Charging and discharging control method and system of marine hybrid power system, medium and upper computer

Abstract

The invention provides a charging and discharging control method and system for a marine hybrid power system, a medium and an upper computer. A charging and inversion all-in-one machine converts alternating current of a diesel generating set into direct current to charge a lithium battery pack; or, the charging and inversion all-in-one machine converts the direct current stored in the lithium battery pack into alternating current to supply power to the alternating current load on the ship, only one-time electric energy conversion process needs to be carried out between the alternating current and the direct current, loss of energy in multiple times of conversion is reduced, and the energy conversion efficiency is improved. And based on a synchronous grid connection measure and frequency droop offset control, the charging and discharging power of the lithium battery pack is controlled so as to match the load demand and enhance the grid connection stability of the ship power grid.

Description

Technical Field

[0001] This application relates to the field of marine power system technology, and in particular to a charging and discharging control method, system, medium and host computer for a marine hybrid system. Background Technology

[0002] In recent years, with increasingly stringent global environmental regulations and the International Maritime Organization's (IMO) ever-improving requirements for ship carbon emissions, energy conservation and emission reduction have become unavoidable and crucial issues in the shipping industry. Traditional ships primarily rely on diesel generators as their power source, which not only consumes large amounts of fuel but also generates significant amounts of pollutants such as sulfur oxides, nitrogen oxides, and carbon dioxide, making it difficult to meet increasingly stringent environmental standards. Meanwhile, the application of new energy technologies (such as fuel cells, battery storage, wind power, and solar energy) in onshore energy systems has matured, providing a feasible technological path for the energy transition of the shipping industry.

[0003] However, marine electrical systems have unique characteristics, such as large load fluctuations, harsh operating environments (high humidity, high salt spray, vibration, etc.), and must meet stringent reliability and safety requirements. Currently, marine electrical systems still face the following technical challenges in integrating new energy sources:

[0004] (1) Low energy conversion efficiency: Traditional ship power systems usually use independent chargers and inverters, and electrical energy needs to be converted multiple times (AC-DC-AC), which leads to increased energy loss and reduced overall system efficiency.

[0005] (2) Insufficient power coordination control: In hybrid-powered ships, lithium battery packs need to operate in coordination with other energy sources such as diesel generators and fuel cells. Existing technologies lack intelligent power allocation strategies, making it difficult to dynamically adjust charging and discharging power according to load demands, which can easily lead to energy waste or battery overload.

[0006] (3) Insufficient system safety and reliability: The harsh operating environment of ships (high humidity, salt spray, vibration, etc.) places high demands on the reliability of charging and discharging equipment. Existing solutions typically use a direct disconnection method during the charging and discharging termination phase, which can easily lead to electrical shocks or battery damage. For example, if a lithium battery pack is suddenly disconnected from the charging and discharging circuit under high voltage and high current conditions, it may generate an electric arc or voltage spike, threatening the safety of power electronic devices.

[0007] (4) Grid connection stability issues: When the battery pack is connected to the ship's power grid, voltage and frequency instability may occur due to load fluctuations or changes in operating conditions, affecting the reliability of power supply. Summary of the Invention

[0008] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a charging and discharging control method, system, medium and host computer for marine hybrid systems, so as to solve the problems of low energy conversion efficiency and insufficient system safety and reliability in the prior art.

[0009] To achieve the above and other related objectives, a first aspect of this application provides a charging and discharging control method for a marine hybrid system. The marine hybrid system includes multiple sets of marine power supply devices, which are connected via a bus tie switch. Each marine power supply device includes multiple diesel generator sets connected in parallel and a lithium battery pack. The lithium battery pack is connected to a busbar via a main circuit breaker and a charging inverter unit connected in sequence. The charging and discharging control method includes: when each main circuit breaker is in an open state and each charging inverter unit is in a remote control safety state, supplying power to each charging inverter unit... A start command is issued to enable each of the charging inverters to start operation after controlling the corresponding lithium battery pack to apply high voltage and performing DC pre-charging. In response to the operation indication signal fed back by each of the charging inverters, each of the charging inverters is controlled to perform reverse power charging on the corresponding lithium battery pack, or to discharge the lithium battery pack through the corresponding charging inverter. In response to the charge / discharge completion signal, each of the charging inverters is controlled to reduce the charging power or discharging power of the corresponding lithium battery pack to zero, and then each of the charging inverters is controlled to exit operation.

[0010] In some embodiments of the first aspect of this application, each diesel generator set is connected to the bus via an output circuit breaker; the integrated charging inverter is connected to the bus via an isolation transformer and an isolation switch connected in sequence; wherein, in response to the operation indication signal fed back by each integrated charging inverter, the method of controlling each integrated charging inverter to perform reverse power charging on the corresponding lithium battery pack includes: in response to the operation indication signal fed back by the integrated charging inverter, sequentially controlling the main circuit breaker to close and the output circuit breaker to close; determining whether the voltage, frequency, and phase of the integrated charging inverter are synchronized with the voltage, frequency, and phase of the diesel generator set, and when synchronized, sequentially controlling the isolation switch to close and the bus tie switch to close, so that all equipment can operate in grid-connected mode; and controlling the integrated charging inverter to adjust the real-time charging power of the lithium battery pack according to the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack, so that the integrated charging inverter can perform reverse power charging on the lithium battery pack.

[0011] In some embodiments of the first aspect of this application, controlling the integrated charging inverter to adjust the real-time charging power of the lithium battery pack based on the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack, so that the integrated charging inverter performs reverse charging on the lithium battery pack, includes: determining the target charging power of the lithium battery pack based on the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack; calculating a first frequency droop offset value of the integrated charging inverter based on a preset first droop coefficient and the target charging power of the lithium battery pack; adjusting a first operating frequency of the integrated charging inverter based on the first frequency droop offset value of the integrated charging inverter; and controlling the integrated charging inverter to adjust the real-time charging power of the lithium battery pack based on the adjusted first operating frequency of the integrated charging inverter, so that the integrated charging inverter performs reverse charging on the lithium battery pack.

[0012] In some embodiments of the first aspect of this application, the method of controlling each lithium battery pack to discharge through the corresponding charging inverter in response to the operation indication signal fed back by each of the charging inverters includes: controlling the main circuit breaker to close in response to the operation indication signal fed back by the charging inverter; and controlling the charging inverter to adjust the real-time discharge power of the lithium battery pack according to the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, so that the lithium battery pack discharges through the charging inverter.

[0013] In some embodiments of the first aspect of this application, the ship's power grid operation mode includes an islanded operation mode; wherein, based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, the method of controlling the charging inverter to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack discharges through the charging inverter includes: when no diesel generator set is detected to be running on the grid, determining that the ship's power grid operation mode is the islanded operation mode; in the islanded operation mode, controlling the disconnect switch to close; and controlling the charging inverter to adjust the real-time discharge power of the lithium battery pack based on the load demand power and the maximum allowable discharge current of the lithium battery pack so that the lithium battery pack discharges through the charging inverter.

[0014] In some embodiments of the first aspect of this application, the ship's power grid operation mode includes a grid-connected operation mode; wherein, based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, controlling the integrated charging inverter to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack discharges through the integrated charging inverter includes: when a diesel generator set is detected to be running on the grid, determining that the ship's power grid operation mode is the grid-connected operation mode; in the grid-connected operation mode, determining whether the voltage, frequency, and phase of the integrated charging inverter are synchronized with the voltage, frequency, and phase of the diesel generator set, and when synchronized, sequentially controlling the closing of the disconnecting switch and the busbar... The circuit breaker is closed to enable all equipment to operate in grid-connected mode. Based on the load power demand, the maximum allowable discharge current of the lithium battery pack, the rated power of the integrated charging inverter, and the current available power of the diesel generator set, the target discharge power of the lithium battery pack is determined. Based on a preset second droop coefficient and the target discharge power of the lithium battery pack, the second frequency droop offset value of the integrated charging inverter is calculated. Based on the second frequency droop offset value of the integrated charging inverter, the second operating frequency of the integrated charging inverter is adjusted. Based on the adjusted second operating frequency of the integrated charging inverter, the integrated charging inverter is controlled to adjust the real-time discharge power of the lithium battery pack, so that the lithium battery pack discharges through the integrated charging inverter.

[0015] In some embodiments of the first aspect of this application, the method for determining the target discharge power of the lithium battery pack includes: calculating the total available discharge power based on the maximum allowable discharge current of the lithium battery pack, the rated power of the charging inverter, and the current available power of the diesel generator set; calculating the output power ratio of the charging inverter and the output power ratio of the diesel generator set based on the load demand power and the total available discharge power; and determining the target discharge power of the lithium battery pack based on the output power ratio of the charging inverter and the output power ratio of the diesel generator set.

[0016] To achieve the above and other related objectives, a second aspect of this application provides a charging and discharging control system for a marine hybrid system, wherein the charging and discharging control system is communicatively connected to the marine hybrid system; the marine hybrid system includes multiple sets of marine power supply devices, which are connected to each other via a bus tie switch; each marine power supply device includes multiple diesel generator sets connected in parallel and a lithium battery pack; the lithium battery pack is connected to the busbar via a main circuit breaker and a charging inverter integrated unit connected in sequence; the charging and discharging control system includes: a pre-charge control module, used to charge each of the main circuit breakers in the open state and the charging inverter integrated unit in the remote control safety state, to charge each of the main circuit breakers in the open state. The charging inverter unit issues a start command to enable each charging inverter unit to start operation after controlling the corresponding lithium battery pack to apply high voltage and perform DC side pre-charging. The charging and discharging control module is used to respond to the operation indication signal fed back by each charging inverter unit to control each charging inverter unit to perform reverse power charging on the corresponding lithium battery pack, or to control each lithium battery pack to discharge through the corresponding charging inverter unit. The shutdown control module is used to respond to the charging and discharging completion signal to control each charging inverter unit to reduce the charging power or discharging power of the corresponding lithium battery pack to zero, and then control each charging inverter unit to exit operation.

[0017] To achieve the above and other related objectives, a third aspect of this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the charging and discharging control method for a marine hybrid system as described above.

[0018] To achieve the above and other related objectives, a fourth aspect of this application provides a host computer, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the charging and discharging control method for a marine hybrid system as described above.

[0019] As described above, the charging and discharging control method, system, medium, and host computer of the marine hybrid system of this application have the following characteristics:

[0020] Beneficial effects:

[0021] (1) Improve energy conversion efficiency: By adopting a charging inverter integrated machine, AC power and DC power only need to go through one power conversion process, reducing energy loss in multiple conversions and improving energy conversion efficiency.

[0022] (2) Enhance system safety and equipment reliability: When starting up, DC side pre-charge is performed first to avoid power-on shock; when stopping, the charging and discharging power is gradually reduced to zero before exiting operation, avoiding the harm caused by "direct cut-off" (such as electrical shock and battery damage), and improving the safety and reliability of the ship system's charging and discharging equipment.

[0023] (3) Improve grid connection stability: Before charging and discharging, the voltage, frequency and phase are synchronized to eliminate grid connection impact. The charging and discharging power of the lithium battery pack is controlled by frequency droop offset control to achieve dynamic optimization of power allocation to match load demand, enhance the grid connection stability of the ship's power grid, improve energy utilization, avoid battery over-discharge / overcharge or inefficient operation of diesel generator set, and improve economy. Attached Figure Description

[0024] Figure 1 The diagram shown is a topology diagram of a marine hybrid system according to an embodiment of this application.

[0025] Figure 2 The diagram shown is a flowchart of a charging and discharging control method according to an embodiment of this application.

[0026] Figure 3 The diagram shown is a schematic representation of the charging process of a lithium battery pack in one embodiment of this application.

[0027] Figure 4 The diagram shown is a schematic representation of the discharge process of a lithium battery pack in one embodiment of this application.

[0028] Figure 5 The diagram shown is a schematic representation of the charging and discharging control system of a marine hybrid system according to an embodiment of this application.

[0029] Figure 6 The diagram shown is a schematic representation of the host computer in one embodiment of this application. Detailed Implementation

[0030] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0031] Before providing a further detailed description of the present invention, the nouns and terms used in the embodiments of the present invention are explained, and the nouns and terms used in the embodiments of the present invention are subject to the following interpretations:

[0032] <1> Bus tie switch: A circuit breaker that connects two bus sections to enable parallel operation or sectional isolation of the bus sections, ensuring power supply flexibility and fault isolation.

[0033] <2> Lithium battery pack: A DC energy storage unit that is rechargeable and dischargeable, composed of lithium-ion cells connected in series and parallel.

[0034] To facilitate understanding of the embodiments of this application, firstly, in conjunction with Figure 1 Detailed explanation. Figure 1 A topology diagram of a marine hybrid system according to an embodiment of the present invention is shown. In this embodiment, the marine hybrid system includes multiple sets of marine power supply devices, which are connected via a bus tie switch. Each marine power supply device includes multiple diesel generator sets connected in parallel and a lithium battery pack. Each diesel generator set is connected to the bus via an output circuit breaker. The lithium battery pack is connected to the bus via a main circuit breaker and a charging inverter unit connected in sequence. The charging inverter unit is connected to the bus via an isolation transformer and a disconnect switch connected in sequence.

[0035] Specifically, the marine hybrid system includes four diesel generator sets (1-4), two lithium battery packs (5-6), two main circuit breakers (7-8), two integrated charging inverters (9-10), four output circuit breakers (11-14), two isolation transformers (15-16), two disconnect switches (17-18), and one bus tie switch (19). This marine hybrid system is an intelligent power conversion system integrating battery charging and inverter discharge functions. It can convert AC power from diesel generator sets or shore power into DC power to charge the lithium battery packs; simultaneously, it can also invert the DC power stored in the lithium battery packs into stable AC power to supply AC loads on board (such as lighting, propulsion, and household appliances), improving system operating economy and reducing pollutant emissions. The isolation transformer has a rated capacity of 625KVA, which steps up the 400V input voltage to 690V. Line 1 (BUS1) and Line 2 (BUS2) are each connected to a set of ship power supply devices. First, a daytime transformer with a rated capacity of 250KVA is connected. This transformer reduces the 690V incoming voltage to 400V and locks the frequency at 50Hz, which can supply power to the AC loads on the ship.

[0036] In embodiments of the present invention, such as Figure 2 The diagram shown illustrates a flowchart of the charging and discharging control method according to an embodiment of the present invention. When the lithium battery pack is low on power, the integrated charging inverter converts the AC power from the diesel generator set into DC power to charge the lithium battery pack. During peak electricity consumption, the integrated charging inverter converts the DC power stored in the lithium battery pack into AC power to supply AC loads on the ship. The charging and discharging control method is implemented through a charging and discharging control system, which can use an AC power distribution board to execute the various steps of the charging and discharging control method. The charging and discharging control method mainly includes the following steps:

[0037] S201: When each of the main circuit breakers is in the open state and each of the charging inverters is in the remote control safety state, a start command is sent to each of the charging inverters so that each of the charging inverters starts operation after controlling the corresponding lithium battery pack to apply high voltage and performing DC side pre-charging.

[0038] In this embodiment, the main circuit breaker being in the open state means that the lithium battery pack is not connected to the high-voltage circuit, preventing high-voltage electric shock or equipment impact (such as capacitor short circuit) due to misoperation before startup, thus providing initial safety assurance. The charging inverter being in the remote control safety state means that the charging inverter relinquishes local control to accept remote commands from the AC distribution board, and the charging inverter passes self-test without any comprehensive alarms, thus meeting the conditions to execute the startup command.

[0039] In this embodiment, the integrated charging inverter has a built-in pre-charging function to pre-charge the internal capacitors. The DC side of the integrated charging inverter is equipped with common-mode protection to prevent damage to the lithium battery pack from common-mode voltage. Upon receiving a start command, the integrated charging inverter closes the main contactor within the lithium battery pack, connecting the high-voltage DC voltage of the lithium battery pack to the DC side of the integrated charging inverter. After detecting the DC side voltage, the integrated charging inverter first closes its internal pre-charging contactor, using a pre-charging resistor on the DC side to current-limit the charging of the internal capacitors, avoiding instantaneous high-current surges. Pre-charging is complete when the capacitor voltage is close to the battery voltage, and the pre-charging resistor is disconnected after the voltage stabilizes. After completing the DC side pre-charging, the inverter in the integrated charging inverter starts and sends an operation indication signal back to the AC distribution board.

[0040] In this embodiment, the AC side of the charging inverter is equipped with an LCL filter to filter the output AC power to obtain a sine wave.

[0041] S202: In response to the operation indication signal fed back by each of the charging inverters, control each of the charging inverters to perform reverse power charging on the corresponding lithium battery pack, or control each of the lithium battery packs to discharge through the corresponding charging inverter.

[0042] In this embodiment, as Figure 3 The diagram illustrates the charging process of a lithium battery pack according to an embodiment of the present invention. Each diesel generator set is connected to the bus via an output circuit breaker; the integrated charging inverter is connected to the bus via an isolation transformer and an isolation switch connected in sequence; wherein, in response to the operation indication signals fed back by each integrated charging inverter, the method of controlling each integrated charging inverter to perform reverse power charging on the corresponding lithium battery pack includes:

[0043] S2021: In response to the operation indication signal fed back by the charging inverter, the main circuit breaker and the output circuit breaker are closed in sequence.

[0044] In this embodiment, after the inverter in the charging inverter unit is started, the main circuit breaker and the output circuit breaker are closed, the charging inverter unit is connected to the lithium battery pack, and the diesel generator set is connected to the ship's power grid.

[0045] S2022: Determine whether the voltage, frequency, and phase of the charging inverter are synchronized with the voltage, frequency, and phase of the diesel generator set, and when synchronized, control the closing of the disconnect switch and the closing of the bus tie switch in sequence so that all equipment can be connected to the grid.

[0046] In this embodiment, the AC power supply to the integrated charging inverter and the diesel generator set must meet the "three synchronizations": same frequency, same phase (same peak voltage waveform), and equal voltage amplitude. If they are not synchronized, a huge circulating current will be generated at the moment of closing, easily burning out electrical components. The synchronization meter on the AC distribution board monitors the voltage, frequency, and phase of both in real time. When the difference is within the allowable range, synchronization is achieved, and the isolating switch and bus tie switch are closed sequentially to ensure all equipment is connected to the grid. At this time, the diesel generator set and the lithium battery pack are connected to the grid simultaneously, and power can flow between them. Synchronization control avoids grid connection impact and ensures a stable connection between the grid and the battery system.

[0047] S2023: Based on the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack, control the integrated charging inverter to adjust the real-time charging power of the lithium battery pack, so that the integrated charging inverter can perform reverse power charging on the lithium battery pack. The method includes:

[0048] (1) Determine the target charging power of the lithium battery pack based on the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack.

[0049] In this embodiment, the current available power of the diesel generator set is equal to the rated power minus the output power. The maximum allowable charging power of the lithium battery pack is obtained by multiplying its rated voltage and maximum allowable charging current. The target charging power is the minimum of the maximum allowable charging power of the lithium battery pack and the current available power of the diesel generator set.

[0050] (2) The first frequency droop offset value of the charging inverter is calculated based on the preset first droop coefficient and the target charging power of the lithium battery pack.

[0051] In this embodiment, the first frequency droop offset value of the charging inverter is obtained by multiplying the preset first droop coefficient by the target charging power of the lithium battery pack.

[0052] (3) Adjust the first operating frequency of the charging inverter according to the first frequency droop offset value of the charging inverter.

[0053] In this embodiment, the first operating frequency of the charging inverter is adjusted according to the first frequency droop offset value of the charging inverter, so that the first operating frequency of the charging inverter is slightly lower than the frequency of the diesel generator set, forming a frequency difference, which causes power to flow from the diesel generator set to the lithium battery pack, realizing reverse power charging.

[0054] (4) Based on the first operating frequency of the adjusted charging inverter, control the charging inverter to adjust the real-time charging power of the lithium battery pack so that the charging inverter can perform reverse power charging on the lithium battery pack.

[0055] In this embodiment, when the first operating frequency of the charging inverter is slightly lower than the frequency of the diesel generator set, the charging inverter dynamically adjusts the voltage and current output on the DC side by comparing the deviation between the adjusted operating frequency and the frequency of the diesel generator set in real time, based on the "frequency-power" droop characteristic. This frequency-power closed-loop control enables adaptive charging power adjustment of the lithium battery pack, while ensuring system power balance and frequency stability.

[0056] In this embodiment, the method of controlling each lithium battery pack to discharge through the corresponding charging inverter in response to the operation indication signal fed back by each of the charging inverters includes:

[0057] (1) In response to the operation indication signal fed back by the charging inverter, control the main circuit breaker to close.

[0058] (2) Based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, control the charging inverter to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack can be discharged through the charging inverter.

[0059] In this embodiment, the ship's power grid operation mode includes an islanded operation mode; wherein, based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, the method of controlling the charging inverter to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack discharges through the charging inverter includes:

[0060] (1) When it is detected that no diesel generator set is running on the grid, the ship's power grid operation mode is determined to be the island operation mode.

[0061] (2) In the islanded operation mode, control the closing of the disconnect switch.

[0062] (3) Based on the load demand power and the maximum allowable discharge current of the lithium battery pack, control the charging inverter to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack can be discharged through the charging inverter.

[0063] In this embodiment, when it is detected that the ship's power grid is not running with a diesel generator set, it is determined that the power grid has entered the "single battery on the grid" islanded operation mode, and the disconnecting switch is closed to establish a discharge circuit.

[0064] In this embodiment, the maximum allowable discharge power of the lithium battery pack is obtained by multiplying its rated voltage and maximum allowable discharge current. The target discharge power is then calculated by taking the minimum of the maximum allowable discharge power and the load demand. Based on the target discharge power, the charging inverter adjusts the real-time discharge power of the lithium battery pack to match the load demand, achieving "discharges only as much as the load."

[0065] In this embodiment, as Figure 4 The diagram shown illustrates the discharge process of a lithium battery pack in an embodiment of the present invention. The ship's power grid operation mode includes a grid-connected operation mode; wherein, based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, the method of controlling the charging inverter to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack discharges through the charging inverter includes:

[0066] S2021A: When a diesel generator set is detected to be running on the grid, the ship's power grid operation mode is determined to be the grid-connected operation mode.

[0067] In this embodiment, when a diesel generator set is detected running on the ship's power grid, it is determined that the power grid has entered the grid-connected operation mode. When the lithium battery pack is connected to the grid, the AC power of the charging inverter and the diesel generator set must meet the "three synchronizations". The principle is similar to that when the lithium battery pack is charging, so it will not be described in detail here.

[0068] S2022B: In the grid-connected operation mode, determine whether the voltage, frequency, and phase of the charging inverter are synchronized with the voltage, frequency, and phase of the diesel generator set, and when synchronized, control the closing of the disconnecting switch and the closing of the bus tie switch in sequence so that all equipment can be connected to the grid.

[0069] In this embodiment, the lithium battery pack is controlled to connect to the grid when the AC power of the charging inverter and the diesel generator set meets the "three synchronizations".

[0070] S2023C: Determine the target discharge power of the lithium battery pack based on the load power demand, the maximum allowable discharge current of the lithium battery pack, the rated power of the integrated charging inverter, and the current available power of the diesel generator set. The methods include:

[0071] (1) The total available discharge power is calculated based on the maximum allowable charging current of the lithium battery pack, the rated power of the charging inverter, and the current available power of the diesel generator set.

[0072] (2) Based on the load demand power and the total available discharge power, calculate the output power ratio of the charging inverter and the output power ratio of the diesel generator set.

[0073] (3) Determine the target discharge power of the lithium battery pack based on the output power ratio of the integrated charging inverter and the output power ratio of the diesel generator set.

[0074] In this embodiment, the maximum allowable discharge power of the lithium battery pack is obtained by multiplying its rated voltage and maximum allowable discharge current. The smaller value between the maximum allowable discharge power of the lithium battery pack and the rated power of the integrated charging inverter is then taken and added to the current available power of the diesel generator set to obtain the total available discharge power.

[0075] In this embodiment, exemplarily, the load power requirement P L =400kW, the maximum allowable discharge power P of the lithium battery pack m =180kW, Rated power of the integrated charging inverter =200kW, Current available power P of the diesel generator set c =250kW, then the total available discharge power P t =min(180kW, 200kW)+250kW=430kW, the output power ratio of the charging inverter is n1=180 / 430=0.42, the output power ratio of the diesel generator set is n2=250 / 430=0.58, then the target discharge power of the lithium battery pack is P1=0.42×400kW=168kW, and the output power of the diesel generator set is P2=0.58×400kW=232kW.

[0076] S2024D: The second frequency droop offset value of the charging inverter is calculated based on the preset second droop coefficient and the target discharge power of the lithium battery pack.

[0077] In this embodiment, the second frequency droop offset value of the charging inverter is obtained by multiplying the preset second droop coefficient by the target discharge power of the lithium battery pack.

[0078] S2025E: Adjust the second operating frequency of the charging inverter based on the second frequency droop offset value of the charging inverter.

[0079] In this embodiment, the second operating frequency of the charging inverter is adjusted according to the second frequency droop offset value of the charging inverter, so that the second operating frequency of the charging inverter is slightly higher than the frequency of the diesel generator set, forming a frequency difference. The DC power of the lithium battery pack is converted into AC power by the charging inverter to power the ship load.

[0080] S2026F: Based on the adjusted second operating frequency of the charging inverter, the charging inverter is controlled to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack can be discharged through the charging inverter.

[0081] In this embodiment, when the second operating frequency of the charging inverter is slightly higher than the frequency of the diesel generator set, the charging inverter dynamically adjusts the voltage and current output on the AC side based on the frequency-power droop characteristic by comparing the deviation between the adjusted operating frequency and the diesel generator set in real time, so as to achieve the adjustment of discharge power.

[0082] S203: In response to the charging / discharging completion signal, after controlling each of the charging inverter integrated machines to reduce the charging power or discharging power of the corresponding lithium battery pack to zero, control each of the charging inverter integrated machines to exit operation.

[0083] In this embodiment, when it is detected that the lithium battery pack has completed charging and discharging, and that the main circuit breaker is in the closed state and the charging inverter is in the remote control safety state, the charging inverter is controlled to gradually reduce the charging power or discharging power of the corresponding lithium battery pack to zero. After controlling the disconnecting switch to open, a stop operation command is sent to the charging inverter, so that the charging inverter controls the lithium battery pack to reduce the high voltage, disconnecting the high-voltage DC output of the lithium battery pack. The charging inverter then completes the shutdown and sends back a stop operation signal. Through the logic of "reducing power first and then opening the circuit breaker," electrical shocks during the shutdown process are avoided, protecting the equipment and the battery.

[0084] It is worth noting that the charging and discharging control method of the marine hybrid system of the present invention has the following advantages:

[0085] (1) Improve energy conversion efficiency: By adopting a charging inverter integrated machine, AC power and DC power only need to go through one power conversion process, reducing energy loss in multiple conversions and improving energy conversion efficiency.

[0086] (2) Enhance system safety and equipment reliability: When starting up, DC side pre-charge is performed first to avoid power-on shock; when stopping, the charging and discharging power is gradually reduced to zero before exiting operation, avoiding the harm caused by "direct cut-off" (such as electrical shock and battery damage), and improving the safety and reliability of the ship system's charging and discharging equipment.

[0087] (3) Improve grid connection stability: Before charging and discharging, the voltage, frequency and phase are synchronized to eliminate grid connection impact. The charging and discharging power of the lithium battery pack is controlled by frequency droop offset control to achieve dynamic optimization of power allocation to match load demand, enhance the grid connection stability of the ship's power grid, improve energy utilization, avoid battery over-discharge / overcharge or inefficient operation of diesel generator set, and improve economy.

[0088] In the embodiments of this application, terms such as "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first frequency droop offset value and the second frequency droop offset value are only used to distinguish different frequency droop offset values ​​and do not limit their order. Those skilled in the art will understand that terms such as "first" and "second" do not limit the quantity or execution order, and that terms such as "first" and "second" do not necessarily imply that they are different.

[0089] It should be noted that, in the embodiments of this application, the words "exemplary" or "for example" indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0090] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0091] Figure 5This is a schematic diagram of the charging and discharging control system of the marine hybrid system provided in this application embodiment. The charging and discharging control system is communicatively connected to the marine hybrid system; the marine hybrid system includes multiple sets of ship power supply devices, which are connected to each other through a bus tie switch. Each ship power supply device includes multiple diesel generator sets connected in parallel and a lithium battery pack; the lithium battery pack is connected to the busbar through a main circuit breaker and a charging inverter integrated machine connected in sequence.

[0092] The charge / discharge control system 500 includes:

[0093] The precharge control module 501 is used to send a start command to each of the charging inverters when each of the main circuit breakers is in the open state and each of the charging inverters is in the remote control safety state, so that each of the charging inverters starts operation after controlling the corresponding lithium battery pack to apply high voltage and performing DC side precharge.

[0094] The charging and discharging control module 502 is used to respond to the operation indication signal fed back by each of the charging and inverter integrated machines, and control each of the charging and inverter integrated machines to perform reverse power charging on the corresponding lithium battery pack, or to control each of the lithium battery packs to discharge through the corresponding charging and inverter integrated machine.

[0095] The shutdown control module 503 is used to respond to the charging and discharging completion signal, control each of the charging inverter integrated machines to reduce the charging power or discharging power of the corresponding lithium battery pack to zero, and then control each of the charging inverter integrated machines to exit operation.

[0096] It should be understood that the specific process of each module performing the above-mentioned corresponding steps has been described in detail in the above method embodiments, and will not be repeated here for the sake of brevity.

[0097] It should also be understood that the module division in the embodiments of this application is illustrative and only represents a logical functional division; in actual implementation, there may be other division methods. Furthermore, the functional modules in the various embodiments of this application can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0098] Figure 6 This is a schematic block diagram of the host computer provided in an embodiment of this application. The host computer includes a memory, a processor, and a computer program stored in the memory. The processor executes the computer program to implement the charging and discharging control method for the marine hybrid system as described above. Figure 6As shown, the host computer 600 includes at least one processor 601, a memory 602, at least one network interface 603, and a user interface 605. The various components in the device are coupled together via a bus system 604. It is understood that the bus system 604 is used to implement communication between these components. In addition to a data bus, the bus system 604 also includes a power bus, a control bus, and a status signal bus. However, for clarity, in… Figure 6 The general will label all buses as bus systems.

[0099] The user interface 605 may include a monitor, keyboard, mouse, trackball, clicker, button, touchpad, or touch screen.

[0100] It is understood that memory 602 can be volatile memory or non-volatile memory, or both. Non-volatile memory can be read-only memory (ROM) or programmable read-only memory (PROM), used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM) and synchronous static random access memory (SSRAM). The memories described in the embodiments of this invention are intended to include, but are not limited to, these and any other suitable categories of memory.

[0101] In this embodiment of the invention, the memory 602 is used to store various types of data to support the operation of the host computer 600. Examples of this data include: any executable program for operation on the host computer 600, such as the operating system 6021 and the application program 6022; the operating system 6021 contains various system programs, such as the framework layer, core library layer, driver layer, etc., for implementing various basic services and handling hardware-based tasks. The application program 6022 may contain various applications, such as a media player, browser, etc., for implementing various application services. The charging and discharging control method of the marine hybrid system provided in this embodiment of the invention can be included in the application program 6022.

[0102] The methods disclosed in the above embodiments of the present invention can be applied to processor 601, or implemented by processor 601. Processor 601 may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by the integrated logic circuit of the hardware in processor 601 or by instructions in the form of software. The processor 601 may be a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Processor 601 can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of the present invention. General-purpose processor 601 may be a microprocessor or any conventional processor, etc. The steps of the accessory optimization method provided in the embodiments of the present invention can be directly reflected as being executed by a hardware decoding processor, or being executed by a combination of hardware and software modules in the decoding processor. The software module may be located in a storage medium, which is located in memory. The processor reads the information in the memory and combines it with its hardware to complete the steps of the aforementioned method.

[0103] In an exemplary embodiment, the host computer 600 may be used by one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), or complex programmable logic devices (CPLDs) to execute the aforementioned method.

[0104] According to the method provided in the embodiments of this application, this application also provides a computer-readable storage medium storing program code, which, when executed on a computer, causes the computer to perform... Figures 2 to 4 The method of any of the embodiments shown.

[0105] As used in this specification, the terms "component," "module," "system," etc., are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a component can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or a computer. As illustrated, applications running on computing devices and computing devices can both be components. One or more components may reside in a process and / or an execution thread, and components may be located on a single computer and / or distributed among two or more computers. Furthermore, these components can be executed from various computer-readable media on which various data structures are stored. Components can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from two components interacting with another component between a local system, a distributed system, and / or a network, such as the Internet interacting with other systems via signals).

[0106] Those skilled in the art will recognize that the various illustrative logical blocks and steps described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this application.

[0107] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0108] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0109] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0110] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0111] In the above embodiments, the functions of each functional unit can be implemented entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. A computer program product includes one or more computer instructions (programs). When the computer program instructions (programs) are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. Computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., high-density digital video discs, DVDs), or semiconductor media (e.g., solid-state disks, SSDs, etc.).

[0112] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0113] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0114] In summary, this application provides a charging and discharging control method, system, medium, and host computer for a marine hybrid system. The integrated charging inverter converts AC power from the diesel generator set into DC power to charge the lithium battery pack; alternatively, the integrated charging inverter converts the DC power stored in the lithium battery pack into AC power to supply AC loads on board. Only one power conversion process is required between AC and DC power, reducing energy loss during multiple conversions and improving energy conversion efficiency. Furthermore, based on synchronous grid connection measures and frequency droop offset control, the charging and discharging power of the lithium battery pack is controlled to match load demand and enhance the grid connection stability of the ship's power grid. Therefore, this application effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0115] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A charging and discharging control method for a marine hybrid system, characterized in that, The marine hybrid system includes multiple sets of marine power supply devices, which are connected to each other via a bus tie switch. Each marine power supply device includes multiple diesel generator sets connected in parallel and a lithium battery pack. The lithium battery pack is connected to the bus via a main circuit breaker and a charging inverter unit connected in sequence. The charging and discharging control method includes: When each of the main circuit breakers is in the open state and each of the charging inverters is in the remote control safety state, a start command is sent to each of the charging inverters so that each of the charging inverters starts operation after controlling the corresponding lithium battery pack to apply high voltage and performing DC side pre-charging. In response to the operation indication signal fed back by each of the charging inverters, control each of the charging inverters to perform reverse power charging on the corresponding lithium battery pack, or control each of the lithium battery packs to discharge through the corresponding charging inverter. In response to the charging / discharging completion signal, each of the charging inverters reduces the charging power or discharging power of the corresponding lithium battery pack to zero, and then controls each of the charging inverters to exit operation.

2. The charging and discharging control method for a marine hybrid system according to claim 1, characterized in that, Each diesel generator set is connected to the busbar via an output circuit breaker; the integrated charging inverter is connected to the busbar via an isolation transformer and an isolation switch connected in sequence; wherein, in response to the operation indication signal fed back by each integrated charging inverter, the method of controlling each integrated charging inverter to perform reverse power charging on the corresponding lithium battery pack includes: In response to the operation indication signal fed back by the charging inverter, the main circuit breaker and the output circuit breaker are closed sequentially. Determine whether the voltage, frequency, and phase of the integrated charging inverter are synchronized with the voltage, frequency, and phase of the diesel generator set, and when synchronized, control the closing of the disconnect switch and the closing of the bus tie switch in sequence so that all equipment can be connected to the grid for operation; Based on the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack, the charging inverter is controlled to adjust the real-time charging power of the lithium battery pack so that the charging inverter can perform reverse power charging on the lithium battery pack.

3. The charging and discharging control method for a marine hybrid system according to claim 2, characterized in that, Based on the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack, the charging inverter controls the real-time charging power of the lithium battery pack to perform reverse power charging on the lithium battery pack in the following ways: The target charging power of the lithium battery pack is determined based on the current available power of the diesel generator set and the maximum allowable charging current of the lithium battery pack. The first frequency droop offset value of the charging inverter is calculated based on the preset first droop coefficient and the target charging power of the lithium battery pack. Adjust the first operating frequency of the charging inverter based on the first frequency droop offset value of the charging inverter. Based on the adjusted first operating frequency of the integrated charging inverter, the integrated charging inverter is controlled to adjust the real-time charging power of the lithium battery pack, so that the integrated charging inverter can perform reverse power charging on the lithium battery pack.

4. The charging and discharging control method for a marine hybrid system according to claim 2, characterized in that, The method of controlling each lithium battery pack to discharge through its corresponding charging inverter in response to the operation indication signal fed back by each of the aforementioned charging inverters includes: In response to the operation indication signal fed back by the charging inverter, the main circuit breaker is controlled to close; Based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, the charging inverter controls the real-time discharge power of the lithium battery pack to enable the lithium battery pack to discharge through the charging inverter.

5. The charging and discharging control method for a marine hybrid system according to claim 4, characterized in that, The ship's electrical grid operation mode includes an islanded operation mode; wherein, based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's electrical grid operation mode, the charging inverter controls the real-time discharge power of the lithium battery pack to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack discharges through the charging inverter, including the following methods: When it is detected that no diesel generator set is on the grid, the ship's power grid operation mode is determined to be the island operation mode; In the islanded operation mode, the disconnect switch is closed. Based on the load power demand and the maximum allowable discharge current of the lithium battery pack, the charging inverter controls the real-time discharge power of the lithium battery pack to enable the lithium battery pack to discharge through the charging inverter.

6. The charging and discharging control method for a marine hybrid system according to claim 4, characterized in that, The ship's power grid operation mode includes a grid-connected operation mode; wherein, based on the load demand power and the maximum allowable discharge current of the lithium battery pack, and based on the ship's power grid operation mode, the method of controlling the charging inverter to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack discharges through the charging inverter includes: When a diesel generator set is detected to be running on the grid, the ship's power grid operation mode is determined to be the grid-connected operation mode; In the grid-connected operation mode, it is determined whether the voltage, frequency, and phase of the charging inverter are synchronized with the voltage, frequency, and phase of the diesel generator set. When they are synchronized, the disconnecting switch and the bus tie switch are closed in sequence to enable all equipment to operate in grid-connected mode. The target discharge power of the lithium battery pack is determined based on the load demand power, the maximum allowable discharge current of the lithium battery pack, the rated power of the charging inverter, and the current available power of the diesel generator set. The second frequency droop offset value of the charging inverter is calculated based on the preset second droop coefficient and the target discharge power of the lithium battery pack. Adjust the second operating frequency of the charging inverter based on the second frequency droop offset value of the charging inverter. Based on the adjusted second operating frequency of the integrated charging inverter, the integrated charging inverter is controlled to adjust the real-time discharge power of the lithium battery pack so that the lithium battery pack can be discharged through the integrated charging inverter.

7. The charging and discharging control method for a marine hybrid system according to claim 6, characterized in that, The methods for determining the target discharge power of the lithium battery pack include: The total available discharge power is calculated based on the maximum allowable discharge current of the lithium battery pack, the rated power of the charging inverter, and the current available power of the diesel generator set. Based on the load demand power and the total available discharge power, the output power ratio of the charging inverter and the output power ratio of the diesel generator set are calculated. The target discharge power of the lithium battery pack is determined based on the output power ratio of the integrated charging inverter and the output power ratio of the diesel generator set.

8. A charging and discharging control system for a marine hybrid system, characterized in that, The charging and discharging control system is communicatively connected to the marine hybrid system; the marine hybrid system includes multiple sets of marine power supply devices, which are connected to each other via a bus tie switch; the marine power supply device includes multiple diesel generator sets connected in parallel and a lithium battery pack; the lithium battery pack is connected to the bus via a main circuit breaker and a charging inverter unit connected in sequence. The charging and discharging control system includes: The pre-charge control module is used to send a start command to each of the charging inverters when each of the main circuit breakers is in the open state and each of the charging inverters is in the remote control safety state, so that each of the charging inverters starts operation after controlling the corresponding lithium battery pack to apply high voltage and performing DC side pre-charge. The charging and discharging control module is used to respond to the operation indication signal fed back by each of the charging inverters, and control each of the charging inverters to charge the corresponding lithium battery pack in reverse power, or control each of the lithium battery packs to discharge through the corresponding charging inverter. The shutdown control module is used to respond to the charging / discharging completion signal, control each of the charging inverters to reduce the charging power or discharging power of the corresponding lithium battery pack to zero, and then control each of the charging inverters to exit operation.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the charging and discharging control method for a marine hybrid system as described in any one of claims 1 to 7.

10. A host computer, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the charging and discharging control method for a marine hybrid system as described in any one of claims 1 to 7.

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