Voltage transformation device and flexible interconnection power distribution system

Abstract

The invention relates to a voltage transformation device and a flexible interconnection power distribution system, and the device comprises a voltage transformation module which comprises a main transformer winding and a series transformer winding, and the high-voltage side of the main transformer winding is connected with the high-voltage side of the series transformer winding in series; the low-voltage side of the main transformer winding is connected with a load; the low-voltage side of the series transformer winding is used as an access end of voltage compensation; one end of the series module is connected to the low-voltage side of the series transformer winding, and the series module is used for collecting voltage on the load side and injecting compensation voltage to the low-voltage side of the series transformer winding so as to adjust the voltage on the load side; one end of the parallel module is connected with the other end of the series module, and the other end of the parallel module is used for being connected with a load and used for collecting current on the load side and injecting compensation current into the load side so as to adjust the current on the load side. By adopting the method and the device, the flexibility and better response capability can be realized when the complicated and changeable operation conditions are dealt with.

Description

Technical Field

[0001] This application relates to the field of electronic power technology, and in particular to a transformer device and a flexible interconnected power distribution system. Background Technology

[0002] In the fields of power system and power electronics technology, especially in the scenarios of power quality control and flexible power allocation in distribution networks, the Hybrid Power Electronic Transformer (HPET), as a novel device that integrates the advantages of traditional transformers and power electronic converters, is receiving widespread attention. Through a partial power electronic converter stage, it achieves rapid and independent control of active and reactive power, providing a potentially effective solution to problems such as voltage fluctuations and harmonics caused by distributed energy grid connection and impulsive load access.

[0003] However, existing hybrid power electronic transformer designs often employ simplified or partially replaced power electronic topologies in order to balance cost and performance. This structural simplification lacks flexibility and responsiveness when dealing with complex and ever-changing operating conditions. Summary of the Invention

[0004] Therefore, it is necessary to provide a transformer and flexible interconnected power distribution system that can improve flexibility and responsiveness under complex operating conditions to address the aforementioned technical problems.

[0005] In a first aspect, embodiments of this application provide a transformer device, the transformer device comprising: The transformer module includes a main transformer winding and a series transformer winding. The high-voltage side of the main transformer winding and the high-voltage side of the series transformer winding are connected in series. The low-voltage side of the main transformer winding is used to connect the load. The low-voltage side of the series transformer winding serves as the access terminal for voltage compensation. The series module is connected at one end to the low-voltage side of the series transformer winding. It is used to collect the load side voltage and adjust the load side voltage by injecting compensation voltage into the low-voltage side of the series transformer winding. The parallel module connects to the other end of the series module, and the other end of the parallel module is used to connect to the load. It is used to collect the current on the load side and adjust the current on the load side by injecting compensation current into the load side.

[0006] In one embodiment, the series module and the parallel module are electrically connected via a DC bus; Parallel modules are used to supply or absorb power from the DC bus to support voltage compensation by series modules.

[0007] In one embodiment, the series module includes a voltage source inverter unit, and the parallel module includes a current source converter unit. Voltage source inverter units are used to convert the DC bus voltage into a compensation voltage. Current source converter units are used to generate compensation current.

[0008] In one embodiment, the main transformer winding and the series transformer winding are integrated in the same transformer tank and wound on the same iron core.

[0009] In one embodiment, the transformer also includes a bypass module; One side of the series module is connected to the low-voltage side of the series transformer winding via a bypass module; The bypass module is used to activate in the event of a failure of the series module in order to maintain continuous power supply to the load.

[0010] In one embodiment, the bypass protection unit includes a reverse parallel thyristor group and a switch branch; The reverse parallel thyristor group is connected in parallel with the switch.

[0011] In one embodiment, the transformer further includes: The maintenance isolation module includes a manual bypass isolating switch connected in parallel to the low-voltage side circuit of the series transformer winding.

[0012] In one embodiment, the manual disconnect switch includes: a rotary disconnect switch or a knife-type disconnect switch.

[0013] In one embodiment, the maintenance isolation module further includes: A series-side disconnect switch is connected in series with a series module. The parallel-side incoming line switch is connected in series in the incoming line circuit of the parallel module.

[0014] In one embodiment, the transformer further includes: The integrated power distribution module provides control power to series and parallel modules and has an external DC interface.

[0015] Secondly, this application also provides a flexible interconnected power distribution system, the system comprising: At least two transformers as described above; The external DC interfaces of the two transformers are connected through a common DC bus.

[0016] The transformer and flexible interconnected power distribution system provided in this application employ an electromagnetic structure in which the main transformer winding and the series transformer winding are connected in series on the high-voltage side, and are configured with independent series and parallel modules respectively. This transformer achieves the decoupling and integration of voltage regulation and current control functions, improving flexibility and responsiveness when dealing with complex and changing operating conditions. Voltage and current compensation can be started independently or jointly as needed, enabling the device to quickly respond to grid voltage fluctuations and load current changes, and perform precise comprehensive power quality management, thereby enhancing the adaptability and control capability of the distribution network to intermittent new energy sources and fluctuating and nonlinear loads. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a transformer device provided in an embodiment of this application; Figure 2 A schematic diagram of a transformer device including a bypass module provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a hybrid power electronic transformer provided in an embodiment of this application; Figure 4 This is a schematic diagram of a hybrid power electronic transformer AC / DC flexible interconnection power distribution system provided in an embodiment of this application. Detailed Implementation

[0019] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0020] Unless otherwise defined, 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. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0021] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0022] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0023] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0024] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0025] As the global energy structure accelerates its transformation towards cleaner and lower-carbon energy sources, distributed energy such as photovoltaic power generation, wind power generation, and energy storage power stations are experiencing explosive growth. According to statistics from the International Renewable Energy Agency (IRENA), the average annual growth rate of global distributed energy installed capacity has exceeded 20% in the past decade. The large-scale integration of distributed power sources into the distribution network is transforming the traditional radial grid structure into a complex multi-source network. Simultaneously, the proportion of nonlinear and impulsive loads, represented by data centers, electric vehicle charging stations, and variable frequency air conditioners, continues to rise. In 2023, the proportion of nonlinear loads in my country's industrial sector reached 38%. This diversified load characteristic exacerbates power quality problems such as grid voltage fluctuations and harmonic pollution. The rigid interconnection mode of traditional power systems, based on circuit breakers and disconnectors, reveals drawbacks when facing intermittent output from new energy sources and dynamic load changes. These drawbacks include slow power quality control response speed (response time reaching hundreds of milliseconds), lack of flexibility in power distribution, and excessively large fault isolation ranges, making it difficult to meet the coordinated operation requirements of modern power grids encompassing "source-grid-load-storage."

[0026] Against this backdrop, traditional distribution transformers, due to their inherent physical structure and working principle, exhibit significant limitations in dealing with complex and ever-changing operating conditions, particularly lacking sufficient flexibility and responsiveness in areas such as power flow regulation, voltage control, and fault isolation.

[0027] Based on this, this application provides a transformer device, which can serve as a novel power conversion device. Its advantages, such as high controllability and high-efficiency conversion, offer a new technical approach to solving the aforementioned problems. The transformer device can be a hybrid power electronic transformer, which, through power electronic conversion technology, enables independent control of active and reactive power and flexible energy transfer between different voltage levels. This demonstrates its great potential in improving the operational performance of power distribution networks.

[0028] In one exemplary embodiment, Figure 1 This is a schematic diagram of the structure of a transformer device provided in an embodiment of this application, as shown below. Figure 1 As shown, the transformer device includes a transformer module 10, a series module 20, and a parallel module 30, wherein: The transformer module 10 includes a main transformer winding 110 and a series transformer winding 120. The high-voltage side of the main transformer winding 110 and the high-voltage side of the series transformer winding 120 are connected in series. The low-voltage side of the main transformer winding 110 is used to connect the load 40. The low-voltage side of the series transformer winding 120 serves as the access terminal for voltage compensation. The series module 20 is connected at one end to the low-voltage side of the series transformer winding 120. It is used to collect the load side voltage and adjust the load side voltage by injecting compensation voltage into the low-voltage side of the series transformer winding 120. The parallel module 30 is connected at one end to the other end of the series module 20. The other end of the parallel module 30 is used to connect to the load 40, to collect the current on the load side, and to adjust the current on the load side by injecting compensation current into the load side.

[0029] The transformer module 10 refers to the core electromagnetic energy conversion component of a hybrid power electronic transformer, used to realize the conversion and transmission of electrical energy between different voltage levels. The main transformer winding 110 refers to the winding section of the transformer module 10 that undertakes the basic voltage conversion and main power transmission tasks. The high-voltage side of the main transformer winding 110 is used to connect to the distribution network, and the low-voltage side of the main transformer winding 110 is used to directly supply electrical energy to the electrical load 40. The series transformer winding 120 refers to the winding section of the transformer module 10 dedicated to dynamic voltage regulation. The high-voltage side of the series transformer winding 120 is connected in series with the high-voltage side of the main transformer winding 110 for voltage coupling, and the low-voltage side of the series transformer winding 120 can serve as the injection port for controlled compensation voltage. The series module 20 refers to a set of power conversion circuits based on power electronic devices, used to monitor the load-side voltage in real time and generate a controllable AC compensation voltage. The parallel module 30 refers to another set of power conversion circuits based on power electronic devices, used to monitor the load-side current in real time and generate a controllable AC compensation current.

[0030] For example, transformer module 10 can be encapsulated in a separate transformer housing. The high-voltage side input terminal of main transformer winding 110 is connected to the power grid input line via high-voltage bushings and cables, and the low-voltage side output terminal of main transformer winding 110 is connected to the load 40 distribution bus via a low-voltage busbar. The high-voltage side of series transformer winding 120 is electrically connected in series with the high-voltage side of main transformer winding 110, i.e., they are connected end-to-end; the low-voltage side of series transformer winding 120 is connected to the AC output terminal of series module 20 via wires. The DC side of series module 20 is connected to an internal DC bus, and its AC output terminal is connected to the low-voltage side of series transformer winding 120; the voltage sensor of series module 20 can be connected to the load side via a signal line to collect voltage signals. The DC side of parallel module 30 is connected to the same internal DC bus, and the AC side of parallel module 30 is connected to the load side via a reactor or filter; the current sensor of parallel module 30 is connected to the load side via a signal line to collect current signals.

[0031] Specifically, through the aforementioned connection structure, this transformer can independently or collaboratively manage the voltage and current quality on the load side. When a voltage drop, surge, or imbalance occurs on the load side, the series module 20, based on the acquired voltage signal, adjusts the on / off state of its internal power electronic switching devices to generate a compensation voltage with controllable amplitude and phase, and injects this compensation voltage into the low-voltage side of the series transformer winding 120. Since the high-voltage side of the series transformer winding 120 is connected in series with the high-voltage side of the main transformer winding 110, the injected compensation voltage is coupled to the high-voltage side via electromagnetic induction and superimposed on the grid voltage, thereby changing the induced voltage on the low-voltage side of the main transformer winding 110, achieving precise and rapid regulation of the voltage at the load 40 terminal. When reactive current, harmonic current, or unbalanced current occurs on the load side, the parallel module 30, based on the acquired current signal, generates a compensation current with equal amplitude but opposite phase, and directly injects it into the connection point of the load 40, thereby canceling out the bad current components and purifying the current of the load 40.

[0032] As an example, the transformer includes a main transformer winding 110 and a series transformer winding 120. A series module 20 is connected to the low-voltage side of the series transformer winding 120, and a parallel module 30 is connected in parallel to the load side. When the system only needs to address voltage issues, the series module 20 is activated; when the system only needs to address current issues, the parallel module 30 is activated.

[0033] In this embodiment, by employing an electromagnetic structure in which the main transformer winding 110 and the series transformer winding 120 are connected in series on the high-voltage side, and by configuring independent series modules 20 and parallel modules 30 respectively, the transformer device achieves the decoupling and integration of voltage regulation and current control functions, improving flexibility and responsiveness when dealing with complex and changing operating conditions. Voltage and current compensation can be started independently or jointly as needed, enabling the device to quickly respond to grid voltage fluctuations and load current changes, and to perform precise comprehensive power quality management, thereby enhancing the distribution network's adaptability and control capabilities for intermittent new energy sources and fluctuating, nonlinear loads.

[0034] In one exemplary embodiment, the series module and the parallel module are electrically connected via a DC bus; Parallel modules are used to supply or absorb power from the DC bus to support voltage compensation by series modules.

[0035] The DC bus refers to a common conductive path used to transmit DC power between series and parallel modules, and can be composed of a positive busbar and a negative busbar. Providing power refers to the parallel modules acting as DC power sources, converting the active power they obtain from the AC side into DC power and supplying it to the DC bus. Absorbing power refers to the parallel modules acting as DC loads, obtaining DC power from the DC bus and converting it into AC power to feed back to the grid or supply local loads.

[0036] For example, the DC bus can be a set of parallel copper busbars installed in the distribution box of the device. The positive and negative terminals of the DC side of the series modules are connected to the positive and negative terminals of the DC bus via cables. The positive and negative terminals of the DC side of the parallel modules are also connected to the positive and negative terminals of the same set of DC buses via cables. A supporting capacitor bank is usually connected in parallel to the DC bus to stabilize the bus voltage and filter out ripple.

[0037] Specifically, the series and parallel modules, connected via a DC bus, form a back-to-back converter system sharing a common DC bus. When the series module needs to consume active power to perform voltage compensation (e.g., when it needs to output in-phase voltage during voltage sag compensation), the required energy can be obtained from the DC bus. At this time, the parallel module can operate in rectification mode, absorbing active power from the grid and transferring it to the series module via the DC bus. Conversely, when the series module generates excess energy (e.g., when it absorbs energy during voltage surge compensation), the energy can be transferred to the parallel module via the DC bus, and then inverted back to the grid by the parallel module. This structure enables real-time energy exchange and support between the two modules.

[0038] As an example, when managing voltage conditions, the series-side module needs to draw power from the parallel side, that is, obtain DC power from the parallel module through the DC bus to generate the required compensation voltage.

[0039] In this embodiment, the power interconnection between series and parallel modules is achieved through a DC bus, constructing an internal energy buffer and scheduling channel. This improves flexibility and responsiveness when dealing with complex and changing operating conditions. When voltage compensation requires instantaneous high-power support, the parallel module can quickly provide energy through the DC bus, ensuring the dynamic response speed and deep compensation capability of voltage regulation, thereby improving the device's efficiency and reliability in dealing with severe grid fluctuations.

[0040] In one exemplary embodiment, the series module includes a voltage source inverter unit, and the parallel module includes a current source converter unit. Voltage source inverter units are used to convert the DC bus voltage into a compensation voltage. Current source converter units are used to generate compensation current.

[0041] Among them, a voltage source inverter unit refers to a power electronic inverter that adopts a voltage source topology, with a supporting capacitor connected in parallel on the DC side to maintain voltage stability, and an AC side that can output a voltage waveform with controllable amplitude and phase. A current source converter unit refers to a power electronic converter that adopts a current source topology or a voltage source topology but is controlled in current output mode, and its output can quickly and accurately track the current command signal.

[0042] For example, a voltage source inverter unit can be composed of a full-bridge or half-bridge insulated-gate bipolar transistor module, a DC-side capacitor, and an AC-side filter inductor. A current source converter unit can also be composed of an insulated-gate bipolar transistor module, a DC-side support capacitor, and an AC-side filter inductor, but its control strategy aims to achieve current control.

[0043] Specifically, the voltage source inverter unit receives voltage commands from the controller and, through pulse width modulation (PWM) technology, inverts the stable DC voltage on the DC bus into an AC compensation voltage with the required frequency, amplitude, and phase. The current source converter unit can receive current commands from the controller and, through current closed-loop control technology (such as hysteresis control, proportional-integral resonant control, etc.), generates a compensation current waveform consistent with the commands, which cancels out the unwanted current components on the load side.

[0044] As an example, the series-side module transmits the acquired voltage signal to the digital signal processor (DSP) core control unit, which calculates and generates a pulse width modulation (PWM) duty cycle command to control the insulated-gate bipolar transistor (IGBT) switch in the voltage source inverter unit to output a compensation voltage. The parallel-side module analyzes the acquired current signal, separates the current component to be compensated through real-time digital computation, and controls the IGBT switch in the current source converter unit to output a compensation current.

[0045] In this embodiment, by configuring voltage source inverter units and current source converter units for the series and parallel modules respectively, the converter types and control modes best suited to their respective functions are adopted, improving flexibility and responsiveness when dealing with complex and changing operating conditions. Voltage source units facilitate precise control of the output voltage amplitude and phase, making them suitable for stable voltage regulation; current source units excel at quickly and accurately tracking current commands, making them suitable for dynamic current compensation, thereby synergistically improving the overall compensation accuracy and response speed of the device.

[0046] In one exemplary embodiment, the main transformer winding and the series transformer winding are integrated in the same transformer tank and wound on the same iron core.

[0047] In this context, the transformer oil tank refers to a sealed metal container filled with insulating and cooling media (such as transformer oil) to house and protect the transformer windings and core. The same core can refer to a complete closed magnetic circuit structure made of laminated silicon steel sheets.

[0048] For example, the main transformer winding and the series transformer winding can be concentrically wound on the same core column, or wound separately on different core columns of the core but forming a closed magnetic circuit through the yoke. The entire core and winding assembly is immersed in the insulating oil of the transformer tank. Insulating bushings for the high and low voltage windings are installed on the tank shell.

[0049] Specifically, the main transformer winding and the series transformer winding share the same core magnetic circuit, resulting in high magnetic flux coupling between the two. When a compensation voltage is injected onto the low-voltage side of the series transformer winding, the resulting change in magnetic flux can be efficiently coupled to the main transformer winding, thereby affecting its output voltage. The integrated design reduces air gaps and leakage flux in the magnetic circuit, lowering no-load losses and stray losses.

[0050] As an example, this structure achieves high integration by sharing a core and the same oil tank, which significantly reduces the size and material cost of the device, while reducing magnetic leakage loss due to the shared magnetic circuit.

[0051] In this embodiment, by integrating the main transformer winding and the series transformer winding into the same oil tank and wound on the same iron core, a high degree of integration in the physical structure and electromagnetic coupling of the device is achieved, improving flexibility and responsiveness when dealing with complex and changing operating conditions. The compact design saves installation space, and the tight magnetic coupling ensures that the compensation voltage can be efficiently and without hysteresis transmitted to the main circuit, thereby improving the response speed of voltage regulation and overall energy efficiency.

[0052] In one exemplary embodiment, Figure 2 This application provides a schematic diagram of the structure of a transformer device including a bypass module, as shown in the embodiment of the present application. Figure 2 As shown, the transformer also includes a bypass module; One side of the series module is connected to the low-voltage side of the series transformer winding via a bypass module; The bypass module is used to activate in the event of a failure of the series module in order to maintain continuous power supply to the load.

[0053] The bypass module can refer to an automatic or controlled circuit switching device used to quickly isolate the main power circuit unit from the main circuit and connect the backup path when the main power circuit unit fails, so as to ensure that the system output is not interrupted.

[0054] For example, the bypass module can be connected across the AC output terminal of the series module and the connection point on the low-voltage side of the series transformer winding. Under normal operation, the bypass module is in a high-blocking open state. When a fault is detected, a control signal triggers the bypass module to switch to a low-impedance on state, thereby providing a path for current to bypass the series module.

[0055] Specifically, when the control unit detects overcurrent, overtemperature, drive failure, or DC bus abnormality in the series module, it immediately blocks all drive pulses of the series module, causing it to stop working. Subsequently, it issues an activation command to the bypass module, causing it to conduct within a very short time, short-circuiting the series module. In this way, the load current flows through the path formed by the bypass module, via the series transformer windings, and the main transformer windings continue to supply power to the load, achieving continuity of power supply.

[0056] As an example, in bypass mode, if a fault is detected in its own power module, the drive signal of the series-connected power module is first blocked, then the bypass module is controlled to connect an inductor branch, while the relevant isolating switch is disconnected. Since the switching speed of electronic devices is in the microsecond range, much faster than the millisecond-level switching speed of mechanical switches, the normal power supply to the load is not affected, achieving uninterrupted system maintenance.

[0057] In this embodiment, by setting a bypass module, the transformer can achieve seamless switching and uninterrupted power supply when the core compensation module fails. This improves flexibility and responsiveness when dealing with complex and ever-changing operating conditions, thereby enhancing the reliability and availability of the transformer and ensuring that critical loads can obtain continuous power under any circumstances, meeting the needs of high-reliability power supply applications.

[0058] In one exemplary embodiment, the bypass protection unit includes a reverse parallel thyristor group and a switch branch; The reverse parallel thyristor group is connected in parallel with the switch.

[0059] Among them, a reverse parallel thyristor group refers to a combination of two thyristors connected in parallel with their anodes facing each other and their cathodes facing each other, enabling bidirectional conduction of alternating current. A switching branch refers to a mechanical switching device, such as a contactor or circuit breaker, used to carry long-term steady-state current.

[0060] For example, the two external terminals of the anti-parallel thyristor group are connected to the output terminal of the series module and the connection point on the low-voltage side of the series transformer winding, respectively. A switching branch (such as an AC contactor) is installed in parallel with the anti-parallel thyristor group, meaning its two main contacts are also connected to the aforementioned two points. The control circuit is connected to the gate drive circuit of the thyristors and the coil circuit of the contactor, respectively.

[0061] Specifically, when bypassing is required, the control strategy can be trigger-then-close. First, a trigger pulse is sent to the reverse-parallel thyristor group to turn it on. Since it is a semi-controlled device, it can maintain conduction even after the pulse is removed until the current crosses zero. Because the thyristor conducts extremely quickly (on the order of microseconds), the current is instantly transferred to the thyristor branch. Subsequently, the closing switch branch (contactor) is controlled. During the closing process, the voltage difference across the contacts of the contactor is very small, thus achieving arc-free or weak-arc closing. After the contactor is fully closed, a turn-off signal can be sent to cause the thyristor to turn off naturally when the current crosses zero, after which the current is carried by the contactor.

[0062] As an example, the bypass module includes devices such as contactors (as switching branches) and anti-parallel thyristor groups, which can perform fast, arc-free bypass switching in the event of a power electronic module failure.

[0063] In this embodiment, by employing a hybrid structure of reverse-parallel thyristor groups and mechanical switch branches in parallel, the bypass protection unit combines the advantages of rapid switching of power electronic devices and low conduction losses of mechanical switches, improving flexibility and responsiveness in the face of complex and changing operating conditions. This design ensures the speed, safety, and long-term economic efficiency of the fault bypass process.

[0064] In one exemplary embodiment, the transformer further includes: The maintenance isolation module includes a manual bypass isolating switch connected in parallel to the low-voltage side circuit of the series transformer winding.

[0065] Among them, a maintenance isolation module can refer to a set of mechanically operated switches that provide electrical safety isolation for equipment inspection and maintenance. A manual bypass disconnect switch refers to a switching device that requires direct manual operation and has a clearly visible disconnect point, used to establish a reliable air insulation gap during maintenance.

[0066] For example, a manual bypass disconnect switch can be connected in series in the connection between the low-voltage side of the series transformer winding and the series module. Its operating handle and status indicator are usually mounted on the housing of the device or the panel of the distribution box for easy observation and operation by the operator. When the moving and stationary contacts inside the switch separate, a visible physical break is formed.

[0067] Specifically, when maintenance is required on series modules, series transformer windings, or related connections, operators must first stop the machine and ensure the equipment is de-energized. Then, they must manually operate the disconnecting switch to the open position. At this point, the switch contacts separate, creating a safe air insulation distance between the isolated circuit segment and the energized parts, thus providing a safe working environment for maintenance personnel.

[0068] As an example, the maintenance unit includes a manual bypass isolating switch QS1, which disconnects when the power module is damaged and requires maintenance. This creates a clear break in the low-voltage side circuit of the transformer winding, ensuring the safety of maintenance personnel.

[0069] In this embodiment, by setting a manual bypass isolating switch, the maintenance isolation module provides an intuitive and reliable physical isolation method for equipment maintenance, improving flexibility and responsiveness when dealing with complex and changing operating conditions. This fundamentally eliminates the risk of accidental electric shock during maintenance, complies with electrical safety regulations, and enhances the maintainability and operational safety of the device.

[0070] In one exemplary embodiment, the manual disconnect switch includes: a rotary disconnect switch or a knife-type disconnect switch.

[0071] Rotary disconnect switches refer to those that use a rotating operating handle to rotate the internal moving contact, thereby connecting or disconnecting it from the stationary contact. Knife-type disconnect switches refer to those that use a knife-shaped moving contact to move up and down or left and right, engaging or disengaging from a clamp-shaped stationary contact to achieve on / off switching.

[0072] For example, rotary disconnect switches typically have a circular operating handle that can be rotated a certain angle (such as 90 degrees) to open or close the circuit. They are compact in structure and require less operating torque. Knife-type disconnect switches typically have a lever-type operating handle that is operated by moving it up and down. When disconnected, a clear vertical or horizontal break is formed between the moving and stationary contacts, providing a clearer visual indication.

[0073] Specifically, both types of disconnect switches meet the safety requirements for forming a clear disconnection point. Users can choose based on factors such as the internal space layout of the distribution box, operating habits, and cost. Both types have a mechanical self-locking function to prevent displacement due to vibration or accidental contact.

[0074] As an example, the manual bypass disconnect switch QS1 can be selected as either knife-type or rotary type depending on the installation space, and its core function is to provide a visible electrical isolation break.

[0075] In this embodiment, by providing two common manual disconnect switch options—rotary and knife switch—the maintenance isolation module can flexibly adapt to different product design requirements and field installation conditions, improving flexibility and responsiveness when dealing with complex and changing operating conditions. This enhances the device's versatility and user-friendliness, ensuring safe and convenient maintenance isolation in various application scenarios.

[0076] In one exemplary embodiment, the maintenance isolation module further includes: A series-side disconnect switch is connected in series with a series module. The parallel-side incoming line switch is connected in series in the incoming line circuit of the parallel module.

[0077] Among them, a series-side disconnect switch refers to a switching device specifically designed to completely isolate a series module from its connecting circuit during maintenance. A parallel-side incoming line switch refers to a switching device designed to completely isolate a parallel module from its AC incoming line side during maintenance.

[0078] For example, the series-side disconnect switch can be installed in series between the AC output terminal of the series module and the connection point of the bypass module. The parallel-side incoming switch can be installed in series between the AC input terminal of the parallel module and the connection point of the load side or the power grid side. These switches can also be manually operated disconnect switches or load disconnect switches with a certain arc-extinguishing capability.

[0079] Specifically, this multi-switch configuration provides more refined maintenance isolation. When only the series module needs maintenance, the series-side disconnect switch and the manual bypass disconnect switch can be disconnected to isolate the series module from both the input and output sides. When only the parallel module needs maintenance, the parallel-side incoming switch can be disconnected to ensure that the parallel module is isolated from all AC energized parts. This allows for independent maintenance of individual functional modules without affecting the integrity of other parts of the device or potentially restricting subsequent operation.

[0080] As an example, the maintenance unit also includes a series-side disconnect switch QS2 and a parallel-side module incoming switch QF1, which, together with the manual bypass disconnect switch QS1, can form multiple safety breakpoints for specific modules in different maintenance scenarios.

[0081] In this embodiment, by adding a series-side isolating switch and a parallel-side incoming switch, the maintenance isolation module achieves modular and refined isolation capabilities for each power unit within the device, improving flexibility and responsiveness when dealing with complex and changing operating conditions. This significantly enhances the targeted nature and safety of maintenance work, supports more flexible operation and maintenance strategies, and reduces the impact of maintenance work on the overall system availability.

[0082] In some exemplary embodiments, Figure 3 A schematic diagram of a hybrid power electronic transformer provided in this application embodiment is shown below. Figure 3 As shown, this hybrid power electronic transformer can be used as a specific implementation of the transformer device provided in the embodiments of this application.

[0083] Wherein: T1 and T2 represent transformer windings, with T1 being the high-voltage side of the main transformer winding and T2 being the high-voltage side of the series transformer winding, and the two are connected in series; T3 is the low-voltage side of the main transformer winding and T4 is the low-voltage side of the series transformer winding, and the low-voltage sides of the two are independent.

[0084] QS1 is a bypass disconnect switch, used to switch to bypass mode during faults or maintenance. QS2 is a series-side disconnect switch, used to isolate series-side modules. QF1 is a parallel-side incoming switch, controlling the connection and disconnection of parallel-side modules. The load refers to the load side powered by the transformer. The bypass module can be composed of devices such as thyristors, enabling rapid switching (microsecond response) during faults. The series-side module can be used to collect load voltage and current for voltage regulation and power quality management. The parallel-side module can collect load current for reactive power compensation, current balance control, and other functions.

[0085] In one exemplary embodiment, the transformer further includes: The integrated power distribution module provides control power to series and parallel modules and has an external DC interface.

[0086] The integrated power distribution module refers to an electrical assembly unit that integrates low-voltage auxiliary power distribution, circuit protection, signal interfaces, and external expansion interfaces. The control power supply refers to the low-voltage DC or AC power required for the operation of controllers, drivers, sensors, and cooling fans within the series or parallel modules. The external DC interface refers to a standardized electrical connection port used to connect the internal DC bus of the device to external DC equipment or a DC network.

[0087] For example, the integrated power distribution module can be a standalone electrical enclosure, internally housing a switching power supply module, miniature circuit breakers, fuses, terminal blocks, and communication modules. The input of the switching power supply is taken from the low-voltage side of the transformer or an external auxiliary power source, and it outputs multiple regulated DC power supplies. The external DC interface typically includes positive and negative DC busbars or sockets, and is connected to the internal DC busbars via DC circuit breakers or contactors.

[0088] Specifically, the integrated power distribution module centrally manages the power supply of all secondary circuits, simplifying internal wiring. Its external DC interface greatly expands the device's application scenarios. For example, the DC output of a photovoltaic power generation system, the DC port of an energy storage battery system, or a DC charging pile can be directly connected to this interface, making the device a key node in a hybrid AC / DC power distribution network.

[0089] As an example, the distribution box contains a power distribution unit that not only provides power to components such as bypass modules, series modules, and parallel modules, but also has a dedicated external DC port for easy connection to distributed DC loads.

[0090] In this embodiment, by integrating a unified power distribution module and providing an external DC interface, the transformer device achieves centralized management of auxiliary power supply and scalability of system functions, improving flexibility and responsiveness when dealing with complex and changing operating conditions. This simplifies system integration, facilitates plug-and-play functionality for DC-type equipment such as new energy sources and energy storage, and supports the construction of a more flexible and efficient smart power distribution network architecture.

[0091] In one exemplary embodiment, this application also provides a flexible interconnected power distribution system, the system comprising: At least two transformers as described above; The external DC interfaces of the two transformers are connected through a common DC bus.

[0092] The flexible interconnected power distribution system refers to a power distribution network system with flexible power dispatching capabilities, which consists of multiple transformer devices as nodes interconnected through a DC network. The common DC bus refers to one or more shared DC conductive channels connecting the DC interfaces of all interconnected nodes in the system.

[0093] For example, each transformer's external DC interface is connected to a common DC bus via cable or copper busbar. The common DC bus can be laid in cable trenches or busbar ducts and can extend to multiple distribution substations. Photovoltaic DC combiner boxes, the DC side of energy storage converters, DC loads, and other equipment can also be connected in parallel to the common DC bus. The system can be configured with a central monitoring unit or employ a distributed control strategy to coordinate the operation of each node.

[0094] Specifically, through a common DC bus, electrical energy can be efficiently transmitted in DC form between different transformers (corresponding to different AC distribution substations). When one substation has a heavy load while another has surplus power, power can flow from the lightly loaded substation to the heavily loaded substation through the common DC bus, achieving load balancing and mutual assistance between substations. Furthermore, distributed energy storage systems connected to the common DC bus can serve as a shared resource, providing peak shaving, valley filling, and emergency support services to all interconnected substations.

[0095] As an example, Figure 4 A schematic diagram of a hybrid power electronic transformer AC / DC flexible interconnection power distribution system provided in this application embodiment is shown below. Figure 4 As shown, Figure 3 The AC and DC ports (i.e. external DC interfaces) of the two hybrid power electronic transformers are interconnected, and their DC sides can also be connected to photovoltaic, energy storage and charging pile equipment to build a flexible AC and DC power distribution system.

[0096] In this embodiment, by flexibly interconnecting multiple transformer devices via a common DC bus, a power distribution system capable of flexible energy dispatch and resource sharing across distribution areas is constructed, improving flexibility and responsiveness in the face of complex and ever-changing operating conditions. This system overcomes the power flow control bottleneck of traditional AC distribution networks, optimizing resource allocation, improving power supply reliability, and promoting the local consumption of distributed renewable energy sources. It is an effective solution for building a highly resilient and intelligent distribution network for the future.

[0097] In some exemplary embodiments, the transformer can have multiple operating modes depending on the operating status of the power grid and the load, which are automatically determined and switched by the control module: No voltage fluctuation state: When the voltage sampling unit detects that the grid voltage is stable within the normal range, the control module controls the series module to stop working and short-circuits the low-voltage side of the series transformer winding through the bypass switch. At this time, only the main transformer winding supplies power to the load to reduce the operating loss of the device itself.

[0098] Voltage status management: When a voltage dip, rise, or imbalance is detected in the grid voltage, the control module activates the series module. The series module draws energy from the DC bus supported by the parallel module to generate the compensation voltage required to compensate for the grid voltage difference, and injects it into the series transformer winding to stabilize the voltage on the load side.

[0099] Current status management: When the current sampling unit detects reactive power, harmonics, or three-phase imbalance in the load current, the control module activates the parallel module. The parallel module generates a corresponding compensation current that is directly injected into the load side to offset the adverse current components and improve the power factor and current waveform.

[0100] Voltage and current quality management: When voltage and current quality issues occur simultaneously, the control module controls the series and parallel modules to work together to perform voltage compensation and current compensation functions respectively, thereby achieving comprehensive management of power quality.

[0101] Bypass protection status: When the control module detects an internal fault (such as overcurrent, overtemperature, or abnormal drive) in a series or parallel module, it immediately blocks the power devices of the faulty module and quickly activates the bypass module to isolate the faulty module from the main circuit, while maintaining continuous power supply to the load to achieve uninterrupted power protection for the system.

[0102] In some exemplary embodiments, when multiple transformers are interconnected through their external DC interfaces to form the flexible interconnected power distribution system, the system supports the following cooperative operation modes: Power sharing mode: When the load rate of a certain distribution area in the system is high, while the load rate of the adjacent area is low, the active power is transferred from the lightly loaded area to the heavily loaded area through the common DC bus by controlling the coordinated operation of the parallel and series modules in each transformer, thereby optimizing the overall load distribution.

[0103] Energy storage peak shaving and valley filling mode: When an energy storage system is connected to the common DC bus, during the peak load period of the system, the energy storage system is controlled to discharge and provide power support to the connected AC transformer area through each transformer device; during the off-peak load period, the energy storage system is controlled to charge and absorb the surplus power, thereby achieving peak shaving and valley filling and smoothing the system load curve.

[0104] Single-area power failure transfer mode: When a certain AC distribution substation in the system loses power due to a fault in the upstream power supply, the critical loads of the lost substation can be restored through the common DC bus by other normally operating substations or distributed power sources (such as photovoltaics and energy storage) connected to the DC bus, thus realizing power transfer in the event of a fault.

[0105] DC power supply mode: When multiple AC substations in the system lose power, but there are still distributed power sources (such as photovoltaics) on the common DC bus that can supply power, the relevant switches can be controlled to allow the DC power supply to directly provide emergency power to some important AC loads through the inverter function of the transformer, so as to maintain the continuity of power supply to the maximum extent.

[0106] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A transformer device, characterized in that, The transformer includes: The transformer module includes a main transformer winding and a series transformer winding. The high-voltage side of the main transformer winding is connected in series with the high-voltage side of the series transformer winding. The low-voltage side of the main transformer winding is used to connect the load. The low-voltage side of the series transformer winding serves as the access terminal for voltage compensation. The series module is connected at one end to the low-voltage side of the series transformer winding. It is used to collect the load side voltage and adjust the load side voltage by injecting compensation voltage into the low-voltage side of the series transformer winding. A parallel module is connected at one end to the other end of the series module. The other end of the parallel module is used to connect to the load, to collect the current on the load side, and to adjust the current on the load side by injecting compensation current into the load side.

2. The transformer device according to claim 1, characterized in that, The series module and the parallel module are electrically connected via a DC bus. The parallel module is used to provide power to or absorb power from the DC bus to support the voltage compensation of the series module.

3. The transformer device according to claim 1 or 2, characterized in that, The series module includes a voltage source inverter unit, and the parallel module includes a current source converter unit. The voltage source inverter unit is used to convert the voltage of the DC bus into the compensation voltage. The current source converter unit is used to generate the compensation current.

4. The transformer device according to claim 3, characterized in that, The main transformer winding and the series transformer winding are integrated in the same transformer oil tank and wound on the same iron core.

5. The transformer according to claim 1, characterized in that, The transformer also includes a bypass module; One side of the series module is connected to the low-voltage side of the series transformer winding via the bypass module; The bypass module is activated in the event of a failure of the series module to maintain continuous power supply to the load.

6. The transformer according to claim 5, characterized in that, The bypass protection unit includes a reverse parallel thyristor group and a switch branch; The reverse parallel thyristor group is connected in parallel with the switch.

7. The transformer according to claim 1, characterized in that, The transformer also includes: The maintenance isolation module includes a manual bypass isolating switch connected in parallel to the low-voltage side circuit of the series transformer winding.

8. The transformer according to claim 7, characterized in that, The manual disconnect switch includes: a rotary disconnect switch or a knife-type disconnect switch.

9. The transformer according to claim 7, characterized in that, The maintenance isolation module also includes: A series-side disconnect switch, wherein the series-side disconnect switch is connected in series with the series module; A parallel-side incoming line switch is connected in series in the incoming line circuit of the parallel module.

10. The transformer according to claim 1, characterized in that, The transformer also includes: An integrated power distribution module is used to provide control power to the series and parallel modules, and is equipped with an external DC interface.

11. A flexible interconnected power distribution system, characterized in that, The system includes: At least two transformer devices as described in any one of claims 1-10; The external DC interfaces of the two transformers are connected via a common DC bus.

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