Power Switching Control Method, Control Device and Storage Medium

Abstract

The present invention provides a power supply switching control method, a control device and a storage medium. The method is applied to a microgrid system, which includes a power conversion system (PCS) for energy storage, a diesel generator and a load. The PCS is connected to the load, and the diesel generator is connected to the load through a switch. The method includes: collecting the current output value of the PCS; after the switch is closed, reducing the current output value of the PCS according to a preset strategy until the output power of the PCS is zero. The present invention can achieve smooth switching of power during the process of switching the main power supply in the microgrid from the PCS to the diesel generator, and avoid sudden application of excessive load to the diesel generator.

Description

Technical Field

[0001] The present invention relates to the technical field of power control, and in particular, to a power supply switching control method, a control device, and a storage medium. Background Art

[0002] Due to economic problems such as the capacity and cost limitations of energy storage systems and the fuel consumption of diesel generators, a microgrid is usually configured with a PCS (Power Conversion System, energy storage converter) and a diesel generator as backups for each other. When the PCS switches from off-grid to on-grid, the working mode of the PCS switches to the PQ mode. The PCS cannot carry a load in the PQ mode, and only the diesel generator can supply power to the load of the PCS. However, the diesel generator cannot fully bear all the loads of the PCS under the condition of suddenly adding a load, resulting in an inability to smoothly switch and control between the two power supply modes and poor stability of the microgrid. Summary of the Invention

[0003] In view of this, the present invention provides a power supply switching control method, a control device, and a storage medium, which can solve the problem of poor grid stability during the power supply switching process of the microgrid.

[0004] In a first aspect, an embodiment of the present invention provides a power supply switching control method, which is applied to a microgrid system. The system includes an energy storage converter PCS, a diesel generator, and a load. The PCS is connected to the load, and the diesel generator is connected to the load through a switch. The method includes:

[0005] Collect the current output value of the PCS;

[0006] After the switch is closed, reduce the current output value of the PCS according to a preset strategy until the output power of the PCS is zero.

[0007] In a possible implementation manner, reducing the current output value of the PCS according to the preset strategy includes:

[0008] Control the current slope of the PCS current loop so that the current output value of the PCS decreases according to the current slope.

[0009] In a possible implementation manner, the method further includes:

[0010] Obtain the remaining energy storage capacity of the PCS;

[0011] Obtain the power of the PCS and the current power of the diesel generator before the switch is closed;

[0012] Adjust the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed.

[0013] In a possible implementation manner, the adjusting the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed includes:

[0014] If the remaining energy storage capacity of the PCS is less than the preset capacity, and the difference between the power of the PCS before the switch is closed and the increased power of the diesel generator after the switch is closed is less than or equal to the preset value, increase the current slope.

[0015] In a possible implementation manner, before closing the switch, the method further includes:

[0016] Control the output voltage of the diesel generator to be the same as the voltage of the PCS.

[0017] In a second aspect, an embodiment of the present invention provides a power supply switching control device, which is applied to a microgrid system. The system includes a power conversion system (PCS), a diesel generator, and a load. The PCS is connected to the load, and the diesel generator is connected to the load through a switch. The device includes: a collection module and a control module;

[0018] The collection module is configured to collect the current output value of the PCS;

[0019] The control module is configured to, after the switch is closed, reduce the current output value of the PCS according to a preset strategy until the output power of the PCS is zero.

[0020] In a possible implementation manner, the control device is configured to:

[0021] Control the current slope of the PCS current loop so that the current output value of the PCS decreases according to the current slope.

[0022] In a possible implementation manner, the control device is configured to:

[0023] Obtain the remaining energy storage capacity of the PCS;

[0024] Obtain the power of the PCS before the switch is closed and the current power of the diesel generator;

[0025] Adjust the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed.

[0026] In a third aspect, an embodiment of the present invention provides a control device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method described in the first aspect above or any possible implementation manner of the first aspect are implemented.

[0027] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the method described in the first aspect above or any possible implementation manner of the first aspect are implemented.

[0028] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows:

[0029] During the process of switching the main power supply in the microgrid from the PCS to the diesel generator, in the embodiment of the present invention, by controlling the output current of the PCS to gradually decrease to 0, the power of the PCS gradually decreases to 0, and the power of the diesel generator gradually increases to the power required by the load. The present invention can achieve smooth power switching during the process of switching the main power supply in the microgrid from the PCS to the diesel generator, and avoid sudden excessive loading of the diesel generator. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a flowchart of the implementation of the power supply switching control method provided by the embodiment of the present invention;

[0032] Figure 2 It is a schematic structural diagram of the power supply switching control device provided by the embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of the control device provided by the embodiment of the present invention. Detailed Embodiments

[0034] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described through specific embodiments with reference to the accompanying drawings.

[0036] Refer to Figure 1 , which shows the implementation flowchart of the power supply switching control method provided by the embodiments of the present invention, and is described in detail as follows:

[0037] In step 101, the current output value of the PCS is collected.

[0038] The dual-power supply mode of PCS power supply and diesel generator power supply is a common mode in microgrid power supply. When the diesel generator is under low load, the energy utilization rate is low, while the battery energy storage system has high efficiency and stable operating conditions under low load. Therefore, in some application scenarios, the battery energy storage system supplies power under low load, and switches to diesel generator power supply when the load is high, which can improve the energy utilization rate of the power grid. In some other application scenarios, due to some reasons, the PCS needs to switch from the off-grid mode to the grid-connected mode. At this time, the diesel generator replaces the PCS as the main power supply to supply power to the load.

[0039] During off-grid discharging, the PCS usually adopts the Vf control strategy of voltage / current double closed-loop control. This control strategy controls the PCS with the output voltage and frequency commands, playing a role in supporting the voltage and frequency in the microgrid.

[0040] When the energy storage system supplies power to the load alone, the energy storage inverter operates in the Vf mode; when the diesel generator supplies power, the energy storage inverter operates in the PQ current source mode. When the PCS switches from the Vf mode to the PQ mode, the load on the diesel generator side suddenly increases, which will cause the sudden increase in torque of the diesel generator to be too large and damage its bearings. Therefore, the diesel generator side cannot suddenly add an excessive load. To solve this technical problem, the embodiments of the present invention provide a power supply switching control method for controlling the power supply switching between the PCS and the diesel generator, which can make the output power of the PCS slowly decrease when the PCS switches from the Vf operating mode to the PQ operating mode, that is, realize the smooth switching of power between the two power supplies.

[0041] The method provided by the embodiments of the present invention is applied to a microgrid system, which includes a power conversion system (PCS) for energy storage, a diesel generator, and a load. The PCS is connected to the load, and the diesel generator is connected to the load through a switch.

[0042] When the main power supply in the microgrid needs to be switched from the PCS to the diesel generator, for example, when the load is large and the energy storage system capacity is insufficient, the diesel generator is controlled to start without load. The diesel generator adopts speed closed-loop control to make the amplitude and frequency of the output no-load voltage constant. In the no-load condition, the diesel generator can be equivalent to a voltage source. To achieve non-impact grid connection, in one possible implementation, before closing the switch, the output voltage of the diesel generator is controlled to be the same as the voltage of the PCS.

[0043] In step 102, after the switch is closed, the current output value of the PCS is decreased according to a preset strategy until the output power of the PCS is zero.

[0044] In the embodiment of the present invention, after the switch is closed, to prevent the active power of the diesel generator from increasing sharply and to protect the bearings of the diesel generator, the power of the PCS should be smoothly transferred to the diesel generator, that is, to achieve smooth power switching in the microgrid system. If the voltage outer loop and current inner loop of the PCS are simultaneously switched to the PQ mode, it will cause the power of the PCS to suddenly become zero and the diesel generator to suddenly add a large amount of load, exceeding the ability of the diesel generator to suddenly add load, which will also damage the diesel generator.

[0045] Therefore, in the embodiment of the present invention, after the switch is closed, the current slope of the PCS current loop is controlled so that the current output value of the PCS decreases according to the current slope. Due to the effect of current loop integration, the output voltage of the PCS will not change suddenly, thus realizing the smooth reduction of the PCS power to zero.

[0046] The larger the current slope, the faster the current of the PCS decreases to zero, and the faster the main power supply is smoothly switched from the PCS to the diesel generator.

[0047] Furthermore, since the diesel generator has a certain ability to suddenly add load, for example, if the power of the load before switching is 300 kw, the diesel generator can suddenly add 150 kw of load without damaging the diesel generator. Based on this, the method provided by the embodiment of the present invention further includes:

[0048] Obtain the remaining energy storage capacity of the PCS;

[0049] Obtain the power of the PCS before the switch is closed and the current power of the diesel generator;

[0050] Adjust the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed.

[0051] In a possible implementation, if the remaining energy storage capacity of the PCS is less than the preset capacity, and the difference between the power of the PCS before the switch is closed and the increased power of the diesel generator after the switch is closed is less than or equal to the preset value, the current slope is increased.

[0052] In the embodiment of the present invention, the energy storage capacity of the PCS refers to the energy storage capacity of the energy storage battery controlled by the PCS. When the PCS is connected to the grid, the PCS is equivalent to a current source, and the energy storage battery is charged. When the PCS is off-grid, the PCS is equivalent to a voltage source, and the energy is released from the energy storage battery to supply power to the load.

[0053] Through the method provided by the embodiment of the present invention, if the remaining energy storage capacity of the PCS is less than the preset capacity, and the remaining load power is within the range of the sudden load power that the diesel generator can bear, the current slope can be increased to accelerate the speed at which the input current of the PCS becomes 0.

[0054] For example, before the switch, the power borne by the PCS is 300 kw. Through the method provided by the embodiment of the present invention, the output current of the PCS gradually decreases after the switch is closed, that is, the output power gradually decreases, and the output power of the diesel generator gradually increases. When the increased power of the diesel generator increases to 200 kw, the load that still needs to be borne by the diesel generator is 100 kw. Assuming that the sudden load that the diesel generator can bear is 150 kw and the remaining energy storage capacity of the PCS is small at this time, the current slope can be increased to accelerate the speed at which the output power of the PCS becomes 0, and the diesel generator quickly bears the remaining load power.

[0055] During the process of switching the main power supply in the microgrid from the PCS to the diesel generator, the embodiment of the present invention controls the output current of the PCS to gradually decrease to 0, so that the power of the PCS gradually decreases to 0, and the power of the diesel generator gradually increases to the power required by the load. The present invention can realize the smooth switching of power during the process of switching the main power supply in the microgrid from the PCS to the diesel generator, and avoid the diesel generator from suddenly adding excessive load.

[0056] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0057] The following is an apparatus embodiment of the present invention. For details not described in detail, reference can be made to the corresponding method embodiments above.

[0058] Figure 2 The structural schematic diagram of the power supply switching control device provided by the embodiment of the present invention is shown. For the sake of convenience of description, only the parts related to the embodiment of the present invention are shown and are described in detail as follows:

[0059] AsFigure 2 As shown in Figure 2 , the power supply switching control device 2 includes: an acquisition module 21 and a control module 22;

[0060] The acquisition module 21 is used to acquire the current output value of the PCS;

[0061] The control module 22 is used to, after the switch is closed, reduce the current output value of the PCS according to a preset strategy until the output power of the PCS is zero.

[0062] During the process of switching the main power supply in the microgrid from the PCS to the diesel generator, in the embodiment of the present invention, by controlling the output current of the PCS to gradually decrease to 0, the power of the PCS gradually decreases to 0, and the power of the diesel generator gradually increases to the power required by the load. The present invention can achieve smooth switching of power during the process of switching the main power supply in the microgrid from the PCS to the diesel generator, and avoid the diesel generator suddenly adding an excessive load.

[0063] In a possible implementation manner, the control device 22 is used to:

[0064] Control the current slope of the PCS current loop so that the current output value of the PCS decreases according to the current slope.

[0065] In a possible implementation manner, the control device 22 is used to:

[0066] Obtain the remaining energy storage capacity of the PCS;

[0067] Obtain the power of the PCS before the switch is closed and the current power of the diesel generator;

[0068] Adjust the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed.

[0069] In a possible implementation manner, the control device 22 is further used to:

[0070] If the remaining energy storage capacity of the PCS is less than the preset capacity, and the difference between the power of the PCS before the switch is closed and the increased power of the diesel generator after the switch is closed is less than or equal to the preset value, then increase the current slope.

[0071] In a possible implementation manner, the control device 22 is further used to:

[0072] Before closing the switch, control the output voltage of the diesel generator to be the same as the voltage of the PCS.

[0073] The power supply switching control device provided in this embodiment can be used to execute the power supply switching control method embodiment described above. Its implementation principle and technical effect are similar, and will not be elaborated here in this embodiment.

[0074] Figure 3 is a schematic diagram of a control device provided by an embodiment of the present invention. As Figure 3 shown, the control device 3 of this embodiment includes: a processor 30, a memory 31, and a computer program 32 stored in the memory 31 and executable on the processor 30. When the processor 30 executes the computer program 32, the steps in the above-mentioned embodiments of each power switching control method are implemented, such as Figure 1 the steps 201 to 102 shown. Alternatively, when the processor 30 executes the computer program 32, the functions of each module / unit in the above-mentioned device embodiments are implemented, such as Figure 2 the functions of the units 21 to 22 shown.

[0075] Exemplarily, the computer program 32 can be divided into one or more modules / units. The one or more modules / units are stored in the memory 31 and executed by the processor 30 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program 32 in the control device 3.

[0076] The control device 3 may include, but is not limited to, a processor 30 and a memory 31. Those skilled in the art can understand that Figure 3 this is only an example of the control device 3 and does not constitute a limitation on the control device 3. It may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the control device may further include input / output devices, network access devices, buses, etc.

[0077] The processor 30 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0078] The memory 31 may be an internal storage unit of the control device 3, such as the hard disk or memory of the control device 3. The memory 31 may also be an external storage device of the control device 3, such as a plug-in hard disk equipped on the control device 3, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Further, the memory 31 may also include both the internal storage unit of the control device 3 and an external storage device. The memory 31 is used to store the computer program and other programs and data required by the control device. The memory 31 may also be used to temporarily store the data that has been output or will be output.

[0079] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be assigned to different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of this application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0080] In the above embodiments, the descriptions of the various embodiments have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0081] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. A professional technician can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0082] In the embodiments provided by the present invention, it should be understood that the disclosed device / control device and method can be implemented in other ways. For example, the device / control device embodiments described above are merely illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical or other forms.

[0083] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0084] In addition, each functional unit in various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0085] If the integrated module / unit is implemented in the form of 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, to implement all or part of the processes in the above method embodiments of the present invention, it can also be completed by a computer program instructing the relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned power supply switching control method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0086] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A power supply switching control method, characterized in that, The method is applied to a microgrid system, which includes a power conversion system (PCS) for energy storage, a diesel generator, and a load. The PCS is connected to the load, and the diesel generator is connected to the load through a switch. The method includes: Collect the current output value of the PCS; After the switch is closed, reduce the current output value of the PCS according to a preset strategy until the output power of the PCS is zero; The reducing the current output value of the PCS according to the preset strategy includes: Control the current slope of the PCS current loop so that the current output value of the PCS decreases according to the current slope; The method further includes: Obtain the remaining energy storage capacity of the PCS; Obtain the power of the PCS before the switch is closed and the current power of the diesel generator; Adjust the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed.

2. The method according to claim 1, characterized in that, The adjusting the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed includes: If the remaining energy storage capacity of the PCS is less than a preset capacity, and the difference between the power of the PCS before the switch is closed and the increased power of the diesel generator after the switch is closed is less than or equal to a preset value, increase the current slope.

3. The method according to claim 1 or 2, characterized in that, Before closing the switch, the method further includes: Control the output voltage of the diesel generator to be the same as the voltage of the PCS.

4. A power supply switching control device, characterized in that, The device is applied to a microgrid system, which includes a power conversion system (PCS) for energy storage, a diesel generator, and a load. The PCS is connected to the load, and the diesel generator is connected to the load through a switch. The device includes: a collection module and a control module; The collection module is used to collect the current output value of the PCS; The control module is used to reduce the current output value of the PCS according to a preset strategy after the switch is closed until the output power of the PCS is zero; The control device is used for: Control the current slope of the PCS current loop so that the current output value of the PCS decreases according to the current slope; The control device is used for: Obtain the remaining energy storage capacity of the PCS; Obtain the power of the PCS before the switch is closed and the current power of the diesel generator; Adjust the current slope according to the remaining energy storage capacity of the PCS, the power of the PCS before the switch is closed, and the increased power of the diesel generator after the switch is closed.

5. A control 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 computer program, it implements the steps of the method according to any one of claims 1 to 3 above.

6. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method according to any one of claims 1 to 3 above.

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