Controllable distribution transformer and voltage regulation method

Abstract

The invention discloses a controllable distribution transformer and a voltage regulation method. The controllable distribution transformer comprises a power supply winding and a control winding, wherein the power supply winding and the control winding are positioned on a low-voltage side; the power supply winding and the control winding are both wound on an iron core of the distribution transformer, a winding on one side of the additional mutual inductor is connected with the power supply winding in series, a winding on the other side of the additional mutual inductor is connected with the control winding in parallel, and the first loop switch and the second loop switch are arranged at the two ends of the winding on one side respectively. The first loop switch, the second loop switch, the side winding and the control switch unit are connected in series, and the control switch unit is connected with the control winding; the power compensation control system controls the first loop switch, the second loop switch and a control switch in the control switch unit according to the voltage at the two ends of the power supply winding so as to control the number of turns connected to the winding and control the voltage value and phase change on the winding, and then series compensation of the voltage at the two ends of the power supply winding is achieved. The working current of the switch can be greatly reduced, and the reliability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical equipment, and more specifically, to a controllable distribution transformer and a voltage regulation method. Background Art

[0002] The impacts of distributed photovoltaics on power grids and users mainly include: impact on local voltage stability of distribution networks, impact on grid frequency stability, contribution to short-circuit current in faults, impact on power quality, and changes in requirements for power factor and reactive power configuration.

[0003] Most of the 10kV distribution lines built in the early stage were single radial distribution power supply, and the system safety was low. In the construction and transformation of urban distribution networks, the establishment of a ring network power supply and open-loop operation mode is gradually considered. In various distribution network structures, changes in static and dynamic voltages will affect line protection and system operation safety. Under steady-state operation, the voltage theoretically decreases gradually along the flow direction of the transmission line. After distributed photovoltaic access, due to the fluctuation of transmission power and the characteristics of distributed loads, the voltage at each node of the transmission line is high or low, resulting in voltage deviation exceeding the technical indicators for safe operation.

[0004] Figure 1 The principle of the influence of distributed photovoltaic access to the distribution network on local voltage is described. After large-scale distributed photovoltaic access, there is a problem of static voltage offset at local nodes of the distribution network. The distribution network, especially the low-voltage network, is sensitive to voltage changes. If you want to suppress this influence, you need to use controllable transformers in the selection of medium and low voltage transformers.

[0005] Therefore, a controllable distribution transformer and a voltage regulation method are needed. Summary of the invention

[0006] The present invention provides a controllable distribution transformer and a voltage regulation method to solve the problem.

[0007] In order to solve the above problems, according to one aspect of the present invention, a controllable distribution transformer is provided, the distribution transformer comprising: a high voltage winding, a distribution transformer core, a power supply winding, a control winding, an additional mutual inductor, a control switch unit, a first circuit switch, a second circuit switch and a power compensation control system;

[0008] Among them, the power supply winding and the control winding are both located on the low-voltage side; the power supply winding and the control winding are both wound on the iron core of the distribution transformer, one side winding of the additional mutual inductor is connected in series with the power supply winding, and the other side winding of the additional mutual inductor is connected in parallel with the control winding, the first loop switch and the second loop switch are respectively arranged at the two ends of one side winding, the first loop switch, the second loop switch, one side winding and the control switch unit are connected in series, and the control switch unit is connected to the control winding; the power compensation control system controls the first loop switch, the second loop switch and the control switch in progress according to the voltage at both ends of the power supply winding, so as to control the number of turns connected to the winding to control the voltage value and phase change on the winding, thereby realizing series compensation of the voltage at both ends of the power supply winding.

[0009] Preferably, the control switch unit comprises: at least two control switches, the number of the control switches is the same as the number of segments of the control winding, and a control switch is provided at the non-grounded side of the control winding and at the connection between any two segmented windings of the control winding.

[0010] Preferably, if the voltage U2 across the power supply winding is greater than a preset voltage upper limit, the voltage U2 across the power supply winding is reduced to perform reverse phase compensation, including: controlling the first circuit switch to be disconnected, the second circuit switch and the control switch K M Closed, this is reverse compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is less than the preset voltage upper limit; wherein M is the number of control switches.

[0011] Preferably, if the voltage U2 across the power supply winding is less than the preset voltage lower limit, the voltage U2 across the power supply winding is increased to perform in-phase compensation, including: controlling the second loop switch to be disconnected, the first loop switch and the control switch K M Closed, this is positive compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is greater than the preset lower limit; wherein M is the number of control switches.

[0012] Preferably, when adjusting the control switch K M When it reaches K1, the lower switch must be closed first, and then the higher switch must be opened; control switch K M The levels down to K1 decrease in sequence.

[0013] Preferably, the power compensation control system is further used for:

[0014] If it is detected that the voltage across the power supply winding is less than a preset voltage threshold, all switches are controlled to be disconnected.

[0015] According to another aspect of the present invention, there is provided a voltage regulation method based on the controllable distribution transformer as described above, the method comprising:

[0016] The power compensation control system obtains the voltage across the power supply winding;

[0017] The power compensation control system controls the first loop switch, the second loop switch and the control switch in the control switch unit according to the voltage at both ends of the power supply winding, so as to control the number of turns connected to the winding to control the voltage value and phase change on the winding, thereby realizing series compensation of the voltage at both ends of the power supply winding.

[0018] Preferably, the control switch unit comprises: at least two control switches, the number of the control switches is the same as the number of segments of the control winding, and a control switch is provided at the non-grounded side of the control winding and at the connection between any two segmented windings of the control winding.

[0019] Preferably, if the voltage U2 across the power supply winding is greater than a preset voltage upper limit, the voltage U2 across the power supply winding is reduced to perform reverse phase compensation, including: controlling the first circuit switch to be disconnected, the second circuit switch and the control switch K M Closed, this is reverse compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is less than the preset voltage upper limit; wherein M is the number of control switches.

[0020] Preferably, if the voltage U2 across the power supply winding is less than the preset voltage lower limit, the voltage U2 across the power supply winding is increased to perform in-phase compensation, including: controlling the second loop switch to be disconnected, the first loop switch and the control switch K M Closed, this is positive compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is greater than the preset lower limit; wherein M is the number of control switches.

[0021] Preferably, when adjusting the control switch K M When it reaches K1, the lower switch must be closed first, and then the higher switch must be opened; control switch K M The levels down to K1 decrease in sequence.

[0022] Preferably, the method further comprises:

[0023] Based on the maximum voltage of the control winding not exceeding S / I k Determine the control winding; where S is the maximum compensation capacitance, I k is the current flowing through the control winding at maximum compensation capacity;

[0024] based on Determine the number of control switches; where n is the number of control switches; a is the percentage of voltage to be adjusted; and λ is the fineness of adjustment of a single control switch.

[0025] Preferably, the method further comprises:

[0026] Determine the number of turns of the control winding, including:

[0027]

[0028] Among them, u b N is the compensation voltage of the secondary winding of the additional transformer; pr is the number of turns of the high voltage winding of the distribution transformer; N3 is the number of turns of the control winding; N f1 N is the number of turns of the primary winding of the additional transformer; f2 is the number of turns of the secondary winding of the additional transformer; U1 is the voltage on the high voltage side;

[0029] The number of turns of each segment winding is evenly distributed according to the number of turns of the control winding and the number of control switches.

[0030] Preferably, the method further comprises: if the power compensation control system detects that the voltage across the power supply winding is less than a preset voltage threshold, controlling all switches to be disconnected.

[0031] The present invention provides a controllable distribution transformer and a voltage regulation method, comprising: a power supply winding and a control winding are both located at a low voltage side; the power supply winding and the control winding are both wound on the core of the distribution transformer, one side winding of an additional mutual inductor is connected in series with the power supply winding, and the other side winding of the additional mutual inductor is connected in parallel with the control winding, the first loop switch and the second loop switch are respectively arranged at two ends of one side winding, the first loop switch, the second loop switch, one side winding and a control switch unit are connected in series, and the control switch unit is connected to the control winding; a power compensation control system controls the first loop switch, the second loop switch and the control switch in progress according to the voltage at both ends of the power supply winding, so as to control the number of turns connected to the winding to control the voltage value and phase change on the winding, thereby realizing series compensation of the voltage at both ends of the power supply winding; compared with a traditional on-load voltage-regulating distribution transformer, the controllable distribution transformer of the present invention reduces the working voltage of the switch, greatly reduces the insulation cost and the equipment size; on the other hand, by appropriately increasing the voltage of the additional winding and increasing the transformation ratio of the auxiliary mutual inductor, the working current of the switch can be greatly reduced, and the reliability is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0033] Figure 1The impact of distributed system access on local voltage of distribution network;

[0034] Figure 2 is a schematic structural diagram of a controllable distribution transformer 200 according to an embodiment of the present invention;

[0035] Figure 3 An example diagram of a controllable distribution transformer in a distributed photovoltaic access area according to an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of reverse compensation according to an embodiment of the present invention;

[0037] Figure 5 A schematic diagram of in-phase compensation according to an embodiment of the present invention;

[0038] Figure 6 FIG. 6 is a flow chart of a voltage regulation method 600 according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0040] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0041] In order to solve the impact of distributed photovoltaic access on the local voltage of the distribution network, the present invention proposes a controllable distribution transformer, which sets the tap switch on the low-voltage side. Taking into account the large current on the low-voltage side, additional transformer technology is used to effectively reduce the switching current of the tap switch, which has higher reliability and economy.

[0042] Figure 2 FIG. 2 is a schematic diagram of the structure of a controllable distribution transformer 200 according to an embodiment of the present invention. Figure 2As shown, the controllable distribution transformer provided in the embodiment of the present invention, compared with the traditional on-load voltage-adjusting distribution transformer, on the one hand, reduces the operating voltage of the switch, greatly reduces the insulation cost and equipment size; on the other hand, by appropriately increasing the additional winding voltage and increasing the auxiliary transformer ratio, the operating current of the switch can be greatly reduced, and the reliability is improved. The controllable distribution transformer 200 provided in the embodiment of the present invention includes: a high-voltage winding 201, a distribution transformer core 202, a power supply winding 203, a control winding 204, an additional transformer 205, a control switch unit 206, a first circuit switch 207, a second circuit switch 208 and a power compensation control system 209.

[0043] Among them, the power supply winding and the control winding are both located on the low-voltage side; the power supply winding and the control winding are both wound on the iron core of the distribution transformer, one side winding of the additional mutual inductor is connected in series with the power supply winding, and the other side winding of the additional mutual inductor is connected in parallel with the control winding, the first loop switch and the second loop switch are respectively arranged at the two ends of one side winding, the first loop switch, the second loop switch, one side winding and the control switch unit are connected in series, and the control switch unit is connected to the control winding; the power compensation control system controls the first loop switch, the second loop switch and the control switch in progress according to the voltage at both ends of the power supply winding, so as to control the number of turns connected to the winding to control the voltage value and phase change on the winding, thereby realizing series compensation of the voltage at both ends of the power supply winding.

[0044] Preferably, the control switch unit comprises: at least two control switches, the number of the control switches is the same as the number of segments of the control winding, and a control switch is provided at the non-grounded side of the control winding and at the connection between any two segmented windings of the control winding.

[0045] Preferably, if the voltage U2 across the power supply winding is greater than the preset voltage upper limit, the voltage across the power supply winding is reduced to perform reverse phase compensation, including: controlling the first loop switch to be disconnected, the second loop switch and the control switch K M Closed, this is reverse compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is less than the preset voltage upper limit; wherein M is the number of control switches.

[0046] Preferably, if the voltage across the power supply winding is less than the preset voltage lower limit, the voltage across the power supply winding is increased to perform in-phase compensation, including: controlling the second loop switch to be disconnected, the first loop switch and the control switch K M Closed, this is positive compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is greater than the preset lower limit; wherein M is the number of control switches.

[0047] Preferably, when adjusting the control switch K M When it reaches K1, the lower switch must be closed first, and then the higher switch must be opened; control switch K M The levels down to K1 decrease in sequence.

[0048] Combination Figure 3 As shown in the figure, five control switches are used as an example to illustrate the controllable distribution transformer of the present invention. Among them, AN is the high voltage winding of the distribution transformer, an is the power supply winding, T is the iron core of the distribution transformer, T1 is the additional mutual inductor, K6 and K7 are the first circuit switch and the second circuit switch respectively, U1 is the high voltage, U2 is the power supply voltage, U3 is the control winding voltage, and U 2E is the induced potential of the power supply winding, Zan is the power load of the distribution network. N3 is the control winding, which is wound on the core of the distribution transformer. f1 The winding is connected in parallel with the control winding, N f2 The winding is connected in series with the power supply winding, and the N f2 The voltage value and phase on the winding are adjusted to achieve series compensation for U2. The control unit includes: control switches K1-K5.

[0049] The working principle of the controllable distribution transformer is as follows: first, the U2 voltage is input into the power compensation control system, and the power compensation control system determines the control switch action according to the real-time value of U2.

[0050] Among them, if the voltage U2 across the power supply winding is greater than the preset voltage upper limit, it is necessary to reduce the voltage value of U2, that is, reverse compensation. The specific control switch strategy is: first control switch K6 to open, K7 and K5 to close, this is reverse compensation, adjust K5 to K1 in sequence until the compensation result satisfies that U2 is less than the preset voltage upper limit. When adjusting K5 to K1, it is necessary to close the next level switch first, and then disconnect the previous level switch. For example, from K5 to K4, first close K4, and then disconnect K5, so as to ensure that the circuit is not disconnected. The reverse compensation principle diagram is as follows Figure 4 As shown. At this time, U2=U 2E -U5, by adjusting the size of U3, the amount of reverse compensation voltage can be adjusted.

[0051] Among them, if the voltage U2 across the power supply winding is less than the preset voltage lower limit, it is necessary to increase the U2 voltage value, that is, in-phase compensation. The specific control switch strategy is: first control switch K7 to open, and K6 and K5 to close. This is forward compensation. Adjust K5 to K1 in sequence until the compensation result satisfies that U2 is greater than the preset voltage lower limit. When adjusting K5 to K1, it is necessary to close the next level switch first, and then disconnect the previous level switch. For example, from K5 to K4, close K4 first, and then disconnect K5, so as to ensure that the circuit is not disconnected. The schematic diagram of in-phase compensation is as follows Figure 5 As shown. At this time, U2=U 2E +U5, the size of U5 is approximately proportional to U3. By adjusting the size of U3, the in-phase compensation value of U2 can be adjusted.

[0052] In the present invention, in order to reduce the current flowing through the control winding at the maximum compensation capacity and reduce the breaking current of the control switch, it is necessary to increase the control winding voltage and increase the transformation ratio of the additional transformer. k To design, assuming that the maximum compensation capacity is S, the maximum voltage value of the control winding needs to be designed as S / I k .

[0053] In the present invention, the adjustment fineness of the control switch needs to be considered according to the design requirements. Assuming that the upper and lower limits of the preset power supply voltage are ±10% of the rated voltage U, each level of adjustment voltage of K1-K5 can be controlled at 5%, and the number of switches is determined by the upper and lower limits of the voltage that may appear in the system.

[0054] Specifically, the design principle of the number of switches is as follows: Assuming the number of switches to be designed is n, the voltage percentage to be adjusted is ±a. In general, considering that the system's requirement for the voltage deviation of the 220V user side is -7%—+10%, the adjustment fineness of a single switch is set to λ. Then, the number of switches is calculated according to For example, if the voltage upper limit may reach ±30% of the rated voltage, a 20% adjustment is required, and 5 switches can be designed. If the voltage upper limit may reach ±20% of the rated voltage, a 10% adjustment is required, and 3 switches can be designed.

[0055] If a special situation occurs, such as a higher voltage stability requirement, for example, a requirement that the voltage stability deviation is less than ±3%, the fineness of adjustment of a single switch is preferably adjusted to 2%. The fineness of adjustment of the control switch in the present invention can be adjusted according to the actual situation.

[0056] Assume that the number of turns of the primary winding of the additional transformer is N f1 , powered by the control winding, the number of turns of the control winding connected to the circuit is N3, then the control winding voltage is:

[0057] U3=e zr ×N3(1)

[0058] where e zr is the turn potential of the main iron core, and its value is: e zr =U1 / N pr

[0059] Then the additional transformer turn potential is e fz =U B / Nf1 The number of turns of the secondary winding is N f2 , which is connected in series with the power supply winding of the distribution transformer, so the compensation amount of the power supply voltage of the distribution transformer is: u b =e fr N f2 .

[0060] E zr Substituting into the above formula, we can get:

[0061]

[0062] Among them, u b N is the compensation voltage of the secondary winding of the additional transformer; pr is the number of turns of the high voltage winding of the distribution transformer; N3 is the number of turns of the control winding; N f1 N is the number of turns of the primary winding of the additional transformer; f2 is the number of turns of the secondary winding of the additional transformer; U1 is the voltage on the high voltage side.

[0063] When the number of turns of the additional transformer winding is determined, the value of N3 can be calculated according to formula (2), and then the number of turns of each segment winding of N3 can be evenly distributed according to the number of switches.

[0064] Preferably, the power compensation control system is further used for:

[0065] If it is detected that the voltage across the power supply winding is less than a preset voltage threshold, all switches are controlled to be disconnected.

[0066] The distribution transformer of the present invention also has a short-circuit protection function. If the power compensation control system detects that the voltage is less than the preset voltage threshold of 100V, it can be determined that the power supply winding is short-circuited. At this time, all switches are controlled to be disconnected. At this time, the power supply winding is equivalent to carrying a large load T1, which can greatly reduce the short-circuit current, thereby protecting the distribution transformer.

[0067] Figure 6 FIG. 6 is a flow chart of a voltage regulation method 600 according to an embodiment of the present invention. Figure 6 As shown, the voltage regulation method 600 based on the controllable distribution transformer as described above provided in the embodiment of the present invention starts from step 601. In step 601, the power compensation control system obtains the voltage across the power supply winding.

[0068] In step 602, the power compensation control system controls the first loop switch, the second loop switch and the control switch in the control switch unit according to the voltage across the power supply winding, so as to control the number of turns connected to the winding to control the voltage value and phase change on the winding, thereby realizing series compensation of the voltage across the power supply winding.

[0069] Preferably, the control switch unit comprises: at least two control switches, the number of the control switches is the same as the number of segments of the control winding, and a control switch is provided at the non-grounded side of the control winding and at the connection between any two segmented windings of the control winding.

[0070] Preferably, if the voltage U2 across the power supply winding is greater than a preset voltage upper limit, the voltage U2 across the power supply winding is reduced to perform reverse phase compensation, including: controlling the first circuit switch to be disconnected, the second circuit switch and the control switch K M Closed, this is reverse compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is less than the preset voltage upper limit; wherein M is the number of control switches.

[0071] Preferably, if the voltage U2 across the power supply winding is less than the preset voltage lower limit, the voltage U2 across the power supply winding is increased to perform in-phase compensation, including: controlling the second loop switch to be disconnected, the first loop switch and the control switch K M Closed, this is positive compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is greater than the preset lower limit; wherein M is the number of control switches.

[0072] Preferably, when adjusting the control switch K M When it reaches K1, the lower switch must be closed first, and then the higher switch must be opened; control switch K M The levels down to K1 decrease in sequence.

[0073] Preferably, the method further comprises:

[0074] Based on the maximum voltage of the control winding not exceeding S / I k Determine the control winding; where S is the maximum compensation capacitance, I k is the current flowing through the control winding at the maximum compensation capacity;

[0075] based on Determine the number of control switches; where n is the number of control switches; a is the percentage of voltage to be adjusted; and λ is the fineness of adjustment of a single control switch.

[0076] Preferably, the method further comprises:

[0077] Determine the number of turns of the control winding, including:

[0078]

[0079] Among them, u b N is the compensation voltage of the secondary winding of the additional transformer;pr is the number of turns of the high voltage winding of the distribution transformer; N3 is the number of turns of the control winding; N f1 N is the number of turns of the primary winding of the additional transformer; f2 is the number of turns of the secondary winding of the additional transformer; U1 is the voltage on the high voltage side;

[0080] The number of turns of each segment winding is evenly distributed according to the number of turns of the control winding and the number of control switches.

[0081] Preferably, the method further comprises:

[0082] If the power compensation control system detects that the voltage across the power supply winding is less than a preset voltage threshold, all switches are controlled to be disconnected.

[0083] The voltage regulation method 600 of the embodiment of the present invention corresponds to the controllable distribution transformer 200 of another embodiment of the present invention, which will not be described in detail herein.

[0084] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0085] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise therein. All references to "a / said / the [means, components, etc.]" are to be openly interpreted as at least one instance of said means, components, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless explicitly stated otherwise.

[0086] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0087] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of 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 produce 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.

[0088] 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 including 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.

[0089] 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 in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A controllable distribution transformer, characterized in that: The distribution transformer comprises: a high voltage winding, a distribution transformer core, a power supply winding, a control winding, an additional mutual inductor, a control switch unit, a first circuit switch, a second circuit switch and a power compensation control system; Among them, the power supply winding and the control winding are both located on the low-voltage side; the power supply winding and the control winding are both wound on the iron core of the distribution transformer, one side winding of the additional mutual inductor is connected in series with the power supply winding, and the other side winding of the additional mutual inductor is connected in parallel with the control winding, the first loop switch and the second loop switch are respectively arranged at the two ends of one side winding, the first loop switch, the second loop switch, one side winding and the control switch unit are connected in series, and the control switch unit is connected to the control winding; the power compensation control system controls the first loop switch, the second loop switch and the control switch in progress according to the voltage at both ends of the power supply winding, so as to control the number of turns connected to the winding to control the voltage value and phase change on the winding, thereby realizing series compensation of the voltage at both ends of the power supply winding.

2. The distribution transformer according to claim 1, characterized in that: The control switch unit comprises: at least two control switches, the number of the control switches is the same as the number of segments of the control winding, and a control switch is arranged at the high voltage end of the control winding and at the connection point of any two segmented windings of the control winding.

3. The distribution transformer according to claim 1, characterized in that: If the voltage U2 across the power supply winding is greater than the preset voltage upper limit, the voltage U2 across the power supply winding is reduced to perform reverse phase compensation, including: controlling the first circuit switch to be disconnected, the second circuit switch and the control switch K M Closed, this is reverse compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 at both ends of the power supply winding is less than the preset voltage upper limit value; wherein, K is set in sequence from the ground side to the high voltage side of the control winding. M to K1, M is the number of control switches.

4. The distribution transformer according to claim 1, characterized in that: If the voltage U2 across the power supply winding is less than the preset voltage lower limit, the voltage U2 across the power supply winding is increased to perform in-phase compensation, including: controlling the second circuit switch to be disconnected, the first circuit switch and the control switch K M Closed, this is positive compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 at both ends of the power supply winding is greater than the preset lower limit value; wherein, K is set in sequence from the ground side to the high voltage side of the control winding. M to K1, M is the number of control switches.

5. The distribution transformer according to claim 3 or 4, characterized in that: Adjust the control switch K M When it reaches K1, the lower switch must be closed first, and then the higher switch must be opened; control switch K M The levels down to K1 decrease in sequence.

6. The distribution transformer according to claim 1, characterized in that: The power compensation control system is also used for: If it is detected that the voltage across the power supply winding is less than a preset voltage threshold, all switches are controlled to be disconnected.

7. A voltage regulation method based on the controllable distribution transformer according to any one of claims 1 to 6, characterized in that: The method comprises: The power compensation control system obtains the voltage across the power supply winding; The power compensation control system controls the first loop switch, the second loop switch and the control switch in the control switch unit according to the voltage at both ends of the power supply winding, so as to control the number of turns connected to the winding to control the voltage value and phase change on the winding, thereby realizing series compensation of the voltage at both ends of the power supply winding.

8. The method according to claim 7, characterized in that The control switch unit comprises: at least two control switches, the number of the control switches is the same as the number of segments of the control winding, and a control switch is arranged at the high voltage end of the control winding and at the connection point of any two segmented windings of the control winding.

9. The method according to claim 7, characterized in that: If the voltage U2 across the power supply winding is greater than the preset voltage upper limit, the voltage U2 across the power supply winding is reduced to perform reverse phase compensation, including: controlling the first circuit switch to be disconnected, the second circuit switch and the control switch K M Closed, this is reverse compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is less than the preset voltage upper limit; wherein M is the number of control switches.

10. The method according to claim 7, characterized in that If the voltage U2 across the power supply winding is less than the preset voltage lower limit, the voltage U2 across the power supply winding is increased to perform in-phase compensation, including: controlling the second circuit switch to be disconnected, the first circuit switch and the control switch K M Closed, this is positive compensation, and adjust the control switch K in turn M to K1, until the compensation result satisfies that the voltage U2 across the power supply winding is greater than the preset lower limit; wherein M is the number of control switches.

11. The distribution transformer according to claim 9 or 10, characterized in that: In adjusting the control switch K M When it reaches K1, the lower switch must be closed first, and then the higher switch must be opened; control switch K M The levels down to K1 decrease in sequence.

12. The method according to claim 8, characterized in that The method further comprises: Based on the maximum voltage of the control winding not exceeding S / I k Determine the control winding; where S is the maximum compensation capacitance, I k is the current flowing through the control winding at maximum compensation capacity; based on Determine the number of control switches; where n is the number of control switches; a is the percentage of voltage to be adjusted; and λ is the fineness of adjustment of a single control switch.

13. The method according to claim 7, characterized in that The method further comprises: Determine the number of turns of the control winding, including: Among them, u b N is the compensation voltage of the secondary winding of the additional transformer; pr is the number of turns of the high voltage winding of the distribution transformer; N3 is the number of turns of the control winding; N f1 N is the number of turns of the primary winding of the additional transformer; f2 is the number of turns of the secondary winding of the additional transformer; U1 is the voltage on the high voltage side; The number of turns of each segment winding is evenly distributed according to the number of turns of the control winding and the number of control switches.

14. The method according to claim 7, characterized in that The method further comprises: If the power compensation control system detects that the voltage across the power supply winding is less than a preset voltage threshold, all switches are controlled to be disconnected.

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