportional control coefficient and the proportional-integral control coefficient;

[0062] A synchronous loop small signal model module is obtained, which is used to establish an s-domain mathematical model in a dq rotating coordinate system. Based on the hybrid synchronous grid-type converter control strategy, when the power synchronous control is subjected to a small disturbance, the active control loop is linearized to obtain a small signal model of active power, and a synchronous loop small signal model in the hybrid synchronous control strategy is obtained;

[0063] A module for establishing a linear relationship between internal potential and output power is used to determine the small signal model of each variable and the small signal matrix model of voltage and current double closed-loop control when the synchronous loop small signal model control system is subject to a small disturbance, and to establish and linearize the relationship between internal potential and output power;

[0064] Determine a small signal model module of a hybrid synchronous grid-type converter, which is used to determine a small signal model of a hybrid synchronous grid-type converter based on the control strategy of the hybrid synchronous grid-type converter and a linear relationship between potential and output power;

[0065] A small interference signal transfer function module is constructed to construct a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter based on the small signal model of the hybrid synchronous grid-type converter.

[0066] Optionally, determining a hybrid synchronous grid-connected converter control strategy module includes:

[0067] The submodule for determining the digital model of the grid-connected system is used to determine the mathematical model of the hybrid synchronous control converter grid-connected system as follows:

[0068]

[0069] Among them, U q is the q-axis voltage amplitude at the grid connection point, K p and K i are the proportional control coefficient and integral control coefficient of the newly added q-axis voltage controller, P ref is the reference value of the converter output active power, P e is the actual value of the converter output active power, m p is the active power droop coefficient, w ref is the reference value of the rotation angular frequency, w hyb is the angular frequency of the hybrid synchronous control strategy;

[0070] In the dq axis rotating coordinate system, the q axis voltage U q The output phase of the hybrid synchronous control module is θ t , grid phase angle θ g The mathematical expression between and is:

[0071] U q =U t sinθ t θ g (2)

[0072] Among them, U t is the voltage amplitude of the converter terminal, θ g is the grid phase angle, θ t It is the output phase angle of the voltage at the terminal of the hybrid synchronous control converter.

[0073] Optionally, a synchronous loop small signal model module is obtained, including:

[0074] Establish the S-domain mathematical model submodule to establish the S-domain mathematical model in the dq rotating coordinate system

[0075]

[0076] Among them, e dq is the dq-axis component of the potential phasor in the converter, u tdq is the dq-axis component of the voltage phasor at the grid connection point, i dq is the dq axis component of the grid-connected point current phasor, and the filter impedance, line impedance and filter capacitance are expressed in matrix form as C L(s) = diag[sL f +R f ], C g (s) = diag[sL g +R g ], C C (s) = diag[sC];

[0077] e dq ,u tdq ,i dq This is achieved by transforming the abc stationary coordinate system into the dq rotating coordinate system. The coordinate transformation rules of each variable are as follows:

[0078]

[0079] Among them, the specific expressions of each component are: abc =[i a i b i c ] T ,u tabc =[u ta u tb u tc] T ,i dq =[i d i q ] T ,u tdq =[u td u tq ] T ,i abc =[i a i b i c ] T , e refabc =[e refa e refb e refc ] T , e refdq =[e refd e refq ] T .

[0080] The active power small signal model submodule is obtained, which is used when the power synchronization control is subject to a small disturbance, Δδ=Δθt-Δθg, and the active control loop is linearized to obtain the small signal model of active power:

[0081]

[0082] According to equations (3) and (4), the small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained:

[0083]

[0084] Optionally, a module for establishing a linear relationship between internal potential and output power includes:

[0085] Determine the small signal model submodule of each variable, which is used when the above control system is subjected to a small disturbance. The small signal model of each variable is expressed as:

[0086]

[0087] Among them, the matrix form of each variable in the dq coordinate system and the αβ coordinate system is expressed as:

[0088]

[0089] In addition, the small signal matrix model of voltage and current dual closed-loop control is expressed as:

[0090]

[0091] Combining the above formula, the relationship between the electromotive force in the converter and the given value of the grid-type control output is obtained:

[0092]

[0093] Among them, the expressions of each component are:

[0094]

[0095] According to the dq coordinate system, the following dynamic relationship exists among the variables:

[0096]

[0097] Establish the relationship between internal potential and output power:

[0098]

[0099] A submodule for establishing a linear relationship between internal potential and output power is used to linearize the above equation to obtain:

[0100]

[0101] Optionally, determining a small signal model module of a hybrid synchronous grid-connected converter includes:

[0102] Determine a hybrid synchronous grid-type converter small signal model submodule, which is used to express the small signal model of the grid-type control converter using hybrid synchronous control based on the hybrid synchronous grid-type converter control strategy and the linear relationship between the potential and the output power as follows:

[0103]

[0104] According to equations (1) to (6), the linearized model of the hybrid synchronous control converter with voltage and current dual closed-loop control is obtained. The input signals of the model are small disturbance signals of active power and reactive power, and the output signals are small disturbance signals of the grid-connected point voltage phase and amplitude.

[0105] Optionally, a small interference signal transfer function module is constructed, including:

[0106] Construct a small interference signal transfer function submodule, which is used to construct the transfer function X between the small interference signal of the active power loop output phase and the small interference signal of the potential phase in the converter θ (s) is:

[0107]

[0108] in,

[0109]

[0110] describes the dynamic interaction channel of the d-axis, G E (s)M q (s) The dynamic interaction channel of the q-axis is described, the reactive power small disturbance signal is ignored, and the linearized model of the hybrid synchronous control converter is organized into a mathematical model of the hybrid synchronous control converter based on the motion equation;

[0111] In the mathematical model of the hybrid synchronous control converter based on the motion equation, the input signal is a small disturbance signal ΔP of the active power reference value. ref , small disturbance signal of internal potential phase angle is the output signal, where X P1 (s) means to ΔP e1 The power feedback channel, X P2 (s) means To ΔE, then to ΔP e2 The coupled power feedback channel, due to the relationship between power and torque: P = Tω, then X P1 (s) and X P2 (s) and the torque component ΔT e1 and ΔT e2 There is a proportional relationship. Further, X P1 (s), X P2 (s) and G h The mathematical expression of (s) is written as:

[0112]

[0113] Among them, the transfer function G h2 The expression of (s) can be written as:

[0114]

[0115] According to the mathematical model of the hybrid synchronous control converter based on the equation of motion, the inner loop control can be used to produce an effect on the grid-type control converter through the forward channel, the power channel and the uncoupled power channel. P1 (s), X P2 The torque component corresponding to (s) can be decomposed into two components: damping torque and synchronizing torque.

[0116] Therefore, the stable operation capability of the grid-following converter under weak power grid can be improved. At the same time, the problem of easy instability of the grid-connecting converter under strong power grid can be avoided. A small signal analysis model of the hybrid synchronous grid-connecting converter is proposed, which can be used to analyze the small disturbance stability of the hybrid synchronous grid-connecting converter grid-connected system. BRIEF DESCRIPTION OF THE DRAWINGS

[0117] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0118] Figure 1 A schematic flow chart of a method for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter according to this embodiment;

[0119] Figure 2 Schematic diagram of a grid-connected system of a grid-following control converter according to this embodiment;

[0120] FIG3 is a schematic diagram of an active outer loop control structure frame according to this embodiment;

[0121] Figure 4 is a schematic diagram of the current inner loop control structure described in this embodiment;

[0122] Figure 5 Schematic diagram of the phase-locked loop control structure block described in this embodiment;

[0123] Figure 6 This is a schematic diagram of the grid-connected structure of the grid-connected control converter described in this embodiment;

[0124] Figure 7 This is a schematic diagram of the voltage and current dual closed-loop control structure described in this embodiment;

[0125] Figure 8 A schematic diagram of a hybrid synchronous control converter grid-connected system according to this embodiment;

[0126] Fig. 9It is a schematic diagram of a block diagram of synchronous phase angle generation of the hybrid synchronous control strategy described in this embodiment;

[0127] Fig.10 is a schematic diagram of a small signal model of a hybrid synchronous control loop according to this embodiment;

[0128] Fig.11 is a schematic diagram of a linearized model of a hybrid synchronous control converter according to this embodiment;

[0129] Fig.12 is a schematic diagram of a mathematical model of a hybrid synchronous control converter based on a motion equation according to the present embodiment;

[0130] Fig.13 is a schematic diagram of the influence of the current control loop on the hybrid synchronous control type converter according to this embodiment;

[0131] Fig.14 is a schematic diagram of the influence of the voltage control loop on the hybrid synchronous control type converter according to this embodiment;

[0132] Fig.15 is a schematic diagram of the influence of the hybrid synchronous control according to this embodiment on the hybrid synchronous control type converter;

[0133] Fig.16 It is a schematic diagram of a system for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter according to the present embodiment. DETAILED DESCRIPTION

[0134] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0135] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0136] According to a first aspect of the present invention, a method 100 for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter is provided. Figure 1 As shown, the method 100 includes:

[0137] S101: Determine a control strategy for a hybrid synchronous grid-connected converter according to the q-axis voltage amplitude at the grid connection point, the proportional control coefficient, and the proportional-integral control coefficient;

[0138] S102: Establishing an s-domain mathematical model in a dq rotating coordinate system, based on the hybrid synchronous grid-type converter control strategy, when the power synchronization control is subject to a small disturbance, linearizing the active control loop to obtain a small signal model of the active power, and obtaining a small signal model of the synchronization loop in the hybrid synchronous control strategy;

[0139] S103: When the synchronous loop small signal model control system is subjected to a small disturbance, the small signal model of each variable and the small signal matrix model of the voltage and current double closed-loop control are determined, and the relationship between the internal potential and the output power is established and linearized;

[0140] S104: Determine a small signal model of the hybrid synchronous grid-connected converter based on the hybrid synchronous grid-connected converter control strategy and the linear relationship between the potential and the output power;

[0141] S105: Based on the small signal model of the hybrid synchronous grid-connected converter, a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter is constructed.

[0142] Specifically, Figure 2 The figure shows a typical grid-following control new energy grid-connected converter. abc is the grid-connected voltage of the converter, and the voltage amplitude is determined by the modulation signal M abc The voltage phase is obtained by the phase-locked loop tracking the grid bus voltage. The outer loop of the entire control strategy is mainly divided into power control outer loop, DC voltage outer loop and AC voltage outer loop, and the inner loop is mainly voltage and current double closed loop control.

[0143] The D-axis control of the grid-following control converter mainly corresponds to the active power outer loop and the DC voltage outer loop, and the principle block diagram is shown in Figure 3.

[0144] Among them, I dref and I qref They are the output values ​​of the outer control loop and the command values ​​of the inner current control loop, respectively called active current command and reactive current command; P ref and P e Output active power command value and measured value for the converter; V dcref With V dc The output values ​​of the above control loops are obtained by passing the input values ​​through the PI controller, where the proportional and integral coefficients of the PI control are expressed as: K pp and K pi , K udcpand K udci .

[0145] The current inner loop control bandwidth in the grid-following control converter control strategy is higher and the response speed is faster. Its control block diagram is as follows: Figure 4 shown.

[0146] Among them, K ip and K ii They represent the proportional and integral coefficients of the inner current loop control, I d and I q They represent the active and reactive components of the converter output current respectively.

[0147] The phase-locked loop control block diagram in the grid-following control converter control strategy is as follows: Figure 5 As shown, where U t is the AC voltage amplitude measured at the grid connection point, U q is the grid voltage U t The q-axis component, K pllp , K plli are the proportional coefficient and integral coefficient of the PI controller in the phase-locked loop, θ pll It is the phase angle control signal output by the phase-locked loop.

[0148] The grid-connected control system can achieve synchronization between the voltage phase at the grid connection point and the AC grid phase without the aid of a phase-locked loop by simulating the rotor motion equation of the traditional synchronous motor. The grid-connected control system of the grid-connected converter mainly consists of two parts: the converter and the AC grid. The control system mainly consists of three parts: the outer loop control, the inner loop control and the power synchronization control. Figure 6 shown.

[0149] The dual inner loop control is mainly carried out in the dq rotating coordinate system. The basic structure includes voltage control, current control, decoupling term and voltage feedforward link. The input signal is the voltage reference value V dqref , the output signal is the voltage modulation signal reference value M dqref ,like Figure 7 shown.

[0150] The present invention proposes a hybrid synchronous structure of a grid-connected new energy grid-connected converter and a small signal analysis model including voltage and current dual closed-loop control. The hybrid synchronous structure can improve the stable operation capability of the grid-connected converter under a weak power grid, and at the same time, can avoid the problem of easy instability of the grid-connected converter under a strong power grid.

[0151] In the first step, a hybrid synchronous grid-connected converter control strategy is proposed.

[0152] refer to Figure 8 As shown in the figure, the hybrid synchronous control strategy adds the q-axis voltage U of the grid-connected point on the basis of the original grid-connected active power synchronous control module.q The control adopts proportional controller and proportional integral controller, and the mathematical model can be expressed as:

[0153]

[0154] Among them, U q is the q-axis voltage amplitude at the grid connection point, K p and K i are the proportional control coefficient and integral control coefficient of the newly added q-axis voltage controller, P ref is the reference value of the converter output active power, P e is the actual value of the converter output active power, m p is the active power droop coefficient, ω ref is the reference value of the rotation angular frequency, ω hyb is the angular frequency of the hybrid synchronous control strategy.

[0155] In the dq axis rotating coordinate system, the q axis voltage U q The output phase of the hybrid synchronous control module is θ t , grid phase angle θ g The mathematical expression between and is:

[0156] U q =U t sinθ t -θ g (2)

[0157] Among them U t is the voltage amplitude of the converter terminal, θ g is the grid phase angle, θ t It is the output phase angle of the voltage at the terminal of the hybrid synchronous control converter.

[0158] By adjusting the coefficient K p and K i , which can make U q The feedback loop does not affect the power phase-locking capability of the active loop of the grid-connected converter during normal operation, and prevents the active loop from synchronizing and losing synchronization with the grid during a fault.

[0159] The second step is to establish a small signal analysis model for the hybrid synchronous control grid-type converter.

[0160] The inner loop control of the hybrid synchronous control converter is AC voltage loop control and current loop control, which is consistent with the inner loop control of the conventional grid-type control converter. The outer loop active power control loop is Fig. 9 In the hybrid synchronous control strategy shown, the outer reactive loop is a common grid-connected inverter that adopts reactive droop control.

[0161] In order to study the small signal model of the converter internal control loop, a dq S-domain mathematical model in rotating coordinate system

[0162]

[0163] Among them, the filter impedance, line impedance and filter capacitance are expressed in matrix form as C for the convenience of research. L (s) = diag[sL f +R f ], C g (s) = diag[sL g +R g ], C C (s) = diag[sC].

[0164] Since the circuit dynamic equation described by the above expression exists in the abc stationary coordinate system, and the voltage and current dual closed-loop control is implemented using a PI controller in the dq rotating coordinate system, the above two parts realize the control principle by transforming the abc stationary coordinate system to the dq rotating coordinate system. The coordinate transformation rules of each variable are as follows:

[0165]

[0166] Among them, the specific expressions of each component are: abc =[i a i b i c ] T ,u tabc =[u ta u tb u tc ] T ,i dq =[i d i q] T ,u tdq =[u td u tq ] T ,i abc =[i a i b i c ] T , e refabc =[e refa e refb e refc ] T , e refdq =[e refd e refq ] T .

[0167] When the power synchronization control is subject to a small disturbance, the virtual power angle Δδ = Δθt-Δθg, and the active power control loop is linearized to obtain the small signal model of active power:

[0168]

[0169] According to equations (3) and (4), the small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained. Fig.10 Shown

[0170]

[0171] When the above control system is subject to a small disturbance, the small signal model of each variable can be expressed as:

[0172]

[0173] Among them, the matrix form of each variable in the dq coordinate system and the αβ coordinate system is expressed as:

[0174]

[0175] In addition, the small signal matrix model of voltage and current dual closed-loop control can be expressed as:

[0176]

[0177] Combining the above formula, the relationship between the electromotive force in the converter and the given value of the grid-type control output can be obtained:

[0178]

[0179] Among them, the expressions of each component are:

[0180]

[0181] According to the dq coordinate system, the following dynamic relationship exists among the variables:

[0182]

[0183] Establish the relationship between internal potential and output power:

[0184]

[0185] Linearize the above equation and get:

[0186]

[0187] The small signal model of the grid-controlled converter using hybrid synchronous control is expressed as

[0188]

[0189] According to formula (1)-formula (6), we can get Fig.11 The linearized model of the hybrid synchronous control converter with voltage and current dual closed-loop control is shown in FIG. The input signal of the model is a small disturbance signal of active power and reactive power, and the output signal is a small disturbance signal of the grid-connected point voltage phase and amplitude.

[0190] Construct the transfer function X between the small interference signal of the active power loop output phase and the small interference signal of the potential phase in the converter θ (s) is:

[0191]

[0192] in,

[0193]

[0194] describes the dynamic interaction channel of the d-axis, G E (s)M q (s) Describes the dynamic interaction channel of the q axis. Ignoring the small disturbance signal of reactive power, Fig.11 The linearized model shown can be rearranged as follows Fig.12 The mathematical model shown.

[0195] In this model, the input signal is a small disturbance signal ΔP of the active power reference value. ref , small disturbance signal of internal potential phase angle is the output signal. P1 (s) means to ΔP e1 The power feedback channel, X P2 (s) means To ΔE, then to ΔP e2 The coupled power feedback channel. Since there is a relationship between power and torque: P = Tω, then X P1 (s) and X P2 (s) and the torque component ΔT e1 and ΔT e2 There is a proportional relationship. Furthermore, X P1 (s), X P2 (s) and G h The mathematical expression of (s) can be written as:

[0196]

[0197] Among them, the transfer function G h2 The expression of (s) can be written as:

[0198]

[0199] according to Fig.11 It can be obtained that the inner loop control can produce an effect on the grid-controlled converter through the forward channel, the power channel and the uncoupled power channel. P1 (s), X P2 The torque component corresponding to (s) can also be decomposed into two components: damping torque and synchronous torque. Based on this model, the influence of hybrid synchronous control with double closed-loop control on the small disturbance synchronization stability of the hybrid synchronous control converter grid-connected system can be studied.

[0200] A simulation model of the hybrid synchronous control converter connected to the AC power grid is built in MATLAB / Simulink to analyze the influence of different parameters on the synchronization stability of the system. The structure diagram of the interconnected system is shown in Figure 12, and the simulation parameters are shown in Figure 1 and Table 2.

[0201] Table 1 Main circuit parameters of hybrid synchronous control converter grid-connected system

[0202]

[0203] Table 2 Control parameters of hybrid synchronous control converter grid-connected system Tab.5-1 Simulation parameters of HYB

[0204]

[0205] The influence of current control loop on hybrid synchronous control converter is as follows: Fig.13 shown.

[0206] At different current control bandwidth f bi The closed-loop transfer function G of the hybrid synchronous control converter is h The Bode plot of (s) is shown above. Generally speaking, the bandwidth of the current control loop is kept at around 100Hz. In this simulation example, the bandwidth of the inner current control loop is set to 90Hz, 110Hz and 130Hz respectively, while the bandwidth of the outer voltage control loop is set to 25Hz. When the bandwidth of the inner current control loop changes, the amplitude-frequency and phase-frequency characteristic curves of the closed-loop transfer function change very little, indicating that the bandwidth of the current control loop has almost zero effect on the entire control loop.

[0207] The influence of voltage control loop on hybrid synchronous control converter is as follows: Fig.14 shown.

[0208] In the simulation example, fbi=100Hz. According to the general rule, the voltage control bandwidth is set between fbi / 5 and fbi / 3. As shown, when the voltage control loop bandwidth continues to decrease, the amplitude-frequency characteristic curve of the closed-loop transfer function Gh(s) of the hybrid synchronous control changes less, while the phase-frequency characteristic curve changes more. It can be seen that the amplitude-frequency characteristic curves of different voltage loop control bandwidths have different phases corresponding to 0dB. When fbv decreases, the corresponding phase is farther and farther away from -180°, that is, the phase margin continues to increase, which is very beneficial to improving the synchronous stability of the converter grid-connected system. Therefore, reducing the voltage loop control bandwidth helps to improve the grid-connected stability of the hybrid synchronous control converter.

[0209] The influence of hybrid synchronous ring on hybrid synchronous control converter is as follows Fig.15 shown.

[0210] In the simulation example, f bi =100Hz, f bv =25Hz, according to general rules, the phase synchronization control bandwidth is generally set at f bi / 10. When the hybrid synchronous control bandwidth f bhyb When it keeps changing, its closed-loop transfer function G h The amplitude-frequency characteristic curve corresponding to (s) does not change much, but the phase-frequency characteristic curve is greatly affected. It can be seen that when f bhyb When the value of is increasing, the phase corresponding to the closed-loop transfer function amplitude-frequency characteristic curve passing 0dB is increasing, and the phase margin is increasing. Therefore, increasing the bandwidth of hybrid synchronous control is beneficial to improving the grid-connected stability of the converter.

[0211] Therefore, the stable operation capability of the grid-following converter under weak power grid can be improved. At the same time, the problem of easy instability of the grid-connecting converter under strong power grid can be avoided. A small signal analysis model of the hybrid synchronous grid-connecting converter is proposed, which can be used to analyze the small disturbance stability of the hybrid synchronous grid-connecting converter grid-connected system.

[0212] Optionally, according to the q-axis voltage amplitude at the grid connection point and the proportional control coefficient and the proportional integral control coefficient, a control strategy of the hybrid synchronous grid-connected converter is determined, including:

[0213] The mathematical model of the hybrid synchronous control converter grid-connected system is determined as:

[0214]

[0215] Among them, U q is the q-axis voltage amplitude at the grid connection point, K p and K i are the proportional control coefficient and integral control coefficient of the newly added q-axis voltage controller, P refis the reference value of the converter output active power, P e is the actual value of the converter output active power, m p is the active power droop coefficient, w ref is the reference value of the rotation angular frequency, w hyb is the angular frequency of the hybrid synchronous control strategy;

[0216] In the dq axis rotating coordinate system, the q axis voltage U q The output phase of the hybrid synchronous control module is θ t , grid phase angle θ g The mathematical expression between and is:

[0217] U q =U t sinθ t -θ g (2)

[0218] Among them, U t is the voltage amplitude of the converter terminal, θ g is the grid phase angle, θ t It is the output phase angle of the voltage at the terminal of the hybrid synchronous control converter.

[0219] Optionally, an S-domain mathematical model is established in a dq rotating coordinate system. When the power synchronization control is subjected to a small disturbance, the active control loop is linearized to obtain a small signal model of the active power. According to the S-domain mathematical model, a small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained, including:

[0220] Establishing the s-domain mathematical model in the dq rotating coordinate system

[0221]

[0222] Among them, e dq is the dq-axis component of the potential phasor in the converter, u tdq is the dq-axis component of the voltage phasor at the grid connection point, i dq is the dq axis component of the grid-connected point current phasor, and the filter impedance, line impedance and filter capacitance are expressed in matrix form as C L (s) = diag[sL f +R f ], C g (s) = diag[sL g +R g ], C C (s) = diag[sC];

[0223] e dq ,u tdq ,i dqThis is achieved by transforming the abc stationary coordinate system into the dq rotating coordinate system. The coordinate transformation rules of each variable are as follows:

[0224]

[0225] Among them, the specific expressions of each component are: abc =[i a i b i c ] T ,u tabc =[u ta u tb u tc] T ,i dq =[i d i q ] T ,u tdq =[u td u tq ] T ,i abc =[i a i b i c ] T , e refabc =[e refa e refb e refc ] T , e refdq =[e refd e refq ] T .

[0226] When the power synchronization control is subject to a small disturbance, Δδ=Δθt-Δθg, the active control loop is linearized, and the small signal model of active power is obtained as follows:

[0227]

[0228] According to equations (3) and (4), the small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained:

[0229]

[0230] Optionally, when the synchronous loop small signal model control system is subjected to a small disturbance, the small signal model of each variable and the small signal matrix model of the voltage and current dual closed-loop control are determined, and the relationship between the internal potential and the output power is established and linearized, including:

[0231] When the above control system is subject to a small disturbance, the small signal model of each variable is expressed as:

[0232]

[0233] Among them, the matrix form of each variable in the dq coordinate system and the αβ coordinate system is expressed as:

[0234]

[0235] In addition, the small signal matrix model of voltage and current dual closed-loop control is expressed as:

[0236]

[0237] Combining the above formula, the relationship between the electromotive force in the converter and the given value of the grid-type control output is obtained:

[0238]

[0239] Among them, the expressions of each component are:

[0240]

[0241] According to the dq coordinate system, the following dynamic relationship exists among the variables:

[0242]

[0243] Establish the relationship between internal potential and output power:

[0244]

[0245] Linearize the above equation and get:

[0246]

[0247] Optionally, based on the hybrid synchronous grid-connected converter control strategy and the linear relationship between the potential and the output power, determining a small signal model of the hybrid synchronous grid-connected converter includes:

[0248] Based on the hybrid synchronous grid-type converter control strategy and the linear relationship between potential and output power, the small signal model of the grid-type control converter using hybrid synchronous control is expressed as

[0249]

[0250] According to equations (1) to (6), the linearized model of the hybrid synchronous control converter with voltage and current dual closed-loop control is obtained. The input signals of the model are small disturbance signals of active power and reactive power, and the output signals are small disturbance signals of the grid-connected point voltage phase and amplitude.

[0251] Optionally, based on the small signal model of the hybrid synchronous grid-connected converter, a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter is constructed, including:

[0252] Construct the transfer function X between the small interference signal of the active power loop output phase and the small interference signal of the potential phase in the converter θ (s) is:

[0253]

[0254] in,

[0255]

[0256] describes the dynamic interaction channel of the d-axis, G E (s)M q (s) The dynamic interaction channel of the q-axis is described, the reactive power small disturbance signal is ignored, and the linearized model of the hybrid synchronous control converter is organized into a mathematical model of the hybrid synchronous control converter based on the motion equation;

[0257] In the mathematical model of the hybrid synchronous control converter based on the motion equation, the input signal is a small disturbance signal ΔP of the active power reference value. ref , small disturbance signal of internal potential phase angle is the output signal, where X P1 (s) means to ΔP e1 The power feedback channel, X P2 (s) means To ΔE, then to ΔP e2 The coupled power feedback channel, due to the relationship between power and torque: P = Tω, then X P1 (s) and X P2 (s) and the torque component ΔT e1 and ΔT e2 There is a proportional relationship. Further, X P1 (s), X P2 (s) and G h The mathematical expression of (s) is written as:

[0258]

[0259] Among them, the transfer function G h2 The expression of (s) can be written as:

[0260]

[0261] According to the mathematical model of the hybrid synchronous control converter based on the equation of motion, the inner loop control can be used to produce an effect on the grid-type control converter through the forward channel, the power channel and the uncoupled power channel. P1 (s), X P2 The torque component corresponding to (s) can be decomposed into two components: damping torque and synchronizing torque.

[0262] According to another aspect of the present invention, there is also provided a system for establishing a small signal analysis model of a hybrid synchronous new energy grid-connected converter, comprising:

[0263] A hybrid synchronous grid-connected converter control strategy determination module 1710 is used to determine a hybrid synchronous grid-connected converter control strategy according to the q-axis voltage amplitude at the grid connection point and the proportional control coefficient and the proportional-integral control coefficient;

[0264] A synchronous loop small signal model module 1720 is obtained, which is used to establish an s-domain mathematical model in a dq rotating coordinate system. Based on the hybrid synchronous grid-type converter control strategy, when the power synchronous control is subjected to a small disturbance, the active control loop is linearized to obtain a small signal model of the active power, and a synchronous loop small signal model in the hybrid synchronous control strategy is obtained;

[0265] The module 1730 for establishing a linear relationship between the internal potential and the output power is used to determine the small signal model of each variable and the small signal matrix model of the voltage and current double closed-loop control when the synchronous loop small signal model control system is subjected to a small disturbance, establish the relationship between the internal potential and the output power and perform linearization;

[0266] A hybrid synchronous grid-type converter small signal model determination module 1740 is used to determine a hybrid synchronous grid-type converter small signal model based on the hybrid synchronous grid-type converter control strategy and a linear relationship between potential and output power;

[0267] The small interference signal transfer function construction module 1750 is used to construct a transfer function between the small interference signal of the active power loop output phase and the small interference signal of the potential phase inside the converter based on the small signal model of the hybrid synchronous grid-type converter.

[0268] Optionally, determining a hybrid synchronous grid-connected converter control strategy module includes:

[0269] The submodule for determining the digital model of the grid-connected system is used to determine the mathematical model of the hybrid synchronous control converter grid-connected system as follows:

[0270]

[0271] Among them, U q is the q-axis voltage amplitude at the grid connection point, K p and Ki are the proportional control coefficient and integral control coefficient of the newly added q-axis voltage controller, P ref is the reference value of the converter output active power, P e is the actual value of the converter output active power, m p is the active power droop coefficient, w ref is the reference value of the rotation angular frequency, w hyb is the angular frequency of the hybrid synchronous control strategy;

[0272] In the dq axis rotating coordinate system, the q axis voltage U q The output phase of the hybrid synchronous control module is θ t , grid phase angle θ g The mathematical expression between and is:

[0273] U q =U t sinθ t -θ g (2)

[0274] Among them, U t is the voltage amplitude of the converter terminal, θ g is the grid phase angle, θ t It is the output phase angle of the voltage at the terminal of the hybrid synchronous control converter.

[0275] Optionally, a synchronous loop small signal model module is obtained, including:

[0276] Establish the S-domain mathematical model submodule to establish the S-domain mathematical model in the dq rotating coordinate system

[0277]

[0278] Among them, e dq is the dq-axis component of the potential phasor in the converter, u tdq is the dq-axis component of the voltage phasor at the grid connection point, i dq is the dq axis component of the grid-connected point current phasor, and the filter impedance, line impedance and filter capacitance are expressed in matrix form as C L (s) = diag[sL f +R f ], C g (s) = diag[sL g +R g ], C C (s) = diag[sC];

[0279] e dq ,u tdq ,i dqThis is achieved by transforming the abc stationary coordinate system into the dq rotating coordinate system. The coordinate transformation rules of each variable are as follows:

[0280]

[0281] Among them, the specific expressions of each component are: abc =[i a i b i c ] T ,u tabc =[u ta u tb u tc] T ,i dq =[i d i q ] T ,u tdq =[u td u tq ] T ,i abc =[i a i b i c ] T , e refabc =[e refa e refb e refc ] T , e refdq =[e refd e refq ] T .

[0282] The active power small signal model submodule is obtained, which is used when the power synchronization control is subject to a small disturbance, Δδ=Δθt-Δθg, and the active control loop is linearized to obtain the small signal model of active power:

[0283]

[0284] According to equations (3) and (4), the small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained:

[0285]

[0286] Optionally, a module for establishing a linear relationship between internal potential and output power includes:

[0287] Determine the small signal model submodule of each variable, which is used when the above control system is subjected to a small disturbance. The small signal model of each variable is expressed as:

[0288]

[0289] Among them, the matrix form of each variable in the dq coordinate system and the αβ coordinate system is expressed as:

[0290]

[0291] In addition, the small signal matrix model of voltage and current dual closed-loop control is expressed as:

[0292]

[0293] Combining the above formula, the relationship between the electromotive force in the converter and the given value of the grid-type control output is obtained:

[0294]

[0295] Among them, the expressions of each component are:

[0296]

[0297] According to the dq coordinate system, the following dynamic relationship exists among the variables:

[0298]

[0299] Establish the relationship between internal potential and output power:

[0300]

[0301] A submodule for establishing a linear relationship between internal potential and output power is used to linearize the above equation to obtain:

[0302]

[0303] Optionally, determining a small signal model module of a hybrid synchronous grid-connected converter includes:

[0304] Determine a hybrid synchronous grid-type converter small signal model submodule, which is used to express the small signal model of the grid-type control converter using hybrid synchronous control based on the hybrid synchronous grid-type converter control strategy and the linear relationship between the potential and the output power as follows:

[0305]

[0306] According to equations (1) to (6), the linearized model of the hybrid synchronous control converter with voltage and current dual closed-loop control is obtained. The input signals of the model are small disturbance signals of active power and reactive power, and the output signals are small disturbance signals of the grid-connected point voltage phase and amplitude.

[0307] Optionally, a small interference signal transfer function module is constructed, including:

[0308] Construct a small interference signal transfer function submodule, which is used to construct the transfer function X between the small interference signal of the active power loop output phase and the small interference signal of the potential phase in the converter θ (s) is:

[0309]

[0310] in,

[0311]

[0312] describes the dynamic interaction channel of the d-axis, G E (s)M q (s) The dynamic interaction channel of the q-axis is described, the reactive power small disturbance signal is ignored, and the linearized model of the hybrid synchronous control converter is organized into a mathematical model of the hybrid synchronous control converter based on the motion equation;

[0313] In the mathematical model of the hybrid synchronous control converter based on the motion equation, the input signal is a small disturbance signal ΔP of the active power reference value. ref , small disturbance signal of internal potential phase angle is the output signal, where X P1 (s) means to ΔP e1 The power feedback channel, X P2 (s) means To ΔE, then to ΔP e2 The coupled power feedback channel, due to the relationship between power and torque: P = Tω, then X P1 (s) and X P2 (s) and the torque component ΔT e1 and ΔT e2 There is a proportional relationship. Further, X P1 (s), X P2 (s) and G h The mathematical expression of (s) is written as:

[0314]

[0315] Among them, the transfer function G h2 The expression of (s) can be written as:

[0316]

[0317] According to the mathematical model of the hybrid synchronous control converter based on the equation of motion, the inner loop control can be used to produce an effect on the grid-type control converter through the forward channel, the power channel and the uncoupled power channel. P1 (s), XP2 The torque component corresponding to (s) can be decomposed into two components: damping torque and synchronizing torque.

[0318] A system 1700 for establishing a small signal analysis model of a hybrid synchronous new energy grid-connecting converter in an embodiment of the present invention corresponds to 100 for establishing a small signal analysis model of a hybrid synchronous new energy grid-connecting converter in another embodiment of the present invention, and will not be repeated here.

[0319] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0320] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0321] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0322] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0323] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0324] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for establishing a small signal analysis model for a hybrid synchronous new energy grid converter. It is characterized in that include: Determine the control strategy of the hybrid synchronous grid-connected converter according to the q-axis voltage amplitude at the grid connection point, the proportional control coefficient, and the proportional-integral control coefficient; Establishing an s-domain mathematical model in a dq rotating coordinate system, based on the hybrid synchronous grid-type converter control strategy, when the power synchronization control is subject to a small disturbance, linearizing the active control loop to obtain a small signal model of the active power, and obtaining a small signal model of the synchronization loop in the hybrid synchronous control strategy; When the synchronous loop small signal model control system is subject to a small disturbance, the small signal model of each variable and the small signal matrix model of the voltage and current double closed loop control are determined, and the relationship between the internal potential and the output power is established and linearized. Based on the hybrid synchronous grid-type converter control strategy and the linear relationship between the potential and the output power, a small signal model of the hybrid synchronous grid-type converter is determined; Based on the small signal model of the hybrid synchronous grid-type converter, a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter is constructed.

2. The method according to claim 1, It is characterized in that According to the q-axis voltage amplitude of the grid-connected point, the proportional control coefficient, and the proportional-integral control coefficient, the control strategy of the hybrid synchronous grid-connected converter is determined, including: The mathematical model of the hybrid synchronous control converter grid-connected system is determined as: Among them, U q is the q-axis voltage amplitude at the grid connection point, K p and K i are the proportional control coefficient and integral control coefficient of the newly added q-axis voltage controller, P ref is the reference value of the converter output active power, P e is the actual value of the converter output active power, m p is the active power droop coefficient, w ref is the reference value of the rotation angular frequency, w hyb is the angular frequency of the hybrid synchronous control strategy; In the dq axis rotating coordinate system, the q axis voltage U q The output phase of the hybrid synchronous control module is θ t , grid phase angle θ g The mathematical expression between and is: IN q =U t sonθ t -θ g (2) Among them, U t is the voltage amplitude of the converter terminal, θ g is the grid phase angle, θ t It is the output phase angle of the voltage at the terminal of the hybrid synchronous control converter.

3. The method according to claim 2, It is characterized in that An S-domain mathematical model is established in the dq rotating coordinate system. When the power synchronization control is subject to a small disturbance, the active control loop is linearized to obtain a small signal model of active power. According to the S-domain mathematical model, a small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained, including: Establishing the s-domain mathematical model in the dq rotating coordinate system Among them, e dq is the dq-axis component of the potential phasor in the converter, u tdq is the dq-axis component of the voltage phasor at the grid connection point, i dq is the dq axis component of the grid-connected point current phasor, and the filter impedance, line impedance and filter capacitance are expressed in matrix form as C L (s) = diag[sL f +R f ], C g (s) = diag[sL g +R g ], C C (s) = diag[sC]; e dq ,u tdq ,i dq This is achieved by transforming the abc stationary coordinate system into the dq rotating coordinate system. The coordinate transformation rules of each variable are as follows: Among them, each quantity specific format: i abc =[i a i b i c ] T , u tabc =[u ta u tb u tc] T , i dq =[i d i q ] T , u tdq =[u td u tq ] T , i abc =[i a i b i c ] T , e refabc =[e refa e refb e refc ] T , e refdq =[e refd e refq ] T . When the power synchronization control is subject to a small disturbance, Δδ=Δθt-Δθg, the active control loop is linearized, and the small signal model of active power is obtained as follows: According to equations (3) and (4), the small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained:

4. The method according to claim 3, It is characterized in that When the synchronous loop small signal model control system is subject to a small disturbance, the small signal model of each variable and the small signal matrix model of the voltage and current double closed-loop control are determined, and the relationship between the internal potential and the output power is established and linearized, including: When the above control system is subject to a small disturbance, the small signal model of each variable is expressed as: Among them, the matrix form of each variable in the dq coordinate system and the αβ coordinate system is expressed as: In addition, the small signal matrix model of voltage and current dual closed-loop control is expressed as: Combining the above formula, the relationship between the electromotive force in the converter and the given value of the grid-type control output is obtained: Δe dq =(G us (s)G E (s)) T Δu refdq +M dq (s)G E (s)Δθ r (10) Among them, the expressions of each component are: According to the dq coordinate system, the following dynamic relationship exists among the variables: Establish the relationship between internal potential and output power: Linearize the above equation and get:

5. The method according to claim 4, It is characterized in that Based on the hybrid synchronous grid-connected converter control strategy and the linear relationship between the potential and the output power, a small signal model of the hybrid synchronous grid-connected converter is determined, including: Based on the hybrid synchronous grid-type converter control strategy and the linear relationship between potential and output power, the small signal model of the grid-type control converter using hybrid synchronous control is expressed as According to equations (1) to (6), the linearized model of the hybrid synchronous control converter with voltage and current dual closed-loop control is obtained. The input signals of the model are small disturbance signals of active power and reactive power, and the output signals are small disturbance signals of the grid-connected point voltage phase and amplitude.

6. The method according to claim 5, It is characterized in that Based on the small signal model of the hybrid synchronous grid-type converter, a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter is constructed, including: Construct the transfer function X between the small interference signal of the active power loop output phase and the small interference signal of the potential phase in the converter θ (s) is: in, describes the dynamic interaction channel of the d-axis, The dynamic interaction channel of the q-axis is described, the reactive power small disturbance signal is ignored, and the linearized model of the hybrid synchronous control converter is organized into a mathematical model of the hybrid synchronous control converter based on the motion equation; In the mathematical model of the hybrid synchronous control converter based on the motion equation, the input signal is a small disturbance signal ΔP of the active power reference value. ref , small disturbance signal of internal potential phase angle is the output signal, where X P1 (s) means to ΔP e1 The power feedback channel, X P2 (s) means To ΔE, then to ΔP e2 The coupled power feedback channel, due to the relationship between power and torque: P = Tω, then X P1 (s) and X P2 (s) and the torque component ΔT e1 and ΔT e2 There is a proportional relationship. Further, X P1 (s), X P2 (s) and G h The mathematical expression of (s) is written as: Among them, the transfer function G h2 The expression of (s) can be written as: According to the mathematical model of the hybrid synchronous control converter based on the equation of motion, the inner loop control can be used to produce an effect on the grid-type control converter through the forward channel, the power channel and the uncoupled power channel. P1 (s), X P2 The torque component corresponding to (s) can be decomposed into two components: damping torque and synchronizing torque.

7. A system for establishing a small signal analysis model for a hybrid synchronous new energy grid converter. It is characterized in that include: A hybrid synchronous grid-connected converter control strategy determination module is used to determine the hybrid synchronous grid-connected converter control strategy according to the q-axis voltage amplitude of the grid-connected point and the proportional control coefficient and the proportional-integral control coefficient; A synchronous loop small signal model module is obtained, which is used to establish an s-domain mathematical model in a dq rotating coordinate system. Based on the hybrid synchronous grid-type converter control strategy, when the power synchronous control is subjected to a small disturbance, the active control loop is linearized to obtain a small signal model of active power, and a synchronous loop small signal model in the hybrid synchronous control strategy is obtained; A module for establishing a linear relationship between internal potential and output power is used to determine the small signal model of each variable and the small signal matrix model of voltage and current double closed-loop control when the synchronous loop small signal model control system is subject to a small disturbance, and to establish and linearize the relationship between internal potential and output power; Determine a small signal model module of a hybrid synchronous grid-type converter, which is used to determine a small signal model of a hybrid synchronous grid-type converter based on the control strategy of the hybrid synchronous grid-type converter and a linear relationship between potential and output power; A small interference signal transfer function module is constructed to construct a transfer function between a small interference signal of an active power loop output phase and a small interference signal of an internal potential phase of the converter based on the small signal model of the hybrid synchronous grid-type converter.

8. The system according to claim 7, It is characterized in that Determine the hybrid synchronous grid-connected converter control strategy module, including: The submodule for determining the digital model of the grid-connected system is used to determine the mathematical model of the hybrid synchronous control converter grid-connected system as follows: Among them, U q is the q-axis voltage amplitude at the grid connection point, K p and K i are the proportional control coefficient and integral control coefficient of the newly added q-axis voltage controller, P ref is the reference value of the converter output active power, P e is the actual value of the converter output active power, m p is the active power droop coefficient, w ref is the reference value of the rotation angular frequency, w hyb is the angular frequency of the hybrid synchronous control strategy; In the dq axis rotating coordinate system, the q axis voltage U q The output phase of the hybrid synchronous control module is θ t , grid phase angle θ g The mathematical expression between and is: IN q =U t sonθ t -θ g (2) Among them, U t is the voltage amplitude of the converter terminal, θ g is the grid phase angle, θ t It is the output phase angle of the voltage at the terminal of the hybrid synchronous control converter.

9. The system according to claim 8, It is characterized in that Get the synchronous loop small signal model module, including: Establish the S-domain mathematical model submodule to establish the S-domain mathematical model in the dq rotating coordinate system Among them, e dq is the dq-axis component of the potential phasor in the converter, u tdq is the dq-axis component of the voltage phasor at the grid connection point, i dq is the dq axis component of the grid-connected point current phasor, and the filter impedance, line impedance and filter capacitance are expressed in matrix form as C L (s) = diag[sL f +R f ], C g (s) = diag[sL g +R g ], C C (s) = diag[sC]; e dq ,u tdq ,i dq This is achieved by transforming the abc stationary coordinate system into the dq rotating coordinate system. The coordinate transformation rules of each variable are as follows: Among them, each quantity specific format: i abc =[i a i b i c ] T , u tabc =[u ta u tb u tc ] T , i dq =[i d i q ] T , u tdq =[u td u tq ] T , i abc =[i a i b i c ] T , e refabc =[e refa e refb e refc ] T , e refdq =[e refd e refq ] T . The active power small signal model submodule is obtained, which is used when the power synchronization control is subject to a small disturbance, Δδ=Δθt-Δθg, and the active control loop is linearized to obtain the small signal model of active power: According to equations (3) and (4), the small signal model of the synchronization loop in the hybrid synchronization control strategy is obtained:

10. The system according to claim 9, It is characterized in that The module for establishing the linear relationship between internal potential and output power includes: Determine the small signal model submodule of each variable, which is used when the above control system is subjected to a small disturbance. The small signal model of each variable is expressed as: Among them, the matrix form of each variable in the dq coordinate system and the αβ coordinate system is expressed as: In addition, the small signal matrix model of voltage and current dual closed-loop control is expressed as: Combining the above formula, the relationship between the electromotive force in the converter and the given value of the grid-type control output is obtained: Δe dq =(G us (s)G E (s)) T Δu refdq +M dq (s)G E (s)Δθ r (10) Among them, the expressions of each component are: According to the dq coordinate system, the following dynamic relationship exists among the variables: Establish the relationship between internal potential and output power: A submodule for establishing a linear relationship between internal potential and output power is used to linearize the above equation to obtain:

11. The system according to claim 9, It is characterized in that Determine the small signal model module of the hybrid synchronous grid-connected converter, including: Determine a hybrid synchronous grid-type converter small signal model submodule, which is used to express the small signal model of the grid-type control converter using hybrid synchronous control based on the hybrid synchronous grid-type converter control strategy and the linear relationship between the potential and the output power as follows: According to equations (1) to (6), the linearized model of the hybrid synchronous control converter with voltage and current dual closed-loop control is obtained. The input signals of the model are small disturbance signals of active power and reactive power, and the output signals are small disturbance signals of the grid-connected point voltage phase and amplitude.

12. The system according to claim 9, It is characterized in that Construct a small interference signal transfer function module, including: Construct a small interference signal transfer function submodule, which is used to construct the transfer function X between the small interference signal of the active power loop output phase and the small interference signal of the potential phase in the converter θ (s) is: in, describes the dynamic interaction channel of the d-axis, The dynamic interaction channel of the q-axis is described, the reactive power small disturbance signal is ignored, and the linearized model of the hybrid synchronous control converter is organized into a mathematical model of the hybrid synchronous control converter based on the motion equation; In the mathematical model of the hybrid synchronous control converter based on the motion equation, the input signal is a small disturbance signal ΔP of the active power reference value. ref , small disturbance signal of internal potential phase angle is the output signal, where X P1 (s) means to ΔP e1 The power feedback channel, X P2 (s) means To ΔE, then to ΔP e2 The coupled power feedback channel, due to the relationship between power and torque: P = Tω, then X P1 (s) and X P2 (s) and the torque component ΔT e1 and ΔT e2 There is a proportional relationship. Further, X P1 (s), X P2 (s) and G h The mathematical expression of (s) is written as: Among them, the transfer function G h2 The expression of (s) can be written as: According to the mathematical model of the hybrid synchronous control converter based on the equation of motion, the inner loop control can be used to produce an effect on the grid-type control converter through the forward channel, the power channel and the uncoupled power channel. P1 (s), X P2 The torque component corresponding to (s) can be decomposed into two components: damping torque and synchronizing torque.

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