CN115662761A - On-load tap changer and voltage regulation method thereof - Google Patents
On-load tap changer and voltage regulation method thereof Download PDFInfo
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Abstract
The invention relates to an on-load tap changer and a method for regulating voltage thereof, wherein the on-load tap changer comprises: the on-load voltage regulation device is connected with a one-phase power supply line of a power grid and comprises a primary side winding, at least one winding switching device and a single-phase Buck circuit, wherein the primary side winding comprises a main winding, a stepless energy taking winding and at least one stepped winding, and the main winding, the stepless energy taking winding and the stepped winding share a magnetic core; the winding switching device is used for controlling the corresponding stepped winding to be switched in or switched out of the corresponding primary side winding; the single-phase Buck circuit is used for converting the winding voltage of the stepless energy-taking winding so as to adjust the amplitude and/or the phase of the output voltage of the primary winding. According to the invention, the circuit voltage is regulated through the single-phase Buck circuit, the stepless energy-taking winding is used as a voltage source of the single-phase Buck circuit, no additional voltage source is required to be arranged, the device is simple, the cost is saved, and the operation of workers is facilitated.
Description
Technical Field
The invention relates to the technical field of transformers, and particularly provides an on-load tap changing transformer and a voltage regulating method thereof.
Background
An on-load voltage regulator is a voltage regulating device which can change the voltage of a primary side winding of a transformer by changing tap gears when the transformer runs under load. The current on-load voltage regulator changes the number of turns connected into a primary side winding coil by adjusting the gear of a connector so as to change the voltage of the primary side winding, but the range of voltage regulation of the on-load voltage regulator is related to the gear and the number of connectors.
In the prior art, the on-load voltage regulator is limited to ensure the stability in the working process of the on-load voltage regulator and the cost of the on-load voltage regulator, and the like, and the number of the connectors on the on-load voltage regulator in the prior art is only a few or more than ten, namely, the regulation gear representing the voltage is few, and fine regulation cannot be performed.
Accordingly, there is a need in the art for a new on-load tap changing solution to address the above problems.
Disclosure of Invention
In order to overcome the above-mentioned drawbacks, the present invention is proposed to solve or at least partially solve the technical problems of the prior art that the voltage has few adjustment steps and cannot be finely adjusted.
In a first aspect, the present invention provides an on-load tap changer comprising:
the on-load voltage regulation device is connected with a one-phase power supply line of a power grid and comprises a primary side winding, at least one winding switching device and a single-phase Buck circuit, wherein the primary side winding comprises a main winding, a stepless energy taking winding and at least one stepped winding, and the main winding, the stepless energy taking winding and the stepped winding share a magnetic core;
the winding switching device is used for controlling the corresponding stepped winding to be switched in or switched out of the corresponding primary side winding;
the single-phase Buck circuit is used for converting the winding voltage of the stepless energy taking winding so as to adjust the amplitude and/or the phase of the output voltage of the primary side winding.
Furthermore, the single-phase Buck circuit comprises a first end, a second end, a third end and a fourth end;
the winding switching device comprises a first end, a second end, a third end and a fourth end;
wherein, the first and the second end of the pipe are connected with each other,
the first end and the second end of the single-phase Buck circuit are respectively connected with the first end and the second end of the stepless energy-taking winding;
the first end and the second end of the winding switching device are respectively connected with the first end and the second end of the secondary winding;
and the third end of the single-phase Buck circuit is connected with the third end and the fourth end of the winding switching device.
Further, the winding switching device includes: a diverter switch and a tap selector, wherein
Both ends of each stepped winding are provided with selection contacts;
the tapping selector is provided with a joint which can be connected with the selection contact, wherein a part between one end of the primary winding, which is connected with the joint, and the first end of the first primary winding is connected with the primary side winding;
the selector switch controls the access of different contacts to control the number of the primary side winding accessed by the stepped winding.
Further, the stepless energy taking winding is connected with the main winding in series,
the single-phase Buck circuit includes:
a first triac, a second triac, a capacitor, an inductor, and an isolation transformer,
wherein, the first and the second end of the pipe are connected with each other,
the input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor;
the second end of the inductor, the first end of the capacitor and the first end of the second three-terminal bidirectional switching element are connected with the first end of the primary winding of the isolation transformer;
the second end of the capacitor and the second end of the second three-terminal bidirectional switch element are connected to the second end of the single-phase Buck circuit and the second end of the primary winding of the isolation transformer;
the control end of the first three-terminal bidirectional switch element and the control end of the second three-terminal bidirectional switch element respectively receive control signals;
the first end of the secondary winding of the isolation transformer is connected with the third end of the single-phase Buck circuit;
and the second end of the secondary winding of the isolation transformer is connected with the fourth end of the single-phase Buck circuit.
Further, single-phase Buck circuit includes:
a first triac, a second triac, a capacitor and an inductor,
wherein the content of the first and second substances,
the input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor;
the second end of the inductor, the first end of the capacitor and the first end of the second three-terminal bidirectional switch element are connected to the third end of the single-phase Buck circuit;
the second end of the capacitor and the second end of the second three-terminal bidirectional switch element are connected to the second end and the fourth end of the single-phase Buck circuit;
and the control end of the first three-terminal bidirectional switch element and the control end of the second three-terminal bidirectional switch element respectively receive control signals.
Further, single-phase Buck circuit includes:
a first triac, a second triac, a capacitor, an inductor, and an isolation transformer,
wherein, the first and the second end of the pipe are connected with each other,
the input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor;
the second end of the inductor, the first end of the capacitor and the first end of the second three-terminal bidirectional switching element are connected with the first end of the primary winding of the isolation transformer;
a second terminal of the capacitor and a second terminal of a second triac are connected to a second terminal of the single-phase Buck circuit and a second terminal of a primary winding of an isolation transformer;
the control end of the first three-terminal bidirectional switch element and the control end of the second three-terminal bidirectional switch element respectively receive control signals;
the first end of the secondary winding of the isolation transformer is connected with the third end of the single-phase Buck circuit;
and the second end of the secondary winding of the isolation transformer is connected with the fourth end of the single-phase Buck circuit.
Further, the first triac and the second triac are both double-transistor common-emitter series triacs.
Further, the winding switching device includes:
a first antiparallel thyristor pair comprising a first thyristor and a second thyristor;
the second inverse parallel thyristor pair comprises a third thyristor and a fourth thyristor;
wherein
The anode of the first thyristor and the cathode of the second thyristor are connected to the first end of the winding switching device;
the cathode of the first thyristor and the anode of the second thyristor are connected to the third end of the winding switching device;
the anode of the third thyristor and the cathode of the fourth thyristor are connected to the second end of the winding switching device;
and the cathode of the third thyristor and the anode of the fourth thyristor are connected to the fourth end of the winding switching device.
In a second aspect, the present invention provides a three-phase on-load tap changer, wherein the primary sides of the three on-load tap changers comprise three phases of on-load tap changers as described in the first aspect, wherein the three on-load tap changers are connected by a delta connection or a star connection to form the three-phase on-load tap changer.
In a third aspect, the present invention provides a method of regulating voltage of an on-load tap changer as in the first or second aspect, the method comprising:
generating an in-phase fundamental voltage, a positive sequence output voltage and a negative sequence output voltage based on the output voltage of a preset single-phase Buck circuit;
synthesizing the in-phase fundamental wave voltage, the positive sequence output voltage and the negative sequence output voltage to generate a time-varying modulation wave;
and controlling the duty ratio of the single-phase Buck circuit in the phase according to the time-varying modulation wave in real time.
Further, the generating the in-phase fundamental wave voltage, the positive sequence output voltage and the negative sequence output voltage based on the output voltage of the preset single-phase Buck circuit includes:
generating fundamental wave voltage of a corresponding phase according to the fixed duty ratio of the single-phase Buck circuit;
generating a first modulation wave matrix of the positive sequence output voltage by adding a sinusoidal component of the first negative sequence, and generating the positive sequence output voltage based on the first modulation wave matrix;
and generating a second modulation wave matrix of the negative-sequence output voltage by adding the sinusoidal component of the second negative sequence, and generating the negative-sequence output voltage based on the second modulation wave matrix.
Further, the real-time control of the duty ratio of the single-phase Buck circuit in the phase according to the time-varying modulation wave includes:
normalizing the time-varying modulated wave to obtain a modulated wave matrix;
and controlling the duty ratio of the single-phase Buck circuit in the phase according to the modulation wave matrix in real time.
And further:
the frequency of the sinusoidal component of the first negative sequence is greater than the frequency of the input voltage of the single-phase Buck circuit;
the frequency of the second negative sequence component is less than the frequency of the input voltage of the single-phase Buck circuit.
Further, the synthesizing the in-phase fundamental wave voltage, the positive sequence output voltage and the negative sequence output voltage to generate the time-varying modulated wave includes:
and eliminating zero sequence components in the positive sequence output voltage and the negative sequence output voltage in the process of synthesizing and generating the time-varying modulation wave.
One or more of the above technical solutions of the present invention include at least one or more of the following
Has the beneficial effects that:
in the technical scheme of the invention, the duty ratio of the single-phase Buck circuit is controlled in real time by arranging the stepless energy-taking winding and the single-phase Buck circuit so that the voltage of the transformer can be adjusted as required, and the output end of the single-phase Buck circuit outputs the preset compensation voltage to act on the primary side winding, thereby finally completing more precise voltage adjustment and being beneficial to keeping the secondary side voltage of the transformer stable. According to the invention, the circuit voltage is regulated through the single-phase Buck circuit, the stepless energy-taking winding is used as a voltage source of the single-phase Buck circuit, no additional voltage source is required to be arranged, the device is simple, the cost is saved, and the operation of workers is facilitated.
Drawings
The disclosure of the present invention will become more readily understood with reference to the accompanying drawings. As is readily understood by those skilled in the art: these drawings are for illustrative purposes only and are not intended to be a limitation on the scope of the present disclosure. Moreover, in the drawings, like numerals are used to indicate like parts, and in which:
fig. 1 is a schematic structural view of an on-load tap changer according to embodiment 1 of the present invention;
fig. 2 is a schematic view of a stepless voltage regulation principle of an on-load tap changer according to embodiment 1 of the present invention;
FIG. 3 is a flow chart illustrating a control method of the single-phase Buck circuit according to an embodiment of the invention;
FIG. 4 is a sub-flow diagram of a method of controlling a single-phase Buck circuit according to an embodiment of the invention;
FIG. 5 is a sub-flow diagram of a control method of a single-phase Buck circuit according to an embodiment of the invention;
fig. 6 is a schematic structural view of an on-load tap changer according to embodiment 2 of the present invention;
fig. 7 is a schematic structural diagram of an on-load tap changer according to embodiment 3 of the present invention;
fig. 8 is a schematic structural diagram of an on-load tap changer according to embodiment 4 of the present invention;
fig. 9 is a schematic structural diagram of an on-load tap changer according to embodiment 5 of the present invention.
Detailed Description
Some embodiments of the invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.
In the description of the present invention, a "module" or "processor" may include hardware, software, or a combination of both. A module may comprise hardware circuitry, various suitable sensors, communication ports, memory, may comprise software components such as program code, and may be a combination of software and hardware. The processor may be a central processing unit, microprocessor, image processor, digital signal processor, or any other suitable processor. The processor has data and/or signal processing functionality. The processor may be implemented in software, hardware, or a combination thereof. Non-transitory computer readable storage media include any suitable medium that can store program code, such as magnetic disks, hard disks, optical disks, flash memory, read-only memory, random-access memory, and the like. The term "A and/or B" denotes all possible combinations of A and B, such as only A, only B or both A and B. The term "at least one of A or B" or "at least one of A and B" means similar to "A and/or B" and may include only A, only B, or both A and B. The singular forms "a", "an" and "the" may include the plural forms as well.
Some terms to which the present invention relates are explained first herein.
Fundamental wave voltage: the fundamental wave is a sinusoidal wave component having a period equal to the longest period of the complex periodic oscillation, that is, a complex wave component having the lowest frequency. The voltage corresponding to the fundamental wave is the fundamental wave voltage.
Positive, negative, zero sequence components: in a three-phase power system, the phasor (which may be an electromotive force, a voltage, or a current, etc.) of a three-phase system is divided into three symmetrical three-phase system components, namely a positive sequence, a negative sequence, and a zero sequence, according to a symmetrical component method, where the positive sequence: phase A leads phase B by 120 degrees, phase B leads phase C by 120 degrees, and phase C leads phase A by 120 degrees. Negative sequence: phase A is 120 degrees behind phase B, phase B is 120 degrees behind phase C, and phase C is 120 degrees behind phase A. Zero sequence: the ABC three phases are the same.
Example 1:
as shown in fig. 1, the on-load tap changer in the embodiment of the present invention mainly includes:
the on-load voltage regulation device is connected with a one-phase power supply line of a power grid and comprises a primary side winding, at least one winding switching device and a single-phase Buck circuit, wherein the primary side winding comprises a main winding, a stepless energy taking winding and at least one stepped winding, and the main winding, the stepless energy taking winding and the stepped winding share a magnetic core.
The on-load voltage regulation device is arranged on the primary side of the transformer. Preferably, in the present embodiment, the load voltage regulation device is provided on the primary winding side of the transformer. In the process of transforming the voltage of the transformer, the turn ratio of the primary side and the secondary side of the transformer and the voltage of two ends of the primary side winding of the transformer determine the voltage of the secondary side. Therefore, in this embodiment, there are two factors that affect the voltage on the secondary winding of the transformer, one is the number of turns of the effective winding on the magnetic core in the on-load tap changer, and the other is the voltage across the effective winding on the on-load tap changer, i.e., the voltage across the primary winding.
The effective winding on the magnetic core in the on-load voltage regulating device mainly comprises a main winding and a stepped winding connected into a primary side winding, wherein the main winding is connected with the stepped winding in series. There is no positional requirement due to the series relationship between the main winding and the stepped winding. However, for convenience of description in this embodiment, a specific implementation is given, and preferably, in this implementation, the first end of the main winding is connected to the power supply line, and the second end of the main winding is connected to the first end of the secondary winding. The main winding is always part of the active winding, and the part of the secondary winding connected into the primary winding is the active winding. In this embodiment, the number of the secondary windings connected to the primary winding is controlled to control the effective winding connected to the magnetic core, thereby controlling the voltage of the transformer on the secondary winding side. In this embodiment, the primary side winding is switched in or out by the stepped winding through the winding switching device.
Meanwhile, in the embodiment, the voltage across the effective winding is controlled by the single-phase Buck circuit, specifically, the amplitude and/or the phase of the output voltage of the primary winding is adjusted by controlling the duty ratio of the single-phase Buck circuit during operation. The single-phase Buck circuit has four terminals in total from the external view, wherein the first end and the second end of single-phase Buck circuit are input terminals for connecting the voltage source of input, and the third end and the fourth end of single-phase Buck circuit are output terminals for outputting compensation voltage thereby influencing the voltage of primary side winding. In this embodiment, after the winding voltage of the stepless energy-taking winding passes through the single-phase Buck circuit, the output end of the single-phase Buck circuit can output preset voltage with amplitude, phase and frequency, and the output end of the single-phase Buck circuit is connected to the main circuit to perform voltage compensation or phase-shifting control. Preferably, in this embodiment, the first terminal and the second terminal of the single-phase Buck circuit are respectively connected to the first terminal and the second terminal of the stepless energy-taking winding.
Here, the generation source of the voltage on the stepless energy-taking winding is described, and the voltage on the stepless energy-taking winding may be obtained by sharing a magnetic core with other windings and by inducing electromotive force, or may be obtained by connecting the stepless energy-taking winding in series with the main winding and the stepped winding. Preferably, in this embodiment, the voltage across the stepless energy-taking winding is obtained by induced electromotive force, i.e. the stepless energy-taking winding is not directly connected in series to the power supply line, and the same stepless energy-taking winding is not directly connected in series to the main winding and the stepped winding. The stepless energy-taking winding obtains voltage in an induced electromotive force mode, and is isolated from a power supply line, so that the stability and the safety of a circuit are facilitated.
In this embodiment, the winding switching device is an on-load tap changer of an electronic power type, and each of the secondary windings corresponds to a winding switching device for controlling the secondary windings. When one winding switching device is observed from the outside, the winding switching device comprises a first end, a second end, a third end and a fourth end, wherein the first end and the second end of the winding switching device are respectively connected with the first end and the second end of the secondary winding, and the third end and the fourth end of the winding switching device are connected with the third end of the single-phase Buck circuit.
In this embodiment, the winding switching device includes at least two pairs of antiparallel thyristors, wherein the first pair of antiparallel thyristors includes a first thyristor and a second thyristor, and the second pair of antiparallel thyristors includes a third thyristor and a fourth thyristor. The anode of the first thyristor and the cathode of the second thyristor are connected to the first end of the winding switching device, and the cathode of the first thyristor and the anode of the second thyristor are connected to the third end of the winding switching device. And the anode of the third thyristor and the cathode of the fourth thyristor are connected to the second end of the winding switching device, the cathode of the third thyristor and the anode of the fourth thyristor are connected to the fourth end of the winding switching device, and the thyristors receive control signals so as to be controlled to be switched on and switched off by the control signals. It will be appreciated that when there are multiple stepped windings, there will be multiple winding switching devices, and from another perspective, the multiple winding switching devices may also divide the stepped windings into multiple controllable stepped windings.
Assuming that the potential of the first end of the stepped winding connected to the primary side winding is greater than the potential of the second end of the stepped winding, when the first inverse parallel thyristor receives a command to turn on and the second inverse parallel thyristor turns off, the corresponding stepped winding is cut out from the primary side winding; when the second inverse parallel thyristor is turned on and the first inverse parallel thyristor is turned off, the corresponding secondary winding is connected to the primary winding. Therefore, the method can be popularized to M stepped windings, if the number of the stepped windings connected into the primary side winding is controlled to be N, only the inverse parallel thyristor connected into the second end of the Nth stepped winding is controlled to be turned on, and the rest inverse parallel thyristors are all in a turn-off state. In the embodiment, the inverse parallel thyristor pair is used for controlling the stepped winding connected to the primary side winding, the structure is simple, and the control is rapid due to the use of electric signal control.
In this embodiment, the single-phase Buck circuit includes: a first triac, a second triac, a capacitor, and an inductor. The input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor. The second end of the inductor, the first end of the capacitor and the first end of the second three-terminal bidirectional switch element are connected to the third end of the single-phase Buck circuit. The second end of the capacitor and the second end of the second three-terminal bidirectional switch element are connected to the second end and the fourth end of the single-phase Buck circuit. The control terminal of the first triac and the control terminal of the second triac receive control signals, respectively. In the single-phase circuit, the fourth terminal of the single-phase Buck circuit is connected to the power supply line.
In this embodiment, the first triac and the second triac are both dual-transistor common-emitter series triacs. Wherein the bi-directional switch with two transistors in common emitter series is composed of two IGBTs (insulated gate bipolar transistors) and a diode on each IGBT. Specifically, the emitters of the two IGBTs are connected, and the collector of each IGBT can receive a control signal, so as to control the turn-on of the corresponding IGBT. And the collectors of the two IGBTs are used as control ends of the corresponding three-terminal bidirectional switch from outside. Each IGBT is connected with a corresponding diode in parallel, wherein the anode of the diode is connected with the emitter of the IGBT, and the cathode of the diode is connected with the grid of the IGBT. As is clear from the above, in the present embodiment, the triac including the IGBT and the diode has a symmetrical structure in view of the device structure, and therefore, any one of the two gates of the triac can be used as the first terminal of the triac.
The function of the single-phase Buck circuit therein is described in detail herein, as shown in FIG. 2. Let Vout be the final output voltage of the primary winding of the transformer, us be the voltage across the main winding and the stepped voltage regulation winding without the influence of the single-phase Buck circuit, and Uab be the compensation voltage output by the single-phase Buck circuit. After the three voltage quantities are shown in a vector diagram, it can be understood through a vector rule that a dotted line circle and the inside of the dotted line circle are the voltage regulation range of the single-phase Buck circuit, umax is the maximum voltage regulation value which can be output by the converter, and as shown in the figure, when Uout is advanced by Us by an angle phi, the converter can be enabled to output Uab which is advanced by Us by an angle theta, and Us and Uab are enabled to be matched to obtain a required voltage value. Since in the ac power supply system Us is not a constant value, but a time-variant value, the compensation voltage Uab output by the single-phase Buck circuit is also a time-variant value here. In other words, in order to maintain the output voltage of the primary winding in the ac power grid, the single-phase Buck circuit needs to control the frequency change of the time-varying component in the duty ratio to output a voltage component of an arbitrary frequency, thereby adjusting the output voltage of the primary winding.
Further, the present invention also provides a method for regulating voltage of an on-load tap changer, wherein the method is used for enabling a single-phase Buck circuit to generate a voltage component with any frequency, and specifically comprises steps S10-S30, as shown in fig. 3,
step S10: the in-phase fundamental voltage, the positive sequence output voltage and the negative sequence output voltage are generated based on the output voltage of the preset single-phase Buck circuit.
In the present embodiment, in which the output voltage of the single-phase Buck circuit is preset, in order to generate an output voltage of an arbitrary frequency, the output voltage to be synthesized is divided into a plurality of independent components, each of which has its own frequency and its own phase sequence. In the embodiment, the output voltage of the preset single-phase Buck circuit is decomposed into an in-phase fundamental wave voltage, a positive sequence output voltage and a negative sequence output voltage. Wherein the homodromous fundamental component is obtained under the condition of constant duty ratio based on the single-phase Buck circuit.
In the present embodiment, steps S101 to S103 are used to generate corresponding in-phase fundamental wave voltage, positive-sequence output voltage and negative-sequence output voltage from the output voltage of the preset single-phase Buck circuit, as shown in fig. 4.
Step S101: and generating the fundamental voltage of the corresponding phase according to the fixed duty ratio of the single-phase Buck circuit.
In this embodiment, the fundamental wave voltage of the single-phase Buck circuit is finally obtained by converting the fixed duty ratio of the single-phase Buck circuit into a modulation wave form, based on the modulation wave form after the conversion of the fixed duty ratio, the voltage at the input end of the single-phase Buck circuit, and the output expression of the single-phase Buck circuit. Here, the fixed duty ratio is a parameter set to generate a fundamental wave voltage, in other words, to decompose a preset output voltage into three parts, and is not a duty ratio in actual operation.
Step S102: a first modulated wave matrix of positive-sequence output voltages is generated by adding sinusoidal components of a first negative sequence, and the positive-sequence output voltages are generated based on the first modulated wave matrix.
In the present embodiment, the sinusoidal component of the first negative sequence is the sinusoidal component introduced for the purpose of decomposing the output voltage in the present embodiment. The sinusoidal component of the first negative sequence is depended on, wherein the sinusoidal component of the first negative sequence defines the amplitude and the phase corresponding to the frequency, and the frequency of the sinusoidal component of the first negative sequence is greater than the frequency of the input voltage of the single-phase Buck circuit. And finally, obtaining a corresponding first modulation wave matrix, and obtaining a positive sequence output voltage based on the first modulation wave matrix, the voltage of the input end of the single-phase Buck circuit and the output expression of the single-phase Buck circuit. The positive sequence output voltage is formed by overlapping a positive sequence component and a zero sequence component.
Step S103: and generating a second modulation wave matrix of the negative-sequence output voltage by adding the sinusoidal component of the second negative sequence, and generating the negative-sequence output voltage based on the second modulation wave matrix.
In the present embodiment, the sinusoidal component of the second negative sequence is the sinusoidal component introduced for the purpose of decomposing the output voltage in the present embodiment. And the amplitude and the phase corresponding to the frequency of the sinusoidal component of the second negative sequence are customized, wherein the frequency of the sinusoidal component of the second negative sequence is less than the frequency of the input voltage of the single-phase Buck circuit. And finally, obtaining a corresponding second modulation wave matrix, and obtaining a negative sequence output voltage based on the second modulation wave matrix, the voltage of the input end of the single-phase Buck circuit and the output expression of the single-phase Buck circuit. The negative sequence output voltage is formed by overlapping a positive sequence component and a zero sequence component.
Step S20: the in-phase fundamental wave voltage, the positive sequence output voltage and the negative sequence output voltage are synthesized to generate a time-varying modulation wave.
In this embodiment, the synthesis of the time-varying modulated wave is the addition of the in-phase fundamental voltage, the positive-sequence output voltage and the negative-sequence output voltage.
Step S30: and controlling the duty ratio of the single-phase Buck circuit in the phase according to the time-varying modulation wave in real time.
In this embodiment, the duty ratio of the single-phase Buck circuit in the phase is controlled in real time through steps S301 to S302, as shown in fig. 5.
Step S301: and normalizing the time-varying modulated wave to obtain a modulated wave matrix.
Step S302: and controlling the duty ratio of the single-phase Buck circuit in the phase according to the modulation wave matrix in real time.
In this embodiment, the modulated wave matrix after normalization is the real-time duty ratio of the single-phase Buck circuit in the corresponding phase. According to the data of the modulation wave matrix, the corresponding control signal can be sent to the single-phase Buck circuit, so that the voltage which needs to be output finally is obtained, and the voltage of the primary side winding is influenced finally.
In other words, the essence of the method for regulating the voltage by using the on-load tap changer is that a time-varying sinusoidal component is added into the duty ratio of the single-phase Buck circuit, an additional quadrature voltage source is virtually generated in the circuit, and an additional output harmonic voltage source related to the duty ratio is generated at the same time, so that the requirement of the single-phase Buck circuit on the additional voltage source during voltage synthesis is met.
Example 2:
the difference between the present embodiment and embodiment 1 is that an isolation transformer is further disposed in the single-phase Buck circuit, wherein the rest of the single-phase Buck circuit is isolated and connected in the power supply line through the isolation transformer, so as to increase the safety of the connection, and the rest of the single-phase Buck circuit is the same as that in embodiment 1. As shown in fig. 6, the details are as follows:
the single-phase Buck circuit includes: a first triac, a second triac, a capacitor, an inductor, and an isolation transformer.
The input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor. The second end of the inductor, the first end of the capacitor and the first end of the second triac are connected to a first end of the primary winding of the isolation transformer. A second terminal of the capacitor and a second terminal of the second triac are connected to a second terminal of the single-phase Buck circuit and a second terminal of the primary winding of the isolation transformer. The control terminal of the first triac and the control terminal of the second triac receive control signals, respectively. And the first end of the secondary winding of the isolation transformer is connected with the third end of the single-phase Buck circuit. And the second end of the secondary winding of the isolation transformer is connected with the fourth end of the single-phase Buck circuit.
The embodiment is the same as embodiment 1 except for the single-phase Buck circuit, and the description thereof is omitted here.
Example 3:
in this embodiment, the stepless energy-taking winding is connected in series with the main winding, that is, the stepless energy-taking winding directly generates voltage at two ends of the stepless energy-taking winding through the power supply line. Connecting the stepless energy-taking winding directly to the power supply line is equivalent to providing an effective number of turns for the primary winding, and has a slight influence on the energy transmission of the transformer. However, because the stepless energy-taking winding is fixed on the magnetic core, and the number of turns of the stepless energy-taking winding is fixed, the voltage at two ends of the stepless energy-taking winding is in a proportional relation with the main winding and the stepped winding on the primary side winding, and is a variable which can be predicted, and the final result cannot be randomized.
In this embodiment, the stepless energy-taking winding is connected in series with the main winding, as shown in fig. 7. In this embodiment, the single-phase Buck circuit includes: a first triac, a second triac, a capacitor, an inductor, and an isolation transformer.
The input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor. The second end of the inductor, the first end of the capacitor and the first end of the second triac are connected to a first end of the primary winding of the isolation transformer. A second terminal of the capacitor and a second terminal of the second triac are connected to a second terminal of the single-phase Buck circuit and a second terminal of the primary winding of the isolation transformer. The control end of the first three-terminal bidirectional switch element and the control end of the second three-terminal bidirectional switch element respectively receive control signals. And the first end of the secondary winding of the isolation transformer is connected with the third end of the single-phase Buck circuit. And the second end of the secondary winding of the isolation transformer is connected with the fourth end of the single-phase Buck circuit.
The embodiments are the same as those of embodiment 1 except for the single-phase Buck circuit and the stepless energy-taking winding, and are not described herein again.
Example 4:
most of the embodiments are consistent with the embodiment 1, and the differences are in the winding switching device, and the winding switching device in the embodiments uses a mechanical on-load voltage dividing switch, as specifically shown in fig. 8.
The winding switching device includes: a change-over switch and a tapping selector are arranged,
wherein, both ends of each stepped winding are provided with selection contacts. The tapping selector is provided with a joint which can be connected with the selection contact, wherein a part between one end of the secondary winding, which is connected with the joint, and the first end of the first secondary winding is connected with the primary side winding. The number of the primary windings connected into the primary side windings can be controlled by controlling the connection of different contacts through the selector switch.
Compared with an electronic power tap changer, the mechanical on-load tap changer is more stable and lower in manufacturing cost.
Example 5:
in this embodiment, a three-phase on-load tap changer is further provided, which includes three on-load tap changing devices, wherein a specific structure of each on-load tap changing device is substantially the same as that of any one of embodiments 1 to 4, and a difference is that the three on-load tap changing devices are connected in a delta connection manner or a star connection manner.
If the delta connection is adopted, as shown in fig. 9, it is preferable that in this embodiment, the circuit is divided into three phases a, B, and C, a fourth end of the a-th phase single-phase Buck circuit is connected to the B-th phase power supply line, a fourth end of the B-th phase single-phase Buck circuit is connected to the C-th phase power supply line, and a fourth end of the C-th phase single-phase Buck circuit is connected to the a-th phase power supply line, and the three are connected in a delta manner.
After the delta connection is formed, the output voltage of the single-phase Buck circuit in embodiment 1 becomes the line voltage between the three phases. In a three-phase system, the propagation of zero sequence voltage components in the line voltage is negligible. In the method for regulating the voltage of the on-load tap changer in embodiment 1, when the positive-sequence output voltage and the negative-sequence output voltage are generated, a zero-sequence voltage component, which is an accessory harmonic of the generation of the positive-sequence voltage and the negative-sequence voltage, is generated. The zero sequence component in the three-phase power grid has very weak propagation capability, so when the step "generating positive sequence output voltage and negative sequence output voltage" in embodiment 1 is performed, the zero sequence component can be eliminated. The zero-sequence component may be omitted when the step of "synthesizing and generating a time-varying modulated wave" in the step of embodiment 1 is performed. In a delta-connected power grid, it is possible to generate voltages of various frequencies or phases and also to reduce the generation of other harmonics.
If a star connection is used, it is preferable in this embodiment to divide the circuit into three phases a, B, and C, wherein the fourth terminals of the single-phase Buck circuits in each phase circuit are connected to each other. Specifically, the fourth end of the A-phase single-phase Buck circuit is connected with the fourth end of the B-phase single-phase Buck circuit, and then the fourth end of the C-phase single-phase Buck circuit is connected at the same time.
The output voltage of the same single-phase Buck circuit of example 1 after the star connection is made becomes the line voltage between the three phases. The beneficial effects of the method for regulating the voltage of the on-load tap changer are the same as those of triangular connection, and are not described again here.
As described above, in the present embodiment, when the on-load voltage regulator is used in the three-phase system, it is possible to generate voltages of various frequencies or phases and also to reduce generation of other harmonics.
In the description of the present invention, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the invention and are not intended to limit the embodiments of the present invention, and that various other modifications and variations can be made by one skilled in the art in light of the above description.
It should be noted that, although the foregoing embodiments describe each step in a specific sequence, those skilled in the art can understand that, in order to achieve the effect of the present invention, different steps do not have to be executed in such a sequence, and they may be executed simultaneously (in parallel) or in other sequences, and these changes are all within the scope of the present invention.
It will be understood by those skilled in the art that all or part of the flow of the method of the above-described embodiment may be implemented by a computer program, which may be stored in a computer-readable storage medium, and the steps of the method embodiments may be implemented when the computer program is executed by a processor. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable storage medium may include: any entity or device capable of carrying said computer program code, media, usb disk, removable hard disk, magnetic diskette, optical disk, computer memory, read-only memory, random access memory, electrical carrier wave signals, telecommunication signals, software distribution media, etc. It should be noted that the computer readable storage medium may contain content that is subject to appropriate increase or decrease as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, computer readable storage media that does not include electrical carrier signals and telecommunications signals in accordance with legislation and patent practice.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
Claims (14)
1. An on-load tap changer, comprising:
the on-load voltage regulation device is connected with a one-phase power supply circuit of a power grid and comprises a primary side winding, at least one winding switching device and a single-phase Buck circuit, wherein the primary side winding comprises a main winding, a stepless energy-taking winding and at least one stepped winding, and the main winding, the stepless energy-taking winding and the stepped winding share a magnetic core;
the winding switching device is used for controlling the corresponding stepped winding to be switched in or switched out of the corresponding primary side winding;
the single-phase Buck circuit is used for converting the winding voltage of the stepless energy taking winding so as to adjust the amplitude and/or the phase of the output voltage of the primary side winding.
2. The on-load tap changer of claim 1,
the single-phase Buck circuit comprises a first end, a second end, a third end and a fourth end;
the winding switching device comprises a first end, a second end, a third end and a fourth end;
wherein, the first and the second end of the pipe are connected with each other,
the first end and the second end of the single-phase Buck circuit are respectively connected with the first end and the second end of the stepless energy-taking winding;
the first end and the second end of the winding switching device are respectively connected with the first end and the second end of the secondary winding;
and the third end of the single-phase Buck circuit is connected with the third end and the fourth end of the winding switching device.
3. The on-load tap changer of claim 2,
the stepless energy taking winding is connected with the main winding in series,
the single-phase Buck circuit includes:
a first triac, a second triac, a capacitor, an inductor, and an isolation transformer,
wherein the content of the first and second substances,
the input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor;
the second end of the inductor, the first end of the capacitor and the first end of the second three-terminal bidirectional switching element are connected with the first end of the primary winding of the isolation transformer;
the second end of the capacitor and the second end of the second three-terminal bidirectional switch element are connected to the second end of the single-phase Buck circuit and the second end of the primary winding of the isolation transformer;
the control end of the first three-terminal bidirectional switch element and the control end of the second three-terminal bidirectional switch element respectively receive control signals;
the first end of the secondary winding of the isolation transformer is connected with the third end of the single-phase Buck circuit;
and the second end of the secondary winding of the isolation transformer is connected with the fourth end of the single-phase Buck circuit.
4. The on-load tap changer of claim 2, wherein the single-phase Buck circuit comprises:
a first triac, a second triac, a capacitor and an inductor,
wherein the content of the first and second substances,
the input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor;
the second end of the inductor, the first end of the capacitor and the first end of the second three-terminal bidirectional switch element are connected to the third end of the single-phase Buck circuit;
the second end of the capacitor and the second end of the second three-terminal bidirectional switching element are connected to the second end and the fourth end of the single-phase Buck circuit;
and the control end of the first three-terminal bidirectional switch element and the control end of the second three-terminal bidirectional switch element respectively receive control signals.
5. The on-load tap changer of claim 2, wherein the single-phase Buck circuit comprises:
a first triac, a second triac, a capacitor, an inductor, and an isolation transformer,
wherein the content of the first and second substances,
the input end of the first three-terminal bidirectional switch element is connected to the first end of the single-phase Buck circuit, and the output end of the first three-terminal bidirectional switch element is connected with the first end of the inductor;
the second end of the inductor, the first end of the capacitor and the first end of the second three-terminal bidirectional switching element are connected with the first end of the primary winding of the isolation transformer;
the second end of the capacitor and the second end of the second three-terminal bidirectional switch element are connected to the second end of the single-phase Buck circuit and the second end of the primary winding of the isolation transformer;
the control end of the first three-terminal bidirectional switch element and the control end of the second three-terminal bidirectional switch element respectively receive control signals;
the first end of the secondary winding of the isolation transformer is connected with the third end of the single-phase Buck circuit;
and the second end of the secondary winding of the isolation transformer is connected with the fourth end of the single-phase Buck circuit.
6. On-load tap changer according to any of claims 3-5,
the first three-terminal bidirectional switch element and the second three-terminal bidirectional switch element are both double-tube common-emitter series bidirectional switches.
7. The on-load tap changer according to any one of claims 3 to 5, wherein the winding switching device comprises:
a first antiparallel thyristor pair comprising a first thyristor and a second thyristor;
a second antiparallel thyristor pair including a third thyristor and a fourth thyristor;
wherein
The anode of the first thyristor and the cathode of the second thyristor are connected to the first end of the winding switching device;
the cathode of the first thyristor and the anode of the second thyristor are connected to the third end of the winding switching device;
the anode of the third thyristor and the cathode of the fourth thyristor are connected to the second end of the winding switching device;
and the cathode of the third thyristor and the anode of the fourth thyristor are connected to the fourth end of the winding switching device.
8. The on-load tap changer of any one of claims 1, wherein the winding switching device comprises: a diverter switch and a tap selector, wherein
Both ends of each stepped winding are provided with selection contacts;
the tapping selector is provided with a joint which can be connected with the selection contact, wherein a part between one end of the primary winding, which is connected with the joint, and the first end of the first primary winding is connected with the primary side winding;
the selector switch controls the access of different contacts to control the number of the stepped windings accessed into the primary side winding.
9. A three-phase on-load tap changer, characterized in that the primary side of the on-load tap changer comprises three on-load tap changers according to any one of claims 1-8, wherein the three on-load tap changers are connected by delta or star connection to form the three-phase on-load tap changer.
10. A method of regulating voltage using an on-load tap changer according to any of claims 1 to 9, comprising:
generating an in-phase fundamental wave voltage, a positive sequence output voltage and a negative sequence output voltage based on the output voltage of a preset single-phase Buck circuit;
synthesizing the in-phase fundamental wave voltage, the positive sequence output voltage and the negative sequence output voltage to generate a time-varying modulation wave;
and controlling the duty ratio of the single-phase Buck circuit in the phase according to the time-varying modulation wave in real time.
11. The method of claim 10, wherein generating the in-phase fundamental voltage, the positive sequence output voltage, and the negative sequence output voltage based on the preset output voltage of the single-phase Buck circuit comprises:
generating in-phase fundamental voltage of a corresponding phase according to the fixed duty ratio of the single-phase Buck circuit;
generating a first modulation wave matrix of the positive sequence output voltage by adding a sinusoidal component of the first negative sequence, and generating the positive sequence output voltage based on the first modulation wave matrix;
and generating a second modulation wave matrix of the negative-sequence output voltage by adding the sinusoidal component of the second negative sequence, and generating the negative-sequence output voltage based on the second modulation wave matrix.
12. The method according to claim 10, wherein the real-time controlling the duty ratio of the single-phase Buck circuit in the phase according to the time-varying modulation wave comprises:
normalizing the time-varying modulated wave to obtain a modulated wave matrix;
and controlling the duty ratio of the single-phase Buck circuit in the phase according to the modulation wave matrix in real time.
13. The method of claim 11,
the frequency of the sinusoidal component of the first negative sequence is greater than the frequency of the input voltage of the single-phase Buck circuit;
the frequency of the second negative sequence component is less than the frequency of the input voltage of the single-phase Buck circuit.
14. The method of claim 11, wherein synthesizing the in-phase fundamental voltage, the positive sequence output voltage, and the negative sequence output voltage to generate a time-varying modulated wave comprises:
and eliminating zero sequence components in the positive sequence output voltage and the negative sequence output voltage in the process of synthesizing and generating the time-varying modulation wave.
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