Power system
By introducing parallel transformers of AC and DC converters into new energy power generation systems, the problem of insufficient transformer capacity is solved, transformer capacity expansion is achieved, the utilization rate of grid cables and the installed capacity of new energy power generation devices are improved, and the safety and reliability of the power system are enhanced.
Patent Information
- Application Number
- CN202421897368.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-06
- Publication Date
- 2025-08-08
- Estimated Expiration
- 2034-08-06
AI Technical Summary
In the prior art, the transformer capacity of the new energy power generation system is insufficient, resulting in the underutilization of the power grid cable utilization space, limiting the installed capacity of the new energy power generation device.
By introducing AC and DC converters into the new energy power generation system, the parallel connection of different transformers is realized, and the capacity of the transformer is expanded by using the converter function of AC and DC converters, and the capacity of the transformer and the converter are fully utilized.
It effectively improves the installed capacity of new energy power generation devices, solves the circulation problem when the transformer is directly connected in parallel, and improves the safety and reliability of the power system.
Smart Images
Figure CN223206831U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of power grid technology, and in particular to a power system. Background Art
[0002] In related technologies, AC power output from renewable energy power generation systems is fed into the AC grid via a transformer installed on a grid cable. The grid cable's capacity is higher than the transformer's, and transformer power utilization is typically around 80%, leaving space available for the grid cable. Utility Model Content
[0003] The present application aims to solve, at least to some extent, one of the technical problems in the related art. To this end, the purpose of the present application is to propose a power system that can realize the parallel connection of different transformers based on AC-DC-AC converters, thereby expanding the capacity of the transformers to fully utilize the capacity of the grid cables, thereby effectively increasing the installed capacity of the new energy power generation device.
[0004] To achieve the above-mentioned objectives, an embodiment of the present application proposes an electric power system, comprising: a first transformer, the primary winding of the first transformer is electrically connected to the AC power grid through a first node, and the secondary winding of the first transformer is electrically connected to the new energy power generation device through a second node; an AC-DC converter and a second transformer, the first AC side of the AC-DC converter is electrically connected to the second node, the second AC side of the AC-DC converter is electrically connected to the secondary winding of the second transformer, and the primary winding of the second transformer is electrically connected to the first node.
[0005] According to the power system of the embodiment of the present application, the primary winding of the first transformer is electrically connected to the AC power grid through the first node, and the secondary winding is electrically connected to the new energy power generation device through the second node. At the same time, the first AC side of the AC-DC-AC converter is electrically connected to the second node, the second AC side of the AC-DC-AC converter is electrically connected to the secondary winding of the second transformer, and the primary winding of the second transformer is electrically connected to the first node. In this way, based on the AC-DC-AC converter, different transformers can be connected in parallel, and then the capacity of the transformer can be expanded to fully utilize the capacity of the grid cable, thereby effectively increasing the installed capacity of the new energy power generation device.
[0006] In some embodiments, the AC-DC converter includes: an ACDC converter, wherein the AC side of the ACDC converter is electrically connected to the second node as a first AC side, and the DC side of the ACDC converter is electrically connected to the DC bus; a bus capacitor, wherein the bus capacitor is electrically connected to the DC bus; and a DCAC converter, wherein the DC side of the DCAC converter is electrically connected to the DC bus, and the AC side of the DCAC converter is electrically connected to the secondary winding of the second transformer as a second AC side.
[0007] In some embodiments, the ACDC converter is a bidirectional ACDC converter, and the DCAC converter is a bidirectional DCAC converter.
[0008] In some embodiments, the system further includes: a first switching device and an energy storage device, wherein the energy storage device is electrically connected to the DC bus through the first switching device.
[0009] In some embodiments, the secondary winding of the first transformer and the first AC side of the AC-DC-AC converter are further electrically connected to an AC load via a second node.
[0010] In some embodiments, the system further includes: a first filtering device and a second switching device, wherein the first filtering device and the second switching device are connected in series between the first AC side and the second node of the AC-DC converter.
[0011] In some embodiments, the system further includes: a second filtering device and a third switching device, wherein the second filtering device and the third switching device are connected in series between the second AC side of the AC-DC converter and the secondary winding of the second transformer.
[0012] In some embodiments, the new energy power generation device includes a photovoltaic power generation device and / or a wind power generation device.
[0013] In some embodiments, when a second transformer is added to an existing line where a first transformer is located, the minimum capacity of the second transformer is greater than or equal to the difference between the line capacity of the original line and the first capacity, where the first capacity is the product of the rated capacity of the first transformer and a first coefficient; the maximum capacity of the second transformer is greater than or equal to the product of the line capacity and a second coefficient; wherein the first coefficient is less than 1 and the second coefficient is greater than 1.
[0014] In some embodiments, the value range of the first coefficient is [0.6, 0.9], and the value range of the second coefficient is (1, 1.5].
[0015] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 Schematic diagram of the structure of the power system according to the first embodiment of the present application;
[0017] Figure 2 is a structural diagram of a power system according to a second embodiment of the present application;
[0018] Figure 3 is a schematic structural diagram of a power system according to a third embodiment of the present application;
[0019] Figure 4Schematic diagram of the structure of the power system according to the fourth embodiment of the present application. DETAILED DESCRIPTION
[0020] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.
[0021] The power system proposed in the embodiments of the present application is described below with reference to the accompanying drawings.
[0022] Figure 1 FIG. 1 is a schematic diagram of a power system according to an embodiment of the present application. Figure 1 The power system includes: a first transformer T1, an AC-DC converter 101, and a second transformer T2. The primary winding of the first transformer T1 is electrically connected to the AC grid via a first node A, and the secondary winding of the first transformer T1 is electrically connected to a new energy power generation device 102 via a second node B. The first AC side of the AC-DC converter 101 is electrically connected to the second node B, and the second AC side of the AC-DC converter 101 is electrically connected to the secondary winding of the second transformer T2. The primary winding of the second transformer T2 is electrically connected to the first node A.
[0023] It should be noted that the AC power grid can be a high-voltage AC power grid, such as a 10 kV power grid. When the AC power grid is a three-phase AC power grid, it may include a U-phase line, a V-phase line, and a W-phase line. Accordingly, the first node A may include three sub-nodes A1, A2, and A3. When the primary winding of the first transformer T1 is electrically connected to the AC power grid via the first node A, specifically, the first end of the primary winding of the first transformer T1 is connected to the U-phase line of the AC power grid via sub-node A1, the second end of the primary winding of the first transformer T1 is connected to the V-phase line of the AC power grid via sub-node A2, and the third end of the primary winding of the first transformer T1 is connected to the W-phase line of the AC power grid via sub-node A3. When the primary winding of the second transformer T2 is electrically connected to the first node A, specifically, the first end of the primary winding of the second transformer T2 is connected to sub-node A1, the second end of the primary winding of the second transformer T2 is connected to sub-node A2, and the third end of the primary winding of the second transformer T2 is connected to sub-node A3.
[0024] The second node B may include three sub-nodes B1, B2, and B3. When the secondary winding of the first transformer T1 is electrically connected to the new energy power generation device 102 via the second node B, specifically, the first end of the secondary winding of the first transformer T1 may be connected to the first end of the new energy power generation device 102 via the sub-node B1, the second end of the secondary winding of the first transformer T1 may be connected to the second end of the new energy power generation device 102 via the sub-node B2, and the third end of the secondary winding of the first transformer T1 may be connected to the third end of the new energy power generation device 102 via the sub-node B1. When the first AC side of the AC-DC-AC converter 101 is electrically connected to the second node B, specifically, the first end of the first AC side of the AC-DC-AC converter 101 may be connected to the sub-node B1, the second end of the first AC side of the AC-DC-AC converter 101 may be connected to the sub-node B2, and the third end of the first AC side of the AC-DC-AC converter 101 may be connected to the sub-node B3.
[0025] The AC power output by the new energy power generation device 102 can be low-voltage AC power, such as 220V AC mains electricity. The new energy power generation device 102 can include a photovoltaic power generation system, a wind power generation system, or both. The photovoltaic power generation system can include a photovoltaic power generation device and a corresponding inverter. The photovoltaic power generation device is used to convert light energy into DC power, and the inverter is used to invert the DC power into low-voltage AC power. The wind power generation system can include a wind power generation device, a converter, and a transformer. The wind power generation device is used to convert wind energy into a first AC power. The converter is used to convert the first AC power into a second AC power. The transformer is used to convert the second AC power into low-voltage AC power.
[0026] The voltage of the primary winding of the second transformer T2 is consistent with the voltage of the primary winding of the first transformer T1 , and the voltage of the first AC side of the AC-DC converter 101 is consistent with the voltage of the new energy power generation device 102 .
[0027] When the new energy generation device 102 is connected to the grid, a portion of the electrical energy is boosted by the first transformer T1 and then transmitted to the AC grid. The remaining electrical energy is first converted by the AC-DC-AC converter 101 before being converted by the second transformer T2 and transmitted to the AC grid. Due to the addition of the conversion link of the AC-DC-AC converter 101, the impedance and connection group (e.g., star connection, delta connection) of the second transformer T2 can be different from those of the first transformer T1. This allows for parallel connection of different transformers, thereby expanding the transformer capacity, fully utilizing the capacity of the grid cables, and increasing the installed capacity of the new energy generation device.
[0028] In the above embodiment, different transformers can be connected in parallel by connecting a transformer in parallel with a transformer + converter, thereby expanding the capacity of the transformer to fully utilize the capacity of the grid cable, thereby effectively increasing the installed capacity of the new energy power generation device. At the same time, through the converter, the circulating current problem existing when two transformers are directly connected in parallel can be effectively solved, thereby improving the safety and reliability of the power system.
[0029] In some embodiments, reference Figure 2 The AC / DC converter 101 includes an ACDC converter 103, a bus capacitor C, and a DC / AC converter 104. The AC side of the ACDC converter 103 is electrically connected to the second node B as a first AC side, and the DC side of the ACDC converter 103 is electrically connected to the DC bus (including the positive DC bus DC+ and the negative DC bus DC-); the bus capacitor C is electrically connected to the DC bus (specifically, one end of the bus capacitor C is connected to the positive DC bus DC+, and the other end of the bus capacitor C is connected to the negative DC bus DC-); the DC side of the DC / AC converter 104 is electrically connected to the DC bus, and the AC side of the DC / AC converter 104 is electrically connected to the secondary winding of the second transformer T2 as a second AC side.
[0030] When the new energy power generation device 102 is connected to the grid, part of the electric energy is boosted by the first transformer T1 and then transmitted to the AC power grid; the other part of the electric energy is first rectified by the ACDC converter 103 to obtain DC power, and then the DCAC converter 104 inverts the DC power into AC power and transmits it to the second transformer T2, and finally converted by the second transformer T2 and transmitted to the AC power grid.
[0031] It should be noted that the AC side voltage of ACDC converter 103 is consistent with the voltage of new energy power generation device 102, such as the AC mains voltage of 220V, which is non-adjustable. The AC side of DCAC converter 104 is electrically connected to the secondary winding of second transformer T2, and its AC side voltage is adjustable. Furthermore, the specific circuit structures of ACDC converter 103 and DCAC converter 104 are not limited, as long as they can achieve the corresponding functions. For example, ACDC converter 103 can be a rectifier, and DCAC converter 104 can be an inverter.
[0032] In the above embodiment, by converting the current of the ACDC converter and the DCAC converter in conjunction with the second transformer, the second transformer and the first transformer can be connected in parallel, thereby expanding the capacity of the first transformer.
[0033] In some embodiments, the ACDC converter 103 is a bidirectional ACDC converter, and the DCAC converter 104 is a bidirectional DCAC converter. In this way, the AC / DC converter 101 can achieve bidirectional transmission of electric energy, thereby enabling the power system to have multiple different operating modes.
[0034] In some embodiments, reference Figure 3 The power system further includes: a first switching device 105 and an energy storage device 106 , and the energy storage device 106 is electrically connected to the DC bus through the first switching device 105 .
[0035] In some embodiments, continue to refer to Figure 3 The secondary winding of the first transformer T1 and the first AC side of the AC-DC-AC converter 101 are also electrically connected to the AC load 107 through the second node B.
[0036] It should be noted that the energy storage device 106 is used to store electrical energy, and the first switch device 105 is used to turn on or off the energy storage device 106 .
[0037] In the case where the ACDC converter 103 is a bidirectional ACDC converter and the DCAC converter 104 is a bidirectional DCAC converter, the power system may include a grid-connected mode and an energy storage mode.
[0038] In the grid-connected mode, the AC power output by the new energy power generation device 102 is first rectified by the ACDC converter 103 to obtain DC power, and then the DCAC converter 104 inverts the DC power into AC power and transmits it to the second transformer T2, and finally the second transformer T2 converts it and transmits it to the AC grid.
[0039] In energy storage mode, the first switching device 105 is turned on, electrically connecting the energy storage device 106 to the DC bus. During peak power generation phases of the new energy generation device 102 (e.g., if the new energy generation device 102 is a photovoltaic power generation device, which generates more power at noon on a sunny day, this is a peak power generation phase), the ACDC converter 103 acts as a power storage converter (PCS), rectifying the AC power output by the new energy generation device 102 into DC power. This power is then transmitted to the energy storage device 106 via the DC bus and the first switching device 105 to charge the energy storage device 106. Because the ACDC converter 103 is a bidirectional ACDC converter, it can also invert the DC power from the energy storage device 106 into AC power to power the AC load 107. Thus, based on the bidirectional power transmission function of the ACDC converter 103, the new energy generation device 102 can charge the energy storage device 106, and the energy storage device 106 can also discharge the power to the AC load 107.
[0040] During a low-power phase of the new energy generation device 102 (for example, if the new energy generation device 102 is a photovoltaic power generation device and generates very little power at night, which is a low-power phase), the DC-AC converter 104 inverts the DC power from the energy storage device 106 into AC power, and then converts it through the second transformer T2 and transmits it to the AC grid. Alternatively, the DC-AC converter 104 rectifies the AC power from the second transformer T2 into DC power to charge the energy storage device 106. In this way, based on the bidirectional power transmission function of the DC-AC converter 104, the AC grid can charge the energy storage device 106, and the energy storage device 106 can also discharge the energy to the AC grid.
[0041] It should be noted that the specific structures of the energy storage device 106, the first switching device 105, the bidirectional ACDC converter, and the bidirectional DCAC converter are not limited herein, as long as they can achieve the corresponding functions. For example, the energy storage device 106 can be a storage battery, the first switching device 105 can be a DC relay, the bidirectional ACDC converter can be a bidirectional rectifier, and the bidirectional DCAC converter can be a bidirectional inverter.
[0042] In the above embodiment, the bidirectional power transmission function of the ACDC converter and the DCAC converter can realize the grid connection of the new energy power generation device and the charging and discharging of the energy storage device.
[0043] In some embodiments, reference Figure 4 The power system further includes: a first filtering device 108 and a second switching device 109, which are connected in series between the first AC side of the AC-DC converter 101 and the second node B.
[0044] In some embodiments, continue to refer to Figure 4 The power system further includes: a second filtering device 110 and a third switching device 111, which are connected in series between the second AC side of the AC-DC converter 101 and the secondary winding of the second transformer T2.
[0045] Specifically, first filter device 108 is used to filter the AC power on the first AC side of AC / DC converter 101 to improve the quality of the AC power. Second filter device 110 is used to filter the AC power on the second AC side of AC / DC converter 101 to improve the quality of the AC power. For example, when new energy generation device 102 is connected to the grid, the first filter device 108 and the second filter device 110 can be used to filter the connected AC power, such as to remove harmonics, to improve the quality of the AC grid.
[0046] The second switching device 109 is used to connect and disconnect the first AC side of the AC-DC-AC converter 101 and the second node B, and the third switching device 111 is used to connect and disconnect the second AC side of the AC-DC-AC converter 101 and the first node A. The cooperation between the second switching device 109 and the third switching device 111 enables corresponding modes. For example, in the grid-connected mode, the second switching device 109 and the third switching device 111 can be controlled to be turned on. In the energy storage mode, during the high-generation phase of the new energy generation device 102, the second switching device 109 can be controlled to be turned on and the third switching device 111 can be turned off. During the low-generation phase of the new energy generation device 102, the third switching device 111 can be controlled to be turned on and the second switching device 109 can be turned off.
[0047] In the case where the ACDC converter 103 is a bidirectional ACDC converter and the DCAC converter 104 is a bidirectional DCAC converter, the power system may include a grid-connected mode and an energy storage mode.
[0048] In grid-connected mode, the first switching device 105 is turned on, and the energy storage device 106 charges the bus capacitor C to prevent high current from causing breakdown of the bus capacitor C. Then, the second switching device 109 and the third switching device 111 are controlled to turn on. At this time, the AC power output by the new energy generation device 102 is first filtered by the first filtering device 108, then rectified by the ACDC converter 103 to obtain DC power. The DC-AC converter 104 then inverts the DC power into AC power, filters it through the second filtering device 110, and transmits it to the second transformer T2. Finally, the second transformer T2 converts it and transmits it to the AC grid, while the first switching device 105 is disconnected. In this way, the capacity expansion and grid connection of the new energy generation device 102 can be achieved through AC-DC conversion, and the filtering device can improve the quality of grid connection.
[0049] In energy storage mode, the first switching device 105 is turned on to electrically connect the energy storage device 106 to the DC bus. During the high-power phase of the new energy generation device 102, the second switching device 109 is turned on and the third switching device 111 is turned off. The AC power output by the new energy generation device 102 is first filtered by the first filtering device 108 and then transmitted to the ACDC converter 103. The ACDC converter 103 rectifies the filtered AC power into DC power, which is then transmitted to the energy storage device 106 via the DC bus and the first switching device 105 to charge the energy storage device 106. Alternatively, the ACDC converter 103 inverts the DC power from the energy storage device 106 into AC power, which is filtered by the first filtering device 108 before being supplied to the AC load 107. In this way, based on the bidirectional power transmission function of the ACDC converter 103, the new energy generation device 102 can charge the energy storage device 106 and the energy storage device 106 can discharge the AC load 107.
[0050] During the low-power phase of the new energy generation device 102, the third switching device 111 is turned on and the second switching device 109 is turned off. The DC-AC converter 104 inverts the DC power from the energy storage device 106 into AC power, filters it through the second filtering device 110, and transmits it to the second transformer T2. The second transformer T2 then converts it and transmits it to the AC grid. Alternatively, the AC power output by the second transformer T2 is filtered by the second filtering device 110 and transmitted to the DC-AC converter 104. The DC-AC converter 104 rectifies the filtered AC power into DC power to charge the energy storage device 106. In this way, based on the bidirectional power transmission function of the DC-AC converter 104, the AC grid can charge the energy storage device 106, and the energy storage device 106 can discharge the energy storage device 106 to the AC grid.
[0051] It should be noted that the specific structures of the first filter device 108, the second switch device 109, the second filter device 110, and the third switch device 111 are not limited herein, as long as they can achieve the corresponding functions. For example, the first filter device 108 and the second filter device 110 can be filter inductors, etc., and the second switch device 109 and the third switch device 111 can be AC relays, etc.
[0052] In the above embodiment, by connecting the transformer in parallel with the transformer + converter, the parallel operation of the transformers can be achieved, thereby reducing the pressure on the transformer line and increasing the renewable energy power generation capacity of the line. At the same time, the optimization of the energy storage device based on the bidirectional ACDC converter and the bidirectional DCAC converter can improve the utilization rate of the energy storage device.
[0053] In some embodiments, when a line where a second transformer T2 is located is added to an existing line where a first transformer T1 is located, the minimum capacity of the second transformer T2 is greater than or equal to the difference between the line capacity of the original line and a first capacity, where the first capacity is the product of the rated capacity of the first transformer T1 and a first coefficient; the maximum capacity of the second transformer T2 is greater than or equal to the product of the line capacity and a second coefficient; wherein the first coefficient is less than 1 and the second coefficient is greater than 1.
[0054] Specifically, the line where the first transformer T1 is located is an existing line. Since the designed capacity of the line is often higher than the capacity of the transformer itself, that is, the capacity of the original line is higher than the capacity of the first transformer T1, the capacity of the original line is not fully utilized. Therefore, the minimum capacity of the second transformer T2 (that is, the newly added transformer) can be determined based on the capacity of the original line and the capacity of the first transformer T1 (that is, the original transformer); at the same time, the maximum capacity of the second transformer T2 is determined based on the capacity of the original line.
[0055] For example, the minimum capacity of the second transformer T2 is ≥ the original line capacity - the rated capacity of the first transformer T1 * the first coefficient k1. The value range of the first coefficient k1 can be [0.6, 0.9]. For example, the first coefficient k1 = 0.8. Exemplarily, the minimum capacity of the second transformer T2 = the original line capacity - the rated capacity of the first transformer T1 * 0.8. The maximum capacity of the second transformer T2 is ≥ the original line capacity * the second coefficient k2. The value range of the second coefficient k2 can be (1, 1.5]. For example, the second coefficient k2 = 1.25. Exemplarily, the maximum capacity of the second transformer T2 = the original line capacity * 1.25.
[0056] It should be noted that during the operation of the first transformer T1 and the second transformer T2, the capacity of both is at about 50%, which can extend the life of the two transformers. In addition, for new lines, the capacity setting method of the second transformer T2 can be the same as above, which will not be detailed here.
[0057] In the above embodiment, the capacity of the second transformer can be flexibly configured according to actual conditions, and the existing line or the newly built line can be fully utilized to increase the installed capacity of the new energy power generation device.
[0058] In summary, according to the power system of the embodiment of the present application, the original line can be expanded by connecting transformers in parallel based on the conversion function of the AC-DC-AC converter, on the basis of the original line, effectively solving the problem of transformers being unable to be connected in parallel and circulating current due to transformer mismatch, thereby realizing the parallel connection of different transformers, and then realizing the expansion of the transformer, so as to make full use of the capacity of the grid cable and effectively increase the installed capacity of the new energy power generation device; at the same time, the AC-DC-AC converter can not only realize AC-DC-AC conversion, but also can be used as a PCS, realizing multiplexing, and the charging and discharging control of the energy storage device can be realized through the AC-DC-AC converter, realizing the discharge of the energy storage device to the grid or the AC load and the charging of the grid and the new energy power generation device.
[0059] It should be noted that, in the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in any one or more embodiments or examples.
[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.
[0061] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.
[0062] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.
Claims
1. A power system, characterized in that: include: a first transformer, wherein a primary winding of the first transformer is electrically connected to the AC grid via a first node, and a secondary winding of the first transformer is electrically connected to the new energy power generation device via a second node; An AC-DC converter and a second transformer, wherein the first AC side of the AC-DC converter is electrically connected to the second node, the second AC side of the AC-DC converter is electrically connected to the secondary winding of the second transformer, and the primary winding of the second transformer is electrically connected to the first node.
2. The system according to claim 1, wherein: The AC-DC-AC converter comprises: an ACDC converter, wherein an AC side of the ACDC converter serves as the first AC side and is electrically connected to the second node, and a DC side of the ACDC converter is electrically connected to a DC bus; a bus capacitor, the bus capacitor being electrically connected to the DC bus; A DCAC converter, wherein the DC side of the DCAC converter is electrically connected to the DC bus, and the AC side of the DCAC converter serves as the second AC side and is electrically connected to the secondary winding of the second transformer.
3. The system according to claim 2, characterized in that The ACDC converter is a bidirectional ACDC converter, and the DCAC converter is a bidirectional DCAC converter.
4. The system according to claim 3, characterized in that Also includes: A first switching device and an energy storage device, wherein the energy storage device is electrically connected to the DC bus through the first switching device.
5. The system according to claim 4, characterized in that The secondary winding of the first transformer and the first AC side of the AC-DC-AC converter are also electrically connected to an AC load via the second node.
6. The system according to any one of claims 1 to 5, characterized in that: Also includes: A first filtering device and a second switching device are connected in series between the first AC side of the AC-DC-AC converter and the second node.
7. The system according to any one of claims 1 to 5, characterized in that: Also includes: A second filtering device and a third switching device, wherein the second filtering device and the third switching device are connected in series between the second AC side of the AC-DC-AC converter and the secondary winding of the second transformer.
8. The system according to any one of claims 1 to 5, characterized in that: The new energy power generation device includes a photovoltaic power generation device and / or a wind power generation device.
9. The system according to any one of claims 1 to 5, characterized in that: When a line where the second transformer is located is newly added to an existing line where the first transformer is located, the minimum capacity of the second transformer is greater than or equal to the difference between the line capacity of the existing line and the first capacity, where the first capacity is the product of the rated capacity of the first transformer and the first coefficient; The maximum capacity of the second transformer is greater than or equal to the product of the line capacity and a second coefficient; wherein the first coefficient is less than 1 and the second coefficient is greater than 1.
10. The system according to claim 9, characterized in that The value range of the first coefficient is [0.6, 0.9], and the value range of the second coefficient is (1, 1.5].