Control methods, electronic equipment, and grid-connected inverters for current source analog grid construction

Abstract

This invention provides a control method, electronic device, and grid-connected inverter for current source simulated grid construction. The method includes: acquiring the current frequency of the grid connection point; determining the current frequency offset and the current frequency change rate of the grid connection point based on the current frequency; determining the active power adjustment amount for current source simulated grid construction based on the current frequency offset and the current frequency change rate of the grid connection point; the active power adjustment amount for current source simulated grid construction includes the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter and the active power adjustment amount of the inertia response of the grid-connected inverter; and performing grid-connected control on the grid-connected inverter based on the active power adjustment amount for current source simulated grid construction to achieve current source simulated grid construction. This application can simulate the output characteristics of traditional current source grid construction, enabling current source-type grid-connected control to possess, to a certain extent, the performance characteristics of voltage source-type grid construction, thereby improving the stability of the power grid when a current source is connected to the grid.

Description

Technical Field

[0001] This invention relates to the field of grid construction technology, and in particular to a control method, electronic equipment, and grid-connected inverter for current source simulated grid construction. Background Technology

[0002] The gradual increase in the coverage of distributed renewable energy in the power system has avoided the problem of high energy consumption in traditional power generation and greatly improved resource utilization.

[0003] Currently, grid-connected inverters adopt the mainstream grid-following control method, under which the grid-connected inverter can be equivalent to a current source. However, this control method lacks spinning reserve capacity and rotational inertia, reducing grid stability. Using virtual synchronous machine control can simulate the output characteristics of synchronous generators, which can increase grid inertia to some extent and thus enhance grid stability; however, it is prone to oscillations in strong grid environments.

[0004] Therefore, how to improve the stability of the power grid when current sources are connected to the grid is an urgent problem to be solved. Summary of the Invention

[0005] This invention provides a control method, electronic equipment, and grid-connected inverter for simulating current source grid connection, in order to solve the problem of poor grid stability when traditional current sources are connected to the grid.

[0006] In a first aspect, embodiments of the present invention provide a control method for a current source analog network, comprising:

[0007] Obtain the current frequency of the grid connection point; the grid connection point is the connection point where the grid-connected inverter is connected to the power grid.

[0008] Based on the current frequency of the grid connection point, determine the current frequency offset and the current frequency change rate of the grid connection point;

[0009] The active power adjustment of the current source simulated grid is determined based on the current frequency offset and the current frequency change rate of the grid connection point. The active power adjustment of the current source simulated grid includes the active power adjustment of the primary frequency regulation response of the grid-connected inverter and the active power adjustment of the inertia response of the grid-connected inverter.

[0010] Based on the active power adjustment of the current source simulated grid, the grid-connected inverter is controlled to follow the grid, so as to realize the current source simulated grid.

[0011] In one possible implementation, the active power adjustment amount for the simulated grid connection of the current source is determined based on the current frequency offset and the current frequency change rate of the grid connection point, including:

[0012] Based on the current frequency offset at the grid connection point, determine the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter;

[0013] Determine the active power adjustment amount of the grid-connected inverter inertia response based on the current frequency change rate at the grid connection point.

[0014] Based on the active power adjustment of the primary frequency regulation response and the active power adjustment of the inertia response of the grid-connected inverter, the active power adjustment of the current source simulated grid is determined.

[0015] In one possible implementation, the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter is determined based on the current frequency offset of the grid connection point, including:

[0016] according to Determine the active power adjustment P of the primary frequency regulation response of the grid-connected inverter. f Among them, K f P is the active frequency modulation coefficient. n f is the rated power of the grid-connected inverter. N Δf is the reference frequency of the power grid, and Δf is the current frequency offset at the grid connection point.

[0017] In one possible implementation, the active power adjustment of the grid-connected inverter's inertia response is determined based on the current frequency change rate at the grid connection point, including:

[0018] according to Determine the active power adjustment P of the inertia response of the grid-connected inverter. in Among them, P n f is the rated power of the grid-connected inverter. N T is the reference frequency of the power grid. J The inertial time constant; This represents the current frequency change rate at the grid connection point.

[0019] In one possible implementation, before performing grid-connected inverter grid-following control based on the active power adjustment of the current source simulated grid to achieve current source simulated grid construction, the control method for current source simulated grid construction also includes:

[0020] Obtain the effective value of the current voltage at the grid connection point;

[0021] Calculate the voltage difference between the effective value of the current voltage at the grid connection point and the rated voltage at the grid connection point;

[0022] Based on the voltage difference, the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter is determined, and the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter is used as the reactive power adjustment of the current source simulated grid.

[0023] Accordingly, based on the active power adjustment of the current source simulated grid, grid-connected inverters are subjected to grid-following control to achieve current source simulated grid construction, including:

[0024] Based on the active power adjustment and reactive power adjustment of the current source simulated network, grid-connected inverters are controlled to follow the grid, so as to realize the current source simulated network.

[0025] In one possible implementation, the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter is determined based on the voltage difference, including:

[0026] according to Determine the reactive power adjustment Q of the primary voltage regulation response of the grid-connected inverter. v Among them, K v S is the reactive power voltage regulation coefficient. N The rated capacity of the virtual synchronous machine is given, where ΔU is the voltage difference. N This is the rated voltage at the grid connection point.

[0027] In one possible implementation, grid-connected inverters are controlled based on the active power adjustment of the current source-simulated grid, including:

[0028] Obtain the active power setpoint and use the sum of the active power setpoint and the active power adjustment of the current source simulated network as the new active power setpoint.

[0029] Based on the new active power setpoint, the grid-connected inverter is subjected to grid-type control.

[0030] In one possible implementation, the rate of change of the current frequency of the grid connection point is determined based on the current frequency of the grid connection point, including:

[0031] Get the current location identifier;

[0032] Retrieve the frequency corresponding to the current location identifier stored in a pre-created array;

[0033] The current frequency change rate of the grid connection point is determined based on the current frequency of the grid connection point, the frequency corresponding to the current positioning identifier, and the duration of a preset number of cycles; the preset number is the size of the array.

[0034] Update the frequency corresponding to the current location identifier stored in the array to the current frequency of the grid connection point, and update the current location identifier.

[0035] Secondly, embodiments of the present invention provide a control device for a current source analog network, comprising:

[0036] The acquisition module is used to acquire the current frequency of the grid connection point; the grid connection point is the connection point where the grid-connected inverter is connected to the power grid.

[0037] The frequency calculation module is used to determine the current frequency offset and the current frequency change rate of the grid connection point based on the current frequency of the grid connection point.

[0038] The active power adjustment module is used to determine the active power adjustment amount of the current source simulated network based on the current frequency offset and the current frequency change rate of the grid connection point. The active power adjustment amount of the current source simulated network includes the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter and the active power adjustment amount of the inertia response of the grid-connected inverter.

[0039] The control module is used to perform grid-connected inverter grid-following control based on the active power adjustment of the current source simulated grid, so as to realize the current source simulated grid.

[0040] Thirdly, embodiments of the present invention provide an electronic device, including a memory and a processor. The memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the control method for current source simulation network as described in the first aspect or any possible implementation of the first aspect.

[0041] Fourthly, embodiments of the present invention provide a grid-connected inverter, including the electronic equipment described in the third aspect above.

[0042] Fifthly, embodiments of the present invention provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the control method for current source simulation network construction as described in the first aspect or any possible implementation thereof.

[0043] This invention provides a control method, electronic device, and grid-connected inverter for current source simulated grid construction. The method simulates the active power adjustment of the primary frequency regulation response and the active power adjustment of the inertia response of the grid-connected inverter using the current frequency offset and the current frequency change rate of the grid connection point. This yields the active power adjustment of the current source simulated grid construction. Based on this active power adjustment, the grid-connected inverter is controlled in a grid-connected manner, thus simulating the active power output characteristics of a traditional current source in grid construction. This allows the current source-type grid-connected control to exhibit, to some extent, the characteristics of a voltage source-type grid construction, thereby improving the stability of the power grid when a current source is connected to the grid. Furthermore, compared to traditional control methods, the method provided in this application requires simpler control loop modification; only the corresponding control for the active power adjustment of the current source simulated grid construction needs to be added to the main control loop. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a typical VSG control block diagram;

[0046] Figure 2 This is a flowchart illustrating a control method for a current source simulation network according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the control loop corresponding to the control method for current source simulation network provided in an embodiment of the present invention;

[0048] Figure 4 This is a schematic flowchart of frequency calculation provided in an embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of the control loop corresponding to the control method for current source simulation network construction provided in another embodiment of the present invention;

[0050] Figure 6 This is a schematic diagram of the experimental verification results of a single frequency modulation provided in an embodiment of the present invention;

[0051] Figure 7 This is a schematic diagram of the experimental verification results of the inertial response provided in an embodiment of the present invention;

[0052] Figure 8 This is a schematic diagram of the control device for simulating a current source network according to an embodiment of the present invention;

[0053] Figure 9 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0054] The present application will be described more clearly below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the function of the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These all fall within the protection scope of the present application.

[0055] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0056] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0057] In the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0058] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0059] Furthermore, the term "multiple" mentioned in the embodiments of this application should be interpreted as two or more.

[0060] As mentioned earlier, the most mainstream control strategy in grid-connected inverters of current distributed generation systems is grid-following control, which uses a phase-locked loop (PLL) to directionally control the grid voltage. In this control mode, the grid-connected inverter can be equivalent to a current source. When the grid is a strong grid with low impedance, the current source mode not only maximizes the utilization rate of renewable energy but also ensures high grid-connected power quality. It also boasts advantages such as strong controllability, ease of achieving maximum power point tracking (MPPT) control, and strong anti-disturbance capability for multi-unit parallel operation. However, due to its lack of spinning reserve capacity and rotational inertia, it causes a decrease in system inertia, reducing system stability. To address this issue, the Virtual Synchronous Generator (VSG) control strategy has been proposed in related technologies. Figure 1 This is a typical control block diagram for a VSG. The control equations for the loop of a typical VSG are:

[0061]

[0062] In the above formula, P ref and P e These are the active power command and the actual active power output from the VSG, respectively; Q ref and Q e These are the VSG output reactive power command and the actual output reactive power, respectively; ω o ω ref U n U and U represent the rated and actual output voltage frequency of the VSG, the grid output voltage amplitude, and the grid rated voltage amplitude, respectively. D, J, k q k u These are the VSG frequency damping coefficient, VSG virtual inertia coefficient, VSG voltage droop coefficient, and VSG reactive inertia coefficient, respectively; E is the VSG reactive loop output excitation voltage.

[0063] VSG control strategy can effectively improve the damping and inertia of the power grid and enhance its stability by simulating the characteristics of a synchronous machine. However, it is prone to oscillations in strong grid environments. In addition, VSG technology is currently rarely used, and its practical application requires further research and verification.

[0064] Therefore, how to improve the stability of the power grid when current sources are connected to the grid is an urgent problem to be solved.

[0065] To address the aforementioned issues, this application provides a control method for current source-simulated grid construction. This method simulates the active power of the primary frequency regulation response and the active power of the inertia response of the grid-connected inverter, thereby simulating the output characteristics of the traditional current source for grid construction. This allows the current source-type grid-connected control to possess, to some extent, the performance characteristics of voltage source-type grid construction, thereby improving the stability of the power grid when the current source is connected to the grid.

[0066] The following is for reference. Figures 2 to 4 This application describes a control method for a current source simulation network provided according to exemplary embodiments. The embodiments of this application can be applied to any applicable scenario.

[0067] It should be noted that the embodiments of this application can be applied to electronic devices, such as servers, computers, or controllers, and the control method for current source simulation network provided by the exemplary embodiments of this application can be executed on such devices.

[0068] It should be noted that the control method for simulating a current source network provided in the exemplary embodiments of this application can be executed on the same device or on different devices.

[0069] See Figure 2 The diagram illustrates a flowchart of the control method for current source simulation network construction provided in an embodiment of the present invention. The control method for the aforementioned current source simulation network construction may include:

[0070] In S201, obtain the current frequency of the grid connection point; the grid connection point is the connection point where the grid-connected inverter is connected to the power grid.

[0071] See Figure 3 The connection point can be Figure 3 The PCC is located in the middle. To the left of the PCC is the grid-connected inverter, and to the right of the PCC is the power grid.

[0072] In this embodiment, the current frequency of the grid connection point can be obtained through a phase-locked loop (PLL).

[0073] In S202, the current frequency offset and the current frequency change rate of the grid connection point are determined based on the current frequency of the grid connection point.

[0074] The current frequency offset of the grid connection point can be the difference between the current frequency of the grid connection point and the reference frequency of the power grid.

[0075] The rate of change of the current frequency of the grid connection point can be the ratio of the difference between the current frequency of the grid connection point and the historical frequency of the grid connection point to the duration of the interval between the current frequency and the historical frequency of the grid connection point.

[0076] For example, if the frequency of the grid connection point obtained in the current cycle is taken as the current frequency of the grid connection point, and the frequency of the grid connection point obtained in the previous cycle is taken as the historical frequency of the grid connection point, then the rate of change of the current frequency of the grid connection point can be the ratio of the difference between the frequency of the grid connection point obtained in the current cycle and the frequency of the grid connection point obtained in the previous cycle to the duration of a single cycle.

[0077] In some possible implementations, to improve the accuracy of the current frequency change rate at the grid connection point, the frequency change rate for multiple consecutive cycles can be calculated, and then the average value can be taken to obtain the current frequency change rate at the grid connection point.

[0078] In S203, the active power adjustment amount of the current source simulated network is determined based on the current frequency offset of the grid connection point and the current frequency change rate of the grid connection point. The active power adjustment amount of the current source simulated network includes the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter and the active power adjustment amount of the inertia response of the grid-connected inverter.

[0079] Frequency regulation control is the response of active power to the grid connection point frequency. It is mainly reflected in the response of the grid-connected inverter's active power to the steady-state frequency deviation (reflected in the current frequency offset) and the dynamic frequency change (reflected in the current frequency change rate), which is the primary frequency regulation and inertia response.

[0080] To simulate the primary frequency regulation and inertia response characteristics of the grid, this embodiment calculates the active power adjustment of the primary frequency regulation response and the active power adjustment of the inertia response of the grid-connected inverter using the current frequency offset and the current frequency change rate of the grid connection point, respectively. Then, based on these active power adjustment values, the active power adjustment of the current source simulated grid is determined. The active power adjustment of the current source simulated grid can be the sum of the active power adjustment values ​​of the primary frequency regulation response and the active power adjustment values ​​of the inertia response of the grid-connected inverter.

[0081] In S204, the grid-connected inverter is controlled to follow the grid based on the active power adjustment of the current source simulated grid to realize the current source simulated grid.

[0082] In this embodiment, based on the grid-connected inverter current source grid-connected control, the active power adjustment of the above-mentioned current source simulated grid construction is added. By comprehensively controlling the grid-connected inverter to follow the grid, current source simulated grid construction can be realized. This allows the more widely used and technically mature current source grid-following control strategy to have voltage source grid construction function to a certain extent.

[0083] This application embodiment analyzes the external characteristics of the output power of the voltage source type grid control strategy, and adds corresponding functions to the current source control block diagram to enable the grid control to have grid performance characteristics to a certain extent, thereby improving grid stability.

[0084] Specifically, in this embodiment, the active power adjustment of the primary frequency regulation response and the active power adjustment of the inertia response of the grid-connected inverter can be simulated by the current frequency offset and the current frequency change rate of the grid connection point. This allows for the acquisition of the active power adjustment of the current source simulated grid. Based on this active power adjustment, the grid-connected inverter is subjected to grid-following control, thereby simulating the output characteristics of the traditional current source for grid-connected active power. This enables the current source-type grid-following control to possess, to some extent, the characteristics of voltage source-type grid-connected control, thus improving the stability of the power grid when the current source is connected to the grid. Furthermore, compared with traditional control methods, the method provided in this embodiment requires simpler control loop modification, only needing to add corresponding control of the active power adjustment of the current source simulated grid on the main control loop.

[0085] The foregoing embodiments illustrate the overall process of current source simulation network construction. The following, in conjunction with... Figure 3 This section provides a more detailed explanation of how to determine the active power adjustment amount for a current source simulated network and how to perform grid-connected inverter control based on the active power adjustment amount. First, it introduces how to determine the active power adjustment amount for a current source simulated network.

[0086] In some embodiments, S203 may include:

[0087] Based on the current frequency offset at the grid connection point, determine the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter;

[0088] Determine the active power adjustment amount of the grid-connected inverter inertia response based on the current frequency change rate at the grid connection point.

[0089] Based on the active power adjustment of the primary frequency regulation response and the active power adjustment of the inertia response of the grid-connected inverter, the active power adjustment of the current source simulated grid is determined.

[0090] The response of the active power of the grid-connected inverter to the steady-state frequency deviation is the primary frequency regulation response of the grid-connected inverter. The steady-state frequency deviation is reflected in the current frequency offset. Therefore, the active power adjustment of the primary frequency regulation response of the grid-connected inverter can be calculated based on the current frequency offset of the grid connection point.

[0091] Among them, see Figure 3 The formula for calculating the active power adjustment of the primary frequency regulation response of the grid-connected inverter, based on the current frequency offset at the grid connection point, can include: Among them, P f K represents the active power of the primary frequency regulation response of the grid-connected inverter. f P is the active frequency regulation coefficient. n f is the rated power of the grid-connected inverter. N Δf is the reference frequency of the power grid, and Δf is the current frequency offset at the grid connection point.

[0092] It should be noted that, Figure 3 k in f This represents a proportional element, where P is the value of P. f The constant part, whose value is

[0093] The response of the active power of the grid-connected inverter to the dynamic change of frequency is the inertia response of the grid-connected inverter. The dynamic change of frequency is reflected in the current frequency change rate. Therefore, the active power of the grid-connected inverter inertia response can be calculated based on the current frequency change rate of the grid connection point.

[0094] Among them, see Figure 3 The formula for calculating the active power of the grid-connected inverter's inertial response, based on the current frequency change rate at the grid connection point, can include: Among them, P in P represents the active power of the inertial response of the grid-connected inverter. n f is the rated power of the grid-connected inverter.N T is the reference frequency of the power grid. J The inertial time constant; This represents the current frequency change rate at the grid connection point.

[0095] It should be noted that, Figure 3 k in in This represents a proportional element, where P is the value of P. in The constant part, whose value is

[0096] In addition, determining the current frequency change rate of the grid connection point based on its current frequency can include:

[0097] Get the current location identifier;

[0098] Retrieve the frequency corresponding to the current location identifier stored in a pre-created array;

[0099] The current frequency change rate of the grid connection point is determined based on the current frequency of the grid connection point, the frequency corresponding to the current positioning identifier, and the duration of a preset number of cycles; the preset number is the size of the array.

[0100] Update the frequency corresponding to the current location identifier stored in the array to the current frequency of the grid connection point, and update the current location identifier.

[0101] The current frequency change rate of the grid connection point is calculated as follows: (current frequency of the grid connection point - frequency corresponding to the current positioning identifier) ​​ / duration of the preset number of cycles.

[0102] This embodiment employs a frequency extraction method to determine the current frequency change rate and current frequency offset at the grid connection point, namely... Figure 3 The frequency was calculated and used to construct a current source simulation network.

[0103] For a detailed flowchart of frequency calculation, please refer to [link / reference]. Figure 4 First, create an array or matrix F of space N to store the frequency information output by the phase-locked loop (PLL). Here, N is the preset quantity mentioned above. The size of N needs to consider both the delay rate and error impact of the frequency change rate. When N is small, the real-time performance of the frequency change rate is better, but the error has a greater impact on the calculation; when N is large, the real-time performance of the frequency change rate is worse, but the error has a smaller impact on the calculation.

[0104] Initialize the elements in F to the reference frequency f of the power grid. N Set the loop variable n, where n is also the current positioning identifier mentioned above. Initialize n = 0. Obtain the current frequency f of the grid connection point output by the phase-locked loop; calculate the current frequency offset Δf = ff of the grid connection point. N ; Calculate the current frequency change rate at the grid connection point Among them, TPLL The duration of a single cycle is the period of the phase-locked loop (PLL) output frequency information; F(n) is updated to the current frequency f of the grid connection point; the current location identifier n is updated. Updating the current location identifier n can include: automatically incrementing the current location identifier n by 1 to obtain a new n; determining whether the new n is greater than N; if so, jumping back to the initialization step of n = 0 and executing it cyclically, i.e., updating n to 0; if not, jumping back to the step of obtaining the current frequency f of the grid connection point output by the PLL (at this time, obtaining the current frequency of the new cycle PLL output) and executing it cyclically, i.e., the updated n is the aforementioned new n.

[0105] This embodiment uses the above method to calculate the current frequency change rate, which can balance accuracy and response speed.

[0106] Finally, the sum of the active power adjustment of the primary frequency regulation response of the grid-connected inverter and the active power adjustment of the inertia response of the grid-connected inverter is the active power adjustment of the current source simulated grid.

[0107] The following section will introduce how to perform grid-connected inverter control based on the active power adjustment of the current source simulated grid.

[0108] In some embodiments, in S204 above, grid-connected inverters are controlled based on the active power adjustment of the current source simulated grid, including:

[0109] Obtain the active power setpoint and use the sum of the active power setpoint and the active power adjustment of the current source simulated network as the new active power setpoint.

[0110] Based on the new active power setpoint, the grid-connected inverter is subjected to grid-type control.

[0111] See Figure 3 The dashed box represents the control loop for grid-connected current source in related technologies, specifically the control loop where the grid-connected inverter acts as the current source. This application's embodiment builds upon this control loop by adjusting the active power setpoint P within it. ref For improvements, see Figure 3 The part outside the dashed box represents the active power setpoint P. ref Adding the active power adjustment of the current source simulated grid as a new active power setpoint, and based on the new active power setpoint, continuing to perform grid-connected inverter grid-following control according to the current source grid-connected control loop, so that the current source grid-following control has, to a certain extent, the performance characteristics of voltage source grid-connected control.

[0112] in, Figure 3 In this context, Vdc represents the DC voltage; L f For filter inductance; i Labc i is the filter inductor current;oabc The current at the grid connection point; u oabc U is the current voltage at the grid connection point. oa U ob U oc These are the phase A voltage, phase B voltage, and phase C voltage at the grid connection point, respectively; u oabc The current voltage at the grid connection point; u oabc The current voltage at the grid connection point; f is the current frequency at the grid connection point; θ is the current phase angle at the grid connection point; C f For filter capacitors; i Cabc Z represents the filter capacitor current. g P is the power grid impedance; e Q represents the actual value of active power. e This represents the actual value of reactive power; i dref The given value for the D-axis current at the grid connection point; i qref The given value for the Q-axis current at the grid connection point; i d The actual value of the D-axis current at the grid connection point; i q The actual value of the Q-axis current at the grid connection point; I d,max This is the maximum limit value for the D-axis current; I q,max This is the maximum limit value for the Q-axis current; i Cd This represents the actual D-axis current of the filter capacitor; i Cq This represents the actual Q-axis current of the filter capacitor; U rd U is the voltage control quantity for the D-axis; rq For Q-axis voltage control; PI indicates PI control; G indicates transfer function; SPWM indicates sinusoidal pulse width modulation.

[0113] See Figure 3 The method provided in this application only modifies the active power setpoint and does not change the main loop of the current source control loop, making it simple to apply and promote.

[0114] The foregoing embodiments described how to perform active power simulation. In order to simulate network construction more accurately, in addition to active power network construction simulation, reactive power network construction simulation is also included. The reactive power network construction simulation is described in detail below.

[0115] In some embodiments, prior to S204 above, the control method for the current source analog network may further include:

[0116] Obtain the effective value of the current voltage at the grid connection point;

[0117] Calculate the voltage difference between the effective value of the current voltage at the grid connection point and the rated voltage at the grid connection point;

[0118] Based on the voltage difference, the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter is determined, and the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter is used as the reactive power adjustment of the current source simulated grid.

[0119] Accordingly, S204 above may include:

[0120] Based on the active power adjustment and reactive power adjustment of the current source simulated network, grid-connected inverters are controlled to follow the grid, so as to realize the current source simulated network.

[0121] Voltage regulation control is the reactive power response to the steady-state deviation of the grid-connected point voltage, which is the primary voltage regulation. The reactive power response of the grid-connected inverter to the steady-state deviation of the grid-connected point voltage is the primary voltage regulation response of the grid-connected inverter. The steady-state voltage deviation is manifested as the voltage difference mentioned above, that is, the voltage difference between the effective value of the current voltage at the grid-connected point and the rated voltage at the grid-connected point. Therefore, in the embodiments of this application, the reactive power adjustment amount of the primary voltage regulation response of the grid-connected inverter can be calculated based on the voltage difference between the effective value of the current voltage at the grid-connected point and the rated voltage at the grid-connected point, that is, the reactive power adjustment amount of the current source simulated grid can be obtained.

[0122] Among them, see Figure 5 The formula for calculating the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter based on the voltage difference can include: Among them, Q v K represents the reactive power adjustment in the primary voltage regulation response of the grid-connected inverter. v S is the reactive power voltage regulation coefficient. N The virtual synchronous generator's rated capacity (i.e., apparent power) is represented by ΔU, which is the voltage difference between the effective value of the current voltage at the grid connection point and the rated voltage at the grid connection point. N The rated voltage of the grid connection point can be understood as the rated voltage of the voltage level at which the grid connection point is located.

[0123] It should be noted that, Figure 5 k in q This represents a proportional element, which is represented by Q. v The constant part, whose value is

[0124] The foregoing embodiments detailed how to determine the reactive power adjustment of a current source simulated network. Next, we will continue to describe how to control the grid-connected inverter based on the active power adjustment and reactive power adjustment of the current source simulated network.

[0125] In some embodiments, in S204 above, the grid-connected inverter's grid-following control based on the active power adjustment amount and reactive power adjustment amount of the current source simulated grid can include:

[0126] Obtain the active power setpoint and use the sum of the active power setpoint and the active power adjustment of the current source simulated network as the new active power setpoint.

[0127] Obtain the reactive power setpoint and use the sum of the reactive power setpoint and the reactive power adjustment of the current source simulated network as the new reactive power setpoint.

[0128] Based on the new active power setpoint and the new reactive power setpoint, the grid-connected inverter is subjected to grid-type control.

[0129] See Figure 5 The dashed box represents the control loop for grid-connected current source in related technologies, specifically the control loop where the grid-connected inverter acts as a current source. Figure 3 The dashed box portion is the same. This application embodiment is based on this control loop, and the active power setpoint P in this control loop is... ref and reactive power setpoint Q ref For improvements, see Figure 5 The part outside the dashed box represents the active power setpoint P. ref Adding the active power adjustment from the current source simulated network, as the new active power setpoint, the reactive power setpoint Q is... ref Adding the reactive power adjustment of the current source simulated grid as a new reactive power setpoint, and based on the new active power setpoint and the new reactive power setpoint, the grid-connected inverter continues to be controlled according to the current source grid-connected control loop, so that the current source grid-connected control has, to a certain extent, the characteristics of voltage source grid-connected control.

[0130] See Figure 5 The method provided in this application only modifies the active power setpoint and reactive power setpoint, without changing the main loop of the current source control loop, and is simple to apply and promote.

[0131] The method provided in this application was experimentally verified. In the experiment, N was set to 26, and the off-grid short-circuit method was used at the output to verify the actual performance of the algorithm. The results of the first frequency modulation are as follows: Figure 6 As shown in the figure, it can be seen that when the grid connection point frequency experiences a step change, the active power of the grid-connected inverter can be adjusted accordingly. Tests were conducted under various operating conditions, and the results are shown in Table 1.

[0132] After the frequency was tuned once, the inertia was tested, and the initial power was set to 0.35P. nThe frequency change rate is 0.5 Hz / s, and the frequency changes sequentially from 50 Hz to 48.1 Hz, 50 Hz, 51.4 Hz, and 50 Hz. The measured waveforms of the grid connection point frequency and the output power of the grid-connected inverter are as follows: Figure 7 As shown in Table 2, when the grid connection frequency changes, the machine can adjust its active power output accordingly. All measured indicators are shown in Table 2 and are satisfactory. Similarly, tests were conducted under various operating conditions, and all test indicators met the requirements.

[0133] Table 1 Operating power 0.3P n Results under different frequency variations

[0134]

[0135]

[0136] Table 2 0.35P n Key Inertia Test Indicators

[0137]

[0138] This application analyzes the response of traditional VSGs to frequency and grid connection voltage, and implements a current source grid-connected simulation control technology based on frequency extraction technology. The loop modification is simple and requires no modification to the main control loop of the current source. When the grid frequency changes, the inverter can respond quickly to the frequency. Furthermore, experimental verification shows that this virtual synchronous machine output characteristic simulation scheme operates well and meets the expected power response rate and accuracy requirements.

[0139] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0140] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0141] Figure 8 A schematic diagram of the control device for simulating a current source network provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below:

[0142] like Figure 8 As shown, the control device 30 for the current source simulation network may include: an acquisition module 31, a frequency calculation module 32, an active power adjustment module 33, and a control module 34.

[0143] The acquisition module 31 is used to acquire the current frequency of the grid connection point; the grid connection point is the connection point where the grid-connected inverter is connected to the power grid.

[0144] The frequency calculation module 32 is used to determine the current frequency offset and the current frequency change rate of the grid connection point based on the current frequency of the grid connection point.

[0145] The active power adjustment module 33 is used to determine the active power adjustment amount of the current source simulated network based on the current frequency offset and the current frequency change rate of the grid connection point. The active power adjustment amount of the current source simulated network includes the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter and the active power adjustment amount of the inertia response of the grid-connected inverter.

[0146] The control module 34 is used to perform grid-following control on the grid-connected inverter based on the active power adjustment of the current source simulated grid, so as to realize the current source simulated grid.

[0147] In one possible implementation, the active power adjustment module 33 is specifically used for:

[0148] Based on the current frequency offset at the grid connection point, determine the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter;

[0149] Determine the active power adjustment amount of the grid-connected inverter inertia response based on the current frequency change rate at the grid connection point.

[0150] Based on the active power adjustment of the primary frequency regulation response and the active power adjustment of the inertia response of the grid-connected inverter, the active power adjustment of the current source simulated grid is determined.

[0151] In one possible implementation, the active power adjustment module 33 determines the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter based on the current frequency offset at the grid connection point, including:

[0152] according to Determine the active power adjustment P of the primary frequency regulation response of the grid-connected inverter. f Among them, K f P is the active frequency regulation coefficient. n f is the rated power of the grid-connected inverter. N Δf is the reference frequency of the power grid, and Δf is the current frequency offset at the grid connection point.

[0153] In one possible implementation, the active power adjustment module 33 determines the active power adjustment amount of the grid-connected inverter's inertia response based on the current frequency change rate at the grid connection point, including:

[0154] according to Determine the active power adjustment P of the inertia response of the grid-connected inverter. in Among them, P n f is the rated power of the grid-connected inverter.N T is the reference frequency of the power grid. J The inertial time constant; This represents the current frequency change rate at the grid connection point.

[0155] In one possible implementation, the control device 30 for the current source analog network may further include a reactive power adjustment module.

[0156] The reactive power adjustment module is used for:

[0157] Based on the active power adjustment of the current source simulated grid construction, the grid-connected inverter is controlled to follow the grid type, so as to obtain the effective value of the current voltage at the grid connection point before the current source simulated grid construction is realized.

[0158] Calculate the voltage difference between the effective value of the current voltage at the grid connection point and the rated voltage at the grid connection point;

[0159] Based on the voltage difference, the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter is determined, and the reactive power adjustment of the primary voltage regulation response of the grid-connected inverter is used as the reactive power adjustment of the current source simulated grid.

[0160] Accordingly, the control module 34 is specifically used for:

[0161] Based on the active power adjustment and reactive power adjustment of the current source simulated network, grid-connected inverters are controlled to follow the grid, so as to realize the current source simulated network.

[0162] In one possible implementation, the reactive power adjustment module determines the reactive power adjustment amount of the primary voltage regulation response of the grid-connected inverter based on the voltage difference, including:

[0163] according to Determine the reactive power adjustment Q of the primary voltage regulation response of the grid-connected inverter. v Among them, K v S is the reactive power voltage regulation coefficient. N The rated capacity of the virtual synchronous machine is given, where ΔU is the voltage difference. N This is the rated voltage at the grid connection point.

[0164] In one possible implementation, within control module 34, grid-connected inverters are controlled based on the active power adjustment of the simulated grid structure using current sources, including:

[0165] Obtain the active power setpoint and use the sum of the active power setpoint and the active power adjustment of the current source simulated network as the new active power setpoint.

[0166] Based on the new active power setpoint, the grid-connected inverter is subjected to grid-type control.

[0167] In one possible implementation, the frequency calculation module 32 determines the current frequency change rate of the grid connection point based on its current frequency, including:

[0168] Get the current location identifier;

[0169] Retrieve the frequency corresponding to the current location identifier stored in a pre-created array;

[0170] The current frequency change rate of the grid connection point is determined based on the current frequency of the grid connection point, the frequency corresponding to the current positioning identifier, and the duration of a preset number of cycles; the preset number is the size of the array.

[0171] Update the frequency corresponding to the current location identifier stored in the array to the current frequency of the grid connection point, and update the current location identifier.

[0172] Figure 9 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. For example... Figure 9 As shown, the electronic device 4 in this embodiment includes a processor 40 and a memory 41. The memory 41 stores a computer program 42, and the processor 40 calls and runs the computer program 42 stored in the memory 41 to execute the steps in the control method embodiments of the various current source simulation network described above, for example... Figure 2 S201 to S204 are shown. Alternatively, the processor 40 is used to call and run the computer program 42 stored in the memory 41 to implement the functions of each module / unit in the above-described device embodiments, for example... Figure 8 The functions of each module are shown.

[0173] For example, the computer program 42 can be divided into one or more modules / units, which are stored in the memory 41 and executed by the processor 40 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 42 in the electronic device 4. For example, the computer program 42 can be divided into... Figure 8 The modules shown.

[0174] The electronic device 4 may include, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will understand that... Figure 9 This is merely an example of electronic device 4 and does not constitute a limitation on electronic device 4. It may include more or fewer components than shown, or combine certain components, or different components. For example, the electronic device may also include input / output devices, network access devices, buses, etc.

[0175] The processor 40 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0176] The memory 41 can be an internal storage unit of the electronic device 4, such as a hard disk or memory. The memory 41 can also be an external storage device of the electronic device 4, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card. Furthermore, the memory 41 can include both internal and external storage units of the electronic device 4. The memory 41 is used to store the computer program and other programs and data required by the electronic device. The memory 41 can also be used to temporarily store data that has been output or will be output.

[0177] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0178] Corresponding to the above-mentioned electronic devices, this application embodiment also provides a grid-connected inverter, including the electronic devices described above.

[0179] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0180] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0181] In the embodiments provided by this invention, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0182] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0183] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0184] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the control method embodiments for the various current source simulation network constructions described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0185] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A control method for a current source analog network, characterized in that, include: Obtain the current frequency of the grid connection point; the grid connection point is the connection point where the grid-connected inverter is connected to the power grid. Based on the current frequency of the grid connection point, determine the current frequency offset and the current frequency change rate of the grid connection point; The active power adjustment amount of the current source simulated grid is determined based on the current frequency offset and the current frequency change rate of the grid connection point; the active power adjustment amount of the current source simulated grid includes the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter and the active power adjustment amount of the inertia response of the grid-connected inverter. Obtain the effective value of the current voltage at the grid connection point; Calculate the voltage difference between the effective value of the current voltage at the grid connection point and the rated voltage at the grid connection point; determine the reactive power adjustment amount of the primary voltage regulation response of the grid-connected inverter based on the voltage difference, and use the reactive power adjustment amount of the primary voltage regulation response of the grid-connected inverter as the reactive power adjustment amount of the current source simulated grid; Based on the active power adjustment of the current source simulated grid, the grid-connected inverter is subjected to grid-following control to realize the current source simulated grid. The step of performing grid-connected inverter grid-following control based on the active power adjustment of the current source simulated grid to achieve current source simulated grid construction includes: Based on the active power adjustment and reactive power adjustment of the current source simulated network, the grid-connected inverter is subjected to grid-following control to realize the current source simulated network. The step of determining the reactive power adjustment amount of the primary voltage regulation response of the grid-connected inverter based on the voltage difference includes: according to Determine the reactive power adjustment amount of the primary voltage regulation response of the grid-connected inverter. ;in, This is the reactive power voltage regulation coefficient. For the rated capacity of the virtual synchronizer, The voltage difference is... The rated voltage of the grid connection point.

2. The control method for current source simulation network according to claim 1, characterized in that, The step of determining the active power adjustment amount of the current source simulated grid based on the current frequency offset and the current frequency change rate of the grid connection point includes: Based on the current frequency offset of the grid connection point, determine the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter; Based on the current frequency change rate at the grid connection point, determine the active power adjustment amount of the grid-connected inverter inertia response; Based on the active power adjustment of the primary frequency regulation response of the grid-connected inverter and the active power adjustment of the inertia response of the grid-connected inverter, the active power adjustment of the current source simulated grid is determined.

3. The control method for current source simulation network according to claim 2, characterized in that, The step of determining the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter based on the current frequency offset of the grid connection point includes: according to Determine the active power adjustment amount of the primary frequency regulation response of the grid-connected inverter. ;in, This is the active frequency regulation coefficient. The rated power of the grid-connected inverter. The reference frequency of the power grid. This is the current frequency offset of the grid connection point.

4. The control method for current source simulation network according to claim 2, characterized in that, The step of determining the active power adjustment amount of the grid-connected inverter inertia response based on the current frequency change rate of the grid connection point includes: according to Determine the active power adjustment amount of the inertia response of the grid-connected inverter. ;in, The rated power of the grid-connected inverter. The reference frequency of the power grid. The inertial time constant; The current frequency change rate of the grid connection point.

5. The control method for current source simulation network according to any one of claims 1 to 4, characterized in that, The active power adjustment based on the simulated grid structure of the current source, used to perform grid-connected inverter grid-type control, includes: Obtain the active power setpoint and use the sum of the active power setpoint and the active power adjustment of the current source simulated network as the new active power setpoint. Based on the new active power setpoint, the grid-connected inverter is subjected to grid-type control.

6. The control method for current source simulation network according to any one of claims 1 to 4, characterized in that, Determining the current frequency change rate of the grid connection point based on its current frequency includes: Get the current location identifier; Retrieve the frequency corresponding to the current location identifier stored in a pre-created array; The current frequency change rate of the grid connection point is determined based on the current frequency of the grid connection point, the frequency corresponding to the current positioning identifier, and the duration of a preset number of cycles; the preset number is the size of the array. Update the frequency corresponding to the current location identifier stored in the array to the current frequency of the grid connection point, and update the current location identifier.

7. An electronic device, characterized in that, It includes a memory and a processor, the memory being used to store a computer program, and the processor being used to call and run the computer program stored in the memory to execute the control method for simulating a current source network as described in any one of claims 1 to 6.

8. A grid-connected inverter, characterized in that, Including the electronic device as described in claim 7.

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