Network construction type converter control method and device based on virtual excitation and terminal equipment

Abstract

The invention discloses a network construction type converter control method and device based on virtual excitation and terminal equipment, an internal potential amplitude is calculated according to a voltage effective value of a grid connection point and a preset voltage reference value by setting an internal potential amplitude generation model, and specifically, a plurality of PID control units are set in the internal potential amplitude generation model, and the internal potential amplitude is calculated according to the voltage effective value of the grid connection point and the preset voltage reference value. And the PID control unit is adopted, so that the response capability of the network-forming converter to disturbance can be effectively enhanced, and rapid adjustment of the internal potential is realized. Secondly, delaying an output result of the PID control unit through the inertia unit so as to maintain the stability of an internal potential amplitude, and then carrying out filtering compensation on the output result of the PID control unit through the correction unit. Therefore, the internal potential is adjusted through the internal potential amplitude generation model to maintain the network construction characteristic to the greatest extent, so that the voltage adjusting function of the converter is enhanced, the grid-connected point voltage level of the network construction converter is maintained, and meanwhile, good dynamic response performance is achieved after an external system is disturbed.

Description

Technical Field

[0001] The present invention relates to the technical field of power system control, and in particular to a control method, device and terminal equipment of a grid-connected converter based on virtual excitation. Background Art

[0002] With the rapid construction of the "double-high" power system, the scale of new energy has gradually expanded, and the converter has become an indispensable interface between new energy and the power system. The grid-type converter can effectively avoid the instability risk introduced by the grid-type converter due to the lack of active frequency and voltage support capabilities. It has been widely recognized and widely used in power systems. The grid-type converter measures the actual value of the power at the grid connection point, compares it with the given value, constructs the internal potential amplitude and phase, and presents it to the outside as a controlled voltage source characteristic, thereby supporting the voltage and frequency of the system. In order to cope with the size of external grid disturbances and exert a strong voltage support capability, the grid-type converter should be able to make full use of its own internal potential control link to maximize the internal potential regulation capability.

[0003] Droop control is currently the most widely used type of grid-forming control strategy, but the droop control structure is simple. After the external grid is disturbed, the internal potential changes significantly with the reactive power change, which is greatly affected by the reactive power and cannot fully exert the voltage support capacity. Using a PI controller to track the voltage measurement value at the grid connection point to the set voltage reference value is also a type of grid-forming control strategy. However, the use of the PI controller strategy cannot eliminate transient errors when the voltage changes drastically, and may even cause overshoot and oscillation, resulting in insufficient voltage regulation capabilities.

[0004] In general, although the existing technology can realize network construction and present the characteristics of a controlled voltage source to the outside, playing a certain supporting role, it is still unable to maintain the internal potential to support the voltage after the external power grid changes or is disturbed. Summary of the invention

[0005] The embodiments of the present invention provide a control method, device and terminal equipment of a grid-connected converter based on virtual excitation, which adjusts the internal potential through an internal potential amplitude generation model to maintain the grid-connected characteristics to the greatest extent, thereby enhancing the voltage regulation function of the converter and maintaining the voltage level of the grid-connected point of the grid-connected converter, while having good dynamic response performance after the external system is disturbed.

[0006] An embodiment of the present invention provides a control method for a grid-connected converter based on virtual excitation, comprising:

[0007] Obtain the active power, reactive power, and voltage RMS of the grid connection point;

[0008] Calculating the internal potential phase according to the active power;

[0009] Calculating a voltage reference value according to the reactive power, a preset reactive power reference value and a preset initial voltage reference value;

[0010] Inputting the voltage effective value and the voltage reference value into a preset internal potential amplitude generation model, so that a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correcting and compensating the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputting the internal potential amplitude;

[0011] A PWM modulation signal is generated according to the internal potential phase and the internal potential amplitude, and the switch tube of the grid-type converter is controlled by the PWM modulation signal.

[0012] Furthermore, the effective value of the voltage at the grid connection point is obtained, including:

[0013] Obtaining an initial voltage signal detected at a grid connection point;

[0014] filtering the initial voltage signal to generate a voltage signal;

[0015] Obtain the preset power frequency voltage cycle and calculate the voltage effective value according to the following formula:

[0016]

[0017] Where T is the power frequency voltage period, v f is the voltage signal after filtering.

[0018] Furthermore, the effective value of the voltage at the grid connection point is obtained, including:

[0019] Obtaining an initial voltage signal detected at a grid connection point;

[0020] filtering the initial voltage signal to generate a voltage signal;

[0021] Converting the voltage signal into a dq coordinate system to obtain a d-axis component and a q-axis component of the voltage signal;

[0022] According to the d-axis component and the q-axis component of the voltage signal, the voltage effective value is calculated by the following formula;

[0023]

[0024] Among them, V d is the d-axis component of the voltage signal, V q is the q-axis component of the voltage signal.

[0025] Further, the calculating of the voltage reference value according to the reactive power, the preset reactive power reference value and the preset initial voltage reference value includes:

[0026] Calculating the reactive power and the reactive power reference value;

[0027] Obtaining a grid-type control strategy for a grid-type converter;

[0028] When the grid-type control strategy is a reactive power droop control strategy, a preset reactive power droop coefficient is obtained, and the voltage reference value is calculated according to the reactive power droop coefficient, the reactive power difference, and the initial voltage reference value;

[0029] When the grid-type control strategy is a PI control strategy, a preset proportional gain and a preset integral time constant are obtained, and the voltage reference value is calculated based on the proportional gain, the integral time constant, the reactive power difference, and the initial voltage reference value.

[0030] Furthermore, the internal potential amplitude generation model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in series in sequence;

[0031] The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including:

[0032] The internal potential amplitude generation model outputs the internal potential amplitude through the following formula:

[0033]

[0034] Among them, E ref The internal potential amplitude is the final output of the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k1, k2, k3, k4 are the number of the PID control unit, the inertial unit, the correction unit, and the linear transfer unit respectively, G1(s) is the PID control unit, K P is the preset magnification factor, K I is the preset integral time constant, K D is the preset differential time constant, G2(s) is the inertia unit, K A is the preset proportionality factor, T Ais the preset time constant, G3(s) is the correction unit, T1 and T2 are both preset time constants, G4(s) is the linear transmission link, a0…a n 、b0……b n are the coefficients of n-order and m-order polynomials respectively, and n and m are the orders of the polynomials respectively.

[0035] Furthermore, the internal potential amplitude generation model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one;

[0036] The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including:

[0037] The internal potential amplitude generation model outputs the internal potential amplitude through the following formula:

[0038] E ref (s)=[k5(G1(s))+k6(G2(s))+k7(G3(s))+k8(G4(s))]ΔV(s);

[0039] Among them, E ref The internal potential amplitude generation model finally outputs the internal potential amplitude, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k5, k6, k7, k8 are the number of the PID control unit, the inertial unit, the correction unit, and the linear transfer unit respectively, G1(s) is the PID control unit, G2(s) is the inertial unit, G3(s) is the correction unit, and G4(s) is the linear transfer link.

[0040] Furthermore, the internal potential amplitude generation model is composed of a series structure sub-model and a parallel structure sub-model connected in series in sequence;

[0041] The series structure sub-model is composed of a plurality of PID control units, a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units connected in series in sequence;

[0042] The parallel structure sub-model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one;

[0043] The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including:

[0044] The internal potential amplitude generation model outputs the internal potential amplitude through the following formula:

[0045]

[0046] Among them, E ref The internal potential amplitude is finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k1, k2, k3, k4 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the series structure sub-model, k5, k6, k7, k8 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the parallel structure sub-model, G1(s) is the PID control unit, G2(s) is the inertial unit, G3(s) is the correction unit, and G4(s) is the linear transfer link.

[0047] Furthermore, the internal potential amplitude generation model is composed of a series structure sub-model and a parallel structure sub-model connected in parallel in sequence;

[0048] The series structure sub-model is composed of a plurality of PID control units, a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units connected in series in sequence;

[0049] The parallel structure sub-model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one;

[0050] The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including:

[0051]

[0052] Among them, E refThe internal potential amplitude is finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k1, k2, k3, k4 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the series structure sub-model, k5, k6, k7, k8 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the parallel structure sub-model, G1(s) is the PID control unit, G2(s) is the inertial unit, G3(s) is the correction unit, and G4(s) is the linear transfer link.

[0053] Another embodiment of the present invention provides a grid-type converter control device based on virtual excitation, comprising:

[0054] A data acquisition module is used to obtain the active power, reactive power, and voltage effective value of the grid connection point;

[0055] An internal potential phase calculation module, used for calculating the internal potential phase according to the active power;

[0056] A voltage reference value calculation module, used for calculating a voltage reference value according to the reactive power, a preset reactive power reference value and a preset initial voltage reference value;

[0057] An internal potential amplitude calculation module, used for inputting the voltage effective value and the voltage reference value into a preset internal potential amplitude generation model, so that a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correcting and compensating the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputting the internal potential amplitude;

[0058] The converter control module is used to generate a PWM modulation signal according to the internal potential phase and the internal potential amplitude, and control the switch tube of the grid-type converter through the PWM modulation signal.

[0059] Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, a grid-type converter control method based on virtual excitation as described in any one of the embodiments is implemented.

[0060] The following beneficial effects are achieved by implementing the present invention:

[0061] The present invention discloses a control method, device and terminal equipment of a grid-type converter based on virtual excitation. The method calculates the internal potential amplitude according to the voltage effective value of the grid-connected point and the preset voltage reference value by setting up an internal potential amplitude generation model. Specifically, a plurality of PID control units are set up in the internal potential amplitude generation model. As is well known, the PID control unit is provided with P (proportional link) for controlling deviation; I (integral link) for reducing steady-state error; D (differential link) for adjusting the rate of change of the deviation signal, which is conducive to accelerating the dynamic response of the converter and reducing overshoot. Therefore, by setting up a plurality of PID control units, the response capability of the grid-type converter to disturbance can be effectively enhanced, and the internal potential can be quickly adjusted. Secondly, the output result of the PID control unit is delayed by the inertial unit so that the output result cannot change suddenly, so as to maintain the stability of the internal potential amplitude, and then the output result of the PID control unit is filtered and compensated by the correction unit to improve the steady-state accuracy of the internal potential amplitude, and further enhance the response capability of the grid-type converter to disturbance, so as to achieve rapid adjustment of the internal potential. Therefore, the present invention enhances the ability to regulate and control the internal potential through an internal potential amplitude generation model, especially when the voltage at the grid-connected point of the converter is disturbed and fluctuates. The internal potential is adjusted to maintain the grid-connected characteristics to the greatest extent, thereby enhancing the voltage regulation function of the converter and maintaining the voltage level of the grid-connected point of the grid-connected converter. At the same time, it has good dynamic response performance after the external system is disturbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a flow chart of a control method of a grid-connected converter based on virtual excitation provided by an embodiment of the present invention.

[0063] Figure 2 It is a structural schematic diagram of a grid-type converter control device based on virtual excitation provided by an embodiment of the present invention.

[0064] Figure 3 It is a schematic diagram of the control structure of a grid-connected converter based on virtual excitation provided in one embodiment of the present invention.

[0065] Figure 4 It is a schematic diagram of the series structure of the internal potential amplitude generation model provided by one embodiment of the present invention.

[0066] Figure 5 It is a schematic diagram of the parallel structure of the internal potential amplitude generation model provided by one embodiment of the present invention.

[0067] Figure 6 It is a schematic diagram of the series-parallel structure of the internal potential amplitude generation model provided by one embodiment of the present invention.

[0068] Figure 7It is a schematic diagram of the parallel-series structure of the internal potential amplitude generation model provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0071] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0072] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0073] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0074] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0075] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0076] See also Figure 1 , is a flow chart of a control method of a grid-connected converter based on virtual excitation provided by an embodiment of the present invention, comprising:

[0077] S1. Obtain the active power, reactive power, and voltage effective value of the grid connection point;

[0078] Preferably, obtaining the effective value of the voltage at the grid connection point includes:

[0079] S101, obtaining an initial voltage signal detected at a grid connection point;

[0080] S102, filtering the initial voltage signal to generate a voltage signal;

[0081] S103, obtaining a preset power frequency voltage cycle, and calculating the voltage effective value according to the following formula:

[0082]

[0083] Where T is the power frequency voltage period, v f is the voltage signal after filtering.

[0084] Preferably, obtaining the effective value of the voltage at the grid connection point includes:

[0085] S111, obtaining an initial voltage signal detected at a grid connection point;

[0086] S112, filtering the initial voltage signal to generate a voltage signal;

[0087] S113, converting the voltage signal into a dq coordinate system to obtain a d-axis component and a q-axis component of the voltage signal;

[0088] S114, calculating the voltage effective value according to the d-axis component and the q-axis component of the voltage signal by the following formula;

[0089]

[0090] Among them, V d is the d-axis component of the voltage signal, Vq is the q-axis component of the voltage signal.

[0091] In a preferred embodiment of the present invention, the measured voltage signal is first filtered through a low-pass filter to remove noise, and a filtered voltage signal v is obtained. f There are two subsequent calculation methods, and you can choose one of them. The first calculation method is to calculate the effective value of the voltage based on the power frequency voltage cycle. This method is direct and effective, but the integral calculation is required, resulting in a large amount of calculation and storage. The second calculation method is to convert the voltage signal in the abc coordinate system to the dq coordinate system through park transformation, and then calculate the effective value of the voltage based on the d-axis component and q-axis component of the voltage signal. This method requires park transformation, but the DC value calculation is faster and more convenient.

[0092] S2. calculating the internal potential phase according to the active power;

[0093] In a preferred embodiment of the present invention, Figure 3 As shown, the inner potential phase is calculated by the active power-frequency outer loop according to the active power, the preset active power reference value, and the rated angular velocity.

[0094] S3, calculating a voltage reference value according to the reactive power, a preset reactive power reference value and a preset initial voltage reference value;

[0095] Preferably, calculating the voltage reference value according to the reactive power, a preset reactive power reference value and a preset initial voltage reference value comprises:

[0096] S31, calculating the reactive power and the reactive power difference of the reactive power reference value;

[0097] S32, obtaining a grid-type control strategy for a grid-type converter;

[0098] S33, when the grid-type control strategy is a reactive power droop control strategy, obtaining a preset reactive power droop coefficient, and calculating the voltage reference value according to the reactive power droop coefficient, the reactive power difference, and the initial voltage reference value;

[0099] S34. When the grid-type control strategy is a PI control strategy, a preset proportional gain and a preset integral time constant are obtained, and the voltage reference value is calculated according to the proportional gain, the integral time constant, the reactive power difference, and the initial voltage reference value.

[0100] In a preferred embodiment of the present invention, the voltage reference value V ref The generation of can be divided into two categories. The first category is to directly use the initial voltage reference value V ref0The second type is to calculate the reference value based on the reactive power deviation, which can be calculated through reactive power droop or PI link according to the grid-type control strategy of the grid-type converter.

[0101] When the grid-type control strategy is a reactive power droop control strategy, the voltage reference value is calculated by the following formula:

[0102] V ref =V ref0 +K q (Q ref -Q);

[0103] When the grid-type control strategy is a reactive power droop control strategy, the voltage reference value is calculated by the following formula:

[0104] V ref =V ref0 +K P (Q ref -Q)+K I ∫(Q ref -Q)dt;

[0105] Among them, V ref is the calculated voltage reference value; V ref0 is the preset initial voltage reference value; K q is the reactive power droop coefficient; Q ref is the reactive power reference value; Q is the reactive power; K P , K I are the proportional gain and integral time constant of the PI control link respectively.

[0106] S4, inputting the voltage effective value and the voltage reference value into a preset internal potential amplitude generation model, so that a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correcting and compensating the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputting the internal potential amplitude;

[0107] In a preferred embodiment of the present invention, the inertial unit adopts a first-order inertial unit, and the correction unit adopts a lead-lag unit. Furthermore, in combination with the specific functional requirements of the grid-forming converter, the internal potential amplitude generation model can use a series-parallel combination of multiple PID control units, inertial units, and correction units, or can use a more universal transfer function description.

[0108] Specifically, the first-order inertial unit can be described by a first-order differential equation. When the input changes suddenly, the output cannot change suddenly immediately, but gradually changes to a new steady-state value according to the exponential law. Specifically, the time constant of the first-order inertial unit is a measure of the inertia of the system. The smaller the time constant, the faster the system responds to the input change; conversely, the larger the time constant, the slower the system responds. The lead-lag unit (Lead-Lag Control) is a commonly used correction device in the control system. It combines the advantages of lead correction and lag correction and can improve the transient performance and steady-state performance of the system at the same time. The lead-lag unit is composed of a lead correction link and a lag correction link connected in series. In the transfer function, the transfer function of this correction device usually contains two factors, one to produce a lead correction effect and the other to produce a lag correction effect. The main function of the lead correction link is to produce a sufficiently large phase lead angle to compensate for the excessive phase lag of the system. This helps to increase the phase margin (PM), thereby improving the dynamic performance of the system, such as fast response characteristics. The main function of the lag correction link is to attenuate the mid- and high-frequency amplitude characteristics and move the amplitude crossing frequency toward low frequencies, thereby improving the static performance of the system, such as steady-state accuracy.

[0109] Preferably, the internal potential amplitude generation model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in series in sequence;

[0110] S41, several PID control units in the internal potential amplitude generation model output initial internal potential amplitudes according to the voltage effective value and the voltage reference, and then correct and compensate the initial internal potential amplitudes through several inertial units, several correction units, and several linear transfer units in the internal potential amplitude generation model, and finally output the internal potential amplitude, including:

[0111]

[0112] Among them, E ref is the internal potential amplitude, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k1, k2, k3, k4 are the number of the PID control unit, the inertial unit, the correction unit, and the linear transfer unit respectively, G1(s) is the PID control unit, K P is the preset magnification factor, K I is the preset integration time constant, K D is the preset differential time constant, G2(s) is the inertia unit, K A is the preset proportionality factor, T Ais the preset time constant, G3(s) is the correction unit, T1 and T2 are both preset time constants, G4(s) is the linear transmission link, a0…a n 、b0……b n are the coefficients of n-order and m-order polynomials respectively, and n and m are the orders of the polynomials respectively.

[0113] In a preferred embodiment of the present invention, Figure 4 As shown, it is a structural schematic diagram of the internal potential amplitude generation model using a pure series structure, wherein several PID control units, several inertial units, several correction units, and several linear transfer units in the internal potential amplitude generation model are sequentially connected in series.

[0114] It should be noted that after the adjustment of the three units of proportion, integration and differentiation, the PID control unit outputs a comprehensive control signal. This control signal not only takes into account the current converter deviation, but also takes into account the converter's historical deviation and future deviation trend, and can more comprehensively reflect the converter's dynamic characteristics.

[0115] Preferably, the internal potential amplitude generation model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one;

[0116] S42, a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correct and compensate the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally output the internal potential amplitude, including:

[0117] The internal potential amplitude generation model outputs the internal potential amplitude through the following formula:

[0118] E ref (s)=[k5(G1(s))+k6(G2(s))+k7(G3(s))+k8(G4(s))]ΔV(s);

[0119] Among them, E ref is the internal potential amplitude finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k5, k6, k7, k8 are the number of the PID control unit, the inertial unit, the correction unit, and the linear transfer unit respectively, G1(s) is the PID control unit, G2(s) is the inertial unit, G3(s) is the correction unit, and G4(s) is the linear transfer link.

[0120] In a preferred embodiment of the present invention, it should be noted that the formulas of the PID control unit G1(s), the inertial units G2(s), the correction units G3(s), and the linear transfer units G4(s) are consistent with those in step S41. Figure 5 The figure is a schematic diagram of the structure of the internal potential amplitude generation model using a pure parallel structure, wherein the plurality of PID control units, the plurality of inertial units, the plurality of correction units, and the plurality of linear transfer units in the internal potential amplitude generation model are connected in parallel one by one.

[0121] Preferably, the internal potential amplitude generation model is composed of a series structure sub-model and a parallel structure sub-model connected in series in sequence;

[0122] The series structure sub-model is composed of a plurality of PID control units, a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units connected in series in sequence;

[0123] The parallel structure sub-model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one;

[0124] S43, a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correct and compensate the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally output the internal potential amplitude, including:

[0125] The internal potential amplitude generation model outputs the internal potential amplitude through the following formula:

[0126]

[0127] Among them, E ref is the internal potential amplitude finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k1, k2, k3, k4 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the series structure sub-model, k5, k6, k7, k8 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the parallel structure sub-model, G1(s) is the PID control unit, G2(s) is the inertial unit, G3(s) is the correction unit, and G4(s) is the linear transfer link.

[0128] In a preferred embodiment of the present invention, it should be noted that the formulas of the PID control unit G1(s), the inertial units G2(s), the correction units G3(s), and the linear transfer units G4(s) are consistent with those in step S41. Figure 6 As shown, it is a structural schematic diagram of the internal potential amplitude generation model using a series-parallel structure. Among them, the internal potential amplitude generation model is mainly series-connected, and the series structure sub-model and the parallel structure sub-model are connected in series in sequence.

[0129] Preferably, the internal potential amplitude generation model is composed of a series structure sub-model and a parallel structure sub-model connected in parallel in sequence;

[0130] The series structure sub-model is composed of a plurality of PID control units, a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units connected in series in sequence;

[0131] The parallel structure sub-model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one;

[0132] S44, a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correct and compensate the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally output the internal potential amplitude, including:

[0133] The internal potential amplitude generation model outputs the internal potential amplitude through the following formula:

[0134]

[0135] Among them, E ref is the internal potential amplitude finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k1, k2, k3, k4 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the series structure sub-model, k5, k6, k7, k8 are respectively the number of PID control units, inertial units, correction units, and linear transfer units in the parallel structure sub-model, G1(s) is the PID control unit, G2(s) is the inertial unit, G3(s) is the correction unit, and G4(s) is the linear transfer link.

[0136] In a preferred embodiment of the present invention, it should be noted that the formulas of the PID control unit G1(s), the inertial units G2(s), the correction units G3(s), and the linear transfer units G4(s) are consistent with those in step S41. Figure 7 The figure shows the schematic diagram of the structure of the internal potential amplitude generation model using the parallel-series structure. The internal potential amplitude generation model is mainly parallel, and the series structure sub-model and the parallel structure sub-model are connected in parallel in sequence.

[0137] S5. Generate a PWM modulation signal according to the internal potential phase and the internal potential amplitude, and control the switch tube of the grid-connected converter through the PWM modulation signal.

[0138] In a preferred embodiment of the present invention, the grid-type converter can be essentially regarded as a controlled voltage source with controlled internal impedance, amplitude and phase. A complete conventional grid-type converter control includes calculation link, inner and outer loop control link, and the active-frequency outer loop and reactive-voltage outer loop respectively determine the phase and amplitude of the internal potential. The reference internal potential generated by the outer loop will enter the PWM modulation link through the current inner loop to generate a modulation signal. Figure 3 As shown, the basic principle of the grid-forming method provided in this embodiment is to apply virtual excitation control as the control strategy for generating the internal potential amplitude, to maintain the grid-forming characteristics to the greatest extent by adjusting the internal potential, while enhancing the voltage regulation function and maintaining the voltage level of the grid-connected point of the grid-forming converter, and at the same time having good dynamic response performance after the external system is disturbed.

[0139] This embodiment provides a control method for a grid-type converter based on virtual excitation, by setting up an internal potential amplitude generation model to calculate the internal potential amplitude according to the voltage effective value of the grid connection point and the preset voltage reference value. Specifically, a number of PID control units are set up in the internal potential amplitude generation model, and it is well known that the PID control unit is provided with P (proportional link) for controlling the deviation; I (integral link) for reducing the steady-state error; D (differential link) for adjusting the rate of change of the deviation signal, which is conducive to accelerating the dynamic response of the converter and reducing overshoot. Therefore, by setting up a number of PID control units, the response capability of the grid-type converter to disturbances can be effectively enhanced, and the internal potential can be quickly adjusted. Secondly, the output result of the PID control unit is delayed by the inertial unit so that the output result cannot change suddenly, so as to maintain the stability of the internal potential amplitude, and then the output result of the PID control unit is filtered and compensated by the correction unit to improve the steady-state accuracy of the internal potential amplitude, and further enhance the response capability of the grid-type converter to disturbances, so as to achieve rapid adjustment of the internal potential. Therefore, the present invention enhances the ability to regulate and control the internal potential through an internal potential amplitude generation model, especially when the voltage at the grid-connected point of the converter is disturbed and fluctuates. The internal potential is adjusted to maintain the grid-connected characteristics to the greatest extent, thereby enhancing the voltage regulation function of the converter and maintaining the voltage level of the grid-connected point of the grid-connected converter. At the same time, it has good dynamic response performance after the external system is disturbed.

[0140] See also Figure 2 , is a schematic diagram of a structure of a grid-type converter control device based on virtual excitation provided by an embodiment of the present invention, comprising:

[0141] A data acquisition module is used to obtain the active power, reactive power, and voltage effective value of the grid connection point;

[0142] An internal potential phase calculation module, used for calculating the internal potential phase according to the active power;

[0143] A voltage reference value calculation module, used for calculating a voltage reference value according to the reactive power, a preset reactive power reference value and a preset initial voltage reference value;

[0144] An internal potential amplitude calculation module, used for inputting the voltage effective value and the voltage reference value into a preset internal potential amplitude generation model, so that a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correcting and compensating the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputting the internal potential amplitude;

[0145] The converter control module is used to generate a PWM modulation signal according to the internal potential phase and the internal potential amplitude, and control the switch tube of the grid-type converter through the PWM modulation signal.

[0146] It should be noted that the device embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. In addition, in the accompanying drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which may be specifically implemented as one or more communication buses or signal lines. A person of ordinary skill in the art may understand and implement it without paying any creative effort.

[0147] Those skilled in the art can clearly understand that for the sake of convenience and brevity, the specific working process of the device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0148] Another preferred embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements a grid-type converter control method based on virtual excitation as described in any one of the above embodiments.

[0149] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, a cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0150] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the terminal device, and uses various interfaces and lines to connect various parts of the entire terminal device.

[0151] The memory can be used to store the computer program, and the processor realizes various functions of the terminal device by running or executing the computer program stored in the memory and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required for a function, etc.; the data storage area can store data created according to the use of the mobile phone, etc. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0152] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A control method for grid-connected converter based on virtual excitation. It is characterized in that include: Obtain the active power, reactive power, and voltage RMS of the grid connection point; Calculating the internal potential phase according to the active power; Calculating a voltage reference value according to the reactive power, a preset reactive power reference value and a preset initial voltage reference value; Inputting the voltage effective value and the voltage reference value into a preset internal potential amplitude generation model, so that a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correcting and compensating the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputting the internal potential amplitude; A PWM modulation signal is generated according to the internal potential phase and the internal potential amplitude, and the switch tube of the grid-type converter is controlled by the PWM modulation signal.

2. A control method for a grid-connected converter based on virtual excitation according to claim 1, It is characterized in that Get the effective value of the voltage at the grid connection point, including: Obtaining an initial voltage signal detected at a grid connection point; filtering the initial voltage signal to generate a voltage signal; Obtain the preset power frequency voltage cycle and calculate the voltage effective value according to the following formula: Where T is the power frequency voltage period, v f is the voltage signal after filtering.

3. A control method for a grid-connected converter based on virtual excitation according to claim 1, It is characterized in that Get the voltage RMS value of the grid connection point, including: Obtaining an initial voltage signal detected at a grid connection point; filtering the initial voltage signal to generate a voltage signal; Converting the voltage signal into a dq coordinate system to obtain a d-axis component and a q-axis component of the voltage signal; According to the d-axis component and the q-axis component of the voltage signal, the voltage effective value is calculated by the following formula; Among them, V d is the d-axis component of the voltage signal, V q is the q-axis component of the voltage signal.

4. A control method for a grid-connected converter based on virtual excitation according to claim 1, It is characterized in that The calculating the voltage reference value according to the reactive power, the preset reactive power reference value and the preset initial voltage reference value comprises: Calculating the reactive power and the reactive power reference value; Obtaining a grid-type control strategy for a grid-type converter; When the grid-type control strategy is a reactive power droop control strategy, a preset reactive power droop coefficient is obtained, and the voltage reference value is calculated according to the reactive power droop coefficient, the reactive power difference, and the initial voltage reference value; When the grid-type control strategy is a PI control strategy, a preset proportional gain and a preset integral time constant are obtained, and the voltage reference value is calculated based on the proportional gain, the integral time constant, the reactive power difference, and the initial voltage reference value.

5. A control method for a grid-connected converter based on virtual excitation according to claim 1, It is characterized in that The internal potential amplitude generation model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in series in sequence; The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including: The internal potential amplitude generation model outputs the internal potential amplitude through the following formula: Among them, E ref The internal potential amplitude generation model finally outputs the internal potential amplitude, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k 1 , k 2 , k 3 , k 4 are the number of the PID control unit, the inertial unit, the correction unit, and the linear transfer unit, respectively, G 1 (s) is the PID control unit, K P is the preset magnification factor, K I is the preset integral time constant, K D is the preset differential time constant, G 2 (s) is the inertial unit, K A is the preset proportionality factor, T A is the preset time constant, G 3 (s) is the correction unit, T 1 , T 2 are preset time constants, G 4 (s) is the linear transmission link, a 0 ……a n , b 0 ……b n are the coefficients of n-order and m-order polynomials respectively, and n and m are the orders of the polynomials respectively.

6. A control method for a grid-connected converter based on virtual excitation according to claim 1, It is characterized in that The internal potential amplitude generation model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one; The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including: The internal potential amplitude generation model outputs the internal potential amplitude through the following formula: E ref (s)=[k 5 (G 1 (s))+k 6 (G 2 (s))+k 7 (G 3 (s))+k 8 (G 4 (s))]ΔV(s); Among them, E ref is the internal potential amplitude finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k 5 , k 6 , k 7 , k 8 are the number of the PID control unit, the inertial unit, the correction unit, and the linear transfer unit, respectively, G 1 (s) is the PID control unit, G 2 (s) is the inertial unit, G 3 (s) is the correction unit, G 4 (s) is a linear transmission link.

7. A control method for a grid-connected converter based on virtual excitation according to claim 1, It is characterized in that The internal potential amplitude generation model is composed of a series structure sub-model and a parallel structure sub-model connected in series in sequence; The series structure sub-model is composed of a plurality of PID control units, a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units connected in series in sequence; The parallel structure sub-model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one; The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including: The internal potential amplitude generation model outputs the internal potential amplitude through the following formula: Among them, E ref is the internal potential amplitude finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k 1 , k 2 , k 3 , k 4 are the number of PID control units, inertial units, correction units, and linear transfer units in the series structure sub-model, k 5 , k 6 , k 7 , k 8 are the number of PID control units, inertial units, correction units, and linear transfer units in the parallel structure sub-model, G 1 (s) is the PID control unit, G 2 (s) is the inertial unit, G 3 (s) is the correction unit, G 4 (s) is a linear transmission link.

8. A control method for a grid-connected converter based on virtual excitation according to claim 1, It is characterized in that The internal potential amplitude generation model is composed of a series structure sub-model and a parallel structure sub-model connected in parallel in sequence; The series structure sub-model is composed of a plurality of PID control units, a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units connected in series in sequence; The parallel structure sub-model is composed of a plurality of the PID control units, a plurality of the inertial units, a plurality of the correction units, and a plurality of the linear transfer units connected in parallel one by one; The plurality of PID control units in the internal potential amplitude generation model outputs an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then corrects and compensates the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputs the internal potential amplitude, including: The internal potential amplitude generation model outputs the internal potential amplitude through the following formula: Among them, E ref is the internal potential amplitude finally output by the internal potential amplitude generation model, ΔV is the difference between the voltage effective value and the voltage reference value, s is the complex frequency, k 1 , k 2 , k 3 , k 4 are the number of PID control units, inertial units, correction units, and linear transfer units in the series structure sub-model, k 5 , k 6 , k 7 , k 8 are the number of PID control units, inertial units, correction units, and linear transfer units in the parallel structure sub-model, G 1 (s) is the PID control unit, G 2 (s) is the inertial unit, G 3 (s) is the correction unit, G 4 (s) is a linear transmission link.

9. A grid-connected converter control device based on virtual excitation, It is characterized in that include: A data acquisition module is used to obtain the active power, reactive power, and voltage effective value of the grid connection point; An internal potential phase calculation module, used for calculating the internal potential phase according to the active power; A voltage reference value calculation module, used for calculating a voltage reference value according to the reactive power, a preset reactive power reference value and a preset initial voltage reference value; An internal potential amplitude calculation module, used for inputting the voltage effective value and the voltage reference value into a preset internal potential amplitude generation model, so that a plurality of PID control units in the internal potential amplitude generation model output an initial internal potential amplitude according to the voltage effective value and the voltage reference, and then correcting and compensating the initial internal potential amplitude through a plurality of inertial units, a plurality of correction units, and a plurality of linear transfer units in the internal potential amplitude generation model, and finally outputting the internal potential amplitude; The converter control module is used to generate a PWM modulation signal according to the internal potential phase and the internal potential amplitude, and control the switch tube of the grid-type converter through the PWM modulation signal.

10. A terminal device, It is characterized in that It includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, it implements a grid-type converter control method based on virtual excitation as described in any one of claims 1 to 8.

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