Method, apparatus and readable storage medium for obtaining output impedance based on asynchronous generator and rectifier system

Abstract

The present application relates to the technical fields of ship direct current micro-grid, and provides a method for obtaining output impedance based on an asynchronous generator and a rectifier system, comprising the following steps: establishing a mathematical model of the asynchronous generator; establishing an average switch continuous model of the rectifier and the filter; establishing a small signal model of the asynchronous generator and the rectifier; based on the mode of using the vector control asynchronous generator, establishing a small signal model of the closed loop control loop; and obtaining an output impedance expression of the rectifier DC side based on the small signal model of the closed loop control loop. Thus, the output impedance of the asynchronous generator and the rectifier can be accurately obtained, which is convenient for impedance stability analysis of the ship direct current micro-grid using the asynchronous generator, and improves the stability of the ship direct current micro-grid.

Description

Technical Field

[0001] This invention relates to the field of marine DC microgrid technology, and in particular to a method, device and readable storage medium for obtaining output impedance based on an asynchronous generator and rectifier system. Background Technology

[0002] Currently, most ship power generation systems use diesel synchronous generators to provide electricity to the ship's power grid. Compared to asynchronous generators, synchronous generators offer advantages such as adjustable reactive power and a fixed AC grid frequency, and ease of grid connection when multiple units are operating. However, synchronous generators suffer from drawbacks such as high cost, difficult maintenance, and low reliability. With the development of power electronics technology and the integration of new energy power generation equipment, DC grid technology has developed rapidly. Using asynchronous generators combined with rectifiers for DC grid connection can effectively avoid problems such as frequency incoordination among multiple units. Furthermore, asynchronous generators offer advantages such as low cost, simple structure, high reliability, self-excitation protection, and strong wide-speed field weakening control capabilities. Therefore, asynchronous generators are gradually becoming an important power generation device for ships.

[0003] A marine DC microgrid employing an asynchronous generator primarily consists of a diesel asynchronous generator, lithium battery-powered propulsion loads, auxiliary loads, and various power electronic conversion devices connecting them to the DC bus. Unlike land-based DC microgrids, marine power grid systems face more complex operating conditions, and propulsion loads account for nearly 70% of the power supply capacity. This necessitates higher requirements for safety, stability, and reliability in marine DC microgrids. Instability in a marine DC microgrid can lead to a complete power outage, rendering operational requirements unavailable and potentially threatening the lives of all personnel on board.

[0004] In order to ensure that the ship's DC microgrid meets the relevant design specifications, it is necessary to study the output impedance of the diesel asynchronous generator and rectifier, and to conduct stability analysis of the ship's DC microgrid through impedance stability analysis technology.

[0005] Currently, the calculation of rectifier output impedance mainly focuses on analyzing application scenarios of large terrestrial power grids. For example... Figure 1 As shown, in land-based power systems, PWM (Pulse Width Modulation) rectifiers employ phase-locked loop control, and the d-axis reference current is always zero. The output impedance can be solved by establishing the system's differential equations. However, this solution method cannot be applied to shipboard DC microgrids using asynchronous generators. The fundamental reason is that the control strategy of asynchronous motors using vector control is relatively complex, and the asynchronous generator and rectifier system has a high degree of nonlinearity. Directly solving for the output impedance by establishing the system's differential equations would be very difficult and not conducive to describing the system's impedance characteristics.

[0006] It should be noted that the information disclosed in this background section is intended only to enhance the understanding of the overall background of the present invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] This invention addresses the problems of existing technologies by providing a method for obtaining the output impedance based on an asynchronous generator and rectifier system. By performing small-signal modeling on the system, the DC-side output impedance of the asynchronous generator and rectifier system can be accurately calculated, which is more conducive to enabling the ship's DC microgrid to meet relevant design specifications.

[0008] An embodiment of the present invention provides a method for obtaining the output impedance based on an asynchronous generator and rectifier system, which includes the following steps: establishing a mathematical model of the asynchronous generator; establishing an average switching continuous model of the rectifier and filter; establishing a small-signal model of the asynchronous generator and rectifier; establishing a closed-loop control loop small-signal model based on the method of using vector control of the asynchronous generator; and obtaining the expression of the DC-side output impedance of the rectifier based on the closed-loop control loop small-signal model.

[0009] In some embodiments, establishing the mathematical model of the asynchronous generator in S100 includes the following steps:

[0010] Based on Kirchhoff's voltage law and current law, the stator voltage equation (1) and the stator output node current equation (2) of the asynchronous generator are obtained:

[0011]

[0012]

[0013] Among them, E sa E sb E sc i is the stator electromotive force of the asynchronous generator; sa i sb i sc i represents the stator current of the asynchronous generator; a i b i c R is the output current of the filter; s L is the stator resistance of the asynchronous generator; s C is the stator inductance of the asynchronous generator; C is the filter capacitor; R is the damping resistor of the filter; v ca v cb v cc d is the voltage across the capacitor of the filter; d / dt is the differential operator;

[0014] Based on the dq transform method, the AC time variables are transformed into the DC time invariant transformation matrix T. abc / dq T abc / dq as follows:

[0015]

[0016] Where ω is the angular frequency; t is time;

[0017] By using the dq transformation method, the time variables of AC power frequency are transformed into the time invariants of DC power frequency. Combining formulas (1), (2), and (3), the following formula is obtained:

[0018]

[0019]

[0020] in, E sd E sq The d-axis and q-axis components of the stator electromotive force dq after transformation of the asynchronous generator; i sd i sq The d-axis and q-axis components of the stator current dq after transformation of the asynchronous generator; v cd v cq These are the d-axis and q-axis components of the three-phase voltage at the filter capacitor terminal after dq transformation; i d i q These are the d-axis and q-axis components of the three-phase input current dq transformed from the AC side of the rectifier, respectively.

[0021] Simplifying formulas (4) and (5), we obtain the time-invariant model in the dq coordinate system:

[0022]

[0023]

[0024] In some embodiments, establishing the average switching continuous model of the rectifier and filter in S200 includes the following steps:

[0025] The function to obtain the switch is as follows:

[0026]

[0027] Among them, S au S bu S cu These are the drive signals for the switching transistors on the three-phase bridge arms, respectively; S al S bl S cl These are the drive signals for the lower switching transistors of the three-phase bridge arms, respectively; and S... aS b S c S represents au S bu S cu ;

[0028] Averaging the switching function yields the following formula:

[0029]

[0030] Among them, T s d is the switching period; i This refers to the duty cycle corresponding to the drive signal of the switching transistor on the three-phase bridge arm;

[0031] Based on Kirchhoff's voltage and current laws, the AC-side loop voltage equation (10) and the DC-side node current equations (11) and (12) are obtained:

[0032]

[0033] i dc =[S a S b S c ][i a i b i c ] T (11)

[0034]

[0035] Among them, v an v bn v cn This is the voltage between the connection point of the two switches in the three-phase bridge arm and the DC voltage reference point; v no The voltage between the DC voltage reference point and the three-phase voltage neutral point; i dc V is the output current on the DC side of the rectifier; L is the inductance on the AC side of the filter; v dc i is the output voltage on the DC side of the rectifier; Load C is the load current on the DC side of the rectifier; dc For the DC side capacitor of the rectifier;

[0036] v dc With v an v bn v cn The relationship between them is as follows:

[0037]

[0038] Where, d a d b dc These are the duty cycles corresponding to the drive signals of the switching transistors on the three-phase bridge arms;

[0039] Based on the three-phase equilibrium characteristics, combining formulas (10) and (13) yields the following formula:

[0040]

[0041] The three-phase equilibrium characteristic is expressed as: (v a +v b +v c =0,i a +i b +i c =0);

[0042] Combining formulas (9), (10), (11), (13), and (14), we obtain the following formula:

[0043]

[0044] i dc =[d a d b d c ][i a i b i c ] T (16)

[0045] Combining formulas (3), (15), and (16), we obtain the following formula:

[0046]

[0047]

[0048] Where, d d d q These are the d-axis and q-axis components of the modulated wave signal after dq transformation of the three-phase bridge arm switch, respectively.

[0049] Simplifying formulas (17) and (18), we obtain the time-invariant model in the dq coordinate system:

[0050]

[0051]

[0052] In some embodiments, the establishment of the small-signal model of the asynchronous generator and rectifier in S300 includes the following steps:

[0053] Combining formulas (6), (7), (12), (19), and (20), we obtain the following formula:

[0054]

[0055] Ignore the d-axis components and ωi sq ωi sd ,ωv cd ,ωv cq Due to the influence of [unclear], the average model of the decoupled and reduced-order asynchronous generator and rectifier is obtained as follows:

[0056]

[0057] Add a small perturbation signal near the steady-state operating point (x0, y0) but: Ignoring both steady-state components and squared disturbance terms, we can obtain the reduced-order signal equations for the asynchronous generator rectifier system:

[0058]

[0059] The output equation corresponding to the reduced-order signal equation is:

[0060]

[0061] Applying the Laplace transform to equations (23) and (24), we obtain the following equations:

[0062]

[0063] in,

[0064] D is a zero matrix;

[0065] Performing matrix operations on formula (25) yields the following formula:

[0066]

[0067] According to formula (26), the transfer function matrix of the asynchronous generator rectifier system is obtained:

[0068]

[0069] Among them, G ie G is the transfer function from the stator terminal electromotive force to the q-axis current of an asynchronous generator; ii G is the transfer function from the rectifier load current to the q-axis current. iq G is the transfer function from the rectifier duty cycle to the q-axis current. ve G is the transfer function from the stator electromotive force of the asynchronous generator to the DC side voltage of the rectifier; vi G is the transfer function from the rectifier load current to the rectifier DC-side voltage;vd This is the transfer function from the rectifier duty cycle to the DC-side voltage of the rectifier.

[0070] In some embodiments, S400 is based on a closed-loop control structure of a vector-controlled asynchronous generator and rectifier system, and combined with formula (27), a small-signal model of the closed-loop control loop is established, wherein the voltage outer loop transfer function G of the asynchronous generator and rectifier system is... PIv =k pv +k iv / s, the inner current transfer function G of the asynchronous generator and rectifier system PIi =k pi +k ii / s;k pv k is the proportional parameter of the outer voltage loop. iv k is the integral parameter of the outer voltage loop. pi The proportional parameter for the inner current loop; k ii These are the integral parameters of the inner current loop.

[0071] In some embodiments, the DC-side output impedance expression of the rectifier in S500 is as follows:

[0072]

[0073] An embodiment of the present invention also provides a device including a memory and a processor. The memory is used to store embedded software programs. The processor is used to execute the embedded software programs stored in the memory, and when the embedded programs are executed, they implement the steps of the method for obtaining output impedance based on an asynchronous generator and rectifier system described in any of the above embodiments.

[0074] An embodiment of the present invention also provides a computer-readable storage medium storing a program for implementing a method for obtaining output impedance. The program for implementing the method for obtaining output impedance is executed by a processor to implement the steps of the method for obtaining output impedance based on an asynchronous generator and rectifier system as described in any of the above embodiments.

[0075] Other features and beneficial effects of the present invention will be set forth in the following description, and some of these features and beneficial effects may be apparent from the description or learned by practicing the invention. The objects of the invention and other beneficial effects may be realized and obtained through the structures specifically pointed out in the description and other contents. Attached Figure Description

[0076] 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, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0077] Figure 1 This is a schematic diagram of an existing three-phase voltage-source PWM rectifier control.

[0078] Figure 2 This is the circuit topology diagram of a diesel asynchronous generator rectifier system;

[0079] Figure 3 This is a control block diagram of an asynchronous generator and rectifier system;

[0080] Figure 4 This is a block diagram of the small-signal control of an asynchronous generator and rectifier system;

[0081] Figure 5 It is a comparison chart of the output impedance amplitude-frequency and phase-frequency curves based on theoretical calculations and simulation measurements. Detailed Implementation

[0082] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0083] In the description of this invention, it should be understood that the terms "center," "lateral," "upper," "lower," "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 component 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 as "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. Additionally, the term "comprising" and any variations thereof mean "at least comprising."

[0084] 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 integrally formed 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 between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0085] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms “a” and “an” as used herein are also intended to include the plural. It should also be understood that the terms “comprising” and / or “including” as used herein specify the presence of the stated features, integers, steps, operations, units, and / or components, without excluding the presence or addition of one or more other features, integers, steps, operations, units, components, and / or combinations thereof.

[0086] Please see Figures 2 to 5 , Figure 2 This is the circuit topology diagram of a diesel asynchronous generator rectifier system. Figure 3 This is a control block diagram of an asynchronous generator and rectifier system. Figure 4 This is a block diagram of the small-signal control of an asynchronous generator and rectifier system. Figure 5 It is a comparison chart of the output impedance amplitude-frequency and phase-frequency curves based on theoretical calculations and simulation measurements.

[0087] An embodiment of the present invention provides a method for obtaining the output impedance based on an asynchronous generator and rectifier system, the method comprising the following steps:

[0088] S100: Establish a mathematical model for the asynchronous generator;

[0089] S200: Establish an average switching continuous model for the rectifier and filter;

[0090] S300: Establish a small-signal model of the asynchronous generator and rectifier;

[0091] S400: Based on the use of vector control asynchronous generator, a small-signal model of closed-loop control loop is established;

[0092] S500: Obtain the DC-side output impedance expression of the rectifier based on the small-signal model of the closed-loop control loop.

[0093] In S100, establishing the mathematical model of the asynchronous generator includes the following steps:

[0094] Based on Kirchhoff's voltage law and current law, the stator voltage equation (1) and the stator output node current equation (2) of the asynchronous generator are obtained:

[0095]

[0096]

[0097] Among them, E sa E sb E sc i is the stator electromotive force of the asynchronous generator; sa i sb i sc i represents the stator current of the asynchronous generator; a i b i c R is the output current of the filter; s L is the stator resistance of the asynchronous generator; s C is the stator inductance of the asynchronous generator; C is the filter capacitor; R is the damping resistor of the filter; v ca v cb v cc d is the voltage across the capacitor of the filter; d / dt is the differential operator;

[0098] Based on the dq transform method, the AC time variables are transformed into the DC time invariant transformation matrix T. abc / dq T abc / dq as follows:

[0099]

[0100] Where ω is the angular frequency; t is time;

[0101] By using the dq transformation method, the time variables of AC power frequency are transformed into the time invariants of DC power frequency. Combining formulas (1), (2), and (3), the following formula is obtained:

[0102]

[0103]

[0104] in, E sd E sq The d-axis and q-axis components of the stator electromotive force dq after transformation of the asynchronous generator; i sd i sq The d-axis and q-axis components of the stator current dq after transformation of the asynchronous generator; v cd v cq These are the d-axis and q-axis components of the three-phase voltage at the filter capacitor terminal after dq transformation; i d i q These are the d-axis and q-axis components of the three-phase input current dq transformed from the AC side of the rectifier, respectively.

[0105] Simplifying formulas (4) and (5), we obtain the time-invariant model in the dq coordinate system:

[0106]

[0107]

[0108] In S200, establishing the average switching continuous model of the rectifier and filter involves the following steps:

[0109] The function to obtain the switch is as follows:

[0110]

[0111] Among them, S au S bu S cu These are the drive signals for the switching transistors on the three-phase bridge arms, respectively; S al S bl S cl These are the drive signals for the lower switching transistors of the three-phase bridge arms, respectively; and S... a S b S c S represents au S bu S cu ;

[0112] Averaging the switching function yields the following formula:

[0113]

[0114] Among them, T s d is the switching period; i This refers to the duty cycle corresponding to the drive signal of the switching transistor on the three-phase bridge arm;

[0115] Based on Kirchhoff's voltage and current laws, the AC-side loop voltage equation (10) and the DC-side node current equations (11) and (12) are obtained:

[0116]

[0117] i dc =[S a S b S c ][i a i b i c ] T (11)

[0118]

[0119] Among them, v an v bn v cn This is the voltage between the connection point of the two switches in the three-phase bridge arm and the DC voltage reference point; v no The voltage between the DC voltage reference point and the three-phase voltage neutral point; i dc V is the output current on the DC side of the rectifier; L is the inductance on the AC side of the filter; v dc i is the output voltage on the DC side of the rectifier; Load C is the load current on the DC side of the rectifier; dc For the DC side capacitor of the rectifier;

[0120] v dc With v an v bn v cn The relationship between them is as follows:

[0121]

[0122] Where, d a d b d c These are the duty cycles corresponding to the drive signals of the switching transistors on the three-phase bridge arms;

[0123] Based on the three-phase equilibrium characteristics, combining formulas (10) and (13) yields the following formula:

[0124]

[0125] The three-phase equilibrium characteristics are expressed as: (va +v b +v c =0,i a +i b +i c =0);

[0126] Combining formulas (9), (10), (11), (13), and (14), we obtain the following formula:

[0127]

[0128] i dc =[d a d b d c ][i a i b i c ] T (16)

[0129] Combining formulas (3), (15), and (16), we obtain the following formula:

[0130]

[0131]

[0132] Where, d d d q These are the d-axis and q-axis components of the modulated wave signal after dq transformation of the three-phase bridge arm switch, respectively.

[0133] Simplifying formulas (17) and (18), we obtain the time-invariant model in the dq coordinate system:

[0134]

[0135]

[0136] In S300, establishing a small-signal model of an asynchronous generator and rectifier involves the following steps:

[0137] Combining formulas (6), (7), (12), (19), and (20), we obtain the following formula:

[0138]

[0139] Ignore the d-axis components and ωi sq ωi sd ,ωv cd ,ωv cq Due to the influence of [unclear], the average model of the decoupled and reduced-order asynchronous generator and rectifier is obtained as follows:

[0140]

[0141] Add a small perturbation signal near the steady-state operating point (x0, y0) but: Ignoring both steady-state components and squared disturbance terms, we can obtain the reduced-order signal equations for the asynchronous generator rectifier system:

[0142]

[0143] The output equation corresponding to the reduced-order signal equation is:

[0144]

[0145] Applying the Laplace transform to equations (23) and (24), we obtain the following equations:

[0146]

[0147] in,

[0148] D is a zero matrix;

[0149] Performing matrix operations on formula (25) yields the following formula:

[0150]

[0151] According to formula (26), the transfer function matrix of the asynchronous generator rectifier system is obtained:

[0152]

[0153] Among them, G ie G is the transfer function from the stator terminal electromotive force to the q-axis current of an asynchronous generator; ii G is the transfer function from the rectifier load current to the q-axis current. iq G is the transfer function from the rectifier duty cycle to the q-axis current. ve G is the transfer function from the stator electromotive force of the asynchronous generator to the DC side voltage of the rectifier; vi G is the transfer function from the rectifier load current to the rectifier DC-side voltage; vd This is the transfer function from the rectifier duty cycle to the DC-side voltage of the rectifier.

[0154] In S400, a closed-loop control structure for an asynchronous generator and rectifier system using vector control is adopted, and a small-signal model of the closed-loop control loop is established based on formula (27). The voltage outer loop transfer function G of the asynchronous generator and rectifier system is... PIv =k pv +k iv / s, the inner current transfer function G of the asynchronous generator and rectifier system PIi =k pi +k ii / s;k pv k is the proportional parameter of the outer voltage loop. iv k is the integral parameter of the outer voltage loop. pi The proportional parameter for the inner current loop; k ii These are the integral parameters of the inner current loop.

[0155] Finally, the expression for the DC-side output impedance of the rectifier in the S500 is obtained as follows:

[0156]

[0157] The circuit topology of an asynchronous generator and rectifier system mainly consists of a diesel engine, an asynchronous generator, an LC filter, and a rectifier. For example... Figure 2 As shown, the three-phase AC power generated by the diesel asynchronous generator is transferred from the AC side of the rectifier to the DC side through a filter. The control method employs dual-loop control, and the control block diagram is shown below. Figure 3 As shown. To easily obtain the DC-side output impedance of the rectifier, from... Figure 3 It can be seen that the voltage on the DC side of the rectifier (V) dc The control block diagram is related to the q-axis component, therefore the d-axis component can be ignored. A small-signal control block diagram of the asynchronous generator and rectifier system is obtained by applying a small-signal perturbation to the q-axis component, as shown below. Figure 4 As shown.

[0158] The following example illustrates the parameter design: 3-phase output voltage of the asynchronous generator is 690V, stator resistance R... s =0.0041Ω, stator inductance L s = 2.9mH, rotor inductance L r =2.9mH, mutual inductance L m =2.8mH, number of pole pairs P=2, magnetic flux linkage The AC side inductance of the LC filter is L = 430μH, the LC filter capacitance is C = 50μF, and the DC side capacitance of the rectifier is C. dc =50mF, DC side output voltage v dc =1000V, DC side load R Load =100Ω, voltage outer loop proportional parameter k pv =20, the integral parameter k of the outer voltage loop iv =80, the proportional parameter k of the inner current loop pi =0.001, the integral parameter k of the inner current loop ii =0.2.

[0159] A perturbation injection method is used to inject perturbation currents of different frequencies into the system from the DC port. The DC port impedance is obtained based on the perturbation voltage response at the DC port. A comparison of the output impedance amplitude-frequency and phase-frequency curves calculated theoretically and measured in simulations is shown below. Figure 5 As shown in Table 1, the detailed measured output impedance data points are as follows.

[0160] Table 1

[0161]

[0162]

[0163] Furthermore, this invention can also be applied to islanded microgrids using squirrel-cage asynchronous generators or wind power generation using squirrel-cage asynchronous generators to perform impedance stability analysis on microgrid systems.

[0164] An embodiment of the present invention also provides a device including a memory and a processor. The memory is used to store embedded software programs. The processor is used to execute the embedded software programs stored in the memory, and when the embedded programs are executed, they implement the steps of the method for obtaining output impedance based on an asynchronous generator and rectifier system described in any of the above embodiments.

[0165] An embodiment of the present invention also provides a computer-readable storage medium storing a program for implementing a method for obtaining output impedance. The program for implementing the method for obtaining output impedance is executed by a processor to implement the steps of the method for obtaining output impedance based on an asynchronous generator and rectifier system as described in any of the above embodiments.

[0166] In summary, one embodiment of the present invention provides a method, device, and readable storage medium for obtaining the output impedance of an asynchronous generator and rectifier system. By establishing a vector-controlled mathematical model of the asynchronous generator and employing a small-signal modeling method, the difficulty in establishing the system's differential equations is addressed. Through analysis of the control structure of the vector-controlled asynchronous generator, the asynchronous generator model is reduced in order, making the system's differential equations easier to solve. This facilitates the description of the system's output impedance characteristics, enables accurate acquisition of the output impedance of the asynchronous generator and rectifier, and facilitates impedance stability analysis of marine DC microgrids using asynchronous generators, thereby improving the stability of the marine DC microgrid.

[0167] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for obtaining output impedance based on an asynchronous generator and rectifier system, characterized in that: The method for obtaining the output impedance based on an asynchronous generator and rectifier system includes the following steps: S100: Establish a mathematical model for the asynchronous generator; S200: Establish an average switching continuous model for the rectifier and filter; S300: Establish a small-signal model of the asynchronous generator and rectifier; S400: Based on the use of vector control asynchronous generator, a small-signal model of closed-loop control loop is established; S500: Obtain the expression for the DC-side output impedance of the rectifier based on the small-signal model of the closed-loop control loop; The transfer function matrix of the asynchronous generator rectifier system is as follows: （27） in, G ie This is the transfer function from the stator terminal electromotive force of the asynchronous generator to the q-axis current. G ii This is the transfer function from the rectifier load current to the q-axis current. G iq This is the transfer function from the rectifier duty cycle to the q-axis current. G ve It is the transfer function from the stator electromotive force of the asynchronous generator to the DC side voltage of the rectifier; G vi It is the transfer function from the rectifier load current to the rectifier DC side voltage; G vd Let i be the transfer function from the rectifier duty cycle to the DC-side voltage of the rectifier. q The q-axis component of the three-phase input current dq on the AC side of the rectifier is represented by this component. v dc This refers to the output voltage on the DC side of the rectifier. i Load e is the load current on the DC side of the rectifier; sq d represents the q-axis component of the stator electromotive force after transformation of the asynchronous generator; q The q-axis component is the transformed modulated wave signal of the three-phase bridge arm switch. In S400, a closed-loop control structure for an asynchronous generator and rectifier system using vector control is adopted, and a small-signal model of the closed-loop control loop is established based on formula (27). The voltage outer loop transfer function of the asynchronous generator and rectifier system is... The inner current transfer function of an asynchronous generator and rectifier system ; k pv This refers to the proportional parameters of the outer voltage loop; k iv These are the integral parameters of the outer voltage loop; k pi This refers to the proportional parameter of the inner current loop; k ii These are the integral parameters of the inner current loop; The expression for the DC-side output impedance of the rectifier in the S500 is as follows: 。 2. The method for obtaining output impedance based on an asynchronous generator and rectifier system according to claim 1, characterized in that: The steps for establishing the mathematical model of the asynchronous generator as described in S100 are as follows: Based on Kirchhoff's voltage and current laws, the stator voltage equation (1) and the stator output node current equation (2) of the asynchronous generator are obtained: （1） （2） in, E sa , E sb , E sc This refers to the stator electromotive force of the asynchronous generator; i sa , i sb , i sc This refers to the stator current of the asynchronous generator. i a , i b , i c This refers to the output current of the filter. R s The stator resistance of the asynchronous generator; L s For the stator inductance of an asynchronous generator; C For filter capacitors; R This is the damping resistor of the filter; v ca , v cb , v cc This is the voltage across the capacitor of the filter; d / dt It is a differential operator; Based on the dq transform method, the time variables of power frequency AC are transformed into the transformation matrix of DC time invariants. T abc / dq , T abc / dq as follows: （3） in, ω Angular frequency; t For time; By using the dq transformation method, the time variables of AC power frequency are transformed into the time invariants of DC power frequency. Combining formulas (1), (2), and (3), the following formula is obtained: （4） （5） in, , , E sd , E sq These are the d-axis and q-axis components of the stator electromotive force dq after transformation of the asynchronous generator. i sd , i sq These are the d-axis and q-axis components of the stator current dq after transformation of the asynchronous generator. v cd , v cq These are the d-axis and q-axis components of the three-phase voltage dq transformed at the filter capacitor terminal, respectively. i d The d-axis component of the three-phase input current dq on the AC side of the rectifier is the transformed component. Simplifying formulas (4) and (5), we obtain the time-invariant model in the dq coordinate system: （6） （7）。 3. The method for obtaining output impedance based on an asynchronous generator and rectifier system according to claim 2, characterized in that: The establishment of the average switching continuous model of the rectifier and filter described in S200 includes the following steps: The function to obtain the switch is as follows: （8） in, S au , S bu , S cu These are the drive signals for the switching transistors on the three-phase bridge arms, respectively. S al , S bl , S cl These are the drive signals for the lower switching transistors of the three-phase bridge arms, respectively; and... S a , S b , S c They represent S au , S bu , S cu ; Averaging the switching function yields the following formula: （9） in, T s For switching cycles; d i This refers to the duty cycle corresponding to the drive signal of the switching transistor on the three-phase bridge arm; Based on Kirchhoff's voltage and current laws, the AC-side loop voltage equation (10) and the DC-side node current equations (11) and (12) are obtained: （10） （11） （12） in, v an , v bn , v cn This is the voltage between the connection point of the two switching transistors in the three-phase bridge arm and the DC voltage reference point; v no This is the voltage between the DC voltage reference point and the three-phase voltage neutral point; i dc This refers to the output current on the DC side of the rectifier. L The inductance is on the AC side of the filter; C dc For the DC side capacitor of the rectifier; v dc and v an , v bn , v cn The relationship between them is as follows: （13） in, d a , d b , d c These are the duty cycles corresponding to the drive signals of the switching transistors on the three-phase bridge arms; Based on the three-phase equilibrium characteristics, combining formulas (10) and (13) yields the following formula: （14） The three-phase equilibrium characteristics are expressed as follows: ; Combining formulas (9), (10), (11), (13), and (14), we obtain the following formula: （15） （16） Combining formulas (3), (15), and (16), we obtain the following formula: （17） （18） in, d d , d q These are the d-axis and q-axis components of the modulated wave signal after dq transformation of the three-phase bridge arm switch, respectively. Simplifying formulas (17) and (18), we obtain the time-invariant model in the dq coordinate system: （19） （20）。 4. The method for obtaining output impedance based on an asynchronous generator and rectifier system according to claim 3, characterized in that: The steps for establishing the small-signal model of the asynchronous generator and rectifier as described in S300 are as follows: Combining formulas (6), (7), (12), (19), and (20), we obtain the following formula: （21） Ignore d-axis components and ωi sq , ωi sd , ωv cd , ωv cq Due to the influence of [unclear], the average model of the decoupled and reduced-order asynchronous generator and rectifier is obtained as follows: （22） At steady-state operating point Add small disturbance signals nearby ,but: , ; Ignoring both steady-state components and squared disturbance terms, the reduced-order signal equations for the asynchronous generator rectifier system are obtained as follows: （23） The output equation corresponding to the reduced-order signal equation is: （24） Applying the Laplace transform to equations (23) and (24), we obtain the following equations: （25） in, , , , , D is a zero matrix; Performing matrix operations on formula (25) yields the following formula: （26） According to formula (26), the transfer function matrix of the asynchronous generator rectifier system is obtained.

5. An electronic device, characterized in that: The electronic device includes: Memory, used to store embedded software programs; A processor is configured to execute an embedded software program stored in the memory, wherein the embedded program, when executed, implements the steps of the method for obtaining output impedance based on an asynchronous generator and rectifier system as described in any one of claims 1 to 4.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a program for implementing a method for obtaining output impedance, which is executed by a processor to implement the steps of the method for obtaining output impedance based on an asynchronous generator and rectifier system as described in any one of claims 1 to 4.

Images