Power conversion system and control method and controller thereof

Abstract

The embodiment of the invention relates to the technical field of power electronics, in particular to a power conversion system, a control method thereof and a controller. The power conversion system comprises a booster circuit, a dual-active bridge DC conversion circuit, an inverter circuit and a controller. Under the condition that the grid-connected switch is switched off and the input voltage of the booster circuit is smaller than a first preset voltage, the controller controls the booster circuit to perform open-loop slow start until the voltage of the first capacitor reaches the first preset voltage; controlling the dual-active-bridge direct-current conversion circuit to slowly start until the voltage of the second capacitor reaches a second preset voltage; and controlling the inverter circuit to slowly start until the voltages at the two ends of the grid-connected switch meet a first preset difference value, and closing the grid-connected switch. Thus, corresponding voltages of the booster circuit, the dual-active-bridge DC conversion circuit and the inverter circuit are slowly started to preset voltages in sequence, current and voltage overshoot and peak during charging and grid connection are avoided, the reliability of the system is improved, and the service life of the system is prolonged.

Description

Power conversion system and its control method, controller Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to power conversion systems and their control methods and controllers. Background Technology

[0002] Power conversion systems, as core equipment connecting DC power sources (such as photovoltaic modules and energy storage batteries) to the AC power grid, are widely used in new energy power generation and energy storage. To meet requirements for electrical isolation, wide voltage range operation, and high efficiency, power conversion systems composed of boost circuits, dual active bridge converter circuits, and inverter circuits are increasingly favored. In this power conversion system, the boost circuit increases the input voltage and achieves maximum power point tracking; the dual active bridge converter circuit provides electrical isolation and further voltage conversion; and the inverter circuit ultimately converts the DC power into AC power that meets grid requirements.

[0003] However, during the startup of a power conversion system, due to the coupling between power stages and the initial voltage of the system bus capacitor being zero or low, direct startup or an improper startup strategy can easily lead to severe transient impact problems, reducing the reliability and lifespan of the entire system. Summary of the Invention

[0004] The purpose of this application is to provide a power conversion system and its control method and controller, which can effectively improve the reliability and lifespan of the power conversion system.

[0005] The objective of this application is achieved through the following technical solution: Firstly, embodiments of this application provide a power conversion system, including: a boost circuit, a dual active bridge DC-DC converter circuit, an inverter circuit, and a controller; a first side of the boost circuit is connected to a power supply module, a second side of the boost circuit is connected to the first side of the dual active bridge DC-DC converter circuit, a first capacitor is connected in parallel to the second side of the boost circuit, the second side of the dual active bridge DC-DC converter circuit is connected to the first side of the inverter circuit, a second capacitor is connected in parallel to the first side of the inverter circuit, and the second side of the inverter circuit is connected to the AC power grid via a grid-connected switch; when the grid-connected switch is open, the controller is configured to: control the boost circuit to perform open-loop slow start when the input voltage of the boost circuit is less than a first preset voltage, until the voltage of the first capacitor reaches the first preset voltage; control the dual active bridge DC-DC converter circuit to perform slow start, until the voltage of the second capacitor reaches a second preset voltage; control the inverter circuit to perform slow start, until the voltage across the grid-connected switch meets a first preset difference, and close the grid-connected switch.

[0006] In some embodiments, the power conversion system includes a plurality of boost circuits, each boost circuit having a first side connected to a corresponding power supply module and a second side connected to the first side of the dual active bridge DC-DC converter circuit; the controller is further configured to: select one of the plurality of boost circuits as the target for open-loop slow start, and the unselected boost circuits are in a blocked state.

[0007] In some embodiments, the controller is configured to: determine that the open-loop soft start of the boost circuit is complete when the input voltage of the boost circuit is greater than or equal to the first preset voltage, and set the flag indicating that the soft start of the boost circuit is complete to 1.

[0008] In some embodiments, the boost circuit includes a first bridge arm, the upper and lower nodes of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch of the first bridge arm are opposite; the controller controls the boost circuit to perform open-loop soft start, specifically including: when the voltage of the first capacitor is less than the first preset voltage and the current of the first inductor is less than the first preset current, driving the boost circuit to operate with a preset duty cycle of the first lower bridge arm switch to charge the first capacitor; when the voltage of the first capacitor is greater than or equal to the first preset voltage and / or the current of the first inductor is greater than or equal to the first preset current, controlling the switch in the boost circuit to be in a blocked state; until the voltage of the first capacitor reaches the first preset voltage and is maintained for a certain period of time, determining that the open-loop soft start of the boost circuit is completed, and setting the flag bit of the boost circuit soft start completion to 1.

[0009] In some embodiments, the boost circuit includes a first bridge arm, the upper and lower nodes of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch included in the first bridge arm are opposite; the controller controls the boost circuit to perform open-loop soft start, specifically further including: when the voltage of the first capacitor is less than the first preset voltage and the current of the first inductor is less than the first preset current, controlling the duty cycle of the preset first lower bridge arm switch to drive the boost circuit to operate in a manner that gradually increases from the initial value with a specified step size, so as to charge the first capacitor; when the voltage of the first capacitor reaches the first preset voltage, determining that the open-loop soft start of the boost circuit is completed, and setting the flag bit of the boost circuit soft start completion to 1.

[0010] In some embodiments, the dual active bridge DC-DC converter circuit includes a first bridge circuit, a second bridge circuit, a resonant circuit, and a transformer; a first side of the first bridge circuit is connected to a second side of the boost circuit, a second side of the first bridge circuit is connected to a first side of the resonant circuit, a second side of the resonant circuit is connected to a first side of the transformer, a second side of the transformer is connected to a first side of the second bridge circuit, and a second side of the second bridge circuit is connected to a first side of the inverter circuit; the controller is configured to control the dual active bridge DC-DC converter circuit to perform a slow start when a flag indicating the completion of the boost circuit's slow start is 1, and / or when the voltage of the first capacitor reaches the first preset voltage, specifically including: controlling the dual active bridge DC-DC converter circuit at an over-resonant frequency. The circuit operates a switching transistor and controls the operating parameters of the switching transistor in the dual active bridge DC-DC converter circuit to increase, thereby charging the second capacitor. After the operating parameters increase from the initial value to the target value, the over-resonance frequency is controlled to decrease to the resonant frequency; or, the operating parameters of the switching transistor in the dual active bridge DC-DC converter circuit are controlled to increase from the initial value to the target value, thereby charging the second capacitor; or, the over-resonance frequency is controlled to decrease to the resonant frequency, thereby charging the second capacitor; wherein, the operating parameters include an inner phase shift angle or a duty cycle; when the voltage of the second capacitor reaches the second preset voltage, the controller is configured to determine that the slow start of the dual active bridge DC-DC converter circuit is complete, and set the flag bit of the slow start completion of the dual active bridge DC-DC converter circuit to 1.

[0011] In some embodiments, the inverter circuit includes a third bridge circuit and a filter circuit; the filter circuit includes a second inductor and a filter capacitor; a first side of the third bridge circuit is connected to a second side of the dual active bridge DC-DC converter circuit; a first interface of the second side of the third bridge circuit is connected to a first side of the second inductor; a second side of the second inductor is connected to a first side of the filter capacitor; and a second side of the filter capacitor is connected to a second interface of the second side of the third bridge circuit. The controller is configured to control the inverter circuit to perform a slow start when a flag indicating the completion of the slow start of the dual active bridge DC-DC converter circuit is 1, and / or when the voltage of the second capacitor reaches the second preset voltage. Specifically, the inverter circuit uses SPWM control to drive the inverter circuit to operate by gradually increasing the amplitude of the modulation wave from an initial value in a specified step size to charge the filter capacitor until the voltage difference between the voltage of the filter capacitor and the voltage of the AC grid meets the first preset difference value, thereby determining that the slow start of the inverter circuit is complete.

[0012] Secondly, embodiments of this application provide a control method for a power conversion system, the power conversion system comprising: a boost circuit, a dual active bridge DC-DC converter circuit, an inverter circuit, and a controller; a first side of the boost circuit is connected to a power supply module, a second side of the boost circuit is connected to the first side of the dual active bridge DC-DC converter circuit, a first capacitor is connected in parallel to the second side of the boost circuit, the second side of the dual active bridge DC-DC converter circuit is connected to the first side of the inverter circuit, a second capacitor is connected in parallel to the first side of the inverter circuit, and the second side of the inverter circuit is connected to the AC power grid via a grid-connected switch; the control method comprises: when the grid-connected switch is open, when the input voltage of the boost circuit is less than a first preset voltage, the controller controls the boost circuit to perform open-loop slow start until the voltage of the first capacitor reaches the first preset voltage; the controller controls the dual active bridge DC-DC converter circuit to perform slow start until the voltage of the second capacitor reaches a second preset voltage; the controller controls the inverter circuit to perform slow start until the voltage across the grid-connected switch meets a first preset difference, and then closes the grid-connected switch.

[0013] In some embodiments, the power conversion system includes a plurality of boost circuits, each boost circuit having a first side connected to a corresponding power supply module and a second side connected to the first side of the dual active bridge DC-DC converter circuit; the controller is further configured to: select one of the plurality of boost circuits as the target for open-loop slow start, and the unselected boost circuits are in a blocked state.

[0014] In some embodiments, the control method further includes: when the input voltage of the boost circuit is greater than or equal to the first preset voltage, the controller determines that the open-loop soft start of the boost circuit is completed, and sets the flag bit indicating the completion of the soft start of the boost circuit to 1.

[0015] In some embodiments, the boost circuit includes a first bridge arm, the upper and lower nodes of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch of the first bridge arm are opposite; controlling the boost circuit to perform open-loop soft start specifically includes: when the voltage of the first capacitor is less than the first preset voltage and the current of the first inductor is less than the first preset current, driving the boost circuit to operate with a preset duty cycle of the first lower bridge arm switch to charge the first capacitor; when the voltage of the first capacitor is greater than or equal to the first preset voltage and / or the current of the first inductor is greater than or equal to the first preset current, controlling the switch in the boost circuit to be in a blocked state; until the voltage of the first capacitor reaches the first preset voltage and is maintained for a certain period of time, determining that the open-loop soft start of the boost circuit is completed, and setting the flag bit of the boost circuit soft start completion to 1.

[0016] In some embodiments, the boost circuit includes a first bridge arm, the upper and lower nodes of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch included in the first bridge arm are opposite; the control of the boost circuit to perform open-loop soft start specifically includes: when the voltage of the first capacitor is less than the first preset voltage and the current of the first inductor is less than the first preset current, controlling the duty cycle of the preset first lower bridge arm switch to increase from the initial value to the target value in a specified step to drive the boost circuit to charge the first capacitor; when the voltage of the first capacitor reaches the first preset voltage, determining that the open-loop soft start of the boost circuit is completed, and setting the flag bit of the boost circuit soft start completion to 1.

[0017] In some embodiments, the dual active bridge DC-DC converter circuit includes a first bridge circuit, a second bridge circuit, a resonant circuit, and a transformer; a first side of the first bridge circuit is connected to a second side of the boost circuit, a second side of the first bridge circuit is connected to a first side of the resonant circuit, a second side of the resonant circuit is connected to a first side of the transformer, a second side of the transformer is connected to a first side of the second bridge circuit, and a second side of the second bridge circuit is connected to a first side of the inverter circuit; when the flag indicating the boost circuit's slow-start completion is 1, and / or when the voltage of the first capacitor reaches the first preset voltage, the controller controls the dual active bridge DC-DC converter circuit to perform a slow-start, specifically including: controlling the dual active bridge DC-DC converter circuit at an over-resonant frequency. The circuit operates a switching transistor, controlling the operating parameters of the switching transistor in the dual active bridge DC-DC converter circuit to rise. After the operating parameters rise from the initial value to the target value, the over-resonance frequency is controlled to drop to the resonant frequency to charge the second capacitor. The operating parameters include an inner phase shift angle or a duty cycle. Alternatively, the second capacitor is charged by controlling the operating parameters of the switching transistor in the dual active bridge DC-DC converter circuit to rise from the initial value to the target value; or, the second capacitor is charged by controlling the over-resonance frequency to drop to the resonant frequency. When the voltage of the second capacitor reaches the second preset voltage, the controller determines that the slow start of the dual active bridge DC-DC converter circuit is complete and sets the flag indicating the slow start completion of the dual active bridge DC-DC converter circuit to 1.

[0018] In some embodiments, the inverter circuit includes a third bridge circuit and a filter circuit; the filter circuit includes a second inductor and a filter capacitor; a first side of the third bridge circuit is connected to a second side of the dual active bridge DC-DC converter circuit; a first interface of the second side of the third bridge circuit is connected to a first side of the second inductor; a second side of the second inductor is connected to a first side of the filter capacitor; and a second side of the filter capacitor is connected to a second interface of the second side of the third bridge circuit. When the flag indicating the completion of the slow-start of the dual active bridge DC-DC converter circuit is 1, and / or when the voltage of the second capacitor reaches the second preset voltage, the controller controls the inverter circuit to perform a slow-start, specifically including: the inverter circuit uses SPWM control, controlling the amplitude of the modulation wave to increase from an initial value to a target value in specified steps to drive the inverter circuit to operate, thereby charging the filter capacitor until the voltage difference between the voltage of the filter capacitor and the voltage of the AC mains satisfies the first preset difference value, thus determining that the slow-start of the inverter circuit is complete.

[0019] Thirdly, embodiments of this application provide a controller for executing the control method described in any of the above claims.

[0020] This application provides a power conversion system and its control method and controller. In view of the possibility of voltage spikes or current overshoots in the initial stage of system startup, this application adopts a sequential slow-start strategy in the power conversion system. The voltages of the boost circuit, the dual active bridge DC-DC converter circuit and the inverter circuit are gradually slowed to the preset voltage. This can effectively avoid current and voltage overshoots and spikes during bus capacitor charging and grid connection, greatly reduce the electrical stress of the devices and improve the system reliability and lifespan. Attached Figure Description

[0021] This application will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 is a schematic diagram of a power conversion system provided in an embodiment of this application.

[0023] Figure 2 is a schematic diagram of another power conversion system provided in an embodiment of this application.

[0024] Figure 3 is a schematic diagram of a boost circuit provided in an embodiment of this application.

[0025] Figure 4 is a schematic diagram of a boost circuit with a slow start provided in an embodiment of this application.

[0026] Figure 5 is a schematic diagram of a dual active bridge DC-DC converter circuit provided in an embodiment of this application.

[0027] Figure 6 is a schematic diagram of the slow-start process of a dual active bridge DC-DC converter circuit provided in an embodiment of this application.

[0028] Figure 7 is a schematic diagram of an inverter circuit provided in an embodiment of this application.

[0029] Figure 8 is a flowchart illustrating a control method for a power conversion system provided in an embodiment of this application.

[0030] Figure 9 is a flowchart illustrating another control method for a power conversion system provided in an embodiment of this application.

[0031] Figure 10 is a structural block diagram of a controller provided in an embodiment of this application. Detailed Implementation

[0032] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] In the description of the embodiments of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0034] The system, composed of a boost circuit, a dual active bridge DC-DC converter circuit, and an inverter circuit, offers advantages such as isolation between the DC and AC sides, elimination of leakage current detection circuitry, and bidirectional energy flow. The boost circuits can be controlled independently, each with its own input voltage meeting the turn-off requirements of the micro-inverter. The dual active bridge DC-DC converter circuit provides both boost and isolation functions, while the inverter circuit converts DC into AC at the same frequency as the power grid.

[0035] In some practical application scenarios, the common control strategy of this system is to establish power balance between the AC and DC parts by controlling the bus voltage (the high-voltage side voltage of the boost circuit or the high-voltage side voltage of the dual active bridge DC-DC converter circuit), and to control the low-voltage side voltage of the boost circuit by controlling the duty cycle of the switching devices in the boost circuit, thereby achieving component-level maximum power point tracking (MPPT).

[0036] However, during system operation, voltage spikes or current overshoots may occur during the initial startup phase, reducing the reliability and lifespan of the entire system.

[0037] Referring to Figure 1, Figure 1 is a schematic diagram of the structure of a power conversion system provided in an embodiment of this application.

[0038] This application provides a power conversion system, including: a boost circuit, a dual active bridge DC-DC converter circuit, an inverter circuit, and a controller. A first side of the boost circuit is connected to a power supply module, and a second side of the boost circuit is connected to the first side of the dual active bridge DC-DC converter circuit. A first capacitor is connected in parallel to the second side of the boost circuit. The second side of the dual active bridge DC-DC converter circuit is connected to the first side of the inverter circuit, and a second capacitor is connected in parallel to the first side of the inverter circuit. The second side of the inverter circuit is connected to the AC power grid via a grid-connected switch.

[0039] When the grid-connected switch is open, the controller is configured to: control the boost circuit to perform open-loop slow start when the input voltage of the boost circuit is less than the first preset voltage, until the voltage of the first capacitor reaches the first preset voltage; control the dual active bridge DC-DC converter circuit to perform slow start, until the voltage of the second capacitor reaches the second preset voltage; control the inverter circuit to perform slow start, until the voltage across the grid-connected switch meets the first preset difference, and close the grid-connected switch.

[0040] In some embodiments, the power supply module can be a component for providing direct current (DC), such as a photovoltaic module or an energy storage battery. A dual active bridge DC-DC converter circuit can, for example, include a dual active bridge converter (DCX) to achieve electrical isolation on the DC side, thereby improving the safety of the power conversion system. An inverter circuit can, for example, include an inverter (INV) to convert high-voltage DC power into AC power that is in phase and frequency with the AC power grid. The AC power grid can be a component for receiving and distributing AC power, such as a power grid or a virtual power grid.

[0041] Grid connection switch K M The first terminal of the grid-connected switch can be electrically connected to the inverter circuit, and the second terminal can be electrically connected to the AC power grid. Grid-connected switch K M For example, it can include a grid-connected relay, which can be used to physically disconnect the inverter circuit from the AC power grid, such as the mains grid, in the event of system failure, maintenance, or shutdown. This ensures that hazards on the AC grid side (such as power outages for maintenance) do not affect the equipment housing the power conversion system, and also prevents equipment-side faults from affecting the AC grid. Grid-connected switch K M It can also be used to execute grid connection commands, transmitting AC power to the AC power grid.

[0042] As can be understood from the above, the initial value of the bus voltage of the power conversion system is 0 at the moment of startup. If it is put into operation directly, the huge instantaneous current will rapidly charge the boost circuit and the dual active bridge DC-DC converter circuit. Under such circumstances, it may cause current overshoot, damaging components such as switching transistors in the system. Furthermore, at the grid-connected switch K... M At the moment of closing, if there is a large difference between the voltage on the second side of the inverter circuit and the voltage of the AC grid (that is, the voltage of the grid-connected switch K), M If the voltage at both ends is too high, a huge inrush current and arcing will occur, damaging the relay contacts. Therefore, it is necessary to provide the inverter circuit with the necessary off-grid operating mode so that it can independently and safely perform voltage establishment and synchronization operations. For this purpose, the controller will first control the grid-connected switch K. M Disconnect the circuit, and then sequentially control the boost circuit, dual active bridge DC-DC converter circuit and inverter circuit to start up slowly.

[0043] In some embodiments, based on the operating principle of the power conversion system, the controller controls the grid-connected switch K. M When disconnected, the controller first initiates a slow start-up of the boost circuit. Specifically, the controller uses a preset slow start-up method to control the boost circuit in an open-loop slow start-up to charge the first capacitor until the voltage U of the first capacitor is reached. dc1 Reaching the first preset voltage U dc1set .

[0044] Afterwards, the boost circuit continues to operate, and the controller controls the voltage U of the first capacitor. dc1 Always reach the first preset voltage U dc1set In this situation, the controller then controls the next stage dual active bridge DC-DC converter circuit to begin a slow start. Specifically, the controller controls the dual active bridge DC-DC converter circuit to start slowly using a preset slow start method to charge the second capacitor until the voltage U of the second capacitor reaches a certain level. dc2 Reaching the second preset voltage U dc2set .

[0045] The dual active bridge DC-DC converter circuit is continuously in operation, and the controller controls the voltage U of the second capacitor. dc2 Always reach the second preset voltage U dc2set In this situation, the controller continues to control the next stage inverter circuit to start slowly, in order to reduce the grid-connected switch K. M The voltage difference between the two ends facilitates smooth grid connection. Specifically, this is reflected in the following: the controller controls the inverter circuit to start up gradually using a preset slow-start method, ensuring that the voltage difference between the second side voltage of the inverter circuit and the AC power received by the AC grid meets a first preset difference value. Afterward, the controller closes the grid connection switch K. M .

[0046] Thus, by employing a sequential slow-start power-up strategy in the power conversion system, this application sequentially slows down the voltages of the boost circuit, dual active bridge DC-DC converter circuit, and inverter circuit to the preset voltages. This effectively avoids current and voltage overshoots and spikes during bus capacitor charging and grid connection, greatly reducing the electrical stress on the devices and improving system reliability and lifespan.

[0047] Referring to Figure 2, which is a schematic diagram of another power conversion system provided in an embodiment of this application.

[0048] In some embodiments, the power conversion system includes multiple boost circuits, each with a first side connected to a power supply module and a second side connected to the first side of a dual active bridge DC-DC converter. The controller can be configured to select one boost circuit from the multiple boost circuits as the target for open-loop slow-start, while the unselected boost circuits are in a waveform-blocking state. Specifically, when the controller closes the grid-connected switch, the unselected boost circuits operate with waveform generation.

[0049] In some specific application scenarios, the power conversion system may include multiple boost circuits, each with its first side connected to a corresponding power supply module. Each power supply module may have the same function or different functions. When the controller performs open-loop soft start-up on the boost circuits, it selects one boost circuit from among the multiple selected circuits. During this process, the other unselected boost circuits are blocked. The controller then controls the grid-connected switch K. M When the circuit is closed and conducting, the unselected boost circuit will operate normally. After that, the power conversion system can enter normal operating mode.

[0050] In some embodiments, the controller may be configured to: determine that the open-loop soft start of the boost circuit is complete when the input voltage of the boost circuit is greater than or equal to a first preset voltage, and set the flag indicating that the soft start of the boost circuit is complete to 1.

[0051] In some embodiments, when the voltage output by the power supply module is greater than or equal to a first preset voltage, the first capacitor is charged through the body diode of the boost circuit, thereby causing the voltage of the first capacitor to reach the first preset voltage. In this case, the controller does not need to perform open-loop soft-start on the boost circuit; it can directly determine that the open-loop soft-start of the boost circuit has been completed and can set the flag indicating completion of the soft-start of the boost circuit to 1, so as to further sequentially perform soft-start on the dual active bridge converter circuit and the inverter circuit.

[0052] Referring to Figure 3, Figure 3 is a schematic diagram of a boost circuit provided in an embodiment of this application.

[0053] In some embodiments, the boost circuit may include a first bridge arm, with a first capacitor connected in parallel between the upper and lower nodes of the first bridge arm, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch included in the first bridge arm are opposite.

[0054] The controller controls the boost circuit to perform open-loop soft start, specifically including: when the first capacitor voltage is less than a first preset voltage and the first inductor current is less than a first preset current, the boost circuit can be driven to operate with a preset duty cycle of the first lower bridge arm switch to charge the first capacitor. When the first capacitor voltage is greater than or equal to the first preset voltage and / or the first inductor current is less than the first preset current, the switch in the boost circuit is controlled to be in a blocked state. Until the first capacitor voltage is detected to reach the first preset voltage and maintained for a certain period of time, the open-loop soft start of the boost circuit is determined to be complete, and the flag indicating the completion of the soft start of the boost circuit is set to 1.

[0055] In some embodiments, the first upper bridge arm switch may include a first switch Q1 and the first lower bridge arm switch may include a second switch Q2. The first capacitor may be a first capacitor C1, and its voltage may be referred to as U. dc1 A first inductor L is connected between the midpoint of the first bridge arm and the power supply module. dc1 A third capacitor C2 is connected in parallel between the midpoint and the lower node of the first bridge arm. Its voltage is the input voltage of the boost circuit, which can be called V. PV1 .

[0056] Referring to Figure 4, Figure 4 is a schematic diagram of a boost circuit performing a soft start according to an embodiment of this application.

[0057] In some embodiments, the process of the controller controlling the boost circuit to perform open-loop soft start may include: the controller may sample the first inductor L. dc1 First inductor current I Ldc1 Input voltage V PV1 and the voltage U of the first capacitor dc1 When the first inductor L dc1 First inductor current I LDC1 Less than the first preset current I set And the voltage U of the first capacitor dc1 Below the first preset voltage U dc1set At this time, the controller can control the drive signal (PWM) of the second switch Q2 to achieve a preset duty cycle D of the first lower bridge arm switch. pset The driving signals of the first switch Q1 and the second switch Q2 are inverted. This causes the power supply module to charge the third capacitor C2, and then charge the first capacitor C1 through the boost circuit. If any of the above conditions are not met (i.e., the first inductor current I...), the power supply module will charge the third capacitor C2, and then charge the first capacitor C1 through the boost circuit. Ldc1 Greater than or equal to the first preset current I set and / or the first capacitor voltage U dc1 Greater than or equal to the first preset voltage U dc1setThe controller immediately stops driving and blocks all switching pulses of the upper and lower transistors in the boost circuit (i.e., "wave blocking"). During this stage, the switching transistors stop working, and the first inductor current I... Ldc1 The voltage decreases naturally through the freewheeling diode. The first capacitor voltage U... dc1 Less than the first preset voltage U dc1set And the first inductor current I LDC1 Less than the first preset current I set The controller then operates again at the preset duty cycle D of the first lower bridge arm switch. pset A wave is emitted to charge the first capacitor C1. This continues until the controller detects the voltage U of the first capacitor. dc1 Stabilized at the first preset voltage U dc1set After maintaining this state for a certain period of time, the flag indicating the completion of the boost circuit's slow start is set to 1. Other unselected boost circuits remain in a blocked state throughout this process.

[0058] Among them, the first preset current I set The decision needs to be made by considering the maximum current that the first switch Q1 and the second switch Q2 can withstand, as well as the open-loop soft-start speed requirements of the power conversion system for the boost circuit. The open-loop soft-start speed requirement for the boost circuit will affect the first preset current I. set The minimum achievable value, and the maximum current that the first switch Q1 and the second switch Q2 can withstand, can affect the first preset current I. set The maximum value that can be achieved. And the preset duty cycle D of the first lower bridge arm switch. pset The upper limit can also be determined by the maximum current that the first switch Q1 and the second switch Q2 can withstand, and the preset duty cycle D of the first lower bridge arm switch. pset The lower limit depends on the open-loop soft-start speed of the boost circuit, the control accuracy of the controller on the duty cycle, the turn-on time of the first switch Q1 and the second switch Q2 (i.e., it is necessary to ensure that the switching devices can be fully turned on), and the response time of the controller, etc.

[0059] In some embodiments, the controller controls the boost circuit to perform open-loop soft start, which may further include: when the first capacitor voltage is less than a first preset voltage and the first inductor current is less than a first preset current, controlling the duty cycle of a preset first lower bridge arm switch to gradually increase from its initial value in a specified step size to drive the boost circuit to charge the first capacitor. When the first capacitor voltage reaches the first preset voltage, it is determined that the open-loop soft start of the boost circuit is complete, and the flag indicating the completion of the soft start of the boost circuit is set to 1.

[0060] In some embodiments, the duty cycle D of the first lower bridge arm switch is used. psetThe power-on process uses a gradual increase method, where the controller controls the duty cycle of the PWM wave of the second switch Q2 to increase slowly from its initial value in specified steps. Simultaneously, the drive signals for the first switch Q1 and the second switch Q2 are inverted. This method achieves the desired voltage U across the first capacitor. dc1 The voltage rises slowly until the first capacitor voltage U... dc1 Greater than or equal to the first preset voltage U dc1set The controller determines that the open-loop soft start of the boost circuit is complete. The specified step size can be fixed or variable.

[0061] Referring to Figure 5, Figure 5 is a schematic diagram of the structure of a dual active bridge DC-DC converter circuit provided in an embodiment of this application.

[0062] In some embodiments, the dual active bridge DC-DC converter circuit may include a first bridge circuit, a second bridge circuit, a resonant circuit, and a transformer. A first side of the first bridge circuit is connected to a second side of the boost circuit, a second side of the first bridge circuit is connected to a first side of the resonant circuit, a second side of the resonant circuit is connected to a first side of the transformer, a second side of the transformer is connected to a first side of the second bridge circuit, and a second side of the second bridge circuit is connected to a first side of the inverter circuit.

[0063] The controller is configured to control the dual active bridge DC-DC converter circuit to perform a soft start when the flag indicating the completion of the boost circuit soft start is set to 1, and / or when the voltage of the first capacitor reaches a first preset voltage. Specifically, this may include: controlling the operation of the switching transistors in the dual active bridge DC-DC converter circuit at an over-resonant frequency, and controlling the operating parameters of the switching transistors in the dual active bridge DC-DC converter circuit to increase, so as to charge the second capacitor. After the operating parameters rise from the initial value to the target value, the over-resonant frequency is controlled to decrease to the resonant frequency.

[0064] In some embodiments, controlling the dual active bridge DC-DC converter circuit to perform a soft start may further include: controlling the operating parameters of the switching transistors in the dual active bridge DC-DC converter circuit to rise from an initial value to a target value in order to charge the second capacitor.

[0065] In some embodiments, controlling the dual active bridge DC-DC converter circuit to perform a soft start may further include: controlling the over-resonant frequency to drop to the resonant frequency to charge the second capacitor. The operating parameters include the inner phase shift angle or the duty cycle.

[0066] When the voltage of the second capacitor reaches the second preset voltage, the controller is configured to determine that the slow start of the dual active bridge DC-DC converter circuit is complete, and set the flag indicating that the slow start of the dual active bridge DC-DC converter circuit is complete to 1.

[0067] It can be understood that the first side of the first bridge circuit can be connected to the second side of the boost circuit, that is, the first port of the first side of the first bridge circuit is connected to the upper node of the first bridge arm, and the second port of the first side of the first bridge circuit is connected to the lower node of the first bridge arm.

[0068] For example, Figure 6 shows a flowchart illustrating the slow-start process of a dual active bridge DC-DC converter circuit. The slow-start process of the dual active bridge DC-DC converter circuit can include: the controller can control the drive signals of the switching devices in the dual active bridge DC-DC converter circuit to a fixed, higher frequency (beyond the resonant frequency), and begin the slow-start process by increasing the inner phase shift angle (or duty cycle). During this process, the controller can monitor the inner phase shift angle (or duty cycle) in real time. When the controller determines that the inner phase shift angle is equal to 180 degrees (or the duty cycle gradually decreases to 0.5), the controller can, based on the stable inner phase shift angle of the drive signal at 180 degrees (or a stable duty cycle of 0.5), adjust the initially higher frequency to decrease to the resonant frequency. When the controller determines that the frequency has decreased to the resonant frequency, it can determine that the slow-start of the dual active bridge DC-DC converter circuit has ended, and set the slow-start success flag of the dual active bridge DC-DC converter circuit to 1.

[0069] It is understandable that, in practical applications, the first preset voltage U dc1set Second preset voltage U dc2set Both can indicate a voltage range. For example, when the first capacitor voltage U... dc1 When the voltage is within the corresponding range, the controller can determine that the open-loop soft start of the boost circuit has been completed. For example, the first preset voltage U dc1set The indicated voltage range is [219, 220], at the first capacitor voltage U dc1 When the voltage equals 219V, it can be confirmed that the boost circuit has completed its open-loop soft start. At this point, the voltage U of the first capacitor... dc1 It may continue to rise to 220V and stabilize at 220V. However, at the same time, the controller will simultaneously activate the dual active bridge converter circuit for a slow start.

[0070] Referring to Figure 7, Figure 7 is a schematic diagram of an inverter circuit provided in an embodiment of this application.

[0071] In some embodiments, the inverter circuit may include a third bridge circuit and a filter circuit; the filter circuit may include a second inductor and a filter capacitor. A first side of the third bridge circuit is connected to a second side of the dual active bridge DC-DC converter circuit, a first interface of the second side of the third bridge circuit is connected to a first side of the second inductor, a second side of the second inductor is connected to a first side of the filter capacitor, and a second side of the filter capacitor is connected to a second interface of the second side of the third bridge circuit.

[0072] The controller can be configured to control the inverter circuit to start slowly when the flag indicating the completion of the slow start of the dual active bridge DC-DC converter circuit is 1, and / or when the voltage of the second capacitor reaches a second preset voltage. Specifically, the inverter circuit can be controlled by SPWM control, which controls the amplitude of the modulation wave to gradually increase from the initial value in a specified step size to drive the inverter circuit to charge the filter capacitor until the voltage difference between the voltage of the filter capacitor and the voltage of the AC grid meets the first preset difference value, thus determining that the slow start of the inverter circuit is complete.

[0073] In some embodiments, the controller can initiate a phase-locked loop (PLL) circuit or algorithm to latch the phase and frequency of the AC grid voltage in real time. Based on this, the controller can generate a sinusoidal modulated wave that is in phase and frequency with the AC grid, with an initial value that can be set to 0 or a very small value (e.g., 5% of the rated amplitude). The controller can control the amplitude of the modulated wave to increase slowly according to a predetermined ramp function. This ramp function can be a linear ramp, an exponential curve, or an S-curve, and its growth slope can be set according to the system's requirements for slow start-up speed and the safe current of the power devices. As the amplitude of the modulated wave increases based on the growth slope, the inverter bridge arm, under, for example, Sine pulse width modulation (SPWM) modulation, generates a gradually increasing AC voltage, which charges the filter capacitor C through the second inductor L.

[0074] During this process, the frequency and phase of the voltage across the filter capacitor C, under the action of the filter circuit, quickly track and lock onto the frequency and phase of the modulation wave, achieving synchronization with the AC grid voltage. Simultaneously, its voltage amplitude slowly increases with the amplitude of the modulation wave. The controller can monitor the voltage difference between the filter capacitor voltage and the AC grid voltage in real time, or calculate its effective / peak value difference. When the voltage difference continuously meets the first preset difference for a set time (e.g., several grid cycles), the inverter circuit's slow start-up is considered complete. The first preset difference can be a critical safety threshold, and its value depends on the grid-connected switch K. M The closing time, the closing inrush current that the grid-connected switch contacts can withstand, and the instantaneous overcurrent capability allowed by the power devices in the inverter circuit are all considered. For example, the first preset difference can be set within 5% to 10% of the peak voltage of the AC grid. Once the slow start is determined to be complete, the controller immediately issues a command to close the grid-connected switch K. M Because the voltage difference between the two ends is extremely small at this time, the closing process will not produce obvious electric arcs and current surges, thus achieving smooth and shock-free grid connection.

[0075] In this application, when the grid connection switch K is disconnected... MUnder the premise that the controller first controls the boost circuit to perform open-loop soft start, and establishes and maintains the first capacitor voltage U in an open-loop manner. dc1 Then, the dual active bridge DC-DC converter circuit is slowly started to establish and maintain the second capacitor voltage U on the second side of the transformer. dc2 Next, the inverter circuit starts up slowly to reduce the grid-connected switch K. M The pressure difference at both ends is then used to finally close the grid-connected switch K. M Therefore, the slow-start control method is not only relatively simple, but the three-stage circuit control is also decoupled and relatively independent. Furthermore, there is no closed-loop control during the slow-start process, so after the slow-start ends, the power conversion system does not switch control loops, and can directly control the second-side voltage of the boost circuit and the second-side voltage (U) of the dual active bridge DC-DC converter circuit. dc1 / U dc2 This includes tracking the MPPT points of each power supply module. Furthermore, there is no current overshoot during the entire slow-start process, and the bus capacitor voltage rises slowly, better protecting the lifespan of power electronic devices.

[0076] Referring to Figure 8, Figure 8 is a flowchart illustrating a control method for a power conversion system provided in an embodiment of this application.

[0077] This application provides a control method for a power conversion system. The power conversion system includes: a boost circuit, a dual active bridge DC-DC converter circuit, an inverter circuit, and a controller. The first side of the boost circuit is connected to a power supply module, the second side of the boost circuit is connected to the first side of the dual active bridge DC-DC converter circuit, a first capacitor is connected in parallel to the second side of the boost circuit, the second side of the dual active bridge DC-DC converter circuit is connected to the first side of the inverter circuit, a second capacitor is connected in parallel to the first side of the inverter circuit, and the second side of the inverter circuit is connected to the AC power grid through a grid-connected switch.

[0078] The control method includes steps S101-S103: S101: When the grid-connected switch is off, the controller controls the boost circuit to perform open-loop slow start when the input voltage of the boost circuit is less than the first preset voltage, until the voltage of the first capacitor reaches the first preset voltage.

[0079] S102: The controller controls the dual active bridge DC-DC converter circuit to start slowly until the voltage of the second capacitor reaches the second preset voltage.

[0080] S103: The controller controls the inverter circuit to start slowly until the voltage across the grid-connected switch meets the first preset difference value, and then closes the grid-connected switch.

[0081] In some embodiments, the power conversion system may include multiple boost circuits, each with a first side connected to a power supply module and a second side connected to the first side of a dual active bridge DC-DC converter. The control method may further include: selecting one boost circuit from the multiple boost circuits as the target for open-loop slow-start, while the unselected boost circuits are in a waveform-blocking state. Specifically, when the controller closes the grid-connected switch, the unselected boost circuits operate with waveform generation.

[0082] In some embodiments, the control method may further include: when the input voltage of the boost circuit is greater than or equal to a first preset voltage, the controller determines that the open-loop soft start of the boost circuit is complete, and sets the flag bit indicating the completion of the soft start of the boost circuit to 1.

[0083] In some embodiments, the boost circuit may include a first bridge arm, with a first capacitor connected in parallel between the upper and lower nodes of the first bridge arm, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch included in the first bridge arm are opposite.

[0084] The controller controls the boost circuit to perform open-loop soft start, which specifically includes: when the first capacitor voltage is less than a first preset voltage and the first inductor current is less than a first preset current, driving the boost circuit to operate with a preset duty cycle of the first lower bridge arm switch to charge the first capacitor. When the first capacitor voltage is greater than or equal to the first preset voltage and / or the first inductor current is less than the first preset current, controlling the switch in the boost circuit to be in a blocked state. Until the first capacitor voltage is detected to reach the first preset voltage and maintained for a certain period of time, it is determined that the open-loop soft start of the boost circuit is completed, and the flag indicating the completion of the soft start of the boost circuit is set to 1.

[0085] The controller controls the boost circuit to perform open-loop soft start, which may further include: when the first capacitor voltage is less than a first preset voltage and the first inductor current is less than a first preset current, controlling the duty cycle of the preset first lower bridge arm switch to gradually increase from its initial value in a specified step size to drive the boost circuit to charge the first capacitor. When the first capacitor voltage reaches the first preset voltage, it is determined that the open-loop soft start of the boost circuit is complete, and the flag indicating the completion of the soft start of the boost circuit is set to 1.

[0086] In some embodiments, the dual active bridge DC-DC converter circuit may include a first bridge circuit, a second bridge circuit, a resonant circuit, and a transformer. A first side of the first bridge circuit is connected to a second side of the boost circuit, a second side of the first bridge circuit is connected to a first side of the resonant circuit, a second side of the resonant circuit is connected to a first side of the transformer, a second side of the transformer is connected to a first side of the second bridge circuit, and a second side of the second bridge circuit is connected to a first side of the inverter circuit.

[0087] When the flag indicating the completion of the boost circuit's slow start is set to 1, and / or when the voltage of the first capacitor reaches a first preset voltage, the controller controls the dual active bridge DC-DC converter circuit to perform a slow start. Specifically, this may include: controlling the operation of the switching transistors in the dual active bridge DC-DC converter circuit at an over-resonant frequency, and controlling the operating parameters of the switching transistors in the dual active bridge DC-DC converter circuit to increase, thereby charging the second capacitor. After the operating parameters rise from their initial values ​​to their target values, the over-resonant frequency is controlled to decrease to the resonant frequency. The operating parameters include the inner phase shift angle or duty cycle. Alternatively, the second capacitor can be charged by controlling the operating parameters of the switching transistors in the dual active bridge DC-DC converter circuit to rise from their initial values ​​to their target values. Or, the second capacitor can be charged by controlling the over-resonant frequency to decrease to the resonant frequency. When the voltage of the second capacitor reaches a second preset voltage, the controller determines that the slow start of the dual active bridge DC-DC converter circuit is complete and sets the flag indicating the completion of the slow start of the dual active bridge DC-DC converter circuit to 1.

[0088] In some embodiments, the inverter circuit may include a third bridge circuit and a filter circuit; the filter circuit may include a second inductor and a filter capacitor. A first side of the third bridge circuit is connected to a second side of the dual active bridge DC-DC converter circuit, a first interface of the second side of the third bridge circuit is connected to a first side of the second inductor, a second side of the second inductor is connected to a first side of the filter capacitor, and a second side of the filter capacitor is connected to a second interface of the second side of the third bridge circuit.

[0089] When the flag indicating the completion of the slow start of the dual active bridge DC-DC converter circuit is 1, and / or when the voltage of the second capacitor reaches the second preset voltage, the controller controls the inverter circuit to start slowly. Specifically, the inverter circuit uses SPWM control to drive the inverter circuit to operate by gradually increasing the amplitude of the modulation wave from the initial value in a specified step size, so as to charge the filter capacitor until the voltage difference between the voltage of the filter capacitor and the voltage of the AC grid meets the first preset difference value, and the slow start of the inverter circuit is determined to be complete.

[0090] Referring to Figure 9, which is a flowchart illustrating another control method for a power conversion system provided in an embodiment of this application.

[0091] In some specific application scenarios, when the power conversion system is powered on, the controller first controls the grid-connected relay K. MThe grid-connected switch is in the open state, physically isolating the inverter circuit from the power grid (AC grid), creating conditions for subsequent independent soft start. Furthermore, the controller can select one of n parallel BOOST circuits (boost circuits) as the main soft start BOOST (e.g., BOOST1) and detect its input voltage. The other BOOST circuits (BOOST2...BOOSTn) remain off (wave-blocked) during this stage. Afterwards, the controller can determine the first capacitor voltage U. dc1 Has the first preset voltage U been reached? dc1set .

[0092] If not achieved, and the first inductor L dc1 First inductor current I LDC1 Less than the first preset current I set If this occurs, the controller initiates the slow-start control program for the BOOST1 circuit. Under this program's control, the BOOST1 circuit begins operation, transferring energy from the photovoltaic module to the low-voltage bus capacitor, causing the first capacitor voltage U to... dc1 The current rises slowly and in a controlled manner, while limiting the first inductor current I. LDC1 Not exceeding the safety threshold I set During this process, when the controller detects the voltage U of the first capacitor... dc1 Greater than or equal to the first preset voltage U dc1set and / or the first inductor current I Ldc1 Greater than or equal to the first preset current I set When this happens, the controller immediately stops driving and completely blocks the switching pulses of the upper and lower transistors in the BOOST1 circuit (i.e., "wave blocking"). During this stage, the switching transistors stop working, and the first inductor current I... Ldc1 The voltage naturally decreases through the freewheeling diode. Wait for the first capacitor voltage U... dc1 Less than the first preset voltage U dc1set And the first inductor current I LDC1 Less than the first preset current I set The controller then operates again at the preset duty cycle D of the first lower bridge arm switch. pset A wave is emitted to charge the first capacitor C1. This continues until the controller detects the voltage U of the first capacitor. dc1 Stabilized at the first preset voltage U dc1set After maintaining this position for a certain period of time, it can be determined that the BOOST1 circuit has successfully completed its soft start. Subsequently, the controller sets the "BOOST circuit soft start successful" flag to 1.

[0093] If the condition is met, the controller can directly determine that the BOOST1 circuit has completed its soft start and set the "BOOST circuit soft start successful" flag to 1.

[0094] After the BOOST phase is completed, based on the established first capacitor voltage U dc1 Start the dual active bridge converter (dual active bridge DC-DC converter circuit) to establish the second capacitor voltage U. dc2 The controller can control the switching transistors of the dual active bridge converter, initially operating them above the resonant frequency, and then transferring energy from the low-voltage side to the high-voltage side by gradually changing the phase shift angle or duty cycle, gradually decreasing the switching frequency to the resonant point, or a combination of both. During this process, the second capacitor voltage U... dc2 It is gently charged to its second preset voltage. When the second capacitor voltage U dc2 Once the voltage stabilizes at the second preset level and the switching frequency remains stable near the resonant frequency, the dual active bridge converter's soft start-up can be considered complete. Subsequently, the controller sets the "Dual Active Bridge Converter Soft Start-up Successful" flag to 1. At this point, the power conversion system possesses the DC high voltage required for inverter grid connection.

[0095] After establishing a stable DC voltage in the first two stages of the circuit, the controller can control the inverter circuit to start operating using modulation methods such as SPWM, but the amplitude of the modulation wave increases slowly from an initial value (e.g., zero). This causes the amplitude, frequency, and phase of the voltage across the filter capacitor at the inverter circuit output to gradually approach the grid voltage. The controller can calculate the grid-connected relay K in real time. M When the voltage difference between the two ends meets the first preset voltage difference, for example, near the zero-crossing point of the grid voltage, the controller issues a command to close the grid-connected relay K. M Alternatively, the controller can directly close the circuit when it detects that the grid voltage is at a zero-crossing point.

[0096] After the grid-connected relay closes, the inverter circuit transitions to the normal grid-connected closed-loop control mode (such as grid voltage-oriented control) and begins to supply power to the grid. At the same time, the controller can start the remaining BOOST circuits one by one, enabling them to begin performing maximum power point tracking (MPPT).

[0097] Referring to Figure 10, which is a structural block diagram of a controller provided in an embodiment of this application.

[0098] This application also provides a controller that can be used to execute any of the control methods described above.

[0099] The controller may include a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the control method provided in the above embodiments.

[0100] The controller may include a memory 110, a processor 120, and a communication interface 130. The memory 110, the processor 120, and the communication interface 130 are connected through internal connection paths.

[0101] The memory 110 is used to store computer programs, which in some implementations may include code for implementing the methods of the embodiments of this application.

[0102] The processor 120 executes the computer program stored in the memory 110 to control the communication interface 130 to receive input data and information, and output operation results and other data. In some implementations, when the solutions of the embodiments of this application are implemented by software or firmware, the computer program used to implement the solutions of the embodiments of this application can be stored in the processor 120 and executed by the processor 120.

[0103] The memory 110 may be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory may be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory may be random access memory (RAM). It should be noted that the memory 110 described herein is intended to include, but is not limited to, any memory of these and other suitable types. As an example, the memory 110 includes random access memory (RAM), cache memory, and read-only memory (ROM). The memory 110 stores a computer program that can be executed by processor 120, causing processor 120 to implement the steps of any of the methods described above.

[0104] The processor 120 can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor 120 can be any conventional processor.

[0105] In implementation, each step of the above method can be completed by the integrated logic circuitry of the hardware in the processor 120 or by instructions in software form. The method disclosed in the embodiments of this application can be directly implemented by the hardware processor, or by a combination of hardware and software modules in the processor 120. The software modules can be located in mature storage media in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in the memory 110, and the processor 120 reads the information in the memory 110 and, in conjunction with its hardware, completes the steps of the above method. To avoid repetition, detailed descriptions are not provided here.

[0106] In some implementations, in addition to the hardware units described above, the controller may also include software modules, such as an operating system, a Basic Input Output System (BIOS), and application software.

[0107] An operating system is used to manage one or more of the hardware and software resources of a controller; it is the kernel and foundation of the controller. The operating system handles fundamental tasks such as managing and configuring memory, determining the priority of system resource allocation and demand, controlling input and output devices, operating the network, and managing the file system. To facilitate user operation, most operating systems provide a user interface for interaction with the system.

[0108] The BIOS is used to perform hardware initialization during the power-on boot phase and to provide runtime services for the operating system and applications. In some implementations, the BIOS can also monitor and display processor temperature and execute temperature protection strategies.

[0109] Application software, also known as an application program, can be understood as software written for a specific user application purpose, and is one of the main categories of computer software. For example, application software can be a program used to achieve purposes such as power control and temperature management.

[0110] It is understood that the specific examples in this application are only intended to help those skilled in the art better understand the implementation of this application, and are not intended to limit the scope of protection of this application.

[0111] It is understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this application.

[0112] It is understood that the various implementation methods described in this application can be implemented individually or in combination, and this application does not limit them.

[0113] Unless otherwise stated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "one or more" as used in this application includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0114] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0115] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes and beneficial effects of the embodiments described above can be referred to the corresponding processes and beneficial effects in other embodiments, and will not be repeated here.

[0116] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0117] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the technical solution in this application, depending on actual needs.

[0118] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0119] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the control method described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0120] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A power conversion system, characterized in that, include: The system comprises a boost circuit, a dual active bridge DC-DC converter circuit, an inverter circuit, and a controller. The first side of the boost circuit is connected to a power supply module. The second side of the boost circuit is connected to the first side of the dual active bridge DC-DC converter circuit. A first capacitor is connected in parallel to the second side of the boost circuit. The second side of the dual active bridge DC-DC converter circuit is connected to the first side of the inverter circuit. A second capacitor is connected in parallel to the first side of the inverter circuit. The second side of the inverter circuit is connected to the AC power grid via a grid-connected switch. When the grid-connected switch is open, the controller is configured to: control the boost circuit to perform open-loop slow start when the input voltage of the boost circuit is less than a first preset voltage, until the voltage of the first capacitor reaches the first preset voltage; control the dual active bridge DC-DC converter circuit to perform slow start, until the voltage of the second capacitor reaches a second preset voltage; control the inverter circuit to perform slow start, until the voltage across the grid-connected switch meets a first preset difference, and then close the grid-connected switch.

2. The power conversion system according to claim 1, characterized in that, The power conversion system includes multiple boost circuits, each with a first side connected to a corresponding power supply module and a second side connected to the first side of the dual active bridge DC-DC converter. The controller is further configured to select one of the multiple boost circuits as the target for open-loop slow start, while the unselected boost circuits are in a blocked state.

3. The power conversion system according to claim 1, characterized in that, The controller is configured to: when the input voltage of the boost circuit is greater than or equal to the first preset voltage, determine that the open-loop soft start of the boost circuit is complete, and set the flag indicating that the soft start of the boost circuit is complete to 1.

4. The power conversion system according to claim 1, characterized in that, The boost circuit includes a first bridge arm, the upper node and the lower node of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch are opposite. The controller controls the boost circuit to perform open-loop soft start, specifically including: when the voltage of the first capacitor is less than the first preset voltage and the current of the first inductor is less than the first preset current, the boost circuit is driven to run with a preset first lower bridge arm switch duty cycle to charge the first capacitor. When the voltage of the first capacitor is greater than or equal to the first preset voltage, and / or the current of the first inductor is greater than or equal to the first preset current, the switching transistor in the boost circuit is controlled to be in a blocked state; until the voltage of the first capacitor reaches the first preset voltage and is maintained for a certain period of time, it is determined that the open-loop soft start of the boost circuit is completed, and the flag bit of the soft start completion of the boost circuit is set to 1.

5. The power conversion system according to claim 1, characterized in that, The boost circuit includes a first bridge arm, the upper node and the lower node of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch are opposite. The controller controls the boost circuit to perform open-loop soft start, specifically including: when the first capacitor voltage is less than the first preset voltage and the first inductor current is less than the first preset current, controlling the duty cycle of the preset first lower bridge arm switch to gradually increase from the initial value in a specified step size to drive the boost circuit to charge the first capacitor; when the first capacitor voltage reaches the first preset voltage, determining that the open-loop soft start of the boost circuit is completed, and setting the flag bit of the boost circuit soft start completion to 1.

6. The power conversion system according to claim 4 or 5, characterized in that, The dual active bridge DC-DC converter circuit includes a first bridge circuit, a second bridge circuit, a resonant circuit, and a transformer; the first side of the first bridge circuit is connected to the second side of the boost circuit, the second side of the first bridge circuit is connected to the first side of the resonant circuit, the second side of the resonant circuit is connected to the first side of the transformer, the second side of the transformer is connected to the first side of the second bridge circuit, and the second side of the second bridge circuit is connected to the first side of the inverter circuit. The controller is configured to control the dual active bridge DC-DC converter to perform a slow start when the flag indicating the completion of the boost circuit's slow start is set to 1, and / or when the voltage of the first capacitor reaches the first preset voltage. Specifically, this includes: controlling the operation of the switching transistors in the dual active bridge DC-DC converter at an over-resonant frequency, and controlling the operating parameters of the switching transistors in the dual active bridge DC-DC converter to increase to charge the second capacitor; after the operating parameters increase from an initial value to a target value, controlling the over-resonant frequency to decrease to the resonant frequency; or, controlling the operating parameters of the switching transistors in the dual active bridge DC-DC converter to increase from an initial value to a target value to charge the second capacitor; or, controlling the over-resonant frequency to decrease to the resonant frequency to charge the second capacitor; wherein the operating parameters include an inner phase shift angle or a duty cycle; when the voltage of the second capacitor reaches the second preset voltage, the controller is configured to determine that the slow start of the dual active bridge DC-DC converter is complete and set the flag indicating the completion of the slow start of the dual active bridge DC-DC converter to 1.

7. The power conversion system according to claim 6, characterized in that, The inverter circuit includes a third bridge circuit and a filter circuit; the filter circuit includes a second inductor and a filter capacitor. The first side of the third bridge circuit is connected to the second side of the dual active bridge DC-DC converter circuit. The first interface of the second side of the third bridge circuit is connected to the first side of the second inductor. The second side of the second inductor is connected to the first side of the filter capacitor. The second side of the filter capacitor is connected to the second interface of the second side of the third bridge circuit. The controller is configured to control the inverter circuit to perform a slow start when the flag indicating the completion of the slow start of the dual active bridge DC-DC converter circuit is 1, and / or when the voltage of the second capacitor reaches the second preset voltage. Specifically, the inverter circuit uses SPWM control to drive the inverter circuit to operate by gradually increasing the amplitude of the modulation wave from the initial value in a specified step size to charge the filter capacitor until the voltage difference between the voltage of the filter capacitor and the voltage of the AC grid meets the first preset difference value, thus determining that the slow start of the inverter circuit is complete.

8. A control method for a power conversion system, characterized in that, The power conversion system includes: a boost circuit, a dual active bridge DC-DC converter circuit, an inverter circuit, and a controller; the first side of the boost circuit is connected to the power supply module, the second side of the boost circuit is connected to the first side of the dual active bridge DC-DC converter circuit, a first capacitor is connected in parallel to the second side of the boost circuit, the second side of the dual active bridge DC-DC converter circuit is connected to the first side of the inverter circuit, a second capacitor is connected in parallel to the first side of the inverter circuit, and the second side of the inverter circuit is connected to the AC power grid through a grid-connected switch; the control method includes: when the grid-connected switch is open, when the input voltage of the boost circuit is less than a first preset voltage, the controller controls the boost circuit to perform open-loop slow start until the voltage of the first capacitor reaches the first preset voltage; the controller controls the dual active bridge DC-DC converter circuit to perform slow start until the voltage of the second capacitor reaches a second preset voltage; the controller controls the inverter circuit to perform slow start until the voltage across the grid-connected switch meets a first preset difference, and then closes the grid-connected switch.

9. The control method according to claim 8, characterized in that, The power conversion system includes multiple boost circuits, each boost circuit having a first side connected to a corresponding power supply module, and each boost circuit having a second side connected to the first side of the dual active bridge DC-DC converter circuit. The control method further includes: the controller is configured to: select one of the multiple boost circuits as the target for open-loop slow start, and the unselected boost circuit is in a blocked state.

10. The control method according to claim 8, characterized in that, The control method further includes: when the input voltage of the boost circuit is greater than or equal to the first preset voltage, the controller determines that the open-loop soft start of the boost circuit is completed, and sets the flag bit indicating the completion of the soft start of the boost circuit to 1.

11. The control method according to claim 8, characterized in that, The boost circuit includes a first bridge arm, the upper node and the lower node of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch are opposite. The control of the boost circuit to perform open-loop soft start specifically includes: when the voltage of the first capacitor is less than the first preset voltage and the current of the first inductor is less than the first preset current, driving the boost circuit to operate with a preset first lower bridge arm switch duty cycle to charge the first capacitor. When the voltage of the first capacitor is greater than or equal to the first preset voltage, and / or the current of the first inductor is greater than or equal to the first preset current, the switching transistor in the boost circuit is controlled to be in a blocked state; until the voltage of the first capacitor reaches the first preset voltage and is maintained for a certain period of time, it is determined that the open-loop soft start of the boost circuit is completed, and the flag bit of the soft start completion of the boost circuit is set to 1.

12. The control method according to claim 8, characterized in that, The boost circuit includes a first bridge arm, the upper node and the lower node of the first bridge arm are connected in parallel with the first capacitor, and the drive signals of the first upper bridge arm switch and the first lower bridge arm switch are opposite. The control of the boost circuit to perform open-loop soft start-up specifically includes: when the voltage of the first capacitor is less than the first preset voltage and the current of the first inductor is less than the first preset current, controlling the duty cycle of the preset first lower bridge arm switch to increase from the initial value to the target value in a specified step size to drive the boost circuit to charge the first capacitor; when the voltage of the first capacitor reaches the first preset voltage, determining that the open-loop soft start-up of the boost circuit is completed, and setting the flag bit of the boost circuit soft start-up completion to 1.

13. The control method according to claim 11 or 12, characterized in that, The dual active bridge DC-DC converter circuit includes a first bridge circuit, a second bridge circuit, a resonant circuit, and a transformer. A first side of the first bridge circuit is connected to a second side of the boost circuit, a second side of the first bridge circuit is connected to a first side of the resonant circuit, a second side of the resonant circuit is connected to a first side of the transformer, a second side of the transformer is connected to a first side of the second bridge circuit, and a second side of the second bridge circuit is connected to a first side of the inverter circuit. When the flag indicating the boost circuit's slow-start completion is 1, and / or when the voltage of the first capacitor reaches the first preset voltage, the controller controls the dual active bridge DC-DC converter circuit to perform a slow-start, specifically including: controlling the switches in the dual active bridge DC-DC converter circuit at an over-resonant frequency. The controller operates the circuit and controls the operating parameters of the switching transistors in the dual active bridge DC-DC converter circuit to increase. After the operating parameters increase from the initial value to the target value, the controller controls the over-resonance frequency to decrease to the resonant frequency to charge the second capacitor. The operating parameters include an inner phase shift angle or a duty cycle. Alternatively, the controller controls the operating parameters of the switching transistors in the dual active bridge DC-DC converter circuit to increase from the initial value to the target value to charge the second capacitor. Or, the controller controls the over-resonance frequency to decrease to the resonant frequency to charge the second capacitor. When the voltage of the second capacitor reaches the second preset voltage, the controller determines that the slow-start of the dual active bridge DC-DC converter circuit is complete and sets the flag indicating the slow-start completion of the dual active bridge DC-DC converter circuit to 1.

14. The control method according to claim 13, characterized in that, The inverter circuit includes a third bridge circuit and a filter circuit; the filter circuit includes a second inductor and a filter capacitor, the first side of the third bridge circuit is connected to the second side of the dual active bridge DC-DC converter circuit, the first interface of the second side of the third bridge circuit is connected to the first side of the second inductor, the second side of the second inductor is connected to the first side of the filter capacitor, and the second side of the filter capacitor is connected to the second interface of the second side of the third bridge circuit. When the flag indicating the completion of the slow start of the dual active bridge DC-DC converter circuit is 1, and / or when the voltage of the second capacitor reaches the second preset voltage, the controller controls the inverter circuit to perform a slow start. Specifically, the inverter circuit uses SPWM control to drive the inverter circuit to operate by gradually increasing the amplitude of the modulation wave from the initial value in a specified step size, so as to charge the filter capacitor until the voltage difference between the voltage of the filter capacitor and the voltage of the AC grid meets the first preset difference value, and the slow start of the inverter circuit is determined to be complete.

15. A controller, characterized in that, The controller is used to execute the control method according to any one of claims 8-14.

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