Method, system, electronic device and storage medium for flexible switching of ship shore power

Abstract

The present application provides a method, system, electronic device and storage medium for flexible switching of ship shore power, including: obtaining the output frequency f and output voltage U of the shore power supply in real time; obtaining the first ratio according to the output frequency and the preset p-f formula, and obtaining the second ratio according to the output voltage and the preset Q-U formula; performing flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold value and the switching type, and the switching type includes: switching when the ship to be switched is berthed and switching when the ship to be switched is offshore. In the flexible switching process, the relevant operations and switching process are completed by the shore power supply, which reduces the operation of the ship personnel. At the same time, in the ship-to-shore power switching process, it is not necessary to obtain parameters such as the size of the ship load and the droop coefficient of the ship generator, which reduces the communication requirements during the switching process.

Description

Technical Field

[0001] The present application belongs to the field of ships, and in particular to a method, system, electronic device and storage medium for flexible switching of ship shore power. Background Art

[0002] In the early days, port shore power was generated by the mains electricity being stepped down by a transformer and stabilized by a voltage stabilizer. When a ship docked at the port, it was necessary to shut down its own generator first, and the ship's load would experience a short power outage before being connected to the shore power, which is the so-called "power off switching". With the increasing power supply requirements for some important loads on board, for example, some important navigation loads may need to be started several hours in advance before leaving the port. The power off switching method obviously cannot meet the power supply requirements. Ships began to use live direct switching to connect to shore power. First, only important loads on the ship side were retained. The ship's generator was connected to the port shore power grid through a synchronization device and immediately exited operation after a short delay, causing the ship's load to be instantly added to the port shore power. This process may affect the grid connection effect of the ship power and shore power due to improper operation, and then cause abnormal operating conditions such as reverse power or overload.

[0003] With the development of power electronics technology, static shore power supplies composed of power devices such as IGBT have flexible voltage and frequency regulation functions through the adoption of appropriate control strategies, and have begun to be used in some civilian ports. At present, most of these shore power products with voltage and frequency regulation functions on the market focus on improving the power supply quality when the shore power is running alone with ship loads. Some shore power products that are actually put into operation still use the short-term power-off switching method. Although a few shore power products from companies such as Siemens and ABB have automatic grid connection functions and can realize the live switching of ship shore power, there are technical defects such as high communication requirements, large amount of ship-side operations, and low load transfer smoothness during the switching process between ship power and shore power. Summary of the invention

[0004] The main purpose of the embodiments of the present invention is to provide a method, system, electronic device and storage medium for flexible switching of ship shore power, so that during the flexible switching process, the relevant operations and switching process are completed by the shore power supply, reducing the operation of ship personnel. At the same time, during the ship-shore power switching process, there is no need to obtain parameters such as the size of the ship load and the droop coefficient of the ship generator, thereby reducing the communication requirements during the switching process.

[0005] In a first aspect, a method for flexible switching of ship shore power is provided, the method comprising:

[0006] Obtain the output frequency f and output voltage U of the shore power supply in real time;

[0007] A first ratio is obtained according to the output frequency and a preset pf formula, and a second ratio is obtained according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply. The first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched. The pf formula and the QU formula are preset formulas according to the virtual synchronous motor VSG strategy;

[0008] Flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and the switching type includes: berthing switching of the ship to be switched and offshore switching of the ship to be switched.

[0009] In a possible implementation, performing flexible switching according to a relationship between the first ratio, the second ratio, and a preset proportion threshold and a switching type includes:

[0010] If the switching type is a berthing switch of the ship to be switched, the proportion threshold is 90%, and if the first proportion is greater than or equal to 90% and the second proportion is greater than or equal to 90%, the flexible switching is completed; or,

[0011] If the switching type is offshore switching of the ship to be switched, the proportion threshold is 10%, and if the first proportion is less than or equal to 10% and the second proportion is less than or equal to 10%, the flexible switching is completed.

[0012] In another possible implementation, the pf formula includes: Among them, P m is the input mechanical power, P e is the electromagnetic power, P ref is the VSG power reference value, m is the frequency modulation coefficient, J is the inertia coefficient, D is the damping coefficient, ω n is the grid synchronization angular velocity, δ is the power angle;

[0013] From formula (5), we can further obtain:

[0014]

[0015] in:

[0016]

[0017] The slope of the Pf curve can be adjusted by changing the parameters D and m in formula (7):

[0018] m i =(kd ) i m0,i=1,2,3.... (8)

[0019] In formula (8), the frequency modulation coefficient m i Take m0 as the initial value and k d The multiple increases or decreases to achieve automatic adjustment of the slope of the Pf curve. It can be seen from formula (7) that the dynamic characteristics of VSG are jointly affected by m, D and J. The coefficient J is adaptively adjusted. Since the coefficient m is much larger than Dω0, the inertia coefficient J is adaptively adjusted according to formula (9) to keep the dynamic characteristics of the shore power supply output basically unchanged, thereby improving the stability of the parallel system. Let:

[0020] J i =(k d ) i J0,i=1,2,3.... (9)

[0021] In formula (9), J0 is the initial inertia coefficient.

[0022] In a second aspect, a system for flexible switching of ship shore power is provided, the system comprising:

[0023] An acquisition module is used to obtain the output frequency f and output voltage U of the shore power supply in real time;

[0024] A ratio acquisition module, used to acquire a first ratio according to the output frequency and a preset pf formula, and acquire a second ratio according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, Q is the reactive power of the shore power supply, the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched, and the pf formula and the QU formula are preset formulas according to the virtual synchronous motor VSG strategy;

[0025] The flexible switching module is used to perform flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and the switching type includes: berthing switching of the ship to be switched and offshore switching of the ship to be switched.

[0026] In a possible implementation, performing flexible switching according to a relationship between the first ratio, the second ratio, and a preset proportion threshold and a switching type includes:

[0027] If the switching type is a berthing switch of the ship to be switched, the proportion threshold is 90%, and if the first proportion is greater than or equal to 90% and the second proportion is greater than or equal to 90%, the flexible switching is completed; or,

[0028] If the switching type is offshore switching of the ship to be switched, the proportion threshold is 10%, and if the first proportion is less than or equal to 10% and the second proportion is less than or equal to 10%, the flexible switching is completed.

[0029] In another possible implementation, the pf formula includes: Among them, P m is the input mechanical power, P e is the electromagnetic power, P ref is the VSG power reference value, m is the frequency modulation coefficient, J is the inertia coefficient, D is the damping coefficient, ω n is the grid synchronization angular velocity, δ is the power angle;

[0030] From formula (5), we can further obtain:

[0031]

[0032] in:

[0033]

[0034] The slope of the Pf curve can be adjusted by changing the parameters D and m in formula (7):

[0035] m i =(k d ) i m0,i=1,2,3.... (8)

[0036] In formula (8), the frequency modulation coefficient m i Take m0 as the initial value and k d The multiple increases or decreases to achieve automatic adjustment of the slope of the Pf curve. It can be seen from formula (7) that the dynamic characteristics of VSG are jointly affected by m, D and J. The coefficient J is adaptively adjusted. Since the coefficient m is much larger than Dω0, the inertia coefficient J is adaptively adjusted according to formula (9) to keep the dynamic characteristics of the shore power supply output basically unchanged, thereby improving the stability of the parallel system. Let:

[0037] J i =(k d ) i J0,i=1,2,3.... (9)

[0038] In formula (9), J0 is the initial inertia coefficient.

[0039] In a third aspect, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for flexible switching of ship shore power provided in the first aspect is implemented.

[0040] In a fourth aspect, a non-transitory computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the method for flexible switching of ship shore power provided in the first aspect is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in describing the embodiments of the present application are briefly introduced below.

[0042] Figure 1 A flow chart of a method for flexible switching of ship shore power provided by an embodiment of the present invention;

[0043] Figure 2 A structural diagram of a system for flexible switching of ship shore power provided by yet another embodiment of the present invention;

[0044] Figure 3 A schematic diagram of the physical structure of an electronic device of the present invention;

[0045] Figure 4a , b is a schematic diagram of relevant parameters during the process of the ship docking of the present invention;

[0046] Figure 5a , b is a schematic diagram of relevant parameters during the process of the ship leaving the shore of the present invention;

[0047] Figure 6a -f is a schematic diagram of the simulation results of load transfer during the ship docking process;

[0048] Figure 7a -f is a schematic diagram of the load transfer simulation results during the ship's departure.

[0049] Specific implementation method

[0050] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar modules or modules with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present invention.

[0051] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, modules and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, modules, components and / or groups thereof. It should be understood that when we refer to a module as being "connected" or "coupled" to another module, it may be directly connected or coupled to the other modules, or there may be intermediate modules. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The term "and / or" used herein includes all or any modules and all combinations of one or more associated listed items.

[0052] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation method of the present application will be further described in detail below in conjunction with the accompanying drawings.

[0053] The technical solution of the present application and how to solve the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0054] like Figure 1 The flowchart of a method for flexible switching of ship shore power provided by an embodiment of the present invention is shown, which is applied to shore power supply, and the method includes:

[0055] Step 101, obtaining the output frequency f and output voltage U of the shore power supply in real time;

[0056] Step 102, obtaining a first ratio according to the output frequency and a preset pf formula, and obtaining a second ratio according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, Q is the reactive power of the shore power supply, the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched, and the pf formula and the QU formula are formulas preset according to the virtual synchronous motor VSG strategy;

[0057] Step 103, performing flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, wherein the switching type includes: berthing switching of the ship to be switched and offshore switching of the ship to be switched.

[0058] In an embodiment of the present invention, the shore power supply is provided with a pf formula and a QU formula according to a VSG (Virtual Synchronous Generator) strategy, and the switching device obtains the output frequency f and the output voltage U of the shore power supply in real time, and substitutes the output frequency f into the pf formula to obtain the first ratio, and substitutes the output voltage U into the QU formula to obtain the second ratio, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply, and the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched. The first ratio and the second ratio are respectively compared with the preset proportion threshold, and at the same time, combined with the switching type, it is determined whether the flexible switching is completed, wherein the switching type includes: switching when the ship to be switched is berthed and switching when the ship to be switched is offshore.

[0059] The flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type includes:

[0060] If the switching type is a berthing switch of the ship to be switched, the proportion threshold is 90%, and if the first proportion is greater than or equal to 90% and the second proportion is greater than or equal to 90%, the flexible switching is completed; or,

[0061] If the switching type is offshore switching of the ship to be switched, the proportion threshold is 10%, and if the first proportion is less than or equal to 10% and the second proportion is less than or equal to 10%, the flexible switching is completed.

[0062] In the embodiment of the present invention, for the berthing switching of the ship to be switched, during the berthing process, the shore power supply gradually replaces the ship generator for power supply, so the proportion of the shore power supply will gradually increase, so the proportion threshold is set to 90%, and when the shore power supply is greater than or equal to 90%, the berthing switching is completed. On the contrary, if it is an offshore switching, during the offshore process, the ship generator gradually replaces the shore power supply for power supply, so the proportion of the shore power supply will decrease, so the proportion threshold is set to 10%, and when the shore power supply is less than or equal to 10%, the offshore switching is completed.

[0063] Wherein, the pf formula includes: Among them, P m is the input mechanical power, P e is the electromagnetic power, P ref is the VSG power reference value, m is the frequency modulation coefficient, J is the inertia coefficient, D is the damping coefficient, ω n is the grid synchronization angular velocity, δ is the power angle;

[0064] From formula (5), we can further obtain:

[0065]

[0066] in:

[0067]

[0068] The slope of the Pf curve can be adjusted by changing the parameters D and m in formula (7):

[0069] m i =(k d ) i m0,i=1,2,3.... (8)

[0070] In formula (8), the frequency modulation coefficient m i Take m0 as the initial value and k d The multiple increases or decreases to achieve automatic adjustment of the slope of the Pf curve. It can be seen from formula (7) that the dynamic characteristics of VSG are jointly affected by m, D and J. The coefficient J is adaptively adjusted. Since the coefficient m is much larger than Dω0, the inertia coefficient J is adaptively adjusted according to formula (9) to keep the dynamic characteristics of the shore power supply output basically unchanged, thereby improving the stability of the parallel system. Let:

[0071] J i =(k d ) i J0,i=1,2,3.... (9)

[0072] In formula (9), J0 is the initial inertia coefficient.

[0073] In the embodiment of the present invention, the output frequency f and output voltage U of the shore power supply are obtained in real time; the first ratio is obtained according to the output frequency and the preset pf formula, and the second ratio is obtained according to the output voltage and the preset QU formula; flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold value and the switching type. In the flexible switching process, the relevant operations and switching process are completed by the shore power supply, which reduces the operation of the ship personnel. At the same time, in the ship-shore power switching process, it is not necessary to obtain parameters such as the size of the ship load and the droop coefficient of the ship generator, which reduces the communication requirements during the switching process.

[0074] like Figure 2 The figure shows a structural diagram of a system for flexible switching of ship shore power provided by an embodiment of the present invention. The system is applied to shore power supply, and the system includes:

[0075] An acquisition module 201 is used to acquire the output frequency f and output voltage U of the shore power supply in real time;

[0076] The ratio acquisition module 202 is used to acquire a first ratio according to the output frequency and a preset pf formula, and acquire a second ratio according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply. The first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched. The pf formula and the QU formula are preset formulas according to the virtual synchronous motor VSG strategy;

[0077] The flexible switching module 203 is used to perform flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and the switching type includes: berthing switching of the ship to be switched and offshore switching of the ship to be switched.

[0078] In an embodiment of the present invention, the shore power supply is provided with a pf formula and a QU formula according to a VSG (Virtual Synchronous Generator) strategy, and the switching device obtains the output frequency f and the output voltage U of the shore power supply in real time, and substitutes the output frequency f into the pf formula to obtain the first ratio, and substitutes the output voltage U into the QU formula to obtain the second ratio, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply, and the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched. The first ratio and the second ratio are respectively compared with the preset proportion threshold, and at the same time, combined with the switching type, it is determined whether the flexible switching is completed, wherein the switching type includes: switching when the ship to be switched is berthed and switching when the ship to be switched is offshore.

[0079] The flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type includes:

[0080] If the switching type is a berthing switch of the ship to be switched, the proportion threshold is 90%, and if the first proportion is greater than or equal to 90% and the second proportion is greater than or equal to 90%, the flexible switching is completed; or,

[0081] If the switching type is offshore switching of the ship to be switched, the proportion threshold is 10%, and if the first proportion is less than or equal to 10% and the second proportion is less than or equal to 10%, the flexible switching is completed.

[0082] In the embodiment of the present invention, for the berthing switching of the ship to be switched, during the berthing process, the shore power supply gradually replaces the ship generator for power supply, so the proportion of the shore power supply will gradually increase, so the proportion threshold is set to 90%, and when the shore power supply is greater than or equal to 90%, the berthing switching is completed. On the contrary, if it is an offshore switching, during the offshore process, the ship generator gradually replaces the shore power supply for power supply, so the proportion of the shore power supply will decrease, so the proportion threshold is set to 10%, and when the shore power supply is less than or equal to 10%, the offshore switching is completed.

[0083] Wherein, the pf formula includes: Among them, P m is the input mechanical power, P e is the electromagnetic power, P ref is the VSG power reference value, m is the frequency modulation coefficient, J is the inertia coefficient, D is the damping coefficient, ω n is the grid synchronization angular velocity, δ is the power angle;

[0084] From formula (5), we can further obtain:

[0085]

[0086] in:

[0087]

[0088] The slope of the Pf curve can be adjusted by changing the parameters D and m in formula (7):

[0089] m i =(k d ) i m0,i=1,2,3.... (8)

[0090] In formula (8), the frequency modulation coefficient m i Take m0 as the initial value and k d The multiple increases or decreases to achieve automatic adjustment of the slope of the Pf curve. It can be seen from formula (7) that the dynamic characteristics of VSG are jointly affected by m, D and J. The coefficient J is adaptively adjusted. Since the coefficient m is much larger than Dω0, the inertia coefficient J is adaptively adjusted according to formula (9) to keep the dynamic characteristics of the shore power supply output basically unchanged, thereby improving the stability of the parallel system. Let:

[0091] J i =(k d ) i J0,i=1,2,3.... (9)

[0092] In formula (9), J0 is the initial inertia coefficient.

[0093] In the embodiment of the present invention, the output frequency f and output voltage U of the shore power supply are obtained in real time; the first ratio is obtained according to the output frequency and the preset pf formula, and the second ratio is obtained according to the output voltage and the preset QU formula; flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold value and the switching type. In the flexible switching process, the relevant operations and switching process are completed by the shore power supply, which reduces the operation of the ship personnel. At the same time, in the ship-shore power switching process, it is not necessary to obtain parameters such as the size of the ship load and the droop coefficient of the ship generator, which reduces the communication requirements during the switching process.

[0094] Figure 3 An example of a physical structure diagram of an electronic device is shown in FIG. Figure 3 As shown, the electronic device may include: a processor 301, a communication interface 302, a memory 303 and a communication bus 304, wherein the processor, the communication interface and the memory communicate with each other through the communication bus. The processor may call the logic instructions in the memory to execute the method for flexible switching of ship shore power, the method comprising: obtaining the output frequency f and output voltage U of the shore power supply in real time; obtaining the first ratio according to the output frequency and the preset pf formula, and obtaining the second ratio according to the output voltage and the preset QU formula, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply, the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched, and the pf formula and the QU formula are preset formulas according to the virtual synchronous motor VSG strategy; flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and the switching type includes: switching when the ship to be switched is berthed and switching when the ship to be switched is offshore.

[0095] In addition, the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0096] On the other hand, an embodiment of the present invention further provides a computer program product, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, when the program instructions are executed by a computer, the computer can execute the method for flexible switching of ship shore power provided by the above-mentioned method embodiments, the method comprising: obtaining the output frequency f and output voltage U of the shore power supply in real time; obtaining a first ratio according to the output frequency and a preset pf formula, and obtaining a second ratio according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply, the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched, and the pf formula and the QU formula are preset formulas according to the virtual synchronous motor VSG strategy; flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and the switching type includes: berthing switching of the ship to be switched and offshore switching of the ship to be switched.

[0097] On the other hand, an embodiment of the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the processor executes the method for flexible switching of ship shore power provided in the above embodiments, the method comprising: obtaining the output frequency f and output voltage U of the shore power supply in real time; obtaining a first ratio according to the output frequency and a preset pf formula, and obtaining a second ratio according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply, the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched, and the pf formula and the QU formula are formulas preset according to the virtual synchronous motor VSG strategy; flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and the switching type includes: switching when the ship to be switched is berthed and switching when the ship to be switched is offshore.

[0098] As shown in Figures 4(a) and 4(b), schematic diagrams of the relevant parameters of the ship during the berthing process of the present invention are shown. When the ship is berthing, f0 and U0 are the frequency and output voltage of the shore power and the generator when they are not loaded; f1 and U1 are the frequency and voltage of the ship generator output before grid connection; f4 and U4 are the frequency and voltage of the system when the ship generator is cut off; P r and Q r Indicates the ship load size. In Figure 4(a), curve ① is the generator Pf droop characteristic curve, and curve ② is the shore power Pf droop characteristic curve after the pre-synchronization process is completed.

[0099] When the ship is at port, the ship generator is loaded and runs at point A1. Its initial frequency f1 before grid connection is slightly lower than 50Hz. The shore power supply runs at point B1 without load. Its output power is zero and the frequency is f0=50Hz. At a certain moment, after the shore power supply is connected to the ship generator through pre-synchronization control, the ship load begins to transfer to the shore power supply. By increasing the slope (negative value) of the shore power supply Pf droop curve, the shore power output characteristic is raised from curve ② to curve ③. The system frequency f2 does not suddenly change at the moment when the Pf curve rises. The shore power active "output" begins to increase gradually, the system frequency gradually rises, and the ship generator active "output" gradually decreases. In this process, the sum of the shore power and the generator power is always equal to the total load size. Finally, the shore power runs stably at point E1 from D1, the generator runs stably at point F1 from C1, and the system frequency rises from f2 to f3. Similarly, by continuously raising the slope of the shore power characteristic curve, the shore power active "output" is continuously increased, the system frequency rises, and the generator active "output" is continuously reduced. When the generator power drops below 10%, the shore power must stop increasing the active power in time to avoid causing reverse power to the generator. Taking the shore power curve raised to curve ④ as an example, after stabilization, the shore power and the generator run at points H1 and G1 respectively. At this time, the system frequency rises to f4. According to the similar triangles ΔA1B1J1 and ΔA1G1K1 in the shaded part of the figure, there is a relationship shown in formula (1).

[0100]

[0101] From formula (1), we can get the proportion of active power output by the generator as

[0102]

[0103] Therefore, when λ≤10% is obtained by detecting the system frequency, it can be determined that the active power ratio borne by the generator has dropped below 10%, and at this time the shore power active power no longer increases.

[0104] Curve ⑤ in Figure 4(b) is the QU droop characteristic curve of the generator, and curve ⑥ is the QU droop characteristic curve of the shore power after the pre-synchronization process is completed. The reactive power transfer process between the ship and the shore is similar to the active power transfer process. When the ship is docked, the generator is loaded and operated at point A2. The system voltage value U1 before grid connection is slightly lower than 400V, and the shore power supply is no-loaded and operated at point B2, with an output voltage U0 = 400V. After the shore power is pre-synchronized and grid-connected with the ship generator, the slope of the shore power supply QU curve is increased, so that the shore power output characteristic is raised from curve ⑥ to curve ⑦. The system voltage U2 does not suddenly change at the moment when the QU curve rises. The shore power reactive "output" begins to increase, the system voltage gradually rises, and the generator reactive "output" gradually decreases. Finally, the shore power runs stably from D2 to point E2, the generator runs stably from C2 to point F2, and the system voltage rises from U2 to U3. Similarly, by continuously raising the slope of the QU curve, the shore power reactive power will continue to increase, the system voltage will rise, and the generator output reactive power will continue to decrease. When the generator reactive power drops below 10%, the shore power stops increasing the reactive power. Taking the shore power curve as an example, when it rises to curve ⑧, the shore power and the generator run at points H2 and G2 respectively after stabilization. At this time, the voltage rises to U4. According to the similar triangles ΔA2B2J2 and ΔA2G2K2 in the shaded part of the figure, there is a relationship as shown in formula (3).

[0105]

[0106] Further, the proportion of reactive power output by the generator is

[0107]

[0108] Therefore, when η≤10% is calculated by detecting the system voltage, it can be judged that the reactive power ratio of the generator has dropped below 10%, and the reactive power output of the shore power supply will no longer increase. When λ≤10% and η≤10% are met at the same time, the generator is cut off, and the shore power is used to supply power to the ship load alone. There is no need to know the ship load size information during the switching process, which reduces the communication requirements.

[0109] As shown in Figure 5 (a) and Figure 5 (b), it is a schematic diagram of the relevant parameters of the ship's departure process of the present invention. When the ship leaves the port, similar to the load transfer process when docking, the shore power supply also automatically adjusts the slope of the droop curve and continuously changes the power distribution ratio with the generator to complete the transfer of the ship's side load. In Figure 5 (a), curve ① is the generator Pf characteristic curve, and curve ② is the initial Pf characteristic curve of the shore power supply. Before grid connection, the generator runs at point A1 without load, and the shore power runs at point B1 with load. At this time, the frequency difference between the two is very small. After pre-synchronization, the generator and the shore power supply are connected to the grid. Similar to the load transfer principle when the ship docks, when leaving the port, by reducing the slope of the shore power Pf droop curve (negative value), the shore power output characteristic is reduced from curve ② to curve ③, the shore power reduces the active "output" to make f gradually decrease, and the generator active "output" increases. After stabilization, the shore power and the generator run at points E1 and F1 respectively, and the steady-state operation point always satisfies that the sum of the output power of the generator and the shore power is equal to the total size of the ship's load. Similarly, by continuously reducing the slope of the shore power Pf droop curve, the system frequency decreases after each stabilization, the shore power output active "output" decreases, and the generator active "output" increases. Finally, when Pk≤10%Pr is detected, the shore power active power is no longer reduced. The reactive power transfer principle in Figure 5(b) is similar to the active power transfer. By continuously reducing the slope of the shore power QU curve, the shore power reactive power is continuously reduced. When Qk≤10%Qr is detected, it means that the shore power reactive power has met the cut-off condition. From the above analysis, it can be seen that in the final stage of load transfer when the ship is docked and leaving the port, since the slopes of the Pf and QU droop curves of the shore power always remain negative, the steady-state operating points of the shore power and the generator are always in the first quadrant. Therefore, the load transfer strategy in the present invention theoretically will not cause reverse power to the generator and the shore power.

[0110] As shown in Figure 6 (af), it is a schematic diagram of the load transfer simulation results during the ship's berthing process. After the shore power is connected to the ship's power grid, the shore power output power increases step by step at t = 0.5s, 1.5s and 2.5s, respectively, and the generator output power decreases step by step. The voltage and frequency of the system also increase step by step at the corresponding time. As shown in Figure 6 (b) and (d), the generator frequency is 49.5Hz and the voltage is 386V before the grid connection. When the shore power is increased for the third time and reaches stability, that is, at t = 3.5s, the system frequency and voltage amplitude are 49.97Hz and 399.2V respectively. By calculation, the indicators λ = 1-(49.97-49.5) / (50-49.5) = 6% < 10%, η = 1-(399.2-386) / (400-386) = 5.7% < 10%, which can be judged that the generator power drops below 10% and can be cut off. The system frequency and voltage curves obtained by simulation are consistent with the predicted curves.

[0111] Compared with the actual measured value of power, the actual measured value of the output active power ratio before the generator stopped running was 30 / 500=6%, and the actual measured value of the output reactive power ratio was 26 / 375=6.9%, which is approximately equal to the value calculated by detecting the system frequency and voltage. The error may be caused by a certain power coupling on the generator side, but it is within the allowable range. The entire load transfer process is smooth and impact-free, with no obvious reverse power phenomenon. Only at the moment of generator removal, the system voltage and frequency have a sudden change, and the transient mutation is less than 5%, which meets the standard requirements.

[0112] As shown in Figure 7 (af), it is a schematic diagram of the simulation results of load transfer during the ship's departure process. After the shore power is connected to the ship generator, the shore power power is gradually reduced at t = 0.5s and 1.5s, and the generator power is gradually increased. The system frequency and voltage are stepped down within the standard allowable range, which is consistent with the theoretical analysis. When the shore power output power is increased for the second time and reaches stability, that is, at t = 3s, the shore power detects that its output active power accounts for 35 / 500 = 7%, and the reactive power accounts for 30 / 375 = 8%. The shore power is cut off, and the frequency and voltage fluctuations at the moment of cutting off are small, which meets the standard requirements. Since the values ​​of kd and kg are small when leaving the port, the slope of the shore power droop curve is adjusted quickly. After two times, the ship load can be transferred from the shore power to the ship generator. From the simulation results of berthing and leaving the port, it can be seen that although the number of load transfers is different, the smoothness of the transfer process is good and the impact is small.

[0113] It should be understood that, although the steps in the flowchart of the accompanying drawings are displayed in sequence as indicated by the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least a part of the steps in the flowchart of the accompanying drawings may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps.

[0114] The above is only a partial implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for flexible switching of ship shore power, characterized in that: The method comprises: Obtain the output frequency f and output voltage U of the shore power supply in real time; A first ratio is obtained according to the output frequency and a preset pf formula, and a second ratio is obtained according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply. The first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched. The pf formula and the QU formula are preset formulas according to the virtual synchronous motor VSG strategy; Perform flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, wherein the switching type includes: switching when the ship to be switched is berthed and switching when the ship to be switched is offshore; The flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and further includes: If the switching type is a berthing switch of the ship to be switched, the proportion threshold is 90%, and if the first proportion is greater than or equal to 90% and the second proportion is greater than or equal to 90%, the flexible switching is completed; The pf formula includes: Among them, P m is the input mechanical power, P e is the electromagnetic power, P ref is the VSG power reference value, m is the frequency modulation coefficient, J is the inertia coefficient, D is the damping coefficient, ω n is the grid synchronization angular velocity, δ is the power angle; From formula (5), we can further obtain: in:

2. The method according to claim 1, characterized in that The flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and further includes: If the switching type is offshore switching of the ship to be switched, the proportion threshold is 10%, and if the first proportion is less than or equal to 10% and the second proportion is less than or equal to 10%, the flexible switching is completed.

3. The method according to claim 1, characterized in that The slope of the Pf curve can be adjusted by changing the parameters D and m in formula (7): m i =(k d ) i m0,i=1,2,3.... (8) In formula (8), the frequency modulation coefficient m i Take m0 as the initial value and k d The multiple increases or decreases to achieve automatic adjustment of the slope of the Pf curve; it can be seen from formula (7) that the dynamic characteristics of VSG are jointly affected by m, D and J. The coefficient J is adaptively adjusted. Since the coefficient m is much larger than Dω0, the inertia coefficient J is adaptively adjusted according to formula (9) to keep the dynamic characteristics of the shore power supply output basically unchanged, thereby improving the stability of the parallel system. Let: J i =(k d ) i J0,i=1,2,3.... (9) In formula (9), J0 is the initial inertia coefficient.

4. A system for flexible switching of ship shore power, characterized in that: The system comprises: An acquisition module is used to obtain the output frequency f and output voltage U of the shore power supply in real time; a ratio acquisition module, configured to acquire a first ratio according to the output frequency and a preset pf formula, and acquire a second ratio according to the output voltage and a preset QU formula, wherein p is the active power of the shore power supply, and Q is the reactive power of the shore power supply, wherein the first ratio is the ratio of the output power of the shore power supply to the total load of the ship to be switched, and the second ratio is the ratio of the reactive power of the shore power supply to the total load of the ship to be switched, and the pf formula and the QU formula are preset formulas according to the virtual synchronous motor VSG strategy; A flexible switching module, configured to perform flexible switching according to the relationship between the first ratio, the second ratio and a preset proportion threshold value and a switching type, wherein the switching type includes: berthing switching of the ship to be switched and offshore switching of the ship to be switched; The performing flexible switching according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type includes: If the switching type is a berthing switch of the ship to be switched, the proportion threshold is 90%, and if the first proportion is greater than or equal to 90% and the second proportion is greater than or equal to 90%, the flexible switching is completed; The pf formula includes: Among them, P m is the input mechanical power, P e is the electromagnetic power, P ref is the VSG power reference value, m is the frequency modulation coefficient, J is the inertia coefficient, D is the damping coefficient, ω n is the grid synchronization angular velocity, δ is the power angle; From formula (5), we can further obtain: in:

5. The system according to claim 4, characterized in that The flexible switching is performed according to the relationship between the first ratio, the second ratio and the preset proportion threshold and the switching type, and further includes: If the switching type is offshore switching of the ship to be switched, the proportion threshold is 10%, and if the first proportion is less than or equal to 10% and the second proportion is less than or equal to 10%, the flexible switching is completed.

6. The system according to claim 4, characterized in that The slope of the Pf curve can be adjusted by changing the parameters D and m in formula (7): m i =(k d ) i m0,i=1,2,3.... (8) In formula (8), the frequency modulation coefficient m i Take m0 as the initial value and k d The multiple increases or decreases to achieve automatic adjustment of the slope of the Pf curve; it can be seen from formula (7) that the dynamic characteristics of VSG are jointly affected by m, D and J. The coefficient J is adaptively adjusted. Since the coefficient m is much larger than Dω0, the inertia coefficient J is adaptively adjusted according to formula (9) to keep the dynamic characteristics of the shore power supply output basically unchanged, thereby improving the stability of the parallel system. Let: J i =(k d ) i J0,i=1,2,3.... (9) In formula (9), J0 is the initial inertia coefficient.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method for flexible switching of ship shore power as described in any one of claims 1-3 is implemented.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for flexible switching of ship shore power as described in any one of claims 1 to 3 is implemented.

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