A power control method and device for a wind turbine and an energy storage device for frequency modulation

Abstract

The present invention relates to a method and device for power control of a wind turbine and an energy storage device for frequency modulation, including: when the frequency of the receiving-end power grid is unstable, selecting the object participating in the frequency modulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system; adjusting the operating state of the object participating in the frequency modulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable. The technical solution provided by the present invention realizes the active frequency support for the receiving-end power grid and improves the stability of the system frequency by identifying the frequency state of the receiving-end power grid and controlling the output of the active power of the wind turbine and the energy storage device to match the frequency state of the receiving-end power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power transmission through flexible DC transmission, and specifically relates to a power control method and device for a wind turbine and an energy storage device for frequency modulation. Background Art

[0002] In recent years, with global warming and the approaching exhaustion of traditional fossil fuels, in order to meet the demand for energy security, renewable energy represented by wind power has been vigorously developed. Due to the significant advantages of flexible DC power grids, such as free reversal of power flow, easy multi-terminal feeding, and strong network adaptability, developing a flexible DC power grid for large-scale wind power grid connection and transmission has become a forward-looking and fundamental choice to break through the technical bottlenecks of "being connected to the grid and being able to generate power" in wind power development, and can form complementary support with existing wind power AC grid connection schemes. When tens of millions of kilowatts of wind power are transmitted through a high-voltage flexible DC power grid, related problems arise. As the proportion of wind power continues to increase, in the case of connecting to the grid through a flexible DC transmission system, due to the isolation effect of DC, the wind power is decoupled from the AC power grid, resulting in the wind power not being able to sense the frequency change on the system side, and the wind power cannot participate in system frequency modulation. The system's moment of inertia and frequency regulation ability continue to decline. In the case of large power deficits caused by AC-DC faults, it is easy to induce frequency problems across the network. In severe cases, it may trigger load shedding actions and result in the loss of a large amount of load, reducing the system frequency stability. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a power control method and device for a wind turbine and an energy storage device for frequency modulation, which can actively support the frequency of the receiving-end power grid by identifying the frequency state of the receiving-end power grid and controlling the power output of the wind turbine and the energy storage device.

[0004] The purpose of the present invention is achieved by the following technical solutions:

[0005] The present invention provides a power control method for a wind turbine and an energy storage device for frequency modulation, and the improvement lies in that the method includes:

[0006] When the frequency of the receiving-end power grid is unstable, select the object participating in the frequency modulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system;

[0007] Adjust the operating state of the object participating in the frequency modulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable.

[0008] Preferably, if the frequency of the receiving-end power grid is not equal to 50 Hz, the frequency of the receiving-end power grid is unstable.

[0009] Preferably, the selecting the object participating in the frequency modulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system includes:

[0010] Selection method a: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is 0, then select the energy storage device as the object participating in the frequency regulation of the receiving-end power grid;

[0011] Selection method b: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is greater than 0, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving-end power grid;

[0012] Selection method c: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is the rated capacity of the wind turbine, then select the energy storage device as the object participating in the frequency regulation of the receiving-end power grid;

[0013] Selection method d: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is less than the rated capacity of the wind turbine, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving-end power grid.

[0014] Further, adjusting the operating state of the object participating in the frequency regulation of the receiving-end power grid includes:

[0015] Based on the selection method a, adjust the energy storage device to the charging mode, and the charging power command value P C = P C，max ;

[0016] Based on the selection method b, adjust the energy storage device to the charging mode, and the charging power command value P C = P C，max , and adjust the active power command value P r output by the wind turbine = 0;

[0017] Based on the selection method c, adjust the energy storage device to the discharging mode, and the discharging power command value P f = P f，max ;

[0018] Based on the selection method d, adjust the energy storage device to the discharging mode, and the discharging power command value P f = P f，max , and adjust the active power command value P r output by the wind turbine = P r,s + P b ;

[0019] Among them, P C，max is the maximum charging power of the energy storage device; P f,max is the maximum discharging power of the energy storage device; Pr,s is the active power output by the wind turbine at the current moment; P b is the reserve active power of the wind turbine.

[0020] The present invention provides a power control device for a wind turbine and an energy storage device for frequency modulation. The improvement lies in that the system includes:

[0021] A selection module, configured to select an object participating in the frequency modulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system when the frequency of the receiving-end power grid is unstable;

[0022] An adjustment module, configured to adjust the operating state of the object participating in the frequency modulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable.

[0023] Preferably, if the frequency of the receiving-end power grid is not equal to 50 Hz, the frequency of the receiving-end power grid is unstable.

[0024] Preferably, the selection module is configured to:

[0025] Selection method a: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is 0, then select the energy storage device as the object participating in the frequency modulation of the receiving-end power grid;

[0026] Selection method b: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is greater than 0, then select the wind turbine and the energy storage device as the objects participating in the frequency modulation of the receiving-end power grid;

[0027] Selection method c: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is the rated capacity of the wind turbine, then select the energy storage device as the object participating in the frequency modulation of the receiving-end power grid;

[0028] Selection method d: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is less than the rated capacity of the wind turbine, then select the wind turbine and the energy storage device as the objects participating in the frequency modulation of the receiving-end power grid.

[0029] Further, the adjustment module is configured to:

[0030] Based on the selection method a, adjust the energy storage device to the charging mode, and the charging power command value P C = P C，max ;

[0031] Based on the selection method b, adjust the energy storage device to the charging mode, and the charging power command value PC = P C，max , adjust the active power command value P output by the wind turbine r = 0;

[0032] Based on the selection method c, adjust the energy storage device to the discharge mode, and the discharge power command value P f = P f，max ;

[0033] Based on the selection method d, adjust the energy storage device to the discharge mode, and the discharge power command value P f = P f，max , adjust the active power command value P output by the wind turbine r = P r,s + P b ;

[0034] Among them, P C，max is the maximum power for charging the energy storage device; P f,max is the maximum power for discharging the energy storage device; P r,s is the active power output by the wind turbine at the current moment; P b is the reserve active power of the wind turbine.

[0035] Compared with the closest prior art, the beneficial effects of the present invention are:

[0036] A power control method and device for a wind turbine and an energy storage device for frequency modulation provided by the present invention, when the frequency of the receiving-end power grid is unstable, select the object participating in the frequency modulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system; adjust the operating state of the object participating in the frequency modulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable. The technical solution provided by the present invention can identify the frequency state of the receiving-end power grid in real time, control the active power behavior of the wind turbine and the energy storage device to match the frequency state of the receiving-end power grid, realize the active frequency support of the wind power through the flexible DC transmission system to the receiving-end power grid, and improve the stability of the system frequency. Description of the Drawings

[0037] Figure 1 is a flowchart of a power control method for a wind turbine and an energy storage device for frequency modulation provided by the present invention;

[0038] Figure 2 is a structure diagram of the frequency control system in an embodiment of the present invention;

[0039] Figure 3 is a structure diagram of a power control device for a wind turbine and an energy storage device for frequency modulation provided by the present invention. Detailed Embodiments

[0040] The following further describes in detail the specific embodiments of the present invention with reference to the drawings.

[0041] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] The present invention provides a power control method for a wind turbine and an energy storage device for frequency modulation, as Figure 1 shown, the method includes:

[0043] When the frequency of the receiving-end power grid is unstable, select the objects participating in the frequency modulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system;

[0044] Adjust the operating state of the objects participating in the frequency modulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable.

[0045] In the optimal embodiment of the present invention, if the frequency of the receiving-end power grid is not equal to 50 Hz, the frequency of the receiving-end power grid is unstable.

[0046] Specifically, the selection of the objects participating in the frequency modulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system includes:

[0047] Selection method a: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is 0, then select the energy storage device as the object participating in the frequency modulation of the receiving-end power grid;

[0048] Selection method b: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity and the real-time active power of the wind turbine is greater than 0, then select the wind turbine and the energy storage device as the objects participating in the frequency modulation of the receiving-end power grid;

[0049] Selection method c: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is the rated capacity of the wind turbine, then select the energy storage device as the object participating in the frequency modulation of the receiving-end power grid, but the power output value of the energy storage device cannot exceed the output power upper limit of the energy storage device and the rated transmission capacity of the flexible DC system;

[0050] Selection method d: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the electricity stored in the energy storage device is greater than zero, and the real-time active power of the wind turbine is less than the rated capacity of the wind turbine, then the wind turbine and the energy storage device are selected as the objects participating in the frequency regulation of the receiving-end power grid. However, the power output values of the wind turbine and the energy storage device cannot exceed the upper limits of their respective output powers and the rated transmission capacity of the flexible DC system.

[0051] In the optimal embodiment of the present invention, when the wind turbine participates in the active power control of the power grid, a certain amount of reserve power needs to be reserved. The reserve active power is reserved by the wind turbine, and each wind turbine can reserve power. The wind turbine with reserved power has no difference from the ordinary wind turbine. For example, if the maximum power that the wind turbine can output at the current moment is 1.2 MW, its output power can be controlled at 1.1 MW, and 0.1 MW is the reserve power.

[0052] Among them, adjusting the operating state of the object participating in the frequency regulation of the receiving-end power grid includes:

[0053] Based on the selection method a, adjust the energy storage device to the charging mode, and the charging power command value P C =P C，max ;

[0054] Based on the selection method b, adjust the energy storage device to the charging mode, and the charging power command value P C =P C，max , adjust the active power command value P r =0;

[0055] Based on the selection method c, adjust the energy storage device to the discharging mode, and the discharging power command value P f =P f，max ;

[0056] Based on the selection method d, adjust the energy storage device to the discharging mode, and the discharging power command value P f =P f，max , adjust the active power command value P r =P r,s +P b ;

[0057] Among them, P C，max is the maximum power for charging the energy storage device; P f,max is the maximum power for discharging the energy storage device; P r,s is the active power output by the wind turbine at the current moment; P b is the reserve active power of the wind turbine.

[0058] In the optimal embodiment of the present invention, when the frequency of the receiving-end power grid returns to stability, or when the adjustable capacity of the wind turbine generator and the energy storage device has been completely used up, the operation is immediately terminated; when controlling, the active power of the energy storage device is preferably adjusted first, and after the adjustable capacity of the energy storage device has been completely used up, the active power of the wind turbine generator is then adjusted.

[0059] In the optimal embodiment of the present invention, the control method can be executed in the application scenarios as Figure 2 shown. Figure 2 The system shown includes:

[0060] Wide-area information monitoring, which monitors in real time the variables reflecting the operating states of the wind turbine generator, the energy storage device, the flexible DC transmission system, and the receiving-end power grid, and has the characteristics of globality and real-time.

[0061] Key variable extraction, which extracts from the massive measurement data the key variables that can reflect the frequency characteristics of the receiving-end power grid, the active power adjustable capacity of the wind turbine generator, the available capacity of the energy storage, and the flexible DC transmission capacity. Such as the frequency f of the receiving-end power grid, the real-time active power P r,s of the wind turbine generator, b the standby power P V of the wind turbine generator, the electric quantity W stored in the energy storage device in real time, and the real-time transmission power P

[0062] of the flexible DC transmission, etc.

[0063] Control mode recognition, which judges the frequency regulation demand of the receiving-end power grid according to the extracted frequency value f of the receiving-end power grid.

[0064] Control object selection, which selects the control object according to the control mode recognition result and the operating states of the wind turbine generator and the energy storage device.

[0065] The present invention provides a power control device for a wind turbine generator and an energy storage device for frequency regulation, as Figure 3 shown. The system includes:

[0066] A selection module, which is used to select the object participating in the frequency regulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system when the frequency of the receiving-end power grid is unstable.

[0067] An adjustment module, which is used to adjust the operating state of the object participating in the frequency regulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable.

[0068] In the optimal embodiment of the present invention, if the frequency of the receiving-end power grid is not equal to 50 Hz, then the frequency of the receiving-end power grid is unstable.

[0069] Specifically, the selection module is used for:

[0070] Selection method a: If the frequency of the receiving - end power grid is greater than 50 Hz, the electricity stored in the energy storage device is less than the rated capacity, and the real - time active power of the wind turbine is 0, then select the energy storage device as the object participating in the frequency regulation of the receiving - end power grid;

[0071] Selection method b: If the frequency of the receiving - end power grid is greater than 50 Hz, the electricity stored in the energy storage device is less than the rated capacity, and the real - time active power of the wind turbine is greater than 0, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving - end power grid;

[0072] Selection method c: If the frequency of the receiving - end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the electricity stored in the energy storage device is greater than zero, and the real - time active power of the wind turbine is the rated capacity of the wind turbine, then select the energy storage device as the object participating in the frequency regulation of the receiving - end power grid;

[0073] Selection method d: If the frequency of the receiving - end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the electricity stored in the energy storage device is greater than zero, and the real - time active power of the wind turbine is less than the rated capacity of the wind turbine, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving - end power grid.

[0074] Specifically, the adjustment module is used for:

[0075] Based on the selection method a, adjust the energy storage device to the charging mode, and the charging power command value P C =P C，max ;

[0076] Based on the selection method b, adjust the energy storage device to the charging mode, and the charging power command value P C =P C，max , adjust the active - power command value P r =0 of the wind turbine output;

[0077] Based on the selection method c, adjust the energy storage device to the discharging mode, and the discharging power command value P f =P f，max ;

[0078] Based on the selection method d, adjust the energy storage device to the discharging mode, and the discharging power command value P f =P f，max , adjust the active - power command value P r =P r,s +P b ;

[0079] Among them, P C，max is the maximum power for the energy storage device to charge; P f,max is the maximum power for the energy storage device to discharge; Pr,s is the active power output by the wind turbine at the current moment; P b is the reserve active power of the wind turbine.

[0080] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0081] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0082] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0083] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific implementation manners of the present invention, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A power control method for a wind turbine and an energy storage device for frequency modulation, characterized in that, The method includes: When the frequency of the receiving-end power grid is unstable, select the objects participating in the frequency regulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system, including: Selection method a: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is 0, then select the energy storage device as the object participating in the frequency regulation of the receiving-end power grid; Selection method b: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is greater than 0, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving-end power grid; Selection method c: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is the rated capacity of the wind turbine, then select the energy storage device as the object participating in the frequency regulation of the receiving-end power grid; Selection method d: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is less than the rated capacity of the wind turbine, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving-end power grid; Adjust the operating states of the objects participating in the frequency regulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable, including: Based on the selection method a, adjust the energy storage device to the charging mode, and the charging power command value ; Based on the selection method b, adjust the energy storage device to the charging mode, and the charging power command value , and adjust the active power command value output by the wind turbine ; Based on the selection method c, adjust the energy storage device to the discharge mode, and the discharge power command value ; Based on the selection method d, adjust the energy storage device to the discharge mode, and the discharge power command value , and adjust the active power command value output by the wind turbine ; wherein, is the maximum power for charging the energy storage device; is the maximum power for discharging the energy storage device; is the active power output by the wind turbine at the current moment; is the reserve active power of the wind turbine.

2. The method according to claim 1, characterized in that, If the frequency of the receiving-end power grid is not equal to 50 Hz, then the frequency of the receiving-end power grid is unstable.

3. A power control device for a wind turbine and an energy storage device for frequency modulation, characterized in that, The device includes: A selection module, configured to select the objects participating in the frequency regulation of the receiving-end power grid according to the frequency of the receiving-end power grid in the flexible DC transmission system when the frequency of the receiving-end power grid is unstable; An adjustment module, configured to adjust the operating states of the objects participating in the frequency regulation of the receiving-end power grid until the frequency of the receiving-end power grid is stable; The selection module is used for: Selection method a: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is 0, then select the energy storage device as the object participating in the frequency regulation of the receiving-end power grid; Selection method b: If the frequency of the receiving-end power grid is greater than 50 Hz, the stored power of the energy storage device is less than the rated capacity, and the real-time active power of the wind turbine is greater than 0, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving-end power grid; Selection method c: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is the rated capacity of the wind turbine, then select the energy storage device as the object participating in the frequency regulation of the receiving-end power grid; Selection method d: If the frequency of the receiving-end power grid is less than 50 Hz, the transmission capacity of the flexible DC system is less than the rated capacity, the stored power of the energy storage device is greater than zero, and the real-time active power of the wind turbine is less than the rated capacity of the wind turbine, then select the wind turbine and the energy storage device as the objects participating in the frequency regulation of the receiving-end power grid; The adjustment module is used for: Based on the selection method a, adjust the energy storage device to the charging mode, and the charging power command value ; Based on the selection method b, adjust the energy storage device to the charging mode, and the charging power command value , adjust the active power command value output by the wind turbine ; Based on the selection method c, adjust the energy storage device to the discharge mode, and the discharge power command value ; Based on the selection method d, adjust the energy storage device to the discharge mode, and the discharge power command value , and adjust the active power command value output by the wind turbine ; Among them, is the maximum power for charging the energy storage device; is the maximum power for discharging the energy storage device; is the active power output by the wind turbine at the current moment; is the reserved active power of the wind turbine.

4. The device according to claim 3, characterized in that, If the frequency of the receiving-end power grid is not equal to 50 Hz, then the frequency of the receiving-end power grid is unstable.

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