Wind farm control system and wind farm including the wind farm control system

Abstract

A wind farm control system and a wind farm including the wind farm control system are provided. The wind farm control system comprises: a first modular multilevel converter connected to a first collector line and configured to control power transmission of the first collector line, wherein the first collector line is used to connect at least one first wind turbine to a power grid; a second modular multilevel converter connected to a second collector line and configured to control power transmission of the second collector line, wherein the second collector line is used to connect at least one second wind turbine to a power grid, wherein the first modular multilevel converter and the second modular multilevel converter are connected together via a DC terminal.

Description

Technical Field

[0001] The present invention relates to the field of wind power generation, and more particularly to a wind farm control system and a wind farm comprising the wind farm control system. Background Art

[0002] Wind energy is a clean renewable resource, and its use is increasingly valued by countries around the world. With the development of the world energy crisis, how to effectively use wind energy to generate electricity has become a hot topic in social development.

[0003] However, in wind farms, there is often a problem of weak power grids at the collection access points. After passing through longer collection lines, the wind turbines are in the power grid, and the power grid at the access point is even weaker, resulting in problems such as difficulty in connecting to the grid and easy disconnection from the grid. Summary of the invention

[0004] An object of the present invention is to provide a wind farm control system and a wind farm comprising the wind farm control system.

[0005] One aspect of the present invention provides a wind farm control system, which includes: a first modular multilevel converter, connected to a first collector line and configured to control power transmission of the first collector line, wherein the first collector line is used to connect at least one first wind turbine to a power grid; a second modular multilevel converter, connected to a second collector line and configured to control power transmission of the second collector line, wherein the second collector line is used to connect at least one second wind turbine to the power grid, wherein the first modular multilevel converter and the second modular multilevel converter are connected together through a DC terminal.

[0006] Optionally, when the difference between the power of the first collector line and the power of the second collector line is greater than a predetermined threshold, the first modular multilevel converter and the second modular multilevel converter respectively change the power of the first collector line and the power of the second collector line, so that the difference between the power of the first collector line and the power of the second collector line is reduced.

[0007] Optionally, when a fault occurs in the second collector line, making it impossible for one or more of the at least one second wind turbines to transmit electricity to the power grid through the second collector line, the first modular multilevel converter and the second modular multilevel converter send the electricity generated by the one or more second wind turbines to the power grid through the first collector line.

[0008] Optionally, when a fault occurs in the second collector line, making it impossible for one or more of the at least one second wind turbines to transmit power to the power grid through the second collector line, the first modular multilevel converter uses a DC voltage and reactive power control method to control the DC bus voltage between the first modular multilevel converter and the second modular multilevel converter to remain constant, the second modular multilevel converter inverts the DC bus voltage to supply power to the one or more second wind turbines, and the first modular multilevel converter and the second modular multilevel converter send the power generated by the one or more second wind turbines after power generation to the power grid through the first collector line.

[0009] Optionally, the wind farm control system also includes: a third modular multilevel converter, connected to a third collector line and configured to control power transmission of the third collector line, wherein the third collector line is used to connect at least one third wind turbine to the power grid; wherein the third modular multilevel converter is connected to the first modular multilevel converter and the second modular multilevel converter through a DC terminal.

[0010] Optionally, when a fault occurs in the second collector line, making it impossible for one or more of the at least one second wind turbines to transmit electricity to the power grid through the second collector line, the first modular multilevel converter and the second modular multilevel converter send the first power of the electricity generated by the one or more second wind turbines to the power grid through the first collector line, and the third modular multilevel converter and the second modular multilevel converter send the second power of the electricity generated by the one or more second wind turbines to the power grid through the third collector line, wherein the difference between the first power and the second power is equal to the difference between the power of the electricity normally transmitted by the first collector line and the power of the electricity normally transmitted by the third collector line.

[0011] Optionally, each bridge arm of the third modular multilevel converter includes multiple sub-modules and a series reactor, wherein the sub-modules of each bridge arm of the third modular multilevel converter are connected in a cascade manner; each bridge arm of the first modular multilevel converter and the second modular multilevel converter includes multiple sub-modules and a series reactor, wherein the sub-modules of each bridge arm of the first modular multilevel converter and the second modular multilevel converter are connected in a cascade manner.

[0012] Optionally, the bridge arms of the first modular multilevel converter include at least one upper bridge arm and at least one lower bridge arm corresponding to the at least one upper bridge arm, wherein the series inductor of each upper bridge arm in the at least one upper bridge arm and the series inductor of the corresponding lower bridge arm in the at least one lower bridge arm are commonly connected to the first collecting line.

[0013] Optionally, each submodule includes: a first insulated gate bipolar transistor, connected between a first node and a second node; a first anti-parallel diode, connected in parallel with the first insulated gate bipolar transistor; a second insulated gate bipolar transistor, connected between the first node and a third node; a second anti-parallel diode, connected in parallel with the second insulated gate bipolar transistor; and a capacitor, connected between the second node and the third node as a submodule DC side capacitor.

[0014] Another aspect of the present invention provides a wind farm, comprising: at least one first wind turbine; at least one second wind turbine; a wind farm control system, comprising: a first modular multilevel converter, connected to a first collector line and configured to control power transmission of the first collector line, wherein the first collector line is used to connect the at least one first wind turbine to a power grid; a second modular multilevel converter, connected to a second collector line and configured to control power transmission of the second collector line, wherein the second collector line is used to connect the at least one second wind turbine to a power grid, wherein the first modular multilevel converter and the second modular multilevel converter are connected together via a DC terminal.

[0015] The wind farm control system of the present invention can control the transmission of power generated by at least one first wind turbine and at least one second wind turbine respectively by adopting a first modular multilevel converter and a second modular multilevel converter. Therefore, the network topology can be actively improved and optimized. The modular multilevel converter can be used as an AC source, thereby increasing the number of wind turbine grid-connected points, equivalently increasing the short-circuit capacity of the AC system, improving the grid characteristics at the end of the grid, making it easier for wind turbines to be connected to the grid and less susceptible to grid fluctuations.

[0016] In addition, the wind farm control system of the present invention can coordinate the power of different collector lines based on the modular multilevel converter, so that the power of the collector lines is in an optimal state, thereby reducing transmission losses.

[0017] In addition, the wind farm control system of the present invention can send the power generated by one or more second wind turbines that cannot transmit power through the faulty second collector line to the power grid through the first collector line through the first modular multilevel converter and the second modular multilevel converter, thereby avoiding the normal grid connection of the wind turbine affected by the fault of the second collector line, thereby improving the power generation efficiency when the collector line fails.

[0018] In addition, the wind farm control system of the present invention can greatly improve the flexibility and controllability of wind farm system operation by connecting a modular multilevel converter at the end of the line, making power control safer and more reliable, while increasing the power generation of the wind farm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects and features of the present invention will become more apparent through the following description in conjunction with the accompanying drawings which exemplarily illustrate an example, in which:

[0020] Figure 1 A block diagram showing a wind farm according to an exemplary embodiment of the present invention;

[0021] Figure 2 A diagram showing the structure of a first modular multilevel converter and a second modular multilevel converter within a wind farm control system according to an example embodiment of the present invention;

[0022] Figure 3 A diagram showing a single submodule of a modular multilevel converter according to an example embodiment of the present invention. DETAILED DESCRIPTION

[0023] Reference will now be made in detail to embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments will be described below with reference to the drawings in order to explain the present invention.

[0024] Figure 1 A block diagram of a wind farm according to an exemplary embodiment of the present invention is shown.

[0025] Reference Figure 1 The wind farm 10 includes at least one first wind turbine 100 , at least one second wind turbine 200 , and a wind farm control system 300 .

[0026] Here, at least one first wind turbine 100 may be connected to the grid via a first collector line 110 so as to transmit the generated power to the grid. In other words, the first collector line 110 may be used to connect at least one first wind turbine 100 to the grid 20. Similarly, at least one second wind turbine 200 may be connected to the grid via a second collector line 210 so as to transmit the generated power to the grid. In other words, the second collector line 210 may be used to connect at least one second wind turbine 200 to the grid.

[0027] In the present invention, the wind farm control system 300 may include a first modular multilevel converter 310 and a second modular multilevel converter 310. The first modular multilevel converter 310 may be connected to the first collector line 110 and configured to control power transmission of the first collector line 110. Similarly, the second modular multilevel converter 320 may be connected to the second collector line 210 and configured to control power transmission of the second collector line 210.

[0028] In addition, the first modular multilevel converter 310 and the second modular multilevel converter 320 are connected together via a DC terminal.

[0029] Since the wind farm control system including the above-mentioned first modular multilevel converter 310 and the second modular multilevel converter 320 is used to respectively control the transmission of the power generated by at least one first wind turbine 100 and at least one second wind turbine 200, the network topology can be actively improved and optimized. The modular multilevel converter can be used as an AC source, thereby increasing the number of wind turbine grid-connected points, equivalently increasing the short-circuit capacity of the AC system, improving the grid characteristics at the end of the grid, making it easier for wind turbines to be connected to the grid and less susceptible to grid fluctuations.

[0030] In an exemplary embodiment of the present invention, when the difference between the power of the first collector line 110 and the power of the second collector line 210 is greater than a predetermined threshold, the first modular multilevel converter 310 and the second modular multilevel converter 320 may respectively change the power of the first collector line 110 and the power of the second collector line 210 so that the difference between the power of the first collector line 110 and the power of the second collector line 210 is reduced.

[0031] That is to say, when there is a large difference in the power of different collector lines in a wind farm, the power of different collector lines can be coordinated based on a modular multilevel converter, so that the power of the collector line is in an optimal state and the transmission loss is reduced. For example, the power of different collector lines can be coordinated based on the intelligent switch of the modular multilevel converter, so that the power of the collector line is in an optimal state and the transmission loss is reduced.

[0032] During the operation of a wind farm, a collector line failure may occur, thereby affecting the power transmission of some or all wind turbines and affecting the power generation efficiency of the wind farm. For example, when at least one second wind turbine includes wind turbine 1, wind turbine 2, wind turbine 3 and wind turbine 4 in order of distance from the power grid, if a collector line failure occurs between wind turbine 2 and wind turbine 3, wind turbine 3 and wind turbine 4 will not be able to connect to the grid and generate electricity normally due to the collector line failure.

[0033] According to an exemplary embodiment of the present invention, when a fault occurs in the second collector line 210, making it impossible for one or more of the at least one second wind turbines (for example, wind turbine 3 and wind turbine 4 in the above example) to transmit power to the grid through the second collector line 210, the first modular multilevel converter 310 and the second modular multilevel converter 320 send the power generated by the one or more second wind turbines that are unable to transmit power through the faulty second collector line 210 to the grid through the first collector line 110.

[0034] Since the power generated by one or more second wind turbines that cannot transmit power through the faulty second collector line 210 is sent to the grid through the first collector line 110 through the first modular multilevel converter 310 and the second modular multilevel converter 320, the normal grid connection of the wind turbines affected by the fault of the second collector line 210 is avoided, thereby improving the power generation efficiency when the collector line fails. In addition, in the present invention, by connecting a modular multilevel converter at the end of the line, the flexibility and controllability of the wind farm system operation will be greatly improved, the power control will be safer and more reliable, and the power generation of the wind farm will be increased.

[0035] More specifically, when the second collector line 210 fails, so that one or more of the at least one second wind turbines cannot transmit power to the grid through the second collector line 210, the first modular multilevel converter 310 uses a DC voltage and reactive power (Vdc / Q) control method to control the DC bus voltage between the first modular multilevel converter 310 and the second modular multilevel converter 320 to remain constant, the second modular multilevel converter 320 inverts the DC bus voltage to supply power to the one or more second wind turbines affected by the fault, and the first modular multilevel converter 310 and the second modular multilevel converter 320 send the power generated by the one or more second wind turbines affected by the fault to the grid through the first collector line 110. Here, the first modular multilevel converter 310 can control the DC voltage, and the second modular multilevel converter 320 can control the system power.

[0036] In addition, optionally, in one embodiment of the present invention, the wind farm control system may further include a third modular multilevel converter (not shown). The third modular multilevel converter may be connected to a third collector line and configured to control power transmission of the third collector line, wherein the third collector line is used to connect at least one third wind turbine to the power grid. Here, the third modular multilevel converter may be connected to the first modular multilevel converter 310 and the second modular multilevel converter 320 through a DC terminal.

[0037] In this embodiment, when the second collector line 210 fails, so that one or more of the at least one second wind turbines cannot transmit power to the grid through the second collector line 210, the first modular multilevel converter 310 and the second modular multilevel converter 320 send the first power of the power generated by the one or more second wind turbines to the grid through the first collector line 110, and the third modular multilevel converter and the second modular multilevel converter 320 send the second power of the power generated by the one or more second wind turbines affected by the fault to the grid through the third collector line. Here, the distribution of line power can be performed with reference to the capacity of the first modular multilevel converter 310, the second modular multilevel converter 320 and the third modular multilevel converter, and the capacity of a single wind turbine. For example, the operation of the third modular multilevel converter can be similar to the operation with reference to the first modular multilevel converter and the second modular multilevel converter.

[0038] According to a preferred embodiment of the present invention, the difference between the first power and the second power is equal to the difference between the power of the electric power normally transmitted by the first collector line 110 and the power of the electric power normally transmitted by the third collector line. In other words, in the present invention, power allocation can be based on the principle of minimizing the power deviation between the normal first collector line 110 and the third collector line, thereby ensuring that the collector line that redistributes power works normally. For example, the first collector line 110 has 10MW more power than the third collector line, and the power of each wind turbine is 5MW, then the power allocated to the first collector line 110 is 10MW more than the power allocated to the third collector line.

[0039] Please note, Figure 1 Only the core components of the present invention are shown, and other well-known components (eg, transformer, etc.) are omitted for simplicity.

[0040] Figure 2 A diagram showing the structure of a first modular multilevel converter (MMC1) and a second modular multilevel converter (MMC2) within a wind farm control system according to an example embodiment of the present invention.

[0041] Reference Figure 2 Each bridge arm of the first modular multilevel converter and the second modular multilevel converter includes a plurality of submodules (SM1 to SMN) and a series reactor, wherein N is a positive integer.

[0042] Here, the submodules of each bridge arm of the first modular multilevel converter and the second modular multilevel converter may be connected in a cascade manner.

[0043] In one example, the bridge arm of the first modular multilevel converter may include at least one upper bridge arm and at least one lower bridge arm corresponding to the at least one upper bridge arm. Figure 2 As shown, the series reactor of each upper bridge arm in at least one upper bridge arm and the series reactor of the corresponding lower bridge arm in the at least one lower bridge arm are commonly connected to the first collector line. For example, the first collector line may include three lines corresponding to three.

[0044] In addition, the first modular multilevel converter and the second modular multilevel converter are connected together via a DC terminal. Figure 2 As shown in , the voltage on the DC side is shown as voltage Udc.

[0045] Here, the second modular multilevel converter may have a similar structure to the first modular multilevel converter, and for the sake of brevity, a detailed description of the second modular multilevel converter will be omitted.

[0046] In addition, optionally, the wind farm control system according to the embodiment of the present invention may further include a third modular multilevel converter (not shown). The third modular multilevel converter may be connected to the first modular multilevel converter and the second modular multilevel converter through a DC terminal. Here, the third modular multilevel converter may have a similar structure to the first modular multilevel converter, and for the sake of simplicity, the specific description of the third modular multilevel converter will be omitted.

[0047] Note that although only an example of two modular multilevel converters (i.e., a first modular multilevel converter and a second modular multilevel converter) and an example of three modular multilevel converters (i.e., a first modular multilevel converter, a second modular multilevel converter, and a third modular multilevel converter) are shown, the present invention is not limited thereto. The number of modular multilevel converters may vary according to the number of collector lines.

[0048] Figure 3 A diagram showing a single submodule of a modular multilevel converter according to an example embodiment of the present invention.

[0049] Reference Figure 3 Here, the submodule may include a first insulated gate bipolar transistor T1, a first anti-parallel diode D1, a second insulated gate bipolar transistor T2, a second anti-parallel diode D2 and a capacitor C.

[0050] exist Figure 3In the embodiment, the first insulated gate bipolar transistor T1 may be connected between the first node A and the second node. The first anti-parallel diode D1 may be connected in parallel with the first insulated gate bipolar transistor T1. The second insulated gate bipolar transistor T2 may be connected between the first node A and the third node B. The second anti-parallel diode D2 may be connected in parallel with the second insulated gate bipolar transistor T2. The capacitor C may be connected between the second node and the third node B as a submodule DC side capacitor. The voltage across the capacitor C is the voltage Uc.

[0051] Here, the submodule transmits voltage Usm and current Ism through the first node A and the third node B. Here, first, second and third are only used to distinguish different components or elements, and do not have other specific meanings. That is, the submodule can transmit voltage Usm and current Ism through the nodes at both ends of an insulated gate bipolar transistor in the submodule.

[0052] In addition, it should be understood that the short-term load forecasting method and / or device according to the exemplary embodiment of the present invention can be implemented as hardware components and / or software components. Those skilled in the art can implement the various program modules for implementing the above method in the device, for example, using a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), according to the processing performed by the defined various program modules.

[0053] In addition, the short-term load forecasting method according to the exemplary embodiment of the present invention can be implemented as a computer program in a computer-readable recording medium. Those skilled in the art can implement the computer program according to the description of the above method. When the computer code is executed in a computer, the method executed by the wind farm control system of the present invention is implemented. In addition, the short-term load forecasting method according to the exemplary embodiment of the present invention can be executed by a short-term load forecasting device including one or more processors and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the method executed by the wind farm control system of the present invention is implemented.

[0054] Although some exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that modifications may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A wind farm control system, the wind farm control system comprising: a first modular multilevel converter connected to a first collector line and configured to control power transmission of the first collector line, wherein the first collector line is used to connect at least one first wind turbine to a power grid; a second modular multilevel converter connected to a second collector line and configured to control power transmission of the second collector line, wherein the second collector line is used to connect at least one second wind turbine to the grid, The first modular multilevel converter and the second modular multilevel converter are connected together through a DC terminal. Among them, when the difference between the power of the first collector line and the power of the second collector line is greater than a predetermined threshold, the first modular multilevel converter and the second modular multilevel converter respectively change the power of the first collector line and the power of the second collector line, so that the difference between the power of the first collector line and the power of the second collector line is reduced.

2. The wind farm control system according to claim 1, wherein: When a fault occurs in the second collector line, making it impossible for one or more of the at least one second wind turbines to transmit power to the grid through the second collector line, the first modular multilevel converter and the second modular multilevel converter send the power generated by the one or more second wind turbines to the grid through the first collector line.

3. The wind farm control system according to claim 2, wherein: When a fault occurs in the second collector line, making it impossible for one or more of the at least one second wind turbines to transmit power to the power grid through the second collector line, the first modular multilevel converter uses a DC voltage and reactive power control method to control the DC bus voltage between the first modular multilevel converter and the second modular multilevel converter to remain constant, the second modular multilevel converter inverts the DC bus voltage to supply power to the one or more second wind turbines, and the first modular multilevel converter and the second modular multilevel converter send the power generated by the one or more second wind turbines after power generation to the power grid through the first collector line.

4. The wind farm control system according to claim 1, wherein: The wind farm control system further comprises: a third modular multilevel converter connected to a third collector line and configured to control power transmission of the third collector line, wherein the third collector line is used to connect at least one third wind turbine to the grid; The third modular multilevel converter is connected to the first modular multilevel converter and the second modular multilevel converter via a DC terminal.

5. The wind farm control system according to claim 4, wherein: When a fault occurs in the second collector line, making it impossible for one or more of the at least one second wind turbines to transmit electricity to the power grid through the second collector line, the first modular multilevel converter and the second modular multilevel converter send the first power of the electricity generated by the one or more second wind turbines to the power grid through the first collector line, and the third modular multilevel converter and the second modular multilevel converter send the second power of the electricity generated by the one or more second wind turbines to the power grid through the third collector line, wherein the difference between the first power and the second power is equal to the difference between the power of the electricity normally transmitted by the first collector line and the power of the electricity normally transmitted by the third collector line.

6. The wind farm control system according to claim 4, wherein: Each bridge arm of the third modular multilevel converter includes a plurality of submodules and a series reactor. Wherein, the submodules of each bridge arm of the third modular multilevel converter are connected in a cascade manner; Each bridge arm of the first modular multilevel converter and the second modular multilevel converter includes a plurality of submodules and a series reactor. The submodules of each bridge arm of the first modular multilevel converter and the second modular multilevel converter are connected in a cascade manner.

7. The wind farm control system according to claim 6, wherein: The bridge arm of the first modular multilevel converter comprises at least one upper bridge arm and at least one lower bridge arm corresponding to the at least one upper bridge arm. The series reactor of each upper bridge arm in the at least one upper bridge arm and the series reactor of the corresponding lower bridge arm in the at least one lower bridge arm are commonly connected to the first collector line.

8. The wind farm control system according to claim 7, wherein: Each submodule includes: a first insulated gate bipolar transistor connected between the first node and the second node; A first anti-parallel diode connected in parallel with the first insulated gate bipolar transistor; a second insulated gate bipolar transistor connected between the first node and the third node; a second anti-parallel diode connected in parallel with the second insulated gate bipolar transistor; A capacitor is connected between the second node and the third node as a submodule DC side capacitor.

9. A wind farm, comprising: at least one first fan; at least one second fan; Wind farm control system, including: a first modular multilevel converter connected to a first collector line and configured to control power transmission of the first collector line, wherein the first collector line is used to connect the at least one first wind turbine to a power grid; a second modular multilevel converter connected to a second collector line and configured to control power transmission of the second collector line, wherein the second collector line is used to connect the at least one second wind turbine to the grid, The first modular multilevel converter and the second modular multilevel converter are connected together through a DC terminal. Among them, when the difference between the power of the first collector line and the power of the second collector line is greater than a predetermined threshold, the first modular multilevel converter and the second modular multilevel converter respectively change the power of the first collector line and the power of the second collector line, so that the difference between the power of the first collector line and the power of the second collector line is reduced.

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