Adaptive droop control method and system for parallel DC converters

Abstract

The invention provides a parallel DC converter adaptive droop control method and system. The method comprises the following steps: identifying equivalent line resistance of each DC converter branch on line; calculating the droop coefficient correction of each branch based on the equivalent line resistance of each branch; acquiring a direct current bus output voltage value, and calculating a direct current bus reference voltage correction of each branch by combining the direct current bus voltage reference value; and introducing the droop coefficient correction and the direct current bus reference voltage correction into a droop control algorithm to generate a voltage loop reference voltage, and further generating a pulse width modulation signal through a voltage and current double-closed-loop controller for controlling each direct current converter. The problem of how to overcome the contradiction between the output current sharing precision and the direct current bus voltage stability caused by mismatching of the circuit resistors of the branch circuits connected in parallel is solved.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically, to an adaptive droop control method and system for a parallel DC-DC converter. Background Technology

[0002] With the rapid development of DC microgrids, energy storage systems, and other fields, the requirements for the capacity and reliability of DC power supplies are increasing. Parallel operation of multiple DC converters is an effective solution to improve system capacity and achieve redundancy. In parallel systems, droop control is widely used due to its advantages such as eliminating the need for interconnection communication lines and ease of modularization. However, traditional droop control has inherent drawbacks. Its control performance is severely affected by the inconsistent equivalent line resistance of each converter branch. To improve the distribution accuracy of the output current, a large droop coefficient is usually required, but this leads to a significant steady-state deviation in the DC bus voltage, causing a decline in power quality. Conversely, if a small droop coefficient is used to maintain the bus voltage level, it will result in severely uneven current distribution among the branches, potentially causing overload of individual converters. Summary of the Invention

[0003] The problem solved by this invention is how to overcome the contradiction between the output current distribution accuracy and the DC bus voltage stability caused by the mismatch of the resistances of the parallel branches.

[0004] To address the above problems, this invention provides an adaptive droop control method for a parallel DC-DC converter, comprising the following steps: S1: Online identification of the equivalent line resistance of each DC converter branch; S2: Calculate the droop coefficient correction for each branch based on the equivalent line resistance of each branch; S3: Obtain the DC bus output voltage value and, in conjunction with the DC bus voltage reference value, calculate the DC bus reference voltage correction amount for each branch; S4: The droop coefficient correction and the DC bus reference voltage correction are introduced into the droop control algorithm to generate the voltage loop reference voltage, and then the voltage and current dual closed-loop controller generates a pulse width modulation signal to control each DC converter.

[0005] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: By identifying the resistance of each branch line online and dynamically correcting the droop coefficient, the circulating current and current distribution errors caused by differences in line parameters are fundamentally eliminated, significantly improving the current sharing accuracy of the parallel system. By introducing a DC bus reference voltage correction, the inherent voltage drop problem of traditional droop control is effectively compensated, ensuring that the DC bus voltage remains stable near the reference value, thus improving the system's power quality. This method reduces the requirements for low-bandwidth communication systems and improves the system's reliability and practicality.

[0006] Furthermore, the equivalent line resistance of each DC converter branch is identified online using a recursive least squares method with a forgetting factor.

[0007] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: the recursive least squares method with a forgetting factor can reduce the weight of historical data, making the identification algorithm less sensitive to random disturbances and measurement noise during system operation, thereby obtaining more accurate and stable line resistance identification results. The method of this application can update the identification results online and continuously, effectively tracking the slow changes in line resistance caused by factors such as temperature changes and loose connections, ensuring the adaptive capability and long-term operational accuracy of the control system.

[0008] Furthermore, the equivalent line resistance identified by the recursive least squares method is subjected to first-order low-pass filtering.

[0009] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: By applying a first-order low-pass filter to the identification results, the drastic fluctuations in the estimated line resistance value caused by measurement noise or system transient processes can be effectively smoothed, avoiding frequent oscillations in control parameters. The filtering process ensures that the line resistance value fed into the subsequent control loop is a gradual change, preventing high-frequency noise from the identification loop from propagating to the power control loop, thereby significantly improving the control stability and reliability of the entire parallel system.

[0010] Furthermore, based on the equivalent line resistance of each branch, the droop coefficient correction amount of each branch is calculated, including the following steps: calculating the average value of the equivalent line resistance of the DC converter branch; subtracting the average value from the equivalent line resistance of each branch itself, and outputting the difference as the droop coefficient correction amount of the corresponding branch after calculation by the proportional-integral controller.

[0011] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: By making the equivalent total resistance (the sum of the line resistance and the resistance converted by the droop coefficient) of each branch more consistent, it fundamentally ensures that the load current can be accurately and proportionally distributed among the parallel branches. The use of proportional-integral control to calculate the correction amount eliminates steady-state current sharing errors caused by differences in line resistance, achieving high-precision adaptive adjustment. This method can automatically and dynamically adjust the droop coefficient based on the real-time identified resistance value of each branch, ensuring that the system maintains optimal current sharing performance regardless of parameter changes or load fluctuations.

[0012] Furthermore, the DC bus output voltage value is obtained, and combined with the DC bus voltage reference value, the DC bus reference voltage correction amount of each branch is calculated, including the following steps: the difference between the DC bus voltage reference value and the DC bus output voltage value is calculated, and the difference is processed by the proportional-integral controller and output as the DC bus reference voltage correction amount of the corresponding branch.

[0013] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: By introducing a proportional-integral controller to calculate the bus voltage deviation, precise control of the DC bus voltage can be achieved, effectively eliminating the inherent steady-state voltage deviation of traditional droop control. This correction method can respond quickly to load changes or system disturbances, effectively suppressing bus voltage fluctuations and improving the dynamic stability of the system by dynamically adjusting the reference voltage value. Through real-time compensation for bus voltage dips, the system has a stronger adaptability to disturbances such as sudden load changes, maintaining the bus voltage within the allowable range and ensuring power supply quality.

[0014] Furthermore, the droop coefficient correction and the DC bus reference voltage correction are introduced into the droop control algorithm to generate the voltage loop reference voltage, including the following steps: The droop control algorithm combines the droop coefficient correction with the initial droop coefficient and combines the DC bus reference voltage correction with the DC bus voltage reference value to generate the voltage loop reference voltage.

[0015] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: By simultaneously introducing droop coefficient correction and reference voltage correction, the system can balance current sharing accuracy and voltage control quality, effectively resolving the contradiction between current sharing and voltage regulation in traditional droop control. The introduction of these two corrections enables independent control of system power distribution and voltage regulation, allowing the system to quickly and smoothly reach a new stable operating point during dynamic processes. This improvement optimizes the traditional droop control framework without requiring a complete redesign of the control system, maintaining the simplicity and engineering practicality of the control structure.

[0016] Furthermore, the equivalent line resistance is identified based on the output voltage, output current, and DC bus output voltage of this branch.

[0017] Compared with existing technologies, the technical advantages of this solution are as follows: It directly identifies resistance based on three key physical quantities that directly determine line voltage drop: output voltage, output current, and DC bus voltage. This ensures the accuracy and reliability of the resistance identification results, laying a solid foundation for subsequent precise control. This method only requires the use of existing conventional sensor measurements, eliminating the need for additional dedicated voltage or current detection devices for identification purposes, thus simplifying the system structure and reducing implementation costs.

[0018] Furthermore, the parallel DC-DC converters exchange the equivalent line resistance information of each branch through a low-bandwidth communication network.

[0019] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: Compared with existing methods that require exchanging high-frequency current information or performing complex iterative calculations, this solution only exchanges slowly changing line resistance parameters, significantly reducing the requirements for communication bandwidth and real-time performance. The low-bandwidth communication network has a simple structure, low cost, and low sensitivity to communication delays and transient interruptions, enhancing the robustness and reliability of the system under complex operating conditions.

[0020] To address the aforementioned problems, this invention provides an adaptive droop control system for a parallel DC-DC converter, used to execute the adaptive droop control method for a parallel DC-DC converter provided by the above-mentioned technical features. The system includes: a data acquisition module, a line resistance identification module, an adaptive compensation module, a central processing module, a voltage and current control module, and a pulse width modulation module. The data acquisition module is used to acquire electrical parameters of each DC-DC converter branch and the DC bus. The line resistance identification module is connected to the data acquisition module and is used to identify the equivalent line resistance of each branch online. The adaptive compensation module is connected to the data acquisition module and the line resistance identification module and is used to generate an adaptive control quantity for correcting the droop control law based on the electrical parameters and the equivalent line resistance. The central processing module coordinates the operation of the data acquisition module, the line resistance identification module, and the adaptive compensation module. The voltage and current control module is connected to the adaptive compensation module and is used to generate a modulation wave based on the voltage loop reference voltage corrected by the adaptive control quantity. The pulse width modulation module is connected to the voltage and current control module and is used to generate switching signals to drive each DC-DC converter based on the modulation wave.

[0021] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: Through the clear division of labor and collaborative cooperation among various functional modules, a closed-loop control of the entire process—from parameter acquisition, online identification, adaptive compensation to pulse width modulation generation—is realized, ensuring the integrity and coordination of system control. The modular design clarifies the responsibilities of each functional unit, reducing system complexity. Simultaneously, the unified coordination of the central processing module ensures stable and reliable system operation, facilitating system maintenance and fault diagnosis. The system architecture is clear, and the functions of each module are well-defined, facilitating integration and deployment on existing hardware control platforms, which is beneficial for the engineering application and standardized production of this control method.

[0022] Furthermore, the adaptive compensation module includes: a droop coefficient correction unit and a reference voltage correction amount; wherein, the droop coefficient correction unit is used to calculate the droop coefficient correction amount based on the equivalent line resistance of each branch; the reference voltage correction unit is used to calculate the DC bus reference voltage correction amount based on the DC bus output voltage value and the reference value; wherein, the droop coefficient correction amount and the DC bus reference voltage correction amount together constitute the adaptive control quantity.

[0023] Compared with existing technologies, the technical effects achieved by adopting this solution are as follows: By separately setting up droop coefficient correction units and reference voltage correction units, the system can independently and accurately adjust power distribution and voltage levels, achieving decoupled optimization for different control objectives. The parallel operation of the two correction units enables the system to simultaneously cope with various operating conditions such as line parameter mismatch and load changes, significantly improving the system's adaptability under different operating conditions.

[0024] In summary, the technical solutions described above in this application have one or more of the following advantages or beneficial effects: i) By accurately identifying the line resistance, the fundamental parameter causing inaccurate circulating current and current sharing, online inconsistencies are eliminated at the source, rather than merely compensating for operational results. ii) Through a dual adaptive compensation mechanism, simultaneously correcting the droop coefficient and the reference voltage, the contradiction between current sharing accuracy and bus voltage stability in traditional droop control is effectively resolved. iii) Only low-bandwidth communication is needed to exchange slowly changing line resistance parameters, avoiding the need for high real-time communication in complex algorithms, improving system reliability and reducing costs. iv) The system architecture is clear, highly modular, easy to implement on existing hardware platforms, and easy to expand and maintain. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating an adaptive droop control method for a parallel DC-DC converter according to an embodiment of the present invention. Figure 2 This is a circuit diagram of a two-parallel three-level DC-DC converter in an embodiment of the present invention; Figure 3 This is a parallel model diagram of the DC-DC converter in an embodiment of the present invention; Figure 4 This is a flowchart of the recursive least squares method for forgetting factors in an embodiment of the present invention; Figure 5 This is a control block diagram of the improved droop control in an embodiment of the present invention; Figure 6 This is a block diagram of the adaptive droop control system for a parallel DC-DC converter in an embodiment of the present invention. Detailed Implementation

[0026] The purpose of this invention is to provide an adaptive droop control method and system for parallel DC-DC converters, which can eliminate the influence of line parameter differences from the source and achieve high-precision current sharing and error-free bus voltage regulation under low communication dependence conditions.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] See Figures 1-6 This invention provides an adaptive droop control method for a parallel DC-DC converter, comprising the following steps: S1: Online identification of the equivalent line resistance of each DC converter branch; S2: Calculate the droop coefficient correction for each branch based on the equivalent line resistance of each branch; S3: Obtain the DC bus output voltage value and, in conjunction with the DC bus voltage reference value, calculate the DC bus reference voltage correction amount for each branch; S4: The droop coefficient correction and the DC bus reference voltage correction are introduced into the droop control algorithm to generate the voltage loop reference voltage, and then the voltage and current dual closed-loop controller generates a pulse width modulation signal to control each DC converter.

[0029] Specifically, see Figure 2 As shown, the parallel system includes at least two DC-DC converters (such as...). Figure 2 As shown, DC-DC converters 1 and 2 preferably have a three-level DC-DC converter as their main circuit. The control method includes: First, the equivalent line resistance of each DC-DC converter branch needs to be identified. Taking DC-DC converter 1 as an example, its line resistance r1 to the common DC bus is a parameter that needs to be identified.

[0030] Next, based on the identified equivalent line resistance of each branch, the droop coefficient correction for each branch is calculated. This correction is used to adjust the droop coefficient of each branch to offset the effects of differences in line resistance.

[0031] Then, obtain the DC bus output voltage value. And in conjunction with the given DC bus voltage reference value Calculate the DC bus reference voltage correction for each branch. This correction is used to compensate for the bus voltage drop caused by conventional droop control. The droop factor for DC-DC converter 1 is... This is the droop factor for DC-DC converter 2; r1 is the line resistance between DC converter 1 and the DC bus, and r2 is the line resistance between DC converter 2 and the DC bus. It is the equivalent load connected in parallel to the DC bus.

[0032] according to Figure 1 Based on Kirchhoff's laws, taking DC converter 1 as an example, the DC bus voltage can be derived as follows: ; Extending this to two DC-DC converters, we can conclude that: .

[0033] Finally, as shown in the above equation, neglecting line resistance, the output current of the DC-DC converter is inversely proportional to the droop factor. When the droop factor is set appropriately, proportional current output can be achieved. In practical applications, there is a certain transmission distance between the DC-DC converter and the DC bus, and line resistance is real. Therefore... The difference between r2 and r2 causes the DC-DC converter output current to not be distributed proportionally. When the droop factor is much larger than the line resistance, the current distribution accuracy is improved, but at the same time, it causes a large bus voltage drop; when the droop factor is small, the DC-DC converter output current cannot be distributed proportionally.

[0034] By improving the voltage deviation and droop coefficient, the improved voltage and current droop control expression can be obtained as (3): .

[0035] in and This is a correction amount for the bus voltage reference value. and This is the droop correction factor. The voltage loop reference voltage is fed into the voltage-current dual closed-loop controller, which ultimately generates a pulse width modulation (PWM) signal to control the switching on and off of the transistors in each DC-DC converter.

[0036] See Figure 1 , Figure 3 and Figure 4 The equivalent line resistance of each DC converter branch is identified online using a recursive least squares method with a forgetting factor.

[0037] Specifically, in the online identification of equivalent line resistance, the recursive least squares (RLS) algorithm with a forgetting factor is employed. First, a mathematical model of the line resistance needs to be established. For DC-DC converter 1, its line resistance... It can be represented as: ; Then perform discretization: .

[0038] in, It is the output voltage of DC-DC converter 1. It is the DC bus output voltage. This is the output current of DC-DC converter 1. After discretizing the model, recursive least squares method is used for online real-time identification. Forgetting factor. The value range is 0.95 to 0.99, and its function is to reduce the weight of old data so that the algorithm can better track system changes.

[0039] See Figure 1 and Figure 4 The equivalent line resistance identified by the recursive least squares method is subjected to first-order low-pass filtering.

[0040] Specifically, the line resistance value directly identified using the recursive least squares method may contain noise or glitches. To obtain a smooth line resistance value for subsequent control, the identified result is subjected to a first-order low-pass filter. The transfer function calculated by the first-order low-pass filter is: .

[0041] in, The cutoff frequency, This is a Laplace operator. The filtered resistance value is smoother, which helps improve system stability.

[0042] See Figure 1 Based on the equivalent line resistance of each branch, the droop coefficient correction amount of each branch is calculated, including the following steps: calculate the average value of the equivalent line resistance of the DC converter branch; subtract the average value from the equivalent line resistance of each branch itself, and output the difference as the droop coefficient correction amount of the corresponding branch after calculation by the proportional-integral controller.

[0043] Specifically, first, the equivalent line resistance values ​​of all parallel DC-DC converter branches are obtained through a low-bandwidth communication network, and their average value is calculated. Then, this average value is subtracted from the equivalent line resistance value of each branch. Finally, this difference is input into a proportional-integral (PI) controller for calculation; the output of the PI controller is the droop correction factor for that branch. The goal of the control is to make the equivalent total resistance of each branch (the sum of the line resistance and the resistance corresponding to the droop factor) tend to be consistent, thereby achieving precise automatic current distribution.

[0044] See Figure 1The DC bus output voltage value is obtained, and the DC bus reference voltage correction amount for each branch is calculated in combination with the DC bus voltage reference value. The steps include: subtracting the DC bus voltage reference value from the DC bus output voltage value, and then using the difference obtained by the proportional-integral controller to calculate the DC bus reference voltage correction amount for the corresponding branch.

[0045] Specifically, the DC bus voltage reference value Compared with the actual collected DC bus output voltage value The difference is calculated to obtain the voltage deviation. This voltage deviation is then input into a PI controller for calculation. The output of the PI controller is the DC bus reference voltage correction for that branch. The goal of the control is to compensate for the voltage dips at the bus, ultimately ensuring... Stable at The control objective after adding the correction is that: .

[0046] Ultimately, uniform distribution and error-free voltage control are achieved among the DC-DC converters: ; .

[0047] See Figure 2 and Figure 3 The droop control algorithm incorporates the droop coefficient correction and the DC bus reference voltage correction to generate a voltage loop reference voltage. This includes the following steps: The droop control algorithm combines the droop coefficient correction with the initial droop coefficient and combines the DC bus reference voltage correction with the DC bus voltage reference value to generate a voltage loop reference voltage.

[0048] .

[0049] in and This is a correction amount for the bus voltage reference value. and This is the droop correction factor. The voltage loop reference voltage is fed into the voltage-current dual closed-loop controller, which ultimately generates a pulse width modulation (PWM) signal to control the switching on and off of the transistors in each DC-DC converter.

[0050] The control structures of parallel DC-DC converters are all the same. The improved droop control is based on a voltage and current dual closed-loop control structure for output voltage droop. Its basic structure includes droop control improved from voltage deviation and droop coefficient, and DC bus voltage outer loop control and output filter inductor current inner loop control.

[0051] The equivalent line resistance is identified based on the output voltage, output current, and DC bus output voltage of this branch.

[0052] Specifically, the input variable relied upon in establishing the mathematical model of the line resistance for identification using the recursive least squares method is based on Ohm's law, which reflects the relationship between the voltage drop and current from the converter output to the DC bus. The specific expression is as follows: .

[0053] The parallel DC-DC converters exchange the equivalent line resistance information of each branch through a low-bandwidth communication network.

[0054] Specifically, to achieve coordinated control among the branches, a low-bandwidth communication network is set up between the parallel DC-DC converters. This network is mainly used to exchange the equivalent line resistance information independently identified by each branch. Each unit broadcasts its own identified resistance value and also receives the resistance values ​​of other units for collaborative operations such as calculating average values.

[0055] See Figure 1 and Figure 6 This invention provides an adaptive droop control system for a parallel DC-DC converter, used to execute the adaptive droop control method for a parallel DC-DC converter provided by the above-mentioned technical features. The system includes: a data acquisition module, a line resistance identification module, an adaptive compensation module, a central processing module, a voltage and current control module, and a pulse width modulation module. The data acquisition module is used to acquire electrical parameters of each DC-DC converter branch and the DC bus. The line resistance identification module is connected to the data acquisition module and is used to identify the equivalent line resistance of each branch online. The adaptive compensation module is connected to the data acquisition module and the line resistance identification module and is used to generate an adaptive control quantity for correcting the droop control law based on the electrical parameters and the equivalent line resistance. The central processing module is used to coordinate the operation of the data acquisition module, the line resistance identification module, and the adaptive compensation module. The voltage and current control module is connected to the adaptive compensation module and is used to generate a modulation wave based on the voltage loop reference voltage corrected by the adaptive control quantity. The pulse width modulation module is connected to the voltage and current control module and is used to generate switching signals to drive each DC-DC converter based on the modulation wave.

[0056] Specifically, the control system includes: a data acquisition module, a line resistance identification module, an adaptive compensation module, a low-bandwidth communication module, a central processing module, a voltage and current control module, and a pulse width modulation module. The data acquisition module acquires the electrical parameters of the parallel DC-DC converter. The online line resistance identification module is configured to perform a recursive least squares method with a forgetting factor and outputs a value reflecting the equivalent line resistance. The adaptive compensation module's input is connected to both the data acquisition module and the line resistance identification module, and it generates an adaptive control quantity based on the electrical parameters and the equivalent line resistance to correct the droop control law. The low-bandwidth communication module is responsible for reliably transmitting the key data required for coordination between different modules. The central processing module receives the electrical parameters from the data acquisition module and issues control commands to the remaining modules. The voltage and current control module generates modulation waves. The pulse width modulation module generates signals to drive the DC-DC converter to turn on and off.

[0057] See Figure 1 and Figure 6 The adaptive compensation module includes a droop coefficient correction unit and a reference voltage correction amount. The droop coefficient correction unit is used to calculate the droop coefficient correction amount based on the equivalent line resistance of each branch. The reference voltage correction unit is used to calculate the DC bus reference voltage correction amount based on the DC bus output voltage value and the reference value. The droop coefficient correction amount and the DC bus reference voltage correction amount together constitute the adaptive control quantity.

[0058] Specifically, the droop coefficient correction module is configured to use PI control to obtain the droop coefficient correction amount for each DC converter by the difference between the average line resistance of multiple DC converters and the line resistance of each DC converter; the DC bus voltage reference voltage correction module is configured to use PI control to obtain the DC bus voltage reference voltage correction amount for each DC converter by the difference between the bus voltage reference voltage of the DC converter and the output voltage value of the common DC bus of multiple DC converter branches.

[0059] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An adaptive droop control method for a parallel DC-DC converter, characterized in that, Includes the following steps: Online identification of the equivalent line resistance of each DC-DC converter branch; Based on the equivalent line resistance of each branch, calculate the droop coefficient correction for each branch. Obtain the DC bus output voltage value and, in conjunction with the DC bus voltage reference value, calculate the DC bus reference voltage correction for each branch. The droop coefficient correction and the DC bus reference voltage correction are introduced into the droop control algorithm to generate a voltage loop reference voltage. Then, a pulse width modulation signal is generated by a voltage and current dual closed-loop controller to control each DC converter.

2. The adaptive droop control method for parallel DC-DC converters according to claim 1, characterized in that, The online identification of the equivalent line resistance of each DC converter branch is performed using a recursive least squares method with a forgetting factor.

3. The adaptive droop control method for parallel DC-DC converters according to claim 2, characterized in that, The equivalent line resistance identified by the recursive least squares method is subjected to first-order low-pass filtering.

4. The adaptive droop control method for parallel DC-DC converters according to claim 3, characterized in that, The calculation of the droop coefficient correction for each branch based on the equivalent line resistance of each branch includes the following steps: Calculate the average value of the equivalent line resistance of the DC-DC converter branch; The difference between the average value and the equivalent line resistance of each branch is calculated, and the resulting difference is processed by a proportional-integral controller to output the droop coefficient correction amount for the corresponding branch.

5. The adaptive droop control method for parallel DC-DC converters according to claim 1, characterized in that, The process of obtaining the DC bus output voltage value and calculating the DC bus reference voltage correction for each branch, in conjunction with the DC bus voltage reference value, includes the following steps: The difference between the DC bus voltage reference value and the DC bus output voltage value is calculated and then processed by a proportional-integral controller to output the DC bus reference voltage correction amount for the corresponding branch.

6. The adaptive droop control method for parallel DC-DC converters according to claim 5, characterized in that, The step of incorporating the droop coefficient correction and the DC bus reference voltage correction into the droop control algorithm to generate a voltage loop reference voltage includes the following steps: The droop control algorithm generates a voltage loop reference voltage by combining the droop coefficient correction amount with the initial droop coefficient and the DC bus reference voltage correction amount with the DC bus voltage reference value.

7. The adaptive droop control method for parallel DC-DC converters according to claim 2, characterized in that, The equivalent line resistance is identified based on the output voltage and current of this branch and the output voltage of the DC bus.

8. The adaptive droop control method for parallel DC-DC converters according to claim 1, characterized in that, The parallel DC-DC converters exchange the equivalent line resistance information of each branch through a low-bandwidth communication network.

9. An adaptive droop control system for a parallel DC-DC converter, characterized in that, The system is used to execute the adaptive droop control method for a parallel DC-DC converter according to any one of claims 1 to 8, the system comprising: The data acquisition module is used to collect electrical parameters of each DC converter branch and DC bus; A line resistance identification module, which is connected to the data acquisition module, is used to identify the equivalent line resistance of each branch online. An adaptive compensation module, which connects the data acquisition module and the line resistance identification module, is used to generate an adaptive control quantity for correcting the droop control law based on the electrical parameters and the equivalent line resistance. A central processing module, which coordinates the operation of the data acquisition module, the line resistance identification module and the adaptive compensation module; A voltage and current control module, which is connected to the adaptive compensation module, is used to generate a modulation wave based on the voltage loop reference voltage corrected by the adaptive control quantity. A pulse width modulation module, which is connected to the voltage and current control module, is used to generate switching signals to drive each DC-DC converter based on the modulation wave.

10. The adaptive droop control system for a parallel DC-DC converter according to claim 9, characterized in that, The adaptive compensation module includes: A droop coefficient correction unit is used to calculate the droop coefficient correction amount based on the equivalent line resistance of each branch. A reference voltage correction unit is used to calculate the DC bus reference voltage correction amount based on the DC bus output voltage value and the reference value. The droop coefficient correction amount and the DC bus reference voltage correction amount together constitute the adaptive control amount.

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