Grid-connected control method for energy storage converters

Abstract

This application relates to a grid-connected control method for an energy storage converter. The method includes: acquiring a first intersection point and a second intersection point within any sampling period of a triangular carrier wave; calculating the current abscissa value of a third intersection point and the current abscissa value of a fourth intersection point within the current sampling period; acquiring the error between the current output power and the target output power; obtaining the historical abscissa values ​​of the third and fourth intersection points; correcting the current abscissa value; determining the rectangular pulse of the current sampling period, and then outputting a rectangular pulse sequence; and controlling the output power of the energy storage converter. Through the technical solution of this application, an accurate equivalent pulse sequence can be generated efficiently, thereby accurately controlling the output power of the PCS (Power Storage Converter).

Description

Technical Field

[0001] This application generally relates to the field of energy storage converter technology, and more particularly to a grid-connected control method for an energy storage converter. Background Technology

[0002] A power conversion system (PCS) is the interface between the power grid and energy storage devices. It is suitable for applications requiring dynamic energy storage. When there is a power surplus, it stores electrical energy; when there is a power shortage, it converts the stored energy and outputs it to the grid, or it can serve as the main power source for a microgrid. Power conversion systems are used in energy storage systems. Figure 1 This is a schematic diagram of a smart grid after the introduction of an energy storage system. For example... Figure 1 As shown, the energy storage converter connects to the public power grid through the energy storage components. During periods of low grid load, it converts the AC power in the grid into DC power to charge the energy storage components. During periods of high grid load, it converts the DC power in the energy storage components into AC power that meets the grid requirements and feeds it back into the public power grid, thus playing a role in peak shaving and valley filling and ensuring the normal operation of the power grid.

[0003] The PCS (Power Control System) consists of a DC / AC bidirectional converter, a controller, and other components. The PCS controller receives control commands and, based on the sign and magnitude of these commands, controls the converter to charge or discharge the energy storage device, while simultaneously smoothing the output of fluctuating power sources such as wind and solar power. The PCS employs dual closed-loop control and SPWM pulse modulation, enabling precise and rapid adjustment of output voltage, frequency, active power, and reactive power.

[0004] SPWM (Sinusoidal PWM) is a very mature and widely used technology. SPWM is based on PWM (Pulse Width Modulation). PWM is based on the principle of area equivalence, meaning that when narrow pulses of equal impulse but different shapes are applied to an inertial circuit, their effects are essentially the same. In other words, a series of narrow pulse signals with different shapes have equal integrals over time (equal areas), resulting in the same final effect. PWM changes the equivalent output voltage by altering the duty cycle of the output square wave. SPWM modifies the modulation pulse method, arranging the pulse width and duty cycle according to a sinusoidal pattern. This allows the output waveform to be converted into a sine wave after appropriate filtering. Therefore, SPWM essentially uses a sequence of pulses with equal amplitude to represent a sine wave. SPWM is widely used in energy storage converters, where the output power can be adjusted by changing the frequency and amplitude of the modulation wave.

[0005] Traditional sampling methods for generating equivalent pulse sequences mainly include three types: natural sampling, symmetric regular sampling, and asymmetric regular sampling. Natural sampling offers high accuracy but incurs excessive computational cost. Symmetric regular sampling, while having relatively lower computational cost, generally has lower accuracy. Asymmetric regular sampling, although more accurate than symmetric regular sampling, still requires significant computation. Therefore, none of these sampling methods can balance computational cost and accuracy, failing to efficiently generate accurate equivalent pulse sequences, thus hindering precise control of the PCS's output power. Summary of the Invention

[0006] To address the aforementioned technical problems in the prior art, this application provides a grid-connected control method for an energy storage converter, aiming to efficiently generate an accurate equivalent pulse sequence and thus accurately control the output power of the PCS.

[0007] This application provides a grid-connected control method for an energy storage converter, wherein the energy storage converter controls its output power using SPWM (Signaled Width Modulation) mode. The SPWM mode includes modulating a triangular carrier wave with a sinusoidal modulation wave to output a rectangular pulse sequence. The method includes: within any sampling period of the triangular carrier wave, acquiring the first and second intersection points of the perpendicular bisector of the peak in the current sampling period and the peak in the next sampling period with the sinusoidal modulation wave; within the current sampling period, calculating the current abscissa value of the third intersection point of the line containing the first and second intersection points with the falling edge of the triangular carrier wave, and the abscissa value of the line with the rising edge of the triangular carrier wave. The current abscissa value of the fourth intersection point; the error between the current output power and the target output power within the current sampling period; the historical abscissa values ​​of the third and fourth intersection points within historical sampling periods, wherein the historical sampling periods are one or more sampling periods prior to the current sampling period; the current abscissa value is corrected based on the error and the historical abscissa value to obtain a corrected abscissa value; the rectangular pulse of the current sampling period is determined based on the corrected abscissa values ​​of the third and fourth intersection points, and then a rectangular pulse sequence is output; the output power of the energy storage converter is controlled based on the rectangular pulse sequence.

[0008] In one embodiment, correcting the current horizontal coordinate value based on the error and the historical horizontal coordinate value to obtain the corrected horizontal coordinate value includes:

[0009] Calculate the relative abscissa values ​​of the third intersection point and the fourth intersection point within the current sampling period, wherein the relative abscissa value of the third intersection point is the difference between the current abscissa value of the third intersection point and the abscissa value at the start of the current sampling period, and the relative abscissa value of the fourth intersection point is the difference between the current abscissa value of the fourth intersection point and the abscissa value at the start of the current sampling period; calculate the average of the relative abscissa values ​​corresponding to the third intersection point and the fourth intersection point within multiple historical sampling periods, and use this average relative abscissa value as the average relative abscissa value of the third intersection point and the fourth intersection point; calculate the confidence level of the current abscissa value based on the error; and correct the current abscissa value based on the current abscissa value, the relative abscissa value, the average relative abscissa value, and the confidence level to obtain the corrected abscissa value.

[0010] In one embodiment, correcting the current horizontal coordinate value based on the current horizontal coordinate value, the relative horizontal coordinate value, the average relative horizontal coordinate value, and the confidence level to obtain the corrected horizontal coordinate value includes: calculating the corrected horizontal coordinate value according to the following equation:

[0011]

[0012] in, The corrected x-coordinate value, The current x-coordinate value, The relative x-coordinate value, The average relative abscissa value, The confidence level is denoted as .

[0013] In one embodiment, calculating the average relative abscissa values ​​corresponding to the third and fourth intersection points within multiple historical sampling periods includes: selecting historical sampling periods similar to the current sampling period from all historical sampling periods preceding the current sampling period of the triangular carrier, wherein the similar historical sampling period refers to a period that differs from the current sampling period by a certain margin. k The historical sampling periods of each sampling period, where k = T s / T t, where T s is the period of the sinusoidal modulation wave. T t is the period of the triangular carrier wave; the average relative abscissa value corresponding to the third and fourth intersection points in multiple similar historical sampling periods is calculated respectively, and used as the average relative abscissa value.

[0014] In one embodiment, calculating the average relative abscissa value corresponding to the third intersection point and the fourth intersection point within a plurality of similar historical sampling periods includes: selecting a qualified similar historical sampling period from the plurality of similar historical sampling periods, wherein the qualified similar historical sampling period refers to a similar historical sampling period whose corresponding power error is within the range of the error corresponding to the current sampling period; and calculating the average relative abscissa value corresponding to the third intersection point and the fourth intersection point within the plurality of qualified similar historical sampling periods as the average relative abscissa value.

[0015] In one embodiment, controlling the output power of the energy storage converter according to the rectangular pulse sequence includes: acquiring the output power of the photovoltaic power generation; and adjusting the output power of the energy storage converter according to the rectangular pulse sequence so that the sum of the output power of the photovoltaic power generation and the output power of the photovoltaic power generation is constant.

[0016] The technical solution of this application has the following beneficial technical effects:

[0017] The technical solution of this application firstly designs an improved sampling method for the SPWM control process of energy storage converters, which improves accuracy while reducing computational load, thus balancing computational load and accuracy. In order to further reduce the potential error introduced by the sampling process, based on the periodicity of the triangular carrier and sinusoidal modulation wave involved in SPWM, when calculating the rectangular pulse of the current sampling period, the sampling data in the current sampling period is combined with the sampling data in the historical sampling period, thereby reducing the potential error caused by random factors and external interference, and further improving the accuracy of the SPWM control process. Attached Figure Description

[0018] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0019] Figure 1 This is a schematic diagram of a smart grid after the introduction of an energy storage system;

[0020] Figure 2 This is a flowchart of a grid-connected control method for an energy storage converter according to an embodiment of this application;

[0021] Figure 3 This is a schematic diagram illustrating the principles of three sampling methods in the existing technology;

[0022] Figure 4 This is a schematic diagram illustrating the principle of the sampling method according to an embodiment of this application;

[0023] Figure 5This is a schematic diagram comparing the sampling method according to the embodiments of this application with the asymmetric rule sampling method in the prior art;

[0024] Figure 6 This is a flowchart illustrating the correction of the current horizontal coordinate value according to an embodiment of this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] It should be understood that when the terms "first," "second," etc., are used in the claims, description, and drawings of this application, they are only used to distinguish different objects and not to describe a specific order. The terms "comprising" and "including" used in the description and claims of this application indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0027] According to a first aspect of this application, this application provides a grid-connected control method for an energy storage converter. The grid-connected control method is applied to an energy storage converter in a power grid, for example... Figure 1 The energy storage converter shown is configured to control its output power using SPWM (Sine Wave Width Modulation), which involves modulating a triangular carrier wave with a sinusoidal modulation wave to output a rectangular pulse sequence.

[0028] Figure 2 This is a flowchart of a grid-connected control method for an energy storage converter according to an embodiment of this application. Figure 2 As shown, the grid connection control method includes steps S201 to S206, which are explained in detail below.

[0029] S201, within any sampling period of the triangular carrier wave, obtain the first and second intersection points of the perpendicular bisector of the peak in the current sampling period and the sinusoidal modulation wave with the peak in the next sampling period.

[0030] S202, within the current sampling period, calculate the current abscissa value of the third intersection point of the line containing the first intersection point and the second intersection point with the falling edge of the triangular carrier, and the current abscissa value of the fourth intersection point of the line with the rising edge of the triangular carrier.

[0031] The above two steps, S201 and S202, briefly describe the sampling process of the method in this application. Based on the inventive concept of this application, the inventors first designed an improved sampling method for the SPWM control process of an energy storage converter. Traditional sampling methods for generating equivalent pulse sequences mainly include three types: natural sampling, symmetrical regular sampling, and asymmetrical regular sampling. Figure 3 The diagram illustrates the principles of the three sampling methods described above. Figure 3 In the diagram, A' and B' are the intersection points of the sinusoidal modulated wave and the triangular carrier wave; A and B are the approximate simulation points of A' and B', respectively. t ' on The high-level time before sampling point C; t '' on The high-level time after sampling point C; t ' off This refers to the low-level time between sampling point C and the end of the previous cycle; t '' off This refers to the low-level time after sampling point C before the start of the next cycle. In the natural sampling method, the intersection points A and B of the sinusoidal modulated wave and the triangular carrier wave are the switching moments of the switching device. t A , t B In the symmetrical regular sampling method, the trough position of each triangular carrier cycle is the sine wave sampling point (point C). At point C, [the sampling point is...]. t A line parallel to the axis intersects the two hypotenuses of the triangular carrier wave at points A and B. Its corresponding... t A , t B This refers to the switching timing of the switching transistor. Unlike the symmetrical regular sampling method, the traditional asymmetric regular sampling method samples twice within each triangular carrier cycle, once at the trough and once at the peak, as shown by points C and D in the figure. Time axes are plotted at points D and C respectively. t The parallel lines intersect the two hypotenuses of the triangular carrier wave at points A and B, and their corresponding... t A , t B This refers to the switching time of the switching transistor.

[0032] according to Figure 3Analysis shows that among the three sampling methods, the natural sampling method has the highest accuracy, but its computational load is too high, requiring two samples in each sampling period and calculating the positions of the two intersection points of the triangular carrier wave and the sinusoidal modulated wave. The symmetrical regular sampling method only requires one sample in the middle of each sampling period and calculates the positions of the two symmetrical intersection points; although the computational load is relatively small, its accuracy is generally lower. The asymmetric regular sampling method has higher accuracy than the symmetrical regular sampling method, but its computational load is relatively high, and its sampling frequency is twice that of the symmetrical regular sampling method.

[0033] The inventors further improved upon the asymmetric regular sampling method, designing a new sampling method called the line segment approximation method. Figure 4 This is a schematic diagram illustrating the principle of the sampling method according to an embodiment of this application.

[0034] like Figure 4 As shown, sampling is performed at the crest position of the triangular carrier wave (the crest and trough are the same), that is, a perpendicular line is drawn to intersect the sine wave at points P1 and P2. The sine wave intersects the triangular carrier wave at points A' and B'. The line segment formed by connecting points P1 and P2 intersects the sine wave at points A and B.

[0035] While traditional natural sampling methods offer high accuracy, they require calculating specific intersection points A' and B', which involves a large computational load and makes them unsuitable for digital control. Symmetrical regular sampling methods, on the other hand, are less accurate and therefore less widely used than asymmetric regular sampling methods. This solution directly compares asymmetric regular sampling methods with line segment approximation methods.

[0036] Figure 5 This is a schematic diagram comparing the sampling method according to the embodiments of this application with the asymmetric rule sampling method in the prior art. Figure 5 As shown, points D and E are the sampling points of the sampling method in this application, and line segment DE intersects the triangular carrier at points A'' and B''. Firstly, the line segment approximation method is consistent with the symmetrical regular sampling method in terms of sampling frequency, requiring only one sampling within each triangular carrier cycle. Therefore, the computational load is significantly reduced compared to the asymmetric regular sampling method. Furthermore, compared to the asymmetric regular sampling method, the intersection point A'' between the line containing the ordinate of point P1 and the triangular harmonic is closer to A' than A'. Similarly, the intersection point B'' is also closer to B', thus enabling a more accurate fitting of the sine wave waveform. Moreover, since the coordinates of points P1 and P2 are known, the equation of the corresponding line segment can be easily calculated, thereby obtaining the coordinate positions of the intersection points A'' and B'' between the equation of the line segment and the triangular carrier. Detailed calculation processes are not elaborated here.

[0037] Based on the above analysis, it can be seen that the line segment approximation method described in this scheme, compared with the traditional sampling method, can improve the accuracy of fitting sine waveforms while greatly reducing the amount of computation.

[0038] S203, obtain the error between the current output power and the target output power within the current sampling period.

[0039] After sampling is completed, the sampled data needs further correction. To do this, the error between the current output power and the target output power within the current sampling period is obtained. Specifically, the current output power is the real-time output power, which can be obtained through the monitoring device in the energy storage converter. Alternatively, the current output power can be the average power within the current sampling period.

[0040] S204, obtain the historical abscissa values ​​of the third and fourth intersection points within the historical sampling period, wherein the historical sampling period is one or more sampling periods prior to the current sampling period.

[0041] Specifically, the sampling data in the current sampling period is corrected based on the sampling data from the historical sampling periods. Preferably, the historical sampling periods are adjacent to the current sampling period, so the correlation between the sampling data of the two periods may be higher, and the reference value is greater.

[0042] S205, correct the current horizontal coordinate value based on the error and the historical horizontal coordinate value to obtain the corrected horizontal coordinate value.

[0043] Figure 6 This is a flowchart illustrating the correction of the current horizontal coordinate value according to an embodiment of this application. Figure 6 As shown, the step of correcting the current horizontal coordinate value based on the error and the historical horizontal coordinate value to obtain the corrected horizontal coordinate value includes the following steps S2051 to S2054.

[0044] S2051, calculate the relative abscissa values ​​of the third intersection point and the fourth intersection point within the current sampling period, wherein the relative abscissa value of the third intersection point is the abscissa difference between the current abscissa value of the third intersection point and the abscissa value at the start of the current sampling period, and the relative abscissa value of the fourth intersection point is the abscissa difference between the current abscissa value of the fourth intersection point and the abscissa value at the start of the current sampling period.

[0045] Specifically, since it is impossible to average the absolute abscissa values, the relative abscissa values ​​of the third and fourth intersection points relative to the starting point of their respective cycles can be calculated, and subsequent calculations can be performed based on the relative abscissa values, thereby ensuring the accuracy of the abscissa value calculation.

[0046] S2052, calculate the average of the relative abscissa values ​​corresponding to the third and fourth intersection points in multiple historical sampling periods, and use them as the average relative abscissa values ​​of the third and fourth intersection points.

[0047] Specifically, in order to eliminate potential errors caused by random factors and other interference factors, the average relative abscissa values ​​corresponding to the third and fourth intersection points in multiple historical sampling periods are calculated respectively.

[0048] Based on the periodicity of the triangular carrier function and the sinusoidal carrier function, a sampling period similar to the current sampling period can be selected from historical sampling periods. Specifically, calculating the average relative abscissa values ​​corresponding to the third and fourth intersection points within multiple historical sampling periods includes: selecting historical sampling periods similar to the current sampling period from all historical sampling periods preceding the current sampling period of the triangular carrier, wherein the similar historical sampling period refers to a period that differs from the current sampling period by a certain margin. k The historical sampling periods of each sampling period, where k = T s / T t, where T s is the period of the sinusoidal modulation wave. T t is the period of the triangular carrier wave; the average relative abscissa value corresponding to the third and fourth intersection points in multiple similar historical sampling periods is calculated respectively, and used as the average relative abscissa value.

[0049] To further improve the accuracy of the average value calculation, a more interesting sampling period can be selected from the aforementioned similar historical sampling periods, such as a sampling period with smaller errors. Specifically, the step of calculating the average relative abscissa value corresponding to the third and fourth intersection points within multiple similar historical sampling periods includes: selecting a qualified similar historical sampling period from the multiple similar historical sampling periods, wherein the qualified similar historical sampling period refers to a similar historical sampling period whose corresponding power error is within the range of the error corresponding to the current sampling period; and calculating the average relative abscissa value corresponding to the third and fourth intersection points within the multiple qualified similar historical sampling periods as the average relative abscissa value.

[0050] S2053, Calculate the confidence level of the current horizontal coordinate value based on the error.

[0051] Specifically, the error indicates the reliability of the current horizontal coordinate value. The larger the error, the lower the reliability of the current horizontal coordinate value, and the more historical data needs to be assigned greater weight for compensation.

[0052] S2054, Based on the current horizontal coordinate value, the relative horizontal coordinate value, the average relative horizontal coordinate value, and the confidence level, the current horizontal coordinate value is corrected to obtain the corrected horizontal coordinate value.

[0053] Specifically, the corrected x-coordinate value is calculated according to the following equation:

[0054]

[0055] in, The corrected x-coordinate value, The current x-coordinate value, The relative x-coordinate value, The average relative abscissa value, The confidence level is denoted as .

[0056] S206, Based on the corrected abscissa values ​​of the third intersection point and the fourth intersection point, determine the rectangular pulse of the current sampling period, and then output the rectangular pulse sequence.

[0057] Specifically, the switching on and off of the control switch is based on the corrected horizontal coordinate value to output a rectangular pulse for the current sampling period. This process is repeated to obtain rectangular pulses for multiple sampling periods, generating a rectangular pulse sequence and outputting it to fit a sine wave.

[0058] S207, control the output power of the energy storage converter according to the rectangular pulse sequence.

[0059] The energy storage converter can actively support the grid voltage and frequency, maintaining stable photovoltaic power generation output by storing and releasing battery energy. This generates a fluctuation curve that complements the photovoltaic power generation output fluctuations shown in the figure, ultimately achieving the effect of smoothly integrating photovoltaic power generation output into the power system. Accordingly, controlling the output power of the energy storage converter based on the rectangular pulse sequence includes: acquiring the photovoltaic power generation output power; and adjusting the output power of the energy storage converter according to the rectangular pulse sequence to keep the sum of its output power and the photovoltaic power generation output power constant.

[0060] The technical principles and implementation details of the grid-connected control method for the energy storage converter of this application have been described above through specific embodiments. The technical solution provided by this application can efficiently generate accurate equivalent pulse sequences, thereby accurately controlling the output power of the PCS.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A grid-connected control method of an energy storage converter, wherein the energy storage converter controls output power by an SPWM method including modulating a triangular carrier wave using a sinusoidal modulation wave to output a rectangular pulse sequence, characterized by, The method comprises the following steps: In any sampling period of the triangular carrier, the first intersection point and the second intersection point of the median line at the wave peak in the current sampling period and the wave peak in the next sampling period and the sinusoidal modulation wave are obtained; In the current sampling period, the current horizontal coordinate value of the third intersection point of the straight line where the first intersection point and the second intersection point are located and the falling edge of the triangular carrier, and the current horizontal coordinate value of the fourth intersection point of the straight line and the rising edge of the triangular carrier are calculated; The error between the current output power and the target output power in the current sampling period is obtained; The historical horizontal coordinate values of the third intersection point and the fourth intersection point in the historical sampling period are obtained, wherein the historical sampling period is one or more sampling periods before the current sampling period; The current horizontal coordinate value is corrected according to the error and the historical horizontal coordinate value to obtain a corrected horizontal coordinate value; According to the corrected horizontal coordinate value of the third intersection point and the fourth intersection point, the rectangular pulse of the current sampling period is determined, and then a rectangular pulse sequence is outputted; The output power of the energy storage converter is controlled according to the rectangular pulse sequence.

2. The grid-connected control method of an energy storage converter according to claim 1, characterized in that, The correction of the current horizontal coordinate value according to the error and the historical horizontal coordinate value to obtain a corrected horizontal coordinate value comprises: The relative horizontal coordinate values of the third intersection point and the fourth intersection point in the current sampling period are calculated respectively, wherein the relative horizontal coordinate value of the third intersection point is the horizontal coordinate difference value between the current horizontal coordinate value of the third intersection point and the horizontal coordinate value at the start of the current sampling period, and the relative horizontal coordinate value of the fourth intersection point is the horizontal coordinate difference value between the current horizontal coordinate value of the fourth intersection point and the horizontal coordinate value at the start of the current sampling period; The average values of the relative horizontal coordinate values corresponding to the third intersection point and the fourth intersection point in multiple historical sampling periods are calculated respectively as the average relative horizontal coordinate values of the third intersection point and the fourth intersection point; The confidence of the current horizontal coordinate value is calculated according to the error; The current horizontal coordinate value is corrected according to the current horizontal coordinate value, the relative horizontal coordinate value, the average relative horizontal coordinate value and the confidence to obtain the corrected horizontal coordinate value.

3. The grid-connected control method of an energy storage converter according to claim 2, wherein, The correction of the current horizontal coordinate value according to the current horizontal coordinate value, the relative horizontal coordinate value, the average relative horizontal coordinate value and the confidence to obtain the corrected horizontal coordinate value comprises calculating the corrected horizontal coordinate value according to the following equation: wherein, is the modified horizontal coordinate value, is the current horizontal coordinate value, is the relative horizontal coordinate value, is the average relative horizontal coordinate value, is the confidence level.

4. The grid-connected control method of an energy storage converter according to claim 2, wherein, The calculation of the average relative horizontal coordinate values corresponding to the third intersection point and the fourth intersection point in multiple historical sampling periods comprises: selecting a similar historical sampling period from all historical sampling periods preceding the current sampling period of the triangular carrier, wherein the similar historical sampling period refers to a historical sampling period that differs from the current sampling period by k one sampling period, wherein k = T s / T t, wherein T s is a period of the sinusoidal modulating wave, T t is a period of the triangular carrier; The average relative horizontal coordinate values corresponding to the third intersection point and the fourth intersection point in multiple similar historical sampling periods are calculated respectively as the average relative horizontal coordinate values.

5. The grid-connected control method of an energy storage converter according to claim 4, wherein, The calculation of the average relative horizontal coordinate values corresponding to the third intersection point and the fourth intersection point in multiple similar historical sampling periods comprises: The qualified similar historical sampling periods are selected from the multiple similar historical sampling periods, wherein the qualified similar historical sampling period refers to the similar historical sampling period whose corresponding power error is within the range of the error corresponding to the current sampling period. The average relative horizontal coordinate values corresponding to the third intersection point and the fourth intersection point in a plurality of qualified similar historical sampling periods are calculated respectively as the average relative horizontal coordinate values.

6. The grid-connected control method of an energy storage converter according to claim 1, wherein, The controlling the output power of the energy storage converter according to the rectangular pulse sequence comprises: Obtaining a photovoltaic power generation output power; According to the rectangular pulse sequence, adjusting the output power of the energy storage converter to be constant with the sum power of the photovoltaic power generation output power.

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