A small-scale capacity-increasing structure and reconstruction construction method for wind turbine foundations in old wind farms

Abstract

The present invention discloses a structure and renovation construction method for a small-scale renovation of an old wind turbine foundation in a wind farm, which includes an original wind turbine foundation, a newly cast reinforced concrete foundation, a vertical anchor cage connection system, and a radial anchor connection system; the connection structure between the bottom section of the new wind turbine tower and the new wind turbine foundation includes a vertical anchor cage connection system and a radial anchor connection system; the vertical anchor cage connection system is fixed inside the original wind turbine foundation, and the radial anchor connection system is fixed inside the newly cast reinforced concrete foundation. The new wind turbine foundation has an expanded middle pier diameter to accommodate the new tower, while the middle pier height remains unchanged, and there is almost no need to increase the height of the middle pier of the newly cast foundation, which greatly reduces the amount of concrete used. At the same time, the structure retains the original vertical anchor cage connection system and uses a radial anchor connection system to strengthen the connection between the bottom section of the new wind turbine tower and the wind turbine foundation, effectively controlling the renovation cost and connection reliability, and realizing the maximum reuse of the original wind turbine foundation and the controllable cost of the new wind turbine foundation.

Description

Technical Field

[0001] The present invention relates to a structure for increasing the capacity of wind turbine foundations in old wind farms for onshore wind power generation by upgrading them from small to large ones and a reconstruction construction method. Background Art

[0002] Currently, older wind farms are facing challenges such as small turbine capacity, low power generation efficiency, and aging equipment, necessitating expansion and upgrading to meet new development needs. To effectively reduce the cost of retrofitting older wind farms and conserve land resources, renovations should be completed within the original turbine locations and foundations whenever possible, minimizing or avoiding new land acquisition and demolition work. However, the challenges and difficulties are as follows:

[0003] (1) The early wind turbines connected to the grid had small unit capacity, low hub height, small rotor diameter, and small load transferred to the foundation. After replacing them with large-capacity units, the hub height was higher and the rotor diameter was larger, and the load transferred to the foundation also increased significantly. The size of the original tower also changed.

[0004] (2) In the current "small to large" wind turbine foundation renovation scheme, the "large to small" approach is usually used. Specifically, a new middle pier is cast on top of the original middle pier to accommodate the installation requirements of a larger wind turbine. In order to ensure that the anchor cage can be correctly arranged, the height of the newly cast middle pier must meet specific height requirements. This results in the need to use a large amount of concrete when renovating the wind turbine foundation. In addition, the foundation after the renovation is significantly higher than the ground surface, which is to some extent not conducive to the stability of the foundation.

[0005] Based on the above situation, how to directly carry out technical transformation based on the old wind turbines to maximize the reuse of the old foundation and control the cost of the new foundation has become a challenge and difficulty faced by the technical transformation of old wind farms. Summary of the Invention

[0006] The purpose of the present invention is to provide a structure and construction method for upgrading the wind turbine foundation of an old wind farm to increase its capacity, so as to address the challenges and difficulties faced by the technical transformation of old wind farms in the above-mentioned background technology. To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0007] A structure for upgrading and increasing the capacity of old wind turbine foundations in wind farms, comprising the original wind turbine foundation, a newly poured reinforced concrete foundation, a vertical anchor cage connection system, and a radial anchor connection system;

[0008] The newly poured reinforced concrete foundation is poured on the original wind turbine foundation to form a new wind turbine foundation together; the outer ring of the newly poured reinforced concrete foundation surrounds and covers the outer ring of the original wind turbine foundation from the top and radially outward, and the middle pier of the newly poured reinforced concrete foundation surrounds the outside of the middle pier of the original wind turbine foundation but is not higher than the middle pier of the original wind turbine foundation, and is adapted to the diameter of the bottom section of the new wind turbine tower;

[0009] The connection structure between the bottom section of the new wind turbine tower and the new wind turbine foundation includes a vertical anchor cage connection system and a radial anchor connection system; the vertical anchor cage connection system is fixed inside the original wind turbine foundation, and the radial anchor connection system is fixed inside the newly poured reinforced concrete foundation.

[0010] On the basis of adopting the above technical solutions, the present invention may also adopt the following further technical solutions, and use these further technical solutions in combination:

[0011] The bottom section of the new wind turbine tower is arranged on the middle pier formed by the middle pier of the newly poured reinforced concrete foundation and the middle pier of the original wind turbine foundation. The bottom of the bottom section of the new wind turbine tower is provided with a tower bottom plate, and vertical holes are reserved on the tower bottom plate. The size, number and position of the vertical holes match the vertical anchor bolts of the vertical anchor cage connection system of the original wind turbine foundation, so as to install the vertical anchor bolts; a wedge-shaped armpit area is provided at the junction of the inner side wall of the bottom section of the new wind turbine tower and the tower bottom plate, the inclined surface of the wedge-shaped armpit area is perpendicular to the radial anchor bolts, and the wedge-shaped armpit area and the side of the tower are provided with through holes, the size, number and position of the holes match the radial anchor bolts of the radial anchor bolt connection system, so as to install the radial anchor bolts.

[0012] The vertical anchor cage connection system retains the connection components of the original wind turbine foundation, including the original foundation lower anchor plate, the vertical anchor bolts, and the original foundation upper anchor plate; when the bottom section of the new wind turbine tower is hoisted, the vertical anchor bolts pass through the vertical holes of the tower bottom plate and are fastened by nuts, reliably connecting the bottom section of the new wind turbine tower with the new wind turbine foundation composed of the newly cast reinforced concrete foundation and the original wind turbine foundation.

[0013] The radial anchor connection system includes an annular anchor plate, a radial anchor and an embedded steel casing; the length of the radial anchor is less than or equal to the inner diameter of the bottom section of the fresh air fan tower, so that the radial anchor is installed from the inside of the bottom section of the fresh air fan tower, and the outer end of the radial anchor is also provided with an external thread for fixing with the embedded steel casing; the embedded steel casing includes a casing body, multiple bamboo-shaped expansion rings located on the outer wall of the casing body, an external thread at the inner end of the casing, and an internal thread at the outer end of the casing; the internal thread at the outer end of the casing matches the external thread at the outer end of the radial anchor for fixing the radial anchor; the casing body is thin at the inner end and thick at the outer end.

[0014] An elastic cushion layer or epoxy resin grouting material is provided between the bottom section of the new wind turbine tower and the newly poured reinforced concrete foundation. The elastic cushion layer or epoxy resin grouting material can prevent local stress concentration on the foundation caused by lateral micro-deformation of the tower.

[0015] The annular anchor plate is formed by splicing two semicircular petals into a circle, the inner diameter of which matches the outer diameter of the bottom section of the fresh air fan tower, and is arranged around the outer wall of the bottom section of the fresh air fan tower; overlapping sections are provided at both ends of each petal of the annular anchor plate, and the overlapping sections and the main body of the annular anchor plate are configured in a step shape; the annular anchor plate is provided with a plurality of sleeve threaded holes passing through the anchor plate along its length direction, the external thread of the inner end of the embedded steel casing matches the thread of the sleeve threaded hole, the inner end of the embedded steel casing is fixed to the annular anchor plate by a threaded connection, and the outer end is tied or welded to the foundation reinforcement.

[0016] The capacity expansion structure of the present invention is further provided with a plurality of levelers. The annular anchor plate is positioned and leveled by the levelers during installation. A support platform for the levelers is processed on the outer ring of the original fan foundation.

[0017] The leveler includes a base, a long screw, a lower nut, an upper nut, a bracket, an annular anchor plate support and a support bolt; a bracket is provided on the base, and the bracket includes a diagonal brace; an annular anchor plate support is provided above the bracket, and the annular anchor plate support is provided with a vertical hole and a support bolt; a matching leveler threaded hole is provided at the bottom of the annular anchor plate, and after the vertical hole is aligned with the leveler threaded hole of the annular anchor plate, the leveler and the annular anchor plate are fixed by the support bolt.

[0018] The outer ring of the original fan foundation and the side of the newly poured reinforced concrete foundation are provided with horizontal foundation outer side embedded bars connected to each other, and the outer ends of the horizontal foundation outer side embedded bars are bent and fixed on the reinforcement of the newly poured reinforced concrete foundation.

[0019] The present invention also provides a method for renovating an old wind farm wind turbine foundation with a small-scale upgrade to a large-scale capacity-increasing structure, which adopts any of the above-mentioned old wind farm wind turbine foundation small-scale upgrade to a large-scale capacity-increasing structure and includes the following steps:

[0020] Step 1: Remove the original wind turbine and tower, excavate the original foundation backfill area, chisel out a small step on the top surface of the original wind turbine foundation outer ring to increase the bite force between the new and old concrete, and chisel out a platform on the top surface of the original foundation outer ring just below the annular anchor plate for arranging the leveler;

[0021] Step 2: Plant pile foundation in the expanded area of the foundation;

[0022] Step 3: Drill holes on the top surface of the outer ring of the original fan foundation to install the leveler, and then level and adjust the height;

[0023] Step 4: Connect the two halves of the semicircular anchor plate and position them on the leveler;

[0024] Step 5: Drill holes on the outer ring surface of the original fan foundation, grout, and place horizontal and vertical rebars on the outside of the foundation;

[0025] Step 6: Tie the reinforcement of the newly poured reinforced concrete foundation. This reinforcement is tied to the vertical planted reinforcement. Tighten the embedded steel casing to the annular anchor plate, and tie the outer end of the embedded steel casing to the reinforcement. In addition, when a hidden beam is added between the pile foundation and the newly poured reinforced concrete foundation, tie or weld the exposed reinforcement of the pile to the hidden beam steel to strengthen the connection between the edge of the newly poured reinforced concrete foundation and the pile.

[0026] Step 7: Support the formwork and cast the newly poured reinforced concrete foundation;

[0027] Step 8: After the strength of the newly poured concrete reaches the requirement, hoist the bottom section of the new wind turbine tower; after successful positioning, connect the bottom section of the new wind turbine tower to the new wind turbine foundation formed by the newly poured reinforced concrete foundation and the original wind turbine foundation through the vertical anchor cage connection system and the existing structure of the original wind turbine foundation connected to the vertical anchor cage connection system; and use the radial anchor connection system to connect the bottom section of the new wind turbine tower to the new wind turbine foundation formed by the newly poured reinforced concrete foundation and the original wind turbine foundation to achieve a reliable connection.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) A radial anchor connection system is used to connect the newly poured reinforced concrete foundation and the bottom section of the new wind turbine tower. The radial anchors are arranged basically parallel to the top surface of the foundation. The bottom section of the new wind turbine tower is arranged above the middle pier of the old wind turbine foundation. There is almost no need to increase the height of the middle pier of the newly poured foundation, which greatly reduces the amount of concrete used.

[0030] (2) The vertical anchor cage connection system can be used to connect the original wind turbine foundation and the bottom section of the new wind turbine tower with an enlarged diameter. This fully utilizes the connection system of the old wind turbine foundation, not only improving the connection reliability, but also effectively controlling the renovation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a cross-sectional view of the wind turbine foundation structure with a small-scale upgrade and large-scale capacity increase according to an embodiment of the present invention;

[0032] Figure 2 A top view of the wind turbine foundation small-scale upgrade and large-scale capacity increase structure according to an embodiment of the present invention;

[0033] Figure 3 This is a cross-sectional view of the connection structure between the bottom section of the new wind turbine tower and the new wind turbine foundation according to an embodiment of the present invention;

[0034] Figure 4 This is a three-dimensional schematic diagram of an annular anchor plate according to an embodiment of the present invention;

[0035] Figure 5 This is a three-dimensional schematic diagram of the embedded steel sleeve according to an embodiment of the present invention;

[0036] Figure 6This is a cross-sectional view of the embedded steel sleeve according to an embodiment of the present invention;

[0037] Figure 7 This is a three-dimensional schematic diagram of a leveler according to an embodiment of the present invention;

[0038] Figure 8 This is a front view of a leveler according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0040] The present invention provides a structure for increasing the capacity of old wind turbine foundations by upgrading them slightly. The structure is suitable for expandable wind turbine foundations (including circular and octagonal expandable wind turbine foundations), thereby maximizing the reuse of the original wind turbine foundations and controlling the cost of new wind turbine foundations.

[0041] See also Figures 1-8 The wind turbine foundation small-scale modification and large-scale capacity expansion structure includes the existing original wind turbine foundation 1, the newly poured reinforced concrete foundation 2, the vertical anchor cage connection system 102, and the radial anchor connection system 202.

[0042] The original wind turbine foundation 1 comprises a middle pier 103 and an outer ring 101, which are reinforced concrete structures and cast as one body. In this embodiment, the outer ring 101 of the original wind turbine foundation 1 is generally conical in shape.

[0043] The newly cast reinforced concrete foundation 2 is cast outside the existing wind turbine foundation 1, forming a new wind turbine foundation. The newly cast reinforced concrete foundation 2 includes a center pier 208 and an outer ring 201. The outer ring 201 surrounds and covers the outer ring 101 of the existing wind turbine foundation 1 from the top and radially outward. The center pier 208 surrounds the outside of the center pier 103 of the existing wind turbine foundation 1 but is not higher than the center pier 103, preferably with the same height. The new center pier 208 is provided so that the outer diameter of the center pier, formed by the center pier 208 of the newly cast reinforced concrete foundation 2 and the center pier 103 of the existing wind turbine foundation 1, matches the outer diameter of the new wind turbine tower bottom section 3, facilitating the arrangement of the new wind turbine tower bottom section 3. Reference numeral 2080 represents the outer contour of the center pier 208, and reference numeral 1030 represents the original outer contour of the center pier 103.

[0044] The center pier 103 of the original wind turbine foundation 1 is higher than its outer ring 101, and the inner end of the outer ring 201 of the newly cast reinforced concrete foundation 2 is higher than the newly built center pier 208. A radial anchor bolt connection system 202 is radially arranged within the newly cast reinforced concrete foundation 2, substantially parallel to the top surface 1011 of the outer ring of the original wind turbine foundation 1. The radial anchor bolt connection system 202 is arranged radially from a top view and, preferably, is inclined to the horizontal plane. The new wind turbine tower base section 3 and the new wind turbine foundation, which is formed integrally with the newly cast reinforced concrete foundation 2 and the original wind turbine foundation 1, are connected via the radial anchor bolt connection system 202 and the vertical anchor cage connection system 102. The vertical anchor cage connection system 102 resides within the original wind turbine foundation 1 and can utilize the structure of the original wind turbine foundation 1 to connect to the new wind turbine tower base section 3.

[0045] The diameter of the new wind turbine tower bottom section 3 is larger than that of the old tower bottom section. To position the new wind turbine tower bottom section 3 above the center pier, an elastic cushioning layer or epoxy resin grouting material 204 is also placed on the side of the new wind turbine tower bottom section 3. The elastic cushioning layer or epoxy resin grouting material 204 is located between the new wind turbine tower bottom section 3 and the inner end of the outer ring 201 of the newly cast reinforced concrete foundation 2 to prevent local stress concentration in the foundation caused by lateral micro-deformation of the tower bottom. The center pier 208 of the newly cast reinforced concrete foundation 2 has been enlarged to match the outer diameter of the new wind turbine tower bottom section 3, based on the center pier 103 of the original wind turbine foundation 1. The height of the center pier 208 of the newly cast reinforced concrete foundation 2 remains the same as the center pier 103 of the original wind turbine foundation 1. The bottom of the new wind turbine tower base section 3 is provided with a tower base plate 301, which is pre-determined with vertical holes. The size, number, and position of the vertical holes match the vertical anchor bolts 1022 in the vertical anchor cage connection system 102 of the original wind turbine foundation 1, allowing the vertical anchor bolts 1022 of the original wind turbine foundation 1 to be installed. A wedge-shaped armpit area 302 is provided at the junction of the inner sidewall of the new wind turbine tower base section 3 and the tower base plate 301. The inclined surface of the wedge-shaped armpit area 302 is perpendicular to the radial anchor bolts 2022. The wedge-shaped armpit area 302 and the tower wall are provided with through holes. The size, number, and position of the holes match the radial anchor bolts 2022 to facilitate the installation of the radial anchor bolts 2022.

[0046] As previously mentioned, in the present invention, the connection structure between the new wind turbine tower bottom section 3 and the new wind turbine foundation includes a vertical anchor cage connection system 102 and a radial anchor connection system 202. The vertical anchor cage connection system 102 retains the components connected to the original wind turbine foundation 1, specifically including the original foundation lower anchor plate 1021, vertical anchor bolts 1022, and the original foundation upper anchor plate 1023. When the new wind turbine tower bottom section 3 is hoisted, the vertical anchor bolts 1022 pass through the reserved holes in the tower bottom plate 301 and are tightened with nuts. Thus, the new wind turbine tower bottom section 3 is connected to the new wind turbine foundation, which is formed integrally by the newly cast reinforced concrete foundation 2 and the original wind turbine foundation 1, by utilizing the vertical anchor cage connection system 102 and the structure of the original wind turbine foundation 1 that cooperates with the vertical anchor bolts.

[0047] The radial anchor connection system 202 includes an annular anchor plate 2021, a radial anchor 2022, and an embedded steel casing 2023. The radial anchor 2022 is designed to be shorter than or equal to the inner diameter of the wind turbine tower bottom section 3 to facilitate installation. Its outer end is also provided with external threads 2022-1 for securing it to the embedded steel casing 2023. The embedded steel casing 2023 includes a casing body 2023-1, multiple bamboo-shaped expansion rings 2023-2 located on the outer wall of the casing, external threads 2023-3 on the inner end of the casing, and internal threads 2023-4 on the outer end of the casing. The internal threads 2023-4 on the outer end of the casing match the external threads 2022-1 on the outer end of the radial anchor, securing the radial anchor 2022. The sleeve body 2023-1 is tapered with a thinner radial inner end and a thicker radial outer end, which helps prevent the embedded steel sleeve 2023 from being pulled out of the wind turbine foundation. The bamboo-shaped expansion ring 2023-2 increases the contact area and bite force between the embedded steel sleeve 2023 and the concrete.

[0048] The annular anchor plate 2021 is formed by joining two semicircular halves together to form a circular shape. Its inner diameter matches the outer diameter of the bottom section 3 of the fresh air turbine tower and is positioned around the outer wall of the bottom section 3 of the fresh air turbine tower. Each halves of the annular anchor plate 2021 is provided with overlapping sections 2021-1 at both ends. These overlapping sections 2021-1 and the main body of the annular anchor plate 2021 form a stepped shape, allowing the two halves to connect. The overlapping sections are provided with threaded holes 2021-2, and the two halves are secured together using overlapping section bolts 2021-3. These overlapping section bolts 2021-3 are embedded within the annular anchor plate 2021 to prevent bulges on the outer surface of the annular anchor plate 2021. Annular anchor plate 2021 is provided with multiple threaded casing holes 2021-4 extending through its length. These holes are internally threaded, and the external threads 2023-3 on the inner end of the embedded steel casing mate with the internal threads of these holes. The inner end of the embedded steel casing 2023 is threadedly secured to annular anchor plate 2021, and the outer end is tied or welded to the reinforcement within the newly poured reinforced concrete foundation 2.

[0049] During installation, the annular anchor plate 2021 is positioned and leveled using levelers 203. At least three levelers 203 are provided along the circumference to ensure the stability of the annular anchor plate 2021. The levelers 203 include a base 2031, a long screw 2032, a lower nut 2033, an upper nut 2034, a bracket 2035, an annular anchor plate support 2036, and support bolts 2037. The bracket 2035 is mounted on the base 2031 and includes a diagonal brace to enhance stability. Above the bracket 2035 is an annular anchor plate support 2036, which is provided with a vertical hole. The bottom of the annular anchor plate 2021 is provided with a leveler threaded hole 2021-5 that matches the vertical hole. After the vertical hole is aligned with the leveler threaded hole 2021-5 of the annular anchor plate, the leveler 203 and the annular anchor plate 2021 are fixed by the support bolt 2037.

[0050] A platform is chiseled out of the top surface of the outer ring 101 of the original wind turbine foundation 1 to accommodate the base 2031 of the leveler 203. Long screws 2032 are drilled into the platform, corresponding to the vertical holes in the base. After installing lower nuts 2033 on the long screws, the base 2031 of the leveler 203 is installed, followed by upper nuts 2034. The upper and lower nuts are used to adjust the height and secure the leveler 203.

[0051] The outer ring 201 of the newly cast reinforced concrete foundation 2 is provided with an outer ring edge 209 that wraps radially outwardly around the outer ring 101 of the original wind turbine foundation and is connected to the outer ring with radial anchor bars 205. To increase the reliability of the connection, the outer ends of the radial anchor bars 205 are bent 90 degrees and fixed to the reinforcement of the newly cast reinforced concrete foundation 2.

[0052] See Figure 3 To strengthen the bond between the new and old concrete, vertical anchor bars 206 were added to the top surface of the outer ring 101 of the original wind turbine foundation, extending beyond the top surface. To enhance the bearing capacity of the newly poured reinforced concrete foundation, pile foundations 207 were installed between the outer ring edge 209 of the newly poured reinforced concrete foundation 2 and the foundation. A concealed beam was added to the connection between the newly poured reinforced concrete foundation 2 and the pile foundation to prevent excessive tensile stress on one side.

[0053] The construction method for implementing a minor renovation of wind turbine foundations in an old wind farm based on the above structure of the present invention is as follows:

[0054] Step 1: Dismantle the original wind turbine and the original tower, excavate the original foundation backfill area, chisel out a small step on the outer ring top surface 1011 of the original wind turbine foundation 1 to increase the bite force between the new and old concrete, and chisel out a platform on the outer ring top surface 1011 of the original wind turbine foundation 1 directly below the designed position of the annular anchor plate 2021 for arranging the leveler 203.

[0055] Step 2: Plant pile foundation 207 in the expanded area of the wind turbine foundation.

[0056] Step 3: Drill holes on the platform carved out from the outer ring top surface 1011 of the original fan foundation 1 to install the leveler 203, and level and adjust the height through the upper and lower nuts.

[0057] Step 4: Connect the two halves of the semicircular annular anchor plate 2021 and position them on the leveler 203 .

[0058] Step 5: Drill holes and grout the surface of the outer ring 101 of the original fan foundation 1 and place radial anchor bars 205 and vertical anchor bars 206 on the outer side of the foundation.

[0059] Step 6: Tie the reinforcement of the newly poured reinforced concrete foundation 2 to the vertical rebar 206. Simultaneously, screw the embedded steel casing 2023 to the annular anchor plate 2021, and tie the outer end of the embedded steel casing 2023 to the reinforcement. Furthermore, if a concealed beam is added between the newly poured reinforced concrete foundation 2 and the pile foundation, tie or weld the exposed pile reinforcement to the concealed beam reinforcement to strengthen the connection between the edge of the newly poured reinforced concrete foundation and the pile.

[0060] Step 7: Support formwork and cast new reinforced concrete foundation 2.

[0061] Step 8: After the newly poured concrete reaches the required strength, hoist the new wind turbine tower bottom section 3. After successful positioning, connect the new wind turbine tower bottom section 3 to the new wind turbine foundation, which is formed by the newly poured reinforced concrete foundation 2 and the original wind turbine foundation 1, through the vertical anchor cage connection system 102 and utilizing the existing structure connected to the vertical anchor cage connection system 102. In addition, use the radial anchor connection system 202 to connect the new wind turbine tower bottom section 3 to the new wind turbine foundation, which is formed by the newly poured reinforced concrete foundation 2 and the original wind turbine foundation 1, to achieve a reliable connection. Specifically, apply structural adhesive to the radial anchor bolts 2022, insert them into the embedded steel casing 2023 from the inside of the tower, tighten the radial anchor bolts 2022, and then tighten the connection between the new wind turbine tower bottom section and the new wind turbine foundation with nuts. Finally, place an elastic cushion or epoxy resin grouting material 204 between the side edge of the new wind turbine tower bottom section and the newly poured reinforced concrete foundation 2.

[0062] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the ideas and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A structure for increasing the capacity of old wind farm wind turbine foundations by small modifications, characterized in that: It includes an original wind turbine foundation (1), a newly poured reinforced concrete foundation (2), a vertical anchor bolt cage connection system (102) and a radial anchor bolt connection system (202); The newly cast reinforced concrete foundation (2) is cast on the original fan foundation (1) and together they form a new fan foundation; the outer ring (201) of the newly cast reinforced concrete foundation (2) surrounds and covers the outer ring (101) of the original fan foundation (1) from the top and radially outward, and the middle pier (208) of the newly cast reinforced concrete foundation (2) surrounds the outside of the middle pier (103) of the original fan foundation (1) but is not higher than the middle pier (103) of the original fan foundation (1), and is adapted to the diameter of the bottom section (3) of the new fan tower; The connection structure between the new wind turbine tower bottom section (3) and the new wind turbine foundation includes a vertical anchor bolt cage connection system (102) and a radial anchor bolt connection system (202); the vertical anchor bolt cage connection system (102) is fixed inside the original wind turbine foundation (1), and the radial anchor bolt connection system (202) is fixed inside the newly poured reinforced concrete foundation (2); The radial anchor bolt connection system (202) comprises an annular anchor plate (2021), a radial anchor bolt (2022) and a pre-buried steel casing (2023); the length of the radial anchor bolt (2022) is less than or equal to the inner diameter of the bottom section (3) of the fresh air blower tower, so that the radial anchor bolt (2022) can be installed from the inside of the bottom section (3) of the fresh air blower tower, and the outer end of the radial anchor bolt (2022) is further provided with an external thread (222-1) for fixing with the pre-buried steel casing (2023); the pre-buried steel casing (2023) is fixed to the radial anchor bolt (2022). The buried steel casing (2023) comprises a casing body (2023-1), a plurality of bamboo-shaped expansion rings (2023-2) located on the outer wall of the casing body, an external thread (2023-3) at the inner end of the casing, and an internal thread (2023-4) at the outer end of the casing; the internal thread (2023-4) at the outer end of the casing matches the external thread (2022-1) at the outer end of the radial anchor bolt and is used to fix the radial anchor bolt (2022); the casing body (2023-1) is thin at the inner end and thick at the outer end; The annular anchor plate (221) is formed by splicing two semicircular petals into a circle, and its inner diameter matches the outer diameter of the bottom section (3) of the fresh air blower tower, and is arranged around the outer wall of the bottom section (3) of the fresh air blower tower; each petal of the annular anchor plate (221) is provided with an overlap section (221-1) at both ends, and the overlap section (221-1) and the main body of the annular anchor plate (2021) are arranged in a step-shaped manner; the annular anchor plate (2021) is provided with a plurality of sleeve threaded holes (2021-4) passing through the anchor plate along its length direction, the outer thread (223-3) of the inner end of the embedded steel casing (2023) matches the thread of the sleeve threaded hole (2021-4), the inner end of the embedded steel casing (2023) is fixed to the annular anchor plate (2021) by threaded connection, and the outer end is tied or welded to the foundation reinforcement.

2. The structure for increasing the capacity of old wind farm wind turbine foundations by upgrading them to larger ones according to claim 1 is characterized in that: The new wind turbine tower bottom section (3) is arranged on the middle pier (208) of the newly poured reinforced concrete foundation (2) and the middle pier (103) of the original wind turbine foundation (1). The bottom of the new wind turbine tower bottom section (3) is provided with a tower bottom plate (301). Vertical holes are reserved on the tower bottom plate (301). The size, number and position of the vertical holes match the vertical anchor bolts of the vertical anchor bolt cage connection system (102) of the original wind turbine foundation, so as to facilitate the installation of vertical anchor bolts. Anchor bolts (1022); a wedge-shaped axillary area (302) is provided at the junction of the inner side wall of the bottom section (3) of the fresh air turbine tower and the tower base plate (301); the inclined surface of the wedge-shaped axillary area (302) is perpendicular to the radial anchor bolts (2022); and through holes are provided in the wedge-shaped axillary area (302) and the side of the tower; the size, number and position of the holes match the radial anchor bolts (2022) of the radial anchor bolt connection system (202) to facilitate the installation of the radial anchor bolts (2022).

3. The structure for increasing the capacity of old wind farm wind turbine foundations by upgrading them to larger ones according to claim 1 is characterized in that: The vertical anchor bolt cage connection system (102) retains the connection components of the original wind turbine foundation (1), including the original foundation lower anchor plate (1021), the vertical anchor bolts (1022), and the original foundation upper anchor plate (1023); when the new wind turbine tower bottom section (3) is hoisted, the vertical anchor bolts (1022) pass through the vertical holes of the tower bottom plate (301) and are fastened by nuts to connect the new wind turbine tower bottom section (3) with the new wind turbine foundation formed by the newly poured reinforced concrete foundation (2) and the original wind turbine foundation (1).

4. The structure for increasing the capacity of old wind farm wind turbine foundations by upgrading them to larger ones according to claim 1, characterized in that: An elastic cushion layer or epoxy resin grouting material (204) is provided between the bottom section (3) of the new fan tower and the newly poured reinforced concrete foundation (2). The elastic cushion layer or epoxy resin grouting material (204) can prevent local stress concentration on the foundation caused by lateral micro-deformation of the tower.

5. The structure for upgrading the wind turbine foundation of an old wind farm to increase its capacity according to claim 1 is characterized in that: A plurality of levelers (203) are also provided, and the annular anchor plate (2021) is positioned and leveled by the levelers (203) during installation; a support platform for the levelers (203) is provided on the outer ring (101) of the original fan foundation (1).

6. The structure for increasing the capacity of old wind farm wind turbine foundations by upgrading them to larger ones according to claim 5, characterized in that: The leveler (203) comprises a base (2031), a long screw (2032), a lower nut (2033), an upper nut (2034), a bracket (2035), an annular anchor plate support (2036) and a support bolt (2037); the base (2031) is provided with a bracket (2035), the bracket (2035) comprising an oblique brace; an annular anchor plate support (2036) is provided above the bracket (2035), the annular anchor plate support (2036) being provided with a vertical hole and a support bolt (2037); the bottom of the annular anchor plate (221) is provided with a matching leveler threaded hole (221-5), and after the vertical hole is aligned with the leveler threaded hole (221-5) of the annular anchor plate, the leveler (203) and the annular anchor plate (221) are fixed by the support bolt (2037).

7. The structure for upgrading the wind turbine foundation of an old wind farm to increase its capacity according to claim 1 is characterized in that: The outer ring (101) of the original fan foundation and the side surface of the newly poured reinforced concrete foundation (2) are provided with foundation outer side horizontal embedded bars (205) connected to each other, and the outer ends of the foundation outer side horizontal embedded bars (205) are bent and fixed to the reinforcement of the newly poured reinforced concrete foundation (2).

8. A construction method for renovating an old wind farm wind turbine foundation from a small one to a large one with increased capacity, characterized in that: This is achieved by the structure for increasing the capacity of old wind farm wind turbine foundations by small-scale upgrading as described in any one of claims 1 to 7, and the specific steps are as follows: Step 1: Remove the original wind turbine and the original tower, excavate the original foundation backfill area, chisel out a small step on the top surface (1011) of the original wind turbine foundation outer ring to increase the bite force between the new and old concrete, and chisel out a platform on the top surface (1011) of the original wind turbine foundation outer ring just below the annular anchor plate (2021) for arranging the leveler (203); Step 2: Planting pile foundation (207) in the expanded area of the foundation; Step 3: Drill a hole on the outer ring top surface (1011) of the original fan foundation to install the leveler (203), and level and adjust the height; Step 4: Connect the two halves of the semicircular annular anchor plate (2021) and position them on the leveler (203); Step 5: Drill holes on the surface of the outer ring (101) of the original fan foundation, grout, and place horizontal planting bars (205) and vertical planting bars (206) on the outer side of the foundation respectively; Step 6: Tie the reinforcement of the newly poured reinforced concrete foundation (2), and tie the reinforcement to the vertical embedded reinforcement; screw the embedded steel casing (2023) to the annular anchor plate (2021), and tie the outer end of the embedded steel casing (2023) to the reinforcement; in addition, when a hidden beam is added between the pile foundation and the newly poured reinforced concrete foundation (2), tie or weld the exposed reinforcement of the pile to the hidden beam reinforcement to strengthen the connection between the edge of the newly poured reinforced concrete foundation (2) and the pile; Step 7: Formwork and pouring of new reinforced concrete foundation (2); Step 8: After the strength of the newly poured concrete reaches the required level, the bottom section (3) of the new fan tower is hoisted; after successful positioning, the bottom section (3) of the new fan tower is connected to the new fan foundation formed by the newly poured reinforced concrete foundation (2) and the original fan foundation (1) through the vertical anchor bolt cage connection system (102) and the existing structure of the original fan foundation (1) connected to the vertical anchor bolt cage connection system (102); and the radial anchor bolt connection system (202) is used to connect the bottom section (3) of the new fan tower to the new fan foundation formed by the newly poured reinforced concrete foundation (2) and the original fan foundation (1) to achieve a reliable connection.

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