A method and device for improving the stability of a multi-inverter grid-connected system with adaptive control

Abstract

The embodiment of the present invention provides a method and device for improving the stability of a multi-inverter grid-connected system with adaptive control. The method includes: obtaining grid information of a target grid-connected point; determining grid component information based on three-phase voltage information and three-phase current information; determining information such as voltage components and current components obtained by the inverter after receiving a control instruction issued by a first module and performing a first control action according to the grid component information; determining the grid impedance in the target axis coordinate system according to information such as voltage components and current components; determining the equivalent output admittance of the inverter based on grid information and the output power of the inverter; determining system stability according to grid impedance and the equivalent output admittance, and performing system stability operation when the system stability does not meet the preset stability conditions; through the present invention, the problem of safety risks of the grid system caused by insufficient stability of the grid system is solved, thereby achieving the effect of improving the stability of the grid system.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electrical engineering technology, and in particular to a method and device for improving the stability of a multi-inverter grid-connected system with adaptive control. Background Art

[0002] In the context of the construction of new power systems, a large number of new energy sources are connected to the grid through power electronic converters. The advantages of power electronic converters are fast dynamic response speed, strong controllability and high efficiency, while the disadvantages are small inertia, weak damping, and even negative impedance characteristics under the control loop, which causes stability problems such as wide-band unstable oscillation, seriously threatening the safe and stable operation of the system. During the operation of the grid-connected inverter, the grid impedance will change with the grid operation state. At the same time, the inverter output impedance will also change with the grid connection point voltage and inverter output power, resulting in unstable oscillation of the grid, and the instability frequency is uncertain.

[0003] In order to solve the problem of grid impedance change, the existing methods usually use active harmonic injection to measure grid impedance. Such methods are highly complex and difficult to implement in engineering practice, and the measurement accuracy is easily affected by the background harmonics of the grid. In order to solve the problem of broadband oscillation when the inverter is connected to the grid, the existing adaptive suppression method mainly determines the oscillation frequency by detecting the oscillation component, and then achieves oscillation suppression by adjusting the damper control parameters online. The shortcomings are: first, the detection of oscillation component and frequency is easily affected by the background harmonics of the grid, and the detection process requires a large amount of calculation and low accuracy; second, this method can only suppress oscillation after the system oscillates and becomes unstable, and cannot predict the occurrence of oscillation when the system stability margin is low, so it cannot effectively prevent oscillation instability. Summary of the invention

[0004] The embodiments of the present invention provide a method and device for improving the stability of a multi-inverter grid-connected system with adaptive control, so as to at least solve the problem of grid risk caused by insufficient stability of the grid system in the related art.

[0005] According to an embodiment of the present invention, a method for improving stability of a multi-inverter grid-connected system with adaptive control is provided, comprising:

[0006] Acquire grid information of the target grid-connected point, wherein the grid information includes output power of the inverter, three-phase voltage information of the target grid-connected point, and three-phase current information of the target grid-connected point;

[0007] Based on the three-phase voltage information and the three-phase current information, determine the grid component information, wherein the grid component information includes a grid phase angle, a grid frequency, a target shaft voltage component, and a target shaft current component;

[0008] Determine, according to the grid component information, target axis first voltage component information at a first moment, target axis first current component information at a first moment, first grid frequency at a first moment, target axis second voltage component information at a second moment, target axis second current component information at a second moment, and first grid phase angle at a second moment, obtained by the inverter performing a first control action after receiving a control instruction sent by the first module;

[0009] Determine the grid impedance in the target axis coordinate system according to the first voltage component information, the second voltage component information, the first current component information, and the second current component information;

[0010] Determining an equivalent output admittance of the inverter based on the grid information and the output power of the inverter;

[0011] The system stability is determined according to the grid impedance and the equivalent output admittance, and when the system stability does not meet a preset stability condition, a system stabilization operation is performed.

[0012] In an exemplary embodiment, determining system stability according to the grid impedance and the equivalent output admittance includes:

[0013] Constructing a system loop gain matrix according to the grid impedance and the equivalent output admittance;

[0014] Performing eigendecomposition processing on the system loop gain matrix to obtain eigenvalues ​​and eigenvalue frequency curves corresponding to the eigenvalues;

[0015] The system stability is determined according to the eigenvalue and the eigenvalue frequency curve.

[0016] In an exemplary embodiment, after determining the system stability according to the characteristic value frequency curve, the method further includes:

[0017] In a case where the characteristic value does not satisfy the characteristic value condition, the first module performs a damping compensation process through a target damper, wherein the system stabilizing operation includes the damping compensation process.

[0018] In an exemplary embodiment, when the characteristic value does not satisfy the characteristic value condition, the first module performs damping compensation processing by using a target damper, including:

[0019] Acquire a third voltage of the first capacitor, and perform a difference process between the third voltage and a preset reference voltage;

[0020] The first controller outputs a first axis current reference value according to the difference processing result; and when the second axis current reference value is a preset value, the target damper outputs a first axis current component and a second axis current component according to the three-phase voltage information;

[0021] A second controller determines a three-phase voltage reference value based on the first axis current component, the second axis current component, the first axis current reference value, and the second axis current reference value;

[0022] The damping compensation switch information is determined according to the three-phase voltage reference value and the virtual current, wherein the virtual current is obtained by filtering the target shaft voltage component through the target filter and then undergoing three-phase virtual transformation processing, and the three-phase virtual transformation processing includes performing three-phase changes on the filtering result and dividing the three-phase transformation result by a preset virtual impedance.

[0023] According to another embodiment of the present invention, there is provided a device for improving stability of a multi-inverter grid-connected system with adaptive control, comprising:

[0024] The first module is used to send control instructions to the inverter;

[0025] an inverter, configured to execute a first control action according to the control instruction;

[0026] The target damper is used to perform damping compensation processing when the characteristic value determined by the grid impedance and the equivalent output admittance of the inverter does not meet the characteristic value condition.

[0027] In an exemplary embodiment, it further includes:

[0028] A power grid information acquisition module, used to obtain power grid information of a target grid-connected point, wherein the power grid information includes output power of an inverter, three-phase voltage information of the target grid-connected point, and three-phase current information of the target grid-connected point;

[0029] A power grid component calculation module, used to determine power grid component information based on the three-phase voltage information and the three-phase current information, wherein the power grid component information includes a power grid phase angle, a power grid frequency, a target shaft voltage component, and a target shaft current component;

[0030] an information determination module, for determining, according to the grid component information, target axis first voltage component information at a first moment, target axis first current component information at a first moment, and first grid frequency at a first moment, and target axis second voltage component information at a second moment, target axis second current component information at a second moment, and first grid phase angle at a second moment, obtained by the inverter performing a first control action after receiving a control instruction sent by the first module;

[0031] An impedance determination module, configured to determine a grid impedance in a target axis coordinate system according to the first voltage component information, the second voltage component information, the first current component information, and the second current component information;

[0032] An admittance determination module, configured to determine an equivalent output admittance of the inverter based on the grid information and the output power of the inverter;

[0033] The system stability operation module is used to determine the system stability according to the grid impedance and the equivalent output admittance, and to perform system stability operation when the system stability does not meet the preset stability condition.

[0034] In an exemplary embodiment, the system stable operation module includes:

[0035] A matrix construction unit, used to construct a system loop gain matrix according to the grid impedance and the equivalent output admittance;

[0036] An eigenvalue determination unit, used for performing eigendecomposition processing on the system loop gain matrix to obtain eigenvalues ​​and eigenvalue frequency curves corresponding to the eigenvalues;

[0037] A stability judgment unit is used to determine the system stability according to the characteristic value and the characteristic value frequency curve.

[0038] In an exemplary embodiment, the apparatus further comprises:

[0039] A damping compensation module is used for, after the system stability is determined according to the characteristic value frequency curve, when the characteristic value does not meet the characteristic value condition, the first module performs damping compensation processing through a target damper, wherein the system stability operation includes the damping compensation processing.

[0040] According to yet another embodiment of the present invention, a computer-readable storage medium is provided, in which a computer program is stored, wherein the computer program is configured to execute the steps of any one of the above method embodiments when run.

[0041] According to yet another embodiment of the present invention, there is provided an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0042] Through the present invention, since the grid impedance and the like are monitored online and the grid stability is adjusted according to the change of the grid impedance, the problem of grid risk caused by insufficient stability of the grid system can be solved, and the effect of accurately regulating the stability margin frequency band of the multi-inverter grid-connected system can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a hardware structure block diagram of a mobile terminal of a method for improving stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention;

[0044] Figure 2 is a flow chart of a method for improving stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention;

[0045] Figure 3 is an example diagram of a grid-connected architecture applicable to a method for improving stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention;

[0046] Figure 4 is a schematic diagram of characteristic values ​​according to an embodiment of the present invention;

[0047] Figure 5 is a circuit structure and control structure diagram of a LV damper according to an embodiment of the present invention;

[0048] Figure 6 is a schematic diagram of a curve showing a change in real and imaginary parts of equivalent output admittance of an LV damper with frequency according to an embodiment of the present invention;

[0049] Figure 7 The present invention is a structural block diagram of a device for improving the stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and in combination with the embodiments.

[0051] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0052] The method embodiments provided in the embodiments of the present application can be executed in a mobile terminal, a computer terminal or a similar computing device. Taking running on a mobile terminal as an example, Figure 1 1 is a hardware structure block diagram of a mobile terminal of a method for improving the stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention. Figure 1 As shown, the mobile terminal may include one or more ( Figure 1Only one is shown in the figure) a processor 102 (the processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA) and a memory 104 for storing data, wherein the mobile terminal may also include a transmission device 106 and an input / output device 108 for communication functions. It can be understood by those skilled in the art that Figure 1 The structure shown is only for illustration and does not limit the structure of the mobile terminal. Figure 1 More or fewer components as shown, or with Figure 1 Different configurations are shown.

[0053] The memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as a computer program corresponding to a method for improving the stability of a multi-inverter grid-connected system with adaptive control in an embodiment of the present invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, to implement the above method. The memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include a memory remotely arranged relative to the processor 102, and these remote memories may be connected to the mobile terminal via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0054] The transmission device 106 is used to receive or send data via a network. The specific example of the above network may include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0055] In this embodiment, a method for improving the stability of a multi-inverter grid-connected system with adaptive control is provided. Figure 2 is a flow chart of a method for improving stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention. Figure 3 A grid-connected architecture applicable to a method for improving the stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention, wherein inverters 1 to n are connected in parallel to a grid-connected bus, and Z g is the grid impedance, v gThe adaptive control module (i.e., the first module, hereinafter referred to as the “module”) controls the q-axis current of the inverter to increase by ΔI by issuing a control instruction. q (Here, the q-axis current of inverter 2 is controlled as an example) and the three-phase voltage v of the grid connection point is collected abc , grid current i gabc Calculate the resistance R of the grid impedance g and inductor L g And by collecting the inverter output power (including P1, Q1, P2, Q2, ..., P n ,Q n ) and the grid-connected point voltage to calculate the total equivalent output admittance Y of the inverter eqs On this basis, by determining the system stability and calculating the system stability margin, when the system is unstable or the stability margin is lower than the threshold, the output frequency ω c Provide LV damper with improved system stability margin.

[0056] like Figure 2 As shown, the process includes the following steps:

[0057] Step S201, acquiring grid information of a target grid-connected point, wherein the grid information includes output power of an inverter, three-phase voltage information of the target grid-connected point, and three-phase current information of the target grid-connected point;

[0058] In this embodiment, the first module collects the three-phase voltage v of the grid connection point. abc (corresponding to the above three-phase voltage information) and three-phase grid current i gabc (corresponding to the above three-phase current information) and the output power of each inverter P1, Q1, P2, Q2, ..., P n ,Q n , where P is the active power and Q is the reactive power.

[0059] There may be multiple grid connection points and inverters in a power grid, and thus there may be multiple corresponding detected three-phase grid currents, three-phase grid voltages, and output powers of the inverters.

[0060] It should be noted that the three-phase current information includes the three-phase grid current i gabc , and can also include the three-phase grid current i gabc The transmission time point, current recording location and other information. Similarly, the three-phase voltage information can also include the three-phase grid voltage v abc The voltage records location and time and other information.

[0061] Step S202, determining grid component information based on the three-phase voltage information and the three-phase current information, wherein the grid component information includes a grid phase angle, a grid frequency, a target shaft voltage component, and a target shaft current component;

[0062] In this embodiment, based on the three-phase grid voltage v ab c, using three-phase phase-locked loop technology to obtain the phase angle θ g (corresponding to the aforementioned grid phase angle) and grid frequency ω g , and use abc / dq transformation (i.e. converting the three-phase current and voltage coordinate system into the two-phase current and voltage coordinate system) to obtain the DC component V of the voltage on the d and q axes (corresponding to the aforementioned target axis) of the grid connection point d 、V q (corresponding to the aforementioned target axis voltage component) and the DC component of the grid d and q axis current I d ,I q (corresponding to the aforementioned target shaft current component).

[0063] Step S203, determining, based on the grid component information, target axis first voltage component information at the first moment, target axis first current component information at the first moment, first grid frequency at the first moment, and target axis second voltage component information at the second moment, target axis second current component information at the second moment, and first grid phase angle at the second moment, obtained by the inverter performing a first control action after receiving a control instruction from the first module;

[0064] In this embodiment, at time t0 (corresponding to the first time mentioned above), the first module issues a control instruction to control the q-axis current of the inverter to increase by ΔI q (Here, control Figure 3 Taking the q-axis current of inverter 2 as an example), it should be noted that ΔI q It needs to be selected according to the actual situation. It should not be too small or too large. If it is too small, it may cause inaccurate grid impedance measurement. If it is too large, it will exceed the inverter capacity and cause inverter overshoot.

[0065] Similarly, at time t0, the first module records the voltage components of the grid connection point d and q axes (corresponding to the first voltage component of the target axis at the first moment) and the DC components of the grid d and q axis currents (corresponding to the first current component of the target axis at the first moment), which are recorded as V d (t0), V q (t0) and I gd (t0),I gq (t0); at the same time, record the grid frequency, denoted as ω g (t0) (corresponding to the first grid frequency at the aforementioned first moment).

[0066] At time t1 (corresponding to the aforementioned second time), the first module records the d-axis and q-axis voltage components of the grid connection point (corresponding to the second voltage component of the target axis at the second time) and the DC components of the d-axis and q-axis currents of the grid (corresponding to the second current component of the target axis at the second time), which are recorded as V d (t1), V q (t1) and I gd (t1),I gq (t1); while recording the phase angle θ g , denoted as θ g (t1) (corresponding to the first grid phase angle at the aforementioned second moment).

[0067] Also at time t1, the first module clears the q-axis current of the control inverter to increase by ΔI q Instructions.

[0068] Step S204, determining the grid impedance in the target axis coordinate system according to the first voltage component information, the second voltage component information, the first current component information, and the second current component information;

[0069] In this embodiment, the resistance R of the grid impedance is calculated g and inductor L g As shown in the following formula 1:

[0070]

[0071] Among them, ω0 is the fundamental frequency of the power grid, ΔI gd , ΔI gq , ΔV d , ΔV q The calculation formulas are shown in Formula 2-3:

[0072]

[0073]

[0074] Where Δθ=θ g (t1)-(t1-t0)gω g (t0).

[0075] Then, the grid impedance is calculated based on the resistance R g and inductor L g , we can get the grid impedance matrix Z' in the dq coordinate system g , where Z' g =[R g +sL g ,-ω0L g ;ω0L g ,R g +sL g], where s is the complex frequency domain Laplace operator.

[0076] Step S205, determining an equivalent output admittance of the inverter based on the grid information and the output power of the inverter;

[0077] In this embodiment, the equivalent output admittance Y of each inverter in the dq coordinate system can be calculated based on the collected inverter output power and grid connection point voltage (i.e., the three-phase grid voltage vabc contained in the aforementioned grid information): eq1 ,Y eq2 ,…,Y eqn (corresponding to the above equivalent output admittance), the total equivalent output admittance matrix Y′ of the inverter in the dq coordinate system eqs , the total equivalent output admittance matrix Y′ eqs It is the superposition of the equivalent output admittance of a single inverter, that is, Y′ eqs =Y eq1 +Y eq2 +...+Y eqn .

[0078] Among them, the equivalent output admittance of a single inverter can be obtained by the following methods:

[0079] 1. When a single inverter component and control parameters are known, they can be directly obtained according to the calculation method described in the open document Wen B, Dong D, Boroyevich D, et al. Impedance-Based Analysis of Grid-Synchronization Stability for Three-Phase Paralleled Converters [J]. IEEE Transactions on Power Electronics, 2016, 31(1): 26-38.

[0080] 2. When the individual inverter components and control parameters are unknown, the impedance measurement method can be used to obtain them. For details, please refer to the literature "Li Yang, Shuai Zhikang, Fang Junbin, et al. Stability verification method of multi-inverter system based on impedance measurement [J]. Automation of Electric Power Systems, 2021, 45(11): 95-101".

[0081] Step S206, determining system stability according to the grid impedance and the equivalent output admittance, and performing system stabilization operation when the system stability does not meet a preset stability condition.

[0082] In this embodiment, when the system stability is low, the damping parameters are automatically adjusted by the LV damper, thereby improving the system stability.

[0083] In the present application, step S204 and step S205 can be swapped, that is, step S205 can be executed first, and then step S204.

[0084] In an optional embodiment, determining the system stability according to the grid impedance and the equivalent output admittance includes:

[0085] Step S2061, constructing a system loop gain matrix according to the grid impedance and the equivalent output admittance;

[0086] In this embodiment, after the coordinate system conversion, based on the grid impedance matrix Z' obtained in the dq coordinate system g And the total equivalent output admittance matrix Y' of the inverter eqs , we can get the system loop gain matrix L m =Y′ eqs Z′ g .

[0087] Step S2062, performing eigendecomposition processing on the system loop gain matrix to obtain eigenvalues ​​and eigenvalue frequency curves corresponding to the eigenvalues;

[0088] In this embodiment, the loop gain matrix L is calculated according to the generalized Nyquist criterion within a certain frequency range (the maximum frequency is generally half of the inverter switching frequency). m Perform eigenvalue decomposition to obtain the loop gain matrix eigenvalues ​​λ1 and λ2 and their curves with respect to frequency.

[0089] Step S2063: determining the system stability according to the eigenvalue and the eigenvalue frequency curve.

[0090] In this embodiment, whether the system is stable can be determined based on whether the eigenvalues ​​λ1 and λ2 are within a specific range or a preset value, or based on the curvature of the eigenvalue frequency curve or the pattern of the curve.

[0091] For example, taking the eigenvalue λ1 as an example, Figure 4 is the curve of the real and imaginary part of the eigenvalue λ1 changing with frequency. We need to pay attention to the frequency f corresponding to the imaginary part of the eigenvalue λ1 Im[λ1] being zero s1 Next, we check whether its real part Re[λ1] is greater than -1. If it is less than -1, it means that the system is unstable. If it is greater than -1, it means that the system is stable.

[0092] In an optional embodiment, after determining the system stability according to the characteristic value frequency curve, the method further includes:

[0093] Step S207: when the characteristic value does not satisfy the characteristic value condition, the first module performs damping compensation processing through the target damper, wherein the system stable operation includes the damping compensation processing.

[0094] In this embodiment, even if the system is stable, there may be a situation where the stability margin is not high, and the system still has the risk of instability. Therefore, when the imaginary part of the eigenvalue is less than a certain value, damping compensation needs to be performed; for example, at the frequency corresponding to the imaginary part of the eigenvalue being zero, when the real part of the eigenvalue is less than -0.3, the LV damper needs to be started for damping compensation.

[0095] In an optional embodiment, when the characteristic value does not satisfy the characteristic value condition, the first module performs damping compensation processing through a target damper, including:

[0096] Step S2071, obtaining a third voltage of the first capacitor, and performing a difference process between the third voltage and a preset reference voltage;

[0097] In this embodiment, the LV damper circuit provided in this embodiment is a control structure such as Figure 5 As shown. The LV damper is mainly composed of a DC voltage stabilizing capacitor C dc (corresponding to the aforementioned first capacitor), a three-phase six-bridge arm circuit composed of six high-frequency devices S1 to S6, and an inductor L f and capacitor C f When the LV damper is running, the DC voltage stabilizing capacitor C dc The voltage V dc (corresponding to the aforementioned first voltage).

[0098] Step S2072, the first controller outputs a first axis current reference value according to the difference processing result; and when the second axis current reference value is a preset value, the target damper outputs a first axis current component and a second axis current component according to the three-phase voltage information;

[0099] In this embodiment, the DC voltage stabilizing capacitor C dc The voltage V dc With the voltage reference value V dcref (corresponding to the aforementioned reference voltage) is given to the PI controller, and the PI controller output is used as the q-axis current reference value I qref (Corresponding to the aforementioned first axis current reference value).

[0100] Step S2073, the second controller determines a three-phase voltage reference value based on the first axis current component, the second axis current component, the first axis current reference value, and the second axis current reference value; sets the d-axis current reference value I dref(corresponding to the aforementioned second axis current reference value) is zero (corresponding to the aforementioned preset value), and the LV damper outputs a three-phase current i a 、i b 、i c After abc / dq transformation, the d-axis and q-axis components I are obtained. d (corresponding to the aforementioned first axis current component) and I q (corresponding to the aforementioned second axis current component), where the phase angle θ used in the dq / abc transformation is determined by the three-phase voltage v at the grid connection point. a 、v b 、v c Obtained through a phase-locked loop.

[0101] Step S2074, determining the damping compensation switch information according to the three-phase voltage reference value and the virtual current, wherein the virtual current is obtained by filtering the target shaft voltage component through the target filter and then performing three-phase virtual transformation processing, and the three-phase virtual transformation processing includes performing three-phase changes on the filtering result and dividing the three-phase transformation result by the preset virtual impedance.

[0102] In this embodiment, the d-axis and q-axis current reference values ​​I dref and I qref Respectively with I d and I q The difference is sent to the current loop PI controller. The output of the current loop PI controller is transformed by dq / abc to obtain the reference value v aref 、v bref 、v cref .

[0103] At the same time, the three-phase voltage v a 、v b 、v c After abc / dq transformation, we get the d-axis and q-axis components V d and V q , V d and V q After the bandpass filter (BPF), the dq / abc conversion is performed and divided by the virtual impedance R v Get the virtual current i av 、i bv 、i cv ; Finally, the reference value v aref 、v bref 、v cref and i av 、i bv 、i cv The signals are added together and the switching signals for controlling the three-phase six-bridge arms are obtained through SPWM.

[0104] In the above process, the BPF transfer function G hfor:

[0105]

[0106] Wherein, parameter B is the bandwidth of the bandpass filter, and the value of B can be set according to actual needs. In the present invention, the value is 200 Hz; parameter K flg1 and K flg2 It is related to the eigenvalue of the loop gain matrix. When the eigenvalues ​​of the loop gain matrix meet the stability margin requirements, K flg1 =K flg2 =0; when only one eigenvalue of the loop gain matrix meets the stability margin requirement, K flg1 =1, K flg2 =0; when the eigenvalues ​​of the loop gain matrix do not meet the stability margin requirements, K flg1 =K flg2 =1; parameter ω x1 and ω x2 is the center frequency of the bandpass filter. These two parameters are respectively related to the frequency ω sent by the module. c1 and ω c2 Related, the value is obtained as follows:

[0107] Ignoring the influence of the voltage outer loop with low response speed and the dq coupling term with small value, the equivalent output admittance matrix Y' of the LV damper in the dq coordinate system ad , Y' ad =[Y ad ,0;0,Y ad ], where Y ad The specific expression is:

[0108]

[0109] Among them, Z f is the LV damper LC series impedance, i.e. Z f =sL f +1 / sC f ; G i is the PI control transfer function of the current control loop, G i =k p +k i / s,k p and k i They are the proportional coefficient and integral coefficient of the current PI controller respectively.

[0110] Figure 6 The parameter ω is shown x1 and ω x2 The real and imaginary parts of the LV damper equivalent output admittance Yad vary with frequency when the speeds are 2π*800rad / s and 2π*1200rad / s, respectively. peak1 and fpeak2 Respectively with parameter ω x1 and ω x2 directly related, so it can be Y ad The specific expression of f peak1 and f peak2 With parameter ω x1 and ω x2 To ensure that the LV damper can effectively compensate for the damping of the multi-inverter grid-connected system, f peak1 and f peak2 The value is determined by the frequency ω sent by the module x1 and ω x2 Determine, that is, f peak1 =ω c1 / 2π and f peak2 =ω c2 / 2π. In determining f peak1 and f peak2 After that, the bandpass filter parameter ω can be obtained by reverse table lookup x1 and ω x2 .

[0111] After completing the above steps, wait for T c time, and then repeat the above steps, where T c The value can be set according to demand. The present invention takes 10 minutes, that is, the module measures the grid impedance once every 10 minutes, and calculates the system stability margin to adjust the LV damper parameters to improve system stability.

[0112] Through the description of the above implementation methods, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0113] In this embodiment, a device for improving the stability of a multi-inverter grid-connected system with adaptive control is also provided. The device is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware for a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0114] Figure 7 is a structural block diagram of a device for improving stability of a multi-inverter grid-connected system with adaptive control according to an embodiment of the present invention. Figure 7 As shown, the device comprises:

[0115] The first module 71 is used to send a control instruction to the inverter;

[0116] The inverter 72 is used to perform a first control action according to the control instruction;

[0117] The target damper 73 is used to perform damping compensation processing when the characteristic value determined by the grid impedance and the equivalent output admittance of the inverter does not meet the characteristic value condition.

[0118] In an optional embodiment, the device further comprises:

[0119] A power grid information acquisition module, used to obtain power grid information of a target grid-connected point, wherein the power grid information includes output power of an inverter, three-phase voltage information of the target grid-connected point, and three-phase current information of the target grid-connected point;

[0120] A power grid component calculation module, used to determine power grid component information based on the three-phase voltage information and the three-phase current information, wherein the power grid component information includes a power grid phase angle, a power grid frequency, a target shaft voltage component, and a target shaft current component;

[0121] an information determination module, for determining, according to the grid component information, target axis first voltage component information at a first moment, target axis first current component information at a first moment, and first grid frequency at a first moment, and target axis second voltage component information at a second moment, target axis second current component information at a second moment, and first grid phase angle at a second moment, obtained by the inverter performing a first control action after receiving a control instruction sent by the first module;

[0122] An impedance determination module, configured to determine a grid impedance in a target axis coordinate system according to the first voltage component information, the second voltage component information, the first current component information, and the second current component information;

[0123] An admittance determination module, configured to determine an equivalent output admittance of the inverter based on the grid information and the output power of the inverter;

[0124] The system stability operation module is used to determine the system stability according to the grid impedance and the equivalent output admittance, and to perform system stability operation when the system stability does not meet the preset stability condition.

[0125] In an optional embodiment, the system stable operation module includes:

[0126] A matrix construction unit, used to construct a system loop gain matrix according to the grid impedance and the equivalent output admittance;

[0127] An eigenvalue determination unit, used for performing eigendecomposition processing on the system loop gain matrix to obtain eigenvalues ​​and eigenvalue frequency curves corresponding to the eigenvalues;

[0128] A stability judgment unit is used to determine the system stability according to the characteristic value and the characteristic value frequency curve.

[0129] In an optional embodiment, the device further comprises:

[0130] A damping compensation module is used for, after the system stability is determined according to the characteristic value frequency curve, when the characteristic value does not meet the characteristic value condition, the first module performs damping compensation processing through a target damper, wherein the system stability operation includes the damping compensation processing.

[0131] It should be noted that the above modules can be implemented by software or hardware. For the latter, it can be implemented in the following ways, but not limited to: the above modules are all located in the same processor; or the above modules are located in different processors in any combination.

[0132] An embodiment of the present invention further provides a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to execute the steps of any of the above method embodiments when running.

[0133] In an exemplary embodiment, the computer-readable storage medium may include, but is not limited to, various media that can store computer programs, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk.

[0134] An embodiment of the present invention further provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0135] In an exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor.

[0136] For specific examples in this embodiment, reference may be made to the examples described in the above embodiments and exemplary implementation modes, and this embodiment will not be described in detail herein.

[0137] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0138] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the stability of a multi-inverter grid-connected system with adaptive control, characterized in that: include: Acquire grid information of the target grid-connected point, wherein the grid information includes output power of the inverter, three-phase voltage information of the target grid-connected point, and three-phase current information of the target grid-connected point; Based on the three-phase voltage information and the three-phase current information, determine the grid component information, wherein the grid component information includes a grid phase angle, a grid frequency, a target shaft voltage component, and a target shaft current component; Determine, according to the grid component information, target axis first voltage component information at a first moment, target axis first current component information at a first moment, first grid frequency at a first moment, target axis second voltage component information at a second moment, target axis second current component information at a second moment, and first grid phase angle at a second moment, obtained by the inverter performing a first control action after receiving a control instruction sent by the first module; Determine the grid impedance in the target axis coordinate system according to the target axis first voltage component information, the target axis second voltage component information, the target axis first current component information, and the target axis second current component information; Determining an equivalent output admittance of the inverter based on the grid information and the output power of the inverter; Determining system stability according to the grid impedance and the equivalent output admittance, and performing system stabilization operation when the system stability does not meet a preset stability condition; Wherein, determining the system stability according to the grid impedance and the equivalent output admittance includes: Constructing a system loop gain matrix according to the grid impedance and the equivalent output admittance; Performing eigendecomposition processing on the system loop gain matrix to obtain eigenvalues ​​and eigenvalue frequency curves corresponding to the eigenvalues; The system stability is determined according to the eigenvalue and the eigenvalue frequency curve.

2. The method according to claim 1, characterized in that After determining the system stability according to the characteristic value frequency curve, the method further includes: In a case where the characteristic value does not satisfy the characteristic value condition, the first module performs a damping compensation process through a target damper, wherein the system stabilizing operation includes the damping compensation process.

3. The method according to claim 2, characterized in that When the characteristic value does not satisfy the characteristic value condition, the first module performs damping compensation processing through the target damper, including: Acquire a third voltage of the first capacitor, and perform a difference process between the third voltage and a preset reference voltage; The first controller outputs a first axis current reference value according to the difference processing result; and when the second axis current reference value is a preset value, the target damper outputs a first axis current component and a second axis current component according to the three-phase voltage information; A second controller determines a three-phase voltage reference value based on the first axis current component, the second axis current component, the first axis current reference value, and the second axis current reference value; The damping compensation switch information is determined according to the three-phase voltage reference value and the virtual current, wherein the virtual current is obtained by filtering the target shaft voltage component through the target filter and then undergoing three-phase virtual transformation processing, and the three-phase virtual transformation processing includes performing three-phase changes on the filtering result and dividing the three-phase transformation result by a preset virtual impedance.

4. An adaptively controlled multi-inverter grid-connected system stability improvement device, characterized in that: include: The first module is used to send control instructions to the inverter; an inverter, configured to execute a first control action according to the control instruction; A target damper is used to perform damping compensation processing when the characteristic value determined by the grid impedance and the equivalent output admittance of the inverter does not meet the characteristic value condition; Also includes: A power grid information acquisition module, used to obtain power grid information of a target grid-connected point, wherein the power grid information includes output power of an inverter, three-phase voltage information of the target grid-connected point, and three-phase current information of the target grid-connected point; A power grid component calculation module, used to determine power grid component information based on the three-phase voltage information and the three-phase current information, wherein the power grid component information includes a power grid phase angle, a power grid frequency, a target shaft voltage component, and a target shaft current component; An information determination module, used to determine, according to the grid component information, target axis first voltage component information at a first moment, target axis first current component information at a first moment, and first grid frequency at a first moment, as well as target axis second voltage component information at a second moment, target axis second current component information at a second moment, and first grid phase angle at a second moment, obtained by the inverter performing a first control action after receiving a control instruction sent by the first module; An impedance determination module, used to determine the grid impedance in the target axis coordinate system according to the target axis first voltage component information, the target axis second voltage component information, the target axis first current component information and the target axis second current component information; An admittance determination module, configured to determine an equivalent output admittance of the inverter based on the grid information and the output power of the inverter; A system stability operation module, used to determine the system stability according to the grid impedance and the equivalent output admittance, and to perform system stability operation when the system stability does not meet the preset stability condition; Wherein, the system stable operation module includes: A matrix construction unit, used to construct a system loop gain matrix according to the grid impedance and the equivalent output admittance; An eigenvalue determination unit, used for performing eigendecomposition processing on the system loop gain matrix to obtain eigenvalues ​​and eigenvalue frequency curves corresponding to the eigenvalues; A stability judgment unit is used to determine the system stability according to the characteristic value and the characteristic value frequency curve.

5. The device according to claim 4, characterized in that The device also includes: A damping compensation module is used for, after the system stability is determined according to the eigenvalue frequency curve, when the eigenvalue does not meet the eigenvalue condition, the first module performs damping compensation processing through a target damper, wherein the system stabilization operation includes the damping compensation processing.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program is configured to execute the method according to any one of claims 1 to 3 when executed.

7. An electronic device comprising a memory and a processor, characterized in that: A computer program is stored in the memory, and the processor is configured to run the computer program to perform the method according to any one of claims 1 to 3.

Images