CN121485661A

CN121485661A - An OLTC topology and driving method for electronic soft-switching technology

Info

Publication number: CN121485661A
Application number: CN202511322945.XA
Authority: CN
Inventors: 王一培; 胡皓; 卢鹏; 曹茂永
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2025-09-16
Filing date: 2025-09-16
Publication date: 2026-02-06

Abstract

This invention discloses an OLTC topology and driving method for electronic soft-switching technology. In this topology, the power supply is connected to a first transformer, the first transformer is connected to a second transformer, and the second transformer is connected to the load. The low-voltage winding of the first transformer is connected to multiple taps. The fixed end of the low-voltage winding of the first transformer and each tap are connected to one end of a separate mechanical switch. The other ends of all mechanical switches are connected in an intermittent manner to form two series switch circuits. Each series switch circuit is connected to a separate electronic switching switch to form two series circuits. The two electronic switching switches are connected in parallel, and the second transformer is connected to the series circuit controlled by each of the two electronic switching switches. The combined use of mechanical switches and electronic switching switches prevents short-circuit current and surge voltage during state switching of the electronic switching switches, thus improving the quality of the output voltage waveform.

Description

OLTC topological structure of electronic soft switching technology and driving method

Technical Field

The invention relates to the technical field of transformers, in particular to an OLTC topological structure of an electronic soft switching technology and a driving method.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

With the large-scale access of new energy and the wide application of distributed power sources, the fluctuation of power grid load is aggravated, and higher requirements are put forward on the switching speed, reliability and voltage regulation precision of the OLTC. The traditional OLTC mainly comprises a mechanical change-over switch, a tapping selector and a driving mechanism, tapping change is realized by driving a mechanical contact through a motor, an arc can be generated in the switching process, contact ablation and insulation aging are caused, the service life of equipment is shortened, potential safety hazards exist, and meanwhile, the action speed is low, the response is delayed, and the requirement of a modern power grid on rapid voltage regulation is difficult to meet. To meet this demand, research on electronic OLTC is continuously advancing. The most critical difference between the electronic OLTC and the mechanical OLTC is that the electronic OLTC adopts a bidirectional power electronic device as a change-over switch, and the controllable switch characteristic is utilized, so that the electronic OLTC has the advantages of arcless switching, quick response, strong controllability and the like, and provides a new direction for improving the OLTC performance.

However, in the current electronic OLTC, when the state of the electronic change-over switch is switched, a spike voltage or a spike current occurs in the switching element due to dead time or overlap, and a protection circuit must be designed to protect the switching element, but the protection circuit design is complicated.

Disclosure of Invention

In order to solve the problems, the invention provides an OLTC topological structure and a driving method of an electronic soft switching technology, and a mechanical switch and an electronic change-over switch are used jointly, so that short-circuit current and surge voltage can not be generated when the electronic change-over switch is used for state change, and the quality of an output voltage waveform is improved.

In order to achieve the above purpose, the invention adopts the following technical scheme:

In a first aspect, an OLTC topology for an electronic soft switching technology is provided, including a power supply, a first transformer, a load, a second transformer, a plurality of mechanical switches, and an electronic transfer switch;

the power supply is connected with a first transformer, the first transformer is connected with a second transformer, and the second transformer is connected with a load;

the fixed end of the low-voltage winding of the first transformer is connected with one end of an independent mechanical switch;

According to the mode of interval connection, the other ends of all the mechanical switches are connected to form two series switch loops, and each series switch loop is connected with an independent electronic change-over switch to form two series circuits; the two electronic change-over switches are connected in parallel, and the second transformer is connected into a series circuit respectively controlled by the two electronic change-over switches.

Further, the first transformer is a series-connected double-winding transformer.

Furthermore, the power supply is a three-phase power supply, and the three-phase power supply is connected in a star mode;

The load adopts star connection.

The power supply is connected in parallel with the first transformer, the positive end of the first transformer is connected with the negative end of the high-voltage winding of the second transformer, the positive end of the high-voltage winding of the second transformer is connected with the two ends of the load, the negative end of the low-voltage winding of the second transformer is connected into a series circuit respectively controlled by the two electronic change-over switches, and the positive end of the low-voltage winding of the second transformer is connected with the fixed end of the low-voltage winding of the first transformer.

Further, the electronic change-over switch adopts a two-way switch with a D-Type structure.

Further, the electronic change-over switch is used for switching the state when the tapping voltage or the tapping current is zero.

Further, the low-voltage winding of the first transformer comprises a plurality of sections of windings, all the windings are sequentially connected in series, and the tap end of each section of winding is connected with an independent tap.

Further, the fixed end of the low-voltage winding of the first transformer is the negative end of the first transformer.

In a second aspect, a driving method of an OLTC topology structure of an electronic soft switching technology according to the first aspect is provided, including:

obtaining tapping voltage and tapping current of an OLTC topological structure of an electronic soft switching technology;

When the tapping voltage or the tapping current is zero, the two electronic change-over switches are controlled to switch states.

Compared with the prior art, the invention has the beneficial effects that:

The invention provides an OLTC topological structure and a driving method of an electronic soft switching technology, wherein the topological structure comprises a power supply, a first transformer, a load, a second transformer, a plurality of mechanical switches and an electronic change-over switch, a low-voltage winding of the first transformer is connected with a plurality of taps, a fixed end of the low-voltage winding of the first transformer and each tap are connected with one end of an independent mechanical switch, the other ends of all the mechanical switches are connected in a spaced connection mode to form two series switch loops, each series switch loop is connected with the independent electronic change-over switch to form two series circuits, the two electronic change-over switches are connected in parallel, the states of the two electronic change-over switches are switched in the series circuits respectively controlled by the two electronic change-over switches, when tapping voltage or tapping current is zero, the two electronic change-over switches are used in a combined mode, short-circuit current and surge voltage are not generated when the electronic change-over switches are switched in the state, the quality of an output voltage waveform is improved, and a protection circuit is additionally arranged, and the burden caused by the increase of the number of semiconductor switches due to the compensation voltage level is eliminated.

Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application.

Fig. 1 (a) shows an initial state of the mechanical OLTC voltage regulation operation.

Fig. 1 (b) shows a transition state after the start of the mechanical OLTC voltage regulation operation.

Fig. 1 (c) shows a voltage compensation state after the mechanical OLTC voltage regulation operation.

Fig. 2 (a) shows an initial state of the gate control switch electronic OLTC.

Fig. 2 (b) shows the voltage regulation operating principle of the gate control switch electronic OLTC under normal conditions.

Fig. 2 (c) shows a transition state of the gate control switch electronic OLTC after the start of the voltage regulation operation.

Fig. 2 (d) shows the voltage compensation state after the voltage regulation operation of the gate control switch electronic OLTC.

Fig. 3 (a) shows a single-winding transformer type OLTC topology.

Fig. 3 (b) shows a series-connected double-winding transformer type OLTC topology.

Fig. 4 is a topology diagram of a single-phase electronic on-load tap-changer.

In fig. 5, (a) is a C-Type or S-Type bidirectional switch structure.

Fig. 5 (b) shows a D-Type bidirectional switch structure.

Fig. 6 (a) is a theoretical waveform diagram of single-phase ZVS switching.

Fig. 6 (b) is a theoretical waveform diagram of single-phase ZCS switching.

Fig. 7 is a topology diagram of a three-phase electronic on-load tap-changer.

In fig. 8 (a), a vector diagram of the compensation phase angle and the compensation voltage is obtained when the three-phase power supply adopts a star connection and the load end adopts a triangle connection.

In fig. 8 (b), the three-phase power supply adopts a star connection, and the phase angle compensation and the voltage vector compensation are performed when the load end adopts the star connection.

Fig. 9 is a theoretical waveform diagram of the proposed three-phase voltage soft switching technique.

Fig. 10 is a single-phase mechanocoelectronic stepless OLTC.

Fig. 11 is a simulation waveform diagram of three-phase input, distribution line current, load current, output terminal voltage, compensation voltage, and start command in order from top to bottom.

FIG. 12 is a waveform diagram of each phase of switching signals and corresponding switching currents in the simulation circuit.

Detailed Description

The invention is further described below with reference to the drawings and examples.

It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

Embodiments of the invention and features of the embodiments may be combined with each other without conflict.

Term interpretation:

OLTC an on-load tap changer (OLTC) is a device that can regulate the output voltage by changing the number of turns of the transformer windings without interrupting the operation of the transformer. As an on-load tap-changer, the on-load tap-changer has the advantages of voltage regulation, on-load switching capability, high automation degree and the like, and is widely applied to various industrial and civil fields, including power transformers, industrial electric equipment, power grid voltage regulation, household appliances and other scenes needing voltage regulation.

ZVS (zero voltage switching) and ZCS (zero current switching) are two soft switching technologies used for reducing power switching loss in the power electronics field, and the core principle is to turn on or off under specific conditions by controlling switching devices (such as MOSFETs and IGBTs) so as to reduce loss and electromagnetic interference in the switching process.

A mechanical MC switch is a switch device for realizing on-off control of a circuit through mechanical action. The core function of the circuit is to switch on or off the circuit current during normal operation, and to rapidly switch off the current through a mechanical mechanism when the circuit has faults such as overload and short circuit, so as to protect the circuit and equipment.

Example 1

Firstly, an application scenario of an OLTC topology structure of an electronic soft switching technology provided in this embodiment is described.

Conventional OLTC exists in two forms, mechanical OLTC and electronic OLTC.

As shown in fig. 1 (a), (b) and (c), the mechanical OLTC structure is composed of a transformer (including a tap), a tap selector, a transition resistor and a change-over switch, and operates by rotation of a driving motor. The basic action principle is as follows:

When the tap selector is in the initial state as shown in fig. 1 (a), if a voltage compensation request occurs at the load end, the tap selector needs to be connected to a specific tap 7 to provide load side voltage compensation. In general, in case of OLTC switching a tap, in order to eliminate an arc voltage caused by a load current, a specific tap of a transformer is selected through a tap selector in a no-load state, and then the switching switch is moved to a central position. At this time, as shown in fig. 1 (b), the tap selector is connected to the tap 7 at a transition stage so that the tap 7 and the tap 8 are simultaneously connected, and an internal circulation current flows due to a potential difference. To suppress the circulation and prevent the transformer and the change-over switch from being damaged, a transition resistor or a reactor is usually installed. After the current stabilizes, as shown in fig. 1 (c), the tap selector disconnects from tap 8 until the switching operation is completed. At this time, if the design of the transition resistor or the reactor is too large, the transition stability of the circuit is adversely affected, and if the design is too small, the service life of the device is affected, so that the design difficulty is high. Even if the design difficulty is overcome, the traditional mechanical OLTC has the defects of low response speed, limited control precision, large maintenance workload and the like.

Fig. 2 (a), (b), (c) and (d) show tap switching circuits implemented using two taps of a gate control switch. Where R1, R2 are resistors for limiting short-circuit current generated during tap switching. Fig. 2 (a) shows an initial state of the voltage regulation operation of the gate control switch electronic OLTC. In fig. 2 (b), the system normally supplies voltage to the load. As the load increases, when it is necessary to compensate for the high voltage of one of the gate control switches of the system, the short-circuit current is reduced by the resistor R1, as shown in fig. 2 (c). After the previous gate control switch is in the off state, the control switch corresponding to the high voltage is turned on to directly supply the high voltage to the load, as shown in (d) of fig. 2. When the power transmission system needs to carry out frequent voltage compensation, compared with the traditional mechanical control switch, the electronic control switch can avoid potential safety hazards such as short-circuit current to a greater extent.

The OLTC topology is mainly divided into a single winding transformer type and a series double winding transformer type according to the connection mode of the tap changer and the transformer winding and the voltage regulating principle, as shown in fig. 3 (a) and (b). In general, the offset voltage range of OLTC varies from ±2.5% to ±20% as required, and in this case, the offset voltage range in the distribution line is ±10% of the rated voltage. The single winding transformer type shown in fig. 3 (a) requires 5 switches, namely switches S1, S2, S3, S4 and S5, and although one transformer can be used for configuration, copper wires and iron core materials are saved, electrical isolation is lost, high voltage side faults can directly affect low voltage side, and safety is low. In the type of series double-winding transformer shown in fig. 3 (b), only 4 transfer switches are needed, namely, S1, S2, S3 and S4, and the series double-winding transformer consists of two transformers, so that the short-circuit impedance of a circuit is improved to a large extent, the potential safety hazard caused by frequent transfer switches is effectively reduced, and the double-winding structure ensures that the fault at the high voltage side cannot bring great influence to the low voltage side. To a certain extent, the series-connected double-winding transformer is more suitable for a power supply system, and comprehensively considered, in the OLTC topological structure of the electronic soft switching technology provided by the embodiment, the series-connected double-winding transformer type is selected.

When using OLTC of a series double winding transformer type, as shown in fig. 4, a topology of a single-phase electronic on-load tap changer is shown. The topology employs a fixed voltage compensation scheme based on a preset tap voltage. The voltage-regulating circuit comprises a circuit, a transformer, an electronic switch, a winding voltage, a Va10, a winding voltage, a compensation voltage value, an I _a and a V _out, wherein the V _in is used as an alternating voltage source for supplying power to the whole circuit, the transformer with a magnetic core is connected in parallel with the alternating voltage source and used for voltage conversion, the S _a1~S_a4 is an electronic switch of a phase and regulates output voltage through the switch and the switch, the V _a5 is the winding voltage marked with a tap of +5% and is used for realizing +5% voltage regulation compensation on the winding at the tap position, the Va10 is the winding voltage marked with the tap of +10% and is used for realizing +10% voltage regulation compensation on the winding at the tap position, the V _aux is a compensation voltage value, the I _a is used for outputting current of the circuit, and the V _out is an output voltage value. In an actual power system, voltage fluctuations are bi-directional, and may occur in situations where the voltage is too high or too low. By means of the bidirectional transmission capability of the single-phase electronic on-load tap-changer, the voltage can be flexibly increased or reduced according to the voltage condition monitored in real time, the output voltage is stabilized in an allowable range, and the load equipment can obtain stable power supply voltage. Because the topological structure has high-speed responsiveness and bidirectional power transmission capability, the topological structure is often arranged at the tail end of a distribution line and is widely applied to micro-grids or renewable energy distributed power supply connection sections as a voltage compensator.

In the topology shown in fig. 4 (a), the output voltage is defined as shown in formula (1).

According to equation (1), by switching the electronic changeover switch, the output voltage can be formed into voltages of 5 phase differences as shown in equation (2). Where k=0, ±1, ±2 is set. The compensation voltage range of the structure is + -10% as can be obtained by a formula.

As shown in fig. 5 (a), a C-Type or S-Type structure in which two IGBTs are formed in an antiparallel manner is a commonly used bidirectional semiconductor switching structure. If the rated current of the semiconductor switching element is insufficient, the C-Type and S-Type structures may be arranged in parallel to boost the rated current, as in the D-Type structure shown in fig. 5 (b). Therefore, in order to meet the rated current requirement of the distribution line, a two-way switch with a D-Type structure is adopted. At this time, since the half-bridge switching element is used, there is an advantage in terms of economy of the switching element. The disadvantage of this topology is that the switching element has to be designed to protect the element due to dead time or overlapping causing spikes or currents in the switching element, and the design is complex.

Therefore, in order to improve the running performance and the grid adaptability of the OLTC, and prevent the occurrence of spike voltage and current during switching, in this embodiment, an OLTC topology structure of an electronic soft switching technology is disclosed, and the topology structure uses a mechanical switch and an electronic switch in combination. In order to verify the feasibility of the method, the embodiment also establishes a complete system of a high-voltage transmission line comprising a Y-Y type power supply, a load, a series double-winding transformer and other modules through a PSIM simulation platform, and the result shows that the switching of each phase of the three-phase transmission line of the topology structure disclosed by the embodiment avoids voltage peaks in the switching process, does not influence other phase lines, and verifies the effectiveness of the proposed switching algorithm and the topology structure.

The OLTC topology structure of the electronic soft switching technology according to the present embodiment includes, as shown in fig. 10, a power supply, a first transformer, a load, a second transformer, a plurality of mechanical switches and an electronic switch;

The first transformer regulates the voltage, and the second transformer supplements the voltage.

The two electronic change-over switches are respectively an electronic change-over switch S _a3 and an electronic change-over switch S _a4, the electronic change-over switch S _a3 and the electronic change-over switch S _a4 are in parallel connection, the mechanical switch adopts a magnetic control switch, as shown in fig. 10, a fixed end of a low-voltage winding of a first transformer and each tap are sequentially connected with the magnetic control switches MC _a1、MC_a2、MC_a3、MC_a4、MC_a5 and MC _aN, the other ends of the magnetic control switches MC _a1、MC_a3 and MC _a5 are connected with the electronic change-over switch S _a3 after being connected with the other ends of the magnetic control switches MC _a2、MC_a4 and MC _aN, and are connected with the electronic change-over switch S _a4, when the S _a4 is independently conducted, a series circuit formed by the magnetic control switches MC _aN、MC_a4, MC _a2 and the like and the corresponding low-voltage winding of the transformer is controlled, and when the S _a3 is independently conducted, a series circuit formed by the magnetic control switches MC _a5、MC_a3, MC _a1 and the like and the corresponding low-voltage winding of the transformer is controlled.

The OLTC topology structure of the electronic soft switching technology provided by the embodiment realizes a soft switching mode and can prevent the electronic change-over switch from being damaged by surge voltage generated when the control switch is switched. The electronic change-over switch is carried out at the moment that the tapping voltage is zero or the tapping current is zero, so that the circulating short-circuit current generated during tapping switching can be reduced to zero, and the impact voltage generated under the overlapping of the dead zones of the switch can be reduced to the minimum.

As shown in fig. 6 (a) and (b), switching signal waveforms of the electronic switch Sa4 and the electronic switch Sa3, and output current waveforms of the distribution lines and tap voltages of 5% and 10% are shown. Wherein V _aux5 is the compensation voltage output waveform in the single S _a3 on state, V _aux10 is the compensation voltage output waveform in the single S _a4 on state, and I _a is the output current waveform of the distribution line. In fig. 6 (a), when 5% of the voltage is compensated in the on state of S _a3, the load current increases to decrease the voltage of the distribution line, and in order to compensate the decreased voltage, S _a3 is switched to the off state, and S _a4 is conducted to compensate 10% of the voltage and the corresponding compensation voltage output waveform. When the distribution phase voltage is subjected to tapping switch switching requirements, the ZVS technology is utilized to switch at the position of a dotted line, namely, a voltage zero crossing point, no voltage peak is generated during switching, the current is non-zero at the moment, and a delay of a plurality of microseconds is needed between two switching signals in order to maintain a current loop.

Fig. 6 (b) shows that the ZCS technique is used to switch when the current is zero, and the switching is stable without generating voltage spikes.

Fig. 7 shows a topological structure diagram of the three-phase electronic on-load tap-changer. The three-phase power supply and the load are connected in star and triangle modes respectively, and four combinations are adopted. It is worth noting that when the three-phase power supply adopts star connection, the compensation mode is simple, but the problem of triple harmonic current can be generated, and when the three-phase power supply adopts triangle connection, the problem of triple harmonic current can not be generated, but the compensation mode is complex. Therefore, the power supply in the OLTC topology structure of the electronic soft switching technology provided by the embodiment is a three-phase power supply, and the three-phase power supply is connected in a star-shaped manner. In fig. 8, (a) and (b) are diagrams of compensating phase angles and compensating voltage vectors of different connection modes of loads when the three-phase power supply adopts star connection.

When the three-phase power supply adopts the star connection, if the load end adopts the triangle connection as shown in fig. 8 (a), the phase voltage of the load end can lead or lag the phase voltage of the input end by 30 degrees. A special case is tried in which when the load side voltage drops suddenly (e.g. an asymmetric drop caused by a system fault), when V _ab is not only reduced in amplitude but also shifted in phase, the Δv _a of the fixed lead compensation 30 ° cannot match the new V _ab phase, resulting in a phase error after compensation. However, if the load terminal shown in fig. 8 (b) is selected to be in a star connection, since the phase of the load terminal voltage is always consistent with that of the power terminal voltage, Δv _a remains in phase with V _ab, and a better practical effect can be obtained on the premise of simulating the actual high-voltage transmission line. Therefore, the load is more suitable in a star connection mode.

Fig. 9 shows a theoretical waveform diagram of the three-phase voltage soft switching technology according to the present embodiment. In the figure, V _an、V_bn and V _cn are voltage waveforms of each phase of three-phase voltage, in which S _a4 and S _a3 are switching signals sent by electronic switches of a phase, S _b4 and S _b3 are switching signals sent by electronic switches of b phase, and S _c4 and S _c3 are switching signals sent by electronic switches of c phase. When the tap change request occurs at approximately 45 degrees of the power distribution a-phase voltage, the b-phase change occurs at the point where the b-phase voltage becomes zero, then the c-phase change occurs at the point where the c-phase voltage becomes zero, and then the a-phase change occurs at the point where the a-phase voltage becomes zero. No voltage surge occurs during switching of each phase, and in this case, since the current is not zero, an overlapping time of several microseconds is required between the two switching signals in order to maintain the current loop, as in the case of a single phase. As shown in the figure, the delay required for switching is 120 degrees at maximum, and it is known that 120 degrees are also required in the switching process, so that the three-phase soft switching technology can avoid voltage spikes when each phase is switched, and the potential safety hazard is greatly reduced.

As shown in fig. 4, taking the a-phase as an example, in the switching method using the electronic change-over switch, the relationship between the output voltage compensation level and the number (M) of bidirectional semiconductor switches is shown in the formula (3).

Therefore, in order to increase the voltage compensation level of the distribution line, the number of semiconductor switches is required to be greatly increased.

In order to eliminate the burden of the number of semiconductor switches caused by the increase of the compensation voltage level, the present embodiment proposes a topology as shown in fig. 10, which adopts a mechanical MC switch and two bidirectional semiconductor switches. As can be seen from the figure, the number of output voltage levels is the same as the number of mechanically marked contacts, and two bidirectional semiconductor switches are required, no matter how many output voltage levels are. If the compensation level is applied by the left marked contact, the compensation voltage is determined by the two silver marked contacts adjacent to the left marked contact, compensated by the voltage drop, and the bi-directional switch achieves soft switching by the above proposed switching scheme. To achieve a voltage regulation of 1%, 21 flag contacts are required.

As shown in FIG. 10, the power supply is connected in parallel with the first transformer, the positive terminal of the first transformer is connected with the negative terminal of the second transformer high-voltage winding, the positive terminal of the second transformer high-voltage winding is connected with the two ends of the load, the negative terminal of the second transformer low-voltage winding is connected into a series circuit respectively controlled by two electronic change-over switches, and the positive terminal of the second transformer low-voltage winding is connected with the fixed end of the first transformer low-voltage winding.

The low-voltage winding of the first transformer comprises a plurality of sections of windings, all the windings are sequentially connected in series, and the tap end of each section of winding is connected with an independent tap.

The fixed end of the low-voltage winding of the first transformer is the negative end of the first transformer.

Simulation is performed through PSIM, and the performance of the OLTC topological structure of the electronic soft switching technology provided by the embodiment is verified.

Fig. 11 and 12 are waveform diagrams of simulation results after simulation. To facilitate the simulation analysis, the peak power supply phase voltage in fig. 11 was set to 100V, the peak load current of the distribution line was 50A, and 5% compensation voltage was applied to compensate for the voltage drop. At 0.2s, the load increases and the peak load current of the distribution line increases to 150A, thereby causing a voltage drop at the terminal voltage of the distribution line as shown at 0.2s in fig. 11 at V _outb and V _outc, to compensate for this voltage drop, a tap changer switching command is issued to apply a 10% compensation voltage. At this time, the zero point occurs for the first time in the a-phase voltage, and the switching signal of the phase is switched from S _a3 to S _a4 as shown in fig. 12. The individual switching of the a phase has no effect on the b and c phase voltages and has very little effect on the current of the distribution line. after 60 degrees after the switching of the a phase, the b phase voltage first appears zero point, and at this time, the switching signal of the b phase is switched from S _b3 to S _b4. In addition, after 60 degrees from the b-phase switching, the c-phase voltage first appears zero, at which time the c-phase switching signal switches from S _c3 to S _c4. In the proposed switching mode, the switching angle is 120 degrees, which indicates a nearly negligible impact on the distribution line. As can be seen in the V _aux waveform in fig. 11, the compensation voltage waveform is good, without spikes and overshoots. In addition, the terminal voltage V _outa、V_outb、V_outc of the distribution line also does not exhibit a voltage change due to the switching of the connector. Meanwhile, since the electronic change-over switch of each phase is switched, the phase switch currents ISn3, ISn4 (n=a, b, c) are all switched at zero as shown in fig. 12, and the terminal voltage and the compensation voltage waveforms in fig. 11 are good at this time. Therefore, as shown in fig. 11 and fig. 12, the simulation result shows that the OLTC topology structure of the electronic soft switching technology provided by the embodiment adopts ZVS and ZCS composite soft switching technology, so that the quality of the output voltage waveform is better improved.

In summary, the OLTC topology of the electronic soft switching technology proposed in this embodiment selects a series transformer type OLTC topology to be more suitable for a distribution line, uses the electronic OLTC to replace a mechanical OLTC to overcome the disadvantages of the conventional mechanical OLTC, improves the semiconductor bidirectional switching structure to be more economical, performs tap switching at the moment when the tap voltage or current becomes zero by the electronic soft switching technology, thereby enabling the circulating short-circuit current or surge voltage generated during tap switching to become zero to further improve the reliability of the system, and simultaneously eliminates the burden caused by the increase of the compensation voltage level to the number of semiconductor switches, and finally verifies the effectiveness of the proposed topology by performing PSIM simulation circuit analysis on the proposed topology.

Example 2

In this embodiment, a driving method of an OLTC topology structure of an electronic soft switching technology disclosed in embodiment 1 is disclosed, including:

While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims.

Claims

1. An OLTC topology for electronic soft switching technology, characterized in that it comprises: a power supply, a first transformer, a load, a second transformer, multiple mechanical switches, and an electronic switching switch;

The power supply is connected to the first transformer, the first transformer is connected to the second transformer, and the second transformer is connected to the load.

The low-voltage winding of the first transformer is connected to multiple taps; the fixed end of the low-voltage winding of the first transformer and each tap are connected to one end of a separate mechanical switch.

Connect the other ends of all mechanical switches in an intermittent manner to form two series switch circuits. Connect each series switch circuit to a separate electronic switching switch to form two series circuits. Connect the two electronic switching switches in parallel, and connect the second transformer to the series circuit controlled by the two electronic switching switches respectively.

2. The OLTC topology of electronic soft-switching technology as described in claim 1, characterized in that the first transformer is a series-connected double-winding transformer.

3. The OLTC topology of electronic soft-switching technology as described in claim 1, characterized in that the power supply is a three-phase power supply, and the three-phase power supply is connected in a star configuration.

4. The OLTC topology of electronic soft-switching technology as described in claim 1, characterized in that the load adopts a star connection.

5. The OLTC topology of electronic soft-switching technology as described in claim 1, characterized in that: the power supply is connected in parallel with the first transformer; the positive terminal of the first transformer is connected to the negative terminal of the high-voltage winding of the second transformer; the positive terminal of the high-voltage winding of the second transformer and the negative terminal of the first transformer are connected to both ends of the load; the negative terminal of the low-voltage winding of the second transformer is connected to a series circuit controlled by two electronic switching switches respectively; the positive terminal of the low-voltage winding of the second transformer is connected to the fixed end of the low-voltage winding of the first transformer.

6. The OLTC topology of electronic soft-switching technology as described in claim 1, characterized in that the electronic switching switch adopts a bidirectional switch with a D-Type structure.

7. The OLTC topology of electronic soft-switching technology as described in claim 1, characterized in that the electronic switching switch is used to switch states when the tap voltage or tap current is zero.

8. The OLTC topology of electronic soft switching technology as described in claim 1, characterized in that the low-voltage winding of the first transformer includes multiple winding segments, all winding segments are connected in series, and the tap ends of each winding segment are connected to separate taps.

9. The OLTC topology of electronic soft-switching technology as described in claim 1, characterized in that the fixed end of the low-voltage winding of the first transformer is the negative terminal of the first transformer.

10. A driving method for an OLTC topology using electronic soft-switching technology as described in any one of claims 1-9, characterized in that it comprises:

Obtain the tap voltage and tap current of an OLTC topology using electronic soft-switching technology;

When the tap voltage or tap current is zero, the two electronic switching switches are controlled to switch states.