Parallel direct-current power module automatic current sharing method and parallel direct-current power supply system

Abstract

This invention belongs to the field of operation and maintenance of parallel DC power supply systems for power stations, specifically relating to an automatic current sharing method for parallel DC power supply modules and a parallel DC power supply system. The method includes: after identifying a master and other slave modules from all parallel DC power supply modules requiring current sharing, the master module stops its own active current regulation and periodically sends its current value to the bus in real time; the slave modules periodically send their own output current value to the bus in real time. Current sharing is adjusted by comparing their own output current value with the current sharing value. The current sharing value is obtained based on the real-time output current value of the master module and the average of the random output current values ​​of slave modules (which are less than the total number of slave modules). The reference current for current sharing not only considers the current value output by the master module but also averages it with the real-time output current values ​​of the random slave modules, enabling rapid stabilization of the current in each parallel DC power supply module and effectively improving the dynamic response, accuracy, stability, and reliability of current sharing.

Description

Technical Field

[0001] This invention belongs to the field of operation and maintenance of parallel DC power supply systems for power stations, and specifically relates to an automatic current sharing method for parallel DC power supply modules and a parallel DC power supply system. Background Technology

[0002] The development trend of power supply in recent years has been a gradual decrease in the number of high-voltage substations and a gradual increase in the number of substations with voltage levels of 110kV and below, along with the development of parallel DC power supply systems (the principle of which is as follows). Figure 1 The stable operation of the pilot station has fundamentally solved the inherent defect that a problem with a single battery can affect the entire battery pack. At the same time, it has realized the functions of online battery capacity assessment and uninterrupted replacement of the entire module. The system expansion is smooth and simple, and the advantages of the DC power supply system in terms of safety, reliability and flexibility are gradually being realized. The market capacity is growing rapidly.

[0003] The biggest difference between parallel DC power supply systems and traditional DC power supply systems lies in the significantly increased number of power modules. This increased number of modules places higher demands on current sharing. Conventional analog current sharing schemes are no longer suitable for parallel DC power supply modules with many external interfaces. Traditional digital current sharing schemes calculate the system average current value through communication data between the current sharing controller (monitoring module) or power modules, and then each module adjusts its own output current based on the average current value to achieve current sharing. This scheme is limited by the communication between the current sharing controller and the power modules; if the current sharing controller fails, current sharing will fail. Furthermore, communication delays and calculation accuracy limit the accuracy and speed of current sharing. The subsequent CAN current sharing method works well when the number of modules is small and the rated output current is large. However, in parallel DC power supply systems, the number of power modules typically exceeds 18, and the rated output current of each module is relatively small. Using this scheme results in poor performance, with each module in a constant adjustment state, leading to instability. Therefore, existing technologies carry certain technical risks.

[0004] Chinese invention patent application CN113708458A discloses a method, device, and system for parallel current sharing control of multiple charging modules. The current sharing control method includes: when the master and slave modules are connected in parallel, obtaining a first output current feedback value of the master module and a second output current feedback value of each slave module; obtaining the average current value of each charging module based on the first and second output current feedback values; obtaining the target voltage setting value and output voltage feedback value of each charging module; adjusting the actual output current value of each charging module based on the difference between the average current value and the first or second output current feedback value, and based on the target voltage setting value and output voltage feedback value. This invention achieves stable output voltage control for each charging module while simultaneously controlling the actual output current of each module. However, this method performs current sharing control on both the master and slave modules, which may still cause each module to remain in an adjustment state for extended periods, making stability difficult. Summary of the Invention

[0005] The purpose of this invention is to provide an automatic current sharing method for parallel DC power supply modules and a parallel DC power supply system, in order to solve the problems of low current sharing speed and the possibility that each module may be in an adjustment state for a long time in the prior art, making it difficult to stabilize.

[0006] To achieve the above objectives, a first aspect of the present invention provides an automatic current sharing method for parallel DC power supply modules, comprising: After identifying one master and other slaves from all parallel DC power supply modules requiring current sharing, the master stops its own active current regulation and periodically sends current values ​​to the bus in real time. The slaves periodically send their own output current values ​​to the bus in real time. Current sharing is adjusted by comparing their own output current values ​​with the current sharing values. The current sharing values ​​are obtained based on the current values ​​received from the master in real time and the average of the output current values ​​of a randomly set number of slaves at this time. This set number is less than the total number of slaves.

[0007] The first aspect of the present invention provides an automatic current sharing method for parallel DC power supply modules. In one possible implementation, determining a master and other slave modules from all parallel DC power supply modules requiring current sharing includes: All parallel DC power supply modules that require current sharing send their ID numbers to the corresponding communication bus via bus communication. All power modules receive the ID numbers of other power modules via bus communication. The contention mechanism is as follows: if the smallest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number smaller than its own. The contention mechanism is as follows: if the largest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number larger than its own.

[0008] The first aspect of the present invention provides an automatic current sharing method for parallel DC power supply modules. In one possible implementation, it further includes: if the host exits after the competition is completed, and the remaining parallel DC power supply modules do not receive the corresponding message sent by the host within a set time, then the remaining parallel DC power supply modules begin to compete for the master and slave positions and perform current sharing adjustment in a manner that determines a host and other slaves from all parallel DC power supply modules that need to share current.

[0009] The first aspect of this invention provides an automatic current sharing method for parallel DC power supply modules. In one possible implementation, the slave device adjusts the current sharing by comparing it with the current received from the master device. The current sharing loop is started. The PID controller in the current sharing loop is adjusted by comparing its own output current value with the current sent by the host. The adjustment stops when the stopping condition is met, thus completing the current sharing. The stopping conditions include: the error between the slave device's own output current value and the master device's transmitted current is within a set current difference threshold.

[0010] The first aspect of the present invention provides an automatic current sharing method for parallel DC power supply modules, in one possible implementation, the number of modules is set to 1 to 3.

[0011] The above-described technical solution of the present invention provides a novel automatic current sharing method for parallel DC power supply modules. Its beneficial effects include: by not actively adjusting the current of the host, and by sending the reference current from the host to the slave, not only considering the current value output by the host itself, but also by averaging the real-time output current values ​​of several random slaves (less than the total number of slaves), the reference current is adjusted in real time. Thus, by comprehensively considering the output current values ​​of any slave in the parallel DC power supply system, the current between the parallel DC power supply modules is quickly stabilized, effectively improving the dynamic response, accuracy, stability, and reliability of the system's current sharing.

[0012] A second aspect of the present invention provides a parallel DC power supply system, comprising parallel DC power supply modules and a bus-type communication subsystem. After determining a master and other slave modules from all parallel DC power supply modules requiring current sharing, the master module stops its own active current regulation and periodically sends current values ​​to the bus in real time. The slave modules periodically send their own output current values ​​to the bus in real time, so as to perform current sharing regulation by comparing their own output current values ​​with the current sharing current values. The current sharing current values ​​are obtained based on the current values ​​received in real time from the master module and the average of the output current values ​​of a randomly set number of slave modules at this time, wherein the set number is less than the total number of slave modules.

[0013] The second aspect of the present invention provides a parallel DC power supply system, in one possible implementation, comprising determining a master and other slave modules from all parallel DC power supply modules requiring current sharing by: All parallel DC power supply modules that require current sharing send their ID numbers to the corresponding communication bus via bus communication. All power modules receive the ID numbers of other power modules via bus communication. The contention mechanism is as follows: if the smallest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number smaller than its own. The contention mechanism is as follows: if the largest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number larger than its own.

[0014] The second aspect of the present invention provides a parallel DC power supply system. In one possible implementation, after the competition is completed, the remaining parallel DC power supply modules other than the master are also used to, if they do not receive a corresponding message sent by the master within a set time, start to compete for master and slave and perform current sharing adjustment in a way that determines a master and other slaves from all parallel DC power supply modules that need to share current.

[0015] The second aspect of the present invention provides a parallel DC power supply system, in one possible implementation where the slave device performs current sharing regulation by comparing the current received from the master device with the current sent by the slave device. The current sharing loop is started. The PID controller in the current sharing loop is adjusted by comparing its own output current value with the current sent by the host. The adjustment stops when the stopping condition is met, thus completing the current sharing. The stopping conditions include: the error between the slave device's own output current value and the master device's transmitted current is within a set current difference threshold.

[0016] The second aspect of the present invention provides a parallel DC power supply system, in one possible implementation, wherein the number of such systems is set to 1 to 3.

[0017] The technical solution of the parallel DC power supply system described above can achieve the same beneficial effects as the automatic current sharing method of the parallel DC power supply module described above. Attached Figure Description

[0018] Figure 1 This is an example diagram of the architecture of an existing parallel DC power supply system in the background art of this invention; Figure 2 This is a flowchart illustrating the automatic current sharing method for parallel DC power modules implemented in the parallel DC power system embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] Parallel DC power supply system implementation method This embodiment provides a technical solution for a parallel DC power supply system. The host stops its own active current sharing and sends a reference current for current sharing to the slaves to the bus. The reference current is obtained by averaging the host's own current and the output current of two other random slave modules. This can effectively improve the speed of current sharing.

[0021] The system includes parallel DC power supply modules and a bus-type communication subsystem. Specifically, after determining one master and other slaves from all parallel DC power supply modules that need current sharing, the master stops its own active current regulation and periodically sends current values ​​to the bus in real time. The slaves periodically send their own output current values ​​to the bus in real time. Current sharing is adjusted by comparing their own output current values ​​with the current sharing value. The current sharing value is obtained based on the current value received from the master in real time and the average of the output current values ​​of a randomly set number of slaves at that time. This set number is less than the total number of slaves.

[0022] Therefore, this system adjusts the reference current in real time by averaging the real-time output current values ​​of several random slave devices (less than the total number of slave devices) without the host actively regulating the current. This approach, by considering not only the host's own output current but also the real-time output current values ​​of any slave device in the parallel DC power supply system, rapidly stabilizes the current between parallel DC power supply modules, effectively improving the system's dynamic response, accuracy, stability, and reliability in current sharing. If only the host's own current is sent to the bus, with a large number of modules, the current regulation of the slave modules would affect the host's current, resulting in a fluctuation adjustment phase and hindering rapid current sharing stability. Therefore, averaging the real-time output current values ​​of the slave devices improves the speed of current sharing stability. However, too many slave devices participating in current sharing could significantly influence the reference current, potentially leading to a large current difference between the host and slave devices when the host does not actively regulate the current. Therefore, the number of random slave devices participating in the averaging calculation is less than the total number of slave devices.

[0023] In a preferred embodiment, the bus-type communication subsystem can be a CAN communication system; CAN communication is a bus-based communication method and is currently the preferred communication method for current sharing in power electronic power module software. In other embodiments, the bus-type communication subsystem can also be implemented using other existing bus communication methods.

[0024] Furthermore, in this embodiment, the number is set to 1 to 3, meaning that theoretically 1, 2, or 3 random slave modules can be selected to participate in the calculation of the current sharing value. However, even with only 1 module, there is still a possibility of fluctuation and adjustment. In other embodiments, more random slave modules can be selected to participate in the calculation of the current sharing value.

[0025] Furthermore, in this embodiment, the method for determining one master and other slave devices from all parallel DC power supply modules requiring current sharing includes: All parallel DC power supply modules that require current sharing send their ID numbers to the corresponding communication bus via bus communication. All power modules receive the ID numbers of other power modules via bus communication. The contention mechanism is as follows: if the smallest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number smaller than its own. The contention mechanism is as follows: if the largest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number larger than its own.

[0026] Based on this, after the competition is completed, the remaining parallel DC power supply modules other than the master are also used to re-compete for master and slave and perform current sharing adjustment if they do not receive a corresponding message from the master within a set time. This is done by determining a master and other slaves from all parallel DC power supply modules that need to share current.

[0027] Through the bus-type communication master-slave competition mechanism of this embodiment, each parallel DC power supply module can become a master or slave, and each parallel DC power supply module can control its own output current to achieve autonomous current sharing. Under this mechanism, if the master power supply module fails, the digital current sharing control will compete for the master and slave positions again, without affecting the current sharing control or the current power system.

[0028] In this embodiment, the slave device adjusts the current sharing by comparing the current received from the master device with the current sent by the slave device. The current sharing loop is started. By comparing its own output current value with the current sent by the host, the PID controller in the current sharing loop is adjusted until the stopping condition is met, and then the adjustment stops to complete the current sharing.

[0029] Specifically, the stopping conditions include: the error between the slave device's own output current value and the master device's transmitted current is within the set current difference threshold.

[0030] See Figure 2The parallel DC power supply system described in this embodiment enables autonomous current sharing digital control of the parallel DC power supply modules. The system mainly consists of a power supply system composed of 24 (which may vary depending on the actual situation) parallel DC power supply modules. The parallel DC power supply modules are connected in parallel with single-phase input, and their positive and negative output buses are connected in parallel. The CAN communication lines are connected in parallel.

[0031] In practice, the autonomous current sharing digital control process implemented by the above-mentioned parallel DC power supply system, based on bus-type communication (specifically CAN communication), includes the following steps: Step 1: After the system is powered on, the 24 parallel DC power supply modules publish their own identity sequence ID number through CAN communication data; Step 2: The identity sequence ID numbers published by the parallel DC power supply modules and other receiving modules are compared to automatically compete for the master / slave status. The competition mechanism is that the module with the smallest ID number becomes the master, and the rest become slaves. DC power supply module 1 has the smallest ID number, so it competes to become the master, and the other 23 modules become slaves. Step 3: After the competition is completed, all modules stop sending identity sequence ID numbers and start sending their own current to the CAN bus. After module 1 becomes the master, it stops running its own current sharing loop and begins to passively adjust its own current, sending the current to the bus. This current is the average of its own current and the output current of the other two random slave modules. This effectively improves the current sharing speed. The remaining slaves start their current sharing loops and adjust the PID controller in the current sharing loop by comparing it with the current received from the master. Finally, the adjustment stops when the error between the output current and the current sent by the master is within 0.1A (the set current difference threshold), and the current sharing is completed.

[0032] Assuming that the parallel DC power supply module 1 fails and automatically disconnects, if the remaining modules do not receive a message from the master within 3 seconds (set time), the remaining slave modules will start competing for the master-slave relationship again. This has no impact on the current sharing control system and the current power system, thus achieving true autonomous current sharing digital control.

[0033] The above-mentioned parallel DC power supply system operates in master-slave mode, with the current sent by the master serving as the basis for adjustment. At the same time, the current sent by the master is not its own current, but the average value of the output currents of the two random slaves. This greatly improves the dynamic response, accuracy, stability and reliability of the current sharing of the system, thereby solving the drawback of the unsatisfactory digital current sharing balance of multiple modules with small currents.

[0034] Implementation Method of Automatic Current Sharing Method for Parallel DC Power Supply Modules This embodiment provides a technical solution for an automatic current sharing method for parallel DC power supply modules. The host stops its own active current sharing and sends a reference current for current sharing to the slave modules to the bus. The reference current is obtained by averaging the host's own current and the output current of two other random slave modules. This effectively improves the speed of current sharing.

[0035] The method includes: determining a master and other slave devices from all parallel DC power supply modules that need current sharing (depending on the specific connection relationship, they can be referred to as parallel DC power supply modules in actual operation, or simply parallel DC power supply modules or parallel DC power supply modules), the master device stops its own active current regulation and periodically sends current values ​​to the bus in real time, and the slave devices periodically send their own output current values ​​to the bus in real time, so as to perform current sharing regulation by comparing their own output current values ​​with the current sharing current values; the current sharing current values ​​are obtained based on the current values ​​sent by the master device in real time and the average of the output current values ​​of a randomly set number of slave devices at this time, and the set number is less than the total number of slave devices.

[0036] Therefore, this method adjusts the reference current in real time by averaging the real-time output current values ​​of several random slave devices (less than the total number of slave devices) without the host actively regulating the current. This approach, by considering not only the host's own output current but also the real-time output current values ​​of any slave device in the parallel DC power supply system, rapidly stabilizes the current between parallel DC power supply modules. This effectively improves the dynamic response, accuracy, stability, and reliability of the automatic current sharing method for parallel DC power supplies. If only the host's own current is sent to the bus, with a large number of modules, the current regulation of the slave modules will affect the host's current, resulting in a fluctuation adjustment phase and hindering rapid current sharing. Therefore, averaging the real-time output current values ​​of the slave devices improves the speed of stable current sharing. However, too many slave devices participating in current sharing can significantly influence the reference current, potentially leading to large current differences between the host and slave devices when the host does not actively regulate the current. Therefore, the number of random slave devices participating in the average calculation is less than the total number of slave devices.

[0037] In a preferred embodiment, the bus-type communication subsystem can be a CAN communication system; CAN communication is a bus-based communication method and is currently the preferred communication method for current sharing in power electronic power module software. In other embodiments, the bus-type communication subsystem can also be implemented using other existing bus communication methods.

[0038] Furthermore, in this embodiment, the number is set to 1 to 3, meaning that theoretically 1, 2, or 3 random slave modules can be selected to participate in the calculation of the current sharing value. However, even with only 1 module, there is still a possibility of fluctuation and adjustment. In other embodiments, more random slave modules can be selected to participate in the calculation of the current sharing value.

[0039] Furthermore, in this embodiment, the method for determining one master and other slave devices from all parallel DC power supply modules requiring current sharing includes: All parallel DC power supply modules that require current sharing send their ID numbers to the corresponding communication bus via bus communication. All power modules receive the ID numbers of other power modules via bus communication. The contention mechanism is as follows: if the smallest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number smaller than its own. The contention mechanism is as follows: if the largest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number larger than its own.

[0040] Based on this, after the competition is completed, the remaining parallel DC power supply modules other than the master are also used to re-compete for master and slave and perform current sharing adjustment if they do not receive a corresponding message from the master within a set time. This is done by determining a master and other slaves from all parallel DC power supply modules that need to share current.

[0041] Through the bus-type communication master-slave competition mechanism of this embodiment, each parallel DC power supply module can become a master or slave, and each parallel DC power supply module can control its own output current to achieve autonomous current sharing. Under this mechanism, if the master power supply module fails, the digital current sharing control will compete for the master and slave positions again, without affecting the current sharing control or the current power system.

[0042] In this embodiment, the slave device adjusts the current sharing by comparing the current received from the master device with the current sent by the slave device. The current sharing loop is started. By comparing its own output current value with the current sent by the host, the PID controller in the current sharing loop is adjusted until the stopping condition is met, and then the adjustment stops to complete the current sharing.

[0043] Specifically, the stopping conditions include: the error between the slave device's own output current value and the master device's transmitted current is within the set current difference threshold.

[0044] The automatic current sharing method of parallel DC power supply modules in this embodiment is applied to perform autonomous current sharing digital control on the parallel DC power supply modules in the parallel DC power supply system. The system mainly consists of a power supply system composed of 24 (which may vary depending on the actual situation) parallel DC power supply modules. The parallel DC power supply modules are connected in parallel with single-phase input, and their positive and negative output buses are connected in parallel. The CAN communication lines are connected in parallel.

[0045] In practice, the autonomous current sharing digital control process based on bus-type communication (specifically CAN communication) implemented by the above-mentioned automatic current sharing method for parallel DC power supply modules includes the following steps: Step 1: After the parallel DC power supply module system is powered on, the 24 parallel DC power supply modules publish their own identity sequence ID number through CAN communication data; Step 2: The identity sequence ID numbers published by the parallel DC power supply modules and other receiving modules are compared to automatically compete for the master / slave status. The competition mechanism is that the module with the smallest ID number becomes the master, and the rest become slaves. DC power supply module 1 has the smallest ID number, so it competes to become the master, and the other 23 modules become slaves. Step 3: After the competition is completed, all modules stop sending identity sequence ID numbers and start sending their own current to the CAN bus. After module 1 becomes the master, it stops running its own current sharing loop and begins to passively adjust its own current, sending the current to the bus. This current is the average of its own current and the output current of the other two random slave modules. This effectively improves the current sharing speed. The remaining slaves start their current sharing loops and adjust the PID controller in the current sharing loop by comparing it with the current received from the master. Finally, the adjustment stops when the error between the output current and the current sent by the master is within 0.1A (the set current difference threshold), and the current sharing is completed.

[0046] Assuming that the parallel DC power supply module 1 fails and automatically disconnects, if the remaining modules do not receive a message from the master within 3 seconds (set time), the remaining slave modules will start competing for the master-slave relationship again. This has no impact on the current sharing control and the current power system, thus achieving true autonomous current sharing digital control.

[0047] The above-mentioned parallel DC power supply method operates in master-slave mode, with the current sent by the master serving as the adjustment basis. At the same time, the current sent by the master is not its own current, but the average value of the output currents of the two random slaves. This greatly improves the dynamic response, accuracy, stability and reliability of the current sharing of the parallel DC power supply system, thereby solving the drawback of the unsatisfactory digital current sharing balance of multiple modules with small currents.

[0048] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or explanatory of the principles of the present invention, and do not constitute a limitation thereof.

Claims

1. A method for automatically balancing the current of parallel DC power supply modules, characterized in that, include: After identifying one master and other slaves from all parallel DC power supply modules requiring current sharing, the master stops its own active current regulation and periodically sends current values ​​to the bus in real time. The slaves periodically send their own output current values ​​to the bus in real time. Current sharing is adjusted by comparing their own output current values ​​with the current sharing values. The current sharing values ​​are obtained based on the current values ​​received from the master in real time and the average of the output current values ​​of a randomly set number of slaves at this time. This set number is less than the total number of slaves.

2. The method for automatic current sharing of parallel DC power supply modules according to claim 1, wherein, The methods for determining a master and other slave devices from all parallel DC power supply modules requiring current sharing include: All parallel DC power supply modules that require current sharing send their ID numbers to the corresponding communication bus via bus communication. All power modules receive the ID numbers of other power modules via bus communication. The contention mechanism is as follows: if the smallest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number smaller than its own. The contention mechanism is as follows: if the largest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number larger than its own.

3. The method for automatic current sharing of parallel DC power supply modules according to claim 2, characterized in that, Also includes: If the master module exits after the competition is completed, and the remaining parallel DC power supply modules do not receive the corresponding message from the master module within a set time, then the remaining parallel DC power supply modules will start competing for the master and slave positions again and perform current sharing adjustment in the manner of determining a master and other slave modules from all parallel DC power supply modules that need to share current.

4. The method for automatic current sharing of parallel DC power supply modules according to any one of claims 1-3, characterized in that, The slave device adjusts current sharing by comparing the current received from the master device with the current sent by the master device. This includes the following methods: The current sharing loop is started. The PID controller in the current sharing loop is adjusted by comparing its own output current value with the current sent by the host. The adjustment stops when the stopping condition is met, thus completing the current sharing. The stopping conditions include: the error between the slave device's own output current value and the master device's transmitted current is within a set current difference threshold.

5. The method for automatic current sharing of parallel DC power supply modules according to any one of claims 1-3, wherein, The quantity can be set to 1 to 3.

6. A parallel type DC power supply system comprising a parallel type DC power supply module and a bus type communication subsystem, characterized by, After identifying one master and other slaves from all parallel DC power supply modules requiring current sharing, the master stops its own active current regulation and periodically sends current values ​​to the bus in real time. The slaves periodically send their own output current values ​​to the bus in real time. Current sharing is adjusted by comparing their own output current values ​​with the current sharing values. The current sharing values ​​are obtained based on the current values ​​received from the master in real time and the average of the output current values ​​of a randomly set number of slaves at that time. This set number is less than the total number of slaves.

7. The parallel DC power supply system according to claim 6, characterized in that, The methods for determining a master and other slave devices from all parallel DC power supply modules requiring current sharing include: All parallel DC power supply modules that require current sharing send their ID numbers to the corresponding communication bus via bus communication. All power modules receive the ID numbers of other power modules via bus communication. The contention mechanism is as follows: if the smallest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number smaller than its own. The contention mechanism is as follows: if the largest ID number is the master and the rest are slaves, the module stops sending ID numbers and withdraws from the contention if it finds an ID number larger than its own.

8. The parallel DC power supply system according to claim 7, characterized in that, After the competition is completed, the remaining parallel DC power supply modules other than the master are also used to re-compete for master and slave and perform current sharing adjustment if no corresponding message is received from the master within a set time. This is done by determining a master and other slaves from all parallel DC power supply modules that need to share current.

9. The parallel DC power supply system according to any one of claims 6-8, characterized in that, The slave device adjusts current sharing by comparing the current received from the master device with the current sent by the master device. This includes the following methods: The current sharing loop is started. The PID controller in the current sharing loop is adjusted by comparing its own output current value with the current sent by the host. The adjustment stops when the stopping condition is met, thus completing the current sharing. The stopping conditions include: the error between the slave device's own output current value and the master device's transmitted current is within a set current difference threshold.

10. The parallel DC power supply system according to any one of claims 6-8, characterized in that, The quantity can be set to 1 to 3.

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