Control method of power supply system and power supply system

Abstract

The application discloses a control method of a power supply system and the power supply system. The power supply system comprises an inverter and a plurality of power conversion devices. Output ends of the plurality of power conversion devices are connected in parallel to the inverter through a common connection end. Each power conversion device comprises an energy storage battery, a power supply sub-device and an energy storage converter. The plurality of power conversion devices comprise a first power conversion device. The control method comprises the following steps: S1. determining a working mode of the first power conversion device, wherein the working mode comprises a running mode and a standby mode; S2. judging whether the first power conversion device needs to be charged or discharged according to a power reference instruction; and S3. determining whether the working mode of the first power conversion device needs to be switched according to an electric quantity state of the energy storage battery in the first power conversion device.

Description

Technical Field

[0001] This case relates to the field of power supply, and in particular to a control method and power supply system for a power supply system. Background Technology

[0002] A power conversion system (PCS) is an interface device connecting users to the power grid and loads. It can operate in both grid-connected and off-grid modes. In off-grid mode, the PCS acts as a voltage source, providing voltage support and forming a local microgrid with local household loads, photovoltaic inverters, and other power-consuming or generating equipment. In off-grid mode, multiple PCS can be connected in parallel, which not only expands capacity but also improves power supply reliability.

[0003] Furthermore, combining energy storage converters with energy storage batteries and photovoltaic inverters enables more flexible power control. However, in off-grid mode, in addition to the basic requirement of parallel operation, energy storage converters also need to consider their coordination with energy storage batteries and photovoltaic inverters. The energy storage batteries in energy storage converters can only charge and discharge within a certain state of charge (SOC) range, while photovoltaic inverters operate in maximum power point tracking (MPP) and do not have energy storage batteries. Therefore, the following scenario needs to be considered to ensure overall power balance: the energy storage batteries stop discharging when the SOC is low and stop charging when the SOC is high. Therefore, to meet the above requirements, the traditional approach is to adjust all energy storage converters so that the SOC of the energy storage batteries of all energy storage converters is similar during normal operation; when the SOC of the energy storage battery of any energy storage converter is low, all energy storage converters shut down; when the SOC of the energy storage battery of any energy storage converter is too high and the photovoltaic inverter is still generating electricity, all energy storage converters synchronously adjust the frequency of their output voltage to reduce the output power of the photovoltaic inverter.

[0004] However, the aforementioned control strategies are relatively complex, requiring the monitoring and control of numerous variables, and necessitating adjustments to the control scheme based on changes in the number of energy storage converters. Furthermore, these control strategies can only employ either a centralized or master-slave approach: a centralized approach requires an additional centralized control unit and communication network, increasing costs; a master-slave approach necessitates the execution of additional power management strategies, placing significant computational burden on the master's microcontroller unit (MCU) and reducing the reliability of parallel operation of the energy storage converters.

[0005] Therefore, how to develop a control method and power supply system that overcomes the above-mentioned deficiencies is an urgent issue that needs to be addressed. Summary of the Invention

[0006] The purpose of this invention is to provide a control method and a power supply system. In this system, the State of Charge (SOC) of the energy storage battery of each power conversion device is stabilized within a certain threshold range. Furthermore, each power conversion device can switch between operating and standby modes based on its own energy storage battery's SOC. Therefore, the power supply system does not need to obtain detailed information on all power conversion devices in the microgrid to make control decisions. In addition, since the control decisions of each power conversion device only affect its own behavior, the coupling between power conversion devices is low, thereby simplifying the control strategy of the power supply system.

[0007] To achieve the above objectives, this invention provides a control method applied to a power supply system. The power supply system includes an inverter and multiple power conversion devices, with the output terminals of each power conversion device connected in parallel to the inverter via a common connection terminal. Each power conversion device includes an energy storage battery, a power supply device, and an energy storage converter. The multiple power conversion devices include a first power conversion device. The control method includes: S1. determining the operating mode of the first power conversion device, wherein the operating mode includes an operating mode and a standby mode; S2. determining whether the first power conversion device needs to be charged or discharged based on a power reference command; and S3. determining whether the operating mode of the first power conversion device needs to be switched based on the state of charge of the energy storage battery in the first power conversion device.

[0008] To achieve the above objectives, this application also provides a power supply system, comprising: an inverter; and multiple power conversion devices, the output terminals of each of the multiple power conversion devices being connected in parallel to the inverter via a common connection terminal. Each power conversion device includes an energy storage battery, a power supply device, and an energy storage converter. The multiple power conversion devices include a first power conversion device, and the first power conversion device performs a control method. The control method includes: S1. determining the operating mode of the first power conversion device, wherein the operating mode includes an operating mode and a standby mode; S2. determining whether the first power conversion device needs to be charged or discharged based on a power reference command; and S3. determining whether the operating mode of the first power conversion device needs to be switched based on the state of charge of the energy storage battery in the first power conversion device. Attached Figure Description

[0009] Figure 1 This is a simplified flowchart illustrating the control method of a preferred embodiment of the present invention.

[0010] Figure 2 for Figure 1 The diagram shows the detailed steps of the control method.

[0011] Figure 3 for Figure 1 The circuit architecture diagram of the power supply system to which the control method shown is applicable.

[0012] Figure 4 for Figure 3 The diagram shows the relationship between the output power of inverter 3 and the frequency of voltage in the power supply system shown.

[0013] The reference numerals in the attached figures are explained as follows:

[0014] 1: Power supply system

[0015] 2: Power conversion device

[0016] 3: Inverter

[0017] COM: Common connection

[0018] 9: Load

[0019] 20: Energy storage battery

[0020] 21: Electronic devices

[0021] 22: Energy Storage Converter

[0022] 4: CAN bus

[0023] 5: Synchronization signal line

[0024] S1~S3: Steps of the control method

[0025] S2A, S2B, S3A~S3G: Sub-steps Detailed Implementation

[0026] Some typical embodiments embodying the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations under different implementation methods, all of which do not depart from the scope of this invention, and the descriptions and illustrations therein are for illustrative purposes only and are not intended to limit this invention.

[0027] The terms "first," "second," etc., used in this case do not specifically refer to order or sequence, nor are they used to limit this case; they are merely used to distinguish elements or operations described using the same technical terms. Secondly, the terms "comprising," "including," "having," and "containing," used in this case, are all open-ended terms, meaning they include but are not limited to. Furthermore, the terms "coupled" or "connected," used in this case, can refer to two or more elements making direct physical or electrical contact, or indirectly making physical or electrical contact with each other.

[0028] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 ,in Figure 1 This is a simplified flowchart illustrating the control method of a preferred embodiment of this case. Figure 2for Figure 1 The diagram shows the detailed steps of the control method. Figure 3 for Figure 1 The circuit architecture diagram of the power supply system to which the control method shown is applicable is as follows: Figure 4 for Figure 3 The diagram shows the relationship between the output power of inverter 3 and the voltage frequency in power supply system 1. The control method described in this case is applicable to… Figure 3 In the power supply system 1 shown, which may be, but is not limited to, a photovoltaic power supply system, an inverter 3 and multiple power conversion devices 2 are included. The inverter 3 may be, but is not limited to, a photovoltaic inverter, and is electrically connected to the common connection terminal COM. Furthermore, the inverter 3 operates in maximum power point tracking (MPP) and does not have a battery storage device. The inverter 3 is used to convert electrical energy received from other energy sources and output electrical energy to the common connection terminal COM. When the inverter 3 is a photovoltaic inverter, it can convert received solar energy (not shown) and provide it to the common connection terminal COM. In some embodiments, at least one load 9 is electrically connected to the common connection terminal COM, and the load 9 can operate by receiving electrical energy through the common connection terminal COM.

[0029] Multiple power conversion devices 2 each have their output terminals electrically connected to a common connection terminal COM, and are electrically connected to an inverter 3 via the common connection terminal COM. Each power conversion device 2 can perform bidirectional power conversion. Furthermore, each power conversion device 2 includes an energy storage battery 20, a power supply unit 21, and an energy storage converter 22. The energy storage battery 20 can be charged or discharged through the energy storage converter 22. The power supply unit 21 can be a photovoltaic power generation unit, which can supply power to the energy storage battery 20 through the energy storage converter 22. The energy storage converter 22 is a bidirectional energy converter. In addition, each power conversion device 2 can execute one of two operating modes: an operating mode and a standby mode. When the power conversion device 2 is in operating mode, it charges or discharges externally; conversely, when the power conversion device 2 is in standby mode, it remains in standby mode and does not charge or discharge externally. It should be noted that charging the power conversion device 2 externally means that the power conversion device 2 receives input electrical energy from the common connection terminal COM, and discharging the power conversion device 2 externally means that the power conversion device 2 outputs electrical energy to the common connection terminal COM. The power conversion device not charging or discharging externally means that the power conversion device 2 does not exchange energy with the common connection terminal COM.

[0030] In some embodiments, the power supply system 1 further includes a CAN bus 4, and each power conversion device 2 is electrically connected to the CAN bus 4. Multiple power conversion devices 2 communicate with each other via CAN bus to transmit output power, operating mode, and other special commands. Furthermore, the power supply system 1 further includes a phase synchronization signal line 5 (synchronization; SYNC), and each power conversion device 2 is electrically connected to the phase synchronization signal line 5. Multiple power conversion devices 2 communicate using the synchronization signal line 5, allowing each power conversion device 2 to correct the phase of its output voltage through the phase synchronization signal line 5, thereby reducing circulating current.

[0031] Because the control methods in this case are applicable Figure 3 The power supply system 1 shown includes any unspecified power conversion device 2, and all power conversion devices 2 can simultaneously execute the control method of this invention. To better understand the technology of this invention, one of the multiple power conversion devices 2 executing the control method of this invention will be referred to as the first power conversion device 2, and the execution of the control method of this invention by the first power conversion device 2 will be used as an example for explanation. The control method of this invention includes the following steps:

[0032] Step S1: Determine the operating mode of the first power conversion device 2, wherein the operating mode includes the running mode and the standby mode.

[0033] Step S2: Determine whether the first power conversion device 2 needs to be charged or discharged based on the power reference command.

[0034] Step S3: Determine whether it is necessary to switch the operating mode of the first power conversion device 2 based on the SOC of the energy storage battery 20 of the first power conversion device 2.

[0035] It should be noted that in step S1, each power conversion device 2 can determine its own operating mode through its controller (not shown), that is, there is no need for an external active control device to provide information on the operating mode of each power conversion device 2.

[0036] It should be noted that in step S2, each power conversion device 2 can, according to its respective power reference command P ref This determines whether charging or discharging is required. Specifically, when the power supply system 1 uses distributed control, each power conversion device 2 calculates its own power reference command P. ref When power supply system 1 adopts centralized control, a single main controller can send a power reference command P to each power conversion device. ref Furthermore, if P ref If P > 0, the power reference command instructs the power conversion device 2 to discharge externally; if P refIf the value is less than 0, the power reference command instructs the power conversion device 2 to charge externally. Power reference command P ref The following steps are used to determine the following: First, calculate the average power P of the power conversion device 2 currently in operation. avg , where the average power P avg The average power is calculated by summing the output power of all operating power conversion devices 2. The output power of each power conversion device 2 can be transmitted via the CAN bus 3. The formula for calculating the average power is: Where P avg P represents the average power, k is the number of power conversion devices 2 in operation mode, and P is the average power. i The output power of the i-th power conversion device 2 in operating mode is given by the command P. Here, i is a positive integer. refi The expression is P refi =P avg -P pvi , where P pvi The power output of the power supply device 21 inside the power conversion device 2 is referenced to command P. refi The expected power of the energy storage battery 20 in the power conversion device 2 in operating mode is given; for the power conversion device 2 in standby mode, P j The output power of the j-th power conversion device 2, where j is a positive integer, corresponds to the power reference instruction P. refj The expression is P refj =P avg The power reference command P refj The expected power of the power conversion device 2 in standby mode is given by the common connection terminal COM.

[0037] It should be noted that in step S3, the SOC of the energy storage battery 20 refers to the state of charge of the energy storage battery 20. When switching the operating mode of the power conversion device 2, this invention needs to comprehensively consider both the power reference command of the power conversion device 2 and the state of charge of its own energy storage battery 20.

[0038] In some embodiments, when step S1 determines that the operating mode of the first power conversion device 2 is the running mode, then sub-step S2A of step S2 is executed to determine whether the first power conversion device 2 needs to be charged or discharged according to the power reference command, that is, to determine whether the energy storage battery 20 in the first power conversion device 2 needs to be charged or discharged. When the determination result of sub-step S2A is that the energy storage battery 20 in the first power conversion device 2 needs to be discharged, then sub-step S3A of step S3 is executed to confirm whether the SOC of the energy storage battery 20 of the first power conversion device 2 is too low. That is, if the SOC of the energy storage battery 20 of the first power conversion device 2 is less than the first lower limit value, then the SOC of the energy storage battery 20 of the first power conversion device 2 is considered to be too low. Furthermore, the operating mode of the first power conversion device 2 can be switched based on the comparison result between the SOC of the energy storage battery 20 of the first power conversion device 2 and the first lower limit value: if the confirmation result of sub-step S3A is that the SOC of the energy storage battery 20 of the first power conversion device 2 is less than the first lower limit value, then the operating mode of the first power conversion device 2 is switched to standby mode; otherwise, if the confirmation result of sub-step S3A is that the SOC of the energy storage battery 20 of the first power conversion device 2 is greater than the first lower limit value, then the first power conversion device 2 maintains the operating mode.

[0039] Furthermore, if the confirmation result of sub-step S3A is that the SOC of the energy storage battery 20 of the first power conversion device 2 is less than the first lower limit, after switching the working mode of the first power conversion device 2 to standby mode, although the first power conversion device 2 does not exchange energy with the common connection terminal COM, the power supply device 21 of the first power conversion device 2 can charge the energy storage battery 20 of the first power conversion device 2 via the energy storage converter 22, thereby increasing the SOC of the energy storage battery 20 of the first power conversion device 2.

[0040] In some embodiments, when step S1 determines that the operating mode of the first power conversion device 2 is the running mode, and the judgment result of sub-step S2A is that the energy storage battery 20 of the first power conversion device 2 needs to be charged, then sub-step S3B of step S3 is executed to confirm whether the SOC of the energy storage battery 20 of the first power conversion device 2 is too high. That is, if the SOC of the energy storage battery 20 of the first power conversion device 2 is greater than the first upper limit value, then the SOC of the energy storage battery 20 of the first power conversion device 2 is considered to be too high. It should be noted that the first lower limit value is less than the first upper limit value, and both can be set according to actual needs. Furthermore, the operating mode of the first energy conversion device 2 can be determined based on the comparison between the SOC of the energy storage battery 20 of the first energy conversion device 2 and the first upper limit value: if the confirmation result of sub-step S3B is that the SOC of the energy storage battery 20 of the first energy conversion device 2 is less than the first upper limit value, then the first energy conversion device 2 maintains the operating mode; conversely, if the SOC of the energy storage battery 20 of the first energy conversion device 2 is greater than the first upper limit value, then sub-step S3C of step S3 is executed, that is, the operating mode of the first energy conversion device 2 is determined based on the number of energy conversion devices 2 currently in the operating mode. Specifically, if the number of energy conversion devices 2 currently in the operating mode is greater than or equal to 2, then the operating mode of the first energy conversion device 2 is switched to standby mode; conversely, if the number of energy conversion devices 2 currently in the operating mode is equal to 1, then the operating mode of the first energy conversion device 2 remains in the operating mode. Furthermore, since only one power conversion device 2 operates in the same mode, i.e., the first power conversion device 2 operates in the same mode, the first power conversion device 2 further adjusts the frequency of its output voltage, i.e., increases the frequency of its output voltage to the common connection terminal COM, causing the inverter 3 to correspondingly reduce its output power. For example... Figure 4 As shown, it is Figure 3 The diagram shows the relationship between the output power of inverter 3 and the voltage frequency in power supply system 1. When the frequency of the voltage at the common connection terminal COM is higher than f1, the output power of inverter 3 decreases from 100% to 0 as the frequency increases. Since only one power conversion device 2 operates in this situation while the rest operate in standby mode, this situation can be considered a special operating mode, namely, a single-machine operation mode.

[0041] In some embodiments, when step S1 determines that the operating mode of the first power conversion device 2 is standby mode, sub-step S2B of step S2 is executed to determine whether the first power conversion device 2 needs to be charged or discharged according to the power reference command. When the determination result of sub-step S2B is that the first power conversion device 2 needs to be discharged, that is, the energy storage battery 20 of the first power conversion device 2 needs to be discharged, then sub-step S3D of step S3 is executed to confirm whether the SOC of the energy storage battery 20 of the first power conversion device 2 is too low. That is, if the SOC of the energy storage battery 20 of the first power conversion device 2 is less than the second lower limit value, it is considered that the SOC of the energy storage battery 20 of the first power conversion device 2 is too low. It should be noted that the second lower limit value is greater than the first lower limit value to achieve the normal operation of the entire power supply system 1. Furthermore, the operating mode of the first power conversion device 2 can be switched based on the comparison between the SOC of the energy storage battery 20 of the first power conversion device 2 and the second lower limit value: if the confirmation result of sub-step S3D is that the SOC of the energy storage battery 20 of the first power conversion device 2 is less than the second lower limit value, then the first power conversion device 2 maintains the standby mode; otherwise, if the confirmation result of sub-step S3D is that the SOC of the energy storage battery 20 of the first power conversion device 2 is greater than the second lower limit value, then the operating mode of the first power conversion device 2 is switched to the running mode.

[0042] Furthermore, if the confirmation result of sub-step S3D is that the SOC of the energy storage battery 20 of the first power conversion device 2 is greater than the second lower limit, then sub-step S3E of step S3 is executed, that is, the method of switching the working mode of the first power conversion device 2 to the operating mode is determined according to the number of power conversion devices 2 currently in the operating mode. Specifically: if the number of power conversion devices 2 currently in the operating mode is greater than or equal to 1, then the working mode of the first power conversion device 2 is directly switched to the operating mode; otherwise, if the number of power conversion devices 2 currently in the operating mode is equal to 0, then sub-step S3F of step S3 is executed to renetwork the first power conversion device 2, and after the first power conversion device 2 is renetworked, the working mode of the first power conversion device 2 is switched to the operating mode.

[0043] In some embodiments, when step S1 determines that the operating mode of the first power conversion device 2 is standby mode, and the judgment result of sub-step S2B is that the first power conversion device 2 needs to be charged, that is, the energy storage battery 20 of the first power conversion device 2 needs to be charged, then sub-step S3G of step S3 is executed to confirm whether the SOC of the energy storage battery 20 of the first power conversion device 2 is too high. That is, if the SOC of the energy storage battery 20 of the first power conversion device 2 is greater than the second upper limit value, then the SOC of the energy storage battery 20 of the first power conversion device 2 is considered to be too high. The second upper limit value is lower than the first upper limit value to ensure the normal operation of the entire power supply system 1. Furthermore, the second lower limit value is lower than the second upper limit value. Furthermore, the operating mode of the first power conversion device 2 can be switched based on the comparison between the SOC of the energy storage battery 20 of the first power conversion device 2 and the second upper limit value: if the SOC of the energy storage battery 20 of the first power conversion device 2 is greater than the second upper limit value, the first power conversion device 2 maintains the standby mode; otherwise, if the SOC of the energy storage battery 20 of the first power conversion device 2 is less than the second upper limit value, the operating mode of the first power conversion device 2 is switched to the running mode.

[0044] Furthermore, if the confirmation result of sub-step S3G is that the SOC of the energy storage battery 20 of the first power conversion device 2 is less than the second upper limit value, then sub-step S3E of step S3 is executed, that is, the method of switching the working mode of the first power conversion device 2 to the operating mode is determined according to the number of power conversion devices 2 currently in the operating mode. Specifically: if the number of power conversion devices 2 currently in the operating mode is greater than or equal to 1, then the working mode of the first power conversion device 2 is directly switched to the operating mode; otherwise, if the number of power conversion devices 2 currently in the operating mode is equal to 0, then sub-step S3F of step S3 is executed to renetwork the first power conversion device 2, and after the first power conversion device 2 is renetworked, the working mode of the first power conversion device 2 is switched to the operating mode.

[0045] Therefore, the power supply system 1 and its control method in this case can stabilize the SOC of the energy storage battery 20 in each power conversion device 2 within a reasonable threshold range, without requiring the SOC of each energy storage battery 20 to be similar. On the one hand, this effectively improves the safety and reliability of the power supply system 1; on the other hand, it simplifies the control strategy of the power supply system 1 and effectively reduces the cost of the power supply system 1.

[0046] In summary, the power supply system and control method provided in this case allow each power conversion device to execute the same control method and flexibly switch between operating and standby modes based on its own energy storage battery's state of charge and power reference commands. Therefore, in most cases, there is no master-slave distinction among the power conversion devices; instead, distributed control is employed. Consequently, the power supply system does not need to obtain detailed information on all power conversion systems in the microgrid for control decisions, making the control strategy relatively simple. Furthermore, since the control decisions only affect the behavior of each power conversion device, the coupling between them is low, effectively improving the stability and reliability of the power supply system.

Claims

1. A control method applied to a power supply system, the power supply system comprising an inverter and a plurality of power conversion devices, wherein an output terminal of each of the plurality of power conversion devices is connected in parallel to the inverter via a common connection terminal, and each power conversion device comprises an energy storage battery, a power supply device, and an energy storage converter, wherein, The plurality of power conversion devices includes a first power conversion device, and the control method includes: S1. Determine an operating mode of the first power conversion device, wherein the operating mode includes an operating mode and a standby mode; S2. Determine whether the first power conversion device needs to be charged or discharged based on a power reference command; and S3. Determine whether it is necessary to switch the operating mode of the first power conversion device based on the charge status of the energy storage battery in the first power conversion device.

2. The control method as described in claim 1, wherein when step S1 determines that the operating mode of the first power conversion device is the running mode, and the determination result of step S2 is that the first power conversion device needs to be discharged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery of the first energy conversion device and a first lower limit value, wherein: If the charge state of the energy storage battery of the first power conversion device is less than the first lower limit value, then the working mode of the first power conversion device is switched to the standby mode. If the charge state of the energy storage battery of the first power conversion device is greater than the first lower limit, the first power conversion device maintains the operating mode.

3. The control method as described in claim 2, wherein, If the state of charge of the energy storage battery of the first power conversion device is less than the first lower limit, then switching the operating mode of the first power conversion device to the standby mode further includes: The power supply device that controls the first power conversion device charges the energy storage battery of the first power conversion device via the energy storage converter.

4. The control method as described in claim 1, wherein, When step S1 determines that the operating mode of the first power conversion device is the operating mode, and the determination result of step S2 is that the first power conversion device needs to be charged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery of the first energy conversion device and a first upper limit value, wherein: If the charge state of the energy storage battery of the first power conversion device is less than the first upper limit value, the first power conversion device maintains the operating mode; If the charge state of the energy storage battery of the first power conversion device is greater than the first upper limit value, then the working mode of the first power conversion device is switched to the standby mode or maintained in the operating mode, depending on the number of power conversion devices currently in the operating mode.

5. The control method as described in claim 4, wherein, Determining whether to switch the operating mode of the first power conversion device to the standby mode or maintain the operating mode based on the number of power conversion devices currently in operation includes: If the number of power conversion devices currently in this operating mode is greater than or equal to 2, then the operating mode of the first power conversion device is switched to the standby mode; If the number of power conversion devices currently in this operating mode is equal to 1, then the operating mode of the first power conversion device is maintained, and the frequency of an output voltage of the first power conversion device is increased.

6. The control method as described in claim 1, wherein, When step S1 determines that the operating mode of the first power conversion device is the standby mode, and the determination result of step S2 is that the first power conversion device needs to be discharged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery of the first energy conversion device and a second lower limit value, wherein: If the charge state of the energy storage battery of the first power conversion device is less than the second lower limit value, the first power conversion device maintains the standby mode. If the charge state of the energy storage battery of the first power conversion device is greater than the second lower limit value, then the working mode of the first power conversion device is switched to the operating mode.

7. The control method as described in claim 6, wherein, If the state of charge of the energy storage battery of the first energy conversion device is greater than the second lower limit, then switching the operating mode of the first energy conversion device to the operating mode further includes: The method for switching the operating mode of the first power conversion device to this mode is determined based on the number of power conversion devices currently in this operating mode, wherein: If the number of power conversion devices currently in this operating mode is greater than or equal to 1, then the operating mode of the first power conversion device is directly switched to this operating mode. If the number of power conversion devices currently in this operating mode is 0, then the operating mode of the first power conversion device will be switched to this operating mode after the first power conversion device is reconnected to the network.

8. The control method as described in claim 1, wherein, When step S1 determines that the operating mode of the first power conversion device is the standby mode, and the determination result of step S2 is that the first power conversion device needs to be charged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery of the first energy conversion device and a second upper limit value, wherein: If the charge state of the energy storage battery of the first power conversion device is greater than the second upper limit value, the first power conversion device maintains the standby mode. If the charge state of the energy storage battery of the first power conversion device is less than the second upper limit value, then the working mode of the first power conversion device is switched to the operating mode.

9. The control method as described in claim 8, wherein, If the state of charge of the energy storage battery of the first power conversion device is less than the second upper limit value, then switching the operating mode of the first power conversion device to the running mode further includes: The method for switching the operating mode of the first power conversion device to this mode is determined based on the number of power conversion devices currently in this operating mode, wherein: If the number of power conversion devices currently in this operating mode is greater than or equal to 1, then the operating mode of the first power conversion device is directly switched to this operating mode. If the number of power conversion devices currently in this operating mode is 0, then the operating mode of the first power conversion device will be switched to this operating mode after the first power conversion device is reconnected to the network.

10. The control method as described in claim 1, wherein, When the operating mode of the first power conversion device determined in step S1 is the operating mode, step S2 further includes: The power reference command is determined based on the average power of all the power conversion devices currently in this operating mode and the output power of the power supply device of the first power conversion device.

11. The control method as described in claim 1, wherein, When the operating mode of the first power conversion device determined in step S1 is the standby mode, step S2 further includes: The power reference command is determined based on the average power of all the power conversion devices currently in this operating mode.

12. A power supply system, comprising: An inverter; and Multiple power conversion devices, each with an output terminal connected in parallel to the inverter via a common connection terminal, each power conversion device comprising an energy storage battery, a power supply unit, and an energy storage converter, wherein... The plurality of power conversion devices includes a first power conversion device, and the first power conversion device is used to perform a control method, the control method including: S1. Determine an operating mode of the first power conversion device, wherein the operating mode includes an operating mode and a standby mode; S2. Determine whether the first power conversion device needs to be charged or discharged based on a power reference command; and S3. Determine whether it is necessary to switch the operating mode of the first power conversion device based on the charge status of the energy storage battery in the first power conversion device.

13. The power supply system as claimed in claim 12, wherein when step S1 determines that the operating mode of the first power conversion device is the operating mode, and the determination result of step S2 is that the first power conversion device needs to be discharged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery of the first energy conversion device and a first lower limit value, wherein: If the charge state of the energy storage battery of the first power conversion device is less than the first lower limit value, then the working mode of the first power conversion device is switched to the standby mode. If the charge state of the energy storage battery of the first power conversion device is greater than the first lower limit, the first power conversion device maintains the operating mode.

14. The power supply system as described in claim 13, wherein, If the state of charge of the energy storage battery of the first power conversion device is less than the first lower limit, then switching the operating mode of the first power conversion device to the standby mode further includes: The power supply device that controls the first power conversion device charges the energy storage battery of the first power conversion device via the energy storage converter.

15. The power supply system as described in claim 12, wherein, When step S1 determines that the operating mode of the first power conversion device is the operating mode, and the determination result of step S2 is that the first power conversion device needs to be charged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery of the first energy conversion device and a first upper limit value, wherein: If the charge state of the energy storage battery of the first power conversion device is less than the first upper limit value, the first power conversion device maintains the operating mode; If the charge state of the energy storage battery of the first power conversion device is greater than the first upper limit value, then the working mode of the first power conversion device is switched to the standby mode or maintained in the operating mode, depending on the number of power conversion devices currently in the operating mode.

16. The power supply system as described in claim 15, wherein, Determining whether to switch the operating mode of the first power conversion device to the standby mode or maintain the operating mode based on the number of power conversion devices currently in operation includes: If the number of power conversion devices currently in this operating mode is greater than or equal to 2, then the operating mode of the first power conversion device is switched to the standby mode; If the number of power conversion devices currently in this operating mode is equal to 1, then the operating mode of the first power conversion device is maintained, and the frequency of an output voltage of the first power conversion device is increased.

17. The power supply system as claimed in claim 12, wherein, When step S1 determines that the operating mode of the first power conversion device is the standby mode, and the determination result of step S2 is that the first power conversion device needs to be discharged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery of the first energy conversion device and a second lower limit value, wherein: If the charge state of the energy storage battery of the first power conversion device is less than the second lower limit value, the first power conversion device maintains the standby mode. If the charge state of the energy storage battery of the first power conversion device is greater than the second lower limit value, then the working mode of the first power conversion device is switched to the operating mode.

18. The power supply system as claimed in claim 17, wherein, If the state of charge of the energy storage battery of the first energy conversion device is greater than the second lower limit, then switching the operating mode of the first energy conversion device to the operating mode further includes: The method for switching the operating mode of the first power conversion device to this mode is determined based on the number of power conversion devices currently in this operating mode, wherein: If the number of power conversion devices currently in this operating mode is greater than or equal to 1, then the operating mode of the first power conversion device is directly switched to this operating mode. If the number of power conversion devices currently in this operating mode is 0, then the operating mode of the first power conversion device will be switched to this operating mode after the first power conversion device is reconnected to the network.

19. The power supply system as claimed in claim 12, wherein, When step S1 determines that the operating mode of the first power conversion device is the standby mode, and the determination result of step S2 is that the first power conversion device needs to be charged, step S3 further includes: The decision to switch the operating mode of the first energy conversion device is determined based on a comparison between the state of charge of the energy storage battery in the first energy conversion device and a second upper limit value, wherein: If the state of charge of the energy storage battery of the first power conversion device is greater than the second upper limit value, the first power conversion device maintains the standby mode. If the battery charge of the energy storage battery of the first power conversion device is less than the second upper limit value, then the working mode of the first power conversion device is switched to the operating mode.

20. The power supply system as claimed in claim 19, wherein, If the state of charge of the energy storage battery of the first power conversion device is less than the second upper limit value, then switching the operating mode of the first power conversion device to the running mode further includes: The method for switching the operating mode of the first power conversion device to this mode is determined based on the number of power conversion devices currently in this operating mode, wherein: If the number of power conversion devices currently in this operating mode is greater than or equal to 1, then the operating mode of the first power conversion device is directly switched to this operating mode. If the number of power conversion devices currently in the parallel operation mode is 0, then the working mode of the first power conversion device will be switched to the operation mode after the first power conversion device is reconnected to the network.

21. The power supply system as claimed in claim 12, wherein, When the operating mode of the first power conversion device determined in step S1 is the operating mode, step S2 further includes: The power reference command is determined based on the average power of all the power conversion devices currently in this operating mode and the output power of the power supply device of the first power conversion device.

22. The power supply system as claimed in claim 12, wherein, When the operating mode of the first power conversion device determined in step S1 is the standby mode, step S2 further includes: The power reference command is determined based on the average power of all the power conversion devices currently in this operating mode.

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