A bus current ripple suppression method, device and medium

Abstract

The application discloses a bus current ripple suppression method, device and medium; the method comprises the following steps: acquiring the electric quantity data of each DC voltage boosting circuit in the current operation state in real time; based on the obtained electric quantity data, the phase shift angle required by each DC voltage boosting circuit is calculated with the minimum total AC component output from all DC voltage boosting circuits to the DC bus as the target; and the driving signal of each DC voltage boosting circuit is phase-modulated according to the obtained phase shift angle. The device and the medium are used to implement the above method. The application has the beneficial effects that in the process of bus current ripple suppression, the phase shift angle can dynamically change instead of being fixed, thereby solving the problem of poor bus current ripple suppression effect when the input voltage and current are different. Directly selecting the minimum current ripple fundamental component or current ripple effective value as the optimization target can effectively reduce the heat generation of the system.

Description

Technical Field

[0001] This application relates to the field of new energy power generation technology, and in particular to a method, equipment and medium for suppressing bus current ripple. Background Technology

[0002] When an inverter system injects sinusoidal alternating current into the grid, its instantaneous power fluctuates. This fluctuation is reflected in the DC bus, causing second-harmonic ripple in the bus current and voltage, i.e., bus current ripple. Bus current ripple can cause a series of problems, including reduced system efficiency, impact on MPPT tracking accuracy, and reduced device lifespan.

[0003] There are two main methods for suppressing bus current ripple in traditional inverter systems: one is the fixed phase shift method, which lags the drive signals of each DC boost circuit according to the number of DC boost circuits operating in the inverter system; the other is the offline traversal method, which calculates the phase shift angle that minimizes the peak-to-peak value of the current ripple for each channel and stores it in flash memory in the form of a mapping table. When needed, the phase shift angle is obtained in real time by looking up the table.

[0004] Fixed phase-shifting methods are commonly used in scenarios where both input and output are connected in parallel and each DC-DC boost circuit has the same power rating. In such cases, a fixed phase-shift angle can achieve good ripple cancellation. However, in photovoltaic applications, each DC-DC boost circuit connects only its output to a common DC bus, while its input is connected to different PV strings. The voltage of the PV strings is affected by the number of PV panels configured by the user, and the current is affected by illumination, shading conditions, and the number of PV strings connected in parallel. This results in differences in the input voltage and current of each DC-DC boost circuit, affecting the ripple cancellation effect of the fixed phase-shift angle.

[0005] The offline traversal method has two main drawbacks: First, it equates minimizing the peak-to-peak value of the current ripple with minimizing the current ripple output to the DC bus. However, the peak-to-peak value of the current ripple does not correspond one-to-one with or have a strict positive correlation with the heating of passive components on the DC bus. Minimizing the peak-to-peak value of the current ripple does not necessarily mean minimizing the heating of passive components, and the phase shift angle obtained through this method usually deviates from the optimal result. Second, each additional DC-DC boost circuit requires adding a dimension to the mapping table, resulting in an exponential growth rate, which is not conducive to extending to applications with more DC-DC boost circuits. Summary of the Invention

[0006] One objective of this application is to provide a bus current ripple suppression method that can solve at least one of the defects in the above-mentioned background art.

[0007] Another object of this application is to provide an electronic device capable of implementing a bus current ripple suppression method that solves at least one of the defects in the above-mentioned background art.

[0008] Another object of this application is to provide a computer-readable storage medium capable of implementing a bus current ripple suppression method that addresses at least one of the defects in the aforementioned background art.

[0009] To achieve at least one of the above objectives, the technical solution adopted in this application is as follows: a bus current ripple suppression method, applied to a photovoltaic system with multiple DC boost circuits connected in parallel to a DC bus, comprising the following steps: real-time acquisition of power data of each DC boost circuit under its current operating state, the power data including input voltage, output voltage, average current, and duty cycle information; based on the acquired power data, dynamically calculating the required phase shift angle of each DC boost circuit with the goal of minimizing the total AC component output from all DC boost circuits to the DC bus; and performing phase modulation on the drive signal of each DC boost circuit according to the obtained phase shift angle.

[0010] Preferably, based on the obtained power data, the fundamental component of the current output from each of the DC boost circuits to the DC bus is extracted; the obtained fundamental component is used as a space vector, and the phase that minimizes the space vector sum of all the DC boost circuits is calculated to obtain the phase shift angle required to minimize the total AC component.

[0011] Preferably, based on the amplitude of the fundamental component corresponding to each DC-DC boost circuit, all DC-DC boost circuits are divided into two groups; the difference between the sum of the amplitudes of the fundamental components corresponding to the two groups of DC-DC boost circuits is minimized; the phase shift angles corresponding to the DC-DC boost circuits in each group are the same, and the phase difference between the phase shift angles corresponding to the two groups of DC-DC boost circuits is π.

[0012] Preferably, when the number of DC boost circuits N≥3, and the corresponding space vectors can be closed to form a closed figure, the calculation of the phase shift angle of each DC boost circuit includes the following process: taking the phase shift angle corresponding to one of the DC boost circuits as a reference, and combining it with the amplitude of each fundamental component, the phase shift angles corresponding to the remaining DC boost circuits are calculated with the goal of maximizing the area of ​​the closed figure formed by the space vectors.

[0013] Preferably, when the number of DC boost circuits N > 3, and the corresponding space vectors can form a closed figure, the calculation of the phase shift angle of each DC boost circuit includes the following process: sorting all current space vectors according to the amplitude of the fundamental component from largest to smallest, and merging the space vectors corresponding to the largest and smallest amplitudes in opposite phases to perform a vector recursive process to obtain a new space vector; performing the vector recursive process again on the new space vector and the unmerged space vectors until the obtained new space vector and the unmerged space vectors can form a closed triangle, and then solving the phase of all current space vectors based on the cosine theorem to obtain the required phase shift angle.

[0014] Preferably, the extraction of the fundamental component includes the following process: obtaining the inductor current waveform of the DC boost circuit in one switching cycle under steady state; extracting the output current waveform of the DC boost circuit from the inductor current waveform; removing the DC component of the output current waveform to obtain the AC component; converting the waveform of the AC component into a rectangular wave while keeping the area unchanged; performing a Fourier expansion on the obtained rectangular wave to obtain the Fourier series expansion of the rectangular wave; and taking the first term of the Fourier series expansion as the fundamental component.

[0015] Preferably, based on the obtained power data, the total AC component output from all the DC boost circuits to the DC bus is directly extracted; and the phase shift angle that minimizes the effective value of the total AC component is calculated.

[0016] Preferably, the AC components of the output current of each of the DC boost circuits are obtained, and all the obtained AC components are added together to obtain the total AC component; the root mean square of the total AC component is calculated to obtain the functional relationship between the effective value of the total AC component and the phase shift angle; the functional relationship is solved in real time online using a neural network model; wherein, the neural network model is pre-trained using a dataset obtained by optimizing the phase shift angle under different values ​​of the power data through an offline optimization algorithm.

[0017] An electronic device includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the above-described bus current ripple suppression method.

[0018] A computer-readable storage medium storing a computer program; when the computer program is executed by a processor, it implements the above-described bus current ripple suppression method.

[0019] Compared with the prior art, the beneficial effects of this application are as follows:

[0020] (1) In the process of suppressing bus current ripple, the phase shift angle can be dynamically changed instead of being fixed, thereby solving the problem of poor bus current ripple suppression effect when the input voltage and current are different.

[0021] (2) Directly selecting the minimum current ripple fundamental component or the effective value of current ripple as the optimization target can effectively reduce the heat generation of the system. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of one specific architecture of a traditional photovoltaic system.

[0023] Figure 2 This is a schematic diagram of the overall working steps of this application.

[0024] Figure 3 The diagram shows the waveform of the inductor current in different DC boost circuits in this application.

[0025] Figure 4 This is a schematic diagram of the extraction process of the fundamental component in this application.

[0026] Figure 5 This is a schematic diagram of the process for solving the phase shift angle based on the spatial vector corresponding to the fundamental component in this application.

[0027] Figure 6 This is a schematic diagram of the process for solving the phase shift angle based on the effective value of the total AC component in this application. Detailed Implementation

[0028] The present application will now be further described in conjunction with specific embodiments. It should be noted that, in the description of this specification, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0029] In the description of this application, it should be noted that the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., which indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of this application.

[0030] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0031] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0034] To facilitate understanding of the technical solution of this application, a brief description of the specific architecture of a traditional photovoltaic system will be provided below. Specifically, as follows... Figure 1As shown, the photovoltaic system includes multiple DC-DC boost circuits, a DC / AC circuit, and multiple PV strings. The number of PV strings is the same as the number of DC-DC boost circuits, so the input terminal of each DC-DC boost circuit is connected to the output terminal of a corresponding PV string; all DC-DC boost circuits are connected in parallel to the DC bus on the DC side of the DC / AC circuit through their output terminals, and the output terminal of the DC / AC circuit is connected to the power grid.

[0035] There are various specific structures for DC boost circuits. For ease of understanding, one typical structure will be described in detail below; for example... Figure 1 As shown, the DC boost circuit includes a capacitor, an inductor, a switching transistor Q1, and a switching transistor Q2. The capacitor is connected in parallel between the positive and negative output terminals of the PV string, the inductor is connected in series between the positive output terminal of the PV string, the switching transistor Q1 is connected in parallel between the output terminal of the inductor and the negative output terminal of the PV string, and the switching transistor Q2 is connected in series between the output terminal of the inductor and the DC positive bus.

[0036] When the DC boost circuit is operating, switching transistors Q1 and Q2 conduct complementaryly; that is, when switching transistor Q1 is on, switching transistor Q2 is off. At this time, the inductor current i... L The output current i of the DC boost circuit increases. o The current is zero; however, when switch Q2 is turned on, switch Q1 is turned off, and at this time the inductor current i L The output current i of the DC boost circuit decreases. o Rise to equal inductor current i L The duty cycle D for controlling the DC boost circuit is the proportion of the on-time of the switching transistor Q1 to the total switching cycle.

[0037] It is understandable that, as can be seen from the working process of the DC boost circuit described above, during the complementary operation of switching transistors Q1 and Q2, the inductor continuously stores and releases energy, which will generate current ripple on the DC bus.

[0038] To suppress the bus current ripple generated by the aforementioned photovoltaic system, one aspect of this application provides a bus current ripple suppression method, such as... Figure 2 and Figure 3 As shown, one preferred embodiment includes the following steps: real-time acquisition of power data of each DC-DC boost circuit under the current operating state, the power data including input voltage, output voltage, average current and duty cycle information; based on the acquired power data, with the goal of minimizing the total AC component output from all DC-DC boost circuits to the DC bus, calculating the required phase shift angle for each DC-DC boost circuit; and performing phase modulation on the drive signal of each DC-DC boost circuit according to the obtained phase shift angle.

[0039] Understandably, the core idea of ​​this application is to dynamically change the phase shift angle instead of keeping it fixed during the process of suppressing bus current ripple based on the input voltage, output voltage, average current, and duty cycle information of each DC boost circuit. The optimization goal is to cancel out the AC components generated by each DC boost circuit, thereby significantly reducing or completely eliminating the current ripple flowing into the DC bus capacitor. This reduces the heating of passive components, decreases the size of the converter, and improves the converter's efficiency. Compared to traditional methods, this approach solves the problem of poor bus current ripple suppression when the input voltage and current differ due to the traditional fixed phase shift angle method.

[0040] It should be understood that the phase shift angle is used to control the turn-on timing of the switching transistors in each DC-DC boost circuit. Since the inductor is in an energy-storing state when the switching transistor Q1 in the DC-DC boost circuit is turned on, the output current i... o The current is zero; however, when the switching transistor Q2 is turned on, the inductor releases energy, and the midpoint of the conduction time roughly corresponds to the output current i. o The pulse center position. Therefore, when defining the phase shift angle, in the multiple DC boost circuits included in the photovoltaic system, the midpoint of the conduction time of the switching transistor Q2 of one of the DC boost circuits can be used as the reference (i.e., the phase shift angle is 0). Then, the lag angle of the midpoint of the conduction time of the switching transistor Q2 of the other DC boost circuits relative to the reference can be regarded as the phase shift angle of the other DC boost circuits.

[0041] Specifically, such as Figure 3 As shown, assume there are three DC-DC boost circuits, and the inductor currents of the three DC-DC boost circuits are labeled as i. L1 i L2 i L3 The midpoint of the conduction time of switch Q2 corresponds to the inductor current i. L The midpoint of the single-cycle falling edge; then, with the inductor current i L1 Taking the midpoint of the corresponding falling edge as a reference, the inductor current i L2 The phase shift angle of the corresponding DC boost circuit is Inductor current i L3 The phase shift angle of the corresponding DC boost circuit is .

[0042] It is understandable that the output current i of each DC boost circuit can be changed by altering the phase shift angle. o The phase of the output current i can thus affect the phase of each output current i. o The superposition method at the DC bus; therefore, each output current i oWith the goal of minimizing the superposition of AC components at the DC bus, the required phase shift angle for each DC boost circuit can be calculated in reverse. Substituting the solution into the DC boost circuit for modulation allows control of the circuit's drive signal, enabling the DC boost circuit to control the switching timing of the transistors according to the calculated phase shift angle.

[0043] It should be noted that there are multiple ways to solve the phase shift angle with the objective of minimizing the superposition of the total AC components at the DC bus. For ease of understanding, two examples will be provided below for detailed explanation.

[0044] Example 1:

[0045] In this embodiment, as Figure 5 As shown, to solve the phase shift angle problem with the objective of minimizing the total AC component superposition at the DC bus, the fundamental component of the current output from each DC boost circuit to the DC bus can be extracted based on the obtained electrical data. Using the obtained fundamental component as a space vector, the phase that minimizes the sum of the space vectors corresponding to all DC boost circuits is calculated, thus obtaining the phase shift angle required to minimize the total AC component. Compared to traditional fixed phase shift methods and offline traversal methods, the technical solution of this embodiment has the advantages of simple calculation process and no need for additional table generation and storage.

[0046] In this embodiment, the fundamental component of the output current of the DC boost circuit is the fundamental component obtained with the switching frequency as the fundamental frequency. For ease of understanding, the extraction process of the fundamental component will be described in detail below.

[0047] like Figure 4 As shown in (a), the inductor current waveform of the DC-DC boost circuit in one switching cycle under steady state is obtained. Since the DC-DC boost circuit can only output when the switching transistor Q2 is turned on, the output current i of the DC-DC boost circuit is... o The waveform corresponds Figure 4 The shaded area in (a) is shown. For example... Figure 4 As shown in (b), the output current i of the DC boost circuit is obtained. o After obtaining the waveform, subtract the DC component from the obtained inductor current waveform to obtain the AC component. The AC component corresponds to... Figure 4 The shaded area in (b). After obtaining the AC component of the output current of the DC boost circuit, as shown... Figure 4 As shown in (c), with the area remaining constant, the waveform of the AC component is converted into a rectangular wave, corresponding to... Figure 4 The shaded area in (c). Figure 4 As shown in (d), the Fourier expansion of the waveform is performed with the center of the rectangular wave region as the origin of the coordinate system, and the Fourier series expansion of the rectangular wave is obtained. The first term of the Fourier series expansion is taken as the fundamental wave component.

[0048] It is important to know that the DC component of the output current of a DC boost circuit is equal to the average value of the output current. Obtaining the DC component is a well-known technique among those skilled in the art, and for ease of understanding, it will be briefly described below. From the aforementioned definition of duty cycle D, it can be seen that a single switching cycle T... s The conduction time of the switching transistor Q1 is equal to D·T s Then the conduction time of the switching transistor Q2, which outputs current in the DC boost circuit, is (1-D)·T. s The average value of the output current of the DC boost circuit can be expressed by the inductor current waveform in (1-D)·T. s Integrating over the time range, the DC component is obtained as (1-D)·I. L Among them, I L This represents the average value of the inductor current.

[0049] The expression for the Fourier expansion series in the rectangular wave region is as follows:

[0050] .

[0051] In the formula, n represents the number of terms in the Fourier expansion series, ω s Represents the switching angular frequency, ω s =2π / T s .

[0052] Based on the expression of the Fourier expansion series, when n is 1, the fundamental component i is obtained. o1 The expression is:

[0053] .

[0054] As can be seen from the above expression, the fundamental component i o1 The amplitude is only related to the average value I of the inductor current. L And related to the duty cycle D; based on the above expression, the fundamental component i o1 It can be viewed as a spatial vector whose magnitude is equal to its amplitude.

[0055] In this embodiment, there are multiple ways to solve the phase shift angle based on the spatial vector corresponding to the fundamental component. Furthermore, the solution of the phase shift angle is also related to the total number of DC boost circuits. For ease of understanding, the specific solution process of the phase shift angle will be described in detail below according to the different total number of DC boost circuits.

[0056] In one specific example, based on the amplitude of the fundamental component corresponding to each DC-DC boost circuit, all DC-DC boost circuits are divided into two groups; the difference between the sum of the amplitudes of the fundamental components corresponding to the two groups of DC-DC boost circuits is the smallest; the phase shift angles corresponding to the DC-DC boost circuits in each group are the same, and the phase difference between the phase shift angles corresponding to the two groups of DC-DC boost circuits is π.

[0057] To facilitate understanding, the above examples will be explained in detail below, using two-channel and three-channel DC boost circuits as examples respectively.

[0058] When there are two DC boost circuits, the way to minimize the sum of the two space vectors is to make the two space vectors out of phase. Then, taking the phase corresponding to one of the space vectors as the zero phase reference, the phase corresponding to the other space vector is π. Accordingly, the phase shift angle between the two DC boost circuits is π.

[0059] When there are three DC-DC boost circuits, we can assume that the amplitudes of the fundamental components corresponding to the three DC-DC boost circuits are A1, A2, and A3, respectively. Assuming A1 is the largest amplitude, then for these three amplitudes, the absolute value of A1 - (A2 + A3) is the smallest. Therefore, when we combine the DC-DC boost circuits corresponding to amplitude A1 as one group and the DC-DC boost circuits corresponding to amplitudes A2 and A3 as another group, the spatial vector sum is minimized. Thus, we can use the DC-DC boost circuit corresponding to amplitude A1 as the reference, and set the phase shift angle of the DC-DC boost circuits corresponding to amplitudes A2 and A3 to π.

[0060] It's important to understand that the optimal effect for suppressing bus current ripple is achieved when the space vector sum of all DC-DC boost circuits is zero. In the example above, this zero space vector sum is only possible when the sum of the amplitudes of the fundamental components corresponding to the two DC-DC boost circuits is equal. Even when the sums of the amplitudes of the fundamental components corresponding to the two DC-DC boost circuits are not equal, inverting the phases of the two fundamental components, while not achieving the optimal effect for current ripple suppression, still provides strong suppression by minimizing the difference in the sums of their amplitudes.

[0061] Those skilled in the art should know that when the total number of DC boost circuits is greater than or equal to three and is divided into two groups of DC boost circuits, if the sum of the amplitudes of the fundamental components corresponding to the two groups of DC boost circuits cannot be equal, then the amplitudes of all fundamental components satisfy the construction condition of a closed polygon, that is, the corresponding space vectors can form a closed polygon by connecting the beginning and end. Then, according to the composition rule of space vectors, the sum of the space vectors at this time is zero, that is, the best suppression of bus current ripple can be achieved. Then, only the phase of the corresponding space vector needs to be solved to obtain the corresponding phase shift angle.

[0062] To facilitate understanding, the following example will be used to illustrate the specific process of calculating the phase shift angle, assuming a DC boost circuit with three channels and corresponding space vectors that can form a closed triangle.

[0063] Specifically, we can let the amplitudes of the fundamental components corresponding to the three DC boost circuits be A, B, and C, respectively. If A > B > C, and A < B + C, then these three spatial vectors can be connected end-to-end to form a triangle. The amplitudes A, B, and C correspond to the three sides of the triangle, and we can let the angles corresponding to the sides A, B, and C be ∠1, ∠2, and ∠3, respectively. Based on the three sides of the triangle, using the law of cosines, we can solve for the specific values ​​of ∠1, ∠2, and ∠3, for example, ∠3 = arco(A + C). 2 +B 2 -C 2 ) / 2AB. When solving for the phase shift angle, the phase of the space vector corresponding to amplitude A can be taken as the reference zero phase. Then, the space vector corresponding to amplitude B should lag the phase of the space vector corresponding to amplitude A by (π-∠3); similarly, the space vector corresponding to amplitude C should lag the phase of the space vector corresponding to amplitude B by (π-∠1). Therefore, the expressions for these three space vectors are:

[0064] .

[0065] Based on the above expressions, the phase shift angle of the DC boost circuit corresponding to amplitude B is -π + ∠3, and the phase shift angle of the DC boost circuit corresponding to amplitude C is -2π + ∠2 + ∠3.

[0066] It should be understood that when performing phase calculations using closed shapes formed by space vectors, if the number of space vectors exceeds three (for example, four space vectors), the specific structural shapes of the closed quadrilateral formed by these four space vectors are infinite. This leads to an infinite number of solutions for the phase shift angle when the number of space vectors is large, which may significantly increase the computational workload of solving the phase shift angle. Therefore, to reduce the computational workload of solving the phase shift angle, this embodiment can provide constraints to solve for specific solutions of the phase shift angle in scenarios with a large number of space vectors. There are multiple ways to solve for specific solutions; for ease of understanding, the area method and the iterative method will be explained in detail below.

[0067] In a specific example, when the number of DC boost circuits N≥3 and the corresponding space vectors can be closed to form a closed figure, the process of calculating the phase shift angle of each DC boost circuit using the area method is as follows: taking the phase shift angle of one DC boost circuit as a reference, and combining the amplitude of each fundamental component, with the goal of maximizing the area of ​​the closed figure formed by the space vectors, the phase shift angles of the remaining DC boost circuits are calculated.

[0068] It is important to note that for solving closed figures with the maximum area, higher-order equations (2^(N-2)) can be constructed using geometric analysis. Since equations of degree 5 and above do not have a general solution, when the number of DC boost circuits N ≥ 5, numerical computation is required to solve the closed figures.

[0069] In a specific example, when the number of DC-DC boost circuits N > 3, and the corresponding space vectors can form a closed figure, the process of calculating the phase shift angle of each DC-DC boost circuit using the iterative method is as follows: Sort all current space vectors according to the amplitude of the fundamental component from largest to smallest, and merge the space vectors corresponding to the largest and smallest amplitudes in opposite phases to perform a vector recursive process to obtain a new space vector; perform the vector recursive process again on the new space vector and the unmerged space vectors until the new space vector and the unmerged space vectors can form a closed triangle, and then solve the phase of all current space vectors based on the cosine theorem to obtain the required phase shift angle.

[0070] Understandably, in each round of vector recursion, a pair of spatial vectors can be merged, reducing the total number of spatial vectors by one. Therefore, through multiple rounds of vector recursion, the total number of spatial vectors can be reduced to a predetermined number, typically three. At this point, the phase of the remaining spatial vectors can be calculated using the triangle rule, thus obtaining the corresponding phase shift angle. For ease of understanding, the specific process of solving the phase shift angle using the iterative method will be described in detail below.

[0071] Specifically, the space vectors corresponding to the N-channel DC boost circuits are A1 to A... N The modules are sorted from largest to smallest as follows: A1 > A2 > A3 > A4 > ... > A N And the module length can satisfy A1 < A2 + A3 + A4 + ... + A N This means that the current N spatial vectors can form a closed figure. Based on the above modulus condition, two conclusions can be derived:

[0072] (1) A1-A N <A2+A3+A4+……+A N-1 .

[0073] (2) A2 <A1<A1+A N-1 -A N <A1+(A2+A3+…+A N-2 )+A N-1 -A N .

[0074] After executing the first round of vector recursion, the magnitude of the current spatial vector can be obtained as: A1-A N A2, A3, ..., A N-1 If the modulus length is A1-A at this time... N If the magnitude A2 is the largest, then according to the above conclusion (1), the current N-1 spatial vectors can still form a closed figure. If the magnitude A2 is the largest at this time, then according to the above conclusion (2), the current N-1 spatial vectors can still form a closed figure. Similarly, after the second round of vector recursion, the current spatial vectors can still form a closed figure. After multiple rounds of vector recursion, the number of current spatial vectors can be reduced to three to form a structurally stable closed triangle. Then, with the lengths of the three sides (corresponding to the magnitudes of the vectors) known, the corresponding phase can be solved using the cosine theorem, and thus the required phase shift angle can be obtained.

[0075] Example 2:

[0076] In this embodiment, as Figure 6 As shown, to solve for the phase shift angle with the objective of minimizing the superposition of the total AC components at the DC bus, the total AC components output from all DC boost circuits to the DC bus can be directly extracted based on the obtained power data; the phase shift angle that minimizes the effective value of the total AC components can then be solved. Compared to traditional fixed phase shift methods and offline traversal methods, the technical solution in this embodiment has the advantages of lower heat generation from passive components and the absence of the need for additional table generation and storage.

[0077] Specifically, such as Figure 6 As shown, the entire process of solving the phase shift angle can be divided into offline training and online solution. In offline training, multiple sets of circuit data with different values ​​can be given in advance. Then, the phase shift angle is optimized and solved under different values ​​of the power data using an offline optimization algorithm to obtain the corresponding solution data. A dataset is constructed based on the obtained solution data, and the constructed neural network model is trained using the obtained dataset. The neural network model obtained through pre-training in offline training can be deployed online to perform online solution. When solving the phase shift angle online, the AC components of the output current of each DC boost circuit can be obtained based on the currently collected power data. All the obtained AC components are added together to obtain the total AC component. The root mean square of the total AC component is calculated to obtain the functional relationship between the effective value of the total AC component and the phase shift angle. The neural network model is used to solve the functional relationship in real time online to finally obtain the required phase shift angle.

[0078] It should be noted that, for obtaining the AC component of a DC-DC boost circuit, the on-time of the switching transistor Q1 can be used as the origin of the coordinate system, then the output current i o The exchange component i o-acThe time-domain expression is:

[0079] .

[0080] In the formula, t represents the working time, and v pv This represents the input voltage of the DC-DC boost circuit, v. bus L represents the DC bus voltage, and L represents the inductance value of the DC boost circuit.

[0081] The effective value i of the total AC component m-ac With phase angle The relationship is as follows:

[0082] .

[0083] In the formula, i o1-ac To io N-ac These represent the AC components corresponding to the output current of the first to Nth DC boost circuits, respectively. , ... These represent the phase shift angles corresponding to the first through Nth DC boost circuits, respectively.

[0084] Another aspect of this application provides an electronic device, in one preferred embodiment of which includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the above-described bus current ripple suppression method.

[0085] Another aspect of this application provides a computer-readable storage medium, in a preferred embodiment of which a computer program is stored on the storage medium; when the computer program is executed by a processor, it implements the above-described bus current ripple suppression method.

[0086] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing bus current ripple, applied to a photovoltaic system with multiple DC boost circuits connected in parallel to the DC bus at their outputs, characterized in that... Includes the following steps: The power data of each DC boost circuit under its current operating state is acquired in real time. The power data includes input voltage, output voltage, average current, and duty cycle information. Based on the obtained power data, with the goal of minimizing the total AC component output from all the DC boost circuits to the DC bus, the required phase shift angle of each DC boost circuit is dynamically calculated. The driving signals of each DC boost circuit are phase-modulated based on the obtained phase shift angle; Based on the obtained power data, the fundamental component of the current output from each of the DC boost circuits to the DC bus is extracted; Using the obtained fundamental component as a space vector, calculate the phase that minimizes the space vector sum of all the DC boost circuits, and obtain the phase shift angle required to minimize the total AC component; When the number of DC boost circuits N > 3, and the corresponding space vectors can be closed to form a closed figure, the calculation of the phase shift angle of each DC boost circuit includes the following process: taking the phase shift angle corresponding to one of the DC boost circuits as a reference, and combining the amplitude of each fundamental component, with the goal of maximizing the area of ​​the closed figure formed by the space vectors, the phase shift angles corresponding to the remaining DC boost circuits are calculated.

2. The bus current ripple suppression method as described in claim 1, characterized in that, The extraction of the fundamental component includes the following process: Obtain the inductor current waveform of the DC boost circuit in one switching cycle under steady state; Extract the output current waveform of the DC boost circuit from the inductor current waveform; The DC component of the output current waveform is removed to obtain the AC component; While keeping the area constant, the waveform of the AC component is converted into a rectangular wave; Perform a Fourier expansion on the obtained rectangular wave to obtain the Fourier series expansion of the rectangular wave; The first term of the Fourier series expansion is taken as the fundamental component.

3. An electronic device, characterized in that, It includes a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program to implement the bus current ripple suppression method as described in claim 1 or 2.

4. A computer-readable storage medium, characterized in that, The storage medium stores a computer program; when the computer program is executed by a processor, it implements the bus current ripple suppression method as described in claim 1 or 2.

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