Control method, device and equipment of energy storage converter and storage medium

Abstract

The invention relates to the field of grid-connected conversion, and provides a control method and device of an energy storage converter, equipment and a storage medium. The method comprises the following steps: determining a feasible region of the energy storage converter according to the maximum current amplitude, the voltage amplitude range and the modulation ratio range of the energy storage converter; determining an intersection point of the feasible region and a rated active power isoline; determining the value range of reactive power and voltage control parameters according to the intersection point; and controlling the grid-connected conversion of the energy storage converter according to the value ranges of the reactive power and voltage control parameters. The value ranges of reactive power and voltage control parameters are calculated according to the intersection point of the feasible region and the rated active power isoline, and due to the homotopy relationship of curves corresponding to reactive power control and voltage control, the voltage output by the energy storage converter is within the voltage range of the feasible region within the value ranges of the reactive power and voltage control parameters, and the voltage output by the energy storage converter is within the voltage range of the rated active power isoline. Therefore, the probability of voltage out-of-limit or current out-of-limit is reduced, and the energy storage converter can output active power more stably.

Description

Control method, device, equipment and storage medium of energy storage converter Technical Field

[0001] The present application relates to the field of grid-connected conversion technology, and in particular to a control method, device, equipment, and storage medium for an energy storage converter. Background Art

[0002] With the continuous development of new energy generation technologies, energy storage technology plays a vital role in new power systems by improving power supply reliability and flexibility. Energy storage converters are the grid-connected interface for energy storage equipment, including electrochemical energy storage devices.

[0003] Energy storage converters controlled by vector control methods can adjust the magnitude and angle of their output voltage or frequency, but vector control methods rely on the grid to generate frequency and internal potential. Energy storage converters controlled by self-synchronous voltage sources, on the other hand, can independently generate frequency and internal power. However, in extremely weak grids, such as those with low short-circuit ratios, self-synchronous voltage source-controlled energy storage converters are prone to voltage or current over-limit during grid-connected conversion, leading to unstable or limited active power.

[0004] Summary of the Invention

[0005] In view of this, the embodiments of the present application provide a control method, device, equipment and storage medium for an energy storage converter to solve the problem in the prior art that the energy storage converter controlled by a self-synchronous voltage source is prone to voltage or current exceeding the limit when performing grid-connected conversion, thereby causing active power to be unstable or limited.

[0006] A first aspect of an embodiment of the present application provides a control method for an energy storage converter, the method comprising: determining a feasible domain of the energy storage converter, the feasible domain meeting preset current change requirements and voltage change requirements; determining the intersection of the feasible domain and the rated active power contour line; determining a value range of reactive and voltage control parameters based on the intersection; and controlling the grid-connected conversion of the energy storage converter based on the value range of the reactive and voltage control parameters.

[0007] The feasible domain is determined by the preset current change requirements and voltage change requirements, and the value range of the reactive power and voltage control parameters is determined based on the intersection of the feasible domain and the rated active power contour. The reactive power and voltage control parameters are selected within the value range of the reactive power and voltage control parameters. Since the shape corresponding to the static characteristics satisfied by constant voltage control and constant reactive power control is a circle, the two satisfy the homotopy relationship. Therefore, it can be determined that the reactive power and voltage control parameters vary monotonically with the homotopy parameters within the feasible domain. The value range of the reactive power and voltage control parameters can be used to determine the monotonic variation range of the homotopy parameters. Within this monotonic variation range, the voltage output by the energy storage converter will not exceed the range of the feasible domain, thereby effectively reducing the probability of voltage and current exceeding the limit. Under the premise of determining the reliability of the current and voltage output by the energy storage converter, it is beneficial for the energy storage converter to output stable active power.

[0008] In a possible implementation, determining the feasible domain of the energy storage converter includes: determining the feasible domain of the energy storage converter based on the preset maximum current amplitude requirement and voltage amplitude range requirement of the energy storage converter; or, determining the feasible domain of the energy storage converter based on the preset maximum current amplitude requirement and modulation ratio range of the energy storage converter; or, determining the feasible domain of the energy storage converter based on the preset maximum current amplitude requirement, voltage amplitude range requirement and modulation ratio range of the energy storage converter.

[0009] When determining the feasible domain of the energy storage converter, it can be determined based on the preset maximum current amplitude requirement and voltage amplitude range requirement, so that the current and voltage within the feasible domain will not exceed the limit. Alternatively, the relationship between the modulation ratio and the voltage output by the energy storage converter can be predetermined, the modulation ratio range of the energy storage converter can be determined based on the voltage amplitude range, and the range of the feasible domain can be determined based on the modulation ratio range and the maximum current amplitude requirement, so that the current and voltage within the feasible domain will not exceed the limit. Alternatively, the feasible domain can be determined based on the maximum current amplitude requirement, the voltage amplitude range, and the modulation ratio range, so that the feasible domain meets the maximum current amplitude requirement while meeting the voltage amplitude range and the modulation ratio range, more reliably ensuring that the current and voltage within the feasible domain will not exceed the limit.

[0010] In a possible implementation, the feasible domain of the energy storage converter is determined based on the maximum current amplitude, voltage amplitude range, and modulation ratio range of the energy storage converter, including: determining a first range based on the contour line corresponding to the maximum current amplitude; determining a second range based on the contour line corresponding to the maximum voltage amplitude and / or the contour line corresponding to the minimum voltage amplitude in the voltage amplitude range; determining a third range based on the contour line corresponding to the highest modulation ratio and / or the contour line corresponding to the lowest modulation ratio in the modulation ratio range; and determining the feasible domain of the energy storage converter based on the intersection of the first range, the second range, and the third range.

[0011] When determining the feasible domain, a first range can be determined based on the contour line corresponding to the maximum current of the energy storage converter, so that the current values ​​within the feasible domain all meet the current requirements of the energy storage converter. A second range is determined based on the minimum voltage amplitude and the maximum voltage amplitude in the voltage amplitude range of the energy storage converter, so that the voltage amplitudes within the feasible domain all meet the voltage requirements of the energy storage converter. A third range is determined based on the modulation ratio range of the energy storage converter, so that the modulation ratios within the feasible domain all meet the modulation ratio requirements. The feasible domain is determined based on the intersection of the first range, the second range, and the third range, and the control parameters are selected based on the feasible domain, so that the energy storage converter can be connected to the grid according to the set modulation ratio range, and the output current and voltage are more stable.

[0012] In a possible implementation, determining the feasible domain of the energy storage converter based on the preset maximum current amplitude and voltage amplitude range of the energy storage converter includes: determining a first range based on the contour line corresponding to the maximum current amplitude; determining a second range based on the contour line corresponding to the maximum voltage amplitude and / or the contour line corresponding to the minimum voltage amplitude in the voltage amplitude range; and determining the feasible domain of the energy storage converter based on the intersection of the first and second ranges. Alternatively, determining a first range based on the contour line corresponding to the maximum current amplitude; determining a third range based on the contour line corresponding to the highest modulation ratio and / or the contour line corresponding to the lowest modulation ratio in the modulation ratio range; and determining the feasible domain of the energy storage converter based on the intersection of the first and third ranges.

[0013] A first range is determined by the maximum current amplitude, and a second range is determined based on the voltage amplitude range. The intersection of the first and second ranges is used as the range of the feasible domain. Within this feasible domain, the current value meets the preset current requirement, and the voltage value meets the preset voltage requirement. Alternatively, the first range is determined by the maximum current amplitude, and a third range is determined based on the modulation ratio range. The intersection of the first and third ranges is used as the range of the feasible domain. Based on the relationship between the modulation ratio and the voltage output by the energy storage converter, the current and voltage within the feasible domain meet the preset amplitude requirements.

[0014] In a possible implementation, before determining the feasible domain of the energy storage converter, the method further includes: representing the grid voltage vector, the grid connection point voltage vector, and the voltage drop vector of the output current of the energy storage converter on the grid impedance by establishing a plane coordinate system; and determining two or three of the current amplitude contour lines, modulation ratio contour lines, and voltage amplitude contour lines of the energy storage converter in the plane coordinate system based on the grid voltage vector, the grid connection point voltage vector, and the voltage drop vector.

[0015] In order to facilitate the description of the range of the feasible domain, a plane coordinate system can be established to represent the grid voltage vector, the grid connection point voltage vector and the voltage drop vector of the output current of the energy storage converter on the grid impedance in the plane coordinate system. Based on the determined voltage vector, the current amplitude contour lines, modulation ratio contour lines and voltage amplitude contour lines in the plane coordinate system are determined respectively, so as to facilitate the determination of the voltage amplitude range, the maximum current amplitude range and the modulation ratio range according to the determined contour lines, and further obtain the feasible domain according to the determined range.

[0016] In a possible implementation, a plane coordinate system is established to represent the grid voltage vector, the grid connection point voltage vector, and the voltage drop vector of the output current of the energy storage converter on the grid impedance, including: establishing a plane coordinate system with the grid voltage vector and the grid connection point voltage vector of the energy storage converter as the origin, and the end of the grid voltage vector as (U g , 0), the end of the grid-connected point voltage vector of the energy storage converter is (x, y), and the grid voltage vector and the grid-connected point voltage vector are determined, wherein U g is the modulus of the grid voltage vector, is the modulus of the grid connection point voltage vector, arctan (y / x) is the directional deviation between the grid connection point voltage vector and the grid voltage vector; according to the grid voltage vector and the grid connection point voltage vector, the voltage drop vector (xU) of the output current of the energy storage converter on the grid impedance is determined. g , y).

[0017] By taking the origin as the starting point of the grid voltage vector and the grid connection point voltage vector, and (x, y) as the end point of the grid connection point voltage vector, it is convenient to quickly determine the equation of the voltage amplitude contour line of the grid connection point. g , 0) is the end of the grid voltage vector, which facilitates the rapid determination of the equation of the active power contour line of the grid connection point of the energy storage converter and the equation of the current amplitude contour line of the energy storage converter.

[0018] In a possible implementation, determining the current amplitude contour line, the modulation ratio contour line, and the voltage amplitude contour line of the energy storage converter in the plane coordinate system according to the grid voltage vector, the grid connection point voltage vector, and the voltage drop vector includes: determining the current amplitude contour line equation of the energy storage converter in the plane coordinate system according to the grid voltage vector, the grid connection point voltage vector, and the voltage drop vector, for example, may be: The modulation ratio contour equation of the energy storage converter in the plane coordinate system is determined according to the grid voltage vector, the grid connection point voltage vector, and the voltage drop vector. For example, it can be: The voltage amplitude contour equation of the energy storage converter in the plane coordinate system is determined according to the grid voltage vector, the grid connection point voltage vector, and the voltage drop vector. For example, it can be: Among them, X g is the impedance of the inductive grid, X f is the impedance of the energy storage converter filter inductor, U dcm is the DC modulation voltage, I s is the current amplitude at the contour line output by the energy storage converter, η is the modulation ratio at the contour line, U s is the voltage amplitude at the contour line of the energy storage converter output.

[0019] After determining the grid voltage vector, grid connection point voltage vector, and output current voltage drop vector on the grid impedance of the energy storage converter and their corresponding relationships, the current amplitude contour line equation, voltage amplitude contour line equation, and modulation ratio contour line equation of the energy storage converter in the plane coordinate system can be obtained. Based on the contour line equations, the current amplitude range, voltage amplitude range, and modulation ratio range can be accurately determined. Based on the contour line equation corresponding to the maximum current amplitude in the current amplitude range, the contour line equation corresponding to the maximum voltage amplitude in the voltage amplitude range and the contour line equation corresponding to the minimum voltage amplitude, as well as the contour line equation corresponding to the maximum modulation ratio and the contour line equation corresponding to the minimum modulation ratio in the modulation ratio range, that is, the intersection of the contour lines, the range of the feasible domain can be accurately determined.

[0020] In a possible implementation, determining the intersection of the feasible region and the rated active power contour line includes: determining the rated active power contour line equation of the energy storage converter in the plane coordinate system according to the grid voltage vector, the grid connection point voltage vector and the voltage drop vector, for example, it can be: P n X g =U g ·y; determine the linear equation of the rated active power to determine the intersection of the feasible region and the rated active power contour line; wherein, X g is the impedance of the inductive grid, P n is the rated active power.

[0021] When determining the intersection of the rated active power and the feasible region, the rated active power contour equation can be first determined. Based on the rated active power contour equation and the determined feasible region, the intersection of the rated active power and the feasible region can be calculated by solving the intersection of the contour equation. When calculating the intersection, the coordinates of the vertices included in the feasible region can be first determined. Based on the vertex coordinates, it can be determined whether the intersection of the rated active power contour line and the contour lines constituting the feasible region belongs to an edge of the feasible region. If the intersection belongs to an edge of the feasible region, it means that the intersection is the intersection of the rated active power contour line and the feasible region.

[0022] In a possible implementation, determining the intersection of the feasible domain and the rated active power contour line includes: when the rated active power contour line does not pass through the feasible domain, adjusting one or more of the maximum current amplitude of the energy storage converter, the maximum voltage amplitude of the energy storage converter, the maximum modulation ratio of the energy storage converter and the DC modulation voltage of the energy storage converter until the rated active power contour line passes through the feasible domain.

[0023] Because the rated active power contour may not intersect the feasible region, it is not convenient to determine the value range of the reactive and voltage control parameters based on the intersection. The feasible region can be expanded by modifying the parameters of the feasible region so that the rated active power contour intersects the feasible region. When modifying the parameters of the feasible region, the maximum current amplitude, maximum voltage amplitude, maximum modulation ratio, and DC modulation voltage can be adjusted based on the amplitude of the current and voltage changes output by the energy storage converter. For example, when the amplitude of the output current change is smaller than the amplitude of the voltage change, the feasible region can be adjusted by preferentially increasing the maximum current amplitude. Alternatively, the type of the vertex of the feasible region with the smallest distance from the rated active power contour can be selected based on the distance between the vertex and the rated active power curve. The vertex type can be determined based on the intersection of different contour lines, including, for example, the intersection of the maximum current amplitude contour line and the maximum voltage amplitude contour line. For example, if the vertex of the feasible region with the smallest distance from the rated active power contour line is the intersection of the minimum modulation ratio and the maximum current amplitude, the maximum current amplitude can be increased to make the rated active power contour line intersect with the feasible region.

[0024] In a possible implementation, determining the value range of reactive power and voltage control parameters according to the intersection point includes: determining the reactive power and voltage values ​​corresponding to the intersection point, wherein the reactive power Q s satisfy: Grid voltage amplitude U s satisfy: U g Indicates the modulus of the grid voltage vector, Q s represents reactive power, (x,y) represents the coordinates of the grid connection point voltage vector in the plane coordinate system, X gRepresents the impedance of the inductive power grid; according to the reactive power and voltage values ​​corresponding to the intersection, combined with the predetermined grid connection point voltage setting value and the grid connection point reactive power setting value, obtain the value range of the reactive and voltage control parameters. According to the reactive power and voltage values ​​corresponding to the intersection, combined with the predetermined grid connection point voltage setting value and the grid connection point reactive power setting value, obtain the value range of the reactive and voltage control parameters, including: according to the reactive power and voltage values ​​corresponding to the intersection, combined with the predetermined grid connection point voltage setting value and the grid connection point reactive power setting value, obtain the value range of the reactive and voltage control parameters as (K vN <K v <K vM ),in, Among them, U s0 is the grid connection point voltage setting value, Q s0 is the reactive power setting value of the grid connection point, M and N are the intersection points, and U M , Q M Represent the voltage and reactive power at the intersection M, U N , Q N Represent the voltage and reactive power of the intersection N respectively. Among them, the energy storage converter satisfies (U s0 -U s )=-K v (Q s0 -Q s ), where U s Indicates the voltage amplitude at the grid connection point, Q s Indicates the reactive power at the grid connection point.

[0025] The range of reactive power and voltage control parameters is calculated based on the intersection point. This range falls within the feasible domain. Therefore, the selected reactive power and voltage control parameters ensure that the voltage output by the energy storage converter is within a preset voltage amplitude range and the output current is less than the maximum current amplitude, thereby preventing the energy storage converter from experiencing current or voltage over-limit issues. Under the premise that the output current and voltage are stable, and the endpoints of the range of reactive power and voltage control parameters lie on the same rated active power contour, the energy storage converter can output stable active power.

[0026] A second aspect of an embodiment of the present application provides a control device for an energy storage converter, the control device comprising: a feasible domain determination unit, for determining the feasible domain of the energy storage converter, the feasible domain meeting preset current change requirements and voltage change requirements; an intersection determination unit, for determining the intersection of the feasible domain and the rated active power contour line; a value range determination unit, for determining the value range of reactive and voltage control parameters based on the intersection; and a grid-connected conversion control unit, for controlling the grid-connected conversion of the energy storage converter based on the value range of the reactive and voltage control parameters.

[0027] A third aspect of an embodiment of the present application provides a control device for an energy storage converter, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method described in any one of the first aspects when executing the computer program.

[0028] A fourth aspect of an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in any one of the first aspects are implemented.

[0029] It can be understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] FIG1 is a schematic diagram of an implementation flow of a control method for an energy storage converter provided in an embodiment of the present application;

[0032] FIG2 is a schematic diagram showing a circuit state of an energy storage converter provided in an embodiment of the present application;

[0033] FIG3 is a schematic diagram of contour lines of external characteristics of an energy storage converter provided in an embodiment of the present application;

[0034] FIG4 is a schematic diagram of the contour range of the external characteristics of an energy storage converter provided in an embodiment of the present application;

[0035] FIG5 is a schematic diagram of a feasible region of an energy storage converter provided in an embodiment of the present application;

[0036] FIG6 is a schematic diagram of static characteristics of reactive power and voltage control parameters provided in an embodiment of the present application;

[0037] FIG7 is a schematic diagram of a curve of a homotopy parameter and reactive power and voltage control parameters provided in an embodiment of the present application;

[0038] FIG8 is a schematic diagram of the relationship between a homotopy curve and a feasible region provided in an embodiment of the present application;

[0039] FIG9 is a schematic diagram of simulation results in which reactive power and voltage control parameters are within a range of values ​​provided by an embodiment of the present application;

[0040] FIG10 is a schematic diagram of simulation results in which reactive power and voltage control parameters are higher than the value range provided in an embodiment of the present application;

[0041] FIG11 is a schematic diagram of simulation results in which reactive power and voltage control parameters are lower than a value range, provided in an embodiment of the present application;

[0042] FIG12 is a schematic diagram of a control device for an energy storage converter provided in an embodiment of the present application;

[0043] FIG13 is a schematic diagram of a control device for an energy storage converter provided in an embodiment of the present application. Modes for Carrying Out the Invention

[0044] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0045] In order to illustrate the technical solution described in this application, specific embodiments are provided below.

[0046] The energy storage converter can include one or more grid-connected interfaces. Through the grid-connected interfaces, electrochemical energy storage equipment, new energy power generation equipment, and other devices can be connected to the grid. Energy storage converters controlled by self-synchronous voltage sources can independently construct frequency and internal potential, unlike traditional vector control methods that rely on grid generation. Therefore, self-synchronous voltage sources play an important role in improving voltage over-limit, reactive power shortages, broadband oscillations, and synchronous instability problems caused by characteristics such as "low inertia" and "low short-circuit ratio" in areas with high penetration of new energy.

[0047] However, when using a self-synchronous voltage source to control an energy storage converter, the converter's current handling capability is very limited, so its ability to output reactive power is limited by its current handling capability. Under low short-circuit ratio conditions, it is not possible to effectively guarantee stable active power output at the grid connection point.

[0048] Moreover, it is difficult for the energy storage converter controlled by the self-synchronous voltage source to simultaneously meet the requirements of ensuring that the current is within its tolerance range while outputting appropriate reactive power to support the voltage at the grid connection point, so that the voltage at the grid connection point is within a reasonable range.

[0049] To address the above-mentioned issues, an embodiment of the present application proposes a control method for an energy storage converter. The execution subject of the method can be a control device of the energy storage converter or an electric energy storage system. The method determines the feasible domain of the energy storage converter by the maximum current amplitude, voltage amplitude range, and modulation ratio range of the energy storage converter, determines the value range of reactive power and voltage control parameters based on the intersection of the feasible domain and the active power contour, and controls the grid-connected conversion of the energy storage converter according to the determined value range of reactive power and voltage control parameters, thereby enabling the energy storage converter to generate stable active power in an extremely weak power grid and reducing the probability of current over-limit or voltage over-limit.

[0050] In order to better understand the embodiments of the present application, the concepts of short-circuit ratio, grid connection point, etc. that appear in the embodiments of the present application are explained in detail below.

[0051] (1) Short Circuit Ratio (SCR) refers to the system short-circuit capacity divided by the equipment capacity.

[0052] Short-circuit capacity refers to the apparent power of a power system when a three-phase short circuit occurs at the short-circuit point under the system's specified operating mode. Short-circuit capacity is a characteristic parameter used to characterize the power system's ability to supply power. Its magnitude is equal to the product of the short-circuit current and the rated voltage at the short-circuit point.

[0053] Equipment capacity is also called installed capacity, which is the sum of the rated capacity or rated power of all electrical equipment installed within the calculation scope.

[0054] Therefore, the greater the short-circuit ratio of the system, the smaller the impact of the switching of the equipment on the system.

[0055] (2) The PCC (Point of Common Coupling) is the point where a power source is connected to the grid or where a user's electrical equipment is connected to the grid. For distributed power sources with a substation, the PCC is the high-voltage bus or node on the high-voltage side of the substation. For distributed power sources without a substation, the PCC is the output aggregation point of the distributed power source.

[0056] In order to better understand the embodiments of the present application, the control method, device, equipment and storage medium of the energy storage converter provided according to the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0057] Referring to FIG1 , an embodiment of the present application provides a control method for an energy storage converter, including:

[0058] In S101 , a feasible region of the energy storage converter is determined, where the feasible region meets preset current change requirements and voltage change requirements.

[0059] The preset current change requirement may include a maximum current amplitude requirement. The preset voltage change requirement may include a voltage amplitude range requirement, or the voltage change requirement may be determined by limiting the modulation ratio, for example, by determining the voltage change requirement by the modulation ratio range. The voltage amplitude range may be determined based on the maximum voltage amplitude, or based on the minimum voltage amplitude, or based on the maximum and minimum voltage amplitudes. The modulation ratio range may be determined based on the maximum modulation ratio, or based on the minimum modulation ratio, or based on the maximum and minimum modulation ratios.

[0060] When determining the feasible domain according to the current change requirements and the voltage change requirements, it can be based on the preset maximum current amplitude, voltage amplitude range and modulation ratio range, or based on the preset maximum current amplitude and voltage amplitude range, or based on the preset maximum current amplitude and modulation ratio range.

[0061] For example, a first range that satisfies the maximum current amplitude requirement, a second range that satisfies the voltage amplitude requirement, and a third range that satisfies the modulation ratio requirement can be determined separately. The intersection of the first, second, and third ranges is calculated, and the resulting intersection is the feasible region of the energy storage converter. Within this feasible region, the maximum current amplitude requirement, the voltage amplitude requirement, and the modulation ratio range requirement can all be met simultaneously.

[0062] Alternatively, a first range that satisfies the maximum current amplitude requirement and a second range that satisfies the voltage amplitude requirement can be determined separately. The intersection of the first range and the second range is calculated, and the obtained intersection area is the feasible region of the energy storage converter.

[0063] Alternatively, a first range meeting the maximum current amplitude requirement and a third range meeting the modulation ratio requirement may be determined separately. The intersection of the first range and the third range is calculated, and the obtained intersection area is the feasible region of the energy storage converter.

[0064] In order to quickly and easily determine the feasible region of the energy storage converter, a plane coordinate system as shown in Figure 2 can be established to represent the circuit state of the energy storage converter. In this plane coordinate system, the direction of the grid voltage vector can be the same as the positive direction of the horizontal axis of the plane coordinate system, and the modulus of the grid voltage vector is U g That is, the grid voltage vector can be expressed in the plane coordinate system as the origin A at the beginning and the end coordinates B (U g ,0). The grid connection point voltage vector can be expressed as a vector starting at the origin A and ending at point C(x,y) in the plane coordinate system. The modulus of the grid connection point voltage vector is And the directional deviation between the grid connection point voltage vector and the grid voltage vector is arctan(y / x).

[0065] It can be understood that the above-mentioned representation of the grid connection point voltage vector, the grid voltage vector and the voltage drop vector of the output current on the grid impedance is an implementation method listed in the embodiment of the present application, and is not limited to this. It can also be based on other positional relationships on the plane coordinate system, including representations such as representing the direction of the grid voltage vector in the vertical coordinate direction, to represent the relationship between the above-mentioned vectors.

[0066] For a single power grid-connected system, the voltage and current in the circuit satisfy the phasor expression: U s =U g +I s Z g , where I s is the output current of the energy storage converter, Z g is the impedance of the power grid. In the plane coordinate system, point B (U g ,0) as the starting point and point C(x,y) as the end point, as the voltage drop vector of the output current of the energy storage converter on the grid impedance. The coordinates of the voltage drop vector are (xU g ,y), the modulus of the voltage drop vector is the output current of the energy storage converter I s and the grid impedance Z g The product of I s Z g .

[0067] Among them, different values ​​of the grid connection point voltage vector correspond to different circuit states of the energy storage converter when it is grid-connected. The angle between the grid connection point voltage vector and the grid voltage vector is used to represent the phase difference between the grid voltage vector and the grid connection point voltage vector. The modulus of the grid connection point voltage vector is used to represent the magnitude of the grid connection point voltage amplitude. For example, the coordinates of the grid connection point voltage vector are (1, 1), which means that the phase difference between the grid connection point voltage vector and the grid voltage vector is 45 degrees, and the grid connection point voltage amplitude of the grid connection point voltage vector is

[0068] After representing the grid voltage vector, the grid connection point voltage vector and the voltage drop vector of the output current of the energy storage converter on the grid impedance on the plane coordinate system, the representation equation of the grid connection point current (or called the current amplitude contour equation), the grid connection point voltage representation equation (or called the voltage amplitude contour equation) and the grid connection point control modulation ratio representation equation (or called the modulation ratio contour equation) can be determined based on the relationship between the grid voltage vector, the grid connection point voltage vector and the voltage drop vector of the output current of the energy storage converter on the grid impedance.

[0069] For example, according to the corresponding relationship of the above vectors in the plane coordinate system, the equation of the current amplitude contour line can be determined as follows:

[0070] Among them, U g Indicates the modulus of the grid voltage vector, X g represents the impedance of the inductive grid, represents the current amplitude at the contour line of the energy storage converter output, and (x,y) represents the coordinates of the grid connection point voltage vector in the plane coordinate system. The current amplitude contour line equation represents the current amplitude contour line formed by the set of corresponding grid connection point voltages when the current amplitude of the energy storage converter output remains unchanged.

[0071] According to the corresponding relationship of the above vectors on the plane coordinate system, the voltage amplitude contour equation can be determined as follows:

[0072] Where (x, y) represents the coordinates of the grid connection point voltage vector in the plane coordinate system, U s is the voltage amplitude at the contour line of the energy storage converter output. The voltage amplitude contour line equation represents the voltage amplitude contour line formed by the set of corresponding grid connection point voltages when the voltage amplitude of the energy storage converter output remains unchanged.

[0073] According to the corresponding relationship of the above vectors in the plane coordinate system, the modulation ratio contour equation can be expressed as:

[0074] Among them, X g is the impedance of the inductive grid, X f is the impedance of the energy storage converter filter inductor, η is the modulation ratio at the contour line, U dcm is the DC modulation voltage, that is, the DC voltage of the grid-connected conversion, U g The modulation ratio amplitude contour equation represents the modulation ratio contour formed by the set of corresponding grid connection point voltages when the modulation ratio of the energy storage converter remains unchanged.

[0075] In the embodiment of the present application, the active power contour equation can also be determined according to the corresponding relationship of the above vectors, which can be expressed as: s X g =U g ·y.

[0076] Among them, X g Indicates the impedance of the inductive grid, P s Indicates active power, U g Represents the modulus of the grid voltage vector. This active power contour equation represents the active power contour formed by the set of grid connection point voltages when the active power remains constant. When the active power is the rated active power, the contour corresponding to the rated active power is obtained, i.e., the rated active power contour.

[0077] In the embodiment of the present application, the reactive power contour equation can be determined based on the corresponding relationship of the above vectors, which can be expressed as:

[0078] Among them, U g Indicates the modulus of the grid voltage vector, Q s represents reactive power, (x,y) represents the coordinates of the grid connection point voltage vector in the plane coordinate system, X g The reactive power contour equation represents the reactive power contour formed by the set of grid connection point voltages when the reactive power remains constant.

[0079] According to the above contour line equation, after setting different current amplitudes, voltage amplitudes, modulation ratios, active power and reactive power at the grid connection point, the contour lines corresponding to the set current amplitudes, voltage amplitudes, modulation ratios, active power and reactive power at the grid connection point can be obtained. For example, in the contour line diagram of the external characteristics of the energy storage converter shown in Figure 3:

[0080] The current amplitude of the set grid connection point is shown in Figure 3a. The current amplitude includes I s1 , I s2 , I s3 , I s4 , and 0 s1 s2 s3 s4 The determined contour line is with point B as the center and r1=X g *I s A circle with a radius of .

[0081] The modulation ratio of the set grid connection point is shown in Figure 3b. The modulation ratio includes η1, η2, η3, and η4, and 0<η1<η2<η3<η4. The determined contour line is As the center of the circle, A circle with a radius of .

[0082] The voltage amplitude of the grid connection point is shown in Figure 3c. The voltage amplitude includes U s1 、U s2 、U s3 、U s4 , and 0 s1 s2 s3 s4 The determined contour line is the one with point A as the center and U s A circle with a radius of .

[0083] The active power of the set grid connection point is shown in Figure 3d. The active power includes P s1 、P​​​​​​​​s2 、P s3 、P s4 、P s5 , and P s1 <P s2 <P s3 =0 <P s4 <P s5 , the determined contour line is parallel to the x-axis and is P away from the x-axis s X g / U g straight line.

[0084] The reactive power of the set grid connection point is shown in Figure 3e. The reactive power includes Q s1 , Q s2 , Q s3 , Q s4 , and Q s1 s2 s3 =0 s4 The determined contour line is the point O (the midpoint of point A and point B) as the center of the circle, A circle with a radius of .

[0085] When determining the feasible domain of the energy storage converter, the first range can be determined based on the current amplitude contour line of the energy storage converter, the second range can be determined based on the voltage amplitude contour line, and the third range can be determined based on the modulation ratio contour line. Then, the feasible domain of the energy storage converter can be determined based on the intersection of the first range, the second range and the third range.

[0086] For example, FIG4 is a schematic diagram showing a method of determining a range based on contour lines of external characteristics of an energy storage converter according to an embodiment of the present application.

[0087] As shown in FIG4a, the output current I of the energy storage converter can be determined according to the preset maximum current amplitude. s Less than the maximum current amplitude I max The first range, that is, with point B as the center and r1=X g *I s A circle with radius o1.

[0088] As shown in FIG4b, according to the preset maximum modulation ratio η max and the minimum modulation ratio η min Determine the third range, that is, As the center of the circle, and The annular area formed by two circles o2 and o3 with radius determined.

[0089] As shown in FIG4c, according to the preset maximum voltage amplitude U smax ​​​and minimum voltage amplitude U smin Determine the second range, that is, take point A as the center and r4=U smax and r5=U smin The annular area formed by two circles o4 and o5 with radius determined.

[0090] FIG5 is a schematic diagram of a feasible region for determining an energy storage converter according to the present invention. As shown in FIG5 , the first range is centered at point B and is r1=X g *I s The area of ​​the circle o1 with a radius of As the center of the circle, and The second range is the annular area formed by two circles o2 and o3 with radius determined by point A, and r4=U smax and r5=U smin The circular area formed by the two circles o4 and o5 with the determined radius. The first intersection is determined based on the first range and the second range, and the second intersection is determined based on the first intersection and the third range, which is the feasible domain determined in the embodiment of the present application.

[0091] In S102, the intersection point between the feasible region and the rated active power contour line is determined.

[0092] After determining the feasible domain of the energy storage converter, when the grid connection point voltage is within the feasible domain, the working state of the energy storage converter can meet the pre-set current amplitude requirements, voltage amplitude range requirements and modulation ratio range requirements.

[0093] In order to further meet the requirements of the active power output of the energy storage converter, the rated active power contour line can be determined according to the active power contour line equation determined above, and the grid connection point voltage can be optimized according to the intersection of the rated active power contour line and the feasible region to improve the stability of the output state of the energy storage converter.

[0094] When determining the intersection of the rated active power contour and the feasible region, the line segments included in the feasible region can be pre-determined to accurately determine the intersection. For example, the line segments included in the feasible region can be determined based on the endpoints included in the feasible region. The intersection of each line segment with the rated active power contour is calculated. The intersection of the line segment included in the feasible region and the rated active power contour is the intersection of the rated active power contour and the feasible region.

[0095] For example, as shown in Figure 5, the rated active power contour line and the contour line that determines the feasible region intersect at (D1, D2, D3, D4, M, N) respectively. The intersection points of the rated active power contour line and the feasible region are M and N. The value ranges of the reactive power and voltage control parameters of the energy storage converter can be further calculated based on the intersection points M and N.

[0096] In a possible implementation, the rated active power contour may not intersect with the contour determined by the pre-set parameters. In order to ensure the stability of the output state of the energy storage converter, one or more of the parameters such as the maximum current amplitude of the energy storage converter, the maximum voltage amplitude of the energy storage converter, the maximum modulation ratio of the energy storage converter, and the DC modulation voltage of the energy storage converter can be adjusted so that the rated active power contour can intersect with the feasible domain determined by the parameters, and the intersection of the rated active power contour and the feasible domain is obtained. According to the grid-connected conversion requirements of the energy storage converter, the maximum current amplitude can be increased, the maximum voltage amplitude of the energy storage converter can be increased, the maximum modulation ratio of the energy storage converter can be increased, and / or the DC modulation voltage of the energy storage converter can be increased.

[0097] In S103, the value ranges of reactive power and voltage control parameters are determined according to the intersection point.

[0098] The reactive power and voltage control parameters are control parameters that constrain the output voltage and reactive power of the energy storage converter. After determining the intersection of the rated active power contour and the feasible region, the control parameter values ​​corresponding to this intersection are used as the boundaries of the reactive power and voltage control parameters to determine the range of their values ​​for the converter.

[0099] As shown in Figure 5, the intersection points of the rated active power contour and the feasible region are M and N, and the corresponding coordinates are (x M ,y M )、(x N ,y N ).

[0100] According to the equation of reactive power contour and voltage amplitude contour determined by the above formula, the coordinates of the intersection points are substituted into the above method to determine the reactive power and voltage amplitude corresponding to the intersection points M and N. For example, the reactive power at point M is Q M , the voltage at point M is U M , the reactive power at point N is Q N , the voltage at point N is U N .

[0101] According to the predetermined grid connection point voltage setting value U s0 And the grid-connected point reactive power setting value Q s0 , the reactive power and voltage control parameters K corresponding to points M and N can be calculated respectively vM, K vN for:

[0102]

[0103] Among them, U s0 is the grid connection point voltage setting value, Q s0 It is the reactive power setting value of the grid connection point. M s0 , then K vM The value is +∞.

[0104] After determining the reactive power and voltage control parameters K corresponding to points M and N, vM , K vN After that, the reactive power and voltage control parameters K can be determined v The value range is (K vN , K vM ), where K vN Less than K vM Reactive power and voltage control parameter K v It can take any value within this range, including values ​​less than zero.

[0105] In S104, the grid-connected conversion of the energy storage converter is controlled according to the value ranges of the reactive power and voltage control parameters.

[0106] After determining the value range of the reactive power and voltage control parameters of the energy storage converter, any value can be taken as the reactive power and voltage control parameters based on the value range to control the grid-connected conversion of the energy storage converter.

[0107] Among them, the reactive power Q of the energy storage converter at the grid connection point under steady-state conditions is s and the voltage amplitude U at the grid connection point s Satisfies the following relationship: (U s0 -U s )=-K v (Q s0 -Q s ), and the grid-connected conversion is controlled according to the corresponding relationship. That is, the reactive power Q s and the grid voltage amplitude U s Subject to the above constraints, and in K v The reactive power Q of the grid connection point can be adjusted within the value range of s and the voltage amplitude U at the grid connection point s constraint relationship.

[0108] Since the shape corresponding to the static characteristics satisfied by constant voltage control and constant reactive power control is a circle, for example, assuming that the set value of the grid connection point voltage amplitude is, the equation for the shape corresponding to the static characteristics of the constant voltage control determined by the plane coordinate system shown in Figure 2 is:​ The equation corresponding to the shape of the static characteristic satisfied by constant reactive power control is: The corresponding shapes are all circles. Since two circles must satisfy the homotopy relationship:

[0109] H(x,y,λ)=λ(U s -U s0 )+(1-λ)(Q s -Q s0 )=0

[0110] Homotopy refers to two topological spaces that transform from one to the other through a series of continuous transformations. The mathematical definition of homotopy can be expressed as follows: given two topological spaces X and Y, and two continuous functions f and g, if there exists a continuous mapping X×[0,1]→Y such that:

[0111]

[0112]

[0113] Then f and g are said to be homotopic.

[0114] That is to say, each homotopy parameter λ corresponds to a function, X→Y, x→H(x,λ), that is, as the parameter λ changes from 0 to 1, H continuously changes from f to g, then f and g are said to be homotopic.

[0115] In the static characteristic diagram of reactive power and voltage control parameters shown in FIG6 , when the homotopy parameter λ is 0, H(x, y, 0) = Q s -Q s0 = 0, this equation is used to represent the curve of constant reactive power control (the inner curve l1 in Figure 6). When the homotopy parameter λ is 1, H(x, y, 1) = U s -U s0 = 0, this equation represents the curve for constant voltage control (outer curve l2 in Figure 6). When 0 < λ < 1, the homotopic curve represented by the function H(x, y, λ) lies between the curves for constant reactive power control and constant voltage control. As λ varies continuously from 0 to 1, the curve gradually expands from the innermost circle corresponding to constant reactive power control to the outermost circle corresponding to constant voltage control.

[0116] When λ is less than 0, the homotopy curve represented by H(x, y, λ) will shrink to the circle corresponding to the constant reactive circle control, causing the grid voltage to further decrease as the active power of the grid increases. When λ is greater than 1, the curve represented by H(x, y, λ) will be outside the curve corresponding to the constant voltage control, which is conducive to the energy storage converter to generate more active power. Therefore, when designing the homotopy parameters, only the case where λ is greater than 0 needs to be considered.

[0117] Since the reactive and voltage control parameters are defined as: Combining the functions of the homotopy relationship, we can see that the corresponding relationship between the reactive power and voltage control parameters and the homotopy parameters is: According to the corresponding relationship between reactive power and voltage control parameters and homotopy parameters, a curve diagram of reactive power and voltage control parameters and homotopy parameters can be obtained as shown in Figure 7. As shown in Figure 7, in the range of λ greater than 0, K v It decreases monotonically with λ. When λ is small, K v The absolute value of is large. At this time, the homotopy curve represented by H(x,y,λ) is close to the inner side of the circle corresponding to constant reactive power control. When λ is large, K v The absolute value of is small. At this time, the homotopy curve represented by H(x, y, λ) is close to the circle corresponding to the constant voltage control, and the static characteristics are close to the constant voltage control.

[0118] From the curves of homotopy parameters and reactive and voltage control parameters shown in Figure 7, it can be seen that in the range of λ greater than 0, K v The value of can be determined by λ. In order to meet the output capacity above the rated active power, the homotopy curve needs to be located between M and N in the relationship diagram between the homotopy curve and the feasible region shown in Figure 8. Since the two points M and N correspond to two critical λ, the corresponding reactive and voltage control parameters K can be determined through the critical λ. v The range of K V,N <K v <K V,M Since the reactive power and voltage control parameters change continuously and monotonically from point M to point N, and the voltage at the critical point falls within the voltage range of the feasible domain, the voltage output by the energy storage converter will not exceed the voltage range in the feasible domain during the process of continuous and monotonic change of the homology parameter λ within the range determined by the critical point, which is beneficial to reducing the voltage over-limit of the output of the energy storage converter. When the voltage output by the energy storage converter is stable, it is beneficial to ensure the stability of the current output by the energy storage converter and reduce the probability of current over-limit. Under the premise of current and voltage stability, it is beneficial to improve the stability of the output active power.

[0119] In order to verify the superiority of the control method of the energy storage converter in the embodiment of the present application, in the case of an extremely weak power grid, for example, the short circuit ratio SCR of the power grid is 1.05, the circuit parameters include: the inductive power grid impedance Xg is 0.953pu, the grid voltage amplitude U g =1.0pu, the impedance of the energy storage converter filter inductor is X f =0.1pu, DC modulation voltage U dum =1.2pu.

[0120] The pre-set constraints include: maximum current amplitude I max =1.2pu, maximum modulation ratio η max =1.0pu, minimum modulation ratio η min =0.6pu, the maximum voltage amplitude at the grid connection point is U smax =1.1pu, the minimum voltage amplitude at the grid connection point is U smin =0.96pu.

[0121] The setting values ​​include: grid connection point voltage setting value U s0 =1.05pu, grid-connected point reactive power setting value Q s0 =0pu, rated active power P n =1.0pu.

[0122] According to the control method of the energy storage converter shown in Figure 1, the range of reactive power and voltage control parameters is calculated to be: -0.072 <K v <0.041. The reactive power and voltage control parameters were verified by computer platform. During the simulation, the active power reference value changed continuously from 0 to P n .

[0123] Take K v =-0.05, the simulation result diagram shown in Figure 9 is obtained. Under the reactive and voltage control parameters, the active power command value of the energy storage converter changes continuously from 0 to P n During the process, the active power output by the energy storage converter remains stable, and the voltage amplitude and current amplitude at the grid connection point do not exceed the limit.

[0124] Take K v = 0.1, which is higher than the calculated value range, and the simulation result diagram shown in Figure 10 is obtained. Under the reactive and voltage control parameters, the active power command value of the energy storage converter changes continuously from 0 to P n In the process, the active power P output by the energy storage converter s The static operating point is lost, and the problem of synchronous instability occurs, which is manifested as a periodic decrease in the voltage amplitude at the grid connection point and a sudden increase in the reference angular frequency of the converter, resulting in a power angle swing problem.

[0125] Take K v=-0.1, which is lower than the calculated value range, and the simulation result diagram shown in Figure 11 is obtained. Under the reactive and voltage control parameters, the active power command value of the energy storage converter changes continuously from 0 to P n During the process of increasing the active power, the active power output by the energy storage converter remains stable. However, the voltage amplitude at the grid connection point exceeds the maximum voltage amplitude U at the grid connection point during the process of increasing the active power. smax =1.1pu, which cannot meet the operating requirements.

[0126] Thus, the control method for the energy storage converter proposed in the embodiments of the present application enables the energy storage converter to output stable active power in extremely weak power grids while reducing the probability of voltage and current exceeding the limit. When the selected reactive power and voltage control parameters are outside the calculated value range, unstable output active power or voltage or current exceeding the limit may occur.

[0127] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean 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 this application.

[0128] FIG12 is a schematic diagram of a control device for an energy storage converter provided in an embodiment of the present application. As shown in FIG9 , the device includes:

[0129] A feasible domain determining unit 1201 is configured to determine a feasible domain of the energy storage converter according to the maximum current amplitude, voltage amplitude range, and modulation ratio range of the energy storage converter, wherein the feasible domain is a region that meets the maximum current amplitude requirement, the voltage amplitude range requirement, and the modulation ratio range requirement;

[0130] An intersection determination unit 1202 is configured to determine an intersection of the feasible region and a rated active power contour line;

[0131] a value range determining unit 1203, configured to determine the value ranges of reactive power and voltage control parameters according to the intersection point;

[0132] The grid-connected conversion control unit 1204 is used to control the grid-connected conversion of the energy storage converter according to the value range of the reactive power and voltage control parameters.

[0133] The control device of the energy storage converter shown in FIG12 corresponds to the control method of the energy storage converter shown in FIG1 .

[0134] Figure 13 is a schematic diagram of a control device for an energy storage converter provided in one embodiment of the present application. As shown in Figure 13 , the control device 13 for the energy storage converter in this embodiment includes a processor 130, a memory 131, and a computer program 132 stored in the memory 131 and executable on the processor 130, such as an energy storage converter control device program. When the processor 130 executes the computer program 132, it implements the steps described in each of the aforementioned embodiments of the energy storage converter control device method. Alternatively, when the processor 130 executes the computer program 132, it implements the functions of each module / unit described in each of the aforementioned apparatus embodiments.

[0135] Exemplarily, the computer program 132 may be divided into one or more modules / units, which are stored in the memory 131 and executed by the processor 130 to complete the present application. The one or more modules / units may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution process of the computer program 132 in the control device 13 of the energy storage converter.

[0136] The control device of the energy storage converter may include, but is not limited to, a processor 130 and a memory 131. Those skilled in the art will understand that FIG13 is merely an example of the control device 13 of the energy storage converter and does not constitute a limitation on the control device 13 of the energy storage converter. The control device 13 may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the control device of the energy storage converter may also include input and output devices, network access devices, buses, etc.

[0137] The processor 130 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0138] The memory 131 may be an internal storage unit of the control device 13 of the energy storage converter, such as a hard disk or memory of the control device 13 of the energy storage converter. The memory 131 may also be an external storage device of the control device 13 of the energy storage converter, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. equipped on the control device 13 of the energy storage converter. Furthermore, the memory 131 may also include both an internal storage unit and an external storage device of the control device 13 of the energy storage converter. The memory 131 is used to store the computer program and other programs and data required by the control device of the energy storage converter. The memory 131 may also be used to temporarily store data that has been output or is to be output.

[0139] In addition, an embodiment of the present application further provides an electric energy storage system, which includes a memory and a processor, and the processor is used to implement the steps of the method shown in Figure 1 when executing a computer program. The electric energy storage system may include a control device and an energy storage device of an energy storage converter. As shown in Figure 6, the control device of the energy storage converter may include a power synchronization control module M1, a reactive voltage control module M2, a reference voltage generation module M3, a signal acquisition and processing module M4, and a modulation and drive module M5. Through the reactive voltage control module M2, the calculated value range of the reactive and voltage control parameters is used to perform grid connection control, reduce the probability of current or voltage exceeding the limit, and enable the energy storage converter to output stable active power.

[0140] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by 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 embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0141] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0142] Those skilled in the art will appreciate that the units and algorithm steps of each example 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 performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0143] In the embodiments provided in this application, it should be understood that the disclosed devices / terminal equipment and methods can be implemented in other ways. For example, the device / terminal equipment embodiments described above are merely illustrative. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0144] The units described as separate components may or may not be physically separate, and 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 these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0145] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0146] If the integrated module / unit is implemented in the form of 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, the present application implements all or part of the processes in the above-mentioned embodiment method, which can also be completed by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed by the processor, it can implement the steps of the above-mentioned various method embodiments. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0147] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A control method for an energy storage converter, characterized in that: The method comprises: Determining a feasible domain of the energy storage converter, wherein the feasible domain meets preset current change requirements and voltage change requirements; Determine the intersection point of the feasible region and the rated active power contour line; Determining the value range of reactive power and voltage control parameters according to the intersection point; The grid-connected conversion of the energy storage converter is controlled according to the value range of the reactive power and voltage control parameters.

2. The method according to claim 1, characterized in that Determining the feasible domain of the energy storage converter includes: Determining the feasible domain of the energy storage converter according to the preset maximum current amplitude and voltage amplitude range of the energy storage converter; Alternatively, the feasible domain of the energy storage converter is determined according to a preset maximum current amplitude and modulation ratio range of the energy storage converter; Alternatively, the feasible domain of the energy storage converter is determined according to a preset maximum current amplitude, voltage amplitude range, and modulation ratio range of the energy storage converter.

3. The method according to claim 2, characterized in that Determining the feasible domain of the energy storage converter according to the preset maximum current amplitude, voltage amplitude range and modulation ratio range of the energy storage converter includes: Determine a first range according to the contour lines corresponding to the maximum current amplitude; Determine the second range according to the contour line corresponding to the maximum voltage amplitude and / or the contour line corresponding to the minimum voltage amplitude of the voltage amplitude range; Determine a third range according to an isovalue line corresponding to the highest modulation ratio and / or an isovalue line corresponding to the lowest modulation ratio in the modulation ratio range; The feasible domain of the energy storage converter is determined according to the intersection of the first range, the second range and the third range.

4. The method according to claim 2, characterized in that: Determining the feasible domain of the energy storage converter according to the preset maximum current amplitude and voltage amplitude range of the energy storage converter includes: Determine a first range according to the contour lines corresponding to the maximum current amplitude; Determine the second range according to the contour line corresponding to the maximum voltage amplitude and / or the contour line corresponding to the minimum voltage amplitude of the voltage amplitude range; The feasible domain of the energy storage converter is determined according to the intersection of the first range and the second range.

5. The method according to claim 2, characterized in that: Determining the feasible domain of the energy storage converter according to the preset maximum current amplitude and modulation ratio range of the energy storage converter includes: Determine a first range according to the contour lines corresponding to the maximum current amplitude; Determine a third range according to an isovalue line corresponding to the highest modulation ratio and / or an isovalue line corresponding to the lowest modulation ratio in the modulation ratio range; The feasible domain of the energy storage converter is determined according to the intersection of the first range and the third range.

6. The method according to claim 1, characterized in that Before determining the feasible region of the energy storage converter, the method further includes: A plane coordinate system is established to represent the grid voltage vector, the grid connection point voltage vector and the voltage drop vector of the output current of the energy storage converter on the grid impedance; Two or three of the current amplitude contour lines, modulation ratio contour lines and voltage amplitude contour lines of the energy storage converter in the plane coordinate system are determined according to the grid voltage vector, the grid connection point voltage vector and the voltage drop vector.

7. The method according to claim 6, characterized in that The grid voltage vector, the grid connection point voltage vector and the voltage drop vector of the output current of the energy storage converter on the grid impedance are represented by establishing a plane coordinate system, including: Establish a plane coordinate system, with the grid voltage vector and the starting point of the grid connection point voltage vector of the energy storage converter as the origin, and the end of the grid voltage vector as (U g , 0), the end of the grid connection point voltage vector of the energy storage converter is (x, y), the grid voltage vector and the grid connection point voltage vector are determined, wherein, U g is the modulus length of the grid voltage vector, is the modulus of the grid-connected point voltage vector, arctan(y / x) is the directional deviation between the grid-connected point voltage vector and the grid voltage vector; Determine the voltage drop vector (xU) of the output current of the energy storage converter on the grid impedance according to the grid voltage vector and the grid connection point voltage vector g , y).

8. The method according to claim 6, characterized in that Determining the current amplitude contour line, the modulation ratio contour line and the voltage amplitude contour line of the energy storage converter in the plane coordinate system according to the grid voltage vector, the grid connection point voltage vector and the voltage drop vector, including: Determine the current amplitude contour equation of the energy storage converter in the plane coordinate system according to the grid voltage vector, the grid connection point voltage vector and the voltage drop vector; Determine the modulation ratio contour equation of the energy storage converter in the plane coordinate system according to the grid voltage vector, the grid connection point voltage vector and the voltage drop vector; The voltage amplitude contour equation of the energy storage converter in the plane coordinate system is determined according to the grid voltage vector, the grid connection point voltage vector and the voltage drop vector.

9. The method according to claim 8, characterized in that: The current amplitude contour equation of the energy storage converter in the plane coordinate system is: The modulation ratio contour equation of the energy storage converter in the plane coordinate system is: The voltage amplitude contour equation of the energy storage converter in the plane coordinate system is: Among them, X g is the impedance of the inductive grid, X f is the impedance of the energy storage converter filter inductor, U dcm is the DC modulation voltage, I s is the current amplitude at the contour line of the energy storage converter output, η is the modulation ratio at the contour line, U s is the voltage amplitude at the contour line of the energy storage converter output, U g is the modulus length of the grid voltage vector.

10. The method according to claim 1, characterized in that Determining the intersection of the feasible region and the rated active power contour line includes: Determine the rated active power contour equation of the energy storage converter in the plane coordinate system according to the grid voltage vector, the grid connection point voltage vector and the voltage drop vector; The intersection point of the feasible region and the rated active power contour line is determined according to the linear equation of the rated active power.

11. The method according to claim 10, characterized in that The rated active power contour equation of the energy storage converter in the plane coordinate system is: n X g =U g y, where X g is the impedance of the inductive grid, P n is the rated active power.

12. The method according to claim 1, characterized in that Determining the intersection of the feasible region and the rated active power contour line includes: When the rated active power contour line does not pass through the feasible domain, adjust one or more of the maximum current amplitude of the energy storage converter, the maximum voltage amplitude of the energy storage converter, the maximum modulation ratio of the energy storage converter and the DC modulation voltage of the energy storage converter until the rated active power contour line passes through the feasible domain.

13. The method according to claim 1, characterized in that Determining the value range of reactive power and voltage control parameters according to the intersection point includes: Determine the reactive power and voltage value corresponding to the intersection, wherein the reactive power Q s satisfy: Grid voltage amplitude U s satisfy: U g Indicates the modulus length of the grid voltage vector, Q s represents reactive power, (x,y) represents the coordinates of the grid connection point voltage vector in the plane coordinate system, X g Indicates the impedance of the inductive grid; According to the reactive power and voltage values ​​corresponding to the intersection points, combined with the predetermined grid connection point voltage setting value and grid connection point reactive power setting value, the value range of the reactive power and voltage control parameters is obtained.

14. The method according to claim 13, characterized in that According to the reactive power and voltage values ​​corresponding to the intersection, combined with the predetermined grid connection point voltage setting value and grid connection point reactive power setting value, the value range of the reactive power and voltage control parameters is obtained, including: According to the reactive power and voltage values ​​corresponding to the intersection, combined with the predetermined grid connection point voltage setting value and grid connection point reactive power setting value, the value range of the reactive power and voltage control parameters is obtained as (K vN <K v <K vM ); in, U s0 is the grid connection point voltage setting value, Q s0 is the reactive power setting value of the grid connection point, M and N are the intersection points, and U M , Q M They represent the voltage and reactive power at the intersection M, U N , Q N They represent the voltage and reactive power at the intersection N respectively.

15. The method according to claim 14, characterized in that The energy storage converter satisfies (U s0 -U s )=-K v (Q s0 -Q s ), where U s Indicates the voltage amplitude at the grid connection point, Q s Indicates the reactive power at the grid connection point.

16. A control device for an energy storage converter, characterized in that: The control device comprises: A feasible domain determination unit, used to determine a feasible domain of the energy storage converter, wherein the feasible domain meets preset current change requirements and voltage change requirements; An intersection determination unit, used to determine the intersection of the feasible region and the rated active power contour line; A value range determination unit, used to determine the value range of reactive power and voltage control parameters according to the intersection point; A grid-connected conversion control unit is used to control the grid-connected conversion of the energy storage converter according to the value range of the reactive power and voltage control parameters.

17. A control device for an energy storage converter, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 15 are implemented.

18. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 15 are implemented.

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