Control Method, System, Device and Storage Medium of Photovoltaic DC Boost Converter

Abstract

The present application relates to a control method, system, device and storage medium for a photovoltaic DC boost converter. The control method includes: obtaining the medium-voltage DC bus voltage and the output voltage of the second DC / DC converter, wherein the medium-voltage DC bus voltage is the voltage generated by the photovoltaic array and transmitted into the medium-voltage DC bus; controlling the first DC / DC converter according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage, so that the medium-voltage DC bus voltage is consistent with the first reference voltage; controlling the second DC / DC converter according to the voltage difference between the output voltage and the second reference voltage, so that the output voltage of the second DC / DC converter is consistent with the second reference voltage. When the parameters of each DC / DC converter cannot be completely guaranteed to be consistent, or when there are load disturbances and input voltage disturbances, each DC / DC converter can not only ensure the balance of the output voltage, but also ensure the stability of the input medium-voltage DC bus voltage.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic direct current, and particularly to a control method, device, and computer device for a photovoltaic direct current boost converter. Background Art

[0002] Currently, the main form of photovoltaic grid connection is to incorporate the photovoltaic output voltage into the direct current grid through a direct current converter, and then invert the direct current output by the photovoltaic array into alternating current through an inverter for grid connection. In order to achieve the connection between the photovoltaic and the high-voltage direct current grid, a cascaded DC / DC converter structure with input parallel and output series connection is often used to achieve voltage boost. In a photovoltaic boost collection system, on the one hand, it is necessary to control the stability of the input-side voltage. Because under different illuminations, when operating at the highest efficiency, the corresponding terminal voltage should also be different. When the photovoltaic terminal voltage can be maintained at the voltage value corresponding to the maximum power point through a direct current converter and the input voltage is kept stable, the output efficiency of the front-stage photovoltaic module will increase, and at the same time, the working stability will also be enhanced. On the other hand, in the output series structure, due to the fact that the component parameters between each module cannot be kept completely consistent, or the input voltage disturbance and load mutation, it will cause the output voltage at the output ends between the modules in the system to be unstable and uneven. Moreover, when the uneven phenomenon cannot be improved, it will further deteriorate and become unstable. Therefore, uniform control is a very important part of the design of input parallel and output series connection.

[0003] To solve the output voltage equalization problem of the IPOS (input parallel / output series) direct current converter, several commonly used methods currently include: common duty cycle control, three-loop control, input current sharing control, etc. The implementation of common duty cycle control is relatively simple and does not require special setting of other modules to achieve voltage equalization or current sharing control. However, in an actual circuit, there are inevitably differences in the component parameters of each module device. The common duty cycle control strategy is not suitable for the series-side voltage equalization control of a combined converter in a high step-up ratio and high-power transmission system. The three-loop control structure generally includes an input voltage loop, an output voltage equalization loop, and a current loop to achieve input voltage stability and output voltage equalization between modules, and has good dynamic performance. However, due to the relatively large number of control links, on the one hand, the design and debugging of the controller will be more complex, and the mutual coupling between the regulator parameters of each module will also affect the control performance. Input current sharing control can ensure the balance of the output voltage by controlling the input current of each module to be equal. This control method is relatively simple, but the control principle is based on the ideal situation where the component parameters of each module are completely consistent. In actual situations, there will be some differences in the component parameters of each module, and the transmission efficiencies are inconsistent. When input current sharing control is adopted, the voltage imbalance caused by this difference cannot be eliminated, and it is not easy to achieve the stability of the input voltage. Summary of the Invention

[0004] Based on this, it is necessary to provide a control method, device, and computer equipment for a photovoltaic DC boost converter that can stabilize the input voltage and equalize the output voltage in response to the above technical problems.

[0005] In a first aspect, an embodiment of the present application provides a control method for a photovoltaic DC boost converter. The photovoltaic DC boost converter includes a photovoltaic array, a medium-voltage DC bus, a first DC / DC converter, a second DC / DC converter, and a high-voltage DC bus. The input ends of the first DC / DC converter and the second DC / DC converter are connected in parallel to the medium-voltage DC bus, and the output ends of the first DC / DC converter and the second DC / DC converter are connected in series to the high-voltage DC bus. The control method includes:

[0006] Obtain the medium-voltage DC bus voltage and the output voltage of the second DC / DC converter, where the medium-voltage DC bus voltage is the voltage generated by the photovoltaic array and transmitted to the medium-voltage DC bus.

[0007] Control the first DC / DC converter according to the voltage difference between the medium-voltage DC bus voltage and a first reference voltage, so that the medium-voltage DC bus voltage is consistent with the first reference voltage.

[0008] Control the second DC / DC converter according to the voltage difference between the output voltage and a second reference voltage, so that the output voltage of the second DC / DC converter is consistent with the second reference voltage, where the second reference voltage is the voltage value obtained by evenly dividing the high-voltage DC bus voltage among the DC / DC converters.

[0009] In the above control method, the first DC / DC converter is controlled according to the voltage difference between the medium-voltage DC bus and the first reference voltage to make the medium-voltage DC bus consistent with the first reference voltage, and the second DC / DC converter is controlled according to the voltage difference between the output voltage of the second DC / DC converter and the second reference voltage to make the output voltage consistent with the second reference voltage. Thus, when the parameters of the DC / DC converters cannot be fully guaranteed to be consistent, or when there are load disturbances and input voltage disturbances, each DC / DC converter can not only ensure the equalization of the output voltage but also ensure the stability of the input medium-voltage DC bus.

[0010] In one of the embodiments of the above first aspect, the controlling the first DC / DC converter according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage includes: determining a first phase-shift angle through linear control according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage, and controlling the first DC / DC converter according to the first phase-shift angle.

[0011] In one embodiment of the above first aspect, the controlling the second DC / DC converter according to the voltage difference between the output voltage and the second reference voltage includes: obtaining the output current of the second DC / DC converter; determining a reference current through linear control according to the voltage difference between the output voltage and the second reference voltage; and controlling the second DC / DC converter according to the current difference between the reference current and the output current.

[0012] In one embodiment of the above first aspect, the controlling the second DC / DC converter according to the current difference between the reference current and the output current includes: determining a second phase shift angle through linear control according to the current difference between the reference current and the output current; and controlling the second DC / DC converter according to the second phase shift angle.

[0013] In one embodiment of the above first aspect, the linear control is PI control.

[0014] In a second aspect, an embodiment of the present application provides a photovoltaic DC boost conversion system, including: a photovoltaic DC boost converter and a controller connected to the photovoltaic DC boost converter;

[0015] The photovoltaic DC boost converter includes: a photovoltaic array, a medium-voltage DC bus, a first DC / DC converter, a second DC / DC converter, and a high-voltage DC bus. The input ends of the first DC / DC converter and the second DC / DC converter are connected in parallel to the medium-voltage DC bus, and the output ends of the first DC / DC converter and the second DC / DC converter are connected in series to the high-voltage DC bus;

[0016] The controller includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the method described in any one of the above embodiments are implemented.

[0017] In one embodiment of the above second aspect, the structures of the first DC / DC converter and the second DC / DC converter are both phase-shifted full-bridge structures.

[0018] In one embodiment of the above second aspect, the photovoltaic DC boost converter further includes a grid-connected inductor, and the grid-connected inductor is connected between the output end of the DC / DC converter and the high-voltage DC bus, where the DC / DC converter is the first DC / DC converter or the second DC / DC converter.

[0019] In a third aspect, an embodiment of the present application provides a control device for a photovoltaic DC boost converter, and the control device includes:

[0020] An acquisition module for acquiring the medium-voltage DC bus voltage and the output voltage of the second DC / DC converter, where the medium-voltage DC bus voltage is the voltage generated by the photovoltaic array and formed by introducing the photovoltaic power into the medium-voltage DC bus;

[0021] A main control module for controlling the first DC / DC converter according to the voltage difference between the medium-voltage DC bus voltage and a first reference voltage, so that the medium-voltage DC bus voltage is consistent with the first reference voltage;

[0022] A slave control module for controlling the second DC / DC converter according to the voltage difference between the output voltage and a second reference voltage, so that the output voltage of the second DC / DC converter is consistent with the second reference voltage, where the second reference voltage is the voltage value obtained by evenly dividing the high-voltage DC bus voltage among the DC / DC converters.

[0023] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method described in any one of the above embodiments are implemented.

[0024] It can be understood that the beneficial effects that can be achieved by the photovoltaic DC boost conversion system described in the second aspect, the control device of the photovoltaic DC boost converter described in the third aspect, and the computer-readable storage medium described in the fourth aspect can refer to the beneficial effects in any one of the embodiments of the control method of the photovoltaic DC boost converter described in the first aspect above, and will not be elaborated here. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic flowchart of the control method of the photovoltaic DC boost converter in an embodiment;

[0027] Figure 2 It is a schematic structural diagram of the photovoltaic DC boost converter in an embodiment;

[0028] Figure 3 It is a main control block diagram in an embodiment;

[0029] Figure 4 It is a slave control block diagram in an embodiment;

[0030] Figure 5 Schematic diagram of the structure of a photovoltaic DC boost converter in another embodiment;

[0031] Figure 6 Waveform diagram of the output voltage and total output current of each DC / DC converter when the system load decreases;

[0032] Figure 7 Waveform diagram of the input voltage when the system load changes;

[0033] Figure 8 Waveform diagram of the input voltage and total output current when the input voltage changes;

[0034] Figure 9 Waveform diagram of the output voltage of each DC / DC converter when the input voltage changes;

[0035] Figure 10 Block diagram of the control device of a photovoltaic DC boost converter in an embodiment. Detailed implementation manners

[0036] For ease of understanding this application, the following will describe this application more comprehensively with reference to relevant drawings. Embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0038] It can be understood that the terms "first" and "second" used in this application are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of these features. The terms "first", "second", etc. may be used in this application to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. In addition, in the description of this application, "a plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0039] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediate element. In addition, in the following embodiments, "connection", if there is a transfer of electrical signals or data between the connected objects, should be understood as "electrical connection", "communication connection", etc.

[0040] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / comprising", "has / including", etc. specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0041] As described in the background art, the existing parallel-input series-output DC converters have problems such as unstable input voltage and unbalanced output voltage. Based on the above problems, the present invention provides a control method, device, and computer device for a photovoltaic DC boost converter.

[0042] In one embodiment, as Figure 1 and Figure 2 shown, a control method for a photovoltaic DC boost converter 200 is provided. The photovoltaic DC boost converter 200 includes: a photovoltaic array 210, a medium-voltage DC bus 220, a first DC / DC converter 240, a second DC / DC converter 250, and a high-voltage DC bus 230. The input ends of the first DC / DC converter 240 and the second DC / DC converter 250 are both connected in parallel to the medium-voltage DC bus 220, and the output ends of the first DC / DC converter 240 and the second DC / DC converter 250 are connected in series to each other and then connected to the high-voltage DC bus 230. The control method includes steps S100 to S300.

[0043] S100. Obtain the voltage of the medium-voltage DC bus and the output voltage of the second DC / DC converter 250.

[0044] Among them, the photovoltaic array 210 is connected to the medium-voltage DC bus 220. The medium-voltage DC bus voltage is the voltage formed after the photovoltaic array 210 generates a photovoltaic voltage and transmits the photovoltaic voltage to the medium-voltage DC bus 220. That is to say, each photovoltaic module in the photovoltaic array 210 generates a photovoltaic voltage after being irradiated by light, and the medium-voltage DC bus voltage is formed after the photovoltaic voltage is input into the medium-voltage DC bus 220. The medium-voltage DC bus voltage is input into the first DC / DC converter 240 and the second DC / DC converter 250 as the input voltage of the DC / DC converter. The second DC / DC converter 250 is a slave controller, and the slave controller can be one or more. The output voltage of the second DC / DC converter 250 refers to the output voltage of each second DC / DC converter 250. If there are multiple second DC / DC converters 250, the output voltages and output currents of the multiple second DC / DC converters 250 are respectively obtained to control one or more second DC / DC converters 250 in a slave control manner subsequently. It should be noted that there is no difference in the structure between the first DC / DC converter 240 and the second DC / DC converter 250, and the difference between the two lies in the control method.

[0045] S200. Control the first DC / DC converter 240 according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage, so that the medium-voltage DC bus voltage is consistent with the first reference voltage.

[0046] Among them, the first DC / DC converter 240 is the main controller, and the main control method is adopted to control the first DC / DC converter 240 to control the medium-voltage DC bus voltage, and the stability of the input medium-voltage DC bus voltage is controlled by controlling the first DC / DC converter 240. The number of the first DC / DC converters 240 is one. The inputs of the first DC / DC converter 240 and the second DC / DC converter 250 are both connected to the same medium-voltage DC bus 220, and the input medium-voltage DC bus voltage is unique. Only by controlling the first DC / DC converter 240 can the input medium-voltage DC bus voltage be controlled. According to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage, the first DC / DC converter 240 is controlled to correct the voltage of the input DC / DC converter, that is, the medium-voltage DC bus voltage, so that the medium-voltage DC bus voltage always remains consistent with the input reference voltage. The first reference voltage is a preset voltage value and can be set according to actual needs. Since the photovoltaic array 210 is directly connected to the medium-voltage DC bus 220, the first reference voltage is less than the open-circuit voltage of the photovoltaic array 210.

[0047] S300. Control the second DC / DC converter 250 according to the voltage difference between the output voltage and the second reference voltage, so that the output voltages of the second DC / DC converter 250 and the first DC / DC converter 240 are equal.

[0048] Among them, the second DC / DC converter 250 is a slave controller, and a slave control method is adopted to control the second DC / DC converter 250 to balance the output voltages of each DC / DC converter. The second reference voltage is determined according to the high-voltage DC bus voltage. Since the high-voltage DC bus voltage is fixed and known, and the output terminals of each DC / DC converter are connected in series, the second reference voltage is the voltage obtained by evenly dividing the high-voltage DC bus voltage among each DC / DC converter, that is, the second reference voltage is the voltage value obtained by dividing the high-voltage DC bus voltage by the number of DC / DC converters in the photovoltaic DC boost converter 200. Each second DC / DC converter 250 is controlled according to the voltage difference between its output voltage and the first reference voltage to correct the output voltage of each DC / DC converter, so that the output voltage of each DC / DC converter is consistent with the second reference voltage. Since the second reference voltages of each second DC / DC converter 250 are the same, the output voltages of each DC / DC converter can be controlled to be the same.

[0049] In the above embodiment, the first DC / DC converter 240 is controlled according to the voltage difference between the medium-voltage DC bus 220 and the first reference voltage to make the medium-voltage DC bus voltage consistent with the first reference voltage, and the second DC / DC converter 250 is controlled according to the voltage difference between the output voltage of the second DC / DC converter 250 and the second reference voltage to make the output voltage consistent with the second reference voltage. Thus, when the parameters of each DC / DC converter cannot be completely guaranteed to be consistent, or when there are load disturbances and input voltage disturbances, each DC / DC converter can not only ensure the balance of the output voltages, but also ensure the stability of the input medium-voltage DC bus 220.

[0050] In one embodiment, step S200 specifically includes: determining a first phase shift angle according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage, and controlling the first DC / DC converter 240 according to the first phase shift angle.

[0051] Specifically, according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage through a linear control method, a first phase-shift angle is determined, and the phase-shift angle of the first DC / DC converter 240 is controlled according to the first phase-shift angle, so that the input medium-voltage DC bus voltage is consistent with the first reference voltage. In one embodiment, a PI control method is used to determine the first phase-shift angle. The medium-voltage DC bus voltage and the first reference voltage are input into the PI controller. The PI controller generates a corresponding first phase-shift angle according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage, and then inputs the first phase-shift angle into the pulse generation controller to generate a pulse control signal, and uses the pulse control signal to control the phase-shift angle of the first DC / DC converter 240, so that the medium-voltage DC bus voltage is consistent with the first reference voltage.

[0052] In one embodiment, step S300 specifically includes:

[0053] S310. Obtain the output current of the second DC / DC converter 250;

[0054] S320. Determine a reference current according to the voltage difference between the output voltage and the second reference voltage;

[0055] S330. Control the second DC / DC converter 250 according to the current difference between the reference current and the output current.

[0056] Specifically, the output current of the second DC / DC converter 250 refers to the output current of each second DC / DC converter 250. The reference current is determined by a linear control method according to the voltage difference between the output voltage and the second reference voltage. Since the larger the voltage difference, the larger the change amount of the reference current output by the linear control, so that the change amount of the output current of the DC / DC converter increases, and further the change amount of the output voltage increases. For example, when the output voltage is less than the second reference voltage, if the voltage difference is larger, the reference current of the current inner loop increases, the output current increases, and further the output voltage rises. Therefore, adopting a voltage-current double-loop structure can improve the response speed of the output voltage, that is, the output voltage can approach the second reference voltage more quickly, and the control sensitivity is improved.

[0057] In one embodiment, a PI control method is used to determine the reference current. The output voltage and the second reference voltage are input into the PI controller. The PI controller obtains the reference current according to the voltage difference between the input voltage and the second reference voltage.

[0058] In one embodiment, step S330 specifically includes: determining a second phase-shift angle according to the current difference between the reference current and the output current; controlling the second DC / DC converter 250 according to the second phase-shift angle.

[0059] Specifically, by controlling the phase shift angle of the second DC / DC converter 250 to make the output voltage consistent with the second reference voltage, the voltage difference between the output voltage and the second reference voltage is used as a reference current to give a change direction to the output current, and then the second phase shift angle is determined according to the current difference between the reference current and the output current. According to this second phase shift angle.

[0060] In one embodiment, a PI control method is used to determine the first phase shift angle. The output current and the reference current are input into a PI controller. The PI controller determines the second phase shift angle according to the current difference between the output current and the reference current, and then sends the second phase shift angle to a pulse generation controller to generate a pulse control signal, which is used to control the phase shift angle of the second DC / DC converter 250 to make its output voltage consistent with the second reference voltage.

[0061] In a specific embodiment, as Figure 3 shown is the main control block diagram. According to the voltage difference between the medium-voltage DC bus voltage U in and the first reference voltage U in_ref , a corresponding first phase shift angle is generated through a PI link (PI control), and then it is sent to a pulse generation controller to generate a phase shift control signal, which is used to control the first DC / DC converter. As Figure 4 shown is the slave control block diagram. A voltage-current double-loop control is adopted. According to the voltage difference between the output voltage U oi and the second reference voltage U oi_ref , a reference current i oi_ref is generated through a PI link. At the same time, a current negative feedback is connected, and then according to the current difference between the reference current i oi_ref and the output current i oi , a corresponding second phase shift angle is generated through a current PI link, and then it is sent to a phase shift controller to generate a phase shift control signal, which is used to control the second DC / DC converter.

[0062] It should be understood that although Figure 1 the steps in the flowchart are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, Figure 1 at least a part of the steps in

[0063] In one embodiment, as Figure 2As shown, a photovoltaic DC boost conversion system is provided, including: a photovoltaic DC boost converter 200 and a controller connected to the photovoltaic DC boost converter 200; the photovoltaic DC boost converter 200 includes: a photovoltaic array 210, a medium-voltage DC bus 220, a first DC / DC converter 240, a second DC / DC converter 250, and a high-voltage DC bus 230. The input ends of the first DC / DC converter 240 and the second DC / DC converter 250 are connected in parallel to the medium-voltage DC bus 220, and the output ends of the first DC / DC converter 240 and the second DC / DC converter 250 are connected in series to the high-voltage DC bus 230; the controller includes a memory and a processor, and the memory stores a computer program. It is characterized in that when the processor executes the computer program, the steps in the above method embodiments are implemented.

[0064] Specifically, the output end of the photovoltaic array 210 is connected to the medium-voltage DC bus 220, and the photovoltaic array 210 generates a photovoltaic voltage and transmits the photovoltaic voltage to the medium-voltage DC bus 220 to form a medium-voltage DC bus voltage. The photovoltaic DC boost conversion system includes at least two DC / DC converters, namely, one is the first DC / DC converter 240 and the other is the second DC / DC converter 250. There is no difference in the structure between the first DC / DC converter 240 and the second DC / DC converter 250. The difference lies in the control methods of the first DC / DC converter 240 and the second DC / DC converter 250. The first DC / DC converter 240 can be any one of the DC / DC converters in the photovoltaic DC boost conversion system. After determining the first DC / DC converter 240, the remaining DC / DC converters are the second DC / DC converter 250. That is to say, the number of the first DC / DC converters 240 is one, and the number of the second DC / DC converters 250 is one or more. U in is the medium-voltage DC bus voltage, i o1 and U o1 are respectively the output current and output voltage of the first DC / DC converter 240, i oi and U oi are the output current and output voltage of each second DC / DC converter 250, where i > 2, I ois the total output current. In practical applications, the number of DC / DC converters depends on the voltage levels of the medium-voltage DC bus 220 and the high-voltage DC bus 230, as well as the voltage that the selected switching devices can withstand. The higher the voltage that the switching devices can withstand, the fewer the number of DC / DC converters. The controller is connected to the photovoltaic DC boost converter 200. After obtaining the corresponding electrical quantities in the photovoltaic DC boost converter 200 and performing corresponding processing, it controls the first DC / DC converter 240 and the second DC / DC converter 250 according to the processing results.

[0065] In one embodiment, the structures of the first DC / DC converter 240 and the second DC / DC converter 250 are both phase-shifted full-bridge structures. The DC / DC converter with a phase-shifted full-bridge structure is a converter with a transformer and an isolated topology. This structure has fewer devices and simpler control.

[0066] In one embodiment, a grid-connected inductor is further included, and the grid-connected inductor L g is connected between the output terminal of the DC / DC converter and the high-voltage DC bus 230, where the DC / DC converter is the first DC / DC converter 240 or the second DC / DC converter 250.

[0067] The grid-connected inductor is connected in series between the output terminal of the DC / DC converter and the high-voltage DC bus 230. The grid-connected inductor L g can be connected to the first DC / DC converter 240 or the second DC / DC converter 250. For example, the positive output terminal of the first DC / DC converter 240 is connected to one end of the grid-connected inductor L g and the other end of the grid-connected inductor L g is connected to the positive pole of the high-voltage DC bus 230. The negative pole of the high-voltage DC bus 230 is connected to the negative output terminal of the second DC / DC converter 250, and the positive output terminal of the second DC / DC converter 250 is connected to the negative output terminal of the first DC / DC converter 240.

[0068] In a specific embodiment, as Figure 3 shown, the output terminals of 4 photovoltaic arrays 210 are connected in parallel to the medium-voltage DC bus 220. The input terminals of 4 DC / DC converters (including 1 first DC / DC converter 240 and 3 second DC / DC converters 250) are connected in parallel to access the medium-voltage DC bus 220. The output terminals of 4 DC / DC converters are connected in series with each other and then connected to the high-voltage DC bus 230. One end of the grid-connected inductor L g is connected to the positive output terminal of the first DC / DC converter 240, and one end of the grid-connected inductor L gThe other end is connected to the positive output of the high-voltage DC bus 230, and the output part of the high-voltage DC bus 230 is connected to the AC power grid 260 through a DC / AC inverter. U in is the medium-voltage DC bus voltage, i o1 and U o1 are respectively the output current and output voltage of the first DC / DC converter 240, i o2 , i o3 , i o4 are respectively the output currents of the three second DC / DC converters 250, U o2 , U o3 , U o4 are respectively the output voltages of the three second DC / DC converters 250, i o is the total output current.

[0069] The beneficial effects produced by the solution of the present invention are illustrated below through experimental data:

[0070] A simulation model of a photovoltaic DC boost converter as shown in Figure 5 was established in Matlab / Simulink. The medium-voltage DC bus voltage is 800V, and the high-voltage DC bus voltage is 10kV. The simulation waveforms are as shown in Figures 6 to 9 . In the figure, the abscissa is time, and the ordinate is current and / or voltage. Among them, Figure 6 and Figure 7 are the waveform diagrams under the condition that the system load changes, Figure 8 and Figure 9 are the waveform diagrams under the condition that the input voltage changes. As shown in Figure 6 and Figure 7 , when the system first operates stably for a period of time and the output current is stable at 2.5A, at t = 0.025s, a load disturbance is applied to the first DC / DC converter. Figure 6 . In the steady state, the output voltages of the four DC / DC converters are kept consistent. When the system reduces the load at 0.025s, each output voltage remains stable, resists the interference and stabilizes. The inductor current i o drops from 2.5A to 2.3A and can also return to the stable state after a short fluctuation. Figure 7 . During the whole process, the input voltage fluctuates slightly and basically remains stable. As shown in Figure 8 and Figure 9 , the system first operates stably for a period of time, the output current is stable at 2.5A, and the input voltage is stable at 800V. At t = 0.015s, the input voltage is disturbed. Figure 8It is a waveform diagram of input voltage and output current when the input voltage changes. When the input voltage drops from 800V to 797V, the output voltages Uo1, Uo2, Uo3, and Uo4 of each DC / DC converter change slightly under the control of the voltage equalization strategy, and the system output current i o The change trend is the same as that of the input voltage U in , decreasing from 2.5A to 2.1A, and then returning to the stable value after fluctuations. The recovery time of the input voltage is 0.5ms, and the response time is very fast. The system output current i o refers to the series current of each DC / DC converter. Figure 9 It is a waveform diagram of the output voltages of the four modules when the input voltage changes. The output voltages Uo1, Uo2, Uo3, and Uo4 of each DC / DC converter are basically not affected.

[0071] In one embodiment, as Figure 10 shown, a control device for a photovoltaic DC boost converter is provided. The control device 300 includes: an acquisition module 310, a main control module 320, and a slave control module 330; the acquisition module 310 is used to acquire the medium-voltage DC bus voltage and the output voltage of the second DC / DC converter, where the medium-voltage DC bus voltage is the voltage generated by the photovoltaic array and formed by introducing the photovoltaic into the medium-voltage DC bus; the main control module 320 is used to control the first DC / DC converter according to the voltage difference between the medium-voltage DC bus voltage and the first reference voltage, so that the medium-voltage DC bus voltage is consistent with the first reference voltage; the slave control module 330 is used to control the second DC / DC converter according to the voltage difference between the output voltage and the second reference voltage, so that the output voltage of the second DC / DC converter is consistent with the second reference voltage, where the second reference voltage is the voltage value obtained by evenly dividing the high-voltage DC bus voltage among each DC / DC converter.

[0072] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0073] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0074] In the description of this specification, the description referring to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0075] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope described in this specification.

[0076] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A control method for a photovoltaic DC boost converter, characterized in that The photovoltaic DC boost converter includes: a photovoltaic array, a medium-voltage DC bus, a first DC / DC converter, a second DC / DC converter, and a high-voltage DC bus. The input ends of the first DC / DC converter and the second DC / DC converter are both connected in parallel to the medium-voltage DC bus, and the output ends of the first DC / DC converter and the second DC / DC converter are connected in series to each other and then connected to the high-voltage DC bus. The control method includes: Obtain the voltage of the medium-voltage DC bus and the output voltage of the second DC / DC converter, where the voltage of the medium-voltage DC bus is the voltage generated by the photovoltaic array and transmitted to the medium-voltage DC bus. Control the first DC / DC converter according to the voltage difference between the voltage of the medium-voltage DC bus and the first reference voltage, so that the voltage of the medium-voltage DC bus is consistent with the first reference voltage. Obtain the output current of the second DC / DC converter; determine a reference current through linear control according to the voltage difference between the output voltage and the second reference voltage; determine a second phase-shift angle through linear control according to the current difference between the reference current and the output current; control the second DC / DC converter according to the second phase-shift angle, so that the output voltage of the second DC / DC converter is consistent with the second reference voltage, where the second reference voltage is the voltage value obtained by equally dividing the voltage of the high-voltage DC bus among each DC / DC converter.

2. The control method according to claim 1, characterized in that The controlling the first DC / DC converter according to the voltage difference between the voltage of the medium-voltage DC bus and the first reference voltage includes: Determine a first phase-shift angle through linear control according to the voltage difference between the voltage of the medium-voltage DC bus and the first reference voltage, and control the first DC / DC converter according to the first phase-shift angle.

3. The control method according to claim 1 or 2, characterized in that, The linear control is PI control.

4. A photovoltaic DC boost conversion system, characterized in that, Includes: A photovoltaic DC boost converter and a controller connected to the photovoltaic DC boost converter; The photovoltaic DC boost converter includes: a photovoltaic array, a medium-voltage DC bus, a first DC / DC converter, a second DC / DC converter, and a high-voltage DC bus. The input ends of the first DC / DC converter and the second DC / DC converter are both connected in parallel to the medium-voltage DC bus, and the output ends of the first DC / DC converter and the second DC / DC converter are connected in series to each other and then connected to the high-voltage DC bus; The controller includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 2.

5. The photovoltaic DC boost conversion system according to claim 4, characterized in that The structures of the first DC / DC converter and the second DC / DC converter are both phase-shifted full-bridge structures.

6. The photovoltaic DC boost conversion system according to claim 4, characterized in that, The photovoltaic DC boost converter further includes a grid-connected inductor, and the grid-connected inductor is connected between the output end of the DC / DC converter and the high-voltage DC bus, where the DC / DC converter is the first DC / DC converter or the second DC / DC converter.

7. A control device for a photovoltaic DC boost converter, characterized in that, The photovoltaic DC boost converter includes: a photovoltaic array, a medium-voltage DC bus, a first DC / DC converter, a second DC / DC converter, and a high-voltage DC bus. The input ends of the first DC / DC converter and the second DC / DC converter are connected in parallel to the medium-voltage DC bus. The output ends of the first DC / DC converter and the second DC / DC converter are connected in series to the high-voltage DC bus. The control device includes: An acquisition module, configured to acquire the medium-voltage DC bus voltage and the output voltage of the second DC / DC converter, wherein the medium-voltage DC bus voltage is the voltage generated by the photovoltaic array and formed by introducing the photovoltaic power into the medium-voltage DC bus; A main control module, configured to control the first DC / DC converter according to the voltage difference between the medium-voltage DC bus voltage and a first reference voltage, so that the medium-voltage DC bus voltage is consistent with the first reference voltage; A slave control module, configured to acquire the output current of the second DC / DC converter; determine a reference current through linear control according to the voltage difference between the output voltage and a second reference voltage; determine a second phase-shift angle through linear control according to the current difference between the reference current and the output current; and control the second DC / DC converter according to the second phase-shift angle, so that the output voltage of the second DC / DC converter is consistent with the second reference voltage, wherein the second reference voltage is the voltage value obtained by equally dividing the high-voltage DC bus voltage among the DC / DC converters.

8. A computer-readable storage medium having a computer program stored thereon, 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 2 are implemented.

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