Methods and related devices for switching operating modes of series-parallel hybrid distribution transformers

Abstract

This invention provides a method and related apparatus for switching the operating mode of a series-parallel hybrid distribution transformer. The method includes acquiring power parameters, including current and voltage parameters; determining a first switching action of the operating mode switching switch based on the current parameters, wherein the first switching action is to switch the operating mode from a current-voltage compensation mode to a dual current compensation mode; and determining a second switching action of the operating mode switching switch based on the voltage parameters, wherein the second switching action is to switch the operating mode from a dual current compensation mode to a current-voltage compensation mode. This method enables smooth switching of the operating mode of the series-parallel hybrid distribution transformer; the switching does not rely on converter control coordination, and is simple, reliable, and effective.

Description

Technical Field

[0001] This invention relates to the field of power distribution network technology, and more particularly to the field of power distribution transformer technology. Specifically, it relates to a method and related apparatus for switching the operating modes of a series-parallel hybrid power distribution transformer. Background Technology

[0002] The series-parallel hybrid distribution transformer is a new type of distribution transformer used in power distribution networks. It consists of a main winding, back-to-back dual converters, a mode switching switch, and a control module. The main winding converts the voltage of the medium-voltage distribution network to low voltage. The back-to-back dual converters are composed of parallel and series converters. The parallel converters perform current compensation, used for harmonic suppression and three-phase current imbalance compensation, while the series converters perform voltage sag compensation. The mode switching switch consists of anti-parallel connected thyristor switches. It is used to change the topology of the series-parallel hybrid distribution transformer, converting series converters to parallel and parallel converters to series. The controller controls the trigger signals of the back-to-back dual converters and the mode switching switch.

[0003] Low-voltage distribution substations face two types of problems: current-related issues such as harmonics, three-phase current imbalance, and insufficient reactive power; and voltage-related issues such as voltage sags and voltage interruptions. Current problems are constant, therefore, the mitigation devices must be constantly connected to the grid; and because they are current-related, parallel devices are used to inject current to resolve them. Voltage problems, such as voltage sags and voltage interruptions, only occur for short periods, so the mitigation devices are only activated when voltage problems occur; and because they are voltage-related, series devices are used to compensate for voltage, resulting in prolonged periods of inactivity for the mitigation devices used to address voltage problems. Considering that both current-related and voltage-related mitigation devices can essentially be power electronic converters, differing only in control schemes and connection methods... In a hybrid series-parallel distribution transformer, the back-to-back dual converters address current issues, while the series converters manage voltage issues. Furthermore, the mode-changing switch can convert the series converter into a parallel converter, allowing for full utilization of the series converter when there are no voltage problems and increasing current compensation capacity. However, the mode-changing switch is composed of thyristor switches. Thyristors are semi-controlled devices, capable of instantaneous conduction but with delayed turn-off. This delayed turn-off leads to uneven mode switching, potentially causing short-circuit problems.

[0004] Therefore, existing technologies suffer from the technical problem of uneven switching of operating modes in series-parallel hybrid distribution transformers, which can easily lead to short circuits. Summary of the Invention

[0005] The main objective of this invention is to provide a method and related apparatus for switching the operating mode of a series-parallel hybrid distribution transformer, so as to solve the technical problem in the prior art that the switching of the operating mode of a series-parallel hybrid distribution transformer is not smooth and is prone to causing short circuits.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for switching the operating mode of a series-parallel hybrid distribution transformer is provided. The series-parallel hybrid distribution transformer includes: a transformer winding, a parallel converter, a series converter, an operating mode switching switch, a coupling transformer, a filter, and a control device. The operating mode switching switch includes a first switch group, a second switch group, a third switch group, a fourth switch group, and a fifth switch group. The first switch group is located between the parallel converter and the transformer winding; the second switch group is located between the parallel converter and the coupling transformer; the third switch group is located between the parallel converter and the coupling transformer; the fourth switch group is located between the series converter and the coupling transformer; and the fifth switch group is located between the coupling transformer and the series converter. Between the low-voltage ports, the parallel converter and the series converter are connected to the transformer winding and the coupling transformer respectively via the operating mode switching switch; the operating modes include current-voltage compensation mode and dual-current compensation mode, and the operating mode switching method includes the following steps: acquiring power parameters; the power parameters include current parameters and voltage parameters; determining a first switching action of the operating mode switching switch based on the current parameters, the first switching action being to switch the operating mode from current-voltage compensation mode to dual-current compensation mode; determining a second switching action of the operating mode switching switch based on the voltage parameters, the second switching action being to switch the operating mode from dual-current compensation mode to current-voltage compensation mode.

[0007] In some implementations, determining the first switching action of the operating mode switching switch based on the current parameters includes: determining an abnormal current state based on the current parameters, wherein the abnormal current state includes at least harmonics, three-phase current imbalance, and reactive power; and determining the first switching action of the operating mode switching switch based on the abnormal current state.

[0008] In some implementations, determining the first switching action of the operating mode switching switch based on the abnormal current state includes: when the abnormal current state is greater than a first preset threshold, performing the first switching action to switch the operating mode from current-voltage compensation mode to dual current compensation mode; when the abnormal current state is not greater than the first preset threshold, maintaining the operating mode as current-voltage compensation mode.

[0009] In some embodiments, determining the second switching action of the operating mode switching switch based on the voltage parameters includes: determining a voltage sag based on the voltage parameters; and determining the second switching action of the operating mode switching switch based on the voltage sag.

[0010] In some embodiments, the second switching action of determining the operating mode switching switch based on the voltage sag includes: when the voltage sag is greater than a second preset threshold, performing the second switching action to switch the operating mode from dual current compensation mode to current voltage compensation mode; when the voltage sag is not greater than the second preset threshold, maintaining the operating mode as dual current compensation mode.

[0011] In some embodiments, performing the second switching action includes: removing the second switch group's conduction signal, delaying for a first preset time, and then conducting the fourth switch group.

[0012] In some implementations, performing the first switching action includes: determining whether the conduction of the second switch group will cause the fourth switch group to turn off; and determining the first switching action based on the determination result.

[0013] In some implementations, performing the first switching action includes: determining whether the conduction of each switch in the second switch group will cause the corresponding phase switch in the fourth switch group to be turned off; and determining the first switching action based on the determination result.

[0014] According to another aspect of the present invention, the present invention also provides a switching device for the operating mode of a series-parallel hybrid distribution transformer. The series-parallel hybrid distribution transformer includes: a transformer winding, a parallel converter, a series converter, an operating mode switching switch, a coupling transformer, a filter, and a control device. The operating mode switching switch includes a first switch group, a second switch group, a third switch group, a fourth switch group, and a fifth switch group. The first switch group is located between the parallel converter and the transformer winding; the second switch group is located between the parallel converter and the coupling transformer; the third switch group is located between the parallel converter and the coupling transformer; the fourth switch group is located between the series converter and the coupling transformer; and the fifth switch group is located between the coupling transformer and the low-voltage port. The parallel converter... The series converter is connected to the transformer winding and the coupling transformer respectively via the operating mode switching switch; the operating modes include current-voltage compensation mode and dual-current compensation mode; the operating mode switching device includes: an acquisition module for acquiring power parameters; the power parameters include current parameters and voltage parameters; a first determination module for determining a first switching action of the operating mode switching switch based on the current parameters, the first switching action being to switch the operating mode from current-voltage compensation mode to dual-current compensation mode; and a second determination module for determining a second switching action of the operating mode switching switch based on the voltage parameters, the second switching action being to switch the operating mode from dual-current compensation mode to current-voltage compensation mode.

[0015] According to another aspect of the present invention, the present invention also provides a storage medium storing a computer program that, when executed by a processor, implements the steps of any of the preceding methods.

[0016] According to another aspect of the present invention, the present invention also provides an electronic device, including at least a memory and a processor, wherein the memory stores a computer program, and the processor, when executing the computer program in the memory, implements the steps of any of the preceding methods.

[0017] The operating mode switching method for a series-parallel hybrid distribution transformer provided by this invention determines a first switching action of the operating mode switching switch based on the current parameters. The first switching action is to switch the operating mode from a current-voltage compensation mode to a dual current compensation mode. A second switching action of the operating mode switching switch is determined based on the voltage parameters. The second switching action is to switch the operating mode from a dual current compensation mode to a current-voltage compensation mode. This method enables smooth switching of the operating modes of the series-parallel hybrid distribution transformer. The switching does not rely on converter control coordination, and it is simple, reliable, and effective. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 This is a circuit diagram of the series-parallel hybrid distribution transformer provided by the present invention;

[0020] Figure 2 This is a flowchart of the steps for switching the operating mode of the series-parallel hybrid distribution transformer provided by the present invention;

[0021] Figure 3 This is a flowchart of the steps for determining the first switching action of the operating mode switching switch based on current parameters, provided by the present invention.

[0022] Figure 4 This is a schematic diagram of the control flow for the first switching action provided by the present invention;

[0023] Figure 5 This is a flowchart of the steps for determining the second switching action of the operating mode switching switch based on voltage parameters, provided by the present invention.

[0024] Figure 6 This is a schematic diagram of the control flow for the second switching action provided by the present invention;

[0025] Figure 7 This is a circuit diagram of the working mode switching provided by the present invention;

[0026] Figure 8 This is a simplified circuit diagram of the working mode switching provided by the present invention;

[0027] Figure 9 This is the equivalent circuit diagram provided by the present invention;

[0028] Figure 10 This invention provides Simulation diagram of the first switching action;

[0029] Figure 11 A and B are provided by this invention. Simulation diagram of the first switching action;

[0030] Figure 12 This is a simulation diagram of the second switching action provided by the present invention;

[0031] Figure 13 This is a structural block diagram of the operating mode switching device for the series-parallel hybrid distribution transformer provided in this disclosure;

[0032] Figure 14This is a schematic diagram of the structure of the electronic device provided in this disclosure. Detailed Implementation

[0033] The specific embodiments of this disclosure will now be described in detail with reference to the accompanying drawings, but these are not intended to limit the scope of this disclosure.

[0034] It should be understood that various modifications can be made to the embodiments disclosed herein. Therefore, the above description should not be considered as limiting, but merely as an example of embodiments. Other modifications within the scope and spirit of this disclosure will be apparent to those skilled in the art.

[0035] The accompanying drawings, which are included in and form part of this specification, illustrate embodiments of the present disclosure and, together with the general description of the disclosure given above and the detailed description of the embodiments given below, serve to explain the principles of the disclosure.

[0036] These and other features of this disclosure will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0037] It should also be understood that although this disclosure has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this disclosure, which have the features described in the claims and are therefore all within the scope of protection defined herein.

[0038] The above and other aspects, features and advantages of this disclosure will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0039] Specific embodiments of the present disclosure are described thereafter with reference to the accompanying drawings; however, it should be understood that the disclosed embodiments are merely examples of the present disclosure and can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to avoid unnecessary or redundant details that could obscure the present disclosure. Therefore, the specific structural and functional details disclosed herein are not intended to be limiting, but merely to serve as the basis and representative basis for the claims to teach those skilled in the art to use the present disclosure in a variety of substantially any suitable detailed structures.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in still another embodiment,” all of which may refer to one or more of the same or different embodiments according to this disclosure.

[0042] The present disclosure will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] To address the technical problem of uneven switching of operating modes in existing series-parallel hybrid distribution transformers, which can easily cause short circuits, this invention provides a method and related apparatus for switching operating modes of a series-parallel hybrid distribution transformer.

[0044] Figure 1 The structural diagram of the series-parallel hybrid distribution transformer provided by the present invention is shown, as follows: Figure 1 As shown, a series-parallel hybrid distribution transformer includes: transformer windings, parallel converters, series converters, operating mode switching switches, coupling transformers, filters, and control devices.

[0045] The transformer winding is used for voltage transformation, stepping down the AC power from the medium-voltage power grid. The parallel converter injects current into the power grid for current compensation. The series converter compensates the voltage in the power grid through a coupling transformer in current-voltage compensation mode, and injects current into the power grid for current compensation in dual-current compensation mode. The coupling transformer transmits the compensated electrical energy from the parallel and series converters to the distribution network through magnetic coupling. The parallel and series converters are connected to the transformer winding and the coupling transformer, respectively, through the operating mode switching switch. The operating modes include current-voltage compensation mode and dual-current compensation mode. The control device controls the operating mode switching switch to enable the parallel and series converters to perform corresponding electrical energy compensation based on the received operating mode.

[0046] To facilitate switching of operating modes, the operating mode switching switch includes a first switch group, a second switch group, a third switch group, a fourth switch group, a fifth switch group, and a sixth switch group. The first switch group is located between the parallel converter and the transformer winding; the second switch group is located between the parallel converter and the coupling transformer; the third switch group is located between the parallel converter and the coupling transformer; the fourth switch group is located between the series converter and the coupling transformer; and the fifth switch group is located between the coupling transformer and the low-voltage port. Each of the first, second, third, fourth, and fifth switch groups consists of three phase switches (A, B, and C). For example, the first switch group includes a first A-phase switch, a first B-phase switch, and a first C-phase switch. The sixth switch group consists of two switches.

[0047] During the switching of the working mode, the conduction states of the second switch group, the fourth switch group, and the fifth switch group need to be changed, as shown in Table 1.

[0048] Table 1 Schematic diagram of the working mode switching switch

[0049]

[0050] Figure 2 The flowchart of the operating mode switching method for the series-parallel hybrid distribution transformer provided by the present invention is shown in Figure 2. The operating mode switching method for the series-parallel hybrid distribution transformer includes the following steps:

[0051] S101, Obtain power parameters; the power parameters include: current parameters and voltage parameters.

[0052] In this step, power parameters are obtained; the power parameters include current parameters and voltage parameters.

[0053] Specifically, the system collects real-time output power parameters such as actual voltage and actual current from the distribution network, and determines the operating mode based on the actual voltage and actual current. This can be achieved by using current transformers to detect the current in phases A, B, and C of the distribution network, as well as in the grounding wire, and by using voltage transformers to detect the voltage in phases A, B, and C of the distribution network.

[0054] For example, the A-phase current of the distribution network can be detected by a first current transformer, the B-phase current of the distribution network can be detected by a second current transformer, the C-phase current of the distribution network can be detected by a third current transformer, the ground current of the distribution network can be detected by a fourth current transformer, the A-phase voltage of the distribution network can be detected by a first voltage transformer, the B-phase voltage of the distribution network can be detected by a second voltage transformer, and the C-phase voltage of the distribution network can be detected by a third voltage transformer.

[0055] S102, based on the current parameters, determine the first switching action of the operating mode switching switch, the first switching action being to switch the operating mode from current voltage compensation mode to dual current compensation mode.

[0056] After completing step S101 above, in this step, the first switching action of the working mode switching switch is determined based on the current parameters.

[0057] Specifically, the series-parallel hybrid distribution transformer has two operating modes: current-voltage compensation mode and dual current compensation mode. After the device starts up, it enters the current-voltage compensation mode, and then determines whether the operating mode switching switch should perform the first switching action based on the current parameters.

[0058] Furthermore, Figure 3 A flowchart illustrating the steps of determining the first switching action of the operating mode switching switch based on the current parameters provided by the present invention is shown in the figure. The steps of determining the first switching action of the operating mode switching switch based on the current parameters include the following:

[0059] S201, determine the abnormal current state based on the current parameters, wherein the abnormal current state includes at least harmonics, three-phase current imbalance, and reactive power.

[0060] In this step, the abnormal current state is determined based on the current parameters. The abnormal current state includes at least harmonics, three-phase current imbalance, and reactive power.

[0061] Specifically, after obtaining the current parameters, the abnormal current state is determined based on the various current values ​​of the distribution network. For example, the balance state of the three-phase current is judged, and the presence of harmonics and reactive power is judged.

[0062] S202, based on the abnormal current state, determine the first switching action of the working mode switching switch.

[0063] After completing step S201 above, in this step, based on the abnormal current state, the first switching action of the working mode switching switch is determined.

[0064] Specifically, when the abnormal current condition exceeds the first preset threshold, it indicates that the current problem is relatively serious and current compensation is required. The first switching action is then performed to switch the operating mode from the current-voltage compensation mode to the dual current compensation mode. When the abnormal current condition does not exceed the first preset threshold, it indicates that the current problem in the power grid is not serious, and the operating mode remains the current-voltage compensation mode.

[0065] The first preset threshold can be set according to the operating status of the power distribution network or according to the experience of the operators.

[0066] Because the operating mode switching switch is composed of anti-parallel thyristors, it has the characteristics of instantaneous conduction and delayed turn-off. In a series-parallel hybrid distribution transformer, the conduction of one set of switches will cause the turn-off of another set of switches. Figure 4 A schematic diagram of the control flow for the first switching action in this patent is shown, as follows: Figure 4 As shown, when performing the first switching action, it is first necessary to determine whether the conduction of the second switch group will cause the fourth switch group to be turned off, and determine the first switching action based on the determination result. When the conduction of the second switch group will cause the fourth switch group to be turned off, the second switch group is turned on.

[0067] Specifically, since each switch group includes three switches, during the judgment process, it is determined whether the conduction of each switch in the second switch group will cause the corresponding phase switch in the fourth switch group to be turned off, and the first switching action is determined based on the judgment result. Therefore, the first switching action includes switching the A, B, and C phase switches respectively. That is, when the conduction of the A phase switch in the second switch group will cause the A phase switch in the fourth switch group to be turned off, the A phase switch in the second switch group is turned on; when the B phase switch and the C phase switch in the second switch group meet the above requirements, the corresponding turning operation is then performed.

[0068] S103, based on the voltage parameters, determine the second switching action of the operating mode switching switch, the second switching action being to switch the operating mode from dual current compensation mode to current voltage compensation mode.

[0069] After completing the above steps, in this step, the second switching action of the operating mode switching switch is determined based on the voltage parameters. The second switching action is to switch the operating mode from dual current compensation mode to current voltage compensation mode.

[0070] Specifically, after the first switching action is completed, the device is in dual current compensation mode. At this time, the second switching action of the working mode switching switch is determined based on the voltage parameters. The second switching action is to switch the working mode from dual current compensation mode to current voltage compensation mode. That is, in this step, the timing of switching the working mode back to current voltage compensation mode is determined based on the voltage parameters.

[0071] Furthermore, Figure 5 A flowchart illustrating the steps of determining the second switching action of the operating mode switching switch based on the voltage parameters is shown, as follows: Figure 5As shown, determining the second switching action of the operating mode switching switch based on the voltage parameters includes the following steps:

[0072] S301, determine the voltage sag based on the voltage parameters.

[0073] In this step, a voltage sag is determined based on the voltage parameters.

[0074] Specifically, voltage sags characterize voltage problems during grid operation. When the voltage drop is large, voltage compensation needs to be provided to the grid.

[0075] S302, determine the second switching action of the operating mode switching switch based on the voltage sag.

[0076] After completing step S301 above, in this step, the second switching action of the operating mode switching switch is determined based on the voltage sag.

[0077] Specifically, when the voltage sag is greater than the second preset threshold, the second switching action is performed to switch the operating mode from dual current compensation mode to current voltage compensation mode; when the voltage sag is not greater than the second preset threshold, the operating mode is kept in dual current compensation mode.

[0078] The second preset threshold can be set according to the operating status of the power distribution network or according to the experience of the operators.

[0079] Figure 6 A schematic diagram of the control flow of the second switching action in this invention is shown. As shown in the figure, when performing the second switching action, the second switch group is first removed from the conduction signal, and after a first preset time, the fourth switch group is turned on; wherein the first preset time can be, for example, 2ms.

[0080] In one specific implementation, the three-phase voltage u of the main winding of a series-parallel hybrid distribution transformer is measured. sabc The phase ωt is obtained through a phase-locked loop. By judging the range of ωt, the corresponding A-phase, B-phase, and C-phase working mode switching switches are turned on, thereby completing the grid commutation and realizing rapid switching of working modes.

[0081] In order to achieve rapid switching of the operating mode switching by quickly reducing the current of the operating mode switching switch to zero, in the first switching action, the second switching group of the operating mode switching switch is turned on at a specific time, so that the current of the fourth switching group of the operating mode switching switch is quickly reduced to zero. In the second switching action, the fourth switching group of the operating mode switching switch is turned on at a specific time, so that the current of the second switching group of the operating mode switching switch is quickly reduced to zero.

[0082] Figure 7 The circuit diagram for switching the operating mode provided by this invention is shown, as follows: Figure 7 As shown, since the switching action is a transient process, the set capacitor voltage does not change during the transient process. Also, considering the converter-side inductance L of the LCL in the filter... 21 Since the current is relatively large, it does not change. The simplified circuit diagram is as follows: Figure 8 As shown.

[0083] The voltage at the outlet of the secondary winding of the main winding of the series-parallel hybrid distribution transformer is:

[0084]

[0085] In the formula, u sa u sb u sc These represent the A-phase voltage, B-phase voltage, and C-phase voltage of the secondary windings of the series-parallel hybrid distribution transformer. N This refers to the effective value of the rated phase voltage of the power distribution system.

[0086] The load can be equivalent to Z L The load impedance angle is Therefore, the load current is:

[0087]

[0088] In the formula, i La i Lb i Lc These are the phase currents of loads in phases A, B, and C, respectively; U N This is the effective value of the rated voltage.

[0089] Upon receiving the operating mode switching command, the current in the fourth switch group of the operating mode switching switch cannot change abruptly. The fifth switch group of the operating mode switching switch is directly turned on. Therefore, based on the relationship between the primary and secondary currents of the coupling transformer T, the current flowing through the fourth switch group of the operating mode switching switch at this time is:

[0090]

[0091] Where N is the autotransformer turns ratio of the hybrid distribution transformer; Ni La Ni Lb Ni Lc The A-phase current, B-phase current, and C-phase current flowing through the working mode switching switch S4.

[0092] If the second switch group is turned on, the voltage across the fourth switch group becomes the voltage at the output of the secondary winding of the main winding of the series-parallel hybrid distribution transformer.

[0093] In order for the voltage and current across the fourth switching group in the working mode switching switch to be out of phase, the following condition must be met within one phase-locked cycle to constitute the turn-off condition:

[0094]

[0095] Solving the above equation yields the following result:

[0096] The time period during which the A-phase switch of the second switch group is turned on causes the A-phase switch of the fourth switch group to be quickly turned off is:

[0097]

[0098] The time period during which the B-phase switch of the second switch group is turned on causes the B-phase switch of the fourth switch group to be quickly turned off is:

[0099]

[0100] The time period during which the C-phase switch of the second switch group is turned on causes the C-phase switch of the fourth switch group to be quickly turned off is:

[0101]

[0102] This shows that when At that time, within one power frequency cycle, when the phase ωt of the phase-locked loop output satisfies (k = 1, 2, 3, 4, 5 and When the power is switched on, the three-phase switches in the second switch group can use the same conduction signal to complete the power grid switching, ensuring rapid switching of operating modes.

[0103] And when At this time, only two phases meet the simultaneous turn-off condition, while the other phase does not. Therefore, the turn-on signal is that two phases turn on first, followed by the other phase. Assume that phases A and B turn on simultaneously, and phase C turns on afterward. The equivalent circuit at this time is as follows: Figure 9 As shown, since the inductor current remains constant, i L2a i L2b i L2c Unchanged, therefore at this time we have

[0104]

[0105] Among them, i 2a i 2b This refers to the current flowing through the second phase A switch and the second phase B switch of the operating mode switching switch. That is, the current Ni in phases A and B at this time. L2a Ni L2bThe current flows through the second A-phase switch and the second B-phase switch of the working mode switching switch and quickly passes through 0. The C-phase current flows to the A and B phases through the neutral point of the coupling transformer, thus the current quickly passes through 0.

[0106] To verify the above results, the load impedance angle was set at [location missing]. hour, System simulation is performed, and the simulation results are as follows: Figure 10 , Figure 11 As shown, from Figure 10 As can be seen from the data, the signal to initiate the first switching action was received at 1.495s; when the load impedance angle is 0°, each phase switch in the second switching group uses the same trigger signal to complete the grid switching, causing the current in the fourth switching group to drop rapidly to 0.

[0107] When the load impedance angle is 70°, if the same trigger signal is used, then as follows: Figure 11 As shown in Figure A, a large short-circuit current is generated, causing damage to the equipment; while as shown in Figure A... Figure 11 As shown in Figure B, based on the phase-locked loop angle range, grid switching can be achieved through the coordination of trigger signals, and the current in the fourth switch group quickly drops to 0.

[0108] When the second switching switch is activated, reactive power compensation is performed before the switchover. Therefore, the current of the second phase A switch, the second phase B switch, and the second phase C switch, which need to be turned off at this time, is:

[0109]

[0110] When a voltage sag occurs, the voltage u of the primary and secondary windings of the series-parallel hybrid distribution transformer... sa u sb u sc Decrease, thus:

[0111]

[0112] Due to u sa u sb u sc The capacitor voltage u decreases. ca u cb u cc The difference remains unchanged, thus causing the product of the differential terms to increase, which in turn increases due to the grid-side inductance L. 22 The smaller current leads to a rapid increase in the rate of change of current, which allows the current to quickly cross zero, thus realizing grid switching.

[0113] In order to utilize the grid commutation caused by the voltage sag without introducing new current branches, it is necessary to delay the conduction of the fourth switch group of the working mode switching switch so that the second switch group of the working mode switching switch can be turned off quickly.

[0114] Figure 12 A schematic diagram of the switching current used to simulate and verify the above results is shown, as follows: Figure 12 As shown in Figure A, a voltage dip occurs at 1.495s, triggering the second switching action signal and removing the trigger signal for the second switching group of the operating mode switching switch. At this time, directly turning on the fourth switching group of the operating mode switching switch would cause a short circuit, preventing rapid switching of the operating mode. Figure 12 As can be seen from B, after the second switch group is turned off, and then the fourth switch group of the working mode switching switch is turned on, the current through the fourth switch group quickly becomes 0.

[0115] The operating mode switching method for a series-parallel hybrid distribution transformer provided by this invention determines a first switching action of the operating mode switching switch based on the current parameters. The first switching action is to switch the operating mode from a current-voltage compensation mode to a dual current compensation mode. A second switching action of the operating mode switching switch is determined based on the voltage parameters. The second switching action is to switch the operating mode from a dual current compensation mode to a current-voltage compensation mode. This method enables smooth switching of the operating modes of the series-parallel hybrid distribution transformer. The switching does not rely on converter control coordination, and it is simple, reliable, and effective.

[0116] To better implement the above methods, a second aspect of this disclosure also provides a working mode switching device for a series-parallel hybrid distribution transformer, which can be integrated into electronic equipment.

[0117] For example, such as Figure 13 As shown, the switching device 200 may include: an acquisition module 210, a first determination module 220, and a second determination module 230, as detailed below:

[0118] Acquisition module 210, the acquisition module is used to acquire power parameters; the power parameters include: current parameters and voltage parameters;

[0119] The first determining module 220 is used to determine a first switching action of the working mode switching switch based on the current parameters. The first switching action is to switch the working mode from the current voltage compensation mode to the dual current compensation mode.

[0120] The second determining module 230 is used to determine a second switching action of the operating mode switching switch based on the voltage parameters. The second switching action is to switch the operating mode from dual current compensation mode to current voltage compensation mode.

[0121] Furthermore, the first determining module 220 includes a first determining unit and a second determining unit, wherein the first determining unit is used to determine an abnormal current state based on the current parameters, and the abnormal current state includes at least harmonics, three-phase current imbalance, and reactive power; the second determining unit is used to determine the first switching action of the working mode switching switch based on the abnormal current state.

[0122] Furthermore, the second determining module 230 includes a third determining unit and a fourth determining unit, wherein the third determining unit is used to determine a voltage sag based on the voltage parameters; and the fourth determining unit is used to determine a second switching action of the operating mode switching switch based on the voltage sag.

[0123] The operating mode switching device for the series-parallel hybrid distribution transformer provided by this invention determines a first switching action of the operating mode switching switch based on the current parameters. The first switching action is to switch the operating mode from current-voltage compensation mode to dual-current compensation mode. A second switching action of the operating mode switching switch is determined based on the voltage parameters. The second switching action is to switch the operating mode from dual-current compensation mode to current-voltage compensation mode. This enables smooth switching of the operating modes of the series-parallel hybrid distribution transformer. The switching does not rely on converter control coordination, and it is simple, reliable, and effective.

[0124] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be performed by instructions, or by instructions controlling related hardware. These instructions can be stored in a computer-readable storage medium and loaded and executed by a processor.

[0125] Therefore, a third embodiment of this disclosure provides a storage medium, which is a computer-readable medium storing a computer program. When executed by a processor, the computer program implements the method provided in the embodiments of this disclosure, including the following steps S11 to S13:

[0126] S11, Obtain power parameters; the power parameters include: current parameters and voltage parameters;

[0127] S12, based on the current parameters, determine the first switching action of the working mode switching switch, the first switching action being to switch the working mode from current voltage compensation mode to dual current compensation mode;

[0128] S13, based on the voltage parameters, determine the second switching action of the operating mode switching switch, the second switching action being to switch the operating mode from dual current compensation mode to current voltage compensation mode.

[0129] Furthermore, when the computer program is executed by a processor, it implements other methods provided in any of the above embodiments of this disclosure.

[0130] The operating mode switching method for a series-parallel hybrid distribution transformer provided by this invention determines a first switching action of the operating mode switching switch based on the current parameters. The first switching action is to switch the operating mode from a current-voltage compensation mode to a dual current compensation mode. A second switching action of the operating mode switching switch is determined based on the voltage parameters. The second switching action is to switch the operating mode from a dual current compensation mode to a current-voltage compensation mode. This method enables smooth switching of the operating modes of the series-parallel hybrid distribution transformer. The switching does not rely on converter control coordination, and it is simple, reliable, and effective.

[0131] The fourth embodiment of this disclosure provides an electronic device, such as... Figure 14 As shown, the electronic device includes at least a memory 310 and a processor 320. The memory 310 stores a computer program, and the processor 320 implements the methods provided in any embodiment of this disclosure when executing the computer program in the memory 310. For example, the method for executing the computer program in the electronic device is as follows:

[0132] S21, Obtain power parameters; the power parameters include: current parameters and voltage parameters;

[0133] S22, based on the current parameters, determine the first switching action of the working mode switching switch, the first switching action being to switch the working mode from current voltage compensation mode to dual current compensation mode;

[0134] S23, based on the voltage parameters, determine the second switching action of the operating mode switching switch, the second switching action being to switch the operating mode from dual current compensation mode to current voltage compensation mode.

[0135] In specific implementation, the above-mentioned acquisition module 210, first determination module 220 and second determination module 230 are all stored in the memory as program units, and the processor executes the above-mentioned program units stored in the memory to realize the corresponding functions.

[0136] The operating mode switching method for a series-parallel hybrid distribution transformer provided by this invention determines a first switching action of the operating mode switching switch based on the current parameters. The first switching action is to switch the operating mode from a current-voltage compensation mode to a dual current compensation mode. A second switching action of the operating mode switching switch is determined based on the voltage parameters. The second switching action is to switch the operating mode from a dual current compensation mode to a current-voltage compensation mode. This method enables smooth switching of the operating modes of the series-parallel hybrid distribution transformer. The switching does not rely on converter control coordination, and it is simple, reliable, and effective.

[0137] The aforementioned storage medium may be included in the aforementioned electronic device; or it may exist independently and not be assembled into the electronic device.

[0138] The aforementioned storage medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to: acquire at least two Internet Protocol (IP) addresses; send a node evaluation request, including at least two IP addresses, to a node evaluation device, wherein the node evaluation device selects an IP address from the at least two IP addresses and returns it; and receive the IP address returned by the node evaluation device; wherein the acquired IP address indicates an edge node in the content delivery network.

[0139] Alternatively, the storage medium may carry one or more programs that, when executed by the electronic device, cause the electronic device to: receive a node evaluation request including at least two Internet Protocol (IP) addresses; select an IP address from the at least two IP addresses; and return the selected IP address; wherein the received IP address indicates an edge node in the content delivery network.

[0140] Computer program code for performing the operations of this disclosure can be written in one or more programming languages ​​or a combination thereof, including but not limited to object-oriented programming languages ​​such as Java, Smalltalk, and C++, as well as conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the passenger's computer, partially on the passenger's computer, as a standalone software package, partially on the passenger's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer can be connected to the passenger's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0141] It should be noted that the storage medium described in this disclosure can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this disclosure, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this disclosure, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium may also be any storage medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the storage medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0142] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0143] The units described in the embodiments of this disclosure can be implemented in software or hardware. The names of the units are not, in some cases, intended to limit the specific unit.

[0144] The functions described above in this document can be performed, at least in part, by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: Field Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application Standard Products (ASSPs), System-on-Chip (SoCs), Complex Programmable Logic Devices (CPLDs), and so on.

[0145] In the context of this disclosure, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium can be, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0146] The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features disclosed in this disclosure that have similar functions.

[0147] Furthermore, while the operations are described in a specific order, this should not be construed as requiring these operations to be performed in the specific order shown or in a sequential order. In certain environments, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of this disclosure. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0148] Although the subject matter has been described using language specific to structural features and / or methodological logic, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are merely illustrative examples of implementing the claims.

[0149] The foregoing has provided a detailed description of several embodiments of this disclosure. However, this disclosure is not limited to these specific embodiments. Those skilled in the art can make various variations and modifications based on the concept of this disclosure, and all such variations and modifications should fall within the scope of protection claimed by this disclosure.

Claims

1. A method for switching the operating modes of a series-parallel hybrid distribution transformer, characterized in that, The series-parallel hybrid distribution transformer includes: a transformer winding, a parallel converter, a series converter, a working mode switching switch, a coupling transformer, a filter, and a control device. The working mode switching switch includes a first switch group, a second switch group, a third switch group, a fourth switch group, and a fifth switch group. The first switch group is located between the parallel converter and the transformer winding; the second switch group is located between the parallel converter and the coupling transformer; the third switch group is located between the parallel converter and the coupling transformer; the fourth switch group is located between the series converter and the coupling transformer; and the fifth switch group is located between the coupling transformer and the low-voltage port. The parallel converter and the series converter are connected to the transformer winding and the coupling transformer, respectively, via the working mode switching switch. The working modes include a current-voltage compensation mode and a dual-current compensation mode. The working mode switching method includes the following steps: Obtain power parameters; the power parameters include: current parameters and voltage parameters; Based on the current parameters, a first switching action of the operating mode switching switch is determined, wherein the first switching action is to switch the operating mode from current voltage compensation mode to dual current compensation mode. Based on the voltage parameters, a second switching action of the operating mode switching switch is determined, wherein the second switching action is to switch the operating mode from dual current compensation mode to current voltage compensation mode. The first switching action of determining the operating mode switching switch based on the current parameter includes: The abnormal current state is determined based on the current parameters, and the abnormal current state includes at least harmonics, three-phase current imbalance, and reactive power. Based on the abnormal current state, the first switching action of the operating mode switching switch is determined, including: When the abnormal current state is greater than the first preset threshold, the first switching action is performed to switch the working mode from the current voltage compensation mode to the dual current compensation mode. When the abnormal current state is not greater than the first preset threshold, the working mode is kept as the current-voltage compensation mode. The second switching action of determining the operating mode switching switch based on the voltage parameters includes: The voltage sag is determined based on the voltage parameters; The second switching action of the operating mode switching switch is determined based on the voltage sag, including: When the voltage drop exceeds the second preset threshold, the second switching action is performed to switch the operating mode from dual current compensation mode to current voltage compensation mode. When the voltage sag is not greater than the second preset threshold, the operating mode remains the dual current compensation mode.

2. The method for switching the operating mode of a series-parallel hybrid distribution transformer according to claim 1, characterized in that, The second switching action includes: removing the second switch group's conduction signal, delaying for a first preset time, and then conducting the fourth switch group.

3. The method for switching the operating mode of a series-parallel hybrid distribution transformer according to claim 1, characterized in that, Performing the first switching action includes: Determine whether the conduction of the second switch group will cause the fourth switch group to turn off; The first switching action is determined based on the judgment result.

4. The method for switching the operating mode of a series-parallel hybrid distribution transformer according to claim 3, characterized in that, Performing the first switching action includes: Determine whether the conduction of each switch in the second switch group will cause the corresponding phase switch in the fourth switch group to be turned off; The first switching action is determined based on the judgment result.

5. A working mode switching device for a series-parallel hybrid distribution transformer, implemented using the working mode switching method for a series-parallel hybrid distribution transformer as described in any one of claims 1-4, characterized in that, The series-parallel hybrid distribution transformer includes: a transformer winding, a parallel converter, a series converter, a working mode switching switch, a coupling transformer, a filter, and a control device. The working mode switching switch includes a first switch group, a second switch group, a third switch group, a fourth switch group, and a fifth switch group. The first switch group is located between the parallel converter and the transformer winding; the second switch group is located between the parallel converter and the coupling transformer; the third switch group is located between the parallel converter and the coupling transformer; the fourth switch group is located between the series converter and the coupling transformer; and the fifth switch group is located between the coupling transformer and the low-voltage port. The parallel converter and the series converter are connected to the transformer winding and the coupling transformer, respectively, via the working mode switching switch. The working modes include a current-voltage compensation mode and a dual-current compensation mode. The working mode switching device includes: The acquisition module is used to acquire power parameters, including current parameters and voltage parameters. The first determining module is used to determine the first switching action of the working mode switching switch based on the current parameters. The first switching action is to switch the working mode from the current voltage compensation mode to the dual current compensation mode. The second determining module is used to determine a second switching action of the operating mode switching switch based on the voltage parameters. The second switching action is to switch the operating mode from dual current compensation mode to current voltage compensation mode.

6. A storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the operating mode switching method for the series-parallel hybrid distribution transformer as described in any one of claims 1 to 4.

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