Voltage regulating transformer

Abstract

The application relates to a voltage regulating transformer which comprises a core, a primary winding, a coarse adjustment winding, a fine adjustment winding, a first switch and a second switch, the primary winding, the coarse adjustment winding and the fine adjustment winding are all wound on the core, the first end of the primary winding is used for connecting a voltage, the last end of the primary winding is connected with the first end of the coarse adjustment winding, the last end of the coarse adjustment winding is connected with a neutral point, the fine adjustment winding comprises a first fine adjustment winding and a second fine adjustment winding which have the same structure, the moving contact of each first switch is connected with a tap led out from the coarse adjustment winding at different positions, the static contact of the first switch is connected with the first fine adjustment winding and the second fine adjustment winding, the moving contact of the second switch is connected with the taps led out from the first fine adjustment winding and the second fine adjustment winding at different positions, so that the number of turns connected between the first switch and the second switch in the first fine adjustment winding is equal to the number of turns connected between the first switch and the second switch in the second fine adjustment winding, and the static contact of the second switch is used for outputting a voltage, thereby improving the use reliability of the voltage regulating transformer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformers, in particular to a voltage regulating transformer. BACKGROUND

[0002] A transformer is a device for changing AC voltage by using the principle of electromagnetic induction, which is used to increase or decrease voltage in a power system and serves as an important equipment for power transmission. A test transformer is a kind of voltage regulating transformer, which is used to provide test power with different voltage levels for test objects and is widely used.

[0003] In some application occasions, the voltage regulating transformer needs to have a high test voltage regulating range, and the number of turns of the secondary side of the voltage regulating transformer may vary from several turns to tens or hundreds of turns. In this case, if the test object connected to the voltage regulating transformer fails, the outlet short circuit of the voltage regulating transformer occurs, and the internal short circuit current is as high as tens of times of the operating current. The fault current has a very obvious influence, which leads to the unreliable use of the traditional voltage regulating transformer. SUMMARY

[0004] Therefore, it is necessary to provide a reliable voltage regulating transformer aiming at the above technical problems.

[0005] A voltage regulating transformer includes a core, a primary winding, a coarse adjustment winding, a fine adjustment winding, a first switch and a second switch. The primary winding, the coarse adjustment winding and the fine adjustment winding are all wound on the core. The first end of the primary winding is used to connect a voltage, the last end of the primary winding is connected to the first end of the coarse adjustment winding, the last end of the coarse adjustment winding is connected to a neutral point, and the fine adjustment winding includes a first fine adjustment winding and a second fine adjustment winding which have the same structure.

[0006] The first switch and the second switch each include two or more moving contacts. The moving contacts of each first switch are connected to a tap led out by the coarse adjustment winding at different positions. The static contacts of the first switch are connected to the first fine adjustment winding and the second fine adjustment winding. The moving contacts of the second switch are connected to the taps led out by the first fine adjustment winding and the second fine adjustment winding at different positions, so that the number of turns between the first switch and the second switch in the first fine adjustment winding is equal to the number of turns between the first switch and the second switch in the second fine adjustment winding. The static contacts of the second switch are used to output a voltage.

[0007] In one embodiment, an electric reactance element is further included, and the static contacts of the second switch are connected to the electric reactance element to output a voltage.

[0008] In one of the embodiments, a voltage regulating module includes one of the coarse adjustment winding, one of the fine adjustment winding, one of the first switch, one of the second switch and one of the reactance element, the voltage regulating transformer includes three of the voltage regulating modules, and the end of the coarse adjustment winding in each of the voltage regulating modules is connected to the neutral point.

[0009] In one of the embodiments, the coarse adjustment winding includes two or more coarse adjustment sub-windings, each of the coarse adjustment sub-windings is connected in series, the first end of the series connection is connected to the end of the primary winding, and the second end of the series connection is connected to the neutral point, and the coarse adjustment winding has two or more taps with one of the coarse adjustment sub-windings as the minimum unit.

[0010] In one of the embodiments, the number of turns of each of the coarse adjustment sub-windings is equal.

[0011] In one of the embodiments, the number of electrical turns of each of the first fine adjustment winding and the second fine adjustment winding is equal to the number of turns of one of the coarse adjustment sub-windings.

[0012] In one of the embodiments, a voltage stabilizing winding is further included, and the voltage stabilizing winding is wound around the iron core.

[0013] In one of the embodiments, a controller is further included, and each of the first switch and the second switch is connected to the controller.

[0014] In one of the embodiments, the controller is configured to, after obtaining an end instruction, first control the second switch to be turned off, and then control the first switch to be turned off.

[0015] In one of the embodiments, a suppression reactance connected to the neutral point is further included.

[0016] The voltage regulating transformer comprises a core, a primary winding, a coarse adjustment winding, a fine adjustment winding, a first switch and a second switch, the coarse adjustment winding and the fine adjustment winding are both wound on the core, a first end of the primary winding is used for connecting a voltage, a last end of the primary winding is connected to a first end of the coarse adjustment winding, a last end of the coarse adjustment winding is connected to a neutral point, the fine adjustment winding comprises a first fine adjustment winding and a second fine adjustment winding which have the same structure, each of the first switch and the second switch comprises two or more moving contacts, the moving contacts of each of the first switch are connected to a tap led out by the coarse adjustment winding at different positions, the static contacts of the first switch are connected to the first fine adjustment winding and the second fine adjustment winding, the moving contacts of the second switch are connected to the taps led out by the first fine adjustment winding and the second fine adjustment winding at different positions, so that the number of turns of the first fine adjustment winding connected between the first switch and the second switch is equal to the number of turns of the second fine adjustment winding connected between the first switch and the second switch, and the static contacts of the second switch are used for outputting a voltage. The voltage regulating transformer can realize first-stage voltage regulation through the first switch and the coarse adjustment winding, and can realize second-stage voltage regulation through the second switch and the fine adjustment winding, so that the voltage regulating transformer does not need to set too many turns of windings, and can have a higher test voltage regulation range, can provide a debugging test power supply with different voltage levels, in addition, the number of turns of the first fine adjustment winding connected between the first switch and the second switch is equal to the number of turns of the second fine adjustment winding connected between the first switch and the second switch, so that the first fine adjustment winding and the second fine adjustment winding are symmetrically connected in parallel, the space transverse leakage magnetic field can be reduced, the axial force of the whole winding is small, the ampere-turns are self-balanced, and the use reliability of the voltage regulating transformer is improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the voltage regulating transformer in an embodiment;

[0018] Figure 2 It is a structural schematic diagram of the voltage regulating transformer after three-phase combination in an embodiment. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0020] In an embodiment, a voltage regulating transformer is provided, which comprises a core, a primary winding, a coarse adjustment winding, a fine adjustment winding, a first switch and a second switch, the coarse adjustment winding and the fine adjustment winding are both wound on the core, a first end of the primary winding is used for connecting a voltage, a last end of the primary winding is connected to a first end of the coarse adjustment winding, a last end of the coarse adjustment winding is connected to a neutral point, the fine adjustment winding comprises a first fine adjustment winding and a second fine adjustment winding which have the same structure, each of the first switch and the second switch comprises two or more moving contacts, the moving contacts of each of the first switch are connected to a tap led out by the coarse adjustment winding at different positions, the static contacts of the first switch are connected to the first fine adjustment winding and the second fine adjustment winding, the moving contacts of the second switch are connected to the taps led out by the first fine adjustment winding and the second fine adjustment winding at different positions, so that the number of turns of the first fine adjustment winding connected between the first switch and the second switch is equal to the number of turns of the second fine adjustment winding connected between the first switch and the second switch, and the static contacts of the second switch are used for outputting a voltage. The voltage regulating transformer can realize first-stage voltage regulation through the first switch and the coarse adjustment winding, and can realize second-stage voltage regulation through the second switch and the fine adjustment winding, so that the voltage regulating transformer does not need to set too many turns of windings, and can have a higher test voltage regulation range, can provide a debugging test power supply with different voltage levels, in addition, the number of turns of the first fine adjustment winding connected between the first switch and the second switch is equal to the number of turns of the second fine adjustment winding connected between the first switch and the second switch, so that the first fine adjustment winding and the second fine adjustment winding are symmetrically connected in parallel, the space transverse leakage magnetic field can be reduced, the axial force of the whole winding is small, the ampere-turns are self-balanced, and the use reliability of the voltage regulating transformer is improved. Figure 1As shown, the voltage regulating transformer includes a core, a primary winding 120, a coarse adjustment winding 100, a fine adjustment winding 200, a first switch 300 and a second switch 400. The coarse adjustment winding 100 and the fine adjustment winding 200 are both wound on the core. A first end of the primary winding 120 is used to connect a voltage. A last end of the primary winding 120 is connected to a first end of the coarse adjustment winding 100. A last end of the coarse adjustment winding 100 is connected to a neutral point. The fine adjustment winding 200 includes a first fine adjustment winding 210 and a second fine adjustment winding 220 which have the same structure. The first switch 300 and the second switch 400 each include two or more moving contacts. The moving contacts of each first switch 300 are connected to a tap led out by the coarse adjustment winding 100 at different positions. The stationary contacts of the first switch 300 are connected to the first fine adjustment winding 210 and the second fine adjustment winding 220. The moving contacts of the second switch 400 are connected to the taps led out by the first fine adjustment winding 210 and the second fine adjustment winding 220 at different positions, so that the number of turns of the first fine adjustment winding 210 connected between the first switch 300 and the second switch 400 is equal to the number of turns of the second fine adjustment winding 220 connected between the first switch 300 and the second switch 400. The stationary contacts of the second switch 400 are used as a voltage output end of the voltage regulating transformer to output a voltage.

[0021] The voltage regulating transformer can realize first-stage voltage regulation through the first switch 300 and the coarse adjustment winding 100, and can realize second-stage voltage regulation through the second switch 400 and the fine adjustment winding 200. Therefore, the voltage regulating transformer does not need to set too many turns of windings, and can have a higher test voltage regulation range, can provide a debugging test power supply with different voltage levels, and the like. In addition, the number of turns of the first fine adjustment winding 210 connected between the first switch 300 and the second switch 400 is equal to the number of turns of the second fine adjustment winding 220 connected between the first switch 300 and the second switch 400, so that the first fine adjustment winding 210 and the second fine adjustment winding 220 are symmetrically connected in parallel, can reduce space transverse leakage magnetic flux, can make the axial force of the whole winding small, can realize ampere-turn self-balancing, and can improve the use reliability of the voltage regulating transformer.

[0022] Specifically, the voltage regulating transformer includes a core, a primary winding 120, a coarse adjustment winding 100, a fine adjustment winding 200, a first switch 300 and a second switch 400. The primary winding 120, the coarse adjustment winding 100 and the fine adjustment winding 200 are all wound on the core, and specifically can be wound on different positions of the core respectively, are used to be electromagnetically induced with the core, and complete electromagnetic conversion and transmission, and the like.

[0023] The first end and the last end of the primary winding 120 refer to two ends of the primary winding 120 as a whole winding, one of the two ends is defined as the first end, and the other end is the last end, and the specific order is not limited. The first end of the primary winding 120 is used to access the voltage, generally accessing the system voltage, and the last end of the primary winding 120 is connected to the first end of the coarse adjustment winding 100. The primary winding 120 and the coarse adjustment winding 100 together serve as the primary side of the voltage regulating transformer.

[0024] The first end and the last end of the coarse adjustment winding 100 refer to two ends of the coarse adjustment winding 100 as a whole winding, one of the two ends is defined as the first end, and the other end is the last end, and the specific order is not limited. The first end of the coarse adjustment winding 100 is connected to the last end of the primary winding 120, and the last end of the coarse adjustment winding 100 is connected to the neutral point. When the voltage regulating transformer is applied to an offshore station, the rated voltage of the primary side of the voltage regulating transformer can be selected as the rated voltage of the offshore generator, so that the voltage regulating transformer can be used with most offshore generators, without the need to take power from the land station, and is convenient to use.

[0025] The primary winding 120 and the coarse adjustment winding 100 are connected in series, and the primary winding 120 and the coarse adjustment winding 100 work together to achieve the basic function of the transformer. The voltage regulating transformer includes a part of series winding and a part of common winding, which can realize transformer autotransformer, improve the space utilization, and is beneficial to reduce the volume of the voltage regulating transformer, so that the voltage regulating transformer is more compact. The types of the first switch 300 and the second switch 400 are not unique, for example, they can be a set of linked load switches or others, as long as they can be realized by those skilled in the art.

[0026] The first switch 300 and the second switch 400 each include two or more moving contacts, and the stationary contacts of the first switch 300 and the second switch 400 can be conductive with different moving contacts to switch different conduction paths. When the stationary contacts of the first switch 300 and the second switch 400 are conductive with different moving contacts, the second switch 400 and the first switch 300 can be connected to different turns of the first fine adjustment winding 210 and the second fine adjustment winding 220, and the first switch 300 and the neutral point can be connected to different turns of the coarse adjustment winding 100, so that the voltage regulating transformer can output different voltages, and two-stage voltage regulation can be realized through the coarse adjustment winding 100 and the fine adjustment winding 200, thereby expanding the voltage regulating range.

[0027] The static contact of the first switch 300 connects the first fine adjustment winding 210 and the second fine adjustment winding 220, and the moving contact of the second switch 400 connects the taps of the first fine adjustment winding 210 and the second fine adjustment winding 220 at different positions, so that the number of turns of the first fine adjustment winding 210 connected between the first switch 300 and the second switch 400 is equal to the number of turns of the second fine adjustment winding 220 connected between the first switch 300 and the second switch 400. It can be understood that the second switch 400 includes two or more groups of moving contacts, each group of moving contacts includes two moving contacts, which are assumed to be a first moving contact and a second moving contact, the first moving contact connects a tap in the first fine adjustment winding 210, and the second moving contact connects a tap in the second fine adjustment winding 220 corresponding to the position of the tap in the first fine adjustment winding 210 connected by the first moving contact. Correspondingly, the static contact of the first switch 300 connects the taps of the first fine adjustment winding 210 and the second fine adjustment winding 220, so that the number of turns of the first fine adjustment winding 210 connected between the first switch 300 and the second switch 400 is equal to the number of turns of the second fine adjustment winding 220 connected between the first switch 300 and the second switch 400.

[0028] Further, the first fine adjustment winding 210 and the second fine adjustment winding 220 have the same structure, are both wound on the iron core, and are symmetrical about the split line of both, that is, the first fine adjustment winding 210 and the second fine adjustment winding 220 are symmetrically connected with the winding middle part as the boundary surface. For example, the first fine adjustment winding 210 is arranged on the upper side in the arrangement mode of the 1st-nth turns, the second fine adjustment winding 220 is arranged on the lower side in the arrangement mode of the nth-1th turns, and the two are centrally symmetrical. At this time, the static contact of the first switch 300 can respectively connect the tap led out at the 1st turn of the first fine adjustment winding 210 and the tap led out at the 1st turn of the second fine adjustment winding 220, and the moving contact of the second switch 400 can respectively connect the tap led out at the 4th turn of the first fine adjustment winding 210 and the tap led out at the 4th turn of the second fine adjustment winding 220, so that the number of turns of the first fine adjustment winding 210 connected between the first switch 300 and the second switch 400 is equal to the number of turns of the second fine adjustment winding 220 connected between the first switch 300 and the second switch 400, both the first fine adjustment winding 210 and the second fine adjustment winding 220 are symmetrically or nearly symmetrically connected with the ampere-turns, the up-down symmetric leakage magnetic field is generated, the axial force of the whole winding is minimized, the ampere-turns are self-balanced, and the working performance of the voltage regulating transformer is improved.

[0029] In one embodiment, as Figure 1As shown, the voltage regulating transformer further comprises a reactance element 500, and the static contact of the second switch 400 outputs voltage after connecting the reactance element 500. The reactance element 500 is connected in series at the secondary side of the voltage regulating transformer, i.e. the test output voltage side, so that the adaptive short-circuit resistance of the voltage regulating transformer can be realized, and the working performance of the voltage regulating transformer is improved.

[0030] Specifically, the primary side winding of the voltage regulating transformer comprises all coarse adjustment windings 100 and primary windings 120, and is connected to the system voltage. The secondary side winding of the voltage regulating transformer comprises all first fine adjustment windings 210, second fine adjustment windings 220 and coarse adjustment windings 100 connected between the first switch 300 and the neutral point, and outputs the test voltage for debugging. The equivalent reactance element 500 of the primary and secondary sides of the voltage regulating transformer is inversely proportional to the square of the number of turns, and a certain reactance element 500 is connected in series. The fewer the turns of the secondary side, the larger the equivalent reactance element 500 of the primary side, the lower the voltage of the secondary side, and the fewer the turns, the more obvious the adaptive short-circuit resistance function realized.

[0031] The specific derivation is as follows: the key to control the short-circuit impact is to limit the size of the fault current. The short-circuit current of the secondary side is calculated by the per-unit method:

[0032]

[0033] The primary side voltage and the number of turns are unchanged, and the parameters are converted to the primary side:

[0034]

[0035] The equivalent impedance per-unit of the reactance element 500 connected in series at the secondary side is calculated as:

[0036]

[0037] In the formula, U s , U k and U L represent the per-unit of the system impedance, the transformer impedance and the reactance element 500 connected in series, respectively, I SC and I N are the short-circuit current and the rated current, respectively, W is the number of turns, and the subscripts 1 and 2 refer to the primary side and the secondary side, respectively. Z0 is the nominal value of the reference impedance of the per-unit algorithm used. The system impedance and the transformer impedance are generally fixed and unchanged. As can be seen from the above derivation, the number of turns of the secondary side is reduced, the rated current I N2 is increased according to the turn ratio, the equivalent impedance of the series reactance at the secondary side is increased according to the square of the turn ratio, and the effect of limiting the current at the secondary side is obvious, so that the adaptive short-circuit resistance function can be realized, and the adaptive short-circuit resistance adjustment is completed.

[0038] It can be understood that the specific value of the reactance element 500 can be determined according to the voltage regulating transformer capacity, impedance and secondary voltage regulation range, and the method can be selected as a theoretical analysis algorithm or a simulation calculation method. The reactance element 500 is the key to adaptive short-circuit resistance, and the series reactance element 500 is determined by demonstration and conversion, without human intervention, to realize the automatic adjustment of the equivalent impedance of the test transformer. The reactance element 500 can be built-in or externally connected in the voltage regulating transformer, and when built-in, the voltage regulating transformer structure can be more compact.

[0039] In one embodiment, as shown in Figure 2 , a voltage regulating module includes a coarse adjustment winding 100, a fine adjustment winding 200, a first switch 300, a second switch 400 and a reactance, the reactance in each voltage regulating module is L A , L B and L C , the voltage regulating transformer includes three voltage regulating modules, and the end of the coarse adjustment winding 100 in each voltage regulating module is connected to the neutral point. Specifically, one voltage regulating module is one phase, the voltage regulating transformer includes three voltage regulating modules, that is, the voltage regulating transformer is a three-phase transformer, the stationary contact of the second switch 400 in each voltage regulating module outputs voltage through the reactance element 500, and the adaptive short-circuit resistance adjustment capability is good. The end of the coarse adjustment winding 100 in each voltage regulating module is connected to the neutral point, the three voltage regulating modules are connected in star type, three-phase voltage can be outputted, and the universality is good.

[0040] In one embodiment, as shown in Figure 1 , the coarse adjustment winding 100 includes two or more coarse adjustment sub-windings, which are CT1-CTN, respectively, each coarse adjustment sub-winding is connected in series, the first end of the series is connected to the end of the primary winding 120, and the end of the series is connected to the neutral point. The coarse adjustment winding 100 draws two or more taps as a minimum unit of one coarse adjustment sub-winding.

[0041] When the coarse adjustment winding 100 includes two or more coarse adjustment sub-windings connected in series, one end of the series connection is the first end of the coarse adjustment winding 100, and the other end of the series connection is the last end of the coarse adjustment winding 100. Further, the coarse adjustment winding 100 is provided with two or more taps, and the number of coarse adjustment sub-windings connected between the first switch 300 and the neutral point can be adjusted when the first switch 300 is switched to a different moving contact from the static contact, with the number of turns of one coarse adjustment sub-winding as the smallest unit of adjustment. The number of coarse adjustment sub-windings is not unique, and is assumed to be N. In this embodiment, the coarse adjustment winding 100 is arranged as 1, 2, 3,..., N groups of common winding structures, and each coarse adjustment sub-winding is switched as a whole during secondary side voltage regulation, to complete the function conversion between the common winding and the series winding. The main air gap is the gap between the connection points of the series winding and the common winding. For example, when the secondary side is connected to CT2, CT3,..., CTN, the main air gap is between CT1 and CT2. For example, when the secondary side is connected to CT3, CT4,..., CTN, the main air gap is between CT2 and CT3. Since the maximum position of the spatial leakage magnetic field is between the main air gaps, controlling the leakage magnetic field of the main air gap controls the spatial magnetic field energy and the stress trend of the winding. Therefore, with one coarse adjustment sub-winding as the switching unit and different numbers of coarse adjustment sub-windings connected, the leakage magnetic field of the main air gap is only shifted, without causing local distortion, which is beneficial to improving the working performance of the voltage regulating transformer. Extending, the coarse adjustment winding 100 further includes the primary winding 120, and the primary winding 120 is connected in series with the coarse adjustment sub-winding at the first end, and the coarse adjustment sub-winding at the first end is connected to the voltage through the primary winding 120. The primary winding 120 and each coarse adjustment sub-winding work together to achieve the basic function of the transformer.

[0042] Further, in one embodiment, the number of turns of each coarse adjustment sub-winding is equal. When the number of turns of each coarse adjustment sub-winding is equal, if the switching between one moving contact of the first switch 300 and another adjacent moving contact is one gear, the number of turns changed when the first switch 300 is switched between gears is the same, and the voltage regulation range is the same. The coarse adjustment winding 100 is arranged as 1, 2, 3,..., N groups of common winding structures, and the coarse adjustment winding 100 is arranged as the smallest unit of one coarse adjustment sub-winding in the electrical wiring diagram. Each coarse adjustment sub-winding is switched as a whole during secondary side voltage regulation, to complete the function conversion between the common winding and the series winding, to make the leakage magnetic field distribution in the main air gap under each operating state substantially the same, to achieve uniform leakage magnetic field distribution, and to further improve the working reliability of the voltage regulating transformer.

[0043] In one embodiment, the number of turns of the first fine adjustment winding 210 and the second fine adjustment winding 220 is equal to the number of turns of one coarse adjustment sub-winding. Specifically, the number of turns here refers to the physical number of turns, which refers to all the turns present. When the number of turns of the first fine adjustment winding 210 and the second fine adjustment winding 220 is equal to the number of turns of one coarse adjustment sub-winding, the first fine adjustment winding 210 and the second fine adjustment winding 220 are symmetrically connected in parallel, the voltage on the first fine adjustment winding 210 is equal to the voltage on the second fine adjustment winding 220, and the voltage on the first fine adjustment winding 210 is half of the voltage on one coarse adjustment sub-winding. When the second switch 400 switches different moving contacts, specifically switches all moving contacts of the first fine adjustment winding 210 and the second fine adjustment winding 220, and the electrical number of turns changes from 0 to the total electrical number of turns, it is considered that one round of voltage regulation of the first fine adjustment winding 210 and the second fine adjustment winding 220 is completed. Then, another moving contact of the coarse adjustment winding 100 can be switched by the first switch 300 to achieve voltage regulation in another numerical range, thereby achieving the continuity of voltage regulation.

[0044] For example, when the total electrical number of turns of the first fine adjustment winding 210 and the total electrical number of turns of the second fine adjustment winding 220 are both 5 turns, the total electrical number of turns of the fine adjustment winding 200 is 10 turns, and the physical number of turns of one coarse adjustment sub-winding is also 10 turns. When the first switch 300 currently connects to one coarse adjustment sub-winding, and assuming that the output voltage is 10V, by adjusting different gears of the second switch 400, the number of turns connected by the first fine adjustment winding 210 is switched from 0 to 5, and the number of turns connected by the second fine adjustment winding 220 is switched from 0 to 5, so that the output voltage changes from 10V to 20V. When the total electrical number of turns of the fine adjustment winding 200 has reached the physical number of turns, the first switch 300 is switched to the next gear, for example, connected to two coarse adjustment sub-windings, so that the output voltage is 20+V, and then different gears of the second switch 400 are switched to achieve voltage regulation in the range of 20-30V. Thus, the output voltage of the voltage regulating transformer can be more continuous, and more voltage can be provided.

[0045] In one embodiment, as shown in FIG. 6, Figure 1 The voltage regulating transformer further comprises a voltage stabilizing winding 600 wound on the core. The voltage stabilizing winding 600 wound on the core can filter out harmonics generated during the operation of the voltage regulating transformer, thereby improving the working performance of the voltage regulating transformer.

[0046] Further, when the voltage regulating transformer comprises three voltage regulating modules, the number of voltage stabilizing windings 600 can also be three. The three voltage stabilizing windings 600 are wound on the core and connected in a triangle shape at the head and tail, thereby filtering out third harmonics and improving the working reliability of the voltage regulating transformer.

[0047] In one embodiment, the voltage regulating transformer further comprises a controller, and the first switch 300 and the second switch 400 are both connected to the controller. When the voltage regulating transformer further comprises the controller, the first switch 300 and the second switch 400 can be electrically operated switches, and the first switch 300 and the second switch 400 are both connected to the controller and can be automatically switched between the on and off states under the control of the controller. In addition, the controller can also control the first switch 300 and the second switch 400 to conduct between different stationary contacts and moving contacts, thereby outputting different voltages and improving the automation level of the voltage regulating transformer.

[0048] Specifically, the type of the controller is also not unique and can be a processing chip and its peripheral circuit, which has a logic operation function. The processing chip can be a single-chip microcomputer, a DSP (Digital Signal Process) chip, or an FPGA (Field Programmable Gate Array) chip. The controller can also be a standalone computer or a computer cluster composed of multiple computers. The controller can control the on state of the first switch 300 and the second switch 400 according to the received instructions, for example, when the controller receives a target voltage value, the controller calculates the number of turns of the coarse adjustment winding 100 and the fine adjustment winding 200 to be used according to the target voltage value, and determines the moving contact of the first switch 300 and the target moving contact of the second switch 400 to be conducted by combining the pre-stored structure of the coarse adjustment winding 100, the fine adjustment winding 200, the first switch 300, and the second switch 400, and the connection relationship between the first switch 300 and the coarse adjustment winding 100 and the connection relationship between the second switch 400 and the fine adjustment winding 200, and controls the first switch 300 and the second switch 400 to conduct the stationary contact and the target moving contact, so that the voltage regulating transformer can automatically output the target voltage without manual intervention, and the operation is convenient.

[0049] In one embodiment, the controller is used to control the second switch 400 to be disconnected first and then control the first switch 300 to be disconnected after obtaining an end instruction. After obtaining the end instruction, it is considered that the test is over, and the voltage regulating transformer no longer needs to provide voltage to the tested product. At this time, the controller controls the second switch 400 to be disconnected first to cut off the power supply of the tested product, and then controls the first switch 300 to be disconnected to cut off the primary side power supply. The secondary side wiring is cut off first and then the primary side power supply is cut off to prevent electromagnetic resonance from affecting the voltage regulating transformer.

[0050] In one embodiment, the voltage regulating transformer further comprises a neutral point connected suppression reactance. When the neutral point is connected to the suppression reactance, the suppression reactance can limit the zero sequence short circuit current in the voltage regulating transformer and improve the safety performance of the voltage regulating transformer.

[0051] The voltage regulating transformer comprises a core, a primary winding 120, a coarse adjustment winding 100, a fine adjustment winding 200, a first switch 300 and a second switch 400. The coarse adjustment winding 100 and the fine adjustment winding 200 are wound on the core. A first end of the primary winding 120 is used for connecting a voltage. A last end of the primary winding 120 is connected to a first end of the coarse adjustment winding 100. A last end of the coarse adjustment winding 100 is connected to a neutral point. The fine adjustment winding 200 comprises a first fine adjustment winding 210 and a second fine adjustment winding 220 which have the same structure. The first switch 300 and the second switch 400 each comprise two or more moving contacts. The moving contacts of each first switch 300 are connected to a tap led out at different positions of the coarse adjustment winding 100. The static contacts of the first switch 300 are connected to the first fine adjustment winding 210 and the second fine adjustment winding 220. The moving contacts of the second switch 400 are connected to the taps led out at different positions of the first fine adjustment winding 210 and the second fine adjustment winding 220, so that the number of turns of the first fine adjustment winding 210 connected between the first switch 300 and the second switch 400 is equal to the number of turns of the second fine adjustment winding 220 connected between the first switch 300 and the second switch 400. The static contacts of the second switch 400 are used as voltage output terminals of the voltage regulating transformer to output a voltage.

[0052] The voltage regulating transformer can realize first-stage voltage regulation through the first switch 300 and the coarse adjustment winding 100, and can realize second-stage voltage regulation through the second switch 400 and the fine adjustment winding 200. Therefore, the voltage regulating transformer does not need to have too many turns of windings, and can have a high test voltage regulation range, can provide a debugging test power supply with different voltage levels, and can reduce space transverse leakage magnetic flux, so that the axial force of the whole winding is small, self-balance of ampere-turns is realized, and the use reliability of the voltage regulating transformer is improved.

[0053] In order to better understand the above-mentioned embodiments, the following will be explained in detail in combination with a specific embodiment. In an embodiment, the voltage regulating transformer is applied to an offshore station, and is taken as a test transformer of the offshore station. Since the test voltage regulation range of the offshore wind power test transformer is wide, the number of turns of the secondary side may change from several turns to tens or hundreds of turns, and the impact of the current is very obvious. Meanwhile, the offshore wind power transformer has a dual contradiction of compactness and reliability. In view of the requirement of the short-circuit resistance of the test transformer, the voltage regulating transformer has the characteristics of self-adaptive impedance regulation, current limiting, high short-circuit resistance, simple structure and easy implementation, and can be widely applied to new offshore wind power projects. The primary side voltage of the voltage regulating transformer is constant, and wide-range voltage regulation is realized by adjusting the number of turns of the secondary side, and the self-adaptive short-circuit resistance is met at any voltage output.

[0054] Specifically, the voltage regulating transformer is based on a self-coupling structure, and a plurality of groups of common windings in a special arrangement are arranged, denoted as coarse adjustment windings 100 (CT). The coarse adjustment windings 100 correspond to the common windings of the traditional self-coupling transformer in the electrical wiring diagram. The CT windings are arranged as 1, 2, 3, …, N groups of common winding structures. The CT windings are taken as the smallest unit in the electrical wiring diagram, and each CT winding is switched as a whole when the voltage is adjusted at the secondary side, so as to complete the function transformation of the common windings and the series windings, make the leakage magnetic distribution in the main air gap (the gap between the connection points of the series windings and the common windings) under the operation state of each stage basically consistent, and realize the uniform leakage magnetic distribution effect. Since the maximum position of the space leakage magnetic field is located between the main air gaps, the control of the leakage magnetic field of the main air gap controls the space magnetic field energy and the stress trend of the winding. For example, when the CT2, CT3, …, CTN are connected at the secondary side, the main air gap at this time is between the CT1 and the CT2. For another example, when the CT3, CT4, …, CTN are connected at the secondary side, the main air gap at this time is between the CT2 and the CT3. Therefore, different CT connection methods only shift the leakage magnetic field amplitude of the main air gap, and do not cause local distortion.

[0055] The fine adjustment windings 200 of the voltage regulating transformer include a first fine adjustment winding 210 and a second fine adjustment winding 220 in parallel connection. The fine adjustment windings 200 (XT) are taken as the smallest unit in the electrical wiring diagram, and are connected in parallel connection to form an ampere-turn self-balancing module. The fine adjustment windings 200 have a height direction electrical connection difference, which affects the space transverse leakage magnetic field. The fine adjustment windings 200 take the wire cake as the smallest unit, and are connected in symmetric connection at the middle part of the winding as the boundary surface. The fine adjustment windings 200 are connected in parallel connection, and realize the ampere-turn self-balancing, that is, when a winding is considered independently, the upper and lower ampere-turns are symmetric or close to symmetric. This method makes the axial force of the whole winding minimum based on the electromagnetic principle. When the fine adjustment windings 200 are connected completely to complete a round of voltage regulation, the number of the coarse adjustment windings 100 is changed to realize the voltage regulation, and the number of the fine adjustment windings 200 is cleared at the same time. The total electrical turns of the fine adjustment windings 200 are equal to the turns of a group of coarse adjustment windings 100. Specifically, the physical turns of the fine adjustment windings 200 are twice the electrical turns, and after the parallel connection, the fine adjustment windings 200 have the same electrical turns as a group of coarse adjustment windings. When the fine adjustment windings 200 are cycled from the minimum connection to the maximum connection, the leakage magnetic distribution on the fine adjustment windings 200 is cycled once.

[0056] The voltage regulating transformer has a series reactance element 500 at the secondary side (test output voltage side). The series reactance element 500 at the secondary side is the key to the self-adaptive anti-short circuit, and the series reactance element 500 needs to be determined by conversion without human intervention, so as to realize the automatic adjustment of the equivalent impedance of the voltage regulating transformer. The structure of the series reactance element 500 at the secondary side can be built-in or externally connected, and the built-in structure can realize the compactness of the offshore wind power. In addition, the neutral point of the self-coupling structure of the voltage regulating transformer can also be increased with the series reactance element 500 for limiting the zero sequence short circuit current.

[0057] The adaptive short-circuit resistance method of the series reactance element 500 is based on three groups of electromagnetic principles: first, the secondary side voltage is directly proportional to the number of turns, the primary side number of turns is not adjusted and the input voltage is constant, the fewer the secondary side number of turns, the lower the output voltage; second, in the short-circuit working condition, the primary side input power is equal to the secondary side output power; third, the equivalent reactance element 500 of the primary and secondary sides is inversely proportional to the square of the number of turns, the fewer the secondary side number of turns, the larger the equivalent reactance element 500 of the primary side. The lower the secondary side voltage, the fewer the number of turns, and the more obvious the adaptive short-circuit resistance function realized.

[0058] The specific derivation is as follows:

[0059] The key to control the impact of short-circuit is to limit the size of the fault current, and the secondary side short-circuit current is calculated as:

[0060] The short-circuit current of the secondary side is calculated by the per-unit method:

[0061]

[0062] The primary side voltage and the number of turns are constant, and the parameters are converted to the primary side:

[0063]

[0064] The equivalent impedance per-unit of the secondary side series reactance element 500 is calculated as:

[0065]

[0066] In the formula, U s , U k and U L represent the per-unit of system impedance, transformer impedance and series reactance element 500 respectively, I SC and I N are short-circuit current and rated current respectively, W is the number of turns, and subscripts 1 and 2 refer to the primary side and the secondary side respectively. Z0 is the nominal value of the reference impedance of the per-unit algorithm used.

[0067] The above derivation shows that the number of turns of the secondary side is reduced, the rated current I N2 is increased according to the turn ratio, the equivalent impedance of the secondary side series reactance is increased according to the square of the turn ratio, the effect of limiting the secondary side current is obvious, and the adaptive short-circuit resistance function is realized. The reactance element 500 can realize the amplitude control of current and leakage magnetic field, and complete the adaptive short-circuit resistance regulation. The series reactance element 500 should fully consider the compactness requirement of offshore wind power and the influence on the test system. The specific value of the series reactance element 500 is determined according to the capacity, impedance and secondary side voltage regulation range of the test transformer, and the method can be selected as theoretical analysis algorithm or simulation calculation method.

[0068] The voltage regulating transformer provided by the application has a constant primary side voltage, a wide range of voltage regulation on the secondary side through regulating the number of turns, no need for manual intervention, and self-adaptive short circuit resistance capability when any voltage output is achieved. The voltage regulating transformer is based on electromagnetic principle, adopts a compact structure, has strong self-adaptability, and has no need for any manual intervention after voltage regulation output, and meets the short circuit resistance capability when any voltage output is achieved. The voltage regulating transformer includes a basic autotransformer structure, a special winding arrangement, an upper and lower parallel fine tuning winding 200, and a test output voltage side series reactance element 500 structure, is based on a plurality of winding autotransformer structures, and realizes self-adaptive short circuit resistance function. The fine tuning winding 200 adopts an upper and lower parallel structure of a group of windings, and the number of turns of the fine tuning winding 200 is about the number of turns of a group of coarse tuning windings 100. The series reactance element 500 can be built-in or externally connected, but is different from the neutral point series reactance mode in the autotransformer structure.

[0069] The self-adaptive short circuit resistance implementation method of the voltage regulating transformer is a process of reducing the leakage magnetic influence through a plurality of coarse tuning windings 100, realizing ampere-turn self-balancing through upper and lower parallel fine tuning windings 200, and realizing equivalent reactance element 500 self-adaptive short circuit resistance adjustment with voltage change through the secondary output side series reactance element 500. Among them, the uniform leakage of the plurality of coarse tuning windings means that when the secondary side is connected to different groups of coarse tuning windings 100, the spatial concentrated leakage field distribution does not change obviously. The ampere-turn self-balancing means that the ampere-turn of the independent winding is symmetrical or close to symmetrical, the amplitude direction leakage is symmetrical up and down, and is realized through upper and lower parallel connection. The secondary output side series reactance element 500 is the key to adapt to the short circuit resistance capability, and the series reactance element 500 needs to be determined through demonstration and conversion.

[0070] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present application.

[0071] The above-described embodiments only express several implementation manners of the application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the application, and these are within the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A voltage regulating transformer, characterized in that, The device includes an iron core, a primary winding, a coarse adjustment winding, a fine adjustment winding, a first switch, and a second switch. The primary winding, the coarse adjustment winding, and the fine adjustment winding are all wound around the iron core. The first end of the primary winding is used to connect to voltage, and the end of the primary winding is connected to the first end of the coarse adjustment winding. The end of the coarse adjustment winding is connected to the neutral point. The fine adjustment winding includes a first fine adjustment winding and a second fine adjustment winding with identical structures. The first fine adjustment winding and the second fine adjustment winding are symmetrical about their dividing line. Both the first switch and the second switch include two or more moving contacts. The moving contacts of each first switch are connected to a tap led out from the coarse adjustment winding at different positions. The stationary contacts of the first switches are connected to the first fine adjustment winding and the second fine adjustment winding. The moving contacts of the second switches are connected to the taps led out from the first fine adjustment winding and the second fine adjustment winding at different positions, so that the number of turns connected between the first switch and the second switch in the first fine adjustment winding is equal to the number of turns connected between the first switch and the second switch in the second fine adjustment winding. The stationary contacts of the second switches are used for output voltage. It also includes a reactor element, and the output voltage is obtained by connecting the stationary contact of the second switch to the reactor element; The coarse adjustment winding includes two or more coarse adjustment sub-windings connected in series. The first end of the series winding is connected to the end of the primary winding, and the end of the series winding is connected to the neutral point. The coarse adjustment winding has two or more taps, with one coarse adjustment winding as the smallest unit. The number of turns of each coarse adjustment winding is equal. The number of turns of the first fine adjustment winding and the second fine adjustment winding is equal to the number of turns of one coarse adjustment winding.

2. The voltage regulating transformer according to claim 1, characterized in that, A voltage regulating module includes a coarse adjustment winding, a fine adjustment winding, a first switch, a second switch, and a reactance element. The voltage regulating transformer includes three voltage regulating modules, and the end of the coarse adjustment winding in each voltage regulating module is connected to the neutral point.

3. The voltage regulating transformer according to claim 1, characterized in that, It also includes a voltage stabilizing winding, which is wound around the iron core.

4. The voltage regulating transformer according to claim 1, characterized in that, It also includes a controller, and both the first switch and the second switch are connected to the controller.

5. The voltage regulating transformer according to claim 4, characterized in that, The controller is used to, upon receiving an end command, first control the second switch to open, and then control the first switch to open.

6. The voltage regulating transformer according to claim 1, characterized in that, It also includes the suppression reactance connected to the neutral point.

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