A power converter dynamic droop control method and system

Abstract

The application provides a power converter dynamic droop control method and system, belongs to the technical field of new energy ship charging control, is applied to a ship shore charging system, comprises a plurality of parallelly connected first AC / DC modules, and a centralized common voltage outer loop regulator is adopted for the voltage outer loop of all the first AC / DC modules, and the method comprises the following steps: the common voltage outer loop regulator reads the deviation value of the DC bus voltage value from the given reference value in real time, generates a unique active power instruction, and sends the active power instruction to the droop controller of each first AC / DC module; when the active power instruction is received, the droop coefficient of each first AC / DC module is dynamically adjusted according to the deviation value. Advantageous effects: by dynamically adjusting the droop coefficient, the dynamic load change of the ship power grid and the module difference are adapted, accurate, adaptive and optimized power distribution among the parallel modules is realized, and the dynamic response capability, voltage stability, overall efficiency and operation reliability of the system are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy ship charging control, and particularly relates to a power converter dynamic droop control method and system. BACKGROUND

[0002] In recent years, under the background of global vigorous advocacy of energy saving and emission reduction and increasing emphasis on environmental protection, new energy ships have been more and more widely used in the field of shipping due to their low pollution and high efficiency. New energy ships mainly rely on electric drive, and efficient and stable charging technology is a key requirement to ensure their normal operation and development.

[0003] At present, the ship charging system generally adopts the parallel mode of multiple AC / DC modules to meet the power demand of ship charging. However, most of the existing ship charging systems adopt a fixed droop coefficient control strategy. When the ship load changes suddenly, this static power distribution mode causes the system to be unable to respond to the real-time load coefficient change on the ship, and it is difficult to dynamically adjust the power distribution between each AC / DC module according to the actual situation, which easily causes circulating current phenomenon, leads to voltage fluctuation, affects the normal operation of ship electrical equipment, and even may cause damage to the equipment, shortening its service life. In addition, the existing communication scheme has high delay, which causes the instructions between the parallel modules to be out of step and the current sharing accuracy to be insufficient. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a power converter dynamic droop control method, and on the other hand, a power converter dynamic droop control system is also provided.

[0005] The technical problem solved by the present application can be realized by the following technical scheme: a power converter dynamic droop control method applied to a shore charging system for ships, the shore charging system comprising a plurality of first AC / DC modules, the plurality of first AC / DC modules being connected in parallel, and a centralized common voltage outer loop regulator being adopted for the voltage outer loop of all the first AC / DC modules, the method comprising: step S1, the common voltage outer loop regulator reading the deviation value of the DC bus voltage value and the given reference value in real time, generating a unique active power instruction, and issuing the active power instruction to the droop controller of each first AC / DC module; step S2, upon receiving the active power instruction, dynamically adjusting the droop coefficient of each first AC / DC module according to the deviation value.

[0006] Preferably, before step S1, the method further includes: step S01, acquiring the grid voltage signal in real time; step S02, inputting the phase information of the grid voltage signal into the common phase-locked loop of the plurality of first AC / DC modules as a phase reference; step S03, encoding the phase reference, and broadcasting the encoded phase reference to each of the first AC / DC modules through the controller local area network bus, so that all the first AC / DC modules are synchronized with the grid phase.

[0007] Preferably, before step S01, the method further includes: detecting whether the common voltage outer loop regulator is normal; if the common voltage outer loop regulator is detected to be normal, proceeding to step S01; if the common voltage outer loop regulator is detected to be abnormal, issuing a warning message and determining whether the voltage outer loop of the first AC / DC module is normal; if the voltage outer loop of the first AC / DC module is normal, then the voltage outer loop of the first AC / DC module is used as the common voltage outer loop, and the active power command is issued, followed by proceeding to step S1; if the voltage outer loop of the first AC / DC module is abnormal, then issuing a fault alarm message and shutting down the system.

[0008] Preferably, step S2 includes: step S21, calculating the active power and reactive power of each of the first AC / DC modules based on the rated AC current value, power factor, and real-time collected grid voltage of each of the first AC / DC modules; step S22, measuring the AC frequency and AC voltage of each of the first AC / DC modules, and calculating the droop coefficient of each of the first AC / DC modules by combining the active power, the reactive power, and the deviation value.

[0009] Preferably, the droop controller includes an active-frequency droop controller and a reactive-voltage droop controller, wherein the active-frequency droop controller is used to calculate the active-frequency droop coefficient, and the reactive-voltage droop controller is used to calculate the reactive-voltage droop coefficient.

[0010] The calculation method for the active power-frequency droop coefficient is as follows:

[0011]

[0012] in, This indicates the active power of the first AC / DC module; This indicates the rated active power of the first AC / DC module; Indicates the DC voltage error value; This represents the active power-frequency droop factor; The bus AC frequency; This is a reference value for the AC frequency.

[0013] The method for calculating the reactive power-voltage droop coefficient is as follows:

[0014]

[0015] in, This indicates the reactive power of the first AC / DC module; This indicates the reactive power reference value of the first AC / DC module; This represents the reactive power-voltage droop coefficient; Indicates the AC voltage of the busbar. This indicates the rated AC voltage.

[0016] Preferably, after step S22, the method further includes step S23, which dynamically adjusts the droop coefficient of each of the first AC / DC modules based on the total power required by the changed load and the rated power of each of the first AC / DC modules.

[0017] Preferably, the system further includes a shipboard charging system that interfaces with the shore charging system. The shipboard charging system includes at least one second AC / DC module, which is connected in parallel with the first AC / DC module. The system also includes: monitoring the operating status of the shore charging system before connecting to the shipboard charging system and setting the reference frequency of the shipboard charging system to be consistent with the AC frequency reference value of the shore charging system; calculating the load rate based on the rated power value of the newly connected shipboard charging system; adjusting the active power of the shipboard charging system based on the load rate; and obtaining the bus AC frequency of the shipboard charging system after the system stabilizes; and deriving the droop coefficient of the newly connected shipboard charging system based on the principle of frequency consistency during parallel steady-state operation, and including the second AC / DC module of the shipboard charging system in the online module list.

[0018] Preferably, the method further includes: monitoring whether an AC / DC module is offline; when an AC / DC module is detected to be offline, sending a first adjustment instruction to the online AC / DC modules, the first adjustment instruction being used to instruct the reduction of the droop coefficient of all online AC / DC modules, so that all online AC / DC modules redistribute the power gap generated by the offline AC / DC module.

[0019] Preferably, the method further includes: monitoring whether an AC / DC module is online; when an AC / DC module is detected to be online, performing pre-synchronization, phase locking, and pre-charging operations, and uploading the rated AC current value of the online AC / DC module; when the rated AC current value of the online AC / DC module is received, adding the online AC / DC module to the online module list, and simultaneously setting the initial value of the droop coefficient of the online AC / DC module to a preset value, so that the initial output current of the online AC / DC module is close to 0, and then gradually reducing the droop coefficient of the online AC / DC module, while simultaneously increasing the droop coefficient of the other online AC / DC modules.

[0020] On the other hand, a dynamic droop control system for a power converter is provided for implementing the dynamic droop control method for a power converter as described above. The system is applied to a shore-based charging system for ships. The shore-based charging system includes multiple first AC / DC modules connected in parallel. The voltage outer loop of all the first AC / DC modules employs a centralized common voltage outer loop regulator, comprising: a common voltage outer loop regulator for real-time reading of the deviation between the DC bus voltage value and a given reference value, generating a unique active power command, and sending the active power command to the droop controller of each first AC / DC module; and a droop controller for dynamically adjusting the droop coefficient of each first AC / DC module based on the deviation value upon receiving the active power command.

[0021] The advantages or beneficial effects of the technical solution of the present invention are as follows: By dynamically adjusting the droop coefficient, the present invention can adapt to the dynamic load changes and module differences of the ship's power grid, realize accurate, adaptive and optimized power distribution among parallel modules, and significantly improve the dynamic response capability, voltage stability, overall efficiency and operational reliability of the system. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the dynamic droop control method for a power converter, as shown in a preferred embodiment of the present invention.

[0023] Figure 2 A topology diagram of a new energy ship charging system in a preferred embodiment of the present invention;

[0024] Figure 3 This is a structural block diagram of the droop control in a preferred embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the pre-synchronization and phase locking process in a preferred embodiment of the present invention;

[0026] Figure 5 This is a flowchart illustrating the dynamic adjustment of the droop coefficient in a preferred embodiment of the present invention.

[0027] Figure 6 This is a schematic diagram of the process for calculating the droop coefficient in a preferred embodiment of the present invention;

[0028] Figure 7 This is a flowchart illustrating the dynamic adjustment of the droop coefficient after a sudden load change, as described in a preferred embodiment of the present invention.

[0029] Figure 8 This is a schematic diagram of the process for controlling multiple busbars in parallel with a gate, as shown in a preferred embodiment of the present invention.

[0030] Figure 9 In a preferred embodiment of the present invention, a waveform diagram showing a sudden load increase of 50KW is provided.

[0031] Figure 10 In a preferred embodiment of the present invention, a waveform diagram of a 50KW load being suddenly unloaded is shown. Detailed Implementation

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

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0035] See Figures 1-9 In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a dynamic droop control method for power converters is provided, which is applied to the charging system of new energy ships. The aim is to achieve power balance distribution by combining dynamic droop control with a high-speed communication network.

[0036] The new energy ship charging system consists of multiple parallel-connected AC / DC modules 200, a high-speed communication network, and a central controller. Each AC / DC module 200 employs droop control as its basic strategy. However, unlike traditional fixed droop coefficients, this invention uses the high-speed communication network to collect real-time data on the status of each AC / DC module 200 and the system status. The status of each module includes, but is not limited to, output power, efficiency, and module temperature. The system status includes, but is not limited to, DC bus voltage, total load demand, and operating mode. The central controller calculates and adjusts the droop coefficient of each AC / DC module 200 in real time based on the dynamic droop control proposed in this invention. This dynamic droop control mechanism enables the system to adapt to dynamic load changes and module differences in the ship's power grid, achieving precise, adaptive, and optimized power distribution among parallel modules, significantly improving the system's dynamic response capability, voltage stability, overall efficiency, and operational reliability.

[0037] The new energy ship charging system includes a shore-based charging system and may also include a shipboard charging system. The shore-based charging system includes multiple first AC / DC modules connected in parallel. The shipboard charging system includes multiple second AC / DC modules connected in parallel. The shore-based charging system and the shipboard charging system are connected in parallel, meaning that multiple first AC / DC modules and multiple second AC / DC modules are connected in parallel.

[0038] AC / DC module 200 includes a first AC / DC module for a shore-based charging system, and may also include a second AC / DC module for a shipboard charging system.

[0039] During the droop control process, the numbering of each AC / DC module 200 can be automatically identified and set. For example... Figure 2 As shown, each AC / DC module 200 is assigned a unique number. Multiple AC / DC modules 200 are connected in sequence between the power grid 100 and the battery load 300. Multiple AC / DC modules 200 and multiple battery loads 300 are controllably connected to the DC bus through circuit breakers (QS1, QS2, ..., QS9).

[0040] like Figure 3 As shown, a centralized unified voltage outer loop is used to isolate the voltage outer loops of all parallel AC / DC modules, and a single centralized common voltage regulator 500 is adopted for all of them. This common voltage regulator 500 is used to read the current DC bus voltage value in real time. Compared with a given reference value The deviation is used to generate a unique active power command. The data is encoded into data frames and distributed to the droop controllers of each AC / DC module via the Controller Area Network (CAN) bus. This avoids bus voltage fluctuations and circulating current problems caused by differences in the dynamic response of independent outer loop regulators. At the same time, the CAN protocol can effectively arbitrate the communication between modules, avoiding communication chaos caused by long-term bus occupancy as the number of modules increases.

[0041] like Figure 5 As shown, the dynamic droop control method for the power converter includes: S001, detecting whether the common voltage outer loop regulator is normal; if the common voltage outer loop regulator is detected to be normal, proceed to step S01; if the common voltage outer loop regulator is detected to be abnormal, proceed to step S002; S002, issuing a warning message and determining whether the voltage outer loop of the first AC / DC module is normal; if the voltage outer loop of the first AC / DC module is normal, then the voltage outer loop of the first AC / DC module is used as the common voltage outer loop, and the active power command is issued, followed by proceeding to step S1; if the voltage outer loop of the first AC / DC module is abnormal, then a fault alarm message is issued, and the system is shut down.

[0042] Specifically, this embodiment of the invention supports redundant control of the outer voltage loop. If the common outer voltage loop regulator malfunctions, such as a fault, the outer voltage loop of the first AC / DC module is used as the common outer voltage loop to communicate with other AC / DC modules.

[0043] The first j The transmitter of the main control board of the AC / DC module is connected to the adjacent AC / DC module via optical fiber. j The main control board of +1 AC / DC module is connected to the receiving end to realize the transmission of active power signals and enhance equipment reliability. Among them, j It is a positive integer, 1≤ j ≤ n -1, n This indicates the total number of AC / DC modules.

[0044] like Figure 4 As shown, it also includes: step S01, acquiring the grid voltage signal in real time; step S02, inputting the phase information of the grid voltage signal into the common phase-locked loop 600 (PLL) of multiple first AC / DC modules as a phase reference; step S03, encoding the phase reference, and broadcasting the encoded phase reference to each first AC / DC module through the controller local area network (CAN) bus, so that all first AC / DC modules are synchronized with the grid phase.

[0045] Specifically, in this embodiment, the central controller collects the phase and amplitude information of the grid voltage signal on the AC bus 401 in real time and inputs it into a common phase-locked loop (PLL) as a phase reference. This phase reference is then encoded into data frames and broadcast to each AC / DC module via the CAN bus. Using the CAN protocol effectively ensures that the data frames sent by the PLL are simultaneously shared by all AC / DC modules, avoiding phase differences caused by different timings of data reception by each AC / DC module due to communication protocol characteristics. This effectively ensures that all parallel AC / DC modules are strictly synchronized with the grid phase.

[0046] like Figure 1 As shown, in step S1, the common voltage outer loop regulator reads the deviation between the DC bus voltage value and the given reference value in real time, generates a unique active power command, and sends the active power command to the droop controller of each first AC / DC module; in step S2, when the active power command is received, the droop coefficient of each first AC / DC module is dynamically adjusted according to the deviation value.

[0047] In a preferred embodiment, such as Figure 6 As shown, step S2 includes: Step S21, calculating the active power and reactive power of each first AC / DC module based on the rated AC current value, power factor, and real-time collected grid voltage of each first AC / DC module; specifically, the host computer receives the rated AC current value of the AC / DC module input by the user through the human-machine interface. By combining the power factor and the real-time collected grid voltage, and according to the power calculation formula, the active power output of each AC / DC module is calculated. P and reactive power Q .

[0048] In step S21, the active power is calculated as follows:

[0049]

[0050] in, This indicates the active power of the AC / DC module; Indicates the grid line voltage; This indicates the rated AC current value of the AC / DC module; This represents the phase difference between phase voltage and phase current;

[0051] The method for calculating reactive power is as follows:

[0052]

[0053] in, This indicates the reactive power of the AC / DC module.

[0054] Power factor is an important indicator of the efficiency of electrical equipment in utilizing electrical energy. It represents the ratio of active power (P) to apparent power (S). In AC circuits, it is the phase difference between phase voltage and phase current. The cosine of the power factor is called the power factor, denoted by the symbol . It means, that is =P / S.

[0055] When the power factor is 1, it is recorded as the rated power of the AC / DC module. The host computer then sets the rated power... The rated power parameters of each AC / DC module are stored as the basis for subsequent power allocation.

[0056] While performing constant voltage control, the current DC bus voltage value is collected in real time. Based on the total power required by the load and the rated power of each AC / DC module, the power of each AC / DC module is adjusted by adaptively adjusting the droop coefficient of each module.

[0057] Step S22: Measure the AC frequency and AC voltage of each first AC / DC module, and calculate the droop coefficient of each first AC / DC module by combining the active power, reactive power and deviation value.

[0058] Specifically, each AC / DC module measures the AC frequency. and AC voltage Based on the droop control formula, the droop coefficient of each module is dynamically adjusted using high-speed communication, thereby achieving precise power distribution among the modules.

[0059] The droop controller 700 includes an active-frequency (P-) controller. f The active-frequency droop controller is used to calculate the active-frequency droop coefficient, and the reactive-voltage droop controller is used to calculate the reactive-voltage droop coefficient.

[0060] The droop control formula is:

[0061]

[0062]

[0063] In the formula, This indicates the active power of the AC / DC module; This indicates the rated active power of the AC / DC module; This represents the active power-frequency droop factor; The bus AC frequency; This is a reference value for the AC frequency. This indicates the reactive power of the AC / DC module; This represents the reactive power reference value of the AC / DC module, which is typically set to 0. This represents the reactive power-voltage droop coefficient; Indicates the AC voltage of the busbar. This indicates the rated AC voltage.

[0064] Existing technologies employ a fixed droop coefficient control strategy. A large droop coefficient results in fast power distribution but poor steady-state accuracy; a small droop coefficient leads to slow dynamic response and significant voltage fluctuations during load changes. Therefore, selecting a suitable droop coefficient is a key challenge in droop control. This invention proposes a new dynamic droop coefficient based on the change in DC bus voltage deviation, introduced outside the active power loop. This coefficient dynamically increases when the DC bus voltage deviation is large, rapidly stabilizing the DC bus; conversely, it stabilizes when the DC bus voltage deviation is small. The entire control strategy dynamically adjusts the droop coefficient, improving system stability while rapidly achieving power distribution.

[0065] While employing a dynamic droop formula, a centralized common voltage outer loop is used outside the power loop to drive the power loop, further maintaining the stability of the DC bus voltage. The overall framework is as follows: Figure 3 As shown, when the load on DC bus 402 increases, the DC side voltage decreases, and the host computer monitors the actual DC bus voltage value in real time. Compared with a given reference value deviation value and the deviation value The signal is encoded into a communication protocol frame and sent to the droop controller 700 via the CAN bus. The droop coefficient is then adjusted using the dynamic droop coefficient formula.

[0066]

[0067] In the formula, This is the initial value of the droop coefficient.

[0068] This invention is based on the deviation value of the DC bus voltage. Adjust the active power-frequency droop coefficient and reactive power-voltage droop factor Obtain the adjusted active-frequency droop coefficient. and reactive power-voltage droop factor Implement droop control. The adjusted droop control formula is as follows:

[0069]

[0070]

[0071] in, This indicates the active power of the AC / DC module; This indicates the rated active power of the AC / DC module; Indicates the DC voltage error value; This represents the active power-frequency droop factor; The bus AC frequency; This is a reference value for the AC frequency. This indicates the reactive power of the AC / DC module; This indicates the reactive power reference value of the AC / DC module; This represents the reactive power-voltage droop coefficient; Indicates the AC voltage of the busbar. This indicates the rated AC voltage.

[0072] The selection of the droop factor has a significant impact on system performance. A larger droop factor allows for better power and current sharing. A smaller droop factor results in poor current sharing performance in parallel connections. However, a large droop factor can cause significant overshoot during dynamic adjustment, potentially leading to system instability. In deviation value As it approaches infinity, it tends to The droop coefficient should be appropriately increased to accelerate the flow uniformity. Within the deviation value... When it is 0, When the droop factor is 0, it returns to its original value. , By combining the DC bus voltage deviation, the droop coefficient is dynamically adjusted to better distribute power when the deviation is large.

[0073] like Figure 9 and Figure 10 As shown, with the dynamically adjusted droop coefficient, the module can achieve rapid current sharing and average distribution of active power. Furthermore, when the load suddenly increases or decreases by 50kW, the output DC bus voltage does not cause large overshoot or system instability.

[0074] In a preferred embodiment, such as Figure 7 As shown, after step S22, the method further includes step S23, which dynamically adjusts the droop coefficient of each first AC / DC module based on the total power required by the changed load and the rated power of each first AC / DC module.

[0075] The following three operating conditions describe the charging of new energy ships based on dynamic droop control according to the present invention:

[0076] Operating Condition 1: AC / DC modules with the same rated power connected in parallel. When multiple AC / DC modules connected in parallel in the system have the same rated power, taking two AC / DC modules connected in parallel as an example, the basic process of dynamic droop control is as follows:

[0077] First, the host computer calculates the active / reactive power of each module. , , , The subscripts 1 and 2 indicate the AC / DC module number. For modules with the same rated power, there are... In steady state, ,in, This indicates the active power of the load. This indicates the reactive power of the load.

[0078] When the active power of the load is Sudden increase to At that moment, the DC bus voltage drops instantaneously, and the deviation value... Increasing the dynamic droop coefficient accelerates the flow equalization velocity until the system reaches a new steady state. This achieves power distribution.

[0079] Operating Condition 2: Parallel Operation of AC / DC Modules with Different Rated Powers. The core objective of parallel operation of two AC / DC modules with different rated power is to ensure that each AC / DC module has the same load rate, avoiding overload of the module with lower rated power, while fully utilizing the capacity of the module with higher power. The basic process of dynamic droop control is analyzed using two AC / DC modules with different rated power in parallel:

[0080] First, the host computer calculates the active and reactive power of each AC / DC module. , , , and load rate For modules with the same rated power, their initial droop coefficient must meet the following requirements. .

[0081] The system has the following characteristics at the initial steady state: ,in This represents the active power of AC / DC module number 1 at the initial steady state. This represents the active power of AC / DC module number 2 at the initial steady state.

[0082] When the load suddenly increases, the system recalculates the total load power and load factor to redetermine the power allocation target. After the load surge, the DC bus voltage drops instantaneously, and the deviation of the bus voltage... As the current increases, the dynamic droop coefficient also increases, accelerating the current sharing speed until the system reaches a new steady state, and the power distribution meets the load rate requirements of each AC / DC module.

[0083] Operating Scenario 3: The onshore AC / DC module is compatible with different models of AC / DC modules on board. When the onshore charging system needs to be connected in parallel with different models of AC / DC modules on board, this embodiment of the invention proposes an online identification strategy for the droop coefficient based on the parallel system. As a preferred embodiment, it also includes a shipboard charging system that interfaces with the onshore charging system. The shipboard charging system includes at least one second AC / DC module, which is connected in parallel with the first AC / DC module. The method further includes: monitoring the operating status of the onshore charging system before connecting to the shipboard charging system and setting the reference frequency of the shipboard charging system to be consistent with the AC frequency reference value of the onshore charging system; calculating the load rate based on the rated power value of the newly connected shipboard charging system; adjusting the active power of the shipboard charging system according to the load rate; and obtaining the bus AC frequency of the shipboard charging system after the system stabilizes; and deriving the droop coefficient of the newly connected shipboard charging system based on the principle of frequency consistency during parallel steady-state operation, and including the second AC / DC module of the shipboard charging system in the online module list.

[0084] Specifically, taking the parallel connection of a shore charging system with two AC / DC modules of different rated power and different models of modules on board as an example, the process of online identification and dynamic droop control of its droop coefficient is analyzed as follows: Before the new module is connected on board, the steady-state operation of the shore parallel system is monitored first to obtain the current output power of the first AC / DC module on shore. Rated power and existing system bus frequency Set the reference frequency of the second AC / DC module on board to Ensure that the new access module is consistent with the initial frequency of the onshore system.

[0085] After the new module is connected, the rated power value is first determined based on the nameplate of the second AC / DC module on the ship. Recalculate the load rate of each AC / DC module. :

[0086]

[0087] In the formula, the subscripts 1, 2 and 3 represent the numbers of the AC / DC modules, respectively.

[0088] Next, a soft-start process is performed through the power control loop of the ship's second AC / DC module, gradually increasing the output power of the ship's second AC / DC module to [a certain value]. Then, the second AC / DC module on the ship is switched to normal operation, realizing the parallel operation of multiple AC / DC modules.

[0089] After the entire system stabilizes, the system bus frequency is obtained. Based on the principle of frequency consistency in parallel steady-state operating systems:

[0090]

[0091]

[0092] The active power-frequency droop factor of the newly connected AC / DC module can then be derived. :

[0093]

[0094] When a newly connected AC / DC module is under heavy load (K>0.9) or light load (K<0.1), its droop characteristic will deviate from linearity. Repeatedly adjust the load to ensure that the load rate is between 0.5 and 0.8. The average of the calculated values ​​is the active power-frequency droop coefficient.

[0095] Similarly, based on the principle of consistent voltage amplitude in parallel steady-state operating systems, the reactive power-voltage droop coefficient of newly connected AC / DC modules can be calculated. :

[0096]

[0097] After identifying the droop coefficient of the newly connected AC / DC module, the system adds it to the online module list, enabling the system to be compatible with the second AC / DC module on board.

[0098] In a preferred embodiment, the method further includes: monitoring whether an AC / DC module is offline; when an AC / DC module is detected to be offline, sending a first adjustment instruction to the online AC / DC modules, the first adjustment instruction being used to instruct the reduction of the droop coefficient of all online AC / DC modules, so that all online AC / DC modules redistribute the power gap generated by the offline AC / DC module.

[0099] Specifically, by detecting the "heartbeat" or periodic status information loss of a certain AC / DC module in real time via the host computer, the AC / DC module is quickly determined to be offline. The central controller immediately sends instructions to other online AC / DC modules to instantly reduce the active power-frequency droop factor. This allows the remaining online AC / DC modules to quickly share the power gap caused by the disconnected branch. After the power redistribution is completed, the system enters a new stable state.

[0100] In a preferred embodiment, the method further includes: monitoring whether an AC / DC module is online; when an AC / DC module is detected to be online, performing pre-synchronization, phase locking, and pre-charging operations, and uploading the rated AC current value of the online AC / DC module; when the rated AC current value of the online AC / DC module is received, adding the online AC / DC module to the online module list, and simultaneously setting the initial value of the droop coefficient of the online AC / DC module to a preset value, so that the initial output current of the online AC / DC module is close to 0, and then gradually reducing the droop coefficient of the online AC / DC module, while simultaneously increasing the droop coefficient of the other online AC / DC modules.

[0101] Specifically, after the newly connected AC / DC module is physically connected and pre-synchronized, phase-locked, and pre-charged, the rated AC current value of the AC / DC module is uploaded via high-speed communication. After the central controller receives the data and confirms that it is correct, it adds the module to the online module list.

[0102] Set the initial value of the droop coefficient of the newly connected AC / DC module to a large value so that its initial output current is close to 0; the host computer gradually decreases the droop coefficient of the newly connected AC / DC module and simultaneously increases the droop coefficient of the other online AC / DC modules, gradually transferring power to the newly connected AC / DC module.

[0103] The data format transmitted from the main station via optical fiber is as follows:

[0104]

[0105] The data format transmitted by the fiber optic cable from the slave station is as follows:

[0106]

[0107] like Figure 8 The diagram shown illustrates the process of controlling the parallel operation of multiple buses. The closing signal must simultaneously meet the following three conditions: First, voltage amplitude matching, meaning the voltage difference between the DC buses to be connected in parallel is less than a preset threshold. ,Right now ,in, Indicates the current DC bus of the system. First, the DC buses to be connected in parallel must meet certain conditions. Second, the voltage change slopes of the DC buses to be connected in parallel should be consistent in direction and similar in magnitude to prevent a situation where one bus voltage is rapidly rising while the other is rapidly falling at the moment of closing, thus preventing the generation of huge instantaneous currents. Third, after meeting the first two conditions, the voltage should remain stable for a period of time. The human-machine interface issues a closing command. After receiving the closing command, the host computer collects the status information of each parallel AC / DC module and circuit breaker. Then, it monitors the bus voltage amplitude of the AC / DC modules in real time and compares the bus voltage change slopes of each AC / DC module. After determining that all synchronization conditions are met and the voltage remains stable for a period of time, it issues a closing command to the relevant circuit breaker.

[0108] When the human-machine interface issues a closing command, the host computer receives the command and collects the status information of each parallel AC / DC module and circuit breaker. Subsequently, the host computer monitors the bus voltage amplitude of the AC / DC modules in real time and compares the slope of the bus voltage change of each AC / DC module. Only after determining that all synchronization conditions are met and remain stable for a period of time, does the host computer issue a closing command to the relevant circuit breaker. The specific process of multi-bus parallel closing control is as follows: S301, the host computer receives the closing command; S302, the host computer collects the status information of each AC / DC module and circuit breaker; S303, real-time detection of the DC bus voltage amplitude and its slope of the AC / DC modules to be closed; S304, determination of whether the DC bus voltage amplitude exceeds the threshold and whether the voltage slope is consistent: if the DC bus voltage amplitude does not exceed the threshold and the voltage slope is consistent, closing operation is initiated; if the DC bus voltage amplitude exceeds the threshold or the voltage slope is inconsistent, a warning is issued and the closing action is stopped.

[0109] On the other hand, a dynamic droop control system for a power converter is provided to implement the dynamic droop control method for a power converter as described above. The system is applied to a shore charging system for ships. The shore charging system includes multiple first AC / DC modules connected in parallel, and the voltage outer loop of all first AC / DC modules adopts a centralized common voltage outer loop regulator, including: a common voltage outer loop regulator 500, used to read the deviation value between the DC bus voltage value and a given reference value in real time, generate a unique active power command, and send the active power command to the droop controller of each first AC / DC module; and a droop controller 700, used to dynamically adjust the droop coefficient of each first AC / DC module according to the deviation value when receiving the active power command.

[0110] Specifically, addressing the limitation of existing technologies in coordinating dynamic control, high-speed communication, and intelligent power management to improve the stability and efficiency of ship charging systems, this invention introduces an intelligent control mechanism that dynamically adjusts the droop coefficient in real-time via high-speed communication. This overcomes the inherent shortcomings of traditional fixed droop control in parallel applications, such as low power distribution accuracy, slow response, poor stability, and low efficiency. Simultaneously, it fully considers the reliability and redundancy of parallel systems with multiple AC / DC modules: the system can connect AC / DC modules with different rated power and efficiency characteristics, automatically adapting to these differences to achieve optimal or acceptable collaborative operation. When a module fails or needs maintenance and shutdown, the droop coefficient of the remaining modules can be dynamically adjusted via real-time high-speed communication, quickly and smoothly transferring the load to healthy modules, ensuring uninterrupted charging or minimal impact on the charging process.

[0111] Compared with existing technologies, the advantages of this invention are as follows: Based on a dynamic droop strategy using high-speed communication, the droop coefficient of each AC / DC module can be dynamically adjusted online in real time to match load changes, effectively suppressing DC bus voltage fluctuations. Furthermore, a new method for controlling the droop coefficient using DC bus voltage deviation is employed in droop control to better distribute power and current. High-speed communication enables power command synchronization between modules, avoiding imbalance in power distribution; real-time monitoring of load demand and system status allows for optimal decision-making based on current conditions, effectively improving system stability and reliability.

[0112] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present invention.

Claims

1. A dynamic droop control method for a power converter, characterized in that, An application is made to a shore-based charging system for ships, the shore-based charging system comprising multiple first AC / DC modules connected in parallel, wherein the outer voltage loop of all the first AC / DC modules adopts a centralized common outer voltage loop regulator, the method comprising: Step S1: The common voltage outer loop regulator reads the deviation between the DC bus voltage value and the given reference value in real time, generates a unique active power command, and sends the active power command to the droop controller of each first AC / DC module. Step S2: Upon receiving the active power command, dynamically adjust the droop coefficient of each of the first AC / DC modules according to the deviation value; It also includes a shipboard charging system that interfaces with an onshore charging system, the shipboard charging system comprising at least one second AC / DC module, the at least one second AC / DC module being connected in parallel with the first AC / DC module; and further includes: Before connecting to the shipboard charging system, monitor the operating status of the shore charging system and set the reference frequency of the shipboard charging system to be consistent with the AC frequency reference value of the shore charging system. Calculate the load rate based on the rated power value of the newly connected shipboard charging system; Based on the load rate, adjust the active power of the shipboard charging system, and after the system stabilizes, obtain the bus AC frequency of the shipboard charging system. Based on the principle of consistent frequency during parallel steady-state operation of the system, the droop coefficient of the newly connected shipboard charging system is deduced, and the second AC / DC module of the shipboard charging system is included in the online module list.

2. The dynamic droop control method for power converters according to claim 1, characterized in that, The procedure preceding step S1 also includes: Step S01: Real-time acquisition of grid voltage signal; Step S02: Input the phase information of the grid voltage signal into the common phase-locked loop of the plurality of first AC / DC modules as a phase reference; Step S03: Encode the phase reference and broadcast the encoded phase reference to each of the first AC / DC modules through the controller local area network bus so that all the first AC / DC modules are synchronized with the power grid phase.

3. The dynamic droop control method for power converters according to claim 2, characterized in that, The procedure preceding step S01 also includes: Check whether the common voltage outer loop regulator is functioning properly; When the common voltage outer loop regulator is detected to be normal, proceed to step S01; When an abnormality is detected in the common voltage outer loop regulator, a warning message is issued, and it is determined whether the voltage outer loop of the first AC / DC module is normal. If the voltage outer loop of the first AC / DC module is normal, then the voltage outer loop of the first AC / DC module is used as the common voltage outer loop, and the active power command is issued, and then the process proceeds to step S1. If the outer voltage loop of the first AC / DC module is abnormal, a fault alarm message will be issued and the system will shut down.

4. The dynamic droop control method for power converters according to claim 1, characterized in that, Step S2 includes: Step S21: Calculate the active power and reactive power of each of the first AC / DC modules based on the rated AC current value, power factor, and real-time collected grid voltage of each of the first AC / DC modules. Step S22: Measure the AC frequency and AC voltage of each of the first AC / DC modules, and calculate the droop coefficient of each of the first AC / DC modules by combining the active power, the reactive power and the deviation value.

5. The dynamic droop control method for power converters according to claim 1, characterized in that, The droop controller includes an active-frequency droop controller and a reactive-voltage droop controller. The active-frequency droop controller is used to calculate the active-frequency droop coefficient, and the reactive-voltage droop controller is used to calculate the reactive-voltage droop coefficient. The calculation method for the active power-frequency droop coefficient is as follows: ； in, This indicates the active power of the first AC / DC module; This indicates the rated active power of the first AC / DC module; Indicates the DC voltage error value; This represents the active power-frequency droop factor; The bus AC frequency; This is a reference value for the AC frequency. The method for calculating the reactive power-voltage droop coefficient is as follows: ； in, This indicates the reactive power of the first AC / DC module; This indicates the reactive power reference value of the first AC / DC module; This represents the reactive power-voltage droop coefficient; Indicates the AC voltage of the busbar. This indicates the rated AC voltage.

6. The dynamic droop control method for power converters according to claim 4, characterized in that, Following step S22, the following is also included: Step S23: Dynamically adjust the droop coefficient of each of the first AC / DC modules according to the total power required by the changed load and the rated power of each first AC / DC module.

7. The dynamic droop control method for power converters according to claim 1, characterized in that, Also includes: Monitor whether any AC / DC modules are offline; When an AC / DC module is detected to be offline, a first adjustment command is sent to the online AC / DC modules. The first adjustment command is used to instruct the droop factor of all online AC / DC modules to be reduced so that all online AC / DC modules can redistribute the power gap generated by the offline AC / DC modules.

8. The dynamic droop control method for power converter according to claim 1, characterized in that, Also includes: Monitor whether an AC / DC module is online; When the AC / DC module is detected to be online, pre-synchronization, phase locking and pre-charging operations are performed, and the rated AC current value of the online AC / DC module is uploaded. When the rated AC current value of the online AC / DC module is received, the online AC / DC module is added to the online module list. At the same time, the initial value of the droop coefficient of the online AC / DC module is set to a preset value, so that the initial output current of the online AC / DC module is close to 0. Then, the droop coefficient of the online AC / DC module is gradually reduced, and the droop coefficient of the other online AC / DC modules is increased simultaneously.

9. A dynamic droop control system for a power converter, characterized in that, For implementing the dynamic droop control method for a power converter as described in any one of claims 1-8, the system is applied to a shore charging system for ships, the shore charging system comprising a plurality of first AC / DC modules connected in parallel, and the voltage outer loop of all the first AC / DC modules employing a centralized common voltage outer loop regulator, including: The common voltage outer loop regulator is used to read the deviation between the DC bus voltage value and the given reference value in real time, generate a unique active power command, and send the active power command to the droop controller of each first AC / DC module. A droop controller is used to dynamically adjust the droop coefficient of each of the first AC / DC modules according to the deviation value when the active power command is received.

Images