Low-voltage flexible voltage regulation device with flexible capacity expansion capability and distributed control method

Abstract

The invention discloses a low-voltage flexible voltage regulation device with flexible capacity expansion capability and a distributed control method, and the system achieves the low-cost and flexible regulation of compensation capacity through the parallel connection of modularized low-voltage voltage regulation devices, and effectively guarantees the stability of load voltage and the quality of power supply. The control method is based on a master-slave distributed architecture, the pilot controller dominates operation mode switching, and issues a synchronization instruction and a reference signal to the following unit to realize multi-mode cooperation; and the following unit performs localized compensation and dynamic circulating current suppression to guarantee the balance and stability of the power of the parallel system. Aiming at the problems of high cost of a voltage regulating device and long supply chain caused by district distribution network transformer grade diversity and large line power difference and voltage fluctuation caused by distributed new energy access, the method realizes high-reliability operation and accurate compensation of a multi-machine parallel system through modular master-slave control; the method is suitable for voltage treatment scenes such as court power distribution networks and micro-grids.

Description

Technical Field

[0001] This invention relates to the field of power quality in distribution networks, particularly to distribution networks in scenarios involving distributed renewable energy access. It presents a parallel collaborative control method for modular, low-cost voltage management devices applicable to distribution networks and similar scenarios. Based on a master-slave control architecture, this method utilizes modular low-voltage regulating devices to achieve flexible system capacity expansion and precise collaborative compensation—an advanced approach. Background Technology

[0002] In recent years, voltage quality issues in renewable energy distribution networks have received widespread attention. Both power suppliers and consumers urgently hope to resolve these voltage quality problems. From the power supplier's perspective, voltage quality is a significant factor hindering the growth of renewable energy penetration. Only by effectively addressing the power quality issues arising from renewable energy grid connection can the national "dual-carbon" targets be met within the stipulated timeframe. From the consumer's perspective, voltage quality issues can directly harm their interests. For example, in a production workshop, voltage fluctuations increase product tolerances and affect the defect rate. Only by ensuring high-quality power supply to the workshop's electrical production equipment can the economic benefits of the products be maximized.

[0003] To address voltage quality issues in power distribution networks, a large number of electrical companies, including ABB, Siemens, and Schneider Electric, have dedicated themselves to researching voltage quality management equipment and have launched a series of products such as Uninterruptible Power Supply (UPS) and Dynamic Voltage Restorer (DVR) to meet users' demands for high-quality power supply. However, these devices are expensive and cannot meet the routine application needs of a large number of power users. Taking UPS power supplies as an example, existing designs can be divided into online UPS and standby UPS. Online UPS always supplies power to the load through power electronic devices, while standby UPS supplies power through a bypass when the grid voltage is normal, switching to power electronic devices only when the grid voltage is abnormal. However, both online and standby UPS require energy storage devices, which puts a huge burden on equipment costs.

[0004] Power electronic bridge arm multiplexing technology is an effective solution to reduce the manufacturing cost of power electronic devices. This technology rationally integrates power electronic bridge arms, which are used in multiple ports in traditional solutions, into a single bridge arm, thereby reducing the number of power electronic devices used. When a single bridge arm is used in multiple output ports, improper control can cause mutual coupling and interference between the outputs of multiple ports, leading to system malfunctions. Therefore, the application of this technology requires solving the coupling problem between multiple ports in the multiplexed bridge arm control. A reasonable modulation strategy to allocate the use of the multiplexed bridge arm in each port can effectively solve this problem.

[0005] Eliminating the isolation transformer is also an effective solution to reduce the manufacturing cost of power electronic equipment. The main functions of an isolation transformer are electrical isolation and voltage transformation. In high-voltage, high-power applications, using an isolation transformer can increase the output voltage level and enhance the equipment's safety factor. However, isolation transformers are expensive to manufacture, bulky, heavy, and difficult to transport and handle, making DVRs with this structure unsuitable for use in homes, offices, and similar settings. Therefore, in scenarios where electrical isolation is not required from the converter itself, a non-isolated converter topology can be used.

[0006] Given the current reality of voltage quality issues in renewable energy distribution networks, and the contradiction between the increasingly strong demand for high-quality power supply from electricity users and the high cost of voltage quality management equipment, the need for low-cost voltage quality management devices is particularly evident. Therefore, it is essential to seek new low-cost voltage quality management device solutions from various perspectives, such as power electronic bridge arm reuse, elimination of isolation transformers, and suppression of DC bus voltage fluctuations to reduce capacity. Some research has already been conducted on the design of low-cost voltage management device solutions, among which bridge arm reuse and transformerless solutions are the most mature; however, these solutions still have room for improvement in terms of cost reduction.

[0007] In summary, this invention addresses the voltage quality issues encountered in new energy distribution networks, as well as the high cost and limited scalability of traditional voltage regulation equipment. It proposes a low-voltage flexible voltage regulator with flexible capacity expansion capabilities and a distributed control method. This method significantly reduces hardware costs and size through innovative topology design. Simultaneously, by combining centralized control with a virtual impedance current sharing strategy, it improves the device's dynamic response speed, stability, and compensation accuracy. This invention not only effectively solves new challenges in distribution networks, such as the coexistence of overvoltage and undervoltage, and rapid voltage fluctuations, but also supports the efficient integration of new energy sources and the achievement of "dual-carbon" goals. It provides an economical and flexible solution for the safe and reliable operation of distribution networks, possessing significant engineering application value and promising prospects for widespread adoption. Summary of the Invention

[0008] This invention proposes a low-voltage flexible voltage regulation device and a distributed control method with flexible capacity expansion capability, which can dynamically compensate for physical line impedance mismatch, realize precise power flow distribution, and also have the function of rapid grid-side voltage compensation.

[0009] The objective of this invention is achieved through the following technical solution: The filter inductor current of the parallel bridge arm of the navigation module is measured using the current sensor described in point 1. Series bridge arm filter inductor current The current of the bidirectional thyristor Follower module parallel bridge arm filter inductor current Series bridge arm filter inductor current The grid-side input voltage is measured based on the voltage sensor. Compensation voltage on the series side of the navigation module and the DC bus voltage of the pilot module and the follower module , ; The navigation controller is used to measure the obtained grid voltage. The grid voltage amplitude is monitored using a second-order generalized integrator phase-locked loop (SOGI-PLL). And obtain the real-time power grid phase angle at that time. According to amplitude With the temporary drop threshold Determine if a power grid dip has occurred; if a dip occurs, issue a dip occurrence command. The navigation module switches to the thyristor forced turn-off mode; The navigation controller is based on the current of the bidirectional thyristor. The current at the moment of the dip is maintained by a sample-and-hold circuit. The polarity is used to obtain the reference current of the navigation module under the forced turn-off mode of the thyristor. The modulation voltage of the series section of the navigation module under the thyristor forced turn-off mode is obtained through current loop control. ; The navigation controller monitors After the thyristor is turned off, the signal switches to voltage compensation mode and sends a mode switching command to the follower module. ; The navigation controller calculates a voltage reference that is in phase with the power grid in voltage compensation mode. The voltage reference that the navigation module needs to compensate for. ; The navigation controller obtains the current reference for each module through a voltage controller based on the obtained compensation voltage reference. Subsequently, through the inner current loop and voltage feedforward, and by adding a virtual impedance element, the modulation voltage of the series section of the navigation module is obtained. ; The navigation controller is based on the obtained DC bus reference voltage. Combined with the measured DC bus voltage The reference current inner loop amplitude of the parallel section is obtained through a proportional-integral controller. Based on the real-time phase of the power grid, the reference compensation current required for the pilot parallel section is calculated. ; The navigation controller, based on the obtained compensation current reference, obtains the modulation voltage of the parallel section of the navigation module through a current controller. ; The navigation controller combines the obtained series and parallel modulation voltages to obtain the total modulation signal. The switching control signal is obtained through special three-bridge-arm SVPWM vector modulation.

[0010] The follower controller receives the power grid phase from the pilot controller via a communication bus. and current loop reference and and the order to temporarily land and mode switching commands When a temporary landing command is received With current reference Switching to synchronous forced turn-off mode, and obtaining the series modulation voltage of the follower module through current loop control. ; The follower controller receives a mode switching command. and Synchronously switching to voltage compensation mode, the modulation voltage of the series section of the follower module is obtained through current control, voltage feedforward, and virtual impedance stages. ; The follower controller receives the power grid phase angle from the pilot controller via a communication bus. Based on the measured DC bus voltage The DC voltage control generates the required compensation current reference to follow the parallel connection. ; The follower controller obtains a compensation current reference based on the DC voltage loop, and then uses a current controller to obtain the modulation voltage of the parallel section of each follower module. ; The follower controller combines the obtained series and parallel modulation voltages to obtain the total modulation signal. The switching control signal is obtained through SVPWM vector modulation of the three bridge arms.

[0011] Compared with the prior art, the beneficial effects of the technical solution of the present invention are: 1. By applying the technical solution proposed in this invention, it is possible to adapt to the differences in transformer substation scenarios, shorten the supply chain and significantly reduce hardware costs and size, realize bridge arm reuse, and save the number of power devices and isolation transformers. 2. Traditional low-voltage voltage regulating devices have a fixed structure, and most hybrid compensation systems are complex and costly. This invention adopts a modular architecture, supports parallel connection of multiple units and flexible expansion of power levels. Adding new modules does not require manual parameter adjustment, and the failure of a single module does not affect the operation of the overall system. At the same time, the integrated design reduces equipment costs.

[0012] 3. The modular design supports multi-machine parallel expansion and can be flexibly applied to single-phase, three-phase three-wire and four-wire systems. It solves complex power quality problems such as "coexistence of overvoltage and undervoltage" and can also work in concert to provide an efficient and economical distributed governance solution for distribution networks with a high proportion of new energy access. Attached Figure Description

[0013] Figure 1 This is the electrical connection structure of a multi-machine parallel system of a modular low-voltage regulating device provided in the embodiments of the present invention; Figure 2 This is a schematic diagram illustrating the implementation process of the modular low-voltage regulating device control method provided in this embodiment of the invention. Figure 3 This is a block diagram of the main follower controller of the modular low-voltage regulating device provided in an embodiment of the present invention; Figure 4 This is a flowchart of the algorithm for a modular low-voltage regulating device provided in an embodiment of the present invention; Figure 5 The simulation operation effect diagram of the modular low-voltage regulating device control provided in the embodiment of the present invention is shown. Figure 6 This is a schematic diagram illustrating the multi-module communication principle and delay generation wd of the modular low-voltage regulating device provided in this embodiment of the invention. Figure 7 This is a schematic diagram of a module of a modular low-voltage regulating device control method embodiment provided by the present invention; Figure 8 This is a schematic diagram of a non-isolated modular low-voltage regulating device provided in an embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The specific operational methods in the method embodiments can also be applied to the device embodiments or system embodiments. It should be noted that in the description of this application, "at least one" refers to one or more, where "multiple" refers to two or more. Therefore, in the embodiments of this application, "multiple" can also be understood as "at least two". "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / ", unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship. Furthermore, it should be understood that in the description of this application, terms such as "first" and "second" are only used for distinguishing the descriptive purpose and should not be construed as indicating or implying relative importance or order. The invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0015] Please refer to Figure 1 The electrical connection structure of the parallel system of low-voltage regulating devices includes: Building such Figure 1 The circuit model includes multiple non-isolated modular low-voltage regulators, controllers, filters, current sensors, and voltage sensors; among which the non-isolated modular low-voltage regulators include a three-bridge-arm series-parallel power converter. Please refer to Figure 2 A schematic diagram illustrating the implementation process of a low-voltage flexible voltage regulator with flexible capacity expansion capabilities and a distributed control method, including: Step S201: Based on the current sensor in step 1, measure the filter inductor current of the parallel bridge arm of the navigation module. Series bridge arm filter inductor current The current of the bidirectional thyristor Follower module parallel bridge arm filter inductor current Series bridge arm filter inductor current The grid-side input voltage is measured based on the voltage sensor. Compensation voltage on the series side of the navigation module and the DC bus voltage of the pilot module and the follower module , ; Step S202: The navigation controller is used to measure the obtained grid voltage. The grid voltage amplitude is monitored using a second-order generalized integrator phase-locked loop (SOGI-PLL). And obtain the real-time power grid phase angle at that time. According to amplitude With the temporary drop threshold Determine if a power grid dip has occurred, and issue a dip occurrence command. When a temporary landing occurs, the navigation module switches to the thyristor forced turn-off mode; Step S203: The navigation controller determines the current of the bidirectional thyristor. The current at the moment of the dip is maintained by a sample-and-hold circuit. The polarity is used to obtain the reference current of the navigation module under the forced turn-off mode of the thyristor. The modulation voltage of the series section of the navigation module under the thyristor forced turn-off mode is obtained through current loop control. ; Optionally, step S203 can be implemented as follows: (1) (2) Please refer to Figure 3 A block diagram of a low-voltage flexible voltage regulator with flexible capacity expansion capability and a distributed control method, including: Step S204: The follower controller receives the descent initiation command and current reference from the pilot module. Switch to synchronous forced shutdown mode; Step S205: The navigation controller monitors... After the thyristor is turned off, the signal switches to voltage compensation mode and sends a mode switching command to the follower module. ; Step S206: The navigation controller calculates the voltage reference in phase with the power grid in voltage compensation mode. The voltage reference that the navigation module needs to compensate for. ; Optionally, step S206 can be implemented as follows: (3) Step S207: The navigation controller obtains the current reference for each module through the voltage controller based on the obtained compensation voltage reference. Subsequently, through the inner current loop and voltage feedforward, and by adding a virtual impedance element, the modulation voltage of the series section of the navigation module is obtained. ; Optionally, step S207 can be implemented as follows: (4) (5) Step S208: Follow the controller to receive mode switching commands via the communication bus. and Synchronously switching to voltage compensation mode, the modulation voltage of the series section of the follower module is obtained through current control, voltage feedforward, and virtual impedance stages. ; Optionally, step S208 can be implemented as follows: (6) Step S209: The navigation controller references the inner loop current amplitude of the parallel section. Based on the real-time phase of the power grid, the reference compensation current required for the pilot parallel section is calculated. ; Optionally, step S209 can be implemented as follows: (7) Please refer to Figure 4 The algorithm flowchart of the non-isolated modular low-voltage regulator provided in this embodiment of the invention.

[0016] Step S210: Based on the obtained compensation current reference, the navigation controller obtains the modulation voltage of the parallel part of the navigation module through the current controller. ; Optionally, step S210 can be implemented as follows: (8) in, This is the proportionality coefficient of the current loop. This is the resonant gain coefficient. This represents the bandwidth at the center frequency.

[0017] Step S211: The navigation controller combines the obtained series and parallel modulation voltages to obtain the total modulation signal. The switching control signal is obtained through SVPWM vector modulation of the three bridge arms.

[0018] Optionally, step S211 can be implemented by the navigation controller obtaining the control signal of the three-bridge arm switch, as shown in the following formula: (9) Step S212: The follower controller receives the power grid phase angle from the pilot controller via the communication bus. Based on the measured DC bus voltage The DC voltage control generates the required compensation current reference to follow the parallel connection. ; Step S213: Based on the obtained compensation current reference, the follower controller obtains the modulation voltage of the parallel part of each follower module through the current controller. The total modulation signal is obtained by combining the obtained series and parallel modulation voltages. The switching control signal is obtained through SVPWM vector modulation of the three bridge arms.

[0019] Please refer to Figure 5 When the number of parallel modules is n=2, (a)~(d) are the simulated waveforms of communication delay under normal conditions, and (a) and (b) show the waveforms of grid voltage and load voltage. The grid voltage drops by 40% from 0.1s to 0.3s. The proposed equipment ensures the normal power supply of the load side voltage through the coordinated compensation of the pilot module and the follower module. Figure 5 (c) and (d) show the output currents of the pilot module and the follower module, respectively. It can be seen that through the proposed control, the system achieves power sharing between the pilot and follower modules under different modes, without overcharging of the DC bus or circulating current issues in either module. Figures (e) to (h) show the waveforms after adding a 150µs communication delay at 0.15s during the 0.1s to 0.3s grid sag of 40%. This demonstrates the impact of the communication delay on the overall system output, showing distortion and imbalance in the output currents of each module. Figures (i) to (d) show... l During the 0.1s~0.3s period when the power grid sags by 40%, and the load doubles at 0.15s, the waveforms of the system voltage and current show that when the load changes, the load-side compensation voltage is not affected, and the output current of the pilot module and the follower module increases synchronously with the increase of the load.

[0020] Please refer to Figure 6 , Figure 6 (a) To achieve information exchange between the pilot and follower modules via full-duplex communication over a relatively high-latency ring Ethernet network. Assume the number of parallel units is... n The Ethernet transmission speed is 100Mbps. The pilot module periodically sends the follower module's current reference (2 bytes), grid phase (2 bytes), grid sag status bit (2 bytes), and mode switching status bit (2 bytes) under thyristor forced commutation mode and dynamic voltage compensation mode, totaling 8 bytes of data. Taking the EtherCAT communication bus as an example, the calculation principle of the data packet refresh time is analyzed. A minimum Ethernet data packet is 84 bytes; if less than 84 bytes, it is automatically padded. An 84-byte data packet can only contain a maximum of 18 bytes of process data. The essence of the bus refresh time is that the data packet needs to pass through each slave station twice to return to the master station. Therefore, the total time for two transmissions at a baud rate of 100Mbps needs to be calculated. When the communication period is 10kHz, the communication direction and interaction data between the pilot and follower modules can be used to calculate the single transmission time. t T for: (10)

[0021] Considering that the master station transmits a clock reference, such as a timestamp, to the slave station via data packets and confirms the synchronization status through the status flags returned by the slave station, two types of additional data are generated: First, additional bytes for the synchronization time value, which are transmitted by the master station to the slave station as the current system time (such as a 64-bit timestamp), synchronization cycle offset, etc., for the slave station to calibrate its local clock. Second, slave station synchronization flag bits. After receiving synchronization information, each slave station will append a 1-bit status flag to the data packet, such as "synchronized" or "synchronization error". The master station uses these flags to confirm the synchronization status of all slave stations.

[0022] Therefore, after adding clock synchronization, the new bus refresh time is: (11) Hardware latency occurs as data packets pass through each slave station; this is the slave station latency of a 100M Cat 5e Ethernet cable interface. Approximately 1 μs, which needs to be added to the total refresh time, thus yielding the communication delay that varies with the number of slave stations n: (12) The sampling period of communication T It must cover the bus transmission time and the processing time of all slave stations. As can be seen from equations (10) to (12), when the sampling period... T When the value is 100µs, the maximum number of slave stations is 42. This can be obtained as follows: Figure 6 (b) shows the curve of communication delay time as a function of the number of following modules.

[0023] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

[0024] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0025] Example module Figure 7 As shown, a low-voltage flexible voltage regulator with flexible capacity expansion capability and a distributed control method include: The first acquisition module 701, based on the current sensor, measures the filter inductor current of the parallel bridge arm of the navigation module, the filter inductor current of the series bridge arm and the current of the bidirectional thyristor, the filter inductor current of the parallel bridge arm of the follower module, and the filter inductor current of the series bridge arm. Based on the voltage sensor, it measures the grid-side input voltage, the series-side compensation voltage of the navigation module, and the DC bus voltage of the navigation module and the follower module. The first determining module 702, the navigation controller, is used to measure the obtained grid voltage. It monitors the grid voltage amplitude through a second-order generalized integrator phase-locked loop and obtains the real-time grid phase angle. Based on the amplitude and the sag threshold, it determines whether a sag has occurred in the grid. When a sag occurs, it issues a sag occurrence command. The navigation module switches to the thyristor forced turn-off mode; The second acquisition module 703, the navigation controller, based on the current of the bidirectional thyristor, maintains the polarity of the current at the moment of the sag through a sample-and-hold circuit, obtains the current reference of the navigation module under the forced turn-off mode of the thyristor, and obtains the modulation voltage of the series part of the navigation module under the forced turn-off mode of the thyristor through current loop control. The second determining module 704, the navigation controller, monitors the thyristor current signal. After the thyristor is turned off, it switches to the voltage compensation mode and sends a mode switching command to the follower module. The third module 705 calculates the voltage reference in phase with the power grid and the voltage reference that the navigation module needs to compensate in voltage compensation mode. Then, through the compensation voltage reference, the voltage controller obtains the current reference of each module. Subsequently, through the current inner loop and voltage feedforward, and by adding a virtual impedance link, the modulation voltage of the series part of the navigation module in voltage compensation mode is obtained. The fourth module 706 obtains the current reference of each module by the navigation controller based on the obtained compensation voltage reference. Then, through the current inner loop and voltage feedforward, and with the addition of a virtual impedance link, the modulated voltage of the series part of the navigation module is obtained. The fifth module 707, the navigation controller, based on the obtained DC bus reference voltage and combined with the measured DC bus voltage, obtains the current inner loop amplitude reference of the parallel part through the proportional-integral controller, and calculates the current reference that needs to be compensated for in the navigation parallel part according to the real-time phase of the power grid. The sixth module 708 obtains the modulation voltage of the parallel part of the navigation module based on the obtained compensation current reference and through the current controller. The fourth determining module 709, the navigation controller, combines the obtained series and parallel modulation voltages to obtain the total modulation signal, and obtains the switching control signal through special three-bridge-arm SVPWM vector modulation; The seventh acquisition module 710 receives the temporary landing command from the pilot controller via the communication bus. With current reference Switch to synchronous forced turn-off mode, and obtain the series modulation voltage of the follower module in synchronous forced turn-off mode through current loop control; The eighth module 711 receives the mode switching command from the controller. and Synchronously switch to voltage compensation mode, and after current control, voltage feedforward and virtual impedance stages, obtain the modulation voltage of the series part of the follower module in voltage compensation mode; The ninth module 712 obtains the compensation current reference obtained by the follower controller based on the DC voltage loop, and obtains the modulation voltage of the parallel part of each follower module through the current controller; The fifth determining module 713 obtains the total modulation signal by combining the series and parallel modulation voltages obtained by the controller, and obtains the switching control signal by three-bridge SVPWM vector modulation; Figure 8 This is a schematic diagram of a modular low-voltage regulating device provided in an embodiment of the present invention.

[0026] The schematic diagram of the non-isolated modular low-voltage regulator is shown below. Figure 8 As shown, it includes: a non-isolated modular low-voltage regulator 801, a controller 802, a memory 803, and a computer program 804 stored in the memory 803 and executable on the controller 802. When the controller 802 executes the computer program 804, it implements the steps in the above-described resonance suppression method embodiments, for example... Figure 2 The steps S201 to S208 are shown. Alternatively, when the controller 802 executes the computer program 804, it implements the power of each module / unit in the above embodiments, for example... Figure 8 The functions of modules 801 to 809 are shown.

[0027] For example, the computer program 804 can be divided into one or more modules / units, which are stored in the memory 803 and executed by the controller 802 to complete the embodiments of the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program 804 in the non-isolated modular low-voltage regulator 8. For example, the computer program 804 can be divided into a first obtaining module, a first determining module, a second obtaining module, a second determining module, a third obtaining module, a fourth obtaining module, a fifth obtaining module, a sixth obtaining module, a fourth determining module, a seventh obtaining module, an eighth obtaining module, and a ninth obtaining module. The functions of the fifth obtaining module and each module are as described above. The multi-machine parallel system and control method based on a non-isolated modular low-voltage regulator may include, but is not limited to, a power conversion circuit 801, a controller 802, and a memory 803. Those skilled in the art will understand that... Figure 8 This is merely an example of a non-isolated modular low-voltage regulator and does not constitute a limitation on non-isolated modular low-voltage regulators. It may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the life assessment terminal equipment for the power transformer may also include input / output devices, network access devices, buses, etc.

[0028] The controller 8 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0029] The memory 8 can be an internal storage unit of the non-isolated modular low-voltage regulator 8, or an external storage circuit of the non-isolated modular low-voltage regulator 8. Examples include plug-in hard drives, smart media cards (SMC), secure digital cards (SD), and flash cards equipped with the non-isolated modular low-voltage regulator 8. Further, the memory 803 can include both internal storage units and external storage devices of the hybrid compensation system device 8. The memory 803 is used to store the computer program and other programs and data required by the non-isolated modular low-voltage regulator. The memory 803 can be used to temporarily store data that has been output or will be output.

[0030] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0031] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not described in detail or in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0032] In the embodiments provided by this invention, it should be understood that the disclosed apparatus / terminal devices and methods can be implemented in other ways. For example, the apparatus / terminal device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some units can be selected to achieve the purpose of this embodiment according to actual needs.

[0033] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0034] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0035] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability, characterized in that, include: Multiple modular non-isolated low-voltage regulators, bidirectional thyristors, DC bus capacitors, a pilot controller, a follower controller, filters, current sensors, and voltage sensors; the non-isolated modular low-voltage regulators consist of three-bridge series-parallel converters; the filters include filter inductors. , and series capacitor The first end of the first current sensor is connected to the power grid, and the second end is connected to the parallel bridge arm (VT1~VT2) of the three-bridge structure in the device; the first segment of the second current sensor is connected to the series bridge arm (VT5~VT6) of the three-bridge structure in the device, and the second end is connected to the filter inductor. The bidirectional thyristor is connected in the following way: its first terminal is connected to the L-line of the power grid, its second terminal is connected to the third current sensor, and the second terminal of the third current sensor is connected to the PCC bus. The voltage sensor is installed on the power grid side, and the device includes the DC bus capacitor and the pilot module series capacitor. superior.

2. A low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability, characterized in that, include: The filter inductor current of the parallel bridge arm of the navigation module is measured using the current sensor described in point 1. Series bridge arm filter inductor current The current of the bidirectional thyristor Follower module parallel bridge arm filter inductor current Series bridge arm filter inductor current The grid-side input voltage is measured based on the voltage sensor. Compensation voltage on the series side of the navigation module and the DC bus voltage of the pilot module and the follower module , ; The navigation controller is used to measure the obtained grid voltage. The grid voltage amplitude is monitored using a second-order generalized integrator phase-locked loop (SOGI-PLL). And obtain the real-time power grid phase angle at that time. According to amplitude With temporary drop threshold Determine if a power grid dip has occurred; if a dip occurs, issue a dip occurrence command. The navigation module switches to the thyristor forced turn-off mode; The navigation controller is based on the current of the bidirectional thyristor. The current at the moment of the dip is maintained by a sample-and-hold circuit. The polarity is used to obtain the reference current of the navigation module under the forced turn-off mode of the thyristor. The modulation voltage of the series section of the navigation module under the thyristor forced turn-off mode is obtained through current loop control. ; The navigation controller monitors After the thyristor is turned off, the signal switches to voltage compensation mode and sends a mode switching command to the follower module. ; The navigation controller calculates a voltage reference that is in phase with the power grid in voltage compensation mode. The voltage reference that the navigation module needs to compensate for. ; The navigation controller obtains the current reference for each module through a voltage controller based on the obtained compensation voltage reference. Subsequently, through the inner current loop and voltage feedforward, and by adding a virtual impedance element, the modulation voltage of the series section of the navigation module is obtained. ; The navigation controller is based on the obtained DC bus reference voltage. Combined with the measured DC bus voltage The reference current inner loop amplitude of the parallel section is obtained through a proportional-integral controller. Based on the real-time phase of the power grid, the reference compensation current required for the pilot parallel section is calculated. ; The navigation controller, based on the obtained compensation current reference, obtains the modulation voltage of the parallel section of the navigation module through a current controller. ; The navigation controller combines the obtained series and parallel modulation voltages to obtain the total modulation signal. The switching control signal is obtained through special three-bridge-arm SVPWM vector modulation; The follower controller receives the power grid phase from the pilot controller via a communication bus. and current loop reference and and the order to temporarily land and mode switching commands When a temporary landing command is received With current reference Switching to synchronous forced turn-off mode, and obtaining the series modulation voltage of the follower module through current loop control. ; The follower controller receives a mode switching command. and Synchronously switching to voltage compensation mode, the modulation voltage of the series section of the follower module is obtained through current control, voltage feedforward, and virtual impedance stages. ; The follower controller receives the power grid phase angle from the pilot controller via a communication bus. Based on the measured DC bus voltage The DC voltage control generates the required compensation current reference to follow the parallel connection. ; The follower controller obtains a compensation current reference based on the DC voltage loop, and then uses a current controller to obtain the modulation voltage of the parallel section of each follower module. ; The follower controller combines the obtained series and parallel modulation voltages to obtain the total modulation signal. The switching control signal is obtained through SVPWM vector modulation of the three bridge arms.

3. The low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability according to claim 2, characterized in that, The navigation controller compares voltage amplitudes. With temporary drop threshold The system determines whether a voltage sag has occurred in the mains grid. If so, it blocks the thyristor gate pulse, switches to the thyristor forced turn-off mode, and sends a sag occurrence command to the follower module. In this mode, the SCR current at the moment of sag is maintained by a sample-and-hold circuit. The polarity is obtained by the following formula for the reference current of the navigation module under the forced turn-off mode of the thyristor. The modulation voltage of the series section of the navigation module under the thyristor forced turn-off mode is obtained through current loop control. ; (1) (2) in This is the thyristor current gain factor. Forced turn-off of the thyristor is achieved through current inner loop control; when the thyristor current... consecutively less than At this time, the forced commutation phase of the thyristor in the navigation module ends, and it waits to enter the dynamic voltage compensation mode; The navigation controller, in dynamic voltage compensation mode, is based on the real-time grid phase angle. The voltage reference in phase with the power grid was calculated. The voltage reference that needs to be compensated for by the pilot As shown in equation (3): (3) In the formula, This indicates the voltage reference amplitude set by the power grid.

4. The low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability according to claim 2, characterized in that, The navigation controller obtains the current reference of each module through a voltage controller. As shown in equation (4): (4) in, For the number of parallel modules, This is the voltage loop proportionality coefficient. This is the resonant gain coefficient. This represents the bandwidth at the center frequency.

5. The low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability according to claim 2, characterized in that, The navigation controller obtains the modulated voltage of the series section of the navigation module through an inner current loop and voltage feedforward, and by adding a virtual impedance element. As shown in equations (5) and (6): (5) (6) in This is the proportionality coefficient of the current loop. This is the virtual resistance at the selected frequency.

6. The low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability according to claim 2, characterized in that, The navigation controller references the inner loop current amplitude of the parallel section. Based on the real-time phase of the power grid, the reference compensation current required for the pilot parallel section is calculated. As shown in equation (7): (7)。 7. The low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability according to claim 2, characterized in that, The navigation controller, based on the obtained compensation current reference, obtains the modulation voltage of the parallel section of the navigation module through a current controller. As shown in the following formula: (8) in, This is the proportionality coefficient of the current loop. This is the resonant gain coefficient. The bandwidth at the center frequency; The navigation controller combines the obtained series and parallel modulation voltages to obtain the total modulation signal. As shown in equation (9): (9)。 8. The low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability according to claim 2, characterized in that, The follower controller receives descent initiation commands, mode switching commands, and current reference commands from the navigation module. and current loop reference After current control, voltage feedforward, and virtual impedance stages, the modulated voltage of the series section of the follower module is obtained. As shown in equation (10): (10)。 9. The low-voltage flexible voltage regulating device and distributed control method with flexible capacity expansion capability according to claim 2, characterized in that, The follower controller references the inner loop amplitude value of its parallel current component. The phase of the power grid received from the navigation controller The required compensation current reference is calculated using equation (7). Then, the modulation voltage of the parallel part of the follower module is obtained through equation (8). .

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