VSG-based energy storage converter control method and device, and storage medium

Abstract

The invention discloses an energy storage converter control method and device based on a VSG and a storage medium, and relates to the technical field of power electronics and power system control, an integration element is introduced into a VSG reactive power control loop, the error of reactive power can be reduced, and the control effect of an energy storage converter is optimized; moreover, when the energy storage converter is switched from an off-grid state to a grid-connected state, a voltage amplitude, frequency and phase angle pre-synchronization link is introduced in the embodiment of the invention, so that the minimum voltage difference at the switching-on moment can be ensured, and seamless switching is realized; finally, in some embodiments of the invention, the invention also provides a VSG parameter optimization method based on the upper limit of the short-circuit ratio, thereby improving the rationality and convenience of parameter selection.

Description

Technical Field

[0001] This invention relates to the field of power electronics and power system control technology, and in particular to a VSG-based energy storage converter control method, device and storage medium. Background Technology

[0002] As a key device connecting energy storage devices to the power grid, the control strategy of the power conversion system (PCS) has a significant impact on system stability. While traditional droop control is simple to implement, it lacks inertial and damping support, making it difficult to meet the operational requirements of weak grids. Virtual Synchronous Generator (VSG) control, by simulating the rotor motion equations and excitation characteristics of a synchronous generator, can effectively improve the frequency and voltage stability of the system, making it particularly suitable for weak grid scenarios with a high proportion of renewable energy integration. The active power loop of the VSG accurately achieves the active power control requirements, but the stability results of reactive power control are slightly deviated, thus affecting the overall control performance. Summary of the Invention

[0003] The purpose of this invention is to provide a VSG-based energy storage converter control method, device, equipment, and storage medium that can reduce reactive power errors and thus optimize the control effect of the energy storage converter.

[0004] To achieve the above objectives, embodiments of the present invention provide a VSG-based energy storage converter control method, comprising: An integral control module is introduced into the VSG reactive power control loop to obtain the reference value of the voltage amplitude output by the reactive power control loop. Obtain the phase angle reference value of the VSG active power control loop output; Based on the voltage amplitude reference value and the phase angle reference value, a three-phase reference voltage is constructed; The three-phase reference voltage is transformed along the dq axis and then input into the outer voltage loop of the voltage-current dual closed-loop control module to obtain the target drive signal, which is used to control the energy storage converter.

[0005] As an improvement to the above scheme, when the energy storage converter switches from off-grid to grid-connected, the method further includes: Input the grid voltage amplitude and the VSG output voltage amplitude into the PI control module to obtain the voltage amplitude pre-synchronization compensation amount; The voltage amplitude reference value and the voltage amplitude pre-synchronization compensation amount are added together to form a new voltage amplitude reference value, which is used to construct the three-phase reference voltage.

[0006] As an improvement to the above scheme, when the energy storage converter switches from off-grid to grid-connected, the method further includes: Input the grid voltage frequency and the VSG output voltage frequency into the PI control module to obtain the voltage frequency pre-synchronization compensation amount; The voltage frequency pre-synchronization compensation is superimposed on the original mechanical power of the active power control loop to obtain a new mechanical power; Obtain the actual rotational angular velocity calculated by the active power control loop based on the new mechanical power; Input the phase of the grid voltage and the phase of the VSG output voltage into the PI control module to obtain the voltage phase pre-synchronization compensation amount; The actual rotational angular velocity and the voltage phase pre-synchronization compensation are added together to obtain a new actual rotational angular velocity, which is used to generate a phase angle reference value.

[0007] As an improvement to the above scheme, the damping coefficient and moment of inertia constant of the VSG are determined in the following way: Enter the target SCR limit; Under the constraint of the target SCR upper limit, the SCR upper limit model is solved to select the damping coefficient and the moment of inertia constant; wherein, the SCR upper limit model is used to quantify the numerical relationship between the SCR upper limit, the damping coefficient and the moment of inertia constant.

[0008] As an improvement to the above scheme, the SCR upper limit model is as follows:

[0009] in, Indicates the upper limit of SCR; Indicates the damping coefficient; Represents the moment of inertia constant; Represents the natural constant; , and Represents the coefficient.

[0010] As an improvement to the above scheme, the coefficients are obtained by least squares fitting.

[0011] To achieve the above objectives, embodiments of the present invention also provide a VSG-based energy storage converter control device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the VSG-based energy storage converter control method as described in any of the above embodiments.

[0012] To achieve the above objectives, embodiments of the present invention also provide a computer-readable storage medium, the computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform the VSG-based energy storage converter control method as described in any of the above embodiments.

[0013] Compared with existing technologies, the VSG-based energy storage converter control method, device, and storage medium provided in this invention introduce an integral element into the reactive power control loop of the VSG, which can reduce reactive power error and thus optimize the control effect of the energy storage converter. Furthermore, when the energy storage converter switches from off-grid to grid-connected, this invention also introduces a pre-synchronization element for voltage amplitude, frequency, and phase angle, thereby ensuring that the voltage difference is minimized at the moment of closing and achieving seamless switching. Finally, in some embodiments of this invention, a VSG parameter optimization method based on the upper limit of the short-circuit ratio is also proposed, thereby improving the rationality and convenience of parameter selection. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a T-NPC three-level inverter circuit; Figure 2 This is a flowchart of a VSG-based energy storage converter control method provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the active power control loop before the improvement; Figure 4 This is a schematic diagram of the reactive power control loop before the improvement; Figure 5 This is a graph showing the change in reactive power output before the improvement; Figure 6 This is a graph showing the change in output reactive power after the improvement; Figure 7 This is a schematic diagram of an amplitude pre-synchronization stage provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of a frequency pre-synchronization stage and a phase pre-synchronization stage provided in an embodiment of the present invention; Figure 9 This is a schematic diagram showing the voltage following the output voltage of phase A VSG during the automatic switching process between grid and off-grid. Figure 10 This is a schematic diagram showing the following results of the phase angle on the output side of phase A of the VSG during the automatic switching process between parallel and off-grid; Figure 11 This describes the relationship between the upper limit of SCR and the change of J when D takes a fixed value. Figure 12 This describes the relationship between the upper limit of SCR and the change of D when J takes a fixed value. Figure 13This is a schematic diagram of the structure of a VSG-based energy storage converter control device provided in an embodiment of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0017] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0018] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0019] It is worth noting that existing research on VSG control mostly focuses on two-level topologies, while research on high-performance T-NPC (Three-Level Neutral Point Clamped) topology energy storage converters is relatively limited. Therefore, this invention uses a T-NPC topology energy storage converter for explanation and illustration. For example, see [link to example]. Figure 1 This is a schematic diagram of a T-NPC three-level inverter circuit, in which... This represents the current flowing through the inductor in phase A; This represents the current flowing through the B-phase inductor; This represents the current flowing through the C-phase inductor; This indicates the first switching transistor in phase A; This indicates the first switching transistor in phase B; This indicates the first switch transistor in phase C; This indicates the second switching transistor in phase A; This indicates the second switching transistor in phase B; This indicates the second switching transistor in phase C; This indicates the third switching transistor in phase A; This indicates the third switching transistor in phase B; This indicates the third switching transistor in phase C; This indicates the fourth switch in phase A; This indicates the fourth switch in phase B; This indicates the fourth switch in phase C; Indicates the upper bridge arm capacitance on the DC side; Indicates the lower bridge arm capacitance on the DC side; Indicates the AC side filter capacitor; Indicates the AC side filter inductor; This indicates the resistance attached to the AC side filter capacitor; This indicates the load on the AC side when the system is operating in an isolated environment. O represents the DC side voltage value; A represents the node between the upper and lower bridge arm capacitors on the DC side; B represents the node between the upper and lower bridge arms of phase A on the AC side; C represents the node between the upper and lower bridge arms of phase B; a represents the point where phase A is connected to the grid or operates under load after AC side filtering; b represents the point where phase B is connected to the grid or operates under load after AC side filtering; c represents the point where phase C is connected to the grid or operates under load after AC side filtering; N represents the center point of the three-phase load Y-connection. This indicates the center point of the Y-connection of the three-phase filter capacitor.

[0020] Furthermore, according to Figure 1 Write the KCL (Kirchhoff's Current Law) and KVL (Kirchhoff's Voltage Law) equations to establish a mathematical model of the control loop. Specifically, write the KVL equations for the loop containing the inductor: (1) in, This represents the electric potential at point A; This represents the electric potential at point B; This represents the electric potential at point C; This represents the electric potential at point a; This represents the electric potential at point b; This represents the electric potential at point c; Indicates the AC side filter inductor; express Regarding time The derivative; This represents the current flowing through the inductor in phase A; This represents the current flowing through the B-phase inductor; This represents the current flowing through the C-phase inductor.

[0021] Furthermore, the KCL equations are written with nodes a, b, and c as reference nodes: (2) in, This represents the current flowing through the inductor in phase A; This represents the current flowing through the B-phase inductor; This represents the current flowing through the C-phase inductor; Indicates the AC side filter capacitor; Indicates from Figure 1 The current flowing into the load at point a; Indicates from Figure 1 The current flowing into the load at point b; Indicates from Figure 1 The current flowing into the load at point c; Indicate Regarding time The derivative, This represents the electric potential at point A; This represents the electric potential at point B; This represents the electric potential at point C.

[0022] Furthermore, by performing a 3 / 2 transformation on equations (1) and (2) respectively, and then converting them to complex frequency domain form, we obtain equations (3) and (4) respectively: (3) in, This represents the d-axis component of the three-phase voltage at points A, B, and C after transformation. This represents the q-axis component of the three-phase voltage at points A, B, and C after transformation. This represents the d-axis component of the three-phase voltage at points abc after transformation. This represents the q-axis component of the three-phase voltage at points abc after transformation. Represents a complex variable; Indicates the AC side filter inductor; Represents angular velocity, and , Represents pi (π). Indicates angular frequency; This represents the d-axis component of the current after transformation of the three-phase current flowing through the inductor. This represents the q-axis component of the current after transformation of the three-phase current flowing through the inductor.

[0023] (4) in, This represents the d-axis component of the three-phase current flowing through the load (or power grid) after transformation. This represents the d-axis component of the current after transformation of the three-phase current flowing through the inductor. This represents the q-axis component of the three-phase current flowing through the load (or power grid) after transformation. This represents the q-axis component of the current after transformation of the three-phase current flowing through the inductor; Represents a complex variable; Indicates the AC side filter capacitor; This represents the d-axis component of the three-phase voltage at points abc after transformation. This represents the q-axis component of the three-phase voltage at points abc after transformation. It represents angular velocity.

[0024] Furthermore, based on (3) and (4), a voltage and current dual closed-loop controller is designed, such as a voltage and current dual closed-loop PI (Proportional-Integral) controller. The output of the voltage and current dual closed-loop controller is a dq-axis modulated signal, which is transformed by a 3 / 2 inverse transformation to obtain a three-phase modulated wave. Finally, the drive is generated through the SVPWM (Space Vector Pulse Width Modulation) module. Figure 1 The PWM (Pulse Width Modulation) signals of each switching transistor.

[0025] Furthermore, the SVPWM module synthesizes the 19 basic space voltage vectors of the T-NPC three-level inverter circuit, specifically defining the switching functions of phases A, B, and C. The expression for the three-phase output voltage is: (5) in, express Figure 1 Point A and The potential difference between them; express Figure 1 Point B and The potential difference between them; express Figure 1 Point C and The potential difference between them; Indicates the DC side voltage value; Represents the switching function of phase A; Represents the B-phase switching function; This represents the C-phase switching function.

[0026] Furthermore, the space voltage vector can be expressed as: (6) in, Represents the space voltage vector; express Figure 1 Point A and The potential difference between them; express Figure 1 Point B and The potential difference between them; express Figure 1 Point C and The potential difference between them; Represents pi; Represents the natural constant; It represents the imaginary unit.

[0027] Substituting the expression for the three-phase output voltage into equation (6), we obtain the relationship between the space voltage vector and the switching function: (7) in, Represents the space voltage vector; Represents the switching function of phase A; Represents the B-phase switching function; Represents the C-phase switching function; Represents the imaginary unit; This indicates the DC side voltage value.

[0028] By combining different switching functions, the large sector, small sector, and reference vector within the voltage vector's range are determined. The application time and transmission sequence of the reference vector are then calculated to complete space vector pulse width modulation. The specific sector division and reference vector application time calculation are mature technologies and will not be elaborated upon here.

[0029] See Figure 2 This is a flowchart of a VSG-based energy storage converter control method according to an embodiment of the present invention, including steps S1 to S4: S1. Introduce an integral control module into the VSG reactive power control loop and obtain the reference value of the voltage amplitude output by the reactive power control loop. S2. Obtain the phase angle reference value of the VSG active control loop output; S3. Construct a three-phase reference voltage based on the voltage amplitude reference value and the phase angle reference value; S4. After the three-phase reference voltage is transformed by the dq axis, it is input into the voltage outer loop of the voltage and current dual closed-loop control module to obtain the target drive signal for controlling the energy storage converter.

[0030] Furthermore, the VSG-based energy storage converter control method described in this embodiment of the invention is an improvement on the existing energy storage converter control system. The existing energy storage converter control system specifically refers to a system that includes a VSG module and a voltage-current dual closed-loop controller. The VSG module includes an active power control loop and a reactive power control loop, and the output of the VSG module is connected to the voltage outer loop of the voltage-current dual closed-loop controller.

[0031] Further, see Figure 3 and Figure 4 These are schematic diagrams of the active power control loop and the reactive power control loop before the improvement, respectively. The active power control loop, by simulating the rotational inertia and damping of a traditional synchronous generator, can more accurately simulate the angular velocity and phase angle of the VSG output side. Figure 3 The mathematical representation of the active control loop shown is given by equations (8) to (14): (8) (9) (10) (11) (12) (13) (14) In equations (8) to (14), Represents the moment of inertia constant; Indicates the actual rotational angular velocity Regarding time The derivative; It represents the mechanical power generated by the prime mover; This represents the angular velocity corresponding to the fundamental frequency; Indicates electromagnetic power; Indicates the damping coefficient; Phase angle reference value The derivative with respect to time; Per-unit value representing angular velocity; This represents the instantaneous value of the AC voltage at point a; This represents the instantaneous value of the AC voltage at point b; This represents the instantaneous value of the AC voltage at point c; This represents the instantaneous value of the current flowing into the load or power grid at point a; This represents the instantaneous value of the current flowing into the load or power grid at point b; This represents the instantaneous value of the current flowing into the load or power grid at point c. Indicates the angular velocity correction amount; The command value representing active power; This represents the power regulation coefficient of the active power control loop; This indicates the phase angle reference value.

[0032] Furthermore, Figure 4 The mathematical representation of the reactive power control loop shown is given by equations (15) to (16): (15) (16) In equations (15) to (16), This indicates the reference value of the voltage amplitude before the improvement; Indicates the reference value of the target voltage amplitude; Indicates the reactive power voltage regulation coefficient; This indicates the actual reactive power generated by the VSG; The command value representing reactive power; This represents the instantaneous value of the AC voltage at point a; This represents the instantaneous value of the AC voltage at point b; This represents the instantaneous value of the AC voltage at point c; This represents the instantaneous value of the current flowing into the load or power grid at point a; This represents the instantaneous value of the current flowing into the load or power grid at point b; This represents the instantaneous value of the current flowing into the load or power grid at point c.

[0033] Understandably, similar to droop control, existing reactive power control loops generate voltage amplitude reference values ​​by controlling the reactive power output.

[0034] However, simulations revealed that while the existing active power control loop can accurately achieve active power control, the stability results of reactive power control are slightly off. Therefore, this invention introduces integral control into the reactive power control loop to optimize the reactive power loop, as shown in equations (17) to (20): (17) (18) (19) (20) In equations (17) to (20), Indicates the target reactive power; Indicates the reactive power command value; Indicates the reactive power voltage regulation coefficient; This represents the actual amplitude of the three-phase voltage; This indicates the command voltage value, which is 311V. The d-axis component represents the AC side voltage; Represents the q-axis component of the AC side voltage; Indicates the reference voltage correction amount; This represents the newly introduced voltage regulation coefficient; Indicates the start time of integration; This indicates the reference value of the voltage amplitude before the improvement; This indicates the improved voltage amplitude reference value.

[0035] Furthermore, in step S3, the three-phase reference voltage is synthesized based on the phase angle reference value generated by the active power control loop and the voltage amplitude reference value generated by the reactive power control loop, as shown in equations (21) to (23): (twenty one) (twenty two) (twenty three) in, Indicates the reference voltage of phase A; Indicates the reference voltage for phase B; Indicates the C-phase reference voltage; The voltage amplitude reference value refers to the voltage amplitude reference value generated by the improved reactive power control loop in this invention. Indicates the phase angle reference value; Represents pi; This represents the sine function.

[0036] Furthermore, by performing a dq-axis transformation on the three-phase reference voltage, the input of the outer voltage loop in the voltage-current dual closed-loop controller is obtained. and ,in, Indicates the reference value for the d-axis voltage component; This represents the reference value for the q-axis voltage component.

[0037] Compared with the prior art, the embodiments of the present invention can reduce the error of reactive power by introducing an integral element into the VSG reactive power control loop, thereby optimizing the control effect of the energy storage converter.

[0038] Furthermore, to verify the effectiveness of the method in the embodiments of the present invention, the embodiments of the present invention are also verified based on PLECS simulation software, see [link to PLECS simulation software]. Figure 5 and Figure 6 The figures show the changes in reactive power output before and after the improvement. As can be seen from the figures, the embodiments of the present invention can effectively solve the problem of reactive power stability deviation.

[0039] It is worth noting that, compared with traditional control strategies, the grid-connected / off-grid switching based on the virtual synchronous machine control strategy does not require a change in control mode during switching, which can reduce the transient impact on the power grid, showing a significant advantage. However, since the system only has one voltage source, the VSG, during islanded operation, no additional control is required for the switching. Therefore, the problem to be solved in seamless grid-connected / off-grid switching is how to ensure that there is no instantaneous voltage difference between the two sides of the switch during the off-grid to grid-connected switching. For example, the derivation formulas for the instantaneous voltage difference are shown in equations (23) and (24):

[0040] (twenty three) (twenty four) In equations (23) to (24), This represents the instantaneous voltage difference between the VSG output side and the grid side; This represents the instantaneous value of the grid-side voltage; This represents the instantaneous value of the voltage on the VSG side; Indicates the voltage amplitude on the grid side; Indicates the frequency of the grid-side voltage; Indicates the phase of the grid-side voltage; Indicates the voltage frequency on the VSG side; Indicates the voltage amplitude on the VSG side; Indicates the voltage phase on the VSG side; Indicates time; Represents the cosine function; This represents the sine function.

[0041] Furthermore, in order to ensure that there is no instantaneous voltage difference on both sides of the switch when switching from off-grid to on-grid, a pre-synchronization link is added to the active power control loop and the reactive power control loop in some embodiments of the present invention.

[0042] As one optional implementation, when the energy storage converter switches from off-grid to grid-connected, the method further includes: Input the grid voltage amplitude and the VSG output voltage amplitude into the PI control module to obtain the voltage amplitude pre-synchronization compensation amount; The voltage amplitude reference value and the voltage amplitude pre-synchronization compensation amount are added together to form a new voltage amplitude reference value, which is used to construct the three-phase reference voltage.

[0043] For example, see Figure 7 This is a schematic diagram of an amplitude / voltage pre-synchronization loop provided in an embodiment of the present invention, wherein the amplitude pre-synchronization loop is added to the reactive power control loop.

[0044] As one optional implementation, when the energy storage converter switches from off-grid to grid-connected, the method further includes: Input the grid voltage frequency and the VSG output voltage frequency into the PI control module to obtain the voltage frequency pre-synchronization compensation amount; The voltage frequency pre-synchronization compensation is superimposed on the original mechanical power of the active power control loop to obtain a new mechanical power; Obtain the actual rotational angular velocity calculated by the active power control loop based on the new mechanical power; Input the phase of the grid voltage and the phase of the VSG output voltage into the PI control module to obtain the voltage phase pre-synchronization compensation amount; The actual rotational angular velocity and the voltage phase pre-synchronization compensation are added together to obtain a new actual rotational angular velocity, which is used to generate a phase angle reference value.

[0045] For example, see Figure 8 This is a schematic diagram of a frequency pre-synchronization link and a phase pre-synchronization link provided in an embodiment of the present invention. The frequency pre-synchronization link and the phase pre-synchronization link are added to the active power control loop. The phase and frequency of the grid voltage can be obtained through a phase-locked loop (PLL).

[0046] Compared with the prior art, the embodiments of the present invention achieve pre-synchronization of the VSG output voltage and the grid voltage in terms of amplitude, phase and frequency by adding a PI control module, which can ensure that the voltage difference is minimized at the moment of closing, thereby achieving seamless switching and ensuring that there is no transient impact on the system when new energy is connected to the grid.

[0047] Furthermore, to verify the effectiveness of the method in the embodiments of the present invention, the embodiments of the present invention are also verified based on PLECS simulation software, see [link to PLECS simulation software]. Figure 9 and Figure 10 This is a schematic diagram showing the following results of the output voltage and phase angle of phase A VSG during the automatic switching process between grid and off-grid. As can be seen from the figure, the output voltage and phase angle of VSG accurately follow the grid side, and no voltage distortion occurs at the switching moment, achieving a smooth mode transition.

[0048] As one alternative implementation, the damping coefficient and moment of inertia constant of the VSG are determined in the following manner: Enter the target SCR limit; Under the constraint of the target SCR upper limit, the SCR upper limit model is solved to select the damping coefficient and the moment of inertia constant; wherein, the SCR upper limit model is used to quantify the numerical relationship between the SCR upper limit, the damping coefficient and the moment of inertia constant.

[0049] It is worth noting that in the single-machine VSG model, when the line parameters and control parameters remain unchanged, the short-circuit ratio (SCR) affects system stability. However, under the virtual synchronous machine control strategy, changing the damping coefficient D and the moment of inertia constant J both affect system stability. Therefore, this embodiment of the invention, from the perspective of the influence of D and J on the adaptability range of the short-circuit ratio, plots the stability domain range for different D and J values ​​and finds that the lower limit of the short-circuit ratio is always 1. Therefore, this embodiment of the invention further fits an upper limit model for SCR to quantify the numerical relationship between the upper limit of SCR, the damping coefficient, and the moment of inertia constant, in order to select appropriate parameters under different short-circuit ratio conditions.

[0050] As one optional implementation, the SCR upper limit model is shown in the following formula: (25) in, Indicates the upper limit of SCR; Indicates the damping coefficient; Represents the moment of inertia constant; Represents the natural constant; , and Represents the coefficient.

[0051] For example, see Figure 11 The graph shows the relationship between the upper limit of SCR and J when D is a fixed value. As can be seen from the graph, when D is a fixed value, the relationship between the upper limit of SCR and J can be fitted by a direct proportional function; see also... Figure 12 , is the relationship between the upper limit of SCR and D when J takes a fixed value. As can be seen from the figure, when J takes a fixed value, the relationship between the upper limit of SCR and D can be fitted by an exponential function. Based on this, the embodiment of the present invention selects the upper limit of SCR model as shown in equation (25) to fit the functional relationship between the upper limit of SCR and D and J.

[0052] As one alternative implementation, the coefficients are obtained by fitting using the least squares method.

[0053] For example, the SCR upper limit model fitted by one embodiment of the present invention is shown in the following formula, and the goodness of fit of the SCR upper limit model is R²=0.9657: (26) in, Indicates the upper limit of SCR; Indicates the damping coefficient; Represents the moment of inertia constant; Represents the natural constant.

[0054] See Figure 13This invention also provides a VSG-based energy storage converter control device 20, including a processor 21, a memory 22, and a computer program stored in the memory 22 and configured to be executed by the processor 21. When the processor 21 executes the computer program, it implements the steps described in the above-described VSG-based energy storage converter control method embodiment, for example... Figure 2 The steps S1 to S4 described above; or, when the processor 21 executes the computer program, it implements the functions of each module in the above-described device embodiments.

[0055] The VSG-based energy storage converter control device can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The VSG-based energy storage converter control device may include, but is not limited to, a processor and memory. Those skilled in the art will understand that the schematic diagram is merely an example of a VSG-based energy storage converter control device and does not constitute a limitation on the VSG-based energy storage converter control device. It may include more or fewer components than illustrated, or combine certain components, or use different components. For example, the VSG-based energy storage converter control device may also include input / output devices, network access devices, buses, etc.

[0056] The processor can 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. The general-purpose processor can be a microprocessor or any conventional processor. This processor is the control center of the VSG-based energy storage converter control device, connecting all parts of the device via various interfaces and lines.

[0057] The memory can be used to store the computer programs and / or modules. The processor implements various functions of the VSG-based energy storage converter control device by running or executing the computer programs and / or modules stored in the memory, and by calling the data stored in the memory. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function, etc.; the data storage area may store data created according to the use of the controller, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0058] The modules integrated into the VSG-based energy storage converter control device, if implemented as software functional units and sold or used as independent products, 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 various method embodiments 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, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0059] Compared with existing technologies, the VSG-based energy storage converter control method, device, and storage medium provided in this invention introduce an integral element into the reactive power control loop of the VSG, which can reduce reactive power error and thus optimize the control effect of the energy storage converter. Furthermore, when the energy storage converter switches from off-grid to grid-connected, this invention also introduces a pre-synchronization element for voltage amplitude, frequency, and phase angle, thereby ensuring that the voltage difference is minimized at the moment of closing and achieving seamless switching. Finally, in some embodiments of this invention, a VSG parameter optimization method based on the upper limit of the short-circuit ratio is also proposed, thereby improving the rationality and convenience of parameter selection.

[0060] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A control method for an energy storage converter based on VSG, characterized in that, include: An integral control module is introduced into the VSG reactive power control loop to obtain the reference value of the voltage amplitude output by the reactive power control loop. Obtain the phase angle reference value of the VSG active power control loop output; Based on the voltage amplitude reference value and the phase angle reference value, a three-phase reference voltage is constructed; The three-phase reference voltage is transformed along the dq axis and then input into the outer voltage loop of the voltage-current dual closed-loop control module to obtain the target drive signal, which is used to control the energy storage converter.

2. The VSG-based energy storage converter control method as described in claim 1, characterized in that, When the energy storage converter switches from off-grid to grid-connected, the method further includes: Input the grid voltage amplitude and the VSG output voltage amplitude into the PI control module to obtain the voltage amplitude pre-synchronization compensation amount; The voltage amplitude reference value and the voltage amplitude pre-synchronization compensation amount are added together to form a new voltage amplitude reference value, which is used to construct the three-phase reference voltage.

3. The VSG-based energy storage converter control method as described in claim 1, characterized in that, When the energy storage converter switches from off-grid to grid-connected, the method further includes: Input the grid voltage frequency and the VSG output voltage frequency into the PI control module to obtain the voltage frequency pre-synchronization compensation amount; The voltage frequency pre-synchronization compensation is superimposed on the original mechanical power of the active power control loop to obtain a new mechanical power; Obtain the actual rotational angular velocity calculated by the active power control loop based on the new mechanical power; Input the phase of the grid voltage and the phase of the VSG output voltage into the PI control module to obtain the voltage phase pre-synchronization compensation amount; The actual rotational angular velocity and the voltage phase pre-synchronization compensation are added together to obtain a new actual rotational angular velocity, which is used to generate a phase angle reference value.

4. The VSG-based energy storage converter control method as described in claim 1, characterized in that, The damping coefficient and moment of inertia constant of VSG are determined in the following way: Enter the target SCR limit; Under the constraint of the target SCR upper limit, the SCR upper limit model is solved to select the damping coefficient and the moment of inertia constant; wherein, the SCR upper limit model is used to quantify the numerical relationship between the SCR upper limit, the damping coefficient and the moment of inertia constant.

5. The VSG-based energy storage converter control method as described in claim 4, characterized in that, The SCR upper limit model is shown in the following formula: in, Indicates the upper limit of SCR; Indicates the damping coefficient; Represents the moment of inertia constant; Represents the natural constant; , and Represents the coefficient.

6. The VSG-based energy storage converter control method as described in claim 5, characterized in that, The coefficients were obtained by fitting using the least squares method.

7. A VSG-based energy storage converter control device, characterized in that, It includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor executes the computer program to implement the VSG-based energy storage converter control method as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform the VSG-based energy storage converter control method as described in any one of claims 1 to 6.

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