Novel transformer capable of realizing transverse power flow control and control method

Abstract

The invention relates to the technical field of power distribution, and discloses a novel transformer capable of realizing transverse power flow control and a control method. The device comprises a novel transformer capable of realizing transverse power flow control, the novel transformer comprises a transformer main body, a controllable voltage source and a controller, the controllable voltage source comprises a power electronic inverter and a coupling winding, and the input end of the power electronic inverter is electrically connected with a secondary winding or a primary winding; the output end of the power electronic inverter is electrically connected with the coupling winding, and the coupling winding is electromagnetically coupled with the secondary winding. The transformer is put into a power distribution network composed of a plurality of transformer areas with complementary load fluctuation characteristics, buses of the complementary transformer areas are connected, and the amplitude and the phase angle of the voltage of the low-voltage side of each transformer area can be adjusted by controlling a controllable voltage source, so that transverse flow of power flow between the transformer areas through the buses is controlled, and the load of each transformer area is balanced. The transformer is adopted to carry out power flow control transformation of a transformer area, and the cost can be reduced while the occupied area of the transformer is not obviously increased.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution, and in particular to a new transformer capable of lateral power flow control and a control method thereof. Background Art

[0002] With the development of new energy technologies such as photovoltaics and electric vehicles, large-scale distributed photovoltaics and electric vehicles are connected to the power grid, resulting in increasingly serious load fluctuations in the distribution network, which is prone to reverse heavy loads or forward heavy loads, or even overloads. In order to solve the above technical problems, a larger capacity distribution transformer is usually replaced, but this approach will greatly increase the construction investment of the distribution network, and the loss of large-capacity transformers will also increase when light load and no-load, which is not conducive to reducing line losses and energy saving. The use of full-power power electronic converters for "back-to-back" lateral power flow transmission can also solve the above technical problems, but power electronic converters also have defects such as large footprint, severe loss and high cost. To this end, it is necessary to design a new distribution solution that can control the power flow horizontally to solve the above technical problems. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a transformer that can control the power flow laterally, which can adjust the voltage of the secondary winding to directly transfer the power flow from a heavy-load area to a light-load area through the bus, thereby realizing the lateral transfer of the power flow, thereby solving the problem of load fluctuations in the distribution network at a lower cost.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows: a new type of transformer capable of lateral power flow control, comprising a transformer body, a controllable voltage source and a controller, the transformer body comprising a primary winding and a secondary winding, the controllable voltage source comprising a power electronic inverter and a coupling winding, the coupling winding being adjacently arranged on one side of the secondary winding, the coupling winding being electromagnetically coupled to the secondary winding, the input end of the power electronic inverter being electrically connected to the secondary winding or the primary winding, the output end of the power electronic inverter being electrically connected to the coupling winding, and the power electronic inverter injecting voltage into the secondary winding in an electromagnetically coupled manner through the coupling winding under the control of the controller.

[0005] Compared with the prior art, the beneficial effect of the present invention is that: by putting the transformer into a substation area or a substation for use, and connecting the busbars of the substation area or the substation with complementary load fluctuation characteristics. When a substation area or a substation is heavily loaded, the phase and amplitude of the voltage on the low-voltage side of the transformer can be adjusted by a controllable voltage source, and the current can be controlled to flow horizontally between the substations or substations to balance the load of each substation or substation, thereby avoiding the substation area or substation from being heavily loaded or even overloaded. The transformer does not need to significantly increase the floor space and cost of the transformer. It only needs to implant a coupling winding on the low-voltage side of the transformer and add a power electronic inverter, so that the substation or substation can adapt to the load fluctuations of the distribution network.

[0006] The above-mentioned transformer, the power electronic inverter includes a rectifier circuit and an inverter circuit, the input end of the rectifier circuit is electrically connected to the primary winding, the output end of the rectifier circuit is electrically connected to the input end of the inverter circuit, and the output end of the inverter circuit is electrically connected to the coupling winding.

[0007] The above-mentioned transformer, the controller includes: a low-voltage side expected voltage calculation module, which is used to calculate the expected voltage output on the low-voltage side according to the power flow conditions of the distribution network; a regulation quantity calculation module, which is used to calculate the difference between the expected voltage and the actual voltage on the low-voltage side to obtain the regulated voltage; a voltage source control module, which is used to control the controllable voltage source according to the amplitude and phase angle of the regulated voltage, so that the amplitude and phase angle of the voltage output by the controllable voltage source are equal to the amplitude and phase angle of the regulated voltage.

[0008] In the above-mentioned transformer, the power electronic inverter is detachably mounted on the transformer body, and the transformer body is provided with a connector for connecting the power electronic inverter, and the connector is electrically connected to the secondary winding and the coupling winding.

[0009] In the above-mentioned transformer, the connector is also electrically connected to the primary winding.

[0010] A method for controlling a lateral current comprises the following steps:

[0011] Connect the buses of multiple substations with complementary load fluctuation characteristics;

[0012] A controllable voltage source is connected to the secondary winding of the transformer in each substation;

[0013] Calculate the expected voltage output on the low voltage side according to the power flow of the distribution network;

[0014] Calculate the difference between the expected voltage and the actual voltage on the low voltage side to obtain the regulated voltage;

[0015] The output voltage of the controllable voltage source is controlled so that the amplitude and phase angle of the voltage output by the controllable voltage source are equal to the amplitude and phase angle of the regulated voltage.

[0016] In the above-mentioned method for controlling the lateral power flow, in the step of calculating the difference between the expected voltage and the actual voltage on the low voltage side to obtain the regulated voltage, the regulated voltage is calculated by combining the following formulas:

[0017] U 1 =R 1 I 1 +jωL l1 I 1 +jωMI 1

[0018]

[0019] Where U 1 is the voltage of the primary winding, U 2 is the voltage output by the secondary winding, R 1 is the resistance of the primary winding, L l1 is the leakage inductance of the primary winding, M is the leakage inductance between the primary winding and the secondary winding, R 2 is the resistance of the secondary winding, L l2 is the leakage inductance of the secondary winding, ω is the angular frequency of the primary input voltage, I 1 is the current of the primary winding, I 2 is the current of the secondary winding, k is the transformation ratio of the transformer, j is the imaginary unit, U C To regulate the voltage.

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a transformer according to a first embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of a transformer according to a second embodiment of the present invention;

[0023] Figure 3 is a schematic structural diagram of a transformer according to an embodiment of the present invention;

[0024] Figure 4 It is a schematic structural diagram of a joint according to an embodiment of the present invention;

[0025] Figure 5 Flow chart of a method for controlling lateral current according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below. Figure 1and Figure 2 , an embodiment of the present invention provides a new type of transformer capable of lateral power flow control, including a transformer body, a controllable voltage source and a controller. The transformer body includes a primary winding and a secondary winding, and the controllable voltage source includes an electronic power inverter and a coupling winding. The coupling winding is arranged on one side of the secondary winding, and the coupling winding is electromagnetically coupled with the secondary winding. The power electronic inverter can draw power from the primary side of the transformer or from the secondary side of the transformer, so the input end of the power electronic inverter is electrically connected to the primary winding or the secondary winding. The output end of the power electronic inverter is electrically connected to the secondary winding. Under the control of the controller, the power electronic inverter converts the electric energy obtained from the primary and secondary sides of the transformer into the required value according to the power flow conditions of the distribution network, and injects voltage into the secondary winding through the coupling winding in an electromagnetically coupled manner to adjust the amplitude and phase of the voltage output on the low-voltage side.

[0027] By putting the transformer into a substation area or substation, and connecting the busbars of the areas or substations with complementary load fluctuation characteristics, when one of the areas or substations is overloaded, the voltage output on the low-voltage side can be adjusted by controlling the controllable voltage source to change the power distribution of the line, so that the current can flow horizontally between the areas or substations through the busbar to balance the load of the areas or substations, so that the substation areas or substations can adapt to the load fluctuations of the distribution network. The transformer only needs to implant a coupling winding on the low-voltage side and add a power electronic inverter to realize the horizontal current control in the distribution network, avoiding the replacement of a transformer with a larger capacity. In addition, the cost and floor space of the power electronic inverter are both smaller than those of the power electronic converter, so that the area or substation can be prevented from being overloaded or even overloaded due to load fluctuations at a lower cost without increasing the floor space of the area or substation.

[0028] Reference Figure 1 and Figure 2 The power electronic inverter includes a rectifier circuit and an inverter circuit. The input end of the rectifier circuit is electrically connected to the secondary winding, the output end of the rectifier circuit is electrically connected to the input end of the inverter circuit, the output end of the inverter circuit is electrically connected to the coupling winding, and the gate of the inverter tube in the inverter circuit is electrically connected to the controller through a drive circuit, and is turned on and off under the control of the controller, thereby adjusting the amplitude and phase angle of the voltage output to the coupling winding, and injecting it into the secondary winding through electromagnetic coupling to achieve regulation and control of the voltage on the low-voltage side.

[0029] Reference Figure 3It can be understood that in some embodiments, the power electronic inverter can be detachably installed on the transformer body in the form of an external unit. When the transformer is used in a substation or transformer substation that does not require lateral flow control, the external power electronic inverter can be removed and only the transformer body can be installed; when the substation needs to be modified for flow control, the controllable voltage source is added to the transformer body to facilitate the transformation of the flow control of the substation or transformer substation. The transformer body is provided with a connector for electrically connecting the power electronic inverter to the transformer, refer to Figure 4 The connectors include three-phase connectors A, B and C for connecting the input end of the rectifier circuit, and three-phase connectors U, V and W for connecting the output end of the inverter circuit. Connectors U, V and W are electrically connected to the three coupling windings corresponding to the secondary windings of the three phases. When the power electronic inverter adopts the following Figure 1 When the power is taken from the primary side of the transformer in the manner shown, the connectors A, B and C are electrically connected to the primary winding of the transformer; when the power electronic inverter adopts the Figure 2 When the power is taken from the secondary side of the transformer in the manner shown, the connectors A, B and C are electrically connected to the secondary winding of the transformer. It can be understood that the power electronic inverter is also provided with connectors matching the connectors on the transformer body.

[0030] In this embodiment, the controller includes a low-voltage side expected voltage calculation module, an adjustment amount calculation module and a voltage control module. The low-voltage side expected voltage calculation module is used to calculate the expected voltage output by the low-voltage side according to the power flow of the distribution network. The adjustment amount calculation module is used to calculate the difference between the expected voltage and the actual voltage on the low-voltage side to obtain the adjustment voltage. The voltage source control module is used to control the controllable voltage source according to the amplitude and phase angle of the adjustment voltage, so that the amplitude and phase angle of the voltage output by the controllable voltage source are equal to the amplitude and phase angle of the adjustment voltage.

[0031] Reference Figure 2 Based on the same inventive concept, the method for controlling the lateral current in an embodiment of the present invention comprises the following steps:

[0032] Connect the buses of multiple substations with complementary load fluctuation characteristics;

[0033] A controllable voltage source is connected to the secondary winding of the transformer in each substation;

[0034] Calculate the expected voltage output on the low voltage side according to the power flow of the distribution network;

[0035] Calculate the difference between the expected voltage and the actual voltage on the low voltage side to obtain the regulated voltage;

[0036] The output voltage of the controllable voltage source is controlled so that the amplitude and phase angle of the voltage output by the controllable voltage source are equal to the amplitude and phase angle of the regulated voltage.

[0037] For an ideal transformer, the voltage and current on the primary and secondary sides satisfy the following relationship:

[0038] U 1 =kU 2 (1)

[0039]

[0040] Among them U 1 is the voltage of the primary winding, U 2 is the voltage output by the secondary winding, I 1 is the current of the primary winding, I 2 is the current of the secondary winding, and k is the transformation ratio of the transformer.

[0041] According to Kirchhoff's law, after the controlled voltage source is injected, the voltage on the low voltage side satisfies:

[0042]

[0043] Among them U C The regulated voltage output by the controlled voltage source. The desired voltage on the low voltage side is calculated according to the power flow conditions, and the desired voltage and the voltage U of the input primary winding are added together. 1 Substituting the value of into (3), the value of the regulated voltage that the controlled voltage source needs to output can be solved, and then the controlled voltage source can be controlled according to the amplitude and phase angle of the regulated voltage so that the output of the controlled voltage source meets the calculated regulated voltage value, thereby controlling the voltage on the low-voltage side and controlling the flow to migrate from the heavy-load area to the light-load area.

[0044] In practice, there is leakage inductance between the primary winding and the secondary winding. When working, there is mutual inductance between the primary winding and the secondary winding. At this time, the voltage equation of the primary winding is:

[0045] U 1 =R 1 I 1 +jωL l1 I 1 +jωMI 2 (4)

[0046] The voltage equation of the secondary winding is:

[0047] U 2 +U C =R 2 I 2 +jωL l2 I 2 +jωMI 1 (5)

[0048] Where R 1is the resistance of the primary winding, L l1 is the leakage inductance of the primary winding, R 2 is the resistance of the secondary winding, L l2 is the leakage inductance of the secondary winding, M is the mutual inductance between the primary winding and the secondary winding, ω is the angular frequency of the voltage input to the primary winding, and j is an imaginary unit. By combining the above equations (3), (4) and (5), the following equation can be obtained:

[0049]

[0050] By substituting the expected voltage and other parameters of the low-voltage side calculated according to the power flow into equation (6), the value of the regulated voltage that the controlled voltage source should output in actual application can be obtained. After simplifying the final regulated voltage result to the standard form of complex number a+jb, the amplitude of the regulated voltage can be obtained as The phase angle is

[0051] The present application is described with reference to the flowcharts and / or block diagrams of the methods, apparatus (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0052] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0053] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0054] In the description of the present invention, "several" means one or more, "more" means two or more, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0055] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0056] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A new type of transformer capable of lateral power flow control, characterized in that: The invention comprises a transformer body, a controllable voltage source and a controller. The transformer body comprises a primary winding and a secondary winding. The controllable voltage source comprises a power electronic inverter and a coupling winding. The coupling winding is adjacently arranged on one side of the secondary winding. The coupling winding is electromagnetically coupled to the secondary winding. The input end of the power electronic inverter is electrically connected to the secondary winding or the primary winding. The output end of the power electronic inverter is electrically connected to the coupling winding. Under the control of the controller, the power electronic inverter injects voltage into the secondary winding through the coupling winding in an electromagnetically coupled manner.

2. The transformer according to claim 1, characterized in that: The power electronic inverter comprises a rectifier circuit and an inverter circuit, wherein the input end of the rectifier circuit is electrically connected to the primary winding, the output end of the rectifier circuit is electrically connected to the input end of the inverter circuit, and the output end of the inverter circuit is electrically connected to the coupling winding.

3. The transformer according to claim 1, characterized in that: The controller comprises: The low-voltage side expected voltage calculation module is used to calculate the expected voltage output on the low-voltage side according to the power flow conditions of the distribution network; The adjustment amount calculation module is used to calculate the difference between the expected voltage and the actual voltage on the low voltage side to obtain the adjustment voltage; The voltage source control module is used to control the controllable voltage source according to the amplitude and phase angle of the regulated voltage, so that the amplitude and phase angle of the voltage output by the controllable voltage source are equal to the amplitude and phase angle of the regulated voltage.

4. The transformer according to claim 1, characterized in that: The power electronic inverter is detachably mounted on the transformer body. The transformer body is provided with a connector for connecting the power electronic inverter. The connector is electrically connected to the secondary winding and the coupling winding.

5. The transformer according to claim 4, characterized in that: The connector is also electrically connected to the primary winding.

6. A method for controlling lateral tidal current, characterized in that: The steps include: Connect the buses of multiple substations with complementary load fluctuation characteristics; A controllable voltage source is connected to the secondary winding of the transformer in each substation; Calculate the expected voltage output on the low voltage side according to the power flow of the distribution network; Calculate the difference between the expected voltage and the actual voltage on the low voltage side to obtain the regulated voltage; The output voltage of the controllable voltage source is controlled so that the amplitude and phase angle of the voltage output by the controllable voltage source are equal to the amplitude and phase angle of the regulated voltage.

7. The method for controlling lateral current according to claim 6, characterized in that: In the step of calculating the difference between the expected voltage and the actual voltage on the low voltage side to obtain the regulated voltage, the regulated voltage is calculated by combining the following formulas: U1=R1I1+jωL l1 I1+jωMI1 In the formula, U1 is the voltage input to the primary winding, U2 is the voltage output from the secondary winding, R1 is the resistance of the primary winding, and L l1 is the leakage inductance of the primary winding, M is the leakage inductance between the primary winding and the secondary winding, R2 is the resistance of the secondary winding, L l2 is the leakage inductance of the secondary winding, ω is the angular frequency of the voltage input to the primary side, I1 is the current of the primary winding, I2 is the current of the secondary winding, k is the transformation ratio of the transformer, j is the imaginary unit, and U C To regulate the voltage.

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