Energy storage system transformer and control method thereof

Abstract

This invention relates to the field of energy storage system technology, and more particularly to an energy storage system transformer and its control method. The energy storage system transformer includes: an iron core, a first winding, and two filter reactor windings. The first winding is located on one side of the iron core along a first direction, and the filter reactor windings are located between the iron core and the first winding. The two filter reactor windings are arranged sequentially along a second direction. This invention integrates the filter reactor windings from the LC filter of the photovoltaic grid-connected system as independent windings within the transformer by placing two filter reactor windings between the iron core and the first winding. The added filter reactor windings do not affect the normal operation of the original power supply windings, nor do they affect the two filter reactor windings in the same phase. This reduces the number of branches in the entire photovoltaic grid-connected system, simplifies the number of electrical equipment, and thus reduces the footprint of the energy storage system transformer.

Description

Technical Field

[0001] This invention relates to the field of energy storage system technology, and in particular to an energy storage system transformer and its control method. Background Technology

[0002] With the grid connection of various new energy power generation methods, the power grid signal exhibits strong transient characteristics, placing higher demands on the capacity, heat dissipation performance, and insulation performance of energy storage system transformers. Poor insulation performance can lead to voltage breakdown and short circuits in the windings, potentially causing major safety accidents. Furthermore, heat dissipation performance is also a critical factor for the safe operation of transformers. Excessive transformer temperature accelerates the insulation aging process, directly damaging the windings and ultimately exacerbating transformer failures. Because transformers operate under the influence of multiple factors, including electrical, thermal, mechanical forces, and environmental factors, their basic insulation material composition and heat dissipation performance are affected and damaged by internal and external factors, leading to a decline in transformer reliability.

[0003] Energy storage systems come in various forms, and integrated energy storage devices are widely used in small and medium-sized power plants due to their advantages such as small footprint, rapid construction, portability, and strong integration. Currently, oil-immersed photovoltaic transformers, based on the load rules and design specifications of oil-immersed power transformers, differ significantly from the actual operating conditions of photovoltaic power generation. Their temperature rise characteristics do not match actual operating conditions, making them unsuitable for the trend towards grid parity for photovoltaic power. Furthermore, due to the strict space constraints in energy storage systems, oil-immersed photovoltaic transformers occupy a large area, which affects the installation and use of the entire energy storage system. Summary of the Invention

[0004] The technical problem to be solved by this invention is: in order to solve the technical problem that the large footprint of existing energy storage system transformers affects the installation and use of the entire energy storage system, this invention provides an energy storage system transformer and its control method, which reduces the footprint of the entire energy storage system transformer by improving the structure of the energy storage system transformer.

[0005] The technical solution adopted by the present invention to solve its technical problem is: an energy storage system transformer, comprising: an iron core, a first winding and two filter reactor windings, wherein the first winding is located on one side of the iron core along a first direction, the filter reactor windings are located between the iron core and the first winding, and the two filter reactor windings are arranged sequentially along a second direction.

[0006] Therefore, by setting two filter reactor windings between the core and the first winding, this method is simpler in structure and easier to operate than existing transformers. The filter reactor winding in the LC filter of the photovoltaic power generation grid-connected system is integrated into the transformer as an independent winding. The added filter reactor winding has no impact on the normal operation of the original power supply winding, and there is no impact between the two filter reactor windings in the same phase. In this way, the number of branches of the entire photovoltaic power generation grid-connected system can be reduced, the number of power equipment can be simplified, and the footprint of the transformer of this energy storage system can be reduced.

[0007] As a further improvement to the above technical solution, it also includes a second winding, a third winding, and a fourth winding, wherein the second winding, the third winding, and the fourth winding are all located along a first direction on the side of the first winding away from the filter reactance winding, and the second winding, the third winding, and the fourth winding are arranged sequentially along the first direction.

[0008] As a further improvement to the above technical solution: the filter reactor winding is a low-voltage winding, the second winding is a low-voltage winding, the third winding is a low-voltage winding, and the fourth winding is a high-voltage winding.

[0009] As a further improvement to the above technical solution: the number of turns of the filter reactor winding is L, the number of turns of the third winding is M, and the number of turns of the fourth winding is N; where: L+N=M.

[0010] As a further improvement to the above technical solution, the filter reactor winding is connected in series with the third winding. Therefore, by using L+N=M and connecting the filter reactor winding and the third winding in series, the impedance balance between the filter reactor winding and the third winding can be improved.

[0011] As a further improvement to the above technical solution: the filter reactor winding and the second winding form a low-voltage split winding, and the third winding and the second winding form a low-voltage split winding.

[0012] A control method for a transformer in an energy storage system includes the following steps:

[0013] S1. Constructing a transformer for an energy storage system;

[0014] S2. Create an excitation current loading surface and add excitation current;

[0015] S3. Solve to obtain the inductance matrix of each phase winding.

[0016] As a further improvement to the above technical solution: In S2, the number of turns of each winding and the parameters of the solver are set, and the filter reactance winding and the low-voltage split winding are connected in series and merged.

[0017] As a further improvement to the above technical solution: In S4, the filter reactance winding inductance matrix The expression is:

[0018] ;

[0019] in: This indicates the inductance value of the fourth winding. This represents the mutual inductance between the first winding and the fourth winding. This represents the mutual inductance between the third winding and the fourth winding. This represents the mutual inductance value between the filter reactance winding and the fourth winding. This represents the mutual inductance value between the other filter reactance winding and the fourth winding. This represents the mutual inductance value between the fourth winding and the first winding. This represents the inductance value of the first winding. This represents the mutual inductance value between the third winding and the first winding. This represents the mutual inductance value between the filter reactance winding and the first winding. This represents the mutual inductance value between the other filter reactance winding and the first winding. This represents the mutual inductance value between the fourth winding and the third winding. This represents the mutual inductance value between the first winding and the third winding. This indicates the inductance value of the third winding. This represents the mutual inductance value between the filter reactance winding and the third winding. This represents the mutual inductance value between the other filter reactance winding and the third winding. This represents the mutual inductance value between the fourth winding and one of the filter reactance windings. This represents the mutual inductance value between the first winding and one of the filter reactance windings. This represents the mutual inductance value between the third winding and one of the filter reactance windings. This represents the inductance value of one of the filter reactance windings. This represents the mutual inductance value between the two filter reactance windings. This represents the mutual inductance value between the fourth winding and the other filter reactance winding. This represents the mutual inductance value between the first winding and the other filter reactance winding. This represents the mutual inductance value between the third winding and the other filter reactance winding. This represents the mutual inductance value between the two filter reactor windings. This represents the mutual inductance value of the other of the aforementioned filter reactance windings. , This indicates that the two filter reactance windings are in Mutually.

[0020] As a further improvement to the above technical solution: In S4, the filter reactance winding and the inductance matrix of the second winding low-voltage split winding are... The expression is:

[0021] ;

[0022] in: , This indicates that the two filter reactance windings are in Mutually;

[0023] The inductance matrix of the third winding and the second winding at low voltage split winding The expression is:

[0024] ;

[0025] in: , This indicates that the two filter reactance windings are in Mutually.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. This invention provides a simpler and easier-to-operate structure compared to existing transformers by setting two filter reactor windings between the core and the first winding. The filter reactor winding in the LC filter of the photovoltaic power generation grid-connected system is integrated into the transformer as an independent winding. The added filter reactor winding does not affect the normal operation of the original power supply winding, nor does it affect the two filter reactor windings in the same phase. In this way, the number of branches in the entire photovoltaic power generation grid-connected system can be reduced, the number of power equipment can be simplified, and the footprint of the energy storage system transformer can be reduced.

[0028] 2. The present invention improves the impedance balance of the filter reactor winding and the third winding by using L+N=M and connecting the filter reactor winding and the third winding in series. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Figure 1 This is a schematic diagram of the transformer in the energy storage system of the present invention;

[0031] Figure 2 This is a flowchart of the control method for the transformer in the energy storage system of the present invention;

[0032] Figure 3 This is a schematic diagram of the solar photovoltaic power generation grid-connected system of the present invention.

[0033] In the diagram: 1. Iron core;

[0034] 2. First winding;

[0035] 3. Filter reactor winding;

[0036] 4. Second winding;

[0037] 5. Third winding;

[0038] 6. Fourth winding. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] like Figure 1As shown, an energy storage system transformer includes: a core 1, a first winding 2, and two filter reactor windings 3. The first winding 2 is located on one side of the core 1 along a first direction, and the filter reactor windings 3 are located between the core 1 and the first winding 2. The two filter reactor windings 3 are arranged sequentially along a second direction. Therefore, by setting two filter reactor windings 3 between the core 1 and the first winding 2, compared to existing transformers, this method has a simpler structure and is easier to operate. The filter reactor windings 3 in the LC filter of the photovoltaic grid-connected system are integrated into the transformer as independent windings. The added filter reactor windings 3 do not affect the normal operation of the original power supply windings, nor do they affect the two filter reactor windings 3 in the same phase. This reduces the number of branches in the entire photovoltaic grid-connected system, simplifies the number of electrical equipment, and thus reduces the footprint of the energy storage system transformer.

[0043] Specifically, a grid-connected solar photovoltaic power generation system includes: solar cell modules, combiner boxes, inverters, LC filters, switch cabinets, and transformers. The LC filters include: reactors and capacitors.

[0044] In other words, by placing the reactor in the LC filter of the solar photovoltaic power generation grid-connected system as an independent winding in the transformer, the reactor can not only be part of the transformer but also part of the LC filter. This reduces the number of branches in the entire photovoltaic power generation grid-connected system, simplifies the number of electrical equipment, and thus reduces the footprint of the transformer in this energy storage system.

[0045] Specifically, to ensure that the transformer has a good filtering effect, the inductance value of the filter reactance winding 3 will not change with the voltage and current, and has good linearity.

[0046] In this embodiment, the system further includes a second winding 4, a third winding 5, and a fourth winding 6. The second winding 4, the third winding 5, and the fourth winding 6 are all located along a first direction on the side of the first winding 2 away from the filter reactor winding 3. The second winding 4, the third winding 5, and the fourth winding 6 are arranged sequentially along the first direction. The filter reactor winding 3 is a low-voltage winding, the second winding 4 is a low-voltage winding, the third winding 5 is a low-voltage winding, and the fourth winding 6 is a high-voltage winding. The number of turns in the filter reactor winding 3 is L, the number of turns in the third winding 5 is M, and the number of turns in the fourth winding 6 is N. The filter reactor winding 3 and the third winding 5 are connected in series. The filter reactor winding 3 and the second winding 4 form a low-voltage split winding, and the third winding 5 and the second winding 4 form a low-voltage split winding; wherein: L + N = M. Therefore, by using L+N=M and connecting the filter reactor winding 3 and the third winding 5 in series, the impedance balance of the filter reactor winding 3 and the third winding 5 can be improved.

[0047] like Figures 2 to 3As shown, a control method for a transformer in an energy storage system includes the following steps:

[0048] S1. Constructing a transformer for an energy storage system;

[0049] S2. Create an excitation current loading surface and add excitation current;

[0050] S3. Solve to obtain the inductance matrix of each phase winding.

[0051] In this embodiment, in S2, the number of turns of each winding and the parameters of the solver are set, and the filter reactance winding 3 and the low-voltage split winding are processed by winding series merging.

[0052] In this embodiment, in S4, the filter reactance winding 3 inductor matrix The expression is:

[0053] ;

[0054] in: This indicates the inductance value of the fourth winding, 6. This represents the mutual inductance between the first winding 2 and the fourth winding 6. This represents the mutual inductance between the third winding 5 and the fourth winding 6. This represents the mutual inductance value between filter reactor winding 3 and fourth winding 6. This represents the mutual inductance value between the other filter reactor winding 3 and the fourth winding 6. This represents the mutual inductance between the fourth winding 6 and the first winding 2. This represents the inductance value of the first winding 2. This represents the mutual inductance between the third winding 5 and the first winding 2. This represents the mutual inductance value between a filter reactance winding 3 and the first winding 2. This represents the mutual inductance value between the other filter reactor winding 3 and the first winding 2. This represents the mutual inductance between the fourth winding 6 and the third winding 5. This represents the mutual inductance between the first winding 2 and the third winding 5. This indicates the inductance value of the third winding, 5. This represents the mutual inductance value between a filter reactor winding 3 and a third winding 5. This represents the mutual inductance value between the other filter reactor winding 3 and the third winding 5. This represents the mutual inductance between the fourth winding 6 and a filter reactance winding 3. This represents the mutual inductance between the first winding 2 and a filter reactor winding 3. This represents the mutual inductance between the third winding 5 and a filter reactor winding 3. This represents the inductance value of a filter reactance winding 3. This represents the mutual inductance between the two filter reactor windings 3. This represents the mutual inductance between the fourth winding 6 and another filter reactance winding 3. This represents the mutual inductance between the first winding 2 and the other filter reactance winding 3. This represents the mutual inductance between the third winding 5 and another filter reactance winding 3. This represents the mutual inductance value between the two filter reactor windings 3. This represents the mutual inductance value of the other filter reactance winding 3. , This indicates that the two filter reactor windings 3 are in the state of Mutually;

[0055] Inductance matrix of low-voltage split windings of filter reactance winding 3 and second winding 4 The expression is:

[0056] ;

[0057] in: , This indicates that the two filter reactor windings 3 are in the state of Mutually;

[0058] The inductance matrix of the third winding 5 and the second winding 4 low-voltage split winding The expression is:

[0059] ;

[0060] in: , This indicates that the two filter reactor windings 3 are in the state of Mutually.

[0061] Specifically, , , These represent the three phases of filter reactor winding 3.

[0062] Specifically, in the filter reactance winding 3-inductor matrix In the expression, , , , , , , , , , .

[0063] Specifically, the inductance matrix of the low-voltage split winding of the filter reactor winding 3 and the second winding 4 In the expression, , , , , , , .

[0064] Specifically, in the low-voltage split winding inductance matrix of the third winding 5 and the second winding 4... In the expression, , , , , , , .

[0065] It should be noted that:

[0066] Taking a 100MW grid-connected photovoltaic power generation system as an example, and configuring a 5th harmonic filter with a capacitor capacitance of 1mF, the following explanation will be provided:

[0067] Table 1 shows a comparison of the harmonic current content on the 10kV side before and after the filter is put into operation. As can be seen from Table 1, the main harmonic current of the photovoltaic inverter is the 5th harmonic current. According to the inductance value of filter reactor winding 3, the 5th harmonic current content decreased from the original 1.38% to 0.54%. This shows that the filter reactor winding transformer can better filter out the tuned harmonic current, reduce the harmonic content, and improve the power quality.

[0068] Table 1

[0069] Before investing 0.83 0.62 1.38 0.46 1.65% After investment 0.81 0.71 0.54 0.22 1.03%

[0070] In summary, this invention, by setting two filter reactor windings 3 between the core 1 and the first winding 2, offers a simpler structure and easier operation compared to existing transformers. The filter reactor windings 3 in the LC filter of the photovoltaic grid-connected system are integrated into the transformer as independent windings. The added filter reactor windings 3 do not affect the normal operation of the original power supply windings, nor do they interfere with each other. This reduces the number of branches in the entire photovoltaic grid-connected system, simplifies the number of electrical equipment, and consequently reduces the footprint of the energy storage system transformer.

[0071] The above description is based on the preferred embodiments of the present invention. Through the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the contents of the specification, but must be determined by the scope of the claims.

Claims

1. A transformer for an energy storage system, characterized in that, include: Iron core (1), and The first winding (2) is located on one side of the core (1) along a first direction; Two filter reactor windings (3) are located between the iron core (1) and the first winding (2), and the two filter reactor windings (3) are arranged sequentially along the second direction.

2. The energy storage system transformer according to claim 1, characterized in that, Also includes: The second winding (4), the third winding (5), and the fourth winding (6) are all located along the first direction on the side of the first winding (2) away from the filter reactor winding (3), and the second winding (4), the third winding (5), and the fourth winding (6) are arranged sequentially along the first direction.

3. The energy storage system transformer according to claim 2, characterized in that, The filter reactor winding (3) is a low-voltage winding, the second winding (4) is a low-voltage winding, the third winding (5) is a low-voltage winding, and the fourth winding (6) is a high-voltage winding.

4. The energy storage system transformer according to claim 2, characterized in that, The number of turns of the filter reactor winding (3) is L, the number of turns of the third winding (5) is M, and the number of turns of the fourth winding (6) is N. Where: L+N=M.

5. The energy storage system transformer according to claim 2, characterized in that, The filter reactor winding (3) is connected in series with the third winding (5).

6. The energy storage system transformer according to claim 2, characterized in that, The filter reactor winding (3) and the second winding (4) form a low-voltage split winding, and the third winding (5) and the second winding (4) form a low-voltage split winding.

7. A control method for a transformer in an energy storage system according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Constructing a transformer for an energy storage system; S2. Create an excitation current loading surface and add excitation current; S3. Solve to obtain the inductance matrix of each phase winding.

8. The control method for the transformer of the energy storage system according to claim 7, characterized in that, In S2, the number of turns of each winding and the parameters of the solver are set, and the filter reactance winding (3) and the low voltage split winding are connected in series and merged.

9. The control method for the transformer of the energy storage system according to claim 8, characterized in that, In S4, the filter reactance winding (3) inductance matrix The expression is: ； in: This indicates the inductance value of the fourth winding (6). This represents the mutual inductance between the first winding (2) and the fourth winding (6). This represents the mutual inductance between the third winding (5) and the fourth winding (6). This represents the mutual inductance value between the filter reactance winding (3) and the fourth winding (6). This represents the mutual inductance value between the other filter reactance winding (3) and the fourth winding (6). This represents the mutual inductance value between the fourth winding (6) and the first winding (2). This represents the inductance value of the first winding (2). This represents the mutual inductance value between the third winding (5) and the first winding (2). This represents the mutual inductance value between the filter reactance winding (3) and the first winding (2). This represents the mutual inductance value between the other filter reactance winding (3) and the first winding (2). This represents the mutual inductance value between the fourth winding (6) and the third winding (5). This represents the mutual inductance value between the first winding (2) and the third winding (5). This indicates the inductance value of the third winding (5). This represents the mutual inductance value between the filter reactance winding (3) and the third winding (5). This represents the mutual inductance value between the other filter reactance winding (3) and the third winding (5). This represents the mutual inductance value between the fourth winding (6) and one of the filter reactance windings (3). This represents the mutual inductance value between the first winding (2) and one of the filter reactance windings (3). This represents the mutual inductance value between the third winding (5) and one of the filter reactance windings (3). This represents the inductance value of one of the filter reactance windings (3). This represents the mutual inductance value between the two filter reactor windings (3). This represents the mutual inductance value between the fourth winding (6) and the other filter reactance winding (3). This represents the mutual inductance value between the first winding (2) and the other filter reactance winding (3). This represents the mutual inductance value between the third winding (5) and the other filter reactance winding (3). This represents the mutual inductance value between the two filter reactor windings (3). This represents the mutual inductance value of the other filter reactance winding (3). , This indicates that the two filter reactance windings (3) are in Mutually.

10. The control method for the transformer of the energy storage system according to claim 9, characterized in that, In S4, the filter reactance winding (3) and the low-voltage split winding inductance matrix of the second winding (4) The expression is: ； in: , This indicates that the two filter reactance windings (3) are in Mutually; The inductance matrix of the third winding (5) and the second winding (4) low-voltage split winding The expression is: ； in: , This indicates that the two filter reactance windings (3) are in Mutually.

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