Power conversion system, method of controlling the same, and controller

Abstract

This application provides a power conversion system and its control method and controller, relating to the field of power electronics technology. The power conversion system includes a DC / DC converter, a first switch, a DC / AC converter, a second switch, and a controller. The input terminal of the DC / DC converter is connected to a DC power supply. The output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter via the first switch, and the AC side of the DC / AC converter is connected to the power grid via the second switch. The controller is used to start the DC / DC converter when the DC power supply meets the start-up conditions of the power conversion system. When the energy input to the DC / DC converter meets its energy loss, the controller controls the first switch to close and start the DC / AC converter. When the energy input to the DC / AC converter meets its energy loss, the controller controls the second switch to close. This application can reduce the number of opening and closing cycles of the switching devices in the power conversion system.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a power conversion system and its control method and controller. Background Technology

[0002] Typically, the input of a power conversion system is connected to a DC power source, and the output is connected to the power grid. In related technologies, the power conversion system starts up and connects directly to the grid when the DC power source meets the startup conditions.

[0003] However, if the DC power supply is insufficient after grid connection (such as when photovoltaic modules are in a low-light environment), the power conversion system will frequently start and stop, resulting in a hiccuping phenomenon.

[0004] This hiccuping phenomenon causes the switching devices in the power conversion system to repeatedly open and close, increasing the number of switching operations and reducing the lifespan of the devices. Summary of the Invention

[0005] This application provides a power conversion system and its control method and controller, which are used to reduce the number of switching devices opening and closing in the power conversion system.

[0006] According to a first aspect of the embodiments of this application, a power conversion system is provided, including a DC / DC converter, a first switch, a DC / AC converter, a second switch, and a controller; The input terminal of the DC / DC converter is used to connect to a DC power supply, the output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter through the first switch, and the AC side of the DC / AC converter is connected to the power grid through the second switch. The controller is configured to start the DC / DC converter when the DC power supply meets the start-up conditions of the power conversion system; control the first switch to close and start the DC / AC converter when the energy input to the DC / DC converter meets its energy loss; and control the second switch to close when the energy input to the DC / AC converter meets its energy loss.

[0007] According to a second aspect of the present application, a control method for a power conversion system is provided. The power conversion system includes a DC / DC converter, a first switch, a DC / AC converter, and a second switch. The input terminal of the DC / DC converter is used to connect to a DC power supply. The output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter through the first switch. The AC side of the DC / AC converter is connected to the power grid through the second switch. The control method includes: The DC / DC converter is started when the DC power supply meets the startup conditions of the power conversion system. When the energy input to the DC / DC converter meets its energy loss, the first switch is controlled to close and start the DC / AC converter. When the energy input to the DC / AC converter meets its energy loss, the second switch is controlled to close.

[0008] According to a third aspect of the embodiments of this application, a controller is provided for implementing the control method of the power conversion system as described in the second aspect.

[0009] In this application, the power conversion system includes a DC / DC converter, a first switch, a DC / AC converter, a second switch, and a controller. The input terminal of the DC / DC converter is connected to a DC power supply. The output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter through the first switch. The AC side of the DC / AC converter is connected to the power grid through the second switch. The DC / DC converter starts when the DC power supply meets the start-up conditions of the power conversion system. When the energy input to the DC / DC converter meets its energy loss requirements, the first switch is controlled to close and the DC / AC converter starts. If the energy input to the DC / DC converter does not meet its energy loss requirements, the first switch will not be closed and the DC / AC converter will not start, thus reducing the number of times the switching devices of the first switch and the DC / AC converter are opened and closed. When the energy input to the DC / AC converter meets its energy loss requirements, the second switch is controlled to close. If the energy input to the DC / AC converter does not meet its energy loss requirements, the second switch will not be closed, thus reducing the number of times the second switch is opened and closed. When the DC power supply is insufficient to support the entire power conversion system, the entire power conversion system can be directly started and connected to the grid, which can reduce the number of opening and closing times of the first switch, DC / AC converter and second switch, and reduce the number of opening and closing times of the switching devices in the power conversion system. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of a power conversion system provided in an embodiment of this application.

[0012] Figure 2 This is a schematic diagram of another power conversion system provided in an embodiment of this application.

[0013] Figure 3 This is a flowchart illustrating a control method for a power conversion system provided in an embodiment of this application. Detailed Implementation

[0014] 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 embodiments of this application, and not all embodiments. 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.

[0015] Please see Figure 1 In one exemplary embodiment, a power conversion system is provided. For example... Figure 1 As shown, the power conversion system includes a DC / DC converter, a first switch, a DC / AC converter, a second switch, and a controller; The input terminal of the DC / DC converter is used to connect to a DC power supply. The output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter through a first switch. The AC side of the DC / AC converter is connected to the power grid through a second switch. The controller is used to start the DC / DC converter when the DC power supply meets the start-up conditions of the power conversion system; when the energy input to the DC / DC converter meets its energy loss, it controls the first switch to close and start the DC / AC converter; when the energy input to the DC / AC converter meets its energy loss, it controls the second switch to close.

[0016] In the exemplary embodiment, the DC power supply can be a photovoltaic string, an energy storage battery, or other types of DC power supply, and this application does not limit it in this regard.

[0017] In the exemplary embodiments, a DC / DC converter refers to a direct current to direct current converter, and a DC / AC converter refers to a direct current to alternating current converter. The number of DC / DC converters in the power conversion system can be one or more, and this application does not limit this. For example, Figure 1 There are two DC / DC converters, namely DC / DC converter 1 and DC / DC converter 2. The input terminal of DC / DC converter 1 is used to connect to DC power supply 1, and the first output terminal of DC / DC converter 1 is connected to the first switch K. 11 The DC side of the DC / AC converter is connected to the first terminal. The input terminal of the DC / DC converter 2 is used to connect to the DC power supply 2. The first output terminal of the DC / DC converter 2 is connected to the first switch K. 12Connect the first DC-side terminal of the DC / AC converter. Connect the second output terminals of DC / DC converter 1 and DC / DC converter 2 to the second DC-side terminal of the DC / AC converter. Connect the DC bus capacitor C between the first DC-side terminal and the second DC-side terminal of the DC / AC converter. dc The AC side of the DC / AC converter is connected to the power grid via the second switch K2. Figure 1 For illustrative purposes only, the number of DC / DC converters in the power conversion system can also be 1, 3, or other numbers, and this application does not limit this.

[0018] In an exemplary embodiment, the DC / DC converter may be a boost circuit for maximum power tracking of the DC power supply and for boosting a lower DC voltage output by the DC power supply to a higher DC bus voltage.

[0019] In an exemplary embodiment, the first switch and the second switch may be a relay, a contactor, or a semiconductor switching device, such as an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET), or other types of switching devices. This application does not limit these types of switching devices.

[0020] In the exemplary embodiment, the start-up condition of the power conversion system can be that the output voltage of the DC power supply is greater than the preset output voltage of the DC power supply, or other start-up conditions. This application does not limit this.

[0021] In an exemplary embodiment, starting the DC / DC converter means sending a PWM (Pulse Width Modulation) signal to each switching device in the DC / DC converter to control the DC / DC converter to boost the output voltage according to a preset DC output voltage.

[0022] In an exemplary embodiment, the energy input to the DC / DC converter satisfies the energy loss of the DC / DC converter, which may mean that the output voltage of the DC / DC converter is consistent with the preset DC output voltage.

[0023] In the exemplary embodiment, while controlling the first switch to close, the output voltage of the DC / DC converter must also be kept constant.

[0024] In the exemplary embodiment, starting the DC / AC converter means sending PWM signals to each switching device in the DC / AC converter to control the DC / AC converter to perform open-loop off-grid frequency conversion output.

[0025] When the DC power supply meets the startup conditions of the power conversion system, the DC / DC converter starts. When the energy input to the DC / DC converter meets its energy loss requirements, the first switch is controlled to close and the DC / AC converter starts. If the energy input to the DC / DC converter does not meet its energy loss requirements, the first switch will not be closed and the DC / AC converter will not start, thus reducing the number of times the first switch and the switching devices of the DC / AC converter are opened and closed. When the energy input to the DC / AC converter meets its energy loss requirements, the second switch is controlled to close. If the energy input to the DC / AC converter does not meet its energy loss requirements, the second switch will not be closed, thus reducing the number of times the second switch is opened and closed. When the energy of the DC power supply is insufficient to support the entire power conversion system, the entire power conversion system starts and connects directly to the grid, reducing the number of times the first switch, the DC / AC converter, and the second switch are opened and closed, and reducing the number of times the switching devices in the power conversion system are opened and closed.

[0026] In some embodiments, such as Figure 2 As shown, the power conversion system also includes a first load; the input terminal of the DC / DC converter is connected to the input terminal of the first load; The controller is specifically used for: The first load is started when the DC power supply meets the startup conditions of the power conversion system. The DC / DC converter is started when the energy input to the first load meets its energy loss.

[0027] In an exemplary embodiment, Figure 2 In the above, the input terminal of DC / DC converter 1 is connected to the input terminal of the first load 1, and the input terminal of DC / DC converter 2 is connected to the input terminal of the first load 2.

[0028] In an exemplary embodiment, the first load may be a fan, a heater, an external power supply, etc. For example, the first load may be a first fan used to dissipate heat from a DC / DC converter, and the input terminal of the DC / DC converter is connected to the input terminal of the first fan through a first voltage conversion circuit. Starting the first load may mean driving the first fan to rotate at a first set speed. Ensuring that the energy input to the first load meets the energy loss of the first load may mean that the speed of the first fan is the same as the first set speed.

[0029] In actual operation of a power conversion system, a primary load is typically required, and the energy loss of this primary load is usually significant. The primary load is started when the DC power supply meets the startup conditions of the power conversion system. The DC / DC converter is started when the energy input to the primary load meets its energy loss requirements. If the energy input to the primary load does not meet its energy loss requirements, the DC / DC converter will not start, thus reducing the number of switching operations on the DC / DC converter.

[0030] In some embodiments, such as Figure 2 As shown, the power conversion system also includes a second load; the DC side of the DC / AC converter is connected to the input terminal of the second load. The controller is specifically used for: After the first switch is closed, the second load is started; The DC / AC converter is started when the energy input to the second load meets its energy loss.

[0031] In an exemplary embodiment, the second load may be a fan, a heater, an external power supply, etc. For example, the second load may be a second fan used to cool a DC / AC converter, with the DC side of the DC / AC converter connected to the input terminal of the second fan via a second voltage conversion circuit. Starting the second load may mean driving the second fan to rotate at a second set speed.

[0032] In actual operation of a power conversion system, a second load is generally required, and the energy loss of the second load is usually relatively large. After the first switch is closed, the second load is started. When the energy input to the second load meets its energy loss, the DC / AC converter is started. If the energy input to the second load does not meet its energy loss, the DC / AC converter will not be started, which can reduce the number of switching operations of the DC / AC converter.

[0033] In some embodiments, the controller is specifically used for: After the first switch is closed, the second load is started if the DC-side voltage of the DC / AC converter is greater than or equal to the preset DC-side voltage.

[0034] In the exemplary embodiment, the DC-side voltage of the DC / AC converter refers to the DC bus capacitance C. dc DC bus voltage.

[0035] After the first switch is closed, the DC / DC converter will apply a voltage to the DC bus capacitor C. dcCharging gradually increases the DC bus voltage. When the DC side voltage of the DC / AC converter is greater than or equal to the preset DC side voltage, it indicates that the DC bus voltage has reached a reasonable level for load testing. At this time, starting the second load can accurately determine whether the energy input to the second load meets the energy loss of the second load. This avoids meaningless energy testing when the DC bus voltage is low and reduces the energy loss of the second load when the DC bus voltage is low.

[0036] In some embodiments, the controller is specifically used for: When the DC-side voltage of the DC / AC converter changes and the operating parameters of the second load are used to determine that the energy input to the second load meets its energy loss, the DC / AC converter is started.

[0037] In the exemplary embodiment, the change in the DC-side voltage of the DC / AC converter can refer to the change in the DC bus voltage within a preset voltage range during the startup of the second load, or the gradual decrease in the DC bus voltage. A change in the DC bus voltage within the preset voltage range means that the DC bus voltage does not change significantly.

[0038] In the exemplary embodiment, the operating parameters of the second load refer to characteristic quantities that can directly reflect the operating status and energy consumption effect of the second load. For example, if the second load is a second fan used to dissipate heat from a DC / AC converter, the operating parameters of the second load could be the rotational speed of the second fan.

[0039] In the exemplary embodiment, determining that the energy input to the second load meets its energy loss based on the changes in the DC-side voltage of the DC / AC converter and the operating parameters of the second load can mean that the energy input to the second load meets its energy loss when the change in the DC bus voltage is within a preset voltage range and the speed of the second fan is consistent with the second set speed. Conversely, when the DC bus voltage gradually decreases, regardless of whether the speed of the second fan is consistent with the second set speed, it is determined that the energy input to the second load does not meet its energy loss.

[0040] In an exemplary embodiment, if it is determined that the energy input to the second load does not meet the energy loss of the second load, the process returns to the step of starting the DC / DC converter when the DC power supply meets the start-up conditions of the power conversion system, thereby starting all DC / DC converters connected to the DC power supply that meet the start-up conditions of the power conversion system and increasing the energy input to the second load.

[0041] By combining the changes in the DC-side voltage of the DC / AC converter with the actual operating status of the second load, and evaluating both the stability of the energy source and the effectiveness of energy consumption, it is possible to accurately determine whether the energy input to the second load meets the energy loss of the second load. This is more accurate than judging based on a single condition, effectively avoiding misjudgments, and ensuring that the DC / AC converter is only started when the energy supply can indeed meet the effective operation of the second load. This reduces the number of switching operations of the DC / AC converter.

[0042] In some embodiments, the controller is specifically used for: When the energy input to the DC / AC converter is determined to meet its energy loss based on the changes in the DC-side voltage and the AC-side voltage of the DC / AC converter, the second switch is controlled to close.

[0043] In an exemplary embodiment, determining that the energy input to the DC / AC converter meets its energy loss based on changes in the DC-side voltage and the AC-side voltage of the DC / AC converter can mean that the energy input meets the energy loss of the DC / AC converter when the change in the DC bus voltage is within a preset voltage range and the AC-side voltage of the DC / AC converter is consistent with the preset AC-side voltage. Conversely, when the DC bus voltage gradually decreases, regardless of whether the AC-side voltage of the DC / AC converter is consistent with the preset AC-side voltage, it is determined that the energy input to the DC / AC converter does not meet its energy loss.

[0044] In the exemplary embodiment, if it is determined that the energy input to the DC / AC converter does not meet the energy loss of the DC / AC converter, the process returns to the step of starting the DC / AC converter when it is determined, based on the change of the DC-side voltage of the DC / AC converter and the operating parameters of the second load, that the energy input to the second load meets its energy loss. The DC / AC converter continues to perform open-loop off-grid frequency conversion output, and after the energy input to the DC / AC converter meets the energy loss of the DC / AC converter, the second switch is controlled to close.

[0045] By combining the changes in the DC-side voltage and the AC-side voltage of the DC / AC converter, and evaluating both the stability of the energy source and the effectiveness of energy consumption, it is possible to accurately determine whether the energy input to the DC / AC converter meets the energy loss requirements of the DC / AC converter. This is more accurate than judging based on a single condition, effectively avoiding misjudgments, and ensuring that the second switch is closed only when the energy supply can indeed meet the effective operation of the DC / AC converter, thus reducing the number of times the second switch is opened and closed.

[0046] In one exemplary embodiment, a control method for a power conversion system is provided. The power conversion system includes a DC / DC converter, a first switch, a DC / AC converter, and a second switch; the input terminal of the DC / DC converter is connected to a DC power supply, the output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter through the first switch, and the AC side of the DC / AC converter is connected to the power grid through the second switch.

[0047] like Figure 3 As shown, the control method of the power conversion system includes: Step S101: Start the DC / DC converter when the DC power supply meets the startup conditions of the power conversion system.

[0048] Step S102: When the energy input to the DC / DC converter meets its energy loss, control the first switch to close and start the DC / AC converter.

[0049] Step S103: When the energy input to the DC / AC converter meets its energy loss, control the second switch to close.

[0050] When the DC power supply meets the startup conditions of the power conversion system, the DC / DC converter starts. When the energy input to the DC / DC converter meets its energy loss requirements, the first switch is controlled to close and the DC / AC converter starts. If the energy input to the DC / DC converter does not meet its energy loss requirements, the first switch will not be closed and the DC / AC converter will not start, thus reducing the number of times the first switch and the switching devices of the DC / AC converter are opened and closed. When the energy input to the DC / AC converter meets its energy loss requirements, the second switch is controlled to close. If the energy input to the DC / AC converter does not meet its energy loss requirements, the second switch will not be closed, thus reducing the number of times the second switch is opened and closed. When the energy of the DC power supply is insufficient to support the entire power conversion system, the entire power conversion system starts and connects directly to the grid, reducing the number of times the first switch, the DC / AC converter, and the second switch are opened and closed, and reducing the number of times the switching devices in the power conversion system are opened and closed.

[0051] In some embodiments, the power conversion system further includes a first load; the input of the DC / DC converter is connected to the input of the first load; Step S101 includes: The first load is started when the DC power supply meets the startup conditions of the power conversion system. The DC / DC converter is started when the energy input to the first load meets its energy loss.

[0052] In actual operation of a power conversion system, a primary load is typically required, and the energy loss of this primary load is usually significant. The primary load is started when the DC power supply meets the startup conditions of the power conversion system. The DC / DC converter is started when the energy input to the primary load meets its energy loss requirements. If the energy input to the primary load does not meet its energy loss requirements, the DC / DC converter will not start, thus reducing the number of switching operations on the DC / DC converter.

[0053] In some embodiments, the power conversion system further includes a second load; the DC side of the DC / AC converter is connected to the input terminal of the second load; In step S102, starting the DC / AC converter includes: After the first switch is closed, the second load is started; The DC / AC converter is started when the energy input to the second load meets its energy loss.

[0054] In actual operation of a power conversion system, a second load is generally required, and the energy loss of the second load is usually relatively large. After the first switch is closed, the second load is started. When the energy input to the second load meets its energy loss, the DC / AC converter is started. If the energy input to the second load does not meet its energy loss, the DC / AC converter will not be started, which can reduce the number of switching operations of the DC / AC converter.

[0055] In some embodiments, activating the second load after the first switch is closed includes: After the first switch is closed, the second load is started if the DC-side voltage of the DC / AC converter is greater than or equal to the preset DC-side voltage.

[0056] After the first switch is closed, the DC / DC converter will apply a voltage to the DC bus capacitor C. dcCharging gradually increases the DC bus voltage. When the DC side voltage of the DC / AC converter is greater than or equal to the preset DC side voltage, it indicates that the DC bus voltage has reached a reasonable level for load testing. At this time, starting the second load can accurately determine whether the energy input to the second load meets the energy loss of the second load. This avoids meaningless energy testing when the DC bus voltage is low and reduces the energy loss of the second load when the DC bus voltage is low.

[0057] In some embodiments, when the energy input to the second load satisfies its energy loss, the DC / AC converter is started, including: When the DC-side voltage of the DC / AC converter changes and the operating parameters of the second load are used to determine that the energy input to the second load meets its energy loss, the DC / AC converter is started.

[0058] By combining the changes in the DC-side voltage of the DC / AC converter with the actual operating status of the second load, and evaluating both the stability of the energy source and the effectiveness of energy consumption, it is possible to accurately determine whether the energy input to the second load meets the energy loss of the second load. This is more accurate than judging based on a single condition, effectively avoiding misjudgments, and ensuring that the DC / AC converter is only started when the energy supply can indeed meet the effective operation of the second load. This reduces the number of switching operations of the DC / AC converter.

[0059] In some embodiments, step S103 includes: When the energy input to the DC / AC converter is determined to meet its energy loss based on the changes in the DC-side voltage and the AC-side voltage of the DC / AC converter, the second switch is controlled to close.

[0060] By combining the changes in the DC-side voltage and the AC-side voltage of the DC / AC converter, and evaluating both the stability of the energy source and the effectiveness of energy consumption, it is possible to accurately determine whether the energy input to the DC / AC converter meets the energy loss requirements of the DC / AC converter. This is more accurate than judging based on a single condition, effectively avoiding misjudgments, and ensuring that the second switch is closed only when the energy supply can indeed meet the effective operation of the DC / AC converter, thus reducing the number of times the second switch is opened and closed.

[0061] For technical details not described in detail in this embodiment, please refer to the specific content of the power conversion system provided in the above embodiments of this application, which will not be repeated here.

[0062] Accordingly, embodiments of this application also provide a controller for executing the control method of the power conversion system provided in any of the above embodiments of this application.

[0063] For technical details not described in detail in this embodiment, please refer to the specific processing content of the control method of the power conversion system provided in the above embodiments of this application, which will not be repeated here.

[0064] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0065] The circuits and circuits in the various embodiments of this application can be merged, divided, and deleted according to actual needs.

[0066] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0067] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power conversion system, characterized in that, Includes a DC / DC converter, a first switch, a DC / AC converter, a second switch, and a controller; The input terminal of the DC / DC converter is used to connect to a DC power supply, the output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter through the first switch, and the AC side of the DC / AC converter is connected to the power grid through the second switch. The controller is configured to start the DC / DC converter when the DC power supply meets the start-up conditions of the power conversion system; control the first switch to close and start the DC / AC converter when the energy input to the DC / DC converter meets its energy loss; and control the second switch to close when the energy input to the DC / AC converter meets its energy loss.

2. The power conversion system according to claim 1, characterized in that, The power conversion system further includes a first load; the input terminal of the DC / DC converter is connected to the input terminal of the first load; The controller is specifically used for: The first load is started when the DC power supply meets the startup conditions of the power conversion system. When the energy input to the first load meets its energy loss, the DC / DC converter is started.

3. The power conversion system according to claim 1 or 2, characterized in that, The power conversion system further includes a second load; the DC side of the DC / AC converter is connected to the input terminal of the second load; The controller is specifically used for: After the first switch is closed, the second load is started; When the energy input to the second load meets its energy loss, the DC / AC converter is started.

4. The power conversion system according to claim 3, characterized in that, The controller is specifically used for: After the first switch is closed, the second load is started if the DC-side voltage of the DC / AC converter is greater than or equal to the preset DC-side voltage.

5. The power conversion system according to claim 3, characterized in that, The controller is specifically used for: When the energy input to the second load meets its energy loss based on the change in the DC-side voltage of the DC / AC converter and the operating parameters of the second load, the DC / AC converter is started.

6. The power conversion system according to claim 5, characterized in that, The controller is specifically used for: When the energy input to the DC / AC converter is determined to meet its energy loss based on the changes in the DC-side voltage and the AC-side voltage of the DC / AC converter, the second switch is controlled to close.

7. A control method for a power conversion system, characterized in that, The power conversion system includes a DC / DC converter, a first switch, a DC / AC converter, and a second switch; the input terminal of the DC / DC converter is used to connect to a DC power supply, the output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter through the first switch, and the AC side of the DC / AC converter is connected to the power grid through the second switch. The control method includes: The DC / DC converter is started when the DC power supply meets the startup conditions of the power conversion system. When the energy input to the DC / DC converter meets its energy loss, the first switch is controlled to close and start the DC / AC converter. When the energy input to the DC / AC converter meets its energy loss, the second switch is controlled to close.

8. The control method for the power conversion system according to claim 7, characterized in that, The power conversion system further includes a first load; the input terminal of the DC / DC converter is connected to the input terminal of the first load; The step of starting the DC / DC converter when the DC power supply meets the startup conditions of the power conversion system includes: The first load is started when the DC power supply meets the startup conditions of the power conversion system. When the energy input to the first load meets its energy loss, the DC / DC converter is started.

9. The control method for the power conversion system according to claim 7 or 8, characterized in that, The power conversion system further includes a second load; the DC side of the DC / AC converter is connected to the input terminal of the second load; The process of starting the DC / AC converter includes: After the first switch is closed, the second load is started; When the energy input to the second load meets its energy loss, the DC / AC converter is started.

10. The control method for the power conversion system according to claim 9, characterized in that, The step of activating the DC / AC converter when the energy input to the second load meets its energy loss includes: When the energy input to the second load meets its energy loss based on the change in the DC-side voltage of the DC / AC converter and the operating parameters of the second load, the DC / AC converter is started.

11. The control method for the power conversion system according to claim 10, characterized in that, The step of controlling the second switch to close when the energy input to the DC / AC converter meets its energy loss includes: When the energy input to the DC / AC converter is determined to meet its energy loss based on the changes in the DC-side voltage and the AC-side voltage of the DC / AC converter, the second switch is controlled to close.

12. A controller, characterized in that, A control method for implementing the power conversion system as described in any one of claims 7 to 11.

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