Wind turbine generator comprising means for electrical power conversion

Abstract

A wind turbine generator (100a-e) comprising a generator (102) and means (104a-e) for electrical power conversion wherein the means (104a-e) comprise: a first power converter (106) for converting AC power from the generator (102) to DC power; a second power converter (108) for converting the DC power from the first power converter (106) into AC power to be provided to a power grid (110); a DC link (112) comprising a positive rail (114) and a negative rail (116) connecting the first power converter (106) to the second power converter (118); and an energy storage device (118a-d) comprising a plurality of supercapacitors (120) connected or connectable to the DC link (112) so as to support operation of one or more of the first and second power converters (106, 108). The energy storage device (118a-d) comprises one or more DC-to-DC converters (122) for connecting one or more of the ultracapacitors (122) of the energy storage device (118a-d) to the DC link (112).

Description

Technical Field

[0001] Aspects of the present invention relate to a wind turbine generator, which includes a generator and means for electric power conversion. Background Art

[0002] Generally, a power grid, such as what is commonly referred to as the public power grid, can have defined parameters, such as a defined frequency, such as 50 Hz or 60 Hz. The stability of the power grid parameters depends on various variables, including the balance between the power generated and consumed in the power grid. Generally, any imbalance between the power generated and the power consumed will cause a change in the grid frequency of the power grid. When more power is generated in the power grid than consumed, the grid frequency increases. When more power is consumed than generated, the grid frequency decreases. Generally, it is important to have a stable grid frequency in the power grid, that is, to keep the frequency fluctuations of the grid frequency as small as possible.

[0003] Generally, a grid code can be specified for the power grid by, for example, a grid operator, where the grid code defines the parameters that a power plant connected to the power grid (such as a power plant including one or more wind turbine generators) must meet, for example, to provide sufficient frequency support to the power grid or to provide sufficient voltage support to the power grid. Summary of the Invention

[0004] The inventors of the present invention have found drawbacks in conventional solutions for providing support to the power grid for a wind turbine generator or a power plant including one or more wind turbine generators. For example, some conventional solutions do not provide sufficiently effective support to the power grid, such as frequency and / or voltage support.

[0005] The object of the present invention is to provide a solution that alleviates or solves the drawbacks and problems of conventional solutions.

[0006] The above and other objects are solved by the subject matter of the independent claims. Other advantageous embodiments of the present invention can be found in the dependent claims.

[0007] According to a first aspect of the present invention, the above and other objects are achieved by a wind turbine generator, which includes a generator and means for electric power conversion, wherein the means includes:

[0008] A first power converter for converting AC (alternating current) power from the generator into DC (direct current) power,

[0009] A second power converter for converting the DC power from the first power converter into AC power to be provided to the power grid,

[0010] A DC link including a positive rail and a negative rail, which connects the first power converter to the second power converter, and

[0011] An energy storage device including a plurality of supercapacitors, the plurality of supercapacitors being connected or connectable to the DC link to support the operation of one or more of the first power converter and the second power converter,

[0012] wherein the energy storage device includes one or more DC-DC converters for connecting one or more of the supercapacitors of the energy storage device to the DC link, and

[0013] wherein the DC-DC converter is connected in series with one or more of the supercapacitors of the energy storage device.

[0014] The advantage of the wind turbine generator according to the first aspect is that improved support is provided to the power grid by the wind turbine generator or by a power plant including one or more wind turbine generators, such as improved frequency and / or voltage support. The advantage of the wind turbine generator according to the first aspect is that the operation of one or more of the first power converter and the second power converter is improved. The advantage of the wind turbine generator according to the first aspect is that the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is improved, thereby improving the operation or control of one or more of the first power converter and the second power converter. The advantage of the wind turbine generator according to the first aspect is that one or more of the first power converter and the second power converter can be controlled in an improved manner according to the so-called grid-forming control (GFC) mode, which will be disclosed in more detail in the following detailed description of the disclosure of the embodiments.

[0015] For some embodiments, the first power converter may be referred to as a rectifier. For some embodiments, the second power converter may be referred to as an inverter. For some embodiments, the supercapacitor may be referred to as a supercapacitance.

[0016] According to an advantageous embodiment of the wind turbine generator according to the first aspect, the energy storage device is configured to supply electrical energy to the DC link to support the operation of one or more of the first power converter and the second power converter.

[0017] According to another advantageous embodiment of the wind turbine generator according to the first aspect, the energy storage device includes one or more cabinets that house at least most of the supercapacitors of the energy storage device. The advantage of this embodiment is the improved arrangement of the supercapacitors. The advantage of this embodiment is that the energy storage is optimized in terms of cost and accessible volume / size.

[0018] According to a first aspect, the DC-to-DC converter is connected in series with one or more of the supercapacitors of the energy storage device. The advantage of this embodiment is that the support provided by the wind turbine generator or the power plant including the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support. The advantage of this embodiment is that the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0019] According to a further advantageous embodiment of the wind turbine generator according to the first aspect, the plurality of supercapacitors have a first terminal and a second terminal,

[0020] wherein the DC-to-DC converter has a first DC side and a second DC side,

[0021] wherein each of the first DC side and the second DC side includes an input terminal and an output terminal,

[0022] wherein one of the positive rail and the negative rail is connected or connectable to the first terminal via the input terminal and the output terminal of the first DC side of the DC-to-DC converter, and the other of the positive rail and the negative rail is connected or connectable to the second terminal without any interconnected DC-to-DC converter, and

[0023] wherein the input terminal and the output terminal of the second DC side of the DC-to-DC converter are connected or connectable to one or more power sources different from the plurality of supercapacitors.

[0024] The advantage of this embodiment is that the support provided by the wind turbine generator or the power plant including the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support. The advantage of this embodiment is that the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0025] According to a further advantageous embodiment of the wind turbine generator according to the first aspect, the input terminal of the first DC side of the DC-to-DC converter is connected or connectable to one of the positive rail and the negative rail, and the output terminal of the first DC side of the DC-to-DC converter is connected or connectable to the first terminal.

[0026] According to an advantageous embodiment of the wind turbine generator according to the first aspect, the power source includes one or more of the following groups:

[0027] · Battery;

[0028] · A local power source;

[0029] · An auxiliary power source for a wind turbine generator;

[0030] · The second power converter; and

[0031] · The DC link.

[0032] The advantage of this embodiment is that the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0033] According to another advantageous embodiment of the wind turbine generator according to the first aspect, the energy storage device comprises:

[0034] One or more first circuits, which include one or more supercapacitors and one or more DC-DC converters for connecting the one or more supercapacitors of the first circuit to the DC link, and

[0035] One or more second circuits, which include one or more supercapacitors that are connected or connectable to the DC link without any interconnecting DC-DC converters.

[0036] The advantages of this embodiment are that the support provided by the wind turbine generator or by a power plant including the wind turbine generator to the power grid, such as frequency and / or voltage support, is further improved. The advantage of this embodiment is that the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter. The advantage of this embodiment is that the flexibility of the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is improved.

[0037] According to another advantageous embodiment of the wind turbine generator according to the first aspect, the energy storage device comprises a plurality of first circuits and a plurality of second circuits. The advantages of this embodiment are that the support provided by the wind turbine generator or by a power plant including the wind turbine generator to the power grid, such as frequency and / or voltage support, is further improved. The advantage of this embodiment is that the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0038] According to a further advantageous embodiment of the wind turbine generator according to the first aspect, the second circuit comprises two or more supercapacitors connected or connectable to the DC link without any interconnected DC-DC converter. The advantage of this embodiment is that the support provided by the wind turbine generator or by a power plant comprising the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support. The advantage of this embodiment is that the electrical energy supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0039] According to a further advantageous embodiment of the wind turbine generator according to the first aspect, the wind turbine generator comprises a controller for controlling the power supply from the first circuit and the second circuit to the DC link. The advantage of this embodiment is that the support provided by the wind turbine generator or by a power plant comprising the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support. The advantage of this embodiment is that the electrical energy supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0040] According to an advantageous embodiment of the wind turbine generator according to the first aspect, the controller is configured to control the power supply from the first circuit and the second circuit to the DC link based on the operating level of one or more of the first power converter and the second power converter. The advantage of this embodiment is that the support provided by the wind turbine generator or by a power plant comprising the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support. The advantage of this embodiment is that the electrical energy supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0041] According to another advantageous embodiment of the wind turbine generator according to the first aspect, one of the first circuit and the second circuit is a default circuit which is initially connected by default for power supply to the DC link. The advantage of this embodiment is that the support provided by the wind turbine generator or by a power plant comprising the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support. The advantage of this embodiment is that the electrical energy supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0042] According to an alternative advantageous embodiment of a wind turbine generator, a DC-to-DC converter is connected in parallel with one or more of the supercapacitors of the energy storage device. The advantage of this embodiment is that the support provided by the wind turbine generator or by a power plant including the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support. The advantage of this embodiment is that the power supply to the DC link during the operation of one or more of the first power converter and the second power converter is further improved, thereby further improving the operation or control of one or more of the first power converter and the second power converter.

[0043] According to yet another advantageous embodiment of the wind turbine generator according to the first aspect, the plurality of supercapacitors have a first terminal and a second terminal,

[0044] wherein the DC-to-DC converter has a first DC side and a second DC side,

[0045] wherein each of the first DC side and the second DC side includes a first terminal and a second terminal,

[0046] wherein the first terminal of the first DC side of the DC-to-DC converter is connected or connectable to the first terminal of the plurality of supercapacitors,

[0047] wherein the second terminal of the first DC side of the DC-to-DC converter is connected or connectable to the second terminal of the plurality of supercapacitors, and

[0048] wherein the first terminal of the second DC side of the DC-to-DC converter is connected or connectable to one of the positive rail and the negative rail, and the second terminal of the second DC side of the DC-to-DC converter is connected or connectable to the other of the positive rail and the negative rail.

[0049] The advantage of this embodiment is that the support provided by the wind turbine generator or by a power plant including the wind turbine generator to the power grid is further improved, such as frequency and / or voltage support.

[0050] According to a second aspect of the present invention, the above and other objects are achieved by a method for converting the AC power of a generator from a wind turbine generator to the AC power to be supplied to the power grid, wherein the method includes:

[0051] Controlling a first power converter to convert the AC power from the generator into DC power;

[0052] Controlling a second power converter to convert the DC power from the first power converter into AC power, the second power converter being connected to the first power converter through a DC link; and

[0053] Electric energy is supplied from an energy storage device to the DC link, the energy storage device including a plurality of supercapacitors and one or more DC - to - DC converters connecting one or more of the supercapacitors of the energy storage device to the DC link so as to support the operation of one or more of the first power converter and the second power converter.

[0054] The advantages of the method according to the second aspect correspond to the advantages of the wind turbine generator according to the first aspect and its embodiments mentioned above or below.

[0055] According to an advantageous embodiment of the method according to the second aspect, the step of supplying electric energy from the energy storage device to the DC link includes supplying electric energy from one or more of the supercapacitors of the energy storage device to the DC link via one or more DC - to - DC converters.

[0056] According to another advantageous embodiment of the method according to the second aspect, the step of supplying electric energy from the energy storage device to the DC link includes supplying electric energy from an energy storage device according to any one of the embodiments disclosed above or below.

[0057] According to a third aspect of the present invention, the above and other objects are achieved by a computer program including instructions which, when executed by a computer, cause the computer to execute the method according to any one of the embodiments disclosed above or below. The advantages of the computer program according to the third aspect correspond to the advantages of the wind turbine generator according to the first aspect and its embodiments mentioned above or below.

[0058] According to a fourth aspect of the present invention, the above and other objects are achieved by a computer - readable medium including instructions which, when executed by a computer, cause the computer to execute the method according to any one of the embodiments disclosed above or below. The advantages of the computer - readable medium according to the fourth aspect correspond to the advantages of the wind turbine generator according to the first aspect and its embodiments mentioned above or below.

[0059] According to one aspect of the present invention, the above - mentioned computer program and / or computer - readable medium are configured to implement the methods and their embodiments described herein.

[0060] According to a fifth aspect of the present invention, the above and other objects are achieved by a control device for controlling the electrical power conversion of the AC power from the generator of a wind turbine generator to the AC power to be supplied to the power grid, wherein the control device is configured to:

[0061] Control a first power converter to convert the AC power from the generator into DC power;

[0062] Control a second power converter to convert DC power from the first power converter into AC power, the second power converter being connected to the first power converter via a DC link; and

[0063] Supply electrical energy from an energy storage device to the DC link, the energy storage device including a plurality of supercapacitors and one or more DC-to-DC converters connecting one or more of the supercapacitors of the energy storage device to the DC link so as to support the operation of one or more of the first power converter and the second power converter.

[0064] The advantages of the control device according to the fifth aspect correspond to the advantages of the wind turbine generator according to the first aspect and its embodiments mentioned above or below.

[0065] It should be understood that all embodiments described with respect to the method aspect of the present invention are also applicable to the control device aspect of the present invention. Therefore, all embodiments described with respect to the method aspect of the present invention can be executed by a control device, which may include one or more controllers, control units or control devices. Embodiments of the control device have advantages corresponding to the advantages of the above-mentioned method and its embodiments.

[0066] According to an advantageous embodiment of the wind turbine generator according to the first aspect, the wind turbine generator includes a control device according to any one of the embodiments disclosed above or below.

[0067] According to a sixth aspect of the present invention, the above and other objects are achieved by a power plant for supplying power to a power grid, wherein the power plant includes one or more wind turbine generators according to any one of the embodiments disclosed above or below.

[0068] The above features and embodiments of the wind turbine generator, method, computer program, computer-readable medium, control device and power plant can be combined in various possible ways to provide further advantageous embodiments.

[0069] Other advantageous embodiments of the wind turbine generator, method, computer program, computer-readable medium, control device and power plant according to the present invention and other advantages of the embodiments of the present invention will become apparent from the detailed description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] For illustrative purposes, embodiments of the present invention will now be shown in more detail by way of examples and with reference to the accompanying drawings, in which like reference numerals are used for like components, wherein:

[0071] Figure 1It is a schematic diagram showing an aspect of an embodiment of a wind turbine generator according to the first aspect of the present invention, to which an embodiment of the method according to the second aspect of the present invention can be applied;

[0072] Figure 2 It is a schematic diagram showing an embodiment of a power plant according to the sixth aspect of the present invention;

[0073] Figure 3 It is a schematic circuit diagram showing an embodiment of a wind turbine generator according to the first aspect of the present invention;

[0074] Figure 4 It is a schematic circuit diagram showing another embodiment of a wind turbine generator according to the first aspect of the present invention;

[0075] Figure 5 It is a schematic diagram showing Figure 3 and Figure 4 related aspects of an embodiment of a wind turbine generator;

[0076] Figure 6 It is a schematic circuit diagram showing another embodiment of a wind turbine generator according to the first aspect of the present invention;

[0077] Figure 7 It is a schematic circuit diagram showing aspects of other embodiments of a wind turbine generator according to the first aspect of the present invention;

[0078] Figure 8A -D is a schematic circuit diagram showing aspects of an embodiment of a wind turbine generator related to Figure 7 ;

[0079] Figure 9 It is a schematic diagram showing Figure 7 and related aspects of an embodiment of a wind turbine generator with Figure 8;

[0080] Figure 10 It is a schematic flowchart showing aspects of an embodiment of the method according to the second aspect of the present invention; and

[0081] Figure 11 It is a schematic diagram showing an embodiment of a control device according to the fifth aspect of the present invention, in which a method according to any one of the embodiments described herein can be implemented. Detailed Description

[0082] Referring to Figures 1 to 9 , a schematic diagram shows embodiments of wind turbine generators 100a - e according to the first aspect of the present invention. Wind turbine generator 100a includes a generator 102. Wind turbine generator 100a includes means 104a - e for electric power conversion.

[0083] Refer to Figure 3 , apparatus 104a includes a first power converter 106 for converting AC power from generator 102 into DC power. Apparatus 104a includes a second power converter 108 for converting the DC power from the first power converter 106 into AC power to be supplied to the power grid 110 (see Figure 2 ). Apparatus 104a includes a DC link 112. The DC link 112 includes a positive rail 114 and a negative rail 116. The DC link 112 and / or the positive and negative rails 114, 116 connect (more specifically, electrically connect) the first power converter 106 to the second power converter 108. For some embodiments, the first power converter 106 may be referred to as a rectifier. For some embodiments, the second power converter 108 may be referred to as an inverter. For some embodiments, each power converter 106, 108 may be referred to as an electrical power converter. For some embodiments, the DC link 112 may be described as connecting the DC side of the first power converter 106 to the DC side of the second power converter 108.

[0084] Refer to Figure 3, the apparatus 104a includes an energy storage device 118a, and the energy storage device 118a includes a plurality of supercapacitors 120. The plurality of supercapacitors 120 are connected or connectable (more specifically, electrically connected / electrically connectable) to the DC link 112 to support the operation of one or more of the first power converter and the second power converters 106, 108, that is, to support the operation (or function, or functionality, or performance, or control) of the first power converter 106, or the second power converter 108, or both the first power converter and the second power converters 106, 108. For some embodiments, the supercapacitors 120 may be referred to as supercapacitance. The energy storage device 118a includes one or more DC-DC converters 122 for connecting (more specifically, electrically connecting) one or more of the supercapacitors 120 in the energy storage device 118a to the DC link 112. More specifically, for some embodiments, one or more DC-DC converters 122 connect one or more of the capacitors 120 in the energy storage device 118a to the DC link 112. For some embodiments, it may be defined that the energy storage device 118a is configured to provide or supply electrical energy to the DC link 112 to support the operation of one or more of the first power converter and the second power converters 106, 108. For some embodiments, the energy storage device 118a may be defined as an electrical energy storage device. For some embodiments, the DC link 112 may be described as a DC circuit. It should be understood that the plurality of supercapacitors 120 includes two or more supercapacitors 120, for example, three, four, five or more supercapacitors 120. For some embodiments, the energy storage device may include one or more additional power sources for providing additional electrical energy to the DC link 112, such as one or more batteries and / or one or more hybrid batteries.

[0085] Referring to Figure 1 , for some embodiments, the wind turbine generators 100a-e may include a rotor 126, and the rotor 126 includes one or more blades 128 or rotor blades 128, such as two or more blades 128, such as three blades 128 or more. The wind turbine generators 100a-e may include a tower 130 and a nacelle 132 mounted on the top of the tower 130. The rotor 126 may be connected (such as rotatably connected or mounted) to the nacelle 132. The rotor 126 may be connected to the generator 102. The rotor 126 is configured to drive the generator 102. The nacelle 132 may house the generator 102. The generator 102 may be a permanent magnet, PM, generator or any other type of generator.

[0086] Referring to Figure 1, the rotor 126 can be rotated by the action of the wind. The rotational energy of the blades 128 and the rotor 126 caused by the wind can be transmitted via a coupling 134 (such as including one or more shafts 136) to the generator 102. Thus, the wind turbine generators 100a-e can be described as being configured to convert the kinetic energy of the wind into mechanical energy or rotational energy by the blades 128, and then convert it into electrical power by the generator 102. Devices 104a-e (such as the first power converter and the second power converter 106, 108) can be described as being connected (more specifically, electrically connected) to the generator 102. The wind turbine generators 100a-e and / or the generator 102 can be connected to the power grid 110 via the devices 104a-e, more specifically via the first power converter and the second power converter 106, 108 of the devices 104a-e.

[0087] Referring to Figure 1 and Figure 3 , the nacelle 132 can house one or more of the first power converter and the second power converter 106, 108. For some embodiments, one or more of the first power converter and the second power converter 106, 108 can be located elsewhere, such as in the tower 130. For example, the first power converter 106 can be located in the nacelle 132, while the second power converter 108 can be located in the tower 130, such as in the lower part of the tower 130. However, other locations of the first power converter and the second power converter 106, 108 are possible. The nacelle 132 can house the energy storage device 118a and / or multiple supercapacitors 120, or the energy storage device 118a and / or multiple supercapacitors 120 can be located elsewhere, such as in the tower 130, or outside the tower 130 and the nacelle 132.

[0088] Referring to Figure 1 , for some embodiments, the energy storage device 118a can include one or more cabinets 124 that house at least a majority of the supercapacitors 120 of the energy storage device 118a (such as substantially all of the supercapacitors 120 of the energy storage device 118a). The cabinets 124 can be located inside or outside the nacelle 132. The cabinets 124 can be located in the tower 130, such as in the top part of the tower 130, for example adjacent to the nacelle 132, or in the bottom part of the tower 130, or anywhere in between. The cabinets 124 can be located outside both the tower 130 and the nacelle 132, and can be placed, for example, on the ground, underground, or on or in the foundation of an offshore wind turbine. The cabinets 124 can be attached to the outside of the tower 130 or the nacelle, such as attached to the top, bottom, or lateral side of the nacelle 132. Inside the nacelle 132, the cabinets 124 can have various different positions relative to the generator 102 and / or the first power converter and the second power converter 106.

[0089] Referring to Figure 1 , the wind turbine generators 100a - e may include a control device 138 or a controller 140 for controlling the wind turbine generators 100a - e. The control device 138 of the wind turbine generator 100a may include the controller 140, which may be referred to as a wind turbine generator controller. The control device 138 of the wind turbine generators 100a - e may be configured to communicate with and / or be connected to a control device 142 of a power plant 144 (see Figure 2 ) that includes one or more wind turbine generators 100a - e, or be part of the control device 142.

[0090] Referring to Figure 1 , for some embodiments, the wind turbine generators 100a - e may be referred to as variable - speed wind turbine generators. It should be understood that the wind turbine generators 100a - e may also include units, components, and / or equipment (such as sensors) required for the wind turbine generators 100a - e. For example, the wind turbine generators 100a - e may be located offshore or onshore.

[0091] Referring to Figure 2 , for some embodiments, the wind turbine generator 100a may be included in or be part of the power plant 144. In Figure 2 , an embodiment of a power plant 144 for supplying power or electrical energy to the power grid 110 according to a sixth aspect of the present invention is schematically illustrated. The power plant 144 includes one or more wind turbine generators 100a - e, for example, two, three, or more wind turbine generators 100a - e. For some embodiments, the wind turbine generators 100a - e may be described as a power source or a generator of the power plant 144. For some embodiments, the power plant 144 may include one or more additional power sources or generators, such as solar panels / photovoltaic panels 146, fuel cells 148, and / or battery units 150. For some embodiments, the power plant 144 may be referred to as a hybrid power plant. The power plant 144 may be connected or connectable to the power grid 110 via a point of common coupling PCC, 152. For some embodiments, the power grid 110 may be referred to as a public power grid, power grid, or electrical network. For example, the power plant 144 may be located offshore or onshore. The power plant 144 may include a control device 142 for controlling the power plant 144. The control device 142 of the power plant 144 may include or be referred to as a power plant controller PPC.

[0092] Referring to Figure 3, for some embodiments, the wind turbine generator 100a may include one or more transformers 147 between the power grid 110 and the device 104a or the second power converter 108. For some embodiments, the wind turbine generator 100a may include one or more circuit breakers 149 between the transformer 147 and the device 104a or the second power converter 108. For some embodiments, the wind turbine generator 100a may include one or more first filters 151 between the circuit breaker 149 and the device 104a or the second power converter 108. For some embodiments, the wind turbine generator 100a may include one or more second filters 153 between the generator 102 and the device 104a or the first power converter 106. For other embodiments, one or more of the transformer 147, the circuit breaker 149, the first filter 151, and the second filter 153 may be located elsewhere or connected differently from Figure 3 that shown in

[0093] Referring to Figure 3 , for some embodiments of the wind turbine generator 100a, the DC-DC converter 122 of the energy storage device 118a may be connected in series with one or more of the supercapacitors 120 of the energy storage device 118a, more specifically, electrically connected in series with one or more of the supercapacitors 120.

[0094] An advantage of the embodiments of the wind turbine generators 100a-e according to the first aspect is that the power supply to the DC link 112 during the operation of one or more of the first power converter and the second power converters 106, 108 is improved, thereby improving the operation or control of one or more of the first power converter and the second power converters 106, 108. By improving the operation of one or more of the first power converter and the second power converters 106, 108, the support provided by the wind turbine generators 100a-e to the power grid is improved, such as frequency and / or voltage support.

[0095] Advantages of embodiments of the wind turbine generator 100a-e according to the first aspect are that one or more of the first power converter and the second power converter 106, 108 can be controlled in an improved manner according to a so-called grid-forming control (GFC) mode, and different functions of the grid-forming control (GFC) mode can be supported in an improved manner, for example, by an improved electrical energy supply to the DC link 112 obtained by embodiments of the wind turbine generator 100a-e. Generally, in the grid-forming control (GFC) mode, one or more of the first power converter and the second power converter 106, 108 make the wind turbine generator 100a behave more like a conventional large synchronous generator compared to a more conventional grid-following (GFL) mode. For several reasons, it is advantageous to make the wind turbine generator 100a-e behave more like a conventional large synchronous generator. For example, generally, an increasing penetration rate of variable-speed wind turbine generators in the grid results in a reduction in the connected portion including conventional large synchronous generators, which leads to a reduction in the inertia in the grid because conventional large synchronous generators provide an inertial response for providing frequency support to the grid, while variable-speed wind turbine generators are typically connected to electrical power via one or more power converters, that is, variable-speed wind turbine generators are decoupled from the grid via one or more power converters, whereby the wind turbine generators cannot provide a true inertial response for providing frequency support to the grid. However, conventional control schemes can be applied to variable-speed wind turbine generators, which enables the variable-speed wind turbine generators to provide a so-called virtual inertial response or inertial simulation response for providing frequency support to the grid, and thus makes the variable-speed wind turbine generators behave more like conventional large synchronous generators. During a frequency drop in the grid, additional electrical power can thus be released from the variable-speed wind turbine generators to the grid through one or more of the conventional control schemes applied to the variable-speed wind turbine generators in order to provide frequency support to the grid. The additional power is obtained from the kinetic energy or rotation stored in the rotating mass or rotor of the wind turbine generator, which typically results in a deceleration of the rotor of the wind turbine generator.

[0096] Typically, in a conventional back-to-back converter system, where the machine-side converter (MSC) corresponding to the above-mentioned first power converter 106 and the line-side converter (LSC) corresponding to the above-mentioned second power converter 108 are both pulse-width modulation (PWM)-based converters, the machine-side converter (MSC) ensures that the generator receives the required power from the DC link. Conventionally, the energy capacity of the DC link is small, which requires the line-side converter (LSC) to control the DC link capacitor voltage level. Typically, in the grid-forming control (GFC) mode, for a back-to-back converter system where both the machine-side converter (MSC) and the line-side converter (LSC) are PWM-based converters, the control strategy is opposite to the above-mentioned conventional control strategy. Typically, in the grid-forming control (GFC) mode, the line-side converter (LSC) supplies the active power required by the grid according to the so-called swing equation with a phase lag, similar to the operation mode of a conventional large synchronous generator. Typically, this means that in the grid-forming control (GFC) mode, the voltage of the DC link will be controlled by the machine-side converter (MSC) because the active voltage vector of the line-side converter (LSC) is used to control the active power to be supplied to the grid. The requirements regarding grid-forming control (GFC) can be included in, for example, the grid code specified by the grid operator for the grid.

[0097] An advantage of the embodiment of the wind turbine generator 100a-e according to the first aspect is that the application of the DC-DC converter 122 enables more efficient utilization of the electrical energy of the plurality of supercapacitors 120. In the absence of a DC-DC converter, an excessive number of supercapacitors would need to be installed to meet the requirements, but only a small portion (such as approximately 10%) of the installed energy of the supercapacitors would be utilized, which means a high cost per installed energy of the supercapacitors 120, i.e., poor energy utilization efficiency. The application of the DC-DC converter 122 provides a lower cost per installed energy of the supercapacitors 120 and / or improved or enhanced utilization of the installed energy of the supercapacitors 120.

[0098] Referring to Figure 3 , by connecting the DC-DC converter 122 in series with one or more of the supercapacitors 120 of the energy storage device 118a, the DC-DC converter 122 may only need to maintain a nominal current, but only needs to maintain approximately 5% to 35% of the voltage, which results in a lower rated power, even lower than the rated power of the DC-DC converter 122 connected in parallel with one or more of the supercapacitors 120 of the energy storage device 118c (see Figure 6),Thereby achieving a lower cost per installed energy of the supercapacitor 120 and / or an improved or enhanced utilization of the installed energy of the supercapacitor 120. The series-connected DC-DC converter 122 can be considered as a trade-off or compromise in terms of energy utilization, cost, and volume / size of energy storage between 1) only supercapacitor connection and 2) supercapacitor combined with a parallel DC-DC converter. Generally, in the absence of any DC-DC converter, the converter DC voltage range allows 10% utilization of the installed energy of the supercapacitor 120. By adding a series-connected DC-DC converter, an additional 5% to 25% of energy can be used. Generally, a further expansion of the voltage range would literally mean that the DC-DC converter is designed for full voltage swing and nominal current, meaning the same rating as the parallel-connected DC-DC converter. Generally, the supercapacitor should be discharged to 50% or 60% of its nominal voltage. Discharging to zero voltage is feasible but will reduce the life or durability of the supercapacitor.

[0099] Referring to Figure 3 , for some embodiments, it can be defined that multiple supercapacitors 120 have a first terminal 154 and a second terminal 156. For some embodiments, it can be defined that the DC-DC converter 122 has a first DC side 158 and a second DC side 160. Each of the first DC side and the second DC side 158, 160 can include an input terminal 162, 164 and an output terminal 166, 168. For some embodiments, one of the positive rail and the negative rail 114, 116 is connected or connectable (more specifically, electrically connected / electrically connectable) to the first terminal 154 via the input terminal and the output terminal 162, 166 of the first DC side 158 of the DC-DC converter 122, while the other of the positive rail and the negative rail 114, 116 is connected or connectable (more specifically, electrically connected / electrically connectable) to the second terminal 156 without any interconnected DC-DC converter. For some embodiments, the other of the positive rail and the negative rail 114, 116 can be directly connected or connectable to the second terminal 156. For some embodiments, the input terminal and the output terminal 164, 168 of the second DC side 160 of the DC-DC converter 122 can be connected or connectable (more specifically, electrically connected / electrically connectable) to one or more power sources 170a-b, 108, 112 different from the multiple supercapacitors 120. For some embodiments, it can be described that the input terminal 162 of the first DC side 158 of the DC-DC converter 122 is connected or connectable to one of the positive rail and the negative rail 114, 116, while the output terminal 166 of the first DC side 158 of the DC-DC converter 122 is connected or connectable to the first terminal 154.

[0100] Reference Figure 4 , schematically illustrates another embodiment of the wind turbine generator 100b, which has a device 104b modified with respect to the Figure 3 device 104a and an energy storage device 118b. In the Figure 3 device 104a of the embodiment of Figure 4 , the input terminal 162 of the first DC side 158 of the DC-DC converter 122 is connected or connectable to the bottom rail of the positive and negative rails 114, 116, while the top rails of the positive and negative rails 114, 116 are connected or connectable to the second terminals 156 of the plurality of supercapacitors 120 without any interconnected DC-DC converter. In the Figure 4 device 104b of the embodiment of Figure 3 , the input terminal 162 of the first DC side 158 of the DC-DC converter 122 is alternatively connected or connectable to the top rails of the positive and negative rails 114, 116, while the bottom rails of the positive and negative rails 114, 116 are connected or connectable to the second terminals 156 of the plurality of supercapacitors 120 without any interconnected DC-DC converter. Otherwise, Figure 4 the embodiment of Figure 3 may correspond to the

[0101] Reference Figure 3 and Figure 5 , for some embodiments, the power sources 170a-b, 108, 112 may include one or more of the following groups:

[0102] · Battery 170a;

[0103] · Local power sources 170a, 170b, 108, 112;

[0104] · Auxiliary power source 170b of the wind turbine generator 100a;

[0105] · Second power converter 108 of the device 104a; and

[0106] · DC link 112 of the device 104a.

[0107] Reference Figure 6 , schematically illustrates another embodiment of the wind turbine generator 100c, which has a device 104c modified with respect to the Figure 3 device 104a and an energy storage device 118c. In the Figure 6In it, the DC - to - DC converter 122 is connected in parallel with one or more of the supercapacitors 120 in the energy storage device 118c. More specifically, it is electrically connected in parallel with one or more of the supercapacitors 120. For some embodiments, each of the first DC side and the second DC side 158, 160 of the DC - to - DC converter 122 may be defined to include a first terminal 166, 168 and a second terminal 162, 164. For some embodiments, the first terminal 166 of the first DC side 158 of the DC - to - DC converter 122 is connected or connectable to the first terminal 154 of a plurality of supercapacitors 120, while the second terminal 162 of the first DC side 158 of the DC - to - DC converter 122 is connected or connectable to the second terminal 156 of the plurality of supercapacitors 120. For some embodiments, the first terminal 168 of the second DC side 160 of the DC - to - DC converter 122 is connected or connectable to one of the positive and negative rails 114, 116, and the second terminal 164 of the second DC side 160 of the DC - to - DC converter 122 is connected or connectable to the other of the positive and negative rails 114, 116. Otherwise, Figure 6 The embodiments of Figure 3 may correspond to

[0108] Referring to Figure 7 , another embodiment of the wind turbine generator 100d is schematically illustrated, which has a device 104d and an energy storage device 118d modified with respect to Figure 3 the embodiments of Figure 7 The energy storage device 118d of Figure 7 includes one or more first circuits 172a1, 172a2. Each first circuit 172a1, 172a2 includes one or more supercapacitors 120 and one or more DC - to - DC converters 122 for connecting one or more supercapacitors 120 of the first circuits 172a1, 172a2 to the DC link 112. Figure 7 The energy storage device 118d of Figure 3 includes one or more second circuits 174a1, 174a2. Each second circuit 174a1, 174a2 includes one or more supercapacitors 120 connected or connectable to the DC link 112, without any inter - connected DC - to - DC converters, that is, there is no DC - to - DC converter between one or more supercapacitors 120 of the second circuits 174a1, 174a2 and the DC link 112. For some embodiments, one or more supercapacitors 120 of the second circuits 174a1, 174a2 may be directly connected or connectable to the DC link 112. Otherwise, Figure 7 The embodiments of Figure 3 may correspond to

[0109] Referring to Figure 7, The advantage of the embodiment of the wind turbine generator 100d according to the first aspect is that the application of one or more DC-DC converters 122 makes the power utilization of the plurality of supercapacitors 120 more efficient. In the absence of a DC-DC converter, the energy utilization rate will be poor, limited by the DC link voltage range. However, in the presence of a DC-DC converter, due to the cost of the DC-DC converter, the cost per MW will become very high because a DC-DC converter rated at the nominal power is required according to the requirements. Figure 7 The advantage of the embodiment is that optimization is achieved, for example, in terms of cost, volume / size of energy storage, and power utilization of the supercapacitors 120. Generally, an energy storage device with a small volume or size is required to minimize the overall volume. For lower-level functions and low energy usage, one or more second circuits 174a1, 174a2 including one or more supercapacitors without any interconnected DC-DC converters can be applied, while for higher-level functions, such as charging or discharging the supercapacitors 120 at a fast rate, one or more first circuits 172a1, 172a2 including one or more supercapacitors and one or more DC-DC converters 122 can be applied. Therefore, Figure 7 The advantage of the embodiment is that the power supply to the DC link 112 during the operation of one or more of the first power converter and the second power converter 106, 108 is improved and becomes more efficient, thereby improving the operation or control of one or more of the first power converter and the second power converter 106, 108. By Figure 7 the embodiment, a lower cost per installed energy of the supercapacitors 120 and / or an improved or enhanced utilization of the installed energy of the supercapacitors 120 is achieved.

[0110] Referring to Figures 8A to 8D , several different embodiments of the first circuit 172b-e and the second circuit 174b-e are schematically illustrated. Figures 8A to 8D One or more of the first circuit and the second circuit 172b-e, 174b-e shown in Figure 7 can replace or supplement one or more of the first circuit 172a1, 172a2 and the second circuit 174a1, 174a2 shown in

[0111] Referring to Figure 7 and Figures 8A to 8D , the first circuit and the second circuit 172a-e, 174a-e shown can be combined in various possible ways, and the number of the first circuit and the second circuit 172a-e, 174a-e can vary to provide additional embodiments of the wind turbine generator. It should be understood that compared with Figure 7 andFigures 8A to 8D Additional first and second circuits 172a-e, 174a-e different from the circuit shown are possible, for example having more or fewer supercapacitors 120 and / or more or fewer DC-to-DC converters 122. For some embodiments, the energy storage device 118d may include a plurality of first circuits 172a1, 172a2 and a plurality of second circuits 174a1, 174a2. For some embodiments, the second circuits 174a1, 174a2, 174c, 174d, 174e may include two or more supercapacitors 120 connected or connectable to the DC link 112 without any interconnected DC-to-DC converters.

[0112] Referring to Figure 9 , another embodiment of the wind turbine generator 100e is schematically illustrated, having a device 104e modified with respect to Figure 7 the embodiment of Figure 9 The wind turbine generator 100e of includes a controller 140 for controlling the power supply from the first and second circuits 172a-e, 174a-e to the DC link 112. For some embodiments, the controller 140 may be configured to control the power supply from the first and second circuits 172a-e, 174a-e to the DC link 112 based on the operating levels of one or more of the first power converter and the second power converter 106, 108. For some embodiments, one of the first and second circuits 172a-e, 174a-e may be a default circuit that is initially connected by default for power supply to the DC link 112. Otherwise, Figure 9 the embodiment of Figure 7 the embodiment of

[0113] Referring to Figures 3 to 9 , one or more of the energy storage devices 118a-d, the plurality of supercapacitors 120, and the DC-to-DC converter 122 may be directly or indirectly connected to the DC link 112 and / or to each other by one or more busbars, cables or wires or any other electrical conductors or by any combination thereof. For example, if the energy storage devices 118a-d are installed near the DC link 112, such as in the nacelle 132 when the DC link 112 is located in the nacelle 132, busbars or any other electrical conductors may be used. For example, if the energy storage devices 118a-d are installed at a relatively long distance from the DC link 112, such as in the tower 130 when the DC link 112 is located in the nacelle 132, cables or any other electrical conductors may be used.

[0114] Referring to Figure 10, schematically illustrates aspects of an embodiment of a method for the conversion of electrical power from AC power of a generator 102 of a wind turbine generator 100a-e to AC power to be supplied to a power grid 110. Embodiments of the method include the following steps:

[0115] · Control 201 a first power converter 106 to convert AC power from the generator 102 into DC power;

[0116] · Control 202 a second power converter 108 to convert the DC power from the first power converter 106 into AC power, wherein the second power converter 108 is connected to the first power converter 106 via a DC link 112; and

[0117] · Provide 203 (or supply) electrical energy from an energy storage device 118a-d to the DC link 112, the energy storage device 118a-d including a plurality of supercapacitors 120 and one or more DC-DC converters 122 connecting one or more of the supercapacitors 120 of the energy storage device 118a-d to the DC link 112, so as to support the operation of one or more of the first power converter and the second power converter 106, 108.

[0118] For some embodiments, the method may be defined to include:

[0119] · Convert AC power from the generator 102 into DC power through the first power converter 106; and

[0120] · Convert the DC power from the first power converter 106 into AC power through the second power converter 108, the second power converter 108 being connected to the first power converter 106 via a DC link 112.

[0121] Referring to Figure 10 , for some embodiments, the step of providing 203 electrical energy from the energy storage device 118a-d to the DC link 112 may include providing 203a electrical energy from one or more of the supercapacitors 120 of the energy storage device 118a-d to the DC link 112 via one or more DC-DC converters 122.

[0122] Referring to Figure 10 , for some embodiments, the step of providing 203 electrical energy from the energy storage device 118a-d to the DC link 112 may include providing 203b electrical energy from the energy storage device 118a-d according to any one of the embodiments disclosed above or below.

[0123] For example, embodiments of the method according to the second aspect of the present invention can be applied to the wind turbine generators 100a-e shown above. However, embodiments of the method according to the second aspect can also be applied to other wind turbine generators.

[0124] Referring Figure 1 and Figure 11 , aspects of an embodiment of a control device 138 for controlling the electrical power conversion of AC power from the generator 102 of the wind turbine generators 100a-e to AC power to be supplied to the power grid 110 are schematically illustrated according to a fifth aspect of the present invention. The embodiment of the control device 138 is configured to:

[0125] · Control 201 the first power converter 106 to convert the AC power from the generator 102 into DC power;

[0126] · Control 202 the second power converter 108 to convert the DC power from the first power converter 106 into AC power, the second power converter 108 being connected to the first power converter 106 via a DC link 112; and

[0127] · Supply 203 electrical energy from the energy storage devices 118a-d to the DC link 112, the energy storage devices 118a-d including a plurality of supercapacitors 120 and one or more DC-to-DC converters 122 connecting one or more of the supercapacitors 120 of the energy storage devices 118a-d to the DC link 112 so as to support the operation of one or more of the first power converter and the second power converters 106, 108.

[0128] Referring Figure 1 , the illustrated embodiment of the control device 138 includes a first control unit 138a for controlling the first power converter 106 to perform Figure 10 step 201 in Figure 10 . The illustrated embodiment of the control device 138 includes a second control unit 138b for controlling the second power converter 108 to perform Figure 10 step 202 in

[0129] Referring Figure 1, for some embodiments, the control device 138 is configured to communicate directly or indirectly with one or more of the following groups, for example, via a signal line (or cable or wire) or wirelessly: wind turbine generators 100a-e; power plant 144; power grid 110; sensors; and other devices or systems of wind turbine generators 100a-e or power plant 144.

[0130] Figure 11 An embodiment of the control device 138 according to a fifth aspect of the present invention is shown schematically and may include a control unit 300, which may correspond to or may include one or more of the above units 138a-c of the control device 138. The control unit 300 may include a computing unit 301, which may be constituted by substantially any suitable type of processor or microcomputer, such as a circuit for digital signal processing (digital signal processor, DSP) or a circuit with a predetermined specific function (application specific integrated circuit, ASIC). The computing unit 301 is connected to a memory unit 302 arranged in the control unit 300. The memory unit 302 provides, for example, stored program code and / or stored data that the computing unit 301 needs in order to perform calculations. The computing unit 301 is also arranged to store partial or final results of the calculations in the memory unit 302.

[0131] Furthermore, with reference to Figure 11 , the control unit 300 may be provided with devices 311, 312, 313, 314 for receiving and transmitting input signals and output signals. These input signals and output signals may contain waveforms, pulses or other attributes, which may be detected as information by the devices 311, 313 for receiving input signals and may be converted into signals that can be processed by the computing unit 301. Then these signals are made available to the computing unit 301. The devices 312, 314 for transmitting output signals are arranged to convert the signals received from the computing unit 301 in order to create output signals, for example, by modulating the signals, which signals may, for example, be transmitted to the wind turbine generators 100a-e or the power plant 144 (see Figure 1 and Figure 2 ) or other parts and / or systems associated with or related to the wind turbine generators 100a-e or the power plant 144. Each connection to the devices for receiving and transmitting input signals and output signals may be constituted by one or more of a cable, a data bus and a wireless connection.

[0132] Herein and in this document, units are generally described as being provided for performing the steps of a method according to an embodiment of the present invention. This also includes that the units are designed and / or configured to perform these method steps.

[0133] With reference to Figure 1, units 138a-c of the control device 138 are shown as separate units in Figure 1 . However, these units 138a-c may be logically separated but physically implemented in the same unit, or may be arranged both logically and physically together. These units 138a-c may correspond, for example, to groups of instructions, which may be in the form of programming code that, when the unit is active and / or for performing its method steps, are input into and utilized by the processor / computation unit 301 (see Figure 11 ).

[0134] Referring to Figure 1 and Figure 11 , a control device 138 according to an embodiment of the present invention that may include one or more control units 300 (such as one or more devices, controllers, or control devices) may be arranged to perform all of the above method steps recited in the claims and in connection with the embodiments described herein. The control device 138 is associated with the above advantages of each corresponding embodiment of the method.

[0135] Referring to Figure 11 , according to a third aspect of the present invention, there is provided a computer program 303 that includes instructions that, when executed by a computer, cause the computer to perform a method according to one or more of the above-disclosed embodiments.

[0136] According to a fourth aspect of the present invention, there is provided a computer-readable medium that includes instructions that, when executed by a computer, cause the computer to perform a method according to one or more of the above-disclosed embodiments.

[0137] Those skilled in the art will understand that the embodiments described herein of the method according to the second aspect may be implemented in a computer program 303 (see Figure 11 ), and when the computer program 303 is executed in a computer, the computer program 303 instructs the computer to perform the method. A computer program generally consists of a computer program product 303 stored on a non-transitory / non-volatile digital storage medium, where the computer program is incorporated into the computer-readable medium of the computer program product. The computer-readable medium includes a suitable memory, such as: ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable PROM), flash memory, EEPROM (electrically erasable PROM), hard disk unit, etc.

[0138] The present invention is not limited to the above embodiments. On the contrary, the present invention relates to and encompasses all different embodiments included within the scope of the independent claims.

Claims

1. A wind turbine generator (100a-e) comprising a generator (102) and means (104a-e) for electric power conversion, wherein, The device (104a-e) includes: A first power converter (106) for converting AC power from the generator (102) into DC power, A second power converter (108) for converting the DC power from the first power converter (106) into AC power to be supplied to the power grid (110), A DC link (112) including a positive rail (114) and a negative rail (116) connecting the first power converter (106) to the second power converter (118), and An energy storage device (118a-d) including a plurality of supercapacitors (120), the plurality of supercapacitors (120) being connected or connectable to the DC link (112) to support the operation of one or more of the first power converter and the second power converter (106, 108), Wherein, the energy storage device (118a-d) includes one or more DC-DC converters (122) for connecting one or more of the supercapacitors (122) of the energy storage device (118a-d) to the DC link (112), and Wherein, the DC-DC converter (122) is connected in series with one or more of the supercapacitors (120) of the energy storage device (118a-d).

2. The wind turbine generator (100a-e) according to claim 1, wherein, The energy storage device (118a-d) includes one or more cabinets (124) accommodating at least most of the supercapacitors (120) of the energy storage device (188a-d).

3. The wind turbine generator (100a-b) according to any one of claims 1 to 2, wherein, The plurality of supercapacitors (120) have a first terminal (154) and a second terminal (156), Wherein, the DC-DC converter (122) has a first DC side (158) and a second DC side (160), Wherein, each of the first DC side and the second DC side (158, 160) includes an input terminal (162, 164) and an output terminal (166, 168), Wherein, one of the positive rail and the negative rail (114, 116) (114, 116) is connected or connectable to the first terminal (154) via the input terminal and the output terminal (162, 166) of the first DC side (158) of the DC-DC converter (122), while the other of the positive rail and the negative rail (114, 116) (114, 116) is connected or connectable to the second terminal (156) without any interconnected DC-DC converter, and Wherein, the input terminal and the output terminal (164, 168) of the second DC side (160) of the DC-DC converter (122) are connected or connectable to one or more power sources (170a-b; 108; 112) different from the plurality of supercapacitors (120).

4. The wind turbine generator (100a-b) according to claim 3, wherein, The input terminal (162) of the first DC side (158) of the DC-DC converter (122) is connected or connectable to one of the positive rail and the negative rail (114, 116) (114, 116), and The output terminal (166) of the first DC side (158) of the DC-to-DC converter (122) is connected or connectable to the first terminal (154).

5. The wind turbine generator (100a-b) according to claim 3 or 4, wherein, The power source (170a-b; 108; 112) includes one or more of the following groups: · A battery (170a); · A local power source (170a-b; 108; 112); · An auxiliary power source (170b) of the wind turbine generator (100a-e); · The second power converter (108); and · The DC link (112).

6. The wind turbine generator (100d-e) according to claim 1 or 2, wherein, The energy storage device (118d) includes: One or more first circuits (172a-e) including one or more supercapacitors (120) and one or more DC-to-DC converters (122) for connecting the one or more supercapacitors (120) of the first circuits (172a-e) to the DC link (112), and One or more second circuits (174a-e) including one or more supercapacitors (120) connected or connectable to the DC link (112) without any interconnection of DC-to-DC converters.

7. The wind turbine generator (100d-e) according to claim 6, wherein, The energy storage device (118d) includes a plurality of first circuits (172a-e) and a plurality of second circuits (174a-e).

8. The wind turbine generator (100e) according to claim 6 or 7, wherein, The wind turbine generator (100e) includes a controller (140) for controlling the power supply from the first and second circuits (172a-e, 174a-e) to the DC link (112), and wherein the controller (140) is configured to control the power supply from the first and second circuits (172a-e, 174a-e) to the DC link (112) based on the operating level of one or more of the first power converter and the second power converter (106, 108).

9. A method for the electrical power conversion of AC power from a generator (102) of a wind turbine generator (100a-e) to AC power to be supplied to a power grid (110), wherein, The method includes: Controlling (201) a first power converter (106) to convert AC power from the generator (102) into DC power; Controlling (202) a second power converter (108) to convert the DC power from the first power converter (106) into AC power, the second power converter (108) being connected to the first power converter (106) via a DC link (112); and Supplying (203) electrical energy from an energy storage device (118a-d) to the DC link (112), the energy storage device (118a-d) including a plurality of supercapacitors (120) and one or more DC-to-DC converters (122) connecting one or more of the supercapacitors (120) of the energy storage device (118a-d) to the DC link (112) to support the operation of one or more of the first power converter and the second power converter (106, 108).

10. The method according to claim 11, wherein, The step of supplying (203) electrical energy from the energy storage device to the DC link includes supplying (203b) electrical energy from the energy storage device (118a-d) according to any one of claims 1 to 8.

11. A computer program (303) comprising instructions or a computer-readable medium comprising instructions, which when executed by a computer, cause the computer to perform the method according to claim 9 or 10.

12. A control device (138) for controlling the electrical power conversion of AC power from a generator (102) of a wind turbine generator (100a-e) to AC power to be supplied to a power grid (110), wherein, The control device (138) is configured to: control (201) a first power converter (106) to convert AC power from the generator (102) into DC power; control (202) a second power converter (108) to convert the DC power from the first power converter (106) into AC power, the second power converter (108) being connected to the first power converter (106) via a DC link (112); and supply (203) electrical energy from an energy storage device (118a-d) to the DC link (112), the energy storage device (118a-d) including a plurality of supercapacitors (120) and one or more DC-to-DC converters (122) connecting one or more of the supercapacitors (120) of the energy storage device (118a-d) in series to the DC link (112) to support the operation of one or more of the first and second power converters (106, 108).

13. The wind turbine generator (100a-e) according to any one of claims 1 to 8, wherein, The wind turbine generator (100a-e) includes the control device (138) according to claim 12.

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