A magnetic control transformer device for a flexible interconnected power distribution grid

Abstract

This invention relates to the field of power distribution, and in particular to a magnetically controlled transformer device for flexible interconnected power distribution networks. The device includes a first transformer, a second transformer, a magnetically controlled circuit, and a start-stop circuit. By connecting the secondary windings of the first and second transformers in series, and connecting the input of the magnetically controlled circuit to the secondary winding of the first transformer and the output to the primary winding of the second transformer, the magnetically controlled circuit only needs to provide a small adjustment voltage to regulate the amplitude and phase of the entire device's output voltage through the transformer coupling effect. This achieves bidirectional flexible scheduling of active and reactive power. Furthermore, since the main power path is primarily carried by the transformer windings, the magnetically controlled circuit only handles power regulation, significantly reducing the capacity requirements of full-power power electronic devices, thus reducing cost and size. Simultaneously, the magnetically controlled circuit is constructed using multiple sub-modules connected in parallel, each of which can be independently sampled, supporting online disconnection of faulty sub-modules, thereby improving system reliability and maintainability.

Description

Technical Field

[0001] This invention relates to the field of power distribution, and in particular to a magnetically controlled transformer for flexible interconnected power distribution networks. Background Technology

[0002] With the large-scale integration of distributed energy, electric vehicle charging facilities, and nonlinear loads, the power distribution network faces problems such as uneven feeder load, voltage exceeding limits, bidirectional power flow, and increased harmonic and three-phase imbalance. Traditional power distribution systems can no longer meet the demands in terms of regulation capability, response speed, and power supply reliability.

[0003] To address these issues, flexible interconnection technology has emerged. Its core is to achieve flexible power scheduling and collaborative power quality management between different areas or AC / DC links of the distribution network through intelligent power electronic devices. However, most current mainstream solutions adopt a full power electronic converter structure, such as smart soft switch (SOP) or energy router. Although these are powerful, the equipment capacity is positively correlated with the investment cost, and they are limited by the voltage and current carrying capacity of individual power devices, making it difficult to economically and efficiently adapt to high current carrying scenarios.

[0004] In addition, existing full-power semiconductor solutions not only require a large number of power devices to meet current carrying capacity and voltage withstand requirements, resulting in complex overall circuit structure, large size, difficult installation and debugging, and heavy maintenance tasks; at the same time, in order to ensure stable system operation, precise coordinated control of the switching state of each power device is required, which leads to cumbersome control strategy design, long debugging cycle, and significantly reduces the overall reliability of the system. Furthermore, although traditional magnetically controlled devices can reduce the capacity of power electronic devices, they are often only used for single voltage regulation functions, lacking multi-port energy interaction and modular redundancy capabilities, and cannot support the multi-objective flexible control requirements of new distribution networks. Therefore, we propose a magnetically controlled transformer device for flexible interconnected distribution networks. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to solve the problems of existing flexible interconnect devices having complex structures, a large number of power devices, high costs, low reliability, and limited functions.

[0006] The above-mentioned technical problems are solved by the following technical solution: This invention proposes a magnetically controlled transformer device for flexible interconnected distribution networks, comprising: a first transformer, whose primary three-phase winding is connected to an AC power grid; a second transformer, whose secondary three-phase winding is connected to an AC power grid or a load; a magnetic control circuit, whose input terminal is connected to the secondary three-phase winding of the first transformer and whose output terminal is connected to the primary three-phase winding of the second transformer; and a start-stop circuit, whose two ends are respectively connected between the output terminal of the magnetic control circuit and the primary three-phase winding of the second transformer, for controlling the operation of the magnetic control circuit; wherein, one end of the secondary three-phase winding of the first transformer is also connected in series with one end of the secondary three-phase winding of the second transformer; the magnetic control circuit is composed of several sub-modules connected in parallel, and the DC side of each sub-module is connected in parallel to form a DC port for connecting to a DC power grid or a load.

[0007] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected power distribution networks described in this invention: each sub-module in the magnetic control circuit includes a power module and a sub-control board. The power module is used to realize bidirectional energy conversion between AC and DC power. The sub-control board is used to collect the operating parameters of its own sub-module, generate drive signals according to the received control commands to control the operation of the power module, and trigger protection actions when an abnormality is detected.

[0008] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected power distribution networks according to the present invention: the power module includes a power circuit, and the power circuit includes an input switch unit, an input filter unit, a conversion unit, an output filter unit, and an output switch unit that are electrically connected in sequence; and the input terminal of the input switch unit constitutes the AC input terminal of the submodule; the output terminal of the output switch unit constitutes the AC output terminal of the submodule.

[0009] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected power distribution networks described in this invention: a DC bus capacitor is connected in parallel on the DC side of the transformer unit, and the positive and negative terminals of the DC bus capacitor respectively constitute the DC positive port and DC negative port of the submodule.

[0010] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected power distribution networks described in this invention: the input switching unit consists of a first contactor, a second contactor, and a starting resistor, and the output terminal of the first contactor, the input terminal of the second contactor, and one end of the starting resistor are all connected to a first node; and the output terminal of the second contactor and the other end of the starting resistor are all connected to a second node, and the second node is connected to the input terminal of the input filtering unit.

[0011] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected power distribution networks described in this invention: the input filtering unit adopts an LCL-type filter circuit, and the input terminal of the LCL-type filter circuit is connected to the output terminal of the input switching unit, and the output terminal is connected to the rectifier-side input terminal of the conversion unit; and the output filtering unit adopts an LC-type filter circuit, and the input terminal of the LC-type filter circuit is connected to the inverter-side output terminal of the conversion unit.

[0012] In a preferred embodiment of the magnetically controlled transformer for flexible interconnected power distribution networks described in this invention: the output switching unit includes a third contactor, and the input terminal of the output switching unit is connected to the output terminal of the output filtering unit.

[0013] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected distribution networks described in this invention: the conversion unit consists of a back-to-back converter and a DC bus capacitor connected in parallel to its DC side, and the back-to-back converter includes a front-stage rectifier bridge and a rear-stage inverter bridge; the AC input terminal of the front-stage rectifier bridge is connected to the output terminal of the input filter unit, and the DC output terminal is connected to the positive and negative terminals of the DC bus; the DC input terminal of the rear-stage inverter bridge is connected to the positive and negative terminals of the DC bus, and the AC output terminal is connected to the input terminal of the output filter unit.

[0014] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected power distribution networks described in this invention: the power module further includes a drive circuit and a protection circuit; the drive circuit receives drive signals from the sub-control board and outputs drive levels to each power switching device in the conversion unit to control their on and off states; the protection circuit monitors the operating status of the power module, and when an abnormality is detected, generates a protection command and sends it to the drive circuit and the sub-control board.

[0015] In a preferred embodiment of the magnetically controlled transformer device for flexible interconnected power distribution networks described in this invention: the primary winding of the first transformer is connected in a delta configuration, the secondary winding of the first transformer is connected in a star configuration, and the primary winding of the second transformer is connected in a delta configuration.

[0016] The beneficial effects of this invention are as follows: By connecting the secondary side of the first transformer and the secondary side of the second transformer in series, and connecting the input terminal of the magnetic control circuit to the secondary side of the first transformer and the output terminal to the primary side of the second transformer, the magnetic control circuit only needs to provide a small adjustment voltage to regulate the output voltage amplitude and phase of the entire device through the transformer coupling effect, thereby achieving bidirectional flexible scheduling of active and reactive power. Moreover, since the main power path is mainly carried by the transformer windings, the magnetic control circuit only undertakes the power regulation, which greatly reduces the capacity requirement of full-power power electronic devices, reducing cost and size. At the same time, the magnetic control circuit is composed of multiple sub-modules connected in parallel, each sub-module can be sampled independently, and online disconnection of faulty sub-modules is supported, improving system reliability and maintainability. Furthermore, the DC sides of each sub-module are connected in parallel to form a unified DC port, which can be connected to the DC distribution network or distributed DC source load, enabling the device to have the capabilities of AC inter-station power mutual assistance, bidirectional AC and DC energy flow, and comprehensive power quality management. Thus, without relying on the full-power conversion architecture, low-cost, high-reliability, and multifunctional flexible distribution network interconnection can be achieved. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein: Figure 1 A schematic diagram of the structure and principle of the magnetically controlled transformer is shown. Figure 2 A schematic diagram of the magnetic control circuit structure is shown; Figure 3 A schematic diagram of the topology of the magnetic control circuit submodule is shown. Figure 4 A schematic diagram of the application of a magnetically controlled transformer in a power distribution network system is shown. Figure 5 The simulation diagram of output voltage and current under steady-state voltage regulation and load shedding conditions is shown. Figure 6 The waveform diagram of the continuous voltage regulation experiment of the magnetic control circuit is shown. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0020] Reference Figures 1-3 This embodiment provides a magnetically controlled transformer device for flexible interconnected power distribution networks, including a first transformer 1 (T1), a second transformer 2 (T2), a magnetic control circuit 3, and a start-stop circuit 4.

[0021] Among them, such as Figure 1 As shown, the primary side of the first transformer 1 adopts a delta connection, with each phase (A1, B1, C1) of its three-phase windings having one end (usually the start or end) for connecting to an external three-phase AC power grid, including but not limited to medium- and high-voltage distribution networks, low-voltage distribution networks, and commercial / civilian three-phase AC power grids. The voltage level of the power grid source can be flexibly selected according to the actual application scenario. The secondary side of the first transformer 1 adopts a star connection (Y connection), with the end ends of its three-phase windings (a1, b1, c1) connected together to form a neutral point N. The start ends of the three-phase windings are respectively led out and connected to the start ends (A2, B2, C2) of the three-phase windings on the secondary side (low-voltage side) of the second transformer 2 and to the three-phase input terminals of the magnetic control circuit 3.

[0022] The secondary side of the second transformer 2 has its three-phase windings' starting ends (A2, B2, C2) connected to the secondary side of the first transformer 1. The tail ends of its three-phase windings are led out to connect to the external three-phase AC power grid load or feeder, that is, to different AC power grid sections that need to output power or receive power, or directly connected AC loads. The primary side of the second transformer 2 (a2, b2, c2) adopts a delta connection (Δ connection), with each phase of its three-phase windings having one end led out to connect to the three-phase output terminals of the magnetic control circuit 3.

[0023] The magnetic control circuit 3 receives electrical energy from the secondary side of the first transformer 1, further performs flexible energy conversion (AC-AC, AC-DC, DC-AC), and outputs it to the primary side of the second transformer 2. It also provides an interface with the DC power grid. The core magnetic control circuit is as follows: T1 secondary side → input terminal of magnetic control circuit 3 → energy conversion of magnetic control circuit → output terminal of magnetic control circuit 2 → T2 primary side → energy is transferred to the series connection point of T1 secondary side through T2, forming a closed-loop magnetic control coupling, thereby realizing power transmission and regulation.

[0024] like Figure 2As shown, the magnetic control circuit 3 adopts a modular design, consisting of multiple sub-modules 31 and a main control board 32. All sub-modules are connected in parallel and are controlled by the main control board 32. The structural parameters of each sub-module 31 are exactly the same. The internal structure of the sub-module 31 mainly includes a power module 311 and a sub-control board 312. The DC ports (DC+, DC-) of all sub-modules 31 are connected in parallel internally to form the total DC port of the device. This DC port is used to connect to an external DC power distribution network or DC load.

[0025] Specifically, by setting up the magnetic control circuit 3, on the one hand, it can receive AC power from the secondary side of T1, and output AC power to the primary side of T2 through the conversion control of submodule 31. Then, through the secondary side of T1 and the secondary side of T2 in series, they can output AC power to the load or AC distribution network together. On the other hand, the energy flow between the DC grid and the AC grid is realized through the DC terminal (DC+, DC-) of submodule 31. When DC power is input from the DC distribution network, the magnetic control circuit can invert it into AC power and deliver the energy to the AC distribution network through T1 and T2. Alternatively, the AC power can be rectified into DC power through submodule 31 and the energy can be output to the DC distribution network through the DC terminal (DC+, DC-) of submodule 31, thus realizing AC / DC hybrid power supply.

[0026] In one embodiment provided in this application, such as Figure 2 As shown, submodule 31 consists of power module 311 and sub-control board 312, wherein sub-control board 312 includes sampling circuit 3121 and sub-control circuit 3122; and power module 311 includes power circuit 3111, drive circuit 3112 and protection circuit 3113.

[0027] The sub-control circuit 3122 can interact with the main control board 32 to exchange commands and transmit data. It receives data collected from the sampling circuit 3121, processes it, and sends commands to control the operation of the power module 311. The sampling circuit 3121 is used to sample the parameters of the target object and the system status information, including the input and output voltage and current values ​​of the three-phase AC and DC ports and the operating temperature of the device. Specifically, it can use Hall sensors, resistor voltage divider sampling, power device built-in temperature sensors, thermistors, etc. to sense signals. The analog small signals output by the sensors are modulated and then sent to the ADC to convert the collected analog signals into digital signals, which are finally transmitted to the sub-control circuit 3122 for data processing.

[0028] Furthermore, the contactor in the power circuit 3111 receives instructions from the sub-control board 312 and can perform start / stop control actions or protection actions to connect and disconnect sub-modules in case of faults. The drive circuit 3112 receives drive signals generated by the sub-control board 312 and provides drive levels to the power circuit 3111 according to the drive signals, which is used to control and change the operating mode of the back-to-back converter. The protection circuit 3113 will activate the protection function when encountering overcurrent, overvoltage, or overtemperature conditions during device operation. In specific implementation, after the sampling circuit 3121 detects that the current, voltage, and temperature of the power module 311 exceed the threshold, the sub-control board 312 controls the protection circuit 3113 to disconnect the faulty power module and connect the redundant backup sub-module 31, thereby achieving fault disconnection and backup access, and thus maintaining the normal and safe operation of the magnetic control circuit system.

[0029] The magnetic control circuit is connected between the secondary side of T1 and the primary side of T2. The magnetic control circuit receives the AC power from the secondary side of T1, performs rectification and inversion control on the control board, and then feeds the transformed AC power into the primary side of T2. Through the excitation effect of T1 and T2, the AC output of the entire device is controlled. The magnetic control circuit precisely controls the amplitude and phase of its output voltage to control the active and reactive power transmitted by the entire device.

[0030] In one embodiment provided in this application, such as Figure 3 As shown, the power circuit 3111 is connected in series with the first transformer 1 and the second transformer 2 in a three-phase manner. The power circuit consists of a first contactor, a second contactor, a starting resistor, an LCL filter, a back-to-back converter, an LC filter, and a third contactor.

[0031] Among them, such as Figure 3As shown, the first contactor QF1 is connected after the three-phase input terminals of this module. It is used for soft starting during initial power-on, conducting the main circuit during normal operation, and quickly physically isolating the input side during faults or maintenance. The starting resistor is connected in parallel with the first contactor QF1. During initial power-on, the first contactor QF1 is open, and the input current is limited by this resistor to prevent excessive inrush current caused by instantaneous capacitor charging. When the DC bus voltage is established to a safe threshold, the first contactor QF1 closes, short-circuiting the resistor to achieve the soft-start function. The LCL filter, as an input filter, consists of an inductor and a capacitor and is located at the input terminal. It is mainly used to filter out the subharmonic currents of the switching frequency generated by the converter, so that the current flowing into the grid meets the harmonic standard requirements. It also reduces the harmonics from the grid entering the converter; the back-to-back converter consists of two voltage source converters connected back-to-back via a common DC bus; the common DC bus capacitor is connected in parallel on the common DC bus, i.e., between DC+ and DC-, which can buffer the instantaneous power imbalance between the AC side and the DC side, filter out the voltage ripple on the DC bus, and provide support for the instantaneous energy exchange of the converter; the LC filter, as the output filter, consists of an inductor and a capacitor, and is located after the output of the back-to-back converter. It is mainly used to further filter out the high-frequency switching ripple voltage of the back-to-back converter output, so that the AC waveform of the input second transformer 2 primary side is sinusoidal, reducing the adverse effects on the transformer and improving the output power quality.

[0032] It should be further explained that the magnetically controlled transformer includes the following operating modes: In one embodiment provided in this application, when the magnetically controlled transformer is connected to the AC power distribution network, T1 converts the primary voltage from the AC power distribution network into a secondary voltage and transmits it to the magnetically controlled circuit 3. The main control board 32 in the magnetically controlled circuit 3 issues a control signal, and the back-to-back converter in the power circuit 3111 in the magnetically controlled circuit 3 rectifies the secondary voltage into DC power and then inverts it into three-phase AC power to be output to the primary side of T2. T2 receives the three-phase voltage from the magnetically controlled circuit 3, connects one end of the secondary three-phase winding to the secondary three-phase winding of T1, and connects the other end to the AC power distribution network or the three-phase voltage of the AC load. It is connected to the AC power distribution network in series through the secondary side of T1, thereby realizing the energy flow between two different AC power distribution networks.

[0033] In one embodiment provided in this application, the three-phase AC input terminal of the magnetically controlled transformer is connected to the AC power distribution network. T1 converts the primary voltage from the AC power distribution network into a secondary voltage and transmits it to the magnetically controlled circuit 3. The main control board in the magnetically controlled circuit 3 issues a control signal, and the magnetically controlled circuit rectifies the secondary voltage into DC power through the back-to-back converter in the power circuit. The DC power is then connected to the DC power distribution network or DC load through the DC port (DC+, DC-) of the submodule, so that power flows from the AC power distribution network into the DC power distribution network.

[0034] In one embodiment provided in this application, the DC port (DC+, DC-) of the magnetically controlled transformer is connected to the DC power distribution network, and the three-phase AC input and output are connected to the AC power distribution network. The main control board in the magnetically controlled circuit 3 sends a control signal to control the back-to-back converter in the power circuit through the sub-control board, which inverts the DC to AC and outputs it to T2. T1 converts the primary voltage from the AC power distribution network into a secondary voltage and transmits it to the magnetically controlled circuit. The back-to-back converter in the power circuit in the magnetically controlled circuit rectifies and inverts the secondary voltage into three-phase AC and outputs it to T2. T2 receives the converted three-phase AC from the AC power distribution network and the DC power distribution network, connects it in series with the secondary side of T1 to the AC power grid, and realizes the flow of power from the DC power grid to the AC power grid.

[0035] By setting up a magnetically controlled transformer for flexible interconnected distribution networks, the capacity requirements of different scenarios can be met by changing the number of sub-modules 31 and their series or parallel connection methods. It can also replace the full-power power electronic flexible interconnection device, which can significantly reduce costs and greatly compress the device size.

[0036] Reference Figure 4 This embodiment provides an application of a magnetically controlled transformer for flexible interconnected distribution networks. The main control board 32 of the magnetically controlled circuit 3 can be configured with a cross-regional power dispatching algorithm to dynamically allocate the power flow between multiple sub-modules at AC / DC interfaces. Specifically, it includes the following application methods: First, flexible interconnection devices that enable connections between stations; such as... Figure 4 As shown in section ②, this magnetically controlled transformer can be used to connect different transformer substations to achieve power flow between them. In transformer substation 1, the primary three-phase winding of T1 is connected to the high / medium voltage AC bus, and one end of the low-voltage three-phase winding of T2 is connected to the output of the main distribution transformer, while the other end is connected to the low-voltage AC bus. In transformer substation 2, the primary three-phase winding of T1 is connected to the high / medium voltage AC bus, and one end of the low-voltage three-phase winding of T2 is connected to the output of the main distribution transformer, while the other end is connected to the low-voltage AC bus. Power transmission between transformer substation 1 and transformer substation 2 is achieved by connecting the DC+ and DC- ports of the magnetically controlled circuit in parallel. Connecting the DC+ port of the magnetically controlled circuit in transformer substation 1 to the DC+ port of the magnetically controlled circuit in transformer substation 2, and connecting the DC- port of the magnetically controlled circuit in transformer substation 1 to the DC- port of the magnetically controlled circuit in transformer substation 2, will enable power transmission between the two transformer substations.

[0037] Second, flexible interconnection devices that enable the interconnection of AC and DC distribution networks; such as... Figure 4As shown in number ③, this magnetically controlled voltage regulating device is used to connect the AC distribution network and the DC distribution network, realizing the power flow between the AC distribution network and the DC distribution network. Specifically, the connection method in the AC distribution network is as follows: the primary three-phase winding of T1 is connected to the high / medium voltage AC bus, one end of the low-voltage three-phase winding of T2 is connected to the output terminal of the main distribution transformer, and the other end is connected to the low-voltage AC bus; the DC port DC+ of the magnetic control circuit 3 is connected to the positive terminal of the DC distribution network, and DC- is connected to the negative terminal of the DC distribution network. Through this structure, power can flow between the AC network and the DC network.

[0038] Third, flexible interconnection devices for connecting different low-voltage AC buses; such as... Figure 4 As shown in number ⑤, this magnetically controlled voltage regulating device is used to connect flexible interconnection devices for distribution networks with different AC buses, which can avoid the closing impact caused by direct connection between two AC buses; the primary side three-phase winding of T1 is connected to AC bus 1, and one end of the low-voltage side three-phase winding of T2 is connected to the output end of the main distribution transformer, and the other end is connected to AC bus 2, which can realize the interconnection operation between the distribution network areas under the jurisdiction of the two AC buses.

[0039] Fourth, magnetically controlled transformers also have other applications, such as... Figure 4 As shown in number ①, it is used to connect high / medium voltage power grids and low voltage power grids, replacing traditional transformers; as Figure 4 As shown in number ④, it is used to connect different loads on the same AC bus within a transformer substation to achieve power balance within the substation; such as Figure 4 As shown in number ④, it is used to connect different loads on the same AC bus within a transformer substation to achieve power balance within the substation; such as Figure 4 As shown in number ⑥, it is connected in series to areas with severe power quality problems to achieve power flow restriction and voltage support; as Figure 4 As shown in number ⑦, reactive power compensation is achieved by connecting to the power grid in parallel.

[0040] Reference Figures 5-6 This embodiment provides a simulation test based on the magnetically controlled transformer.

[0041] A simulation platform for a magnetically controlled transformer was built using MATLAB / Simulink. The steady-state control simulation conditions are as follows: the load is a parallel resistive-inductive load with a rated power of 200kVA at 380V and a power factor of 0.8. The d-axis reference values ​​of the output voltage of the flexible interconnected magnetically controlled transformer are: 311.1V (rated voltage) from 0.5-0.7s, (100+10)% of the rated voltage (342.2V) from 0.7s-1.0s, (100-10)% of the rated voltage (280.0V) from 1.0s-1.3s, and (100+10)% of the rated voltage (342.2V) from 1.3s-2.0s; the DC capacitor voltage reference value is always 620V; the q-axis reference values ​​of the output voltage and rectifier input current of the flexible interconnected magnetically controlled transformer are always 0; at 1.6s, half of the load is suddenly disconnected, and the simulation results are as follows. Figure 5 As shown: Under the above operating conditions, the output voltage uload of the flexible interconnected magnetically controlled transformer (e.g.) Figure 5 (See diagram above) and output current iload (e.g.) Figure 5 The following figure shows the changes. The results indicate that the flexible interconnected magnetically controlled transformer can achieve continuous, fast and accurate voltage regulation within a range of ±10%, with a voltage regulation accuracy of over 0.5% and a voltage regulation time of less than 30ms. There are almost no voltage or current spikes during the voltage regulation process. When the load is suddenly disconnected, the output voltage and current of the flexible interconnected magnetically controlled transformer have almost no spikes, and the DC capacitor voltage fluctuation does not exceed 20V.

[0042] Furthermore, to verify the voltage regulation function of the magnetic control circuit in the magnetically controlled transformer and to experimentally demonstrate its high-speed continuous voltage regulation capability, a test platform was built, which included the power circuit within the submodule, the sub-control board, the main control board, the hand control panel, the voltage sensor, the current sensor, and the waveform recorder. The hand control panel is used to control the start-up, shutdown, and continuous voltage regulation of the submodule, and the waveform recorder is used to measure the voltage and current of the submodule in real time.

[0043] Based on the aforementioned test platform, the full-power operation capability and continuous voltage regulation function of the submodule were verified using voltage regulation operation. The experimental waveforms of the modular power circuit operating in continuous voltage regulation mode are shown below. Figure 6 As shown, CH1 is the DC voltage, CH2 and CH3 are the voltages of phase a and phase b of the rectifier, and CH4 and CH5 are the output voltages of phase a and phase b of the inverter. (The inverter output voltage is shown in the image.) Figure 6 As can be seen, the inverter output voltage regulation time is less than 100ms when the voltage rises from 0Vrms to 190Vrms and 380Vrms, and then falls back to 190Vrms and 0Vrms. The voltage regulation process is smooth and rapid, and the output voltage after regulation is a stable power frequency sine wave. This indicates that the submodule 31 in the magnetic control circuit 3 can achieve smooth, rapid and stable continuous voltage regulation.

[0044] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A magnetically controlled transformer for flexible interconnected power distribution networks, characterized in that: include, The first transformer (1) has its primary three-phase windings connected to the AC power grid; The second transformer (2) has its secondary three-phase windings connected to the AC power grid or load; The magnetic control circuit (3) has its input terminal connected to the secondary three-phase winding of the first transformer (1) and its output terminal connected to the primary three-phase winding of the second transformer (2); and, The start-stop circuit (4) is connected at both ends to the output end of the magnetic control circuit (3) and the primary three-phase winding of the second transformer (2), respectively, and is used to control the operation of the magnetic control circuit (3); Among them, one end of the secondary three-phase winding of the first transformer (1) is connected in series with one end of the secondary three-phase winding of the second transformer (2); the magnetic control circuit (3) is composed of several sub-modules (31) connected in parallel, and the DC side of each sub-module is connected in parallel to form a DC port for connecting to the DC power grid or load.

2. The magnetically controlled transformer for flexible interconnected power distribution networks according to claim 1, characterized in that: Each sub-module (31) in the magnetic control circuit includes a power module (311) and a sub-control board (312). The power module (311) is used to realize bidirectional energy conversion between AC and DC. The sub-control board (312) is used to collect the operating parameters of this sub-module, generate drive signals according to the received control instructions to control the operation of the power module, and trigger protection actions when an abnormality is detected.

3. The magnetically controlled transformer for flexible interconnected power distribution networks according to claim 2, characterized in that: The power module (311) includes a power circuit (3111), and the power circuit (3111) includes an input switching unit (31111), an input filtering unit (31112), a conversion unit (31113), an output filtering unit (31114), and an output switching unit (31115) that are electrically connected in sequence; and, The input terminal of the input switch unit (31111) constitutes the AC input terminal of the submodule (31); The output terminal of the output switch unit (31115) constitutes the AC output terminal of the submodule (31).

4. The magnetically controlled transformer for flexible interconnected power distribution networks according to claim 3, characterized in that: The DC side of the conversion unit (31113) is connected in parallel with a DC bus capacitor, and the positive and negative terminals of the DC bus capacitor constitute the DC positive port and DC negative port of the submodule (31), respectively.

5. The magnetically controlled transformer for flexible interconnected distribution networks according to claim 3 or 4, characterized in that: The input switch unit (31111) consists of a first contactor (QF1), a second contactor (QF2) and a starting resistor, and the output terminal of the first contactor (QF1), the input terminal of the second contactor (QF2) and one end of the starting resistor are all connected to the first node; as well as, The output terminal of the second contactor (QF2) and the other end of the starting resistor are connected together to the second node, which is connected to the input terminal of the input filter unit (31112).

6. The magnetically controlled transformer for flexible interconnected power distribution networks according to claim 5, characterized in that: The input filtering unit (31112) employs an LCL-type filter circuit, and the input terminal of the LCL-type filter circuit is connected to the output terminal of the input switching unit (31111), while the output terminal is connected to the rectifier-side input terminal of the conversion unit (31113); and, The output filtering unit (31114) adopts an LC-type filtering circuit, and the input terminal of the LC-type filtering circuit is connected to the inverter-side output terminal of the conversion unit (31113).

7. The magnetically controlled transformer for flexible interconnected distribution networks according to claim 6, characterized in that: The output switch unit (31115) includes a third contactor (QF3), and the input terminal of the output switch unit (31115) is connected to the output terminal of the output filter unit (31115).

8. The magnetically controlled transformer for flexible interconnected distribution networks according to any one of claims 3, 4, 6 or 7, characterized in that: The conversion unit (31113) consists of a back-to-back converter and a DC bus capacitor connected in parallel to its DC side, and the back-to-back converter includes a front-stage rectifier bridge and a rear-stage inverter bridge. The AC input terminal of the front-stage rectifier bridge is connected to the output terminal of the input filter unit (31112), and the DC output terminal is connected to the positive and negative terminals of the DC bus. The DC input terminal of the subsequent inverter bridge is connected to the positive and negative terminals of the DC bus, and the AC output terminal is connected to the input terminal of the output filter unit (31114).

9. The magnetically controlled transformer for flexible interconnected distribution networks according to claim 8, characterized in that: The power module (311) also includes a drive circuit (3112) and a protection circuit (3113). The drive circuit (3112) receives drive signals from the sub-control board and outputs drive levels to each power switching device in the conversion unit (31113) to control their on and off states. The protection circuit (3113) is used to monitor the operating status of the power module (311). When an abnormality is detected, it generates a protection command and sends it to the drive circuit (3112) and the sub-control board (312).

10. The magnetically controlled transformer for flexible interconnected distribution networks according to claim 1 or 9, characterized in that: The primary winding of the first transformer (1) is connected in a delta configuration, the secondary winding of the first transformer (1) is connected in a star configuration, and the primary winding of the second transformer (2) is connected in a delta configuration.

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