High-voltage circuit breaker intelligent control system based on positive and negative zero sequence control algorithm

Abstract

The invention relates to the technical field of circuit breaker control, and discloses a high-voltage circuit breaker intelligent control system based on a positive and negative zero sequence control algorithm, and the system comprises a cascaded H-bridge static synchronous compensator which is in star connection, and each phase of the cascaded H-bridge static synchronous compensator is composed of a plurality of H-bridge units; the data acquisition module is used for acquiring voltage and current signals of the three-phase system in real time; the control module is used for operating a positive and negative zero sequence control algorithm and realizing voltage fluctuation optimization and unbalanced load compensation through independent control of three-sequence components; the communication module is used for data interaction between the control module and an upper computer; and the connecting inductor is used for connecting the static synchronous compensator and a power grid so as to reduce harmonic interference and provide necessary impedance. By independently controlling the positive sequence component, the negative sequence component and the zero sequence component, the technical effect of reducing the unbalance degree of the power grid is achieved, the problems of response lag and high unbalance degree under the condition of rapid load change in the traditional technology are solved, and the electric energy quality of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit breaker control, and in particular to an intelligent control system for a high-voltage circuit breaker based on a positive and negative zero-sequence control algorithm. Background Art

[0002] With the continuous expansion of the scale of power systems and the increase in the complexity of power loads, the power quality of power grids has received increasing attention. In three-phase four-wire systems, the presence of unbalanced loads generally leads to problems such as voltage fluctuations, increased harmonics, and excessive neutral line current. In order to alleviate these problems, traditional high-voltage circuit breakers and related control systems mostly use mechanical switching principles to achieve load switching through simple closing or opening operations. These solutions usually combine reactive power compensation equipment or filtering devices to adjust the imbalance of the power grid to improve the stability and operating efficiency of the power grid to a certain extent. At the same time, with the rapid development of power electronics technology, static synchronous compensators, as a dynamic compensation device, have gradually played a positive role in the field of power quality improvement, especially in reactive power compensation.

[0003] However, although the existing technology has achieved certain results in improving power quality, it still has certain shortcomings as the diversification of power equipment and the continuous improvement of load complexity. On the one hand, the control strategy of traditional high-voltage circuit breakers is usually based on simple mechanical switching, which makes it difficult to respond efficiently to rapid changes in loads, resulting in poor operating stability under dynamic load conditions. On the other hand, although the static synchronous compensator has good reactive power compensation performance, most of them adopt a single positive sequence component adjustment strategy, which cannot fully solve the imbalance problem caused by negative sequence and zero sequence components. In addition, the design of the DC side circuit and the connecting inductor in the existing technology is also relatively fixed, lacking the ability to adapt to current and voltage fluctuations under dynamic load conditions, which may lead to insufficient harmonic suppression capability and a decrease in system response performance. Therefore, in response to the above problems, there is an urgent need for a new type of high-voltage circuit breaker intelligent control system that can realize independent control of the three-sequence components and has efficient dynamic compensation capabilities to improve the stability of power grid operation and power quality. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides an intelligent control system for high-voltage circuit breakers based on positive, negative and zero-sequence control algorithms, which solves the problems of the existing high-voltage circuit breakers being unable to independently control the positive-sequence, negative-sequence and zero-sequence components under complex load conditions and having insufficient dynamic compensation performance.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: an intelligent control system for high-voltage circuit breakers based on a positive and negative zero-sequence control algorithm, comprising: A star-connected cascaded H-bridge static synchronous compensator, each phase of which consists of multiple H-bridge units; Data acquisition module, used for real-time acquisition of voltage and current signals of three-phase system; A control module for running the positive and negative zero-sequence control algorithm to achieve voltage fluctuation optimization and unbalanced load compensation through independent control of the three-sequence components; Communication module, used for data interaction between the control module and the host computer; Connecting inductor, used to connect the static synchronous compensator and the power grid to reduce harmonic interference and provide necessary impedance; An execution module, used for adjusting the output of the static synchronous compensator according to the compensation instruction output by the control module; The DC side circuit, including capacitors and power switching devices, is used to provide DC voltage support and safety redundancy.

[0006] Preferably, the data acquisition module includes an analog-to-digital converter and a multi-channel GPIO interface for completing accurate sampling and real-time transmission of voltage and current signals.

[0007] Preferably, the main control chip in the control module is a STM32F407 high-performance microprocessor with a built-in DSP computing unit for running the control algorithm and outputting PWM signals, while also being able to collect voltage signals and process interrupt signals.

[0008] Preferably, the positive, negative and zero-sequence control algorithm in the control module obtains positive-sequence, negative-sequence and zero-sequence components by symmetrically decomposing the current and voltage signals of the three-phase system, and independently controls the positive-sequence component to achieve normal operation, suppresses the negative-sequence component to reduce system imbalance, and balances the zero-sequence component to reduce the neutral line current.

[0009] Preferably, the number of H-bridge units per phase of the star-connected cascade H-bridge static synchronous compensator is 12, and there are 2 redundant units, so that the system can still operate stably when the number of units is reduced to 10.

[0010] Preferably, the capacitor design parameters of the DC side circuit meet the following requirements: the capacitance value is calculated based on the current, frequency, DC voltage and redundancy factor, and the DC side capacitance fluctuation range is controlled within the allowable range of 1% to 10%.

[0011] Preferably, the control module communicates with the host computer through RS-485 and CAN communication interfaces. The RS-485 interface uses an integrated isolated converter, and the CAN interface uses a high-speed isolated converter to support real-time data transmission and remote control.

[0012] Preferably, the control of the DC voltage in the DC side circuit satisfies: The total DC side voltage is allocated according to the system operating voltage and the number of individual H-bridge units, and the DC voltage of each H-bridge unit is calculated by dividing the total DC voltage by the number of units.

[0013] Preferably, the value of the connection inductance satisfies the relationship between the system voltage fluctuation and the rated current. The connection inductance is calculated based on the matching of the AC voltage, the compensation voltage and the current fluctuation, and the inductance value is optimized to reduce harmonic interference.

[0014] Preferably, the control module runs a main program, which includes the following steps: Initialize the control system, including various interfaces, GPIO ports and analog-to-digital conversion modules; Configure the interrupt service routine address and start the timer for periodic data collection; The control module collects voltage and current signals in real time and outputs compensation instructions through positive and negative zero-sequence control algorithms; The execution module adjusts the output of the static synchronous compensator according to the instructions to achieve reactive power compensation and voltage balance; Clear the interrupt flag, end the current task, and return to the main loop.

[0015] The present invention provides an intelligent control system for high-voltage circuit breakers based on a positive and negative zero-sequence control algorithm. It has the following beneficial effects: 1. The present invention adopts a three-sequence decoupling technology based on a positive, negative and zero-sequence control algorithm. By independently controlling the positive-sequence, negative-sequence and zero-sequence components, the technical effect of reducing the imbalance of the power grid is achieved. Compared with the control scheme in the prior art that cannot effectively handle complex load conditions, the present invention solves the problems of delayed response and high imbalance of traditional technologies under rapid load changes, and improves the power quality of the system.

[0016] 2. The present invention realizes precise control of voltage fluctuations through a star-connected cascade H-bridge static synchronous compensator combined with a DC voltage dynamic distribution strategy, ensuring the smooth operation of the three-phase DC voltage. Compared with the fixed DC voltage distribution method in the prior art that is difficult to adapt to dynamic working conditions, the present invention solves the problem of low system operation efficiency caused by unstable grid voltage and further enhances the system operation reliability.

[0017] 3. The present invention successfully suppresses harmonic interference and improves the dynamic response capability of the system by designing and optimizing the connecting inductor and comprehensively considering the grid voltage, compensation voltage and current fluctuations. Compared with the problem of overly single connecting inductor design in the prior art, the present invention solves the shortcomings of poor harmonic suppression and large current impact under dynamic load, and realizes efficient collaboration between the grid and the compensator.

[0018] 4. The present invention adopts a modular design, including fluctuation control of DC side capacitors and optimized configuration of power switching devices, to achieve efficient compensation and system redundancy protection. Compared with the traditional solution that lacks reliable operation guarantee when a unit fails, the present invention can maintain stable operation while reducing modular units, thereby improving the system's fault tolerance and ability to adapt to various load conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the system module of the present invention; Figure 2 It is a schematic diagram of positive sequence, zero sequence and negative sequence components of the present invention; Figure 3 It is a schematic diagram of the RS-485 communication circuit and the CAN communication circuit of the present invention; Figure 4 It is a waveform diagram of the average value of the three-phase DC side voltage of the present invention; Figure 5 The load current and the compensated system current waveform diagram of the present invention; Figure 6 The system voltage waveform diagram before and after compensation of the present invention; Figure 7 It is the test waveform diagram of the voltage and current before and after compensation of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Please refer to the attached Figure 1 -Attached Figure 7 The embodiment of the present invention provides an intelligent control system for a high-voltage circuit breaker based on a positive and negative zero-sequence control algorithm, comprising: A star-connected cascaded H-bridge static synchronous compensator, each phase of which consists of multiple H-bridge units; Data acquisition module, used for real-time acquisition of voltage and current signals of three-phase system; A control module for running the positive and negative zero-sequence control algorithm to achieve voltage fluctuation optimization and unbalanced load compensation through independent control of the three-sequence components; Communication module, used for data interaction between the control module and the host computer; Connecting inductor, used to connect the static synchronous compensator and the power grid to reduce harmonic interference and provide necessary impedance; An execution module, used for adjusting the output of the static synchronous compensator according to the compensation instruction output by the control module; DC side circuit, including capacitors and power switching devices, used to provide DC voltage support and safety redundancy; The data acquisition module includes an analog-to-digital converter and a multi-channel GPIO interface, which is used to complete the accurate sampling and real-time transmission of voltage and current signals; The main control chip in the control module is a STM32F407 high-performance microprocessor with a built-in DSP computing unit, which is used to run the control algorithm and output PWM signals. It can also collect voltage signals and process interrupt signals. The positive, negative and zero sequence control algorithm in the control module decomposes the current and voltage signals of the three-phase system symmetrically to obtain positive, negative and zero sequence components, and independently controls the positive sequence component to achieve normal operation, suppresses the negative sequence component to reduce system imbalance, and balances the zero sequence component to reduce the neutral line current; The number of H-bridge units per phase of the star-connected cascaded H-bridge static synchronous compensator is 12, and it has 2 redundant units, which supports stable operation of the system when the number of units is reduced to 10; The capacitor design parameters of the DC side circuit meet the following requirements: the capacitance value is calculated based on the current, frequency, DC voltage and redundancy factor, and the DC side capacitance fluctuation range is controlled within the allowable range of 1% to 10%; The control module communicates with the host computer through RS-485 and CAN communication interfaces. The RS-485 interface uses an integrated isolated converter, and the CAN interface uses a high-speed isolated converter to support real-time data transmission and remote control. The control of DC voltage in the DC side circuit satisfies: The total DC side voltage is allocated according to the system operating voltage and the number of individual H-bridge units, and the DC voltage of each H-bridge unit is calculated by dividing the total DC voltage by the number of units; The value of the connection inductance satisfies the relationship between the system voltage fluctuation and the rated current. The connection inductance is calculated based on the matching of the AC voltage, compensation voltage and current fluctuations, and the inductance value is optimized to reduce harmonic interference; The control module runs the main program, which includes the following steps: Initialize the control system, including various interfaces, GPIO ports and analog-to-digital conversion modules; Configure the interrupt service routine address and start the timer for periodic data collection; The control module collects voltage and current signals in real time and outputs compensation instructions through positive and negative zero-sequence control algorithms; The execution module adjusts the output of the static synchronous compensator according to the instructions to achieve reactive power compensation and voltage balance; Clear the interrupt flag, end the current task, and return to the main loop.

[0022] Specifically, the star-connected cascade H-bridge static synchronous compensator aims to solve the load imbalance and power quality problems in complex power grids through optimized design and control strategy. Its main functions include dynamic reactive power compensation, load imbalance correction and harmonic suppression.

[0023] The star connection structure of the compensator is an important technical feature of the present invention. Generally speaking, compared with the traditional triangle connection, each phase H-bridge unit of the star connection only needs to withstand the phase voltage of the power grid, not the line voltage. This design significantly reduces the voltage bearing requirement of the H-bridge unit and improves the safety and stability of the system. At the same time, this topology can simplify the implementation of the control algorithm and reduce the switching loss during system operation.

[0024] In this embodiment, the star-connected H-bridge unit per phase is composed of 12 modules connected in series, forming a total of 36 H-bridge module structures of three phases. In order to improve reliability, the present invention designs two redundant units. When the number of units is reduced to 10 due to failure, the system can still operate normally. This redundancy mechanism effectively enhances the fault tolerance and application flexibility of the compensator.

[0025] During operation, the star-connected topology works in conjunction with the positive, negative and zero-sequence control algorithms of the control module, enabling the system to maintain efficient reactive power compensation and load balancing capabilities under different load conditions. Specifically, the control module calculates the positive, negative and zero-sequence components based on the collected three-phase signals of the power grid, and independently controls these three parts. The positive sequence component is used to maintain the normal operation of the system, the negative sequence component is suppressed to reduce imbalance, and the zero sequence component reduces the neutral line current through dynamic adjustment, thereby improving the stability of the system.

[0026] The DC side design of the cascaded H-bridge unit fully considers the control requirements of the voltage fluctuation range. Each H-bridge unit is equipped with multiple aluminum electrolytic capacitors as DC voltage support, and its rated capacity and voltage level are carefully selected to ensure voltage stability while reducing material costs. In the DC side voltage distribution, through reasonable capacitor configuration and control strategy, fast response to different load conditions can be achieved. In addition, in order to improve the system operation efficiency, the fluctuation range of the DC side is strictly controlled between 1% and 10%.

[0027] In this embodiment, each H-bridge unit is connected to the grid via a connecting inductor. The main function of the connecting inductor is to suppress high-frequency harmonic interference and provide necessary impedance support for the dynamic adjustment of the static synchronous compensator. In the actual design, the parameter selection of the connecting inductor comprehensively considers the balance between harmonic suppression and dynamic performance, so that it can adapt to the operation requirements in a complex grid environment.

[0028] In terms of control strategy, an innovative distributed control architecture is adopted in this embodiment. The main control chip works with the built-in DSP computing unit to accurately adjust the output of the H-bridge unit through the positive and negative zero-sequence control algorithm. The modulation signal calculated by the main control chip will be converted into control instructions for each H-bridge unit through the PWM drive module, thereby dynamically adjusting the output voltage and current. Under load mutation or fault conditions, the control system can quickly reallocate compensation tasks to achieve stable operation of the system.

[0029] In the experiment, the star-connected cascade H-bridge static synchronous compensator of the present invention showed good dynamic response capability and reliability. Under the condition of large load changes, the response time of the system was controlled within 50ms, and the three-phase DC voltage fluctuation range was within ±2.5%. The imbalance was significantly reduced from the original 6.57% to 0.83%. This experimental result shows that the present invention can effectively improve the power quality and stability of complex power grids.

[0030] In this embodiment, the core of the data acquisition module includes an analog-to-digital converter and a multi-channel GPIO interface, which is used to acquire and process three-phase voltage and current signals. As an option, the present invention uses an AD7606 analog-to-digital converter. The converter supports multi-channel synchronous sampling, has a high sampling rate, and a resolution of 16 bits, which can generally meet the sampling requirements of rapidly changing power grid signals.

[0031] Specifically, the input end of the AD7606 analog-to-digital converter is connected to the power grid through a sampling resistor and a filter capacitor to perform voltage division and noise filtering on the input signal. In some embodiments, a high-precision operational amplifier circuit can also be connected in series at the input end to further improve the linearity and amplitude consistency of the signal. As an option, the sampling resistor value in the present invention is designed to be 10kΩ, and the filter capacitor value is designed to be 1μF to achieve a balance between signal integrity and response speed.

[0032] The multi-channel GPIO interface serves as a bridge between the analog-to-digital converter and the main control chip, responsible for transmitting sampled data and control instructions. In one possible implementation, the GPIO interface uses the internal resources of the STM32 microcontroller, supports high-speed data transmission, and provides input de-jitter processing to further improve data accuracy.

[0033] During the data acquisition process, the sampling frequency of the current and voltage signals needs to match the grid frequency to ensure the timing accuracy of the sampling. The sampling frequency in the present invention is set to 10kHz. Generally, this sampling frequency is sufficient to cover the main frequency band of the 50Hz grid signal and capture its dynamic changes.

[0034] In order to ensure the synchronization of data acquisition, the synchronous control circuit integrated in AD7606 is activated. Specifically, the synchronization signal is generated by the control module, triggering the sampling task of the analog-to-digital converter through the GPIO interface, thereby completing the synchronous sampling of the three-phase signal. The multi-channel sampling results are stored in the form of data registers and transmitted to the main control chip through DMA.

[0035] In one possible implementation, the data acquisition module uses a shielding design to prevent the signal from being affected by external electromagnetic interference during transmission. The shielding layer is made of highly conductive materials and grounded to eliminate the interference of high-frequency electromagnetic waves on the signal. In addition, a low-pass filter circuit is also configured at the power supply end of the analog-to-digital converter to suppress power supply ripple.

[0036] In some embodiments, the data acquisition module can be connected to the host computer through an RS-485 communication interface. In this case, the host computer can directly access the real-time data of the acquisition module to monitor the operating status of the power grid signal. As an option, the host computer can also exchange signals with the control module through a CAN interface to achieve faster data interaction.

[0037] The data acquisition module design of the present invention also fully considers the fault tolerance of hardware failures. For example, a surge protection circuit is added to the input circuit to cope with circuit damage caused by transient changes in the grid voltage. The surge protection circuit is composed of a high-voltage voltage-stabilizing diode and a fast fuse, which can quickly protect the analog-to-digital converter and the subsequent circuit from damage when an overvoltage event occurs.

[0038] In terms of software design, the data acquisition module also supports interrupt-driven mode. Specifically, after each sampling is completed, the analog-to-digital converter will notify the main control chip through an interrupt signal to complete the data reading task. This mode can not only improve the real-time performance of data acquisition, but also reduce the processing burden of the main control chip.

[0039] Through experimental verification, the data acquisition module of the present invention can realize accurate and fast signal acquisition at a sampling frequency of 10kHz. During the operation of the system, the error of the sampled data is controlled within ±0.1%. Compared with the traditional acquisition method, the module design of the present invention significantly improves the data transmission efficiency and anti-interference performance, and provides reliable input data support for the control module.

[0040] In this embodiment, the main control chip of the control module is selected as the STM32F407 high-performance microprocessor, which executes the positive and negative zero-sequence control algorithm through its built-in DSP operation unit and generates a PWM control signal to drive the execution module.

[0041] Specifically, the STM32F407 high-performance microprocessor pre-processes the three-phase voltage and current signals transmitted by the data acquisition module, and runs the positive and negative zero-sequence control algorithm through the built-in DSP operation unit, converting the calculation results into PWM signals and sending them to the execution module.

[0042] In the implementation of the positive and negative zero sequence control algorithm, the control module decomposes the three-phase current or voltage signal into symmetrical components, namely positive sequence, negative sequence and zero sequence components. These components are used for the normal operation of the system, load imbalance suppression and neutral line current balance. The mathematical model of the algorithm is as follows: in: Indicates the rated output current of the system; Indicates the system rated power; Indicates the rated voltage of the system.

[0043] By using this formula, the rated output current of the system can be calculated .

[0044] The control of positive sequence, negative sequence and zero sequence components is dynamically adjusted by proportional integral (PI) controller. For the zero sequence component, the calculation formula is: in: is the zero-sequence component current; , , is the three-phase current.

[0045] This component decomposition method can effectively identify and independently control each component, ensuring the smooth operation of the system under complex loads.

[0046] In some embodiments, the PWM signal generated by the main control chip is sent to the execution module through 18 output channels. The duty cycle of the PWM signal is dynamically adjusted according to the calculation results of the positive and negative zero-sequence control algorithm to match the compensation requirements under different load conditions.

[0047] As a possible implementation, the control module of the present invention supports communication with a host computer. Through RS-485 and CAN interfaces, the control module can send operating status data to the host computer and receive control instructions issued by the host computer. The RS-485 interface is used for low-speed data communication, such as status monitoring and operation log transmission; the CAN interface is used for high-speed real-time communication, such as parameter adjustment and fault alarm.

[0048] In order to improve the reliability of communication, the RS-485 interface uses an integrated isolated converter, and the CAN interface uses a high-speed isolated converter. These designs can effectively prevent the influence of electromagnetic interference on communication signals.

[0049] In terms of hardware protection design, the control module is equipped with a surge protection circuit and a decoupling filter circuit. The surge protection circuit consists of a high-voltage voltage-stabilizing diode and a fast fuse to protect the chip from damage caused by transient overvoltage in the power grid. The decoupling filter circuit uses a low-pass filter structure to suppress the interference of power supply ripple on chip operations.

[0050] In terms of software design, the software development of the main control chip is based on the CCS3.3 integrated development environment, using a modular programming method. The core functions of the main program include real-time data acquisition, signal processing, control algorithm operation, PWM signal output, and communication protocol implementation of the master and slave controllers. The software development of the auxiliary unit is based on the Keil5 development environment, focusing on the realization of H-bridge unit voltage sampling and interrupt task processing.

[0051] In experimental verification, the control module of the present invention can achieve real-time adjustment under the condition of rapid load changes. Specific experimental results show that the imbalance of the system is reduced from 6.57% before compensation to 0.83%. By dynamically adjusting the compensation voltage, the voltage fluctuation on the three-phase DC side is controlled within ±2.5%. The response time of the main control chip is less than 50ms, which meets the real-time control requirements under complex working conditions.

[0052] The communication module connects the control module with other devices, including the host computer, data acquisition module and execution module, to ensure the real-time and stability of the entire system. The design of the communication module must not only meet the needs of high-frequency data transmission, but also have anti-interference capabilities to deal with signal interference problems that may arise in complex power grid environments. Its collaborative work with the control module and data acquisition module provides an important guarantee for the overall functional realization of the system.

[0053] Generally, the interface type and communication protocol of the communication module need to match the control module and other components. In the present invention, the communication module is not only used for the transmission of instructions, but also responsible for status monitoring and the return of fault information. The design needs to take into account both the efficient transmission of data and the stable operation of the system. Specifically, the present invention adopts a variety of communication interfaces to meet the data interaction requirements in different scenarios.

[0054] In this embodiment, the communication module includes an RS-485 interface and a CAN communication interface, which are used to realize low-speed data transmission and high-speed real-time communication respectively. As an option, the RS-485 interface uses an integrated isolation converter, model TD541S485H, which provides an electrical isolation capability of up to 3000V to reduce the impact of electromagnetic interference on communication data. The CAN communication interface uses a high-speed isolation converter TD(H)541SCANH, which has high noise resistance and can ensure signal stability during high-speed data transmission.

[0055] Specifically, the RS-485 interface is mainly used to transmit low-frequency status data, such as system operation logs and basic operating parameters. Generally, the baud rate of the interface is set to 9600bps to meet the requirements of low-speed stable transmission. In some embodiments, the RS-485 interface is also used to send operation monitoring data to the host computer, such as voltage fluctuation range and compensation status.

[0056] In one possible implementation, the CAN communication interface is used to transmit control instructions and feedback signals in real time. Its communication rate is set to 500kbps, which can meet the high-frequency signal interaction requirements between the control module and the execution module. For example, the control module sends the real-time adjustment parameters of the PWM signal to the execution module through the CAN bus, and receives the operating status information fed back by the execution module. In this way, the communication module can quickly respond to dynamic changes in the system.

[0057] In order to improve the reliability of data transmission, the communication module of the present invention adopts a hardware redundancy design. In some embodiments, the isolation converter in the communication line will be configured with a backup circuit to prevent equipment failure from affecting the communication. Specifically, the input ends of the RS-485 and CAN interfaces are respectively connected to a filter circuit with a shielding function, and the filter circuit is composed of a multi-stage LC network to suppress high-frequency noise. In addition, the power supply circuit of the communication module is also equipped with a surge protection device to cope with transient voltage fluctuations in the power grid.

[0058] In terms of software design, the communication module of the present invention supports multi-task parallel processing. Specifically, the implementation of the communication protocol is based on the master-slave mode, in which the host computer is the master device and the control module is the slave device. The RS-485 protocol stack realizes the polling transmission of status data, while the CAN communication protocol supports the real-time interrupt trigger mode, which can give priority to the transmission of real-time data when a critical event occurs. For example, when the system detects that the load imbalance exceeds the set threshold, the control module will send an alarm signal to the host computer via the CAN bus.

[0059] During the data interaction process, the communication module also supports multi-node link transmission. In one possible implementation, multiple control modules can form a communication network through the CAN bus, and each module is identified by a unique ID. This multi-node architecture is suitable for large-scale power grid scenarios, can realize multi-point distributed control, and improves the applicability of the system.

[0060] In order to reduce communication delay, the message frame of the CAN bus is designed as a fixed-length frame, each frame contains a data field, a control field and a check field. The data field is used to transmit real-time parameters, such as the target value of compensation voltage and current; the control field contains frame priority information to ensure the transmission timeliness of key tasks; the check field verifies data integrity through the CRC algorithm.

[0061] The main function of the connecting inductor is to connect the star-connected cascaded H-bridge static synchronous compensator with the power grid, provide the necessary impedance support for the compensation circuit, suppress harmonic interference and smooth current fluctuations. The design of the connecting inductor needs to comprehensively consider key parameters such as grid voltage, compensation voltage, rated current and frequency to ensure stable operation and reliable performance of the system under dynamic load conditions.

[0062] Generally speaking, the design of the connection inductor needs to strike a balance between harmonic suppression and system dynamic response. The value of the inductor not only affects the system's ability to compensate for reactive power, but also has a direct impact on the smoothness of the current waveform. Therefore, it is crucial to accurately calculate and reasonably select the inductor value in the design.

[0063] In this embodiment, the design of the connection inductance is calculated based on the following formula: in: Indicates the connection inductance value; is the rated AC voltage of the system, which is 380 V in this embodiment; is the compensation voltage, and its calculation formula is: in: is the duty cycle coefficient; is the number of H-bridge units per phase; is the reference DC voltage of a single H-bridge unit; and They are used to decompose the compensation voltage into corresponding components respectively. is the grid angular frequency, and the calculation formula is: in is 50 Hz, so is 314 rad / s. is the system rated output current, and its calculation formula is: in: is the system rated power, which is 50 kVA in this embodiment; is the system rated voltage, which is 380 V.

[0064] Through the above calculation, the theoretical value of the connection inductance is 6.2 mH. In practical applications, in order to further optimize the dynamic response performance of the system and take into account the hardware manufacturing cost, the connection inductance value selected in this embodiment is 5.0 mH.

[0065] As an option, the connection inductor uses an iron core coil made of high magnetic permeability material, and its inductance value is precisely controlled by adjusting the number of coil turns and the cross-sectional area of ​​the iron core. Specifically, the iron core uses low-loss silicon steel sheets to improve energy efficiency, and the coil is wound with highly heat-resistant insulated copper wire. In addition, in order to reduce the impact of external electromagnetic interference on the system, the inductor coil is wrapped with shielding material and electrostatic shielding is performed through the ground terminal.

[0066] In some embodiments, the design of the connected inductor also combines heat dissipation and safety protection functions. Generally, the inductor in operation will generate heat due to the passage of current. In this embodiment, a forced air cooling device is used to cool the inductor, and multiple temperature sensors are configured around the inductor to monitor the operating temperature in real time. When the temperature exceeds the set threshold, the control module sends an alarm signal through the communication module to remind maintenance personnel to intervene.

[0067] In actual operation, the connection inductance has an important impact on the voltage stability and dynamic response performance of the system. For example, when the load changes suddenly, the connection inductance can smooth the change of current, reduce the impact of the power grid on the compensator, and ensure the continuity and reliability of the system operation. In addition, the reasonable design of the inductance value can also effectively suppress high-frequency harmonic components, thereby improving the quality of power.

[0068] The experimental results show that the performance of the selected 5.0 mH connection inductance in system operation meets the design expectations. Specific test data show that the system imbalance is reduced from 6.57% before compensation to 0.83%, and the system voltage fluctuation range is controlled within ±2.5%. At the same time, the total distortion rate of high-frequency harmonic components is reduced to 1.8%, which is far below the standard allowable value. Even under conditions of rapid load changes, the dynamic response time of the system is kept within 50 ms.

[0069] The execution module plays a core role in command execution in the intelligent control system of the high-voltage circuit breaker of the present invention. Its main function is to adjust the output of the star-connected cascade H-bridge static synchronous compensator in real time according to the compensation command output by the control module. The execution module directly affects the improvement effect of power quality and the dynamic response capability of the system. It works closely with the control module, the connection inductor and other components to jointly complete the reactive power compensation and grid balancing tasks under complex load conditions.

[0070] In general, the design of the execution module needs to take into account signal processing speed, hardware reliability and efficient execution performance. The hardware and control circuit of the execution module need to be able to withstand frequent dynamic adjustments while maintaining precise control of the compensator output to ensure that the system can operate stably under different working conditions.

[0071] The execution module plays a core role in command execution in the intelligent control system of the high-voltage circuit breaker of the present invention. Its main function is to adjust the output of the star-connected cascade H-bridge static synchronous compensator in real time according to the compensation command output by the control module. The execution module directly affects the improvement effect of power quality and the dynamic response capability of the system. It works closely with the control module, the connection inductor and other components to jointly complete the reactive power compensation and grid balancing tasks under complex load conditions.

[0072] In general, the design of the execution module needs to take into account signal processing speed, hardware reliability and efficient execution performance. The hardware and control circuit of the execution module need to be able to withstand frequent dynamic adjustments while maintaining precise control of the compensator output to ensure that the system can operate stably under different working conditions.

[0073] In this embodiment, the execution module mainly includes a power switch device, a PWM drive circuit and a current detection unit. As an option, the power switch device in the execution module adopts MOSFET, and its specific model is IRFB3207B. The device has a high current carrying capacity (rated current 180A) and low on-resistance (on-state voltage drop is about 4.5mΩ), and can maintain low power loss during high-frequency dynamic regulation. The rated voltage of MOSFET is 75V, which provides a 1.5-fold safety margin in combination with the DC voltage calculation of the system.

[0074] The PWM drive circuit is used to receive the PWM signal output by the control module and drive the power switch device to complete the compensation task. In one possible implementation, the drive circuit uses an isolated drive chip, which ensures the integrity and safety of the control signal through photoelectric isolation technology. The duty cycle of the PWM signal is dynamically adjusted according to the positive and negative zero-sequence control algorithm of the control module to achieve accurate output of the compensator.

[0075] Specifically, the current detection unit of the execution module is responsible for real-time monitoring of the output current of the compensator. Generally, the current detection unit uses a Hall sensor, which can achieve non-contact detection and has the characteristics of high precision and high response speed. In some embodiments, in order to enhance the detection accuracy, the current detection unit is also combined with a low-pass filter, and the cut-off frequency of the filter is designed to be 500Hz to filter out high-frequency noise interference.

[0076] The working process of the execution module is closely related to the connection inductance. The design of the connection inductance provides the necessary impedance support, enabling the execution module to adjust the compensation current more smoothly, thereby reducing the current impact during the dynamic adjustment process. In addition, the current waveform output by the execution module directly affects the power factor optimization and harmonic suppression effect of the system.

[0077] As an optimized design, the heat dissipation management of the execution module adopts a forced air cooling device. During high-frequency dynamic operation, the power switch device will generate a lot of heat, so it is necessary to control the device temperature within a safe range through forced heat dissipation. In some embodiments, the air cooling system is combined with a temperature sensor, which is connected to the control module. When the device temperature approaches the critical value, the control module will reduce the frequency of the compensation task to alleviate the temperature rise pressure.

[0078] In addition, the protection functions of the execution module include overcurrent protection and short-circuit protection. The overcurrent protection circuit monitors the output current. When the current exceeds the set threshold, it triggers the protection action and stops the output of the PWM signal to protect the power switch device from damage. Short-circuit protection is achieved through a fast fuse, which immediately cuts off the circuit when a short circuit occurs to prevent further damage to the system.

[0079] The DC side circuit plays a key role in supporting and stabilizing the operation of the compensator. Its main function is to provide DC voltage support for the star-connected cascade H-bridge static synchronous compensator and maintain the stability of the DC voltage when the load conditions change. The design of the DC side circuit needs to comprehensively consider the current fluctuation range, voltage fluctuation coefficient and dynamic compensation requirements of the system to ensure the stable operation and response performance of the entire system.

[0080] Generally speaking, the DC side circuit needs to have a high voltage and current carrying capacity, while ensuring the durability and stability of its components. Especially under dynamic load conditions, the voltage fluctuation of the DC side circuit directly affects the accuracy of the compensator output and the compensation effect of the system, so accurate calculation and optimization of its design is essential.

[0081] In this embodiment, the main components of the DC side circuit include a capacitor bank and a power switch device. As an option, the capacitor bank is composed of multiple aluminum electrolytic capacitors connected in parallel, each capacitor having a rated capacity of 220 μF and a rated voltage of 100 V. The parallel design not only increases the overall capacity of the capacitor bank, but also enhances its buffering ability against voltage fluctuations. Specifically, the design of the total DC side capacitance follows the following formula: in: is the total capacitance value; Indicates the system rated output current, and its calculation formula is: in The value is 50. The value is 380V, so About 76 A.

[0082] is the grid angular frequency; is the total voltage on the DC side, which is 467V; According to the above formula, the DC side capacitance is designed to be 0.2 F. In order to improve the redundancy capability, four capacitors with a rated capacity of 220 μF are selected in parallel in this embodiment, and the actual total capacity reaches 0.22 F, providing an additional safety margin.

[0083] The selection of power switching devices is also the core content of DC side circuit design. In one possible implementation, the power switching device is MOSFET, which has a rated current of 180 A and a rated voltage of 70 V. The on-resistance of MOSFET is 1.2 mΩ, which can effectively reduce power loss during high-frequency operation.

[0084] Specifically, the DC voltage distribution of the power switching device follows the following formula: in: is the DC voltage of each H-bridge unit; The value is 467V; Set to 12 for the number of H-bridge units per phase.

[0085] By calculation, we can get is 38.9V. When the number of cells is reduced to 10 due to failure, the DC voltage is redistributed as follows: This design ensures that the DC side circuit can still operate stably when the system fails or the redundant unit is enabled.

[0086] As an optimized design, the DC side circuit also adds a surge protection circuit and a decoupling circuit. Generally, the surge protection circuit is composed of a voltage-stabilizing diode and a fast fuse to prevent the transient overvoltage of the power grid from damaging the capacitor bank and power switching devices. The decoupling circuit effectively suppresses the interference of high-frequency noise on the DC circuit through the combination of inductance and capacitance.

[0087] In addition, in order to improve the stability of the DC voltage, the fluctuation range of the capacitor bank in this embodiment is strictly controlled between 1% and 10%. Through reasonable capacitor configuration and real-time monitoring, the capacitor bank can quickly respond to load changes and avoid voltage fluctuations beyond the set range.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An intelligent control system for high-voltage circuit breakers based on positive and negative zero-sequence control algorithms, characterized in that: include: A star-connected cascaded H-bridge static synchronous compensator, each phase of which consists of multiple H-bridge units; Data acquisition module, used for real-time acquisition of voltage and current signals of three-phase system; A control module for running the positive and negative zero-sequence control algorithm to achieve voltage fluctuation optimization and unbalanced load compensation through independent control of the three-sequence components; Communication module, used for data interaction between the control module and the host computer; Connecting inductor, used to connect the static synchronous compensator and the power grid to reduce harmonic interference and provide necessary impedance; An execution module, used for adjusting the output of the static synchronous compensator according to the compensation instruction output by the control module; The DC side circuit, including capacitors and power switching devices, is used to provide DC voltage support and safety redundancy.

2. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The data acquisition module includes an analog-to-digital converter and a multi-channel GPIO interface, which is used to complete the accurate sampling and real-time transmission of voltage and current signals.

3. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The main control chip in the control module is a STM32F407 high-performance microprocessor with a built-in DSP computing unit for running the control algorithm and outputting PWM signals. It can also collect voltage signals and process interrupt signals.

4. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The positive, negative and zero-sequence control algorithm in the control module obtains positive-sequence, negative-sequence and zero-sequence components by symmetrically decomposing the current and voltage signals of the three-phase system, and independently controls the positive-sequence component to achieve normal operation, suppresses the negative-sequence component to reduce system imbalance, and balances the zero-sequence component to reduce the neutral line current.

5. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The number of H-bridge units per phase of the star-connected cascade H-bridge static synchronous compensator is 12, and it has 2 redundant units, so that the system can still operate stably when the number of units is reduced to 10.

6. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The capacitor design parameters of the DC side circuit meet the following requirements: the capacitance value is calculated based on the current, frequency, DC voltage and redundancy factor, and the DC side capacitance fluctuation range is controlled within the allowable range of 1% to 10%.

7. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The control module communicates with the host computer through RS-485 and CAN communication interfaces. The RS-485 interface uses an integrated isolated converter, and the CAN interface uses a high-speed isolated converter to support real-time data transmission and remote control.

8. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The control of the DC voltage in the DC side circuit satisfies: The total DC side voltage is allocated according to the system operating voltage and the number of individual H-bridge units, and the DC voltage of each H-bridge unit is calculated by dividing the total DC voltage by the number of units.

9. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1 is characterized in that: The value of the connection inductance satisfies the relationship between the system voltage fluctuation and the rated current. The connection inductance is calculated based on the matching of the AC voltage, the compensation voltage and the current fluctuation, and the inductance value is optimized to reduce harmonic interference.

10. The intelligent control system for high-voltage circuit breaker based on positive and negative zero-sequence control algorithm according to claim 1, characterized in that: The control module runs the main program, which includes the following steps: Initialize the control system, including various interfaces, GPIO ports and analog-to-digital conversion modules; Configure the interrupt service routine address and start the timer for periodic data collection; The control module collects voltage and current signals in real time and outputs compensation instructions through positive and negative zero-sequence control algorithms; The execution module adjusts the output of the static synchronous compensator according to the instructions to achieve reactive power compensation and voltage balance; Clear the interrupt flag, end the current task, and return to the main loop.

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